Influence of the photoactivation distance on the color and whiteness stability of resin-based composite after bleaching and aging.

OBJECTIVES: To evaluate the influence of photoactivation distance on color stability and whiteness changes after bleaching and water storage of a resin-based composite (RBC). METHODS: Twenty disc-shaped specimens (12 mm x 1 mm; n = 5) from a nanofilled RBC (Filtek Z350 XT) were photoactivated from two distances (0 and 8 mm) and bleached using either an at-home (HB) or an in-office (OB) bleaching protocol. Specimens were stored in distilled water up to 6 months (aged specimens). A spectrophotometer (Vita Easyshade) was used to measure CIE L*a*b* coordinates. Color stability was calculated using CIEDE2000 (ΔE00) metric, and whiteness variations using the whiteness index for dentistry (ΔWID). The 50:50 % visual thresholds were used to analyzed ΔE00 values (PT- perceptibility, and AT- acceptability) and ΔWID values (WPT- whiteness perceptibility, and WAT- whiteness acceptability). Color parameters L*, a*, b* and ΔWID were analyzed using repeated measures two-way ANOVA. RESULTS: After bleaching, RBC specimens photoactivated from 0 mm showed ΔE00 values below AT and the ones from 8 mm had values above AT. After OB, ΔWID values were below WPT, but all other comparisons were above WAT. CONCLUSIONS: Bleaching protocol did not influence on color change, but water storage (aging) did influence on color (ΔE00) and whiteness (ΔWID) changes. However, RBC specimens photoactivated from 8 mm showed color changes above AT after bleaching. CLINICAL SIGNIFICANCE: Color instability is one of the major causes for replacing esthetic restorations. The whiteness index for dentistry (WID) was able to show the "whiter-darker" effect on RBC after bleaching and aging. Dentists should be aware that RBC may appear darker after HB. Regardless of the photoactivation distance, OB did not show a perceptible difference immediately after bleaching. However, OB and HB showed a darker effect after aging procedure.

Edge chipping test in dentistry: A comprehensive review.

OBJECTIVE: Literature on edge chipping test applied to dental materials and structures has been systematically reviewed with regard to the evaluation methods and parameters used. DATA: A systematic search of the literature retrieved 3484 relevant studies. After removing duplicates, 1848 records were screened by titles and abstracts and 1797 were excluded; 51 papers were assessed full text for eligibility. Twenty papers were included in this study and they were organized according to the dental materials and structures tested as follows: 2 studies on human tooth, 9 on dental ceramics, 5 on polymer-based composites, and 4 studies evaluated both ceramic and polymer-based materials. SOURCES: MEDLINE/PubMed, Scopus and Web of Science databases were searched up to June 2019 without restriction on date and language. STUDY SELECTION: In vitro studies using edge chipping test on dental materials and structures were included. CONCLUSIONS: Different methods have been used for edge chipping test, regardless of reported parameters. There is significant evidence that edge chipping test is a relevant approach to predict chipping behavior of dental materials and tooth tissues because chips produced from most edge chipping studies are similar to clinically reported chipping failures.

Physical and chemical properties of model composites containing quaternary ammonium methacrylates.

OBJECTIVE: Investigate physical and chemical properties of model composites formulated with quaternary ammonium salt monomers (QAS) at different concentrations and alkyl chains lengths METHODS: QAS with 12 dimethylaminododecyl methacrylate (DMADDM) and 16 dimethylaminohexadecyl methacrylate (DMAHDM) chains lengths were synthesized and incorporated at 5 and 10% in model composites, resulting in four groups: G12.5 (DMADDM 5%), G12.10 (DMADDM 10%), G16.5 (DMAHDM 5%), G16.10 (DMAHDM 10%). One group was used as control group (CG 0%). Degree of conversion (DC); water sorption (WS) and solubility (SL); hygroscopic expansion (HE); degradation temperature (DT); glass transition temperature (Tg) and polymerization shrinkage (PS) were determined. Knoop hardness (KNH), flexural strength (FS) and elastic modulus (EM) were measured before and after storage Data were submitted to ANOVA and Tukey's test (p≤0.05). RESULTS: DC ranged between 76.1 (G12.10) and 70.7 (G16.5) %; CG had the lowest WS, SL and HE. There was no statistical difference for PS and FS. KHN values ranged between 30.2 (GC) and 25 (G16.10) and after storage the performance was depended on QAS concentration and chain length. For EM, CG had the highest values before and after storage and no difference was observed in the QAS groups before storage. After storage, the results were dependent on QAS concentration (3.5-4.3GPa). SIGNIFICANCE: In general, the addition of QAS increased composite's degradation compared with the CG. In the tested QAS, the addition of DMADDM at 5% concentration resulted in a less degradable material.

Clinical Time Required and Internal Adaptation in Cavities restored with Bulk-fill Composites.

AIM: The aim of this study was to compare the restorative time required and the internal adaptation after thermomechanical aging of class I restorations using either the conventional incremental technique or bulk-fill technique. MATERIALS AND METHODS: Cavities (Class I) were prepared on the occlusal surface of human third molars. 40 teeth were divided into four experimental groups according to the restorative technique (n = 10): G1 = 3 mm increment of Surefill SDR Flow + 1 mm Filtek P60; G2 = 3 mm increment of Filtek Bulk-Fill + 1 mm Filtek P60; G3 = Filtek P60 inserted with incremental technique; G4 = 3 mm increment of Filtek Z350 Flow XT + 1 mm increment of Filtek P60. The required restorative clinical time for each technique was marked. Specimens were submitted to thermomechanical loading (20,000 mechanical cycles-80 N/thermal cycling-5/55°C for 30 seconds). After, samples were sectioned, ratio of internal gaps to interface length (%) was recorded using dye-staining-gap technique. Data were submitted to analysis of variance (ANOVA) and Tukey's test (95% significance). RESULTS: There was no significant difference in gap formation and none of the groups was completely gap-free. However, a significant reduction on required restorative clinical time was observed for G1 (167 ± 7 seconds), G2 (169 ± 4 seconds), and G4 (169 ± 8 seconds) when compared with G3 (204 ± 8 seconds). CONCLUSION: No significant difference in gap formation was found among bulk-fill and conventional incremental restorative technique tested; however, the use of a bulk-fill composite reduced 20% of the required restorative clinical time. CLINICAL SIGNIFICANCE: None of the restorative techniques applied were able to prevent internal gap formation. The use of bulk-fill composite reduced the required clinical time to perform class I restorations.

Influência dos agentes clareadores na dureza e cor de materiais restauradores diretos

Avaliar, in vitro, a variação de cor e dureza de três materiais restauradores (3M ESPE): Ketac Molar Easymix (KME); Vitremer (VT) e resina composta Filtek Z250 (Z250) após o clareamento com peróxido de carbamida a 37% (PC37- Whiteness Super) e peróxido de hidrogênio a 35% (PH35- Whiteness HP Maxx). Materiais e método: foram confeccionados 108 corpos de prova (CP), sendo 36 para cada material, avaliados inicialmente (baseline) e após cada aplicação dos agentes clareadores realizadas em subseqüentes 7 períodos, ou seja, após 1, 7, 14, 21, 28, 35 e 42 dias. As avaliações colorimétricas (coordenadas CIELAB) dos CP foram realizadas usando um espectrofotômetro (Easyshade, Vita Zahnfabrik, Bad Sackingen, Alemanha) sob fundo branco e em ambiente clínico. Para a avaliação da dureza (H), usou-se um durômetro (Pantec HVS 10, Panambra Ind. e Téc. SA, São Paulo, SP Brasil) com penetrador tipo Vickers. Os resultados das diferenças de cor (∆E*ab), diferenças de L* (∆L*) e H foram calculados e avaliados estatisticamente usando análise de variância (ANOVA) e as diferenças avaliadas pelo teste Tukey (α=0,05). Resultados: após o clareamento, houve alterações significativas no valor de ∆E*ab para os dois materiais a base de ionômero de vidro (KME e VT), com ambos os clareadores (PC37 e PH35) mostrando efeito similar para cada material. Não houve diferença na H dos materiais. Conclusão: após 42 dias, agentes clareadores alteraram a cor dos materiais ionoméricos e não alteraram a dureza dos materiais testados.