Context: Provisional crowns are essential intermediate restorations in fixed prosthodontics, and marginal fit is a key determinant of periodontal health, pulpal protection, and long-term clinical success. Present CAD/CAM technologies allow for production by subtractive milling or additive manufacturing, each with inherent technical properties potentially influencing marginal fit. Comparative in-vitro evidence under controlled conditions, however is still limited in this regard, and controlled assessments have to be applied to inform fabrication method choice. Methods: The laboratory-based experimental setup was used to compare the marginal fit of provisional crowns produced through digital CAD design followed by fabrication through 3D printing (n = 10) or milling (n = 10). Both the groups used a standardized tooth preparation and master die. All the crowns were produced from PMMA-based materials following the manufacturer's suggested parameters. Marginal gap was measured at four standardized positions on each crown—mid-buccal, mid-lingual, mid-mesial, and mid-distal—using a 50× magnification stereomicroscope. The data were 40 measurements per group. The data were tested for normality and compared using independent samples t-tests with the significance level at p < 0.05. Intra- and inter-examiner reliability were also tested using intraclass correlation coefficients (ICCs). Outcomes: The group mean marginal gap in the 3D-printed cohort was 95.8 ± 8.5 μm, whereas the milled cohort had a mean of 73.1 ± 7.0 μm. The mean difference recorded between the cohorts was 22.7 μm, the difference that was statistically significant (t = 8.56, p < 0.001), with a substantial effect size (Cohen's d = 1.92). Site-specific tests also revealed that at all four marginal sites measured, the milled crowns had consistently smaller gaps, with p-values of less than 0.001 for all the tests. Intraclass correlation coefficients (ICCs) for intra- and inter-examiner measurements were greater than 0.97, reflecting excellent measurement reliability. Qualitative synthesis revealed that the crowns 3D-printed showed slightly greater variability at the marginal areas, which was generally because of small differences in junction surface smoothness, whereas the milled crowns showed more uniform adaptation. Conclusion: Within the constraints of this in vitro investigation, milled provisional crowns exhibited significantly reduced marginal discrepancies with improved fit uniformity over their 3D-printed counterparts. Both techniques yielded results within clinical acceptable margins, demonstrating, however, that although milling may be more suited, 3D printing is also a useful alternative if manufacturing efficiency or material usage is the priority.
Reem Almutairi (Fri,) studied this question.