Registration accuracy of soft tissue information scan captured using an intraoral scanner and implant position scan recorded using extraoral and intraoral photogrammetry systems

Abstract

Statement of problem: Implant scanning workflows require the integration of digital scans containing different information, including soft tissue and implant position information scans. These digital scans captured by using intraoral scanners (IOSs) with or without photogrammetry (PG) systems are sequentially registered for manufacturing an implant-supported prosthesis. However, the registration accuracy of soft tissue and implant position information scans remains unknown.

Purpose: The purpose of this in vitro study was to measure the registration accuracy of the soft tissue information scan recorded using an IOS and implant position information scans recorded using 3 extraoral and 1 intraoral PG system.

Material and methods: A maxillary edentulous stone cast with 6 implant abutment analogs (MultiUnit Abutment Replica) was obtained. Three markers were attached on the palatal surface of the cast on the anterior palatine raphe and in the right and left first molar positions. A healing abutment was hand tightened into each implant abutment and the cast was digitized by using a laboratory scanner (T710). Subsequently, a complete arch soft tissue information scan was recorded by using an IOS (Elite). Four groups were created depending on the PG system used to capture the implant position scans: iCam4D, Grammee, OxoFit, and Elite (n=30). The soft tissue scan and PG scans were aligned using a program (DentalCAD), except for the Elite group in which the corresponding IOS software program was used to align these 2 scans. The registered scans were imported into another program (Geomagic), and the measurement point of each implant abutment geometry was located (intersection between the longitudinal axis and the apical z-plane). Eighteen linear measurements were performed between the markers and measurement points in the control scan and each specimen. Trueness was analyzed using the 1-way ANOVA test, and precision was evaluated using the Levene test (α=.05).

Results: No significant trueness discrepancies were found among the groups tested (P=.270). Additionally, the Levene test showed no significant precision discrepancies among the groups tested (P=.130). The mean ±standard deviation registration discrepancy between the soft tissue and implant position information scans ranged from 103 ±38 µm to 116 ±52 µm.

Conclusions: The extraoral and intraoral PG systems tested did not impact the registration accuracy between the soft tissue and implant position information scans.