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Apical Gap, Adaptation, and Trueness of Direct and Indirect Customized Post-and-Core Restorations Fabricated by the
Hadi Ranjzad1, Jalal Toumaj2, Farzaneh Ostovarrad3
1Department of Prosthodontics, Dental Sciences Research Center, School of Dentistry, Guilan University of Medical Sciences, Rasht, Iran, gums.ac.ir.
Background:
Customized post-and-core restorations can be fabricated using direct or indirect workflows, combined with conventional casting or digital techniques, including milling and selective laser melting (SLM). However, evidence on how these approaches influence apical gap, adaptation, and trueness remains limited. This study aimed to evaluate these outcomes in direct and indirect post-and-core restorations fabricated by casting, milling, and SLM.
Methods:
Eighty-four mandibular molar post-and-core restorations were fabricated in six groups (n = 14) combining two methods (direct and indirect) with three techniques (casting, milling, and SLM). The apical gap was measured on parallel digital radiographs; adaptation was assessed by quantifying the mass of light-body silicone captured between the post and canal walls; trueness was calculated as root mean square (RMS) deviation in Geomagic. Data were analyzed using mixed-effects models with Bonferroni-adjusted pairwise and paired t-tests (α = 0.05).
Results:
For apical gap, fabrication technique had no significant effect within either workflow (direct: p = 0.639; indirect: p = 0.138); whereas, direct casting demonstrated a significantly smaller apical gap than indirect casting (p = 0.009). For adaptation, direct casting showed superior performance compared with direct milling (p = 0.050); in contrast, indirect SLM demonstrated better results than indirect casting (p = 0.036); direct casting also yielded better adaptation than indirect casting (p < 0.001). For trueness, direct milling was less true than direct casting or SLM (p < 0.001); indirect casting was less true than indirect milling or SLM (p = 0.011). Across all groups, RMS values were evaluated against the conservative (0.05 mm) and permissive (0.10 mm) thresholds. All specimens (84/84, 100%) exceeded 0.05 mm, and 72 of 84 specimens (85.7%) exceeded 0.10 mm, with group-level proportions above 0.10 mm, ranging from 71.4% (casting) to 100% (milling).
Conclusions:
Both fabrication technique (casting, milling, and SLM) and method (direct and indirect) affected apical gap, adaptation, and trueness. The most favorable combinations were direct casting and indirect SLM.
