Bacterial contamination as a factor in healing of pulp exposures

Development of a novel direct dental pulp-capping material using 4-META/MMA-TBB resin with nano hydroxyapatite

In the case of dental pulp exposure, direct pulp capping is often performed to preserve vital dental pulp tissue. Numerous studies regarding the development of direct pulp-capping materials have been conducted, but materials with an appropriate sealing ability, which induce dense reparative dentin formation, have not been developed. Although nano hydroxyapatite (naHAp) is a bone-filling material with bioactivity and biocompatibility, the inductive effects of naHAp on reparative dentin formation remain unclear. In the present study, the effects of dental adhesive material 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate tri-n-butylborane [4-META/MMA-TBB or Super-bond (SB)], which included 10%, 30%, and 50% naHAp (naHAp/SB) on odontoblastic differentiation of dental pulp stem cells (DPSCs) and reparative dentin formation were investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer analysis were performed to verify the existence of naHAp particles on the surface of naHAp/SB discs. The tensile adhesive strength of naHAp/SB was measured using a universal testing machine. As a result, 10% naHAp/SB and 30% naHAp/SB showed almost the same tensile adhesive strength as SB but 50% naHAp/SB showed significantly lower than the other experimental group. WST-1 proliferation assay and SEM analysis revealed that naHAp/SB did not affect the proliferation of DPSCs. Calcium release assay, quantitative RT-PCR, and western blotting analysis demonstrated that naHAp/SB did not release calcium ion but 30% naHAp/SB increased the expression of calcium-sensing receptor (CaSR) in DPSCs. Additionally, quantitative RT-PCR, western blotting analysis, Alizarin Red S- and von Kossa staining revealed that 30% naHAp/SB induced odontoblastic differentiation of DPSCs, which was inhibited by a MEK/ERK inhibitor and CaSR antagonist. Furthermore, 30% naHAp/SB promoted dense reparative dentin formation in an experimentally-formed rat dental pulp exposure model. These findings suggest that 30% naHAp/SB can be used as an ideal direct pulp capping material.

Which procedures and materials could be applied for full pulpotomy in permanent mature teeth? A systematic review

Objective: Coronal pulpotomies were recently re-investigated as an alternative to root canal treatment in vital permanent teeth. General dentists may be interested in knowing how to perform full pulpotomy, in particular in face of difficult endodontic cases of vital teeth. Material and methods: A systematic review was undertaken on the PubMed and Cochrane databases in order to determine which procedure should be applied for pulp capping and coronal restoration in routine dental practice. Fifty-three publications were included and allocated to one of two methodological categories: histological and clinical studies. Results and conclusions: There is no evidence to recommend one single procedure for full pulpotomy in vital permanent teeth that can be indicated for different pulpal diagnoses which differ greatly in terms of the inflammation process from healthy teeth to irreversible pulpitis. For each clinical case, all actions aiming to prevent pre-operative contamination, to control per-operative infection and to achieve a complete seal above the radicular pulp sections are unavoidable steps that should be complied with. Reproducing procedures adopted in high quality trials could insure high success rates.

Effects of the exposure site on histological pulpal responses after direct capping with 2 calcium-silicate based cements in a rat model

Objectives

Direct pulp capping is a treatment for mechanically exposed pulp in which a biocompatible capping material is used to preserve pulpal vitality. Biocompatibility tests in animal studies have used a variety of experimental protocols, particularly with regard to the exposure site. In this study, pulp exposure on the occlusal and mesial surfaces of molar teeth was investigated in a rat model.

Materials and Methods

A total of 58 maxillary first molars of Wistar rats were used. Forty molars were mechanically exposed and randomly assigned according to 3 factors: 1) the exposure site (occlusal or mesial), 2) the pulp-capping material (ProRoot White MTA or Bio-MA), and 3) 2 follow-up periods (1 day or 7 days) (n = 5 each). The pulp of 6 intact molars served as negative controls. The pulp of 12 molars was exposed without a capping material (n = 3 per exposure site for each period) and served as positive controls. Inflammatory cell infiltration and reparative dentin formation were histologically evaluated at 1 and 7 days using grading scores.

Results

At 1 day, localized mild inflammation was detected in most teeth in all experimental groups. At 7 days, continuous/discontinuous calcified bridges were formed at exposure sites with no or few inflammatory cells. No significant differences in pulpal response according to the exposure site or calcium-silicate cement were observed.

Conclusions

The location of the exposure site had no effect on rat pulpal healing. However, mesial exposures could be performed easily, with more consistent results. The pulpal responses were not significantly different between the 2 capping materials.

Dentinogenic Specificity in the Preclinical Evaluation of Vital Pulp Treatment Strategies: A Critical Review

Reviews on the clinical performance of vital pulp treatment strategies and capping materials repeatedly showed an insufficient grade of evidence concerning their therapeutic validity. The biological mechanisms underlying the regenerative potential of pulp-dentin complex have attracted much attention during the last two decades, since new pulp treatment modalities have been designed and tested at the preclinical level. It has been recognized that evaluation should be based on the specific ability of therapeutic interventions to signal recruitment and differentiation of odontoblast-like cells forming a matrix in a predentin-like pattern, rather than uncontrolled hard tissue deposition in a scar-like form. The aim of the present article was to critically review data from histological experimental studies on pulp capping, published during the last 7 decades. A comprehensive literature search covering the period from 1949 to 2015 was done using the Medline/Pubmed database. Inclusion of a study was dependent on having sufficient data regarding the type of capping material used and the unit of observation (human permanent tooth in vivo or animal permanent dentition; primary teeth were excluded). The post-operatively deposited matrix was categorized into three types: unspecified, osteotypic, or dentin-like matrix. One hundred fifty-two studies were included in the final evaluation. Data from the present systematic review have shown that only 30.2% of the 152 experimental histological pulp capping studies described the heterogenic nature of the hard tissue bridge formation, including osteotypic and tubular mineralized tissue. Structural characteristics of the new matrix and the associated formative cells were not provided by the remaining 106 studies. Analysis showed that more careful preclinical evaluation with emphasis on the evidence regarding the dentinogenic specificity of pulp therapies is required. It seems that selection of appropriate vital pulp treatment strategies and pulp capping materials would be further facilitated in terms of their therapeutic validity if international consensus could be reached on a select number of mandatory criteria for tissue-specific dentinogenic events.

Rat molar teeth as a study model for direct pulp capping research in dentistry

The aim of this review is to evaluate the suitability of rat molar teeth in preclinical evaluation of medical devices for direct pulp capping. The ISO standard 7405 states clearly that only non-rodent mammals are suitable species for animal research in dentistry. Furthermore, without clear justification a considerable number of researchers previously rejected results of animal experiments concerning preclinical evaluation of the biocompatibility of dental materials undertaken in rat molar teeth. However, in the past 50 years about 70 studies have been published using rat molar teeth in order to evaluate direct pulp capping, pulpotomies and tissue reactions after pulp exposure. Numerous studies showed that the healing of rat molar pulp tissue after direct pulp capping is histologically comparable with humans and other animal species pulp tissue. Rat molar teeth, including pulp tissue, can be seen anatomically, histologically, biologically, and physiologically as miniature human molar teeth. Hence, the essential biological reactions of the pulp tissue and the interaction during the different stages of wound healing of rat molar teeth are comparable with that of other mammals. Rat molar teeth are a valid study model in order to provide valuable data concerning pulp tissue reaction after direct pulp capping and related questions in dentistry. Therefore, the use of rats may significantly reduce the number of currently used higher animals in research. Tests in higher developed animals should be limited to experiments which clarify inconsistent results. However, some technical difficulties, like the small size of rat molar teeth must be dealt with before undertaking any research.

Dissolution of bio-active dentine matrix components by mineral trioxide aggregate

OBJECTIVES

To analyze the soluble components of setting and set mineral trioxide aggregate (MTA), assess the abilities of two varieties of MTA and Ca(OH)(2) solutions to solubilise dentine matrix proteins (DMPs) and determine if these extracts contain signalling molecules important to pulpal repair and regeneration.

METHODS

The metallic ion composition of solutions of white and grey MTA (pH 11.7), 0.02M Ca(OH)(2) (pH 11.9) and 10% EDTA (pH 7.2) was determined using atomic absorption spectroscopy. Extracellular dentine matrix components from powdered human dentine were extracted using all solutions over 14 days. Extracts were analysed for concentrations of non-collagenous proteins (NCPs) and glycosaminoglycans (GAGs), and protein profiles were examined using 1D-polyacrylamide gel electrophoresis (1D-PAGE). ELISAs for TGF-beta1 and adrenomedullin (ADM) were also performed.

RESULTS

Aluminium, calcium, potassium, and sodium ions were detected in both white and grey MTA solutions. MTA and Ca(OH)(2) solutions liberated similar amounts of GAGs and NCPs although yields were considerably lower than those obtained using the EDTA solution. 1D-PAGE analysis demonstrated differences in protein profiles solubilised from dentine for all solutions. All extracts contained TGF-beta1 and ADM, EDTA solution liberated significantly greater amounts of TGF-beta1, and Ca(OH)(2) and grey MTA solutions released more ADM.

CONCLUSIONS

These data imply that when placed clinically soluble components of set and setting MTA may release dentine matrix components that potentially influence cellular events for dentine repair and regeneration.

Advances since the paper by Zander and Glass (1949) on the pursuit of healing methods for pulpal exposures: historical perspectives

Clinical observations and experimental studies in humans and laboratory animals have demonstrated that healing and repair of pulpal exposures by caries, trauma, or iatrogenic causes are possible with a variety of wound treatment methods. Yet clinical trials have shown that predictable long-term pulp tissue preservation may be an elusive goal and has led to doubts about pulp capping and pulpotomy as valid clinical procedures. Nevertheless substantial knowledge has accumulated over the years on the mechanisms and the treatment factors that are important to promote/support continued vital pulp functions. This article highlights some key contributions to our current knowledge base, which have come to light during the more than 50 years since a pioneering experimental study by Zander and Glass was published in the Triple O journal.

Octacalcium phosphate–based cement as a pulp-capping agent in rats

OBJECTIVE

The purpose of this study was to evaluate the pulpal response to an octacalcium phosphate (OCP)-based cement used as a pulp-capping material.

STUDY DESIGN

The pulps of 60 maxillary first molars of male Sprague-Dawley rats were exposed and then capped directly by using either OCP-based cement or a calcium hydroxide slurry (control). Histologic examinations were performed at 1, 2, and 5 weeks after the surgical procedure, and the results were analyzed statistically by using the Mann-Whitney U test (P<.05).

RESULTS

One week after pulp capping, the initial formation of reparative dentin in the exposed areas was more notable in the calcium hydroxide group than in the OCP-based cement group. At 2 weeks, reparative dentin covered by a layer of odontoblast-like cells was observed in both groups. However, at 5 weeks, reparative dentin consisting of regular dentinal tubules was observed more frequently in the OCP-based cement group.

CONCLUSION

OCP-based cement allowed favorable healing processes to occur in the dental pulp.

Pulpal response to exposure with Er:YAG laser

OBJECTIVE

The purpose of this study was to evaluate the pulpal response to the Er:YAG laser after accidental exposure of the pulp.

STUDY DESIGN

Cavities were prepared, and pulps were exposed by either Er:YAG laser or mechanically by a slow-speed conventional handpiece (control group) in 76 maxillary first molars of male Wistar rats. Rats were killed immediately, at 3 days, 1 week, and 2 weeks. Histopathologic examinations of the pulp at the exposure site were performed and evaluated with the Mann-Whitney U test (P <.05).

RESULTS

The Er:YAG laser group showed no bleeding and no dentin chips at the exposure site immediately after pulp exposure. However, they displayed an area of blood extravasation near the exposure site. Subsequently, the Er:YAG laser group formed dentin bridges at the exposure site more frequently than the control group. The Er:YAG laser group demonstrated more reparative dentin formation near the exposure site than the control group, especially at 2 weeks, which was highly significant (P <.01).

CONCLUSION

According to the results of this study, Er:YAG laser-exposed pulp tissue demonstrated good healing capacity with the formation of a dentin bridge and reparative dentin. However, further investigations are suggested to study the effect of the blood extravasation, which appeared near the laser exposure sites.

Dycal versus Nd:YAG laser and Vitrebond for direct pulp capping in permanent teeth

PURPOSE

To determine the efficacy of laser-assisted direct pulp capping by comparing the survival rates of permanent teeth treated with Nd:YAG laser and Vitrebond (3M Corporation, St. Paul, MN) direct pulp caps to permanent teeth treated with the traditional calcium hydroxide direct pulp cap over intervals of up to 54 months.

SUMMARY BACKGROUND DATA

While there are case reports and evaluations of various laser techniques in the literature, statistical studies comparing the success of laser-assisted applications to traditional techniques are needed. This is a retrospective investigation of one such laser assisted application.

METHODS

A retrospective chart review of all active and inactive patients resulted in the identification of 83 patients who received direct pulp caps in a total of 93 permanent teeth; 29 with calcium hydroxide and 64 with Nd:YAG laser and Vitrebond.

RESULTS

Life table analysis of the data of this retrospective study demonstrated that the teeth treated with the laser and Vitrebond direct pulp cap showed significantly greater survival rates than those treated with Dycal direct pulp cap over intervals of nine to 54 months postoperatively. The cumulative proportion of teeth surviving postoperatively for the Dycal (L.D. Caulk Corporation, Milford, CT) direct pulp cap was 89.7% at 1 month declining to 79.4% at 3 months and 76% at 6 months and then continued to decline in the final two intervals finishing after 54 months at 43.6%. For the laser and Vitrebond direct pulp cap the cumulative proportion surviving stood at 98.4% after 1 month, declining to 93.8% at 3 months and 90.3% after 6 months but then held steady in the final 2 intervals finishing at 90.3% after 54 months.

CONCLUSION

The laser and Vitrebond direct pulp cap produces a significantly more predictable pulpal response after the first 6 months than the Dycal direct pulp cap. The survival rate of teeth treated with the laser and Vitrebond direct pulp cap is significantly greater than those treated with the Dycal direct pulp cap over intervals of 9 to 54 months. Direct pulp capping is a worthwhile procedure that should be performed when indicated, especially in light of the 90.3% survival rate achieved with the laser and Vitrebond direct pulp cap at 54 months.

In vitro antimicrobial activity of calcium hydroxide cements on Streptococcus sanguis NCTC 7864

Several studies have questioned the antimicrobial role of calcium hydroxide cements. This study assessed the antimicrobial activity of four commercially available calcium hydroxide cements on Streptococcus sanguis NCTC 7864 using inoculated Mueller-Hinton growth medium. Growth curves from optical density analysis, pH measurements, and viability counts were compared over a 24 h period. Significant differences occurred (P < 0.05) between pH measurements but not the growth curves or the viability counts. All cements exerted a cidal effect although this cannot be attributed to an increase in alkalinity alone.

Calcium hydroxide in restorative dentistry

This paper reviews the various calcium hydroxide preparations available for use in restorative dentistry and their constituents. The significance of individual constituents in relation to the properties of such materials and their mode of therapeutic action with respect to the dentine pulpal response and antibacterial activity is discussed. Applications of calcium hydroxide in restorative dentistry are also reviewed.

Experimental bacterial anachoresis in dog dental pulps capped with calcium hydroxide

The pulps of 36 permanent dog teeth were mechanically exposed and capped with Dycal, calcium hydroxide powder mixed with saline, or Teflon. At 2, 14, and 28 days postoperatively, nine teeth treated with the materials were extracted (treated control teeth): A suspension of streptococci was then injected intravenously. Twenty-four h later the dogs were killed and both the 27 treated teeth (experimental group) and 6 unoperated control teeth were removed in tissue blocks. Tissue sections were examined for the presence of bacteria, hard tissue formation, inflammatory cell response and necrosis. Bacteria were not observed in the unoperated and treated control teeth or in three of four teeth capped with Teflon for 29 days. In all the remaining specimens colonies of gram-positive cocci were found.

Pulp capping: conserving the dental pulp--can it be done? Is it worth it?

Emphasis has shifted from the "doomed" organ concept of an exposed pulp to one of hope and recovery. The era of vital-pulp therapy has been greatly enhanced with the introduction of calcium hydroxide (CH) products. The sequence of events leading to dentinal bridge formation with various CH formulas is detailed. Those factors usually considered liabilities to direct pulp capping (pulps cariously exposed, contaminated by saliva, previously carious or restored, periodontally involved, or from older patients and primary teeth) are disputed. Those factors that must be considered to improve the success rate of pulp capping are emphasized: control bleeding, make certain the CH contacts vital-pulp tissue, minimize dentinal chip invasion, avoid embolization of CH particles, and be aware of the depth of penetration of the chemical cautery effect.

Pulpal healing after luxation injuries and root fracture in the permanent dentition

Pulpal healing patterns were studied in a clinical material of 637 luxated and 95 root-fractured permanent incisors followed routinely for up to 11 years. It was found that pulpal healing patterns could generally be divided into 3 groups according to the degree of injury sustained by the pulp: little, moderate or severe. Thus after luxation injuries, pulp survival could be without radiographic change (PS), with pulp canal obliteration (PCO) or nonhealing (pulp necrosis (PN]. After root fracture, similar healing patterns could be observed: healing by hard tissue union of fragments (HT), by connective tissue union of fragments (CT) or by nonunion due to interposition of granulation tissue between fragments (GT) resulting from PN of the coronal fragment. In both trauma situations, healing or nonhealing could be determined by type of luxation injury, stage of root development and type of fixation used (forceful application of orthodontic bands vs. passively applied acid-etch fixation). Pulpal healing complications (PN or GT) were based on clinical findings (coronal discoloration, loss of pulpal sensibility) and radiographic findings (resorption processes of the lamina dura at the root apex or at the level of the root fracture). However, in both injury groups the same changes could also be seen to be intermediate steps in the pulpal healing process. Based on findings from these studies, hypotheses for the mechanics of pulpal healing are proposed as well as guidelines for acute and later treatment of dental luxations, root fractures and the diagnosis of healing complications.

Pulp response to and cariogenicity of Lactobacillus casei in monoinfected gnotobiotic rats

The maxillary molar pulps of germ-free rats were mechanically exposed and suspensions of a strain of freshly grown Lactobacillus casei were applied to the pulp wounds. The pulps were left open to the oral environment, and the animals were maintained within the isolator until death. In the majority of teeth, pulp necrosis was evident and apical inflammation was present in 40% of the specimens. The remaining monoinfected animals were bred and the litters were placed on a 46% sucrose diet to determine the cariogenicity of the test strain of L. casei in the mandibular molars. The organism proved to be noncariogenic. The effects of mechanical exposure of the maxillary molars in these animals were similar to those observed in the direct-inoculation study, with the exception of a reduced incidence of apical inflammation.

Pulp response to Streptococcus mutans

The maxillary molar pulps of germ-free rats were mechanically exposed, and suspensions of a strain of freshly grown Streptococcus mutans were applied to the pulp wounds. The pulps were left open to the oral environment, and the animals were maintained in the isolator until they were killed in groups after 2, 7, and 28 days. After 2 days there was little evidence of any pulp response. In the 7-day group early pulp necrosis was present. No evidence of inflammatory infiltration was detected in either the 2- or 7-day animals. After 28 days there was extensive pulp necrosis in many specimens. Dentine bridges were present in fewer than one fourth of the teeth.

Capping of monkey pulps with Dycal and a Ca-eugenol cement

Capping of 120 teeth in four monkeys was performed with Dycal or with a calcium-eugenol cement. The observation periods were 8 days or 90 days. The monkeys were killed, and the teeth were examined histologically. After 8 days, the pulp-tissue reactions were basically the same in the two groups. The tissue adjacent to the exposure site was characterized by varying amounts of necrotic tissue, inflammatory cells, and extravasated erythrocytes. Capping material and dentin chips were displaced into the pulp tissue. Particles from the capping materials were found in vessels, macrophages, and foreign body cells. After 90 days, more hard-tissue formation occurred in the Dycal group than in the Ca-eugenol cement group. The hard tissue was formed by either fibroblasts or the original odontoblasts.

Pulp response in sound and carious teeth: a pilot study

This article describes a pilot investigation in which the response of the pulps in both sound and carious rat molar teeth to traumatic exposure and treatment with three different compounds was assessed. Two of the compounds appeared to give a more favorable response in carious teeth. These results are discussed, and future experiments described.

The response of four calcium hydroxides on monkey pulps

Dentinal bridge formation and pulpal responses of four calcium hydroxide materials, pulp capping medicaments, MPC, Experimental MPC-12, Dycal and Pulpdent, were evaluated in primary and permanent monkey teeth. A total of 60 primary and 60 permanent teeth were used with each material placed in a Class V cavity exposure in Rhesus monkey teeth. The materials were placed on the exposed pulp tissue and were histologically evaluated at 3 days, 5 weeks and 8 weeks. After perfusion the teeth were processed using routine histological procedures. The 3-day pulpal responses in both primary and permanent teeth were moderate, characterized by disruption of the pulpal tissue directly beneath the exposure site and a zone of acute inflammation and hemorrhage in the underlying pulp. The 5-week response showed histological differences between the four medicaments, with Dycal producing the least amount of pulpal irritation with reparative dentin bridges occurring in 50% of the permanent teeth. Experimental MPC-12 stimulated one reparative dentin bridge, while Pulpdent and MPC showed no evidence of bridge formation. Pulpal responses to Dycal were moderate and moderate to severe for the other calcium hydroxide compounds. No reparative dentin bridges were seen in the primary teeth at 5 weeks with any of the materials, and the pulpal responses were of a moderate degree at that time. Eight-week responses were similar to the 5-week responses Dycal provoked a slight to moderate pulpal response with 50% success at bridging. Experimental MPC-12 initiated pulpal responses in the moderate to severe range with some bridging evident. Pulpdent incited moderate to severe histological responses with three teeth demonstrating bridge formation, and MPC provoked severe pulpal responses with no bridging. Primary teeth showed some bridging for all compounds except those treated with MPC, in which no evidence of bridging occurred, and moderate to severe pulpal responses were present.

Microscopic study of the pulps of human teeth following vital root resection

The effects of vital root resection upon the remaining pulp were studied in twenty-six periodontally involved human molars. The pulp was extirpated 14 days after the intervention. Granulomatous tissue present in the pulp chamber protruded from the site of the exposure as a polyp in eleven cases. Mild chronic inflammatory changes were present in the coronalmost part of the radicular pulp. The apical pulp was not affected at this time interval.