This document discusses principles for designing removable partial dentures (RPDs). It covers biomechanical considerations like the types of movements that occur in RPDs and factors that influence stress transmission to abutment teeth. Design considerations are presented to help control stresses, including using indirect retention, splinting abutments, and designing clasps and denture bases to minimize lever forces. Different designs are recommended for tooth-supported versus tissue-supported RPDs.
3. CONTENTS
1. INTRODUCTION
2. BIOMECHANICS OF RPD.
3. BIOMECHANICAL CONSIDERATIONS.
4. POSSIBLE TYPE OF MOVEMENT TAKING PLACE.
5. DIFFERENCES IN DESIGN BETWEEN TOOTH SUPPORTED AND TISSUE
SUPPORTED PROSTHESIS.
6. FACTORS CONTRIBUTING TO AMOUNT OF STRESS TRANSMITTED TO THE
ABUTMENT.
7. DESIGN CONSIDERATIONS OF PROSTHESIS TO CONTROL STRESS.
8. RPI RPA CONCEPT.
9. DESIGN CONSIDERATION FOR OBTURATOR PROSTHESIS.
10.REFERENCE.
6. • REMOVABLE PARTIAL DENTURE FORCES IN ORAL CAVITY.
• CAUSES MOVEMENT OF VARIOUS COMPONENT OF THE RPD.
• SO ITS IMPORTANT TO UNDERSTAND THE MOVEMENTS TAKING
PLACE ON THESE COMPONENTS AND LOGICALLY HELP DESIGN
THEM IN ORDER TO CONTROL THE MOVEMENTS TAKING PLACE IN
THEM.
• WHAT ARE THE TYPES OF MOVEMENTS TAKING PLACE IN THE
ORAL CAVITY????
7. BIOMECHANICAL CONSIDERATIONS
• DESIGNING OF AN RPD IS BASED ON BOTH BIOLOGICAL AND MECHANICAL
CONSIDERATIONS.
• MOST OF US DENTIST CONSIDER THE MECHANICAL ASPECTS BUT IT IS ALSO
IMPORTANT TO UNDERSTAND THE BIOLOGICAL ASPECT.
• BIOLOGICAL ASPECTS :-
1. WHETHER TOOTH USED FOR SUPPORT CAN BEAR THE LOADS FALLING ON IT.
2. THE TYPE OF UNDERLYING MUCOSA.
• THE RESISTANCE TO LOAD FROM A TOOTH IS BASED ON THE AMOUNT OF FORCE
FALLING ON IT, THE DURATION OF FORCE AND DIRECTION OF FORCE APPLIED.
8. • MECHANICAL ASPECTS:-
1. A RPD LEVER, MAINLY DISTAL EXTENSION.
• BASED ON THE TYPE OF LEVER THE FORCES APPLIED
ON THE ABUTMENT TEETH VARIES.
• THE LEVER HAS THE POTENTIALITY TO INCREASE THE
FORCES FALLING ON THE TOOTH.
2. CANTILEVER TYPE DESIGN RPD SHOULD BE
AVOIDED.
3. TOOTH TENDS TO WITHSTAND VERTICAL FORCES
THAN NON VERTICAL FORCES BECAUSE OF THE
NUMBER OF PDL FIBRES INVOLVED.
4. AN ABUTMENT TOOTH WILL WITHSTAND NON
VERTICAL FORCES IF THE FORCES ARE APPLIED AS
CLOSE TO THE HORIZONTAL AXIS OF ROTATION.
9.
10. POSSIBLE TYPE OF MOVEMENTS
TAKING PLACE.
• GREATEST MOVEMENT TOOTH TISSUE SUPPORTED RPD.
• MOST COMMON MOVEMENT TAKING PLACE ROTATIONAL MOVEMENT.
• ROTATIONAL MOVEMENT DIFFERENT PLANES, IN A DYNAMIC COMPLEX
WAY.
• THIS MOVEMENT IS BASED :-
1. QUALITY OF TISSUE,
2. AMOUNT OF FUNCTIONAL LOAD APPLIED AND
3. ALSO ON THE QUALITY OF THE DENTURE BASE.
• USUALLY THERE ARE THREE TYPES OF ROTATIONAL MOVEMENTS TAKING
PLACE:
11. • FIRST ROTATION
• AXIS OF ROTATION HORIZONTAL PLANE
• EXTENDS THROUGH THE REST OF DISTAL
ABUTMENTS.
• THIS AXIS IS CALLED FULCRUM LINE.
• ROTATION OF DENTURE IN SAGITTAL
PLANE(TOWARDS OR AWAY FROM RIDGE)
• GREATEST MAGNITUDE OF ALL MOVEMENTS.
• NOT NECESSARILY DAMAGING AS ROTATION
IS IN APICAL DIRECTION.
12. • SECOND FULCRUM LINE SAGITTAL
PLANE.
• IT EXTENDS FROM THE DISTAL ABUTMENT
OCCLUSAL REST TO THE CREST OF THE RIDGE
• CLASS I SITUATION TWO SUCH LINES,
ONE ON EACH SIDE OF THE ARCH.
• ROTATIONAL MOVEMENT OCCURS IN THE
FRONTAL PLANE OR FACIOLINGUAL
DIRECTION(ROCKING MOVEMENT OF
DENTURE)
• LESSER MAGNITUDE
• INDUCES HORIZONTAL STRESS ON THE
ABUTMENT.
• IT IS MODERATELY DAMAGING.
13. • THE THIRD FULCRUM MIDLINE JUST
LINGUAL TO ANTERIOR TEETH.
• FULCRUM LINE VERTICALLY
• ROTATIONAL MOVEMENT IN THE
HORIZONTAL PLANE (IE, THE FLAT,
ARCUATE MOVEMENTS OF THE
PROSTHESIS).
• THE FORCE RESULTING FROM THIS
MOVEMENT IS ALMOST ENTIRELY
HORIZONTAL.
• FORCES CAN BE EXTREMELY DAMAGING
AND SHOULD RECEIVE SIGNIFICANT
ATTENTION DURING THE DESIGN
PROCESS.
14. DIFFERENCE IN DESIGN BETWEEN TOOTH
SUPPORTED AND TISSUE SUPPORTED
PROSTHESIS
• TOOTH SUPPORTED:-
• CLASS 3,CLASS 4
• DERIVE SUPPORT FROM TEETH
• THE MOVEMENT POTENTIAL IS LESS BECAUSE
THE TEETH PROVIDE RESISTANCE TO
FUNCTIONAL LOADING.
• SINGLE UNIVERSAL DESIGN CAN BE
FOLLOWED FOR TEETH SUPPORTED
PROSTHESIS
• THE DENTURE BASE IS MADE UP OF METAL
BASES.
• TISSUE SUPPORTED:-
• SEEN IN CLASS1 AND CLASS2 CASES.
• TISSUE MAXIMUM AMOUNT OF SUPPORT
(TISSUE PROVIDES PRIMARY SUPPORT AND
TEETH PROVIDE SECONDARY SUPPORT).
• TOO MUCH TISSUE MOVEMENT BECAUSE OF
THE DYNAMIC STATE OF THE TISSUE.
• MULTIPLE COMPLEX DESIGN HAVE TO
FOLLOWED.
• DENTURE BASE ACRYLIC RESIN
15. FACTORS CONTRIBUTING TO THE AMOUNT OF STRESS
TRANSMITTED TO THE ABUTMENT
1. LENGTH OF EDENTULOUS SPAN:-
• THE LONGER THE EDENTULOUS SPAN THE
LONGER THE DENTURE BASE GREATER THE
LEVERAGE FORCE TRANSMITTED TO THE
ABUTMENT TEETH.
• LOAD ARTIFICIAL TEETH THE LENGTH OF
EDENTULOUS RIDGE(DENTURE BASE)
DETERMINES THE FORCE ASSOCIATED WITH
ABUTMENT.
• TRY RETAINING POSTERIOR TEETH TO PREVENT
THIS PROBLEM.
• OTHER FACTOR LIKE THICKNESS OF MUCOSA,
AMOUNT OF OCCLUSAL FORCE ALSO
CONTRIBUTES TO IT.
16. 2. QUALITY OF RIDGE SUPPORT:-
• LARGE WELL ROUNDED RIDGES BETTER STRESS
DISTRIBUTION
• SMALL THIN, KNIFE LIKE RIDGES ARE VERY POOR.
• TALL BROAD RIDGE LONGER DENTURE FLANGE
WITHSTAND LATERAL FORCES.
• THICKNESS AND HEALTH OF THE MUCOPERIOSTEUM
ALSO INFLUENCE THE LOADS TRANSFERRED TO
ABUTMENT TEETH.
• 2 MM THICK HEALTHY MUCOSA BEAR GREATER
FUNCTIONAL LOADS.
• THIN FRIABLE, FLABBY MUCOSA ARE VERY POOR IN
WITHSTANDING STRESSES.
Factors influencing magnitude of stress
17. 3. CLASP FLEXIBILITY:-
• A FLEXIBLE CLASP IS MORE SOUGHT IN CASE OF TOOTH TISSUE SUPPORTED DENTURES
BECAUSE IT TRANSMITS LESS LOAD TO THE TOOTH STRUCTURE.
• WROUGHT WIRE CLASP IS MOST COMMONLY USED.
• IT HAS TENDENCY TO PRODUCE VERY HIGH AMOUNT OF LATERAL STRESS.
• BUT NOT INDICATED IN CASES WITH POOR RIDGES AS IT CANNOT WITH STAND LATERAL
STRESSES LEADING TO HEAVY STRESSES ON THE RIDGES.
4. CLASP DESIGN:-
• IT SHOULD BE PASSIVE.
• IT SHOULD BE SUCH THAT IT DOESN'T APPLY FORCE ON THE TEETH WHILE IT IS SEATED ON
THE TEETH.
• SO COMPLETE SEATING OF PROSTHESIS IS MANDATORY.
• RECIPROCAL ARM SHOULD DESIGNED THAT IT LIES IN THE ABOVE THE HEIGHT OF CONTOUR.
Factors influencing magnitude of stress
18. 5. LENGTH OF THE CLASP
• A LONGER CLASP IS MORE FLEXIBLE.
• AND A CURVED PATH THAN A STRAIGHT PATH ON THE
TOOTH SURFACE WILL PROVIDE MORE FLEXIBILITY
6. MATERIAL USED FOR CLASP CONSTRUCTION:-
• CO CR ALLOYS BASED CLASP APPLY MORE FORCE ON THE
ABUTMENT TEETH THAN GOLD BASED ALLOY.
• SO THINNER DIAMETER CO CR CLASP CAN BE USED TO
REDUCE THE AMOUNT OF FORCE APPLIED.
7. SURFACE CHARACTERISTICS OF AN ALLOY:-
• GOLD CROWNS MORE RESISTANCE TO CLASP THAN
ENAMEL.
• ABUTMENT RESTORED WITH GOLD EXPERIENCES MORE
FORCES THAN INTACT ENAMEL.
Factors influencing magnitude of stress
19. 8. OCCLUSAL HARMONY:-
• IT PLAYS AN IMPORTANT ROLE.
• DEFLECTIVE CONTACTS SHOULD BE AVOIDED.
• PROSTHESIS OPPOSING NATURAL DENTITION FACE MORE FORCES THAN FROM A
NATURAL DENTITION.
• OCCLUSAL FORCE SHOULD BE DIRECTED TO MIDDLE OF RESIDUAL ALVEOLAR
RIDGE CLOSER TO THE ABUTMENT.
Factors influencing magnitude of stress
20. DESIGN CONSIDERATION-
CONTROLLING STRESS
• DIRECT RETENTION:-
• THE RETENTIVE CLASP ARM DESTRUCTIVE
FORCES -ABUTMENT
• SO RETENTIVE CLASP ARM SHOULD PROVIDE
ADEQUATE RETENTION WITH LEAST FORCES.
• THIS CAN BE DONE BY PROVIDING RETENTION
FROM OTHER COMPONENTS OF DENTURE.
• THE SUPPORT AND STABILITY OF THE
PROSTHESIS ALSO MAY BE IMPROVED.
• OTHER COMPONENTS THAT PROVIDE
ADDITIONAL RETENTION ARE:-
• ADHESION COHESION.
• FRICTIONAL GRIP.
• NEUROMUSCULAR CONTROL.
21. • CLASP POSITION :-
• OFTEN, THE SPATIAL DISTRIBUTION OF RETENTIVE CLASPS IS MORE IMPORTANT TO
RETENTION THAN THE NUMBER OF CLASPS.
• THE FOLLOWING CONFIGURATIONS CAN BE FOLLOWED WHILE DETERMINING CLASP
POSITION.
1. QUADRILATERAL CONFIGURATION:- IT IS USED IN CLASS 3 SITUATION WITH
MODIFICATION SPACE.
2. TRIPODAL CONFIGURATION:- CLASS 2 MODIFICATION 1
3. BILATERAL CONFIGURATION
Design considerations
22. 1. QUADRILATERAL CONFIGURATION:-
• CLASS 3 WITH MODIFICATION SPACE.
• CLASP ASSEMBLY ON BOTH ABUTMENT TEETH ADJACENT TO
EDENTULOUS SPACE.
• IN CASE OF ABSENCE OF MODIFICATION SPACE CLASP
ASSEMBLY ANTERIORLY AND POSTERIORLY ARE GIVEN ON THE
DENTULOUS OPPOSITE ARCH.
2. TRIPODAL CONFIGURATION:-
• CLASS 2 WITH MODIFICATION SPACE.
• CLASP PRESENT ADJUSTMENT TO THE EDENTULOUS SPACE.
• ON THE MODIFICATION SPACE SIDE CLASP ON BOTH THE
ABUTMENT TEETH.
• IF MODIFICATION IS ABSENT CLASP PLACED AS FAR ANTERIORLY
AND POSTERIORLY ON THE TEETH.
• NOT AS EFFECTIVE AS QUADRILATERAL CONFIGURATION BUT
BETTER IN CLASS 2 CASES.
3. BILATERAL CONFIGURATION:-
• CLASS 1 SITUATIONS.
• PROVIDES LEAST STRESS REDUCTION.
23. • CLASP DESIGN:-
• CAST CIRCUMFERENTIAL CLASP:-
• CLASS 2 AND CLASS 1 CASES CLASP ASSEMBLY
INVOLVING DISTO OCCLUSAL REST AND RETENTIVE TIP
INVOLVING MESIOFACIAL UNDERCUT IS PREVENTED.
• TERMINAL END OF SUCH CLASP TIPPING FORCES ON
THE ABUTMENT TEETH.
• A CLASP THAT ORIGINATES FROM THE MESIOOCCLUSAL
REST AND ENGAGES THE DISTOFACIAL UNDERCUT OR A
REVERSE CIRCULATE CLASP SHOULD BE USED.
• VERTICAL PROJECTION CLASP:-
• T CLASP OR MODIFIED T CLASP CAN BE USED ON AN
ABUTMENT ADJACENT TO THE DISTAL EXTENSION SPACE.
• IT IS USED WHEN THE A DISTOFACIAL UNDERCUT IS SEEN
ON THE ABUTMENT.
• IT IS NOT INDICATED IN CASE OF MESIOFACIAL
UNDERCUT.
• I CLASP IS BETTER USED INVOLVING MESIOFACIAL
UNDERCUT AND MESIOOCCLUSAL REST SEAT.
• IT DOESN’T APPLY ANY STRESS ON TEETH.
24.
25. • COMBINATION CLASP:-
• USED WHEN A DISTAL EXTENSION IS PRESENTED WITH A MESIOFACIAL
UNDERCUT.
• FLEX MORE AND IN MULTIPLE SPATIAL PLANES..
• COMBINATION OF BOTH CAST AND WROUGHT WIRE IS USED.
• WROUGHT WIRE IS USED AS THE RETENTIVE ARM AND CAST METAL IS USED
AS THE RECIPROCAL ARM
• MORE FLEXIBLE AND PRODUCES LESS STRESS ON THE ABUTMENT.
26. SPLINTING OF ABUTMENT TEETH:-
• TOOTH WITH DECREASED PERIODONTAL SUPPORT CAN BE SPLINTED TOGETHER
• IT STABILIZES THE ABUTMENT IN A MESIO-DISTAL DIRECTION.
• SPLINT EXTENDS ANTERIORLY BEYOND THE CANINE THE STABILIZATION EFFECT IS PRESENT EVEN IN
FACIOLINGUAL DIRECTION.
• ON OF THE MOST COMMON CONSIDERATION FOR FIXED SPLINTING IS LONE STANDING ABUTMENT
ADJACENT TO DISTAL EXTENSION EDENTULOUS SPACE.
• SUCH A TOOTH CAN GET DAMAGED DUE TO ROTATIONAL FORCES.
• FIXED SPLINTING IN THIS SITUATION SERVES THE PURPOSE.
27. • SPLINTING REMOVABLE PROSTHESIS
• NOT DONE IF FIXED SPLINTING IS
POSSIBLE.
• THE SPLINTING CONSISTS OF CLASPING
MORE THAN ONE TOOTH ON EACH SIDE
OF THE ARCH AND USING ADDITIONAL
RESTS FOR INCREASED SUPPORT.
• NOT ALL CLASPS TO BE RETENTIVE.
• PREPARED GUIDING PLANES MAY
PROVIDE ADDITIONAL HORIZONTAL
STABILITY.
• RESULTS IN DECREASED MOBILITY.
• CROSS ARCH STABILIZATION
28. INDIRECT RETENTION
• IT PREVENTS RESIST ROTATION AND OR DISPLACEMENT OF A REMOVABLE PARTIAL DENTURE.
• IT IS LOCATED ON THE OPPOSITE SIDE OF THE PREVIOUS FULCRUM LINE AS FAR AS POSSIBLE.
• USED IN CLASS 1 REMOVABLE PARTIAL DENTURES.
• NOT AS USEFUL IN CLASS2 SITUATION, IT IS USED ONLY IF A MODIFICATION SPACE IS
PRESENT.
• CLASS 3 SITUATION USUALLY DOESN’T NEED A INDIRECT RETAINER AS THERE IS NO LEVER
EFFECT.
• CLASS 4 SITUATION IT JUST OPPOSITE TO THE CLASS 1 SITUATION WITH INDIRECT RETAINER
PRESENT AS FAR POSTERIORLY AS POSSIBLE.
29.
30. • OCCLUSION:-
• A SMOOTHLY FUNCTIONING OCCLUSION TMJ
• THE CONTACTS OF THE REMAINING NATURAL TEETH SHOULD BE THE SAME
WHETHER THE REMOVABLE PARTIAL DENTURE IS IN MOUTH OR NOT.
• THE NUMBER OF TEETH REPLACING THE NATURAL TEETH SHOULD BE REDUCED
TO DECREASE THE AMOUNT OF FORCE FALLING ON THE RIDGE.
• ARTIFICIAL POSTERIOR TEETH SHOULD HAVE SHARP CUSP WITH LOW INCLINE
PLANE IN ORDER TO INCREASE THE CUTTING EFFICIENCY AND PREVENT
HORIZONTAL INTERFERENCES FORCE.
31. DENTURE BASES:-
• THE DENTURE BASE SHOULD EXTEND AS MUCH DENTURE BEARING AREA AS POSSIBLE IN ORDER
TO DISSIPATE THE FORCES FALLING ON THE PROSTHESIS.
• DENTURE FLANGES SHOULD BE AS LONG AS POSSIBLE.
• MAXILLARY DENTURE BASE EXTEND MAXILLARY TUBEROSITY.
• MANDIBULAR DENTURE BASE RETROMOLAR PAD.
• OVEREXTENSION OF DENTURE BASE SHOULD BE AVOIDED.
• ACCURATE ADAPTATION OF DENTURE BASE IS NECESSARY FOR PROPER RETENTION OF DENTURE
BASE.
• THE EXTERNAL POLISHED SURFACE OF THE DENTURE SHOULD BE CONTOURED PROPERLY IN
ORDER TO AID IN RETENTION OF THE DENTURES.
32. MAJOR CONNECTORS:-
• A MAJOR CONNECTOR MAXIMUM COVERAGE AREA DISSIPATE THE OCCLUSAL FORCES
FALLING ON IT.
• IN MAXILLA A PALATAL FULL COVERAGE MAJOR CONNECTOR IS MORE PREFERRED AS IT CONTACTS
ALL THE REMAINING TEETH WITH A LINGUAL PLATE THUS HELPS IN DISSIPATING THE FORCES.
• IN MANDIBLE THE LINGUAL PLATE MAJOR CONNECTOR IS MOST PREFERRED BECAUSE IT COVERS
THE WHOLE LINGUAL SURFACE OF ANTERIOR TEETH.
• THUS DISTRIBUTING THE FORCES TO ALL THE TEETH.
• IT IS PARTICULARLY HELPFUL IN SPLINTING PERIODONTALLY WEAKENED TEETH.
• IT ALSO PROVIDES RIGIDITY AND CROSS ARCH STABILIZATION.
33. MINOR CONNECTOR
• THE MINOR CONNECTOR CONNECTING THE GUIDE PLANE TO THE MAJOR
CONNECTOR PLAYS A VERY IMPORTANT ROLE IN DISSIPATING FUNCTIONAL
STRESSES. BECAUSE OF ITS CLOSE ADAPTATION TO THE ABUTMENT TEETH.
• THIS MINOR CONNECTOR HELPS IN TWO MAJOR FUNCTIONS.
• IT PROVIDES A SINGLE PATH OF INSERTION.
• IMPROVED STABILITY BY PROVIDING INCREASED RESISTANCE TO HORIZONTALLY
DIRECTED FORCES
• ADDITIONAL GUIDE PLANES CAN BE INCORPORATED ON OTHER TEETH TO HELP
DISSIPATE THE LATERAL STRESSES FALLING ON THE SINGLE TOOTH.
34. REST AND REST SEATS:-
• REST SEATS ARE ESSENTIAL AS THEY TRANSMIT FORCE VERTICALLY ALONG THE
LONG AXIS OF THE TEETH.
• REST SEATS PREVENT FORMATION OF ANY LATERAL STRESSES.
• REST SEATS SHOULD BE DESIGNED IN SUCH A WAY THAT THEY ARE LESS THAN 90
DEGREES TO THE PATH OF INSERTION.
• THUS HELPING THE REST SEAT TO GRAB THE TOOTH SECURELY AND PREVENT ITS
MIGRATION.
• OCCLUSAL REST SEATS SHOULD BE ROUNDED AND SOME AMOUNT OF SPACE
SHOULD BE PRESENT BETWEEN THE REST AND REST SEAT TO ALLOW FREE
MOVEMENT AS A MOVEMENT OF BALL AND SOCKET JOINT.
35. RPI RPA CONCEPT.
• THIS DESIGN CONCEPT WAS PROPOSED TO ACCOMMODATE FUNCTIONAL
MOVEMENT IN DENTURE WHILE CHANGING THE FULCRUM LINE.
• RPI STAND FOR REST PROXIMAL PLATE I BAR
• RPA IS A MODIFICATION OF RPI WHERE INSTEAD OF I BAR ACKERS CLASP IS
USED.
36. DESIGN PRINCIPLE FOR A OBTURATOR
PROSTHESIS.
• MOVEMENT POTENTIAL WHEN COMPARED TO NORMAL DENTURE IS MORE IN OBTURATOR
PROSTHESIS.
• SUPPORT, STABILIZATION AND RETENTION ARE PLACED ADJACENT TO AND FAR FROM DEFECT
POSSIBLE.
• TEETH ADJACENT TO RESECTION MARGINS ARE INCISORS THEY SHOULD BE SPLINTED.
• CINGULUM REST FOR ANTERIOR TEETH ARE GIVEN.
• MULTIPLE OCCLUSAL RESTS ARE USUALLY SUGGESTED TO IMPROVE STABILITY.
• USUALLY A EMBRASURE CLASP IS GIVEN DISTALLY.
• MAXIMUM COVERAGE OF PALATE SHOULD BE DONE FULL PALATAL COVERAGE IS USUALLY
PREFERRED
37. REFERENCES
• MC CRACKENS REMOVAL PARTIAL DENTURE. 11TH EDITION.
• STEWARTS CLINICAL REMOVABLE PROSTHODONTICS. 3RD EDITION
• MAXILLARY RIDGE REHABILITATION WITH OBTURATOR PROSTHESIS IJCD DEC 2013
2(6).
• BEUMER J, CURTIS TA, FIRTELL DN. MAXILLOFACIAL REHABILITATION,
PROSTHODOTICS AND SURGICAL CONSIDERATIONS.
38. • NEXT PRESENTATION BY DR DEEPTHI SONIA
• TOPIC :- PRINCIPLES OF TOOTH PREPARATION
• DATE:- !4-07-14
Editor's Notes
The amount of tissue movement taking place depends on occlusal force falling on it from opposing arch.
The functional force falling on the arch is based on factors such as opposing type dentition whether artificial or natural, occlusal harmony.
These type of prosthesis always tends to place undue forces on the dentures.
Requires some kind of indirect retention to prevent lifting up of denture due to sticky foods.
The distal extension denture base material should be always by acrylic resin as it helps in relining of the denture bases due to tissue changes.
Therefore the practitioner should be vary of the amount of force that would be falling on a abutment in the oral cavity.
Many other factors also determine the amount force falling on the abutment like thickness of mucosa, occlusal force etc but the length of edentulous span stands out to be the main factor.
So when treatment is planned every effort should be done to retain the posterior teeth.
Mesial tipping of clasp arm and gap created would cause food impaction.
Extremely weak tooth to strong teeth shouldn’t be attached.