Interdisciplinary treatment for a compensated Class II partially edentulous malocclusion: Orthodontic creation of a posterior implant site

A 36-year-old woman with good periodontal health sought treatment for a compensated Class II partially edentulous malocclusion associated with a steep mandibular plane (SN-MP, 45°), 9 missing teeth, a 3-mm midline discrepancy, and compromised posterior occlusal function. She had multiple carious lesions, a failing fixed prostheses in the mandibular right quadrant replacing the right first molar, and a severely atrophic edentulous ridge in the area around the mandibular left first and second molars. After restoration of the caries, the mandibular left third molar served as anchorage to correct the mandibular arch crowding. The mandibular left second premolar was retracted with a light force of 2 oz (about 28.3 cN) on the buccal and lingual surfaces to create an implant site between the premolars. Modest lateral root resorption was noted on the distal surface of the mandibular left second premolar after about 7 mm of distal translation in 7 months. Six months later, implants were placed in the mandibular left and right quadrants; the spaces were retained with the fixed appliance for 5 months and a removable retainer for 1 month. Poor cooperation resulted in relapse of the mandibular left second premolar back into the implant site, and it was necessary to reopen the space. When the mandibular left fixture was uncovered, a 3-mm deep osseous defect on the distobuccal surface was found; it was an area of relatively immature bundle bone, because the distal aspect of the space was reopened after the relapse. Subsequent bone grafting resulted in good osseous support of the implant-supported prosthesis. The relatively thin band of attached gingiva on the implant at the mandibular right first molar healed with a recessed contour that was susceptible to food impaction. A free gingival graft restored soft tissue form and function. This severe malocclusion with a discrepancy index value of 28 was treated to an excellent outcome in 38 months of interdisciplinary treatment. The Cast-Radiograph Evaluation score was 13. However, the treatment was complicated by routine relapse and implant osseous support problems. Retreatment of space opening and 2 additional surgeries were required to correct an osseous defect and an inadequate soft tissue contour. Orthodontic treatment is a viable option for creating implant sites, but fixed retention is required until the prosthesis is delivered. Bone augmentation is indicated at the time of implant placement to offset expected bone loss. Complex restorative treatment may result in routine complications that are effectively managed with interdisciplinary care.

Highlights

  • This is the first report for placing an implant in a posterior site opened with orthodontics.

  • Bundle bone produced by PDL distraction is susceptible to disuse atrophy.

  • Light forces reduce PDL necrosis and rapidly translate a mandibular premolar.

  • Implant spaces opened with orthodontics should be held with a fixed retainer.

  • Bone augmentation at the time of implant placement offsets expected bone loss.

Permanent teeth may be lost to trauma, caries, or periodontal disease. Marked reductions in width and height of the alveolar ridge can occur after tooth extraction and often compromise prosthetic restoration. Preprosthetic ridge augmentation with on-lay bone grafting is often required before or in conjunction with implant placement. If the periodontium is healthy, orthodontic site development is a viable alternative for producing new bone and attached gingiva. Movement of a healthy tooth through an edentulous area to increase the ridge dimensions to receive an implant is a promising method, but there is a risk of lateral root resorption. Orthodontic tooth movement can expand the alveolar process, and placing implants in these sites has been suggested, but to our knowledge, there are no documented reports for implant placement in orthodontically generated sites in posterior segments. This case report describes routine complications associated with orthodontically generated implant sites, and how these minor complications were solved efficiently. An excellent functional and esthetic result was achieved, as documented by a Cast-Radiograph Evaluation score of 13.

Diagnosis and etiology

A 36-year-old woman sought consultation for space management in the mandibular left posterior area ( Figs 1 and 2 ) and was treated to an excellent dentofacial result ( Figs 3 and 4 ). She was diagnosed with a skeletal Class I and a compensated dental Class II malocclusion with a missing maxillary left canine ( Figs 1 and 2 ). The etiology of the complex malocclusion was unrestorable caries and the extraction of the mandibular left first and second molars, about 7 years previously ( Fig 5 ). The adjacent third molar drifted mesially and tipped into the space, resulting in an atrophic edentulous space that was about 14 mm in length ( Figs 2 and 5 ). Clinical and radiographic evaluations showed multiple carious lesions and a failing mandibular right fixed prosthesis replacing the first molar ( Figs 1 and 5 ). In addition, the mandibular left central incisor was missing, resulting in a mandibular midline deviation of about 3 mm to the left ( Figs 1 and 2 ). The patient reported that her upper right first premolar and upper left canine were extracted by her family dentist when she was 13 years of age, because they were blocked out to the buccal aspect ( Fig 1 ). The maxillary right second molar was missing (unknown etiology), and the adjacent third molar had drifted into the second molar space. The American Board of Orthodontics Discrepancy Index was 28 points as shown in the Supplemental material . The implant sites (mandibular right and left first molars) scored an additional 4 points for complexity ( Supplemental material ). Overall, this mutilated malocclusion was a severe problem requiring a carefully sequenced, interdisciplinary approach. The posttreatment radiographs ( Fig 6 ) and superimposed cephalometric tracings ( Fig 7 ) documented the interdisciplinary treatment.

Fig 1
Pretreatment facial and intraoral photographs.

Fig 2
Pretreatment dental models (casts).

Fig 3
Posttreatment facial and intraoral photographs.

Fig 4
Posttreatment study models (casts).

Fig 5
Pretreatment cephalometric ( above ) and panoramic ( below ) radiographs.

Fig 6
Posttreatment cephalometric ( above ) and panoramic ( below ) radiographs.

Fig 7
Superimposed cephalometric tracings showing protraction and uprighting of the mandibular left third molar and retraction of the mandibular incisors.

Treatment objectives

The treatment objectives were to (1) restore all carious lesions; (2) maintain the skeletal dimensions of the maxilla and the mandible for all 3 planes; (3) perform preprosthetic tooth movement, including protracting and uprighting the mandibular third molar to reduce the edentulous space ( Figs 8 and 9 ), retracting the second premolar to the position of the first molar, and placing an implant in the space opened between the second and first premolars ( Figs 9 and 10 ); (4) perform prosthetics, including removing the mandibular right fixed prosthesis and restoring the second premolar and first molar with crowns, and placing a dental implant-supported prosthesis in the edentulous ridge of the area of the first molar; (5) manage the soft tissues, including when uncovered, evaluate each implant for an apically repositioned flap or free gingival graft to increase the buccal keratinized tissue and soft tissue volume; and (6) finish the orthodontics, including optimizing dentofacial esthetics with orthodontic detailing.

Fig 8
Month 0, irregular dentition at the start of active treatment. Month 7, the mandibular left segment is being aligned, and the edentulous space is decreased; note the lingual elastic chain between the left molar and second premolar. Month 16, the initial alignment is complete.

Fig 9
A, The mandibular left space (first molar) was reduced, space opening begins ( arrow ), and the mandibular right space (first molar) was maintained. B, The edentulous ridge for the right first molar space was very narrow, so the second premolar was moved distally with an open-coil spring ( arrow ) on the buccal surface. C, Buttons with power chains on the lingual surface resulted in equal retraction loads on both surfaces.

Fig 10
The mandibular left second premolar was moved into the edentulous ridge in the area of the first molar, and a small area of lateral root resorption was noted ( arrow ).

Treatment objectives

The treatment objectives were to (1) restore all carious lesions; (2) maintain the skeletal dimensions of the maxilla and the mandible for all 3 planes; (3) perform preprosthetic tooth movement, including protracting and uprighting the mandibular third molar to reduce the edentulous space ( Figs 8 and 9 ), retracting the second premolar to the position of the first molar, and placing an implant in the space opened between the second and first premolars ( Figs 9 and 10 ); (4) perform prosthetics, including removing the mandibular right fixed prosthesis and restoring the second premolar and first molar with crowns, and placing a dental implant-supported prosthesis in the edentulous ridge of the area of the first molar; (5) manage the soft tissues, including when uncovered, evaluate each implant for an apically repositioned flap or free gingival graft to increase the buccal keratinized tissue and soft tissue volume; and (6) finish the orthodontics, including optimizing dentofacial esthetics with orthodontic detailing.

Fig 8
Month 0, irregular dentition at the start of active treatment. Month 7, the mandibular left segment is being aligned, and the edentulous space is decreased; note the lingual elastic chain between the left molar and second premolar. Month 16, the initial alignment is complete.

Fig 9
A, The mandibular left space (first molar) was reduced, space opening begins ( arrow ), and the mandibular right space (first molar) was maintained. B, The edentulous ridge for the right first molar space was very narrow, so the second premolar was moved distally with an open-coil spring ( arrow ) on the buccal surface. C, Buttons with power chains on the lingual surface resulted in equal retraction loads on both surfaces.

Fig 10
The mandibular left second premolar was moved into the edentulous ridge in the area of the first molar, and a small area of lateral root resorption was noted ( arrow ).

Treatment alternatives

The first alternative for restoring the mandibular left edentulous area was to augment the ridge and place 2 implants. However, that approach required an additional implant and was less predictable because of the complexity of the surgeries to augment the severe bone atrophy of the implant site. In addition, the mesial inclination of the mandibular left third molar ( Fig 5 ) was at risk for long-term periodontal problems, periodontitis, or peri-implantitis, caused by food impaction and plaque accumulation between the third molar and the distal implant. The second option was a removable partial denture to replace the missing mandibular left molars, but the mesial inclination of the third molar was expected to encroach on the path of denture insertion. That problem would require extraction of the third molar or restorative procedures to prepare it for a surveyed crown. The patient rejected both alternative treatment approaches because of additional surgery, the potential for the long-term compromise of the virgin third molar, and the increased risk of periodontal problems.

Treatment progress

A full fixed Damon Q appliance (Ormco, Glendora, Calif) was used with the archwires and accessories specified by the manufacturer. Mechanics began in the mandibular arch with a 0.014-in nickel-titanium archwire, and 5 months later a 0.014 × 0.025-in nickel-titanium archwire was inserted. Lingual buttons and power chains were placed on the mandibular canine and second premolar to control rotation. In the month 7 of treatment, the mandibular archwire was switched to a 0.017 × 0.025-in beta-titanium alloy wire. Another lingual button and power chain were placed on the mandibular left third molar to provide a mesial protraction force ( Fig 9 ). By the end of month 16 of treatment, all rotations were corrected, and the edentulous space was reduced to 8 mm ( Fig 8 ), but the width of the edentulous ridge was still narrow (about 3 mm) due to severe resorption of the buccal plate of bone ( Fig 9 ). The mandibular left second premolar was retracted orthodontically to generate an implant site between the premolars. Buccal and lingual forces were applied with an open-coil spring placed on the archwire between the first and second premolars, and lingual buttons with a power chain were placed between the first premolar and the third molar ( Fig 9 ). The force was applied very gently, about 2 oz (28.3 cN) on each surface to control lateral root resorption. After 7 months of retracting the mandibular left second premolar at a rate of 1 mm per month, the orthodontically generated implant site was about 7 mm in length ( Fig 10 ). The space was maintained for 6 months with fixed appliances. A periapical radiograph showed only minor lateral root resorption on the distal side of the root of the second premolar ( Fig 10 ).

Extraction of blocked-out permanent teeth (maxillary right second molar and first premolar, and left canine) during adolescence corrected crowding in the maxillary arch, so only minor orthodontic treatment was needed to correct the mesial-in rotation of both lateral incisors ( Fig 11 ). After bonding with the Damon Q appliance, interproximal reduction was performed on the maxillary right and left incisors to create space. The archwire sequence was 0.016-in nickel-titanium, 0.016 × 0.022-in nickel-titanium, and 0.016 × 0.022-in stainless steel to align the dentition ( Fig 12 ). After 32 months of active treatment, both arches were well aligned, and the bilateral edentulous spaces in the mandibular first molar areas were prepared for implants ( Figs 12 , A , and 13 , A ).

Dec 12, 2018 | Posted by in Orthodontics | Comments Off on Interdisciplinary treatment for a compensated Class II partially edentulous malocclusion: Orthodontic creation of a posterior implant site
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