Temperature variation in pulp chamber during dental bleaching in presence or absence of light activation / Variação da temperatura na câmara pulpar durante o clareamento dental na presença ou ausência de fotoativação

Purpose: In addition to the chemical damage due to bleaching gels penetration into the pulp during pulp vitality dental bleaching, another possible aggressive factor could be the heat generated by the exothermal oxidation reaction of the bleaching gel, which may also be aggravated by the use of light activation. This study assessed the temperature variation in the pulp chamber in human teeth, using three different bleaching gels with or without LED light activation. Methods: Thirty human pre-molars were cut longitudinally to obtain buccal and lingual halves. The 60 specimens were divided into 3 groups, and the bleaching gel used varied as follows: 35% hydrogen peroxide (WHP); 37% carbamide peroxide (W) and 38% hydrogen peroxide (OX). Half of the specimens were submitted to bleaching with light activation and, the other half, without light activation. The light source used was the light emitting diode appliance (LED, 3-Light, Clean Line), and the intrapulpal temperatures were measured by using a digital thermometer. Data were analyzed by ANOVA and Tukey´s tests (alpha=5%). Results: The intrapulpal temperatures (in oC) were as follows: without light activation (WHP= 0.68b; W= 0.40b; OX= 0.48b); with light activation (WHP= 2.35a; W= 1.60a; OX= 1.80a ). Conclusion: LED light activation of bleaching gels increased the temperature in the pulp chamber, but did not achieve the critical temperature value of 5.5 oC.

Objetivo: Além da agressão química devido à penetração dos géis clareadores na polpa durante o clareamento de dentes com vitalidade pulpar, outro possível fator agressor pode ser o calor gerado pela reação de oxidação exotérmica do gel clareador, que pode também ser agravada pela fotoativação. Este estudo avaliou a variação da temperatura na câmara pulpar de dentes humanos, utilizando-se três diferentes géis clareadores, com ou sem fotoativação.Metodologia: Trinta pré-molares humanos foram cortados longitudinalmente para obtenção de duas metades: vestibular e lingual. Os 60 espécimes foram divididos em 3 grupos e os agentes clareadores utilizados variaram como segue: peróxido de hidrogênio 35% (WHP), peróxido de carbamida 37% (W) e peróxido de hidrogênio 38% (OX). Metade dos espécimes foi submetida ao clareamento com fotoativação e, a outra metade, sem fotoativação. A fonte de luz utilizada foi o aparelho à base de diodo emissor de luz (LED, 3-Light, Clean Line) e as temperaturas foram medidas por um termômetro digital. Os dados foram analisados por análise de variância e teste de Tukey (alfa=5%).Resultados: Os resultados de temperatura foram: sem fotoativação (WHP= 0.68b; W= 0.40b; OX= 0.48b); com fotoativação (WHP= 2.35a; W= 1.60a; OX= 1.80a).Conclusão: A fotoativação dos géis clareadores com LED contribuiu para um maior aumento de temperatura na câmara pulpar, mas não se atingiu a temperatura crítica de 5,5oC.

Effect of different finishing times on surface roughness and maintenance of polish in nanoparticle and microhybrid composite resins.

The objective of the study was to evaluate the effect of immediate polishing, after 24 h and after 1 week, on the surface roughness of two micro-hybrid resins (Esthet-X; Opallis) and one nanoparticle resin (Filtek Z350), as well as verifying maintenance of the polish after 1 year, simulated by means of thermal cycling. Forty-three specimens of each material were made and divided into a control group and three experimental groups. The control group specimens received no surface treatment. Group 1 received finishing with an extra-fine diamond drill and posterior polishing with the systems Enhance and PoGo, immediately after polymerization. Group 2 received the same procedures; however, these were carried out after 24 h of storage. Group 3 received the surface treatment after 7 days of storage. After that, the surface roughness was evaluated by a profilometer. After the initial reading, the specimens were submitted to thermal cycling for 10,000 cycles. After thermal cycling, a new roughness reading was taken. The results showed a higher roughness value for the resin Esthet-X, and the resins Opallis and Z350 presented the same roughness values. As regards the time when polishing was performed, specimens polished immediately after polymerization presented higher roughness values in comparison with the other two periods. After thermal cycling, the statistical analysis showed that the Opallis resin polish had been maintained, whereas for the other two resins, there was a significant reduction in surface smoothness. The surface roughness was influenced by the material and also by the period of polishing; the surface roughness of all tested materials were at a clinically acceptable level.

In vitro assessment of chemical activation efficiency during in-office dental bleaching.

PURPOSE: This study compared five types of chemical catalyzing agents added to 35% hydrogen peroxide gel, with regard to their capacity of intensifying in-office dental bleaching results. METHODS: One-hundred and twenty bovine incisors were used, of which the crowns and roots were cut in the incisor-apical direction, to acquire the dimensions of a human central incisor. The specimens were sectioned in the mesiodistal direction by means of two longitudinal cuts, the lingual halves being discarded. The vestibular halves received prophylaxis with a bicarbonate jet, ultrasound cleaning and acid etching on the dentinal portion. Next, the specimens were stored in receptacles containing a 25% instant coffee solution for two weeks. After the darkening period, initial measurement of the shade obtained was taken with the Easy Shade appliance, which allowed it to be quantified by the CIELab method. The samples were divided into six groups, corresponding to the chemical activator used: a) none (CON); b) ferric chloride (CF); c) ferrous sulphate (SF); d) manganese gluconate (GM); e) manganese chloride (CM); f) mulberry root extract (RA). Each group received three 10-minute applications of the gels containing the respective activating agents. Next, a new shade measurement was made. RESULTS: The Analysis of Variance and Tukey tests (alpha = 5%) showed statistically significant differences for the shade perception values (p = 0.002). Groups GM, CM and RA showed significantly higher means than the control group. CONCLUSION: The presence of some chemical activators is capable of resulting in a significant increase in tooth shade variation.

A scanning electronic microscopy study of the action of different desensitizing agents on bovine dentin.

This study sought to use scanning electronic microscopy (SEM) to evaluate the dentinal tubule occlusion potential of different desensitizing agents. Ten slices of bovine dentin were divided into six fragments, cleaned (using ultrasound), and etched for 15 seconds with a 35% phosphoric acid solution. All but one of the groups received a different desensitizing agent; the sixth group served as a control and received no additional treatment. After the agents were applied, the dentin specimens were analyzed by SEM and scores were assigned based on the extent of tubular obliteration. Only three agents demonstrated tubular sealing that was significantly different from that of the control group.

Restabelecimento da estética e função em paciente portador de bulimia nervosa: relato de um caso clínico / Recovering aesthetic and function for a patient with bulimia nervosa: clinical case report

Um desgaste dental severo na presença de periodonto sadio apresenta alterações impares no diagnóstico, plano de tratamento, metodologia reabilitadora e controle do paciente. Entretanto, uma reabilitação sistematizada e integrada levará a um prognóstico favorável e adequado. A bulimia nervosa representa doença psicossomática, favorecendo a dissolução das estruturas duras do órgão dental, levando ao aparecimento de sensibilidade e a uma aparência antiestética, além de perda de dimensão vertical devido a um desgaste rápido da estrutura dental. Este artigo ilustra a reconstrução de uma dentição severamente desgastada, por ocorrência de bulimia nervosa, associando restabelecimento da dimensão vertical de oclusão e uso de coroas cerâmicas puras e restaurações metálicas fundidas

Shear bond strengths of a ceramic system to alternative metal alloys.

STATEMENT OF PROBLEM: The success of metal-ceramic restorations is influenced by the compatibility between base metal alloys and porcelains. Although porcelain manufacturers recommend their own metal systems as the most compatible for fabricating metal-ceramic prostheses, a number of alloys have been used. Purpose This study evaluated the shear bond strength between a porcelain system and 4 alternative alloys. MATERIAL AND METHODS: Two Ni-Cr alloys: 4 ALL and Wiron 99, and 2 Co-Cr alloys: IPS d.SIGN 20 and Argeloy NP were selected for this study. The porcelain (IPS d.Sign porcelain system) portion of the cylindrical metal-ceramic specimens was 4 mm thick and 4 mm high; the metal portion was machined to 4x4 mm, with a base that was 5 mm thick and 1 mm high. Forty-four specimens were prepared (n=11). Ten specimens from each group were subjected to a shear load on a universal testing machine using a 1 mm/min crosshead speed. One specimen from each group was observed with a scanning electron microscope. Stress at failure (MPa) was determined. The data were analyzed with a 1-way analysis of variance (alpha=.05). RESULTS: The groups, all including IPS d.Sign porcelain, presented the following mean bond strengths (+/-SD) in MPa: 4 ALL, 54.0+/-20.0; Wiron, 63.0+/-13.5; IPS d.SIGN 20, 71.7+/-19.2; Argeloy NP, 55.2+/-13.5. No significant differences were found among the shear bond strength values for the metal-ceramic specimens tested. CONCLUSION: None of the base metal alloys studied demonstrated superior bond strength to the porcelain tested.