IADR Abstract Archives

Maxillary Upper First Molar Changes in Buccolingual Angulation and Arch Width Before and After Eruption of Second Molars

Objectives: Buccolingual inclination of maxillary first molars and intermolar width have been shown to decrease with growth for subjects with Class I occlusion. Class II occlusions have not been studied. Our aim was to investigate changes in buccolingual inclination and intermolar width of Angle Class I and II occlusions in nontreated subjects before and after maxillary second molar eruption.
Methods: The sample included 24 subjects, 12 with Class I and 12 with Class II occlusions from the Forsyth/Moorrees Twin Study. Siblings and only one twin per pair were included. Models taken yearly for six consecutive years, three before and three after the eruption of the maxillary second molars, were scanned using a 3D scanner. MotionView™ software was used to calculate the distance between the most occlusal point of the buccal groove of the maxillary first molars as the intermolar width. The buccolingual inclination was calculated by comparing the differences in distances of each cusp height to a standardized occlusal plane. The distances were used in a mathematical formula using the sin value to find the angulation of the cusps. ANOVA for repeated measures was used to compare the l inclination and width over the 6 time points. Independent t-test was performed to compare Class I and II subjects.
Results: There was no significant change in arch width over time, either in the entire group or in comparing Class I and Class II groups. The distobuccal cusp inclined significantly by 3° in the entire group (P=0.01) after eruption of the second molar, and this cusp also inclined 4° more in Class I compared with Class II occlusions (P=0.02) during the same interval.
Conclusions: Inconsistent changes in maxillary first molar buccolingual inclination and width occur during the eruption of the second molar. A larger sample is needed to further investigate these changes.
Grant Support: Supported by American Association of Orthodontists Foundation.
IADR/AADR/CADR General Session
2015 IADR/AADR/CADR General Session (Boston, Massachusetts)
Boston, Massachusetts
2015
2952
Craniofacial Biology
  • Santana, Lillelenny  ( Boston University , Waltham , Massachusetts , United States )
  • Bamashmous, Mohamed  ( Boston University , Waltham , Massachusetts , United States )
  • Kantarci, Alpdogan  ( The Forsyth Institute , Boston , Massachusetts , United States )
  • Will, Leslie  ( Boston University , Waltham , Massachusetts , United States )
    • American Association of Orthodontists Foundation.
    NONE
    Poster Session
    Molecular and Clinical Orthodontics I
    Friday, 03/13/2015 , 03:30PM - 04:45PM
    Paired ttest comparing the arch width and U6 torque before and after the eruption of U7
    Paired ttest comparing the arch width and U6 torque before and after the eruption of U7
    Before eruption U7 After eruption U7
    Parameters Mean STD Mean STD P value
    Age 11.13 1.18 12.17 1.12
    Arch width 50.99 2.83 51.26 2.90 0.14
    RU6 MB angulation 28.66 4.30 27.62 5.41 0.17
    DB angulation 8.12 4.17 9.73 4.32 0.06
    DL angulation 42.94 1.67 41.99 7.59 0.53
    LU6 MB angulation 27.47 4.62 27.03 6.29 0.64
    DB angulation 8.74 6.24 11.76 7.42 0.01
    DL angulation 42.90 2.16 42.41 6.64 0.72

    Ttest comparing arch width and U6 torque between Class I and Class II subjects
    Ttest comparing arch width and U6 torque between Class I and Class II subjects
    BEFORE ERUPTION U7
    Parameters Mean Class II SD Class II Mean Class I SD Class I P value
    Age 10.75 0.97 11.50 1.51
    Arch width 50.01 2.80 51.97 2.64 0.09
    RU6 MB angulation 29.99 3.54 27.33 5.03 0.15
    DB angulation 6.02 4.13 10.23 3.96 0.02
    DL angulation 42.44 1.77 43.44 1.34 0.13
    LU6 MB angulation 27.19 5.57 27.76 3.61 0.77
    DB angulation 8.29 6.76 9.20 5.67 0.73
    DL angulation 42.46 2.04 43.34 2.11 0.31
    AFTER ERUPTION U7
    Mean Class II SD Class II Mean Class I SD Class I P value
    Age 11.83 0.83 12.50 1.51 0.20
    Arch width 50.14 2.91 52.38 2.66 0.06
    RU6 MB angulation 29.22 4.84 26.02 5.70 0.15
    DB angulation 8.41 3.62 11.04 4.93 0.15
    DL angulation 40.20 9.90 43.78 1.04 0.24
    LU6 MB angulation 28.38 7.16 25.69 4.55 0.29
    DB angulation 12.80 7.65 10.72 6.70 0.49
    DL angulation 41.00 8.68 43.82 1.17 0.29