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The Influence of Bur Blade Concentricity on High-speed Tooth-cutting Interactions: A Video-rate Confocal Microscopic Study

Department of Conservative Dentistry, United Medical and Dental Schools of Guy's and St. Thomas' Hospitals, Guy's Dental School, London Bridge, London, SE1 9RT, United Kingdom

R.J. Cook

Department of Conservative Dentistry, United Medical and Dental Schools of Guy's and St. Thomas' Hospitals, Guy's Dental School, London Bridge, London, SE1 9RT, United Kingdom

This study aimed to determine the degree of eccentricity between different tungsten carbide bur manufacturing techniques and to study the effect of bur inaccuracy on dental enamel. Error in bur concentricity may arise from malalignment of the steel shaft and carbide head in a two-piece construction bur. Cutting blades rotate at multiple radii from the shaft axis, potentially producing vibrations and damage to the cut substrate. Techniques now allow for the manufacture of one-piece tungsten carbide burs with strength adequate to withstand lateral loading. A comparison of tungsten carbide dental cutting tools revealed the true extent of concentricity errors. Variation in alignment of the cutting head and shaft in the two-part constructions incurred between 20 and 50 µm of additional axial error. High-speed cutting interactions with dental enamel between carbide burs were studied by means of a video-rate confocal microscope. A cutting stage fitted to a Tandem Scanning Microscope (TSM) allowed for real-time dynamic image acquisition. Images were captured and retrieved by means of a low-light-level camera recording directly to S-VHS videotape. Videotape showing the interactions of high-speed rotary cutting instruments (at 120,000 rpm) were taken under simulated normal wet-cutting environments, and the consequent damage to the tooth tissue was observed as it occurred. Concentrically engineered bur types produced a superior quality cut surface at the entry, exit, and advancing front aspects of a cavity, as well as less subsurface cracking. Imaging of the coolant water film local to recent cutting operations showed regular spherical cutting debris of 6 to 18 um diameter from the concentric tools, whereas the less-well-engineered burs produced ragged, irregular chips, with 25-40 um diameter debris, indicating far more aggressive cutting actions. This study has shown that there is reduced substrate damage with high-concentricity carbide burs.

Key Words: Bur • cutting • enamel • confocal • tungsten carbide

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Journal of Dental Research, Vol. 74, No. 11, 1749-1755 (1995)
DOI: 10.1177/00220345950740110601


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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Watson, T.F. Articles by Cook, R.J. Search for Related Content PubMed PubMed Citation Articles by Watson, T.F. Articles by Cook, R.J. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB TUNGSTEN CARBIDE TUNGSTEN COMPOUNDS Social Bookmarking                         What's this?