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Evaluation of cutting efficiency, surface roughness, and diameter of diamond rotary instruments on laboratory and
Selva Malar Munusamy1, Yee Shien Chung1, Mohideen Salihu Farook1
1Department of Restorative Dentistry, Faculty of Dentistry, Universiti Malaya, Kuala Lumpur, Malaysia.
Background:
Replacement of diamond rotary instruments is critical for optimizing cutting efficiency. The authors aimed to assess and compare the cutting efficiency, surface roughness, and diameter of coarse-grit and medium-grit diamond rotary instruments after repeated cuts on indirect composite materials.
Methods:
Medium-grit (115 μm) and coarse-grit (150 μm) diamond rotary instruments (NTI; Kahla GmbH) were tested on 2-mm-thick Ceramage (Shofu) (CM) and Lava Ultimate (3M ESPE) (LU) specimens and divided into 4 groups of 8 samples per group: LU-coarse, LU-medium, CM-coarse, and CM-medium. A high-speed handpiece with a cutting load of 0.9 N, speed of 400,000 rpm, and water flow rate of 25 mL/min was used. Cutting efficiency was assessed by measuring cutting time and surface roughness (roughness average) was measured using a surface analyzer and diameter was measured using calipers. Data were analyzed statistically using 2-way analysis of variance (ANOVA), followed by 1-way ANOVA with Tukey honestly significant difference post hoc test (P < .05). For comparison between cuts, 1-way repeated measures ANOVA was used for cutting time and surface roughness and paired samples t test was used for diameter (P < .05).
Results:
Coarse-grit diamond rotary instruments had significantly higher (P < .05) cutting efficiency than medium-grit diamond rotary instruments at cut 1. At cut 10, significant differences (P < .05) in mean cutting time, surface roughness, and diameter were observed, with coarse-grit diamond rotary instruments having pronounced wear patterns compared with medium-grit diamond rotary instruments.
Conclusions:
Differences in cutting time, surface roughness, and diameter after repeated cuts on indirect composite materials was instrument dependent. Coarse-grit rotary instruments had greater deterioration and wear than medium-grit rotary instruments.
Practical Implications:
Medium-grit diamond rotary instruments can be suggested for prolonged use (cut 10) on computer-aided designed and computer-aided manufactured composites. Diamond rotary instruments are recommended for replacement after cut 10 or 5 minutes of use on indirect composite materials.
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