Petrini Prosthodontics
Breanna Mangels
It has been more than eight decades since the introduction of polymethylmethacrylate (PMMA) in prosthetic dentistry. Despite so many advances in material science, the use of PMMA is unabated. Its ability to be molded into desired shape and biocompatibility, are significant for its success. Certain clinical conditions do however contraindicate its uses in prosthesis, and pave way for base metal alloy denture bases. These conditions are so common, yet they are missed clinically by even most astute clinicians. This case series in the form of multiple case reports provides the reader a glance into the clinical indications for metal denture bases in complete denture prosthodontics. Each case has been explained on the basis of its particular indication. The advantages and disadvantages of metal denture bases in such situations has been discussed. A case of menopause, sorption related denture changes, need for improving oral stereognostic ability and cases where poor adaptation of denture base acrylic is inevitable are key description of this article.
The functioning of a mechanical device in a biological environment requires an act of balance that depends on knowledge and understanding of both, especially the interaction of one upon the other. The biological environment of the complete denture prosthesis is not limited to the mouth since the oral mucosa that it interacts with receives input from various systems of the body. The first reaction of the oral mucosa to the complete denture prosthesis is the same as it would react to any foreign body. Besides aging, nutritional and hormonal influences affect mucosal reaction. Therefore, the response is not a static one, but it alters with time and cannot be predicted at any time of functioning. Simultaneously, the complete denture prosthesis itself is not a static entity since sorption of saliva is continuously taking place (denture base resin) and dimensional changes bring changes in occlusion. To make the matters complicated, the underlying residual alveolar bone itself keeps changing with denture use and alters the denture foundation thereby initiating a secondary response from the oral mucosa to accommodate its changes. For the last eight decades, since its introduction in 1937, 1 polymethyl methacrylate resins have been successfully used for varied dental applications since they have acceptable physical, biological and aesthetic characteristics, 2 available to a dental clinician as well as the patient at a moderate cost. There are, however relatively very less clinical indications where complete denture metal base (CDMB) is indicated over polymethyl methacrylate. Whenever, one thinks of metal bases they are related more to fabrication of major connectors in cast partial denture. Certain designs of metal bases in removable partial denture allow accommodation of bony exostoses and tori, 3 without compromising the retentive properties. In complete dentures, the use of metal denture bases is thought mostly as a medium to strengthen the denture base where frequent denture base is breaking. Advantages of alloy denture bases include its excellent strength to volume ratios which allows the complete denture base to be made thin while still maintaining rigidity and fracture resistance, 4 high thermal conductivity 5 and less interference with phonation with complete dentures. 6
This article in its form of multiple case reports reviews the indications of clinical cases where a metal denture base was fabricated for the mandibular complete denture. The article is in the form of case series that has been assimilated on the basis of each clinical indication. The aim of the case series is to clinically represent each indication for metal denture base. The article also discusses the scientific reason for doing so.
An elderly female patient aged 52 years reported with chief complaint of burning sensation while using her complete dentures that were fabricated one year back. The burning was more pronounced in the lower arch and would usually exaggerate, if she would forget to clean them over some days. The patient was a housewife by occupation and had three married children. Patients medical history was non-contributory except for the fact that she had developed xerostomia that was not related to any drug use. Patient climacteric history revealed that she had developed menopause at the age of 47 years. Dental history revealed that the patient was completely edentulous at the age of 48 years and since then she had changed three dentures along with three different dentists. The reason for frequent changing of dentures was the burning sensation that was associated with denture use. The patient also had perceived altered taste perception with use of dentures. Examination of old dentures revealed a well fabricated denture with no evidence of any vertical dimension alteration or extension of denture flanges. Retention and stability of the existing dentures was satisfactory, while the denture hygiene was not visibly good since mandibular denture had food debris accumulation on the tissue surface. Evidence of bone resorption under the denture was also visible. Extra oral and intra oral examination revealed normal clinical findings except for the presence of bony exostoses in the maxillary posterior region. The bony protuberance was within the range of 1 cm. The mucosa overlying the bony exostoses was thin. The treatment options that were presented to her was implant supported fixed complete denture, implant supported mandibular overdenture or conventional complete denture with metal denture bases. Due to economic considerations, patient opted for mandibular complete denture metal base while maxillary was to be fabricated of PMMA resin. Routine clinical and laboratory procedures for complete denture fabrication were done except for the mandibular complete denture fabrication. The design of the metal (Wiron 99; Bego, Bremen, Germany) denture base (Figure 1A) was predetermined and was cast (Figure 1B) before the recording of jaw relations. After metal trial clinically (Figure 1C), routine laboratory procedures were followed for metal denture base fabrication (Figure 1D). With a metal denture base in the mandibular complete denture prosthesis, the patient reported to have less burning sensation without alteration of taste perception.
An elderly male patient aged 62 years reported to department of prosthodontics with a chief complaint of annoyance over accumulation of food debris in the mandibular denture which he was wearing since last two years. The patient exclaimed that when food gets under the denture, he is not able to perceive it unless the food particles are big enough. Patients medical, social and drug history were non-contributory to existing condition. The existing denture made of heat cure denture base resin did not seem to have any technical or clinical drawbacks. The denture was properly polished despite which food accumulation under the denture and the sides was present. Extra oral examination disclosed a severely long maxillary lip (Figure 3A) while other clinical features were within normal limits. Intra oral examination disclosed well-formed maxillary and mandibular residual alveolar ridges. Patient was presented with various treatment options that included implant supported fixed or removable complete dentures and a new conventional complete denture with mandibular metal denture base to which the patient consented unconditionally. Routine clinical procedures for complete denture and cast metal base fabrication were done. The meshwork wax pattern (Moyco Industries, Inc, Philadelphia, PA) was used as a design for cast denture base (Figure 3B) which was sprued at multiple places. The cast metal denture base was finished, polished (Figure 3C) following which routine jaw relation procedures were done. The cast alloy was incorporated into the final denture (Figure 3D) and the denture was delivered to the patient (Figure 3E). The patient was satisfied with the outcome of the denture especially non accumulation of food debris and thermal conductivity of the new dentures.
A male patient aged 65 years reported to the department of prosthodontics for fabrication of a new denture. Patients medical history did not signify any abnormality. The patient was a farmer by occupation. Patient had been completely edentulous for last 8 years and had been wearing one complete denture during his entire tenure of complete edentulism. Extra oral examination disclosed maxillary long lip while other clinical features were normal. Intra oral examination revealed well-formed maxillary residual alveolar ridge while the mandibular ridge was resorbed. Other intra oral features were within the normal limits. The occlusal surface of the ridge was wavy with some areas higher than the other (at four places). Irregularity of the mandibular residual alveolar ridge was also present in the lateral direction. Treatment options given to the patient was an implant supported fixed or removable prosthesis which was rejected due to economic issues. The second option he consented was maxillary and mandibular complete denture with mandibular denture having a hybrid of metal and resin denture base. Routine clinical and laboratory procedures for the fabrication of complete denture were performed. A metal denture base (Wiron 99; Bego, Bremen, Germany) was tried in the patient mouth for adaptation (Figure 4A). Teeth were then arranged on casts mounted on a semi adjustable articulator (Artex; Girrbach Dental) (Figure 4B) following which a trial was done. Final denture was processed with heat cure denture base resin (DPI, India) (Figure 4C) and denture was then delivered to the patient who reported at his follow up that he was satisfied with the outcome of the treatment.
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