فهرست مطالب arash shisheian

This study aimed to compare the marginal fit of temporary restorations fabricated by the conventional chairside method, 3D printing, and milling.

In this in vitro, experimental study, 14 temporary restorations were conventionally fabricated over an implant abutment and analog that had been mounted in a phantom model at the site of canine tooth, using auto-polymerizing acrylic resin and putty index. In digital manufacturing, the original model was scanned, and the final restoration was designed. Fourteen temporary restorations were milled out of polymethyl methacrylate (PMMA) blocks, and 14 others were printed by a 3D printer. Temporary crowns were placed on the abutment, and images were obtained from specific areas under a stereomicroscope at x100 magnification to measure the amount of marginal gap. Data were analyzed using one-way ANOVA and Tukey’s test (α=0.05).

The mean marginal gap values for the temporary crowns in the 3D printing, milling, and chairside groups were 91.40, 75.28 and 51.23 µm, respectively. The crowns that were conventionally fabricated chairside exhibited the lowest marginal gap, and the difference in this respect was significant among the three groups (P<0.05).

Temporary crowns fabricated by the chairside method showed significantly smaller marginal gap; however, the marginal gap of all three groups was within the clinically acceptable range.

Acrylic resin teeth wear resistance has an important role in the denture longevity. This study aimed to clarify the effect of glaze coating on wear resistance of three types of artificial acrylic teeth.

In this in vitro study, the wear resistance rate of three of acrylic denture teeth (GENIUS, STON and CLASSIC) was compared with Ivoclar teeth (n=25/group). The wear resistance was measured by estimating the weight loss in pre and post removing glaze coating, following 5000 cycles in the chewing simulator device. Data analysis was made using paired t test, one-way ANOVA and Tukey’s post hoc test.

ANOVA test showed that there was no significant difference between the mean amount of wear of GENIUS, CLASSIC, STON and IVOCLAR teeth in the first stage (P <0.061), but this difference was significant (P <0.001) in the second stage. The result of Tukey post hoc test showed that wear rates of GENIUS were significantly lower than other groups (P<0.001). Comparison between the mean wear rates of each dental group at the first and second stages showed a significant difference between average teeth wear resistance of CLASSIC, STON and IVOCLAR in the first and second stages (P <0.001).

In conclusion, the teeth wear resistance of STON and CLASSIC were similar to IVOCLAR. Also, after removing the glaze coating, the teeth wear resistance decreased in all groups but was not statistically significant for group GENIUS.

Intraosseous implants can be placed using three different techniques: immediate, early, and delayed. The aim of this study was to compare the changes in the marginal bone level around implants after immediate and delayed im-plant placement. In the present prospective cohort study, 26 implants were placed in 26 patients divided into two groups. In group 1, 13 implants were placed immediately, while in group 2, 13 implants were placed with a delay of more than 4 months after tooth extraction. The marginal bone level was measured on periapical radiographs taken using the parallel technique at implant placement time and 6 and 12 months after implantation. The measurements were made using a digital caliper with an accuracy of 0.01 mm, and the data were analyzed using repeated-measures analysis of variance (ANOVA) and Mauchly's sphericity test. The statistical significance was set at P<0.05. The mean distances between the crestal bone and the implant shoulder in group 1 were 1.12 mm, 1.48 mm, and 1.77 mm at implant placement time and 6 and 12 months postoperatively, respectively. In group 2, these distances were 1.26 mm, 1.46 mm, and 1.71 mm, respectively. There were no significant differences in marginal bone resorption between the two groups (P>0.05). There was no significant difference in crestal bone loss around implants placed with immediate and delayed techniques.