Class III malocclusion with traumatic unilateral maxillary central incisor loss treated using orthodontic miniscrews: a case report

A female, aged 23 years and 1 month, presented to the outpatient clinic of Tohoku University Hospital, Japan, with chief complaints of protruding teeth and crowding of the mandibular anterior segment. At 12 years of age, the patient fell and suffered trauma to the maxillary incisors. Her maxillary left central incisor was avulsed and could not be saved. Extraoral photographs showed facial symmetry and a straight profile (Fig. 1). Intraoral photographs and a dental cast analysis revealed Angle Class III molar relationships on both sides, and a 3.8 mm overjet and a 1.3 mm overbite. Mild crowding was present involving the maxillary and mandibular incisors. Arch length discrepancies of −1.0 mm and −2.0 mm were measured in the maxilla and mandible, respectively (Figs. 1 and 2). The crown of the maxillary left central incisor was attached to the adjacent teeth, and the maxillary left lateral incisor margin revealed a fracture (Figs. 1 and 2). A panoramic radiograph identified maxillary and mandibular third molars on both sides. The maxillary left central incisor was absent and the maxillary left lateral incisor was non-vital (Fig. 3). In comparison with Japanese norms,¹¹ a lateral cephalometric analysis showed a skeletal Class III skeletal relationship, an ANB angle of −2.3°, a low mandibular plane angle (MP-SN) of 26.9° and a normal gonial angle of 117.5° (Fig. 3, Table I). A long mandibular ramus height (Ar-Go) of 54.6 mm and a long mandibular body length (Go-Me) of 77.0 mm were noted (Fig. 3, Table I). The maxillary right central incisor was significantly inclined labially (U1-SN: 125.1°), but the mandibular central incisors were normally inclined (L1-Mp: 92.5°) (Fig. 3, Table I). The upper and lower lips protruded with respect to the E-line (E-line to upper lip: 0.5 mm; E-line to lower lip: 3.3 mm). A posteroanterior cephalometric analysis revealed that the upper dental midline coincided with the facial midline, but the lower dental midline had shifted to the left by 1.5 mm (Fig. 3). No occlusal cant was observed (Fig. 3). There were no clicking sounds in either temporomandibular joint (TMJ) during maximum mouth opening and closing. Magnetic resonance imaging (MRI) of the TMJ showed neither displacement nor deformation of either disc during maximum opening and closing. A 6 degrees of freedom jaw movement recording system (GNATHO-HEXAGRAPH III, GC Corp., Tokyo, Japan), consisting of a head frame, facebow, light-emitting diodes, charge-coupled device cameras, and a personal computer, was used to record jaw movements. The patient was seated in an upright but relaxed position with the head unsupported and naturally oriented.¹² A head frame and facebow, each with three light-emitting diodes, were secured to the head and the connector, respectively.¹² The connector was bonded to the labial surfaces of the lower incisors and bent to ensure uninhibited movement of the mandible and lip.¹³ The points of the lower central incisors and condyles were recorded on both sides using a stylus containing two light-emitting diodes. The three-dimensional positions of porion and the infraorbital points on the skin were also recorded. The maximum mouth opening, closing, protrusive, and lateral jaw movements were recorded using the jaw-tracking system. In comparison with Japanese norms, the all-path lengths of the incisors and condyles during lateral jaw movements were reduced.¹² Moreover, the path lengths of the incisors and balancing side during lateral jaw movement were shorter on the left side than the right side (Fig. 4, Table II).

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The patient was diagnosed as having an Angle Class III dental malocclusion, a skeletal Class III jaw-base relationship, a low mandibular plane angle, and traumatic loss of the maxillary left central incisor.

The treatment objectives were to create optimal overbite and overjet relationships, obtain a Class II molar relationship on the left side and a Class I on the right side, close the space of the absent maxillary left central incisor, and improve the protrusion and crowding of mandibular anterior teeth. The use of miniscrews was planned to achieve these objectives by mesialising the maxillary left dentition and distalising the other three quadrants.

Two alternative treatment options were considered to close the space of the lost maxillary left central incisor and improve the protrusion and crowding: orthodontic treatment using miniscrew anchorage following the extraction of the maxillary right first premolar and mandibular first premolars or non-extraction orthodontic treatment (except for the extraction of the third molars). The patient refused extraction of the first premolar teeth; therefore, the second option was selected.

After the extraction of the upper right third molar and lower third molars, 0.018-inch preadjusted edgewise appliances were placed on the maxillary and mandibular arches. 0.014-inch nickel-titanium arch wires were inserted for levelling and alignment of the dentitions. Seven months after the start of treatment, miniscrews (AbsoAnchor; Dentos Inc., Taegu, Korea), 1.4 mm in diameter and 5.0 mm long, were placed in the buccal alveolar bone between the maxillary right second premolar and first molar, the mandibular second premolar and first molar on both sides, and the maxillary left canine and first premolar. 0.016 × 0.022-inch stainless steel wires were placed in the maxillary and mandibular dentitions. The mandibular dentition was distalised by sliding mechanics supported by the miniscrew anchorage (Fig. 5). Simultaneously, distalisation was performed from the maxillary right canine to the second molar. The maxillary left dentition was mesialised using the miniscrew anchorage to close the space of the lost central incisor. Finally, using elastic chain and closing-loop mechanics, the anterior teeth were retracted to close the space (Fig. 5). The attached crown of the maxillary left central incisor was continually modified and preserved in the space to improve the aesthetics. Subsequently, 0.017 × 0.025-inch stainless steel wires were inserted for detailing. The total active treatment duration was 36 months. After appliance removal, the maxillary and mandibular teeth were stabilised using a Begg-type retainer. An all-ceramic crown was placed on the maxillary left lateral incisor to represent a central incisor.

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A harmonious facial profile was achieved due to the retracted upper and lower lips. The dental midlines were coincident with the facial midline (Fig. 6). Posttreatment intraoral photographs and dental casts illustrated the well-aligned arches and sound interdigitation of the teeth (Figs. 6 and 7). An adequate overjet and overbite were established. A Class II molar relationship was achieved on the left side and a Class I on the right side (Figs. 6 and 7). An all-ceramic crown with dimensions similar to the maxillary right central incisor was placed on the maxillary left lateral incisor to achieve a standard upper and lower tooth size ratio. A posttreatment panoramic radiograph showed acceptable root parallelism, without alveolar bone loss (Fig. 8). However, moderate apical root resorption was observed in the maxillary right central and lateral incisors. A posttreatment cephalometric evaluation with superimposed tracings demonstrated a counterclockwise rotation of the mandible. The maxillary right first molar was distalised by 2.0 mm and the maxillary left first molar was mesialised by 2.0 mm. The mandibular first molars were distalised by 5.0 mm and intruded by 1.0 mm. The upper incisors were intruded by 1.5 mm and retracted by 3.5 mm, and the lower incisors were lingually inclined by 7.3°, intruded by 1.0 mm, and retracted by 4.5 mm (Figs. 8 and 9, Table I). A superimposition of the dental casts before and after treatment was evaluated using a three-dimensional scanner (Geomagic Qualify 2013, Geomagic, NC, USA) (Fig. 10).^14–16 The tooth movements were similar to the movement of the upper and lower incisors and molars of the superimposed cephalometric tracings before and after treatment (Figs. 9 and 10). There were no symptoms of TMJ dysfunction and the articular disc of the TMJ revealed no changes on the posttreatment MRI. The incisal and condylar movements during lateral jaw movements were symmetric. However, the path lengths were shorter than the Japanese norm (Fig. 11, Table II).

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After 2 years of retention, the occlusion and facial aesthetics of the patient remained stable. Postretention intraoral photographs and dental casts showed that the molar and canine relationships had been maintained, but there was slight relapse of the mandibular left central incisor (Figs. 12 and 13). A further cephalometric analysis demonstrated mild relapse of the maxillary and mandibular central incisors and the mandibular left first molar (Figs. 14 and 15, Table I). Stable and symmetric incisal and condylar movements were still present during maximum mouth opening and closing and protrusive and lateral jaw movements (Fig. 16, Table II). The patient was satisfied with the treatment results.

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