James L. Vaden

Age effects on orthodontic treatment: Adolescents contrasted with adults

Skeletodental treatment changes in 30 adolescent girls and 26 women who had Class II, Division 1 malocclusions were contrasted cephalometrically, primarily with the McNamara analysis. The data show that adult treatment does not obligate the practitioner to longer treatment. In this study, both age groups were treated in 2.5 years on the average. Apical base corrections were achieved with equal facility in both groups by the posterior remodeling of point A, and this (in conjunction with unrestrained mandibular growth) is the major source of correction in the adolescents. In adults, in whom growth is trivial, an appreciable source of sagittal correction is the steepening of the occlusal plane. Several sequelae of Class II elastic force occurred as by-products of molar correction in the adults: increased mandibular molar eruption, increased maxillary molar intrusion, increased maxillary incisor eruption, increased mandibular incisor intrusion, and steepening of the occlusal plane.

Age effects on orthodontic treatment: Skeletodental assessments from the Johnston analysis

We have compared differences in treatment outcomes dependent on patient age, either adolescent (means = 12.5 years at start) or adult (means = 27.6). Subjects were female patients whose Class II, Division 1 malocclusions were treated with Tweed edgewise mechanics and four-premolar extractions. Cephalometric records were assessed according to the Johnston analysis. The functional occlusal plane remained stable during mechanotherapy in the adolescents, whereas it steepened considerably in the adults. Differential mandibular growth in adolescents contributed 70% of the total molar correction, with orthodontic tooth movement accounting for the other 30%. Maxillary growth in the adults detracted from the Class II molar correction; tooth movement accounted for virtually all of the correction.

Straight talk about extraction and nonextraction: a differential diagnostic decision.

At one stage or another, orthodontics is usually a space management procedure, particularly during the correction of a Class I or Class II malocclusion. Orthodontists use space that is available or create space to correct malocclusions. There are anterior, posterior, lateral, and vertical dimensions of the dentition and its supporting structures. If the muscular balance is normal, the clinician should try to respect these dimensions. The orthodontic clinician should not be an extractionist or a nonextractionist. Rather, the clinician should use differential diagnostic skills and artistic ability to arrive at the most appropriate treatment outcome for each patient.

Effects of patient age on postorthodontic stability in Class II, division 1 malocclusions.

The increase in the proportion of adults in the typical orthodontic practice merits closer scrutiny of the treatment differences involved in adult vis-à-vis adolescent patients. Orthodontic treatment in the adolescent relies heavily on growth; in the adult, the practitioner must reposition teeth within the nongrowing arches. This difference may create the potential for greater postretention relapse in the adult; alternatively, continued growth in the subadult might detract from stability of the case. Two samples of Class II, Division 1 cases, all treated by one specialist, were examined an average of 5 years out of treatment. One group had been treated during adolescence (approximately 12 years of age), the other in adulthood (approximately 28 years). The orthodontic corrections were stable in both groups, but for different reasons: Posttreatment changes in the bony and dental structures of the adults were minimal. Bony changes (i.e., continued midface and mandibular growth) were appreciable in adolescents, and this growth--notably growth of the mandible--compensated for unfavorable drift of the dental elements (primarily mesial shift of the maxillary molar) after treatment. In sum, orthodontic corrections in adults were found to be at least as stable as those in the conventional adolescent patient.

A LONGITUDINAL CEPHALOMETRIC STUDY OF POSTORTHODONTIC CRANIOFACIAL CHANGES

Although the orthodontist focuses great efforts on diagnosis and treatment of the patient, less attention is paid to posttreatment changes that occur because of relapse and continued growth, especially over the long term. This cephalometric study describes 36 patients who were recalled x = 5.5 years after treatment and again x = 14.4 years after treatment. Most linear dimensions increased significantly from the end of treatment to first recall (ca. 16 to 21 years), presumably as a result of continued adolescent growth, but few changes achieved significance thereafter (ca. 21 to 30 years). Arch relationships (eg, ANB, NAP, AOBO, Y-axis) continued to improve after treatment, probably as a result of late growth of the mandible producing a more orthognathic profile. There was little change from first to second recall in any of the variables. Results suggest that if relapse occurs, it is likely to be evident soon after treatment and diminish thereafter and that continued craniofacial growth generally augments the orthodontic correction.

Postorthodontic dental changes: a longitudinal study.

The conventional adolescent orthodontic patient is treated during a phase of active growth, but growth of the skeletodental complex continues after treatment and into adulthood at a much slower pace. Selection of orthodontic diagnostic and treatment regimens that produce stable and esthetic dental relationships is a continual endeavor for the orthodontic specialist. Patients should be recalled for long periods of time and the results evaluated. The present longitudinal study was completed on 36 individuals, all of whom had received comprehensive orthodontic treatment. Dental changes were assessed from cephalograms for the in-treatment period (ca. 12 to 15 years of age), posttreatment to first recall (0 = 22 years of age), and first to second recall period (0 = 30 years of age). There was considerable change in the absolute locations of the teeth, but, in reality, these changes are almost wholly attributable to growth of the bony reference structures, not dental changes per se. Growth proceeded at a very slow pace after the first recall (ca. 22 to 30 years of age ). Dental relationships, eg., FMIA, IMPA, 6L angulation, exhibited no systematic change after treatment.

Clinical ramifications of posterior and anterior facial height changes between treated and untreated Class II samples

Some clinicians have suggested that one primary difference between successful and unsuccessful Class II treatment outcomes is the relative change of anterior and posterior facial heights. Successfully treated cases are claimed to exhibit greater increases in posterior facial height (PFH, articulare to gonion) than in the anterior facial height (AFH, menton to palatal plane). This conjecture was tested here by recalling a treated Class I sample and a treated Class II sample and by comparing the differences found in these samples to an untreated Class II sample at the same ages. The PFH/AFH ratio increased significantly more in the treated Class I and Class II samples during the active phase of treatment than in the untreated Class II sample at the same ages. During the years from posttreatment to recall (mean = 6 yrs), there was a significant increase in the PFH/AFH ratio in the treated Class II sample due to a greater increase in PFH than AFH. This ratio continued to improve after all appliance therapy had been discontinued, and it did not occur in the treated Class I sample nor in the untreated Class II sample. The conclusion was that the patient with a Class II malocclusion, if treated, continues to change favorably over time. This favorable change, in turn, helps maintain the Class II correction.

The Twee-Merrifield philosophy

Charles Tweeds concepts have been simplified, enhanced, and expanded by Levern Merrifield. Merrifields ideas have augmented Tweeds to give orthodontics the Tweed-Merrifield philosophy. Adherence to the philosophy allows the orthodontic specialist to define objectives for the face, the skeletal pattern, and the teeth, and to diagnose and treat a malocclusion to efficiently reach these predetermined objectives.

Lower incisor space analysis: A contrast of methods

Two current methods to assess spacing-crowding among lower anterior teeth are described and contrasted. These are the anterior space analysis of Merrifield and the irregularity index of Little. There is only a modest correlation between these methods (rs = +0.53) because they provide complementary information; space analysis is more attuned to tooth displacements while the irregularity index is susceptible to axiversions. Cases illustrating major divergences between the two methods are illustrated.

Adult versus adolescent Class II correction: A comparison

The interest of the adult patient in orthodontics has increased as the demographics of the specialty of orthodontics has changed. There are major intreatment and posttreatment differences in Class II malocclusion correction between the adolescent and the adult. This article outlines the differences--and the similarities--between adolescent and adult Class II malocclusion correction. The differences and similarities are illustrated with case reports of a representative adolescent from the adolescent group and a representative adult from the adult group.