Effects of boron on the mechanical properties of polymethylmethacrylate denture base material.

PURPOSE: The objective of this study was to determine whether the addition of different types of boron (Borax, Boric Acid and Colemanite) to polymethyl methacrylate denture base resin would improve flexural and impact strengths, and surface hardness of polymethyl methacrylate. MATERIALS AND METHODS: Borax, Boric acid, Colemanite were added to heat polymerized polymethyl methacrylate specimens were prepared for flexural strength (65x10x2.5 mm), impact strength (50x6x4 mm), and hardness (20x6x4 mm) tests according to the manufacturers' instructions (n=10). To determine flexural strength of the specimens, they were loaded until failure on a universal testing machine using a three point bending test. Specimens were subjected to the Charpy impact test machine. Hardness of the specimens was measured with an analog shoremeter Shore D. The data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (α=0.05). RESULTS: The highest mean flexural strength value was seen in 3% Borax group and followed by 1% Colemanite group. In addition, the highest mean impact strength value was recorded in 1% Colemanite group, and differences between 1% Colemanite group and control group were found to be statistically significant (p=0,001). Furthermore, there was significant difference in hardness between control group and all other groups (p<0.001). CONCLUSION: The addition of 1% Colemanite to polymethyl methacrylate improved the mechanical properties of PMMA.

Effects of high-frequency bio-oxidative ozone therapy in temporomandibular disorder-related pain.

OBJECTIVE: It was the aim of this study to compare the efficacy of ozone therapy and drug treatment in patients with painful temporomandibular joint (TMJ) disorder (TMD). SUBJECTS AND METHODS: A total of 63 patients with TMD were enrolled; 33 were treated with bio-oxidative therapy and 30 with a ketoprofen tablet thiocolchicoside capsule 2 × 1 for 7 days. Maximum voluntary interincisal mouth opening (MMO) was measured in millimeters using a scale and recorded during the pre- and posttreatment periods. The patients evaluated their subjective pain using a visual analogue scale (VAS). Data were analyzed using the Mann-Whitney U test, the Kolmogorov-Smirnov test, and the independent t test. RESULTS: The mean MMO of the group that received ozone therapy during the pretreatment period was 46.51 ± 8.2 mm, and it immediately increased to 48.78 ± 7.5 mm after 1 week of ozone therapy, which was statistically significant (p = 0.04). For those who received medication, the mean MMO during the pretreatment period was 46.30 mm, and at the end of 1 week it was 46.9 mm. In the ozone group, 29% of patients showed a gradual decrease in their VAS pain scores compared to pretreatment values (6.3 ± 2.1 to 3.0 ± 2.2). In the medication group, 24% of patients showed a significant decrease in VAS pain scores during the follow-up period (6.9 ± 1.4 to 5.0 ± 1.5). CONCLUSION: This study showed that bio-oxidative therapy was a more effective treatment than medication therapy for relieving TMJ pain.

Evaluation of "all-on-four" concept and alternative designs with 3D finite element analysis method.

PURPOSE: The aim of the present study was to evaluate the effect of the forces on the implant and supporting alveolar ridge in "all on four" concept and alternative designs using finite element analysis. MATERIALS AND METHODS: Different treatment alternatives with various implant designs were performed in an edentulous mandible. In Design 1, implants were placed according to "All-on-Four" concept; Design 2, two long (13 mm long, 4 mm diameter) and two short (7 mm long, 4 mm diameter) implants; Design 3, four long and two short implants; and Design 4, two long and four short implants were placed vertically. A force of 100 N for each tooth, a total of 300 N load was applied. Finite element analysis was used to evaluate and compare the different designs. RESULTS: The stress concentration within the cortical bone was significantly higher than the trabecular bone around the neck of the implants. The maximum stress values were located around the cortical bone of the distal implant for all designs. The reduction in the number of implants did not diminish the success of the design. CONCLUSIONS: In the presence of vertically resorbed posterior mandibula, although the "all on four" concept is a feasible approach clinically, short implants had decreased the amount of force transmitted to the supporting bone.

Histopathological evaluation of the effects of fiber reinforced acrylic resins on living tissues.

OBJECTIVE: The aim of this study was the histopathological evaluation of the effects of the fiber reinforced acrylic resins on living tissues. MATERIALS AND METHODS: The study was performed on 21 rabbits. Three groups, each including seven subjects, were formed. There was no applied plate in the control group. For the second group, heat-polymerized acrylic resin plates were inserted. For the third group, heat-polymerized acrylic resin plates containing proportionally 5% chopped silanated E type glass fiber were inserted. Plates were fixed to the palatine bone of the rabbits with titanium screws. Before the implementation of the plates and 1 month after the plates were applied, soft tissue samples were taken from the buccal mucosa of the rabbits. Also, tissue samples were taken from the control group. All samples were evaluated histopathologically. RESULTS: In the control group, only a focal atrophy was observed. In the acrylic group, large decomposition containing erythrocytes under the parahyperkeratotic region and micro-vesicle like spongiotic tissue reactions were observed. In the fiber reinforced acrylic group, widespread focal atrophy, bulgy look of the epithelium cells similar to apoptosis, over-distension and sub-corneal decomposition had been observed. In terms of atrophy and hyperkeratosis there were no statistically significant differences among groups. However, in respect to sub-corneal decomposition, there was a statistically significant difference in the fiber reinforced group (p < 0.01). CONCLUSIONS: The statistically significant difference in the sub-corneal decomposition of the fiber reinforced group had made us think that fiber edges had a traumatic effect on the reaction.

Prevalence of respiratory abnormalities and pneumoconiosis in dental laboratory technicians.

A preventable occupational disease, pneumoconiosis that is often widespread on to a very kind of quartz, carbon and metal dust exposed work place.The data for the prevalence of pneumoconiosis and respiratory findings among dental laboratory technician is insufficient. The aim of this study is to determine the prevalence of pneumoconiosis and respiratory findings among dental laboratory technicians, working in province of Sivas. For this reason all the dental technicians (except 2, totally 36) participated in the study. A questionnaire which contains demographic characteristics, work conditions and symptoms were applied to all participants. Also spirometric measurements and chest x-rays were performed. The x-rays of dental technicians were evaluated by a radiologist and a chest disease specialist according to the ILO-2000 classification of pneumoconiosis. Almost half of the all participants have dyspnea and phlegm expectoration. The prevalence of pneumoconiosis was 5 (13.8%) among 36 dental technicians. There were no statistically significant differences between two groups with regard to respiratory symptoms. Values of lung function parameters of the dental technician group were not significantly different from those of control group except FEV(1). In conclusion, dental laboratory technicians are at significant risks for occupational respiratory diseases so the primary prevention rules are essential for these work places.