POSTERIOR PALATAL SEAL & VIBRATING LINESPOSTERIOR PALATAL SEAL & VIBRATING LINES

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Amar Bhochhibhoya

PG Resident, Department of Prosthodontics & Maxillofacial Prosthetics,

People’s Dental College & Hospital, Nayabazar

20/09/2011 12/10/2011

CONTENTS

IntroductionAnatomic and Physiologic ConsiderationsFunctionsParameters of Posterior palatal seal(PPS)Techniques of recording PPSTroubleshootingSummary References

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Definition

The soft tissue area at or beyond the junction of the hard and soft palates on which pressure,within physiologic limits, can be applied by a complete removable denture prosthesis to aid in its retention

GPT-8

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• The proper placement of PPS begins with initial oral examination.

• The morphologic contours of the hard and soft palate should be considered

• Retention and stability that is achieved from adhesion, cohesion, and interfacial surface tension are able to resist only those dislodging forces that act perpendicular to the denture base.

• Horizontal forces and lateral torquing of maxillary denture can only be resisted by adequate boarder seal.

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Functions of PPS• Compensating for dimensional change during

curing• Prevents food from getting under the denture• Reduces the tendency of the patient to gag• Added strength across the denture• Makes the distal border less noticeable to the

tongue

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Soft palateSoft palate is a movable muscular fold, suspended from the posterior border of the hard palate. It separates the nasopharynx from oropharynx.

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Anatomic and Physiologic Considerations

Muscles of soft palate• Tensor veli palatini• Levator veli palatini• Palatopharyngeus• Palatoglossus• Musculus uvulae

Tensor Veli Palatini :Thin flat triangle muscle, when taut, can influence the denture contour in the hamular notch area.

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Levator Veli Palatni : Thick rounded muscle on contraction elevates the soft palate.

• The action of this muscle bilaterally is critical in closing off the oropharynx from the nasopharynx during swallowing, as well as in determining the position of the vibrating line.

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Palatoglossus Muscles : when the palatoglossus muscles

contracts they draw the tongue and soft palate towards each other.

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Classification of Soft Palate

• Based on angle that the soft palate makes with the hard palate

House classification : – –Class I: – Class II– Class III:

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Class I:– Horizontal, minimal muscular activity– >5mm space available for post damming– Ideal for retention

Class II:– 1-5 mm of space available for post damming– Good retention is usually possible

Class III:– Most acute contour in relation to hard palate– <1mm movable tissue available for post damming– Retention is usually poor

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Less area can be covered by denture base

More soft palate is markedly displaced in function

More muscle activity necessary for velopharyngeal closure

More acute angle

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PALATAL VAULT :

• Flat • Rounded • U-Shaped• V-shaped

Flat vault resists vertical displacement but offers less resistance to anterior or lateral displacement of the maxillary denture---reduction in stability-----loss of retention in function.

V-shaped denture may be responsible for undue pressure on the lateral aspects of the palatal vault. Any vertical or torquing force tends to break the seal --- loosen and dislodges the denture.

V-Shaped palate presents the deep, narrow fissure in the midline of the vault may not have been accurately recorded in the final impression.

If the fissure extends through the PPS area it must be occluded by the denture to complete the peripheral seal at the posterior border of the denture.

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Placement of PPS across mid-palatal suture demand careful attention .PPS should also extend into mid palatal fissure Cord like band of tissue extending between the posterior nasal spine & aponeurosis of tensor vili palatini muscles should receive slight amount relief.

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Fovea PalatinaeGlandular indentations in the soft palate created by

the coalescence of the ducts from mucous glands located near the midline.

They always found in the soft tissue and close to the vibrating line.

Winland and Young 1973 – depicted the majority of PPS designs taught in the U.S. dental schools as posterior to the fovea palatinae.

Sicher – describes the fovea as situated immediately behind the boundary between the hard and soft palate.

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Nagle and Sears ---- fovea mark the posterior limit of the hard palate.

Swenson ---- the vibrating line passes about 2mm in front of the fovea palatinae.

Lye ---- fovea palatinae are located on average 1.31mm anterior to the anterior vibrating line.

Chen ----- fovea that were located either on or behind the anterior vibrating line.

Therefore, the position of the fovea does not represents the junction of hard and soft palate. The fovea palatinae should be used only as guidelines to the placement of the posterior palatal seal.

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• Postpalatal seal • Pterygomaxillary sealPPS

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Postpalatal seal: –extends medially from one tuberosity to the other

Pterygomaxillary seal: - extends through the pterygomaxillary notch

continuing for 3-4mm anterolaterally approximating the mucogingival junction.

band of loose connective tissue lying between the pterygoid hamulus and the distal portion of the maxillary tuberosity.

It is important to note the exact position of the hamular process (located 2-4mm posteromedial to the distal limit of the maxillary residual ridge)

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• T burnisher, mouth mirror may be used to record the actual depth of each notch and thus the amount of displaceable tissue.

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Vibrating line

• Definition- is an imaginary line across posterior part of the palate marking the division between movable & immovable tissues of the soft palate.

• Swenson described it as a vibrating area. • Silverman as anterior and posterior flexion line. • Johnson ah line (posterior flexion line); blow line

(anterior flexion line).

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• It extends from one hamular notch to the other.

• Vibrating line is not to be confused with the junction of hard & soft palate because it is always on soft palate

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Techniques to observe vibrating line

• phonation of ‘ah” sound causing soft palate to vibrate or lift• having the patient hold is nose & attempt to

blow through it (Valsalva maneuver)

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• The anterior vibrating line located by the palpatory method showed a general tendency to be slightly anterior to the line of flexion located by the Valsalva maneuver.

• This is so, because the palpatory method locates the anatomical junction of the hard and soft palate as opposed to the physiologic line of flexion at the junction of the movable and immovable parts of the soft palate located by the Valsalva maneuver

Determination of Degree of Distinction Between Anterior and Posterior Vibrating Line –A Pilot Study VN Malik,Vikas Vaibhav, JIDA, Vol. 5, No. 2, February 2011

• Over extension at the hamular notches--- pressure on the pterygoid hamulus & interference with the pterygomandibular raphae

• When the mouth is opened wide, pterygomandibular raphae is pulled forward.

• If denture extends too far into hamular notch, the mucous membrane covering raphae will be traumatized.

• Posterior border of denture should extend at least to Vibrating line. It should end 1-2 mm posterior to vibrating line.

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Anterior vibrating line Imaginary line located at the junction of the attached

tissue overlying the hard palate and the movable tissue immediately adjacent to soft palate.

Valsalva maneuver or “ah” with short vigorous bursts

Posterior vibrating line Imaginary line at the junction of the aponeurosis of

the tensor veli palatini muscle and the muscular portion of the soft palate.

Demarcation between part of soft palate with limited movement and the remainder that is markedly displaced during function

“ah” in short brusts in a normal , unexaggerated fashion

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Rajeev M. Narvekar and Marc B. Appelbaum in 1989They used ultrasound instrumentation as an non-invasive

procedure to locate PPS region.

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Ultrasonic transducer

Is a synthetic ceramic that has piezoelectric properties which transform mechanical energy into electrical energy and vice versa.

Couplant Used as a conductor of the sound energy between skin and ultrasonic transducer.

Commercially available tooth paste was used as a couplant and placed on the head of transducer.

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The transducer was inserted in the mouth, the junction of the hard and soft palate was noted on the screen.

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• The width of PPS area between the anterior & posterior vibrating line is always less when measured with ultrasound than that of conventional method irrespective of patient classification.

• The width of PPS area is more in patients of class I than that among the patients belonging to class II irrespective of method of measurement.

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Location of Anatomic Position of Posterior Palatal Seal Area By Conventional And Unconventional (Ultrasound Method) Methods – A Comparative study. Sreedevi .Ba*, Premanandam .Ia, Gopinadh Annea Department of Prosthodontics, SIBAR Institute of Dental Sciences, Guntur, India. Jr. of Orofac. Scie. 1(1)2009

PARAMETERS OF PPS

1. Shape2. Size3. Location4. Displacibility

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Recommended Shape:

1.Single bead 2.Double bead 3.Butterfly shaped PPS 4.Butterfly shaped PPS with bead on distal angle of

dentures.

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A review on posterior palatal seal,Sudhakara V Maller , Karthik. K. S, Department of Prosthodontics,KSR Institute of Dental Science and Research, JIDAS VOL.1 Issue .1,2010

The PPS design should reflect the anatomical and functional limits of each patient throat form.

Therefore, no single design is suitable for the average patient yet there are basic design parameters that can be helpful starting points.

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Class I – offers a broad shallow base A butterfly PPS design is particularly useful for these patients.

Class II – A modified (narrower) butterfly design is common due to a reduction in the amount of displaceable tissue and the greater angulation of the soft palate.

Class III – The dramatic drop of the soft palate which leaves little room for the denture extension and is well suited for a simple bead design

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SizeSilverman performed a study on 92 patients evaluating

the PPS clinically radiographically, histologically and found the following findings:-– The greatest mean anteroposterior width of PPS is 8.0 mm

(with 5-12 mm of range).– The mean width was found to be different for right

(8.2mm) and left side (8. 1mm).– The interhamular notch was found to be 35.8 mm (25-

48mm range)– The interhamular notch distance was found to be different

for males (37.1 mm) and females (35.6 mm)

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Location

• Location of PPS is not consistent and show lot of variation, but on an average anterior vibrating line is 1.31 mm distal to fovea palatini .

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Displacement /Compressibility• Lot of variation has been found within the

PPS. But low compressibility has been observed in midpalatal raphe region.

• High compressibility has been in the lateral part of cupids bow.

• It's variation depends on the form of palatal vault: – Class I palate - shallow PPS– Class II palate - medium PPS– Class III palate - deep PPS

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DENTURE BASE THICKNESS

B. LEVIN - advices use of thin denture base for class I soft palate ( PPS is not deep but wide) and thicker denture bases for class III soft palate ( PPS is deep but not wide) ,medium thickness for class II soft palate

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Techniques of Recording PPS

• Conventional approach• Fluid Wax Technique• Arbiratory Scraping of Master cast

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Conventional approach

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Conventional approach:Advantages of placing seal in the tray: Trial base will be more retentive, this can produce more

accurate maxillomandibular records. Patients will be able to experience the retentive qualities

of the trial base, giving them the psychologic security of knowing that retention will not be the problem.

The practitioner will be able to determine the retentive qualities of the finished denture, leaving nothing to chance at the insertion appointment.

Disadvantages: It is not physiologic technique and therefore depends

upon accurate transfer of the vibrating lines and careful scraping of the cast.

The potential for overcompression of the tissue is great.43

Fluid wax technique

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Fluid wax technique

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Fluid wax technique: Advantages:It is physiologic technique displacing tissue with their

physiologically acceptable limits. Over compression of tissue is avoided. PPS is incorporated into the trial base for added retention. Mechanical scraping of the cast is avoided.

DisadvantagesMore time is necessary during the impression appointment. Difficulty in handling the materials and added care during

the boxing procedure. Heating unit is required to condition the wax. Difficulty may be experienced in handling the materials.

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The procedure for establishing PPS during final impression stage with green stick modling compound

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Establishing PPS during final impression stage,Izharul Haque Ansari, J Prosthet Dent 1997;78:324-6.

In empirical technique the effectiveness of PPS of denture is

confirmed only at the insertion appointment.

Establishing the PPS at final impression stage confirms the

effectiveness of PPS and allows the dentist to control its

localization and the amount of tissue displacement.

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Accurate location of postpalatal seal area on the maxillary complete denture cast

49Accurate location of postpalatal seal area on the maxillary complete denture cast, Brian Myung W. Chang, DDS, and Robert F. Wright, DDS, Harvard School of Dental Medicine, Boston,Mass, J Prosthet Dent 2006;96:454-5.

• Under extension• Under post damming• Over post damming• Over extension

Troubleshooting

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UNDER EXTENSION

Most common cause for poor posterior palatal seal. It may be produced due to one of the following reason:-

1. Use of fovea palatini as the landmark for terminating the denture base

2. Patient anxiety to gagging

3. Improper delineation of the anterior & posterior vibrating line.

4. Excessive trimming of the posterior border of the denture

OVER EXTENSION

The denture base can lead to ulceration of the soft palate

The most frequent complaint from the patient will be that swallowing is painful & difficult.

If hamuli are covered by the denture base , the patient will experience sharp pain, specially during function.

Correction: The overextension can be removed with a bur & then carefully repolished.

UNDER POSTDAMMING

If mouth is wide open while recording the posterior palatal seal the mucosa over the hamular notch becomes stretched. This will produce a space between the denture base & tissue.

Inserting a wet denture into a patient’s mouth & inspecting the posterior border with the help of mouth mirror. If air bubble are seen to escape under the posterior border it indicates under damming.

Correction: The master cast can scraped in the posterior palatal area or the fluid wax impression can be repeated with proper patient position.

OVER POSTDAMMING

This commonly occur due to excess scraping of the master cast

Upon insertion of the denture the posterior border will be displaced inferiorly

Correction: Reduction of the denture border with a carbide bur, followed by lightly pumicing the area while maintaining its convexity

Current Concepts for Determining the Postpalatal Seal in Complete Dentures

Purpose: In 2001, a survey of U.S. dental schools was conducted to determine the concepts and techniques used for establishing the postpalatal seal (PPS) in a predoctoral dental curriculum.

Materials and Methods: The questionnaire was mailed to the chairperson of the prosthodontic/restorative departments of 54 U.S. dental schools. Of these, 44 returned the completed survey, resulting in a response rate of 82%.

Current Concepts for Determining the Postpalatal Seal in

Complete Dentures, Behnoush Rashedi, DMD, MS, MSEd and Vicki C. Petropoulos, DMD, MS,J Prosthodont 2003;12:265-270.

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Results: • 80% of the schools are teaching a combination of phonation

with other methods for locating the vibrating line. • The 1 vibrating line concept for establishing the PPS is taught

by 80% of schools• 77% of these schools locate the posterior termination of the

maxillary denture on the vibrating line• Carving the PPS in the maxillary master cast is taught by 95%

of the schools. Most of the schools teach the students to carve the PPS to a depth of 1.0 –1.5 mm in the maxillary master cast

• Compressibility of the palatal tissues is a consideration during PPS carving for 91% of the schools. The butterfly pattern is the most frequently (75%) described pattern for PPS carving

Conclusions: There is some variability from school to school on performing the PPS in the maxillary denture, although some trends are evident. 57

Summary • PPS provides peripheral seal, and there by enhances retention

and stability of maxillary denture.• PPS preparation is an integral part of maxillary complete

denture fabrication, requiring an assessment of physiological and technical parameters.

• The PPS should be prepared with an understanding of patient palatal throat form, anatomical boundaries, extent and depth of displaceable tissues.

• No step in the denture construction should be stopped short of perfection. Yet, many dentures are worn which have imperfections built into them, provided they have peripheral seal sufficient to hold them in place

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References

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• Essentials of Complete Denture Prosthodontics, 2nd edition, Winkler• Syllabus of Complete dentures,4th edition, Charles M.

Heartwell,Arthur O. Rahn• Prosthodontic Treatment for Edentulous Patient, 12th edition, Zarb-

Bolender• Impressions for Complete Dentures,1984,Benard Levin• Silverman S.L. “Dimensions and displacement patterns of the

posterior palatal seal”. J. P.D. 1971.• Izharul Haque Ansari “Establishing the posterior palatal seal during

the final impression stage”. J. P.D. 1997.• Determination of Degree of Distinction Between Anterior and

Posterior Vibrating Line –A Pilot Study VN Malik,Vikas Vaibhav, JIDA, Vol. 5, No. 2, February 2011

• Current Concepts for Determining the Postpalatal Seal in Complete Dentures, Behnoush Rashedi, DMD, MS, MSEd and Vicki C. Petropoulos, DMD, MS,J Prosthodont 2003;12:265-27

• Accurate location of postpalatal seal area on the maxillary complete denture cast, Brian Myung W. Chang, DDS,a and Robert F. Wright, DDS,Harvard School of Dental Medicine, Boston,Mass, J Prosthet Dent 2006;96:454-5.

• A review on posterior palatal seal,Sudhakara V Maller , Karthik. K. S, Department of Prosthodontics,KSR Institute of Dental Science and Research, JIDAS VOL.1 Issue .1,2010

• Location of Anatomic Position of Posterior Palatal Seal Area By Conventional And Unconventional (Ultrasound Method) Methods – A Comparative study. Sreedevi .Ba, Premanandam .Ia, Gopinadh Annea Department of Prosthodontics, SIBAR Institute of Dental Sciences, Guntur, India. Jr. of Orofac. Scie. 1(1)2009

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Thank you…..61