Long term dental transversal stability of Class II division 1 treated with cervical headgear

ABSTRACT Introduction: In several conditions, outcome stability is a great challenge for Orthodontics. Previous studies have reported that relapse commonly occurs along the years after orthodontic treatment finishing. Objective: The aim of the present study was to evaluate in the long-term transversal dental arch changes of Class II division 1 patients treated with cervical headgear and fixed appliance. Methods: Plaster study casts of 20 patients treated with cervical headgear without dental extractions were 3D-scanned and evaluated in three distinct times: initial (T1), immediate post-treatment (T2) and long-term retention (T3 - minimum 20 years). Transversal teeth distance of maxillary and mandibular canines, premolars and first molars were measured. Results: A statistically significant increase during treatment was observed for all maxillary teeth transversal distances (p< 0.05). In turn, a significant reduction was observed in the long term (p< 0.05). For the mandibular teeth, canine transversal distance presented statistically significant constriction in the retention period (p< 0.05). Mandibular first molars distance was significantly expanded by treatment (p< 0.05) and remained stable in the long term. The changes observed for the other teeth or other times were considered not statistically relevant. Conclusions: For the accessed sample, transversal changes occurred during treatment and retention phases in Class II division 1 patients treated with cervical headgear and fixed appliance. Relapse was considered statistically relevant, even with the institution of a retention protocol.


INTRODUCTION
Orthodontic treatment aims at achieving adequate functional and aesthetics aspects of the dental and maxillofacial complex, thus promoting better life quality. Treatment outcome stability is of great interest for both professionals and patients; however, it is still considered a challenge. Transversal dental changes are commonly observed after appliance removal and several studies have shown progressive stability loss. [1][2][3][4][5][6][7] In the other hand, the literature also provides evidences of balance, usually presenting reduced width modifications over time. 8,9 Class II division 1 patients frequently present significant constriction of maxillary dental arch. 10 Studies aiming at evaluating Class II patients during active growth stage treated without dental extraction have noted that during treatment molar area is significantly expanded, remaining stable in the retention period. 3,9 However, the great majority of the studies evaluated short retention periods. 3,5,8,11,[13][14][15][16][17][18] Moreover, these researches were mainly performed using post-graduation programs sample, a design in which patients are treated by a varied sort of techniques or professionals and with several retention protocols.
Oliveira MB, Santos JN, Lima VM, Fonte TFL, Araujo TM, Vogel CJ, Rêgo EB Long term dental transversal stability of Class II division 1 treated with cervical headgear 5 Headgear therapy has proved to effectively assist on managing Class II malocclusion in growing patients. Classical articles, 19,20 more recent researches [21][22][23] and updated meta-analysis 24 have demonstrated positive skeletal effects with the use of extraoral forces applied to the maxillary bone. However, occlusal stability is not well addressed in the Class II treatment studies. Understanding teeth behavior in the retention phase is considered crucial for good professional practice and patient expectations fulfillment. A relatively recent survey has found that despite a decline trend in the use of headgear in USA/ Canada, the majority (62%) of the interviewed practitioners were still using the device for Class II correction. 25 In this context, the present study aimed at evaluating long term transversal changes (mean period of 25 years retention) using a sample of Class II division 1 patients treated with cervical headgear and no extractions, conducted by a single experienced operator employing the same technique and similar retention protocols.

MATERIAL AND METHODS
The present study was performed using non-probability sampling method (convenience sample). To collect the sample, an experienced clinician actively sought former patients who had been treated from the mid 1970s to the early 1990s with the following initial diagnose criteria: (1) Angle Class II

RESULTS
The search revealed 54 orthodontic cases meeting the inclusion criteria; 34 patients could not be found or refused to participate. Those who did not accept, reported living too far away, had scheduling conflicts, expressed radiation fears or simply refused to participate for unspecified reasons. Twenty patients (14 females and 6 males) agreed to attend the recall appointment and accepted to make part in the sample of the present research.
Oliveira MB, Santos JN, Lima VM, Fonte TFL, Araujo TM, Vogel CJ, Rêgo EB Long term dental transversal stability of Class II division 1 treated with cervical headgear 10 The mean period of headgear use was 2 years / 1 month, and the mean period of fixed appliance was 3 years / 3 months.
Total treatment mean time was 4 years / 4 months. Table 1 shows the overall and individual characterization of the patients included in the study, by gender and age at the three phases    Table 2.

DISCUSSION
Relapse evaluation in the long term has always been subject of interest among orthodontists and researchers. In this regard, patient's records have been source of comparison throughout the periods of treatment for quantification and severity of the alterations. Commonly, X-rays, 2 plaster models 4,6,9,18 or both X-rays and models 17 are employed. The present study evaluated transversal dental changes using plaster study casts of patients treated using the same technique and employing similar protocol of retention for all patients. It is believed that treatment uniformity can be valuable for stability evaluation. The literature accessed showed few studies with similar methodology. 6,17 The great majority of the published studies used samples belonging to post-graduation programs treated by various professionals, possibly using different techniques. 1,2,3,9,11,15,16,18,26 The sample of the present study was treated without extraction, using cervical headgear and fixed appliance. Mean age in T 1 was 11 years and 9 months, similar to previous stud- ance. This study brings the detailed retention use based on patients report (Table 2). Other studies have reported varied types of retention appliance, 6,9 but did not describe the effectively used protocol. 5,8,17,18 Angle Class II division 1 malocclusion is usually featured by the transversal constriction of the maxillary arch because of its anterior displacement in relation with the mandible.
Increased overjet and overbite can be commonly observed.
Intense lingual crown torque for posterior mandibular teeth is also commonly noted as compensation. Studies comparing Class II and Class I malocclusion showed a significant constriction of maxillary arch in Class II subjects. 10,27 In this context, it is expected that after treatment, the maxillary arch becomes broader, since posterior area is progressively divergent. Mandibular posterior teeth tend to a mild expansion due to torque correction.
A statistic significant increase during treatment was observed for all maxillary teeth distances, followed by a significant reduction in the long term (p<0.05). Pancherz et al., 9 evaluating 32-years retention period, and did not find statistic differences for the canines. Molars behavior was similar to the observed in the present study.
In the current research, mandibular canine position was not significantly modified by the treatment. It is believed that this care is considered of great importance for outcome stability. 28 Advantages and disadvantages may be attributed to the headgear therapy. Headgear is a very versatile device, permitting a varied sort of adjustments to fit to the specific morphological and growth pattern of the patient. Additionally, the device does not represent a high cost for the treatment, and is considered not difficult to be installed by the professional and/or worn by the patient. 31 However, the success of the therapy is highly dependent on patient compliance. 32 In addition, there is an increasing concern of children and parents regarding social and psychological aspects, and many professionals have tried to experience more aesthetic/discrete options or non-compliance approaches. 31,33 Limitations of the present study are important to be high-