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Kim, Woo, Pae, and Kim: Clinical convergence angle and rounding radius on tooth preparation for zirconia all-ceramic crown
ORIGINAL ARTICLE

J Korean Acad Prosthodont 2011;49(1):22-28.

Published online: 18 December 2011

DOI: https://doi.org/10.4047/jkap.2011.49.1.22

Clinical convergence angle and rounding radius on tooth preparation for zirconia all-ceramic crown

Hye-Eun Kim, MD, Yi-Hyung Woo, DMD, MSD, PhD, Ahran Pae, DMD, MSD, PhD, Hyeong-Seob Kim, DMD, MSD, PhD∗

Department of Prosthodontics, Division of Dentistry, Graduate School, Kyung-Hee University, Seoul, Korea

Corresponding Author: Hyeong-Seob Kim Department of Prosthodontics, School of Dentistry, Kyung-Hee University, #1, Hoegi-Dong, Dongdaemun-Gu, Seoul, 130-701, Korea +82 2 958 9340: e-mail, odontopia@khu.ac.kr

Received 9 December 201015 December 2010       Accepted 8 January 2011

Copyright © 2011 The Korean Academy of Prosthodontics

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

This article attempted to examine how teeth for restoration is made in a clinical practice and utilize it as future educational material of teeth formation and basic data for additional research.

Materials and methods

This experiment investigated the models sent to milling center for production of zirconia crowns. After scanned with Lava CAD/CAM System (3M ESPE, Seefeld, Germany), they are measured on ‘ImageJ (version 1.32j, National Institutes of Health, USA)’ program and compared and analyzed. Convergence angle from mesio-distal surfaces and bucco-lingual surfaces of each teeth are measured. Also, bucco-lingual diameter of the region lowered as much as 0.4 mm from incisal edge in anterior teeth except canines.(This measure is defined as the Peak 0.4) The analysis of data between each group was conducted by Windows SPSS statistic program, and was proved significant on 95% confidence level by independent t-test, one-way ANOVA and multiple analysis (Sheffe ′ test).

Results

The mean value of convergence angle was 18.67° . It is ranked as molar (26.70°) > premolar (16.87°) > anterior teeth (14.81°) in the order of mesio-distal convergence angle; anterior teeth (22.32°) > molar (20.93°) > premolar (15.41°) in the order of bucco-lingual convergence angle. The mean value of Peak 0.4 was 1.18 mm.

Conclusion

Convergence angle of abutment of zirconia all ceramic crown has difference depending on the location in the arch. Due to the nature of production of zirconia all ceramic crown, convergence angle of abutment and line angle finishing degree can have an effect on internal suitability of restoration. (J Korean Acad Prosthodont 2011;49:22-8)

Keywords: Zirconia, Tooth preparation, Convergence angle, Rounding radius

REFERENCES

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Fig. 1.
The theory of measurement.
jkap-49-22f1.tif
Fig. 2.
The angle measured with the ImageJ.
jkap-49-22f2.tif
Fig. 3.
Measurement of Peak 0.4 with the ImageJ.
jkap-49-22f3.tif
Fig. 4.
Distribution of Peak 0.4.
jkap-49-22f4.tif
Table 1.
Numbers of examined teeth with regard to tooth and dental arch
  Incisors/Canines Premolars Molars Total
Maxilla       373
Right 143 40 14 197
Left 132 37 7 176
Mandible       123
Right 18 29 27 74
Left 13 17 19 49
Total 306 123 67 496
Table 2.
Assessment of measurement reliability
  Incisors/Canines Premolars Molars
First 25.41 19.95 22.24
Second 26.02 19.77 21.99
Table 3.
Mean mesio-distal and bucco-lingual convergence angles of dies
  M-D B-L Total
Mean 16.93 20.42 18.67
SD 8.04 9.35 8.89
P .000∗    

M-D: mesio-distal surface, B-L: bucco-lingual surface

∗ : The difference is significant at the level of 0.05

Table 4.
Mean convergence angle of anteroposterior position of the teeth in arch
  M-D B-L Total
Incisors/Canines
Mean 14.81 22.32 18.57
SD 6.00 9.48 8.77
Premolars
Mean 16.87 15.41 16.14
SD 7.16 7.43 7.32
Molars
Mean 26.70 20.93 23.82
SD 10.27 8.66 9.89

M-D: mesio-distal surface, B-L: bucco-lingual surface

Table 5.
Multiple comparison (Sheffe′test) of anteroposterior position of the teeth in arch
  M-D B-L Total
Incisors/Canines - Premolars
P .005∗ .000∗ .000∗
Incisors/Canines Molars
P .000∗ .269 .000∗
Premolars Molars
P .000∗ .000∗ .000∗

M-D: mesio-distal surface, B-L: bucco-lingual surface

∗ : The difference is significant at the level of 0.05

Table 6.
Mean convergence angle on maxilla and mandible
  M-D B-L Total
Maxilla (n = 373)      
Mean 16.01 21.24 18.62
SD 6.76 9.64 8.72
Mandible (n = 123)      
Mean 19.72 17.95 18.84
SD 10.60 7.95 9.39
P .000∗ .000∗ .000∗

M-D: mesio-distal surface, B-L: bucco-lingual surface

∗ : The difference is significant at the level of 0.05

Table 7.
Mean convergence angle depending on right and left of arch
  M-D B-L Total
Right (n = 271)    
Mean 17.14 21.05 19.09
SD 8.07 9.55 9.05
Left (n = 225)    
Mean 16.67 19.66 18.17
SD 8.00 9.08 8.68
P 0.525 .100 .103

M-D: mesio-distal surface, B-L: bucco-lingual surface

∗ : The difference is significant at the level of 0.05

Table 8.
Overall mean convergence angle depending on types of definitive prosthesis
  M-D B-L Total
Zirconia Metal-ceramic Zirconia Metal-ceramic Zirconia Metal-ceramic
Mean 16.93 16.91 20.42 16.19 18.67 16.55
SD 8.04 10.73 9.35 11.19 8.89 10.96
P .985   .000∗   .000∗  

M-D: mesio-distal surface, B-L: bucco-lingual surface

∗ : The difference is significant at the level of 0.05

Table 9.
Mean convergence angle of incisors, premolars, and molars depending on types of definitive prosthesis
  M-D B-L Total
Zirconia Metal-ceramic Zirconia Metal-ceramic Zirconia Metal-ceramic
Incisors/Canines
Mean 14.81 12.14 22.32 17.71 18.57 14.51
SD 6.00 8.01 9.48 13.55 8.77 11.05
P .001∗   .002∗   .000∗  
Premolars
Mean 16.87 14.01 15.41 12.15 16.14 12.75
SD 7.16 9.92 7.43 9.56 7.32 9.67
P 0.129   .009∗   .002∗  
Molars
Mean 26.70 23.35 20.93 17.23 23.82 20.29
SD 10.27 10.52 8.66 9.11 9.89 10.29
P .037∗   .008∗   .001∗  

M-D: mesio-distal surface, B-L: bucco-lingual surface

∗ The difference is significant at the level of 0.05

Table 10.
Mean Peak 0.4 of examined teeth
  Maxilla (n = 484) Mandible (n = 50) Total
Mean 1.16 1.34 1.18
SD 0.22 0.34 0.24
Range 0.65 - 2.54    
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