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. 2021 Jul 19;22(1):23.
doi: 10.1186/s40510-021-00371-7.

Analysis of pretreatment factors associated with stability in early class III treatment

Yasuko Inoue  1 , Toru Deguchi  2 , James K Hartsfield Jr  3 , Wakako Tome  4 , Noriyuki Kitai  4
Affiliations

Analysis of pretreatment factors associated with stability in early class III treatment

Yasuko Inoue et al. Prog Orthod. .

Abstract

Background: The purpose of this study was to identify pretreatment factors associated with the stability of early class III treatment, since most orthodontists start the treatment with their uncertain hypotheses and/or predictions. Subjects consisted of 75 patients with a class III skeletal relationship (ANB < 2° and overjet < 0 mm) who had been consecutively treated with rapid maxillary expansion and facemask and followed until their second phase treatment. The patients were divided into two groups according to whether they showed relapse in follow-up. The stable group maintained their positive overjet (n = 55), and the unstable group experienced relapse with a zero or negative overjet (n = 20). Two general, three dental, and 13 cephalometric pretreatment factors were investigated to determine which factors were associated with stability.

Results: Sex, pretreatment age, and anteroposterior functional shift, which were hypothesized as associated factors, were not related to the stability of early class III treatment. Significant differences were detected between the two groups in the horizontal distance between the maxillary and mandibular molars in centric relation. Cephalometric variables, such as the mandibular length (Ar-Me), Wits appraisal, SN to ramus plane angle (SN-Rm), gonial angle, incisor mandibular plane angle (IMPA), and Frankfort plane to mandibular incisor angle (FMIA) showed significant differences between the groups. The horizontal distance was the most influential factor by logistic regression analysis.

Conclusions: Hypothesis (related to sex, age, functional shift) were rejected. Several cephalometric factors related to the mandible were associated with stability. The horizontal distance between the maxillary and mandibular molars in centric relation was the best predictor of early class III treatment relapse.

Keywords: Cephalometric; Early class III; Mounted cast models; Pretreatment factors; Stability.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Horizontal and vertical distances on the mounted dental casts. The horizontal distance between the mesial contact point of the maxillary first molar and the mesial contact point of the mandibular first molar was measured bilaterally. The vertical distance between the mesiobuccal cusp of the maxillary second primary molar and the mesiobuccal cusp of the mandibular second primary molar was measured bilaterally
Fig. 2
Fig. 2
Linear measurements. (1) Maxillary length (ANS-PNS), (2) mandibular length (Ar-Me), and (3) Wits appraisal
Fig. 3
Fig. 3
Angular measurements. (1) SNA angle, (2) SNB angle, (3) ANB angle, (4) SN to SN-Ar (SN-Ar), (5) SN to ramus plane angle (SN-Rm), (6) mandibular plane angle (SN-Md), (7) gonial angle, (8) upper incisor to palatal plane angle (U1-PP), (9) incisor mandibular plane angle (IMPA), and (10) Frankfort mandibular incisor angle (FMIA)
Fig. 4
Fig. 4
The percentage of stable cases relative to the pretreatment horizontal distance. The open triangle indicates an outlier. The occurrence of unstable cases started when the horizontal distance was more than 0.5 mm, and when this distance exceeded 3.5 mm, the percentage of stable cases was 0
See this image and copyright information in PMC

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