Isolation and characterization of a human cementocyte-like cell line, HCY-23

Abstract Cementum is the mineralized tissue covering the tooth root that functions in tooth attachment and post-eruptive adjustment of tooth position. It has been reported to be highly similar to bone in several respects but remains poorly understood in terms of development and regeneration. Here, we investigate whether cementocytes, the residing cells in cellular cementum, have the potential to be protagonist in cementum homeostasis, responding to endocrine signals and directing local cementum metabolism. Cells from healthy erupted human teeth were isolated using sequential collagenase/EDTA digestions, and maintained in standard cell culture conditions. A cementocyte-like cell line was cloned (HCY-23, for human cementocyte clone 23), which presented a cementocyte compatible gene expression signature, including the expression of dentin matrix protein 1 ( DMP1 ), sclerostin ( SOST ), and E11/gp38/podoplanin ( E11 ). In contrast, these cells did not express the odontoblast/dentin marker dentin sialoprotein ( DSPP ). HCY-23 cells produced mineral-like nodules in vitro under differentiation conditions, and were highly responsive to inorganic phosphate (Pi). Within the limits of the present study, it can be concluded that cementocytes are phosphate-responsive cells, and have the potential do play a key role in periodontal homeostasis and regeneration.

Influence of Photoinitiator on Accelerated Artificial Aging and Bond Strength of Experimental Resin Cements

Abstract The goal of this study was to evaluate in vitro the effect of the photoinitiator phenylpropanedione (PPD), alone or combined with camphorquinone (CQ), on color stability of photoactivated resin cements and their bond strength to ceramics using a micro-shear test. Four resin cements were used: a commercial brand cement (RelyX Veneer®) and 3 experimental cements with different types and concentration of photoinitiators. For color analysis, ceramic discs were cemented on bovine dentin specimens to simulate indirect restorations (n=8) and were exposed to UV for 120 h and tested for color alteration using a reflectance spectrophotometer and the CIEL*a*b* system. Data were analyzed by Anova and Tukey's test at 5% significance level. The color test results did not present statistically significant difference for the ∆E for all the studied cements, neither for ∆L, ∆a and ∆b. For the bond strength, all the studied cements showed statistically significant differences to each other, with the highest result for the RelyX Veneer® (29.07 MPa) cement, followed by the cement with CQ (21.74 MPa) and CQ+PPD (19.09 MPa) cement; the lowest result was obtained by the cement using only PPD as a photoinitiator (13.99 MPa). So, based on the studied parameters, PPD was not advantageous as photoinitiator of resin cements, because it showed a low value of bond strength to the ceramics and no superior color stability.

Resumo O objetivo deste estudo foi avaliar in vitro o efeito do fotoiniciador fenilpropanodiona (PPD), isoladamente ou em associação com a CQ, sobre a estabilidade de cor de cimentos resinosos fotoativados e sua resistência de união adesiva à cerâmica, por teste de microcisalhamento. Foram utilizados 4 cimentos resinosos, sendo um comercial (RelyX Veneer®) e 3 experimentais, diferindo entre si quanto ao tipo e concentração dos fotoiniciadores. Para a análise de cor foram cimentados discos cerâmicos sobre dentina bovina, simulando restaurações indiretas (n=8), sendo expostos a 120 h de UV e testados quanto às alterações de cor, que foram mensuradas empregando a escala CIEL*a*b*, por meio de espectrofotômetro de reflectância. Os dados obtidos foram verificados quanto à distribuição normal, submetidos a Anova e ao teste complementar Tukey, todos com significância de 5%. Os resultados do teste de cor não apresentam diferença estatisticamente significante para o ∆E dos 4 cimentos estudados, tampouco para ∆L, ∆a e ∆b. Para a resistência de união, todos os cimentos estudados apresentaram diferenças estatisticamente significantes entre si, com o maior resultado para o cimento comercial RelyX Veneer® (29,07 MPa), seguido pelo cimento com CQ (21,74 MPa), e cimento de CQ+PPD (19,09 MPa); o menor resultado foi obtido com o cimento utilizando apenas o PPD como fotoiniciador (13,99 MPa). Portanto, para os parâmetros estudados, o PDD não se mostrou vantajoso como fotoiniciador de cimentos resinosos, pois apresentou baixo valor de resistência de união à cerâmica e não demonstrou superioridade quanto à estabilidade de cor.

Microtensile Bond Strength of Adhesive Systems in Different Dentin Regions on a Class II Cavity Configuration

Abstract The aim of this study was to evaluate microtensile bond strength (µTBS) of self-etch and etch-and-rinse adhesives systems compared in different dentin regions (central-CD or proximal-PD) in a class II cavity configuration. A class II (mesial-oclusal-distal) cavity configuration was simulated on 20 extracted human third-molars (4 mm wide/3 mm deep). Etch-and-rinse adhesive (Scotchbond Multi Purpose, n=5, SBMP and Optibond FL, n=5, OPFL) and self-etch adhesives (Clearfil SE Bond, n=5, CSE and Optibond XTR, n=5, OPXTR) were applied. Class II restorations were performed by incremental technique and photo-activated (Bluephase/G2). Samples were sectioned to beam shape (1 mm² cross-section), placed on Geraldeli's device for µTBS test (0.5 mm/min cross-head speed). Fracture patterns were analyzed on stereomicroscope and classified as cohesive-resin, adhesive, mixed/resin or mixed/dentin. Samples (n=4) were prepared for scanning electron microscope observation. Data were submitted to one-way ANOVA with Split-Plot arrangement and Tukey's test (α=0.05). There were no statistically significant differences among SBMP, OPFL, CSE and OPXTR on CD (p>0.05). However, on PD for SBMP and OPFL, µTBS values were significantly lower compared to CSE and OPXTR (p<0.05). In all groups, mixed failure pattern was more frequently observed, except for SBMP/CD (adhesive). In class II type cavity configuration, PD location negatively influenced bond strength of etch-and-rinse adhesive systems. Opposite to self-etching adhesives, which presented higher bond strength values compared to etch-and-rinse adhesives in PD.

Resumo O objetivo deste estudo foi avaliar a resistência de união à microtração (µTBS) de sistemas adesivos auto-condicionantes e convencionais comparados por entre diferentes regiões dentinárias (central-DC ou proximal-DP) em um preparo cavitário classe II. Um preparo cavitário classe II (mesio-ocluso-distal) foi simulado em 20 terceiros molares humanos (4 mm largura/3 mm profundidade). Adesivos convencionais (Scotchbond Multi Purpose, n=5, SBMP e Optibond FL, n=5, OPFL) e adesivos auto-condicionantes (Clearfil SE Bond, n=5, CSE e Optibond XTR, n=5, OPXTR foram aplicados. As restaurações classe II foram realizadas usando a técnica incremental e fotoativadas (Bluephase/G2). As amostras foram seccionadas em forma de palito (1 mm2 secção transversal), posicionadas no dispositivo de Geraldeli para o teste µTBS (velocidade transversal de 0,5 mm/min). O padrão de fratura foi analisado em estereoscópio e classificado em coesivo-resina, adesivo, misto/resina, misto/dentina. Amostras (n=4) foram preparadas para observação em microscópio eletrônico de varredura. Os dados foram submetidos a ANOVA um fator e teste de Turkey (α=0,05). Não houve diferença estatística significante entre SBMP, OPFL, CSE, e OPXTR em DC (p>0,05). Entretanto, para SBMP e OPFL em DP, valores µTBS foram significativamente menores comparados com CSE e OPXTR (p<0,05). Em todos os grupos, o padrão de fratura misto foi o mais frequentemente observado, exceto em SBMP/CD (adesivo). Em um preparo classe II, a localização da DP influenciou negativamente a resistência de união de sistemas adesivos convencionais. Oposto aos adesivos auto-condicionantes, que em DP apresentaram valores de resistência de união maiores comparados com adesivos convencionais.