Association of dentoskeletal morphology with incisor inclination in angle class II patients: a retrospective cephalometric study

Abstract

Introduction: The purpose of this study was to identify possible dentoskeletal parameters associated with variation of anterior tooth inclination in Angle Class II subdivisions.

Methods: Pre-treatment lateral radiographs of 144 Class II patients (68 males, 76 females) aged 9 to 17 years were classified for upper incisor inclination into three groups (proclined, normally inclined, retroclined) homogeneous for gender and skeletal jaw relationship. The effect of age on the 22 cephalometric variables was controlled by covariance analysis.

Results: Multivariate analysis of the cephalometric parameters indicated significant inter-group differences. Systematic associations with incisor inclination were revealed using rank correlation: Lower incisor proclination, Wits appraisal and gonial angle significantly decreased (0.04 ≥ p ≥ 0.002), while intercisal angle, mandibular total and corpus length and nasolabial angle increased (0.04 ≥ p ≥ 0.001) with decreasing incisor proclination.

Conclusions: Clear-cut classification criteria and control of confounding effects may clarify conflicting previous findings on dentoskeletal differences between Class II subdivisions in the mixed dentition. Only minor dentoskeletal differences appear to be associated with incisor inclination. The increased interincisal and nasolabial angle in Class II division 2 subjects are due to reclination of both upper and lower incisors. Jaw positions and chin prominence are not significantly different between the subdivisions. However, Wits appraisal is decreased in Class II division 2. The increased mandibular length observed in Class II division 2 requires further scrutinization.

Figure 1

Skeletal landmarks and soft tissue parameters: upper/lower central incisor inclination (∠U1-NL, ∠L1-ML, ∠L1-NB, ∕L1-NB, ∠U1-L1); sagittal parameters (∠SNA, ∠SNB, ∠ANB, ∠SNPg, ∠PgNB, ∕Wits, mandibular total (∕Go-Pg) and corpus (∕Go-Gn) lengths, maxillary length (∕A’-PNS); vertical parameters (∠ML-NSL, ∠NL-NSL, ∠ML-NL, ∠ArGoMe, ramus length (∕Ar-Go), F(acial) H(eight) index (∕N-ANS: ∕ANS-Gn), Jarabak’s ratio (∕S-Go : ∕N-Me); soft tissue parameters (∠nasolabial angle, ∠H(oldaway)-angle).

Figure 2

Age-adjusted group means (■) and 95 percent confidence intervals (□): a - mandibular total length (GoPg in millimeters); b - gonial angle (ArGoMe in degrees).