prostho sheet # 16 - Zaid M. Al-Zu’bi & Mohammed A. Okdeh.

RPD
 This lecture is an introduction to the removal partial dentures. (RPD)
Prostheses in general are of two types:
1- Removable: divided into either complete denture; in which all teeth are replaced by artificial ones, or partial dentures; in which part of the teeth (which are the missing teeth) are replaced, while the rest are intact.
• Note: when teeth are missed, the supporting tissues surrounding these teeth will be missed as well, so the denture (partial or complete) should by default replace the tooth and any other missing structures surrounding it.
• Usually, these prosthesis are supported by mucosa, teeth; in the case of the fixed dentures, or by metal implants that is implanted inside the bone holding the tooth in its position.
2- Fixed: supported by abutments; the "abutment teeth" referring to the teeth supporting the bridge.
• Note: there are certain cases in which we can’t apply the fixed bridge as a treatment, as in the case of multiple missing teeth in different quadrants, for example: upper left 1st premolaris missed with upper right 2nd molar.
• Or if there are no enough abutments to prop the bridge, so I tend to use the removable bridge instead of the fixed one.
• If the patient was a child or teenager who lost two or three of his teeth, I can’t treat him using the fixed partial denture; the support will be defected due to the immature gingiva, in addition to that, we can’t depend on the deciduous teeth as abutments.So we apply a temporary bridge “removable” until the maturation occurs, and the permanent teeth erupt, so we can apply the fixed bridge by then.
• Again and again, you should follow the patient’s desire in anyway.
• If the patient told you that he has a problem with the oral hygiene, he doesn’t take care of his teeth, or if he brushes his teeth once per month or year!! , well, you have to take this into consideration, spreading of the caries through the abutments will affect the stability of the bridge, especially if they were damaged to the extent that we have to extract them, so consequently remove the fixed bridge, and treatment failure eventually. So it’s much easier for him to use the removable bridge, simply he pull it out, clean it and return it back.
• In the case of the periodontal diseases, removable dentures can be used to fix the teeth in their position, instead of rocking, because of the poor hold.
• If the patient has a severe bone loss for any reason, for example, he had extracted his teeth for a long time, so bone resorption took place during that period. And to fix this problem, the prosthesis that you have to put has to replace the teeth, as well as the bone which has been lost.
• The patients who have very poor maxillo-mandibular relations; excessive protruded mandible, or retruded maxilla, so the teeth are not in their perfect positions to perform the ideal occlusion, and when we apply a fixed bridge, it will follow the current position of the teeth, and so no benefit gained. While the removable denture, allows you to modify the teeth positions and thus perform the desired occlusion.
• One of the most important matter in using the transitional (temporary) partial denture, is to prevent space loss; when certain teeth are missed, other teeth try to migrate, incline, decline or whateverbecause of the space that allow these movements, and consequently losing space, super eruption may occur and all relations certainly will be altered. So a very important goal of such dentures is to minimize any kind of teeth movement till the permanent treatment takes place.


 When not to use the partial dentures (RPD)?

• If the patient (young specially) doesn’t accept a removable prosthesis inside his mouth.
• If the patient has severe dental caries, or severe periodontal disease.
• If the patient lacks the control on his oral hygiene, because any prosthesis you put in his mouth whether fixed or removable, will increase plaque formation and gum inflammation.
• If the conditions of the teeth like inclination, stability, and position are not suitable to receive a removable denture, then a bridge is more preferable to be used.

 What are the benefits of the partial denture?

• As any prosthetic treatment, it revises the normal appearance, function (speech and mastication), stabilization of the occlusion plane (prevents tilting or super eruption or… etc.), and it’s considered as a transitional phase before the complete denture sets.

 What are the main components of the partial denture?
• Mainly the partial denture consists of :
- Saddle area (denture base): holds and protects the teeth.
- Connecting components: connects stuffs together; for example: the major connector connects two saddles which each other, while there is a minor connectors connect the other components with the major connector.
- Support components (occlusal rest): help the denture to transmit the forces to the surrounding tissue and therefore avoid breaking down.
- Retention: Through clasps: fix the denture during mastication.

 What are the kinds of the RPDs?
1) Permanent: made of metal (cobalt acromion) + acryl.
2) Temporary: mainly made of Acryl, it may be associated with metal and may not.



 What is the rotational access?
- It’s an imaginary access around which the denture rotates.
- The occlusal rests we talked about are considered as fulcrums; if a force is applied in front of these fulcrums, the part beyond them will lift off, and vice versa.

 General considerations when treating by RPD:
• Do not treat a patient unless there is a real indication to treat.
• Be sure that all the pieces we put (supporters and connectors) , are not in contact with the gingiva, otherwise, the gingiva inflames as a response to the pressure exerted by these components, bone resorption follows, and eventually, gingival recession takes place.
• Do not let any of the denture components to cling in between the teeth. If so, they will work as a wedge separating the teeth of each other, ending up into teeth movement.
• Again, the dentures we put inside the patients mouth increase the plaque accumulation, so you should instruct your patient to take care of his periodontal health in order to preserve the denture strength, periodontium, and oral health in general.
• The denture contributes in transmitting more forces on the teeth that hold the denture.
• Always check the occlusion while establishing the denture, any occlusal interference lead the forces to be concentrated on one area, and thus weakening and maybe crushing of that area.


Treatment planning:
Any treatment you decide to deliver in your career will have 3 main phases:
1- Preparatory phase: it's the stage in which you prepare your patient to receive the proper treatment you decided for him/her.
2- Treatment phase: it’s the treatment itself. In our case it is the removable partial denture (i.e. RPD).
3- Following up phase: to periodically check for the function and effectiveness of your treatment.
For example a patient with an inflamed gingiva, cavitated right molars and some missing teeth came to you, and after examination and patient's approval you decided to construct a removable partial denture for him. The first step according to the plan above should be filling of the cavitated teeth and scaling and polishing of the gingiva to heal the inflamed tissues. Treatment phase, the second phase, includes the steps of constructing a RPD which will be given later on. The last phase (the following up) is any procedure that aims to maintain oral health and treatment compatibility after delivery, and that includes the removal of any deposits of plaque (as the presence of the RPD in the mouth increases the rate of plaque accumulation.), the elimination of any carious attack, the prevention of inflammation and resorption of the supporting tissues (bone and gingiva), and any other procedure that deals with conditions affecting the function of the RPD.

Appointments:
like the complete denture, appointments of the partial denture begins with history and examinationand this appointment includes the medical and dental history of the patient, additional preparatory steps can be done in this appointment. Moreover a primary impression could be taken, if the oral health and environment are suitable.
You remember that impression compound was the material used in recording details of the primary impression in complete dentures, and you remember also that one of the drawbacks of this material was its rigidity that limits its use in the presence of undercuts, and as teeth in RPD provides a very good example of undercuts, this material can't be used. Thus, we use a material with an increased elasticity instead (alginate is the most used material).
Radiographs and photographs can also be taken during this session. We all know the purpose of taking radiographs, but you may ask what point of photographs is?!?!?!?!
Actually, photographs are used as documents to prove the value of what you have done! And it's used to allow your patient to compare between before and after treatment. And by this you guarantee that your work will not be underestimated, especially in the court!!
Another difference between complete dentures and partial dentures is the observation of the conditions of present teeth: position, health, mold, occlusion, shape......etc. to improve the selection of the artificial teeth to be used, and to take any abnormality into consideration.
"" LISTEN TO YOUR PATIENTS as your treatment depends on the patients' needs, not on what you want or what you think is better for your patient. Listening demarcates the line between success and failure"“(28:19).
Lab procedures that follow this first appointment are similar to those of complete dentures, from making primary casts to obtaining special trays. An additional use of the primary casts is the checking of occlusion by mounting them on the articulator. This step makes the invisible lingual surfaces of teeth visible and clear.
Partial dentures require an extra step called surveying. This step is performed via a machine called the surveyor, which is an instrument used to determine the relative parallelism of two or more surfaces of the teeth or another parts of the dental arch. We put the cast in the machine and a pencil included in the machine start to draw on the tooth and the cast, it draws a line (the survey line) that shows the maximum contour of the tooth. This drawn line helps us to decide the undercuts from non-undercut areas, so we make sure that the material used in the undercuts is resilient enough. More details will be given as we move on.

RPD design:
Many methods on how to make a RPD were introduced, but still there are some standards that everyone has agreed on.
1- The saddle: it's the part where all teeth rest.
2- Supporting components: it's the rounded pieces that rest on the occlusal surfaces of teeth (called also occlusal rest) and it gives stability to the RPD.
3- Connectors: both major and minor ones, the major connector connects between the two sides of the RPD, while the minor connectors connect the major connector and the saddle with other smaller parts.
4- Retentive component, which gives retention to the RPD. (Clasps)



* Bracing and reciprocation:
- Bracing: is the resistance of the denture to the movement from side to side horizontally or to go posteriorly. Thus any component that helps in preventing this kind of movement is known as bracing component.
- Reciprocation: is the prevention of teeth movement upon insertion or removal of the RPD, because whenever you are inserting or removing the RPD the retentive components will cause the corresponding tooth to slightly move. And this will eventually cause bone loss, bone trauma. Soft tissue loss and tooth mobility. So a reciprocal component that opposes this movement is needed.
- the 2nd appointment: includes the preparation of teeth to receive the supporting component by creating a small class II cavity in the enamel of the needed teeth.
The secondary impression should be taken during this session, and you may perform the occlusal registration if sufficient teeth are present. Then mounting of the secondary casts could be done with the transfer of the relation to the articulator.
Selection of the artificial teeth could be made, as well. and this actually is a big challenge because it's harder to match the artificial teeth appearance with real present ones, making the selection in RPD's much more harder than in complete dentures.
Obtained information and needs are now sent to the lab technician. Where he prepares the metal parts and makes the casts to be used by him.
""Treat your patient as a human being....never look to him as an etching tooth. Again it's the needs and the complaints of the patient what determine your role, not what your sense tell you. You are dealing with real people in real life...and this put dentistry in the list of highly stressful careers"".
- in the 3rd appointment we do the first try-in by trying the metal alone at first, then we set the teeth on the saddle and again try-in the RPD to check for any defect and correct any mistake. Then send it to the lab to get the completed RPD.
- the 4th appointment is the appointment in which you insert the RPD and look for any problem in occlusion, in retention....etc. and correct any problem. Then move on to home instruction on how to clean the RPD, how and when to wear it, and to train him to use it correctly. And it's very important to tell the patient not to put the RPD in acidic cleaning materials; otherwise corrosion of the metallic part will cause it to blacken. Another important rule is not to play with, modify or try to fix the RPD on his own. Otherwise the metal will end up broken or at least distorted.

- Review and Following up:
Post insertion appointments are very important in checking the denture's function and performance under continuous use.


-Prevention of problems with RPD:
To enhance the outcomes of your treatment and to increase the durability of the denture some steps may be followed:
1- Regular review and follow up.
2- Good design of the denture.
3- Denture, teeth, and oral hygiene.
All these steps will guarantee you a successful treatment and a great work.

The End

 Done by: Zaid M. Al-Zu’bi
Mohammed A. Okdeh.
 Last lecture by dr. Mahmoud Omairi

God bless you…