ABSTRACT
This case report describes the orthodontic treatment of a 10-year-old female patient with a combination of Angle Class III malocclusion, a missing maxillary right lateral incisor, a supernumerary tooth with a short root on the lingual side of the maxillary incisor, a skeletal Class III jaw base relationship caused by a diminutive maxilla, and retroposition of the maxilla. We chose to close the space of the missing tooth, as well as the space created by extraction of the maxillary lateral incisor, by forward movement of the canine and premolars using a maxillary protractor with edgewise appliances. As a result, both the maxillary premolars and the molars were moved mesially, and a Class II molar relationship with tight interdigitation was achieved. Our results suggest that the combination of maxillary protractor and nontorque brackets was effective not only for correcting skeletal Class III malocclusion, but also for forward movement of the maxillary posterior teeth.
INTRODUCTION
The characteristics of Class III malocclusion include a large or protrusive mandible, a deficient or retrusive maxilla, a protrusive mandibular dentition, a retrusive maxillary dentition, or any combination of these.1–3 Among Japanese people, the incidence of Class III malocclusion is significantly higher than it is among whites,4,5 and a retruded maxilla is encountered more often than a large mandible in persons with skeletal Class III malocclusion.6 In such cases, orthodontic treatment is needed to correct the skeletal discrepancy. If left untreated, the malocclusion tends to worsen,7,8 and these patients will ultimately comprise a substantial percentage of those seeking orthognathic surgery as adults.9
Congenitally missing teeth affect the occlusal relationship between the maxilla and the mandible. Class III is the most frequent malocclusion seen among subjects who are lacking only maxillary teeth, whereas the absence of only mandibular teeth is frequently associated with Class II malocclusion. The issue of how to treat maxillary lateral agenesis with a skeletal Class III jaw relationship is always a matter of some controversy, mainly because treatment takes longer, is more difficult, and can be performed in a variety of ways.
The present case report describes orthodontic treatment for a patient with an Angle Class III malocclusion, a missing maxillary right lateral incisor, a peg-shaped maxillary left lateral incisor, a skeletal Class III jaw base relationship caused by a small maxilla, and retroposition of the maxilla.
CASE REPORT
Case Summary
A female patient, 10 years and 10 months old, was brought to the clinic by her parents, who were worried about the protrusion of the girl's mandible and about a maxillary lateral incisor that had not erupted. The patient's medical history showed no contraindications to orthodontic therapy. In the family history, the girl's mother had mandibular protrusion. The patient had a concave profile, with protrusion of the lips. Intraorally, she had an Angle Class III molar and premolar relationship on the left side and an Angle Class I molar and premolar relationship on the right side, with an overbite of +0.8 mm and an overjet of −1.0 mm. A supernumerary tooth was present on the lingual side of the maxillary incisors, and it had a short root. The maxillary left lateral incisor was peg-shaped and small. The maxillary dentition spacing was +5.8 mm, and +2.0 mm was present in the mandibular arch. The maxillary dental midline was almost coincident with the facial midline, but the mandibular dental midline deviated 1.5 mm to the right with respect to the facial midline (Figures 1 and 2). Panoramic, periapical, and occlusal radiographs revealed the absence of the maxillary right lateral incisor (Figure 3). Lateral cephalometric measurements (Table 1) showed a skeletal Class III jaw base relationship (ANB = −2.9°) with the maxilla in retroposition (SNA = 75.3°) in comparison to normal values for female Japanese of corresponding age. The maxillary incisors were labially inclined relative to the FH plane (U1-to-FH = 121.6°). The mandibular incisors were within a range of 1.0 standard deviation of the Japanese normative mean relative to the mandibular plane angle (L1-to-MP = 97.7°) and FH plane (FMIA = 53.9°). The size of the maxilla was small, while the mandible was large.
(A) Pretreatment cephalograph. (B) Pretreatment panoramic radiograph. (C) Occlusal and periapical radiographs.
(A) Pretreatment cephalograph. (B) Pretreatment panoramic radiograph. (C) Occlusal and periapical radiographs.
Diagnosis
The patient was diagnosed with an Angle Class III malocclusion with a missing maxillary right lateral incisor. In addition, she had a peg-shaped maxillary left lateral incisor, a skeletal Class III jaw base relationship caused by a small maxilla, and retroposition of the maxilla.
Treatment Plan
In consultation with the patient and parents, a treatment plan was devised based on the diagnostic records, and the following treatment objectives were developed: (1) enucleation of the supernumerary tooth and the short root on the lingual side of the maxillary incisors; (2) extraction of the maxillary left lateral incisor to achieve bilateral symmetry in the absence of the maxillary right lateral incisor; (3) maxillary protraction therapy in maxillary retrognathism and production of skeletal changes with anterior movement of the maxilla; (4) closure of the space caused by the missing and extracted teeth by forward movement of the canines and premolars using a maxillary protractor with edgewise appliances; (5) achievement of Class II molar occlusion and normal incisor relationships with edgewise appliances; and (6) retention to achieve stabilization of improved tooth alignment and facial esthetics.
Treatment Alternatives
The first alternative involved orthodontic treatment—placing the maxillary right canine into its natural position within the dental arch—to open space for prosthodontic replacement of the right lateral incisor. However, considering esthetic issues as well as the patient's age, we found it difficult to prescribe treatment that would require a 10-year-old to use a removable prosthesis until age 18, when she could receive a fixed prosthesis or implant. We felt that the use of a removable retainer with an artificial lateral incisor during adolescence might not be easy for the patient.
The second alternative was orthodontic treatment with extraction of the mandibular premolars. The position of the mandibular anterior teeth was slightly forward, but axial inclination was N-L. Retroclination of the mandibular permanent incisors has been reported in many studies of maxillary protraction.10 If the mandibular premolars were extracted, excessive retroclination of the mandibular incisors would a cause for concern.
Our patient was judged as able to obtain excellent occlusion and profile without extraction of the mandibular premolars. In addition, the patient expressed the desire to avoid extraction, so we opted for mandibular nonextraction therapy.
Treatment Progress
Caries control and oral hygiene instruction were performed. Treatment was started in the maxilla by extraction of the supernumerary tooth and the left lateral incisor. Subsequently, standard edgewise appliances (0.018-inch × 0.025-inch) were immediately placed on the maxillary incisors, canines, and first molars. After a 7-month period of leveling and mesial space closure with an elastomeric chain between the incisor and canine, a palatal bar was placed on the first molars, together with edgewise appliances on the first premolars. At the same time, an open-coil spring was placed between the first premolar and the first molar to advance the first premolar on a 0.016-inch × 0.016-inch stainless steel wire and maintain rigidity. The elastic bands were connected from Kobayashi hooks on the first premolar to a protractor, and then the intraoral component was pulled forward using about 150 g of elastic force unilaterally in a 20° to 30° direction downward from the occlusal plane. In addition, the patient wore a protraction facial mask for more than 13 hours a day for 18 months, not only as anchorage for the advancement of the maxilla but also to effect mesial movement of the maxillary posterior teeth. Mesial movement was performed with the maxillary first premolar, second premolar, and first molar, sequentially (Figures 4 and 5). When moving the first molar to the mesial, a tip-back bend was given to the 0.017-inch × 0.025-inch stainless steel wire arch to prevent mesial tipping, and the wire was reduced for easy movement. During mesial movement of the first molar, fixed appliances were put into place on the remaining teeth. The patient wore Class III elastics. Finally, both canines were reshaped slightly on the incisal edge. Sixty-six months were needed for treatment, including time for growth observation. Retention consisted of a bonded lingual wire on the maxillary and mandibular teeth, including the canines. In addition, wrap-around retainers were fabricated to maintain alignment.
Intraoral views of treatment. (A) Start of leveling. (B) Start of advancement of the first premolar. (C) End of advancement of the first premolar and start of advancement of the second premolar. (D) Start of advancement of the first molar. (E) End of space closure.
Intraoral views of treatment. (A) Start of leveling. (B) Start of advancement of the first premolar. (C) End of advancement of the first premolar and start of advancement of the second premolar. (D) Start of advancement of the first molar. (E) End of space closure.
RESULTS
As a result of treatment and appliance use, mutually acceptable overbite and overjet were obtained, and a Class II molar relationship with tight interdigitation was achieved. Also, the space in the anterior dental region was closed. There was an improvement in lip closure and lip protrusion (Figures 6 through 8). Superimposition of the pretreatment and posttreatment tracings according to anterior cranial base showed that the SNA angle increased from 75.3° to 77.2° and the SNB angle decreased from 78.2° to 77.5°, such that the ANB angle increased from −2.9° to −0.3°. Ramus inclination increased from 90.9° to 96.0°. The gonial angle decreased from 127.1° to 122.6°. Mandibular plane angle (FMA) was almost the same as pretreatment. Tipping movements of both maxillary and mandibular incisors occurred lingually by 17.1° at U1 and by 12.9° at L1, such that the interincisal angle of these teeth showed an increase. Furthermore, the maxillary molars had moved to the mesial with no tipping of the posterior crowns (Figure 9; Table 1). The posttreatment panoramic radiograph showed no root resorption (Figure 8). There were no signs or symptoms of any temporomandibular disorder during the treatment and retention periods. Acceptable occlusion and facial profile were also maintained during the 3-year retention period (Figures 10 through 13).
(A) Posttreatment cephalograph. (B) Posttreatment panoramic radiograph.
Superimpositions of pretreatment (solid line) and posttreatment (dotted line) cephalometric tracings. (A) Superimposed on sella-nasion plane at sella. (B) Superimposed on palatal plane at ANS. (C) Superimposed on mandibular plane at menton.
Superimpositions of pretreatment (solid line) and posttreatment (dotted line) cephalometric tracings. (A) Superimposed on sella-nasion plane at sella. (B) Superimposed on palatal plane at ANS. (C) Superimposed on mandibular plane at menton.
(A) Cephalograph 3 years after treatment. (B) Panoramic radiograph 3 years after treatment.
(A) Cephalograph 3 years after treatment. (B) Panoramic radiograph 3 years after treatment.
Superimposed posttreatment (solid line) and postretention (dotted line) cephalometric tracings.
Superimposed posttreatment (solid line) and postretention (dotted line) cephalometric tracings.
DISCUSSION
Maxillary Protractor
Various types of maxillary protractors have been clinically modified and used for treating patients with severe skeletal Class III malocclusions.11–13 The use of reverse headgear for the treatment of Class III malocclusion was described more than 100 years ago.14 It has been demonstrated that reverse headgear can be an effective method in the treatment of Class III malocclusion with a retrusive maxilla. Other studies have confirmed the efficacy of maxillary protractor treatment with rapid maxillary expansion.15,16 Some researchers have also concluded that protraction therapy is useful in Class III malocclusions with maxillary retrognathism and produces favorable dentoalveolar, skeletal, and profile changes.17,18 In the present patient, maxillary protractors with fixed appliances were chosen in the hope of not only providing anchorage for the advancement of the maxilla but also moving the maxillary posterior teeth mesially.
A downward increase in point A has been reported in recently published clinical studies on maxillary protractors.19 In addition, animal studies have shown that the forward movement and anterior displacement of the maxilla can be proven by histological changes.20,21 In this case, as the cephalometric skeletal structures changed, the ANB angle showed a significant increase as the result of an increase in the SNA angle and a decrease in the SNB angle. It seems that the orthopedic forces on the maxilla and the mandible were effective and advantageous for this patient.
Regarding mandibular changes induced by a maxillary protractor, clockwise rotation of the mandible has been reported in several studies.18,22–24 Others have also concluded that the mandible was positioned backward, and posterior rotation of the mandible was significant following maxillary protractor therapy. Because the chin is one of the anchorage regions for a protraction device, a force can be applied directly to the mandible.10,25 Using such a device in the present patient, maxillary protractor therapy resulted in backward relocation of the ramus plane and closing of the gonial angle, with no significant change in the mandibular plane angle. These findings suggest that the forward movement of point B was restricted by changing the mandibular growth and forward movement of the maxilla by the remodeling of the circummaxillary sutures. From these results, we believe that this maxillary protractor therapy led to good results skeletally.
Proclination and forward movement of the maxillary incisors and retroclination of the mandibular incisors have been reported in many studies of maxillary protraction.10,23,25,26 In the present patient, both the maxillary incisors and the mandibular incisors were tipped lingually. In addition to providing root buccal torque, this combination of maxillary protractor and nontorque brackets has also been extremely effective in the forward displacement of maxillary and alveolar bone.
Orthodontic Treatment in Patients with Missing Teeth
Congenitally missing teeth affect the occlusal relationship between the maxilla and the mandible, including the inclination of neighboring teeth, extrusion of antagonistic teeth, and midline shift. In addition, when orthodontic treatment is performed in a patient with missing teeth, problems concerning the missing teeth must be considered, along with the relationships between the jaws, gnathic growth, discrepancy, and esthetic concerns. Therefore, treatment strategies and decisions about a treatment regimen tend to become difficult.27 Class III is the most frequent malocclusion seen in patients with missing maxillary teeth. In persons with congenitally missing maxillary teeth with skeletal Class III, the consequences can be significant and may necessitate surgery.
The present patient was diagnosed as having an Angle Class III malocclusion with the absence of the maxillary right lateral incisor and a peg-shaped maxillary left lateral incisor, together with a skeletal Class III jaw base relationship caused by a small maxilla and retroposition of the maxilla. Extraction of the small, peg-shaped left lateral incisor was carried out, along with treatment to achieve bilateral symmetry. The maxillary posterior teeth have drifted sufficiently, the spaces have closed, and there is no tipping of the posterior crowns.
Some authors prefer an implant or prosthetic solution because they feel that some aspects of space closure are disadvantageous. When the option is to close the space left by maxillary lateral incisor agenesis, the dentist must rely on some important variables such as the different color, shape, and size of the canine in the lateral site; the different root prominences; and the different height of the gingival scallops. On the other hand, Carlson28 described how the spaces might be physically closed without orthodontic treatment when maxillary lateral incisors were missing. He reported that the space may be closed as long as the facial configuration is not adversely affected. In addition, Nordquist et al29 reported a follow-up survey of patients in whom the maxillary incisor was congenitally absent, and the space was closed by orthodontic treatment and by prosthodontic treatment. There was no difference in occlusal function between the two, and when the spaces were closed, the periodontium was healthier. Furthermore, Senty30 reported that there was no apparent change in facial balance when maxillary canines were moved mesially. Therefore, we chose to close the space of the missing and extracted teeth by forward movement of the canine and premolars using maxillary protraction with edgewise appliances. As a result, not only the maxillary premolars but also the molars moved mesially, and a Class II molar relationship with tight interdigitation was achieved. The root resorption is slightly greater than normal and the gingival contour is a little higher than normal, but both are at acceptable levels without significant biological damage. The patient was pleased with her smile and appearance, and she was happy not to have required a prosthetic device.
However, we must consider the following two points about the first premolar with regard to the position of the canine. First, it is important that the lingual cusp of the first premolar not cause arthritis of the jaw. Secondly, rotation should be mesial. Then the first premolar can serve as an adequate substitute for the canine, both functionally and esthetically.31
In addition, many clinical treatments, such as crown torque, reshaping, and bleaching of the canine, should be considered. These techniques can provide additional improvements that will help mimic the look of a natural intact dentition and the function of unilateral incisors.32
The duration of treatment for this patient was 66 months, including growth observation, but the results reinforced by the long-term record make this treatment outcome very good despite the risks involved.
CONCLUSION
The combination of maxillary protractor and nontorque brackets was effective not only for correcting skeletal Class III malocclusion but also for accomplishing forward movement of the maxillary posterior teeth.