Cutting efficiency of diamond burs in CADCAM dental ceramics and resulting surface characteristics
Date
2015
DOI
Authors
Abualsaud, Reem
Version
OA Version
Citation
Abstract
Objectives: the purpose of this study is to evaluate the cutting efficiency of diamond burs under different conditions (diamond grits, Cutting force, and coolant) when machining 3 CAD/CAM dental ceramics. Also, the study aims at examining the resulting surface topography, edge chipping and kerf size.
Materials and methods: Coarse, medium, and fine grit diamond burs (n=10) from 3 manufacturers (Meisinger, Komet, and Brasseler) were used to make 3 cuts each, in fully sintered zirconia blocks (TZ-3YSB-E, TOSOH), fully crystalized lithium-disilicate (IPS e.max CAD, Ivoclar), and feldspathic porcelain blocks (VitaBIocs TriLuxe Forte, Vita) using an electric handpiece running at 200,000 rpm. The cutting forces for zirconia and e.max were 1.47N and 1.96N and for TriLuxe Forte 0.98N. Three Cooling liquids (tapwater, 0.9% saline, and 1:5 mouthwash) at a rate of 100ml/min were used. The ceramic blocks were fixed on a sliding base running on 2 rods using frictionless ball bearings. The cutting distance was recorded using LVDT connected to LabView software. Average cutting rate was calculated for each cut. Instruments weighed and evaluated using SEM before, during and after experiments. Kerfs and edge chippings seen around each cut were recorded using optical microscope connected to a high definition video micrometer. The blocks were then sectioned to reveal machined surfaces for surface roughness measurement. Statistical analysis was conducted using student t-teSt, ANOVA and Tukey post hoc test at [alpha]=0.05.
Results: one-way ANOVA revealed a significant difference in material removal rate between the three substrates (P<0.0001) and the three consecutive cuts. For e.max and TriLuxe Forte, there was a significant difference in cutting rate between coarse and medium burs (P<0.01). However, coarse and medium burs were not significantly different from each other when machining zirconia for Meisinger and Komet burs but were significantly different for Brasseler burs (P<0.0001). Fine burs were significantly different than other grits for the three manufacturers (P<0.0001). T-test showed a significant difference between the two cutting forces for zirconia and e.max (P<0.05). A significant difference in cutting rate was seen between the different cooling liquids. However, the difference was material dependent. Mouthwash resulted in significantly larger cutting rates with e.max and TriLuxe Forte (P<0.01) compared to water. Saline produced significantly larger cutting rates with zirconia and e.max compared to water (P<0.05). Edge chipping was found to be significantly larger on exit side compared to entry side for all substrates (P<0.01). Larger diamond grits resulted in significantly larger chippings for zirconia and e.max (P<0.05) but not for TriLuxe Forte (P>0.05). Large diamond grits produced significantly larger kerfs (P<0.0001). Surface roughness was found to be significantly larger in TriLuxe Forte than other substrates (P<0.0001).
Conclusions: A significant differences in material removal rate was found between the three substrates with feldspathic porcelain being the highest followed by e.max then zirconia. Also, bur cutting rate was found to decline with consecutive cuts. Similar grits from different manufacturers behave differently under similar testing conditions. However, fine diamond burs had significantly smaller cutting rates than other grits for all manufacturers. Increasing the cutting force can improve material removal rate. In this study, it was found that the effect of cooling liquid is material dependent with mouthwash improving feldspathic porcelain removal rate and saline improving that of zirconia. Edge chipping increased when the diamond grits were bigger and it was found to be more on bur exit side. Feldspathic porcelain had the highest surface roughness values compared to other substrates.
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Thesis (DScD) --Boston University, Henry M. Goldman School of Dental Medicine, 2015 (Department of Restorative Sciences and Biomaterials).
Includes bibliographic references: leaves 128-132.
Thesis (DScD) --Boston University, Henry M. Goldman School of Dental Medicine, 2015 (Department of Restorative Sciences and Biomaterials).
Includes bibliographic references: leaves 128-132.
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This work is protected by copyright. Downloading is restricted to the BU community. If you are the author of this work and would like to make it publicly available, please contact open-help@bu.edu.