18-2-2014 Prosthodontis-1 Angy Awni Kokash

In the last semester we dealt with completely edentulous arches & constructed “Complete Dentures” in the practical prosthodontics sessions ,now it’s time to go for partially edentulous cases and attempt to make “removable partial dentures”.

- If we want to make a scan for any random specimen of the society regarding the presence of their teeth , we’ll find three categories :A) completely edentulous people.B) partially edentulous people.C) fully dentate people.

-The removable partial denture is basically the prosthesis that is given to type B) patients whom I mentioned above.

-In this lecture , we’ll come through some terminologies and their definitions.

-Prosthodontics : the field of dentistry that deals with replacement of missing hard tissue (teeth) as well as soft tissue (e.g. cleft palate in congenitally defected patients) with an artificial part called “prosthesis”.

-what do we mean by the term “removable” here in our topic??that the constructed denture can be removed by the patient himself.

-Fixed removable partial dentures are out of our scope here …they’re called “crown & bridges”.

-Some people might have congenitally missing teeth “partial hypodontia” ;most commonly the upper 2 ,lower 5 ,wisdom teeth and so on .

18-2-2014 Prosthodontis-1 Angy Awni Kokash -In dentistry there are always many options to treat patients of missing teeth…for example ;maryland bridges ,conventional bridges ,implants (according to the amount of bone remaining ,width and height) and also we can go for removable partial dentures as well.

-The choice of many patients would be the fixed partial dentures (bridges) but sometimes the criteria of this category of treatment isn’t met so the dentist would go to the option of removable partial dentures as the treatment of choice.

-Partial dentures can be made of acrylic (PMMA) as the complete denture either soft (much higher cost) or hard (the same as the heat cured PMMA) or metallic (the base is made of metal such as Co-Cr ,Ti ,or vanadium -V- or any other metal alloy).

metallic base (frame) with an acrylic partial denture on top

note the clasps (made of stainless steel ) used as a mechanical retention form

soft acrylic partial denture

18-2-2014 Prosthodontis-1 Angy Awni Kokash -Some considerable points about the metallic frame (base) over which we place the partial denture….1)mesh area …the one that is perforated on the saddle edentulous area for example.

2) a casted clasp in the metal frame itself (note the above figure).3)the O-ring or the anterioposterior major connector.

-Each part I mentioned earlier will be further explained with its functions in the upcoming lectures.

-Indications of the partial denture : (When to choose it as the choice of treatment?)1)long edentulous span the patient has a long missing area of teeth e.g. a patient with a missing uppers 4,5,6 can’t have fixed bridge because what is left as anterior & posterior abutment teeth(3,7) are not enough for supporting the bridge .in this particular case implants are the choice if the specific criteria of bone I previously mentioned is found…or either a removable partial denture.

18-2-2014 Prosthodontis-1 Angy Awni Kokash 2)free-end saddle …

3)patient’s oral hygiene bad oral hygiene has always bad effects on the removable partial denture ,so it’s an important point to be considered.4)when there’s need to restore both soft & hard tissuesfor example the patient had an adverse trauma to his/her upper anteriors and some of the bony alveolar tissue is lost we can’t construct a bridge because the tooth will appear too long , so the removable partial denture(RPD) is the choice.as a result the flanges of the RPD will compensate for the lost soft tissue and the artificial teeth will compensate for the hard lost tissue.5)age this is a very critical point , now in young age groups the mandible won’t be fully formed and there’s still bony deposition & it differs from males to females .so a 13 year old child with a trauma to his anterior teeth can’t have a bridge or implants because there would be bony depositions on the fixed bridge (which means failure of treatment) instead the dentist will make him a RPD until he can have a bridge when full bone deposition is complete (approximately 18to19 years old).6)patient’s desirewe have to respect this point as much as possible regarding the case & try to give the patient all the available options with their odds and cons and let him choose.7)cost when comparing the cost of the RPD with that of fixed ,the RPD is of much less prize. Also the economic state of the patient must be considered while choosing the intended treatment.

-Indications of the acrylic RPD : 1)esthetic wise it will do the job.2)space maintainer for example the left upper central incisor is lost …in this case the RPD will prevent drifting of the right upper adjacent central mesially and the

There are no teeth posteriorly for example lowers 4,5,6,7,8 are missing …here we call the case (arch) ;free end saddle.**it can be bilateral or unilateral.

18-2-2014 Prosthodontis-1 Angy Awni Kokash adjacent canine from drifting distally.this topic is of prime importance in pediatric dentistry.3)reestablish the occlusal relationship4)intrum of restoration during treatment the acrylic RPD is a transitional state not permanent so as the paitent to get used to the idea to wear a complete removable denture.

-Terminologies

*Appliance :devices that are worn by the patient for a short period of time, such as: night guard (occlusal split) that’s used for patients suffering from bruxism and also for boxers, space maintainers and many orthodontics appliances .*Prosthesis :devices that are used for a long period of treatment such as: complete dentures, RPD, crown and bridges , obturators .note: Obturators are removable devices used to close opened palates to restore the separation between the oral & nasal cavities (opened due to tumor , gun shots or congenital disorders with a cleft in the palatal suture).*Provisional RPD : an example on this is the transitional state between partial edentulism to complete edentulism in which we use the acrylic RPD.*Abutment :natural teeth or artificial ones (post-crown or an implant) that support the prosthesis either fixed or removable from two sides, for example: if 5 and 6 were removed , 4 and 7 are the terminal abutments on both sides.*Denture Surveyor :a mechanical device that was invented by Dr. A.J. Fortunati in 1918, used to design the plan of partial denture making, it help us in measuring the relative parallelism between teeth surfaces and undercut areas, in other words it is used to measure the amount of undercuts of abutment teeth mainly as well as the edentulous area. This device has a pencil that is able to draw a surveying line at the most bulging area of teeth surfaces to know where to put the

18-2-2014 Prosthodontis-1 Angy Awni Kokash clasps of the denture – which is usually under this line.

Note : The undercuts are needed for partial denture’s retention and if the surface of the abutment tooth is smooth, composite must be used to build up undercuts.

*Mechanism of surveying :the procedure of analyzing and delineating the contour of abutment teeth as well as the edentulous area.

*Undercuts :that part of the tooth that lies between the survey line and the gingival margin.*Types of undercuts:

1- Hard tissue undercuts ;in the tooth surfaces (esp. buccal undercuts in upper posterior teeth mainly) but in lingually tilted teeth the undercut is foud lingually located .

2- Soft tissue undercuts close to the edentulous area in the ridge itself, irregularities and undercuts that are present due to deformation of the area after tooth extraction.

3- True and false undercutsfor each type 1 or 2 mentioned above there could be true or false undercuts .the true ones are naturally found in the patient’s teeth and soft tissue the false ones are artificially made by the technician while tilting the surveyor anterioposteriorly or laterally.

Note : the bevel of the surveying pencil (analyzing rod) in which we draw the survey line is placed toward the edentulous area of the cast .*Common path of insertion of RPD :the common way by which the partial denture is adapted in the oral cavity.there can be a single path of insertion,dual or multiple paths.*Common path of displacement of RPD :just the opposite … the common oath of denture’s removal or dislodgement during function e.g. because of sticky food.and it’s perpendicular to the occlusal plane.

The surveyor defines the paths of denture’s insertion and removal

18-2-2014 Prosthodontis-1 Angy Awni Kokash

*Components of RPD: clasps, rests, minor connector, major connector and saddle area.

*Clasps (direct retainer): it’s the retainer of the prosthesis in its place. clasps are of two types ; occlusally approaching clasp or gingivally approaching clasp.

note: In complete dentures; the peripheral seal, posterior dam area and the flanges are sources of negative pressure that gives retention but in RPD the clasps are used for retention ( mechanical retention ).

*Rests : the part of the RPD that rest on abutment teeth to support the denture and to prevent it from sinking toward the gingival ( limit the downward movement of the denture) . -any occlusally approaching clasp must have a rest.-Types of rests: 1) occlusal rests on premolars and molars .2) ledges on canines ( esp. in the upper arch where the cingulum is more prominent) and the incisal hook (not favored esthetically but we may use it when no premolars are present).

*Major connector:

Notice the C shaped clasp posteriorlyalso the dr. mentioned sth about reciprocal clasps

18-2-2014 Prosthodontis-1 Angy Awni Kokash a rigid (not flexible) part of the denture that connects one part to the other, it must be rigid to resist the biting force, for the maxilla for example ,it’s called the anterioposterior palatal strap with an opening (O-ring) another type for the maxilla is the horse-shoe shaped major connector and makes full coverage of the palate.*Minor connector :also it’s rigid and connects the major connector to the denture base and other components such as rests.*Saddle area :gap or space in the dental arch (it is the edentulous area where teeth are lost and it’s replaced by the mesh).*Guiding plane :the adjacent proximal surfaces facing the edentulous area, it guides the denture towards insertion.

*RPD are classified according from where they get the support to:

1- Tooth-borne RPD ,they get supported by adjacent teeth: for example when 6 is missing 5 and 7 will give support to the metallic partial denture. There will be two rests so it won’t sink into the mucosa ( rests will carry the partial denture). Like class 3 that I’ll mention later on .

2- Mucosal-borne RPD ,as in acrylic partial denture , we don’t have stoppers or rests, so the denture will be supported by mucosa.

3- Tooth & mucosal borne RPD ,as in the case of free-end saddle either uni or bilateral. For example when there are no teeth distal to 4,, here the denture will resist the biting forces by abutment 4 as well as the mucosa.

*Classification of partially edentulous arches:according to Edward Kennedy. (there are other classifications but this is the mostly used one).any classification must begin from the most posterior area of the arch.

18-2-2014 Prosthodontis-1 Angy Awni Kokash

*All classes have modification except for class IV , when there are several spaces in the arch we classify it according to the most posterior area as I mentioned earlier and the additional edentulous areas are called modifications.

- For example …we say class 1 modification 1 if there’s only one extra missing tooth or part or modification 2 and so on …

-The ideal impression material that is used of partially dentate and dentate patients is Alginate .- Afterwards , a study cast is poured (Diagnostic cast) , its advantages ;1) it will help us educate the patient and explain the treatment plan to him also to let him

1) Class I: bilateral free- end saddle an edentulous area behind the natural standing teeth…no abutment posteriorly

2) Class II: unilateral free-end saddle

3) Class III: a unilateral edentulous area bounded by natural teeth …with an anterior and posterior abutments

4) Class IV: single, bilateral, crossing midline , anterior to the natural teeth edentulous area. For sure the two centrals are involved.

18-2-2014 Prosthodontis-1 Angy Awni Kokash know the final outcome … to avoid misunderstanding.2) enables initial surveying .3) enables technicians to do the specific design of the RPD.4) to construst a special tray.

-The trays that are used in dentistry ….they can be either perforated or non-perforated ,plastic or metal .-Also …the flanges of the tray must be shallower when the impression is intended for edentulous patients.

GooD LucK