Class III treatment using facial mask: Stability after 10 years

Early Class III malocclusion treatment may not have long-term stability due to mandibular growth. Although some features of this malocclusion point to a better prognosis, it is practically impossible for the orthodontist to foresee cases that require new intervention. Many patients need retreatment, whether compensatory or orthodontic-surgical. The present study reports the case of a Class III patient treated at the end of the mixed dentition with the use of a face mask followed by conventional fixed appliances. The case remains stable 10 years after treatment completion. It was presented to the Brazilian Board of Orthodontics and Dentofacial Orthopedics (BBO) as a requirement for the title of certified by the BBO.


INTRODUCTION
This study reports the case of a 12-year and 4-month-old patient referred to treatment with chief complaint of "crossed front teeth and protruded lower lip".The patient sought improvements in smile and facial esthetics. He was in good general health without relevant register in his medical history, and presented in regular oral hygiene with a few white spot lesions and mild gingivitis. His parents reported that anterior crossbite was not present in deciduous dentition, it only appeared after permanent incisors eruption.

DIAGNOSIS
Facial assessment (Fig 1) revealed absence of passive labial seal, a concave profile and protruded lower lip; thereby suggesting anteroposterior skeletal relationship (Class III).The patient was at the end of the second transitional period of the mixed dentition with Class III molar relationship (Figs 1 and 2).He presented unbalanced maxillomandibular transverse relationship which resulted in functional unilateral posterior crossbite from tooth #12 to #16 and lower midline deviation to the right when in maximum intercuspation.  and 2 mm) as well as protruded and buccally tipped mandibular incisors (1-NB = 29 o and 7 mm). These dental features indicated dentoalveolar and skeletal components of Class III malocclusion.
In functional terms, there was little anterior mandibular shift to the right from centric relation to maximum intercuspation.
Panoramic radiograph (Fig 3), taken at the end of the second transitional period of the mixed dentition, did not reveal any abnormalities. Cephalometric analysis (

TREATMENT PLAN
Treatment planning initially aimed at correcting maxillomandibular discrepancy by means of a face mask followed by rapid expansion of the maxilla which also contributed to correct the transverse deficiency. To this end, a modified Haas appliance associated with hooks in the region of canines used as support for protraction of the maxilla was used. Patient and parents were aware of the need for strong compliance to achieve treatment success. They were also informed that unpredictable mandibular growth could create the need for a new intervention and potential orthognathic surgery during adulthood.
Thus, they were presented with an alternative approach: wait for growth completion during adolescence and have orthodontic treatment with fixed appliances and potential orthognathic surgery carried out in the future. Patient's parents agreed on the early approach and follow-up to monitor the possibility of new interventions. A pre-adjusted, metallic, fixed orthodontic Roth prescription appliance would be installed in both maxillary and mandibular arches. After treatment finishing, the retention phase would begin with the use of a removable wraparound retainer in the maxillary arch and an intercanine bar in the mandibular arch.

TREATMENT PROGRESS
The modified Haas appliance was manufactured based on a Hyrax expander. Maxillary expansion followed an activation protocol of ¼ turn every 12 hours for 14 days. Figure 5 illustrates the final outcomes. After 14 days, the expansion appliance remained stabilized and therapy with Petit face mask began (Fig 6). A 600-g force was applied 14 hours a day for 6 to 8 months so as to overcorrect overjet. However, the patient reported having applied force 12 hours a day and, for this reason, 6 months were rendered necessary to correct anterior crossbite. He was then advised to wear the appliance while sleeping for 4 months so as to achieve protraction stability.

A B
After removing the expander and discontinuing protraction, a removable 0.8-mm stainless steel wire palatal bar was installed to achieve transverse stability and adjust first molars rotation. During the same appointment, pre-adjusted, metallic, fixed orthodontic Roth prescription brackets were bonded on maxillary teeth, except for unerupted canines. Alignment and leveling procedures began with the use of 0.016-in NiTi archwire followed by 0.016, 0.018 and 0.020-in stainless steel archwire associated with omega loops on molars mesial surface until canines erupted so as to preserve dental arch circumference. At treatment finishing, 0.019 x 0.025-in stainless steel rectangular archwire was used. Fluoride-varnish at 5 ppm (Duraphat ® , Colgate, Germany) was applied every three months to prevent white spot lesions 1 (Fig 7).   On the mandibular arch, bracket bonding was carried out with individualized angulation for teeth #43 and 33 so as bracket slots were perpendicular to the root axis, thereby favoring format compensation. The sequence of archwires used for alignment and leveling was similar to that used in the maxillary arch: 0.019 x 0.025-in stainless steel rectangular archwire associated with intermaxillary Class III elastics 16 hours a day.
Importantly, maxillary canines and second molars eruption was delayed, which increased total treatment time (41 months). Left mandibular second molar was mesially and buccolingually tipped while the patient and his parents were anxious for treatment conclusion. Thus, the appliance was completely removed with only the TMA rectangular archwire remaining on teeth #36 and 37 to correct #37 positioning. This wire segment was removed after 4 months when the patient brought his final exams to the last appointment. Additionally, the patient was referred to extraction of tooth #48 which was the only mesially tipped third molar he had.
A removable wraparound retainer was continuously used in the maxillary arch for 6 months during the day and at night for 2 years during the retention phase. In the mandibular arch, however, a 0.8-mm stainless steel wire intercanine bar was installed and used for life.

RESULTS
Patient's final exams (Figs 8 to 12)revealed harmonious lip repositioning as well as improvements in facial profile which became slightly convex. Maxillomandibular relationship was restored to normality and ANB angle increased from 0.5 o to 2 o . Such improvements were due to maxillary advancement (SNA increased in 2 o ).Class III relationship was corrected by maxillary incisors buccal tipping (1-NA increased in 11 o and 3 mm).Mandibular incisors practically remained in their original position. Treatment was completed without further shifts between centric relation and maximum intercuspation. Occlusion guidance was restored (protrusion and laterality).
Cephalometric tracings superimposition (Fig 12A) revealed facial growth down and forward. Particularly due to protraction, the maxilla advanced towards the nasion point, thereby resulting in a balanced maxillomandibular relationship. Partial maxillary superimposition ( Fig 12B)revealed buccal incisors tipping and little molar extrusion as a result of alveolar protraction and development expected for that period. Partial mandibular superimposition (Fig 12B) revealed mandibular growth as well as compensatory alveolar growth in molar and incisors regions.    In view of the above, it is reasonable to assert that treatment results were in accordance with treatment initial objectives. The patient was highly satisfied with his final facial and dental esthetics and remained aware of the need for a long-term follow-up to monitor mandibular growth and occlusal relationship.
Total treatment time was long due to early treatment approach, delayed maxillary canines and second molars eruption as well as patient's absence at some appointments. New examinations were requested ten years after orthodontic treatment completion (Figs 13 to 17). They revealed excellent occlusal stability and facial balance. Both panoramic radiograph (Fig 14) and lateral cephalogram (Fig 15A) revealed all aspects were within standards of normality. The patient was advised in terms of periodontal care and the need for extracting tooth #48. Control and cephalometric tracings superimposition (Fig 16) revealed little residual mandibular growth which did not compromise facial and dental features achieved at treatment completion.