Polymerization shrinkage is a critical factor affecting the longevity and acceptability of dental composite resins. The aim of this work was to evaluate the effect of light intensity and irradiation time on the polymerization process of a photo cured dental composite resin by measuring the Vickers hardness number (VHN) and the volumetric polymerization shrinkage. Samples were prepared using a dental manual light-curing unit. The samples were submitted to irradiation times of 5, 10, 20 and 40 s, using 200 and 400 mW.cm-2 light intensities. Vickers hardness number was obtained at four different moments after photoactivation (immediate, 1 h, 24 h and 168 h). After this, volumetric polymerization shrinkage values were obtained through a specific density method. The values were analyzed by ANOVA and Duncan's (p = 0.05). Results showed increase in hardness values from the immediate reading to 1 h and 24 h readings. After 24 h no changes were observed regardless the light intensities or activation times. The hardness values were always smaller for the 200 mW.cm-2 light intensity, except for the 40 s irradiation time. No significant differences were detected in volumetric polymerization shrinkage considering the light intensity (p = 0.539) and the activation time (p = 0.637) factors. In conclusion the polymerization of the material does not terminate immediately after photoactivation and the increase of irradiation time can compensate a lower light intensity. Different combinations between light intensity and irradiation time, i.e., different amounts of energy given to the system, have not affected the polymerization shrinkage.

Este estudo teve como objetivo avaliar a correlação entre grau de conversão e microdureza em resinas compostas, e o efeito do conteúdo de partículas e do tipo de unidade fotoativadora sobre esses parâmetros. Três resinas compostas (Artglass®, Solidex® e Zeta LC®) foram polimerizadas em três diferentes unidades laboratoriais (UniXS®, Solidilite® e unidade Experimental). Para cada material, quinze corpos-de-prova foram confeccionados em uma matriz metálica, e submetidos às análises do grau de conversão, através de espectroscopia de infravermelho, e da microdureza. O conteúdo de partículas inorgânicas foi determinado por análise termogravimétrica (TGA). O comportamento conjunto das variáveis - grau de conversão e microdureza - foi medido através do coeficiente de correlação de Pearson. Para a resina Artglass®, o grau de conversão variou de 37,5% a 79,2%, com valores de microdureza de 32,4 a 50,3 (r = 0,904). Para a resina Solidex®, o grau de conversão variou de 41,2% a 60,4%, com valores de microdureza de 33,3 a 44,1 (r = 0,707). Para a resina Zeta LC®, os valores de conversão e microdureza foram, respectivamente, de 62,0% a 78,0% e de 22,6 a 33,6 (r = 0,710). Concluiu-se que o uso das diferentes unidades resultou em variações dos valores de conversão em função das características específicas de cada unidade. Para cada material, uma forte correlação entre conversão e microdureza foi observada. Além disso, quando materiais diferentes foram comparados, observou-se que o conteúdo de partículas inorgânicas afetou diretamente os valores de microdureza, não interferindo no grau de conversão.

The purpose of this study was to evaluate the correlation between degree of conversion and microhardness in dental composites, as well as the effect of the inorganic content and type of photo-curing unit on these parameters. Three indirect composites (ArtglassTM, SolidexTM and Zeta LCTM) were polymerized by means of three different laboratorial units (UniXSTM, SolidiliteTM and an experimental device). For each material, fifteen samples were prepared using a metal matrix. The degree of conversion was analyzed by means of infrared spectroscopy, and microhardness was also assessed. The inorganic content was measured by means of thermogravimetric analysis (TGA). The Pearson’s test was carried out in order to determine correlations. The degree of conversion of ArtglassTM ranged from 37.5% to 79.2%, and its microhardness, from 32.4 to 50.3 (r = 0.904). The degree of conversion of SolidexTM ranged from 41.2% to 60.4%, and its microhardness, from 33.3 to 44.1 (r = 0.707). The degree of conversion and the microhardness of Zeta LCTM ranged from 62.0% to 78.0% and from 22.6 to 33.6, respectively (r = 0.710). It was concluded that the utilization of different photo-curing units caused variations on the degree of conversion, as a result of specific characteristics of each unit. For each material, there was strong correlation between the degree of conversion and microhardness. In addition, when different materials were compared, microhardness was more affected by filler content than by the degree of conversion.

Com o objetivo de avaliar a percepção dos pacientes quanto ao risco de se contrair o vírus da imunodeficiência humana (HIV) durante o atendimento odontológico e suas atitudes em relação a continuar ou não o seu tratamento caso venham a saber que seu cirurgião-dentista (CD) atende pacientes com AIDS ou que seja HIV soropositivo, foram realizadas 518 entrevistas entre militares da Polícia Militar de Minas Gerais e seus dependentes, que haviam terminado tratamento com 233 CD diferentes. Observou-se que a grande maioria dos participantes (88,4%) acredita que o HIV possa ser transmitido durante o tratamento odontológico e que muitos entrevistados não continuariam o tratamento se seu CD atendesse pacientes com AIDS (42,9%) ou fosse HIV soropositivo (45%). Aqueles entrevistados que haviam sido atendidos por profissionais que utilizavam os artigos do equipamento para proteção individual (EPI) de forma adequada se mostraram mais dispostos a continuar o tratamento caso viessem a saber que seu CD atende pacientes com AIDS. No entanto, o uso adequado do EPI não é um fator encorajador para que os pacientes continuem tratando-se com seu CD caso venham a saber que ele é HIV soropositivo. Estes achados sugerem que maiores informações devem ser repassadas para o público leigo, informando-o sobre os verdadeiros riscos de se infectar pelo HIV e suas formas de prevenção na Odontologia.

With the objective of assessing patients’ perception of acquiring HIV virus in the dental practice and evaluating their attitudes towards continuing the treatment with dentists who treat HIV individuals or who are HIV positive themselves, 518 interviews were carried out with members of the Military Police of Minas Gerais and their dependents who had recently completed their treatment with 233 different practitioners. It was observed that the vast majority of the participants (88.4%) believed that HIV virus could be transmitted during dental procedures. Several interviewees reported that they would not return to their dentists if s/he was caring for HIV patients (42.9%) nor if s/he was HIV positive her/himself (45.0%). Those participants treated by dentists who adopted adequate barrier techniques were more likely to continue their treatment if the professional was treating HIV patients. However, there was not a direct association between the adoption of barrier techniques and the acceptance of being treated by an HIV positive dentist. The present findings suggest that more information should be transmitted to the public about the risk of HIV infection and its prevention in the dental setting.