Evidence for bacterial causation of adverse pulpal responses in resin-based dental restorations

Molecular toxicology of substances released from resin-based dental restorative materials

Resin-based dental restorative materials are extensively used today in dentistry. However, significant concerns still remain regarding their biocompatibility. For this reason, significant scientific effort has been focused on the determination of the molecular toxicology of substances released by these biomaterials, using several tools for risk assessment, including exposure assessment, hazard identification and dose-response analysis. These studies have shown that substances released by these materials can cause significant cytotoxic and genotoxic effects, leading to irreversible disturbance of basic cellular functions. The aim of this article is to review current knowledge related to dental composites' molecular toxicology and to give implications for possible improvements concerning their biocompatibility.

In vivo outcomes of indirect pulp treatment using a self-etching primer versus calcium hydroxide over the demineralized dentin in primary molars

OBJECTIVE

To evaluate the clinical and radiographic outcomes (24 months) of indirect pulp treatment (IPT) in primary teeth when a self-etching primer or a calcium hydroxide layer was used over the remaining carious dentin.

STUDY DESIGN

Primary molar teeth with deep carious lesions without signs and symptoms of irreversible pulpitis were divided into two groups, according to the capping material: Experimental group (1): self-etching adhesive system (Clearfill SE Bond); and Control group (2): calcium hydroxide liner (Dycal). Both groups were followed up after application of a resin restoration (3M - Z250).

RESULTS

After 2 years of clinical and radiographic follow-up, no statistical difference was found between groups (p = 1). The overall success rate reached 87%.

CONCLUSION

These results demonstrate that IPT has a high clinical and radiographic performance in primary teeth and is not dependent on the capping material used over the demineralized dentin.

Tensile bond strength and SEM analysis of enamel etched with Er:YAG laser and phosphoric acid: a comparative study in vitro

Er:YAG laser has been studied as a potential tool for restorative dentistry due to its ability to selectively remove oral hard tissue with minimal or no thermal damage to the surrounding tissues. The purpose of this study was to evaluate in vitro the tensile bond strength (TBS) of an adhesive/composite resin system to human enamel surfaces treated with 37% phosphoric acid, Er:YAG laser (lambda=2.94 microm) with a total energy of 16 J (80 mJ/pulse, 2Hz, 200 pulses, 250 ms pulse width), and Er:YAG laser followed by phosphoric acid etching. Analysis of the treated surfaces was performed by scanning electron microscopy (SEM) to assess morphological differences among the groups. TBS means (in MPa) were as follows: Er:YAG laser + acid (11.7 MPa) > acid (8.2 MPa) > Er:YAG laser (6.1 MPa), with the group treated with laser+acid being significantly from the other groups (p=0.0006 and p= 0.00019, respectively). The groups treated with acid alone and laser alone were significantly different from each other (p=0.0003). The SEM analysis revealed morphological changes that corroborate the TBS results, suggesting that the differences in TBS means among the groups are related to the different etching patterns produced by each type of surface treatment. The findings of this study indicate that the association between Er:YAG laser and phosphoric acid can be used as a valuable resource to increase bond strength to laser-prepared enamel.

Histological evaluation of direct pulp capping with a self-etching adhesive and calcium hydroxide on human pulp tissue

AIM

To evaluate human pulp tissue response following direct pulp capping with a self-etching adhesive: Clearfil SE BOND (SB).

METHODOLOGY

Forty-five sound teeth from 20 subjects were used. Forty-one teeth had their pulp mechanically exposed at the base of a Class 1 cavity preparation and were divided into two groups: group 1, teeth were capped with SB (n = 21), and group 2, with calcium hydroxide cement (CH) (n = 20). Four teeth were maintained intact as an untreated control group. After 7, 30 and 90 days, respectively, 15 teeth were extracted and processed for light microscopic examination. Pulp healing and bacterial microleakage were assessed by haematoxylin and eosin, Masson trichrome and Brown and Brenn stain techniques. The data were analysed statistically by using the Mann-Whitney U test.

RESULTS

After the 7-day observation period, the inflammatory reaction in the SB group was slight and significantly less severe than that of the CH group (P < 0.05). After the 30- and 90-day observation periods, the inflammatory reaction was slight in both groups, but specimens with dentine bridge formation in the SB group were significantly less common than those in the CH group (P < 0.05).

CONCLUSIONS

Clearfil SB had good biocompatibility with human pulp tissue, but its ability to induce reparative dentine was significantly lower than that of calcium hydroxide.

Pulpal responses to bacterial contamination following dentin bridging beneath hard-setting calcium hydroxide and self-etching adhesive resin system

To evaluate the pulp healing to bacterial contamination beneath a hard-setting calcium hydroxide (DY: Dycal, L.D. Caulk Co.) and a self-etching adhesive resin (2V: Clearfil Liner Bond 2V, Kuraray Medical Inc.) following dentin bridge formation. Class V cavities were prepared on 30 monkey teeth, and the pulps were exposed with a carbide bur through the cavity floor. Each exposed pulp was capped with either DY or 2V. The cavities were restored with a hybrid resin composite. The resin composite was removed at 180 days after capping, and then cavities were left open to the oral environment for 2 weeks to obtain bacteria contamination DY (BDY) and 2V (B2V; n = 10). A non-bacterial-contaminated group capped with DY was used as control. After bacterial challenges, inflammatory cell infiltration, incidence and differentiation of dentin bridges were evaluated histologically. There were significant differences in the presence of inflammatory cell infiltration among all groups (P < 0.05). No moderate or severe inflammatory reaction was found in Group DY. Group BDY showed moderate or severe inflammatory cell infiltration in 50%, and showed four necrotic specimens. Although no statistically significant difference was found in the formation and differentiation of dentin bridges among all groups, tunnel defects in dentin bridges were detected in 70% (DY), 80% (BDY), and 50% (B2V). Group B2V showed a significantly lower presence of inflammatory cell infiltration than Group BDY (P < 0.05). Bonding agent is supposed to seal the exposure site, and the remaining bonding agent on the cavities was effective as the barrier in the dentin bridges after bacterial challenges.

In vitro and in vivo studies on the toxicity of dental resin components: a review

In vitro and in vivo studies have clearly identified that some components of restorative composite resins, adhesives, and resin-modified glass ionomer cements are toxic. The mechanisms of cytotoxicity are related firstly to the short-term release of free monomers occurring during the monomer-polymer conversion. Secondly, long-term release of leachable substances is generated by erosion and degradation over time. In addition, ion release and proliferation of bacteria located at the interface between the restorative material and dental tissues are also implicated in the tissue response. Molecular mechanisms involve glutathione depletion and reactive oxygen species (ROS) production as key factors leading to pulp or gingival cell apoptosis. Experimental animal approaches substantiate the occurrence of allergic reactions. There is a large gap between the results published by research laboratories and clinical reports.

New developments in dental adhesion

Numerous simplified adhesives have been introduced to the dental market within the last few years, sometimes without comprehensive testing to validate the performance claimed by the respective manufacturers. Mild self-etch adhesives are unable to etch enamel to provide adequate retention for bonded restorations. Although high early resin-dentin bond strength values can be achieved with some self-etch adhesives, their resistance to thermal and mechanical stresses over time is disappointing. In light of the current drawbacks attributed to all-in-one self-etch adhesives, etch-and-rinse adhesives are still the benchmark for dental adhesion in routine clinical use. This article summarizes current issues and factors related to the performance of adhesives.

An overview of the dental pulp: its functions and responses to injury

The dental pulp is a unique tissue and its importance in the long-term prognosis of the tooth is often ignored by clinicians. It is unique in that it resides in a rigid chamber which provides strong mechanical support and protection from the microbial rich oral environment. If this rigid shell loses its structural integrity, the pulp is under the threat of the adverse stimuli from the mouth, such as caries, cracks, fractures and open restoration margins, all of which provide pathways for micro-organisms and their toxins to enter the pulp. The pulp initially responds to irritation by becoming inflamed and, if left untreated, this will progress to pulp necrosis and infection. The inflammation will also spread to the surrounding alveolar bone and cause periapical pathosis. The magnitude of pulp-related problems should not be underestimated since their most serious consequence is oral sepsis, which can be life threatening, and hence correct diagnosis and management are essential. Clinicians must have a thorough understanding of the physiological and pathological features of the dental pulp as well as the biological consequences of treatment interventions.

Effects of a new antibacterial adhesive on the repair capacity of the pulp-dentine complex in infected teeth

AIM

To evaluate the effects of a self-etching/priming adhesive system, containing the antibacterial monomer 12-methacryloyloxy-dodecylpyridinium bromide (MDPB), on the repair capacity of the pulp-dentine complex in infected cavities in dog's teeth.

METHODOLOGY

Class V cavities with a residual dentine thickness ranging from 0.3-0.8 mm were prepared on the buccal surface of permanent teeth in four dogs. Pulpal exposures were performed in half of the cavities. Millipore filters that had been incubated for 3 h in a 10(5) milky suspension of a-streptococci were placed in the cavities, which were then filled temporarily. After 24 h, the filters were removed and both the exposed and non-exposed cavities were washed with sterile saline and assigned to four groups which were treated with either the experimental antibacterial adhesive system, or Clearfil SE bond, Dycal and Teflon discs. Stereotype connective tissue reactions (inflammatory cell response and/or tissue necrosis) and pulp-specific reparative tissue responses (reduction of odontoblasts and tertiary dentine formation) were assessed at post-operative periods of 4 and 8 weeks.

RESULTS

Neither severe inflammation nor tissue necrosis was observed, either in the dentinal cavities or pulpal exposures treated with the self-etch adhesive containing MDPB. Rates of tertiary dentine formation in infected dentinal cavities treated with this system were comparable with those observed after dentine treatment with the Ca(OH)2-based material. Dentinal bridging was not seen in pulpal exposures treated with the experimental adhesive.

CONCLUSIONS

The new antibacterial adhesive system maintained pulp vitality and primary odontoblastic function in infected nonexposed and exposed cavities but interfered with reparative dentine formation in infected pulpal exposures.

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.

Endodontic complications after plastic restorations in general practice

AIM

To test the hypothesis that dentine and pulp protection by conditioning-and-sealing is no less effective than using a conventional calcium hydroxide lining.

METHODOLOGY

A cohort of healthy adults requiring a new or replacement restoration in a posterior tooth was recruited in six general practices. All procedures received local Ethics Committee approval. Exclusion criteria included signs and symptoms of pulp necrosis or inflammation, and patients unable to commit to a long-term trial. Cavity preparations were randomized to receive a calcium hydroxide lining or conditioning-and-sealing with a smear-removing bonding system. Choice of bulk restorative material (composite resin or amalgam) was at the discretion of the dentist. The key outcome measure was evidence of pulpal breakdown identified at unscheduled (emergency) or scheduled recall examinations. Postoperative sensitivity was recorded on 100 mm VAS at 24 h, 4 days and 7 days. Pulp status was assessed at 6, 12, 24 and 36 month recall, and at any emergency recall appointment. The relationship between pre-treatment and treatment variables and pulp breakdown was assessed by logistic regression (P = 0.05).

RESULTS

A total of 602 teeth were recruited, with comparable numbers of cavities lined (288, 47.8%) or conditioned and sealed (314, 52.2%). The majority (492, 81.7%) were replacement restorations, and amalgam was the most common bulk restorative material (377, 62.6%). A total of 390 (64.8%) restored teeth were reviewed at 6 months, 307 (51%) at 12 months, 363 (60.3%) at 24 months, and 279 (46.3%) at 36 months post-restoration. Sixteen cases of pulp breakdown were identified within 36 months of restoration placement, 11 presenting as emergencies and five detected at routine recall examination. Logistic regression showed that preoperative pain, cavity treatment by lining or conditioning-and-sealing and the use of rubber dam isolation had no association with pulp breakdown. Pulp breakdown was associated with deep or pulpally exposed cavities (P < 0.001, odds ratio 7.8) and with composite rather than amalgam restorations (P = 0.001, odds ratio 2.13). Re-coding to identify teeth with pulp exposures revealed that pulpal exposure was the key determinant of adverse pulp outcomes (P < 0.0001, odds ratio 28.4) and that composite resin restorations were again more likely to be associated with pulp breakdown than amalgam (P = 0.017, odds ratio 3.92).

CONCLUSIONS

Considered within the context of routine primary dental care: Dentists can be confident that pulps will be equally well protected from post-restorative breakdown up to 36 months by calcium hydroxide lining and conditioning-and-sealing with adhesive resins. Residual dentine thickness appears to be a key determinant of pulp responses after restorative dental treatment. In deep and pulpally exposed cavities in posterior teeth, composites were associated with more pulpal breakdown than amalgams.

Self-etch vs etch-and-rinse adhesives: effect of thermo-mechanical fatigue loading on marginal quality of bonded resin composite restorations

OBJECTIVE

This study evaluated the marginal integrity of dentine adhesives bonded to enamel and dentine, before and after thermo-mechanical loading (TML).

METHODS

MO cavities with proximal boxes beneath the CEJ were prepared in extracted human third molars. Direct resin composite restorations (Tetric Ceram) were bonded with 3-step etch-and-rinse (Syntac Classic, Solobond Plus, OptiBond FL), 2-step etch-and-rinse (Admira Bond, Single Bond), 2-step self-etch (AdheSE, Clearfil SE Bond), and 1-step self-etch (all-in-one) adhesives (Adper Prompt, Xeno III, iBond). Marginal gaps were analyzed using SEM of epoxy resin replicas. Bonded interfaces before TML were examined with TEM to identify pre-existing attributes for subsequent marginal disintegration.

RESULTS

In enamel, high percentages of gap-free margins were initially identified for all adhesives. After TML, etch-and-rinse adhesives exhibited significantly higher percentages of gap-free margins (approximately 90%) compared with two-step self-etch (approximately 75%) and all-in-one (approximately 55%) adhesives (p<0.05). iBond did not completely etch through the enamel smear layer. In dentine, 89-100% gap-free margins were initially observed. After TML, there were no statistical differences among etch-and-rinse (62-70%) and two-step self-etch (62-63%) adhesives (p>0.05). The all-in-one adhesives exhibited significantly less gap-free margins (<40%) in dentine (p<0.05), with iBond showing the worst marginal integrity (15%). The presence of pre-existing water channels within the adhesives probably expedited water sorption when restorations were under functional stresses.

CONCLUSION

Enamel bonding was more effective with phosphoric acid-etching. Etch-and-rinse and 2-step self-etch adhesives showed promising marginal adaptation to dentine and may have a better clinical prognosis than the all-in-one bonding approach.

Future directions in bonding resins to the dentine-pulp complex

Resin-based materials are rapidly becoming the primary restorative material to replace tooth structure and the low percentage of biological problems reported for resin-based restorations is testimony to their relative biocompatibility. Despite considerable advances in the understanding of the mechanisms, which govern the integration of resin composite materials with the dentine-pulp complex, considerable potential for improvement remains. Most of these improvements centre around a better understanding of the biological and microbiological risks of resin materials and will only be possible with improved in vitro and in vivo models. There are also a number of possible future developments in materials, clinical techniques and diagnostic methods that may improve the long-term success and reliability of resin-based restorations. The remainder of this paper describes the most likely avenues for future improvements.

Biocompatibility of resin-based materials used as pulp-capping agents

AIM

To evaluate and compare the response of pulps of rats capped with resin-modified glass-ionomer cement (RMGIC) or self-etching adhesive system.

METHODOLOGY

Class I cavities were prepared on the occlusal surface of 54 maxillary first molars of 27 rats. Pulp exposure was performed on the cavity floor. The following resin-based materials were applied as pulp-capping agents: G1, Clearfil Liner Bond 2V (CLB 2V; Kuraray Co., Japan); G2, Vitrebond (VIT; 3M/ESPE, USA). In group 3 (control group), a calcium hydroxide/saline paste (CH; Labsynth, Brazil) was used. The cavities were restored with amalgam. After 7, 30 and 60 days, the animals were sacrificed and the jaws were processed for microscopic evaluation.

RESULTS

Despite the inflammatory response caused by the experimental and the control materials at 7 days, pulpal healing associated with calcified barrier formation was observed at 60 days following the pulp therapy. Both resin-based materials promoted a large zone of cell-rich fibrodentine matrix deposition on the pulp horn related to the pulp exposure site, which was larger to VIT than to CLB 2V specimens. Tertiary dentine underneath the fibrodentine matrix was deposited by a layer of elongated pulpal cells. The remaining pulpal tissue exhibited normal histological characteristics. In the control group, healing and dentine-bridge formation was observed at 30 days. Pulpal breakdown occurred only when bacterial infection occurred.

CONCLUSION

Both experimental pulp-capping agents allowed pulpal healing characterized by cell-rich fibrodentine and tertiary dentine deposition as well as calcified barrier formation.

BIOLOGICAL RISKS OF RESIN-BASED MATERIALS TO THE DENTIN-PULP COMPLEX

Over the past 30 years, restorative dentistry has seen a revolution in materials, restorative techniques, and patient priorities. This revolution has been made possible with the development of new resin-based materials which can be bonded to the tooth structure. Not all of these changes have been without controversy or concern, and some have raised questions about the biological safety of these new materials and techniques. It is the purpose of this review to present recent and relevant information about the biological risks and consequences of resin-tooth bonding and how these risks are affected by the material, its clinical properties, and its manipulation by the practitioner. These biological risks are complex and interactive, and are still incompletely defined. In broad terms, these risks can be divided into those stemming from the toxicological properties of the materials themselves (direct biological risks) and those stemming from microbiological leakage (indirect biological risks).

Direct capping of human pulps with a dentin bonding system or with calcium hydroxide cement

OBJECTIVE

To study human pulp reactions to direct cappings with a dentin adhesive compared with a calcium hydroxide cement, especially with respect to formation of hard tissue in the exposure site.

STUDY DESIGN

Direct pulp cappings were made in 34 caries-free premolars scheduled for extraction due to orthodontic treatment. Half of the teeth were capped with a dentin adhesive, the other half with a calcium hydroxide cement. After periods of from 7 to 70 days, the teeth were extracted and processed for light microscopical examination.

RESULTS

No postoperative sensitivity was experienced. A slight inflammatory reaction was seen in both groups in the short observation period. In the long observation period, significantly more "dentin bridging" was seen in the calcium hydroxide group than in the dentin adhesive group (P < .05).

CONCLUSION

The findings from the present limited material is in accordance with previous findings from human studies and contraindicate use of dentin adhesives for direct pulp capping.

Quantitative evaluation of bacteria adherent to polyelectrolyte HEMA-based hydrogels

The use of adhesive poly(HEMA)-based hydrogels is standard practice in dental restorative procedures. Microorganisms, which potentially can cause oral pathologies, may colonize these polymers. In the present work, bacterial adhesion to polymers prepared with 2-hydroxyethyl methacrylate (HEMA) and to different molar ratios of 2-acrylamido-2-methylpropane-sulfonic acid (AMPS) and/or to 2-methacryloyloxyethyl-tri-methyl-ammonium chloride (METAC) co-monomers were tested. A colorimetric assay system that utilizes the Microbo revelation medium (Microbo srl, Rome, Italy) for microbial counts is shown to be capable of counting the number of adherent bacterial cells without removing them from polymer surfaces. In conditions that mimic those present in the oral cavity, similar bacterial adhesion percentages on the same polymer were observed with the different bacteria belonging to both gram-positive and gram-negative genera, such as Streptococcus sobrinus and Streptococcus oralis (resident microorganisms in the oral cavity) and Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa (transient microorganisms in the oral cavity). It is determined that the physico-chemical characteristics of poly(HEMA)-based hydrogels are the major factors promoting bacterial adhesion, which increased with increasing water content in the swollen polymers, reaching maximal values on the cationic polymers.

Apoptosis: an introduction for the endodontist

Apoptosis plays an important role in many aspects of endodontics, yet there is a paucity of information in this regard in the endodontic literature. Apoptosis is a single deletion of scattered cells by fragmentation into membrane-bound particles that are phagocytosed by other cells. It is a key process in the embryological development of the tooth, periodontal ligament and supporting oral tissue in the progression of oral disease, bone resorption, immunological response and inflammation, and in wound healing and certain pharmacological effects. The understanding of the ability of clinical materials to induce or inhibit apoptosis and the investigation of apoptosis as it relates to the pathogenesis of pulpal and periradicular pathology may eventually lead to new treatment approaches for the endodontist. The purpose of this review is to familiarize the clinical endodontist with current knowledge on apoptosis as it relates to the pulp and periradicular tissues.

Analysis of pulpal reactions to restorative procedures, materials, pulp capping, and future therapies

Every year, despite the effectiveness of preventive dentistry and dental health care, 290 million fillings are placed each year in the United States; two-thirds of these involve the replacement of failed restorations. Improvements in the success of restorative treatments may be possible if caries management strategies, selection of restorative materials, and their proper use to avoid post-operative complications were investigated from a biological perspective. Consequently, this review will examine pulp injury and healing reactions to different restorative variables. The application of tissue engineering approaches to restorative dentistry will require the transplantation, replacement, or regeneration of cells, and/or stimulation of mineralized tissue formation. This might solve major dental problems, by remineralizing caries lesions, vaccinating against caries and oral diseases, and restoring injured or replacing lost teeth. However, until these therapies can be introduced clinically, the avoidance of post-operative complications with conventional therapies requires attention to numerous aspects of treatment highlighted in this review.

Bond failure at dentin-composite interfaces with 'single-bottle' adhesives

OBJECTIVES

Significant differences in interfacial fracture toughness (intK(1c)) among six dentinal adhesives have been reported. Resulting fractured test specimens were examined under SEM to determine differences in micromorphology, which might account for the respective intK(1c) results.

METHODS

Interfacial fracture toughness specimens were assembled from bovine dentin and P50 resin composite under moist conditions, using one of five 'single-bottle' adhesives; either Single Bond, One Step, Optibond Solo, Prime & Bond 2.1, Bond 1 or a resin-modified glass ionomer, Fuji Bond LC. After fracture toughness testing, four fractured specimens from each group were sectioned transversely, critical-point dried and examined under SEM.

RESULTS

Most bond failures occurred at the interface between adhesive resin and the top of the hybrid layer. Single Bond and One Step gave the highest intK(1c) results and showed good resin infiltration at this interface. Average film thickness of unfilled adhesives was 30 microm. When this intermediate adhesive layer was too thin, resin infiltration was poor and associated with low fracture toughness. Filled adhesives, Optibond Solo and Fuji Bond LC, formed thick films varying from 60 to 250 microm which failed cohesively, effectively sealing the dentin surface despite moderate fracture toughness results.

CONCLUSIONS

Most bond failures occurred between the adhesive and hybrid layers. Good resin infiltration at the top of the hybrid layer combined with an intermediate adhesive layer of adequate width produced a fracture-resistant interface. Filled adhesives failed cohesively, providing a good dentin seal, despite material fracture.

Differential induction of apoptosis by capping agents during pulp wound healing

Effects of capping agents on two waves of apoptosis during pulp wound healing were examined. After cavity preparation of rat molars, cavities were filled with calcium hydroxide, zing oxide eugenol cement, or 4-META/MMA-TBB resin (4MMT) and some were unfilled. One hour or 1 day after filling, we examined the distribution and the number of apoptotic cells by terminal deoxynucleotidyl transferase-mediated labeling (TUNEL) assay. One hour after filling, there were no differences in distribution patterns or the number of apoptotic odontoblasts among the four groups. One day after filling, we found differences in distribution patterns and the number of apoptotic pulp cells among the four groups. Especially in the 4MMT group, the distribution pattern of apoptotic cells was more broadly spread, and the number of apoptotic cells was significantly larger than those of other groups. These results suggest that capping agents may have an effect on pulp apoptosis and that 4MMT may actively induce apoptosis during pulp wound healing.

The mechanism of pulpal wound healing

The favourable response of exposed pulp tissue against a variety of materials used for pulp capping in experimental conditions, as observed by hard tissue (reparative dentine) formation, demonstrates an intrinsic capacity of pulp tissue for healing. However, in the clinical situation, in which a pulpal exposure is usually accompanied by a long-term external irritation with the subsequent long-term inflammatory response to that irritation, the outcome of pulp capping procedures is not as predictable. While some of the factors related to the defensive reactions and healing after pulp exposure and capping procedures are well understood, the mechanisms and importance of others remain less well-known. Understanding the mechanisms regulating the spread of inflammation and necrosis in pulp tissue, and the factors regulating healing after closure of the wound, would facilitate the development of new and better treatment procedures with more predictable outcomes. In this review, some of the aspects considered to be important in pulpal wound healing are discussed.

The effects of dentin permeability on restorative dentistry

The permeability properties of dentin determine its sensitivity and the degree of pulpal response to restorative procedure materials and microleakage. Most pulpal reactions are due to bacteria or bacterial products that permeate across dentin. These reactions can be prevented if dentin is sealed with resins as soon as it is exposed. In the future, restorative dentists may employ topical application of biologic growth factors to permeate across dentin to modify the formation of reactionary or reparative dentin, thereby lowering dentin permeability and protecting the pulp.