Editorial Type:
Article Category: Case Report
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Online Publication Date: 06 May 2024

Strategic treatment for a patient with missing lateral incisor and first molar accompanied by posterior scissor bite and an impacted premolar

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Page Range: 581 – 591
DOI: 10.2319/011024-30.1
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ABSTRACT

Managing orthodontic treatment for adults with missing permanent teeth can be intricate, especially when dealing with a posterior scissor bite and an impacted tooth. This case report presents successful treatment of a female patient with dental and skeletal Class II malocclusion, high mandibular plane angle, missing maxillary left lateral incisor and mandibular right first molar, as well as right posterior scissor bite, and a deeply impacted mandibular left second premolar. In the maxilla, the right second molar and right lateral incisor were strategically extracted to eliminate the scissor bite and enhance frontal esthetic balance. In the mandible, the edentulous space caused by early loss of the first molar was successfully closed and the impacted second premolar was guided into its proper position after surgical exposure. Finally, symmetric frontal esthetics, well-aligned dentition with ideal intercuspation and an improved profile were achieved, which remained stable in the 17 month follow-up.

Keywords: Congenital missing tooth; Lateral incisor extraction; Canine substitution; Impacted tooth; Scissor bite; Edentulous space closure

INTRODUCTION

Hypodontia has been reported to be the most prevalent dentofacial malformation and the maxillary lateral incisor was reported to be one of the most likely missing teeth.1,2 Absence of the maxillary lateral incisor creates an imbalance in potential maxillary and mandibular dental arch lengths as well as frontal esthetics and function.3 Edentulous spaces caused by missing mandibular first molars are also frequent in adults, which may lead to tipping or migration of adjacent teeth, super-eruption of opposing teeth, and reduced alveolar bone height and width.4 Additionally, early loss of the mandibular first molar could cause overall changes in occlusion and considerable periodontal problems.5 There are different options for treating missing permanent teeth. In recent years, a trend for orthodontic space closure rather than prosthodontic approaches has been observed.6–8 Treatment planning may be difficult when dealing with missing permanent teeth.

Scissor bite can be defined as the condition when the buccal cusps of the lower teeth occlude lingually to the lingual cusps of the upper teeth.9 Posterior scissor bite may be easier to treat in the deciduous and mixed dentitions. However, greater difficulty and prolonged treatment time may be encountered in adult patients.10 Especially in skeletal Class II patients with a high mandibular plane, the extrusive force from the cross-elastics commonly used may result in clockwise rotation of the mandible, cant of the occlusal plane, or anterior open bite.11

Impacted teeth are one of the most challenging conditions encountered by orthodontic clinicians, and often entail interdisciplinary treatment.12 Traction, extraction or autotransplantation of the impacted teeth require careful evaluation and treatment planning.

This report illustrates successful management of a complex malocclusion characterized by Class II dental and skeletal relationships with missing permanent teeth in both arches, posterior scissor bite, and an impacted mandibular premolar. Strategic treatment in this complicated case avoided prosthodontic restorations and improved esthetics as well as function, without using intricate orthodontic appliances.

Diagnosis and Etiology

A 24-year-old woman presented to the clinic seeking orthodontic treatment for her crooked teeth, chewing problem, and unpleasing smile. As shown in the extraoral photographs, she had a slightly convex profile. The smile was not pleasing, with the upper and lower dental midlines deviating to the left. Intraoral photographs and the dental casts showed there was a missing maxillary left lateral incisor, mandibular right first molar, and mandibular left second premolar. An end-on Class II molar relationship was observed on her left side, while the mandibular right first molar was missing. The canines on both sides were Class II. Moderate anterior crowding was noted in both arches. In addition, the right second molars were in a scissor-bite relationship, with labial eruption of the upper molar and lingual tipping of the lower molar, both of which were vertically elongated. A canted maxillary occlusal plane, observed in the facial frontal view, was also noted on the dental cast (Figures 1 and 2).

Figure1. Pretreatment intra- and extraoral photograph.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Figure 2.Figure 2.Figure 2.
Figure 2. Pretreatment dental casts.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Lateral cephalometry indicated a skeletal Class II relationship (ANB: 4.58) with maxillary and mandibular retrusion (SNA: 74.99; SNB: 70.41). There was a severe, high mandibular plane angle (SN-MP: 45.8). The inclination of maxillary and mandibular incisors was within normal limits (U1-SN: 100.71; IMPA: 89.92) (Table 1 and Figure 3). The panoramic radiograph showed that there was moderate alveolar bone resorption in the mandibular right second molar area and a horizontally impacted mandibular left second premolar. Condylar asymmetry was noted on the panoramic radiograph, which may contribute to the transverse occlusal cant. However, no muscle or joint pain or other symptoms associated with temporomandibular disease were noted (Figure 3). Cone-beam computed tomography (CBCT) showed the crown of the impacted mandibular premolar was in close contact with the root of the mandibular left first molar (Figure 4).

Figure 3.Figure 3.Figure 3.
Figure 3. Pretreatment panoramic radiograph and cephalogram.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Figure 4.Figure 4.Figure 4.
Figure 4. Pretreatment CBCT images indicating the impacted premolar. CBCT indicate cone-beam computed tomography.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Table 1. Skeletal and Dental Changes in Cephalometric Analysis
Table 1.

The patient was diagnosed as having dental and skeletal Class II malocclusion, high mandibular plane angle with a congenitally missing maxillary lateral incisor, early loss of a mandibular first molar, and an impacted mandibular premolar.

Treatment Objectives

The treatment objectives were: (1) to achieve a symmetric smile, (2) relieve crowding and scissor bite, (3) align the mandibular impacted second premolar, (4) close the edentulous space caused by early loss of the permanent first molar, (5) normalize the overjet and overbite, and (6) improve facial profile.

Treatment Alternatives

The following different approaches were discussed with the patient:

  1. Extraction of the maxillary right first premolar, third molar, and the impacted mandibular left second premolar, correcting the posterior scissor bite, followed by a dental implant for restoration of the mandibular first molar and recontouring of the maxillary left canine.

  2. Extraction of the maxillary right lateral incisor and second molar, eliminating the posterior scissor bite, closing the mandibular edentulous space, and aligning the impacted mandibular left second premolar into occlusion.

Potential benefits and risks of the treatment plans were explained to the patient. She refused to have postorthodontic restorations, and finally chose the second option.

Treatment Progress

Her orthodontic treatment commenced on April 9, 2020. The maxillary right lateral incisor and second molar were extracted before bonding. Next, preadjusted straight-wire appliances (MBT prescription, Shinya, China) were bonded to both arches. Archwires (0.012-inch nickel-titanium, 0.016-inch nickel- titanium, 0.016 × 0.022-inch nickel-titanium and 0.019 × 0.025-inch nickel-titanium) were placed for alignment and leveling of both arches with correction of the right posterior scissor bite. When rectangular archwires were used, more bite opening curve was added to the left side for differential intrusion of the maxillary anterior teeth, with more intrusion on the left side.

Classical sliding mechanics using 0.019 × 0.025-inch stainless steel archwires was used to close the spaces in both arches with power chain. Lingual buttons were attached to the mandibular right second molar and first premolar for cross-elastics since lingual inclination was encountered during space closure. Power chain was connected from the mandibular left first premolar to the right second premolar, joining them as a single unit. This facilitated mesial movement of the right second molar. Open coil springs were used to obtain enough space for the mandibular second premolar (Figure 5).

Figure 5.Figure 5.Figure 5.
Figure 5. Treatment progress, indicating closure of the right edentulous space and obtaining space for the impacted premolar simultaneously.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

At 14 months, the mandibular left second premolar was exposed by the periodontist and a lingual button was attached on the buccal surface. Power chain was applied for rotation correction (Figure 6).

Figure 6.Figure 6.Figure 6.
Figure 6. Treatment progress indicating alignment of the mandibular left second premolar after surgical exposure.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Interarch elastics were used to improve intercuspation and coordinate the upper and lower midlines. The active treatment duration was 29 months. At the end of treatment, brackets were debonded and the treatment outcomes were assessed. Full-time, removable, vacuum-formed retainers were prescribed for the first 3 months, then switched to nightwear.

Treatment Results

After treatment, frontal symmetry was achieved, with improved esthetics. Facial balance was more harmonious, with a nice smile and well-aligned dentition (Figures 7 and 8). Full Class II molar relationship was attained, and the canted maxillary occlusal plane was corrected. The patient was fully satisfied with the outcome. Panoramic radiography showed overall root parallelism was acceptable, except for between the maxillary right first and third molars after space closure. Overall, root resorption was mild; however, significant root resorption of the mandibular right second molar was noted. Lateral cephalometric analysis showed that there was a 1.14 decrease in the ANB angle and a 4.03-degree decrease in U1/SN, without worsening of the high mandibular plane angle (Table, Figures 9 and 10). At 17-month follow-up, the outcome was stable (Figures 11 and 12).

Figure 7.Figure 7.Figure 7.
Figure 7. Posttreatment intra- and extraoral photographs.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Figure 8.Figure 8.Figure 8.
Figure 8. Posttreatment dental casts.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Figure 9.Figure 9.Figure 9.
Figure 9. Posttreatment panoramic radiograph and cephalogram.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Figure 10.Figure 10.Figure 10.
Figure 10. Cephalometric superimposition of pretreatment (black) and posttreatment (gray). (A) SN plane; (B) maxillary plane; (C) mandibular plane.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Figure 11.Figure 11.Figure 11.
Figure 11. Seventeen-month follow-up intra- and extraoral photographs.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

Figure 12.Figure 12.Figure 12.
Figure 12. Seventeen-month follow-up panoramic radiograph.

Citation: The Angle Orthodontist 94, 5; 10.2319/011024-30.1

DISCUSSION

The congenitally missing left lateral incisor presented a unique challenge for achieving a balanced and harmonious smile. A recent systemic review suggested that space closure was superior to prosthetic replacement in patients with maxillary lateral incisor agenesis, and that absence of a Class I relationship of the canines was not related to occlusal dysfunction or with signs and symptoms of temporomandibular disorders.13 In specific cases like this, strategic extraction contributed to improved symmetry and maintained acceptable esthetics with better cost-effectiveness. Extraction of the maxillary right lateral incisor mirrored natural symmetry, creating a more visually pleasing appearance overall. The remaining teeth exhibited good alignment and color and the patient expressed satisfaction with the final outcome. However, any decision to extract upper lateral incisors still deserves further attention due to its potential significant impact on both symmetry and frontal esthetics. Of note, difficulty may be encountered in obtaining adequate esthetics and function in patients after space closure because of the differences in color, shape, and root torque control for the substituted canine. Also, adequate position of the substituted canine gingival zenith is critical for obtaining gingival symmetry.

Scissor-bite correction may be a difficult issue in adults and often requires adjunctive measures such as use of a lingual arch, miniscrew anchorage, or other complex orthodontic appliances and the commonly used cross-elastics required patient cooperation, with the risk of molar extrusion.11,14 In this case, the significant discrepancy in occlusion on the right side and the high mandibular plane angle warranted a more immediate correction compared to milder scissor bite case in which ordinary orthodontic appliances might have been sufficient. Extraction of the upper right second molar played a crucial role in quickly addressing the right scissor bite. Before extractions, the super-erupted right second molar contributed to a significant bite discrepancy. Extracting the maxillary second molar instantly eliminated the physical barrier causing the scissor bite, offering the patient immediate relief and improved chewing function. For adults, selective extraction can be a viable option when achieving optimal results necessitates minimizing treatment time and complexity. Though the active treatment duration was as long as 29 months, the actual treatment course could possibly have been shorter since, due to the pandemic, isolation was mandated, which made keeping regular appointments impossible.

Exposing and erupting an impacted mandibular second premolar added complexity to the treatment plan but was essential for achieving a complete dentition. Obtaining enough space is crucial when guiding impacted teeth into occlusion.15 In this case, once the impacted premolar was exposed by the periodontist, it was brought into occlusion within 4 months. Of note, it has been reported that impacted mandibular second premolars may develop a variable degree of distal inclination, which could bring substantial risk to the roots of adjacent teeth.16 Thus, in this case, initial attachment of the buccal tube to the mandibular left first molar was oriented to make the crown tip mesially to avoid root contact with the impacted second premolar; the molar was rebonded at the finishing adjustment. Orthodontists play a crucial role in treatment planning and coordination to maximize the benefits to patients. Interdisciplinary collaboration with periodontists and oral surgeons may also be required for managing impacted teeth and ensuring an optimal outcome.

CONCLUSIONS

  • This case report highlights the importance of strategic treatment planning for comprehensive orthodontic treatment of complicated malocclusions.

  • Esthetic and functional goals can be achieved without intricate orthodontic appliances.

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Copyright: © 2024 by The EH Angle Education and Research Foundation, Inc.
Figure 2.
Figure 2.

Pretreatment dental casts.

Figure 3.
Figure 3.

Pretreatment panoramic radiograph and cephalogram.

Figure 4.
Figure 4.

Pretreatment CBCT images indicating the impacted premolar. CBCT indicate cone-beam computed tomography.

Figure 5.
Figure 5.

Treatment progress, indicating closure of the right edentulous space and obtaining space for the impacted premolar simultaneously.

Figure 6.
Figure 6.

Treatment progress indicating alignment of the mandibular left second premolar after surgical exposure.

Figure 7.
Figure 7.

Posttreatment intra- and extraoral photographs.

Figure 8.
Figure 8.

Posttreatment dental casts.

Figure 9.
Figure 9.

Posttreatment panoramic radiograph and cephalogram.

Figure 10.
Figure 10.

Cephalometric superimposition of pretreatment (black) and posttreatment (gray). (A) SN plane; (B) maxillary plane; (C) mandibular plane.

Figure 11.
Figure 11.

Seventeen-month follow-up intra- and extraoral photographs.

Figure 12.
Figure 12.

Seventeen-month follow-up panoramic radiograph.

Contributor Notes

a  Attending Doctor, Second Clinical Division, Peking University School and Hospital of Stomatology, Beijing, China.
b  Orthodontic Resident, Second Clinical Division, Peking University School and Hospital of Stomatology, Beijing, China.
c  Associate Chief Physician, Second Clinical Division, Peking University School and Hospital of Stomatology, Beijing, China.
Corresponding author: Dr Boxi Yan, #66 Anli Road, Chaoyang district, 100101, Beijing, China (e-mail: docbxyan@gmail.com)
Received: 01 Jan 2024
Accepted: 01 Mar 2024
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