Immediately loaded two implants supporting a ball-retained mandibular overdenture are associated with more marginal bone resorption and increased probing depths when compared with conventionally loaded implants after 3 years. The bone resorption and probing depths at distal and labial sites are significantly higher than those at mesial and lingual sites. Clinical outcomes do not differ significantly between loading protocols.

Definite pressure impression technique for implant-retained mandibular overdenture is associated with minimal denture deformation during function when compared with mucostatic and selective pressure techniques. Reinforcement of the denture base over the implants may be recommended to increase resistance of fracture when mucostatic or selective pressure impression technique is used.

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Purpose: This study was conducted to evaluate the effect of rein forcement of different concentrations of nano-ZrO 2 and nano-Al 2 O 3 on the flexural strength and impact strength of repaired acrylic resin denture bases. Materials and Methods: A total of 100 specimens were prepared from heat-polymerized acrylic resin and then they were equally divided for the flexural and impact strength tests. 50 specimens were assigned for each testing group. For the flexural strength testing, metallic rectangular molds with rectangular-shaped (65 mm length x10 mm width x 2.5 mm thickness) were prepared. While specimens for the impact strength testing were prepared using rectangular-shaped molds with dimensions of (50 mm length x6mm width x4mm thickness). The prepared intact specimens were cut vertically in two halves along their long axis. For the flexural and impact strength testing, a repair gap was done. Specimens for each strength test were divided into one control group (specimen repaired with autopolymerizing acrylic resin with no fillers) and two repair groups with 2 concentrations (2% and 5%) of nano-ZrO 2 fillers and two repair groups with 2 concentrations (2% and 5%) of nano-Al 2 O 3 fillers. Flexural strength was measured using an Instron mechanical testing machine and impact strength was measured by Izod impact tester. Results: For the flexural strength results, the highest flexural strength was recorded with the 5% nano-ZrO 2 fillers repair group followed by the 2% nanoZrO 2 group which also recorded higher significant mean value than the control group. In both nano-Al 2 O 3 groups, there was a highly significant reduction in the flexural strength for both concentrations. For the impact strength results, the highest impact strength was recorded for the 2% nanoZrO 2 fillers repair group followed by the 5% nano-ZrO 2 group which also recorded higher significant mean values than the control group. In the 2% nano-Al 2 O 3 repair group, there was a non-significant difference in the impact strength mean values compared with the control group. While the repair group reinforced with 5% nano-Al 2 O 3 showed significant reduction in impact strength. Conclusions:The incorpora tion of nano-ZrO 2 into repair resins may improve the flexural and impact strength of the repaired denture base whereas nano-Al 2 O 3 caused reduction of both strengths.

To evaluate the effect of flexible lingual flanges on the retention of conventional mandibular complete denture. Material and methods: Ten completely edentulous patients were selected for this study with ages ranged from 50-60 years. All patients had received heat cured acrylic resin denture without modification (Group І) then heat cure lingual flanges were removed and replaced by flexible lingual flanges (Group ІІ). All patients were instructed to use their resin dentures for equal periods of three months when retention of denture base were measured after one month and at the end of three months, period of two week interval was left between each group as a washing period. results: The results of this study showed that there was a significant difference between them, as the flexible lingual flanges (group ІІ) was better than the heat cured acrylic resin denture base (group І). Conclusion: Within the limitation of this study, it was concluded that retention of the mandibular denture modified with flexible acrylic resin "versacryl" was higher than that of the conventional heat cured acrylic resin denture. Retention was increased by time in each study group. The use of flexible acrylic resin in mandibular complete dentures (as lingual flange) could be considered as an alternative effective treatment. IntroduCtIonPolymethylmethacrylate (PMMA) resin has been successfully used for various applications in dentistry for many years. It has many advantages, particularly its appearance and ease of manipulation, but it still has certain poor mechanical properties. Fractures may occur during use due to unsatisfactory impact and transverse strength. Dimensional stability is of considerable importance as a clinical problem as well. Therefore, in the clinical practice of dentistry, there are many circumstances in which the need to adjust denture base acrylic resin is necessary (1) .