RESUMO
Objective@#To measure the position of the mandibular nerve canal at the mandibular second molar by CBCT image data, analyze the theoretical implantation range of trans-alveolar implantation, and provide a theoretical solution to insufficiency of posterior mandibular bone volume in clinical practice. @*Methods@#Eighty patients with missing mandibular second molars whose vertical bone height of the edentulous area was less than 9 mm were selected for CBCT image measurement, and the distances from the mandibular nerve canal to the buccal cortex, lingual cortex, and alveolar crest were measured to simulate trans-inferior alveolar nerve implantation. The angular range of the buccolingual inclination of the implant was also measured.@*Results@#The distances from the mandibular nerve canal to the buccal cortex, lingual cortex and alveolar crest at the mandibular second molar were(6.913±1.222)mm, (2.859±0.891)mm and (7.991±0.783)mm, respectively. The distance from the mandibular nerve canal to the buccal cortex was significantly greater than that to the lingual cortex. And, 75% of the patients could be implanted by the inferior alveolar nerve. The minimum angle of buccolingual inclination of the simulated implant was 19.360°±7.086°, and the maximum angle was 39.462°±6.924°. @*Conclusion@#The mandibular nerve canal at the mandibular second molar is inclined toward the lingual side, which ensures sufficient buccal bone volume. Most patients with severe mandibular atrophy can still adopt implants of conventional length by trans-inferior alveolar nerve implantation to keep a safe distance from the nerve canal.
RESUMO
A reconstrução óssea de mandíbulas atróficas para o posicionamento de implantes dentários ainda é um grande desafio na Implantodontia atual. Para um ganho ósseo vertical, a técnica de enxerto interposicional com a utilização de enxerto de osso autógeno, ou algum substituto ósseo, apresentou excelentes resultados. Neste relato de caso, um paciente com 58 anos de idade e ausências entre os elementos 34 e 38 apresentava 3 mm de altura entre a crista óssea e o nervo alveolar inferior pelo exame de TCFC, impossibilitando o posicionamento de implantes sem enxertos prévios para ganho em altura e espessura. Com a utilização de rhBMP-2 como osteoindutor, associada ao beta-TCP como osteocondutor, foi possível regenerar o local com pouca morbidade e com ganho ósseo satisfatório (8 mm) para o posicionamento dos implantes. Após sete meses da consolidação do enxerto, implantes de diâmetro estreito (3,3 mm) foram posicionados e o paciente foi reabilitado sem complicações ou intercorrências durante todo o tratamento. Os autores sugerem que essa técnica tem um grande potencial para reconstruções de regiões atróficas, com um excelente ganho ósseo vertical, pouca morbidade e grande previsibilidade de resultados.
Bone reconstruction of atrophic mandibles for correct implant positioning is a great challenge on contemporary dentistry. Also, the interpositional graft technique using autogenous or bone substitute materials for vertical augmentation has presented excellent outcomes. This case report presents a 58 years-old patient with tooth loss from 34 to 38 regions having 3 mm from the bone crest to the inferior alveolar nerve canal according to the CBCT exam preventing implant placement without previous grafts for horizontal and vertical augmentation. With the aid of rhBMP-2 (osteoinductive) and beta-TCP (osteoconductive) materials it was possible to regenerate the area with less morbidity and satisfactory bone gain (8 mm) for implant placement. Seven months after graft healing narrow diameter implants (3.3 mm) were positioned and the patient rehabilitated without complications during the course of treatment. The authors suggest that this technique has a great potential for reconstruction of atrophic sites with excellent vertical bone gain, less morbidity, and great outcome predictability.