Two-Phase Treatment of a Class III with Severe Anterior Open Bite and Hyperdivergent Growth Pattern: A Digital Workflow Option

Patients with anterior open bite tend to exhibit significant skeletal and dentoalveolar maxillary transverse constriction.^1-3 When a skeletal Class III malocclusion is involved, early protraction treatment can promote maxillary development.⁴ Facemask therapy can produce purely skeletal changes, but it also tends to create undesirable side effects such as excessive forward movement, extrusion of the upper molars, and proclination of the upper incisors.⁵

When associated with maxillary skeletal expansion, the mechanics of Class III therapy seem to rely on simultaneous weakening and opening of the circummaxillary sutures. Recent studies have shown no significant enhancement of maxillary protraction with additional expansion, however, except when the Liou protocol was used.⁶ To provide an effective and efficient option with minimal side effects, Maino and colleagues developed a protocol for alternating expansion and constriction of the maxillary complex with a hybrid palatal expander anchored to both bone and teeth, followed by facemask therapy.⁷ A three-dimensional surgical guide was developed for reliable palatal miniscrew insertion.^8,9

This case report demonstrates a two-phase approach to treatment of a complex Class III malocclusion in the vertical, transverse, and sagittal dimensions, using the skeletal Alt-RAMEC protocol for Class III (SKAR III) and a completely digital workflow.

Diagnosis and Treatment Planning

A 9-year-old female presented in the first stage of the transitional dentition (Fig. 1). She had a well-proportioned face with good mandibular symmetry; the upper midline was slightly deviated to the left with respect to the facial midline, and there was a pronounced anterior open bite. The patient also displayed a long lower facial third and a recessive chin. Intraoral examination found maxillary transverse constriction, lower anterior crowding, excessive overjet, and 6mm of negative overbite. A long-term tongue-thrust habit had contributed to the development and perseverance of the open bite (Fig. 1B).

The panoramic radiograph indicated the presence of all permanent teeth at the proper stages of eruption. According to the cephalometric analysis (Table 1), the patient had a hyperdivergent growth pattern (FMA = 29.3°) and a Class I sagittal skeletal relationship (Wits appraisal = 0mm). The upper incisors were proclined with respect to the palatal plane (U1-PP = 116.2°), but the lower incisors were normally inclined with respect to the mandibular plane (IMPA = 95.9°).

One option in this case was to wait until the end of growth to see if the anterior open bite would self-correct; in most cases, however, this condition worsens with growth.¹⁰ Another alternative was to perform orthognathic surgery after growth, in conjunction with pre- and postsurgical orthodontics. This would have led to the development of a complex malocclusion with anterior open bite and upper-­incisor proclination, causing severe functional and esthetic problems during adolescence. Therefore, an interceptive phase of orthopedic treatment was planned to eliminate the tongue-thrust habit and thus prevent worsening of the malocclusion while promoting optimal development of the masticatory system.

Treatment Progress

For the first phase of treatment, a customized RPE was digitally designed with bite blocks and an anterior tongue crib (Fig. 2A). This would provide the necessary transverse expansion while controlling the vertical dimension (Fig. 3). The tongue crib enabled natural closure of the open bite by blocking the tongue from interpositioning and by correcting its posture.^11,12 The RPE was activated once per day for 40 days to obtain an overcorrection of the transverse dimension and resolve the bilateral crossbite of the deciduous canines (Fig. 2B).

The appliance was kept in place for 10 months to stabilize the result (Fig. 4). At the end of this phase, a new lateral cephalogram revealed a hyperdivergent Class III growth pattern (FMA = 33.4°), which was corroborated by familial traits observed in the parents. Cephalometric analysis confirmed a worsening of the sagittal maxillary relationship, with reduced values for both ANB and the Wits appraisal (Table 1).

The miniscrew positions were determined by superimposing cone-beam computed tomography images on the stereolithographic (STL) image of the digital model (Fig. 6). To ensure safe insertion, a 3D surgical guide was printed using the MAPA system.⁸

Under the SKAR III protocol, one week of expansion alternated with one week of constriction for five weeks¹³ (Fig. 7). This mobilized the upper jaw and thus improved the efficiency of a Petit facemask, promoting further expansion and canine eruption. The facemask was used in conjunction with 16oz, 1⁄8" extraoral elastics for five months, until a sagittal Class III overcorrection and an improvement in the profile had been achieved.

Discussion

The use of an anterior tongue crib in the initial orthopedic phase was essential in correcting this patient’s parafunctional habits and anterior open bite.¹⁸ Bite blocks are commonly used in hyper­divergent patients to control posterior eruption, to facilitate anterior skeletal growth, and to maintain posterior facial height.¹⁹ Timing is an important factor in the correction of Class III malocclusion, since sutural ossification can inhibit a response to facemask treatment in adults.²⁰ Despite the general effectiveness of early treatment with a facemask and RPE,¹³ however, a certain percentage of patients experience unfavorable growth with excessive clockwise mandibular rotation.²¹

The SKAR III protocol, with its repeated opening and closing of the expansion screw, increases mobilization of the circummaxillary sutures and thus enhances the appliance’s skeletal effects.¹³ Skeletal anchorage can prevent such unwanted dental side effects as mesial movement and extrusion of the upper molars, as well as proclination of the upper incisors from the indirect force.²² By maximizing the skeletal effects of the orthopedic appliance, we can often avoid orthognathic surgery, with its risks, expense, and increased treatment time.

Indirect bonding can ensure more accurate and precise bracket placement in less chairtime than with direct bonding.^15,23 The CAD/CAM system used in our patient minimized positioning errors, with no rebracketing and only one archwire bend needed to refine the case. Digital indirect bonding can reportedly reduce orthodontic treatment time by 26% over traditional indirect bonding.²⁴ In fact, the digital workflow was the key to successful resolution of this complex case. Thanks to careful treatment timing and accurate digital planning, the effectiveness of the appliances was maximized while unwanted side effects were minimized.