Ahmet Ozkomur

Intrapulpal Heat Generation during Provisionalization: Effect of Desensitizer and Matrix Type

PURPOSE This study investigated the effect of different matrices and application of a desensitizer on pulpal temperature rise during direct provisionalization. MATERIALS AND METHODS The apical third of a second premolar was resected and pulpal tissue was removed. Silicone heat-conducting medium was injected, and a J-type thermocouple was inserted into the pulp chamber and sealed. The tooth was embedded in acrylic resin with its cervical line 1 mm higher than the base. Addition and condensation silicone impression materials were mixed and placed inside plastic molds. Impressions were taken before tooth preparation. The tooth was then prepared with a 1.5-mm shoulder finish line. The experimental model was kept in a 36 degrees C water bath. Four provisional materials were applied in sequence onto the prepared tooth using matrices. Each provisional resin was used in combination with each matrix (n = 12). Then a dentin desensitizer was coated on the prepared tooth and provisionalizations were made in the same manner. The thermocouple was connected to the data-logger. During setting of the resins, pulp temperatures were recorded and transferred to the computer. Measurements were conducted for each test group by calculating the temperature rise as the difference between the start and highest temperature reading. RESULTS The type of the silicone matrix used and the use of desensitizer did not affect the intrapulpal heat generation during direct provisionalization. CONCLUSION Application of a desensitizer and different type of matrix seems to be noneffective on intrapulpal heat rise, although the type of provisional material used may be effective.

Diamondlike carbon coating as a galvanic corrosion barrier between dental implant abutments and nickel-chromium superstructures.

PURPOSE The objectives of this study were to evaluate the galvanic corrosion behavior between titanium and nickel-chromium (Ni-Cr) alloy, to investigate the effect of diamondlike carbon (DLC) coating over titanium on galvanic corrosion behavior between titanium and Ni-Cr alloy, and to evaluate the effect of DLC coating over titanium abutments on the fit and integrity of prosthetic assemblies by scanning electron microcopy (SEM). MATERIALS AND METHODS Five Ni-Cr and 10 titanium disks with a diameter of 5 mm and thickness of 3 mm were prepared. DLC coating was applied to five titanium disks. Electrode samples were prepared, and open circuit potential measurements, galvanic current measurements over platinum electrodes, and potentiodynamic polarization tests were carried out. For the SEM evaluation, 20 Ni-Cr alloy and 10 gold alloy superstructures were cast and prepared over 30 abutments. DLC coating was applied to 10 of the abutments. Following the fixation of prosthetic assemblies, the samples were embedded in acrylic resin and cross sectioned longitudinally. Internal fit evaluations were carried out through examination of the SEM images. RESULTS Titanium showed more noble and electrochemically stable properties than Ni-Cr alloy. DLC coating over the cathode electrode served as an insulating film layer over the surface and prevented galvanic coupling. Results of the SEM evaluations indicated that the DLC-coated and titanium abutments showed no statistically significant difference in fit. Hence, no adverse effects on the adaptation of prosthetic components were found with the application of DLC coating over abutment surfaces. CONCLUSIONS DLC coating might serve as a galvanic corrosion barrier between titanium abutments and Ni-Cr superstructures.

Influence of ozone and paracetic acid disinfection on adhesion of resilient liners to acrylic resin

PURPOSE The aim of this study was to evaluate the effect of paracetic acid (PAA) and ozone disinfection on the tensile bond strength (TBS) of silicone-based resilient liners to acrylic resins. MATERIALS AND METHODS One hundred and twenty dumbbell shaped heat-polymerized acrylic resins were prepared. From the mid segment of the specimens, 3 mm of acrylic were grinded off and separated parts were reattached by resilient liners. The specimens were divided into 2 control (control1, control7) and 4 test groups of PAA and ozone disinfection (PAA1, PAA7, ozone1 and ozone7; n=10). While control groups were immersed in distilled water for 10 min (control1) and 7 days (control7), test groups were subjected to PAA (16 g/L) or ozone rich water (4 mg/L) for 1 cycle (10 min for PAA and 60 min for ozone) per day for 7 days prior to tensile tests. Measurements of the TBS were analyzed using 3-way ANOVA and Tukeys HSD test. RESULTS Adhesive strength of Mollosil decreased significantly by application of ozone disinfection. PAA disinfection had no negative effect on the TBS values of Mollosil and Molloplast B to acrylic resin. Single application of ozone disinfection did not have any negative effect on TBS values of Molloplast B, but prolonged exposure to ozone decreased its adhesive strength. CONCLUSION The adhesion of resilient liners to acrylic was not adversely affected by PAA disinfection. Immersion in ozonated water significantly decreased TBS of Mollosil. Prolonged exposure to ozone negatively affects adhesion of Molloplast B to denture base materials.

Effects of Hard Thin-Film Coatings on Adhesion of Early Colonizer Bacteria Over Titanium Surfaces.

Purpose:The purpose of this in vitro study was to evaluate the effect of diamond-like carbon (DLC) and titanium (Ti) nitride coatings over Ti surfaces on the adhesion of early colonizer bacteria. Materials and Methods:Specimens were divided into 3 groups (n = 10) according to different surface modifications: titanium nitride (TiN)-coated Ti discs (experimental group 1), DLC-coated Ti discs (experimental group 2), and uncoated polished Ti discs (control group). Discs were incubated in bacterial cell suspension (Streptococcus mutans and Streptococcus sanguis) for 1 hour, and the single colonies formed by adhering bacteria were counted by fluorescence microscopy. Surface roughness and topography were examined by atomic force microscopy. Results:The surface roughness of DLC was lower than TiN coating and the control group. Statistically significant reduction of the number of adherent bacteria was observed on DLC-coated surfaces. Conclusions:DLC coating over Ti surfaces strongly inhibits the adhesion of early colonizer oral bacteria.

KİMYASAL TEMİZLEYİCİLERİN AKRİLİK DİŞLERİN YÜZEY SERTLİKLERİNE ETKİSİ

Aim: The aim of this study was to investigate the effect of three chemical denture cleansers on the Knoop hardness of the acrylic denture teeth. Material and Method: Premolar and molar acrylic denture teeth from two manufacturers were embedded in cold cured acrylic resin. The occlusal surfaces of teeth were flat grounded and polished. The specimens were randomly divided into 4 groups and immersed in three different chemical disinfection (Protefix, Corega Tabs and %1 NaOCl) and distilled water (Control group) for 8 hours/day during 7 days. The specimens were submitted to Knoop hardness measurements procedures. Data were analyzed with one way ANOVA and Tukey’s statistical test. Result: All Vitapan group exhibited higher Knoop hardness values than Major Dent groups both in control and experimental groups. The tested chemical denture cleaning methods did not show any significant effect on Knoop hardness of the artificial teeth. Conclusion: Within the limitations of this study it can be concluded that exposure of artificial teeth to chemical disinfectants did not affect the hardness of the acrylic teeth