Abstract
The purpose of this in vivo study was to compare the marginal and internal gap widths of monolithic zirconia crowns fabricated by CAD/CAM technique and metal-ceramic crowns fabricated by conventional technique. 10 participants needing a single restoration were selected. Zirconia crowns using CAD/CAM technology (Group A) (n=10) and metal-ceramic crowns (Group B) (n=10) using lost wax casting technique were fabricated for each selected tooth. The marginal and internal gaps of crowns were recorded using a replica technique with light body silicone material stabilized with a regular set putty. Each replica was sectioned buccolingually and mesiodistally and then evaluated at five pre-determined sites. The points measured were PM for marginal gap, PA for axial gap, PAO for axio-occlusal transition gap and PO and PCO for occlusal gaps using a stereomicroscope at 30× magnification. The Paired Sample (t) test was used to detect significant differences between the two groups in terms of marginal and internal fit (α= 0.05). The mean for the marginal gap was 77.42μm (±39.5μm) for Group A compared with 95.86μm (±55.12μm) for Group B. Mean values for internal gap was 87.24 (±21.7 µm) for Group A and 132.91 µm (± 50.63 µm) for Group B. Significant differences were observed between both the groups for marginal (p=.010) and internal (p=.000) fit. The CAD/CAM fabricated zirconia crowns demonstrated a better accuracy of fit when compared to metal-ceramic crowns fabricated by conventional technology. Key words:Marginal fit, Internal fit, Computer-aided design/computer-aided manufacturing (CAD/CAM).
Highlights
Metal-ceramic crowns remain the most commonly used crowns for fabricating full coverage restorations, since they combine the high strength properties of metal with the cosmetic appearance of ceramic [1]
The point clouds obtained in scanning are transformed through a computer-aided design (CAD) software algorithm into a smooth and continuous surface, which can lead to some internal inaccuracies further leading to interfering contacts at the incisal/occlusal edge and are proven to be detrimental if they occur at the margin.[3]. CAD/computer-aided manufacturing (CAM) technology can be divided into two categories according to the technique used: subtractive manufacturing technique and additive manufacturing technique
This study was designed to compare the marginal and internal fit of single unit monolithic zirconia crowns fabricated by CAD/CAM technique and metal-ceramic crowns fabricated by conventional technique
Summary
Metal-ceramic crowns remain the most commonly used crowns for fabricating full coverage restorations, since they combine the high strength properties of metal with the cosmetic appearance of ceramic [1]. The horizontal marginal misfit measured perpendicular to the path of draw of the casting is called the horizontal marginal discrepancy. Beuer et al [8] have reported that a 50 μm space in the chamfer area is expected to result in better seating at the margin area, but most authors agree to 120μm being the clinically acceptable maximum marginal gap for a good long-term prognosis, a value-based criterion established by Mc Lean and von Franhoufer [9]. A few studies have compared metal-ceramic crowns and CAD/CAM restorations in patients [13]. This study was designed to compare the marginal and internal fit of single unit monolithic zirconia crowns fabricated by CAD/CAM technique and metal-ceramic crowns fabricated by conventional technique. The null hypothesis was that no significant differences would be found in the marginal and internal fit of crowns fabricated with these two techniques
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