Effects of inter-implant tooth loss and scan body material on digital impression accuracy: an in vitro study

BACKGROUND: The accuracy of digital implant scanning and the optimal choice of scanning bodies remain debated, particularly in cases involving multiple missing teeth between implants. This study aimed to investigate the influence of the number of missing teeth between implants on trueness, precision, and inter-implant distance deviation in digital implant impressions. METHODS: Three maxillary models containing two implants and varying edentulous spans were fabricated: S1 (no missing teeth), S2 (one missing tooth), and S3 (two missing teeth). Titanium (Ti) and polyetheretherketone (PEEK) scanning bodies were used. Scanning was performed using both industrial and intraoral scanners. Data from the industrial scanners served as the control group, whereas data from the intraoral scanners constituted the experimental group. A three-dimensional deviation analysis using reverse engineering software (Geomagic Control X) quantified trueness, precision, and inter-implant distance deviation. A two-way analysis of variance (ANOVA) evaluated the effects of tooth loss, scanning body material, and their interaction on scanning accuracy. RESULTS: The number of missing teeth considerably affected scanning accuracy. As tooth loss increased, mean trueness deteriorated in both Ti (S1: 0.18 ± 0.03 mm, S2: 0.35 ± 0.01 mm, S3: 0.56 ± 0.03 mm, p < 0.001) and PEEK (S1: 0.19 ± 0.15 mm, S2: 0.62 ± 0.11 mm, S3: 0.88 ± 0.08 mm, p < 0.001) groups. Moreover, precision worsened in both Ti (S1: 0.07 ± 0.02 mm, S2: 0.16 ± 0.04 mm, S3: 0.36 ± 0.17 mm, p < 0.001) and PEEK (S1: 0.11 ± 0.02 mm, S2: 0.28 ± 0.08 mm, S3: 0.77 ± 0.17 mm, p < 0.001) groups. Inter-implant distance deviations increased in Ti (S1: 0.28 ± 0.04 mm, S2: 0.32 ± 0.08 mm, S3: 0.37 ± 0.10 mm, p = 0.072) and PEEK (S1: 0.29 ± 0.11 mm, S2: 0.33 ± 0.03 mm, S3: 0.81 ± 0.11 mm, p < 0.001) groups. In the intergroup comparison between Ti and PEEK scanning bodies, significant differences were observed in the following parameters: Trueness: S2 (p < 0.001), S3 (p < 0.001); Precision: S1 (p < 0.001), S2 (p < 0.001), S3 (p < 0.001); Distance Deviation: S3 (p < 0.001).Two-way ANOVA showed a strong interaction between tooth loss and scanning body material. CONCLUSIONS: Increased inter-implant tooth loss considerably reduced digital scanning accuracy. Ti scanning bodies provided superior spatial positioning accuracy compared with PEEK under the study conditions.