Sedat Güven

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.

Evaluation of stress distributions in peri-implant and periodontal bone tissues in 3- and 5-unit tooth and implant-supported fixed zirconia restorations by finite elements analysis

Objective: In this study, it is aimed to compare the distribution of stress on periodontal and peri-implant bone tissues in 3- and 5-unit-dental and implant-supported zirconia restorations using finite element analysis. Materials and Methods: Stress distribution formed in periodontal and peri-implant bone tissues as a result of chewing forces was analyzed in dental and implant-supported three-dimensional (3D) finite element models of zirconia restoration with 5-unit placed on the numbers of 43, 44, 45, 46, and 47 and with 3-unit placed on the number of 45, 46, and 47. Four different loading conditions were used. 200 Nforce was applied in 30° from the buccal inclination of number 43, 45, and 47 restorations separately and totally 850 Nforce was applied in 30° from the buccal inclination of whole restoration. The study was performed through static nonlinear analysis with the 3D finite element analysis method. Results: Stress accumulation in bone tissues in the tooth-supported model was found less than in implant-supported models. Stress accumulation was observed in the cervical portion of the implant in implant-supported models, and stress accumulation was observed surrounding bone of roots in tooth-supported models. The highest stress values were occurred in 5 unit implant-supported model in all loadings. Conclusion: In posterior restorations increased in the number of supported teeth and implant can reduce the destructive forces on periodontal and peri-implant bone tissues and may allow longer period retention of the restorations in the mouth.

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.

Three-dimensional finite-element analysis of a single implant-supported zirconia framework and its effect on stress distribution in D4 (maxilla) and D2 (mandible) bone quality

The aim of this in-silico study was to compare stress distributions in implants and zirconia frameworks of mandibular and maxillary implant-supported crowns. For comparison, vertical and oblique loading forces were used. Three-dimensional finite-element implant models of a mandibular section of bone (D2) and a maxillary section of bone (D4) with missing second molars and their zirconium-based superstructures were used. Zimmer dental implants of 13 mm in length and 4.7 mm in diameter were modelled. A load of 200 N was applied toward vertical and oblique (30° to the vertical) directions. Maximum and minimum von Mises stress values of the implants and the zirconia framework were calculated. The highest stress value was concentrated in the zirconia framework of the maxillary implant-supported model with the oblique loading force (301.17 MPa). The lowest stress value was concentrated in the mandibular implant-supported model. And the stress values in the maxilla were higher than in the mandible. The maxilla (D4) showed higher stress values than in the mandible (D2), because the trabecular bone is weaker and less resistant to deformation than the cortical bone. Stress values with oblique loading forces were higher than with vertical loading forces. Because of the high Youngs modulus of zirconia (low elastic properties), zirconia frameworks showed higher stress values than the implants.

Three-dimensional finite-element analysis of two ceramic inlay restorations with different cavity designs

The aim of this in silico investigation was to examine the influence of two ceramic inlay materials with different cavity designs on stresses in the inlay. Finite-element analysis and three-dimensional modelling were used to examine the stress in ceramic inlays resulting from a 250-N point load on occlusal surfaces. The adhesion properties and von Mises stress values in the enamel, dentin, ceramic materials and cement linings were simulated. Two ceramic inlay materials: porcelain ceramic (Empress II, Ivoclar Vivadent, Liechtenstein) and zirconia ceramic (ICE Zirkon, Zirkonzahn SRL, Gais, Italy), as well as two cavity corner designs: rectangular and rounded, were evaluated. The obtained von Mises stress results indicated that the maximum and minimum forces were concentrated in the enamel and dentin, respectively. The stress values in the dentin and inlay material were similar in the porcelain ceramic and zirconia ceramic groups. However, in the enamel, the stress values in the zirconia ceramic group were significantly lower than those in the porcelain ceramic group. Additionally, cavities with rounded corners were subject to significantly less stress compared to those with rectangular corners. Thus, the zirconia ceramic inlay demonstrated better performance under applied stress, based on the reduced stress values in the tooth structure. Cavities with rounded corners showed less stress than those with rectangular corners, which could be attributed to the enhanced stress distribution capabilities of rounded corners.

Evaluation of mental foramen location in the 10–70 years age range using cone‑beam computed tomography

Introduction: Mental foramen (MF) locations were determined according to gender and age in terms of the vertical distance from the surrounding anatomical structures and the vertical and horizontal size of the MF. Materials and Methods: One hundred-seven male and 103 female patients in the age group between 10 and 70 years were included in our retrospective study and were examined using cone-beam computed tomography (CBCT). The right and the left MF locations were determined from panoramic and cross-sectional images. On the cross-sectional CBCT images, the distance of the MF upper limit from the alveolar crest edge, the distance of the MF lower limit from the lower edge of the mandible, and vertical size of the MF were measured. Results: MF location differed in males and females (P < 0.001); it was generally located at the first and second premolar in females, and at the level of the second premolar in males. However, the MF location was not different on the right and left sides (P = 0.436). The distance of the MF from the surrounding anatomic structures were found to be lower in females than in males in all measurements (P < 0.001). The horizontal size of the MF was found to be less on the left side (P < 0.001). Conclusions: Knowing both the position and the distance of the MF from the surrounding anatomical structures is not only useful information for surgery, but will also help avoid complications such as paresthesia.

Examination of stress distribution and fracture resistance in five-unit tooth- and implant-supported partial fixed zirconia prosthesis

In this study, stress distribution and fracture strength values of zirconia frameworks were compared in five-unit tooth- and implant-supported fixed zirconia prosthesis. Three-dimensional finite element stress analysis and static non-linear analysis were used. Because of the boundary conditions determined for these methods, the tooth- and implant-supported models only included the regions of tooth numbers 43–47. The highest stress value (901.845 MPa) was measured in Model 1 (five-unit tooth-supported fixed zirconia bridge) at the mesial gingival neck area of restoration number 45. This stress value was within the ultimate strength of zirconia (900–1200 MPa). Stress values for connector regions were not in the ultimate strength value of zirconia. Stress values in the tooth-supported fixed zirconia bridge were more than the values in the implant-supported fixed zirconia bridge. The highest stresses in Model 2 (five-unit implant-supported fixed zirconia bridge) occurred in the restoration that the model was installed on. The obtained results showed that five-unit tooth-supported posterior zirconia fixed bridge prostheses are not recommended and that the second premolar region is most seriously affected in terms of stress.

MANYETİK REZONANS GÖRÜNTÜLEMENİN DİŞ HEKİMLİĞİNDE KULLANIMI VE DENTAL MATERYALLERE ETKİLERİ

Radyolojik goruntuleme yontemlerinden biri olan Man- yetik Rezonans Goruntuleme, hastaliklarin tanisina cok onemli katkilari bulunmasindan dolayi yaygin bir sekil- de medikal alanda kullanilmaktadir. Bu goruntuleme tekniginde kuvvetli manyetik alan olusmasi ve vucutta bulunan metalik objelerin bu manyetik alandan etkile- simleri hasta acisindan potansiyel saglik riskleri olustu- rabilmektedir. Dis hekimligi alaninda yaygin bir sekilde kullanilan Dental implantlar, Ortodontik braketler ve teller, Metal destekli sabit ve hareketli restorasyonlar vb. gibi iceriginde metal bulunan objelerin varliginda Manyetik Rezonans Goruntulemesi esnasinda olusabi- lecek manyetik alan etkilesimlerinin yeterince bilinmesi gerekir. Goruntuleme esnasinda hasta acisindan olusa- bilecek riskleri en asgari duzeye indirebilmek icin vu- cutta bulunan ve manyetik alandan etkilenen metalik objeler ile ilgili gerekli tedbirlerin alinmasi gerekir. Anahtar Kelimeler: Manyetik Rezonans Goruntuleme, dental alasimlar, manyetik alan etkilesimi MAGNETIC RESONANCE IMAGING IN DENTISTRY AND ITS EFFECT ON DENTAL MATERIALS ABSTRACT Magnetic resonance imaging (MRI) is one of the radiologic imaging techniques, using widely in medical field due to significant contribution to the diagnosis of diseases. Formation of the strong magnetic field and its interaction with metallic objects in the body may cause potential risks for patient. In the presence of metal containing objets in dentistry such as dental implants, orthodontic brackets and wires, metal-supported fixed and removable restorations, adequate information about the features of magnetic field and its interaction with the metallic objects should be known. To take necessary measures related with the magnetic field interactions, will reduced risk level during imaging. Keywords: Magnetic Rezonance Imaging, dental alloys, magnetic field interactions

Effects of crown retrieval on implants and the surrounding bone: a finite element analysis

PURPOSE The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal. MATERIALS AND METHODS Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant (3.7 mm × 10 mm) with a straight abutment, and the other model was designed as a 30-degree inclined implant (3.7 mm × 10 mm) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone. RESULTS The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment. CONCLUSION The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations. CLINICAL IMPLICATIONS These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.

Measuring the resistance of different substructure materials by sticking them to dentine with two different resin cements in vitro

INTRODUCTION The resistance of three different substructure materials - metal (Cr-Co), zirconium (Zr), and ceramics (IPS Empress II) - was measured by sticking them to dentine with two different resin cements, a dual-cure resin cement (Panavia F 2.0 Light) and a self-adhesive resin cement (BisCem). MATERIALS AND METHODS In an in vitro study, 72 central upper front teeth were selected with no decay or apparent breakage and with complete development, removed for periodontal reasons. Labial and incisal surfaces of all teeth were prepared. Molds were obtained to prepare metal (Co-Cr), Zr, and ceramic (IPS Empress II) blocks for use in the study. The compressive strengths of the obtained material infrastructures were examined after thermal cycle processing by performing cementation to the teeth with two different cements. The data obtained were analyzed statistically. The Mann-Whitney U-test was used for comparisons of the groups with two options, and Kruskal-Wallis variance analysis was used to compare more than two groups. P<0.05 were considered statistically significant. RESULTS While the highest result between samples was 117.86 ± 47.94 N in the dual-cure (Panavia)-ceramic group, the lowest value was observed at 6.53 ± 3.12 N in the self-adhesive (BisCem)-metal group. There was a significant difference between dual-cure (Panavia) and self-adhesive (BisCem) groups. CONCLUSION In this study, we measured the bond strength; our most durable resistance groups were found to be, in order, Panavia-ceramics >Panavia-metal >Panavia-Zr >self-adhesive-ceramics >self-adhesive-Zr >and self-adhesive-metal.