Introduction: Polyether ether ketone (PEEK) has low surface energy and high resistance to chemical surface treatments. Therefore, different surface treatments such as laser conditioning should be investigated. There is a gap of information regarding the efficacy of laser irradiation in the surface treatment of PEEK, and the efficacy of several laser types needs to be evaluated for this purpose. This study aimed to assess the effect of surface treatment with erbium-doped yttrium aluminum garnet (Er:YAG) and carbon dioxide (CO2) lasers on shear bond strength (SBS) of PEEK to composite resin veneers. Methods: In this experimental study, 60 rectangular-shaped PEEK samples (7 x 7 x 2 mm) were used. The samples were mounted in auto-polymerizing acrylic resin in such a way that only one surface measuring 7x7 mm remained exposed. The samples were then randomly divided into 3 groups (n=20) of control, Er:YAG laser surface treatment (Power=1.5 W, energy density=119.42 J/cm2 , irradiation time=20 s) and CO2 laser surface treatment (Power=4 W, energy density=159.22 J/cm2 , irradiation time=50 s). The bonding agent and PEEK opaque were applied on the surface of samples and they were veneered with a composite resin using a hollow plastic cylinder with an internal diameter of 4 mm. The SBS was then measured and the data were analyzed using one-way ANOVA, Tukey HSD test and Dunnett’s test at 0.05 level of significance. Results: The SBS of the 3 groups was significantly different (P<0.001). The Tukey HSD test revealed that the Er:YAG laser had higher SBS than the CO2 laser group (P<0.001). The Dunnett’s test showed that both Er:YAG and CO2 laser groups yielded higher SBS than the control group (P<0.001). Conclusion: The Er:YAG and CO2 laser treatments can increase the SBS of PEEK to composite resin veneers, although the Er:YAG laser seems to be more effective for this purpose.

Overhang refers to the extension of restoration material from the cavity. It has an important role in decay, plaque accumulation and periodontal disease, so the aim of this study is determining the frequency of restoration overhang in patients in Anzali, Guilan. Materials and methods: This descriptive cross-sectional study was completed using 293 patients who visited for routine checkups. The overhangs were examined on the basis of the cavity type, restoration type, tooth location, and age by direct observation using an explorer, dental floss. After the initial diagnosis of the overhang, the radiographic reports were examined for final confirmation. Results: 41.2%, 0%, 18.2%, and 38.1% were observed in cavity classes II, III, IV, and V, respectively. 35.8%, 38.2%, 28.1%, and 25% were observed in mesial, distal, buccal, and lingual regions, respectively. The highest rate of overhang frequency in the first molar teeth was 50% and the lowest overhang amount occurred in the lateral and canine teeth at 25% and 27.3%, respectively. Most amalgam restorations had overhang (37.7%) and the highest amount of overhang was in the upper jaw (42.5%). The highest amount of overhang frequency was observed on the left (41.6%). There was no significant difference in overhang frequency between men and women. The lowest and highest amounts of overhang were observed in the age groups of <30 (26.9%) and 30-39 (47.8%), respectively, and was found to be statistically significant. Conclusion: The overall frequency of restoration overhang was 36.6%, most of which was in class II amalgam restoration in the left first molar teeth in 30-39 year-olds.

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Aim:Transferring an accurate copy of the patient's soft and hard tissue to the dental laboratory is of essential importance. Various methods of implant impression have different outcomes on dimensions of final cast. This study aimed to compare two methods of implant impression on abutment level with and without impression coping on two parallel implants. Materials and methods:In this experimental study, a resin model with two holes for fixing the implant was made. The first and second implants had a 4 and 11 mm distance to canine respectively. In this study two methods were used for impression: first was direct (without impression coping) and second was indirect (with the impression coping). Ten impressions were prepared for a total of 10 stone casts. For analyzing the abutment analogs positions, each cast was analyzed using a cruicial malformation and malarticulatoin (CMM) in three dimensions (X, Y, and Z). The difference in dimensions of final casts and laboratory models were analyzed using Independent t-test. Results:The results did not show a significant difference between direct and indirect methods in Z and Y axis in absolute transmission (Δr). The dimensional changes in the X-axis in the direct method was 0.647 ± 0.155 which is 0.067 ± 0.146 more than the indirect method. A significant difference (p = 0.044) was observed between the two methods in X-axis.Conclusion: Based on the results, this research found the indirect impression on abutment surface to be more accurate than the direct one. In general, two methods were not significantly different, and dentists can use the simple method of the direct impression for making implant prosthetics.Clinical significance: Reconstruction of implant's accurate position in the process of impression, along with a tension-free insertion, is the first step in having an accurate prosthesis. Abutment level impression with the impression coping is slightly more accurate than the one without impression coping.

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