Peter E. Murray

Recommendations for using regenerative endodontic procedures in permanent immature traumatized teeth.

The regeneration of immature permanent teeth following trauma could be beneficial to reduce the risk of fracture and loss of millions of teeth each year. Regenerative endodontic procedures include revascularization, partial pulpotomy, and apexogenesis. Several case reports give these procedures a good prognosis as an alternative to apexification. Care is needed to deliver regenerative endodontic procedures that maintain or restore the vitality of teeth, but which also disinfect and remove necrotic tissues. Regeneration can be accomplished through the activity of the cells from the pulp, periodontium, vascular, and immune system. Most therapies use the hosts own pulp or vascular cells for regeneration, but other types of dental stem cell therapies are under development. There are no standardized treatment protocols for endodontic regeneration. The purpose of this article is to review the recent literature and suggest guidelines for using regenerative endodontic procedures for the treatment of permanent immature traumatized teeth. Recommendations for the selection of regenerative and conventional procedures based on the type of tooth injury, fracture type, presence of necrosis or infection, periodontal status, presence of periapical lesions, stage of tooth development, vitality status, patient age, and patient health status will be reviewed. Because of the lack of long-term evidence to support the use of regenerative endodontic procedures in traumatized teeth with open apices, revascularization regeneration procedures should only be attempted if the tooth is not suitable for root canal obturation, and after apexogenesis, apexification, or partial pulpotomy treatments have already been attempted and have a poor prognosis.

The Comparison of the Effect of Endodontic Irrigation on Cell Adherence to Root Canal Dentin

The purpose of this study was to compare the effect of 10 different endodontic irrigation and chelating treatments on dental pulp stem cell (DPSC) attachment to root canal surfaces. Thirty-eight extracted human nondiseased single-canal teeth were cleaned and shaped using ProTaper and ProFile rotary instrumentation (Tulsa Dentsply, Tulsa, OK). The irrigation treatments investigated were 6% sodium hypochlorite, 2% chlorhexidine gluconate, Aquatine Endodontic Cleanser, and Morinda citrifolia juice. The irrigation treatments were used in conjunction with EDTA or MTAD. The instrumented teeth were immediately placed in cell culture with confluent DPSCs for 1 week. The number of attached DPSCs appeared to be correlated with the cytotoxicity of the root canal irrigating solution (analysis of variance, p < 0.0001). The presence or absence of the smear layer had little influence on DPSC activity (chi-square, p > 0.05). The results suggest that biocompatible irrigants are needed to promote DPSC attachment to root canal dentin, which is essential to accomplish some regenerative endodontic therapies.

Dental pulp stem cell migration.

INTRODUCTION The purpose of this in vitro study was to investigate the migration of dental pulp stem cells (DPSCs) in response to chemotactants and extracellular matrix proteins (EMPs). This DPSC signaling information is needed to help understand tooth regeneration after injury and to develop some future regenerative endodontic therapies. METHODS DPSCs were released by trypsinization and plated on transwell filters. The chemotactants were recombinant sphingosine-1-phosphate (S1P), fibroblast growth factor (FGF), epidermal growth factor (EGF), or transforming growth factor beta-1 (TGF-β1), and the EMPs were collagen-1, collagen-IV, laminin, and fibronectin. Data were analyzed by using analysis of variance (ANOVA) statistical tests for cell migration. RESULTS S1P induced more vigorous DPSC migration in comparison with the other TGF- β1, FGF, or EFG chemotactants (ANOVA, P < .05). Laminin induced more vigorous DPSC migration in comparison with the other EMPs (ANOVA, P < .05). CONCLUSIONS The EMPs, particularly laminin, and chemotactants, particularly S1P and TGF-β1, were found to be important promoters of DPSC migration. The interplay between the EMPs, blood lipid, serum, and chemotactants suggests that the migration of DPSC is highly regulated. Specific chemotactants and EMPs might mediate the process of pulp-dentin regeneration after tooth injury, and they could be used as part of regenerative endodontic therapy.

Cell Survival within Pulp and Periodontal Constructs

The purpose of this study was to measure cell survival and degradation within tissue-engineered dental constructs. Dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PLSCs) were seeded on three types of tissue engineering scaffolds: a synthetic open-cell D,D-L,L-polylactic acid (polymer) scaffold, a bovine collagen scaffold (collagen), and a calcium phosphate bioceramic (calcium phosphate) scaffold. The dental pulp and periodontal constructs (n = 144) were maintained in cell culture for between 3 and 14 days. The cell survival and degradation within the constructs were measured using histologic criteria. The DPSC and PLSC survival was optimal in the polymer and collagen constructs but not the calcium phosphate constructs, especially over longer time periods. These in vitro results suggest that both the polymer and collagen scaffolds and the DPSCs and PLSCs can be combined to create pulp and periodontal constructs for use in future regenerative dental treatments.

Anesthetic Efficacy of the Gow-Gates Injection and Maxillary Infiltration with Articaine and Lidocaine for Irreversible Pulpitis

The aim of this randomized, double-blinded study was to compare the anesthetic efficacy of 4% articaine with 1:100,000 epinephrine (AE) with 2% lidocaine with 1:100,000 epinephrine (LE) for Gow-Gates blocks and maxillary infiltrations in patients experiencing irreversible pulpitis in mandibular and maxillary posterior teeth. Forty patients diagnosed with irreversible pulpitis of a posterior tooth randomly received either AE or LE by using a Gow-Gates injection or maxillary infiltration. Endodontic access was initiated after no response to Endo-ice 15 minutes after solution deposition. Success was defined as none to mild pain on a visual analogue scale after access. Chi-square and analysis of variance statistical tests were used to analyze the data. Successful endodontic treatment substantially reduced the assessment of pulpitis pain by patients (analysis of variance, P < .0001). Overall anesthetic success in both dental arches was 87.5%. Anesthetic success was not influenced by tooth arch (chi(2), P > .7515) or gender (chi(2), P > .1115). AE proved to be as effective but not superior to LE (P > .6002). These results demonstrated the similar anesthetic effectiveness of AE and LE when used during the endodontic treatment of teeth diagnosed with irreversible pulpitis.

Stem cell responses in tooth regeneration

Scientific advances in the creation of restorative biomaterials, in vitro cell culture technology, tissue grafting, tissue engineering, molecular biology, and the human genome project provide the basis for the introduction of new technologies into dentistry. This review is intended to facilitate the development of stem cell therapy for use with established therapeutic modalities to restore and regenerate oral tissues. Teeth have been shown to mineralize in response to injury for many decades, but only in recent years has the position of the stem cells been localized around blood vessels. The cells have been identified as myofibroblastoid pericytes. The ability to control the differentiation and proliferation of these cells is being examined to create stem cell therapies that can solve dental problems more effectively than current treatment regimes. Although the problems of introducing these technologies are substantial, the potential benefits to patients and the profession are equally promising - a cure for caries and diseases, a cure for oral cancer, correction of congenital defects, and the regeneration of teeth and tissues to restore oral functions. The purpose of this review is to describe how these new technologies can most usefully be employed in dentistry to enable clinicians to satisfy patient demand for a nondefective dentition.

Comparison of operative procedure variables on pulpal viability in an ex vivo model

AIM To measure and compare the responses of pulp tissue to cavity preparation and restoration variables using a novel tooth slice culture model. METHODOLOGY Experimental cavities (265) were continuously cut, under carefully controlled conditions, into the dentine of the labial aspect of 28-day-old Wistar rat incisors, and slices of these teeth maintained in organ culture for up to 2 weeks. The experimental variables examined were: the preparation method, remaining dentine thickness, coolant, drill speed, conditioning with EDTA and filling materials. The reactions of the dentine-pulp complex to the experimental variables were measured using pathohistometric analysis and the correlations between variables were determined using analysis of variance statistical tests. RESULTS In rank order of surgically induced restorative pulpal injury, from the most to the least injurious were: remaining dentine thickness, absence of coolant during cavity preparation, bur speed, cavity conditioning treatments and the filling material. CONCLUSIONS To reduce pulp injury and to promote pulpal repair activity, the correct use of appropriate materials are important. However, of relatively greater importance is the operative technique adopted, the need to avoid the excess removal of dentine and to minimize trauma during preparation.

A Scanning Electron Microscopic Evaluation of the Effectiveness of the F-file versus Ultrasonic Activation of a K-file to Remove Smear Layer

The objective of this study was to compare the effectiveness of F-files and ultrasonics to remove the smear layer from instrumented root canals when irrigated with sodium hypochlorite and EDTA. Sixty healthy human premolar teeth were instrumented with ProTaper file series to F3, and the canals were enlarged with Profiles 35/.06, 40/.06, and 45/.06. The canals were then instrumented with either the F-file or an ultrasonically activated #20 K-file with or without EDTA. The removal of smear layer was visualized using blind scanning electron microscopic micrographs. There appeared to be little difference between the F-file and the ultrasonically activated #20 K-file in removal of the smear layer with or without EDTA. The effect of ultrasonic activation appeared to be self-limiting with high-volume flushes of irrigant. It appears the F-file was not any more beneficial in removing smear layer. Conversely, smear layer removal appears to be mostly influenced by the introduction of an EDTA rinse.

Diode laser debonding of ceramic brackets

INTRODUCTION Our objective was to investigate the effectiveness of debonding ceramic brackets with a diode laser. METHODS Two types of ceramic brackets (monocrystalline and polycrystalline) were bonded to bovine maxillary central incisors. The diode laser was applied to brackets in the experimental groups for 3 seconds. Shear bond strength and thermal effects on the pulp chamber were assessed at 2 laser energy levels: 2 and 5 W per square centimeter. Analysis of variance (ANOVA) was used to determine significant differences in shear bond strength values. RESULTS The diode laser was ineffective with polycrystalline brackets and effective with monocrystalline brackets in significantly (P <0.05) lowering the shear bond strength. There were no significant adhesive remnant index score differences between any groups tested. CONCLUSIONS Diode laser use significantly decreased the debonding force required for monocrystalline brackets without increasing the pulp chamber temperature significantly. Diode lasers did not significantly decrease the debonding force required for polycrystalline brackets.

Proliferation of mature ex vivo human dental pulp using tissue engineering scaffolds.

INTRODUCTION The purpose of this study was to measure and compare the proliferation of mature human dental pulp tissue using three types of tissue engineering scaffolds. METHODS Mature human teeth were collected immediately after extraction for routine dental treatment reasons. Three types of tissue engineering scaffolds were investigated (1) open-polylactic acid (polymer) scaffolds, (2) bovine collagen (collagen) scaffolds, and (3) calcium phosphate bioceramic (calcium phosphate) scaffolds. The scaffolds were placed in direct contact with the dental pulp of the tooth slices from 7 to 30 days. Neutral-red dye was added to the culture media to stain metabolically active cells. The specimens were processed for histology. The numbers of proliferating cells were counted per unit area of scaffold according to ISO criteria. RESULTS The proliferating dental pulp cells had a fibroblast phenotype, no cells of other phenotypes were observed, and none of the cells appeared to be mineralizing. The average rate of mature vital dental cell proliferation was 1.305 cells per day in the calcium phosphate scaffolds compared with 7.195 (a rate increase of 551%) in the collagen scaffolds and 13.885 (a rate increase of 1,064%) in the polymer scaffolds. CONCLUSIONS Tissue engineering scaffolds can enhance the proliferation of mature dental pulp tissue. The rate of dental pulp proliferation is dependent on the chemical composition of the scaffold. Within the limitations of this study, the polymer scaffolds were more optimal than collagen or calcium phosphate scaffolds for mature dental pulp proliferation.