Letícia Borges Jacques

Effect of cantilever length and framework alloy on the stress distribution of mandibular-cantilevered implant-supported prostheses.

OBJECTIVES The purpose of this in vitro study was to analyze the stress distribution on components of a mandibular-cantilevered implant-supported prosthesis with frameworks cast in cobalt-chromium (Co-Cr) or palladium-silver (Pd-Ag) alloys, according to the cantilever length. MATERIAL AND METHODS Frameworks were fabricated on (Co-Cr) and (Pd-Ag) alloys and screwed into standard abutments positioned on a master-cast containing five implant replicas. Two linear strain gauges were fixed on the mesial and distal aspects of each abutment to capture deformation. A vertical static load of 100 N was applied to the cantilever arm at the distances of 10, 15, and 20 mm from the center of the distal abutment and the absolute values of specific deformation were recorded. RESULTS Different patterns of abutment deformation were observed according to the framework alloy. The Co-Cr alloy framework resulted in higher levels of abutment deformation than the silver-palladium alloy framework. Abutment deformation was higher with longer cantilever extensions. CONCLUSION Physical properties of the alloys used for framework interfere with abutment deformations patterns. Excessively long cantilever extensions must be avoided.

Compressive strength of glass ionomer cements using different specimen dimensions

The purpose of this study was to evaluate the compressive strength of two glass ionomer cements, a conventional one (Vitro Fil - DFL) and a resin-modified material (Vitro Fil LC - DFL), using two test specimen dimensions: One with 6 mm in height and 4 mm in diameter and the other with 12 mm in height and 6 mm in diameter, according to the ISO 7489:1986 specification and the ANSI/ADA Specification No. 66 for Dental Glass Ionomer Cement, respectively. Ten specimens were fabricated with each material and for each size, in a total of 40 specimens. They were stored in distilled water for 24 hours and then subjected to a compressive strength test in a universal testing machine (EMIC), at a crosshead speed of 0.5 mm/min. The data were statistically analyzed using the Kruskal-Wallis test (5%). Mean compressive strength values (MPa) were: 54.00 +/- 6.6 and 105.10 +/- 17.3 for the 12 mm x 6 mm sample using Vitro Fil and Vitro Fil LC, respectively, and 46.00 +/- 3.8 and 91.10 +/- 8.2 for the 6 mm x 4 mm sample using Vitro Fil and Vitro Fil LC, respectively. The resin-modified glass ionomer cement obtained the best results, irrespective of specimen dimensions. For both glass ionomer materials, the 12 mm x 6 mm matrix led to higher compressive strength results than the 6 mm x 4 mm matrix. A higher variability in results was observed when the glass ionomer cements were used in the larger matrices.

Ageing of silorane-based and methacrylate-based composite resins: Effects on translucency

OBJECTIVES Verify if media and time of storage affect the translucency of a silorane-based composite (Filtek P90) compared to two methacrylate-based composites (Z350 and ROK), and compare two methods of translucency evaluation. METHODS Specimens were divided into two groups (n=7) according to the storage media (deionized water or red wine). With a spectrophotometer (SP60) in reflectance mode, the CIE L*a*b* parameters and opacity percentage readings were conducted at baseline, 24h, 30 days, and 180 days. Data were analyzed using two-way repeated measures ANOVA and Tukey (p<0.05). Pearson correlation measured the relationship between translucency parameter and opacity percentage. RESULTS When stored in water, P90 showed an increase, whereas Z350 decreased in translucency. ROK did not exhibit any tendency over time. When stored in wine, the translucency of all materials decreased. A negative relationship was found between translucency parameter and opacity percentage. When stored in water, the a* values for P90 decreased, whereas Z350 and ROK showed values increasing over time. When stored in wine, the L* parameter tended to decrease over time, an effect that was less intense for P90. Moreover, the b* parameter for P90 decreased, whereas methacrylate-based composites increased over time. CONCLUSIONS P90 was more stable in red wine than the other materials and became more translucent in water whether metacrilate-based materials became more opaque. Both media as well as storage time affected the translucency of the materials tested. Translucency could be measured with both methods tested. CLINICAL SIGNIFICANCE Silorane-based composites seemed to be more stable than methacrylate-based composites in red wine and became more translucent over time in water, which was different than methacrylate-based composites. More studies are needed to clarify silorane-based composites performance.

Effect of lipstick on composite resin color at different application times

Objectives The aim of this study was to evaluate the influence of the contact of two lipsticks, one with common fixer and one with ultra fixer, on the color of a composite resin immediately, 30 min and 24 h after photoactivation. Material and methods Ninety specimens were prepared with a composite resin, Filtek-Z350. Specimens were polished and divided into 9 groups (n=10) according to time elapsed after photoactivation (A- immediately; B- 30 min; C- 24 h) and the contact with lipstick (UF- lipstick with ultra fixer; F- lipstick with common fixer). The control group was represented by specimens that did not have any contact with lipstick (C- without lipstick). Color measurements of the specimens were carried out using a spectrophotometer (Easyshade - CIE L* a* b* system). For UF and F groups, the baseline color of the specimens was measured immediately before pigmentation and the lipsticks were applied dry after 1 hour. The excess lipstick was removed with absorbent paper and final color checking was performed, including the control group. Differences between the final and baseline color measurements were calculated and data were analyzed statistically by the Kruskal-Wallis test at 5%. Results The means between the differences of color values were: AUF: 16.0; AF: 12.4; AC: 1.07; BUF: 9.51; BF: 8.3; BC: 0.91; CUF: 17.7; CF: 12.41; CC: 0.82. Conclusion Groups where lipstick was applied showed greater staining than the control group at the three evaluation times. The lipstick with ultra fixer stained more than the lipstick with common fixer. Time elapsed between photoactivation and contact with lipstick had a similar influence on the groups that received lipstick application.

Influence of Bleaching Agents on Color and Translucency of Aged Resin Composites.

OBJECTIVES Evaluate the influence of two bleaching agents (16% carbamide peroxide-CP and 35% hydrogen peroxide-HP) on color and translucency of one resin composite (Filtek Z350 XT) in two opacities (enamel and dentin) previously aged in deionized water or red wine. METHODS Sixty specimens of each material were divided in two groups (n = 30): aged in water or red wine for 14 days. Then the specimens were divided in three subgroups (n = 10): control/no treatment, treated with 16% carbamide peroxide (Mix Night), treated with 35% hydrogen peroxide (Mix One). Color readings were performed 24 hours after polishing (baseline); after the 14 days of aging; and after bleaching treatment. Color coordinates CIE L*a*b* were measured using a spectrophotometer (SP60 X-Rite). Color change (CIEDE2000) and translucency parameter were calculated. Data were analyzed with repeated measures two-way ANOVA, and Student-Newman-Keuls tests (5%). RESULTS Bleaching decreased color change in stained resin composites (aged in red wine), whereas increased it in non-stained enamel resin composites (aged in water). CP had better bleaching results with stained resin composites than HP. Translucency of non-stained dentin resin composite decreased with aging, but did not change with bleaching. For stained resin composites, aging caused reduced translucency, whereas bleaching increased it. CLINICAL SIGNIFICANCE Effective bleaching of discolored resin composites aged in an acidic and alcoholic media rich in staining agents was achieved, improving color and translucency. Carbamide peroxide showed better performance than hydrogen peroxide for the bleaching of stained resin composites. (J Esthet Restor Dent 29:368-377, 2017).

Resin push-out bond between fiber post and root dentin: Evaluation of different cementation approaches

Background: Resin push-out bond between fiber post and root dentin can be achieved in various ways. This study evaluates the bond strength of glass fiber posts cemented into root canal using different luting techniques. The null hypothesis tested was that no difference would be observed among the strategies for post cementation. Materials and Methods: The canals of 50 roots were prepared with the custom drill of glass fiber post and divided into five groups (n = 10), according to the strategy for post cementation: G1- conventional adhesive procedure (single-bottle etch and rinse light-cured adhesive + resin cement (Relyx ARC)); G2- conventional adhesive procedure (single-bottle etch and rinse light-cured adhesive + resin cement (AllCeram); G3- self-adhesive resin cement (Relyx Unicem, 3M/ESPE); G4- self-adhesive resin cement (Relyx Unicem, 3M/ESPE) with previous dentin acid etching; and G5- resin glass ionomer cement (Relyx Luting 2, 3M/ESPE). After post cementation, the specimens were kept for 24 h in 100% humidity. Afterwards, each root was sectioned into 2 mm slices to be pushed-out. The data were submitted to one-way analysis of variance (ANOVA) and Tukeys test (5%). Failure analyses were followed after testing. Results: The self-adhesive resin cement with dentin acid pretreatment (G4: 22.3 ± 2.8) had the highest bond strength values (MPa) (G3: 16.3 ± 4.4 > G1: 7.0 ± 3.9 > G2: 4.9 ± 2.5 > G5: 3.7 ± 2.2) (P Conclusion: Simplified self-adhesive resin cement promoted the highest bond strength when compared to conventional adhesive cementation and glass ionomer.

The Effect of Brushing and Aging on the Staining and Smoothness of Resin Composites.

OBJECTIVES To evaluate the staining and smoothness of resin composites undergoing aging in water or red wine and simulated brushing with or without dentifrice. METHODS The resin composites (Z250 microfilled and Z350XT nanofilled) were tested according to aging media (deionized water or red wine) and surface treatment (no brushing, brushed with water, or brushed with dentifrice). Specimens (n = 10) were subjected to three aging cycles (5 days) of continuous immersion in the aging media; each followed by simulated brushing (585 strokes). Color coordinates (CIEL*a*b*) were measured with a spectrophotometer (SP60, EX-Rite) and roughness (Ra) measured with a contact profilometer (Surftest SJ-201P, Mitutoyo), in five time points across the experiment. Surface morphology was analyzed using AFM (SPM-9600, Shimadzu) at the end of the experiment. Data for color change (ΔE00 ) and Ra were analyzed by two-way repeated measures ANOVA and Tukey test (p < 0.05). RESULTS Color change was observed for all groups, and it was always greater for Z350. Surface treatment did not influence the ΔE00 values for the groups aged in water. However, brushing decreased ΔE00 for the groups aged in red wine. In general, ΔE00 increased with time. Little to no differences in smoothness were observed with aging and brushing. The surface morphology analyses showed exposed/lost filler particles for brushed Z250. Such observations were not so clear for Z350. CONCLUSIONS Within the limitations of the present experiment, short-time simulated toothbrushing with soft-bristle toothbrush and low abrasive dentifrice did not increase roughness and reduced staining for both nanofilled and microfilled materials. CLINICAL SIGNIFICANCE Staining and surface degradation of the resin composites was reduced, but not prevented by brushing alone. Thus, minimizing the restoration exposure to staining substances is important for maintaining the aesthetic appearance of the restoration. (J Esthet Restor Dent 29:E44-E55, 2017).

Avaliação do efeito de enxaguatórios bucais na rugosidade superficial de resinas acrílicas quimicamente ativadas

O objetivo neste trabalho foi avaliar o efeito de dois enxaguatorios bucais (Periogard [PER] (Colgate-Palmolive Ind. Com. Ltda – Sao Paulo, SP, Brasil) e Listerine [LIS] (Johnson & Johnson Healthcare Products – Skillman-NJ,EUA)) na rugosidade de superficie de duas resinas acrilicas polimerizaveis quimicamente (Duralay [DUR] (Reliance Dental – Worth, IL, EUA] e Dencrilay [DEN] (Dencril Caieiras, SP, Brasil)), tendo como grupo controle o soro fisiologico [SOR], totalizando 6 grupos (n=8). Para a confeccao dos corpos-de-prova (CP) foram utilizadas 48 matrizes de poliacetal com um orificio central cilindrico de 5 mm de diâmetro por 5 mm de profundidade. A resina acrilica foi manipulada e inserida no orificio com seringa plastica, com a matriz posicionada sobre uma lâmina de vidro. Outra lâmina foi pressionada sobre a matriz e esse conjunto foi colocado numa panela de pressao durante a polimerizacao. As faces correspondentes aos diâmetros dos cp foram regularizadas com lixa d’agua 220 e as faces que apresentaram menos irregularidades receberam o acabamento com as demais lixas (320, 400, 600, 1200) sob refrigeracao com agua, em uma politriz. Apos 24 horas de armazenagem em agua foram realizadas as leituras iniciais num rugosimetro na escala Ra. Os CP foram imersos nas solucoes para bochecho durante 10 minutos por dia, por 10 dias. Entre os intervalos de imersao nas solucoes para bochechos as resinas ficaram armazenados em soro fisiologico. Nesse periodo, o grupo controle ficou todo o tempo armazenado em soro fisiologico. Em seguida, os CP foram submetidos a leitura final de rugosidade (Ra), pelo mesmo avaliador. Os resultados iniciais foram: DUR+LIS=0,20; DUR+PER=0,21; DUR+SOR=0,25; DEN+LIS=0,33; DEN+SOR=0,33; DEN+PER=0,36; e finais: DUR+PER=0,28; DUR+LIS=0,28; DEN+SOR=0,31; DUR+SOR=0,34; DEN+PER=0,43; DEN+LIS=0,43. A analise de variância e o teste de Tukey (5%) mostraram que a resina acrilica Duralay apresentou menor rugosidade de superficie e as solucoes aumentaram significantemente as suas rugosidades com o tempo. Nao houve diferenca significante entre as solucoes testadas.