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Comparative evaluation of marginal gaps of lithium disilicate crowns measured using stereomicroscopy and
1Adelaide Dental School, The University of Adelaide, Adelaide, Australia. james.dudley@adelaide.edu.au.
Objectives:
This study compared the marginal gaps of CAD-CAM lithium disilicate (LDS) crowns measured using two-dimensional (stereomicroscopy) and three-dimensional (micro-computed tomography) instruments at 12 and 360 measurement points.
Materials And Methods:
Twenty-four typodont model lower left first molars were prepared for LDS crowns by undergraduate dental students in a dental simulation clinic. An LDS crown was constructed for each preparation using a Trios 3 scanner / Sirona inLab MC X5 milling unit at a cement space of 100 μm. Each crown was placed onto its corresponding original tooth preparation, and the marginal gap was measured using stereomicroscopy and micro-computed tomography (micro-CT) at 12 and 360 selected measurement points. The mean marginal gap (MMG) was calculated using each measurement method.
Results:
The MMG measured by stereomicroscopy was 82.54 μm with 12 measurement points and 85.74 μm with 360 measurement points. For micro-CT, the MMG was 96.56 μm with 12 points and 89.83 μm with 360 points. A two-way repeated-measures ANOVA demonstrated no significant main effect of measurement instrument (F₁,₂₃ = 0.35, p = 0.56, ηp² = 0.015) and no significant main effect of measurement density (F₁,₂₃ = 1.24, p = 0.28, ηp² = 0.051). There was no significant interaction between measurement instrument and measurement density (F₁,₂₃ = 0.87, p = 0.36, ηp² = 0.036).
Conclusions:
No statistically significant differences in MMG measurements were detected between stereomicroscopy and micro‑CT for LDS crowns under the present in vitro conditions. The number of measurements made did not significantly influence the marginal gap values obtained using either measurement instrument.
Clinical Relevance:
The marginal accuracy of LDS restorations is critical for long-term clinical success. Assessing in vitro crown marginal gap using stereomicroscopy and micro-computed tomography provided comparable marginal gap measurements irrespective of the number of measurement points. Extending marginal gap measurements to in vivo studies is essential to substantiate clinical observations.
