Effect of Light Sources on Bond Strength of Different Composite Resins Repaired with Bulk-Fill Composite / Efecto del tipo de fuente luz en la resistencia adhesiva de distintas resinas compuestas reparados con una resina bulk-fill

Abstract: The aim of this study was to evaluate and compare the effects of different light sources on shear bond strength when bulk-fill composite was used for the repair of different composite resins. A total of 126 samples made from six resin composites with different properties were aged (thermal-cycling with 5000 cycle), exposed to the same surface treatments and adhesive procedure. Then, they were repaired with a bulk-fill composite. At the polymerization step, each group was divided into three subgroups (n=7) and light cured with a QTH light source for 40s and two different LED light sources for 20s. Subsequently, the specimens were aged in distilled water at 37 ºC for 4 weeks and then subjected to shear bond strength test. Then, the specimens were examined under a stereomicroscope to identify modes of failure and visualized by Scanning Electron Microscope. Data obtained from the study were analyzed using ANOVA and Tukey HSD Test (α=0.05). In all groups, the light curing units had an impact on shear bond strength (p<0.05). Among the study groups, the greatest bond strength values were observed in the specimens repaired using the LED and the specimens repaired with the QTH light curing unit had the lowest bond strength values. It was concluded that the content of composite resins and light curing units may influence bond strength of different composites repaired with the bulk-fill composite.

Resumen: El objetivo de este estudio fue evaluar y comparar los efectos de diferentes fuentes de luz sobre la resistencia de la unión al cizallamiento cuando se utiliza una resina bulk-fill para la reparación de diferentes resinas compuestas. Se envejecieron un total de 126 muestras fabricadas con seis compuestos de resina con diferentes propiedades (ciclo térmico con 5000 ciclos), expuestas a los mismos tratamientos de superficie y procedimiento adhesivo. Luego, fueron reparadas con una resina bulk- fill. En el paso de polimerización, cada grupo fue dividido en tres subgrupos (n=7) y fotopolimerizado con una fuente de luz QTH por 40s y dos fuentes de luz LED por 20s. Posteriormente, los especímenes se envejecieron en agua destilada a 37 ºC durante 4 semanas y luego se sometieron a una prueba de resistencia adhesiva de cizalla. Luego, los especímenes fueron examinados bajo un estereomicroscopio para identificar los modos de falla y visualizados por el Microscopio Electrónico de Barrido. Los datos obtenidos del estudio fueron analizados usando el ANOVA y la prueba Tukey HSD (α=0.05). En todos los grupos, las unidades de fotopolimerización tuvieron un impacto en la fuerza de adhesión al cizallamiento (p<0,05). Entre los grupos de estudio, los mayores valores de fuerza de adhesión se observaron en los especímenes reparados utilizando el LED y los especímenes reparados con la unidad de fotopolimerización QTH tuvieron los valores de fuerza de adhesión más bajos. Se llegó a la conclusión de que el contenido de las resinas compuestas y las unidades de fotopolimerización pueden influir en la fuerza de adhesión de los diferentes compuestos reparados con resinas bulk-fill.

Effect of acid etching and different Er:YAG laser procedures on microleakage of three different fissure sealants in primary teeth after aging.

The purpose of this study was to evaluate the effects of different surface conditioning procedures on microleakage and unfilled area proportions of three fissure sealants(Aegis, Helioseal and Helioseal F) in primary molar teeth. One hundred and fifty teeth were randomly divided into five main groups according to surface conditioning procedures. Main groups were; acid-etching(Group A); laser 3.75 W(Group B) and 5 W(Group D); acid-etching combined with laser 3.75 W(Group C) and 5 W(Group E). Samples were aged by thermocycling and water bath. Afterwards, they were immersed in basic fuchsin solution for 24 h and bucco-lingual sections were obtained from each tooth. Digital images were taken using a stereo-microscope and the microleakage and unfilled area proportions were assessed by using a software system. Consequently, Aegis FS containing amorphous calcium phosphate was found to exhibit the lowest microleakage in all surface conditioning procedures. Unfilled areas were not detected in Groups C and E of all FSs.

Temperature rises during application of Er:YAG laser under different primary dentin thicknesses.

OBJECTIVE: The present study investigated the effects of the Er:YAG laser's different pulse repetition rates on temperature rise under various primary dentin thicknesses. BACKGROUND DATA: The Er:YAG laser can be used for restorative approaches in clinics and is used to treat dental caries. There are some reports that explain the temperature rise effect of the Er:YAG laser. Recently, the Er:YAG laser has been found to play an important role in temperature rises during the application on dentin. METHODS: Caries-free primary mandibular molars were prepared to obtain dentin discs with 0.5, 1, 1.5, and 2 mm thicknesses (n=10). These discs were placed between the Teflon mold cylinders of a temperature test apparatus. We preferred three pulse repetition rates of 10, 15, and 20 Hz with an energy density of 12.7 J/cm2 and a 230 µs pulse duration. All dentin discs were irradiated for 30 sec by the Er:YAG laser. Temperature rises were recorded using an L-type thermocouple and universal data loggers/scanners (E-680, Elimko Co., Turkey). Data were analyzed by two-way ANOVA and Tukey tests. RESULTS: Whereas the lowest temperature rise (0.44±0.09 °C) was measured from a 10 Hz pulse repetition rate at a dentin thickness of 2 mm, the highest temperature rise (3.86±0.43 °C) was measured from a 20 Hz pulse repetition rate at a 0.5 mm dentin thickness. CONCLUSIONS: Temperature rise did not reach critical value for pulpal injury in any primary dentin thicknesses irradiated by a high repetition rate of the Er:YAG laser.

Effect of external tooth bleaching on dental plaque accumulation and tooth discoloration.

OBJECTIVES: Treatment of dental discolorations with external bleaching is becoming very common in dentistry, however, possible irreversible alterations on enamel surface due to bleaching procedures is a topic of discussion. The aim of this study was to evaluate the clinical effects of bleaching by measuring the dental plaque accumulation on human enamel and tooth discoloration in vivo. STUDY DESIGN: Forty-four teeth in eleven patients not revealing any restorations or periodontal problems were enrolled in this study. Bleaching agent applied only to labial surfaces of incisors using commercial 35% hydrogen peroxide gel. Dental plaque and tooth color measured in the same group of participants, at the end of non-brushing periods lasting 3 and 5 days, respectively, before and after bleaching. RESULTS: The results of the comparison of pre- and post-bleaching measurements showed that, after a non-brushing period lasting 3 day, discoloration scores and plaque accumulation scores for bleached surfaces were lower than the non-bleached surface scores. However, at the end of a non-brushing period lasting 5 day, even the color measurement score in post-bleaching period was lower than the pre-bleaching counterpart, plaque index measurements showed higher plaque accumulation scores in the bleached group. CONCLUSIONS: According to these results, bleaching with 35% hydrogen peroxide seem to favor plaque accumulation after non-brushing period lasting 5 day and tooth discoloration after bleaching is not in correlation with the amount of plaque accumulation.

Effect of external tooth bleaching on dental plaque accumulation and tooth discoloration

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Objectives: Treatment of dental discolorations with external bleaching is becoming very common in dentistry, however, possible irreversible alterations on enamel surface due to bleaching procedures is a topic of discussion. The aim of this study was to evaluate the clinical effects of bleaching by measuring the dental plaque accumulation on human enamel and tooth discoloration in vivo. Study Design: Forty-four teeth in eleven patients not revealing any restorations or periodontal problems were enrolled in this study. Bleaching agent applied only to labial surfaces of incisors using commercial 35 % hydrogen peroxide gel. Dental plaque and tooth color measured in the same group of participants, at the end of non-brushing periods lasting 3 and 5 days, respectively, before and after bleaching.Results: The results of the comparison of pre- and post-bleaching measurements showed that, after a non-brushingperiod lasting 3 day, discoloration scores and plaque accumulation scores for bleached surfaces were lower than the non-bleached surface scores. However, at the end of a non-brushing period lasting 5 day, even the color measurement score in post-bleaching period was lower than the pre-bleaching counterpart, plaque index measurements showed higher plaque accumulation scores in the bleached group.Conclusions: According to these results, bleaching with 35 % hydrogen peroxide seem to favor plaque accumulation after non-brushing period lasting 5 day and tooth discoloration after bleaching is not in correlation with the amount of plaque accumulation

Bond strength of adhesives to dentin involving total and self-etch adhesives.

OBJECTIVE: Currently, the trend in dentin adhesion seems to be shifting from moist bonding systems to self-etching systems and from several application steps to single steps. However, recent studies have indicated that the performance of single-step adhesives was lower than the 2-step self-etch or total etch systems. In the present study, microtensile bond strength of a total etch, 2-step self-etch and single-step self-etch adhesives was comparatively evaluated. METHOD AND MATERIALS: The superficial occlusal dentin of 12 noncarious extracted human molars was exposed, finished with wet 600-grit silicon carbide paper, and a block of resin composite bonded with adhesives according to the manufacturers' instructions. The teeth were kept in tap water for 24 hours at 37 degrees C and sectioned to produce beams, with adhesive areas of +/- 0.9 mm2 (4 beams per tooth were obtained). The specimens were stressed at a crosshead speed of 1 mm per minute until the bonds ruptured. RESULTS: The mean bond strengths were calculated as MPa and compared by performing analysis of variance and Tukey tests to identify significant differences between the materials (P = 0.05). The mean bond strength of Clearfil SE Bond was significantly higher than that of OptiBond Solo Plus and iBond (P <.05). OptiBond Solo Plus gave significantly higher bond strengths than iBond (P <.05). CONCLUSIONS: The self-etching adhesive system Clearfil SE Bond (2 step) had higher bond strength than the 1-bottle self-etching adhesive iBond (single application) and the 2-step single-bottle system OptiBond Solo Plus (total etch). However, the 1-bottle adhesive system OptiBond Solo Plus (total etch system) had higher bond strength than the 1-bottle self-etching adhesive system iBond.

Cytotoxicity evaluation of two different composites with/without fibers and one nanohybrid composite.

In this study, cytotoxicity of two different composites with/without fibers (Adoro/Vectris and SculpturePlus/FiberKor) and one nanohybrid composite (Artglass) were investigated and compared. Composites used in the study were prepared as cylindrical discs of 2 mm depth and 8 mm diameter according to ISO 10993 recommendation. Adoro/Vectris and SculpturePlus/ FiberKor groups were divided into composite, fiber, and composite+fiber groups. Agar diffusion method was employed, and cytotoxicity rankings were determined using lysis index scores. For statistical analysis, Kruskal-Wallis and Mann-Whitney U tests were used. Amongst the composites, Adoro was found to be less cytotoxic than Sculpture Plus and Artglass materials--which were of the same cytotoxicity ranking. Between the fiber and composite materials, the former were found to be more cytotoxic than the latter; in particular, Vectris was found to be more cytotoxic than FiberKor. It was observed that upon combining with the fibers, the cytotoxic effect of the composites increased. This cytotoxicity enhancement was manifested as an additional effect in Adoro/Vectris group but as a synergistic effect in SculpturePlus/FiberKor group.

Surface roughness of new microhybrid resin-based composites.

BACKGROUND: Rough, poorly polished resin-based composite (RBC) surfaces contribute to staining, plaque accumulation, gingival irritation and recurrent caries. Proper finishing and polishing enhance both the esthetics and the longevity of restored teeth. METHODS: The authors evaluated the influence of various finishing and polishing techniques on the surface roughness of four microhybrid RBCs. Thirty samples of each material were cured under Mylar matrix strips (Yates and Bird/Motloid, Chicago). All microhybrid RBC specimens were finished with multifluted carbide burs, except for the Mylar matrix strip samples, and then were polished using one of four finishing systems: Sof-Lex contouring and polishing disks (3M ESPE, St. Paul, Minn.); Enhance Finishing System (Dentsply-Caulk, Milford, Del.) followed by Prisma Gloss (Dentsply-Caulk) polishing paste application; Astropol finishing, polishing and high-gloss polishing system (Ivoclar Vivadent, Schaan, Liechtenstein); and Astrobrush polishing system (Ivoclar Vivadent). The authors tested the samples to obtain average surface roughness and analyzed the values. RESULTS: The use of the Astrobrush technique caused the greatest roughness on all RBC specimens. The smoothest surface was produced with a carbide bur followed by aluminum oxide disks, Astropol technique and Enhance technique. Overall, there were differences in surface quality among the materials. InTen-S (Ivoclar Vivadent) had statistically lower surface roughness values after finishing and polishing with the Astrobrush technique, compared with the other RBCs. CONCLUSION: The highest surface roughness values were achieved after the Astrobrush technique was used. The Sof-Lex aluminum oxide disks, and Enhance and Astropol techniques provided the smoothest surface. CLINICAL IMPLICATIONS: The Sof-Lex, Enhance and Astropol techniques produced a smooth surface after the finishing and polishing of materials, while the Astrobrush technique yielded the least favorable results.

Fracture resistance of endodontically treated premolars restored with ormocer and packable composite.

In this study, mesiodistocclusal (MOD) cavity preparations of endodontically treated maxillary premolars that were enlarged to size #50 were restored using three restorative materials (one ormocer, one packable composite, and one high-copper amalgam) and two application techniques (with or without coronal radicular technique). Copper rings were filled with self-curing polymethylmethacrylate resin and the teeth were placed into resin up to the level of the CEJ. The teeth were grouped according to the restorative material and technique, mounted in a Universal Testing Machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. The group restored with packable composite without radicular extension showed the highest resistance to fracture (p < 0.05). Both groups restored with amalgam were significantly weaker than all the other groups (p < 0.05).