Evaluation of model accuracy and implant analog position in stone and additively manufactured models with different resin viscosities

This in vitro study aimed to assess the trueness and precision of additively manufactured (AM) dental models using resins of different viscosities and conventional stone models, along with the positional accuracy of implant analogs. Three model groups were created using a reference model with four parallel implants on both posterior sides: stone models (ST), AM models fabricated with low-viscosity resin (AM-A), and high-viscosity resin (AM-K). Each group included eight samples (n = 8). ST models were generated from polyether impressions with Type IV dental stone, while AM models were manufactured 3D printer according to the manufacturers’ guidelines. Scan bodies (SBs) were placed at the implant analog (IA-1 and IA-2) and multi-unit abutment (MA-1 and MA-2) levels. All models were scanned using a high-resolution desktop scanner. Root mean square (RMS) values of the models and SBs, as well as 3D and angular deviations of the implant analogs and inter-implant deviations, were calculated using metrology software (Geomagic Control X). Statistical analysis was performed using the Kolmogorov–Smirnov test for normality, Levene’s test for homogeneity of variances, one-way ANOVA, and the Games–Howell post hoc test (α = 0.05). Significant differences were found in RMS trueness among the groups (p < 0.043), with the ranking AM-A > AM-K > ST, whereas the AM-K group showed the lowest precision. Analysis of the RMS values of the SB regions, as well as the 3D and angular deviation measurements of the implant analogs, revealed comparable results between the AM-A and ST groups, while the AM-K group frequently demonstrated significant deviations. Interimplant deviation values were generally similar across the groups. In addition, significant differences between implant and abutment-level SBs were observed in all groups (p < 0.018). In terms of model trueness, AM models exhibited higher trueness compared to stone models. Deviation analysis of analogs showed the AM-A group yielded outcomes comparable with ST, while AM-K showed the highest deviations, indicating resin viscosity affects the positional accuracy of implant analogs. SBs at the multi-unit abutment level showed greater accuracy than those at the implant level.