Nedim Gunes

A Three Dimensional Analysis of Reconstruction Plates used in Different Mandibular Defects

ABSTRACT In this study, the reasons of breaking of the reconstruction plates used in mandibular continuity or mandibular defects were investigated. The study was conducted on 3 cases in which reconstruction plates were used for tumor resection or invasive wound. The objective was to evaluate the mechanical stress in reconstruction plates by means of the finite element method. Three dimensional model of reconstruction plate was exposed to chewing force. A commercial finite element solver (ANSYS) was then applied to this plate to compute the stresses generated in chewing situation. Stress analyses have been carried out by applying Von Mises Yielding Criteria. In the standard reconstruction plate, the results of the finite element analysis revealed that stress resulting from the simulated functional loadings which far exceeded the strengths of the components. The main application of this study was the prediction of fractures as a consequence of known forces. If it was assumed that the patient executes several thousand masticatory movements within a week, a dynamic strain would be present due to the large number of changes in loading, so that there was a danger of a fatigue fracture at the point of the stress concentration (as seen in the analysis), as is also confirmed by clinical practice.

Pentoxifylline and electromagnetic field improved bone fracture healing in rats

Background The aim of this study was to evaluate the effects of a phosphodiesterase inhibitor pentoxifylline (PTX), electromagnetic fields (EMFs), and a mixture of both materials on bone fracture healing in a rat model. Materials and methods Eighty male Wistar rats were randomly divided into four groups: Group A, femur fracture model with no treatment; Group B, femur fracture model treated with PTX 50 mg/kg/day intraperitoneal injection; Group C, femur fracture model treated with EMF 1.5±0.2 Mt/50 Hz/6 hours/day; and Group D, femur fracture model treated with PTX 50 mg/kg/day intraperitoneal injection and EMF 1.5±0.2 Mt/50 Hz/6 hours/day. Results Bone fracture healing was significantly better in Group B and Group C compared to Group A (P<0.05), but Group D did not show better bone fracture healing than Group A (P>0.05). Conclusion It can be concluded that both a specific EMF and PTX had a positive effect on bone fracture healing but when used in combination, may not be beneficial.

Long-term effects of antihypertensive medications on bone mineral density in men older than 55 years

Introduction In this study, we investigated the effects of long-term antihypertensive treatment with calcium channel blockers or beta blockers on the bone mineral density of maxilla, as determined by cone-beam computed tomography (CBCT). Material and methods This retrospective study was conducted on CBCT images of men older than 55 years who had received different dental indications. Data were grouped into three categories according to the antihypertensive medication history of the patients: group A included patients who had been taking beta-blocker treatment for more than 5 years, group B included patients who had been taking calcium channel blocker treatment for more than 5 years, and the control group included patients who had never used any hypertensive medications before. Results Statistically significant differences were observed between the beta blocker and calcium channel blocker groups. Conclusion In hypertension treatment, beta blockers may be preferred to calcium channel blockers in patients at high risk for osteoporosis and bone resorption.

Comparison of the effects of different loading locations on stresses transferred to straight and angled implant-supported zirconia frameworks: a finite element method study

The paper presents three-dimensional (3D) finite element models of straight and angled implants and their zirconium-based superstructures. The key objective was to compare the influence of different loading conditions on the stress distribution of straight and angled implants and the zirconia frameworks. 3D finite element straight- and angled-implant models of a mandibular section of bone with missing second molars and their zirconium-based superstructures were used. The straight and angled implants were 4.7 × 13-mm screw-type dental implant systems. Total loads of 300 N were applied in a vertical direction and in an oblique (30° to the vertical) direction buccolingually. Maximum and minimum von Mises stress values of the titanium structures (abutment and implant body) and zirconia frameworks were calculated. When the two groups were examined, the highest stress value was in the zirconia framework of the angled implant-supported model with an oblique loading force (731.46 MPa). The lowest stress values were concentrated in the straight implant-supported model. Thus, the stress values in the angled implant-supported crown were higher than those in the straight implant-supported model. Stress values with oblique loading forces were higher than the values with vertical loading forces. The highest stress value in the zirconia framework was similar to the ultimate strength of the zirconia.

A comparison of the effects of methylprednisolone and tenoxicam on pain, edema, and trismus after impacted lower third molar extraction.

Background The aim of the present study was to compare the effects of preemptive intravenous tenoxicam and methylprednisolone administrations on extraction of impacted third molars. Material/Methods This was a placebo-controlled, randomized, double-blind, clinical trial. A total of 60 adult patients ages 18–40 years with the complaints of impacted third molar teeth were included in the study. Results The postoperative swelling ratios (p<0.05) and pain scores (p<0.05) were significantly better in both study groups than in the control group and there was no statistically significant difference between methylprednisolone and tenoxicam groups with regards to the edema and pain relief. Conclusions Preoperative administration of 80 mg methylprednisolone achieves better control of trismus than tenoxicam without any significant differences in edema and pain control in impacted third molar teeth extraction.

Displaced lower third molar tooth into the submandibular space: Two case reports.

The aim of this article is to emphasize that the accidental displacement of a lower third molar during extraction is a rare, but potentially serious complication. We present two case reports on a lower third molar tooth dislodged into the submandibular space following its removal from the sockets and the subsequent management of this rare complication. Differences in the direction of displacement, the size of fragment, delay in retrieval, and tissue reactions can all influence this potential serious complication and hence no one technique is uniformly applicable. Though a rare complication, clinicians must be aware of possible lower third molars dislodgement into tissue spaces and the necessity to initiate prompt and appropriate management.

Systemic and local zoledronic acid treatment with hydroxyapatite bone graft: A histological and histomorphometric experimental study.

In this study, the aim was to compare the relative efficacy of systemic and local zoledronic acid (ZA) on a hydroxyapatite (HA) bone graft in a rat critical-size calvarial bone defect. In total, 84 female rats were divided into four groups: Empty control (EC) group with no treatment applied; HA group, in which only HA bone graft material was used in the calvarium; and HA plus local ZA (HA+LZA) and HA plus systemic ZA (HA+SZA) groups, in which animals received ZA locally or systemically, respectively, with HA bone graft material in the calvarium. A 5-mm standardised critical-size calvarial bone defect was created with a standard trephine drill and the respective treatment was applied. Rats were sacrificed 7, 14 and 28 days later. The numbers of osteoclasts and osteoblasts, and degree of bone formation were evaluated histopathologically and histomorphometrically. Statistically significant differences were detected between the HA, HA+LZA and HA+SZA groups and the EC group for new bone formation (P<0.05). Osteoblast numbers in the HA+LZA and HA+SZA groups were significantly higher compared with those in the EC and HA groups (P<0.05). No statistically significant difference was detected between the HA+LZA and HA+SZA groups in new bone formation or osteoblast number (P>0.05). Bone formation was significantly higher in the HA group than in the EC group (P<0.05). The numbers of osteoclasts in the HA+LZA and HA+SZA groups were significantly higher than those in the groups EC and HA (P<0.05); however, there was no significant difference between groups HA+LZA and HA+SZA (P>0.05). Within the limitations of this study, systemic or local administration of ZA enhanced new bone formation with a HA bone graft in a rat critical-size calvarial defect model.