Hypoxia upregulates the expression of the pluripotency markers in the stem cells from human deciduous teeth.

OBJECTIVES: Cultivation under hypoxia promotes different responses in the mesenchymal stem cells and it has been producing promising results for clinical applications. Pulp tissue from deciduous teeth is a source of stem cells which has a high proliferative potential but this is usually discarded. This study has evaluated the effects of hypoxia on proliferation, apoptosis, and the expression of the pluripotency-related genes of the stem cells from human exfoliated deciduous teeth (SHED). MATERIALS AND METHODS: The cells were isolated from dental pulp (n = 5) and characterized as mesenchymal stem cells, in accordance with the International Society for Cell Therapy. The cells were cultivated under hypoxia (3% oxygen) and compared to the normoxia cells (21% oxygen). The proliferation rate was evaluated by the Ki67 antibody for up to 7 days, while the metabolic activity was measured by the wst-8 assay for up to 14 days. The apoptotic cells were analyzed by Annexin V and propidium iodide staining at 24 h and 4 and 7 days. The expression of the pluripotent genes (OCT4, SOX2, and NANOG) was quantified by qPCR after 24 h, or 7 days, when cultivated under hypoxia or normoxia. RESULTS: No differences in the metabolic activity, the proliferation rate, and the apoptosis of SHED when cultivated under hypoxia or normoxia (p > 0.05) were observed. The expression of the pluripotent genes was significantly higher after 24 h and 7 days of the cells that were exposed to hypoxia (p < 0.01). CONCLUSION: These findings have indicated an increase of the pluripotency-related genes within 7 days as being the main advantage of SHED culture under hypoxia. CLINICAL RELEVANCE: Hypoxia culture may help maintain the quiescent state of the SHED, which could be advantageous for their future clinical applications.

Longevity and associated risk factors in adhesive restorations of young permanent teeth after complete and selective caries removal: a retrospective study.

OBJECTIVE: The aim of this retrospective university-based study has been to evaluate the longevity and factors associated with failures of adhesive restorations performed in deep carious lesions of permanent molars after complete (CCR) and selective caries removal (SCR). MATERIALS AND METHODS: The sample was composed of composite resin and resin-modified glass ionomer cement (RMGIC) restorations placed in permanent molars of children attending a university dental service who were followed up for up to 36 months. Information collected retrospectively from clinical records was used for analyzing data. The following factors were investigated: gender, caries experience, visible plaque and gingival bleeding indexes, operator's experiences, number of restored surfaces, and type of capping and restorative materials. The Kaplan-Meier survival test was used to analyze the longevity of the restorations. Multivariate Cox regression analysis with shared frailty was used to assess the factors associated with failures (p < 0.05). RESULTS: Four hundred seventy-seven restorations carried out in 297 children (9.1 ± 1.7 years) were included in the analysis. The survival of the restorations reached 57.9 % up to 36 months follow-up with an overall annual failure rate of 16.7 %. There was no difference in restoration longevity when CCR or SCR was performed (p = 0.163); however, CCR presented more pulp exposure (p < 0.001). Multi-surface restorations showed more failures than single-surface (HR 3.22, 95 % CI 1.49; 6.97), and teeth restored with RMGIC had a lower survival rate than those restored with composite resin (HR 4.11, 95 % CI 1.91; 8.81). Patients with evidence of gingivitis had more risk of failure in their restorations (HR 2.88, 95 % CI 1.33; 6.24). CONCLUSION: Overall, adhesive restorations performed in young permanent molars of high caries risk children presented limited survival, regardless of the caries removal technique. Risk factors for failure were identified as multi-surface fillings, RMGIC restorative material, and poor oral hygiene, reflected by gingival bleeding. CLINICAL RELEVANCE: Composite fillings associated with a strict caries preventive regimen may play an important role in the survival of restorations placed in high caries risk children.

Carious deciduous teeth are a potential source for dental pulp stem cells.

OBJECTIVE: The objectives of this study are to isolate, cultivate, and characterize stem cells from the pulp of carious deciduous teeth (SCCD) and compare them to those retrieved from sound deciduous teeth (SHED--stem cells from human exfoliated deciduous teeth). MATERIAL AND METHODS: Cells were obtained of dental pulp collected from sound (n = 10) and carious (n = 10) deciduous human teeth. Rate of isolation, proliferation assay (0, 1, 3, 5, and 7 days), STRO-1, mesenchymal (CD29, CD73, and CD90) and hematopoietic surface marker expression (CD14, CD34, CD45, HLA-DR), and differentiation capacity were evaluated. RESULTS: Isolation success rates were 70 and 80 % from the carious and sound groups, respectively. SCCD and SHED presented similar proliferation rate. There were no statistical differences between the groups for the tested surface markers. The cells from sound and carious deciduous teeth were positive for CD29, CD73, and CD90 and negative for CD14, CD34, CD45, and HLA-DR and were capable of differentiating into osteogenic, chondrogenic, and adipogenic lineages. CONCLUSION: SCCD demonstrated a similar pattern of proliferation, immunophenotypical characteristics, and differentiation ability as those obtained from sound deciduous teeth. These SCCD represent a feasible source of stem cells. CLINICAL RELEVANCE: Decayed deciduous teeth have been usually discarded once the pulp tissue could be damaged and the activity of stem cells compromised. These findings show that stem cells from carious deciduous teeth can be applicable source for cell-based therapies in tissue regeneration.

Effect of prolonged air drying on the bond strength of adhesive systems to dentin.

This in vitro study evaluated the effect of air-drying time on degree of solvent evaporation (DE), dentin microtensile bond strength (µTBS), and degree of conversion (DC) of 5 adhesive systems: Adper Single Bond 2, XP Bond, Prime & Bond 2.1, OptiBond Solo, and Adper Easy One. For DE testing, 20 µL of each material was submitted to measurements in a digital balance after an air stream of 3, 5, 10, 20, 30, or 60 seconds; the weight loss was computed and converted to a percentage (DE). For µTBS testing, 50 sound human molars were divided into groups (n = 5). The 5 adhesive systems were applied either in accordance with manufacturers' instructions for solvent drying time (control) or with a prolonged drying time (20-30 seconds). After composite resin was built up on the hybridized surfaces, the teeth were stored for 24 hours and then sectioned to obtain beams that were loaded until fracture. For DC testing, specimens of each adhesive and air-drying condition (n = 3) were evaluated by means of attenuated total reflectance Fourier transform infrared spectroscopy. Data were submitted to 2-way analysis of variance, t test, and Spearman test for correlation analysis. Prolonged air drying resulted in significantly greater DE than did the time suggested by the manufacturers. The adhesives XP Bond and Adper Easy One showed significantly greater µTBS with prolonged air drying. The DC was not affected by air-drying time. No statistically significant correlation was found between DC and µTBS values. Depending on the material, bond strength can be improved by prolonged air-drying times.

Biofilm removal and gingival abrasion with medium and soft toothbrushes.

PURPOSE: To compare the removal of dental biofilm with soft and medium filament toothbrushes. MATERIALS AND METHODS: Twenty-five patients refrained from performing mechanical or chemical plaque control for 96 hours prior to the experiment in order to allow dental biofilm accumulation on the tooth surfaces. After the period of dental biofilm accumulation, quadrants were randomised and participants brushed different quadrants with soft and medium toothbrushes, with or without dentifrice. After plaque disclosure, the Quigley-Hein (Turesky) plaque index was assessed by a blinded examiner before and after toothbrushing. In addition, photographs before and after brushing were taken for evaluation of gingival abrasion. RESULTS: The results revealed that medium toothbrushes removed high amounts of dental biofilm compared to soft toothbrushes (P < 0.05). Considering gingival abrasion, intergroup analysis demonstrated a statistically significant difference on the cervical regions, with a higher proportion of abrasions in the medium toothbrush group (P < 0.01). CONCLUSION: Medium toothbrushes have a greater ability to remove biofilm and cause gingival abrasion than do soft toothbrushes.

The effects of hypoxia on in vitro culture of dental-derived stem cells.

The culture of cells under hypoxia is considered one of the hot topics of tissue engineering, especially when exploring the proliferation capacity, a critical step for cellular-based therapies. The use of in vitro hypoxic environment aims to simulate the oxygen concentrations found in stem cell niches. Dental tissues are attractive sources of stem cells, as they are obtained from discarded tissue, after third molar extraction and exfoliation deciduous teeth, respectively. However, small amounts of cells are obtained from these sources. Thus, optimizing the in vitro conditions for proliferation and differentiation of these cells is essential for future regenerative strategies. This review presents a summary of the results regarding the effect of hypoxia on dental-derived stem cells after an electronic search on PubMed databases. The studies show increased differentiation potential and paracrine action of dental-derived stem cells under hypoxic environment. There are controversies related to proliferation of dental-derived stem cells under induced hypoxia. The lack of standardization in cell culture techniques contributes to these biases and future studies should describe in more detail the protocols used. The knowledge regarding the effect of hypoxia on dental-derived stem cells needs further clarification for assisting the clinical application of these cells.

Dental avulsion: are the dentist prepared to the correct management?

To evaluate the knowledge of dentists from the health units (HU) of Porto Alegre -Brazil, regarding the management of avulsion of permanent teeth.Material and Methods:All dentists (n = 117) from HU were invited to answer a self-applied questionnaire regarding the treatment and preservation of avulsed permanent teeth in different clinical scenarios, based on the guidelines of the International Association of Dental Trauma (IADT). The professional data were also collected. The correlation between the performance of each professional and professional data was performed, (StudentÆs t test, PearsonÆs and SpearmanÆs correlations), assuming 5% significance.Results:The response rate was 56.41%. The mean performance rate of the dentists regarding the clinical questions was 69.3%, but 37.4% had poor performance (less than 70% correct). The greatest number of hits was where the patient comes with the already replanted teeth (89.2%); 87.3% agreed in situations where the injured child reaches two hours of trauma with the tooth in a liquid medium, however in cases that period of trauma was more than two hours and tooth was dehydrated, the professionals performance was reduced (64.9%). There was a lack of knowledge about the use of intracanal medication (error rate of 56.9%); 41% are mistaken about the period to start endodontics procedures; 32.8% did the wrong about contention of avulsed teeth and clinical and radiographs follow-up. Dentists with postgraduate performed better than those without (p = 0.011)...

Contaminação das resinas compostas em clínicas de instituição de ensino / Contamination in composite resins from dental clinics of university

Objetivo: Avaliar, por meio de análise microbiológica, a contaminação nas resinas compostas utilizadas em clínicas odontológicas de uma Instituição de Ensino na cidade de Santa Maria, RS, Brasil. Método: Foi realizado um levantamento quanto ao número de acadêmicos que utilizam cada clínica, bem como o semestre à qual pertenciam. Um total de 100 amostras estavam disponíveis para a análise nas 3 diferentes clínicas. Incrementos de 2 mm foram removidos de cada tubete de resina composta disponível de forma asséptica e imersos em 5ml do meio de cultura BHI (Brain Heart Infusion). Após 24 horas de incubação em estufa bacteriológica à 37ºC foi feita a primeira leitura, e após 48 horas, a última. Um grupo controle negativo para o meio de cultura foi realizado. As amostras nas quais ocorreu o turvamento do meio de cultura foram consideradas contaminadas. Resultados: 51% das amostras analisadas encontravam-se contaminadas, apresentando variação do percentual de ocorrência entre as clínicas incluídas. Conclusão: Em algum momento do procedimento restaurador, executado pelos acadêmicos, ocorre uma falha geradora da contaminação. Assim, há risco de infecção cruzada, havendo a necessidade de buscar alternativas para barrar essa contaminação durante o procedimento.

Purpose: The aim of this study was to assess microbiologically the composite resins used in dental clinics of a University in Santa Maria, RS, Brazil. Method: Were analyze a total of 100 samples available in 3 different clinics. Increments of 2 mm were removed from the tubes of resin and cultured in 5 ml of BHI (Brain Heart Infusion). After 24 hours of incubation in a bacteriological incubator at 37°C, was made the first analysis, and after 48 hours, the last one. A negative control group for the method was performed. The samples on which turbidity was found were considered contaminated. Results: The contamination was present in 51% of composite resins analyzed, showing a difference in the incidence between clinics. Conclusion: In the restorative procedure, performed by students, there is a fail wich generates contamination. This failure has potential to cause crossed infection. Thus shows the need of search for alternatives to prevent the contamination during the procedure.