Marginal fit of crowns fabricated via simultaneous digital workflows for integrated fiber post-and-core and crown: an...

For teeth with extensive structural defects, the post-and-core crown is a well-established, but multi-visit approach to preserving the natural tooth. Digital workflows enable simultaneous fabrication of the post-and-core and crown; however, the marginal fit of the crown produced by these workflows-a critical indicator of clinical performance-has not been systematically assessed. This in vitro study aimed to compare crown fit between two simultaneous digital workflows and a conventional sequential method.

Thirty intact mandibular first premolars were randomly assigned to three groups (n = 10): traditional step-by-step workflow (TSS group), digital cast splicing method (DSM group), and physical polyether cast (PPC group). All restorations were fabricated using computer-aided design and manufacturing (CAD-CAM) and subsequently cemented. Marginal and internal fit were assessed using microcomputed tomography (micro-CT). The adhesive volume and surface area of the abutment teeth were quantified three-dimensionally to calculate the average intracoronary cement thickness (AICT). The crown fit was evaluated in two dimensions at 16 locations, including the marginal gap (MG), axial wall gap (AWG), axial occlusal intersection gap (AOG), and occlusal gap (OG). Statistical analyses were conducted using appropriate parametric or non-parametric tests with a significance level of α = 0.05.

No significant differences were observed among the three workflows for AICT (P = .083) and AOG (P = .204). Significant inter-group differences were found for MG (P = .022), AWG (P = .004), and OG (P < .001) regarding the 2D parameters. Specifically, the DSM group exhibited a larger MG than the TSS and PPC groups; the PPC group demonstrated a larger AWG than the TSS and DSM groups; and the TSS group showed a larger OG than both the PPC and DSM groups. Despite these statistical differences, all measured values remained within the 120 μm threshold.

Simultaneous digital fabrication of integrated post-and-core crowns achieved a clinically acceptable marginal fit. Within the limitations of this in vitro study, digital workflows represent a reliable alternative to conventional multi-visit protocols for the fabrication of integrated post-and-core and crowns.

This study involves ex vivo experiments using extracted teeth (biological samples) and does not qualify as a clinical trial. Therefore, clinical trial registration does not apply to this study.