Comparison of the accuracy of different impression procedures in case of multiple and angulated implants Accuracy of impressions in multiple and angulated implants

Background: There is no consensus in the literature regarding the impression procedures in the presence of multiple and angulated implants. Methods: Three maxillary master models with 6 implants bilaterally positioned in anterior, premolar and molar regions were fabricated. In model 1, all implants were placed in parallel; in models 2 and 3, anterior implants were buccally inclined and posterior implants were distally inclined in 10- and 20-degrees, respectively. Three different impression copings (hexed, non-hex, multi-unit) and two different impression techniques (splinting and non-splinting) were tested. A total of 180 impressions (n = 10 per group) were made using mono-phase vinyl polysiloxane. Master models and duplicate casts were scanned by a 5-axis laboratory scanner and data were transferred to a software program for the alignment of master and duplicate copings. Coronal and angular deviations were calculated, and data were statistically analyzed. Results: For angulated models, the lowest deviation values were detected at the splinted non-hex coping group (P < 0.05). Conclusions: Implant angulation, impression coping type, and splinting the impression copings had significant effects on the accuracy of impressions.