José Augusto César Discacciati

In situ evaluation of the polymerization kinetics and corresponding evolution of the mechanical properties of dental composites

Polymer composites have been used in dental applications for more than 25 years. Although their properties and behavior have been systematically improved, they still are not able to produce dental restorations chemically, dimensionally and mechanically stable for long periods of time. Low degrees of monomer conversion and poor processing control are some of the main features responsible for the materials instability. In this work, the monomer conversion of dental composites during visible light irradiation was in situ monitored by infrared spectroscopy. The relationship between degree of conversion and mechanical properties was obtained by evaluating the microhardness of composites with different degrees of conversion. The relationship obtained was then used to identify the evolution of the mechanical properties during photopolymerization.

Effect of light intensity and irradiation time on the polymerization process of a dental composite resin

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 Duncans (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.

Atendimento odontológico ao portador do HIV: medo, preconceito e ética profissional

OBJECTIVE To describe the ethical aspects involved in the dental care provided to patients who are HIV-positive or who have AIDS. METHODS Literature review (textbooks and MEDLINE and LILACS databases), with an emphasis on the work developed at the School of Dentistry, Federal University of Minas Gerais, Brazil. We examined the social representation of AIDS, the risk of HIV infection during office visits, the refusal to provide care, referral to other professionals without justification, special charges and office visit hours for HIV-positive patients, and the confidentiality of the serological status of the patient. RESULTS There is still prejudice and ignorance about the risk of HIV and AIDS infection, on the part of dental surgeons and of patients. CONCLUSIONS An educational project should be undertaken at dental offices and at universities that train new professionals. In addition, the role of national and regional professional associations in providing information concerning ethical aspects involved in the care of HIV/AIDS patients should be reinforced.

Verificação da dispersão de respingos durante o trabalho do cirurgião-dentista

The professionals and patients involved in dental examinations are at risk for infection by various disease-causing bacteria, viruses, and fungi, such as those responsible for hepatitis, tuberculosis, herpes, and AIDS. It is known that aerosols and spatter containing pathogenic microorganisms can spread during an examination. Nevertheless, some dental clinics are designed to have multiple examination areas in the same room, with no physical barriers between them. The objective of this study was to verify the reach of spatter resulting from the use of a triple syringe and high-rotation turbine during five simulated exams in a collective clinic, bearing in mind that spatter can contain the patients saliva and blood. To facilitate tracking of the spatter, aniline dye (pink, blue, yellow, green, and brown) was added to the water in the appropriate receptacle in each of the five units. The room, the equipment, and the patients and operators clothing were covered with white paper. A high concentration of spatter was observed on the chair, the operator, and the floor of each unit, and it also appeared on the chairs and trays of the surrounding units. The maximum distance reached by spatter was 1.82 m from a point on the chair corresponding to the position of the patients mouth. During real simultaneous examinations, the surrounding chairs and their patients and operators, as well as the trays containing sterilized instruments, are within spatter range. Therefore, there is a real possibility of cross-infection, and physical barriers should be placed between the units. This study also confirmed the need for protection of the operators face, body, hair, and arms, since these regions were heavily affected by spatter.Todas as pessoas envolvidas em um atendimento odontologico estao sujeitas a contaminacao por bacterias, virus e fungos que podem causar diversas enfermidades, dentre as quais se destacam a hepatite, a tuberculose, o herpes e a AIDS. Sabe-se que, durante um atendimento, ha possibilidade de ocorrer dispersao de respingos e aerossois contendo microrganismos patogenicos. No entanto, algumas clinicas odontologicas sao projetadas com varios consultorios no mesmo ambiente, sem divisorias entre eles. O objetivo deste trabalho foi verificar qual o alcance dos respingos provenientes da utilizacao de seringa triplice e turbina de alta rotacao em cinco atendimentos clinicos simulados em uma clinica de atendimento coletivo, considerando que estes respingos podem conter saliva e sangue do paciente. Para isso, anilina de diferentes cores (rosa, azul, amarela, verde e marrom) foi adicionada a agua do reservatorio de cada um dos cinco equipamentos. Todo o ambiente fisico, assim como a roupa do operador e do paciente, foram cobertos com papel crepom branco. Constatou-se grande concentracao de respingos sobre as cadeiras, sobre o operador, sobre o piso, cadeiras vizinhas e bandejas clinicas das unidades vizinhas. A distância maxima atingida pelos respingos foi de 1,82 m, medindo-se a partir do ponto correspondente a boca do paciente. Durante um atendimento real, coletivo e simultâneo nesta clinica, as cadeiras vizinhas e seus respectivos pacientes e operadores, bem como as bandejas clinicas contendo instrumental esterilizado situam-se dentro da area de abrangencia dos respingos. Portanto, existe uma possibilidade real de ocorrer contaminacao cruzada, havendo necessidade de colocacao de barreiras fisicas entre os equipamentos. O estudo evidenciou tambem a necessidade de protecao de toda a face, o corpo, o cabelo e os bracos do operador, uma vez que estas foram regioes muito atingidas pelos respingos.

Definitive Presurgical CAD/ CAM-Guided Implant-Supported Crown in an Esthetic Area

This paper describes the digital workflow from cone beam computer tomography (CBCT) to the installation of a definitive presurgical zirconium individual crown in a 19-year-old woman requiring implant replacement of a maxillary right lateral incisor. The patient had agenesis of this tooth and had completed the orthodontic treatment. CBCT was conducted and diagnostic casts were digitized. Virtual planning was completed by defining a prosthetically driven implant and a stereolithographic surgical template was produced. Good adaptation of a stereolithographic surgical template was verified in the working cast. Implant and abutment were installed in this cast using a stereolithographic surgical template, and a CAD/CAM definitive zirconium crown was produced. Flapless computer-guided implant surgery was performed. The abutment was connected, and a definitive zirconium crown was cemented using resin cement. The digital workflow presented herein shows high accuracy for a virtually planned implant with flapless guided placement, allowing the successful delivery of a definitive presurgical zirconium single crown in an esthetic area in a single visit. The patient was revaluated after 1 year of function with an excellent outcome of the treatment.