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This article describes and illustrates an alternative procedure for making an immediate removable partial denture with a metal framework and a dual path of insertion. It has several advantages over the conventional method for making immediate removable partial dentures and some disadvantages.
A technique for primary retention of removable partial dentures has been described. A soft-tissue-borne restoration provides an increase in primary retention without an increase in forces to the abutment teeth, and the restoration requires a minimal outlay of time and money.
An orderly sequence of steps for construction of an interim acrylic resin partial denture has been presented. The technique allows the dentist to fabricate an effective restoration that has a definite path of insertion and removal that can be placed in the patient's mouth with little time spent on adjustment and correction. This technique may be used with heat- or cold-curing acrylic resin.
A simplified method of removing a fixed partial denture has been described. The principle of the Class I or II lever systems is used to deliver force along the path of withdrawal. Carefully applied, this technique may permit removal of a restoration with minimal trauma to the prosthesis and supporting teeth. Where reasonable pressure fails to dislodge the restoration, it should be sacrificed rather than risk permanent damage to the abutment.
Both high- and low-heat removable partial denture alloys were soldered with combinations of different solders and heat sources. The soldered specimens were subjected to tensile strength testing, and a ranking of joint strength was developed. Joint strengths that were 85% as strong as the as-cast metal were created in both alloy types when 0.800 fine solder was used with an electrosoldering device as a heat source. All other combinations tested resulted in greater reductions in joint strength.
Several removable partial denture retainers were tested on a photoelastic cast of a human maxilla that had undergone a surgical resection through the midline. The conclusions based on the results of these tests are as follows. Physiologic adjustment of all the designs tested revealed a dramatic reduction in stresses when the framework were placed into position. Under load, the physiologically adjusted frameworks produced less potentially damaging stresses in the supporting structures than the unadjusted frameworks. High stresses were located at the premolar region for all the designs. Lingual retainers produced higher stress concentration than buccal retainers. In the anterior region, the I-bar retainer with a cingulum rest was the best combination for transmitting the occlusal forces along the long axis of the tooth. From the perspective of the equitability of stress transfer, the tested designs from best to worse are infrabulge I-bar retainer, either buccal or lingual retention; light wire circumferential retainer with buccal retention; and the circumferential cast buccal retention, swing-lock system.
This study compared the moduli of elasticity of three provisional crown and fixed partial denture resins. Eighteen specimens of each resin were reinforced with carbon graphite fibers and 18 resin specimens from each group contained no fibers. Six specimens of each resin, with and without fibers, were tested within 6 hours of fabrication, after 30 days, and after 60 days of water storage. The mean moduli of elasticity of all the resins increased significantly with fiber incorporation. Water storage did not have a significant effect on the moduli of elasticity of the resins tested.
When the master cast for a removable partial denture is lost and a well-fitting framework remains, it may be necessary to replace the master cast. A two-step impression procedure is described that combines the altered-cast technique and the use of a modified disposable tray. Finger pressure is maintained on the major connector throughout the making of both impressions, to prevent framework movement and loss of contact with prepared rest seats.
The retention of five nominally identical partial denture casting fitted to a master model was measured on an Instron testing machine in the direction of the guide planes and also at angles inclined to them. It was found that: the maximum retention was considerably reduced when the clasps were removed; the guide planes offered some frictional resistance to displacement, the magnitude being critically dependent on the fit; for frameworks with or without clasps a significant increase (P less than 0.01) in retention occurred when the pull was at 22 degrees but not at 12 degrees to the guide planes, and that there was no statistically significant difference between the retention in the forward and backward directions for either a 12 degrees or a 22 degrees tilt of the dislodging force.
Multiple-unit fixed partial dentures routinely require an intraoral index to ensure accurate fit. One of the most commonly used materials is Duralay acrylic resin, which has yielded satisfactory clinical results, but one disadvantage has been a prolonged setting time. This study compared the setting times of two autopolymerizing resins, Duralay and G. C. Pattern resin. The dimensional accuracy of these materials was also compared with one light-cured resin, G.C. Unifast light-cure resin. All three materials were suitable to relate castings with clinically acceptable outcomes, and chairside time could be saved with the use of recently introduced indexing materials.
The fracture of removable partial denture castings does not occur in a random manner but rather at characteristic sites that are determined by the designs of the castings. These sites will be located where elastic stresses resulting either from handling or from normal function are likely to be concentrated. Regions of abrupt change in cross-sectional areas and internal voids also have been shown to cause stress concentration. In many instances the regions of stress concentration that are present may act as sites for crack initiation, with fatigue as the ultimate mode of failure.
Many dentists and patients believe that removable partial dentures have an unesthetic appearance when they replace anterior teeth because of the visible clasps. Two methods of obtaining inconspicuous retention have been described.
STATEMENT OF PROBLEM: The framework of removable partial dentures often breaks where the metal retention for the resin denture base attaches to the clasp and major connector. PURPOSE: To study these failure factors, various types of three-dimensional simulated denture frameworks were designed to measure their ultimate strengths and stiffnesses under static load. This study also sought to determine which could be recommended for long-term clinical service. MATERIAL AND METHODS: Three groups of three-dimensional frameworks (double, T-shaped, and trussed structure) were designed, and two groups of classic framework designs (uniform and nonuniform skeleton) were used with an acrylic resin block as a control (n = 5 per group). Fatigue strength, stiffness and amount of strain, and free-end displacement under dynamic loads were measured for each framework. The fatigue strength was determined with a constant-loading fatigue test by counting the number of loading cycles required to induce catastrophic failure. RESULTS: With 20 kgf of load, four T-shaped samples and three trussed structure samples failed at 30,000 to 60,000 loading cycles. No samples of double structure group failed until 100,000 loading cycles. CONCLUSIONS: Three-dimensional frameworks, especially the double structure, have significant differences in fatigue strength and can provide long-term clinical service.
STATEMENT OF PROBLEM: Comprehensive restorative dental treatment often necessitates the use of interim fixed partial dentures (FPDs) with high stiffness, especially in long-span restorations or areas of heavy occlusal stress. PURPOSE: This in vitro study evaluated the fracture load of interim FPDs made with various materials and span lengths. MATERIAL AND METHODS: Groups (n = 3) of interim FPDs were fabricated with prosthodontic resin materials on 2 abutments with 3 different pontic widths of 3 units (12 mm), 4 units (19 mm), and 5 units (30 mm). The following materials were tested: (1) a thermoplastic polymer (Promysan Star), (2) Promysan Star with a veneering composite (Vita Zeta), (3) a nonimpregnated polyethylene fiber reinforced resin (Ribbond) with a veneering composite (Sinfony), (4) an impregnated fiber reinforced composite system (Targis/Vectris), and (5) a conventional polymethyl methacrylate, Biodent K+B, (control group). After 5000 thermocycles in 2 water baths at 5 degrees and 55 degrees C, the FPDs were temporarily fixed with a provisional cement on the corresponding abutments and subjected to 3-point bending until fracture by a universal testing machine. Statistical analysis consisted of an analysis of variance (ANOVA, 1-way, 2-way) and Bonferroni-Dunn's multiple comparisons post hoc analysis for test groups (alpha = .05). RESULTS: Fracture resistance (N) differed significantly for 3 (mean: 640 +/- 146 N), 4 (626 +/- 229 N), and 5 unit (658 +/- 98 N) Targis/Vectris FPDs compared with the corresponding Promysan (284 +/- 21 N to 125 +/- 73 N), Biodent K+B (247 +/- 91 N to 218 +/- 85 N), and Promysan/Vita Zeta (95 +/- 15 N to 82 +/- 6 N) groups (P < .05). Significant differences were obtained for the 4 and 5 unit Targis/Vectris FPDs compared with the Sinfony/Ribbond FPDs (281 +/- 25 N - 252 +/- 74 N) for the corresponding pontic spans. CONCLUSION: Within the limitations of this in vitro study the impregnated fiber reinforcement may considerably enhanced the fracture resistance of interim FPDs of different span lengths.
We studied the accuracy of 167 removable partial denture frameworks made in five commercial dental laboratories according to detailed instructions given by dental students, under the supervision of experienced teachers. Fewer than one half of the frameworks proved to be perfect. Some of the faults were accepted in the clinic, but 42% had to be corrected: 26% in the clinic, and 16% in the laboratory. Laboratory problems could be blamed for two-thirds of the faults, and one-third seemed to be attributable to the clinic. The advantages of, for example, new impression materials seemed to disappear under other factors.
Conveniently sized sections from six removable partial denture castings were examined metallographically for porosity. Abrupt changes in cross sectional areas were the site of porosity in some specimens; also seen were small generalized areas of porosity unlikely to be disclosed radiographically.
The metal and resin interface of removable partial dentures is weakened by the poor bond strength between the two materials. This study was designed to test the hypothesis that surface treatments--consisting of air abrasion, with aluminum oxide, tin plating and oxidation, and silanation, either alone or in combination--will improve the bond strength of acrylic resin to metal. Statistical analysis revealed that air abrasion, tin plating/oxidation, and silanation all showed significantly higher bond strength than either abrasion and tin plating, abrasion and silanation, or abrasion alone. Air abrasion demonstrated the greatest effect on improving bond strength. The mean bond strength of samples subjected to a combination of air abrasion, tin plating and oxidation, and silanation was significantly greater than any other combination treatment.
Modern understanding of the retention mechanism of partial denture assumes that the path of insertion and the path of displacement of denture form a definite angle. The denture is possible to insert in a given direction only after forming guide planes which, in the same time, possible take part in retention of denture. The aim of this work was to test the hypothesis that the preparation of guide planes and bending of models in the surveyor brings, the rigid parts of framework to increase the ability of denture to be kept on supporting tissue. The research was performed on the frameworks of denture which were of same design and models with and without preparation guide planes. Total of 60 framework removings from the vertical direction were made under the different conditions of the measurement, using universal electronic machines.