Experimental methodologies to evaluate the masking ability of dental materials: A systematic review.

OBJECTIVE: To conduct a systematic review on the masking ability of discolored substrates, analyzing the capacity and quality of the response produced by the different methodologies and techniques applied to overcome this clinical challenge. MATERIALS AND METHODS: The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The electronic search was conducted in MEDLINE/PubMed, Scopus and Web of Science databases, without date restriction. In vitro studies, written in English, applying different methodologies to evaluate masking ability were included. The variables of interest were: type, color and thickness of the restorative and/or cement material; use of pigments in the restorative material and/or cement; color of the substrate; and background color used for the evaluations. RESULTS: Database search retrieved 307 eligible papers with a final inclusion of 47 published papers. Approximately 98% of the studies used ΔE, 36% used TP, and only 6% used CR to evaluate the masking ability of restorative materials. CONCLUSIONS: The most appropriate methodology to evaluate the masking ability is using color difference equations (ΔE) associated with the perceptibility and acceptability thresholds. CLINICAL SIGNIFICANCE: As different methodologies have been used to evaluate the masking ability of esthetic restorative materials on colored substrates, there is an urgent need to reach a consensus and propose a method, which is suggested by the present systematic review.

Quantitative and qualitative analyses of ceramic chipping.

OBJECTIVE: To evaluate edge chip resistance (ReA) and fractographic features of ceramic systems submitted to edge chipping. METHODS: Samples were fabricated using the following materials: YZ-yttria-stabilized tetragonal zirconia ceramic (IPS e.max® Zir-CAD); LG-leucite-reinforced glass-ceramic (IPS Empress® CAD); LD-lithium-disilicate glass-ceramic (IPS e.max® CAD); ZF- YZ veneered by a pressable fluorapatite glass-ceramic (IPS e.max® Zir-CAD + IPS e.max® Zir-Press); ZD- YZ-LD fused together by a glass-ceramic (IPS e.max® Zir-CAD + IPS e.max® crystall./connect + IPS e.max® CAD). Half of the sample size was bonded (B) to a dentine analogue substrate (NEMA G10) and the remaining samples were kept non-bonded (NB). Structures were indented (n = 25) at different edge distances (d = 0.3, 0.4, 0.5, 0.6, 0.7 mm) using a universal testing machine to produce chips. Force (F) and d values were recorded and ReA was calculated. Data were statistically analyzed using ANOVA, Student t and Tukey tests (α = 0.05). Chipping was evaluated visually and under optical and scanning electron microscopy based on fractography principles. RESULTS: Data (F vs d) showed a positive linear trend for all groups. There was no significant difference in ReA values at d = 0.5 mm (SE0.5) between NB and B for same ceramic system. Fracture pattern was similar between NB and B for same ceramic system at d = 0.5 mm. CONCLUSIONS: Bonding neither influenced ReA values nor the fracture pattern that were similar between NB and B structures from same ceramic system. The greater the distance from structure edge, the lesser the chance of chipping occurred.

Non-silicate nanoparticles for improved nanohybrid resin composites.

OBJECTIVE: Zirconia and alumina nanoparticles were coated with a silica-rich layer (ALSI and ZRSI) and used to prepare experimental nanohybrid resin composites, which were characterized and compared to a control commercial resin composite (Filtek Z350 XT). METHODS: Silica nanoparticles with sizes compatible to ALSI (Aerosil 150) and ZRSI (Aerosil OX 50) were tested as references. The volume of nanoparticles was equivalent across the composites, which also had consistent content of glass microparticles. CC conversion, viscosity, depth of cure, surface topography, hardness, opacity, radio-opacity, and edge chipping resistance (ReA) were tested after 24 h. Flexural strength (σf) and fracture toughness (KIC) were also tested after 15 K thermal cycles. Data were analyzed using one-way or two-way ANOVA and Tukey's test (α = 0.05). RESULTS: ALSI and ZRSI yielded resin composites with lower viscosity and more irregular nanoagglomerates compared to nanosilica-based composites. CC conversion and depth of cure were lower for ZRSI composite, which had higher opacity, radio-opacity, and hardness. ReA was higher for ALSI composite. Composites with ALSI and ZRSI showed stable σf after aging, whereas the control and Aerosil 150 resin composites showed significant degradation. The commercial and nanosilica-based composites showed up to 42% reduction in KIC after aging, whereas resin composites with ZRSI and ALSI showed a more stable KIC. SIGNIFICANCE: ALSI and ZRSI generated nanohybrid resin composites with improved and/or more stable physical properties compared with nanosilica-based and commercial composites. This study suggests that changing the composition of nanofillers is a simple method to enhance the performance of nanohybrid composites.

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.

Efeito da radioterapia na resistência de união entre dentina humana e resina composta / Effect of radiotherapy on the bond strength between human dentin and composite resin

Objetivo: O objetivo deste estudo experimental é avaliar o efeito da radiação com raios X de alta energia na resistência de união entre dentina humana e resina composta. Métodos: Trinta terceiros molares humanos hígidos foram seccionados, produzindo superfícies oclusais planas de dentina, e distribuídos aleatoriamente em dois grupos (n=15): um não irradiado e restaurado com Resina Composta Filtek Z-250, 3M-ESPE® (G1, n=15 ­ grupo controle), outro irradiado e restaurado com Resina Composta Filtek Z-250, 3M-ESPE® (G2, n=15). O protocolo de radiação utilizado foi de 70 Gy no total. As amostras foram cortadas em palitos (área média de 1 mm2) e submetidas ao teste de microtração. Os dados foram comparados por meio do teste t-student (p <0,05). O padrão de fratura foi examinado em microscopia óptica e submetido ao teste exato de Fischer (p <0,05). Resultados: não houve diferença significativa entre o grupo de dentes não irradiados e irradiados (p=0,738). O grupo controle e o grupo irradiado apresentaram predominância no padrão de fratura de falhas coesivas em resina e/ou mistas e falhas adesivas foram verificadas somente no grupo dos dentes irradiados. Conclusões: A radiação não interfere significativamente na resistência de união da dentina humana restaurada com resina composta e que não houve influência significativa entre os grupos estudados em relação ao padrão de fratura(AU)

Objective: The aim of this experimental study is to evaluate the effect of high-energy x-rays radiation on the bond strength between human dentin and composite resin. Methods: Thirty healthy human third molars were sectioned, producing plane occlusal surface of dentine, and they were randomly distributed in two groups (n=15): one non-irradiated and restored with Composite Resin Filtek Z-250, 3M-ESPE® (G1, n=15 ­ control group), another was irradiated and was restored with Filtek Z-250, 3M-ESPE® (G1, n=15). The radiation protocol used was 70 Gy in total. The samples were cut in sticks (average area of 1 mm2) and were submitted to microtensile test. Data were compared using the t-student (p<0.05) test. The fracture pattern was examined in optical microscopy and was submitted to Fisher's exact test (p<0.05). Results: there was no significant difference between the group of non-irradiated and irradiated teeth (p=0.738). The control group and the irradiated group showed predominance in the fracture pattern of cohesive resin faults and/or mixed and adhesive failures were verified only in the group of irradiated teeth. Conclusions: The radiation does not significantly interfere in bond strength of human dentin restored with composite resin and there was no significant influence between the studied groups in relation of the fracture pattern(AU)

Effect of ionizing radiation on properties of restorative materials.

OBJECTIVE: To evaluate the effect of ionizing radiation from high energy X-ray on properties of restorative materials. METHODS: Study materials (3M-ESPE) were: Z250-microhybrid resin-based composite (Filtek Z-250); Z350-nanofilled resin-based composite (Filtek Z-350XT); VIT-resin-modified glass ionomer cement (Vitremer); and KME-conventional glass ionomer cement (Ketac Molar Easymix). Sixty bar-shaped and cylinder-shaped specimens were fabricated from each material. Specimens were light activated (980mW/cm2, Radii, SDI) for 60s (3×20s for Z250 and Z350) and 120s (3×40s for VIT) and thirty specimens from each shape were irradiated (IR) with 1.8Gy/day for 39days (total IR=70.2Gy). IR and non-irradiated (NI) specimens were evaluated for flexural strength (σ, n=30) followed by fractography (SEM), diametral tensile strength (DTS, n=30), hardness (H, n=10), surface roughness (Ra, n=10) and chemical composition (n=3). The IR effect on each material property was statistically analyzed using Student's t test (α=0.05). Data from σ and DTS were also analyzed using Weibull statistics. RESULTS: IR significantly increased the mean σ values of VIT and KME and the mean DTS value of VIT (p<0.05). IR increased Ra and H values for VIT and decreased H value for Z-250 (p<0.05). The remaining materials and properties were not significantly affected by IR (p>0.05). There was no significant change on materials composition after IR. SIGNIFICANCE: The recommended radiotherapy protocol for head and neck cancer altered some material properties, mainly for glass ionomer cements. Such variations on material properties are not related to chemical composition changes.