Influence of cavity preparation with Er,Cr:YSGG laser and restorative materials on in situ secondary caries development.

OBJECTIVE: The aim of this study was to evaluate the influence of cavity preparation and restorative materials containing fluorides in the prevention of secondary caries lesion development in situ. METHODS: A total of 120 blocks obtained from human teeth were divided into two groups and standardized cavities were prepared using diamond burs (DB) or Er,Cr:YSGG-laser [20 Hz, 4.0W, 55% water, 65% air (LA)]. They were divided into three subgroups according to the restorative material (n=20): glass-ionomer cement (GI), resin modified glass-ionomer (RM) or composite resin (CR). Blocks were fixed in palatal intra-oral appliances worn in situ by 20 human volunteers, who dropped 20% sucrose solution eight times daily. After 21 days, blocks were removed and restorations were cross-sectioned to evaluate microhardness [Knoop hardness number (KHN)] underneath enamel surface from 30 to 200 µm. Factors "cavity preparation," "restorative materials," and "depth" were evaluated by three way ANOVA, followed by Tukey test (p<0.05). RESULTS: The results showed lower microhardness in cavities prepared with DB than in cavities prepared with LA. At 30 µm, there were no statistical significant differences with regard to "cavity preparation" or "restorative materials" factors. In depth evaluation, the enamel microhardness progressively increased as a function of depth for the GI groups. In the groups prepared with LA at 60 µm/90 µm, there were no significant differences between GI and RM materials, whose microhardnesses were significantly higher than that of CR. CONCLUSIONS: Cavity preparation using Er,Cr:YSGG laser increases caries resistance of enamel walls, and reduce caries lesion depth development regardless of fluoride presence in the restorative material. CR showed higher caries lesion development than GI, and RM showed intermediate results.

Efeito do preparo cavitário com laser de Er:YAG e materiais que liberam flúor na prevenção de lesões de cárie / Effect of cavity preparation with Er:YAG laser and fluoride releasing materials on the prevention of caries lesion

O objetivo desse estudo foi avaliar a influência da técnica de preparo cavitário e de materiais restauradores contendo flúor na prevenção da secundária. Dentes humanos foram seccionados em 72 blocos e distribuídos em dois grupos. Cavidades com 1,6 mm de diâmetro foram preparadas com pontas diamantadas ou laser de Er:YAG laser (6 Hz, 300 mJ, 47 J.cm elevado a 2). Cada grupo foi dividido em três subgrupos e restaurados com cimento de ionômero de vidro, ionômero de vidro modificado por resina ou uma resina composta. Os espécimes foram termociclados e submetidos a ciclagem de pH. As lesões de cárie artificial foram ranqueadas utilizando uma escala ordinal por inspeção visual. Os testes de Kruskal-Wallis e Dunn (α = 0,05) não demonstraram diferenças no desenvolvimento de lesões entre as cavidades resturadas com o mesmo material e preparadas com pontas diamantadas ou laser de Er:YAG laser. O laser de Er:YAG utilizado para o preparo cavitário com 6 Hz, 300 mJ, 47 J.cm elevado a 2 não demonstrou a habilidade de garantir maior ácido resistência aos preparo.

The objective of this study was to evaluate the influence of the cavity preparation technique and fluoride-containing restorative materials on the prevention of the secondary caries. Human teeth were sectioned into 72 blocks and distributed into 2 groups. Cavities measuring 1.6 mm were performed with diamond burs or Er:YAG laser (6 Hz, 300 mJ, 47 J.cm to the -2 power). Each group was divided into 3 sub-groups, and restored with a glass-ionomer cement, resinmodified glass-ionomer, or composite resin. The specimens were thermal cycled and submitted to pH cycling. Artificial caries were scored using an ordinal scale based on visual inspection. Kruskal-Wallis and Dunn test ((α = 0,05) showed no differences in the caries lesion development between the cavities restored with the same material and prepared with diamond burs or Er:YAG laser. The Er:YAG laser used for cavity preparation used with 6 Hz, 300 mJ, 47 J.cm to the -2 power did not show the ability to guarantee significantly more acid-resistance against acid challenge.

Light-activation through indirect ceramic restorations: does the overexposure compensate for the attenuation in light intensity during resin cement polymerization?

OBJECTIVES: This study evaluated the effects of light exposure through simulated indirect ceramic restorations (SICR) on hardness (KHN) of dual-cured resin cements (RCs), immediately after light-activation and 24 h later. MATERIAL AND METHODS: Three dual-cured RCs were evaluated: Eco-Link (Ivoclar Vivadent), Rely X ARC (3M ESPE), and Panavia F (Kuraray Medical Inc.). The RCs were manipulated in accordance to the manufacturers' instructions and were placed into cylindrical acrylic matrixes (1-mm-thick and 4-mm diameter). The RC light-activation (Optilux 501; Demetron Kerr) was performed through a glass slide for 120 s (control group), or through 2-mm or 4-mm thick SICRs (IPS Empress II; Ivoclar Vivadent). The specimens were submitted to KHN analysis immediately and 24 h after light-activation. The data obtained at the 2 evaluation intervals were submitted to 2-way ANOVA repeated measures and post-hoc Tukey's test (pre-set alpha of 5%). RESULTS: Lower KHN was observed when light-activation was performed through SICRs for Eco-Link at all evaluation intervals and for Rely X ARC 24 h later. For Panavia F, no significant difference in KHN was observed between control and experimental groups, regardless of evaluation interval. Most groups exhibited higher KHN after 24 h than immediately after light-activation, with the exception of Rely X ARC light-activated through SICR, as no significant difference in KHN was found between evaluation intervals. CONCLUSIONS: Light overexposure did not compensate for light intensity attenuation due to the presence of SICR when Rely X and Eco-Link were used. Although hardness of such RCs increased over a 24-h interval, the RCs subjected to light overexposure did not reach the hardness values exhibited after direct light exposure.

Light-activation through indirect ceramic restorations: does the overexposure compensate for the attenuation in light intensity during resin cement polymerization?

OBJECTIVES: This study evaluated the effects of light exposure through simulated indirect ceramic restorations (SICR) on hardness (KHN) of dual-cured resin cements (RCs), immediately after light-activation and 24 h later. MATERIAL AND METHODS: Three dual-cured RCs were evaluated: Eco-Link (Ivoclar Vivadent), Rely X ARC (3M ESPE), and Panavia F (Kuraray Medical Inc.). The RCs were manipulated in accordance to the manufacturers' instructions and were placed into cylindrical acrylic matrixes (1-mm-thick and 4-mm diameter). The RC light-activation (Optilux 501; Demetron Kerr) was performed through a glass slide for 120 s (control group), or through 2-mm or 4-mm thick SICRs (IPS Empress II; Ivoclar Vivadent). The specimens were submitted to KHN analysis immediately and 24 h after light-activation. The data obtained at the 2 evaluation intervals were submitted to 2-way ANOVA repeated measures and post-hoc Tukey's test (pre-set alpha of 5 percent). RESULTS: Lower KHN was observed when light-activation was performed through SICRs for Eco-Link at all evaluation intervals and for Rely X ARC 24 h later. For Panavia F, no significant difference in KHN was observed between control and experimental groups, regardless of evaluation interval. Most groups exhibited higher KHN after 24 h than immediately after light-activation, with the exception of Rely X ARC light-activated through SICR, as no significant difference in KHN was found between evaluation intervals. CONCLUSIONS: Light overexposure did not compensate for light intensity attenuation due to the presence of SICR when Rely X and Eco-Link were used. Although hardness of such RCs increased over a 24-h interval, the RCs subjected to light overexposure did not reach the hardness values exhibited after direct light exposure.

A influência do preparo cavitário e materiais restauradores na prevenção da cárie secundária: estudo in situ / The influence af cavity preparatian with Er, Cr: YSGG-laser and secandary caries preventian: in situ study

Trabalhos da literatura demonstram a capacidade dos lasers de alta potência utilizados com parâmetros subablativos tornar o esmalte dental ácido-resistente, porém não se sabe se o calor residual resultante da irradiação pode também tornar o esmalte adjacente às paredes mais ácido resistentes. Este estudo avaliou in situ a influência do preparo cavitário utilizando o laser de Er,Cr:YSGG e materiais restauradores contendo flúor na prevenção de lesões de cárie. Terceiros molares humanos foram seccionados em 30 blocos de esmalte dental e distribuídos em dois grupos para o preparo de cavidades (1,6 rnm0) com pontas diamantadas ou com o laser de Er,Cr:YSGG (20 Hz, 4 W, 22 J/cm2). Depois disso, foram divididos em três sub-grupos e restaurados com ionômero de vidro, ionômero de vidro modificado por resina ou resina composta. Os blocos foram fixados em dispositivos intra-orais, utilizados por voluntários durante 21 dias e tratados com sacarose 20% oito vezes por dia. As lesôes cariosas foram avaliadas pelo ensaio de microdureza Knoop superficial (KHN) a 100 11m da margem do preparo, considerando na ANOVA dois fatores "Preparo" e "Material" e a interação de ambos, seguido pelo teste T ukey. Em seguida, os blocos foram seccionados e a microdureza subsuperficial foi avaliada a 100 11m da margem da cavidade nas profundidades de 30, 60, 90, 120, 150 e 200 11m. Considerou-se na Análise de variância três fatores "Profundidade", "Preparo" e "Material", seguido pelo teste Tukey. Observou-se menor desenvolvimento de lesões cariosas ao redor das cavidades preparadas com laser do que em torno das cavidades preparadas com pontas diamantadas. Houve efeito sinérgico cariostático subsuperficial entre o laser de Er,Cr:YSGG e o híbrido de ionômero de vidro e resina composta.

Severa I researches in the literature show the potential of high intensity lasers used in subablative parameters to modify the dental enamel providing more acid resistance. However, their ability to improve acid resistance during cavity preparation is unknown. The influence of the cavity preparation technique and the types of restorative materiais containing fluorides in the prevention of in situ development of secondary caries lesions were evaluated. Human teeth were sectioned in 30 blocks and distributed into 2 groups. Cavity preparations measuring 1.6 mm were performed with diamond burs or Er,Cr:YSGG laser (20 Hz, 4 W, 22 J/cm2). After that, each group was divided in 3 sub-groups that were restored using a glass-ionomer cement, a resin-modified glass-ionomer or a composite resin. The restored slabs were fixed in palatal intra-oral appliances worn in situ for human volunteers, which dropped a 20% sucrose's solution 8 times a day. After 21 days they were removed and a superficial microhardness analysis were done (KHN) 100 11m from cavity margin. The data were evaluated by 2-way ANOVA and T ukey considering the factors "Preparation" and "Material': After that, enamel slabs were sectioned and subsuperficial microhardness evaluation were performed at 30, 60, 90, 120, 150 e 200 11m from surface. The data were evaluated by 3-way ANOVA and Tukey considering the factors "Subsurface", "Preparation" and "Material': Less caries development were observed around the cavities prepared with the Er,Cr:YSGG laser. There were a synergistic effect between the Er,Cr:YSGG laser and the resin-modified glass-ionomer.

Cavity preparation and influence of restorative materials on the prevention of secondary caries.

OBJECTIVE: This in vitro study evaluated the influence of cavity preparation using the Er:YAG laser and restorative materials containing fluoride on preventing caries lesions. BACKGROUND: It has been suggested that cavity preparation using the Er:YAG laser has a potential for improving resistance to secondary caries on enamel. METHODS: Forty unerupted human third molars teeth were sectioned into 72 blocks of dental enamel and distributed into two groups to prepare cavities measuring (1.6 mm diameter) with diamond burs (DB) or Er:YAG laser (LA; 6 Hz, 300 mJ, 47 J/cm(2)). After that, each group was divided into three subgroups and restored with a glass-ionomer cement (GI), a resin-modified glass-ionomer (RM), or a composite resin (CR). Blocks were thermal cycled and submitted to a pH challenge to develop artificial caries-like lesions. Lesions were evaluated by Knoop microhardness test. An average of four indentations was used. Statistical analyses were performed by ANOVA followed by Tukey's test. RESULTS: The results (in Knoop hardness number) for DB cavity preparation were GI, 235.5 (+/-75.5); RM, 137.1 (+/-64.1); and CR, 39.3 (+/-26.5). For LA cavity preparation, the results were GI, 410.0 (+/-129.7); RM, 310.3 (+/-119.5); and CR, 96.4 (+/-57.4). CONCLUSIONS: There was less development of caries lesion around LA-prepared cavities than around the DB-prepared cavities; however, no synergistic cariostatic effect was observed between the Er:YAG laser and glass ionomer cement.