Micrometric measurement of the density of stained odontoblast processes

The embryological, structural and functional unit of the dentine-pulp complex shares the odontoblast, located in the border of the dentine pulp, with basal nuclei and organelles. The odontoblast process emerges from its apical pole. It is formed by microtubules, microfilaments and vesicles covered by membranes penetrating the dentinal tubules, isolated from the inter-tubular matrix, along the extent of the dentine. The objective of this study was to evaluate the efficacy of three staining techniques: hematoxylin-eosin, periodic acid-Schiff and Schmorl, by staining the process, from beginning to end, and compare the results with the erosion technique. Thirty human teeth were employed in the trial; after their extraction the pulp was fixated, the pieces demineralized in nitric acid at 8%, the collagen filaments eliminated with Type II Collage-nase, the tissue was stained, and the measurements were made. The portions with no pulp were prepared with the erosion technique. Results: Comparing the best results obtained by staining with the values obtained with the erosion technique, the former showed lower values. Conclusion: Staining techniques show lower density of the staining processes compared with the dentinal tubules in the erosion technique.

Dental pulp tissue engineering

Dental pulp is a highly specialized mesenchymal tissue that has a limited regeneration capacity due to anatomical arrangement and post-mitotic nature of odontoblastic cells. Entire pulp amputation followed by pulp space disinfection and filling with an artificial material cause loss of a significant amount of dentin leaving as life-lasting sequelae a non-vital and weakened tooth. However, regenerative endodontics is an emerging field of modern tissue engineering that has demonstrated promising results using stem cells associated with scaffolds and responsive molecules. Thereby, this article reviews the most recent endeavors to regenerate pulp tissue based on tissue engineering principles and provides insightful information to readers about the different aspects involved in tissue engineering. Here, we speculate that the search for the ideal combination of cells, scaffolds, and morphogenic factors for dental pulp tissue engineering may be extended over future years and result in significant advances in other areas of dental and craniofacial research. The findings collected in this literature review show that we are now at a stage in which engineering a complex tissue, such as the dental pulp, is no longer an unachievable goal and the next decade will certainly be an exciting time for dental and craniofacial research.

A polpa dental é um tecido conjuntivo altamente especializado que possui uma restrita capacidade de regeneração, devido à sua disposição anatômica e à natureza pós-mitótica das células odontoblásticas. A remoção total da polpa, seguida da desinfecção do canal radicular e seu preenchimento com material artificial proporciona a perda de uma significante quantidade de dentina deixando como sequela um dente não vital e enfraquecido. Entretanto, a endodontia regenerativa é um campo emergente da engenharia tecidual, que demonstrou resultados promissores utilizando células-tronco associadas à scaffolds e moléculas bioativas. Desta forma, esse artigo revisa os recentes avanços obtidos na regeneração do tecido pulpar baseado nos princípios da engenharia tecidual e fornece aos leitores informações compreensivas sobre os diferentes aspectos envolvidos na engenharia tecidual. Assim, nós especulamos que a combinação ideal de células, scaffolds e moléculas bioativas pode resultar em significantes avanços em outras áreas da pesquisa odontológica. Os dados levantados em nossa revisão demonstraram que estamos em um estágio no qual, o desenvolvimento de tecidos complexos, tais como a polpa dental, não é mais inatingível e que a próxima década será um período extremamente interessante para a pesquisa odontológica.

Influence of the microenvironment on gene and protein expression of odontogenic-like and osteogenic-like cells

Progenitor cells play an important biological role in tooth and bone formation, and previous analyses during bone and dentine induction have indicated that they may be a good alternative for tissue engineering. Thus, to clarify the influence of the microenvironment on protein and gene expression, MDPC-23 cells (mouse dental papilla cell line) and KUSA/A1 cells (bone marrow stromal cell line) were used, both in vitro cell culture and in intra-abdominal diffusion chambers implanted in 4-week-old male immunodefficient mice (SCID mice). Our results indicate that KUSA/A1 cells differentiated into osteoblast-like cells and induced bone tissue inside the chamber, whereas, MDPC-23 showed odontoblast-like characteristics but with a low ability to induce dentin formation. This study shows that MDPC-23 cells are especial cel ls, which possess morphological and functional characteristics of odontoblast-like cells expressing dentin sialophosphoprotein in vivo. In contrast, dentin sialophosphoprotein gene and protein expression was not detected in both cell lines in vitro. The intra-abdominal diffusion chamber appears as an interesting experimental model for studying phenotypic expression of dental pulp cells in vivo.

Indirect cytotoxicity of a 35 percent hydrogen peroxide bleaching gel on cultured odontoblast-like cells

The aim of this study was to evaluate the trans-enamel and trans-dentinal effects of a 35 percent hydrogen peroxide (H2O2) bleaching gel on odontoblast-like cells. Enamel/dentin discs obtained from bovine incisors were mounted in artificial pulp chambers (APCs). Three groups were formed: G1- 35 percent H2O2; G2- 35 percent H2O2 + halogen light application; G3- control. The treatments were repeated 5 times and the APCs were incubated for 12 h. Then, the extract was collected and applied for 24 h on the cells. Cell metabolism, total protein dosage and cell morphology were evaluated. Cell metabolism decreased by 62.09 percent and 61.83 percent in G1 and G2, respectively. The depression of cell metabolism was statistically significant when G1 and G2 were compared to G3. Total protein dosage decreased by 93.13 percent and 91.80 percent in G1 and G2, respectively. The cells in G1 and G2 exhibited significant morphological alterations after contact with the extracts. Regardless of halogen light application, the extracts caused significantly more intense cytopathic effects compared to the control group. After 5 consecutive applications of a 35 percent H2O2 bleaching agent, either catalyzed or not by halogen light, products of gel degradation were capable to diffuse through enamel and dentin causing toxic effects to the cells.

O objetivo deste estudo foi avaliar os efeitos citotóxicos de um agente clareador com 35 por cento de peróxido de hidrogênio (H2O2) sobre células da linhagem odontoblástica. Foram confeccionados discos de esmalte/dentina obtidos de incisivos bovinos, os quais foram posicionados em câmaras pulpares artificiais (CPAs). Três grupos foram formados: G1: gel clareador; G2: gel clareador + luz halógena e G3: controle. Após 5 aplicações consecutivas do gel clareador sobre o esmalte, os extratos foram obtidos e aplicados por 24 h sobre as células. Foram realizadas avaliações do metabolismo celular, morfologia das células e expressão total de proteína. O metabolismo celular para G1 e G2 reduziu em 62,09 por cento e 61,83 por cento, respectivamente. A redução do metabolismo celular foi estatisticamente significante quando se comparou G1 e G2 com G3. A expressão de proteína total reduziu em 93,13 por cento e 91,80 por cento para G1 e G2, respectivamente. As células em G1 e G2 apresentaram importantes alterações morfológicas após contato com os extratos. Foi possível concluir que independente da catalização ou não do gel clareador por luz halógena, os componentes que se difundiram através dos tecidos duros do dente após sua quinta aplicação sobre o esmalte, causaram intensos efeitos citotóxicos para as células.

Efeito da sialoadenectomia sobre a incorporaçäo de 3H-prolina nas células e matriz do esmalte jovem e dentina de incisivos de camundongos, estudados através de radioautografia / Sialoadenectomy effect on 3H-proline incorporation in cells and matrix of young enamel and incisors dentin of mice, studied by radioautography

Estudaram-se os efeitos da remoçäo das glândulas salivares maiores sobre a incorporaçäo de 3H-prolina pelos ameloblastos secretores e odontoblastos de incisivos de camundongos. Animais sialoadenectomizados e controles foram injetados com 3H-prolina, sendo sacrificados e perfundidos 30 min, 2h, 12h e 24h após. Cortes de 1*m obtidos de incisivos inferiores incluídos em Polybed foram radioautografados. A distribuiçäo percentual de gräos de prata reduzida/100*m* sobre as referidas células, assim como em suas respectivas matrizes, foi sempre maior nos animais sialoadenectomizadas, nos diferentes intervalos de tempo. Duas hipóteses poderiam explicar esses resultados: 1. um aumento na biossíntese protéica provavelmente devida à falta do fator submandibular inibidor da insulina (SII) associada a um relativo aumento do pool de 3H-prolina devido à remoçäo das glândulas salivares; 2. um decrécimo na degradaçäo protéica devido ao hipotireoidismo que eventualmente ocorre nos animais sialoadenectomizados