Overdentures ..

Todays topic is going to be about overdentures , or tooth supported overdenture .

Lets start with the definition : its any removable dental prosthesis that covers and rests on one or more remaining natural teeth , the roots of natural teeth , and/or dental implants

so it will rest on the remaining teeth , or remaining roots or dental implants , so it could be .

Tooth supported

Implant supported

Other synonyms for the over denture is - Overlay denture - Overlay prosthesis - Superimposed prosthesis

Because simply they have lots of advantages

Psychological benefit

loss of teeth can distrubt the emotional experience keeping some of the teeth in his mouth will give the patient mental preparation for becoming edentulous

Its very harsh for the person especially young patients to tell him that we are going to extract all of your teeth , and you will become edentulous patient , or patient who had a bridge or fixed prosthesis and suddenly you tell him that we will extract all of your teeth and you will become fully edentulous and you have to wear removable thing , so you should think about the psychology of your patient , and how you can disturb the emotional experience if he become fully edentulous , so by keeping some of the teeth in his mouth

Why overdenture should be considered as choice in our treatment planning ?

indirectly you will give the patient mental preparation for becoming edentulous .

So we will move in different stages before the patient become fully edentulous , so the overdenture will be like a transitional stage .

Proprioception periodontal mechanoreceptors allow a finer discrimination of food texture , tooth contact , and levels of functional loading . this will allow more control over mandibular movement and chewing food .

Proprioceptors are found in the PDL of the teeth , when we have premature contact on one of the teeth in the RCP , a reflex in the jaw will be established , that will lead to forward positioning of the mandible , or during eating , if you crush hard object suddenly between you teeth ,the jaw will be opened suddenly as a reflex (opining reflex) , proprioceptors also can help to know the exact position of the mandible , so the edentate patients dont have these reflexes .

Effect on ridge resorption Overdentures can preserve the edentulous ridge , by reducing the amount of resorption , Atwood and tallagren conducted a study in the 60s , they claim that : the amount of bone resorption underneath complete denture in the mandible is four times more than the maxilla

crum and roony claimed that by the retention of the canines we can reduce the bone resorption rate by 8 times , because they gained 0.6mm resorption with OD after 4 years of wearing , compared to 5 mm in CD cases .

Now do you think that this feature is important in overdenture cases ? Yes , because loosing most of the bone will reduce the retention for CD , but if we keep the canines and do not extract them , then the patient will not reached to the flat ridge stage , the PDL will transmit tensile forces to the bone , and these tensile forces will keep the bone in its poison

Improve stability and retention Overdentures are not like complete dentures which relies on the physiological retention only , but they rely on actual mechanical retention . eg : attachments , magnets , friction all of these things can help to stabilize the overdenture , but the disadvantage is that you are going to increase the cost , and also the maintenance , and the patient will frequently come back because of attachments fracture or any other complications , so its a highly demanding prosthesis with increased cost and long term maintenance time .

But if the overdenture is going to server as a transitional stage , which mean from dentate patient to fully edentulous patient , in this case we cant use attachments or magnets , because we aim to introduce the complete denture concept for the patient and training him how to get regular for them , but if we give him attachments the patient expectations will increase , because he will think that the denture will be retentive like the OD with the attachments , so in this case the attachments are contraindicated .

also the patient is going to pay a lot of money for something that will not stay for long time .

Magnets : can be used as an attachments , its less costly compared to other types of attachments , with less load on the abutment , but the main disadvantage is that it can corrode in the oral cavity even if it was coated with SS or titanium , and they dont provide lateral stability .

Minimizing horizontal forces on the abutment teeth. Picture slide 2 page 4 : Lets suppose that this patient came to your clinic , do you think that we can utilize this canine and use them as an abutments for chrome cobalt partial denture or acrylic partial denture ? No .. Because if you examine the canines you can notice this gingival recession as a result of chronic periodontitis , so large clinical crowns will be formed .

So we will have a problem in the crown/root ratio , in this situation they will serve as a lever arm , when the fulcrum point go down , horizontal forces will be applied to the tooth . so bad prognosis will be anticipated for the canines , and this will prevent us from putting clasp or rest seat around them , because they are not appropriate abutments for RPD .

How we can solve this problem ?

we cut the tooth after RCT , and put OD above it , so the horizontal forces will be minimized , and less damage to the tooth structure , so better prognosis .

if we suppose that the tooth is mobile , by the reduction of the crown length , the mobility of the tooth is going to be reduced , we decreased the load !

Correction of occlusion and aesthetics If you find any occlusal irregularities ( the occlusal plane is going up & down) , by the formation of OD the occlusal plane can be corrected .

Imagine that we had covered the abutments by OD , by this we are protecting the bacteria from mechanical wash and the chemical activity of the saliva that can help in the teeth protection . But we should not forget the activity of the food bolus because by the friction between the food and the tooth surface every loose fragments covering the tooth is going to be removed , and also the tongue mobility plays an important role in teeth cleaning . Because of these reasons the chance for dental caries is going to increase , so protective manner and habits must be implemented .

o strict oral and denture hygiene instructions ( by cleaning of the root stumps).

o dietary advice ( to reduce the sugar consumption that will lead to the reduction of caries activity )

By this we have finished all of the advantages for OD construction , but what about the disadvantages ?

o careful smoothening and polishing of the domed root face , this will facilitate the plaque removal by the patient , so the plaque accumulation will be reduced.

o sealing the root canal coronally with glass-ionomer cement ,

because this material release fluoride and it can be easily recharged with brushing the teeth by fluoridated toothpaste .

o regular topical application of fluoride using fluoride varnish in the clinic and fluoride toothpaste at home , we can prescribe TP with 5000 PPM fluoride , but its very dangerous and you cant by it over the counter , and you will need special prescription .

o the use of remineralizing agent eg : CPP-ACP .

Another disadvantage is that we will need to perform RCT for the teeth that we are going to use them as an abutment for the OD , because we are going to cut them , so we will have high chance for endangering the pulp , but does we need to perform RCT for all the teeth ?

The answer is No. because in old age group the pulp chamber will be calcified , and will recede down , so no need to perform RCT for them , so we are going to keep the teeth vital in this case , but what is the importance of keeping the teeth vital ?

o By the mechanical debridement , the remaining tooth structure will become weaker

o the propriocepters ( sensory receptor that receive information about the exact body position and movement ) are concentrated more in the pulp , and they can differentiate between heavy and low load , but after RCT and devitalizing the pulp , we are going to remove this proprioceptors , so if Im going to perform 2 bridge one will be constructed over vital abutment teeth , and on the other side the abutments are not vital , unconsciously you will apply higher forces on the non-vital abutments compared to the vital one .

Another disadvantage of overdenture is that it might initiate periodontal disease , it has been reported that gingival bleeding around all overdenture abutment teeth after 4 years in all abutment teeth , and obvious bleeding around 12 % of the abutments after 3 years .

Also if you failed to do a good treatment planning from the beginning it would be very difficult achieve a successful over denture , and many problems will be anticipated such as increasing the vertical dimension , and achieving poor aesthetics , dont forget that this prosthesis is demanding high demand especially if we are going to use attachments .

Normally when you extract the teeth there will be bone resorption followed by remodelling to the buccal plate so in complete denture there will be a space for the buccal flange , but in over denture no bone resorption will occur no enough space for the acrylic , so without a proper treatment plane its more easy to fall into poor aesthetic , and the denture will be bulky with lips protrusion .

Types of over denture : 1) Transitional over dentures 2) Immediate over dentures 3) Definitive over dentures

Transitional over dentures : If we have an old partial denture , and we know that the remaining teeth are going to be used as an abutments for complete overdenture , so we prepare these remaining teeth and add artifical teeth to the old partial denture on top of newly prepared teeth , in other words , we turned the old partial denture to new over denture

immediate over dentures ,:

All the clinical and laboratory procedure are the same as immediate complete denture , in immediate complete we take impression for the teeth and we cut them in the lab , but in the immediate over denture we cut the teeth and prepare them into dome shape above the gum level .

Attachment are not common with immediate over denture , because its not a definitive prosthesis , and there will be relining under it , so putting attachments will not be practical .

Most common problem encountered is the labial undercut ,because it indicate the need of openface denture , because teeth are still there and the bone doesnt resorb , so if we put a flange there will be bulging , we can solve the problem by doing an openface denture , and thats why its advised to prescribe denture adhesive to improve retention .

definitive over denture ,

We fabricate them in order to replace the existing transitional over denture and the immediate over denture .

This prosthesis can also be planed from the start and all the necessary work on the abutment is done in the patient mouth before we start fabrication the prosthesis .

Attachment could be incorporated in this type of overdenture and they could be BAR or STUD type .

NOW What is the first step that I should think about it when I am going to do treatment planning for overdenture ? I should think about teeth , which teeth I should extract? , which teeth I should retain? , why I should retain them ? , what I am going to do with the existing teeth and if they are suitable abutment for overdenture ? , should I use centrals , laterals , canines or premolars ? should I use two abutment in each side ? should I use one abutment in one side and two abutment in other side ? should the abutment be close to each other or far ? So these are very important questions we should ask during our treatment planning .

What teeth should be used as an abutment for overdentures ?

Many factors should be considered .

1) The mobility and periodontal status of the teeth . The tooth should be healthy with healthy periodontium , but if we have compromised tooth with good prognosis still they can be suitable as an abutment even with horizontal bone loss , but it should be stable and not extremely mobile ( grade 1 mobility ) .

* Teeth with grade 2 or 3 mobility with vertical bone loss are not suitable as an abutment .

* Always make sure that the teeth have good band of attached gingival , because it contribute to the periodontal health stability for that tooth , if we doesnt have an attached gingiva the pocket will increase in that tooth also periodontal problem will increases , in order to solve this problem we can do an apical repositioning flap to re-establish the attached gingival length .

2)Abutment location .. * You need at least one abutment per quadrant , which means one abutment on the right side and other on the left side (at least) .

* For mandibular arch canines and premolars are regarded as the best abutments

* In the maxilla , incisors are most frequently used , the problem with canines in maxilla is that the canines are supporting the nasio-labial fold and when we extract them we can easily notice the depression of the lip , so if we plan to retain the canine and use it as an abutment we will end up with bulky prosthesis , thats why canines are not the first choice as an abutment in maxilla .

* Lower incisors and upper laterals are not ideal to be used as an abutment because they have small periodontal ligament .

* If we want to use two teeth in one quadrant they should not be close to each other , we need a space between them .

3) Endodontic and prosthodontic status *single rooted teeth are easier and less expensive to manage endodontically.

* not every single tooth require RCT treatment .

* the type of attachment if used will be influenced by the available space for teeth sitting and interocclusal space .

* if the inter arch space is minimal , I can use any type of attachment because some attachments need 7mm space so it will not work in area where there is 3mm space only .

tooth supported over denture can be classified according to its design into :

Vital tooth with simple reduction. Tooth reduction with cast cooping of vital abutment dome shape or

thimble . Endodontic therapy with amalgam plug . Endodontic therapy with post and cooping . Endodontic therapy with cast cooping and attachment . Telescopic overdenture .

this picture explains what we have talked about : (slide1. pg10)

Vital tooth with thimble shape cooping, have parallel surface ,so that

prostheses will go up and down on a parallel walls with some friction .

we can do a reduction with cast cooping .

RCT with amalgam plug or glass inomer plug .

RCT with post and a diaphragm on top of it , which is cooping but with

post .

RCT with attachment , it could be ball attachment like what we se here

, or sica attachment, rothermann attachment or post attachment .

Or we do it as telescopic crowns (page 10 slide 2 )

Attachments classification : 1) intracoronal , inside the crown surface . 2) extracoronal , outside the crown surface . 3) stud attachment , like ball attachment rotherman attachment and

sica attachment .

4) bar attachment , that pass between two teeth .

Clinical and laboratory steps It will depend on the type of overdenture that is going to be fabricated .

if I want to fabricate immediate or transitional over denture:

1.I have to do all the needed RCT before we start , even the vital tooth which I know that I might have to do RCT treatment after I prepare it , so I do RCT treatment then I cut the crown

2. obtain an impression of the existing teeth and ridge (before you cut the teeth )

3.modify the cast by reducing the teeth to a dome shape slightly higher than what is intended inside the patient mouth and obtain an index . it means that if I want to fabricate an immediate over denture I am going to do index on the cast for the existing teeth at full length then I cut them on the cast at level higher than what we are going to cut inside the patient mouth ( in another words reduction from ptn natural teeth will be more than what we reduced from the cast ) , why ??!!

because if the patient natural teeth after reduction was taller than reduced teeth of the cast , the overdenture will not fit inside the patient mouth , but if ptn natural tooth was shorter , there will be a space between the over denture and the tooth and what I shall do is just relining

some may ask why not to cut at the same level ??!! because its impossible to get the same reduction for natural tooth and the cast tooth

4.process the overdenture in acrylic

5.use the index to reduce the tooth intra-orally to a dome shape more than the tooth on the cast

6 .seal the access of the RCT with amalgam or GIC .

7.fit the denture inside the patient mouth

8.the next appointment: polish all overdenture abutment and apply a fluoride varnish, reline the over denture to close the space between the abutment and the over denture , ( you should do a small perforation in the denture to permit excess acrylic to go out during relining so that will not affect the vertical dimension )

In immediate over denture all of our work are a guessing work , however in definitive over denture there is no guessing, every thing was ready in patient mouth then I take the impression for our definitive overdenture.

in other words , in immediate over denture we process the denture over a cast that we have prepared so it will not be like what is inside the patient mouth , but in the definitive we process on cast which represent the ptn mouth ( we do not prepare the cast , we prepare the patient tooth ,then take the impression and pour it ,so that the amount of reduction is the same as inside the patient mouth and the cast represent 100% ptn mouth )

if the overdenture is going to be a definitive prosthesis and attachments are to be used then :

1. primary impression taken of the ridge and the prepared abutments

2. metal casting will be fabricated on the first cast

3. the casting will be tried in the mouth and pickup impression is taken so our procedure will be two steps , the first one is attachment fabrication on our first impression , the second step we do pickup impression for the attachment inside the patient mouth and fabricate our denture on it .

4. the final denture is fabricated

5. the casting are then cemented and the denture is seated

Picture page 14 slide 1 here we have two canines in the mandible , in these two canines we are going to put a ball attachments , so at first we will do RCT then prepare it for post space , then take impression for the post space ( using a lentulo spiral we enter the impression material into the prepared tooth and using a wire we take the impression for the post ) , the lab will fabricate a cooping with ball attachment so we do try in and make sure that the post is fitting well , when I make sure that the post is fit we put the two posts into the ball attachment and then into the canines , then we take the impression , after I take the impression I will return the attachment into the impression which I had already took , then I pour the impression , because I picked the attachment from ptn mouth with my impression thats why we call it pick up impression , then I fabricate the over denture on the cast with attachment .

slide 2 page 14 If I want to do a bar attachment , I prepare the tooth for post and take impression for them and pour this impression so I get a cast with a space that I will fabricate the post with metal bar on the cast , I remove the bar from the cast and put it in ptn mouth , then I take another impression when the bar is placed in the patient mouth , I pour it in the lab so I get a cast with the bar on it . after that I fabricate the record block with clips on it so it attaches the bar , then I remove the attachment from the cast an insert it in ptn mouth and do bite registration on it , in the day of insertion the clips will be on the overdenture and cement the attachment in ptn mouth and insert the overdenure

maintenance

its important to arrange a programme of review appointment to allow proper maintenance of the over denture .

regular application of topical fluoride should be made to the abutments

temporary or permanent relining procedure will be required to compensate for alveolar resorption in regions where extractions were carried out at the time of fitting the denture

if cares of root surface poses a problem in spite of topical fluoride application , gold cooping can be considered as a secondary procedure

if the patient unable to control the denture as well as had been anticipated , magnets or stud attachments may be placed on the abutments to enhance retention

In long term study it was reported that treatment needs were greatest after 6 years . By that time , 36% of lower overdentures had lost stability . approximately 6% of upper and lower dentures had to be remade .

End of the lecture

BY : rokon athamneh

alaa khutaba