Incisor inclination changes produced by two compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusionsby Robert A. Miller, Long Tieu, Carlos Flores-Mir

The Angle Orthodontist

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Year
2013
DOI
10.2319/062712-528.1
Subject
Orthodontics

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Original Article

Incisor inclination changes produced by two compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusions

Robert A. Millera; Long Tieub; Carlos Flores-Mirc

ABSTRACT

Objective: To compare the changes in incisor inclination between two compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusions.

Materials and Methods: Among Class II malocclusion patients a total of 38 consecutive patients treated with the Xbow appliance and later with full brackets (XB) were compared to 36 consecutive patients treated with Forsus connected to the archwire while on full brackets (FO). Evaluated cephalometric variables were overjet, overbite, skeletal Class II, lower incisor inclination, and upper incisor inclination. Factors that were analyzed were gender, treatment type, age at start of treatment (T1), and treatment length. Independent t-tests, x2, multiple analysis of variance, and

Pearson correlations were applied.

Results: No differences in incisor inclination between both treatment protocols were identified. At

T1 no statistical difference for any cephalometric variable was demonstrated with regard to gender and treatment type. Gender was also not associated with a different treatment time or age at T1.

The mean treatment time was 24.2 months for XB and 30.2 months for the FO group (P 5 .037).

XB patients averaged 10 fewer months of fixed edgewise appliances compared to FO patients.

Neither gender nor treatment type had any influence on the changes of the evaluated dependent variables between T1 and the end of treatment. Lower incisors proclined more the longer the treatment (P 5 .005). Both overjet and upper incisor inclination were affected by age at T1 (P 5 .001 and P 5 .014, respectively).

Conclusions: Both compliance-free Class II correction protocols for the treatment of mild to moderate Class II malocclusions appear to generate the same amount of incisor inclination. Large variability was identified. (Angle Orthod. 0000;00:000–000.)

KEY WORDS: Xbow; Forsus; Incisor inclination

INTRODUCTION

The controversy over lower incisor proclination from treating the Class II nonextraction patient persists today.

While some authors1–3 claim that the gingival/periodontal condition is worsened in patients who undergo incisor proclination, others4,5 have found no association between

Class II mechanics and gingival recession or bone loss.

In this regard HerbstTM appliances, the most popular ‘‘bite jumping’’ Class II correctors, have been studied,6 and no before increase in gingival recession was found in treated adolescents and children. Even considering this, some authors7,8 have suggested avoiding proclining incisors in adults because of a lack of resiliency of these tissues. To consolidate this controversy two systematic reviews9,10 have explored all of the available evidence.

Both concluded that there is no strong clinically important association between the degree of incisor proclination and increased gingival recession. The authors of these studies hypothesized that it is the combination of thin attached gingival coverage, poor oral hygiene, and inflammation that facilitates incisal gingival recession when proclining teeth. a Private Practice, Culpeper, Va. b Orthodontic Graduate Student, University of Alberta, Edmonton, AB, Canada. c Associate Professor and Head of the Division of Orthodontics, University of Alberta, Edmonton, AB, Canada.

Corresponding author: Dr Carlos Flores-Mir, Associate

Professor and Head, Division of Orthodontics, University of

Alberta, 5528 Edmonton Clinic Health Academy, 11405-87

Avenue NW, 5th Floor, Edmonton AB T6G 1C9 (e-mail: cf1@ulberta.ca)

Accepted: August 2012. Submitted: June 2012.

Published Online: October 3, 2012

G 0000 by The EH Angle Education and Research Foundation,

Inc.

DOI: 10.2319/062712-528.1 1 Angle Orthodontist, Vol 00, No 0, 0000

In a systematic review11 evaluating treatment changes resulting from Herbst therapy, it was determined that dental changes were more significant than skeletal changes in the final occlusal results. Since most of the correction is dento-alveolar, auxiliary devices that are mainly believed to produce dentoalveolar changes, such as the ForsusTM device, may serve as a good alternative. The Fatigue Resistant Device, more commonly known by its trade name ‘‘Forsus,’’ has gained widespread acceptance in recent years as a replacement for other Class II treatment alternatives while in full fixed edgewise appliances. This device was developed by 3M Unitek (3M Unitek, Monrovia, Calif). Since its introduction in 2001 several modifications12 have been made by the manufacturer to enhance fatigue resistance and improve patient comfort. The development of the Forsus evolved through a combination of trial and error and CAD/CAM technology. When fully compressed, the spring force is approximately 200 g and was designed to correct a Class II malocclusion in 6 months while simultaneously enduring the demanding oral environment. It is mentioned that the available attachment variations makes it universally appealing, easily modified to adapt to various oral sizes and shapes.

Lately the Forsus spring has been used as the mechanism of force for the XbowTM Class II corrector (Xbow). The Xbow (pronounced crossbow) is a patented appliance that uses the Forsus springs as a phase 1 appliance for treatment in the late mixed or early permanent dentition.13 In a recent study,14 the Xbow was shown to correct dentally a mild to moderate Class

II malocclusion in approximately 4.5 months; then it was removed to allow some musculoskeletal and dental relapse to occur prior to initiation of full fixed edgewise appliances. This result has shown to compare quite favorably with the reported Herbst effects.15 Some control of the lower incisors inclination is believed to be achieved by a low position of the lingual arch and a higher position of the labial arch of the lower framework.