completedenture theory and practice

COMPLETE DENTURETHEORYAND PRACTICE

Mostafa FayadLecturer of Removable Prosthodontic

Faculty Of Dental MedicineAl-Azhar University

Cairo- Egypt

2011

2nd ed

COMPLETE DENTURE THEORY AND PRACTICE

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Table of contents

Subjects1 introduction2 Anatomy and Physiology in Complete Denture3 diagnosis4 Impression Trays and techniques5 Relief Areas and post dam6 Record Base and occlusion rim7 JAW RELATION8 Occlusion & articulators9 SELECTION , arrangement of artificial teeth and WAXING-UP10 try in11 Processing Dentures12 Denture insertion13 Complaints14 SEQUALAE OF WEARING CD15 PREPARATION OF THE MOUTH16 Management of Problematic patients17 FAILURE OF C. D18 Nausea & gagging19 SINGLE COMPLETE DENTURE20 Combination syndrome21 TEETH supported OVERDENTURE22 Implant Overdentures23 Geriatric Edentulous Patient24 Duplication25 Relining and rebasing26 Repair27 Biomechanics28 Neutral Zone29 Esthetics in Complete Denture30 phonetics in Complete Denture31 masticatory function3233

COMPLETE DENTURE THEORY AND PRACTICE Introduction to CD 1

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Introduction

Prosthetics : It is the art and science of designing, supplying and fitting artificial replacement for

missing part of the human body.

Prosthesis : Is the artificial appliance which replaces a lost part of the human body.

Prosthodontics: It is a branch of dental science which deals with replacement of missing teeth

and associated structures by using artificial devices to restore function and esthetics.

Prosthodontics

1- Fixed prosthodontics.

2- Removable prosthodontics : a- complete denture b- partial denture

3- Maxillofacial prosthodontics.

Removable Prosthodontics is the art and science of replacement of missing teeth and oral

tissues with a prosthesis designed to be removed by the wearer. It includes removable complete

and removable partial prosthodontics.

Dentulous : A condition in which natural teeth are present in the mouth.

Edentulous : A condition in which all natural teeth are lost.

Partially Edentulous : A condition in which some of the natural teeth are lost.

Retention is a quality inherent in a prosthesis acting to resist dislodging forces along the path

of placement.

Stability is the quality of prosthesis to be firm, steady, or constant, to resist displacement by

functional horizontal or rotational forces.

Support is the quality of prosthesis to resist vertical tissue ward force.

Supporting area is the foundation area on which a dental prosthesis rests.

Complete Denture Prosthodontics : It involves the replacement of the lost natural dentition and

associated structure of the maxilla and mandible for patients who have lost all their natural teeth.

Objectives of Complete Denture Prosthodontics

1- Restoration of the masticatory function.

2- Restoration of the normal appearance.

3- Correction of speech defects resulting from loss of natural teeth.

4- Preservation of the alveolar bone and tempromandibular joints.

5- Satisfaction and comfort of the patient .


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Denture surfaces

Complete denture consists of denture base that rest on the supporting structure and to

which an artificial teeth attached to it.

It has three surfaces:

1-Fitting surface, (intaglio surfaces, impression surface) determined by the impression.

2-Polished surface; includes the facial (labial and buccal) and lingual and palatal

surfaces.

3-Occlusal surface that makes contact with the opposing denture.

Denture borders: The margin of the denture base at the junction of the polished and

impression surface.

Denture flanges

The vertical extension of the denture base that extends from the cervix of the teeth to the

borders of the denture flanges; they are named according to location into:

Labial flange; the portion of flange that occupies the labial vestibule.

Buccal flange; the portion of flange that occupies the buccal vestibule.

Lingual flange; the portion of mandibular denture flange that occupies the alveololingual

sulcus.


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The differences between natural teeth and artificial teeth

Natural Teeth Artificial Teeth

Type of supportThe teeth are supported by periodontal tissue which gives support, positional adjustment of teeth and proprioceptive response.

Area of support in both jawsAbout 90 cm square.

Amount of masticatory forcesFrom 5 - 17.5 pounds.

Effect of masticatory forcesThe masticatory forces are transmitted to the bone in the form of tension through the periodontal ligament. This tension is well accepted by the alveolar bone and may even service as stimulus for alveolar bone remolding

Effect of pressure on teethEach tooth receives individual pressure and moves independently.

Effect of non-vertical components of forcesWell tolerated.

Incising forcesNot affect posterior teeth.

Proprioceptive responseThe proprioceptive mechanism act as a useful alarm protecting both the supporting structures of the tooth and the substance of the crownfrom the effects of excessively vigorous masticatory movements.

All teeth are on bases and supported by mucosa which is not created to be covered.

About 35 cm square of edentulous mouth.

About 10- 15% of its value in natural dentition.

The force is not directed to the entire alveolar bone but is applied only on its surface in the form of compression. This compression has limited tolerance by the bone and may cause alveolar bone resorption.

Teeth move as a unit on a base.

Cause trauma to the supporting tissue and reduce stability to the denture.

Cause tipping of the denture base specially if the teeth are not balanced articulated.

By the loss of natural teeth there is no proprioceptive mechanism.


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Steps of Complete Denture Construction

Clinical Steps Laboratory Steps1-History taking and examination of the mouth. -Preparing the mouth for dentures.

2-Taking of preliminary impressions (in stock trays)

5-Taking of final impressions (in special trays) and determining of the posterior palatal seal.

8-Recording of jaws relations, face bow transfer and selection of teeth.

11-Trying in the waxed denture.

15-Registration of new centric relation and face bow transfer for clinical remount (if needed).

17-Delivery of the finished denture and instruction for their use.

18-Review of the denture (inspection and aftercare).

3-Casting of the preliminary impression (using plaster of paris).

4-Construction of special trays.

6-Boxing in and casting of the final impression (using dental stone).

7-Construction of occlusion record blocks.

9-Mounting of the casts with the record blocks on the articulator.

10-Setting-up of the teeth and waxing-up.

12-Processing of the denture (flasking, wax elimination, packing, curing and deflasking).

13-Laboratory remounting of the denture and correction of occlusion by selective grinding.

14-Finishing and polishing.

16-Remount of the denture on articulator for adjustment of occlusion (if needed).


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Classification System for Complete Edentulism

The American College of Prosthodontists has developed a classification system for complete edentulism based on diagnostic findings. These guidelines may help practitioners determine appropriate treatments for their patients. Four categories are defined, ranging from Class I to Class IV, with Class I representing an uncomplicated clinical situation and a Class IV patient representing the most complex and higher-risk situation.

Each class is differentiated by specific diagnostic criteria. This system is designed for use by dental professionals who are involved in the diagnosis of patients requiring treatment for complete edentulism.

Potential benefits of the system include:

1)better patient care,

2) improved professional communication,

3) more appropriate insurance reimbursement,

4) a better screening tool to assist dental school admission clinics, and

5)standardized criteria for outcomes assessment.

Diagnostic Criteria

The diagnostic criteria used in the classification system are.

1. Bone height--mandibular

2. Maxillomandibular relationship

3. Residual ridge morphology maxilla

4. Muscle attachments

Bone Height: Mandible only

The results of a radiographic survey of residual bone height measurement are affected by the variation in the radiographic techniques and magnification of panoramic machines of different manufacturers.

To minimize variability in radiographic techniques, the measurement should be made on the radiograph at that portion of the mandible of the least vertical height.


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A measurement is made and the patientis classified as follows:

Type I (most favorable): residual bone height of 21mm or greater measured at the least verticalheight of the mandible

Type II: residual bone height of 16 to 20 mmmeasured at the least vertical height of the mandible

Type III: residual alveolar bone height of 11 to 15mm measured at the least vertical height of the mandible

Type IV: residual vertical bone height of 10 mm or less measured at the least vertical height of the mandible

The continued decrease in bone volume affects:

1) denture-bearing area;

2) Tissues remaining for reconstruction;

3) Facial muscle support/attachment;

4) Total facial height; and

5) Ridge morphology.

Residual Ridge Morphology: Maxilla Only

Residual ridge morphology is the most objective criterion for the maxilla, because measurement of the maxillary residual bone height by radiography is not reliable.

Type A (most favorable)

Anterior labial and posterior buccal vestibular depth that resists vertical and horizontal movement of the denture base.

Palatal morphology resists vertical and horizontal movement of the denture base.

Sufficient tuberosity definition to resist vertical and horizontal movement of the denture base.

Hamular notch is well defined to establish the posterior extension of the denture base.

Absence of tori or exostoses.


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Type B

Loss of posterior buccal vestibule.

Palatal vault morphology resists vertical and horizontal movement ofthe denture base.

Tuberosity and hamular notch are poorly defined, compromising delineation of the posterior extension of the denture base.

Maxillary palatal tori and/or lateral exostoses are rounded and do not affect the posterior extension of the denture base.

Type C

Loss of anterior labial vestibule.

Palatal vault morphology offers minimal resistance to vertical and horizontal movement of the denture base.

Maxillary palatal tori and/or lateral exostoses with bony undercuts that do not affect the posterior extension of the denture base.

Hyperplasic, mobile anterior ridge offers minimum support and stability).-of the denture base.

Reduction of the post malar space by the coronoid process during mandibular opening and/or excursive movements.

Type D

Loss of anterior labial and posterior buccal vestibules.

Palatal vault morphology does not resist vertical or horizontal movement of the denture base.

Maxillary palatal tori and/or lateral exostoses (rounded or undercut) that intcrfere with the posterior border of the denture.

Hyperplasic, redundant anterior ridge.

Prominent anterior nasal spine.


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Muscle Attachments: Mandible only

The effects of muscle attachment and location are most important to the function of a mandibular denture .these characteristics are difficult to quantify.

Type A (most favorable)

Attached mucosal base without undue muscular impingement during normal function in all regions.

Type B

Attached mucosal base in all regions exccpt labial vestibule

Mentalis muscle attachment near crest of alveolar ridge.

Type C

Attached mucosal base in all regions except antcrior buccal and lingual vestibules (canine to canine).

Genioglossus and mentalis muscle attachments near crest of alveolar ridge.

Type D

Attached mucosal basc only in the posterior lingual region.

Mucosal base in all other regions is detached.

Type E No attached mucosa in any region.

Maxillomandibular Relationship

It characterizes the position of the artificial teeth in relation to the residual ridge and/or to opposing dentition. Examine the patient and assign a class as follows:

Class I (most favorable): Maxillomandibular relation allows tooth position that has normal articulation with the teeth supported by the residual ridge.

Class II: Maxillomandibular relation requires tooth position outside the normal ridge relation to attain esthetics, phonetics, and articulation (eg, anterior or posterior tooth position is not supported by the residual ridge; anterior vertical and/or horizontal overlap exceeds the principles of fully balanced articulation).

Class III: Maxillomandibular relation requires tooth position outside the normal ridge relation to attain esthetics, phonetics, and articulation (ie crossbitc-anterior or posterior tooth position is not supported by the residual ridge).


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Factors Influencing the Outcome of Prosthetic Treatment

The successful outcome of prosthetic treatment depends upon

(1) The dentist who makes a diagnosis, prepares a treatment plan and undertakes the clinical work.

(2) The dental technician who constructs the various items which culminate in the finished dentures.

(3) The patient who is faced with coming to terms with the loss of all the natural teeth and then of having to adapt to the dentures and accept their limitations.

The patients contribution

The patient must:

Be able to come to terms with the loss of the natural teeth and their artificial replacement

Become accustomed to the sensation of the dentures, a process known as habituation

Learn to control the dentures

Accept and hopefully appreciate the new appearance.

Psychological effects of tooth loss

In an investigation of patients receiving prosthetic treatment, most having lost their remaining natural teeth several years previously and seeking replacement dentures, 45%

admitted to having found it difficult to accept the loss (Davis et al. 2000).

Many of those who had difficulties took longer than a year to get over the loss, and more than a third had still not accepted it by that time.

They expressed feelings of sadness, anger and depression and many felt that these last extractions had made them feel prematurely old and lost a part of themselves.

There was loss of confidence, a restriction in choice of food and a lowered enjoyment of that food. Relationships with others were affected and many patients avoided looking at

themselves without their dentures in place.



Habituation

Habituation has been defined as: A gradual diminution of responses to continued or repeated stimuli.

When new dentures are placed in the mouth, they stimulate mechanoreceptors in the oral mucosa. Impulses arising from these receptors, which record touch and pressure, are

transmitted to the sensory cortex with the result that the patient can feel the dentures.

For the first-time denture wearer this bombardment of the sensory nervous system almost inevitably results in pronounced salivation which, fortunately, only lasts for a few hours.

The continuing stimulation of these receptors does not result in a corresponding

continuous stream of impulses. The receptors adapt to this stimulation and as a

consequence the patient begins to lose conscious awareness of the new shapes in the

mouth.

Control of the dentures

The patients ability to control dentures involves a learning process that, initially, is aconscious endeavour.

The learning process has come to the rescue. As a result of repetition, new reflex arcs have been set up in the central nervous system and the conscious effort has been replaced

by a subconscious behaviour pattern.

The patients perception of appearance

Because a pleasing appearance is a subjective evaluation, there is obviously room for the dentist and patient to have differing opinions. However, open disagreement does not

predispose to successful treatment and so it is vitally important that the dentist should

take careful notice of a patients views on appearance.



Factors predicting treatment outcome

Age of the patient:

- In general, as patients grow older, it takes longer for them to adapt successfully to new dentures

Quality of care provided and previous complete denture experience

- In cases where examination of the mouth indicates that the prognosis for

dentures is poor, it is essential for the dentist to warn the patient in advance of

the difficulties and to describe the steps that will be taken to minimize them.

The patients expectations and attitude towards dentures

- a patients attitude to dentures can be a useful predictor of satisfaction or

dissatisfaction.

Opinion of a third party

- Negative comments from friends and relationscan cause disappointment

and rejection of the prostheses, while positive comments can promote

cheerful acceptance of the treatment.

General health.

- Significant impairment of general bodily or mental health may affect the learning process adversely, with the result that the patient becomes discouraged because of major difficulties in mastering new dentures.



Transition from the Natural to the Artificial Dentition

Methods of transition

The various methods of making the transition from natural to artificial dentition may be

considered under the following headings.

Transitional partial dentures

Transitional partial dentures restore existing edentulous areas. They may be worn for a

short period of time before the remaining natural teeth are extracted and the dentures are

converted accordingly.

Overdentures

Overdentures are fitted over retained roots and derive some of their support from that

coverage. Special attachments may be fi xed to the root faces to provide mechanical

retention for the denture. If, in due course, the roots have to be extracted, the overdenture

can be converted into a complete denture.

Immediate dentures

Immediate dentures are constructed before the extraction of the natural teeth and are

inserted immediately after removal of those teeth.

Clearance of remaining natural teeth before making dentures

This approach differs from all those mentioned previously in that, after the extractions,

time is allowed for initial healing and alveolar bone resorption to occur before providing

complete dentures.

It is common practice for a period of several months to be allowed for healing and initial

alveolar modelling. This delay before taking impressions will produce more stable

supporting areas for the dentures, although resorption will continue indefinitely but at a

slower rate.



Disadvantages:

Loss of masticatory function and appearance during the healing period.

The undesirable mental and physical effects on a patient.

Tongue and cheeks may invade the future denture space, making adaptation to

subsequent dentures more difficult.

Difficulty in assessing vertical and horizontal jaw relationships when

constructing new dentures.

The difficulty in restoring appearance if all information on the natural dentition

has been lost.

Factors influencing the decision of remaining teeth extraction:

1. The condition of the teeth and supporting tissues

Useful teeth can be retained if:

It is feasible to undertake appropriate treatment to eliminate any disease present

If there is confidence in the patients ability to maintain good oral health.

The presence of gross caries or advanced periodontal disease, coupled with no patient response

to oral hygiene instruction, makes the decision of whether or not to extract the teeth a simple one

2. The position of the teeth

a)Natural teeth opposing an edentulous ridge

The natural teeth generate high occlusal loads on of the denture, which may result in:

Rapid destruction of the denture-bearing bone

The production of a flabby ridge

Complaints of a loose denture

A deteriorating appearance as the denture sinks into the tissues

Fracture of the denture base.



Only in extreme cases should the dentist consider trying to reduce the occlusal loads by

extracting sound teeth in the opposing arch.

b)Over-eruption of the teeth

Extraction of over-erupted teeth may be required because they:

Excessively reduce the vertical space available for the opposing prosthesis

Have a poor appearance.

endodontic therapy followed by decoronation of over-erupted teeth

3. Age and health of the patient

It is true that early extractions may reduce problems of adaptation to dentures, but this advantage must be balanced against the immediate probability of reduced oral function

and comfort in a patient who may be happy with a few remaining natural teeth and,

perhaps, a partial denture.

One view that is regularly propounded is that every effort should be made to retain useful, strategic teeth which may either help to stabilize a partial denture or which may

be converted into overdenture abutments.

4. The patients wishes

The following two scenarios occur occasionally and might cause the dentist some difficulty:

(1) Hopeless teeth that the patient wants to retain.

The dentist should carefully explain to the patient about the condition of the teeth and the

possible harmful consequences of retaining them.

(2) Sound, useful teeth that the patient wants extracted.

The dentist explains to the patient the nature of the clinical situation and to emphasise the

harm that unnecessary extraction of the remaining teeth would cause. If the patient still

need tooth extraction , the appropriate action by the dentist is most likely to withdraw

from the case, as to extract the teeth without clinical justification would be unethical.

COMPLETE DENTURE THEORY AND PRACTICE Anatomy and Physiology 2

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Anatomy and Physiology In Relation toComplete Denture Construction

Effect of tooth loss

Anatomy

Anatomical Landmarks of Prosthetic Interest

Musculuture

Oral Mucosa

Salivary glands

Physiology

Physiology of bone

Physiology of muscles

Physiology of mucous membrane

Histology


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Tooth Extraction

Extraction of teeth may be indicated upon several lines of thought including:

Extensive caries,

Development problems i.e. hypoplastic enamel,

Periodontally compromised teeth with severe mobility and/or furcation involvement.

Such teeth have poor prognosis and the clinician may convey this unto the patient and offer possible treatment alternatives that may include extraction.

Prior to delving into the concept of immediate dentures, one must understand what tooth extraction entails. The dentist must understand possible sequelae, time taken for bone healing and possible consequences. Below describes the pathological processes that take upon an immediate precedent once extraction occurs.

Extraction of teeth emulates processes similar to fracture healing. The large cavitation formed where the tooth used to be required a large amount of epithelial migration, collagen deposition, contraction and remodeling during healing; thus, due to the nature of the cavitation bone healing at the socket undergoes secondary intention.

Immediately following injury, bleeding occurs from torn vessels with subsequent formation of a haematoma with presenting accumulating granular leukocytes. Tissue damage signals an acute inflammatory response insinuating five cardinal. Connective tissue changes that accompany the inflammatory response cause a loosening of the periosteal attachment to the bone; the haematoma attains a fusiform shape.

Two to three days later, macrophages invade the clot to remove fibrin, red cells, inflammatory exudates and debris. Bone fragments undergo necrosis and are attacked by the infiltrating macrophages. Post-demolition, ingrowth of capillary loops and mesenchymals cells occurs; these cells have osteogenic potential contributing to the haematoma. Migration of epithelium occurs at the bony crest and eventually migrates until it becomes level with the adjacent gingiva.

Following one week post-extraction, young fibrous tissue has penetrated most of the socket; the proliferating epithelium may be tenous with possible complete coverage. There may be initial signs of osteogenesis on parts of the socket wall and trabecular bone.

After two to three weeks, the invading cellular infiltrate has reduced but continued vascularity with development of new fibrous tissue and woven bone. Furthermore,


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osteoclastic activity occurs on the alveolar crests, labial plate and young bone in the base of the socket; connective tissue beneath the surface epithelial layers matures.

After several months, the woven bone still undergoes remodeling while the overlying oral mucosa has fully developed; the alveolar crests are being reabsorbed via osteoclasts. Complete replacement by lamellar bone occurs after two to three years.

Effect of tooth loss

When natural teeth are present the occlusal forces are absorbed by the hydrodynamic effect of the periodontal ligament. This complete mechanism is related to the maintenance of integrity of the alveolar process. But the loss of teeth deprives these processes of the stimulus.

Under dentures all forces are transmitted to surface of the alveolar process as pressure. Control of excessive pressure is an important consideration in CD construction.

After loss of Teeth

Alveolar bone resorbed

The orbicularis oris muscle loses its support

The amount of vermillion border shown on the upper lip is reduced

The philtrum becomes flattened.

The Nasolabial Sulcus becomes more prominent with aging due to loss of teeth and loss of vertical dimension.

The mandible become closure to the nose .

Lack of support of the facial muscles

The shape and size of the alveolar ridges change when the natural teeth are removed. The alveoli become mere holes in the jawbone and begin to fill up with new bone, but at the same time the bone around the margins of the tooth sockets begin to shrink away. This shrinkage, or resorption, is rapid at first, but it continues at a resorbed rate throughout life.

The maxilla resorbs upward and inward while the mandible resorb downward and out word so many patient appear pragmatic.


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Maxilla

The shape and size of the alveolar ridges change when natural teeth are removed.

The alveoli become mere holes in the jawbone and begin to fill up with new bone, but at the same time the bone around the margins of the tooth sockets begins to shrink away.

This shrinkage or resorption is rapid at first, but continues at a reduced rate throughout life.

The resorption of the alveolar process causes the foundation of the maxillary denture to become smaller and otherwise change shape. If the denture is made soon after teeth are removed, the apparent foundation may be large, but it also may be tender to pressure. This is the result of in complete healing and a lack of cortical bone over the crest of the residual alveolar ridge.

If teeth have been out for many years, the residual ridge may become quite small and the crest of the ridge may lack smooth cortical bony surface under the mucosa.

There may be large nutrient canals and sharp bony spicules. These conditions limit the amount of pressure that can be applied on the denture without creating pain.

Mandible:

When teeth are removed the bony foundation offer mandibular denture becomes shorter vertically and narrower buccolingually.

The bony crest of residual ridge becomes narrower and sharper. Often sharp bony spicules remain and cause tenderness when pressure is applied by denture.

The total width of bony foundation becomes greater in the molar region as resorption continues; the reason being the width of inferior border of mandible from side to side is greater than width of alveolar process from side to side.

Shrinkage of alveolar process in anterior region moves RR lingually first. Then as resorption continues the foundation moves progressively further forward. Bone loss continues on the mandible below level of alveolar process.

With resorption of alveolar process occlusal contours of RR often develop that make them curved from a low level anteriorly to a high level posteriorly causing severe problems in denture stability.

The total area of support from the mandible is significantly less than from maxillae. The available denture bearing area for edentulous mandible is 14cm2 whereas for edentulous maxillae its 24cm2. This means that mandible is less capable of resisting occlusal forces


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than the maxilla are and extra care must be taken if available support is to be used to advantage.

The rate of resorption in the mandible is much higher (4X) than in the maxilla

The Dentition Function Curve

0

20

40

60

80

100

120

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Age

Fu

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ion

(%

age)

Dentate Partially dentate Edentulous

A modelforunderstandingdentalfunction over time

The Dentition Function Curve

Ideal maxillary ridge:

Abundant keratinized attached tissue

Square arch

Palate U-shaped in cross-section

Moderate palatal vault

Absence of undercuts

High frenum attachments

Well-defined hamular notches

Ideal mandibular ridge:

Well defined retromolar pad

Blunt mylohyoid ridge

Deep retromylohyoid space

Low frenum attachments

Absence of undercuts

Abundant attached keratinized mucosa

Adequate alveolar height


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A classification of jaw form following tooth loss

Zarb classified the edentulous anterior jawbone into shape (quantity) and quality.

Quantity, Shape (types A though E) reflects a range of resorptive patterns relative to the

demarcation of the alveolar and basal jawbone.

A: most of the alveolar ridge is present.

B: Moderate alveolar ridge resorption has occurred.

C: Only basal bone remains.

D: Some resorption of the basal bone has taken place

E: Extreme resorption of the basal bone has taken place

Quality (types 1 through 4) reflects a range of cortical and cancellous patterns:

1. Almost the entire jaw is comprised of homogenous compact bone.

2. A thick layer of compact bone surrounds a core of dens trabecular bone.

3. A thin layer of cortical bone surrounds a core of dense trabecular bone.

4. A thin layer of cortical bone surrounds a core of low density trabecular bone.

Both parameters have been employed frequently in planning oral implant treatment.


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Alveolar Ridge preservation

Residual ridge is the portion of the residual bone and its soft tissue covering that remains

after the removal of teeth

One of the most important objectives of prosthodontic restoration is the preservation of the supporting structures rather than the restoration of the missing

parts.

The success or failure of a removable complete denture is dependent on many factors, which include the condition of the alveolar ridge ,health of oral mucosa and

amount of the masticatory force of the opposing dental arch.

Causes of Alveolar Ridge resorption see flat ridge


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Alveolar ridge maintenance

1) Periodontal diseases prevention

2) Conservation of remaining teeth. Retention of residual tooth roots in key locations

3) Root submergence

4) A traumatic extraction

5) Alveolar ridge maintenance (ARM) deals with the placement of osteo promotive

materials at extraction sites in an attempt to maintain the physiologic and anatomic

integrity

6) The impression should allow the fabrication of denture base that will provide the best

distribution of physical forces by accurate impression

7) Role of vertical dimension

- High vertical dimension will increase stress on residual ridge leading to ridge

resorption

- Jaw relation technique

- Occlusal plane

8) The occlusal table play an important role in ridge preservation

9) Role of occlusal surface morphology

- anatomical teeth cause more stresses on the ridge

- Semi anatomical teeth cause less stresses on the ridge

- flat teeth cause the least stresses on the ridge

10) Role of selected teeth material

- Acrylic teeth less stresses

- porcelain teeth more stresses

11) Premature contacts need to clinical remounting to decrease stress on the alveolar ridge

12) Balanced occlusion - Different Occlusal schemes

13) Denture base material and Well adapted and properly extended dentures base

14) over denture to slow down or prevent the resorption of residual ridge

15) role of implant in ridge preservation

16) Alveolar Ridge Augmentation

17) alveolar ridge augmentation using autogenous bone grafts from the iliac crest

18) Vertical Ridge Augmentation Using Alveolar Distraction Osteogenesis


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Anatomical Landmarks of Prosthetic Interest

These are anatomical guides that help in denture construction. These landmarks are either bony landmarks or soft tissue landmarks.

a- BONY LANDMARKS : Some bony landmarks are difficult to palpate, while others are easily palpated and

identified.

The bony landmarks have the advantage of their being fixed in place. The measurement produced by bony landmarks can be duplicated with more

accuracy than measurements between soft tissue landmarks .

b- SOFT TISSUE LANDMARKS Easily identified Have the disadvantage of changing their relation according to their mobility

[ I ] Extra-oral Landmarks Of Prosthetic Importance

Landmark Description Significance1- Inter-pupillary line - Imaginary line running between the

two pupils of the eye when the pt. is looking straight forward.

- Establishing the anterior Occlusal plane of the artificial teeth of the denture.

2- Ala-tragus line (Camper's line)

- Imaginary line running from the Inferior border of the ala of the nose to the superior border of the tragus of the ear.

- Establishing the posterior occlusal plane of the artificial teeth of the denture.

3- Canthus-tragus line - Imaginary line running from the outer canthus of the eye to the superior border of the tragus of the ear.

- Locating the position of the condyles.



4- Naso-labial sulcus - Depression that extends from the ala of the nose in a downward and lateral direction to the corner of the mouth.

The sulcus becomes more prominent with aging and due to loss of teeth and vertical dimension. It can be modified by proper degree of jaw separation and tooth positioning. Plumpers (thick denture flanges) improve the condition but it may interfere with muscular activity.

5- Vermillion border - The transitional epithelium between the mucous membrane of the lip and the skin.The amount of vermillion border shown on the lips depends on1-The bulk of the orbicularis oris

muscle.2- The amount of the labial alveolar bone. 3-The alignment of the anterior teeth.

After loss of teeth, the amount of vermillion border shown on the upper lip is reduced. The condition can be corrected by thickening of the labial flange of the denture and proper positioning of the anterior teeth.

6- Mento-labial sulcus - Depression runs horizontally between the lower lip and chin.

Its curvature indicates the character of the maxillo-mandibular relationship and the degree of over-closure.

Class 1 normal ridge relationship: The sulcus shows a gentle curvature with obtuse angle

Angle class II (retruded mandibular relation): The sulcus forms an acute angle

Angle class III (protruded mandibular relationship): sulcus forms an angle of almost 180

7- Philtrum - It is a diamond shaped depression at the center of the upper lip and base of the nose.

After loss of teeth, the philtrum becomes flattened. This condition can be improved by construction of proper denture with an appropriate arch-form and tooth alignment .



8- Modiolus - The point of meeting of buccinator and other facial muscles distal to the angle of the mouth. The modiolus is held in position by the arch-form of the maxillary teeth.

With the loss of teeth the modiolus drops. The appearance can be improved by proper positioning of the maxillary teeth.Narrowing of the lower denture base related to the modiolus is usually necessary to avoid displacement

9- Angle of the mouth(commissure of the lips)

- Point of meeting between the upper and lower lip.

- (Angular Chilitis): Inflammation and ulceration as a result of:1- Prolonged edentulism.2- vertical dimension of complete denture.3- Vitamin B deficiency.

10- The Angle of the Mouth and the Outer Canthus of the Eye

The distance from the outer canthus of the eye to the angle of the mouth was used by Wills to determine the vertical dimension of the edentulous patient at rest by making the distance from the base of the nose to the lower edge of mandible equal to it.

A, The Philtrum, naso-labial sulcus, commissure of the lips& mento-labial sulcus.B, Modiolus and Orbicularis Oris muscle.



The muscles contributing to the modiolus (dotted circle)



[ II ] Intra-oral landmark of prosthetic importance

The denture base must extend as far as possible without interfering in the health or

function of the tissues. The amount of biting force an edentulous ridge will tolerate is directly

proportional to the amount of surface area covered

Force directed to a large bearing area is more equally distributed and much less per sq.

mm. than the same force directed against a smaller area. Consequently, if we hope to assist a patient

to achieve maximum biting force and preserve the supporting structure over a longer period of time, The

maximum amount of denture bearing area must be covered.

The denture foundation can be divided into:

Denture bearing/stress bearing areas. (denture foundation area) it is the surfaces of the oral structures available to support a denture. or the tissues (teeth and/or residual ridges)

that serve as the foundation for removable partial or complete dentures.

Peripheral limiting or sealing areas

Anatomic Landmarks of the Denture Bearing Area (supporting structures):

In the Maxilla In the Mandible

1-The residual ridge and hard palate

2- The incisive papilla

3- The palatine rugae

4-Median palatine raphe

5- Maxillary tuberosity

6- Torus palatinus

7- Fovea palatinae

8- Incisive fossae

9- Canine eminence

10- Buttress of the zygomatic bone

11- Palatal gingival vestige

1- Residual alveolar ridge

2- Retromolar pad

- 3- Internal oblique ridge

(mylohyoid ridge).

- 4- External oblique ridge

- 5- Buccal shelf of bone

- 6- Mental foraman

- 7- Genial tubercles

- 8- Torus mandibularis



Anatomic Landmarks that Limit the Periphery of the Denture (limiting structures):

In Relation to Maxillary Denture In Relation to Mandibular Denture

1- Labial frenum

2- Labial vestibule

3- Buccal frenum

4- Buccal vestibule

5- Pterygo maxillary notch (Hammular

notch)

6- Vibrating line.

1- Labial frenum

2- Labial vestibule

3- Buccal frenum

4- Buccal vestibule

5-Masseter muscle influencing area

6-Retromolar pad and inferior border of the

ramus

7- Pterygomandibular raphe

8- Plato glossal arch

9- Lingual pouch

10-Mylohyoid muscle influencing area

11- Lingual frenum

ANATOMY OF MAXILLARY DENTURE FOUNDATION

The maxillary denture is supported by two maxillae and the palatine bones. The palatine

processes of the maxillae are joined together at the midline in the median suture

The two palatine processes of the maxillae and the palatine bone form the foundation of the hard

palate and provide considerable support for dentures.

There are two maxillae, each consisting of a central body and three processes.

(a) The frontal process of the maxillae is directed upwards. It articulates anteriorly with

the nasal bone, posteriorly with the lacrimal bone and superiorly with the frontal bone.

(b) Zygomatic process of maxilla is short but stout and articulates with the zygomatic

bone.

(c) The alveolar process of maxilla bears sockets for teeth. The alveolar process arises

from lower surface of the maxilla. It consists of two parallel plates of cortical bone

buccolingual or labiolingual, which unite behind the last molar tooth to form the alveolar

tubercle. When teeth are present the cortical plates are connected by inter alveolar or

interdental septa.



Zygomatic process or malar process which is located opposite first molar region is one of

the hard areas found in mouths that have been edentulous for a long time. Some dentures

requires relief over this area to aid in retention and prevent soreness of underlying tissues.

The crest of the residual alveolar ridge

covered with a layer of fibrous connective tissues, Most favorable for supporting the denture because of its firmness and position. The residual ridge and most part of the hard palate are considered the major or primary

stress bearing areas in upper jaw.

The resorption of residual ridge limits its ability to support unlike the palate which is resistant to resorption, so the residual ridge may be considered as secondary supporting

area. (ZARB)

Factors that influence the form and size of supporting bone of basal seat include.

(1) Its original size and consistency.

(2) The patients general health and resistance.

(3) Forces developed by surrounding musculature.

(4) Severity and location of periodontal disease.

(5) Forces accruing from wearing of dental restorations.

(6) Surgery at the time of removal of teeth.

(7) The relative length of time the different parts of jaws have been edentulous.

Hard palate

It is a partition between oral and nasal cavities. Its anterior two thirds are formed by palatine process of maxillae and its posterior

1/3 by horizontal plates of palatine bone.

The center of the palate may be very hard because the layer of soft tissue covering the bone in the region of median palatal suture is extremely thin.

The soft tissue covering the hard palate varies considerably in consistency and thickness in different locations even though the epithelium is keratinised

throughout. Antero laterally the submucosa of hard palate contains adipose tissue

and posterolaterally it contains glandular tissue. The tissues should be recorded in

a resting condition, because when they are displaced in the final impression, they



tend to return to normal form within completed denture base creating an unseating

force on denture base or causing soreness in patients mouth. Proper relief of final

impression trays aids in recording these tissue in an undistorted form. In addition

the secretions from the palatal glands can be an important factors in selection of

final impression material.

The glandular region of either side of the mid line in the posterior part of the hard palate should be covered by the denture so it can aid in retention, but it

should not provide significant support for the denture because of the relatively

higher resiliency at this site. The mucous glands in this region are relatively thick

and they cover the blood vessels and nerves coursing forward in the palate from

greater palatine foramen. These vessels and nerves anastomose with vessels and

nerves passing through the nasopalatine canal and into the region of basal seat of

incisive papilla.

Incisive papilla

It covers the incisive foramen and is located on the line immediately behind and between the central incisions.

Its position varies with different patients. It is located on the centre of ridge after resorption has occurred in mouths that have been edentulous for long time.

The location of incisive papilla gives an indication as to the amount of resorption of residual ridge and thus is an aid in determining vertical dimension and proper

position teeth.

Incisive foramen (Nasoplatine foramen)

The Nasoplatine nerves and blood vessels in submucosa exit the palate at right angles to the margins of this bony fossa or foramen. Therefore even though the foramen is covered

with protective pad of fibrous CT called incisive papilla, the denture base should be

relieved over this area. Failure to relieve the denture base will result in pressure on the

nerves and blood vessels with resultant decrease in blood supply to anterior part of palate

and nerve irritation with accompanying burning symptoms.

The location of incisive foramen gives an indication as to the amount of resorption of theResidual ridge. It comes nearer to crest of the ridge as resorption progresses. thus aid in

determining the vertical dimension and the proper position of maxillary anterior teeth.



Palatine rugae

The rugae in the anterior part of the hard palate are irregularly shaped rolls of soft tissue. They should not be distorted in an impression technique since rebounding tissue tends to

unseat the dentures.

This area contributes to stress bearing role as well as retention, though in secondary capacity.

Median palatine suture (mid palatal suture)

The two horizontal palatine processes of the maxillary bone fuse in the midline to formthe mid palatal suture.

The submucosa in this region is extremely thin and non resilient little or no stress can be placed in this region during find impression making or the completed denture lest the

denture tend to rock over the center of palate when vertical forces are applied to the teeth.

In addition this part of mouth is highly sensitive and excess pressure can create

excruciating pain.

Proper relief in the impression tray or completed denture is essential for accommodating this nature of tissue.

Posterior nasal spine, greater/lesser palatine nerves and vessels

The posterior border of the horizontal plates of the palatine bones unites in midline to form the sharp posterior nasal spine. The posterior margins of the hard palate serve as the

anterior attachment for aponeurosis of soft palate.

On each side of the hard palate the greater palatine foramen is located medial to the third molar at the junction of the maxilla and horizontal plate of palatine bone. A groove

extends anteriorly from the foramen and contains the anterior (greater) palatine nerve and

blood vessels. Because the nerve and blood vessels course though a groove, rarely must

the denture base over the area be relieved.

In some instance bony spines are located near the greater palatine foramen. If these bony

projection present problems, the denture base should be relieved over these areas, or the

spines should be surgically removed.



Tuberosity region

The tuberosity region often hangs abnormally low because the maxillary posterior teeth are retained after the mandibular molars have been lost and not replaced, the maxillary

teeth extrude bringing the process with them often the low lying tuberosity is complicated

by excess fibrous connective tissue.

This excess soft tissue can prevent proper location of occlusal plane if not removed. In addition rough and irregular bone can be irritated by denture base.

Palatine fovea

They are ductal openings into which ducts of other palatal mucosal glands drain. They serve no function. According to Lye the fovea palatine are located on average of 1.31mm

anterior to anterior vibrating line.

Sharp spiny process

There are sharp spiny processes on the maxillary and palatine bone, usually they have no problem with complete denture but with resorption they can irritate the soft tissue lies

between them and denture base.

ANATOMY OF PERIPHERAL OR SEALING AREAS

The functional anatomy of the mouth determines the extent of basal surface of a denture.

The denture base should include the maximum surface possible within the limits of health

and function of the tissues it covers and contacts.

Labial frenum

The lip movement near the maxillary labial frenum isvertical and thus the notch becomes long and narrow.

If the frenum is pulled too far laterally during border

molding, the notch will become too wide and the

peripheral seal will be lost.

In some cases depressions are recorded beside the labial frenum notch due to muscle

band consisting of the origins of the nasal septal depressor muscle and the orbicularis

oris. In these cases the denture must be adequately relieved as not to disturb the function

of these muscles.



Labial vestibule

In region of labial vestibule, three objectives of an impression should be fulfilled.

The impression must supply sufficient support to the upper lip to restore the relaxed contour (for appearance) of the lip. The thickness of labial flange must be developed

according to amount of bone that has been lost from labial side of ridge.

Secondly the labial flange of impression must have sufficient height to reach the reflecting mucous membrane of the labial vestibular space without distorting it.

Thirdly there must be no interference of labial flange with action of lip in function.Buccal frenum

The muscle movements around the buccal frenum are both vertical and horizontal thus a wider notch should be formed compared with

the labial frenum. It will become a V-shaped notch.

Generally the frenum runs obliquely and posteriorly therefore its anterior movement should be recorded by pursing the lips such as when whistling during

border molding.

Buccal vestibule

The size of the buccal vestibule varies with the contraction of the buccinator, the position of the mandible and the amount of bone lost from the maxilla.

The thickness of the distal end of buccal flange of denture must be adjusted to accommodate the ramus and coronoid process and the masseter as

they function. When mandible moves forwards or to the opposite

side the width of buccal vestibule is reduced. When masseter

contracts under heavy closing pressure it also reduces the size of

space available for distal end of buccal flange.

If border molding in the buccal space is inadequate, the denture will lose its seal because of the ingress of air under the denture base when the buccal vestibule is opened during

situations in which the patient laughs and opens the mouth widely.

In the rare case when it is hard to determine the width of the vestibule and thus the width

of the denture border due to severe alveolar ridge resorption, the appropriate width of the

vestibule can be estimated by using the remnants of the lingual gingival margin as a

guide. [HAYAKAWA]



The buccolingual breadth of the dentate alveolar ridge (the horizontal breadth of

the alveolar process from the lingual gingival margin to the maximal projection of

the buccal surface of the ridge) is remarkably constant for every tooth position. So

the remnants of the lingual gingival margin can be located in the edentulous

mouth, the cheek position can also deduced by using it as a landmark.

For example , the average measurement of the buccolingual breadth BLB in the

dentate molar region is 10-12 mm, However, after extraction of the teeth, the

remnant move outward 3-4 mm from the position in the dentate mouth, so the

width of the vestibule should be estimated by deducting this value from the mean

buccolingual breadth of dentate patient. [See Palatal gingival vestige]

Pterygoid process

It projects downwards from the greater wing and body of sphenoid behind the third molar tooth. Inferiorly it divides into medial and lateral pterygoid plates,

which are fused anteriorly but separated posteriorly by the v-shaped pterygoid

fossa.

The fused anterior borders of the two plates articulate medially with the plate of palatine bone and are separated laterally from the posterior surface of the body of

maxilla by pterygomaxillary fissure.

The medial pterygoid plate is directed backwards. It has medial and lateral surfaces and a free posterior border. The upper end of this border divides to



enclose a triangular depression called scapoid fossa. Medial to this fossa there is a

small pterygoid tubercle, which projects into the foramen lacerum. It hides from

view the posterior opening of the pterygoid canal. The lower end of the posterior

border is prolonged downwards and laterally to form the pterygoid hamulus.

The lateral pterygoid plate is directed backwards and laterally. It has medial and lateral surfaces and a free posterior border. The lateral surface forms medial wall

of infra-temporal fossa. The medial surface gives origin to muscles. The posterior

border sometimes has a projection called pterygo spinous process, which projects

towards the spine of sphenoid.

Pterygo maxillary (hamular) notch

The pterygoid hamulus is a thin, curved process at the terminal end of medial pterygoid plate of sphenoid bone. The exact position of hamular process is located

2-4 mm posteromedial to distal limit of maxillary residual ridge

Although the pterygoid hamulus does not help in support of dentures, the area between the maxillary tuberosity of maxilla and the hamulus is critical to design

of maxillary denture. It is used as a boundary of the posterior border of maxillary

denture back of tuberosity.

The posterior palatal seal must be placed through the centre of the deep part of hamular notch since no muscle or ligament is present at a level to prevent the

placement of extra pressure. The submucosa of mucous membrane is thick and

made up of loose areolar tissue.

Additional pressures also can be placed on this tissue at the centre of the notch to complete the posterior palatal seal.

Posterior palatal seal

It is divided into two separate but confluent areas based on anatomic boundaries. The posterior palatal seal extends medially from one tuberosity to another.

Laterally the pterygo maxillary seal extends through the pterygo maxillary notch

continuing for 3-4mm antero laterally approximating the mucogingival junction.

The pterygo maxillary seal occupies the entire width of pterygo maxillary notch, which is defined as band o loose CT lying between the pterygoid hamulus of

sphenoid bone and distal portion of maxillary tuberosity.



The notch is covered by pterygo mandibular fold, which extends from posterior aspect of

tuberosity posterior-inferiorly to insert into retromolar pad. This fold of tissue can influence the

posterior border seal if the mouth is in a wide-open position during final impression procedure.

Vibrating lines

The PPS lies between the anterior and posterior vibrating lines. It is an imaginary line across the posterior part of the palate marking the division

between the movable and immovable tissues of the soft palate. This can be

identified when the movable tissues are functioning

It should be described as area not line The anterior vibrating line located at the junction of attached tissues overlying

the hard palate and movable tissues of the immediately adjacent soft palate. This

should not be confused with anatomic junction of hard and soft palate.

It can be located by patient performing Valsalva Maneuver or instructing patient

to say Ah in short vigorous bursts. This places the soft palate inferiorly at its junction with hard palate. Due to projection of posterior nasal spine the anterior vibrating line is not a

straight line between the hammular processes. The anterior vibrating line is

always on soft palatal tissues. As soft palate extends posteriorly the action of

palatal muscles become more exaggerated.

The posterior vibrating line is an imaginary line at the junction of aponeurosis of tensor veli palatini muscle and muscular portion of soft palate.

It represents the demarcation between that part of soft palate has limited or

shallow movement during function and the remainder of soft palate that is

markedly displaced during functional movements.

It can be visualized by instructing patient to say Ah in normal unexaggerated

fashion. The posterior vibrating line marks the most distal extension of denture

base. The vibrating line is located and marked using an indelible pencil or marker,

and the impression tray is trimmed to this line

The distal end of the denture : should extend at least to vibrating line and in some instances it may extend 1 to 2 mm posterior to vibrating line .[ ZARB] Should cover the tuberosity and extend to hamular notch.



Techniques used in locating the vibrating line.

1- The clinician will often visualize the position of this line by having the patient say

"Ahh" and noting that the soft palatal tissues will usually lift while the hard palatal tissues

remain immobile. When the patient says "ah" the oft palate rises up and returns to its original

position when the patient relaxed

2- The Valsalva maneuver in which the patient is asked attempt to blow air through their

nose while the nostrils are gently pinched closed. While gently holding the tongue down with

a mouth mirror, the clinician will often easily visualize the line because the soft palate will

drop dramatically at the vibrating line using this technique. Blowing out through the nose

while closing the nostril causes a downward expansion of the soft palate

3- Other features indicating the position of this line may include a rather sharp color

change between the hard and soft palatal tissues at the vibrating line

4- Presence of the fovea near the line. According to Lye the fovea palatine are located on

average of 1.31mm anterior to anterior vibrating line.

5- Lastly, and often the easiest to visualize, may be the rather significant angular change

between the rather flat hard palate and the moderately to severely sloping soft palate. This

junction indicates the vibrating line.

A = "clinical" junction of hard and soft palates. B=ah-line ,C=fovea palatinae , D: anatomical junction of hard and soft palates.

The hard palate possesses a portion made up of a 4-5 mm thickness of submucosa which contain muscle insertions a well as glandular tissue. Even though the hard palate is

supported by bone, it is affected by the Levator and tensor muscles of the velum palatini

and so it is considered to be movable.



Clinically, from only inspection and palpation, it is difficult to determine whether the palate is supported by bone or not. So, the term,

"clinical' hard and soft palates, should be advocated

In the posterior part of the submucosa of the palate, the palatine glands

extend anteriorly from the soft palate to the first molar region taking the

shape of a mountain on either side of the midline.

The thickness is 4-6 mm in the soft palate and 2-3 mm even in the anterior part on the

hard palate. Thus there is no need to be anxious regarding how far the posterior border can be

extended. If the border is placed only on these palatine glands which possess a cushioning

effect, this would be adequate for retention, even if it is placed slightly anteriorly. A little

more extension may not lead to much better retention. If it is overdone the situation will be

worse than that of under extension and will lead to a gag reflex and irritation of the movable

mucosa. Therefore it is recommended that the posterior border is determined by carefully

avoiding the portion moving around the vibrating line whilst saying "ah".

Some clinicians might extend the posterior border posteriorly so as to cover the foveae

palatinae by considering the anatomical junction of the two palates, but this concept is not re-

commended. [HAYAKAWA]

Classification of soft palate

Based on angle that soft palate makes with hard palate. The more acute the angle, the

more muscle activity that will be necessary to achieve velopharyngeal closure (closing

nasopharynx).

The more the soft palate is markedly displaced in function, the less that can be covered

by denture base.

The more resorbed the edentulous ridge, more difficult in determining the soft palatal

configuration.



A Broad PPS

B - Medium width PPS

C Narrow PPS

Class I Horizontal. Minimal muscular activity. Allows wide PPS but not very deep. Since more tissue surface is covered it yields more retentive denture base.Class III The most acute contour. Marked elevation of the musculature to create velopharyngeal closure. Usually seen in conjunction with high v-shaped palatal vault. Small area for posterior seal. Deeper than class IClass II Designates those palatal contours that lie some where between class I and class III.

ANATOMY OF MANDIBULAR DENTURE FOUNDATION

The mandible is the movable membrane of the stomatognathic system. The body of

mandible is horse-shoe shaped. The distal portion of each site continuous upwards and

backward into the mandibular ramus.

The ramus divides superiorly into the condylar process and coronoid process. The

condyle (head) is the articular surface of the condylar process.

The connection of condyle with ramus is the slightly constricted mandibular neck.

Superior to the neck, the condyle is bent anteriorly so that the articular surface faces upward and

forward.

The coronoid process is a triangular bony projection that varies in size and shape. The

convex anterior border of coronoid process continues in to anterior border of ramus.

When the mandible is protruded the anterior border of ramus extends towards the

alveolar tuberosity, which is medial to ramus. If the distobuccal flange of denture is too thick, it

will cause discomfort when mandible is protruded and may dislodge denture during lateral

excursions.



The total area of support from the mandible is significantly less than from maxillae. The

available denture bearing area for edentulous mandible is 14cm2 whereas for edentulous

maxillae its 24cm2. This means that mandible is less capable of resisting occlusal forces than the

maxilla are and extra care must be taken if available support is to be used to advantage.

Crest of residual ridge

The underlying bone of crest of RR is cancellous made up of spongy trabeculae. Therefore crest of lower RR may not be favourable as primary stress bearing area for

lower denture.

Proper relief to be provided for crest of lower ridge during making final impression.Retro molar region and pad

The distal end of mandibular denture region is bounded by the anterior border of ramus, thus including the retro molar pad

posteriorly, which defines the posterior limit.

The retro molar which is triangular soft pad of tissue at distal end of lower ridge must be covered by denture to perfect the seal.

It contains some glandular tissue, some fibers of temporalis tendon, fibers of superior pharyngeal constrictor enter it from lingual and pterygo mandibular raphe enters the pad

at its supero posterior inside corner. The action of these limits the denture during

impression procedures.

The posterior half of the retromolar pad is filled with resilient glandular tissues. The peripheral seal of the denture can be obtained when the denture border is placed on this

tissue. The distal end of the denture should be placed at a point 213 of the way up the

retromolar pad .

As the ternporalis muscle fibers attach to the distal portion of the retromolar pad, stimulation from this muscle prevents the pad from resorption. So, the retromolar pad is

also used as a landmark for orientation of the occlusal plane. Therefore the retromolar

pad must be included in the impression. [HAYAKAWA]

Retromolar pappilea is small pear shape area just anterior to the retromolar bad it is dense fibrois connective tissue. [HEARTWELL]



Mylohyoid ridge

If the denture border is short of the mylohyoid ridge, it will dig into the residual ridge and cause pain. The border is shortened to remove

this pain, but shortly after, the shortened border again impinges upon

the residual ridge. This repetition will make the denture into a cord-

like and has poorer retention and stability.

Border molding of the mylohyoid ridge area should be performed to cover the ridge 4-6 mm beyond it. At the insertion appointment the

impression surface of the denture on the mylohyoid ridge is relieved so

that pain during mastication will be diminished.

In addition, when the lingual denture border is extended properly as mentioned above, the lingual polished surface can be shaped into a

concave form(the concave shelf) which is important [or the retention and

stability of the denture]

When making an impression of this region, some think that the movement of the mylohyoid muscle would be recorded by moving the tip of longue toward the

opposite side, However, tongue movement is due to the action of the genioglosus muscle,

The mylohyoid muscle contracts during swallowing.

The patient is instructed to slightly touch the corner of the mouth with the tongue. A exaggerated tongue movements during impression making

will be the cause of under extended borders, excessive movements

should be avoided. If the tongue is protruded over the dental arch, the

lingual sulcus will become shallow and an extremely shortened border will be obtained.

During ordinary function like mastication the tongue is not protruded outside dental arch

The impression should be made to cover 4-6' mm beyond the mylohyoid ridge. This is the length of the denture border in the mylohyoid ridge area. [HAYAKAWA]

The outline of the denture base can be determined easily and automatically by using these

indexes. It is just necessary to connect the index lines, namely lines placed 1 mm beyond

the external oblique ridge, 2\3 of the way from the anterior border of the retromolar pad

and 4 to 6 mm below the mylohyoid ridge. [HAYAKAWA]



Lingual tuberosity

It is an irregular bony prominence on distal end of mylohyoid line. When this area is excessively prominent or rough it may present an undesirable undercut

requiring surgical intervention.

External oblique ridge (line)

It is a ridge of dense bone extending from just above the mental foreman in a superiorand distal direction to become continuous with anterior border of ramus.

In most individuals the external oblique ridge is the anatomic guide for lateral termination of buccal flange of mandibular denture.

Buccal shelf area

The area between the buccal frenum and the anterior edge of the masseter muscle. The buccal shelf may be very wide and is at right angles to vertical occlusal forces, providing

excellent resistance to such forces.

Some buccinator fibers are located under the buccal flange because the mandibular attachment of this muscle is close to crest of ridge in molar region. The inferior part of

buccinator is attached to buccal shelf of mandible and thus contraction of muscles does

lift the lower denture.

Mental foremen

It is located on the lateral surface of body of mandible between the first and second bicuspids about halfway between the lower border of mandible and the alveolar crest.

If the loss of RR is extensive, the foramen occupies a more superior position and denture base must be relieved over the foramen to keep the denture base from irritating the

mental neurovascular bundle failing which the pressure exerted will cause numbness of

lower lip.

Mental spines (Genial tubercles)

They are situated on lingual aspect of mandibular body in midline slightly above the body. These bony elevations are often divided into a superior and an inferior section and

sometimes into right and left prominences.



When loss of RR is extensive these spines are more superior position than crest of existing ridge, requiring surgically intervention.

The denture flange covering the genial tubercles may be widely eliminated in many dentures for fear that the tubercle would be

irritated by settling of the denture due to occlusal forces.

However, if the denture border ends on the hard tissues, no

peripheral seal will be possible. The denture border must be

extended over the genial tubercles (and proper relief is done) in favor of improving the

peripheral seal.

Lingual ledge

On side of genial eminence, a sharp bony ridge or crest which projects horizontally toward the tongue and then falls off abruptly maybe palpated. This is a frequent source of

annoyance to denture. The ledge is a crescent shaped prominence located bilaterally

between genial tubercle and anterior end of mylohyoid ridge, which maybe continuous. It

exists in normal mandible as a slightly curved elevation but becomes more and more

prominent as the resorptive process reduces mandibular ridge and body.

In mouths containing moderately resorbed RR, the lingual ledge maybe palpated for below the level of the floor of the mouth and is not involved in denture impressions

unless the impression tray is over - extended. Where slightly resorbed the high

mandibular ridges are present, the ledge is not palpable. The presence of soreness of

lesions in this region explains the denture border impinging on the thin overlying mucosa,

thus not covering the lingual ledge completely.

Labial frenum

Usually a single narrow band but may consist of two or more band. The activity of thisarea tends to be vertical so the labial notch in denture should be narrow.

The mandibular labial frenum is usually shorter and often wider than maxillary labial frenum.

Labial sulcus

The part of denture extending from labial frenum to buccal frenum is labial flange or labial sulcus in edentulous mouth.



This flange is limited in extension because the fibers of orbicularis oris and incisive labi inferioris are fairly close to ridge crest. Muscles fibres are mainly horizontal. Mentalis

muscle originates from mental tubercles and inserts into lower lip (orb oris). It is a

vertical muscle and may be very active in some patients.

The orbicularis oris is the major muscle in this region. as its muscle fiber run horizontally, care must be taken not to

overextend the impression border in cases with weak muscle

tension in this region.

The mentalis muscle is one of the muscles constituting the lower lip. Its muscle fibers are vertical and the origin attaches high on

the mandibular alveolar process therefore the labial vestibule becomes narrow when this

muscle contract .

However, if the lip is pulled too much as a result of being over conscious about this contraction during border molding, the vestibule will become too shallow because the

attachment of the muscle is higher than the base of the labial vestibule

Excessive activity in this area results in short flange which may not provided seal for finished dentures.

In patient exhibiting strong muscle tension of these muscles in this region, this causes the lower up to fall inward and the

impression border becomes thin and short. As a result, the

completed denture might have an insufficient peripheral seal.

In general, the instruction is given to bite the operator's

fingers which are placed between the tray and the maxillary ridge. A the masticatory

muscles become tense and the lower lip becomes loose as a reflex, the impression is then

made in this situation

When ridge is fair to good the labial borders should be thin (1-2mm) since thicker border will distort the lips. When ridge is flat a thicker border is needed for lip and checks

support and to provide better seal.

In general a thicker border creates better seal than thin border. Wider borders tend to create favourable inclined plane and reduce the potential of losing peripheral seal.



Thicker border should be used with discretion, since they may cause discomfort poor

esthetics or interference with normal muscle movements.

Buccal frenum

It is usually in the area of first premolar. It may be a single band but often two or morebands.

The oral cavities in this are horizontal as well as vertical (i.e. movements such aspuckering, grinning etc) so wider clearance is usually needed.

The contour of denture will be little narrower in this area due to activity of depressor anguli oris muscle.

Buccal vestibule

Extends from buccal frenum posteriorly to outside back corner of retromolar pad andfrom crest of RAR to cheek.

The buccinator in cheek extends from modiolus (ant) to pterygomandibular raphe (post).

Labial and buccal borders are not as critical for borders seal because they shape of the

lips and checks create a facial seal. That is why it is possible to have a denture with open or short

flange (often used for immediate dentures) and still have good retention.

Masseter region

Pain may occur on the buccal side of the retromolar pad region during mastication even though the de-

nture is properly designed. This is due to the

masseter muscle, a strong elevator, which is lateral

to the retromolar pad and covers the buccinator

muscle.

When the masseter muscle contracts, its enlargement presses the denture border with the cramped buccinator muscle. As the

denture occludes it cannot move during function of the elevators. When the distobuccal

border of the denture base is extended into the functioning area of the masseter muscle,

the mucosa will be pressed against the denture base leading to pain.



to avoid such a situation, the movement of the masseter muscle is recorded in the impression by creating its reactive contraction through pushing the tray during the border

molding procedure. The tension of the masseter muscle will make a concavity in the

distobuccal outline of the impression. Another way is to reduce the over lengthened

border through observing the redness or displacement of the denture after insertion of

the new denture made by connecting the index line.

An active masseter muscle will create a concavity in the outline of distobuccal border. The distobuccal border of mandibular impression encounters

the action of masseter to a greater or lesser degree depending on

the shape of the mandible and the origin of muscle.

If ramus of mandible has a perpendicular surface and origin of muscle on zygomatic arch is medial ward; the muscle pulls

more directly across the distobuccal denture border, therefore it forces buccinator and

tissues inward, reducing the space in this region. If the opposite is true, greater retention

is allowed on distobuccal portion of mandibular impression.

The relative size of masseter will influence its action on the buccinator; a masseter that is of smaller diameter will have less influence (perhaps none) on the border.

Distal extension of mandibular impression

The distal extent of mandibular impression is limited by the ramus of mandible, thebuccinator fibers that cross from the buccal to lingual as they attach to the pterygo

mandibular raphe and the superior constrictor and sharpness of lateral bony borders of

retro molar fossa (formed by continuation of external and internal oblique ridges

ascending the ramus).

If the impression extends on to the ramus, the buccinator and the adjacent tissues will becompressed between hard denture border and the sharp external oblique ridge, which will

not only cause soreness but also limit the function of buccinator, which is a part of the

kinetic chain of swallowing.

The desirable distal extension is slightly lingual of these bony prominences and includes the pear-shaped retro molar pad which forms a splendid soft tissue seal.



Pterygomandibular raphe

The pterygo mandibular raphe or ligament originates from the pterygoid hamulus ofmedial pterygoid plate and attaches to distal end of pterygoid ridge.

It is partly the origin of buccinator muscle laterally and the superior constrictor muscle medially.

It is quite prominent in some patients and may even require and notch like clearance in maxilla denture. A simple wide-open digital and visual inspection will usually determine

whether clearance is required or not.

If extreme opening is allowed in making the impression the pterygo mandibular ligament make a notch distal to alveolar tubercle

Alveololingual sulcus

It is the space between the residual ridge and tongue. It extends posteriorly from lingual

frenum to retromylohyoid curtain. Part of it is available for the lingual flange of denture.

The alveololingual sulcus can be considered in 3 regions

1. The anterior region (Premylohyoid fossa)

This extends from lingual frenum to where the mylohyoid ridge curves down below thelevel of sulcus.

This fossa results from the concavity of mandible joining the convexity of mylohyoid ridge.

Lingual border of impression in anterior region show make definite contact with mucous membrane of mouth when tip of tongue touches upper incisors.

Anterior lingual flange area

The border of the impression in this area is mainly influenced by the lingual frenum and

the genioglossus muscle. The genioglossus muscle and the Lingual frenum which lie over the

muscle move actively and are easily traumatized therefore their movement and tension must

be recorded exactly during border molding. Thus the patient must be instructed to make

appropriate tongue movements in order to record the exact depth and width of the notch

made by the lingual frenum.



To provide adequate clearance in this area the patient is instructed to make some overactive

movement such a licking the Lower lip , by moving the tip of the tongue from side to side.

Inadequate clearance may result in pain or inflammation. Tongue movement is never

requested during, impression making. However this is the only area where functional

movement of the tongue is necessary.

Lingual frenum

Fibrous band of tissue that overlies the centre of genioglossus muscle. It is usually a narrow single band of tissue but may be broad and exist as two or more frenums.

It is rather shallow, sensitive and resistant. It should be registered in function because at rest the height of its attachment is deceptive. In function it comes quite close to crest of

ridge although at rest it is much lower.

It originates at midline from under surface of tongue and often terminates at the sublingual (salivary) caruncles. In other instances it crosses and bisects the sublingual

crescent space and attaches to lingual aspect of mandibular ridge. Often it fans out to find

a broad insertion in alveolar mucosa.

This structure should be palpated for tension during tray adjustment procedure. Careful clearance is needed in the denture because the lingual frenum is attached to tongue and

inadequate clearance may result in pain or displacement of denture.

They may be attached or near the crest of ridge. The lingual frenum maybe very short or tongue-tie the patient can hardly protrude the tongue. Accessory frenums may occur in

almost any area of vestibule.

It is influenced by genioglossus muscle and some what by anterior portions of sublingual glands. The action of these muscles may raise and protrude the tongue.

Frenums are basically fibrous connective tissue. They do not contract or expand like muscles but rather are ligaments. They are accessory limiting structures for tongue, lips,

and muscles of cheek.



2. The middle region

The part of alveololingual sulcus extends from premylohyoid fossa to distal end ofmylohyoid ridge curving medially from the body of mandible.

When mylohyoid muscle and tongue are relaxed, the muscle drapes back under mylohyoid ridge.

If the lingual flange slopes towards the tongue, the tongue can rest on top of flange and aid in stability of lower denture on RR it also prevents displacing the denture during

tongue movements and swallowing thus maintaining the seal.

The length and width of mylohyoid flange is determined by membranes attachment oftongue to mylohyoid ridge and width of hyoglossus muscle and can only be determined

by skilful border molding and impression.

The lingual borders in mylohyoid areas are formed by contact wi

completedenture theory and practice

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