Korean J Orthod.  2015 May;45(3):113-120. 10.4041/kjod.2015.45.3.113.

Comparison of occlusal contact areas of class I and class II molar relationships at finishing using three-dimensional digital models

• Lee H
• Kim M
• Chun YS

• KMID: 1974802
• DOI: http://doi.org/10.4041/kjod.2015.45.3.113

Abstract

OBJECTIVE
This study compared occlusal contact areas of ideally planned set-up and accomplished final models against the initial in class I and II molar relationships at finishing.
METHODS
Evaluations were performed for 41 post-orthodontic treatment cases, of which 22 were clinically diagnosed as class I and the remainder were diagnosed as full cusp class II. Class I cases had four first premolars extracted, while class II cases had maxillary first premolars extracted. Occlusal contact areas were measured using a three-dimensional scanner and RapidForm 2004. Independent t-tests were used to validate comparison values between class I and II finishings. Repeated measures analysis of variance was used to compare initial, set up, and final models.
RESULTS
Molars from cases in the class I finishing for the set-up model showed significantly greater contact areas than those from class II finishing (p < 0.05). The final model class I finishing showed significantly larger contact areas for the second molars (p < 0.05). The first molars of the class I finishing for the final model showed a tendency to have larger contact areas than those of class II finishing, although the difference was not statistically significant (p = 0.078).
CONCLUSIONS
In set-up models, posterior occlusal contact was better in class I than in class II finishing. In final models, class I finishing tended to have larger occlusal contact areas than class II finishing.

Keyword

Tooth movement; Contact area; Molar; Orthodontic treatment; Occlusion

MeSH Terms

Bicuspid
Molar*
Tooth Movement

Figure

• 

  Figure 1 Classification of class I and II finishings. A, Class I finishing viewed from the buccal aspect. B, Class I finishing viewed from the lingual aspect. C, Class II finishing viewed from the buccal aspect. D, Class II finishing viewed from the lingual aspect.

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  Figure 2 Calculation of occlusal contact areas of set-up models using the Boolean function (RapidForm 2004) in mm2 areas. A, Occlusal contact area of class I finishing. B, Occlusal contact area of class II finishing.

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  Figure 3 Images of the RapidForm 2004 used to calculate the occlusal contact areas. A, Image of the maxillary model sample with the first molar excised. B, Image of the excised maxillary first molar. C, Buccal aspect of the occluded first molars. D, Image of the excised mandibular first molar. E, Image of the mandibular model sample with the first molar excised. F, Image and measurement of the occlusal contact point (boxed in red).

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