Physicochemical and mechanical properties of preheated composite resins for luting ceramic laminates.

This study analyzed and compared the physicochemical and mechanical properties of preheated resin composite with light-cured resin cement for luting indirect restorations. 210 specimens of resin cement/resin composite were prepared according to preheating treatment heated (Htd) or not (NHtd). Light-cured resin cement (Variolink Veneer, Ivoclar), and resin composite (Microhybrid-Z100, 3 M; Nanohybrid-Empress direct, Ivoclar; and Bulk fill-Filtek One, 3 M) were used (n = 10). Resin cement specimens were not preheated. The response variables were (n = 10): film thickness, microhardness, liquid sorption and solubility. Data were analyzed by 2-way ANOVA and Tukey HSD post-test (α = 0.05). Bulk fill NHtd resin had the highest film thickness values (p < 0.001). Microhybrid and nanohybrid Htd resins had the smallest thicknesses and did not differ from the cement (p > 0.05). The highest microhardness values were found for Bulk fill NHtd and Bulk fill Htd resins. The nanohybrid and microhybrid Htd resins showed the lowest microhardness values, with no difference in cement (p > 0.05). For liquid sorption, there was no significant difference between the groups (p = 0.1941). The microhybrid Htd resin showed higher solubility values than the other materials (p = 0.0023), but it did not differ statistically from resin cement (p > 0.05). Preheating composite resins reduced the film thickness. After heating, nanohybrid and Bulk fill resins retained stable microhardness, sorption, and solubility values.

Chitosan-induced biomodification on demineralized dentin to improve the adhesive interface.

Objectives: Metalloproteinase-inhibiting agents, such as chitosan, can prevent collagen degradation in demineralized dental substrates, thereby improving the adhesive interface. This study evaluated the bond strength (BS) and chemical and morphological characterization of the adhesive interface after applying chitosan solution to demineralized dentin. Materials and Methods: The 80 third molars were selected. Forty teeth underwent caries induction using the pH cycling method. The teeth were divided according to the treatment: distilled water (control) and 2.5% chitosan solution. The surfaces were restored using adhesive and composite resins. Half of the specimens in each group were aged, and the other half underwent immediate analyses. The teeth were sectioned and underwent the microtensile bond strength test (µTBS), and chemical and morphological analyses using energy-dispersive spectroscopy and scanning electron microscopy, respectively. Data analysis was performed using 3-way analysis of variance. Results: For µTBS, sound dentin was superior to demineralized dentin (p < 0.001), chitosan-treated specimens had higher bond strength than the untreated ones (p < 0.001), and those that underwent immediate analysis had higher values than the aged specimens (p = 0.019). No significant differences were observed in the chemical or morphological compositions. Conclusions: Chitosan treatment improved bond strength both immediately and after aging, even in demineralized dentin.

Reproducibility of skeletal and dental maturation parameters / Reprodutibilidade de parâmetros de maturação esqueléticos e dentários

ABSTRACT Objective: Amongst other factors, the effectiveness of orthodontic treatment in children and adolescents depends on the identification of most appropriate intervention timing, which has been traditionally based on the identification of maturational stages. There is a wide variety of radiographic methods to identify these phases, either through skeletal parameters, or dental calcification. Considering that the reliability of any given assessment tool is required to enable its safe clinical use, and aiming an appropriate implementation of these parameters in future researches, this study was performed to assess the reproducibility of radiographic growth evaluation methods. Methods: Lateral teleradiographs, hand-wrist, and panoramic radiographs of sixty-eight orthodontic patients randomly selected from files of the Orthodontics Graduation Course (Guarulhos University, Guarulhos, SP, Brazil) were evaluated by two examiners to access both intra- and inter-examiner reproducibility of the assessment methods conceived by Baccetti et al.; Fishman; Greulich and Pyle; Nolla and Demirjian et al. Results: All methods analyzed showed satisfactory intra- and inter-examiner reliability. Among those that evaluated skeletal maturity, a relatively better performance was observed for Baccetti's method. Fishman's and Greulich's parameters presented similar rates, as did Nolla's and Demirjian's. Conclusion: The assessment tools analyzed presented adequate reproducibility and might potentially be used as assessment tools to evaluate children and adolescent's craniofacial growth. Further researches could evaluate the accuracy of radiographic dental calcification parameters for the identification of craniofacial growth stages.

RESUMO Objetivo: Entre outros fatores, a efetividade do tratamento ortodôntico em crianças e adolescentes depende da identificação do momento de intervenção mais apropriado, que tem sido baseado nos estágios de maturação. Uma variedade de métodos radiográficos identifica essas fases através de parâmetros esqueléticos e da calcificação dentária. Considerando que a confiabilidade de qualquer ferramenta de avaliação é necessária para permitir seu uso clínico e aplicação segura de seus parâmetros em pesquisas futuras, este estudo acessou a reprodutibilidade de métodos radiográficos de avaliação do crescimento. Métodos: Telerradiografias laterais, radiografias carpais e panorâmicas de 68 pacientes ortodônticos randomicamente selecionados dos arquivos do Curso de Graduação em Ortodontia (Universidade de Guarulhos, Guarulhos, SP, Brasil) foram avaliadas por dois examinadores para acessar a reprodutibilidade intra e inter-examinador dos métodos de avaliação concebidos por Baccetti et al.; Fishman; Greulich e Pyle; Nolla e Demirjian et al. Resultados: Todos os métodos analisados mostraram confiabilidade intra e inter-examinador satisfatória. Dentre os que avaliam maturidade esquelética, um desempenho relativamente melhor foi observado para o método de Baccetti e colaboradores. Os parâmetros de Fishman e de Greulich e Pyle apresentaram valores similares, assim como os de Nolla e de Demirjian e colaboradores. Conclusão: As ferramentas de avaliação analisadas apresentaram reprodutibilidade adequada e podem ser utilizadas para avaliação do crescimento craniofacial de crianças e adolescentes. Pesquisas futuras poderiam avaliar a acurácia dos parâmetros radiográficos de calcificação dentária para a identificação dos estágios de crescimento craniofacial.

Chitosan improves the durability of resin-dentin interface with etch-and-rinse or self-etch adhesive systems.

OBJECTIVE: Degradation of the dentin-resin interface can occur due to hydrolysis of exposed collagen, resulting in reduced bond strength. This study assessed the effect of dentin treatment with chitosan combined with an etch-and-rinse or self-etch adhesive system on improvement of bond strength and preservation of the interface durability. METHODOLOGY: Enamel was removed from 80 molars and the teeth were divided into two groups: without chitosan (control) or with 2.5% chitosan gel (1 min). They were further subdivided into two subgroups according to the adhesive system: etch-and-rinse or self-etch. Dentin was restored using a composite resin. Half of the specimens from each restored group were subjected to interface aging and the remaining specimens were used for immediate analysis. The specimens were sectioned and subjected to microtensile bond strength (µTBS) test (n=10), chemical composition testing using Fourier-transform infrared (FTIR) spectroscopy (n=4) and energy-dispersive spectroscopy (EDS) (n=5), and morphological analysis of the adhesive interface using scanning electron microscopy (SEM) (n=5). Data were analyzed using three-way ANOVA. RESULTS: Chitosan improved the µTBS of the adhesive interface when compared with the control group (p=0.004). No significant differences were observed in dentin adhesion between the adhesive systems (p=0.652). Immediate µTBS was not significantly different from that after 6 months (p=0.274). EDS and SEM did not show significant differences in the chemical and structural composition of the specimens. FTIR showed a decrease in the intensity of phosphate and carbonate bands after using chitosan. CONCLUSIONS: Dentin treatment with chitosan combined with an etch-and-rinse or self-etch adhesive system improved the immediate and preserved the 6-month bond strength of the adhesive interface.