Current	December 04	December 03	December02
November 05	November 04	November03	November02	December01	March01	December00
October 05	October 04	October03	October02	November01	February01	November00
September 05	September 04	September03	September02	October01	January01	October00

Week of September 17,  2001

Title: Philosophies and practices regarding the management of the endodontic smear layer: Results from two surveys.

Author: H. Dwight Moss, Allemang, et al.

Journal: JOE AUG 2001 pp537-539

Prepared by: Gregory Dearing, D.M.D.

Purpose: To report on the findings of 2 surveys.
(1) Asked the philosophies and techniques regarding smear layer removal taught to pre-doctoral dental students and post-doctoral endodontic residents in the United States.
(2) Asked how practicing endodontists in the United States manage the smear layer.

Smear Layer Composition= Caused by instrumentation

1. Dentin
2. Remnants of pulpal tissue
3. Odontoblast processes
4. Microorganisms

Factors in smear layer removal

1. Apical and coronal micro-leakage
2. Bacterial penetration on tubules
3. Adaptation of filling materials

Materials and Methods:

• 63 Dental Schools surveyed
• 2500 Endodontists surveyed

Results:

• More than 3/4 of dental students and 2/3 of Endodontic residents are not being taught routine smear layer removal
• Slightly more then 1/2 of endodontists responded that they routinely remove the smear layer

Conclusion:

There is no clear consensus in the endodontic community, either academically or clinically, as to whether the smear layer should be removed or be allowed to remain before obturation of the root canal space.

Title: Conservative Management of an Accidentally Resected Root: A 3-Year Follow-Up.

Author: Daoudi et al.

Journal: JOE: 27(8):543, August 2001.

Submitted by: Paul Slusarz D.M.D.

Purpose: To describe a nonsurgical treatment approach in the management of accidentally resectioned root (A case report).

Case History:

• A 58-yr-old female patient presented with the chief complaint of sharp, spontaneous, and continuous pain in tooth #19. The pain developed approximately 2 weeks after surgical removal of #18.
• Radiographic examination demonstrated a large bony defect that corresponded to the extraction site, in addition to an oblique resection of the distal root of #19.
• Tooth #19 was diagnosed as having irreversible pulpitis.
• Tx. options were presented as follows:
  
  1. Preparation of a positive apical stop and using a biocompatible material as an apical barrier against which the filling can be condensed. (this option was chosen)
  2. Obturating the root canal followed by placing a retrograde filling surgically.
  3. Performing root amputation at the furcation level.

Materials & Methods:

• An apex locator was used to determine the length of the distal root and a modified double flare technique was used to prepare the root canals.
• Ca(OH)₂ was placed and the access was sealed with IRM.
• Pt. was symptoms free at 6 week recall.
• Sterile Ca(OH)₂ was used to create and apical barrier to avoid overfilling of he distal root. The powder was carried to the canal using an amalgam carrier and a hand plugger fitted with a rubber stop was used to pack the powder until resistance was felt.
• Warm vertical condensation technique was used to obturate the two mesial canals, and the distal canal was obturated using warm lateral condensation.

Results:

The tooth was monitored closely over a 3-year follow-up. It remained symptom-free and demonstrated signs of complete healing and bone deposition around the resectioned root.

Title:  Adhesive sealing of the pulp chamber

Journal: J of Endodontics VOL. 27, No. 8, August 2001

Authors: Sema Belli,  et al

Prepared by: Nima Dayani, DDS

Purpose: To evaluate quantitatively the sealing properties of

1. Clearfil SE Bond: a self-etching primer system
2. One-Step: a wet bonding system
3. C&B Metabond: a 4-methacryloylox ethyl trimellitate anhydride adhesive system
4. IRM: a reinforced zinc oxide-eugenol

placed in pulp chambers of extracted human molars treated with NaOCl.

MATERIALS AND METHODS:

Crown segments were prepared. The roots were then cut 2 mm below the furcation. The pulp tissue then removed and orifices obturated with gutta percha without sealer. Specimens were then randomly divided into four treatment groups of 10 each. In each group the entire floor of the pulp chamber was treated with one of the four materials listed above and then the gutta percha points were removed. The upper-cut surfaces of the crown segments were then assembled.  This assembly was connected to an apparatus. The function of this apparatus was to measure the amount of water filtered through each tooth and hence quantitatively evaluate the seal by each material at various time points (immediately, 1 d, 1 wk, and 1 mo).

Scanning Electron Microscopy (SEM): Parallel specimens prepared exactly like the test specimens, were prepared for SEM evaluation.

A two-way analysis of variance (ANOVA) was used (bonding material and time as the two factors)

Results/ Discussion: All of the adhesive resins produced seals that were superior to those produced by IRM. The IRM results obtained in this study confirmed the good sealing qualities of low power-to-liquid ratios of zinc oxide-eugenol and IRM.

FYI-
Swartz et al 1983,  found that the failure rate was almost twice as high in cases without an adequate restoration compared with cases that were properly restored. Therefore several materials have been used within the pulp chamber in an attempt to provide a second seal against the leakage of bacteria

Clinical tips - If adhesive resin seals are to be placed over gutta percha-filled canals in single-root teeth that have no pulpal floor, then as much as half of the bonded surface area will be composed of gutta-percha. Preliminary studies indicate that One-Step does did not polymerize well on-gutta-percha. This may be because the acetone solvent of One-Step may leach some component from gutta-percha that inhibits polymerization.

The three resin systems tested were equally effective, however each system has a different protocol to follow. Some required placement of filled resins. Filled resins are more difficult to remove for re-treatment; therefore the authors used transparent composite resins to permit visualization of the underlying gutta percha.

The IRM powder-liquid ratio used in this study is the one recommended by the manufacturer. The apparent clinical success of IRM even though it leaked some is probably due to the antibacterial properties of zinc and the anti-inflammatory properties of eugenol

To Top

Week of September 24, 2001

Title: Response of Human Pulpal Tissue to Orthodontic Extrusive Applications

Journal: J Endod 2001; 27: 508-511

Author: Subay, RK

Reviewed by: Kimberly Pham, D.M.D.

Purpose:  To investigate histologically the human dental pulp tissue to two different extrusive force applications for 10 and 40 days. Extrusive forces are by means of sectional orthodontic appliance and ¼- inch 4.5 oz elastics.

Materials and Methods:

• 40 maxillary and mandibular first premolars from 15 patients scheduled for extraction.
• Group 1 -  20 teeth were extruded with the use of a fixed sectional orthodontic appliance. Ten teeth were extracted at 10 days and the rest of the teeth at 40 days.
• Group 2 -  20 teeth were extruded by means of ¼-inch 4.5 oz elastics. Extractions were made after test periods of 10 and 40 days.
• The extracted teeth were fixed, demineralized, washed, dehydrated, sectioned and stained and examined for inflammatory response, soft tissue response, and hard tissue response.

Results:

• None of the teeth in the groups showed an inflammatory response or reparative dentine formation in the test periods.
• Five teeth from the elastics group and two teeth from the sectional appliance group showed large and numerous pulp stones in the serial sections (17.5% of all cases)
• Seven teeth from the sectional appliance group and two teeth from the elastics group showed odontoblast aspiration into the dentin tubules (22.5%)

Discussion:

• According to Trowbridge (Pathways of the Pulp. 5^th ed. St Louis:Mosby-year Book, 1991:308-49) and Seltzer (The Dental Pulp. 2^nd ed. Philadelphia: JB lippincott,1975: 194-314) , there seems to be no correlation between the presence of the pulp stones and the orthodontic force application in this study. It has been stated that there is no certain cause of pulp stone formation.

Conclusion:  Extrusive forces applied in this study did not cause significant pathological changes in human pulp tissue.

Title:  Qualitative Description of a New Preparation Technique: the Balanced force Motion Using the Endographe

Journal: JOE: 27(8): 503-507, August 2001

Author: Blum, J.-Y. et al.

Prepared by: Lance Isaac, D.M.D.

Purpose: The purpose of this study was to use a novel device, the Endographe, to describe a new root canal preparation technique: the balanced-force motion. Because the forces and torque exerted by experienced endodontists were recorded on Endogrammes, an objective explanation of the technique is presented.

Materials and Methods: A computerized recording system was developed, having 3 transducers, electronic amplifiers, analogue-to-digital converters, a PC-compatible computer, and Endopro® software. The evaluation device is composed of two perpendicularly linked transducers for the measurement of extracanal forces, and a new holder with the transducers forming an angle of 45 degrees to the median axis is able to measure torque.
Five endodontists participated in this study, and 100 central or lateral mandibular incisors, freshly extracted, were chosen for their similarity of proportion and root canal anatomy. The assignment of ‘tooth practitioner’ was randomized.
Gates-Glidden burs were used to prepare the coronal part and ensure apical patency for the other instruments. The balanced-force technique with conventional instruments was then used for the body of the canal. For the apical part either the watch-winding pull with conventional instruments or the reversed balanced-force technique with manual GT files was used. The Endographe is able to measure the forces applied to real teeth over time, meaning that over the entire course of a root canal preparation, practitioners can see at any given moment exactly what their hands are doing and how much force they are applying.

Results: The Endogrammes of the endodontists were compared qualitatively, and were found to be similar among endodontists for the coronal phase and showed low vertical forces in contrast with the lateral forces. For the body, the Endogrammes were highly specific and described perfectly the different steps of instrument work. For the apical part, the Endogrammes of the conventional instruments showed a lack of vertical forces, while manual GT files showed torque and force applied inversely to that of conventional instruments.

Conclusion: These objective data indicate the correct way of working with the different techniques incorporated into the balanced-force motion technique. In fact, viewing the Endogrammes of these preparations in chronological order is very interesting, because it shows how quickly the practitioners were able to modify their own way of working.

Title: Influence of structure on nickel-titanium endodontic instruments failure

Author: Gregoire Kuhn, et al.

Journal: JOE:27(8):516-520, August 2001

Reviewer: Mark Wang, D.M.D.

Purpose: To investigate fatigue characteristics of superelastic nickel-titanium files and subsequently the process history of fracture life.

Material & Methods:

• NiTi files studied were: Maillefer (Profile) & Micro-Mega (Hero) in different geometrical shapes.
• The studied files had length 25 mm; taper 0.04-0.06; size 20-40.
• Thermal treatments: annealing at 350, 400, 450, 510, 600 & 700^º C in salt bath for 10 min, and at 600 & 700^° C for 15 min, and subsequent water quench.
• The files were microstructuraly studied with scanning electron microscopy (SEM), X-ray diffraction (XRD), and microhardness.

Results:

XRD:

• Alloys are fully austenite at room temperature.
• XRD scans of all specimens show a (110) texture

Microhardness:

• Results show s statistically significant difference among these instruments (p<0.005).
• Table 2 shows the average value for each instrument.

     SEM:

• Size 20 Profile 0.06 taper :noncurved body region show significant machining marks along the faces of the flutes; the cutting edges and ridges of curved body region show irregularities and cracks .
• Size 20 Hero 0.06 taper shows less machining damage, but some beginning cracks are observed in deep flutes.

Discussion & Conclusion:

• Endodontic files are very work-hardened, and there is a high density of defects in the alloy that can disturb the phase transformation.
• The microhardness Vickers confirmed these observations (dislocations and precipitates).
• The X-rays show that experimental spectrum lines are extended, typical of a distorted lattice.
• The surface state of the files (SEM) is an important factor in failure and fracture initiation.

To Top

---

Temple University School of Dentistry. All contents copyright (C) 1996. All rights reserved.
Created: September 20, 2000 Revised: URL:

Roy H. Stevens, DDS, MS; Wanda Gordon, D.M.D. - Comments to author:	wgordon@dental.temple.edu
Questions or problems regarding this page? Please mail:	webmaster@dental.temple.edu