What question did this study set out to answer?

The aim is to assess and compare the accuracy of different manufacturing techniques for interim fixed dental prostheses.

April 12, 2026Open Access

Internal fit and marginal adaptation of digitally fabricated interim fixed dental prostheses

Puntos clave

The aim is to assess and compare the accuracy of different manufacturing techniques for interim fixed dental prostheses.
Used a maxillary typodont cast to simulate clinical scenarios.
Scanned the cast with an intraoral scanner and designed the FDPs using software.
Produced the FDPs using milling, SLA, and DLP techniques and scanned for gaps with micro-computed tomography.
Analyzed gaps using Image J software and statistical methods including 2-way ANOVA.
Milled FDPs showed higher gaps than SLA and DLP printed FDPs across all span lengths.
For 3-unit FDPs, milling had the largest marginal gap (112 µm) compared to DLP (99 µm) and SLA (45 µm).
For 4-unit FDPs, milling again had the highest gap (147 µm), with DLP (102 µm) and SLA (83 µm) following.
For 6-unit FDPs, milling reported 135 µm, while DLP and SLA had lower gaps at 104 µm and 78 µm, respectively.

Resumen

ABSTRACTStatement of problem The clinical performance of interim fixed dental prostheses (FDPs) depends on their accuracy, which is influenced by manufacturing technique, material type, and span length. Rapid advancements in these factors warrant updated evaluation of their impact on FDPs accuracy. Purpose The aim of the present study was to assess the accuracy of stereolithography (SLA) and digital light processing (DLP) 3-dimensional (3D) printing of interim FDPs of different span lengths and compare these methods with the milling technique. Material and methods A maxillary typodont cast was used to simulate 3 clinical situations of missing maxillary anterior teeth. The abutment teeth were prepared, the cast was scanned using an intraoral scanner, and the scans were exported as standard tessellation language (STL) files into a software program for designing the FDPs. The designs were exported to a milling machine, SLA 3D printer, and DLP 3D printer for production. Specimens were divided into 3 groups according to manufacturing technique (n=24) and 3 subgroups according to span length (n=8), with a total number of 72 specimens. The FDPs were seated onto their corresponding casts, and the assemblies were scanned using micro-computed tomography (µCT). The produced scans were assessed for internal and marginal gaps using the Image J software program. Gaps were evaluated at the incisal, axial, and marginal regions. The data were analyzed using 2-way ANOVA models, and modeling was followed by post hoc comparisons of estimated marginal means using F-tests and pairwise t tests with Kenward-Roger degrees-of-freedom approximation. Results Milled FDPs exhibited higher incisal, axial and marginal gaps for all span lengths than the SLA and DLP 3D printed groups. For marginal gaps, the results were as follows: 3-unit FDPs: the highest mean gap was recorded in milling (112 ±9 µm), followed by DLP (99 ±19 µm), and the lowest in SLA (45 ±9 µm) P P P Conclusions 3D printed FDPs had fewer marginal and internal gaps than milled FDPs for different span lengths. All digitally fabricated FDPs exhibited marginal gap values within ranges commonly reported as clinically acceptable.

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