Tomie Nakakuki de Campos

Infiltração marginal de agentes cimentantes em coroas metálicas fundidas

One of the main goals of the luting agent, which bonds the cast restoration to the prepared tooth, is to seal the gap between them. Standardized preparations were made on 20 extracted teeth in order to evaluate microleakage. The crowns were made in NiCr, and in one group of 10 crowns zinc phosphate was used as the luting agent; in the other 10, Panavia 21 was used. The samples were thermocycled and then put into methylene blue solution (0.5%). After buccolingual sectioning of the cemented crowns, the samples were examined with a magnifier. There was a significant difference between the two groups: 100% of the zinc phosphate cemented crowns presented microleakage reaching the dentin and the pulp and 100% of the samples with Panavia 21 did not suffer any microleakage. So, as to the marginal microleakage with cast metal crowns in NiCr, the Panavia 21 luting agent presented better results than did zinc phosphate.

Holographic interferometry method for assessment of static load stress distribution in dog mandible

This study compared the transmission of tensions in fresh, fixed and macerated dog mandibles in order to clarify the diversity of behavior of bone tissues under dry and moist conditions. Double-exposure holographic interferometry was applied and holograms were obtained from 12 fresh hemi-mandibles under static load (control group), which were randomly assigned to 2 groups: 6 were fixed in 10% formalin and 6 were macerated. The specimens were submitted to the same initial force and their respective holograms were obtained. Analysis of the holograms showed that the fresh specimens transmitted significantly less tension than the fixed and macerated ones (p<0.05), and the tension direction was different. An average two-fold tension increment was observed in the experimental conditions. The holographic interferometry method was efficient in quantifying and qualifying tension transmission. However, depending on the type of analysis, the anatomical specimens must be fresh because macerated specimens will produce different results.

Evaluation of the apical seal after intraradicular retainer removal with ultrasound or carbide bur

There are situations in which intraradicular retainers have to be removed and replaced. The objective of this research was to evaluate the apical seal after the removal of a custom cast post and core with a carbide bur or with an ultrasound apparatus. Twenty five roots of extracted human incisors were used. They were endodontically treated and prepared to receive the posts. The posts and cores were cast with 2 types of dental alloys, CuAlZn and PdAg, and were cemented with zinc phosphate cement. After 24 hours, they were removed using the two above mentioned techniques. Then, the roots had their external surface made impermeable by two layers of cyanoacrylate adhesive, leaving only the cervical area for dye penetration. The teeth were immersed in rhodamine for 24 hours. They were then cut and observed under an optical microscope and analyzed with appropriate software (Imagelab). The results were submitted to ANOVA, and they evidenced that, regarding the alloy factor, PdAg posts presented a larger mean infiltration value (2.23 +/- 0.48 mm) as compared to the posts made of CuAlZn (1.39 +/- 0.48 mm) (p = 0.025). Regarding the technique factor, there was no significant difference (p = 0.9) between the removal of the intraradicular retainer using ultrasound (1.99 +/- 0.62 mm) or using a rotating cutting instrument (1.62 +/- 0.62 mm). Under these experimental conditions, it was possible to conclude that the degree of apical leakage was directly related to the alloy type, and it was present in both techniques used.

Stress analysis of fresh, fixed and macerated dog mandibles. Holographic interferometric double exposition method

In this work we studied some of the main effects of the bone tissue behaves in different ways according to dry or humid conditions, this research intended to evaluate stress transmission in dog mandibles, through holographic interferometric, in such conditions: fresh, formalin fixed and macerated. The experimental set up was made to get holograms at same place, to view a distribution of fringe at the jaw of dog. The deformation was find less on the presence of periodontal ligament in the fresh samples made the tooth and bone behave as distinct structures, while the fixed and macerated samples, bone and teeth behave as a rigid body. The macerated and fixed hemi-mandibles suffered more torsion during displacement than the fresh ones.

Influence of core materials in the microleakage of cast crowns

Endodontically treated teeth can be restored with prosthetic crowns over cast metal cores or prefabricated posts with composite resin cores. Prosthetic failure is frequently observed possibly due to microleakage. To verify the influence of the core materials in the microleakage of cast crowns, this research studied three experimental conditions: (a) teeth with partial dental remaining core with prefabricated post and partial composite resin cores, (b) teeth with cast metal posts/cores, and (c) teeth with prefabricated posts and composite resin cores. Teeth preparations were standardized, duplicated and the crowns were made in NiCr alloy, which were cemented with zinc phosphate cement. The specimens were submitted to thermocycling and mechanical stresses. They were immerged in a 0,05% aqueous solution of basic fuchsin for 8 hours during 3 days. The crowns were sliced buccal-lingually, and their microleakage was evaluated by glass magnification, according to a score scale. There was no statistical difference between conditions (a) and (c). Microleakage at cervical region of axial wall was observed in both cases. Condition (b) showed higher microleakage, which reached medium third of axial wall.

Development of an experimental optoelectronic device to study the amplitude of mandibular movements

This study aimed to present a wireless mandibular motion tracking device and optoelectronic data acquisition system developed to analyze the real-time spatial motion of the entire mandible during mouth opening and closing with no restriction of any movement. The procedures were divided into three phases: confection of a kinematic arch, dynamic digital video image acquisition, and image processing and analysis by using graphic computation. Four sequences of jaw opening/closing movements were recorded in lateral view: two from the maximum intercuspation (MIC) and the other two from a forced mandibular retruded position. Jaw motion was recorded by a digital video camera and processed as spatial coordinates corresponding to the position variation of the markers in the kinematic arch. The results showed that the method was capable of recording and processing the dynamics of the mandibular movements during jaw opening/closing using pixel-magnitude points. The mandible showed points with less displacement located near the temporomandibular joint during the opening/closing movements from the mandibular retruded position. When the jaw movements were recorded from MIC, these points were located near the mandibular foramen.

Avaliação da temperatura desenvolvida durante a remoção de pino intra-radicular, com instrumentos cortantes rotatórios em alta rotação

Due to the concern with the damaging effects of heat distribution on periodontal tissues, this study had the objective of evaluating the temperature generated during the removal of posts with burs in high speed handpieces. Fixed thermopars around the medium and apical regions of the roots of extracted superior central incisors, connected to digital thermometers, were used to obtain temperature measurements during wearing down. Analysis of variance demonstrated a statistically significant difference, to the level of 5%, between the regions where the temperature was taken and the alloys used. When comparing the differences between the regions of roots, the medium portion presented a variation of 9.1oC, and the apical region recorded a 6.2oC amplitude. The alloy containing CuAlZn (GOLDENT) reached the largest amplitude, 10.3oC; the alloys made of CuAl (DURACAST), 6.3oC; and the one made of PdAg (PORS-ON4), also 6.3oC. The factors that probably interfered were: degree of refrigeration, pressure, and intermittent wearing down. Based on the methodology used, we may conclude that the removal of posts by using burs in high speed can generate critical temperature variations, depending on the region of the root and the alloy being used.