Faculty Bibliography

OBJECTIVE: The purpose of this study was to determine the composition of the microbial flora present in teeth after the failure of root canal therapy in a North American population. These results were then compared with those of the previous Scandinavian studies. STUDY DESIGN: Fifty-four root-filled teeth with persistent periapical radiolucencies were selected for retreatment. After removal of the root-filling material, the canals were sampled with paper points, and by reaming of the apical dentin. Both samples were grown under aerobic and strict anaerobic conditions. Then the bacterial growth was analyzed. RESULTS: The microbial flora was mainly of 1 to 2 strains of predominantly gram-positive organisms. Enterococcus faecalis was the most commonly recovered bacterial species. CONCLUSIONS: Bacteria were cultivated in 34 of the 54 teeth examined in the study. E faecalis was identified in 30% of the teeth with a positive culture.

This study was performed to assess if laser Doppler flowmetry (LDF) is an improved method for the detection of revascularization of replanted teeth. Teeth were extracted and reimplanted under different experimental conditions. LDF readings were taken before extraction and weekly for 3 months. In control teeth, LDF baseline readings were taken and then repeated after the apical blood vessels were cut surgically. At the end of 3 months it was determined radiographically and histologically whether revascularization had occurred, i.e. vitality had returned. RESULTS: LDF readings correctly predicted the pulp status (vital vs. non-vital) in 83.7% of the readings. 73.9% (17 of 23) were correct for the vital teeth and 95% (19 of 20) were correct for the non-vital teeth. Fisher's exact test (2-tail) indicated that there was no significant association between the efficacy of LDF and tooth type (P = 0.166), although P2 was the least accurate tooth tested. Wilcoxon's matched-pair signed rank test demonstrated that in the revascularized (vital) teeth, the flux value between the baseline and week 2 dropped significantly (P = 0.0001), increased significantly from week 2 to week 4 (P = 0.0001) and then decreased steadily until week 12. However, at week 12 the flux was still significantly higher than at week 2 (P = 0.010). In the teeth that failed to revascularize, the flux value dropped significantly by weeks 1 and 2 (P = 0.004 and P = 0.0001, respectively). Flux values did not increase from week 2. A Fast Fourier Transform (FFT) analysis confirmed a pulse of dominant frequency of 2 Hz in the teeth that returned to vitality and the lack thereof in those that stayed non-vital. One tooth in which the flux value evaluation indicated a non-vital tooth but the radiographic/histologic findings showed vital (false negative) possessed a pulse of dominant frequency and proved by this method to have successfully revascularized.

Earlier research has shown that cutaneous experimental pain can elevate the vibrotactile threshold at the same skin locus. The purpose of this study was to determine whether vibrotactile and pain thresholds in a clinical (temporomandibular disorders [TMD]) population are consistent with the hypothesis that chronic pain causes a similar elevation. Specifically, we predicted that TMD subjects with soreness (low palpation-pain threshold) at a given skin site would have relatively high vibrotactile thresholds at the same location. Measurements on the skin overlying the masseter in 18 individuals with TMD showed that pain sensitivity was negatively correlated with sensitivity to 20-Hz vibration (presumed to activate a rapidly adapting mechanoreceptive channel), but not with sensitivity to 200-Hz vibration (thought to activate primarily a slowly adapting channel, because the Pacinian channel is lacking in the orofacial region). There was no relationship between vibration thresholds over the masseter and pain threshold at other orofacial sites, including the contralateral masseter. Vibrotactile and pain thresholds were uncorrelated in control participants without chronic pain (n = 18). The results indicate that in TMD, a localized relationship exists between pain sensitivity and the sensitivity of a low-frequency vibrotactile channel.

The purpose of this study was to evaluate the extent of bacterial reduction with nickel-titanium rotary instrumentation and 1.25% NaOCl irrigation. Also, the additional antibacterial effect of calcium hydroxide for >1 wk was tested. Forty-two subjects with radiographic and clinical signs of chronic apical periodontitis were recruited. The canals were sampled before treatment, during and after instrumentation, and after treatment with calcium hydroxide and the samples incubated anaerobically for 7 days at 37 degrees C. The bacteria from each sample were quantified and the log10 values were used for calculations and comparisons. The initial sample confirmed infection of the canals. There was a significantly greater pattern of reduction of bacteria when NaOCl was used as an irrigant, compared with sterile saline (p < 0.05). After instrumentation with NaOCl irrigation, 61.9% of canals were rendered bacteria-free. The placement of calcium hydroxide for at least 1 wk rendered 92.5% of the canals bacteria free. This was a significant reduction, compared with NaOCl irrigation alone (p = 0.0001). The results of this study indicate that NaOCl irrigation with rotary instrumentation is an important step in the reduction of canal bacteria during endodontic treatment. However this method could not consistently render canals bacteria-free. The addition of calcium hydroxide intracanal medication should be used to more predictably attain this goal.