Research and education
Convergence of the axial walls of full veneer crown preparations in a dental school environment,☆☆

https://doi.org/10.1016/0022-3913(91)90457-8Get rights and content

Abstract

This research report used a simple and accurate method of measuring the convergence of full veneer crown preparations. A random sample of 909 dies was selected from all dies of full veneer crown preparations done at the University of Colorado, School of Dentistry student clinic over a 6-year period. All preparations were accomplished by third- and fourth-year dental students under either normal clinic conditions or under special (proficiency) testing conditions. The mean convergence angles were 19 degrees (S.D. ± 9.8 degrees) for nonexamination conditions and 15.7 degrees (S.D. ± 5.5 degrees) for examination procedures. These angles are far in excess of those normally recommended in the fixed prosthodontic textbooks. The values obtained in this investigation agree with the findings of most of the current published studies on the subject.

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Cited by (63)

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    Further in vivo studies on the fracture resistance of zirconia copings, depending on the width of chamfer preparation, are necessary to ensure reliable preparation recommendations and perhaps avoid unnecessary loss of sound tooth structure. Based on current literature,5-19,24 a TOC between 6 and 20 degrees was defined as being acceptable, although textbooks on fixed prosthetics usually recommend lower values.3,4 Nevertheless, 44.2% of the preparations did not fulfil this requirement.

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    2015, Journal of Prosthetic Dentistry
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    Many relevant studies had to be excluded because they reported grouped values or ranges or did not provide enough information. Some of the included articles failed to specify anatomic location (mandible versus maxilla)29,35,36,39,41,44-46,48,50 or type of tooth (incisor, canine, premolar, or molar),36,38,50 and 1 article reported only a single cross section.45 The TOC angle was the most commonly reported parameter.

  • Convergence angles of metal ceramic crowns prepared by dental students

    2014, Journal of Prosthetic Dentistry
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    One study found that a mean convergence angle of 23.7 and 11.3 degrees of taper were clinically achievable and varied depending on the preparation conditions.24 Average convergence angles were reported by different authors as 19.2 degrees,29 16 degrees,39 15 degrees,13 and 17.3 degrees.25 Another study of preparations found that 12.7% of prepared teeth were within a taper range of 2 to 5 degrees and had an average taper of 9.5 degrees (19.0-degree convergence angle).27

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Murray H. Personal communication, Chapel Hill, NC: University of North Carolina School of Dentistry 1987.

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Supported in part by BRSG grant No. 023 2-5-36925.

a

Assistant Professor, Division of Fixed Prosthodontics.

b

Professor and Chairman, Division of Fixed Prosthodontics; Acting Chairman, Department of Restorative Dentistry.

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