Derya Ozdemir Dogan

Purpose: To assess the fracture resistance of single‐tooth implant‐supported crown restorations made with different CAD/CAM blocks.Materials and Methods: Thirty‐six titanium abutments were put on dental implant analogs (Mis Implant). For each of three test groups (n = 12/group), implant‐supported, cement‐retained mandibular molar single crowns were produced. Crowns were made of lithium disilicate glass (LD) IPS e.max CAD, feldspathic glass ceramic (FEL) Vita Mark II, and resin nano‐ceramic (RNC) Lava Ultimate. The crowns were cemented with self‐adhesive resin cement RelyX Unicem 2. After chewing cycling, crowns were tested to failure in a universal testing machine. Fracture values were calculated as initial (F‐initial) and maximum fracture (F‐max).Results: The study groups were ranked, in order of having highest value, (LD > FEL) > RNC for F‐initial load value and (LD > RNC) > FEL for F‐max load value. This demonstrated that there was no parallel change in the F‐initial and F‐max values presenting the fracture resistance of specimens.Conclusions: There was no accordance between the F‐initial and F‐max values of the LD, RNC, and FEL after chewing simulation with thermocycling resembling 5 years of clinical functional use. LD had the highest fracture resistance during the fracture test. RNC had low fracture resistance; however, it had considerably high fracture resistance during the fracture test. FEL had considerably low fracture resistance values.

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.

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.

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.