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This manuscript attempts to discuss intracoronal and extracoronal precision attachments. A clinical technique is presented which describes the use of intracoronal precision attachments to retain maxillary and mandibular removable partial dentures. Laboratory techniques are also described in this procedure.
In a cross-sectional study the fit of direct retainers was assessed after 8 years of use. A total of 101 metal frame removable partial dentures (RPD) were investigated, including 54 extension base prostheses without any tooth supported replacement and 47 tooth supported prostheses that replaced only premolars and molars. Of the frameworks studied, about 60% of the clasps showed a space between retainers and abutments. Logistic regression analyses demonstrated that the age of the RPD and the type of opposing dentition significantly influenced the fit of the clasps. The relative risks and a backward regression analysis revealed that the variable non-rigid extension base RPD had the greatest influence on clasp fit. It was concluded that in extension base RPDs a rigid design should be preferred.
Using a representative sample of 5028 dentulous Finnish adults the occurrence of periodontal pockets was studied separately for the maxillae and the mandibles among removable partial denture (RPD) wearers and non-wearers. RPD(s) were worn in 11.2% of the 3444 maxillae with at least four natural teeth remaining, and in 7.7% of the 4706 corresponding mandibles (P less than 0.001). Periodontal pockets were more frequently observed in maxillae than mandibles. Wearing of RPDs highly significantly (P less than 0.0001) increased the odds of having periodontal pockets in general (4 mm or more) as well as the odds of having deeper periodontal pockets (exceeding 6 mm). This phenomenon was observed both in the maxillae and in the mandibles. These results suggest that wearing of RPD is a threat to periodontal tissues and that dentists should take care to frequently recall their patients fitted with RPD(s). During the recall visits more attention should be paid to the periodontal conditions of patients wearing RPD(s).
Three rosette strain gauges were attached to a fixed bilateral cantilevered crossarch maxillary bridge and one linear strain gauge to an attachment-retained removable partial denture (RPD), to study the functional deformation pattern in this combined reconstruction. The deformation under clinical conditions at maximum habitual biting and at maximum unilateral loading was very complex, with both elongation and contraction in different parts of the fixed reconstruction. Even though this complexity in the functional deformation was found both with and without the RPD incorporated, the RPD seemed to provide a more even and favorable distribution of the masticatory forces in the fixed reconstruction.
PURPOSE: The aim of this study was to analyze the techniques, production problems, and 2-year results of attachment-retained removable partial denture (RPD) treatment provided by general practitioners in Sweden. MATERIALS AND METHODS: At a major dental laboratory, consecutive cases involving new production of crowns, or of fixed partial dentures (FPDs) and RPDs retained with precision attachments, were studied. Parameters of the dentition, crown or FPD, type and brand of attachment, etc, as well as early satisfaction by dentist and patient, were recorded using specially designed forms at the dental laboratory and questionnaires for the dentists. After 2 years, questionnaires were again sent out to the dentists to record complications and patients' and dentists' opinions of the results. The sample gathered totaled 83 constructions. After 2 years, responses for 57 patients, all of whom had distal-extension RPDs, were received. Most drop-outs in the study were explicable. RESULTS: The most frequently cited reasons for using attachments were esthetics and need for crowning the teeth abutting the RPD. McCollum rigid slide attachment was the predominant brand used (43% of constructions). Dentists and patients were dissatisfied with 6% of the constructions. During the first 2 years, 22 of 57 constructions were complication-free. Seventeen had attachment complications and 9 had serious complications related to the abutment teeth or RPDs. A comparison between these 2 groups revealed that those with complications had every second abutment root-canal treated and a root post, while the group without complications had every fifth abutment root-canal treated. CONCLUSION: There were many technical and biotechnical complications and failures; the exact ratio, however, depended on the definition of "complications" and "failure." The 2-year results also deviated considerably from the dentists' opinions of the early results.
OBJECTIVE: The color stability of laboratory-made composite veneers was compared to that of artificial resin teeth under in vivo conditions. METHOD AND MATERIALS: Veneers and resin teeth of removable partial dentures were measured colorimetrically with reflection spectrophotometry; the color changes were characterized in the Commission Internationale d'Eclairage L*a*b* color space. The color was first determined 24 hours after manufacture and again after 6, 12, and 18 months at incisal, cervical, and centrofacial tooth positions. The denture teeth and veneers were measured, cleaned to eliminate the influence of surface discoloration, and measured again at every recall. The food consumption and tooth cleaning habits of the patients were taken into account. RESULTS: In all groups the maximum color changes from the baseline measurement were delta L* = 2.1, delta a* = 0.4, and delta b* = 1.8. The changes in the delta E* values were between 1.0 and 2.5 units. Despite polishing, the delta E* values increased by approximately 0.2 to 0.3 units in relation to the previous measurement with increased wearing time. External discolorations were eliminated by polishing, depending on the type of material; the maximum color change because of polishing was between 0.8 and 2.0 units for delta E*. The resin teeth showed no significant changes in the delta E* values. CONCLUSION: After a wearing period of 18 months, the discolorations of the tested materials were clinically acceptable. The artificial resin teeth showed statistically smaller color changes than did the veneering materials.
This clinical report describes the fabrication and a three-year follow-up of maxillary and mandibular cast overlay removable partial dentures for the restoration of severely worn dentition with accompanying loss of vertical dimension of occlusion. The frameworks supported porcelain veneers for esthetics, and metal occlusal surfaces for strength and durability.
The pattern and severity of root caries in a selected older population, living in the community and attending a general dental practice in Bexhill, East Sussex, England, is reported. A total of 146 patients were examined to determine the relationship among removable partial dentures, their design, and root caries. Of those patients, 57% wore removable dentures and had a higher prevalence of exposed root surfaces and root caries, particularly on abutment teeth. In addition, root caries lesions on abutment surfaces were found to be larger and more active than those on nonabutment surfaces.
PURPOSE: The purpose of this study was to evaluate denture base displacement caused by tongue movements during speech. MATERIALS AND METHODS: Ten patients with new Kennedy Class I mandibular removable partial dentures participated in this study. All prostheses were made according to a standardized protocol. Denture base displacements when speaking a test sentence were measured with a computer-aided device that was developed for this purpose. It included 4 Hall sensors, mounted on a paraocclusal splint and magnets, embedded in the denture bases. Vertical and transverse base displacements were calculated from Hall voltages. Clasp retention was measured with a dynamometer. RESULTS: Mean displacements were 145 microns seating, 72 microns unseating, 87 microns buccally, and 74 microns lingually. Seating and unseating displacements differed statistically significantly in absolute values. Mean clasp retention was 2.5 N. No correlation was found between clasp retention and unseating base displacements. CONCLUSION: Tongue movements during speech induced only minimal displacements in the dentures investigated. Additionally, tongue activity was found to be denture stabilizing rather than denture displacing in this study.
The freehand technique for preparing parallel guide planes offers several advantages. There is a direct transfer of the index from the surveyor to the mouth. The procedure adds little time to routine removable partial denture construction. The method is effective. The only disadvantage of the method is the inability of the dentist to clinically establish perfect parallelism. An occlusal divergence of 3 to 4 degrees from absolute parallelism may result. Care in making the index and increased skill will reduce inaccuracies.
Surveys of the dental profession and dental laboratories show that up to 60% of cases received by laboratories have little or no input from dentists into the design of their patients' removable partial dentures (RPD). Thus, there is a clear mandate for dental schools to teach RPD design in new ways that will give their students confidence and allow their graduates to approach the task readily and easily. This computer-aided learning program addresses that need. In designing it, we have exploited the unique properties of computers as a learning tool. The program uses Quicktime VR to simulate a three-dimensional perspective of diagnostic casts. It is also possible to incorporate animated diagrams to illustrate various points. Control of timed answers promotes the use of inquiry-based learning and allows the program to be interactive and completely problem-oriented. Students can practice at their own pace, on a variety of virtual cases, and thus learn the craft behind the art of designing RPDs. With this foundation, discussions with experts in the field regarding the patients they treat in senior years and as graduates can be conducted at a higher and more productive level. Student evaluation so far has been very encouraging.
The resin-bonded prosthesis provides an alternative for tooth replacement in that the prosthesis can be combined with other dentures. The prosthesis was used conservatively in this case, with modified abutment teeth to improve the function of the removable partial denture. Decreased expense, shorter chair time, and the noninvasive nature of the procedure make the prosthesis an option for patients with special problems.
STATEMENT OF PROBLEM: Situations may arise in dental laboratories that could result in a time lapse between preparing the wax pattern of the removable partial denture framework and its casting into the cobalt-chromium alloy. PURPOSE: This study investigated the effect of storage time of the wax pattern before casting and the influence of the palatal major connector design on the accuracy of its fit on the master casts. MATERIAL AND METHODS: Forty-two frameworks were prepared with two designs of major connectors, which were divided into three subgroups according to the storage time of the wax patterns: 24 hours, 1 week, and 1 month. Discrepancies in the fit of the connectors to their respective casts were measured at specific locations for both connector designs. RESULTS: In both framework design groups, there was a significant deterioration in fit (p < 0.0005) of the major connectors with the increase in storage time of their wax patterns on their respective refractory casts. Gap discrepancies were more pronounced towards the center of the palate. CONCLUSIONS: The greatest discrepancies appeared at the middle sections of the connectors more than at the lateral section (p < 0.0005). Furthermore, frameworks with modified palatal plate major connectors exhibited greater inaccuracies in their fit than those with the anterior posterior palatal strap design, as evidenced by the increase in mean gap discrepancies under the palatal plate design (p < 0.0005).
A 30-month follow-up study was conducted on 36 patients to evaluate the effects of the lingual plate as a major connector in distally extended removable partial dentures (RPDs) on tooth stabilization. At the same time, the study evaluated the effects of lingual plate-type RPDs and lingual bar-type RPDs on periodontal health. The most striking finding of the study was that, with the exception of gingival recession (GR), periodontal conditions improved with both types of RPDs. At the end of 30 months, there were significant differences in plaque index, GR and tooth mobility (TM) values between treatment groups (P < 0.05). Plaque accumulation was greater in the lingual plate treatment group; however, this did not result in periodontal breakdown. There were no statistically significant differences between treatment groups with respect to pocket depth, gingival index or attachment loss (P > 0.05). Moreover, patients treated with lingual plate-type RPDs demonstrated less TM when compared with patients treated with lingual bar-type RPDs at the end of 30 months follow-up. Overall study findings established that with adequate checks on oral and denture hygiene at regular intervals, patients with RPDs may even experience improved periodontal health. Moreover, the clinical interpretation of decreased TM observed in patients treated with lingual plate-type RPDs may be questionable as the plaque accumulation was greater in the lingual plate treatment group inspite of periodic recalls.
This study explores the application of computer-aided design and manufacture (CAD/CAM) to the process of electronically surveying a scanned dental cast as a prior stage to producing a sacrificial pattern for a removable partial denture (RPD) metal alloy framework. These are designed to retain artificial replacement teeth in the oral cavity. A cast produced from an impression of a patient's mouth was digitally scanned and the data converted to a three-dimensional computer file that could be read by the computer-aided design (CAD) software. Analysis and preparation were carried out in the digital environment according to established dental principles. The CAD software was then used to design the framework and generate a standard triangulation language (STL) file in preparation for its manufacture using rapid prototyping (RP) methods. Several RP methods were subsequently used to produce sacrificial patterns, which were then cast in a chromium-cobalt alloy using conventional methods and assessed for accuracy of fit. This work demonstrates that CAD/CAM techniques can be used for electronic dental cast analysis, preparation, and design of RPD frameworks. It also demonstrates that RP-produced patterns may be successfully cast using conventional methods and that the resulting frameworks can provide a satisfactory fit.
The increased emphasis on physical appearance in contemporary society has increased the demand for esthetic dental restorations. Although the success of implant dentistry has expanded the scope of esthetic fixed prostheses, many patients demand a removable partial denture (RPD) for health, anatomic, psychological, or financial reasons. Fabricating an esthetically pleasing RPD while avoiding the unsightly display associated with conventional clasp assemblies often presents a challenge to dentists. This article examines using lingual clasps, proximal undercuts (also known as rotational path insertion), and acetal resin clasps as simple and effective means of improving RPD esthetics.
The use of teeth-implant, mucosa-supported removable dentures for rehabilitation of partially edentulous patients involves highly complex biomechanical aspects. This type of prosthesis associates 3 kinds of support that react differently to the functional and parafunctional forces developed in the oral cavity. Although the construction of removable partial dentures may seem paradoxical when osseointegrated implants are placed, in some cases, this option is an excellent alternative to solve difficulties related to the anatomic, biologic, psychomotor, and financial conditions of the patient. This article reports on a case in which a teeth-implant, mucosa-supported removable partial denture was the option of choice for a patient with financial and anatomic limitations, having a large structural loss of the residual alveolar ridge caused by trauma by a gunshot injury at the mandible. The 5-year follow-up did not reveal any type of biomechanical or functional problem.
The periodontal disease variables manifested in the individuals with partial dentures were more severe, which suggests that the contribution of denture status is significant. Age, while related to increased bone loss, did not appear to be of significance. Common sense suggests that poor oral hygiene in persons wearing removable partial dentures also is a contributing factor.