Cytotoxic effects of cleansing solutions recommended for chemical lavage of pulp exposures

Purpose: To evaluate the in vitro cytotoxic effects of three cleansing solutions used for chemical lavage of pulp exposures. Materials and Methods: the immortalized odontoblast cell line (MDPC-23) was plated (30,000 cells/cm(2)) and incubated for 72 hrs in 24-well dishes. After counting the cell number under inverted light microscopy, 20 mul of the experimental and control solutions were added to 980 mul of fresh culture medium. Then, hydrogen peroxide (3%, H2O2), sodium hypochlorite (6%, NaOCl) or calcium hydroxide-saline solution (5g of Ca(OH)(2) in 10 mi of sterile distilled water) were added to wells for experimental Groups 1, 2 and 3, respectively. The positive and negative control groups received Syntac Sprint bonding agent (SS) and phosphate buffered saline (PBS), respectively. Following incubation for 120 min the cell number was counted again, the cell morphology was evaluated by scanning electron microscopy (SEM) and the cell metabolism was determined by the methyltetrazolium (MTT) assay. The scores obtained from cell counting and MTT assay were analyzed with an ANOVA followed by Fisher's PLSD tests. Results: H2O2 NaOCl solutions, and SS bonding agent were more cytotoxic than Ca(OH)2 or PBS. In the groups with H2O2 Or SS, only a few cells remained attached to the bottom of wells. The difference between these two groups was not statistically significant. H2O2, NaOCl and SS depressed the mitochondrial enzyme response by 97.7%, 97.3%, and 95.0%, respectively. on the other hand, Ca(OH)2 depressed the metabolic activity of cells by only 5%. While H2O2, NaOCl and SS caused extreme changes on the cell morphology, neither Ca(OH)2 nor PBS promoted dramatic changes in the cell morphology.

Evaluation of mineral trioxide aggregate and calcium hydroxide cement as pulp-capping agents in human teeth

This study evaluated the histomorphologic response of human dental pulps capped with mineral trioxide aggregate (MTA) and Ca(OH)(2) cement (CH). Pulp exposures were performed on the occlusal floor of 40 human permanent premolars. After that, the pulp was capped either with CH or MTA and restored with composite resin. After 30 and 60 days, teeth were extracted and processed for histologic exam and categorized in a histologic score system. The data were subjected to Kruskal-Wallis and Conover tests (alpha = .05). All groups performed well in terms of hard tissue bridge formation, inflammatory response, and other pulpal findings. However, a lower response of CH30 was observed for the dentin bridge formation, when compared with MTA30 and MTA60 groups. Although the pulp healing with calcium hydroxide was slower than that of MTA, both materials were successful for pulp capping in human teeth.

Current status of pulp capping with dentin adhesive systems: a review

Several studies have assessed the morphology and thickness of hybrid layer, the dentin bend strengths as well as sealing ability of dentin adhesive systems. However, few in vivo studies have evaluated the biocompatibility of the adhesive systems following application to deep dentin or directly to the pulp of human teeth. Many studies performed in non-human primate teeth or teeth of rats have reported pulp healing and dentin bridging following pulp capping with bonding agents. In addition, a few clinical and radiographical reports of the success of resin pulp capping have been described in the dental literature.Objectives: the aim of this review was to evaluate the literature on pulp responses following total acid etching and application of adhesive resins on deep cavities or pulp exposures. In addition, the clinical/radiographical evidence for the apparent success of vital pulp therapy and results obtained from animal and human studies were compared and discussed.Significance and conclusions: the self-etching adhesive systems may be useful and safe when applied on dentin, In contrast, persistent inflammatory reactions as well as delay in pulpal healing and failure of dentin bridging were seen in human pulps capped with bonding agents. The results observed in animal teeth cannot be directly extrapolated to human clinical conditions. Consequently, vital pulp therapy using acidic agents and adhesive resins seems to be contraindicated. (C) 2000 Academy of Dental Materials. Published by Elsevier B.V. Ltd. All rights reserved.

Response of human dental pulp to dentin adhesive systems

Many in vivo studies have stated that the response of the dentin/pulp complex does not depend on the dental material used as the liner or pulp-capping agent. However, several in vitro studies have reported the metabolic cytotoxic effects of resin components applied to fibroblast and odontoblast cell lines. The aim of this study was to evaluate the human pulp response following direct pulp capping with current bonding agents and calcium hydroxide (CH). Sound premolars scheduled for orthodontic extraction had their pulp tissue mechanically exposed. After hemorrhage control and total acid conditioning, the experimental bonding agents, including All Bond 2, Scotchbond MP-Plus, Clearfil Liner Bond 2, and Prime & Bond 2.1 were applied on the pulp exposure site. CH saline paste was used as the control pulp-capping agent. All cavities were restored with Z-100 resin composite according to the manufacturer's instructions. Following extractions, the teeth were processed for microscopic evaluation. In the short term, the bonding agents elicited a moderate inflammatory pulp response with associated dilated and congested blood vessels adjacent to the pulp exposure site. A mild inflammatory pulp response was observed when Clearfil Liner Bond 2 or CH was applied on the pulp exposures. With time, macrophages and giant cells engulfing globules and components of all experimental bonding agents displaced into the pulp space were seen. This chronic inflammatory response did not allow complete pulp repair, which interfered with the dentin bridge formation. Pulp exposures capped with CH exhibited an initial organization of elongated pulp cells underneath the coagulation necrosis. CH stimulated early pulp repair and dentin bridging that extended into the longest period. The bonding agents evaluated in the present study cannot be recommended for pulp therapy on sound human teeth.

Response of human dental pulp capped with MTA and calcium hydroxide powder

Objectives: To compare the response of human dental pulp capped with a mineral trioxide aggregate (MTA) and Ca(OH) 2 powder. Methods and Material: Pulp exposures were performed on the occlusal floor of 40 permanent premolars. The pulp was then capped with either Ca(OH) 2 powder (CH) or MTA and restored with resin composite. After 30 days (groups CH30 and MTA30) and 60 days (groups CH60 and MTA60), the teeth were extracted and processed for HE and categorized in a histological score system. The data were subjected to Kruskal-Wallis and Conover tests (α=0.05). Results: In regard to dentin bridge formation, CH30 showed a tendency towards superior performance compared to MTA30 (p>0.05), although the products showed comparable results at day 60. In the item Inflammation and General State of the Pulp (p>0.05), CH showed a tendency towards presenting a higher inflammatory response. In the item Other Pulpal Findings, MTA and Ca(OH) 2 showed equal and excellent performance after 30 and 60 days (p>0.05). Conclusion: After 30 days, Ca(OH) 2 powder covered with calcium hydroxide cement showed faster hard tissue bridge formation compared to MTA. After 60 days, Ca(OH) 2 powder or MTA materials showed a similar and excellent histological response with the formation of a hard tissue bridge in almost all cases with low inflammatory infiltrate. © Operative Dentistry, 2008.

Evaluation of two mineral trioxide aggregate compounds as pulp-capping agents in human teeth

Aim: The present randomized, controlled prospective study evaluated the histomorphological response of human dental pulps capped with two grey mineral trioxide aggregate (MTA) compounds. Methodology: Pulp exposures were performed on the occlusal floor of 40 human permanent pre-molars. The pulp was capped either with ProRoot (Dentsply) or MTA-Angelus (Angelus) and restored with zinc oxide eugenol cement. After 30 and 60 days, teeth were extracted and processed for histological examination and the effects on the pulp were scored. The data were subjected to Kruskal-Wallis and Conover tests (α = 0.05). Results: In five out of the 40 teeth bacteria were present in pulp tissue. No significant difference was observed between the two materials (P > 0.05) in terms of overall histological features (hard tissue bridge, inflammatory response, giant cells and particles of capping materials). Overall, 94% and 88% of the specimens capped with MTA-Angelus and ProRoot, respectively, showed either total or partial hard tissue bridge formation (P > 0.05). Conclusions: Both commercial materials ProRoot (Dentsply) and MTA-Angelus (Angelus) produced similar responses in the pulp when used for pulp capping in intact, caries-free teeth. © 2009 International Endodontic Journal.

Response of human pulps capped with different self-etch adhesive systems

The aim of this study was to evaluate the response of human pulps capped with a calcium hydroxide hard-setting cement or with two-step self-etch adhesive systems. Pulp exposures were performed on the occlusal floor, and the bleeding control was performed with saline solution. The exposed pulp tissue was capped with Clearfil LB 2V (2V) or Clearfil SE Bond (SE) and restored with a composite resin. In control group, the pulpal wound was capped with Ca(OH)(2) cement and restored with Clearfil LB 2V or Clearfil SE Bond + composite resin. After 30 and 90 days, the teeth were extracted, processed for hematoxylin and eosin, and categorized in a histological score system. The pulpal response was worse for groups capped with the self-etch adhesive systems (2V and SE) in both periods of evaluation, when compared to their respective control groups at 90 days (p < 0.05). For both self-etch systems evaluated, the pulp tissue exhibited moderate to severe inflammatory cell infiltrate involving the coronal pulp with chronic abscesses. Dentin bridging was observed in a few specimens. For the calcium hydroxide groups, almost all specimens showed dentin bridge formation, with few scattered inflammatory cells and normal tissue below the pulp exposure site. Calcium hydroxide should be used as the material of choice for pulp capping, and the use of two-step self-etch adhesives for human pulp capping is contraindicated.

Effects of Antibacterial Agents on Dental Pulps of Monkeys Mechanically Exposed and Contaminated.

The purpose of this study was to compare the effectiveness of antibacterial agents and mineral trioxide aggregate in the healing of bacterial contaminated primate pulps. Study Design: The experiment required four adult male primates (Cebus opella) with 48 teeth prepared with buccal penetrartions into the pulpal tissues. The preparations (Cebus opella) with 48 teeth prepared with buccal penetrations into the exposed to cotton pellets soaked in a bacterial mixture consisting of microorganisms normally found in human pulpal abscesses obtained from the Endodontic Clinic of UNESP. Following bacterial inoculation (30 minute exposure), the pulpal tissue was immediately treated with either sterile saline, Cipro HC Otic solution (12), diluted Buckley formecresol solution (12) or Otosporin otic solution (12) for 5 minutes. After removal of the pellet, hemostasis was obtained and a ZOE base applied to the DFC treated pulps and the non-treated controls (12). After hemostasis, the other exposed pulps were covered with mineral trioxide aggregate (ProRoot). The pulpal bases were all covered with a RMGI (Fuji II LC). The tissue samples were collected at one day, two days, one week and over four weeks (34 days). Results: Following perfusion fixation, the samples were demineralized, sectioned, stained and histologically graded. After histologic analysis, presence of neutrophilic infiltrate and areas of hemorrhage with hyperemia were observed . The depth of the neutrophilic infiltrate depended on the agent or material used. The pupal tissue treated with Otic suspensions demonstrated significantly less inflammation (Kruskal Wallis non parametric analysis, H=9.595 with 1 degree of freedom; P=0.0223) than the formocresol and control groups. The hard tissue bridges formed over the exposure sites were more organized in the MTA treatment groups than in the control and ZOE groups (Kruskal Wallis non parametric analysis, H=18.291 with 1 degree of freedom; P=0.0004). Conclusions: Otic suspensions and MTA are effective in treating bacterial infected pulps and stimulate the production of a hard tissue bridge over the site of the exposure.

Reparação tecidual pulpar sob ação bioestimuladora do laser de baixa intensidade (LILT), e do diodo emissor de luz (LED): estudo em macacos prego

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Primate Pulpal Healing after Exposure and TheraCal Application

Aim: The purpose of this in vivo study was to compare the effectiveness of a new light cured resin based dicalcium/tricalcium silicate pulp capping material (TheraCal LC, Bisco), pure Portland cement, resin based calcium hydroxide or glass ionomer in the healing of bacterially contaminated primate pulps. Study design: The experiment required four primates each having 12 teeth prepared with buccal penetrations into the pulpal tissues with an exposure of approximately 1.0 mm. The exposed pulps of the primate teeth were covered with cotton pellets soaked in a bacterial mixture consisting of microorganisms normally found in human pulpal abscesses. After removal of the pellet, hemostasis was obtained and the pulp capping agents applied. The light cured resin based pulp capping material (TheraCal LC) was applied to the pulpal tissue of twelve teeth with a needle tip syringe and light cured for 15 seconds. Pure Portland cement mixed with a 2% Chlorhexidine solution was placed on the exposed pulpal tissues of another twelve teeth. Twelve additional teeth had a base of GIC applied (Triage, Fuji VII GC America) and another twelve had a pulp cap with VLC DYCAL (Dentsply), a light cured calcium hydroxide resin based material. The pulp capping bases were then covered with a RMGI (Fuji II LC GC America). The tissue samples were collected at 4 weeks. The samples were deminerilized, sectioned, stained and histologically graded. Results: There were no statistically significant differences between the groups in regard to pulpal inflammation (H= 0.679, P=1.00). However, both the Portland cement and light cured TheraCal LC groups had significantly more frequent hard tissue bridge formation at 28 days than the GIC and VLC Dycal groups (H= 11.989, P=0.009). The measured thickness of the hard tissue bridges with the pure Portland and light cured TheraCal LC groups were statistically greater than that of the other two groups (H= 15.849, P=0.002). In addition, the occurrence of pulpal necrosis was greater with the GIC group than the others. Four premolars, one each treated according to the protocols were analyzed with a microCT machine. The premolar treated with the light cured TheraCal LC demonstrated a complete hard tissue bridge. The premolar treated with the GIC did not show a complete hard tissue bridge while the premolar treated with VLC Dycal had an incomplete bridge. The pure Portland with Chlorhexidine mixture created extensive hard tissue bridging.Conclusion: TheraCal LC applied to primate pulps created dentin bridges and mild inflammation acceptable for pulp capping.

A New Opportunity to Pulp Bagasse in Australia?

Despite the large quantity of sugarcane grown in Australia, no bagasse is pulped in the country. This is largely because of an established pulp industry based on the abundant native hardwood resources. However, increasing demand for fibre and the limited availability of additional forest areas make bagasse pulping attractive. Issues relating to infrastructure and economics are discussed, and scenarios of acceptable risk identified. It is shown that there should be scope for the production of bleached bagasse pulp in Australia.

Experimental study of Australian sugarcane bagasse pulp permeability

In this experimental study the permeability of Australian bagasse chemical pulps obtained from different bagasse fractions were measured in a simple permeability cell and the results compared to one another as well as to eucalypt, Argentinean bagasse and pine pulps. The pulps were characterised in terms of the permeability parameters, the specific surface area, Sv, and the swelling factor, α. It was found that the bagasse fraction used affects these parameters. Fractionation of whole bagasse prior to pulping produced pulps that have permeability properties that compare favourably with eucalypt pulp. The values of Sv and α for bagasse pulp also depend on whether a constant or a variable Kozeny factor is used.

Stem cell regulatory gene expression in human adult dental pulp and periodontal ligament cells undergoing odontogenic/osteogenic differentiation

Introduction During development and regeneration, odontogenesis and osteogenesis are initiated by a cascade of signals driven by several master regulatory genes. Methods In this study, we investigated the differential expression of 84 stem cell–related genes in dental pulp cells (DPCs) and periodontal ligament cells (PDLCs) undergoing odontogenic/osteogenic differentiation. Results Our results showed that, although there was considerable overlap, certain genes had more differential expression in PDLCs than in DPCs. CCND2, DLL1, and MME were the major upregulated genes in both PDLCs and DPCs, whereas KRT15 was the only gene significantly downregulated in PDLCs and DPCs in both odontogenic and osteogenic differentiation. Interestingly, a large number of regulatory genes in odontogenic and osteogenic differentiation interact or crosstalk via Notch, Wnt, transforming growth factor β (TGF-β)/bone morphogenic protein (BMP), and cadherin signaling pathways, such as the regulation of APC, DLL1, CCND2, BMP2, and CDH1. Using a rat dental pulp and periodontal defect model, the expression and distribution of both BMP2 and CDH1 have been verified for their spatial localization in dental pulp and periodontal tissue regeneration. Conclusions This study has generated an overview of stem cell–related gene expression in DPCs and PDLCs during odontogenic/osteogenic differentiation and revealed that these genes may interact through the Notch, Wnt, TGF-β/BMP, and cadherin signalling pathways to play a crucial role in determining the fate of dental derived cell and dental tissue regeneration. These findings provided a new insight into the molecular mechanisms of the dental tissue mineralization and regeneration

A study into the permeability and compressibility of Australian bagasse pulp

This is an experimental study into the permeability and compressibility properties of bagasse pulp pads. Three experimental rigs were custom-built for this project. The experimental work is complemented by modelling work. Both the steady-state and dynamic behaviour of pulp pads are evaluated in the experimental and modelling components of this project. Bagasse, the fibrous residue that remains after sugar is extracted from sugarcane, is normally burnt in Australia to generate steam and electricity for the sugar factory. A study into bagasse pulp was motivated by the possibility of making highly value-added pulp products from bagasse for the financial benefit of sugarcane millers and growers. The bagasse pulp and paper industry is a multibillion dollar industry (1). Bagasse pulp could replace eucalypt pulp which is more widely used in the local production of paper products. An opportunity exists for replacing the large quantity of mainly generic paper products imported to Australia. This includes 949,000 tonnes of generic photocopier papers (2). The use of bagasse pulp for paper manufacture is the main application area of interest for this study. Bagasse contains a large quantity of short parenchyma cells called ‘pith’. Around 30% of the shortest fibres are removed from bagasse prior to pulping. Despite the ‘depithing’ operations in conventional bagasse pulp mills, a large amount of pith remains in the pulp. Amongst Australian paper producers there is a perception that the high quantity of short fibres in bagasse pulp leads to poor filtration behaviour at the wet-end of a paper machine. Bagasse pulp’s poor filtration behaviour reduces paper production rates and consequently revenue when compared to paper production using locally made eucalypt pulp. Pulp filtration can be characterised by two interacting factors; permeability and compressibility. Surprisingly, there has previously been very little rigorous investigation into neither bagasse pulp permeability nor compressibility. Only freeness testing of bagasse pulp has been published in the open literature. As a result, this study has focussed on a detailed investigation of the filtration properties of bagasse pulp pads. As part of this investigation, this study investigated three options for improving the permeability and compressibility properties of Australian bagasse pulp pads. Two options for further pre-treating depithed bagasse prior to pulping were considered. Firstly, bagasse was fractionated based on size. Two bagasse fractions were produced, ‘coarse’ and ‘medium’ bagasse fractions. Secondly, bagasse was collected after being processed on two types of juice extraction technology, i.e. from a sugar mill and from a sugar diffuser. Finally one method of post-treating the bagasse pulp was investigated. The effects of chemical additives, which are known to improve freeness, were also assessed for their effect on pulp pad permeability and compressibility. Pre-treated Australian bagasse pulp samples were compared with several benchmark pulp samples. A sample of commonly used kraft Eucalyptus globulus pulp was obtained. A sample of depithed Argentinean bagasse, which is used for commercial paper production, was also obtained. A sample of Australian bagasse which was depithed as per typical factory operations was also produced for benchmarking purposes. The steady-state pulp pad permeability and compressibility parameters were determined experimentally using two purpose-built experimental rigs. In reality, steady-state conditions do not exist on a paper machine. The permeability changes as the sheet compresses over time. Hence, a dynamic model was developed which uses the experimentally determined steady-state permeability and compressibility parameters as inputs. The filtration model was developed with a view to designing pulp processing equipment that is suitable specifically for bagasse pulp. The predicted results of the dynamic model were compared to experimental data. The effectiveness of a polymeric and microparticle chemical additives for improving the retention of short fibres and increasing the drainage rate of a bagasse pulp slurry was determined in a third purpose-built rig; a modified Dynamic Drainage Jar (DDJ). These chemical additives were then used in the making of a pulp pad, and their effect on the steady-state and dynamic permeability and compressibility of bagasse pulp pads was determined. The most important finding from this investigation was that Australian bagasse pulp was produced with higher permeability than eucalypt pulp, despite a higher overall content of short fibres. It is thought this research outcome could enable Australian paper producers to switch from eucalypt pulp to bagasse pulp without sacrificing paper machine productivity. It is thought that two factors contributed to the high permeability of the bagasse pulp pad. Firstly, thicker cell walls of the bagasse pulp fibres resulted in high fibre stiffness. Secondly, the bagasse pulp had a large proportion of fibres longer than 1.3 mm. These attributes helped to reinforce the pulp pad matrix. The steady-state permeability and compressibility parameters for the eucalypt pulp were consistent with those found by previous workers. It was also found that Australian pulp derived from the ‘coarse’ bagasse fraction had higher steady-state permeability than the ‘medium’ fraction. However, there was no difference between bagasse pulp originating from a diffuser or a mill. The bagasse pre-treatment options investigated in this study were not found to affect the steady-state compressibility parameters of a pulp pad. The dynamic filtration model was found to give predictions that were in good agreement with experimental data for pads made from samples of pretreated bagasse pulp, provided at least some pith was removed prior to pulping. Applying vacuum to a pulp slurry in the modified DDJ dramatically reduced the drainage time. At any level of vacuum, bagasse pulp benefitted from chemical additives as quantified by reduced drainage time and increased retention of short fibres. Using the modified DDJ, it was observed that under specific conditions, a benchmark depithed bagasse pulp drained more rapidly than the ‘coarse’ bagasse pulp. In steady-state permeability and compressibility experiments, the addition of chemical additives improved the pad permeability and compressibility of a benchmark bagasse pulp with a high quantity of short fibres. Importantly, this effect was not observed for the ‘coarse’ bagasse pulp. However, dynamic filtration experiments showed that there was also a small observable improvement in filtration for the ‘medium’ bagasse pulp. The mechanism of bagasse pulp pad consolidation appears to be by fibre realignment. Chemical additives assist to lubricate the consolidation process. This study was complemented by pulp physical and chemical property testing and a microscopy study. In addition to its high pulp pad permeability, ‘coarse’ bagasse pulp often (but not always) had superior physical properties than a benchmark depithed bagasse pulp.