Marginal and internal fit evaluation of conventional metal-ceramic versus zirconia CAD/CAM crowns

N Paul,Mr Dhakshaini,Kn Raghavendra Swamy,S Sowmya,M Meravini

doi:10.4317/jced.55946

Abstract

BackgroundThe 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. Material and Methods10 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). ResultsThe 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. ConclusionsThe 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

Introduction

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

Material and Methods

Point PM has

Results

Discussion

Conclusions