Influence of scan body design on accuracy of the implant position as transferred to a virtual definitive implant cast.
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STATEMENT OF PROBLEM: Previous studies have analyzed factors influencing intraoral scanneraccuracy; however, how the intraoral scan body design affects the implant position on the virtual definitive cast is unclear. PURPOSE: The purpose of this invitro study was to measure the discrepancies of the implant replica positions of the virtual definitive implant cast obtained by using 3 different scan body designs when performing a digital scan. MATERIAL AND METHODS: A partially edentulous typodont with 3 implant replicas (Implant Replica RP Branemark system; Nobel Biocare Services AG) was prepared. Three groups were determined based on the scan body system evaluated: SB-1 (Elos Accurate Nobel Biocare), SB-2 (NT Digital Implant Technology), and SB-3 (Dynamic Abutment). Each scan body was positioned on each implant replica of the typodont, and was digitized by using an intraoral scanner (iTero Element; Cadent) as per the manufacturer's scanning protocol at 1000 lux illuminance. A standard tessellation language (STL) file was obtained. Before the scan bodies were removed from the typodont, a coordinate measuring machine(CMM Contura G2 10/16/06 RDS; Carl Zeiss Industrielle Messtechnik GmbH) was used to measure the scan body positions on the x-, y-, and z-axis. The linear and angular discrepancies between the position of the scan bodies on the typodont and STL file were calculated by using the best fit technique with a specific program (Calypso; Carl Zeiss Industrielle Messtechnik GmbH). The procedure was repeated until 10 STL files were obtained per group. The Shapiro-Wilk test revealed that the data were not normally distributed. The data were analyzed by using the Mann-Whitney U test (=.05). RESULTS: The coordinate measuring machine was unable to measure the scan body positions of the magnetically retained SB-3 group because of its mobility when palpating at the smallest pressure possible. Therefore, this group was excluded. No significant differences were found in the linear discrepancies between the SB-1 and SB-2 groups (P>.05). The most accurate scan body position was obtained on the z-axis. However, the SB-1 group revealed a significantly higher XZ angular discrepancy than the SB-2 group (P<.001). CONCLUSIONS: The scan body systems tested (SB-1 and SB-2 groups) accurately transferred the linear implant positions to the virtual definitive implant cast. However, significant differences were observed in the XZ angular implant positions between the scan body systems analyzed.
