Influence of repositioning guides' color and usage on precision in tooth color measurement with a clinical spectrophotometer

Abstract Repositioning guides are commonly employed in clinical studies to ensure consistent tooth color measurements. Yet, their influence on measured color remains uncertain. Objective This study evaluated the impact of repositioning guides' color and usage on tooth color measurement using a clinical spectrophotometer. Methodology In total, 18 volunteers participated in this study, in which the color of their upper left central incisor and upper left canine was measured with or without repositioning guides (control). The guides were made from pink, blue, or translucent silicone, as well as an acetate-based bleaching tray. Tooth color was measured in triplicates using a clinical spectrophotometer based on the CIELAB system. The standard deviations of these readings were used to estimate reproducibility, and color differences (ΔE00) between the measurements with guides and the control were calculated. Results Repositioning guides had a minimal effect on L* values and no effect on b* values. The use of pink silicone increased a* values, whereas blue or translucent silicone reduced them. Irrespective of the evaluated tooth, the lowest ΔE00 values were observed for the translucent silicone and bleaching tray. The usage of guides only affected data variability for the L* color coordinate. Conclusion Using repositioning guides can significantly impact the precision of tooth color measurement with a clinical spectrophotometer.

Background and surrounding colors affect the color blending of a single-shade composite

Abstract This study evaluated the background and effect of surrounding colors on the color blending of a single-shade composite used in a thin layer. Disc-shaped specimens (1.0 mm thickness) were built with the Vittra APS Unique composite surrounded (dual specimens) or not surrounded (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built with only control composites. The specimen color was measured against white and black backgrounds with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WID) was calculated for simple specimens. Differences (ΔE00) in color and translucency parameters (ΔTP00) between the simple/dual specimens and the controls were calculated. The translucency adjustment potential (TAP) and color adjustment potential (CAP) were estimated based on the ratios between data from simple and dual specimens. The Vittra APS Unique composite showed higher WID values than the controls. No differences between ΔTP00_SIMPLE and ΔTP00_DUAL were observed for any of the shades. The composite shade did not affect TAP values. The lowest values of ΔE00_SIMPLE and ΔE00_DUAL were observed for shade A1 regardless of the background color. For the white background, ΔE00_SIMPLE values did not differ from those of ΔE00_DUAL for all shades. Only A1 showed ΔE00_DUAL values lower than ΔE00_SIMPLE when the black background was used. The highest modulus of CAP (negative values for the white background) was observed when shade A1 surrounded the Vittra APS Unique composite. The color blending ability of the single-shade resin composite used in a thin layer was affected by both the surrounding shade and background color.

Effect of surrounded shade and specimen`s thickness on color adjustment potential of a single-shade composite

Abstract This study evaluated the effect of surrounded shade and specimens` thickness on the color adjustment potential (CAP) of a single-shade composite. The composite Vittra APS Unique was surrounded (dual specimens) or not (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens of the control composite were also confectioned. Opacity and whiteness index for dentistry (WID) were calculated for simple specimens. Color differences between the simple (ΔE*SIMPLE)/ dual specimens (ΔE*DUAL) and the controls were calculated. CAP was calculated based on the ratio between ΔE* SIMPLE and ΔE* DUAL. The tested composite presented lower opacity (53 to 62% vs. 80 to 93%) and higher WID (≈ 42 vs. 18 to 32) than controls. Irrespective of the specimens' thickness (1.0/ 1.5 mm), the lowest values of ΔE* SIMPLE (11.1/ 10.8) and ΔE*DUAL (7.2/ 6.1) were observed using the surrounding shade A1. The shade A3 yielded higher ΔE*SIMPLE (16.4/ 17.1) and ΔE* DUAL (11.3/ 12.3) than the A2 (ΔE*SIMPLE = 13.4/ 14.6; and ΔE* DUAL = 9.7/ 10.3). The specimen`s thickness significantly affected the CAP (0.35 and 0.44 for 1.0 and 1.5 mm, respectively) only for shade A1, which had the highest CAP values. The shade A3 resulted in higher CAP values (0.31) than A2 (0.27) when 1.0-mm thick specimens were used, but similar values were observed for 1.5 thick specimens (≈ 0.29). In conclusion, both surrounding shade and specimen thickness can affect the CAP of a single-shade resin composite.

Resumo Este estudo avaliou o efeito da cor circundante e da espessura da amostra no potencial de ajuste de cor (PAC) de uma resina monocromática. O compósito Vittra APS Unique foi circundado (amostras duplas) ou não (amostras simples) com um compósito controle (cor A1, A2 ou A3). Amostras simples do compósito controle também foram confeccionadas. A opacidade e o índice de brancura para odontologia (IBO) foram calculados para as amostras simples. As diferenças de cor entre amostras simples (ΔE*SIMPLE) / duplas (ΔE*DUAL) e os controles foram calculados. PAC foi calculado baseado na razão entre ΔE* SIMPLE e ΔE* DUAL. O compósito testado apresentou menor opacidade (53 a 62% vs. 80 a 93%) e maior IBO (≈ 42 vs. 18 a 32) que os controles. Independente da espessura da amostra (1,0/ 1,5 mm), os valores mais baixos de ΔE* SIMPLE (11,1/ 10,8) e ΔE*DUAL (7,2/ 6,1) foram observadas quando a resina circundante era A1. A cor A3 resultou em maior ΔE*SIMPLE (16,4/ 17,1) e ΔE* DUAL (11,3/ 12,3) do que A2 (ΔE*SIMPLE = 13,4/ 14,6; e ΔE* DUAL = 9,7/ 10,3). A espessura das amostras afetou significativamente o PAC (0,35 e 0,44 para 1,0 e 1,5 mm, respectivamente) apenas para a cor A1, que teve os maiores valores de PAC. A cor A3 resultou nos maiores valores de PAC (0,31) que A2 (0,27) quando amostras de 1,0 mm de espessura foram usadas, mas valores similares foram observados para amostras de 1,5 mm (≈ 0,29). Como conclusão, tanto a cor circundante como a espessura das amostras podem afetar o PAC de um compósito resinoso monocromático.

Fracture resistance of extensive bulk-fill composite restorations after selective caries removal

Abstract This study evaluated the effect of selective carious tissue removal on the fracture strength and failure mode of composite restorations in molars presenting only the buccal cusps. Deep cavities were prepared on the occlusal surface, and the lingual cusps were removed. Carious lesions in the middle of the pulpal wall were artificially induced with acetic acid (pH = 4.5) for 35 days. The demineralized dentin was left intact or was completely removed prior to restoration with a bulk-fill composite (n = 10). Images of the specimens were obtained by optical coherence tomography (OCT) before and after the caries induction/removal. The mechanical resistance to fracture by axial compressive loading and the failure type and extension were determined. The pulpal wall/composite interface of the fractured specimens was analyzed by OCT. The data were analyzed for significance with t-tests (α = 0.05). The deepest cavities and a more frequent occurrence of pulpal exposure were observed more often for non-selective carious tissue removal. The protocol of carious tissue removal did not affect the fracture strength (p = 0.554). An increased occurrence of catastrophic failures involving the roots was observed for non-selective carious tissue removal. Some occurrences of restoration displacement or cracks throughout the resin-dentin were observed only for the selective carious tissue approach. Selective carious tissue removal is a feasible approach to extensively damaged teeth since it reduced the occurrence of pulpal exposure and root fractures, without compromising the fracture strength.

Does Maintaining a Bottle of Adhesive Without the Lid Significantly Reduce the Solvent Content?

This study aimed to evaluate the effect of maintaining a bottle of adhesive without its lid on the solvent loss of the etch-and-rinse adhesive systems. Three 2-step etch-and-rinse adhesives with different solvents (acetone, ethanol or butanol) were used in this study. Drops of each adhesive were placed on an analytical balance and the adhesive mass was recorded until equilibrium was achieved (no significant mass alteration within time). The solvent content of each adhesive and evaporation rate of solvents were measured (n=3). Two bottles of each adhesive were weighted. The bottles were maintained without their lids for 8 h in a stove at 37 ºC, after which the mass loss was measured. Based on mass alteration of drops, acetone-based adhesive showed the highest solvent content (46.5%, CI 95%: 35.8-54.7) and evaporation rate (1.11 %/s, CI95%: 0.63-1.60), whereas ethanol-based adhesive had the lowest values (10.1%, CI95%: 4.3-16.0; 0.03 %/s CI95%: 0.01-0.05). However, none of the adhesives bottles exhibited significant mass loss after sitting for 8 h without their lids (% from initial content; acetone - 96.5, CI 95%: 91.8-101.5; ethanol - 99.4, CI 95%: 98.4-100.4; and butanol - 99.3, CI 95%: 98.1-100.5). In conclusion, maintaining the adhesive bottle without lid did not induce significant solvent loss, irrespective the concentration and evaporation rate of solvent.

Este estudo avaliou o efeito da manutenção do frasco do adesivo sem sua tampa na perda de solvente de sistemas adesivos convencionais. Três adesivos convencionais de 2 passos com diferentes solventes (acetona, etanol ou butanol) foram usados neste estudo. Gotas de cada adesivo foram colocadas em uma balança analítica e a massa dos adesivos foi registrada até a obtenção do equilíbrio (nenhuma alteração significativa com o tempo). O conteúdo de solvente de cada adesivo e a taxa de evaporação dos solventes foram mensurados (n=3). Dois frascos de cada adesivo foram pesados. Os frascos foram mantidos sem suas tampas por 8 h em uma estufa a 37 ºC, seguido pela mensuração da pera de massa. Baseado na alteração de massa das gotas, o adesivo a base de acetona demonstrou o maior conteúdo de solvente (46,5%, IC 95%: 35,8-54,7) e de taxa de evaporação (1,11 %/s, IC95%: 0,63-1,60), enquanto que o adesivo à base de etanol teve os menores valores (10,1%, IC95%: 4,3-16,0; 0,03 %/s IC95%: 0,01-0,05). Entretanto, nenhum dos frascos dos adesivos exibiu perda significante de massa após ficar por 8 h sem suas tampas (% do conteúdo inicial; acetona - 96,5, IC95%: 91,8-101,5; etanol - 99,4, IC95%: 98,4-100,4; e butanol - 99,3, IC95%: 98,1-100,5). Em conclusão, a manutenção do frasco do adesivo sem tampa não induziu perda significante de solvente independente da concentração e da taxa de evaporação do solvente.