A 3-Dimensional Finite Element Analysis of Resected Mandibular Bone to Determine the Most Stable Implant Positions for a Fixed Prosthesis.

This study was conducted to determine the most secure implant positioning on the marginally resected mandible to support a fixed complete denture through finite element analysis. Three or 4 implants were placed at near, middle, or far positions from the resected margin in a simulation model with a symmetrical marginal defect in the mandibular symphysis. The height of the residual bone was 5, 10, or 15 mm. The 4 possible implant patterns for 3 or 4 implants were defined as (1) asymmetrically isolated position 1 to position 2, (2) asymmetrically isolated position 1 to position 3, (3) asymmetrically isolated with greater-length position 1 to position 2, and (4) 2 implants symmetrically positioned on each side of the defect. The von Mises stress in the resected and peri-implant bone with respect to the occlusal force was calculated. Initially, because the peri-implant bone stress around the isolated implant at the near position was greater than at the middle and far positions regardless of the residual bone height, the near position was excluded. Second, the von Mises stress in the resected bone region was >10 MPa when the isolated implant was at the far position, and it increased inversely depending on the bone height. However, the stress was <10 MPa when the isolated implant was placed at the middle position regardless of the bone height, and it was significantly lower compared with the far position and equivalent to the symmetrically positioned implants. Furthermore, the use of a greater-length implant reduced peri-implant bone stress, which was even lower than that of the symmetrically positioned implants. These results suggest that the asymmetrically positioned 3-implant-supported fixed denture, using a greater-length isolated implant, placed neither too close to nor too far from the resected margin, can be an effective alternative to the symmetrically positioned 4-implant-supported fixed denture.

Multidisciplinary approach for treatment of a dentigerous cyst - marsupialization, orthodontic treatment, and implant placement: a case report.

BACKGROUND: Dentigerous cysts are common odontogenic cysts associated with unerupted teeth. We describe a previously unreported case of a multidisciplinary approach using surgical, orthodontic, and implant treatment to establish the occlusion for a patient with a maxillary dentigerous cyst. CASE PRESENTATION: An 18-year-old Japanese woman visited our hospital with a chief complaint of gingival swelling in her anterior maxillary region, midline diastema, and tooth crowding. Her main symptom was this gingival swelling. A panoramic radiograph revealed a radiolucent area, 30 mm in diameter, round in shape, and with well-demarcated margins including the maxillary canine. Computed tomography revealed a cystic cavity filled with homogeneous fluid of the same density as water, and a distolingually inclined canine. Our clinical diagnosis was maxillary dentigerous cyst with an unerupted distolingually inclined canine. The selected treatment was marsupialization of the dentigerous cyst, followed by orthodontic traction of the unerupted canine, and simultaneous orthodontic treatment of the midline diastema and tooth crowding. The orthodontic traction failed because the canine did not erupt completely, and the canine was extracted. The treatment plan was then changed to implant treatment after the tooth crowding and midline diastema had been improved. Because the alveolar ridge width was inadequate, the implant was placed after a two-stage implant treatment; therefore, a satisfactory occlusion could be achieved. Our patient did not experience any complications, and the cyst has not recurred. A radiograph taken 7 years after marsupialization of the dentigerous cyst revealed that the cystic cavity had been replaced by new bone. CONCLUSIONS: In general, orthodontic traction of an unerupted tooth after marsupialization should be the best option. However, if orthodontic traction fails, a multidisciplinary approach involving implant treatment may be necessary. We describe a case in which a multidisciplinary approach involving surgical, orthodontic, and implant treatment was used to establish a satisfactory occlusion for a patient with a dentigerous cyst.