Pulp capping materials exert an effect on the secretion of IL-1β and IL-8 by migrating human neutrophils

Pulp repair is a complex process whose mechanisms are not yet fully understood. The first immune cells to reach the damaged pulp are neutrophils that play an important role in releasing cytokines and in phagocytosis. The objective of this study was to analyze the effect of different pulp-capping materials on the secretion of interleukin-1 beta (IL-1β) and interleukin-8 (IL-8) by migrating human neutrophils. Neutrophils were obtained from the blood of three healthy donors. The experimental groups were calcium hydroxide [Ca(OH)2], an adhesive system (Single Bond), and mineral trioxide aggregate (MTA). Untreated cells were used as control. Transwell chambers were used in performing the assays to mimic an in vivo situation of neutrophil chemotaxis. The pulp-capping materials were placed in the lower chamber and the human neutrophils, in the upper chamber. The cells were counted and the culture medium was assayed using ELISA kits for detecting and quantifying IL-1β and IL8. The data were compared by ANOVA followed by Tukey's test (p < 0.05). The secretion of IL-8 was significantly higher in all groups in comparison to the control group (p < 0.05). The adhesive system group showed higher IL-8 than the MTA group (p < 0.05). The secretion of IL-1β was significantly greater only in the MTA group (p < 0.001). It was concluded that only MTA is able to improve the secretion of IL-1β, and all materials tested increased IL-8 secretion. These results combined with all the other biological advantages of MTA indicate that it could be considered the material of choice for dental pulp capping.

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.

Cytotoxicity of substances leached from a conventional and a self-etching adhesive system on human pulp fibroblasts / Citotoxicidade de substâncias liberadas de sistemas adesivos convencional e auto-condicionante sobre fibroblastos de polpa humana

The use of adhesives for direct dental pulp capping is not advisable, due to its harmful effects to the tissue. However, new adhesive systems are often released, and self-etching systems seem to be less toxic than conventional ones. The purpose of this study was to compare the in vitro cytotoxicity of substances leached from calcium hydroxide and two adhesive systems on human dental pulp fibroblasts. Cell culture media conditioned by Calcium Hydroxide (CH), Single Bond (SB), Clearfill Protect Bond primer (CP) or Clearfill Protect Bond resin (CB) were applied to human pulp fibroblasts. Fresh cell culture medium was used in the Control group. The number of viable cells was obtained through the MTT reduction assay. Data were compared by ANOVA and Tukey’s test (p≤0.05). The mean number of viable cells was 3.9x103(±0.75) for the control group, which was similar to those found in the CH group (4.31x103±0.87). Statistical differences were found among the groups (p<0.001), with the cell viability decreasing significantly with SB (0.09x103±0.06) and CP (0.28x103±0.08) when compared to CH and control groups. CB (2.37x103±0.72) was significantly less cytotoxic than CP and SB, but more cytotoxic than CH. It was concluded that Single Bond and Clearfill Protect Bond primer release substances that decrease cell viability of human dental pulp cells in culture. According to this study the use of bonding systems for direct pulp capping is not recommended, since they are cytotoxic

O uso de adesivos dentinários sobre a polpa não é recomendável, devido aos efeitos deletérios provocados sobre o tecido. Entretanto, novos sistemas adesivos são frequentemente lançados, e sistemas autocondicionantes parecem ser menos tóxicos que os sistemas convencionais. O objetivo deste estudo foi comparar in vitro, a citotoxicidade de substâncias liberadas pelo hidróxido de cálcio e dois sistemas adesivos utilizando fibroblastos de polpa humana. Meios de cultura celular condicionados por Hidróxido de cálcio (CH), Single Bond (SB), Clearfill Protect Bond primer (CP) ou Clearfill Protect Bond resin (CB) foram testados em fibroblastos de polpa humana. Meio fresco de cultivo celular foi utilizado no grupo centrole. O número de células viáveis foi obtido através do teste da redução do MTT. Os dados foram comparados por ANOVA e teste de Tukey (p≤0,05). O número médio de células viáveis foi de 3,9x103(±0,75) para o grupo controle, que foi similar ao encontrado para o grupo CH (4,31x103±0,87). Houve diferenças estatísticas entre os grupos (p<0.001), sendo que a viabilidade celular decresceu significantemente com SB (0,09x103±0,06) e CP (0,28x103±0,08), quando comparados ao CH e controle. CB (2,37x103±0,72) foi menos citotóxico que CP e SB, mas mais citotóxico que CH. Conclui-se que o Single Bond e o Clearfill Protect Bond primer liberam substâncias que diminuem a viabilidade celular de fibroblastos humanos em cultura. De acordo com este estudo, o uso de sistemas adesivos para capeamento direto não é recomendado, uma vez que são citotóxicos.

Interleukin-1 beta and interleukin-8 in healthy and inflamed dental pulps

After aggression to the dental pulp, some cells produce cytokines in order to start and control the inflammatory process. Among these cytokines, interleukin-1 beta (IL-1β) and interleukin-8 (IL-8) emerge as important ones. OBJECTIVE: The purpose of this study was to analyze the location, distribution and concentration of these cytokines in healthy and inflamed dental pulps. MATERIAL AND METHODS: Twenty pulps, obtained from healthy third molars (n=10) and from pulpectomies (n=10) were used for the study, with half of each group used for immunohistochemistry and half for protein extraction and ELISA assays. Fibroblasts obtained from healthy dental pulps, stimulated or not by Escherichia coli lipopolysaccharide (LPS), in order to simulate aggression on the cell cultures, were also used and analyzed by ELISA for IL-1β and IL-8 as complementary information. Data obtained from immunohistochemistry were qualitatively analyzed. Data obtained from ELISA assays (tissue and cells) were statistically treated by the t-test (p<0.05). RESULTS: Immunohistochemically, it was observed that inflamed pulps were strongly stained for both cytokines in inflammatory cells, while healthy pulps were not immunolabeled. ELISA from tissues quantitatively confirmed the higher presence of both cytokines. Additionally, cultured pulp fibroblasts stimulated by LPS also produce more cytokines than the control cells. CONCLUSIONS: It may be concluded that inflamed pulps present higher amounts of IL-1β and IL-8 than healthy pulps and that pulp fibroblasts stimulated by bacterial LPS produce higher levels of IL-1β and IL-8 than the control group.

Thermal curves of acrylic resins in microwave curing / Curvas térmicas de resinas acrílicas polimerizadas por energia de microondas

The use of microwave polymerization on acrylic resins is a clean and easy method to make complete dentures. It is observed that this kind of process may cause a higher porosity when compared to the conventional heated water bath, probably because of the excessive temperature increase. The objective of this study was the qualitative observation of the thermal curves generated on acrylic by the application of microwave energy in different polymerization cycles. Wax model dentures were reproduced, resulting in four specimens, within each one 7 thermocouples were positioned, havingdifferent reading sites of the specimens while the resin was polymerized in a conventional microwave oven. Four cycles were used: 1) three minutes at 475W; 2) 13 minutes at 95W + 1,5 minute at 475W; 3) three minutes at 475W with 150ml of water; and 4) seven minutes at 95W + seven minutes at 95W. The thermocouples were linked to data acquisition equipment, resulting in time-versus-temperature charts. It was concluded that lower power settings led to lower temperature increases. The use of minimum water load caused lower temperature peaks. The used method has a great value for temperature readings when polymerizing microwave acrylic resins