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Week of December 10, 2003 |
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Title: Evaluation of cytotoxicity of MTAD using the MTT-Tetrazolium method Author: Zhang, Torabinejad, and Li Journal: JOE, vol. 29 (10) October 2003 Reviewer: Michael Moreno, D.M.D. Purpose: The purpose of this study was to test the cytotoxicity of MTAD compared with that of currently used irrigants and medications. Materials and Methods: Test materials included: eugenol, 3% hydrogen peroxide, 5.25% NaOCl, REDTA, Peridex, Pulpdent paste, and MTAD. Four concentrations of NaOCl were evaluated for cytotoxicity (5.25%, 2.63%, 1.31%, and 0.66%). L929 fibroblasts were grown in Eagle’s medium and test materials were added at specified concentrations ranging from 10 to 50,000 ug/ml. Cytotoxicity of test materials were evaluated after a 24h incubation period by determining the absorbance of each well using the Biorad Benchmark microplate reader at 570 nm. In addition the cytotoxicity of test materials was compared using the 50% inhibitory dose (ID50) of each material. Results: Dose-related curves were generated by plotting the percentage inhibition of cell proliferation at each dose tested. All test materials induced a dose related inhibition effect on L929 cells. The cytotoxicity of NaOCl decreased as its concentration was reduced. The ID50 of MTAD was significantly higher than those of eugenol and 3% H2O2, lower than that for 1.31% and 0.66% NaOCl, and comparable to Peridex, REDTA, 5.25% and 2.63% NaOCl, and Pulpdent. MTAD is less cytotoxic than REDTA, Peridex, 5.25% NaOCl, and Pulpdent. The least cytotoxic material was 0.66% NaOCl. Conclusion: MTAD is less cytotoxic than eugenol, 3% H2O2, Ca(OH)2 paste, 5.25% NaOCl, Peridex, and EDTA and more cytotoxic than 2.63%, 1.31%, and 0.66% NaOCl.
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Title: Identification of hard tissue after experimental pulp capping using dentin sialoprotein (DSP) as a marker Author: Andelin, W.E. et al. Journal: JOE vol 29, (10), Oct. 2003 Reviewer: Allyson Byrne, D.M.D. Purpose: To identify the hard tissue formed early in experimental pulp exposures capped with MTA or (BMP)-7 using DSP as a marker. * D’Souza et al showed that DSP is a specific biochemical marker for functional odontoblasts M&M: 35 max molars from male rats were used. Calculus was removed and pulps were exposed in class I cavity preps.
Rats were killed after 2 weeks, maxillas removed, sectioned, fixed, decalcified and dehydrated. Sections prepared for histological analysis and immunohistochemical detection of DSP. Sections were examined by three investigators microscopically for amount of DSP staining, morphology of hard tissue formation (dentil-like, or bone-like) and presence of complete bridge formation. Results:
Untouched third molars shoed normal resting odontoblasts and primary dentin that stained for DSP indicating that these cells are metabolically active in a normal tooth. Conclusion: Previous pulp capping studies have evaluated the nature of the dentin bridge formed by visual examination only. The use of DSP as a marker in this study has shown that there is a difference in the protein makeup of the hard tissue formed under two different pulp capping materials. The results of this study suggest that MTA may provide a healing environment for regeneration of pulp and dentin (not bone).
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Title: Aerotolerance of an endodontic pathogen Author: Thomas et al. Journal: Journal of Endodontics Vol.29, No.10 October 2003 Reviewer: Rahul Gupta, D.D.S. Purpose: To determine the length of time it takes to kill obligate anaerobic bacteria in a root canal exposed to room air or 3% hydrogen peroxide. Methods and Materials: Twenty-five, human, permanent canine teeth with single canal were used. All teeth were cleaned/shaped. Two layers of nail polish were coated on the cementum to eliminate that route for bacterial contamination. The teeth were autoclaved twice to kill native bacteria. In an anaerobic gas chamber, the root canal of the teeth were inoculated with a 2-day bacterial growth suspension of P.endodontalis using a 27-gauge needle to fill each root canal and then immersing all the teeth in a single flask of bacterial culture. The liquid medium was prereduced, anaerobically sterilized, brain-heart infusion broth with cysteine and resazurin, a sensitive indicator of oxygenation. The teeth remained in the actively growing culture for 2 days, allowing contamination of dentinal tubules. Then the contaminated teeth were divided into five groups of five teeth each.
Results: Group I and Group III teeth – showed bacterial growth at 18 h and 7 days. Group II and Group IV teeth – showed no bacterial growth at 18 h and 7 days. Discussion: This study demonstrates that atmospheric air exposure for up to 45 min was not effective for killing an obligate anaerobe. We conclude that bacteria may survive in biofilm on the canal walls and/or within the network of dentinal tubules. There was attempt by the authors to accurately simulate clinical conditions of opening a tooth alone or access with hydrogen –peroxide irrigation. It seems that accessing infected teeth alone is not sufficient to kill anaerobic bacteria. Hydrogen peroxide apparently kills or retards bacterial growth with as little as 5 min of exposure. Hydrogen peroxide oxidizes chloride ions within bacteria into toxic hypochlorous acid. This action may be clinically effective against anaerobic and facultative endodontic pathogens, too.
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Title: Histologic analysis of the cleaning capacity of mechanical endodontic instruments activated by the ENDOflash system Author: L. Fariniuk et al Journal: JOE 2003; 29(10): 651-653 Reviewer: Fernando Meza, D.M.D. Purpose: To evaluate microscopically the cleaning capacity of four new motor-driven stainless steel instruments and equipment in the root canal. Materials & Methods: 22 human extracted maxillary molars were divided into four groups of five. Two negative controls were used. Working length (WL) was established at 1 mm from visualization of file at apical foramen. Mechanical instrumentation was performed at 250 rpm with ENDOflash handpiece. Manual instrumentation was performed using balanced force technique. The sequence of #15 to #35 was used in all groups. Distilled water used for irrigation. Group 1: ENDOflash .02 Group 2: Profile .04 Group 3: Pow-R .04 Group 4: NiTiflex The apical third of each instrumented distobuccal root was sectioned and processed for optical microscopy. A grid was placed over the images to evaluate the total area of the canal and the area containing debris. Results: Remaining debris (greatest to least): 36.44% ENDOflash files > 32.47% Nitiflex files > 22.61% Pow-R files > 2.86% Profiles Conclusion: Among the groups studied, the ProFile taper .04 group with the highest cleaning percentage (97.14%), may lead to a satisfactory level of debridement for successful root canal treatment if used in conjunction with an effective endodontic irrigating solution. |
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Title: An in vitro evaluation of the sealing ability of a new root canal obturation system. Authors: Kardon B.P. et al,. Journal: Journal of Endodontics Reviewer: Brett Strong, DDS Purpose: To evaluate the sealing ability of a urethane methacrylate resin-based sealer, EndoRez, utilizing a fluid filtration model. Materials & Methods: - 64 single rooted lower premolars were used. Excess calculus and soft tissue was removed with scalers. - Each tooth was instrumented to a #40 size file utilizing Profiles 0.04 taper. Irrigation with 5.25% NaOCl and 17%EDTA occurred during and after the cleaning and shaping treatment. - Three groups of 20 teeth each were created: o Group A: #40 standardized gutta-percha cone was fitted, and the canal was filled with EndoRez sealer. The gutta-percha point was then seated and seared off at the CEJ. o Group B: A single cone technique was utilized with a #40 gutta-percha cone and AH Plus sealer. o Group C: Warm vertical condensation was created with a #40 gutta-percha cone. AH Plus sealer was placed in canal and compaction of the gutta-percha cone to within 4mm of apex was performed. Obutra II was used to backfill the canal within 2-3mm of the CEJ. o Two positive and two negative controls were created. - Teeth were stored in 37oC and 100% humidity for 7 days to allow sealer to set. No coronal seal was present. - Each tooth was tested for microleakage utilizing the fluid-filtration device. - A chi-square test was used to compare the leakage between different groups. - Group A and B had two samples each prepared for SEM evaluation. Results: - Root length had no predictive value on leakage. - Group A : 3/19 samples showed leakage of >50mm within 30 minutes, and 8/19 samples had >1.5mm after two 30 minute sessions. - Group B and C: Only 2/40 samples had >1.5mm after two 30 minute sessions. - Group A (EndoRez) showed significantly more leakage than Group B (single cone/AH Plus) a Group C (warm vertical/AH Plus). - Groups B and C showed no significant leakage differences. - SEM evaluation of EndoRez revealed a sponge like appearance to the sealer when set. Discussion: The authors suspect that the porosity seen with EndoRez may be an intrinsic property of the sealer, or may have been due to the constant exposure of the sealer to oxygen. More research should be performed to determine if EndoRez is an adequate alternative to the current root canal sealers being sold on the market.
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Week of December 17, 2003 |
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Title: Scanning electron microscope observations of new and used nickel-titanium rotary files Author: S. Alapati, et. al. Journal: JOE Vol. 29, no. 10, 667, October 2003 Reviewer: Vahid Atabakhsh, D.D.S. Purpose: To observe microscopic differences in new versus used tip designs of ProFile 0.04 taper and Lightspeed 25mm long ISO size 25 nickel titanium rotary instruments with SEM. Materials and Methods: ProFile 0.04 taper and Lightspeed rotary NiTi 25 mm ISO size 25 were selected. Instruments from the same package were subject to 1, 3, or 6 uses of simulated clinical instrumentation in extracted teeth with small curved mesial canals of mandibular molars. 4 mm sections of used and new (control) files were sectioned using a slow speed, water cooled diamond saw. After cleaning ultrasonically with ethanol, they were viewed using SEM at a wide range of magnifications. Results:
Discussion: These observed surface flaws mentioned above due to manufacturing flaws may potentially lead to instrument fracture. Presently, these flaws and rollover are unavoidable. During clinical use, this rollover becomes flattened, perhaps with some decrease in cutting efficiency. Some tooth structure deposits adhere tenaciously to these rotary instruments after simulated clinical use, perhaps by mechanical retention, despite extensive ultrasonic cleaning. Thus it may not be possible to remove these following in vivo use in root canals. The role of these deposits in fracture of NiTi instruments in under study.
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Title: The crystallization of sodium hypochlorite on gutta-percha cones after the rapid-sterilization technique: an SEM study Author: Short et al. Journal: JOE 2003;29(10):670-673 Reviewed: Hung Do, D.D.S. Purpose: To use the rapid-sterilization technique in conjunction with the SEM and an elemental analysis machine (EAM) to: 1. identify the presence of sodium-chloride crystals 2. recognize crystallization of sodium hypochlorite on gutta-percha cones 3. determine if alcohol removes the crystals that may form on gutta-percha cones Materials and Methods:
Results: 1.
Control group had no crystals
present 2.
GPs immersed w/ 5.25% &
2.5% NaOCl and allowed to air dry had crystals
present 3.
GPs immersed w/ 5.25% &
2.5% NaOCl and rinsed off with ethyl alcohol,
isopropyl alcohol, or distilled water showed no crystal formation. Relevance: a. sterilization of GPs decreases risk of contamination b.
if rapid sterilization
technique is used, make sure to rinse off the chloride crystals since they
can impair the obturation seal |
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Title: A comparison of the cleaning efficacy of short-term sonic and ultrasonic passive irrigation after hand instrumentation in molar root canals. Author: Sabins et al. Journal: JOE 29(10), October 2003, 674-678. Reviewed By: Aaron Doms, D.D.S. Purpose: To see if sonic and ultrasonic passive
irrigation for 30 or 60 seconds in instrumented molar root canals would
result in cleaner canals. Material & Methods: 100 canals from extracted human molars were instrumented to size #35 flex-o-file to working length, with 0.5mm step-back filing up to size #60. 1ml of 5.25% sodium hypochlorite was used in between each file as irrigant. Then the canals were divided into 5 groups with 20 canals each as follows: 1) control – no further treatment except final rinse 2) passive sonic (1-8 kHz) irrigation for 30 seconds & final rinse 3) passive irrigation for 60 seconds & final rinse 4) passive ultrasonic (25-40 kHz) irrigation for 30 seconds & final rinse 5) passive ultrasonic irrigation for 60 seconds & final rinse Then the roots were split and images were made, transferred to a computer, and enlarged to 100x the original size. Lines were superimposed over the canals at 0, 3 and 6mm from the apical constrictions. The total number of pixels with debris in them were counted and statistically analyzed. Results: The following table shows the mean
percentage of remaining debris:
Conclusion: Passive activation of endodontic files for irrigation with NaOCl with sonic or ultrasonic energy in canals, for as little as 30 seconds after hand instrumentation, produced canals with significantly less debris than canals instrumented by hand files alone. Passive use of ultrasonic files with NaOCl irrigation produced significantly cleaner canals than did the passive use of sonic files with NaOCl irrigation. |
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Author: Thomas et. al. Journal: JOE 2003;29(10):662-663 Reviewed
By: Jessy
Tseng, D.D.S. Purpose: To determine
if there is a measurable difference in accuracy of length determination by
electronic apex locator (EAL) when stainless-steel (SS) and nickel-titanium (NiTi) files were used in the same tooth Materials and Methods:
- A #10
SS file was placed into the canal until the tip reached the major foramen
- Each tooth was mounted in
an alginate model. - Each tooth was
instrumented to size 20 before taking EAL measurements. - All
measurements of canal length were to the apex designation on the Root ZX or
the apex location as visualized with microscope. - Four
file types tested: SS hand files, NiTi hand files, NiTi rotary Lightspeed files
and NiTi rotary Profile .04 files. - Files with apical sizes
of #20, #25 and #30 were used for all file groups Results:
Conclusion:
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