Preparation of composite retentive areas for removable partial denture retainers

A method is presented in which light-polymerized composite material is used to obtain retention for a removable partial denture when usable natural tooth undercuts are unavailable. The desired contour is waxed on a diagnostic cast with the use of a surveyor, captured in a light-polymerizing temporary restorative material, and reproduced in composite resin on the abutment teeth.

Effects of chemical disinfectants on the transverse strength of denture base acrylic resins

The disinfection of dental prostheses by immersion in a chemical solution should be capable of rapid inactivation of pathogenic microorganisms, without causing any adverse effect on the denture base resins. This study evaluated the effect of disinfection immersion on the transverse strength of two heat-cured resins. The denture base resins (Lucitone 550 and QC 20) were polymerized according to the manufacturers' instructions. After polymerization, the specimens were polished, and then stored in water at 37 degreesC for 50 +/- 2 h prior immersion in one of the following solutions for 10 min: 4% chlorhexidine, 1% sodium hypochlorite and 3.78% sodium perborate. The specimens were submitted to disinfection twice, simulating when dentures come from the patient and before being returned to the patient. Ten specimens were made for each group. The transverse strength was evaluated by a 3-point bend test. The flexural strength of the two denture base acrylic resins evaluated remained unaffected after immersion in the three solutions evaluated. In general, the QC 20 resin specimens exhibited lower transverse strength than the Lucitone 550 resin specimens, regardless of immersion solutions.

Flexural strength of autopolymerizing denture reline resins with microwave postpolymerization treatment

Statement of problem. Microwave postpolymerization has been Suggested as a method to improve the mechanical strength of repaired denture base materials. However, the effect of microwave heating oil the flexural strength of the autopolymerizing denture reline resins has not been investigated.Purpose. This study analyzed the effect of microwave postpolymerization on the flexural strength of 4 autopolymerizing reline resins (Duraliner II, Kooliner, Ufi Gel Hard, and Tokuso Rebase Fast) and 1 heat-polymerized resin (Lucitone 550).Material and methods. For each material, 80 specimens (64 X 10 X 3.3 mm) were polymerized according to the manufacturer's instructions and divided into 10 groups (n = 8). Control group specimens remained as processed. Before testing, the specimens were Subjected to postpolymerization in a microwave oven using different power (500, 5,50, or 650 W) and time (3, 4, or 5 Minutes) settings. Load measurements (newtons) were made at a crosshead speed of 5 mm/min using a 3-point bending device with a span of 50 mill. The flexural strength values were calculated in MPa. Data analyses included 3-way and 2-way analysis of variance and the Tukey Honestly Significant Difference test (alpha=.05).Results. The flexural strengths of resins Duraliner 11 and Kooliner were significantly increased (P=.0015 and P=.0046, respectively) with the application of microwave irradiation using different time/power combinations. The materials Lucitone 550, Tokuso Rebase Fast, and Ufi Gel Hard demonstrated no significant strength improvement compared to the corresponding control. Only after microwave postpolymerization irradiation for 3 minutes at 550 W did Lucitione 550 show significantly higher flexural strength than Tokuso Rebase Fast and Ufi Gel Hard relining resins.Conclusion. Microwave postpolymerization irradiation can be an effective method for increasing the flexural strength of Duraliner II (at 650 W) and Kooliner (at 550 W and 650 W for 5 minutes).

Study of denture-induced fibrous hyperplasia cases diagnosed from 1979 to 2001

Objective: the purpose of this research was to study the cases of inflammatory fibrous hyperplasia (IFH) at the Clinic of Semiology, Department of Bioscience and Oral Diagnosis, Sao Jose dos Campos Dental School, State University of São Paulo, Brazil. Methods and materials: A total of 141 clinical file cards indicating a final diagnosis of IFH, from the archives of the Department of Bioscience and Oral Diagnosis and dated from 1979 to 2001, were included in the study. of these files, 50 indicated a diagnosis of denture-induced fibrous hyperplasia. Sex, age, race, duration, and clinical features that confirm their classification in the non-neoplastic proliferating process were analyzed statistically. Results: of the 50 analyzed cases of denture-induced lesion, 22% occurred in men and 78% in women. Patients in the age group of 41 to 50 years presented the highest frequency of the lesion. Conclusions: Inflammatory fibrous hyperplasia occurs more frequently in women (71.63%), and denture-induced lesions appear mainly in patients over 40 years of age (70% of cases). Patients with denture-induced hyperplasia reported pain associated with the lesion (70%).

Clinical evaluation of abutment teeth of removable partial denture by means of the Periotest method

Prosthodontics should be one of the means of establishing conditions for the maintenance of periodontal health. The forces applied to the abutment teeth and their effects are very important considerations in the design and construction of the removable partial dentures. This 6-month follow-up clinical study evaluated the degree of mobility of abutment teeth of distal extension and tooth supported removable partial dentures by using Periotest. Two types of clasp design were selected for evaluation. In cases with unilateral and bilateral distal-extension, a clasp design including a T clasp of Roach retentive arm, a rigid reciprocal arm and a mesial rest were used. For the abutments of tooth-supported removable partial dentures, a second clasp design with a cast circumferential buccal retentive arm, a rigid reciprocal clasp arm and a rest adjacent to the edentulous ridges was selected. A total of 68 abutment teeth was analysed. Periotest values were made at the time of denture placement (control) and at 1, 3 and 6 months after the denture placement. The statistical analysis was performed using Friedman test. All analysis was performed at a 0.05 level of significance. The results revelled that no significant changes in tooth mobility were observed during the 6-months follow-up (P > 0.05). In conclusion, our findings suggest that adequate oral hygiene instructions, careful prosthetic treatment planning and regular recall appointments play an important role in preventing changes in abutment tooth mobility caused by removable partial denture placement.

Effect of microwave sterilization and water storage on the Vickers hardness of acrylic resin denture teeth

Statement of problem. Acrylic resin denture teeth soften upon immersion in water, and the heating generated during microwave sterilization may enhance this process.Purpose. Six brands of acrylic resin denture teeth were investigated with respect to the effect of microwave sterilization and water immersion on Vickers hardness (VHN).Material and Methods. The acrylic resin denture teeth (Dentron [D], Vipi Dent Plus [V], Postaris [P], Biolux [B], Trilux [T], and Artiplus [A]) were embedded in heat-polymerized acrylic resin within polyvinylchloride tubes. For each brand, the occlusal surfaces of 32 identical acrylic resin denture posterior teeth were ground flat with 1500-grit silicon carbide paper and polished on a wet polishing wheel with a slurry of tin oxide. Hardness tests were performed after polishing (control group, C) after polishing followed by 2 cycles of microwave sterilization at 650 W for 6 minutes (MwS group), after polishing followed by 90-day immersion in water (90-day Wim group), and after polishing followed by 90-day storage in water and 2 cycles of microwave sterilization (90-day Wim + MwS group). For each specimen, 8 hardness measurements were made and the mean was calculated. Data were analyzed with a 2-way analysis of variance followed by the Bonferroni procedure to determine any significance between pairs of mean values (alpha=.01).Results: Mircrowave sterilization of specimens significantly decreased (P <.001) the hardness of the acrylic resin denture tooth specimens P (17.8 to 16.6 VHN, V (18.3 to 15.8 VHN), T (17.4 to 15.3 VHN), B (16.8 to 15.7 VHN), and A (17.3 to 15.7 VHN). For all acrylic resin denture teeth, no significant differences in hardness were found between the groups Mws, 90-day Wim, and 90-day Wim + MwS, with the exception of the 90-day Wim + MwS tooth A specimens (14.4 VHN), which demonstrated significant lower mean values (P <.001) than the 90-day Wim (15.8 VHN) and MwS (15.7 VHN) specimens.Conclusions. For specimens immersed in water for 90 days, 2 cycles of microwave sterilization had no effect on the hardness of most of the acrylic resin denture teeth.

Composite occlusal surfaces for acrylic resin denture teeth

Acrylic resin denture teeth often exhibit rapid occlusal wear, which may lead to a loss of chewing efficiency and a loss of vertical dimension of occlusion. The use of metal occlusal surfaces on the acrylic resin denture teeth will minimize occlusal wear. Several articles have described methods to construct metal occlusal surfaces; however, these methods are time-consuming, costly, and sometimes considered to be unesthetic. These methods also require that the patient be without the prosthesis for the time necessary to perform the laboratory procedures. This article presents a quick, simple, and relatively inexpensive procedure for construction of composite occlusal surfaces on complete and partial dentures.

Thermal behaviour of polymetallic metal carbonyls with Fe-Fe, Fe-Hg and Hg-Hg bonds containing Lewis bases.

The thermal behaviour of polymetallic metal carbonyls containing Fe-Fe, Fe-Hg and Hg-Hg bonds and Lewis bases, such as [Fe-3(CO)(8)(L)(2)] (L = 1,10-phenantroline,2,2'-bipyridine), [Fe(CO)(4)(HgCl)(2)] and [Fe(CO)(4)(HgCl)(2)(L)(2)] (L = 1,10-phenantroline,2-quinolinethiol), have been investigated by thermal analysis (TG), Thermal studies give evidence that the thermal decomposition mechanisms and starting temperatures are strongly influenced by the Lewis bases. The thermal decompositions under synthetic air yielded, in all cases, the final solid product Fe2O3 which presence was confirmed by X-ray powder diffraction technique.