Class II malocclusion: The aftermath of a “perfect storm” Alexandros K. Tsourakis, DDS, MS, Lysle E. Johnston, DDS, MS, PhD, FDS RCS(E)  Seminars in Orthodontics  Volume 20, Issue 1, Pages 59-73 (March 2014) DOI: 10.1053/j.sodo.2013.12.006 Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 1 Cephalometric regional superimposition (“Pitchfork Analysis 21”)—maxillary displacement relative to cranial base and mandibular excess. This superimposition also is used to measure upper tooth movement. Lower tooth movement is measured from a separate mandibular superimposition: mean functional occlusal plane orientation and D-point registration (by perpendiculars dropped from the occlusal plane). Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 2 Occlusal progression over time: yearly averages for all groups and sub-groups from ages 5 to 16 years. Note the stability of the mesial- and distal-step groups. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 3 Cumulative mandibular excess and U6 and L6 mesial movement in mesial-step subjects, ages 5–16 years. Note the lack of a L6 mesial shift (actually some distal uprighting) and the apparent balance between mandibular excess and U6 mesial drift. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 4 Cumulative mandibular excess and U6 and L6 mesial movement in distal-step subjects from ages 5 to 16 years. On average, there may be a slight, temporary mesial shift of about 1mm at age 10 years. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 5 Cumulative mandibular excess and U6 and L6 mesial movement in flush-terminal-plane subjects who progressed to a Class I molar relationship. On average, there was no obvious late mesial shift until about age 12 years, and then only about 1mm. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 6 Cumulative mandibular excess and U6 and L6 mesial movement in flush-terminal-plane subjects who went on to an end-to-end molar relationship. In this group, there was on average a 1–2mm late mesial shift spread throughout the span of the study, but most pronounced for ages 11–13 years. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 7 Cumulative mandibular excess and U6 and L6 mesial movement in flush-terminal-plane subjects who settled into a molar Class II relationship. Note the mandibular growth deficit relative to maxilla up to age 12 years, while the upper molars continue to drift forward into a Class II relationship. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 8 Cumulative increments of mandibular excess from age 5 to 16 years in the three sub-groups of the flush-terminal-plane group. Note the early (8–12 years) deficit in the mandibular excess for the Class II subgroup. This deficit is followed by what appears to be “catch-up” growth from ages 12 to 16 years. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 9 Cumulative maxillary permanent first-molar mesial movement in the three sub-groups of the flush-terminal-plane group. Note the continuous mesial drift of the upper molars, with the greatest mesial drift seen in the Class II group from ages 13 to 16 years, roughly coinciding with the mandibular “catch-up” growth depicted in Fig. 7. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 10 Terminal-plane management. In this diagrammatic summary of the present findings, note that mandibular excess and upper molar movement tend to balance (± 6–8mm) and that lower molar “mesial drift” is, on average, negligible in comparison (−1 to +2mm). A. Given any terminal plane, a major concern might be the preservation of lower leeway space. Flush and distal-step terminal planes, however, require additional steps to achieve a Class I molar relationship. B. Flush terminal plane—the effect of a maxillary holding device (Nance button, pendulum, NiTi coils, Distal Jet, Headgear, etc.) to produce a 1/2 cusp change by preventing maxillary dentoalveolar compensation. C. Distal step—U6 “distalization” (1/2 cusp), plus a period in which the upper molars are prevented from compensating for an additional 1/2 cusp of normal mandibular excess. The total of B and C would produce a Class I molar relationship. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 11 Early treatment with functional appliances. A. Mandible advanced by the functional appliance (which advancement is assumed to have no impact on the normal, favorable pattern of growth). B. For a time, the mandibular excess would produce no maxillary dentoalveolar compensation, thereby allowing displacement A. to be converted into a change in the occlusion by the normal pattern of mandibular excess. C. Variable lower anchorage loss caused by the functional appliance. The sum, B + C, more or less equals the distal-step changes illustrated in Fig. 10. Both approaches make use of the usual pattern of growth (mandible > maxilla) by controlling maxillary dentoalveolar compensation. The choice between the two is a practice management decision, although the functional appliance probably would produce a slightly more protrusive dentition. Seminars in Orthodontics 2014 20, 59-73DOI: (10.1053/j.sodo.2013.12.006) Copyright © 2014 Elsevier Inc. Terms and Conditions