Effects of lipopolysaccharide on proliferation, migration and osteogenic differentiation of apical papilla cells from early and late stage of root development.

The aim of this study was to investigate the effects of lipopolysaccharide on cell proliferation, migration and osteogenic differentiation of apical papilla cells from early and late stage of root development. After challenging with various lipopolysaccharide concentrations to apical papilla cells from both stages of root development for 168 h, cell proliferation and migration were investigated. Osteogenic differentiation was examined by Alizarin red staining, and gene expressions of bone/cementum or dentin-related genes were examined by polymerase chain reaction. Lipopolysaccharide did not affect cell proliferation and migration in both groups. Lipopolysaccharide at 1 and 5 µg mL-1 increased Alizarin red staining in apical papilla cells from early-stage but not the late-stage cells. Bone sialoprotein (bone/cementum marker) gene expression increased in both early and late stage of root development at 5 µg mL-1 . These results might explain bone/cementum generation in regenerative endodontic procedures.

Mechanical stress induced S100A7 expression in human dental pulp cells to augment osteoclast differentiation.

OBJECTIVES: Mechanical injury of dental pulp leads to root resorption by osteoclasts/odontoclasts. S100 proteins have been demonstrated to be involved in inflammatory processes and bone remodeling. This study aimed to investigate the effect of mechanical stress on S100A7 expression by human dental pulp cells (HDPCs) and the effect of S100A7 proteins on osteoclast differentiation. MATERIALS AND METHODS: Isolated HDPCs were stimulated with compressive loading (2 and 6 hr), or shear loading (2, 6, and 16 hr). S100 mRNA expression and S100A7 protein levels were determined by real-time PCR and ELISA, respectively. Osteoclast differentiation was analyzed using primary human monocytes. The differentiation and activity of osteoclasts were examined by TRAcP staining and dentine resorption. In addition, the expression of S100A7 was analyzed in pulp tissues obtained from orthodontically treated teeth. RESULTS: Compressive and shear mechanical stress significantly upregulated both mRNA and protein level of S100A7. Dental pulp tissues from orthodontically treated teeth exhibited higher S100A7mRNA levels compared to non-treated control teeth. S100A7 promoted osteoclast differentiation by primary human monocytes. Moreover, S100A7 significantly enhanced dentine resorption by these cells. CONCLUSIONS: Mechanical stress induced expression of S100A7 by human dental pulp cells and this may promote root resorption by inducing osteoclast differentiation and activity.

Effects of Lipopolysaccharide on the Proliferation and Osteogenic Differentiation of Stem Cells from the Apical Papilla.

INTRODUCTION: Stem cells from the apical papilla (SCAPs) were suggested as the stem cell source in regenerative endodontic procedures. However, bone and/or cementum-like structure were observed in root canals. Lipopolysaccharide (LPS) in infected root canals might alter SCAPs' osteogenic differentiation pattern. The objectives of this study were to investigate the effects of LPS on SCAPs' proliferation and osteogenic differentiation. METHODS: The mesenchymal stem cell characteristics of SCAPs were confirmed. Cell viability was tested with Porphyromonas gingivalis LPS at concentration between 0.001 and 5 µg/mL. SCAPs were pretreated with those concentrations for 168 hours. Then SCAPs were further investigated for cell proliferation by resazurin-based assay. Mineralization capacity was determined by alizarin red S staining. Odontoblast marker was determined by DSPP gene expression. General bone and cementum markers, BSP and OPN, were also determined. Determination of the expression levels of these genes was performed by polymerase chain reaction. RESULTS: SCAPs demonstrated the mesenchymal stem cell characteristics. All LPS concentrations did not affect cell viability. Pretreatment with LPS also did not affect cell proliferation and mineralization in every concentration. There was no significant difference between DSPP and OPN gene expression levels at all concentrations. However, LPS at 5 µg/mL significantly increased BSP gene expression. CONCLUSIONS: Under the limitations of this in vitro study, LPS did not affect SCAP proliferation and mineralization. However, LPS at high concentration, 5 µg/mL, increased BSP gene expression.

Comparison of stem cell behaviors between indigenous high and low-CD24 percentage expressing cells of stem cells from apical papilla (SCAPs).

CD24 was suggested as a marker to SCAPs and has been reported for a decade. CD24 has been shown to involve stem cell activities such as self-renewal, proliferation and differentiation. However, the percentage variations of CD24 positive cells were reported among the studies. It is possible that this variation may affect these SCAPs behaviors. In this study, the variation was confirmed. To elucidate the influence of CD24 positive cells quantity on SCAPs stem cell behaviors, the 3 cell lines with the most maximum and the least numbers of CD24 positive cells (High-CD24 and Low-CD24 group) were selected to study. Both groups expressed the same mesenchymal stem cell markers and negative to hematopoietic marker. High-CD24 group demonstrated less self-renewal capacity by lower colony-forming-unit count and pluripotency marker gene expressions. However, cell proliferation was not different. In contrast, osteogenic and adipogenic differentiation were better than Low-CD24 group. The early stage of root development demonstrated higher CD24 expressing cells than later stage. In conclusion, quantity of CD24 expressing cells influenced SCAPs self-renewal and multi-lineage differentiation but did not influence on cell proliferation. Stage of root development influenced to CD24 expressing cell numbers.

Response of inflamed pulps of rat molars after capping with pulp-capping material containing fluocinolone acetonide.

INTRODUCTION: Capping inflamed dental pulp tissue is currently a controversial issue. To reduce pulp inflammation and stimulate pulp healing, a pulp-capping material containing fluocinolone acetonide (PCFA) has been developed. This study was aimed to evaluate the inflammatory response and hard tissue formation of inflamed dental pulps of rat maxillary molars after capping with Dycal, mineral trioxide aggregate (MTA), or PCFA. METHODS: Sixty maxillary rat molars were exposed to the oral environment for 48 hours. The exposed pulps were randomly divided into 6 groups (n = 10) according to pulp-capping materials (Dycal, MTA, or PCFA) and time (8 or 30 days). The cavities were capped and sealed with Fuji II LC. The animals were sacrificed after 8 and 30 days. Histologic specimens were prepared and evaluated for inflammatory response and hard tissue formation. RESULTS: Eight days after pulp capping, all experimental groups showed disruption of the odontoblast layer in areas corresponding to the pulpal exposure. Acute inflammation was found in 80%, 60%, and 40% of samples in the Dycal, MTA, and PCFA groups, respectively. PCFA significantly decreased the pulp inflammation compared with Dycal. After 30 days, slight to moderate inflammation was found in all experimental groups. Hard tissue formation was found in 78%, 63%, and 100% of samples in the Dycal, MTA, and PCFA groups, respectively. No significant difference was found among the experimental groups. CONCLUSIONS: Pulp capping with PCFA reduced the inflammation and stimulated hard tissue formation in the exposed pulps of rat molars. It may be used as a pulp-capping agent in inflamed pulps.

Incorporation of anti-inflammatory agent into calcium hydroxide pulp capping material: an in vitro study of physical and mechanical properties.

The aims of this study were to investigate the release of fluocinolone acetonide from an experimental pulp capping material containing fluocinolone acetonide (PCFA) and compare some physical and mechanical properties with Dycal(®). The PCFA is a hard-setting calcium hydroxide cement composed of 50 mmol/L fluocinolone acetonide. Conditioned media from the setting material was collected for determination of fluocinolone acetonide release by high performance liquid chromatography and pH measurement by pH meter. The setting time, compressive strength, disintegration, and acid soluble arsenic content were measured according to ISO 3107:2004. Dycal(®) was used as control. Fluocinolone acetonide could release at a range of suitable concentrations from PCFA. The pH, setting time, and acid soluble arsenic content of PCFA were significantly higher than those of Dycal(®). The compressive strength and disintegration of PCFA were comparable to control. PCFA may be considered as an alternative in pulp capping of inflamed dental pulp tissue.

Setting time and flowability of accelerated Portland cement mixed with polycarboxylate superplasticizer.

INTRODUCTION: Important limitations of mineral trioxide aggregate for use in clinical procedures are extended setting time and difficult handling characteristics. The removal of gypsum at the end stage of the Portland cement manufacturing process and polycarboxylate superplasticizer admixture may solve these limitations. METHODS: Different concentrations of polycarboxylate superplasticizer (0%, 1.2%, 1.8%, and 2.4% by volume) and liquid-to-powder ratios (0.27, 0.30, and 0.33 by weight) were mixed with white Portland cement without gypsum (AWPC-experimental material). Type 1 ordinary white Portland cement mixed with distilled water at the same ratios as the experimental material was used as controls. All samples were tested for setting time and flowability according to the International Organization for Standardization 6876:2001 guideline. The data were analyzed by two-way analysis of variance. Then, one-way analysis of variance and multiple comparison tests were used to analyze the significance among groups. RESULTS: The data are presented in mean ± standard deviation values. In all experimental groups, the setting times were in the range of 4.2 ± 0.4 to 11.3 ± 0.2 minutes, which were significantly (p < 0.05) lower than the control groups (26.0 ± 2.4 to 54.8 ± 2.5 minutes). The mean flows of AWPC plus 1.8% and 2.4% polycarboxylate superplasticizer groups were significantly increased (p < 0.001) at all liquid-to-powder ratios compared with control groups. CONCLUSIONS: Polycarboxylate superplasticizer at concentrations of 1.8% and 2.4% and the experimental liquid-to-powder ratios reduced setting time and increased flowability of cement, which would be beneficial for clinical use.

Effect of fluocinolone acetonide on human dental pulp cells: cytotoxicity, proliferation, and extracellular matrix formation.

INTRODUCTION: The goal of vital pulp therapy is to maintain pulp vitality and function. Fluocinolone acetonide is a potent topical glucocorticoid used in the treatment of skin disorders and oral lesions that could possibly be used to resolve inflammation and stimulate the healing process of inflamed dental pulp. The purpose of this study was to investigate the effects of fluocinolone acetonide (0.1-50 µmol/L) on cytotoxicity, cell proliferation, and fibronectin and type I collagen synthesis in human dental pulp cells (HDPCs). METHODS: HDPCs were prepared from freshly extracted human third molars. MTT assay was used to determine toxicity and cell proliferation. Western blot analysis was performed to detect fibronectin and type I collagen synthesis. RESULTS: Low concentrations of fluocinolone acetonide were not only nontoxic but also significantly stimulated cell proliferation (P < .05). Fluocinolone acetonide significantly stimulated fibronectin and type I collagen synthesis (P < .05). CONCLUSIONS: Low concentrations (0.1-10 µmol/L) of fluocinolone acetonide might have the potential to stimulate healing of inflamed dental pulp.

Stress distribution with different restorations in teeth with curved roots: a finite element analysis study.

INTRODUCTION: The aim of this study was to investigate and compare stress distribution in various degrees of curved roots with different post and restorations by finite element analysis (FEA). METHODS: Sixteen 3-dimensional FEA models were created and adapted by using computer software based on external anatomy of mandibular second premolar. A 50-N load was applied. Tensile and compressive stresses were plotted. RESULTS: The stress distribution pattern showed that degrees of root curvature in this study (15, 30, and 45 degrees) had little effect. When the elastic modulus of post and core materials was similar to that of root dentin, tensile stresses were low and concentrated on the external root surface. With higher elastic modulus of materials, tensile stresses were increased and concentrated on the post and post apex. CONCLUSIONS: Within the limitations of this study, the suitable restoration in endodontically treated mandibular premolar with limited loss of tooth structure was resin composite that was filled in the coronal third of the root canal. However, when the post and core were indicated, the glass-fiber post and resin composite core were the materials of choice for restoration.

Patterns of vertical root fracture: factors affecting stress distribution in the root canal.

Previous studies have indicated that vertical root fracture tends to occur in a buccolingual direction, where dentin thickness is greatest. Factors potentially influencing the location and direction of root fracture include root canal shape, external root morphology, and dentin thickness. In this finite-element study, simulated root sections were varied systematically with respect to canal size and shape, external root morphology, and dentin thickness to determine their relative contribution to vertical root fracture. Similar models were constructed based on cross-sections of human tooth roots that had been fractured clinically or experimentally. Finite-element models demonstrated that canal curvature seems more important than external root morphology, in terms of stress concentration, and that reduced dentin thickness increases the magnitude but not the direction of maximum tensile stress. Models based on actual root fractures showed a strong similarity between tensile-stress distribution and fracture patterns.

Finite element analysis and strain-gauge studies of vertical root fracture.

Vertical root fracture seems to result from stresses generated within the root canal and typically occurs in a buccolingual direction through the thickest part of dentin. Because stresses in the canal wall are difficult to measure experimentally, we have attempted to correlate stress patterns derived from finite element models of maxillary and mandibular incisors with strain measurements on the root surfaces of extracted teeth. Finite element analysis indicated that circumferential tensile stresses were concentrated on the buccal and lingual surfaces of the canal wall, corresponding to areas of greatest canal wall curvature. Surface stresses were much lower and were consistently tensile on the proximal root surfaces but variable on the buccal and lingual surfaces. The measurement of root surface stresses does not provide a reliable picture of internal stresses in the root. Canal wall curvature is a major factor in stress concentration and hence in the pattern of fracture.

Effects of root canal sealers on vertical root fracture resistance of endodontically treated teeth.

The aim of this study was to compare vertical forces at fracture of endodontically treated mandibular incisors obturated with different types of root canal sealer. Four groups of 10 teeth each were tested; group 1 served as positive and negative controls (five teeth each), and groups 2, 3, and 4 were obturated by lateral condensation with gutta-percha and AH Plus, Tubliseal, or Ketac-Endo, respectively. All teeth were loaded vertically using a plugger tip inserted into the canal space until fracture occurred; the load at fracture and the pattern of fracture were recorded. Statistical analysis was performed using a one-way analysis of variance and post hoc Scheffé test at the 95% level of confidence. Force at fracture of roots obturated with Ketac-Endo was significantly higher than those obturated with AH Plus and Tubliseal. Most fracture lines were in a buccolingual direction. The results suggested that Ketac-Endo strengthens endodontically treated roots and may be used for weak roots, which are likely to be susceptible to vertical root fracture.