Research
The microbiology laboratory in the Department of Endodontology is directed by Dr. J. Craig Baumgartner. Our laboratory has been fortunate to have Dr. Kwang-Shik Bae, an associate professor from Seoul National University, Seoul, Korea for two years; and Dr. Tian Xia an associate professor, Department of Oral and Maxillofacial Surgery, West China University of Medical Sciences, Chengdu, Sichuan, PR China for two years. In addition, Bev Watkins, a microbiologist and Dr. Larry David, a biochemist at OHSU School of Dentistry, have made significant contributions to the lab.
The studies in our state-of-the-art anaerobic laboratory have progressed from basic cultivation of microorganisms associated with endodontic infections to the use of molecular methods to detect the presence of specific strains of bacteria and even specific virulence factors. We have recently cultivated and sequenced the 16 S RDNA gene of bacteria named Prevotella tannerae.
Antimicrobial efficacy of the EndoVac compared to needle irrigation
Todd Miller, DDS, J. Craig Baumgartner, DDS, PhD
The purpose of this investigation was to compare the antimicrobial efficacy of irrigation with the EndoVac® versus needle irrigation in the apical 5mm of roots infected with Enterococcus faecalis. Bilaterally matched, extracted human teeth were sterilized and inoculated with E. faecalis. Specimens from Group A were irrigated using the EndoVac system, while those in Group B were irrigated with a 30 gauge side vented needle. Following chemomechanical preparation, the root ends were resected and pulverized in liquid nitrogen to expose E. faecalis in dentinal tubules or other recesses away from the main root canal system. The number of colony forming units (cfu) of E. faecalis per mg was determined from the pulverized root ends. Irrigation with EndoVac (Group A) had a mean of 31.6 cfu/mg and needle irrigation (Group B) had a mean of 157 cfu/mg. This represents a bacterial reduction of 99.7% in Group A and 98.8% in Group B when compared to positive controls. Although there was no statistically significant difference between Group A and Group B, there was a trend towards fewer cfu/mg when using the EndoVac®.
Comparison of push-out bond strengths of Resilon with 3 different sealers
Danielle Stiegemeier, J. Craig Baumgartner, Jack Ferracane
The purpose of this study was to evaluate the push-out bond strengths of different obturating materials. 40 single rooted human extracted teeth were used in this study. Teeth were cleaned and shaped using 5.25% NaOCl, 15% EDTA and sterile water as irrigants. The teeth were then filled with Resilon and RealSeal, Resilon and RealSeal SE, Resilon and MetaSeal, or gutta-perch and Kerr EWT sealer. The roots were then sectioned into 1mm thick slices and subjected to compressive loading to displace the obturating material toward the coronal side of the slice. The bond strength was then calculated and subjected to statistical analysis. Slices were examined under stereomicroscope at 10x power to determine mode of failure. The push-out bond strengths of MetaSeal and gutta-percha with Kerr EWT were statistically significantly higher than either RealSeal or RealSeal SE. MetaSeal and gutta-percha with Kerr EWT did not differ significantly.
INFLAMMATION-INDUCED REGULATION OF BDNF EXPRESSION IN RAT TRIGEMINAL GANGLION NEURONS.
Leila Tarsa*, J. Craig Baumgartner and Agnieszka Balkowiec. Department of Integrative Biosciences, Department of Endodontics, Oregon Health & Science University School of Dentistry, Portland, OR.
Our recent studies show that the neurotrophin brain-derived neurotrophic factor (BDNF) is (1) expressed by adult trigeminal ganglion (TG) neurons, (2) present in axons and axon terminals in the subnucleus caudalis of the spinal trigeminal nucleus, the major central target of trigeminal nociceptors, and (3) released from TG neurons by electrical stimulation in vitro. These data suggest that BDNF plays a role in activity-dependent plasticity of trigeminal nociceptive pathways, which provide sensory information from several clinically relevant structures, such as the meninges, temporo-mandibular joint (TMJ) and teeth. From the clinical standpoint, one of the most important forms of plasticity is chronic inflammatory pain. Therefore, we have begun testing the hypothesis that BDNF is a mediator of functional changes that take place in trigeminal nociceptive pathways during chronic inflammation. We are examining whether inflammatory stimulation of peripheral endings of trigeminal nociceptors leads to upregulation of BDNF expression in TG neurons. For these studies, we use 3-week-old Sprague Dawley rats, in which the right-side maxillary first and second molars are drilled to expose tooth pulp in order to evoke inflammation by contact with mouth flora. Following 7 or 14 days, TGs and maxillae are dissected from paraformaldehyde-perfused animals, and processed for BDNF immunohistochemistry and histological evaluation of tooth inflammation, respectively. In the in vitro portion of the study, we are focusing on cellular mechanisms underlying upregulation of BDNF expression in TG neurons during inflammation. Newborn TG neurons are grown for 3 days in the presence or absence of well-established inflammatory mediators, interleukin-1b (IL-1b) and interleukin-6 (IL-6). Our data indicate that IL-6, but not IL-1b, dramatically increases the number of BDNF-immunoreactive TG neurons. Our study suggests that BDNF is a candidate molecular mediator of activity-dependent changes in trigeminal nociceptive pathways following inflammation.
Supported by NIH, HL-076113 grant to A.B.
GUTTA-PERCHA OBTURATION OF LATERAL GROVES AND DEPRESSIONS USING WARM VERTICAL COMPACTION, THERMAFIL® PLUS OBTURATORS, AND GT® OBTURATORS
Ryan M. Lavene, DDS, J. Craig Baumgartner, DDS, PhD & J. Gordon Marshall DMD
The purpose of the study was to compare the flow of gutta-percha using warm vertical compaction, Thermafil® Plus Obturators, and GT® Obturators into lateral grooves and depressions in the apical 7 mm of the root canal system. A split-tooth model was used with a maxillary canine with artificial lateral grooves and depressions prepared in the canal at 1, 3, 5, and 7 mm from working length. Obturations were performed by warm vertical compaction of gutta-percha and Roth 801 sealer using the Elements Obturation Unit (Sybron Endo, Orange, CA) or the DownPak (Hu-Friedy, Chicago, IL) inserting the plugger tip 3, 4, or 5 mm from working length. Thermafil® Plus (Dentsply, Tulsa, OK) and GT® Obturators (Dentsply, Tulsa, OK) with ThermaSeal® Plus sealer were also evaluated as obturating techniques. The Elements Obturation Unit and the DownPak resulted in similar movement of gutta-percha into lateral grooves and depressions except at the 1 mm level where the Elements Obturation Unit performed significantly better than the DownPak when the plugger was inserted 3 mm from working length. Thermafil and GT Obturators showed excellent flow of gutta-percha into lateral grooves and depressions but extended past the root-end 60% and 30% of the time, respectively.
ANTIMICROBIAL EFFICACY OF IRRIGATION WITH THE ENDOACTIVATOR
Michael Wheatley DDS, J. Craig Baumgartner, DDS, PhD
The purpose of this investigation was to compare the antimicrobial efficacy of irrigation with the EndoActivator versus no irrigant activation in the apical 5mm of roots infected with Enterococcus faecalis. Bilaterally matched human teeth were sterilized and inoculated with E. faecalis. Following chemomechanical root canal preparation, the root-ends were resected and pulverized in liquid nitrogen to expose E. faecalis in dentinal tubules or other recesses away from the main root canal system. The number of colony forming units (CFU) of E. faecalis per mg was determined from the pulverized root-ends. Group A had a mean of 1.74 X 103 cfu/gm and Group B had a mean of 9.37 X 102 cfu/gm. This represents a bacterial reduction of 98.7% in Group A and 99.3% in Group B when compared to positive controls. There was no statistically significant difference between Group A and Group B but the difference was significant between Group A and control and Group B and control. The trend was towards fewer cfu/gm when using the EndoActivator but the difference was not significant.
MICROBIAL LEAKAGE OF ROOTS FILLED WITH RESILON
David Wilson, DDS Craig Baumgartner, DDS, PhD J Gordon Marshall, DMD.
Resilon has been introduced as a promising root canal filling material. The purpose of this in vitro study was to evaluate bacterial leakage in teeth obturated with either Resilon or gutta-percha/Kerr EWT using warm vertical compaction. Twenty-three bilaterally matched pairs of single-rooted human teeth were instrumented to an ISO #40/.04 taper and obturated with either Resilon or gutta-percha. Teeth were placed into a split chamber model, subjected to polymicrobial leakage, and observed for turbidity in the lower chamber for 112 days. The failure rate of each material was statistically evaluated using a two-tailed t test for differences between proportions (p<0.05). Twelve out of 23 (52%) of the Resilon and 19 out of the 23 (83%) of the gutta-percha groups demonstrated bacterial leakage over the 112-day period. Differences between gutta-percha and Resilon were statistically different with a P value of 0.028.
Comparison of the EndoVac irrigation system and needle root canal irrigation
John Johnson, DDS & J. Craig Baumgartner, DDS, PhD
Rotary instruments have shown success in enlarging canal space while maintaining original canal shape, and sodium hypochlorite has been shown to dissolve pulp tissues and disinfect the canal space. However, several studies have demonstrated that significant amounts of debris and bacteria can remain in the apical third of the canal system, which may contribute to treatment failure. The EndoVac system is a new product designed to deliver irrigants safely and effectively throughout the root canal system, including the apical third. The purpose of this in vivo study is to compare the EndoVac system and conventional irrigation techniques to effectively debride the apical third of the root canal. Eleven matched pairs of anterior teeth were studied, half irrigated with the EndoVac system, and half with needle root canal irrigation. Results indicated there was no difference in remaining debris between the two techniques at 1 and 3 mm from the apex. The EndoVac system appears to be able to provide cleaning similar to conventional irrigation syringes, while minimizing the potential of NaOCl accidents.
