The effects of different designs of impression copings on the accuracy of impression in the parallel and non-parallel implants

Abstract

Aim: In this study, the effect of the different impression coping designs on the accuracy of parallel and non-parallel implant impressions is investigated. For this purpose, the distance and angle of the impression copings in the initial model and the final casts will be compared. Materials and Methods: This research was performed experimentally in the laboratory and Impression Coping with Dentis, DIO, and Osstem brands were selected for the study. Impression copings are placed in two parallel positions, at an angle of zero degrees and in the non-parallel state, at an angle of 30 degrees to each other. Two gypsum models were prepared from each of the desired brands. In one model, 2 analogs of 4.5 mm were placed in parallel with a distance of 10 mm, and in the other model, 2 analogs of 4.5 mm with an angle of 30 degrees and a distance of 10 mm were placed. All groups were impressioned using the open tray method with Betasil additive silicone impression material. After the impression, the cast of all groups was cast at a specific time. Finally, to check the accuracy using a 3shape E3 laboratory scanner, the amount of change in distances and angles was determined and recorded in different groups. Data were analyzed by two-way ANOVA and Kruskal-Wallis test. Results: It was found that in parallel mode, based on the distance difference in the impressions of the studied copings, the lowest impression accuracy was observed for Osstem and the highest for DIO. Based on the angle difference, the lowest accuracy was observed for Osstem and the highest accuracy was observed for DIO. In non-parallel mode, based on the distance difference, the lowest accuracy was observed for DIO and the highest for Osstem. Based on the angle difference, the lowest accuracy was observed for Dentis and the highest accuracy was observed in DIO. According to Kruskal-Wallis nonparametric test, the accuracy of distance-based impression was statistically significant between possible parallel and non-parallel combinations, so that based on distance, the lowest accuracy was observed for Osstem degree 30 degrees and the highest for Parallel*Osstem. On the other hand, according to this test, the accuracy of angle-based impression was not statistically significant (p-value = 0.30) between the possible combinations of the brand and the angle of the impression of the copings, so that the lowest accuracy was observed for Osstem*30 degrees and the highest for Parallel*DIO. Conclusion: In all combinations of implantation type and selection of the brand type of impression coping under study, a degree of error is inevitable and the shape of the impression coping does not have a significant effect on the accuracy of the impression at a distance and angle. The method of parallel and non-parallel implantation did not affect the distance accuracy for DIO and Dentis brands and the only significant effect was observed in the Osstem brand so that the distance accuracy in parallel mode is higher than non-parallel mode with 30 angles. These results can help dentists choose a better implant technique and type of impression coping.