Microcomputed tomography a noninvasive method to evaluate the fit of a restoration as compared to conventional replica technique

Abstract

Aim: The aim of the study was to compare the assessment methods used to evaluate the fit of Ni-Cr metal copings. Settings and Design: Comparative- Invitro study design. Materials and Methods: A stainless steel die simulating a prepared first maxillary premolar was used as a master die. Wax pattern copings were fabricated by the conventional dipping wax technique ( n = 20) on the master die and were cast in Ni-Cr alloy. The finished copings were fitted on the master die and scanned by the micro-computed tomography (CT) scanner. Multiple projections of the sample were reconstructed to evaluate the marginal and internal fit at 5 predetermined locations. The same copings were used for the replica technique and were evaluated under a stereomicroscope in the same locations. Statistical Analysis Used: Shapiro–Wilk's test and Unpaired t -test Results: The marginal fit values observed were 127.71 and 95.06 μm, chamfer area fit values were 151.97 and 132.7 μm, axial area fit values were 62.36 and 46.14 μm, axio-occlusal area fit values were 139.52 and 123.6 μm, occlusal area fit values were slightly higher with 217.91 and 193.1 μm, respectively, in replica and micro-CT technique. There was no statistically significant difference observed in the fit between the two assessment methods (α > 0.05). Conclusions: There was no difference observed in the marginal and internal fit of Ni-Cr metal copings with the two methods of assessment. However, the micro-CT technique proved to be simpler, noninvasive, and time-saving assessment method.

Fit of metal-ceramic crowns

“…Our results showed that the marginal fit of both copings was similar, but internal fit was better for cast copings. The higher values obtained for the occlusal surface when compared with the axial wall are also described in previous studies 13,20,21,24 , despite the fact that milled copings are believed to have lower marginal discrepancies, since their fabrication has fewer steps. According to the literature, cement film thickness varies considerably, but most authors describe 120 µm as the clinically acceptable maximum thickness for a long-term good prognosis 25 .…”

“…Lately, micro-CT imaging has also been used to assess the marginal and internal fit of crowns and fixed partial dentures 11,28,39 . Both non-destructive methods are considered effective to evaluate the adaptation of indirect restorations 20,24 .…”

Comparison of Marginal Integrity and Surface Roughness of Selective Laser Melting, CAD-CAM and Digital Light Processing Manufactured Co-Cr Alloy Copings

“…Contemporary CoCr alloys have gained popularity as compared with conventional gold alloys due to improved corrosion resistance and low cost [23]. The available literature showed multiple techniques, i.e., the direct-view measurement technique, the silicone replica technique, and cross-sectioning to measure the marginal misfit of fabricated copings [26]. The micro-computed tomography (CT), on the other hand, is comparatively an advanced method to assess the fit of indirect restoration through processing of scanned specimens slices, reconstructing the assembly by using software and gaging the misfit [27].…”

Fit accuracy of removable partial denture metal frameworks produced by CAD-CAM – a clinical study

“…1,10,12,20 In the present study, the measurement of the thickness and volume of the silicone specimens was made by micro-CT technique due to its advantages to other analog or digital measurement techniques (for example, methods using gauges, microscopes, or scanners), such as specimen preservation, high-resolution power, high precision, simple methodology, specimen digitization by just one scan, and the ability to measure the total thickness and simultaneously the volume of the specimen. 1,[10][11][12][21][22][23] No differences in thickness and volume were found between the two groups of frameworks, so the null hypothesis could not be rejected. These findings are in line with the results of a previous laboratory study, 1 whose authors also did not declare differences in the fit accuracy of RPD metal frameworks produced by a similar CAD-CAM protocol with those produced by a conventional protocol.…”