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A Review O n Posterior Pa la ta l Seal

Sudhakara V Maller 1 2, Karthik. K. S.

Review

- Professor & Head Of The Department Of Prosthodontics,

Ksr Institute Of Dental Science And Research, Tiruchengode.

2- Senior Lecturer, Department Of Prosthodontics,

Ksr Institute Of Dental Science And Research, Tiruchengode.

Address for correspondence :

Sudhakara V Maller,

Department Of Prosthodontics

KSR Institute Of Dental Science And Research,

KSR Kalvinagar, Tiruchengode,Namakkal Dist- 637215.

Phone Number: 9443051313.

E- Mail Id: [email protected]

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Abstract:

Recording and replicating the extent of posterior palatal seal and its

borders is one of the most important steps in successful treatment of

the edentulous patients. Recording of the anterior and posterior

vibrating lines determines the posterior most extent of the denture

and proper incorporation of post-dam in the edentulous maxillary

denture. Incorporation of this post-dam reproduces exact seal in the

maxillary denture for proper retention. The aim of this article is to

provide some background about the importance of recording

posterior palatal seal and methods of recording posterior palatal seal

for retentive longevity of complete denture prosthesis treatment.

Keywords: Posterior Palatal Seal, Vibrating Lines, Denture Retention

Introduction:Complete dentures may suffer from a lack of

proper border extension, but none are moreimportant than the posterior limit and the posteriorpalatal seal on maxillary complete dentures. Theposterior border is terminated on a surface thatcontinues and is movable in varying degrees and notat a turn of tissue as are the other denture borders.

Deficiencies of the distal border may be in thelength of the denture base, or the depth of theposterior palatal seal or both. These errors may leadto inadequate retention, due to the lack of peripheral

8seal .

So it is important to discuss the factorsassociated with complete denture retention, theimportance of the posterior palatal seal, its location,design, placement and influence on processing.Posterior palatal seal is described as the soft tissues

along the junction of hard and soft palate on whichpressure with in physiologic limits of the tissues can beapplied by a denture to aid in retention of thedenture. (GPT)

Historical review1883: Ames and the Greene brothers

introduced atmospheric pressure as a means ofdenture retention and recommended the use offunctional denture borders as opposed to passiveborders in the fabrication of complete dentures.

1886: Wilson described adhesion as the primarydeterminant in denture retention.1907: Green brothers "Modeling compound"

1920: Hall revived interest in the use of atmosphericpressure as a retentive factor by interpreting anddemonstrating the functional denture borders.

1948: Stanitz used a lab model to suggest thatatmospheric pressure is in equilibrium with fluidpressure exerted on molecules within a capillary tube

with a liquid level in a container as well as theattraction of two glass slabs. These models explainedhow fluid film contributed to denture retention.

1951: Craddock described the gripping action of thebuccinator muscle on the buccal flange of themandibular denture and also coined the term "pearshaped pad".

1962: Stamoulis believed that atmospheric pressurecombined with intimate tissue contact and peripheral

1seal comprise the most critical retentive forces .Retention is the resistance in the movement of a

denture away from its tissue foundation especially in avertical direction. A quality of a denture that holds it tothe tissue foundation and /or abutment teeth. GPT-7.

1964: Fish discussed determinants of retention anddifferentiated between tissue, polished, and occlusalsurfaces and how each permits the dentist toincorporate mechanical, biologic, and physicalfactors of the denture retention.

Determination of vibrating lines and adding ofposterior palatal seal is observed as an importantsteps in retention of maxillary dentures.

Vibrating lines lies at the junction of soft palateand the hard palate. Soft palate is a movable,muscular fold, suspended from the posterior border of

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the hard palate. It separates the nasopharynx fromoropharynx.

Vibrating lines are imaginary lines across theposterior part of the palate, marking the division

between the movable and immovable tissues of softpalate. This can be identified when the movabletissues are in function.

The anatomic structures the help in recordingof these vibrating lines are palatine aponeurosis,hamular process, median palatal raphe, foveapalatini,

Posterior palatal seal: it is a seal area at theposterior border of maxillary denture. It can bedivided into 2 areas pterygomaxillary seal, Post

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palatal sealPterygomaxillary: seal extends throughpterygomaxillary notch continuing 3-4mmanterolaterally, approximating the mucogingivaljunction. It occupies entire width of hamular notch(loose connective tissue lying between pterygoidhamulus of the sphenoid bone and distal portion ofmaxillary tuberosity). The notch is covered bypterygomaxillary fold (extend from posterior aspect oftuberosity to pad). This fold influences the posterior

border seal if mouth is wide open during finalimpression procedure.

Post palatal seal: is an area between anterior andposterior vibrating line found medially from onetuberosity to other. It appears to be a cupids bow.

VIBRATING LINES: These are imaginary lines whichdelineate the PPS. There are two vibrating lines,- Anterior vibrating line- Posterior vibrating line

ANTERIOR VIBRATING LINE:- It demarcates zoneof transition between no movement of the tissueoverlying hard palate and some movement of thetissue of the soft palate. It serves as an anterior borderof PP'S. It extends laterally into pterygomaxillary notch. It always occurs in soft palate.

Methods of eliciting anterior vibrating line:-Valsalva manouevre ask patient to blow air

gently through nose with nostrils closed with fingers.Ask patient to say 'ah' with short vigourous bursts.

POSTERIOR VIBRATING LINE:- Imaginary line atthe junction of the aponeurosis of the tensor veli

palatini muscle and the muscular portion of the softpalate. It demarcates the part of soft palate that haslimited /shallow movement during function (quivers)and the remainder of soft palate that is markedly

displaced during functional movements. It is elicitedby asking the patient to say 'ah' in short bursts in anormal, unexaggerated fashion. Posterior vibratingline marks the most distal extension of denture base.

RATIONALE AND IMPORTANCE OF POSTERIOR4

PALATAL SEALAddition of PPS transforms a base with adhesive

retention into very stable base with resistance tohorizontal forces. It forms a partial vacuum whensubjected to force and enhance retention and stability.

The partial vacuum created does not damage oralstructures and lasts for a very short duration. Careshould be taken not to give excessive border seal as itoccurs with over scrapping .Adequate distal extensionof denture base within physiologic limit helps inincreasing surface area coverage.

IMPORTANCE AND FUNCTIONS OF PPS1. It maintains contact of denture with soft tissue

during functional movements of stomatognathicsystem, by which it decreases gag reflex.

2. Decreases food accumulation with adequatetissue compressibility.3. Decrease patient discomfort of tongue with

posterior part of denture.4. Compensation of volumetric shrinkage that

occurs during the polymerization of PMMA5. Increases retention and stability by creating

partial vacuum.6. Increased strength of maxillary denture base.

III. Designs of the posterior palatal sealThe most common Posterior palatal seal

configuration described by Winland and Young.1. A bead posterior palatal seal2. A double bead posterior palatal seal3. A butterfly posterior palatal seal4. A butterfly posterior palatal seal with a bead on the

posterior limit5. A butterfly posterior palatal seal with the hamular

notch area cut to half the depth of a #9 bur6. A posterior palatal seal constructed in reference to

House's classification of palatal forms;

PARAMETERS OF PPSPPS has specific characteristics with different

parameters :2, 5, 6

A Review O n Posterior Palatal Seal Sudhakara Maller & Karthik



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1. Size.2. Shape3. Location4. Displacibility.

1) SizeSilverman performed a study on 92

patients evaluating the PPS clinicallyradiographically, histologically and found thefollowing findings:-

The greatest mean anteroposterior width of PPS is8.0 mm (with 5-12 mm of range).

The mean width was found to be different for right(8.2mm) and left side (8. l mm).

The interhamular notch was found to be 35.8 mm(25-48mm range)

The interhamular notch distance was found to bedifferent for males (37.1 mm) and females (35.6 mm)

2] ShapeClass I a butterfly shaped pps with 3 - 4 mm width.Class II- pps is narrow with 2 3 mm of width.Class III a single beading made on the posteriorvibrating line

3] LocationLocation of PPS is not consistent and show lot ofvariation, but on an average anterior vibrating line is1.31 mm distal to fovea palatini .

4] Displacement /CompressibilityLot of variation has been found within the PPS. But lowcompressibility has been observed in midpalatal rapheand hamular notch region. High compressibility hasbeen in the lateral part of cupids bow. It's variationdepends on the form of palatal vault: -Class I_palate - shallow PPSClass II palate - medium PPSClass III palate - deep PPSFactors influencing pps: The accuracy of PPSreproduction in complete denture depends on various

factors:Configuration of hard palate.Investing medium.Factors involved in processing of acrylic resin.Denture base thickness.Head position.

2,5Configuration of hard palate :Hard palate has been classified by

Various authors :Nicholas Tapering, Square, Arched /flatHeartwell, Elinger, Sharry - based on different slopes,

FlatHighMedium

Curing method: the cause of dimensional change ofpps are :

Polymerization shrinkage [8 %]Linear shrinkage during cooling [0.44 %]

DENTURE BASE THICKNESS: - the effect ofthickness of denture base on pps has been interpretedwith contradictory statements:-

B. LEVIN - advices use of thin denture base forclass I soft palate ( pps is not deep but wide) andthicker denture bases for class III soft palate ( pps isdeep but not wide) ,medium thickness for class II softpalate .

Effect of head position on pps :

The maximum depression (downward andforward position) of the soft palate when FH plane is30 degrees to the horizontal plane and tongue isfirmly positioned against mandibular anterior teeth. Aproperly positioned maxillary tray handle can serve assubstitute for missing incisors. At no time the patientshould protrude the tongue beyond the approximatedposition of the incisal edges as this will fore-hasten theposterior border on the final impression. The headand tongue translates the mandible anteriorly. Thesoft palate will be brought downward and forward

due to indirect attachments of mandible and insertionof palatoglossus muscle into the side of the tongue.Flexion of the head also contributes to moving excessimpression material and saliva out of the mouth,rather than progressing down the pharynx, whilemaintaining the 30 flexion of the head and anteriortongue position. The patient is asked to rotate thehead so that all functional positions of the soft palateare recorded.Different methods of recording PPS: -1) Conventional method.2) Fluid wax technique.3) Arbitrary scraping.

I) CONVENTIONAL APPROACH-Silverman: Ask patient to have astringent

mouthwash to remove stringy saliva and keep hishead upright. Dry the pps area with gauze andpalpate for the hamular notch using a T burnisher /mouth mirror. Mark them with an indelible pencil ornote visually to ensure that they are not covered by thedenture. T-burnisher is passed along posterior angleof maxillary tuberosity until it drops into the

pterygomaxillary notch. Extend the mark from thepterygomaxillary notch 3-4mm antero-lateral to themaxillary tuberosity, approximating the mucogingival

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junction . This completes marking of pterygomaxillaryseal. Ask patient to say 'ah in short bursts in anunexaggerated fashion. Observe movements of softpalate and mark posterior vibrating line and then

connect it to the pterygomaxilliary seal. Advice patientnot to close mouth to prevent smudging of markings.The resin /shellac tray is then inserted into the mouthand seated firmly into place. Upon removal from themouth, the indelible lines should be transferred on thetray. The tray is then returned to the master cast tocomplete the transfer of the posterior extension.

Mark anterior vibrating line usinga) T-burnisher (by checking the compressibility,in width and depth) - usually termination of

glandular tissue coincides with anterior vibrating line.b) Valsalva maneuver: - place special tray inside themouth and get the markings on the tray which is latertransferred to the master cast.

The area of cast before the anterior andposterior vibrating lines is usually narrow in mid-palatal region due to the presence of posterior nasalspines.

Master cast is scored using a Kinsley scraper.Deepest area of seal is located on either side ofmidline (l/3rd distance anteriorly from posterior

vibrating line). It is scraped approximately 1.0 -1.5mm. The tissue covering the median palatal raphehas little sub-mucosa and cannot withstand the samecompressive forces as the tissues lateral to it. The areais scraped to the depth of approximately 0.5-1.0mm.

Within the out line of the cupids bow, the cast isscraped to a depth of about half the amount to whichthe palatal tissues in the area can be compressed,being tapered progressively shallower anteriorly untilit feathers out in the area of the anterior vibrating line.Then add additional amount of resin on tray overscraped area and try in patient's mouth by asking himto say 'ah', and then check for any gap between trayand soft palate. If gap is found then repeat scraping tilladequate seal is attained.

Advantage: -1. Highly retentive trial bases make recording jaw

relations easier and precise.2. Give psychological confidence to patient that

retention will not be a problem in completedenture.

3. Dentist is able to determine the retention of final

denture.4. Patient will be able to realize the posterior extent of

denture, which may ease the adaptation period.

Disadvantages: -1. Not a physiological technique and thereforedepends upon accurate transfer of vibrating line andcareful scrapping.

2. Potential for over compression is more.

II) FLUID WAX TECHNIQUE: -Start with locating and transfer of anterior and

posterior vibrating line similar to conventionalapproach. Then with markings made, finalimpression is made using ZOE/impression plaster(not with elastomeric impression material as they areresilient, non adherent to wax and distort wax whenreseated into oral cavity).

Impression waxes used are: -a] IOWA wax (white)- Dr.Earl. S. Smith.b] KORECTA wax no.4 (orange)- Dr. O. C. Applegatec] K.I physiologic paste (yellow - white) Dr. C.SHowkins.d] Adaptol (green) Dr.Nathen G. Kyne.

The melted wax is painted into the impressionsurface (within the outline of the seal area). The wax isapplied slightly in excess of the estimated depth andallowed to cool below mouth temperature to increase

its consistency and make it more resistant to flow. Thisimpression is carried to the mouth and held in placeunder gentle pressure for 4-6 min allowing time forthe material to flow. Head position is critical (the FHplane to be at 30 to the horizontal plane)

After 4 min remove impression tray and trimexcess (or) if no tissue contact is established then addand redo the procedure. Ask the patient not to rinsewith cold water, between the procedure (contraction oftissues and act to decrease flow properties of wax).Examine the surface morphology of wax at anteriorvibrating line. It should be a brief edge, if a step isfound this indicates poor flow of material.

Advantages:1. It is physiologic technique of displacing tissues.b) No over compression of tissues.c) PPS is incorporated into trial denture base for

added retention.d) No mechanical scraping of cast.

Disadvantage:a) Time consuming.

b) Cumbersome procedure. - Difficulty in handlingmaterial and additional care to be taken duringboxing procedure.



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III) ARBITRARY SCRAPING:-Winkler- Arbitrarily mark anterior and

posterior vibrating line and scrape about 1- 1.5mm. Itis the least accurate method used to mark the PPS.

There is a high potential for over post-damming as it isa non physiologic technique of recording.

Light bodied elastomers have also been usedto record the pps along with putty impressionprocedures.

WHEN TO RECORD PPS:There are two schools of thought as to when to

record pps.a) Before try in - provide the patient withpsychological confidence

b) After try in - prevent displacement of occlusal rimin posterior region leading to occlusal error in 2ndmolar region due to improper seating of bases duringjaw relation.

PROBLEMS WITH PPS11: -1. Under-extension of denture:-

It is the most common cause of seal failureand mainly occurs due to use of fovea palatinea asa guideline for marking anterior and posteriorvibrating line. By doing so 4 - 12 mm of tissue

coverage loss occur leading to decreasedretention.2. Over extension:

It mainly occurs due to over extension ofdenture base by dentist for increased retentioncausing physiological violation of soft palatemusculature. It mainly shows with symptoms of:

A] Mucosal ulcerationsB] Physiological violation of soft palate musculature.C] Sharp pain if pterygoid hamulus is covered.D] Painful swallowing.It can be managed by selectively relieving the pressureareas and decrease the distal length.3. Under post-damming: mainly occurs due to

Due to improper depth of post-damming,Use of improper techniqueRecording PPS in a wide open position

-causes toughening of pterygomandibularligament which shorten the pterygomaxillary seal.It can be diagnosed using 2 tests:-

Seat dentures in patient's mouth and ask patient tosay 'ah', and with mouth mirror view for any gap.Place wet denture base and press slowly in midpalatal

region and bubbles escaping at any point on distaldenture border indicates area of under postdamming.

4. Over post-damming:-Commonly occurs due to aggressive

scraping of cast. If it occurs in Pterygomaxillaryseal the denture is displaced downward. If moderate

post-damming is present then mild irritation is found.It can be overcome by selectively relieving dentureborder with a carbide bur, followed by light pumicing.

Addition of pps to existing denture:-Existing denture may have poor length and

depth of PPS. Properly examine existing dentures. Ifthere are other problems in the dentures (verticaldimension, centric, esthetics etc.) then new denturesare to be made. If only PPS is short then correctionshould be undertaken. Different authors using

different materials have advised various techniques,1) Heat cure material.2) Self cure acrylic resin.3) Light cure resin.

Summary:The placement of the correct posterior palatal seal

is not a difficult procedure once the anatomy andphysiology of the area are understood. Carefulexamination during the diagnostic phase of thetreatment can alleviate many potential problems.

Following established techniques for the placement ofthe border seal will ensure a more retentive prosthesisfor the patient, whose satisfaction is the main concernof the prosthodontist.

References:

1. Blahoua, Z. and Neuman, M. Physical Factorsin the Retention of Dentures. J Prosthet Dent1971.25: 30-5.

2. Nikoukari, H. A study of posterior palatal sealswith varying palatal forms. J Prosthet Dent1975.34: 605-613.

3. Sidney I Si lverman, DDS. Dimensions anddisplacement patterns of the posterior palatalseal. J Prosthet Dent 1971.25:470-488.

4. Hardy, I.R. and Kapur, K.K. Posterior borderseal - Its rationale and importance. J ProsthetDent 1958.8:386-397.

5. Stephen Galzier, BS, David N Firtell, DDS, MA,and Larry L Harmon, DDS. Posterior peripheralseal distortion related to height of maxillaryridge. J Prosthet Dent 1980.43:508-510.

6. W in land , RD and Youn g JM . Maxi ll ar y complete denture posterior palatal seal:Va riat ions in s ize, shape and locat ion.

J. Prosthet Dent 1973.29:256-261.7. Avant, W. E. A comparison of complete denturebases having different types of posterior palatalseal. J Prosthet Dent 1973.29:484-493.




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8. Chen, M. Reliability of the Fovea Palatini forDetermining the Posterior Border of the MaxillaryDenture. J Prosthet Dent 1980.43:133-137.

9. Firtell, D. et al. Posterior Palatal Seal Distortion

Related to Processing Temperature. J ProsthetDent 1981.45:598-601.10. Barco MT, et al. The effect of relining on the

accuracy and stability of maxillary completedentures- An in vitro and in vivo study.J. Prosthet Dent 1979.42: 17-22.

11. Sheldon Winkler. Essentials of complete dentureprosthodontics, second edition.

12. George A. Zarb, Charles L. Bolender. Boucher'sProsthodontic Treatment for Edentulous Patients, tenth

edition.13. Alexander R. Halperin, Gerald N. Graser: Masteringthe art of complete dentures. Quintessence PublishingCo., Inc. 1988.



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