Effect of CPP-ACP paste with and without CO2 laser irradiation on demineralized enamel microhardness and bracket shear bond strength

ABSTRACT Introduction: Many patients seeking orthodontic treatment already have incipient enamel lesions and should be placed under preventive treatments. The aim of this in vitro study was to evaluate the effect of CPP-ACP paste and CO2 laser irradiation on demineralized enamel microhardness and shear bond strength of orthodontic brackets. Methods: Eighty caries-free human premolars were subjected to a demineralization challenge using Streptococcus mutans. After demineralization, the samples were randomly divided into five equal experimental groups: Group 1 (control), the brackets were bonded without any surface treatment; Group 2, the enamel surfaces were treated with CPP-ACP paste for 4 minutes before bonding; Group 3, the teeth were irradiated with CO2 laser beams at a wavelength of 10.6 µm for 20 seconds. The samples in Groups 4 and 5 were treated with CO2 laser either before or through CPP-ACP application. SEM photomicrographs of a tooth from each group were taken to observe the enamel surface. The brackets were bonded to the buccal enamel using a conventional method. Shear bond strength of brackets and ARI scores were measured. Vickers microhardness was measured on the non-bonded enamel surface. Data were analyzed with ANOVA and Tukey test at the p< 0.05 level. Results: The mean shear bond strength and microhardness of the laser group were higher than those in the control group and this difference was statistically significant (p< 0.05). All groups showed a higher percentage of ARI score 4. Conclusion: CO2 laser at a wavelength of 10.6 µm significantly increased demineralized enamel microhardness and enhanced bonding to demineralized enamel.

RESUMO Introdução: muitos pacientes, ao buscar o tratamento ortodôntico, já apresentam lesões incipientes no esmalte e precisam ser submetidos a tratamentos preventivos. O objetivo do presente estudo in vitro foi avaliar o efeito da pasta CPP-ACP e da irradiação com laser de CO2 na microdureza do esmalte desmineralizado e na resistência ao cisalhamento de braquetes ortodônticos. Métodos: oitenta pré-molares humanos hígidos foram submetidos a desmineralização usando Streptococcus mutans. Após a desmineralização, as amostras foram divididas aleatoriamente em cinco grupos experimentais: Grupo 1 (controle), os braquetes foram colados sem qualquer tratamento de superfície; Grupo 2, a superfície do esmalte foi tratada com pasta CPP-ACP por 4 minutos antes da colagem; Grupo 3, os dentes foram irradiados com laser de CO2 no comprimento de onda de 10,6 µm, por 20 segundos; Grupos 4 e 5, as amostras foram tratadas com laser de CO2 antes ou durante a aplicação de CPP-ACP. Foram feitas fotomicrografias por Microscopia Eletrônica de Varredura (MEV) de um dente de cada grupo, para avaliação da superfície do esmalte. Os braquetes foram colados ao esmalte na face vestibular, usando-se o método convencional. Foram medidos a resistência ao cisalhamento dos braquetes e o escore do Índice de Adesivo Remanescente (ARI). A microdureza Vickers foi medida nas superfícies do esmalte onde não foi realizada colagem. Os dados foram analisados com ANOVA e teste Tukey ao nível de p< 0,05. Resultados: a média da força de resistência ao cisalhamento e da microdureza do grupo laser foi superior à do grupo controle, com diferença estatisticamente significativa (p < 0,05). Todos os grupos apresentaram maior porcentagem do escore ARI=4. Conclusões: o laser de CO2 no comprimento de onda de 10,6 µm aumentou significativamente a microdureza do esmalte desmineralizado e melhorou a adesão dos braquetes nele.

Effect of Head Position on Maxillofacial Transverse Measurements Made on the Skull and Cone Beam Computed Tomography Scans

Article Incorrect patient positioning and the resultant image distortion occur in many radiographic examinations. This study aimed to assess the effect of tilting, rotation and tipping of the head on the accuracy of maxillofacial transverse measurements made on cone beam computed tomography (CBCT) scans. The CBCT scans were obtained in central position of 10 dry human skulls. Using three-dimensional (3D) Dolphin software, six positions namely 10° and 20° tilts, rotations and tips were reconstructed of central position. Transverse distances between landmarks were measured on 3D scans and the skulls. The intraclass correlation coefficient (ICC) and the Bland-Altman plot were used to compare the mean values measured by the two observers. For most landmarks, no significant differences were noted between the mean transverse distances measured in the six positions and those measured in central position on 3D scans (p>0.005). In conclusion, all measurements of transverse distances made on 3D scans in different positions were underestimated compared to the actual values measured on the skull.

Web-based evaluation of experts' opinions on impacted maxillary canines forced eruption using CBCT

AIM: This study aims at examining the difficulty in performing forced eruption of impacted maxillary canines, using CBCT information and according to experienced orthodontist's opinion. The second aim was to find the most important factors related to this decision. METHODS: Based on a careful literature review on impacted maxillary canines, ten main factors were selected to assess difficulties associated with impacted teeth. Thirty six consecutive patients with 50 impacted maxillary canines were examined and variables were measured for each impacted tooth using Dolphin 3D software. Ten orthodontists assessed the radiographs of teeth and provided their opinion on the difficulty in bringing impacted teeth into occlusion named subjective degree of difficulty (SDD). The correlation established between mean SDD of each tooth and measured variables were analyzed by means of linear regression. RESULTS: Mean SDD was 6.45 ± 1.22 for all 50 teeth. Linear regression showed a high coefficient of correlation between mean SDD and age, dilacerations, vertical height, angulation and horizontal overlap (P < 0.05). CONCLUSION: To predict the difficulty of impacted maxillary canines forced eruption, according to the opinion of experienced orthodontists, the factors age, dilaceration, angulation, overlap and vertical distance from the occlusal plane are the most important variables. .

OBJETIVO: o presente estudo tem o objetivo de avaliar, de acordo com a opinião de ortodontistas experientes, a dificuldade de se realizar a erupção forçada de caninos superiores impactados, com base em informações fornecidas por tomografia computadorizada de feixe cônico. O objetivo específico foi identificar os fatores mais importantes relacionados a essa opção de tratamento. MÉTODOS: com base em uma revisão meticulosa da literatura sobre caninos superiores impactados, selecionamos os dez principais fatores utilizados para avaliar a dificuldade em tratar dentes impactados. Trinta e seis pacientes, com um total de 50 caninos superiores impactados, foram avaliados. As variáveis para cada dente impactado foram obtidas utilizando o programa Dolphin 3D. Dez ortodontistas avaliaram as radiografias referentes aos dentes selecionados e opinaram sobre a dificuldade em alinhar dentes impactados. O grau de dificuldade foi denominado Grau de Dificuldade Subjetivo (GDS). A relação entre o valor médio de GDS de cada dente e as variáveis obtidas foi analisada por regressão linear. RESULTADOS: o valor médio de GDS foi de 6,45 ± 1,22, para todos os dentes. A regressão linear gerou um alto coeficiente de relação entre o valor médio de GDS e as variáveis idade, dilaceração, altura vertical, angulação e sobreposição horizontal (p < 0,05). CONCLUSÃO: de acordo com a opinião de ortodontistas experientes, para prever a dificuldade em se realizar a erupção forçada de caninos superiores impactados, as variáveis idade, dilaceração, angulação, sobreposição e distância vertical do plano oclusal são as mais importantes. .