RESIDUAL RIDGE RESORPTION

INTRODUCTION DEFINITIONS CLASSIFICATION OF RRR PATHOLOGY OF RRRPATHOPHYSIOLOGY OF RRRPATHOGENESIS OF RRREPIDEMIOLOGY OF RRRETIOLOGY OF RRR DIAGNOSTIC AIDS TO DETECT RRRCONSEQUENCES OF RRRMANAGEMENTCONCLUSION

INTRODUCTION Resorption is defined as loss of tissue substance through physiologic or pathologic processes. The tissues remaining following the extraction of the teeth (Residual alveolar ridge) changes shape and are reduced in size at varying rates in different individuals and in the same individual at different times.

DEFINITIONS :

Bone is defined as a highly vascularised, living, constantly changing, mineralized connective tissue. [Grays Anatomy]

Alveolar process may be defined as that part of the maxilla and mandible that form and supports the sockets of the teeth. [Orbans Dental Histology]

Classification of RRR :According to Branemark et al in 1985, ridges were classified on the basis of bone quantity and quality by radiographic means. BONE QUANTITY : (Branemark)Class A : Most of the alveolar bone is present Class B : Moderate residual ridge resorption occurs Class C : Advanced residual ridge resorption occurs Class D : Moderate resorption of the basal bone Class E : Extreme resorption of the basal bone

BONE QUALITY :

Class 1 : Almost the entire jaw is composed of homogenous compact bone. Class 2 : A thick layer of compact bone surrounds a core of dense trabecular bone. Class 3 : A thin layer of cortical bone surrounds a core of dense trabecular bone. Class 4 : A thin layer of cortical bone surrounds a core of low-density trabecular bone.

BY WICAL AND SWOOPE :

Class I : Upto one third of the original vertical height lost. Class II : From one third to two thirds of the vertical height lost. Class III : Two third or more of the mandibular height lost.

BY KALK AND BAATA :Degree of alveolar bone resorption in mandible :Class 0 : Moderate resorption ; both the genial tubercle and the mylohyoid lines are below the level of the alveolar ridge. Class 1 : High degree of resorption ; the genial tubercle and the mylohyoid are either just below the highest point of the alveolar ridge or at the same level. Class 2 : Extensive resorption ; the genial tubercle is above the level of the alveolar ridge, and the mylohyoid lines are at the same level or above the alveolar ridge.

Degree of alveolar bone resorption in maxilla :

Class 0 : Little, if any, resorption with there being a difference in height between the lowest point on the mucosal membrane and the highest point on the alveolar ridge. There is no flabby ridge. Class I : Extensive degree of resorption. The alveolar ridge is narrow and there is little difference in height between the lowest points on the mucosal membrane and palate and the highest point on the alveolar ridge. There may be a flabby ridge.

NIELS CLASSIFICATION :

Class 1 : Approximately 0.5 inch of space exists between mylohyoid ridge and floor of mouth. Class 2 : Less than 0.5 inch of space exists between mylohyoid ridge and floor of mouth. This is favorable for lower denture.Class 3 : The mylohyoid muscle is at the same level as the mylohyoid ridge. Retention of the lower denture is almost impossible.

ATWOODS CLASSIFICATION : Order 1 : Pre-extraction Order 2 : Post-extractionOrder 3 : High, well rounded Order 4 : Knife-edge Order 5 : Low, well round Order 6 : Depressed

MERCIERS CLASSIFICATION :Group 1 : High crestal muscles and non resorbed ridge. Group 2 : Painful atrophic ridge Group 3 : Absence of residual ridge ZELSTERS CLASSIFICATION :Group 1 : High muscle attachment & minimal RRR. Group 2 : Severe residual ridge resorption with pain. Group 3 : Absence of residual ridge.Group 4 : Severe resorption of basal bone.

MISCHS CLASSIFICATION : Based on bone density.BONE -DENSITY D1 -Dense cortical bone. D2 -Thick dense to porous cortical bone on crest and cortical tabecular bone with in. D3 - Thin porous cortical bone on crest and fine trabecular bone with in D4 - Fine trabecular bone D5- Immature, non mineralized bone

Classification according to the American college of prosthodontists :1. Based on Bone Height (Mandible only)Type I : Residual bone height of 21 mm or greater measured at the least vertical height of the mandible.Type II : Residual bone height of 16 - 20 mm measured at least vertical height of the mandible. Type III : Residual alveolar bone height of 11 - 15 mm 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.

CELLS OF BONE Osteoprogenitor cells Osteoblast cells. Osteocytes Osteoclast cells.COMPOSITION OF BONE

ORGANIC PART 33% - 35%

Collagen 88% - 90% (Type I)Non collagen 10% - 11%.Glycoproteins 6% - 9% (Mono, Di, Poly and Oligosaccharides). Proteoglycanes 0.8% (sulfated and Non sulfated)Sialoproteins 0.35%Lipids 0.4%

INORGANIC PART 65% - 67%

Calcium & Phosphates 95% (Hydroxyapatite Crystals Ca10(Po4)6 (OH)2) Magnesium Trace elements Nickel, Iron, Fluoride, Cadmium, Magnesium, Zinc and Molybdenum.

*Uninucleated cells that synthesize both collagenous and noncollagenous bone protein.*They are responsible for mineralization and are derived from a multipotent mesenchymal cell. *They constitute a cellular layer over the forming bone surface. *Osteoblasts exhibit high levels of alkaline phosphate on the outer surface of their plasma membranes.OSTEOBLASTS

**Other enzymes that participate in their activity are *ATPase and pyrophosphates *Type I and type V collagen *Several noncollagenous proteins, *A variety of cytokines.

*As osteoblasts secrete bone matrix, some of them become entrapped in lacunae and are then called osteocytes.*The number of osteoblasts that become osteocytes varies depending on the rapidity of bone formation.*The more rapid the formation, a more osteocytes are present per unit volume. OSTEOCYTE

OSTEOCLAST *Compared to all other bone cells and their precursors, the multinucleated osteoclast is a much larger cell. *They are generally seen in a cluster rather than singly. *Osteoclast is characterized by acid phosphatase within its cytoplasmic vesicles and vacuoles, which distinguishes it from other giant cells and macrophages.

*Osteoclast are also rich in lysosomal enzymes. **Typically osteoclasts are found against the bone surface occupying shallow, hollowed out depressions, called Howships lacunae.

Thus the sequence of resorptive events is considered to be Attachment of osteoclasts to mineralized surface of bone. Creation of a sealed acidic environment through action of the proton pump, which demineralizes bone and exposes the organic matrix. Degradation of this exposed organic matrix to its constituent amino acids by the action of released enzymes.

Uptake of mineral ions and amino acids by the cell.

CLASSIFICATION OF BONE1. According to density as *Compact bone *Trabecular bone. 2. According to bone mass *Fine Trabeculae, *Coarse Trabeculae, *Porous Compacta and *Dense Compacta. 3. Microscopically bones are composed of *Woven bone, *Lamellar bone, *Bundle bone and *Composite bone.

Woven boneHighly cellular.Formed rapidly (30-50 m/ day or more) in response to growth or injury.Low mineral content.Random fiber orientation and minimal strength.Stabilize unloaded Endosseous implants during initial healing.

Lamellar bonePrinciple load bearing tissue of adult skeleton.Predominant component of mature cortical and trabecular bone.Formed relatively slowly (

Bundle boneCharacteristic of ligament and tendon attachments along bone-forming surfaces.Sharpeys fibers from adjacent connective tissue insert directly into bone.Bundle bone is formed adjacent to the periodontal ligament of natural teeth.

Composite boneHigh quality lamellar bone deposited on a woven bone matrix.Got adequate strength for load bearing.Important in achieving stabilization of an implant during the rigid integration process.

**Alveolar Bone forms the bony sockets of the jaw bones in which the roots of the natural teeth are suspended by the attachment of the periodontal ligament fibers (Gomphosis ) **Some alveolar bone is formed during tooth development, but the majority of alveolar bone formation occurs during tooth eruption.

*The presence of alveolar bone in the jaw bones is totally dependent on the roots of the natural teeth; without the teeth the alveolar bone need not exist.

PATHOLOGY OF RRRGROSS PATHOLOGY :Patient has expression My gums have shrunk Basic structural change is reduction in size of bony ridge under the mucoperiosteum

Localized loss of bone structure

Overlying mucoperiosteum

Excessive & redundant No redundant soft tissue

Difficult to understand Lammie postulates

LAMMIE postulates ; one factor in RRR may be a cicatrizing mucoperiosteum that is seeking a reduced area , resulting in pressure resorption of the underlying bone

Longitudinal radiographic cephalometric studies have provided excellent visualisation of gross patern of bone loss from lateral view point

Careful superimposition of portions of tracings of lateral ceph. With reduction of bone in size and shape

Gross anatomic studies of dried jaw bones have shown a wide variety of shapes and sizes of residual ridgesA simplified method for categorizing residual ridge form is order 1----order 6

Uses : useful clinically as well as for research purpose : helps to differentiate various stages of RRR in pts.

In dry specimens*External cortical surface of maxilla and mandible are uniformly smooth & crestal area of residual ridge shows porosities and imperfections

*Bones with more severe RRR display gross porosities of medullary bone on the crest of ridge

Gross bone loss of residual ridge revealed by superimposition of portion of two cephalometric radiographs made 16 years apart

RRR does not stop with the residual ridge but may go well below where the apices of teeth areThere can be a thin cortical plate on inferior border of mandible or virtually no maxillary alveolar process

Panoramic radiograph showing severe RRR in both maxilla and mandible in contrast to dentulous area that support three mandibular teeth

Radiographs of mid-saggital sections of eight mandibles illustrating various orders of residual ridge form Atwood DA JPD 1971 Vol.26

Clinical examination of ridge form depends on Good judgment of clinician Palpation in the mouth accurately determines underlying boneLateral ceph. determines amount of bone and rate of RRR over a period of timePanoramic radiographs simple & useful method of estimating amount of RRR

*Original alveolar crest ht. can be predicted by measurement of distance from inferior border of mandible to mental foramina Wical and Swoope

MICROSCOPIC PATHOLOGY :

Evidence of osteoclastic activity on the external surface of crest of residual ridgeScalloped margins of howships lacunae contain visible osteoclasts

Why there is only decrease in size of residual ridges ??? Reason : Scalloped external surface contain osteoclasts onlyExternal surface of bone is covered by fibrous non osteogenic periosteum

ATWOOD DA : JPD 1963There is wide variation in configuration density and porosity of not only residual ridge but also entire cross-section of anterior mandibleMandibular osteoporosis occurs with Increased variation in density of osteonsIncreased no. of incompletely closed osteonsIncreased endosteal porosityIncreased plugged osteons

**Remodeling changes occur in the mandible that account for the typical edentulous facial anatomy.The overall length of the mandible does not decrease but may in fact increase as new bone is added to the mental protuberance, thus accentuating the chin point.

There is an anterior displacement of the mandible (protrusive position) because of residual ridge reduction, mandibular rotation (Change in the angulation of the body relative to the mandibular ramus), and deposition of bone in the mental region. Reduction in the residual ridges occurs in an inferior direction in the molar and premolar areas, but in both an inferior and lingual direction in the incisor region.There is generalized thinning of the anterior and posterior aspects of the mandibular ramus.

PATHOPHYSIOLOGY OF RRR BONE REMODELLINGOSTEOBLASTSOSTEOCLASTSBONE FORMATIONBONE RESORPTIONExceeds in case of*OSTEOPOROSIS*PDL DISEASE Exceeds in case of*GROWTH

RESIDUAL RIDGE RESORPTIONPATHOLOGIC PROCESS??PHYSIOLOGIC PROCESS??Bone once lost cannot be built back by removing causative factorsRemoval of tooth eliminates the raison d etry for alveolar boneClinical facts :1. RRR not inevitable 2. RRR varies & can proceed far beyond alv. bonePractical terms rate of resorption so much that patient ends up with no cortical bone at crest of ridge

EXTERNAL OSTEOCLASTIC ACTIVITYENDOSTEAL BONE FORMATION Fails to keep paceAbsence of cortical layer of boneExposure of medullary layer to external surfaceDefects on the crest of ridge

Pathogenesis of RRR:RRR is a chronic progressive irreversible cumulative disease which proceeds slowly over a long period of time from one stage to next

Carlson and Pearson at alPost extraction study of mandibular bone lossFirst 2 yrsFirst 5 yrs3 to 5 yrs Pts. with Least RRR Mean RRR Most RRR0.752.754.50.41.362.90.130.51.8 **measurments in mm

Tallgren Atwood & Coy studied rate of residual ridge resorption for 25 years Mean ratio of anterior maxillary RRR to anterior mandibular RRR was 1:4RRR is more in mandible than in maxilla and reverse can also occur

So one must treat the PARTICULAR PATIENT, NOT THE AVERAGE PATIENT

EPIDEMIOLOGY OF RRR :MethodsLongitudinal cephalometric; time consuming and expensivePanoramic methodology or radiograph By palpationThere have been no large scale studies of RRR Longitudinal cephalometric studies of few subjects have been done Methods of Measure Bone Formation:-Tetracycline labelingBone seeking tracer such as Ca-45.

RRR occurs worldwide in Males and females Young and oldSickness and healthWith or without denturesUnrelated to primary reason for the extraction of teeth ( caries & pdl disease ) Studies also suggest incresed knife edge tendency (KET) in mandibular residual ridge in women compared to men.KET = Change in area /Change in height

As Age Advances

Mineral content in bones

Increase Decrease

MALES FEMALES

Due to osteoporosis that takes place in females

Leading to knife edge ridges

Etiology of RRR :RRR is a multifactorial biochemical disease caused by a combination of ANATOMIC FACTORSMECHANICAL FACTORSMETABOLIC FACTORS (1998 by Leili Jahamgeri )PROSTHETIC FACTORS GENETIC FACTORS

1. ANATOMIC FACTORSRRR ANATOMIC FACTORS LIKESIZE & SHAPE OF RIDGETYPE OF BONE REMOVEDAMOUNT OF BONEQUALITY OF BONESPACES BETWEEN RIDGES MUSCLE ATTACHMENTS ACTION OF TONGUE

2. MECHANICAL FACTORSRRR FORCE DAMPING EFFECT

AmountDuration FrequencyDirection &Distribution FORCE

Dampening effect takes place in the mucoperiosteum, which is a viscoelastic material.

Maxillary bone (RR) is frequently broader, flatter and more cancellous than its mandibular counterpart. So it is ideally constructed for the absorption and dissipation of energy.

Frost pointed out that the trabacule in cancellous bone are arranged parallel to direction of compression deformation.

METABOLIC FACTORS :

RRR BONE RESORPTION FACTORS BONE FORMATION FACTORS BONE RESORPTION FACTORSLOCAL SYSTEMIC -Endotoxins from dental plaque-Osteoclast activating factor-Prostaglandin-Heparin-Trauma - Correct amount of circulating- Osteoporosis- Hypophosphetemia Parathormone Calcitonine EstrogenAndrogenThyroxineVitamin-DFlouride

PROSTHETIC FACTORS INCREASED OCCLUSAL FORMVERTICAL DIMENSIONAL CHANGESCUSP FORMEXCESSIVE LOAD BY OVERLY FITTING DENTURES

OTHERS :BONE LOSS DUE TO UNKNOWN CAUSESAGE RELATED BONE LOSSGENETIC FACTORSDRUG THERAPY

RRR ANATOMIC FACTORS + BONE RESORPTION FACTORS + FORCE BONE FORMATION FACTORS DAMPING

In addition to the three major categories of factors (anatomic, metabolic and mechanical), the importance of time since extraction to the bone loss should be emphasized by adding in an inverse ratio.RRR ANATOMIC FACTORS + BONE RESORPTION FACTORS + FORCE BONE FORMATION FACTORS DAMPING + 1

TIME

Various etiologic factors and their correlation Etiologic factor Correlation with RRR SourceAnatomic factorMandible 4 x more RRR than max.*Tallegren *Atwood & coyShort & square faceIncreased RRR*Tallegren Large alv. process Increased RRR*Wictorin Density of alveolar boneNo correlation of RRR with bone density*Wilson*Atwood & coyLabial alveoloplasty Increased RRR*Gazabatt et al*Wictorin

Various etiologic factors and their correlation Etiologic factor Correlation with RRR SourceProsthodontic Immediate dentures Decreased RRR*Wictorin*Carlson et al Overdentures Decreased RRR*Crum & Rooney Zero degree teeth Increased RRR*Winter et alWoelfel et al

Metabolic and systemic factors Etiologic factor Correlation with RRR Source*Wictorin*Carlson et al Osteoporosis No correlation with the ridge heightSmaller max. ridgeKnife edge type mandible* Atwood & Coy*Nishimura et al*Mercier & Inoue Age & sexNo correlation with the rate of RRR*Atwood & Coy Calcium & vit D supplementDecreased RRR

*Wical & Brussee Sodium flouride supplementNo correlation but better calcificationFenton & El-Kassem

Functional factors Etiologic factor Correlation with RRR Source*Kelly *Carlson et alRegular denture wearingNo correlation with the rate of RRRStatistically insignificant trend* Atwood & Coy*Bergman *Nicol et al Intensive denture wearingIncreased RRRCombination syndrome*CampbellOther factors Bioelectric potential Decreased RRR by exogenous pulsed electromagnetic field in dogs

*Van der Kuij et al

DIAGNOSTIC AIDS TO DETECT RRRRadiographic : widely used to detect bone resorption and formation by taking periodic radiographs.Tetracycline labeling : Injected into the body through oral or pariental administration and should be repeated after every week for 5 weeks. This tetracycline is taken up by the bone, only in the new sites of bone formation tetracycline can be readily identified in the bone as tetracycline calcium chelate formed is fluoroscent and can be viewed by fluorescence microscopy.

Mercury porosimetry : Osteocytes are also capable of bone resorption (i.e. periosteocytic lacunar bone resorption). To determine the quantitative importance of osteocytic resorption mercury porosimetry was used to makes a comparison between osteocytic and osteoclastic bone resorption. In this method mercury is introduced into pores by pressure and a measure of the pore volume as a function of pore diameter is obtained

Since osteocyte lacunae, canaliculi, and vascular canals constitute a system of pores, this method can be applied to measure the volume of different classes of bone pores. Thus with this method it was able to quantitate osteocyte lacunae canalicular volume, which enlarges as a result of osteoclastic resorption and vascular canal volume, which enlarges as a result of osteoclastic resorption.

PG s AS MEDIATORS OF RRR

PROSTAGLANDINS: MEDIATOR OF RRR

Prostaglandins (PG) has been demonstrated to mediate bone resorption in vitro and in vivo. PG is not stored in cells in their final form but is quickly released in response to mechanical, physiologic and pathologic stimuli.

Its half life is short (less than 1min) and its various effects are limited only to adjacent cells, therefore it is important to note that PG works as a local hormone.

The pharmacologic effect of NSAIDs such as indomethacin that are known to be inhibitors of PG bio synthesis have been investigated in order to control bone resorption in orthodontic tooth movement and in periodontal disease.

PROSTAGLANDINS: MEDIATOR OF RRR

These findings indicate that PG may have an important biologic role in the pathophysiology of localized bone resorption in the oral cavity.

Bone resorption is a cellular phenomenon in which osteoclasts remove calcified substances from the bone.

It is hypothesized that osteoblasts are involved in bone resorption by coupling with osteoclasts, because the cellular receptor against various bone resorbing hormones (including PG) have been found in osteoblasts but not in osteoclasts.

PROSTAGLANDINS: MEDIATOR OF RRR

PGs are released from many kinds of cells including inflammatory cells such as neutrophilic granulocytes and macrophages as well as local mesenchymal cells such as osteoblasts and cells of the periodontal ligament. Mechanical stimulation of osteoblastic cells in vitro caused a significant elevation cAMP and PG synthesis.

These findings may suggest the connective tissue contraction associated with extraction site and afterwards towards the crest of the residual ridge. The phenomenon may explain a mechanism of localized bone resorption at the crest area of the residual ridges by the PG activities. The continuous and localized bone resorption in RRR may be caused by continuous synthesis of local PG.

OSTEOPOROSIS

Osteoporosis is a systemic disease in the elderly. Osteoporosis shows a decrease in the skeletal mass without alteration in the chemical composition of bone.

Loss of the spongy spicules of bone that support the weight bearing parts of the skeleton can be seen in radiographs of regions of the skeleton that bear heavy loads, such as the vertebral column, epiphysis of long bones, the mandible and the fingers.

OSTEOPOROSIS

Osteoporosis is common in aging individuals, especially post menopausal women when the estrogenic blood level is low.

In elderly men and women, osteoporosis is caused by a variety of factors such as calcium loss, calcium deficiency, hormonal deficiency, change in protein nutrition and decreased physical activity.

Progressive loss of alveolar bone may be a manifestation of osteoporosis

Consequences of RRR :Apparent loss of sulcus width and depth. Displacement of muscle attachment close to the ridge. Loss of vertical dimension of occlusion. Reduction of the lower face height. An anterior rotation of the mandible. Increase in relative prognathiaChanges in inter alveolar relationship following RRR Morphological changes of the alveolar bone such as sharp, spiny uneven residual ridges.Location of mental formina close to the ridge crest.

Prosthodontic treatment modalities :1. COMPLETE DENTURES Well fitting complete denturesExerts Pressure on the alveolar boneFavourable UnfavourablePreserves alveolar boneResorption of alveolar boneCampbell et al ( 1973 ) Edentulous patients wearing dentures had smaller residual ridges as compared to those not wearing dentures

WHY THERE IS MORE RESORPTION SEEN IN MANDIBLE THAN MAXILLA ???1. Mandible provides a smaller surface area of support for the dentures2. Amount of cancellous bone is lesser as compared to maxilla *Dentures help to preserve the horizontal dimensions of residual ridge to some extent & vertical dimensions undergo resorption especially in mandible( 4 times) * Irreversible alveolar bone loss results from extraction regardless of how soon a denture is provided ( Atwood DA )

For maxillaExtent of alveolar bone loss is a function of composition of opposing dentitionMaxilla opposing natural mandibular anteriors Less resorption Maxilla opposing artificial mandibular anteriors

More resorptionCombination syndrome**More resorption in anterior mandible seen in patients . wearing dentures day and night

2. OVERDENTURES :Distribute masticatory load between edentulous ridge and abutmentTransfer occlusal forces to alveolar bone through periodontal ligament of retained rootsProprioceptive feedback from pdl prevents RRR

Crum & Rooney et al Measured the mean vertical bone loss in anterior mandible of 5.2 mm after 5 years for immediate dentures as compared to 0.6mm for immediate overdentures

3. REMOVABLE PARTIAL DENTURES :Loss of periodontal attachment & marginal bone loss adjacent to abutment

Patients Free of pdl diseaseAdequate plaque control Minimum bone loss occurs**Occlusal problems occurs within 5 years as a result of vertical RRR with distal extension bases

4. FIXED PARTIAL DENTURES :

Marginal bone loss is minimum & is almost same as of uninvolved teethMean annual rate of bone loss ~ 0 mm for up to 15 years if adequate plaque control is maintained

5. IMPLANT SUPPORTED PROSTHESIS:Majority of bone loss (1-2mm ) occurs during healing and remodelling periodsAnnual bone loss with implants is 0-0.08mm BONE LOSSImplant supported overdentureImplant fixed prosthesisMaxilla Mandible >Single implant prosthesis>Multiple implant prosthesis

Why more bone loss in maxilla with implants???Poor bone quality in maxillaIncreased mucosal irritation surrounding shorter abutments required

Jacob et al 11 % reduction in bone ht. distal to implant overdenture4 % reduction in bone ht. distal to implant fixed prosthesis

Management of RRR 1) Two important factors to be considered are ;1. Attitude of the patient2. Role of any systemic diseases as etiologic factors

PREVENTION OF RRRPreventing loss of teethCorrect diagnosis & management of etiologic factorsCorrect hormonal & nutritional deficiencies if any.Remove dentures for atleast 8-12 hours for tissue restBitting with fork & knife i.e placing small masses of food over posterior teeth ( Heartwell )

Management 1)Treatment of systemic factors involved in RRR2)Prosthodontic management a) Methods to improve denture foundationb) Design of the dentures c) Impression proceduresd )Other options ;OverdenturesSubmerged rootsHollow denturesMetal based dentures3)Surgical management

1)Treatment of systemic factors involved in RRR

Role of systemic disease as an etiological factor in gross alveolar resorption must be consideredSystemic conditions like osteoporosis, hormonal imbalance and dietary deficiencies plays an important role in RRRProsthodontist should always consider the possibility of systemic cause for gross alveolar resorption

2. Prosthodontic management

Oral tissues - change shape with time

Pressure transmitting surface

Poorly adapted to the oral mucosa Resulting in

Deformation of the denture supporting tissues

Must be corrected

A)METHODS TO IMPROVE DENTURE FOUNDATION

Use of temporary soft linerRegular finger massage of denture bearing mucosaRest for denture supporting tissuesCorrection of old prosthesis to restore VDGood nutrition especially for geriatric patientsConditioning of patients musculature by jaw exercises , co-ordination & Preparing the patient psychologically

A course of treatment with tissue conditioning materials is often indicated.These materials allow deformed tissues to resume their normal shape Abraded artificial teeth cause loss of facial height

Failure to carry out such corrective therapy can result in continuing distortion of oral tissues by dentures

B) DESIGN OF THE DENTURE ;a)Broad area of coverage to decrease force per unit area ( SNOW SHOE EFFECT )b)Decrease number of dental units & decreased bucco-lingual width of teeth ( decreased force to penetrate bolous of food )c)Avoidance of inclined planes ( to minimise dislodgement of denture & shear forces )d) Centralization of occlusal contacts ( to increase stability & maximise compressive forces )e)provision of adequate tongue room & adequate inter-occlusal distance

f) morphology of occlusal table ; Anatomic vs Non anatomic teethKyadd (1960 ) found that 33 o & 200 teeth caused more deformation and lateral stresses on the ridge than non anatomic teeth ( Cusp Trauma )g) occlusal pattern ;Cuspless flat plane occlusion Anatomic teeth with compensating curvesCareful setting & selective grinding to minimise lateral stresses

h) Muscular Control ( Neutral Zone )Gardette (1800 ) first noted potential of muscular forces in denture controlFish (1933) introduced concept of denture controlThe secondary supporting surface i.e polished surface should have their shape determined by oral musculature ( neutral zone )i ) Tooth Material Acrylic vs Porcelein The property of transmission of impact forces is more important than wear resistance when considering health of alveolar ridges

Acrylic teeth

Cushioning effect

Absorbs more forces than porcelein teeth PLUS Denture base material acrylic or metal

C ) IMPRESSION PROCEDURES ;Bernard Levin ---Primary impression made with alginate and less water ( 25 % )Mac Cold & Tyson ( BDJ 1997 )---Use of admixed technique for impressions ( 3:7 )Functional reline technique---use of open and close mouth proceduresProcedures for severely atrophied mandible (JPD 1993 ; 73 : 574 )--- peripheral borders are developed functionally with tissue conditioning material and final impression is taken with polysulphide impression material

Other options Overdentures :distribute masticatory load b/w edentulous ridge and abutmentRate of bone loss 0.8 mm in first yearSubmerged roots : vital or non-vital prevents resorption of ridgesHollow dentures; ( JPD 1988 ; 59 :4)Used in advanced atrophy of maxilla with adequate interocclusal distanceDouble flask technique of Challian & barnetts is used for maxilla ( weight reduction 25 % )Holtz technique with modifications for mandible

Metal based dentures ; ( JPD 1987 ;57:6 )Metal based denture with soft liner is advocated in patients with severely atrophic residual ridgesMetal base providesWeight necessary to facilitate retentionMaintain Adequate strength with modest extensionsThe soft liner accomodates ridge irregularities and changes

Exercise stimulation of edentulous areasExercise stimulation is a practical & desirable part of complete denture therapy.Exercise stimulation for a period of 12 weeks is usually adequate in most severe cases.If bone reorganization is accomplished by frequently induced intermittent stimuli, the supporting structures can be prepared for the occlusal function within limits of individual tolerance Intermittent use of Exogenous pulsed electromagnetic fields is demonstrated the effectiveness in decrease in the rate of residual ridge resorption

Dietary guidelines for patients at risk of losing bone

Maintain a high daily calcium intakeObtain four servings of low fat dairy foods or obtain equivalent amounts of calcium dailyTake calcium supplements if dietary intake is lowChoose calcium citrate maleate if patient has achlorhydriaIf lactose intolerant, treat milk with lactase tablets or drops

Dietary guidelines for patients at risk of losing bone

Prevent negative calcium balanceLimit daily alcohol and caffeine intakeConsume about 6 ounces of protein from meat, poultry and fishUse small amounts of processed foods high in sodium

Dietary guidelines for patients at risk of losing bone

Obtain 4000 I.U of Vitamin D daily

Spend 15 minutes in the sun 3 times a weekChoose a multivitamin or calcium supplement that contains 4000 I.U of Vitamin D.

Discuss calcium or drug interactions that interface with calcium bioavailability with the physician

NutrientEffect on metabolism CalciumIncreases bone mass, decreases rate of bone loss in post menopausal women Vitamin DIncreases intestinal absorption of calcium, decreases bone resorption. PhosphorusHigh intake may increase calcium urinary loss SodiumHigh intake increases urinary calcium losses FluorideStimulate osteoblasts, increases trabecular bone mass. CaffeineHigh intake increases calcium urinary losses AlcoholHigh intake accelerates menopause, toxic effects on osteoblasts, increased calcium urinary losses

Surgical treatment

Preprosthetic surgery includes ;

Ridge preservation procedure as a preventive measure

Corrective or recontouring procedures of the defects and abnormalities

Ridge extension proceduresRelative methods e.g., sulcus extension (vestibuloplasty)Absolute methods e.g., ridge augmentation method

Surgical treatment

Reconstruction methods like correction of abnormal ridge relationship

Provision of accessory undercutsCreating favourable undercuts Modified denture construction procedure e.g., immediate denture where construction of the denture proceeds surgery

Ridge augmentationIt is aimed at :Increase in the ridge height and width providing a large denture bearing area , Protection of neuro vascular bundles Restoration of proper maxillomandibular arch relationship. Ridge augmentation has been tried with: Bone transplantsAutogenous and homogenous cartilageHydroxyapatite porous replamine formAcrylic implants.Tri calcium phoshpate

IMPLANTS ;ADVANCED RRR: Surgical management ( IJP 1993)With introduction of osseointegration by Branemark reconsrtuction of advanced RRR has become a successful procedure The various problems associated with RRR and stability of removable soft tissue borne dentures have aroused interest in dental implantology to provide stable mechanical support to the dental prosthesis.

IMPLANT SUPPORTED PROSTHESIS.Maintenance of alveolar boneMaintenance of occlusal vertical dimension.Height of alveolar bone is found to be maintained as long as the implant remains healthy.Improved psychological health. Regained proprioception.Increased stability, retention and phonetics.

Maintenance of structure and function of muscles of mastication and facial expression.Immune to caries. Overall volume of bone is maintained. Efficiency to take up stress and strain.There is 20 fold decrease in the loss of structure with implants when compared with resorption that occurs with removable prosthesis.

CONCLUSION : The etiology of residual ridge resorption is a subtle combination of local and systemic factors, but the exact processes involved are poorly understood.

There is no reliable clinical measurement, which might predict the future rate of alveolar ridge resorption in a particular edentulous patient.

The best possible method is to preserve as many teeth or roots, as possible, followed by over-dentures which may act as effective means of preserving adjacent alveolar bone.

The use of endosseous implants to support fixed or removable prostheses has been shown to preserve adjacent remaining alveolar bone. But as with natural teeth, implants are not immune to bone loss.

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