Bulent Piskin

Annealing of Co-Cr dental alloy: effects on nanostructure and Rockwell hardness.

PURPOSE The aim of the study was to evaluate the effect of annealing on the nanostructure and hardness of Co-Cr metal ceramic samples that were fabricated with a direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS Five groups of Co-Cr dental alloy samples were manufactured in a rectangular form measuring 4 × 2 × 2 mm. Samples fabricated by a conventional casting technique (Group I) and prefabricated milling blanks (Group II) were examined as conventional technique groups. The DMLS samples were randomly divided into three groups as not annealed (Group III), annealed in argon atmosphere (Group IV), or annealed in oxygen atmosphere (Group V). The nanostructure was examined with the small-angle X-ray scattering method. The Rockwell hardness test was used to measure the hardness changes in each group, and the means and standard deviations were statistically analyzed by one-way ANOVA for comparison of continuous variables and Tukeys HSD test was used for post hoc analysis. P values of <.05 were accepted as statistically significant. RESULTS The general nanostructures of the samples were composed of small spherical entities stacked atop one another in dendritic form. All groups also displayed different hardness values depending on the manufacturing technique. The annealing procedure and environment directly affected both the nanostructure and hardness of the Co-Cr alloy. Group III exhibited a non-homogeneous structure and increased hardness (48.16 ± 3.02 HRC) because the annealing process was incomplete and the inner stress was not relieved. Annealing in argon atmosphere of Group IV not only relieved the inner stresses but also decreased the hardness (27.40 ± 3.98 HRC). The results of fitting function presented that Group IV was the most homogeneous product as the minimum bilayer thickness was measured (7.11 Å). CONCLUSION After the manufacturing with DMLS technique, annealing in argon atmosphere is an essential process for Co-Cr metal ceramic substructures. The dentists should be familiar with the materials that are used in clinic for prosthodontics treatments.

Florid cemento-osseous dysplasia: a case report

Florid cemento-osseous dysplasia (FCOD) has been described as a condition that characteristically affects the jaws of middle-aged black women. It usually exhibits as multiple radiopaque cemetum-like masses distributed throughout the jaws. Radiographically, FCOD appears as dense, lobulated masses, often symmetrically located in various regions of the jaws. Computed tomography, because of its ability to give axial, sagittal, and frontal views, is useful in the evaluation of these lesions. This paper presents the case of a patient who was diagnosed with FCOD on the basis of clinical and radiographic findings.

Conventional multi-slice computed tomography (CT) and cone-beam CT (CBCT) for computer-aided implant placement. Part II: reliability of mucosa-supported stereolithographic guides.

PURPOSE Deviations of implants that were placed by conventional computed tomography (CT)- or cone beam CT (CBCT)-derived mucosa-supported stereolithographic (SLA) surgical guides were analyzed in this study. MATERIALS AND METHODS Eleven patients were randomly scanned by a multi-slice CT (CT group) or a CBCT scanner (CBCT group). A total of 108 implants were planned on the software and placed using SLA guides. A new CT or CBCT scan was obtained and merged with the planning data to identify the deviations between the planned and placed implants. Results were analyzed by Mann-Whitney U test and multiple regressions (p < .05). RESULTS Mean angular and linear deviations in the CT group were 3.30° (SD 0.36), and 0.75 (SD 0.32) and 0.80 mm (SD 0.35) at the implant shoulder and tip, respectively. In the CBCT group, mean angular and linear deviations were 3.47° (SD 0.37), and 0.81 (SD 0.32) and 0.87 mm (SD 0.32) at the implant shoulder and tip, respectively. No statistically significant differences were detected between the CT and CBCT groups (p = .169 and p = .551, p = .113 for angular and linear deviations, respectively). CONCLUSIONS Implant placement via CT- or CBCT-derived mucosa-supported SLA guides yielded similar deviation values. Results should be confirmed on alternative CBCT scanners.

Efficacy of a modified mandibular advancement device for a totally edentulous patient with severe obstructive sleep apnea

BackgroundIt has been asserted that the success rate of oral appliances was more satisfactory for mild to moderate obstructive sleep apnea (OSA) than severe ones; besides, there is a lack of literature about mandibular advancement device (MAD) application for edentulous patients with OSA.ReportThis clinical case shows fabrication method and treatment efficacy of a modified MAD, which is aiming to displace bulky masseter muscles laterally, to provide more space for tongue on totally edentulous patient with severe OSA.

Adhesion between glass fiber posts and resin cement: evaluation of bond strength after various pre-treatments

Abstract Purpose. To evaluate surface roughness and bond strength of glass fiber posts to a resin cement after various surface treatments. Materials and methods. Sixty individually formed glass fiber posts with a diameter of 1.5 mm and a length of 20 mm were used for this study. They were randomly assigned to six groups of pre-treatment (n = 10/group): Group C, untreated (control); Group SB, sandblasted; Group SC, silica coated; Group HF, hydrofluoric acid-etched; Group N, Nd:YAG laser irradiated; Group E, Er:YAG laser irradiated. Surface roughness of the posts was measured before and after pre-treatment. The posts were then bonded to resin cement and tensile bond strengths were determined in a universal testing machine. For statistical analysis, two-way ANOVA and post-hoc comparison tests (α = 0.05) were performed. Results. The highest bond strength value was observed in group HF, followed by group SC. There was a statistically significant difference in bond strength between group C and groups HF, SC and E (p < 0.001, p = 0.002 and p = 0.041, respectively). Posts of group SB and group N showed the highest surface roughness. Conclusions. The findings of the present study reveal that hydrofluoric acid-etching, silica coating and Er:YAG laser irradiation provided a significant increase in bond strength between glass fiber posts and resin cement.

Radiofrequency heating and magnetic field interactions of fixed partial dentures during 3-tesla magnetic resonance imaging

OBJECTIVE This study evaluated the heating and magnetic field interactions of fixed partial dentures in a 3-Tesla (3T) magnetic resonance imaging (MRI) environment. STUDY DESIGN Three substructure materials (Co-Cr, Ni-Cr, ZrO₂) were used to fabricate twelve 4-retained bridges and 12 crowns. Specimens were evaluated at 3T for radiofrequency heating and magnetic field interactions. One-way analysis of variance (ANOVA) test was used to compare continuous variables of temperature change. Significance was set at P < .05. Translational attraction and torque values of specimens were also evaluated. RESULTS None of the groups exhibited excessive heating (mean temperature change, < 1.4 °C), with maximum increase at the end of the T-1. Moreover, in all groups, only relatively minor magnetic field interactions that would not cause movement in situ were observed. CONCLUSION The study findings indicated that patients with fixed partial dentures (single crown or bridge) fabricated from Co-Cr, Ni-Cr, and zirconia substructures may safely undergo MRI at up to 3T.

A suspected case of malignant hyperthermia after tooth extraction: case report.

w e t d d s c e t c Malignant hyperthermia (MH) is a rare, life-threatening, hereditary skeletal muscle disorder characterized by a hypermetabolic response following exposure to potent, volatile anesthetics or depolarizing muscle relaxants, such as halothane, desflurane, sevoflurane, and succinylcholine. MH is associated with genetic mutaions of the ryanodine receptor gene (RYR1), which odes the skeletal muscle calcium-release channel. Inreased Ca concentrations in extracellular fluid play n essential role in the pathogenesis of MH. A number of serious clinical signs can be observed during an MH onset, including generalized muscular rigidity, masseter muscle spasm, brown-colored urine, increased carbon dioxide production, increased oxygen consumption, metabolic and respiratory acidosis, and heat stroke. The speed of an MH attack may vary, with the first clinical symptoms observable within minutes after administration of the drug in some cases and a delay of several hours in others. Early diagnosis and appropriate management play a critical role in the successful treatment of MH. Hyerventilation with oxygen, intravenous administraion of dantrolene, and external body cooling are vital teps in the medical management of a severe attack. Dantrolene prevents calcium-related muscle contractions by inhibiting calcium release from the sarcoplasmic reticulum of skeletal muscle; however, given the

Effect of dental technician disparities on the 3-dimensional accuracy of definitive casts

Statement of problem Studies that evaluated the effect of dental technician disparities on the accuracy of presectioned and postsectioned definitive casts are lacking. Purpose The purpose of this in vitro study was to evaluate the accuracy of presectioned and postsectioned definitive casts fabricated by different dental technicians by using a 3‐dimensional computer‐aided measurement method. Material and methods An arch‐shaped metal master model consisting of 5 abutments resembling prepared mandibular incisors, canines, and first molars and with a 6‐degree total angle of convergence was designed and fabricated by computer‐aided design and computer‐aided manufacturing (CAD‐CAM) technology. Complete arch impressions were made (N=110) from the master model, using polyvinyl siloxane (PVS) and delivered to 11 dental technicians. Each technician fabricated 10 definitive casts with dental stone, and the obtained casts were numbered. All casts were sectioned, and removable dies were obtained. The master model and the presectioned and postsectioned definitive casts were digitized with an extraoral scanner, and the virtual master model and virtual presectioned and postsectioned definitive casts were obtained. All definitive casts were compared with the master model by using computer‐aided measurements, and the 3‐dimensional accuracy of the definitive casts was determined with best fit alignment and represented in color‐coded maps. Differences were analyzed using univariate analyses of variance, and the Tukey honest significant differences post hoc tests were used for multiple comparisons (&agr;=.05). Results The accuracy of presectioned and postsectioned definitive casts was significantly affected by dental technician disparities (P<.001). The largest dimensional changes were detected in the anterior abutments of both of the definitive casts. The changes mostly occurred in the mesiodistal dimension (P<.001). Conclusions Within the limitations of this in vitro study, the accuracy of presectioned and postsectioned definitive casts is susceptible to dental technician differences.

Evaluation of surface roughness and bond strength of quartz fiber posts after various pre-treatments

Abstract Purpose. Debonding at the post-adhesive interface is a major problem for quartz fiber posts. The objective of this study was to evaluate surface roughness and bond strength of quartz fiber posts after various surface treatments. Materials and methods. Sixty-six quartz fiber posts were randomly divided into six experimental groups (n = 11) including group C, untreated (control); group SB, sandblasted; group SC, silica coated; group HF, hydrofluoric acid-etched; group N, Nd:YAG laser irradiated; group E, Er:YAG laser irradiated. Surface roughness of the posts was measured before and after pre-treatment. They were then bonded to resin cement and tensile bond strength was determined in a universal testing machine. Furthermore, two-way ANOVA and post hoc comparison tests (α = 0.05) were performed on all data. Results. The highest mean force value was observed in group SB and followed by group E. Tukey’s HSD test showed that there was no statistical difference between group SB and group E (p = 0.673). The highest mean roughness value was observed in group SB and a significant difference was found between group SB and all other groups (p < 0.001). This study reveals that sandblasting and Er:YAG laser irradiation provided a significant increase in bond strength between quartz fiber posts and resin cement. Conclusions. Sandblasting or Er:YAG laser-irradiation of the surface of the quartz fiber post before cementation is recommended for increasing retention.

Can Impression Procedures Affect Certain Vital Functions of Edentulous Patients? A Clinical Study

PURPOSE The most suitable treatment conditions and timing for medically unstable patients with severe systemic diseases about to undergo invasive dental treatment are well documented in the literature; however, no medical guides or recommendations identify these conditions for noninvasive dental treatments in such patients. The aim of this clinical study was to determine the effect of impression procedures on arterial oxygen saturation (AOS) and pulse rates (PRs) of edentulous subjects. MATERIALS AND METHODS A total of 28 Caucasian edentulous participants (15 females, 13 males) were included in the study. Pulse oximetry recordings (150 seconds) were performed for each participant at three stages; recording at rest (CON), during mandibular impressions (MANIs), and maxillary impressions (MAXIs). The mean values of PR, AOS, and event scores (ESs) indicating desaturation were obtained from the records. The comparisons of mean PR and AOS values were performed with the Bonferroni-corrected Wilcoxon-signed ranks test. The ESs were analyzed with the McNemar Test. RESULTS The mean AOS values of MANI and MAXI did not display significant changes when compared with CON; however, the ESs obtained in both MANI and MAXI were significantly higher than those of CON (p = 0.008, p = 0.004). In addition, mean PR values obtained in MAXI were significantly higher than CON (p = 0.009). CONCLUSIONS According to the results of this clinical study, the impression procedures may affect the PR values and lead to desaturation events in edentulous patients; however, further studies evaluating blood gas levels, which indicate precise AOS values, are necessary to support the results of this study.