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Fit accuracy of inlay-retained fixed partial dentures fabricated using additive and subtractive manufacturing
İzim Türker Kader1, Simge Dagistan1, Elif Nur Köroğlu1
1Department of Prosthodontics, School of Dental Medicine, Bahçeşehir University, Istanbul, Turkey.
Objectives:
To evaluate the effect of additive and subtractive manufacturing workflows on the fit accuracy of inlay-retained fixed partial dentures (IRFPDs) using three-dimensional (3D) analysis.
Methods:
Standardized inlay preparations were performed on typodont mandibular second premolar and molar abutments, and digital models were obtained. IRFPDs were designed using CAD software and fabricated using two additive manufacturing (AM) workflows-stereolithography (AM-SLA) and digital light processing (AM-DLP)-and one subtractive manufacturing (SM) workflow (SM-CS) (n = 15 per group). Fit accuracy was evaluated using a triple-scan protocol based on three standard tessellation language (STL) datasets. The datasets were aligned using best-fit alignment procedures in 3D metrology software (Geomagic Control X). Internal and marginal deviations were quantified using root mean square (RMS) and average gap values. Between-specimen variability in fit measurements was assessed among independently fabricated restorations within each group. Statistical analyses were performed using one-way ANOVA or Kruskal-Wallis tests followed by post hoc comparisons (α = 0.05).
Results:
Significant differences in trueness were observed among the groups (P < 0.05). The AM-SLA group showed significantly lower internal deviations than the AM-DLP and SM-CS groups, with no significant difference between the latter two. For marginal trueness, SM-CS showed higher RMS values than both AM groups, while AM-SLA showed lower average gap values than SM-CS. Variability in internal fit differed significantly, with AM-DLP showing greater variability than AM-SLA (P < 0.05), whereas variability in marginal fit did not differ significantly among the groups (P > 0.05).
Conclusions:
The tested manufacturing workflows influenced the fit accuracy of IRFPDs, particularly internal trueness and variability in internal fit. The AM-SLA workflow demonstrated superior internal fit under the investigated material and processing conditions, while variability in marginal fit was comparable among the groups.
Clinical Significance:
Under the investigated material and processing conditions, the AM-SLA workflow demonstrated superior internal trueness and lower variability in internal fit for inlay-retained fixed partial dentures, potentially supporting more consistent internal adaptation in minimally invasive restorative treatments.
