Asymmetric severe skeletal Class II division 1 patient with temporomandibular joint disorder treated with zygomatic anchorage devices and Ni-Ti alloy wires
ABSTRACT
Objective:
To describe the orthodontic treatment of a nongrowing 30-year-old woman with asymmetric severe skeletal Class II malocclusions (asymmetric Angle Class II), large overjet (16 mm), large overbite (8 mm), two congenitally missing mandibular incisors (presenting a deciduous anterior tooth), and signs and symptoms of temporomandibular joint disorder (TMD).
Materials and Methods:
We used novel improved super-elastic Ni-Ti alloy wires (ISWs) combined with Ni-Ti alloy coil springs, power hooks, and a zygomatic implant as reinforced anchorage to provide a constant and continuous mild force to the dentition.
Results:
We successfully distalized maxillary molars, premolars, and retracted anterior teeth and corrected the asymmetric Angle Class II molar relationship using this system of zygomatic anchorage in conjunction with ISWs, Ni-Ti alloy open-coil springs, and crimpable power hook. The maxillary molars were distalized, and postero-occlusal relationships were improved to achieve Class I canine and molar relationships on both sides. Intrusion of the upper molars made the mandibular plane close. Ideal overbite and overjet relationships were established. Facial esthetics were improved with decreased upper and lower lip protrusion, and no symptoms of TMD were observed after treatment.
Conclusion:
The orthodontic treatment described here is a promising anchorage technique alternative to traditional techniques to improve severe skeletal Class II with TMD.
INTRODUCTION
Severe skeletal Class II adult patients with mandibular retrusion are often treated by an orthognathic surgical approach (ie, mandibular advancement) with the aim of improving both the occlusion and facial profile.
Although the orthognathic surgical approach can induce dynamic skeletal improvement, there are several risks for temporomandibular joints (TMJs). Previous studies have suggested that condylar resorption and atrophy are observed after surgical mandibular advancement.1–6 Therefore, this type of intervention is sometimes unfavorable for patients with temporomandibular joint disorders (TMD).
However, the recent widespread use of implant anchorage techniques can dramatically improve the profile without orthognathic surgery. Indeed, our previous study introduced the asymmetrical molar distalization technique with light continuous force for improved super-elastic Ni-Ti alloy wires (ISWs) and zygomatic anchorage.
In this report, we describe the treatment of a female patient with TMD and severe Class II skeletal pattern using a combination of zygomatic anchorage, ISWs, Ni-Ti alloy open-coil springs and closed-coil springs, and crimpable power hook.
Diagnosis and Etiology
The patient was a 30-year-old woman who presented with moderate crowding and difficulty in closing her lips. Other family members had no history of malocclusion. While she was in elementary and junior high school, her protruded maxillary anterior teeth were traumatized by collision with an object. Pretreatment facial photographs show a convex profile and protrusion of both upper and lower lips, both of which exceeded the E-line (upper lip +5.0 mm, lower lip +7.0 mm) and were strained upon closure (Figure 1). The patient exhibited a gummy smile. During lip closure, the mentolabial fold was observed in the chin area. The maxillary midline was coincident with the facial midline. A 3-mm deviation of the chin to the right of the midline was also evident. The right molar relationship was full-cusp Class II, whereas the left molar relationship was half-cusp Class II. The patient had an 8.0-mm overbite and a 16.0-mm overjet. Lateral and anteroposterior cephalometric radiographs and a dental panoramic radiograph were taken before treatment (Figure 2). The cephalometric analysis (Table 1) and the tracing demonstrated a Class II skeletal relationship (ANB = 7.8°), mainly due to the retruded mandible. The SNA angle was within the normal range (83.9°), and the SNB angle was small (76.1°). The FMA angle showed a large value (35.7°). The angle between the maxillary incisors and the SN plane was 112.0°, the angle between the lower incisors to the mandibular plane was 99.3°, and the interincisal angle was 105.0°. Both lower central incisors were congenitally missing, but a deciduous anterior incisor was still present. The patient showed an anterior functional mandibular deviation with premature contact. Thus, when the mandible was in centric occlusion, the condyle was located more anteriorly in the glenoid fossa than in centric relation. The patient had lockjaw when she was 7 years old. Moreover, the patient had symptoms of TMD (a clicking sound and pain). In addition, she had a daytime light clenching, tooth-contacting habit (TCH).7,8 Based on these findings, the patient was diagnosed as severe skeletal Class II with asymmetrical molar relationships. Daytime somnolence was measured by the Epworth sleepiness scale (ESS).9 The ESS score was 10 (within the normal range).
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Treatment Objectives
The treatment objectives for this patient were to (1) improve the profile, which was her chief complaint; (2) establish Class I molar and canine relationships; and (3) create ideal occlusion with appropriate overbite and overjet.
Treatment Alternatives
Bilateral sagittal split osteotomy is generally used as a means of correcting skeletal discrepancy and facial asymmetry in adults, but there are risk factors that can exacerbate TMD. As the patient refused to undergo surgery, we decided to use a nonsurgical approach. The patient showed a full-cusp Class II (right side) and a half-cusp Class II (left side) molar relationship with a large overjet (16.0 mm) and congenital loss of two mandibular incisors. Moreover, a functional mandibular forward deviation was observed, and the anterior positioned condyle in the glenoid fossa was apparent. Therefore, we decided to extract the maxillary first premolars, the third molars, and mandibular deciduous teeth to achieve Angle's Class I molar relationships. The traditional method for a nonsurgical approach with extraction of the maxillary premolars usually uses transpalatal arch and J-hook headgear or cervical headgear as the anchorage. However, this case required a large amount of maxillary molar distalization (more than 3.0 mm). In these circumstances, the external anchorage was insufficient to complete our goal. Therefore, we took a nonsurgical approach with maxillary premolar extraction and chose zygomatic anchorage for distalization of maxillary molars.
Treatment Progress
Before orthodontic treatment, we took notice of the TCH to the patient and instructed her to remove it. Moreover, we instructed her to perform jaw-opening exercises at the same time.
Y-shaped anchor plates (Orthoanchor Super-Mini-Anchor-plate System [SMAP], Dentsply-Sankin, Tokyo, Japan) were implanted onto the zygomatic process of the maxilla through the buccal mucosa under local anesthesia, and the bilateral maxillary first premolars, the bilateral maxillary third molars, and the right mandibular third molar were extracted. The left mandibular third molar was extracted subsequently, in accordance with the patient's request. The plates were contoured to fit the bone surface. The head of the plate was intraorally exposed and positioned outside the dentition. After a month for healing, integration, and adaptation, 0.018 × 0.025-inch slot preadjusted edgewise appliances (Dentsply-Sankin and Tomy, Tokyo, Japan) were bonded to each tooth, and 0.016 × 0.022-inch ISWs (L&H Tomy, Tokyo, Japan) were used for leveling.
During leveling of the posterior teeth, an Ni-Ti open-coil (100 gf) spring (coil springs, Tomy) was placed between the first molars and second premolars to move the first and second molars distally (Figure 3A). To prevent a reciprocal reaction, we ligated one end of an open-coil spring directly to SMAP without touching the second premolar brackets (Figure 3A). Then, a canine and a second premolar distal drive were performed (Pro-Chain, Dentsply-Sankin; Figure 3B,C).
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
After completion of the distal movement of the maxillary canines and second molars, two crimpable power hooks (American Orthodontics, Sheboygan, Wis) were attached to the archwire bilaterally between the maxillary lateral incisor and canine. Then, distal movement of the anterior segment was initiated using sliding mechanics (Figure 3D,E). Elastics were used to correct the right side lower midline shift problem. Elastic prescriptions were No. 13 with No. 45, No. 22 with No. 42, and No. 25 with No. 33. ISWs of 0.018 × 0.025 inches (L&H Tomy) were used for detailing. Finally, the left mandibular third molar was extracted, and the lateral incisors were built up with composite resin.
After 4 years of edgewise appliance treatment, a circumferential-type retainer was placed in the maxilla and a Hawley-type retainer and fix retainer were placed in the mandible.
RESULTS
Posttreatment photographs show a remarkable improvement in lip profile with a significant retraction of the anterior teeth and vertical dimensional control. Although mandibular deviation to the right still remains, the midline deviation was corrected, and the dental midlines were aligned with the facial midline using asymmetrical molar distalization (Figure 4). The postero-occlusal relationships were improved to achieve Class I canine and molar relationships on both sides, and ideal overbite and overjet relationships were established. Posttreatment cephalographs and panoramic radiographs are shown in Figure 5. Posttreatment cephalometric analysis is shown in Table 1. Superimposition of these radiographs before and after treatment (Figure 6) showed that the ANB and FMA angles were improved. Since the mandibular jaw position was relocated backward approximately 3.0 mm compared with the initial position, SNB was not improved despite autorotation of the mandible. In addition, the maxillary incisor edge was intruded by 3.0 mm (maxillary incisors apex intruded 5.0 mm) and displaced by 16.0 mm, and the apex moved 7.0 mm, distal to their initial positions. In the mandible, the central incisor edge was intruded 6.0 mm. Moreover, the right maxillary molars were distalized 5.0 mm on the right and 3.0 mm on the left and intruded 3.0 mm; the mandibular molar on the right side was moved 1.0 mm mesially. Facial esthetics were improved with decreased upper and lower lip protrusion. The maxillary intercanine width increased 1.5 mm, while the mandibular intercanine width increased 0.5 mm. Excellent changes were accomplished with dental retraction and vertical molar control. Maxillary center and left incisors are vital. The microdont was built up with composite resin. Posttreatment stability of the occlusion was observed after 1 year (Figures 7–9). One year after the end of the active treatment, the occlusion was acceptable. The ESS score was 10 (within the normal range).
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
DISCUSSION
When assessing occlusion, the most popular indication for molar relationship is Angle's classification. Angle advocated that the maxillary first permanent molar is the key to occlusion, and he believed that maxillary permanent first molars always erupted in a normal position.10,11 However, the maxillary first molar is not always in the correct position for ideal occlusion.12 Therefore, maxillary molar distalization is an important technique to treat cases similar to that presented in this report, because the patient had a large overjet (maxillary molars erupted excessive mesially), so that bilateral premolar extraction alone was insufficient to provide space for overjet correction. In 1921, Case13,14 introduced a method that distalized the maxillary molar by using an extraoral system to achieve anchorage reinforcement. Previous studies reported maxillary molar distalization with similar applications.15–18 However, there were some difficulties in left-right asymmetrical and three-dimensional control of orthodontic force, reciprocal force in distalization, unesthetic appearance, and dependence on the patient's compliance. In 1999, Sugawara19 introduced surgical miniplates for orthodontic anchorage. Our previous study introduced asymmetrical maxillary molar distalization in nonextraction cases using SMAP and ISWs.20 In this case, we also applied a force system—“arranged two-phase molar distalization of the maxillary segment with SMAP and ISWs”—to distalize maxillary molars as described previously.20 Moreover, distal movement of the anterior segment was performed using SMAP and crimpable power hooks.
Ni-Ti alloy wire has special properties of shape memory and super elasticity because Ni-Ti alloy wire undergoes stress-induced martensitic transformation and thermoelastic martensitic transformation.21 Therefore, we need to consider both temperature and stress elements at the same time to achieve a stable optimum force. The body temperature is 37°C, while the oral temperature changes between 3°C and 60°C,22 when the patient eats and drinks hot and cold food or drink during the orthodontic treatment period. Under these conditions, the load exerted by the conventional Ni-Ti alloy wire can increase dramatically. Moreover, although the oral temperature returns to 37°C, the force from the wire does not return sufficiently,22 considerably larger force hysteresis than orthodontists first assumed.21 ISW can provide a more constant light continuous force than conventional Ni-Ti wire irrespective of the oral environment.21
Some doctors have difficulty when using ISWs to treat severe Class II extraction cases or deep bite cases. However, if side effects are observed, these can be changed to positive effects, as ISW has many favorable properties. The force provided by ISW cannot always overwhelm the occlusal force that causes difficulties in tooth movement. However, this also provides advantages for intruding mandibular anterior teeth in patients with exaggerated curves of Spee. In the current case, the patient had a strong occlusal force combined with deep bite, curve of Spee, and elongation and labial inclination of the mandibular anterior teeth. When the crown-buccal torsional angle (+30°) was applied to the ISW with a heat bender (Soarer-X, Tomy), the posterior teeth were locked in position by occlusal force, and the reciprocal force occurred mainly to intrude and upright the mandibular anterior teeth (Figure 10).
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Vertical and horizontal control of maxillary anterior teeth during the “space-closing” phase is one of the most difficult and important stages with sliding mechanics in severe Class II cases. In the current case, we had to retract anterior teeth approximately 16 mm backward at the incisal edge. Therefore, we had to control the anterior teeth accurately. A previous study reported that in sliding mechanics, an extension arm (longer than 8.0 mm) can modify the location of the center of rotation of the anterior segment at the upper crown incisal edge.23 Therefore, we applied this method (Figure 11). We also applied Ni-Ti coil springs. We heated or bent the wire appropriately. When we treat patients with implant anchorage and ISW, maxillary molars often intrude excessively. Therefore, the intrusion should be controlled by bending the archwires or intermaxillary elastics. An appropriate control of the vertical dimensions of all the teeth can result in an enhanced, favorable skeletal change.
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
TCH was defined as a habitual behavior in which the upper and lower teeth are continuously brought together with minimal force in a nonfunctional situation (ie, contact but not clenching).7,8 Previous studies indicated that TCH is a risk factor for TMD pain.7,8 Previous reports indicated that any light contact of teeth would increase masseter muscle activity and that keeping teeth in contact, no matter how light, could contribute to the development and perpetuation of TMD pain.24,25 Therefore, we took notice of TCH and tried to make her stop TCH by means of behavior modification. Moreover, we instructed her to perform manual jaw-opening exercises by herself, according to the previous report.26 Two months later, TCH and TMD pain disappeared.
In the current case, the mandibular jaw position was relocated backward approximately 3.0 mm compared with the initial position. The follow-up three-dimensional computed tomography (3D-CT) showed that the condyles on both sides were in the center of the glenoid fossa (Figure 12). Before treatment, we observed that the patient initially showed a mandibular anterior functional shift to compensate for the mandibular retrusion, approximately 3.0 mm from inspection and initial computer-raised mandibular scan (CMS) sagittal data (tapping data; K6, K7, Morita, Osaka, Japan; Figure 13). Moreover, from the initial 3D-CT and TMD symptoms, it was predicted that the mandibular jaw position would move backward. Moreover, when we moved the teeth using implant anchorage, the vertical dimensions changed more dramatically than in nonuse cases. In such cases, it is important to predict the possibility that the mandibular jaw position might change dramatically and to pay attention to TMD symptoms. Finally, CMS data of the case showed that the mandibular jaw movement was smooth and the occlusion was stable (after removal of the mandibular anterior functional shift; Figure 13).
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
Citation: The Angle Orthodontist 84, 5; 10.2319/010414-13.1
CONCLUSION
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This case report demonstrated the effectiveness of a nonsurgical approach for treating a severe Class II patient (asymmetrical molar relationship) with TMD, using zygomatic anchorage, ISWs, and Ni-Ti alloy coil springs, open-coil springs, and power hook. The ISW has low stiffness and sometimes cannot overwhelm the occlusal force. However, this indicates that the ISW might reduce the wedge effect (becoming open bite) or hard occlusal interference or irregular loading to the TMJ area or teeth. Therefore, we consider the ISW suitable for patients with TMD.
Pretreatment facial and intraoral photographs.
Pretreatment lateral and posteroanterior cephalometric and panoramic radiographs.
(A) Distal movement of maxillary molars. Preventing the flare out of anterior teeth with Pro-chain. (B) Achieving maxillary molar distalization. Canine distal drive. (C) Canine and second premolar distal drive. (D) Anterior retraction. (E) Completion of anterior retraction. Distal apical movement of incisors.
Posttreatment facial and intraoral photographs.
Posttreatment lateral and posteroanterior cephalometric and panoramic radiographs.
Superimposed tracings of the pretreatment (solid line) and posttreatment (dot line) cephalometric radiographs.
One-year retention facial and intraoral photographs.
One-year retention lateral and posteroanterior cephalometric and panoramic.
Superimposed tracings of the posttreatment (solid line) and 1 year postretention (dot line) cephalometric radiographs.
(A) The crown-buccal torsional angle (+30°) were applied to the lower arch wire in both sides between the canine and first premolar. (B) When the lower archwire wire was placed into the bracket slots of multibrackets, an intrusive force was delivered to the lower anterior teeth.
(A) Controlled crown-lingual tipping. (B) Controlled root-lingual movement.
(A) Initial 3D-CT of temporomandibular joint (TMJ). (B) Follow up 3D-CT of TMJ.
Computer-raised mandibular scan data (tapping data). (A) Pretreatment trajectories. (B) Posttreatment trajectories. Closure pathway endpoint became stable after treatment (2.6 mm → 0 mm). Numbers indicate millimeters.
Contributor Notes