Partial Denture

Chapter I: Introduction

Types of Partial Denture:  Temporary acrylic plate or transitory denture Permanent cast partial denture In temporary; support is by muco-periosteum & retention is by wrought iron clasp.  Permanent is a bio-mechanical appliance

Biological objectives:  Restoration of lost teeth Rehabilitation of lost thing Restoration of aesthetic Creation & maintenance of proper oral hygiene Maintenance of state of health Equal distraction of forces to remaining tissue.

Mechanical Objectives:  The appliance needs minimum cutting of remaining tissue Stresses should be distributed equally to the denture so that it can withstand the stresses of

mastication The design of the denture should be such that it can be easily inserted & removed by the pt.

 Partial Denture: It is removable prostheses for partially dentate pt. to re-established function & aesthetics

It consists of: Saddle areaMeans of RetentionMeans of Support Connectors

Parts of Partial Denture

Saddle area: Is that part of the partial denture which overlies on ridge & carry teeth.

 Saddle area has 2 subdivisions: Conventional SaddlesGum fit Saddles Conventional saddles cross the alveolar ridge to the depth of

labio-buccal sulcus while gum fit finishes of at the cervical area.

Indications of gum fit saddle:  1. Gum fit are used for anterior teeth because the colour

of the acrylic may differ from gum so, for aesthetic purposes especially when the number of missing teeth is less.

2. In the bulbous ridge, because deep undercuts do not allow insertion & removal of partial denture

3.Procline pre-maxialla or bulging anterior segment.  4. Procline Premaxialla or bulging anterior segment

KENNEDY Classification of partial denture or (Kennedy APPLEGATE Classification):

Kennedy class I:

Is a bilateral free end saddle i.e all the remaining natural teeth are anterior to a bilateral edentulous situation.

 Kennedy class II:

Is a unilateral free-end saddle i.e the remaining teeth of either left or right side are anterior to the edentulous situation.

Kennedy’s class III: (Kennedy apple gate):

An Edentulous area bounded by teeth; but the teeth in the posterior segment are unable to assume total support for the required prosthesis.

  Class IV:

Is bounded anterior segment

Kennedy’s apple gate Class V:

Edentulous situation bounded by teeth (anterior & posterior to it0, but teeth anterior to it is not suitable for abutment surface while the posterior bounded is suitable.

  Kennedy apple gate Class VI:

Edentulous situation where the boundary teeth are capable of providing adequate support.

Classification of Partial Dentures  

Other Classification of Partial Dentures:

Another method of dividing P.D into basic types is consider the manner in which the pressure is applied to the occlusal surfaces of the teeth, & in this:

 Tooth-borne: It is a type which has a small projection called “occlusal rest”.

Which are placed on the occlusal surfaces of natural teeth so that the vertical masticatory loading is transmitted via the teeth bearing the rest & not via the mucosa underlying the denture.

 Tissue-borne: Is one in which the vertical load is received directly by the

mucosa with out any resistance from the natural teeth. Tooth & Tissue borne: Is one in which the vertical loading is transmitted partly by the

teeth & partly by the mucosa

Chapter 2: Means of

Retention

 Retention is achieved depending on the principle of tensile friction. i.e (if a metal is displaced & it tries to come back to the normal area due to stress or force, This friction is known as tensile friction)

This tensile friction should be within the physiological limits of that particular tooth otherwise the tooth will damage. This tensile friction is controlled by:

Extending the wire more into the undercutsBy selecting a suitable metal alloy. E.g. silver-copper alloy gets

tarnish but silver, copper & palladium alloy is good to resist tarnishing., chromium—cobalt alloy are very hard.

When the undercut is less deep we select harder alloy. By the diameter of the wire, more the diameter of the wire more

will be friction & vice-versa

Surveyor: Objects of Survey are: 1, To not down & locate areas of undercuts 2, To measure the depth of undercuts 3, To devise ways & means to utilize the favourable undercuts & avoid

unfavourable undercuts:   How to reduce under cut depth?? By: Changing the path of insertion Selective grinding of the natural tooth but dentine should not be exposed By filling Inlay or onlay Crowning of the tooth If all these fails go for extraction   4, Design of the partial denture i.e. the 4 parts of it:  Saddle area (edentulous areas) Means of Retention (Infra bulge area) Means of Support (Supra bulge area) Connecting areas.   5, To determine the path of insertion & path or removal of partial denture.  Surveyor has 3 Parts: 1, Horizontal plate form 2, Vertical standard 3, Surveying table

Clasp has 4 parts  1, Body 2, Retaining arm 3, Reciprocating arm 4, Occlusal extension or occlusal rest   Body lies on the proximal surface of the tooth near the

saddle area Retaining arm: it arises from the body & engage the

undercut & provide retention. The reciprocating area is on lingual side or buccal side

which remain above the guide line The occlusal rest which extend to to the occlusal surface;

but it should not interfere with occlusion so, that whether the surface can be utilized? ; otherwise slight grinding on the occlusal depth but it should be within the enamel limits.

Clasp

Indications of clasps:  1, Bars clasps are indicated when the undercut are very deep,

because they are more resilient. 2, If the undercut is available on the buccal surface of the

proximal end away from the vacant space, conventional circumferential clasp is the ideal clasp.

3, if the undercut is not deep enough & similar undercut is available on the remote proximal end on lingual surface; average circumferential clasp may be given.

4, If undercut is located close to the vacant space, back action clasp is given

5, Single body mesio—distal clasp can be given on canine; they can be conventional type or average.

  6, split body mesio—distal clasp & embrasure clasps are selected

to contact the free end saddle of the opposite side. 7, When there is vacant space on both sides of the abutment tooth,

a split circumferential clasp can be given.

1, Conventional circumferential clasp 2, Average circumferential clasp 3, Back action clasp4, Mesio—distal clasp 5, Embrasure Clasps6, Split circumferential clasp

Types of circumferential clasp

T bar is given on bicuspidL bar I barC barU bar Combination of C & I

 Bars Clasps

Chapter 3: Steps in the procedure of P.D

Steps for the procedure of a partial denture normally involve the following:

Examination & evaluation of partially edentulous Pt. Study model impression Study model & this involve: Initial diagnosis Initial Examination Diagnosis  Oral Rehabiliation: This may consist of: Creation of oro—dental hygiene e.g. scaling Operative & conservative measures Axial anatomy may be modified to get rid of undesirable undercuts Inlay, onlay, or crowining If all fails go for extraction  Master model impression & model surveying (i.e. design of P.D) Duplication & construction of the wax pattern Casting procedure Maxillo—mandibular relations Arrangement of the teeth & trial Processing & insertion Charge your fees

Chapter 4: Evaluation of the Pt.

Identification: The same as C.D

Mental Classification: Philosophical Exacting Antagonistic PassiveGeneral systemic status

Examination of the Patient: General Examination: In which we see Size & shape of the face & jaw Muscular development Muscle tone Face form Colour of skin, eyes & hair

Visual examination to identify the oral condition in health & disease; in this we justify.

Condition of occlusion.Radiographic Examination to know.

Local Examination:

Chapter 5: Design of Partial Denture

Examination of the oral condition gives us some information about the design but to know definitely the exact shape & form of the denture that would be suitable for a particular mouth we have to study carefully the curves & contours of the study models.

Retention is one of the basic requirement of partial denture. Retention primarily depends upon those parts which involve the infra buldge area or undercuts on axial surfaces of the teeth. The undercuts can only be involve up to certain extent so that the stresses exerted upon the teeth during insertion & removal are within the physiological limits of tolerance of the periodontia. For this purpose curves & contours of all axial surfaces of the teeth that come in contact with the denture have to be studied; The procedure of studying it is called surveying.

Surveying is carried out with the following objectives:

1, To note down & locate areas of undercuts 2, To measure the depth of the undercut3, To devise ways & means to utilize desirable

undercuts & get rid of undesirable undercuts.4, To determine the path of insertion &

removal of denture. 5, To design the saddle areas, means of

retention, the means of support & connectors.

Chapter 6: Duplication of (Master) Models

 Master models have to be duplicated to make the working model. The various procedures are carried out on the working model & the master model is

used for reference. If the working model is spoiled or gets distorted during various functional procedures, the master model can again be duplicated to get a working model, Any of the duplicating material can be used for this purpose, The material may have an alginate base, colloid base or an agar base.

 The alginate base is not very popular because it sets very firmly & the investment material is a much weaker & softer substance, & manufacturer instructions should be strictly followed for manipulation.

 Reversible hydrochloroide (Coloid) & agar usually produce very satisfactory results.

 The master model is centred in the duplicating flask & is seated with the base of the duplicating material is poured at a temperature just a few degree above it is melting point. The duplicating material should not be heated unnecessary dehydrate the master model & stick to it.

 For cooling again the instructions of the manufacturers should be followed. Separation of the model from the duplicating material is best accomplished by blowing a jet of compressed air on the borders of the model, This will loosen the model which can now be easily separated.

 The suface of the master model should be carefully examined for any duplicating material sticking to it. If any material sticking to it the whole procedure of duplication should be repeated. The duplicating material may stick to the master model if it is heated to a very high temperature or if the master model was very dry before duplication so for this reason the master model should preferably soaked with water before duplication.

 Now the working model is poured in investment material & is allowed to remain undisturbed for 45 mins. So that the investment material is fully set. Silica bounded investment material are superior to other variety & is more distortion resistance.

The duplicating model should never be pulled out of the duplicating material. The material should always be cut away from the working model.

 Put the working model in a dry oven for one hour at a prescribed temperature (150--250° C). Allow it to cool & then give it a dip in the molten resin or wax. Bees wax is usually preferred; this procedure strengthen the working model. This resin or wax soaked model is again put in the oven for a few minutes so that all the wax is absorbed by the model. Take care that there is no wax or resin unabsorbed on the occlusal surfaces of the teeth. Allow the model to cool down & the working model is ready for the wax pattern.

The End Dr.Fawaz Al Shorafat