Shear Bond Strength of Composite and Ceromer Superstructures to Direct Laser Sintered and Ni-Cr-Based Infrastructures Treated with KTP, Nd:YAG, and Er:YAG Lasers: An Experimental Study.

OBJECTIVE: The aim of this study was to examine the shear bond strength (SBS) of ceromer and nanohybrid composite to direct laser sintered (DLS) Cr-Co and Ni-Cr-based metal infrastructures treated with erbium-doped yttrium aluminum garnet (Er:YAG), neodymium-doped yttrium aluminum garnet (Nd:YAG), and potassium titanyl phosphate (KTP) laser modalities in in vitro settings. METHODS: Experimental specimens had four sets (n = 32) including two DLS infrastructures with ceromer and nanohybrid composite superstructures and two Ni-Cr-based infrastructures with ceromer and nanohybrid composite superstructures. Of each infrastructure set, the specimens randomized into four treatment modalities (n = 8): no treatment (controls) and Er:YAG, Nd:YAG, and KTP lasers. The infrastructures were prepared in the final dimensions of 7 × 3 mm. Ceromer and nanohybrid composite was applied to the infrastructures after their surface treatments according to randomization. The SBS of specimens was measured to test the efficacy of surface treatments. Representative scanning electron microscopy (SEM) images after laser treatments were obtained. RESULTS: Overall, in current experimental settings, Nd:YAG, KTP, and Er:YAG lasers, in order of efficacy, are effective to improve the bonding of ceromer and nanohybrid composite to the DLS and Ni-Cr-based infrastructures (p < 0.05). Nd:YAG laser is more effective in the DLS/ceromer infrastructures (p < 0.05). KTP laser, as second more effective preparation, is more effective in the DLS/ceromer infrastructures (p < 0.05). SEM findings presented moderate accordance with these findings. CONCLUSIONS: The results of this study supported the bonding of ceromer and nanohybrid composite superstructures to the DLS and Ni-Cr-based infrastructures suggesting that laser modalities, in order of success, Nd:YAG, KTP, and Er:YAG, are effective to increase bonding of these structures.

Evaluation of temperature rises during the application of different power levels of potassium titanyl phosphate and neodymium-doped:yttrium aluminum garnet lasers to external primary root canals.

BACKGROUND/PURPOSE: Nowadays, laser systems play crucial roles in endodontic treatments. Therefore, these systems should be investigated in terms of parameters that may prevent periodontal tissues damages during laser irradiation. In this context, the purpose of this study was to evaluate temperature rises during the application of different power levels of potassium titanyl phosphate (KTP) and neodymium-doped:yttrium aluminum garnet (Nd:YAG) lasers to external primary root canals. MATERIALS AND METHODS: Sixty primary mandibular molars were selected and chemomechanical preparation was performed. KTP laser treatment was applied to 30 of these 60 samples and the remaining 30 received Nd:YAG laser treatment. The teeth samples received laser application (KTP or Nd:YAG) at three different power levels (1 W, 1.5 W, and 2 W, respectively, applied to 10 samples from each group). Nine holes were drilled (1 mm in diameter) through the level of the coronal, middle, and apical third of each tooth canal to provide entry for a Type L thermocouple wire, which was used to measure temperature changes. Data were assessed with two-way analysis of variance and the Tukey test. RESULTS: All power levels indicated statistically significant differences between Nd:YAG and KTP laser systems (P < 0.05). Moreover, the same regional (apical, middle, and coronal) comparisons performed between Nd:YAG and KTP laser systems showed statistically significant differences (P < 0.05). CONCLUSION: All parameters of KTP laser indicated lower temperature rises than Nd:YAG laser. Therefore, KTP laser may be preferable to protect the periodontal tissues from harmful thermal effects during the endodontic treatment of primary root canals.

The Effects of Er:YAG, Nd:YAG, and Ho:YAG Laser Surface Treatments to Acrylic Resin Denture Bases on the Tensile Bond Strength of Silicone-Based Resilient Liners.

OBJECTIVE: The present study was to assess the effect of surface treatments of Er:YAG, Nd:YAG, and Ho:YAG lasers on the tensile bond strength of a silicone-based resilient liner to an acrylic denture in an in vitro setting. METHODS: Experimental dumbbell-shaped specimens (75 mm) were produced by combining two acrylate pieces fabricated from heat-polymerized acrylic resin (36 mm) with 3 mm of Molloplast(®)-B filling between them. The specimens (n=200) were randomly divided in half for thermocycling, and each 100 specimen set was randomized into five groups (n=20) with different surface treatments: control (no surface treatment), sandblasting, Er:YAG laser, Nd:YAG laser, and Ho:YAG laser. A tensile bond strength test was performed. The effect of the laser surface treatments was examined with scanning electron microscopy. RESULTS: Only the Er:YAG laser increased the tensile bond strength compared with the other treatments. The other laser groups showed lower bond strengths. The Ho:YAG laser resulted in considerably reduced tensile bond strength. The scanning electron microscopy images showed that applying laser surface treatments modified the surface of the denture base resin. CONCLUSIONS: There was not an overall improvement with the use of the studied laser modalities in the adhesion quality of resilient denture liner to acrylic resin, although Er:YAG laser showed a potential to improve their adhesion. These laser modalities need to be subjected to further studies to determine optimal setup for use in prosthodontics.

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.

Antibacterial effects of two different types of laser and aqueous ozone against Enterococcus faecalis in root canals.

OBJECTIVE: The purpose of this study was to investigate the antibacterial effects of two different types of laser and aqueous ozone in human root canals infected by Enterococcus faecalis. BACKGROUND DATA: Many techniques have been developed to find an alternative to sodium hypochlorite as a disinfection agent for infected root canals. However, no study has evaluated the exactly the same antimicrobial agent with sodium hypochlorite (NaOCl). METHODS: Eighty mandibular premolar teeth with single roots and canals were selected. Following root canal preparation and irrigation, sterilization was performed in an autoclave. E. faecalis was incubated in the root canals and kept at 37°C for 24 h. The teeth contaminated with E. faecalis were divided into one negative control group (NaOCl) and three experimental groups; (Er:YAG laser, KTP laser, and aqueous ozone groups)(n=20). A disinfection procedure was performed for 3 min in order to standardize all groups. After this procedure, the microbial colonies were counted. RESULTS: The results indicated that whereas the NaOCl group exhibited the highest antibacterial effect among all groups, the aqueous ozone showed the highest antibacterial effect among the experimental groups. Whereas a statistically significant difference was noted between the aqueous ozone and laser groups (p<0.05), the difference between the Er:YAG and KTP lasers was not statistically significant (p>0.05). CONCLUSIONS: The results showed that when aqueous ozone was applied with the aim of disinfecting the root canals, it exhibited a higher antibacterial effect than the KTP and Er:YAG lasers. However, the antibacterial effect of the aqueous ozone was insufficient when compared with NaOCl.