Kenneth N. Namerow

Comparison between a Novel Nickel-Titanium Alloy and 508 Nitinol on the Cyclic Fatigue Life of ProFile 25/.04 Rotary Instruments

ProFile 25/.04 instruments manufactured from three variants of Nitinol (1A, 1B & 2AS) were compared with stock production ProFile 25/.04 instruments and fatigue tested to failure. Cyclic fatigue testing was performed by rotating instruments at 300 RPM in a simulated steel root canal with 5 mm radius and 90 degrees curve until instrument separation. Time to failure was recorded. Torsion testing was undertaken by clamping 3 mm of each instrument tip between brass plates and rotating it at 2 RPM until failure. Data were recorded for torque and angle at fracture. Statistical differences were found with nickel-titanium variant 1B (M-Wire NiTi) nearly 400% more resistant to cyclic fatigue than stock ProFile 25/.04 (P < .001). Torsion testing found differences between all 508 Nitinol groups and M-Wire NiTi (P < .001). ProFile 25/.04 files manufactured from M-Wire NiTi have significantly greater resistance to cyclic fatigue while maintaining comparable torsional properties.

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.

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.

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.

A Practitioner Survey of Opinions Toward Regenerative Endodontics

The success of regenerative endodontic procedures requires practitioner acceptance, but little or no evidence is available. The purpose of this survey was to collect the opinions of attendees of the 2008 Endodontic Board of Diplomates 2008 Summer Conference on the issue of regenerative endodontic procedures (REPs). After Nova Southeastern University institutional review board approval, 100 copies of a survey were circulated, and 56 completed surveys were returned anonymously. The survey found that 96% of participants thought that more regenerative therapies should be incorporated into treatments. Although only 14% of participants had used umbilical cord or stem cell banking for themselves or a relative, 63% thought that stem cell banking would be useful to regenerate dental tissues. Most (89%) of the participants would be willing to save teeth and dental tissues for stem cell banking. These results suggest that endodontic practitioners are supportive and optimistic about the future use of REPs.

Effect of aquatine endodontic cleanser on smear layer removal in the root canals of ex vivo human teeth

Objectives The purpose of this study was to measure and compare the root canal cleanliness and smear layer removal effectiveness of Aquatine Endodontic Cleanser (Aquatine EC) when used as an endodontic irrigating solution in comparison with 6% sodium hypochlorite (NaOCl). Material and Methods Forty-five human teeth were randomly allocated to five treatment groups; the pulp chamber was accessed, cleaned, and shaped by using ProTaper and ProFile rotary instrumentation to an ISO size #40. The teeth were then processed for scanning electron microscopy, and the root canal cleanliness and removal of smear layer were examined. Results The most effective removal of smear layer occurred with Aquatine EC and NaOCl, both with a rinse of EDTA. Conclusions Aquatine EC appears to be the first hypochlorous acid approved by the FDA to be a possible alternative to the use of NaOCl as an intracanal irrigant. Further research is needed to identify safer and more effective alternatives to the use of NaOCl irrigation in endodontics.

A Survey of Dental Residents’ Expectations for Regenerative Endodontics

INTRODUCTION The objective was to survey a group of dental residents regarding their expectations for using regenerative endodontic procedures as part of future dental treatments. METHODS After institutional review board approval, the opinions of 32 dentists who were having postgraduate residency training to become specialists in a dental school were surveyed. The survey had 40 questions about professional status, ethical beliefs, judgment, and clinical practice. RESULTS It was found that 83.9% of dentists had no continuing education or training in stem cells or regenerative endodontic procedures. Results showed that 96.8% of dentists are willing to receive training to be able to provide regenerative endodontic procedures for their patients. Of the total group, 49.1% of dentists already use membranes, scaffolds, or bioactive materials to provide dental treatment. It was determined that 47.3% of dentists agree that the costs of regenerative procedures should be comparable with current treatments. It was also found that 55.1% of dentists were unsure whether regenerative procedures would be successful. CONCLUSIONS Dentists are supportive of using regenerative endodontic procedures in their dental practice, and they are willing to undergo extra training and to buy new technology to provide new procedures. Nevertheless, dentists also need more evidence for the effectiveness and safety of regenerative treatments before they will be recommended for most patients.