Objective: The purpose of this study is to determine the relationship between cone beam CT (CBCT) voxel size and tooth root fracture detection. Materials and Methods: Vertical and horizontal root fractures were induced in a total of 30 teeth, and 15 teeth were left intact. Teeth were imaged with projection digital radiography and the Kodak 9000 3D CBCT system with a native voxel size of 76 μm. The CBCT voxels were then downsampled to 100 μm, 200 μm and 300 μm. Five blinded observers evaluated both sets of images with a 1 week washout interval between each set of observations. Results: CBCT outperformed the projection images for fracture detection for all voxel sizes except 300 μm (p<0.05). No significant differences were found between the different voxel sizes (p>0.05). Conclusion: Although voxel size does not impact the interpretation of root fractures, in vitro, CBCT outperformed projection imaging for voxel sizes less than 300 μm.

Objective: The purpose of this study is to determine the relationship between cone beam CT (CBCT) voxel size and tooth root fracture detection. Materials and Methods: Vertical and horizontal root fractures were induced in a total of 30 teeth, and 15 teeth were left intact. Teeth were imaged with projection digital radiography and the Kodak 9000 3D CBCT system with a native voxel size of 76 μm. The CBCT voxels were then downsampled to 100 μm, 200 μm and 300 μm. Five blinded observers evaluated both sets of images with a 1 week washout interval between each set of observations. Results: CBCT outperformed the projection images for fracture detection for all voxel sizes except 300 μm (p<0.05). No significant differences were found between the different voxel sizes (p>0.05). Conclusion: Although voxel size does not impact the interpretation of root fractures, in vitro, CBCT outperformed projection imaging for voxel sizes less than 300 μm.

Cone-beam computed tomography (CBCT) has become increasingly popular in dentistry. It is usually associated with radiation doses that are lower than those seen with conventional computed tomography (CT) but greater than those seen with dental radiography. Because exposure to ionising radiation is associated with risks, the radiation protection principles of justification and optimisation should be applied. These are especially important in children and young people due to their greater risk of developing stochastic effects. Justification requires a balancing of the radiation risk with the potential benefits and the latter is dependent on diagnostic efficacy. There has been a proliferation of articles published on dental CBCT and there is a need to review this systematically so that diagnostic efficacy can be judged. In terms of optimisation, radiation dose reduction can be achieved in various ways, but the use of barrier materials to protect younger patients in CBCT has not been adequately tested. Reduction in exposure parameters in CBCT will lower doses but at the expense of a loss of image quality. While some efforts have been made to relate radiation exposure and image quality in CBCT, there is a need to develop low-dose CBCT protocols specifically for children and young people. The first aim of this thesis was to survey current uses of CBCT in children and young people in three United Kingdom dental hospitals. The second aim was to determine the efficacy of thyroid shielding in a child phantom testing several different designs, materials and thickness of thyroid shields. The third aim was to evaluate the evidence on diagnostic efficacy of dental CBCT for root fractures in permanent, non-endodontically treated, anterior teeth by conducting a systematic review. The fourth aim was to evaluate objective and subjective image quality in a laboratory study to determine a low-dose CBCT protocol which maintains adequate diagnostic image quality for a clinical indication in children. Finally, the aim was to evaluate this low-dose protocol in terms of image quality in real clinical situations. A high adherence to the European guidelines No 172 on radiation protection in dental CBCT was found amongst the surveyed hospitals. Thyroid shielding was found to be effective in dose reduction when performing a large field of view CBCT scan in a child phantom, but design influenced efficacy. The systematic review showed that research articles investigating CBCT diagnostic accuracy for vertical and horizontal root fractures had deficiencies in methodology, while only one study was identified addressing higher levels of diagnostic efficacy. A low-dose imaging protocol was identified in a laboratory study, which has been shown to be an effective tool in dose reduction providing an adequate diagnostic image quality and reducing radiation doses considerably for clinical indications in the anterior maxilla in children and young people.

Fraturas radiculares verticais (FRV) são fraturas longitudinais que acontecem na raiz dos dentes. O diagnóstico clínico da FRV é um desafio, já que os pacientes não apresentam sinais e sintomas patognomônicos. Embora apresente limitações, a radiografia periapical deve ser o primeiro exame a ser realizado, pois possui menor custo e dose de radiação do que os exames tomográficos. O objetivo deste trabalho foi avaliar a contribuição de novas técnicas de processamento de imagens para o realce da FRV em radiografias periapicais digitais, visando facilitar sua detecção pelos odontologistas. O método de pré-processamento de imagem proposto foi composto de quatro etapas: ajuste geométrico+ negativo, filtragem de ruído, realce de contraste adaptativo e correção Gamma. Trinta radiografias periapicais digitais de dentes (fraturados ou não) tratados endodonticamente e com pino metálico instalado foram adquiridas. Resultados objetivos mostraram que o método desenvolvido aumentou o valor médio da razão contraste-ruído em 173% em comparação com o método de processamento tradicional fornecido pelo fabricante do equipamento. Testes subjetivos foram realizados com dez especialistas (radiologistas e endodontistas), que classificaram as imagens segundo a presença ou ausência de fratura. Os resultados indicaram que o método proposto melhorou a taxa de detecção de FRV pelos especialistas em 14%, em comparação com o método comercial, mas a especificidade foi reduzida. Dessa forma, a proposta deste trabalho pode ser utilizada como uma ferramenta complementar ao método de processamento tradicional, de modo a aumentar a sensibilidade do exame sem comprometer sua especificidade. / Vertical root fractures (VRF) are longitudinal fractures that occur at the root of the teeth. The clinical diagnosis of VRF is a challenge, since the patients have no pathognomonic signs and symptoms. Although it presents limitations, periapical radiography should be the first examination to be performed, because it has a lower cost and radiation dose than tomographic exams. The aim of this work was to evaluate the contribution of new image processing techniques for the enhancement of VRF in digital periapical radiographs, in order to facilitate its detection by dentists. The proposed image preprocessing method was composed of four steps: geometric adjustment+negative, noise filtering, adaptive contrast enhancement and Gamma correction. Thirty digital radiographs of teeth (fractured or not) treated endodontically and with installed metal pin were acquired. Objective results showed that the method developed increased the mean value of the contrast-to-noise ratio by 173% compared to the traditional processing method provided by the equipment manufacturer. Subjective tests were performed with ten examiners (radiologists and endodontists), who classified the images according to the presence or absence of fracture. The results indicated that the proposed method improved the detection rate of VRF by the examiners by 14% compared to the commercial method, but the specificity was reduced. Therefore, the proposal of this work can be used as a complementary tool to the traditional processing method, in order to increase the sensitivity of the test without compromising its specificity.