Comparison of marginal and internal fit of 3-unit zirconia frameworks fabricated with CAD-CAM technology using direct and indirect digital scans

Abstract

Statement of problem. Accurate marginal and internal fit of dental restorations are essential for their long-term success. The fit of zirconia restorations prepared using digital scan systems has not been fully evaluated.Purpose. The purpose of this in vitro study was to compare the marginal and internal fit of 3-unit zirconia frameworks fabricated using direct and indirect digital scans.Material and methods. In a maxillary model, the left first premolar and first molar were prepared to receive 3-unit zirconia fixed dental prostheses. Conventional impressions were made using stock trays and 2-step putty/wash polyvinyl siloxane material and were scanned using laboratory scanner (Conventional Impression-Laboratory scanner [CIL] group). The impressions were then poured, and the stone casts were scanned (Dental Cast-Laboratory scanner [DCL] group). Digital scans were made using TRIOS (TRIOS Intraoral scanner [TRI] group) and CS3600 (CS3600 Intraoral scanner [CSI] group) scanners (n=10). Zirconia copings were designed and milled from presintered blocks and subsequently sintered. Marginal, mid-axial, axio-occlusal, and mid-occlusal discrepancies were measured using the silicone replica technique with stereomicroscopy at ×50 magnification. The data were analyzed using 1-way ANOVA (a=.01).Results. The ANOVA revealed significant differences among the studied groups in terms of all studied characteristics (P.01). Marginal gap was significantly higher in the DCL group (106 ±45 mm) compared with all other groups (P.01). However, no significant differences were observed in marginal gap between the TRI (60 ±15 mm) and CSI (55 ±13 mm) groups (P>.01). Internal gap in the mid-occlusal and axio-occlusal regions were significantly higher in the CIL (238 ±92 mm and 227 ±95 mm) and DCL (248 ±71 mm and 216 ±68 mm) groups than those recorded in the TRI (104 ±27 mm and 126 ±31 mm) and CSI (128 ±16 mm and 147 ±28 mm) groups (P.01). Internal discrepancies in the mid-axial position were similar between the TRI (70 ±15 mm) and CSI (72 ±23 mm) groups (P>.01), but these values were significantly lower than those recorded in the CIL (88 ±31 mm) and DCL (85 ±30 mm) groups (P.01). Conclusions.Within the limitations of this study, zirconia frameworks in the TRI and CSI groups had lower marginal and internal gaps compared with those in the DCL and CIL groups. Marginal gap in all groups was within a clinically acceptable range. (J Prosthet Dent 2020;123:105-12)

Effect of Tooth Types on the Accuracy of Dental 3D Scanners: An In Vitro Study

“…The introduction of dental computer-aided design and computer-aided manufacturing (CAD-CAM) has enabled the use of a digital workflow instead of a conventional workflow that relies on operator experience and skills [1][2][3][4][5]. The first digital workflow was partially digital and used a desktop scanner accompanied by impression taking and the fabrication of a working model [6][7][8][9]. Since then, the introduction of intraoral scanners in the 1980s has enabled a fully digital workflow [1][2][3]10].…”

“…Since then, the introduction of intraoral scanners in the 1980s has enabled a fully digital workflow [1][2][3]10]. This has reduced the effects of the operator's experience and possible errors in the material (impression and dental stone) [3,7,8,11,12]. Advances in digital workflows have made it possible to evaluate temporomandibular joint (TMJ)-related diseases through cone-beam-computed tomography (CBCT) scans [13,14].…”

Scanning Accuracy of Bracket Features and Slot Base Angle in Different Bracket Materials by Four Intraoral Scanners

“…Also, there was a difference in the roundness of the line angle of the inner surface where the wall of the slot and the base meet according to the type of scanner. (figure 3,4) In the case of a bracket that is much smaller than that of an intraoral prepared tooth or implant scan body, the difference in scanning accuracy for errors in slot base or line angle seems to be due to the difference in the principle of the IOS [28][29][30]. The CS3600 and i500 use the principle of triangulation.…”

Effect of the volumetric dimensions of a complete arch on the accuracy of scanners

“…5 The first-proposed digital workflow was a partially digital workflow accompanied by impression taking and definitive model fabrication. 3,6 Subsequently, the development of an intraoral scanner in the 1980s has enabled a fully digital workflow. 3,6 The first step of the digital workflow is to obtain a virtual model of the patient.…”