RESUMO
Purpose: The main goal of this study was to evaluate the impact of different ionizing radiation doses on the mineral (carbonate/phosphate ratio, crystallinity index [CI]) and organic (amide III/phosphate, amide I sub-band ratios) structures, as well as the microhardness, of enamel and dentin, along with their influence on the bonding strength stability of the etch-and-rinse (ER) and self-etch (SE) dental adhesive strategies.Materials and methods: Enamel and dentin human tissue specimens were irradiated (with 0, 20, 40, and 70 Gy radiation doses, respectively) and sectioned to perform an attenuated total reflection-Fourier transform IR spectroscopy assay (ATR-FTIR) and the Vickers microhardness (VHN) test to conduct a biochemical and biomechanical evaluation of the tissues. Regarding the adhesive properties, restored enamel and dentin specimens exposed to the same radiation doses were submitted to microshear bond strength (µSBS) tests for enamel in immediate time (IM) and to microtensile bond strength (µTBS) tests after for IM and 12-month (12 M) period of time, Mann-Whitney U tests were implemented, using the ATR-FTIR data for significant differences (α < 0.05), and three- and two-way analyses of variance, along with post-testing, were performed on the µTBS and µSBS data (MPa), respectively (Tukey post hoc test at α = 0.05).Results: The ATR-FTIR results showed a significant decrease (p < .05) in the amide III/phosphate ratio after 20 Gy for the enamel and after 40 Gy for the dentin. The CI was significantly reduced for both tissues after a dose of 70 Gy (p < .05). All radiation doses significantly decreased microhardness values, relative to the respective enamel and dentin controls (p < .05). In both tissues and adhesive strategies, the decrease in bond strength was influenced by ionizing radiation starting from 40 Gy. The ER strategy showed high percentages of enamel cohesive failure. In general, ER in both tissues showed greater and more stable bond strength than SE against increased radiation doses and long term.Conclusions: It is possible to conclude that structural alterations of enamel and dentin are generated by all radiation doses, decreasing the microhardness of dental hard tissues and influencing bond strength over time, starting at 40 Gy radiation dose. The etch-and-rinse strategy demonstrates better adhesive performance but generates cohesive fractures in the enamel.
Assuntos
Restauração Dentária Permanente , Dente Molar/efeitos da radiação , Radioterapia/efeitos adversos , Dente/efeitos da radiação , Esmalte Dentário/citologia , Esmalte Dentário/efeitos da radiação , Dentina/citologia , Dentina/efeitos da radiação , Dureza/efeitos da radiação , Humanos , Dente Molar/citologiaRESUMO
The dental caries is a progressive destruction of the teeth tissue due to the disbalance in the normal molecule interactions between the enamel and the bio!lm, which alters the demineralization-remineralization process. Milk fermentation produces caseinphosphopeptides with proved remineralizing capacity of the enamel. The presence of these peptides in fermented milk with ke!r grains has been described. The purpose of this work was to evaluate in vitro the capacity of milk ke!r to prevent the demineralization of dental enamel. Bovine incisors (n=68, 17 per group) were treated for 72 h with different solutions: I: artificial saliva at pH 7.2 , II: demineralizing solution at pH 4.5, III: supernatant of kefir fermented milk at pH 4.5, IV: milk supernatant at pH 4.5. The effects of treatments were evaluated by the change in the weight of the specimens, calcium concentration in the solution and by scanning electron microscopy (SEM) of the enamel. Kefir milk supernatant prevented the demineralization process, that was evidenced by a change in weight and calcium concentration that were not different from group I, although the pH was 4.5. In contrast, group IV showed a decrease in weight and an increase in calcium concentration, compared with group I (one way ANOVA, p<0.05). Images of SEM agree with the values of weight and calcium concentration. These results indicate that kefir milk supernatant has a protective effect on enamel demineralization in vitro. (AU)
La caries dental es una patología debido a un desequilibrio en las interacciones moleculares normales entre el esmalte y la biopelícula, que altera el proceso de desmineralización remineralización. La fermentación de la leche produce fosfopéptidos de caseína con probada capacidad remineralizante del esmalte, y se ha descripto la presencia de estos péptidos en la leche fermentada con granos de kéfir. El propósito de este trabajo fue evaluar in vitro la capacidad del kéfir de leche para prevenir la desmineralización del esmalte dental. Sesenta y ocho incisivos bovinos (17 por grupo) fueron tratados durante 72 h con diferentes soluciones: I: saliva artificial, pH 7.2, II: solución desmineralizante, pH 4.5, III: sobrenadante de leche fermentada con kefir, pH 4.5, IV: sobrenadante de leche, pH 4.5. El proceso de desmineralización se evaluó mediante el cambio en el peso de las muestras, la concentración de calcio en la solución y microscopía electrónica de barrido (SEM) del esmalte. El sobrenadante de leche fermentada con kéfir impidió el proceso de desmineralización, que se evidenció por un cambio en el peso y la concentración de calcio que no discreparon del grupo I, a pesar de haber tenido un pH de 4.5. En contraste, el grupo IV mostró una disminución en el peso y un aumento en la concentración de calcio, en comparación con el grupo I (ANOVA a un criterio, p<0.05). Las imágenes SEM concuerdan con los cambios en el peso y la concentración de calcio en los grupos estudiados. Los datos obtenidos demuestran que el sobrenadante de la leche tratada con kéfir tiene un efecto protector sobre la desmineralización del esmalte in vitro, inducida por el pH ácido. (AU)
Assuntos
Animais , Bovinos , Desmineralização do Dente/prevenção & controle , Kefir/microbiologia , Saliva Artificial/administração & dosagem , Remineralização Dentária/métodos , Técnicas In Vitro , Bovinos , Caseínas/uso terapêutico , Cálcio/análise , Desmineralização do Dente/patologia , Desmineralização do Dente/terapia , Biofilmes , Cárie Dentária/prevenção & controle , Esmalte Dentário/citologia , Esmalte Dentário/fisiopatologia , Leite/microbiologia , Formaldeído/administração & dosagemRESUMO
The aim of the present work was to investigate birefringence and morphology of the secretory-stage enamel organic extracellular matrix (EOECM), and structural and mechanical properties of mature enamel of upper incisors from adult rats that had been treated with pamidronate disodium (0.5 mg/kg/week for 56 days), using transmitted polarizing and bright-field light microscopies (TPLM and BFLM), energy-dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM) and microhardness testing. BFLM showed no morphological changes of the EOECM in pamidronate and control groups, but TPLM revealed a statistically significant reduction in optical retardation values of birefringence brightness of pamidronate-treated rats when compared with control animals (p0.05). The present study indicates that pamidronate can affect birefringence of the secretory-stage EOECM, which does not seem to be associated with significant changes in morphological and/or mechanical properties of mature enamel.
Assuntos
Esmalte Dentário/efeitos dos fármacos , Esmalte Dentário/ultraestrutura , Difosfonatos/farmacologia , Animais , Conservadores da Densidade Óssea/farmacologia , Esmalte Dentário/química , Esmalte Dentário/citologia , Microscopia Eletrônica de Varredura , Pamidronato , Ratos , Raios XRESUMO
AIM: To test the hypothesis that changes in enamel component volumes (mineral, organic, and water volumes, and permeability) are graded from outer to inner enamel after a short bleaching procedure. MATERIALS AND METHODS: Extracted unerupted human third molars had half of their crowns bleached (single bleaching session, 3 × 15 min), and tooth shade changes in bleached parts were analyzed with a spectrophotometer. Ground sections were prepared, component volumes and permeability were quantified at histological points located at varying distances from the enamel surface (n=10 points/location), representing conditions before and after bleaching. RESULTS: Tooth shade changes were significant (p<0.001; 95% CI=-1/-8; power=99%), and most of the enamel layer was unaffected after bleaching, except at the outer layers. Multiple analysis of covariances revealed that most of the variance of the change in enamel composition after bleaching was explained by the combination of the set of types of component volume (in decreasing order of relevance: mineral loss, organic gain, water gain, and decrease in permeability) with the set of distances from the enamel surface (graded from the enamel surface inward) (canonical R(2)=0.97; p<0.0001; power>99%). CONCLUSIONS: Changes in enamel composition after a short bleaching procedure followed a gradient within component volumes (mineral loss>organic gain>water gain>decrease in permeability) and decreased from the enamel surface inward.
Assuntos
Esmalte Dentário/química , Esmalte Dentário/efeitos dos fármacos , Clareamento Dental/efeitos adversos , Esmalte Dentário/citologia , Dureza/efeitos dos fármacos , Humanos , Peróxido de Hidrogênio/farmacologia , Microscopia Eletrônica de Varredura , Microscopia de Polarização , Minerais/análise , Dente Serotino/efeitos dos fármacos , Espectrofotometria/métodos , Propriedades de Superfície , Clareamento Dental/métodos , Clareadores Dentários/farmacologia , Desmineralização do Dente , Permeabilidade Dentária/efeitos dos fármacosRESUMO
PURPOSE: To evaluate the effects of radiation therapy on deciduous teeth. MATERIALS AND METHODS: The enamel and dentin microhardness (n = 12) was evaluated at 3 depths, both before (control) and after each 10 Gy of irradiation and up to a dose of 60 Gy. The morphology was evaluated via scanning electron microscopy (SEM) (n = 8). The data were analyzed using a two-way analysis of variance (ANOVA) and Tukey's test (α = 5%). RESULTS: The enamel microhardness, as a whole, increased (p < 0.05) after a dose of 60 Gy (211.4 KH), mostly in the superficial enamel. There was a significant difference between the values of nonirradiated dentin microhardness (28.9 KH) compared with dentin that was irradiated with doses of 10 Gy (23.8 KH), 20 Gy (25.6 KH), 30 Gy (24.8 KH), and 40 Gy (25.7 KH) (p < 0.05). There was no difference between nonirradiated dentin and dentin irradiated with 60 Gy (p > 0.05). The highest mean value of microhardness (29.9 KH) (p < 0.05) was found in the middle dentin. The groups that were irradiated with doses of 30 and 60 Gy exhibited greater surface changes in their enamel and dentin compared with the nonirradiated groups for all regions, exhibiting an amorphous surface upon increase of the irradiation doses. CONCLUSIONS: The enamel microhardness increased at a dose of 60 Gy, whereas the value of the dentin microhardness did not change. A progressive disruption of enamel and dentin morphology was found with the increased radiation dose.
Assuntos
Esmalte Dentário/efeitos da radiação , Dentina/efeitos da radiação , Radioterapia/efeitos adversos , Dente Decíduo/efeitos da radiação , Esmalte Dentário/citologia , Esmalte Dentário/ultraestrutura , Dentina/citologia , Dentina/ultraestrutura , Dureza/efeitos da radiação , Testes de Dureza , Humanos , Técnicas In Vitro , Fenômenos Mecânicos , Microscopia Eletrônica de Varredura , Dosagem Radioterapêutica , Dente Decíduo/citologia , Dente Decíduo/ultraestruturaRESUMO
Reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) is a single membrane-anchored MMP-regulator and regulates matrix metalloproteinases (MMP) 2, 9 and 14. In turn, MMPs are endopeptidases that play a pivotal role in remodeling ECM. In this work, we decided to evaluate expression pattern of RECK in growing rat incisor during, specifically focusing out amelogenesis process. Based on different kinds of ameloblasts, our results showed that RECK expression was conducted by secretory and post-secretory ameloblasts. At the secretory phase, RECK was localized in the infra-nuclear region of the ameloblast, outer epithelium, near blood vessels, and in the stellate reticulum. From the transition to the maturation phases, RECK was strongly expressed by non-epithelial immuno-competent cells (macrophages and/or dendritic-like cells) in the papillary layer. From the transition to the maturation stage, RECK expression was increased. RECK mRNA was amplified by RT-PCR from whole enamel organ. Here, we verified the presence of RECK mRNA during all stages of amelogenesis. These events were governed by ameloblasts and by non-epithelial cells residents in the enamel organ. Concluding, we found differential expression of MMPs-2, -9 and RECK in the different phases of amelogenesis, suggesting that the tissue remodeling is rigorously controlled during dental mineralization.
Assuntos
Matriz Extracelular/metabolismo , Incisivo/enzimologia , Incisivo/crescimento & desenvolvimento , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinase 9 da Matriz/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Amelogênese , Animais , Esmalte Dentário/citologia , Esmalte Dentário/enzimologia , Embrião de Mamíferos/metabolismo , Proteínas Ligadas por GPI , Regulação da Expressão Gênica no Desenvolvimento , Incisivo/citologia , Masculino , Glicoproteínas de Membrana/genética , Transporte Proteico , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Proteínas Supressoras de Tumor/genéticaRESUMO
The enamel-related periodontium (ERP) in rat incisors is related to bone resorption. In these teeth the face of the socket related to the enamel is continuously removed at the inner side and newly formed at the outer side. CSF-1, RANKL and OPG are regulatory molecules essential for osteoclastogenesis. To verify the effects of impeded eruption on bone remodeling, the tooth eruption was prevented by immobilization of lower rat incisor and CSF-1, RANKL and OPG distribution in the ERP was analyzed after 18 days of immobilization and in normal eruption. The region of the alveolar crest of the rat incisor was used. Immunohistochemistry and tartrate-resistant acid phosphatase (TRAP) were performed. The immunostaining of the dental follicle was quantified using Leica QWin software. Positive-TRAP osteoclasts were counted, and both groups were compared. In the normal incisor, the number of osteoclasts was significantly greater than in the immobilized tooth. In the dental follicle, there was no significant difference in the immunostaining intensity for CSF-1 and OPG between the groups (p > 0.05), but for RANKL the immobilized incisor group showed immunostaining intensity smaller than the normal incisor group (p < 0.01). These findings suggest that changes in the ERP, in the immobilized incisor, modify the RANKL/OPG ratio, in the presence of CSF-1, altering the metabolism of cells that participate in the bone remodeling.
Assuntos
Processo Alveolar/fisiologia , Remodelação Óssea/fisiologia , Esmalte Dentário/citologia , Incisivo/citologia , Fator Estimulador de Colônias de Macrófagos/análise , Osteoprotegerina/análise , Ligamento Periodontal/citologia , Ligante RANK/análise , Fosfatase Ácida/análise , Processo Alveolar/citologia , Ameloblastos/citologia , Animais , Biomarcadores/análise , Matriz Óssea/citologia , Reabsorção Óssea/patologia , Reabsorção Óssea/fisiopatologia , Contagem de Células , Saco Dentário/citologia , Imobilização , Imuno-Histoquímica , Isoenzimas/análise , Masculino , Osteoclastos/fisiologia , Ratos , Ratos Wistar , Fosfatase Ácida Resistente a Tartarato , Erupção Dentária/fisiologia , Alvéolo Dental/citologiaRESUMO
The consumption of alcohol during pregnancy causes fetal congenital malformations, including craniofacial and orodental defects, as a result of interference with normal embryonic development. In this work, we examined the effects of alcohol on tooth development and enamel formation in rats. Alcohol was administered to female rats in the drinking water starting at a concentration of 1% followed by weekly increases to 5%, 10%, 15%, 20% and 25%. In the seventh week, the rats were mated and continued to receive 25% alcohol until delivery. On postnatal day 5, three offsprings of each mother were killed and their hemimandibules removed, processed and embedded in araldite. Sections 1 µm thick were cut and stained with 1% toluidine blue and histomorphometric analysis of the dental germ and enamel matrix was done. During the postnatal period, the body weights of the offspring from treated dams were significantly smaller than the controls. In addition, the relative volumes of the tooth germ and enamel matrix were always smaller in the offspring of dams treated with alcohol. These results indicated that the ingestion of alcohol during pregnancy interfered with the development of the tooth germ and the secretion of the enamel matrix.
Assuntos
Animais , Feminino , Ratos , Amelogênese , Esmalte Dentário , Etanol , Esmalte Dentário , Etanol/administração & dosagem , Germe de Dente/crescimento & desenvolvimento , Odontogênese , Germe de Dente , Amelogênese/fisiologia , Esmalte Dentário/citologia , Dente Molar , Ratos Wistar , DenteRESUMO
Prerequisites of tooth formation, cell proliferation in the tooth-forming tissues, calcium accumulation and the enzymatic activities of alkaline (ALP) and acid phosphatases (ACP) were investigated by immunohistochemical and histochemical methods in various developmental stages of the Mexican Axolotl, Ambystoma mexicanum. During the growth of replacement teeth, the tooth-forming tissues continually recruit cells from the surrounding regions. The basal layer of the oral epithelium, the dental lamina and sometimes even the outer enamel epithelium provide cells for the differentiated inner enamel epithelium, in which the active ameloblasts are localized. The differentiating odontoblasts are derived from proliferating cells situated basally to the replacement teeth in the mesenchymal tissue. When differentiation has started and the cells have become functional, proliferative activity can no longer be observed. Calcium is accumulated close to the site of mineralization in the inner enamel epithelium and in the odontoblasts as it is in mammals, elasmobranchii and teleostei. The activities of ACP and ALP related to the mineralization of the replacement teeth are separated spatially and not sequentially as they are in mammals. However, the results indicate a similar function of these enzymatic components in relation to tooth formation and maturation of mineral deposition. Most of the substantial processes related to tooth formation reported from other vertebrates occur in a manner similar to that in Ambystoma mexicanum, but there also seem to be basic mechanisms present that are realised in a unique way in this urodele.
Assuntos
Fosfatase Ácida/metabolismo , Fosfatase Alcalina/metabolismo , Ambystoma mexicanum/crescimento & desenvolvimento , Cálcio/metabolismo , Odontogênese/fisiologia , Ambystoma mexicanum/fisiologia , Ameloblastos/citologia , Animais , Diferenciação Celular , Divisão Celular , Esmalte Dentário/citologia , Células Epiteliais/citologia , Histocitoquímica , Mucosa Bucal/citologia , Odontoblastos/citologia , Dente/citologiaRESUMO
Development of the periodontium involves a series of complex steps that result in the formation of root dentine, cementum, bone and fibres of the ligament. These precisely controlled and timed events require the participation of the enamel organ derived epithelial cells of Hertwig's (HRS) and ectomesenchymal cells of the dental follicle. These events involve rapid turnover of the tissues and cells, including disappearance of epithelial cells of HRS. Thus, it seemed likely to us that programmed cell death (apoptosis) may play a role in the development of the periodontium. Fragments of first molars, obtained from 14- and 29-day-old rats, were fixed in glutaraldehyde-formaldehyde and processed for light and electron microscopy. For the TUNEL method for detection of apoptosis, specimens were fixed in 4% formaldehyde and embedded in paraffin. Results confirmed that epithelial cells of HRS maintain a close relationship with the forming dentine root, and that they may become trapped in the dentino-cemental junction. Some of the epithelial cells exhibited ultrastructural features which are consistent with the interpretation that they were undergoing programmed cell death, i.e. apoptosis. Periodontal fibroblast-like cells showed typical images of apoptosis and engulfed apoptotic bodies. TUNEL positive structures were present in all corresponding regions. It seems therefore that apoptosis of epithelial cells of HRS and fibroblast-like cells of the periodontal ligament constitutes an integral part of the developmental process of the tissues of the periodontium.