Measurement of Distance Between the Mental Foramina using Cone-Beam Computed Tomography: A Pilot Study with a Possible Method for Planning Mandibular Implants

Objective: To identify the average number of dental implants that can be placed in the lower anterior region to support a fixed mandibular prosthesis based on the distance between the mental foramina, using a cone beam computed tomography (CBCT) scan through a new method of measurement. Material and Methods: Eighty-two CT scans from a total sample of 1,465 exams were selected. The method to measure the space between the foramina was developed using the BlueSky Plan3 software in Dicom format and the axial reconstruction views were chosen for measurements. Descriptive analysis of data was conducted categorical variables were compared using the χ2 test (p <0.05). Results: The mean age of individuals who underwent the scans was 63.51 ± 9.49 years old with a minimum and maximum age of 40 and 86 years old, respectively. The mean linear measurement between the foramina was 40.52 ± 3.92mm. In males the mean distance was 41.93 ± 3.98 mm, and for females it was 39.99 ± 3.80mm, with a significant difference between the means (p = 0.043). There was no positive association between the presence of the anterior loop and gender (p = 0.719). The results showed that the vast majority of subjects (n = 80) could be rehabilitated using a protocol with 4 implants of 3.3mm diameters. Conclusion: Seventy-seven patients would be able to receive protocols of 4 implants with diameters of 3.75 or 4.0mm, and only 4 subjects would be able to be rehabilitated with 6 implants with diameters of 3.75 mm according to the protocol originally described by Brånemark.

Risk factors for implant failure: a retrospective study in an educational institution using GEE analyses

Abstract This study aimed to evaluate dental implant outcomes and to identify risk factors associated with implant failure over 12 years via dental records of patients attending an educational institution. Dental records of 202 patients receiving 774 dental implants from 2002 to 2014 were analyzed by adopting a more reliable statistical method to evaluate risk factors with patients as the unit [generalized estimating equation (GEE)]. Information regarding patient age at implantation, sex, use of tobacco, and history of systemic diseases was collected. Information about implant location in the arch region and implant length, diameter, and placement in a grafted area was evaluated after 2 years under load. Systemic and local risk factors for early and late implant failure were studied. A total of 18 patients experienced 25 implant failures, resulting in an overall survival rate of 96.8% (2.84% and 0.38% early and late implant failures, respectively). The patient-based survival rate was 91.8%. GEE univariate and multivariate analyses revealed that a significant risk factor for implant failure was the maxillary implant (p = 0.006 and p = 0.014, respectively). Bone grafting appeared to be a risk factor for implant failure (p = 0.054). According to GEE analyses, maxillary implants had significantly worse outcomes in this population and were considered to be a risk factor for implant failure. Our results suggested that implants placed in a bone augmentation area had a tendency to fail.

Histologic and Tomographic Findings of Bone Block Allografts in a 4 Years Follow-up: A Case Series

Abstract The aim of this paper is to report histologic and tomographic findings of fresh frozen bone block allografts bearing dental implants in functional occlusion in a long-term follow-up. Four patients with implants functionally loaded for 4 years on augmented ridges requiring additional mucogingival surgery or implant placement were included in this case series. Cone-beam tomography scans were compared volumetrically between the baseline (first implant placement) and current images. Biopsies of the grafts were retrieved and sent to histological analysis. Volumetric reduction of the grafts varied from 2.1 to 7.7%. Histological evaluation demonstrated well-incorporated grafts with different degrees of remodeling. While data presented in this report are from a small sample size and do not allow definitive conclusions, the biopsies of the grafted sites were very similar to the host's native bone. Remodeling of the cortical portion of the allografts seems to take longer than the cancellous portion. The presence of unincorporated graft remains did not impair the implant success or the health of the surrounding tissues. This is the first time histologic and tomographic long term data of bone allograft have been made available in dentistry.

Resumo O objetivo deste artigo é relatar achados histológicos e tomográficos de aloenxertos ósseos em bloco com implantes dentários em oclusão funcional em um acompanhamento de longo prazo. Quatro pacientes com implantes funcionalmente carregados por 4 anos em rebordos alveolares enxertados, que necessitaram de cirurgia mucogengival ou instalação de implantes adicionais foram incluídos nesta série de casos. Imagens de tomografia cone-beam foram comparados volumetricamente entre o momento inicial (instalação do implante original) e imagens atuais. Biópsias dos enxertos foram coletadas e enviadas para análise histológica. A redução volumétrica dos enxertos variou entre 2,1-7,7%. A avaliação histológica demonstrou enxertos bem incorporados com diferentes graus de remodelação. Embora os dados apresentados neste relato sejam de uma amostra pequena e não permitam conclusões definitivas, as biópsias dos sítios enxertados apresentaram características muito similares ao osso nativo. A remodelação da porção cortical dos aloenxertos parece levar mais tempo do que a porção esponjosa. A presença de remanescentes do enxerto não incorporado não demonstrou impacto no sucesso dos implantes ou na saúde dos tecidos circunjacentes. Este é o primeiro relato com dados histológicos e tomográficos em longo prazo de enxertos ósseos alógenos disponível na odontologia.