Evaluating the effect of repeated use of milling burs on surface roughness and adaptation of digitally fabricated ceramic veneers

Abstract

This study aimed to evaluate how repeated use of milling diamond burs with different coarseness affects surface roughness, and marginal and internal adaptation of CAD/CAM veneers. Methods: Forty leucite-reinforced glass-ceramic veneers were milled in 2 groups based on the milling mode (with fine or extra-fine bur sets). In each group, every 10 veneers were milled with a new bur set. All veneers were cemented to bovine teeth and then polished. Labial surface roughness was measured before cementation, and after polishing. Marginal and internal discrepancies were measured using a field emission scanning electron microscope. Three-way and two-way mixed repeated measures ANOVA were applied to assess changes in surface roughness values of veneers and discrepancy values, respectively. The Bonferroni correction was applied for multiple comparisons. Results: Repeated use of a milling diamond bur set had a significant effect on surface roughness of the veneers (P < .001). Mean surface roughness of the fine milling mode was significantly higher in comparison to that of extra-fine mode before (P ¼ .002) and after (P ¼ .01) polishing. After polishing a significant decrease in surface roughness occurred in fine (P ¼ .02), but not in extra-fine milling mode (P ¼ .99). Repeated use of milling burs significantly affected marginal and internal adaptation between some repeated uses. Conclusions: Marginal and internal adaptation were significantly affected by repeated use of milling diamond burs up to 10 times between some repeated uses. However, no specific pattern could be established. Clinical significance: Repeated use of milling burs could affect surface roughness, surface microcracks, critical defects, and adaptation of CAD/CAM restorations. Therefore, it plays a major role in clinical success of the restorations.

Fit, Precision, and Trueness of 3D-Printed Zirconia Crowns Compared to Milled Counterparts

“…On the other hand, milled crowns were manufactured consecutively using the same zirconia disc. The subtractive manufacturing procedure induces changes in the milling burs, starting after the first mill [ 58 ]. This eventually affects the trueness of the produced restoration and the precision thereafter.…”

Clinical performance of single implant prostheses restored using titanium base abutments: A systematic review and meta‐analysis

“…Manufacturers of TBA can standardize the cement gap within their prescribed digital library, while allowing for adequate ventilation of cement. The age of the milling tools (Payaminia et al, 2021); CAD milling strategies (Zimmermann et al, 2018); and surface treatment protocol (Arce et al, 2018) are factors that can influence the accuracy of the internal fitting surface of the implant prosthesis. Industrialization of the process standardizes these parameters, unlike traditional manual processes where the dental technician can easily influence the intimacy of fit.…”

Effects of repeated use of tungsten carbide burs on the surface roughness and contact angles of a CAD-CAM PMMA denture base resin

“…21 According to the manufacturer of the CEREC/inLab MC XL, the life of a diamond rotary instrument ranges from 4 to 15 or more mills, whereas the life of a tungsten carbide bur ranges from 20 to 60 or more mills. 22 Manufacturers of the GN-I and Cadim dental CAD-CAM systems assert that diamond rotary instruments may be used to fabricate more than 10 ceramic complete crowns, although 10 is the recommended maximum number of repeated machining procedures. 23 Hotta et al 4 indicated that tungsten carbide burs can be used to fabricate up to 51 titanium crowns.…”

“…24 The lifespan of an individual bur can be affected by the size of the bur tip, the size and material composition of the milled block, and the complexity of the restoration. 22 Roperto et al 24 reported that the surface quality of CEREC CAD-CAM milling burs used in excess of the number of procedures prescribed by the manufacturer was similar to that of burs that were used in accordance with the manufacturer's instructions. While the study authors claimed that burs could continue to be used beyond the recommendations of the manufacturer without reducing restoration quality, their study assessed bur wear only, without examining restoration quality.…”

“…The effect of rotary instruments on the surface properties of CAD-CAM ceramic materials has been evaluated. 5,22,24,25 However, the authors are unaware of a previous study that investigated the effects of rotary instrument quality on the surface properties of CAD-CAM PMMA denture base material. Moreover, while previous studies have addressed the overall quality of CAD-CAM materials with regard to machinability, there is little information regarding the effects of repeating milling and bur wear on the surface quality and thus the clinical performance of the definitive restoration.…”