Scanning accuracy of abutment level scan body according to insertion angles and depths of dental implants.

Abstract

Statement of problem: Abutment level scanning using an abutment base-scan body is a convenient option for obtaining digital implant scans. However, few studies have investigated the effects of implant angulation and depth on intraoral scanning accuracy.

Purpose: The purpose of this in vitro study was to explore ways to improve the accuracy of implant prostheses by comparing intraoral scans at conventional fixture and abutment levels under various implant conditions (angle and depth).

Material and methods: An implant was placed in the maxillary right first molar position of a partially edentulous dentiform at 3 different depths (bone crest level and 3 mm and 6 mm below the crest), and at 3 different angles (0 degrees, 25 degrees, and 35 degrees toward the palatal side). Digital scans were made using a high precision extraoral 3-dimensional (3D) scanner (E4) for the master reference model and an intraoral scanner (i700) for the test model. A conventional scan body was used in the control group, and an abutment base-scan body was used in the experimental group. Each scan was performed 10 times by a single clinician. The standard tessellation language (STL) files of the scans were analyzed using a 3D metrology software program (Gom Inspect) and superimposed on the occlusal surfaces, and the root mean square (RMS) error discrepancies were calculated at 5 specific points on the scan body. The accuracy of the control and experimental groups was compared by converting the deviation values to absolute values and averaging them based on the depth and angle conditions. Statistical analysis included independent samples t tests, Welch t tests, and 1-way analysis of variance (ANOVA) with a Scheffé post hoc test to compare mean differences among groups based on the implant angle and depth (α=.05).

Results: The experimental group showed significantly higher accuracy (P<.05) than the control group under most conditions. A significant correlation between the implant angulation and depth was observed in the control group. One-way ANOVA, followed by a Scheffé post hoc test, revealed that the control group showed significantly higher accuracy at the 0-mm depth condition and 0-degree condition (P<.05). However, the experimental group showed significantly higher accuracy in the 3-mm depth condition (P<.05). The experimental group also demonstrated higher accuracy (P<.05) with shorter visible supramucosal lengths.

Conclusions: The accuracy of intraoral scanning using the abutment base-scan body system was comparable with that of the conventional fixture level digital scans with scan bodies. Additionally, when the implant is angled toward the palatal side or is deeply placed, the abutment-level scan body can be a useful option during digital scanning.