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    Effect of different framework materials of resin-bonded bridges on load to fracture values and stress distribution
    (Wolters Kluwer Medknow Publications, 2018) Baran, Ilgi; Arslan, Merve; Gungor, Hamiyet
    Purpose: The aim of this study was to compare in vitro fracture strengths (FSs) of metal- and fiber-reinforced frameworks of resin-bonded bridges and to evaluate stress distribution with finite element analysis (FEA). Materials and Methods: Totally 80 extracted maxillary central and maxillary canine teeth were used for in vitro part of this study as two groups; metal-reinforced framework (n = 20) [(metal-supported resin-bonded bridge (MR-RB)] and fiber-reinforced frameworks (n = 20) [fiber-reinforced resin-bonded bridge (FR-RB) were prepared for three unit resin-bonded bridges. All bridges were loaded from lateral pontic at 1 mm/min crosshead speed and fracture values were recorded. MannuWhitney U-test was used for statistical analysis, and fracture patterns were evaluated visually. FEA was carried out in the second part of the study, and stress distribution of MR-RB and FR-RB structures was analyzed using one of the models from in vitro specimens as main model. Results: The mean FSs of MR-RB and FR-RB were 637.47 151.91 N and 224.86 80.97 N, respectively. Fiber-reinforced specimens were found to distribute stress more homogeneous and connectors in each framework were the regions where stress concentrated mostly. Conclusion: In vitro FSs of MR-RB and the stress concentration of the point that the forces were applied were higher as compared to other parts of the restoration. Furthermore, in contrast to FR-RB specimens, retainer tooth fractures were observed in MR-RB specimens.
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    Influence of Cantilever Extension and Crown-to-Implant Ratio in Posterior Maxilla: A Finite Element Analysis
    (Amer Scientific Publishers, 2018) Gungor, Hamiyet; Baran, Ilgi; Karaagaclioglu, Lale
    This study aimed to evaluate the effect of increased cantilever extension length and crown-to-implant ratio on stress distributions, both in peri-implant bone and implant structure under oblique loads, using three-dimensional finite element analysis method. Six three-dimensional models of an atrophic posterior maxilla were created with a solid implant (4.1 x 10 mm) placed in first maxillar premolar site. One implant supported two-unit fixed dental prostheses were modeled using three different cantilever extension lengths (5, 7 and 9 mm) and two different crown-to-implant ratio (1/1 and 1.5/1). An oblique load of 300 N was applied to each model. The minimum and maximum principal stresses and von Mises stresses were evaluated. The highest minimum principal stress value was 129.8 MPa in cortical bone and the highest von Mises stress value at the implant structure was 449.3 MPa. Regarding the simulation outcomes it can be concluded that increasing cantilever extension length and crown-to-implant ratio will also increase the stress distribution in peri-implant bone and implant structure. While crown-to-implant ratio has greater effect than cantilever extension length in the stress concentration in cortical bone, cantilever extension length is found to be more prominent stress factor for the implant structure.
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    Management of Limited Vertical Bone Height in the Posterior Mandible: Short Dental Implants Versus Nerve Lateralization With Standard Length Implants
    (Lippincott Williams & Wilkins, 2016) Dursun, Erhan; Keceli, Huseyin Gencay; Uysal, Serdar; Gungor, Hamiyet; Muhtarogullari, Mehmet; Tozum, Tolga Fikret
    Inferior alveolar nerve lateralization (IANL) and short dental implants (SDI) are 2 viable implant-based treatment approaches in the presence of atrophied posterior mandible. Despite the risks of dysfunction, infection, and pathologic fractures in IANL, it becomes possible to place standard implants. The purpose of this study was to compare SDI and IANL approaches from clinical and radiographic aspects. Fifteen subjects having unilateral atrophic mandibles were allocated to SDI and IANL treatment groups. Following surgical procedures, early postoperative complications, implant survival, and periimplant clinical and radiographic parameters including probing pocket depth, attachment level, keratinized tissue amount, vertical tissue recession, and marginal bone loss were recorded at baseline and 1-year after prosthetic rehabilitation. In both groups, no implant was lost. Except usual postoperative complications, 2 patients had transient paraesthesia after IANL. According to time-dependent evaluation, both groups showed significant increase in probing pocket depth and attachment level at 1-year follow-upcompared with baseline (P < 0.05). Except a slight but significant increase in mesial surface of SDI group (P < 0.05), no remarkable time-dependent change was identified in vertical tissue recession. Keratinized tissue amount did not exhibit any inter-or intragroup difference during whole study period. Marginal bone loss did not show any difference between IANLand SDI groups at follow-up. SDI placement or standard length implant placement with IANL can be considered promising alternatives in the treatment of atrophic mandibular posterior regions. However, SDI may be preferred in terms of lower complication risk.