The effect of cavity restoration variables on odontoblast cell numbers and dental repair

Urchin-like multiscale structured fluorinated hydroxyapatite as versatile filler for caries restoration dental resin composites

Caries is one of the most prevalent human diseases, resulting from demineralization of tooth hard tissue caused by acids produced from bacteria, and can progress to pulpal inflammation. Filling restoration with dental resin composites (DRCs) is currently the most common treatment for caries. However, existing DRCs suffer from low fracture strength and lack comprehensive anti-caries bioactivity including remineralization, pulp protection, and anti-cariogenic bacteria effects. In this study, inspired by plant roots' ability to stabilize and improve soil, fluorinated urchin-like hydroxyapatite (FUHA) with a three-dimensional whisker structure and bioactive components of calcium, phosphorus, and fluorine was designed and synthesized by a dynamic self-assembly method. Furthermore, versatile FUHA particles with different loading fractions were used as functional fillers to fabricate methacrylate-based DRCs, where the urchin-like hydroxyapatite (UHA) filled DRCs and commercial DRCs (Z350XT and BEAUTIFIL II) served as the control groups. The results demonstrated that FUHA with 50 wt% loading in resin matrix endowed DRC (F5) with excellent physicochemical properties, dentin remineralization property, cell viability, promotion of dental pulp stem cells mineralization, and antibacterial properties. Meanwhile, F5 also presented good clinical handling and aesthetic characteristics. Therefore, structure/functional-integrated FUHA filled DRCs have potential as a promising strategy for tooth restoration and anti-caries bioactivity.

The scientific management of deep carious lesions in vital teeth using contemporary materials—A narrative review

Aim

The aim of this article is to review the scientific evidence for deep caries removal in permanent vital teeth and the choice of dentine replacement material and restoration of the teeth to maintain long term tooth vitality and function.

Method

The two position statements namely the European Society of Endodontology and the American Association of Endodontists position statements on vital pulp therapy will be scrutinized and compared with regards to the deep caries removal strategy and assessed for evidence of best practice. The properties of materials used to manage vital pulps and the best way to restore the teeth will be reviewed and guidance on the full management of vital teeth will be suggested.

Conclusions

Promoting new treatment modalities for reversible and irreversible pulpitis allowing for pulp preservation should be considered. Although debatable, cases with deep caries should be managed by complete non-selective caries removal which will allow for pulpal management if needed and a more predictable outcome can be expected when using the new materials and treatment modalities of vital pulp therapy.

Raman Spectroscopy-Based 3D Analysis of Odontogenic Differentiation of Human Dental Pulp Stem Cell Spheroids

Numerous efforts have been made to establish three-dimensional (3D) cell cultures that mimic the structure, cell composition, and functions of actual tissues and organs in vitro; however, owing to its intrinsic complexity, precise characterization of 3D differentiation remains challenging and often results in high variations in the resulting differentiated spheroids. This study reports a 3D Raman mapping-based analytical method that helps us to identify the crucial factors responsible for inducing variability in differentiated stem cell spheroids. Human dental pulp stem cell spheroids were generated at various cell densities using the hanging drop (HD) and molded parafilm-based (MP) methods and were then further subjected to odontogenic differentiation. Thereafter, the 3D cellular differentiation in these spheroids was analyzed based on three different Raman peaks, namely, 960, 1156/1528, and 2935 cm^-1, which correspond to hydroxyapatite (HA, odontogenic differentiation marker), β-carotene (precursor of HA), and proteins/cellular components (cell reference). By correlating such cell differentiation-related peaks and water/medium peaks (3400 cm^-1), we discovered that the diffusion of the medium containing various nutrients and differentiation factors was crucial in determining the variations in 3D differentiation of stem cell spheroids. Odontogenic differentiation was majorly induced at the outer shell of HD spheroids (up to ∼20 μm), whereas odontogenic differentiation was markedly induced in MP spheroids (up to 40-50 μm). Considering the challenges associated with high variations in spheroid and organoid differentiation, we conclude that the proposed Raman-based 3D analysis plays a pivotal role in stem cell-based regenerative therapy and drug screening.

A survey assessing the knowledge and perception of dental practitioners on the need for prophylactic endodontic treatment in abutment teeth for fixed partial dentures

Background:

Tooth preparation for fixed prosthodontic procedures often induces enough thermal or mechanical stresses on the pulp. The extent of pulpal injury and ability to repair depends on factors like amount of remaining dentin, extent of heat produced, and permeability of dentinal tubules. However, there is no infallible method to predict the pulpal response and so the treatment outcome.

Aim:

This survey tries to assess the knowledge and perception among dental practitioners on the need for prophylactic endodontic therapy in abutment teeth for fixed partial denture (FPD).

Setting and Design:

Questionnaire-based survey.

Methodology:

An observational study was then conducted among 303 dental practitioners in the state of Tamil Nadu and 250 participants responded.

Statistical Analysis Used:

Descriptive statistics and multiple linear regression analysis.

Results and Conclusion:

The survey further imparts light on the clinical outcomes that help minimize the incidence of biological failure underneath a FPD.

Human pulp response to conventional and resin-modified glass ionomer cements applied in very deep cavities

OBJECTIVES

This study assessed the human pulp response after adhesive restoration of cavities by indirect pulp capping with a conventional or a resin-modified glass ionomer cement.

MATERIALS AND METHODS

Deep cavities prepared in 26 human premolars were lined with Riva Light Cure (Riva LC), Riva Self Cure (Riva SC), or Dycal, and then restored with composite resin. Four teeth were used as intact control. After time intervals of 7 or 30 days, the teeth were extracted, processed for histological evaluation of the pulp, and the remaining dentin thickness (RDT) between the cavity floor and the pulp was measured.

RESULTS

At 7 days, a slight pulp inflammation associated with discrete tissue disorganization was observed in most of t the teeth lined with Riva LC and Riva SC. Moderate pulp inflammation occurred in one tooth lined with Riva LC. Bacteria were identified in one specimen of the same group that exhibited no pulp damage. At 30 days, slight pulp inflammation and discrete tissue disorganization persisted in two specimens treated with Riva LC, in which a thin layer of tertiary dentin was deposited. Mean RDTs ranged from 383.0 to 447.8 μm.

CONCLUSIONS

Riva LC produced more damage to the pulp than Riva SC. However, the initial pulp damage decreased over time and after 30 days both GICs were labeled as biocompatible.

CLINICAL RELEVANCE

In this study conducted with human teeth, the conventional and the resin-modified glass ionomer cements investigated were shown not to cause post-operative sensitivity or persistent pulp damage when applied as liners in very deep cavities, thereby indicating their biocompatibility.

Novel metformin-containing resin promotes odontogenic differentiation and mineral synthesis of dental pulp stem cells

This represents the first report on the development of metformin-containing dental resins. The objectives were to use the resin as a carrier to deliver metformin locally to stimulate dental cells for dental tissue regeneration and to investigate the effects on odontogenic differentiation of dental pulp stem cells (DPSCs) and mineral synthesis. Metformin was incorporated into a resin at 20% by mass as a model system. DPSC proliferation attaching on resins was evaluated. Dentin sialophosphoprotein (DSPP), dentin matrix phosphoprotein 1 (DMP-1), alkaline phosphatase (ALP), and runt-related transcription factor 2 (Runx2) genes expressions were measured. ALP activity and alizarin red staining (ARS) of mineral synthesis by the DPSCs on resins were determined. DPSCs on metformin-containing resin proliferated well (mean ± SD; n = 6), and the number of cells increased by 4-fold from 1 to 14 days (p > 0.1). DSPP, ALP, and DMP-1 gene expressions of DPSCs on metformin resin were much higher than DPSCs on control resin without metformin (p < 0.05). ALP activity of metformin group was 70% higher than that without metformin at 14 days (p < 0.05). Mineral synthesis by DPSCs on metformin-containing resin at 21 days was 9-fold that without metformin (p < 0.05). A novel metformin-containing resin was developed, achieving substantial enhancement of odontoblastic differentiation of DPSCs and greater mineral synthesis. The metformin resin is promising for deep cavities and perforated cavities to stimulate DPSCs for tertiary dentin formation, for tooth root coatings with metformin release for periodontal regeneration, and for root canal fillings with apical lesions to stimulate bone regeneration.

Changes of CD90 expression and immunoreactive cell localisation in rat dental pulp after cavity preparation

CD90 expression and immunoreactive cell localisation in rat dental pulp cells after cavity preparation was investigated. Cavity preparation was performed on the maxillary first molar of 8-week-old Wistar rats (n = 36), and immunohistochemistry and quantitative real-time PCR were performed. CD90-immunoreactivity was observed among subodontoblastic cells in the control group. One day after cavity preparation, the CD90-immunoreactivity disappeared under the cavity area. While CD90-immunoreactivity was faint after 3 days, the re-arrangement of odontoblasts was detected in contact with dentine. After 5 days, the odontoblasts were observed beneath the dentine, and CD90-immunoreactive cells were localised under the odontoblast layer. Immunofluorescence showed co-localisation of CD90 and nestin was detected after 3 days. After 5 days, CD90-immunoreactivity increased at the subodontoblastic layer. mRNA expression of CD90 and DSPP decreased after cavity preparation, and gradually recovered (P < 0.01). These results suggest that CD90-immunoreactive cells in the subodontoblastic layer contribute to regeneration of odontoblast and subodontoblastic layers following cavity preparation.

Guidelines for the Management of Traumatic Dental Injuries: 1. Fractures and Luxations of Permanent Teeth

Traumatic dental injuries (TDIs) of permanent teeth occur frequently in children and young adults. Crown fractures and luxations are the most commonly occurring of all dental injuries. Proper diagnosis, treatment planning and followup are important for improving a favorable outcome. Guidelines should assist dentists and patients in decision making and for providing the best care effectively and efficiently. The International Association of Dental Traumatology (IADT) has developed a consensus statement after a review of the dental literature and group discussions. Experienced researchers and clinicians from various specialties were included in the group. In cases where the data did not appear conclusive, recommendations were based on the consensus opinion of the IADT board members. The guidelines represent the best current evidence based on literature search and professional opinion. The primary goal of these guidelines is to delineate an approach for the immediate or urgent care of TDIs. In this first article, the IADT Guidelines for management of fractures and luxations of permanent teeth will be presented.

Criteria and treatment decisions in the management of deep caries lesions: Is there endodontic overtreatment?

Background

The aim of this study was to investigate the diagnostic criteria and treatment decisions in the management of deep caries lesions (DCLs). The null hypothesis tested was that DCLs are managed according to the current scientific evidence.

Material and Methods

A total of 288 dentists were contacted directly or by mail, and 125 (43%) were included in the study. Dentists were requested to answer a questionnaire about the routine approach to the diagnosis and treatment of DCLs. Logistic regression analyses were carried out to calculate odds ratios (OR).

Results

Pulp sensitivity tests were used by 65% of dentists when assessing pulpal health in cases of DCLs, particularly those who had followed courses in cariology (OR = 3.8; p = 0.005). Dentine hardness was the most frequent criterion used during DCLs excavation (98%). Two thirds of the respondents (65%) removed carious tissue until they felt hard dentine, and feeling hard dentine correlated with caries removal even at the risk of pulpal exposure (OR = 15.8; p = 0.0000). Acute transient pain or sensitivity to cold or heat (reversible pulpitis) were considered by 58% of respondents as a reason to provide endodontic therapy.

Conclusions

The null hypothesis tested is rejected. The evidence-based more conservative approach on the management of DCLs is not being translated to clinical dentistry. Root canal treatment is being indicated in cases of DCLs in which the diagnosis is reversible pulpitis. Likewise, it can be concluded that non-conservative management of DCLs, with endodontic overtreatment, could be occurring.

Key words:Deep caries lesions, dental pulp capping, dental pulp health, dentists, endodontic therapy, pulpal diagnosis, reversible pulpitis, treatment decisions.

Wnt-Responsive Odontoblasts Secrete New Dentin after Superficial Tooth Injury

The objective of our experiments was to identify new therapeutic strategies to stimulate dentin formation in an adult tooth. To address this objective, we evaluated dentin production in 2 acute trauma models: one involving a pulp exposure and the other involving a superficial dentin injury. Molecular, cellular, and histologic analyses revealed that in response to a severe injury, where the pulp is exposed to the oral cavity, cell death is rampant and the repair response initiates from surviving pulp cells and, to a lesser extent, surviving odontoblasts. When an injury is superficial, as in the case of a dentin injury model, then disturbances are largely confined to pulp tissue immediately underneath the damaged dentin tubules. We found that the pulp remained vital and innervated; primary odontoblasts upregulated HIF1α; and the rate of mineralization was significantly increased. A tamoxifen-inducible Axin2^CreERT2/+; R26R ^mTmG/+ reporter strain was then used to demonstrate that a population of long-lived Wnt-responsive odontoblasts, which secreted dentin throughout the life of the animal, were responsible for depositing new dentin in response to a superficial injury. Amplifying Wnt signaling in the pulp stimulates dentin secretion, and in the dentin injury model, we show that a liposomal formulation of human WNT3A protein passes through dentinal tubules and is capable of upregulating Wnt signaling in the pulp. These data provide strong proof of concept for a therapeutic pulp-capping material to stimulate Wnt signaling in odontoblasts and thus improve the pulp repair response.

[Vital pulp therapy of damaged dental pulp]

The development of an expert consensus on vital pulp therapy can provide practical guidance for the improvement of pulp damage care in China. Dental pulp disease is a major type of illness that adversely affects human oral health. Pulp capping and pulpotomy are currently the main methods for vital pulp therapy. Along with the development of minimal invasion cosmetic dentistry, using different treatment technologies and materials reasonably, preserving healthy tooth tissue, and extending tooth save time have become urgent problems that call for immediate solution in dental clinics. This paper summarizes the experiences and knowledge of endodontic experts. We develop a clinical path of vital pulp therapy for clinical work by utilizing the nature, approach, and degree of pulp damage as references, defense and self-repairing ability of pulp as guidance, and modern technologies of diagnosis and treatment as means.

Calcium hydroxide liners: a literature review

OBJECTIVE

This review integrates the literature on cavity liners and current concepts of pulp protection with the aim of establishing a better understanding of the role of calcium hydroxide as a cavity liner.

MATERIALS AND METHODS

A search was conducted through PubMed, MEDLINE, and Ovid for articles with the criteria for the following terms: cavity liners and bases, pulp protection, and calcium hydroxide liners. No specific inclusion or exclusion criteria were applied as to what articles would be included in this review. It was hoped that the extent of the literature reviewed would be as comprehensive as possible.

CONCLUSION

This review underlines the fact that calcium hydroxide liners should only be used in the deepest spots in the cavity where the remaining dentine thickness is ≤0.5 mm. A protective layer of resin-modified glass ionomer should always follow the application of calcium hydroxide liners.

NURR1 Downregulation Favors Osteoblastic Differentiation of MSCs

Mesenchymal stem cells (MSCs) have been identified in human dental tissues. Dental pulp stem cells (DPSCs) were classified within MSC family, are multipotent, can be isolated from adult teeth, and have been shown to differentiate, under particular conditions, into various cell types including osteoblasts. In this work, we investigated how the differentiation process of DPSCs toward osteoblasts is controlled. Recent literature data attributed to the nuclear receptor related 1 (NURR1), a still unclarified role in osteoblast differentiation, while NURR1 is primarily involved in dopaminergic neuron differentiation and activity. Thus, in order to verify if NURR1 had a role in DPSC osteoblastic differentiation, we silenced it during all the processes and compared the expression of the main osteoblastic markers with control cultures. Our results showed that the inhibition of NURR1 significantly increased the expression of osteoblast markers collagen I and alkaline phosphatase. Further, in long time cultures, the mineral matrix deposition was strongly enhanced in NURR1-silenced cultures. These results suggest that NURR1 plays a key role in switching DPSC differentiation toward osteoblasts rather than neuronal or even other cell lines. In conclusion, DPSCs represent a source of osteoblast-like cells and downregulation of NURR1 strongly prompted their differentiation toward the osteoblastogenesis process.

Semaphorin 3A Induces Odontoblastic Phenotype in Dental Pulp Stem Cells

In cases of pulp exposure due to deep dental caries or severe traumatic injuries, existing pulp-capping materials have a limited ability to reconstruct dentin-pulp complexes and can result in pulpectomy because of their low potentials to accelerate dental pulp cell activities, such as migration, proliferation, and differentiation. Therefore, the development of more effective therapeutic agents has been anticipated for direct pulp capping. Dental pulp tissues are enriched with dental pulp stem cells (DPSCs). Here, the authors investigated the effects of semaphorin 3A (Sema3A) on various functions of human DPSCs in vitro and reparative dentin formation in vivo in a rat dental pulp exposure model. Immunofluorescence staining revealed expression of Sema3A and its receptor Nrp1 (neuropilin 1) in rat dental pulp tissue and human DPSC clones. Sema3A induced cell migration, chemotaxis, proliferation, and odontoblastic differentiation of DPSC clones. In addition, Sema3A treatment of DPSC clones increased β-catenin nuclear accumulation, upregulated expression of the FARP2 gene (FERM, RhoGEF, and pleckstrin domain protein 2), and activated Rac1 in DPSC clones. Furthermore, in the rat dental pulp exposure model, Sema3A promoted reparative dentin formation with dentin tubules and a well-aligned odontoblast-like cell layer at the dental pulp exposure site and with novel reparative dentin almost completely covering pulp tissue at 4 wk after direct pulp capping. These findings suggest that Sema3A could play an important role in dentin regeneration via canonical Wnt/β-catenin signaling. Sema3A might be an alternative agent for direct pulp capping, which requires further study.

Managing Carious Lesions

The International Caries Consensus Collaboration undertook a consensus process and here presents clinical recommendations for carious tissue removal and managing cavitated carious lesions, including restoration, based on texture of demineralized dentine. Dentists should manage the disease dental caries and control activity of existing cavitated lesions to preserve hard tissues and retain teeth long-term. Entering the restorative cycle should be avoided as far as possible. Controlling the disease in cavitated carious lesions should be attempted using methods which are aimed at biofilm removal or control first. Only when cavitated carious lesions either are noncleansable or can no longer be sealed are restorative interventions indicated. When a restoration is indicated, the priorities are as follows: preserving healthy and remineralizable tissue, achieving a restorative seal, maintaining pulpal health, and maximizing restoration success. Carious tissue is removed purely to create conditions for long-lasting restorations. Bacterially contaminated or demineralized tissues close to the pulp do not need to be removed. In deeper lesions in teeth with sensible (vital) pulps, preserving pulpal health should be prioritized, while in shallow or moderately deep lesions, restoration longevity becomes more important. For teeth with shallow or moderately deep cavitated lesions, carious tissue removal is performed according to selective removal to firm dentine. In deep cavitated lesions in primary or permanent teeth, selective removal to soft dentine should be performed, although in permanent teeth, stepwise removal is an option. The evidence and, therefore, these recommendations support less invasive carious lesion management, delaying entry to, and slowing down, the restorative cycle by preserving tooth tissue and retaining teeth long-term.

Cavity lining in primary teeth

DATA SOURCES

Embase, Medline, Cochrane Central, Biomed Central and Open Grey databases and bibliographies of identified studies.

STUDY SELECTION

Randomised controlled trials investigating humans with primary caries lesions receiving operative treatment involving caries removal and restoration, with minimum two treatment groups comparing different cavity treatments before restoration (no lining versus lining) were included.

DATA EXTRACTION AND SYNTHESIS

Data were extracted independently by two reviewers and study quality assessed using the Cochrane risk of bias tool. Random effect meta-analysis was carried out.

RESULTS

Three studies involving a total of 89 patients were included. All the studies involved primary teeth and were conducted in Brazil. Follow-up periods ranged from 26-53 months. All the studies were considered to be at high risk of bias. Restoring the cavity without lining did not significantly affect the risk of failure. The quality of the evidence was low.

CONCLUSIONS

Current evidence does not support strong recommendations to use or not to use liners after caries removal and before restoring cavities. Our findings are restricted to primary teeth after selective excavation, with only one liner (calcium hydroxide) being used for comparison.

Evaluation of Biocompatibility of an Etch-and-Rinse Adhesive System Based in Tertiary Butanol Applied in Deep Cavity

The aim of this study was to evaluate biocompatibility of an etch-and-rinse adhesive system based in tertiary butanol applied in deep cavity human teeth with approximately 1 mm of remaining dentin by observing histological changes of the pulp tissue of humans at intervals of 01, 07, 14 and 21 days. Twenty third molars with indication for xtraction from patients of both sexes, presenting no systemic alterations were used. Class I cavity was made deeper and then, XP BOND adhesive system and resin Filtek Z250 were applied. The sample was divided into four groups according to the time intervals between the application of adhesive system and extraction. Morphologic criteria analysed considered the presence of hyperemia, type of inflammatory cell response, organization of odontoblast cells layer, organization of pulp tissue and the presence or absence of bacteria. Data were submitted to Fisher Exact Test p> 0.05. We observed mild inflammatory infiltrate, preserved pulp tissue morphology, disorganization of the odontoblast layer in most specimens, as well as absence of bacteria at the intervals of 01, 07, 14 and 21 days. In some cases there was pulp hyperemia. The etchand- rinse adhesive system based in tertiary butanol showed satisfactory behavior in the conditions studied.

Immunohistochemical study of the inflammatory response of the dental pulp

Defense reactions of the dental pulp involve a variety of biological reactions, in which the immune system plays a very important role. The class II major histocompatibility complex (MHC) molecule expressing cells, termed dendritic cells and lymphocytes in human dental pulp are highly sensitive to exogenous antigenic stimuli. Their drastic changes in number and localization are induced by dental caries. This study investigated the responses of the immune system in two different clinical conditions: shallow and deep cavities. Cells were identified immunohistochemically by using the following monoclonal antibodies: HLA-DR, CD45RO and CD20. Initial pulpal response was characterized by a localized accumulation of HLA-DR antibody-positive cells in the pulp tissue beneath the dentinal tubules communicating with the caries lesion. In the pulp of progressed caries, a large number of HLA-DR-positive cells was observed with a marked increase of other kinds of immunocompetent cells. This might indicate the occurrence of antigen presentation locally in the pulp tissue, which is very important for the immune response. Results obtained in this study demonstrated that dental pulps respond to the progression of the carious lesion and cellular and humoral immune responses occur in the pulp tissue.

Changes in cell density and morphology of selected cells of the ageing human dental pulp

OBJECTIVES

The aim of this study was to determine the changes in cell density and morphology of selected cells of the ageing human dental pulp.

BACKGROUND

Changes in cell density and morphology of dental pulp cells over time may affect their capability to respond to tooth injury.

MATERIALS AND METHODS

One hundred thirty-one extracted teeth were obtained from individuals between the ages of 6 and 80 years. The apical 1/3 of the root region was removed from all teeth prior to routine processing for producing histological slides. The histology slides were used to study the changes in cell density and morphology of selected pulp cells; odontoblasts, subodontoblasts and fibroblasts in the crown and root regions of the dental pulp. Student's t-test and one-way anova were used for statistical analyses.

RESULTS

In all age groups, the cell density for all types of cells was found to be higher in the crown than in the root (p < 0.05). In general, the pulp cell density was found to decrease with age in both the crown and root regions. However, it was noted that the reduction of coronal odontoblasts occurred later in life (40-49 years) when compared to that of subodontoblasts or fibroblasts (30-39 years).

CONCLUSIONS

The density of the coronal pulp cells reduces and these cells undergo morphological changes with ageing of individuals and this may affect the pulp's ability to resist tooth injury.

Evaluation of antibacterial effects of pulp capping agents with direct contact test method

Objectives:

Calcium hydroxide has been used in dentistry as a major capping material having the capacity to introduce the formation of a mineralized dentin bridge, but it has no direct inducing effect to the pulp cells. The purpose of this study was to evaluate the antibacterial properties of three different pulp capping agents using a direct contact test (DCT).

Materials and Methods:

The antibacterial properties of three pulp capping agents were evaluated a DCT. For the DCT, wells (n = 12) of 96-microtiter plates were coated with the tested cements (Dycal, Dentsply, USA; DiaRoot BioAggregate, Diadent, Holland; Calcimol LC, Voco, Germany) and Kalzinol (zinc oxide/eugenol cement, Dentsply, USA) was used as control material. A Lactobacillus casei suspension was placed on the surface of each specimen for 1 h at 37°C. Bacterial growth was monitored for 16 h with a temperature-controlled microplate spectrophotometer. The kinetics of the outgrowth in each well were recorded continuously at 650 nm every 30 min. The data were analyzed by one-way ANOVA, and Tamhane's T2 multiple comparison test. The level of significance was determined as P < 0.05.

Results:

All pulp capping agents showed an increase in the logarithmic growth rate of L. casei when compared with the control group (P < 0.05). Therefore, all pulp capping agents did not show antibacterial activity.

Conclusions:

The tested pulp capping agents haven't got antibacterial properties. Therefore, they should be used carefully when pulp is exposed or only very thin dentin remained over the pulp to avoid bacterial contamination.

Pulpal and periradicular response to caries: current management and regenerative options

The pulp-dentin complex is a strategic and dynamic barrier to various insults that plague the dentition. Researchers have yet to understand the complete potential of this shifting junction and its components. The most common cause of injury to the pulp-dentin complex is carious breakdown of enamel and dentin. In recent years, there has been a change in restorative management of caries. The emphasis is on strategies to preserve dentin and protect the pulp. This article provides a brief review of the effect of caries on the pulp, of subsequent events on the periradicular tissues, and of current understanding of treatment modalities.

A prospective clinical study of polycarboxylate cement in periapical surgery

OBJECTIVE

To evaluate the clinical efficacy of polycarboxylate cement as retrograde filling material.

DESIGN

A prospective clinical study was made of 25 patients subjected to periapical surgery with ultrasound and magnifying loupes, in which polycarboxylate cement was used as retrograde filling material. Measurements were made of the area and diameter of the lesions pre- and postoperatively, and 6 and 12 months after the operation. The apical resection and retrograde filling areas were also measured, and the prognosis following surgery was recorded.

RESULTS

A total of 23 patients with 31 apicoectomized teeth were studied (2 patients being lost to follow-up). The mean area of the periapical lesions before surgery was 52.25 mm2, with a mean major diameter of 6.1 mm and a mean lesser diameter of 4.8 mm. The success rate after 12 months was 54.7%, according to the criteria of Von Arx and Kurt. The prognosis was poorer in females, in larger lesions, and in cases with larger retrograde filling areas.

CONCLUSIONS

Polycarboxylate cement offers good results, with important bone regeneration after periapical surgery.

A method to isolate and culture expand human dental pulp stem cells

Dentinal repair in teeth occurs through the activity of specialized cells known as odontoblasts that are thought to be maintained by a precursor population associated with the perivascular cells within dental pulp tissue. We have previously isolated candidate dental pulp stem cells (DPSC) from adult human third molars, with the ability to generate clonogenic cell clusters (CFU-F: colony-forming units-fibroblastic), a high proliferation rate, and multi-potential differentiation in vitro. When cultured DPSC are transplanted into immunocompromised mice, they generated a dentin-like structure lined with human odontoblast-like cells that surrounded a pulp-like interstitial tissue, composed of collagen and a vascular network. The present protocol describes a methodology to generate highly purified preparations of human DPSC. This process involves the enzymatic digestion of fresh samples of human dental pulp tissue followed by the isolation of DPSC using magnetic bead cell separation, based on their expression of mesenchymal stem cell associated markers.

The effect of dentine-bonding agents on substance P release in human dental pulp

AIM

To quantify the effect of dentine-bonding agents on Substance P (SP) release in healthy human dental pulp tissue.

METHODOLOGY

Forty pulp samples were obtained from healthy pre-molars where extraction was indicated for orthodontic reasons. In thirty of these pre-molars, a standardized Class V cavity preparation was performed, and teeth were divided equally into three groups: (i) Unetched-cavity control group: Class V cavities only; (ii) Experimental Group I: 'One-step' self-etch bonding agent was placed in the cavity; and (iii) Experimental Group II: 'Two-step' total-etch bonding agent was placed in the cavity. The remaining ten healthy pre-molars where extracted without treatment and served as an intact-teeth control group. SP was measured by radioimmunoassay.

RESULTS

Greater SP release was found in the 'one-step' bonding agent group, followed by the 'two-step' bonding agent group and the unetched-cavity control group. The lower SP values were for the intact-teeth control group. anova showed statistically significant differences between groups (P = 0.0001). Tukey HSD post hoc tests showed statistically significant differences in SP release between the intact-teeth control group and the three other groups (P < 0.01) and between the unetched-cavity control group and the 'one-step' bonding agent group (P < 0.05). No significant difference was found between the 'two-step' bonding agent and the unetched-cavity control group.

CONCLUSION

Dentine-bonding agents placed over Class V cavity preparations increased SP release. One-step dentine-bonding agents increased SP release most.

The effects of erroneous mixing of zinc carboxylate cements

The mechanical properties of luting agents are determined by the mixing ratio of powder and liquid. The purpose of this in vitro study was to evaluate the therapeutic range of zinc carboxylate cements by investigating the mechanical properties of such cements when formulated using erroneous powder/liquid ratios. Using the recommended powder/liquid ratio as a standard, four different mixing ratios (25% and 50% more or less powder) were used to prepare each carboxylate cement (Aqualox, Carboco, Durelon). A veneering composite (Sinfony) was used as control. Vickers hardness and three-body abrasion were evaluated. In each carboxylate cement, both a 25% and 50% increase in liquid content resulted in significantly lower Vickers hardness, whereas a higher powder content altered the saturation concentration but did not result in increased hardness; this effect was particularly obvious in Carboco. Durelon showed a linear relationship between wear and powder/liquid ratio, whereas Carboco and Aqualox displayed a more exponential increase in wear in mixings with an increased liquid content. The mechanical properties of carboxylate cements were altered in mixtures with an increased liquid content, but not in those with a high powder content. Mixing ratio errors greater than 25% may significantly affect the clinical performance of carboxylate cements.

In vitro evaluation of microleakage of various types of dental cements

Introduction. Microleakage is defined as the clinically undetectable seepage of oral fluids containing bacteria and debris between cement layer and tooth restoration. Objective. This in vitro study investigated the effect of different dental cements (zinc-phosphate, polycarboxylate, glass-ionomer and resin cement) on microleakage in different ceramic crown systems (metal ceramic crown, metal ceramic crown with a porcelain margin, Empress 2 and In Ceram all-ceramic crowns) fixed on extracted human teeth. Methods. One hundred and sixty intact human premolars were randomized to four groups of forty teeth each, according to the different ceramic crown systems. They were prepared in a standardized manner for metal-ceramic and all-ceramic crowns. Crowns were made following a standard laboratory technique, and each group of crowns were divided into four groups according to the different cement agents and cemented on their respective abutments. The specimens were subjected to thermocycling, placed in methylene blue solutions, embedded in resin blocks and vertically cut in the bucco-oral and meso-distal direction. The microleakage in the area of tooth-cement interface was defined as linear penetration of methylene blue and was determined with a microscope to assign microleakage scores using a five-point scale. Results. A significant association was found between a cement type and degree of microleakage (p=0.001). No statistically significant differences were found among the different ceramic crown systems luted with the same dental cement. The smallest degree of microleakage was observed in specimens luted with resin cement (X=1.73), followed by glass-ionomer cement (X=2.45) and polycarboxylate cement (X=3.20). The greatest degree of microleakage was detected in the crowns fixed with zincphosphate cement (X=3.33). Conclusion. The investigated dental cements revealed different sealing abilities. The use of resin cement resulted in the percentage of 0 microleakage scores. Due to this feature, the resin cement is to be recommended in everyday clinical practice.

An immunohistochemical evaluation of cell adhesion molecules in human dental pulp after tooth preparation and application of temporary luting cements

OBJECTIVE

The aim of this study was to determine if temporary luting cements used with provisional restorations alter the expression of cell adhesion molecules (CAMs) in human dental pulp.

STUDY DESIGN

Twenty-five healthy human premolars and third molars scheduled to be extracted for orthodontic reasons were randomly assigned to 5 experimental groups. Group 1 included untreated teeth as negative control. In groups 2-5, provisional crowns were cemented to the prepared teeth with either eugenol-containing or eugenol-free temporary cement and extracted 24 or 48 h after the treatment. Expression ratio and staining intensity of CAMs, including E-selectin, P-selectin, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and platelet endothelial cell adhesion molecule 1 (PECAM-1), was investigated in the pulp samples. The assessment of immunohistochemical reactions was performed by 2 independent observers using a semiquantitative scale.

RESULTS

Significant reductions were recorded in the expression ratio and/or the staining intensity of E-selectin, ICAM-1, and VCAM-1 in samples removed 48 h after treatment with eugenol-containing cement compared with intact teeth. This reduction was significant only for ICAM-1 for 48-h eugenol-free samples. Moreover, the eugenol-free cement group indicated considerably higher E-selectin, ICAM-1, and VCAM-1 expression compared with the eugenol-containing group (P < .005) 48 h after the application. The PECAM-1 reactivity was similar for all of the experimental groups.

CONCLUSION

Application of temporary luting cements after tooth preparation for full crown causes alterations in the expression of endothelial CAMs in the dental pulp.

Immunohistochemical evaluation of endothelial cell adhesion molecules in human dental pulp: effects of tooth preparation and adhesive application

OBJECTIVE

Studies have demonstrated that restorative procedures can initiate pulpal inflammation. Adhesion molecules on endothelial cells mediate the leukocyte-endothelium interaction, which is the fundamental event of inflammation. The aim of this study was to evaluate possible changes in the endothelial cell adhesion molecules (CAMs) of human dental pulp with tooth preparation, and after the application of one-step self-etch adhesive.

MATERIALS AND METHODS

Twenty healthy human premolars and third molars scheduled to be extracted for orthodontic reasons were randomly assigned to four experimental groups. Group 1 involved sound intact teeth representing the controls. In group 2, teeth were prepared for full crown and extracted within 2h. Groups 3 and 4 comprised the teeth coated with one-step self-etch adhesive, iBond Gluma inside following the preparation and extracted after 24 and 48h, respectively. Tissue distribution and staining intensity of CAMs including E-selectin, P-selectin, ICAM-1, VCAM-1 and PECAM-1 was investigated in the pulp samples using monoclonal antibodies and the streptavidin-biotin-horse-radish immunoperoxidase procedure. The assessment of immunohistochemical reactions was performed by two independent observers using a semi-quantitative scale.

RESULTS

All the CAMs evaluated were expressed by the healthy pulp tissues. Significant alterations in the distribution and staining intensity of CAMs were detected following tooth preparation. One-step self-etch adhesive tested in the present study induced inflammatory reactions in the pulp (P<0.05, Mann-Whitney U-test).

CONCLUSION

It seems evident that tooth preparation for full crown and application of one-step self-etch adhesive on prepared teeth had a potential to interfere with the inflammatory response.

Antimicrobial properties of nanocrystalline tetracalcium phosphate cements

The antimicrobial properties of cements prepared from mechanically activated tetracalcium phosphate (maTTCP) were tested with the agar diffusion test using Streptococcus salivarius, Staphylococcus epidermidis, and a clinically isolated plaque mixture. All maTTCP cements showed a significantly higher antimicrobial potency as revealed by inhibition zones of approximately 3-5 mm width, compared with a commercial Ca(OH)(2)//salicylate cement which only produced small inhibition zones around the cement specimens of 1.5 mm or less. This behavior was explained by the formation of amorphous Ca(OH)(2) during setting of maTTCP cements, which is thought to have a higher solubility and may release more OH(-) ions than conventional Ca(OH)(2)//salicylate cements. In fact, the pH value in the agar gel around the specimens was higher in the case of maTTCP cements (7.8-8.7) compared with the Ca(OH)(2)//salicylate control (7.0-8.0). The maTTCP cements did not affect the photoactivation of resin-based composites, and their antimicrobial activity is making them interesting candidates for the use as pulp-capping agents, endodontic sealers, or cavity liners in dentistry.

The effect of cavity preparation on substance P expression in human dental pulp

Substance P (SP) plays an important role during neurogenic inflammation of dental pulp. The purpose of this study was to use a radioimmunoassay for determining the effect of cavity preparation on SP expression in healthy human dental pulp. Ten pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic reasons. Deep cavity preparation (<1 mm remaining dentine thickness) was performed before extraction in five of these bicuspids. All samples were processed and I-SP labeled; SP was quantified by competition assay. The results revealed SP expression in all human pulp samples. Mann-Whitney's U test revealed statistically significant higher expression in pulp from teeth where cavity preparation had been performed compared to control values (p < 0.05). These findings suggest that SP is released during common dental procedures (such as cavity preparation) and its expression may have an important clinical significance in terms of experiencing inflammation and pain.

Dental pulp stem cells

Postnatal stem cells have been isolated from a variety of tissues. These stem cells are thought to possess great therapeutic potential for repairing damaged and/or defective tissues. Clinically, hematopoietic stem cells have been successfully used for decades in the treatment of various diseases and disorders. However, the therapeutic potential of other postnatal stem cell populations has yet to be realized, because of the lack of detailed understanding of their stem cell characteristics at the cellular and molecular levels. Furthermore, there is limited knowledge of their therapeutic value at the preclinical level. Therefore, it is necessary to develop optimal strategies and approaches to overcome the substantial challenges currently faced by researchers examining the clinical efficacy of different postnatal stem cell populations. In this review, we introduce methodologies for isolating postnatal stem cells from human dental pulp and discuss their potential role in tissue regeneration.

Antimicrobial potency of alkali ion substituted calcium phosphate cements

Potassium and sodium containing nanoapatite cements were produced by the reaction of mechanically activated CaNaPO(4) (CSP), CaKPO(4) (CPP) and Ca(2)KNa(PO(4))(2) (CPCP) with a 2.5% Na(2)HPO(4) solution. The cements exhibited clinically acceptable setting times of approximately 5 min and compressive strengths of 5-10 MPa. The antimicrobial properties of the cements were tested with the agar diffusion test using Streptococcus salvarius, Staphylococcus epidermis and Candida albicans. All types of alkali ion containing cements showed a significantly higher antimicrobial potency with inhibition zones of approx. 4-11 mm than a commercial calcium hydroxide cement which resulted in small inhibition zones around the cement samples of a maximum of 1.5 mm. The antimicrobial properties of all the cements were not found to diminish even after longer incubation times. This behaviour was attributed to the formation of soluble alkaline metal phosphates during setting which increased the pH value in the agar gel around the alkali containing calcium phosphate cement to 8.5-10.7 compared to 6.5-8.0 for the Ca(OH)(2) product. The high antimicrobial potency of alkali-calcium phosphate cements may find an application in dentistry as pulp capping agents, root fillers or cavity liners.

Effects of Multiple Dentinal Lesions on the Rat Pulp

The purpose of this study was to compare the effects of single and multiple dentinal lesions on the dental pulps of rats. 3H-proline was used to measure pulpal reactionary dentin deposition, and 3H-thymidine was used to measure pulpal cell proliferation by radioautography. Data were compared by factorial analysis of variance and a post-hoc Tukey test. A significant increase in radiolabeled collagenous proteins within reactionary dentin and pulpal cell labeling indices were evident coincident to single dentinal injuries, compared with controls (p < 0.001). After double injuries, the radiolabeled collagenous proteins within reactionary dentin and the pulpal labeling indices remained significantly greater than in controls (p < 0.01); however, each was significantly less than after single injuries (p < 0.05). These data suggest that pulpal cell proliferation and collagenous protein deposition into reactionary dentin are decreased subsequent to a previous dentinal injury. Thus, the healing potential of the dental pulp could be decreased by recent tooth cavity preparation.

Nanocrystalline tetracalcium phosphate cement

Calcium hydroxide cements can lack long-term stability and achieve sustained release by matrix-controlled diffusion of hydroxyl ions. Tetracalcium phosphate (TTCP) hydrolyzes slowly to form calcium hydroxide and a thin insoluble apatite layer that prevents further reaction. In this study, mechanical amorphization was used to create a setting calcium-hydroxide-releasing cement from TTCP. The effect of high-energy ball milling of TTCP on the mechanical properties of the cement was investigated. X-ray diffraction data were used to determine the phase composition of the set cements. An accelerated in vitro test compared pH of water after prolonged boiling of nanocrystalline TTCP cements and a calcium salicylate material. As milling time increased, cement compressive strength and degree of conversion increased. Hydroxyl ion release from the cement was comparable with that from a calcium salicylate material. This new cement system offers the antimicrobial potential of calcium salicylate materials combined with the long-term stability of insoluble apatite cements.

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.

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).

CELLS AND EXTRACELLULAR MATRICES OF DENTIN AND PULP: A BIOLOGICAL BASIS FOR REPAIR AND TISSUE ENGINEERING

Odontoblasts produce most of the extracellular matrix (ECM) components found in dentin and implicated in dentin mineralization. Major differences in the pulp ECM explain why pulp is normally a non-mineralized tissue. In vitro or in vivo, some dentin ECM molecules act as crystal nucleators and contribute to crystal growth, whereas others are mineralization inhibitors. After treatment of caries lesions of moderate progression, odontoblasts and cells from the sub-odontoblastic Höhl's layer are implicated in the formation of reactionary dentin. Healing of deeper lesions in contact with the pulp results in the formation of reparative dentin by pulp cells. The response to direct pulp-capping with materials such as calcium hydroxide is the formation of a dentinal bridge, resulting from the recruitment and proliferation of undifferentiated cells, which may be either stem cells or dedifferentiated and transdifferentiated mature cells. Once differentiated, the cells synthesize a matrix that undergoes mineralization. Animal models have been used to test the capacity of potentially bioactive molecules to promote pulp repair following their implantation into the pulp. ECM molecules induce either the formation of dentinal bridges or large areas of mineralization in the coronal pulp. They may also stimulate the total closure of the pulp in the root canal. In conclusion, some molecules found in dentin extracellular matrix may have potential in dental therapy as bioactive agents for pulp repair or tissue engineering.

Class II antigen-presenting dendritic cell and nerve fiber responses to cavities, caries, or caries treatment in human teeth

Major histocompatibility complex (MHC) class II molecule-expressing cells are distributed in human dental pulp, and have been shown to accumulate beneath caries lesions. The responses of these cells and nerve fibers were analyzed under 5 different clinical conditions: shallow and deep experimental cavities, active and slow untreated caries, and treated caries. Under deep cavities, class II molecule-expressing dendritic cells displaced the injured odontoblasts during a period of one month, while such a response was not observed in shallow cavities and untreated or treated carious teeth. The class II molecules seen in the neural elements under active caries were no longer detectable in treated carious teeth. However, six months after treatment, clusters consisting of dendritic cells, T-lymphocytes, and nerve fibers still remained locally in the subodontoblastic area. These results indicate that dental pulps respond differently to cavity preparation and restoration between normal and caries conditions, and that immunoresponses persist for many months, even after caries treatment.

Remaining dentine thickness and human pulp responses

AIM

To evaluate pulp responses as a function of remaining dentine thickness (RDT) of 98 class V cavity preparations in 49 teeth of 31 patients aged 10-16 years.

METHODOLOGY

Shallow cavities were restored with amalgam, deeper cavities or pulp exposures were restored with amalgam lined with calcium hydroxide or with zinc oxide eugenol. Teeth were extracted after 3-89 days for orthodontic reasons. Following processing for light microscope analysis, the number of odontoblasts, pulp inflammation, and repair was recorded.

RESULTS

In comparison with independent odontoblasts, the numbers of odontoblasts were reduced by 13.6% beneath a RDT of 2.5-0.5 mm, 33.7% beneath a RDT of 0.5-0.01 mm and 99.0% beneath pulp-exposed cavities. Reparative dentine was observed following pulp exposure and reactionary dentine was observed with a mean RDT of 0.77 mm (2.5-0.01 mm). Reactionary dentine secretion was influenced by RDT and restorative materials. Pulp inflammation was not influenced by RDT in the present study.

CONCLUSIONS

Cavity RDT mediates a powerful influence on underlying pulp tissue vitality but it has little effect on reactionary dentine secretion and inflammatory activity. Gross tissue injury explains the poor pulp capping prognosis following exposure and underlies the need to avoid this type of injury. Following restoration, a RDT of 0.5 mm or greater is necessary to avoid evidence of pulp injury.

Analysis of incisor pulp cell populations in Wistar rats of different ages

Pulp cell function and viability is important for maintaining tooth vitality throughout life. However, the effects of ageing on pulpal cell populations and pulp tissue remodelling are still unclear. The aim here was to quantify age-related cell-density changes in the pulp of rat incisor teeth, using histomorphometric analysis and ANOVA. Mandibular (n=35) and maxillary (n=34) incisors were carefully extracted from 20 Wistar rats aged between 1 and 18 months, fixed and processed for light microscopy. Cell counts were performed in mature and immature regions at both labial and lingual aspects of all teeth. Odontoblast and subodontoblast cell densities were reported per mm of pulp-dentine border and core fibroblast density per mm2 pulp tissue. Irrespective of age, odontoblast and subodontoblast densities were lower in the immature than the mature regions of both maxillary and mandibular incisors (P<0.001). However, in both regions odontoblast and subodontoblast densities decreased significantly with increasing age (P<0.0001). The age-related reduction in odontoblasts was significantly greater in mature than immature regions (P<0.02) but not influenced by other variables. In contrast, the age-related reduction in subodontoblasts was significantly different between mandibular and maxillary teeth (P=0.012) but not influenced by site. Unlike odontoblasts and subodontoblasts, core fibroblasts showed small but significant increases with increasing age (P<0.0001). These age-related reductions in the density of odontoblasts and subodontoblasts may partly explain the slower rate of secondary dentine secretion and decreased pulp repair activity associated with ageing.

Hierarchy of variables correlated to odontoblast-like cell numbers following pulp capping

OBJECTIVES

Following tooth pulp exposure, pulpal repair is accomplished by dentine bridge secretion by odontoblast-like cells. However, little information is available about the hierarchy of variables, which influence odontoblast-like cell numbers. The purpose of this study was to examine correlations between pulp capping events and odontoblast-like cell numbers.

METHODS

Two hundred and fifty standardised pulp exposed cavities were prepared in non-human primate teeth according to ISO usage guidelines. Exposed pulps were capped with Calcium hydroxide [Ca(OH)(2)], and multi-step and self-etching primer composite resins. Teeth were collected from 3 to 60-days to observe pulp reactions. Statistical analysis was evaluated using analysis of variance.

RESULTS

The hierarchy of variables correlated to odontoblast-like cells were the dentine bridge area (P = 0.0001), time since pulp exposure (P = 0.0001), odontoblast numbers opposite the exposure site (P = 0.0002), and pulp capping materials (P = 0.0313). Other pulp capping variables were found to be less likely to be correlated with odontoblast-like cell numbers.

CONCLUSIONS

The area of dentine bridge formation is directly related to the numbers of odontoblast-like cells, cell activity is time dependent, and the cell numbers are much lower than original odontoblast cells. The time-lag between the appearance of odontoblast-like cells at the site of pulp exposure, and the limited numbers of these cells, explain why pulpal repair is difficult to achieve successfully following pulp exposure.