octabstracts

Department of Endodontology


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Week of October 3, 2000

Title: Anaphylactic Shock during Endodontic Treatment due to Allergy to Formaldehyde in a Root Canal Sealant

Author: Haikel, Y. and et al

Journal: Journal of Endodontics, Vol 26(9): 529-531, September 2000

Prepared by: Andrew W. Chan, DDS

Purpose: To highlight the problem with the use of formol in root canal sealers and the risks associated with apical extrusion leading to a possible anaphylactic reaction.

Introduction: The use of formaldehyde in different forms (gas, solution, or solid) is widespread: industry, disinfectants, cosmetics, medications, and root canal sealers. Through irritant, or more rarely immunoallergic mechanisms, formaldehyde (formol, formalin, trioxymethylene) might be the cause of a variety of pathological reactions: digestive lesions after ingestion, nasal, laryngeal, bronchial, or pulmonary lesions after inhalation and dermatological lesions, such as cutaneous necrosis or contact dermatitis. Two cases of anaphylactic accidents in response to formol have been reported in dentistry.

Case History: A 41 yr. old male presented with a periapical granuloma on #24 requiring RCT. Dental treatment consisted of debridement of the necrotic root canal without local anesthesia, followed by canal obturation using a root canal sealant (Spad) performed with an engine-driven spiral compactor. Allergy testing was performed after the accident. The tests remained negative for common environment allergens. Tests with the standard battery ICDRG remained negative, including those for standardized formaldehyde. The level of IgE to formol was very high to the Radio Allergo Sorbent Test (RAST).

Discussion: The role of formol in respiratory and cutaneous pathosis is well established, causing rhinitis, asthma, and contact dermatitis. An IgE-dependent allergic reaction is, however, rarely proven. The present reported case was of interest due to: evidence of an IgE-dependent mechanism based on the initiation of an anaphylactic shock immediately after canal obturation, positive cutaneous test and RAST class 4 formol and the unusual character of this type of reaction in dentistry despite the widespread use of formaldehyde and the frequency of root canal treatments.

Title: Effect of various mixing ratios on antibacterial properties and hardness on endodontic sealers.

Author: Fuss, Z. et al.

Prepared by: Barry Hoch

Journal: JOE 26(9):519. September 2000.

Purpose: To evaluate the antimicrobial properties of three endodontic sealers at various controlled consistencies using agar diffusion and direct contact tests, as well as the hardness of the sealers mixed to the same consistencies.

Materials and Methods:

AH26, CRCS and Roth’s cement were prepared to 4 different consistencies within the range of the manufacturers’ recommendations by varying powder-to-liquid or powder-to-paste ratios. Sealers were designated 1 (heaviest) to 4 (lightest).
Inocula of E. faecalis were prepared using streptomycin-supplemented media and streptomycin-resistant E. faecalis.
Sealers were subjected to agar diffusion test (ADT) within 20 min from mixing and examined for bacterial inhibition zones after 24 h incubation at 37 C. Halo diameters were measured from 2 perpendicular locations for each sample by two inspectors and analyzed using Student’s t-test.
Direct contact test (DCT) was used to test sealers fresh and at 24 h. Sealers were placed on walls of microtiter plate, bacterial suspension added and allowed to evaporate, BHI broth was added to the plates, wells were vortexed (group A), inoculum was transferred to other wells with fresh medium (group B), and bacterial outgrowth was followed by continued densitometric measurements every 30 min for 15 h. Positive controls had only inoculum, negative controls had only sealers. Tests were repeated at least twice.
Hardness was tested by placing sealers in different concentrations into Teflon molds. After setting for 1 week, samples were tested at 3 random points under load of 10 g for 10 s with a Microhardness tester. Indentations were interpreted to KHN (Knoop hardness number) and analyzed by Student’s t-test.

Results:

Light consistencies of RC showed larger zones than heavier mixes.
There were no sig. differences among the various consistencies of AH26. CRCS had similar zones to AH26 at the 2 heaviest consistencies but no zones were detected with the 2 lighter consistencies of CRCS.
In DCT, RC and CRCS showed complete inhibition of bacterial growth at all consistencies. Freshly mixed AH26 showed complete inhibition at all consistencies but at 24 h, the heavier consistencies (1, 2, 3) did not completely inhibit growth.
For the hardness test, RC did not completely set in 1 wk and could not be tested. For AH26 and CRCS, lower KHN generally were obtained with lighter consistencies. AH26 was significantly harder than CRCS at all consistencies.

Discussion:

Antibacterial and physical properties may be affected by changing the powder-to-liquid or powder-to-paste ratio. These differences may explain some discrepancies in the literature re: antibacterial properties of sealers. Strict methodology must therefore be considered before making comparisons between studies and exact proportions should be specified for future studies, as well as for clinical use of these materials.

This paper has much value in addressing the large range of clinically acceptable sealer consistencies and the effect of different mixes on properties of sealers. It also reminds us of the necessity of closely analyzing research methodology.

Title: Pulp Capping of Carious exposures: treatment Outcome after 5 and 10 Years: A Retrospective Study

Author: Barthel CR et al

Journal: JOE: 26, (9) 525-528

Prepared by: Micah Oller

Purpose: A retrospective study to determine the treatment outcome of pulp-capped teeth after 5 to 10 years.

Materials and Methods: In the Dept. of Operative Dentistry in the Dental School in Berlin 401 pulp cappings (353 pts) were performed in 1984-1987 (10 yr. group) or 1990 to 1992 (5 yr. group). All pulps were exposed during caries excavation (caries exposure). If the tooth was symptomatic or if the exposure >1mm root canal treatment was done. In general, caries excavation was done with a rubber dam in place and was checked by a floor instructor. The caries free-condition was determined using a mirror and explorer. No caries indicator dye was used. The cavity was cleansed by 3% H₂O₂ and a setting of Ca(OH)₂ paste was placed on the wound. On top of the medication, a base of Zn(PO)₄ cement or GI cement was applied. The teeth were restored with amalgam, composite, gold or temporary restorations.

Criteria for Success or Failure at Follow-up: A pulp capping was considered "successful" when 1) the tooth responded clearly to sensitivity testing (w/ both CO₂ test and EPT responding positively) and 2) there was an absence of clinical symptomology. Pulp capping was considered a "failure" if the tooth was extracted, root canal treated, or if periapical rarefaction was noted radiographically. They were questionable if there was unclear clinical symptoms and an absence of radiological pathology.

Follow-up Examination: Patient charts were evaluated for the area of exposure, the of base used and type of restoration. Clinical examination was done (i.e. pulp testing, percussion etc.). Pocket depth and radiographs were taken.

Results: Only 97 patients (27%) with 123 (30.7%) pulp caps could be followed-up.

70% of the patients were 21-40 years old.
9/123 teeth were extracted, 65/123 were root canal treated, and 5/123 showed radiographic signs of apical rarefaction.
15/123 shoed questionable vitality testing and/or clinical symptomolgy, such as pain on palpation in the apical area of the tooth without radiological signs.
44.5% of teeth in the 5yr group and 79.9% in the 10 yr. group had a positive root canal treatment or extraction.

Discussion:

Possible factors include:

Lack of homeostasis. (Studies have shown that a blood clot has an adverse effect on the healing of pulpotomized teeth Sanley et al)).
The type of setting used
An aqueous suspension of Ca(OH)₂ released 3X more Ca++ than setting products. It may be speculated that the lower pH resulted in weaker healing.

The age of the patient and the type of tooth did not influence success.
The 5 year group had a higher tendency for failure when a temporary restoration was placed.
A questionable teeth showed radiographic signs of calcific metamorphosis in their pulp space.
The authors state direct pulp cap should be avoided however, if it is provided the tooth/teeth should be monitored and a definitive restoration should be placed.

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Week of October 10, 2000

Title: Cleaning efficacy of two apical preparation regimens following shaping with hand files of greater taper.

Author: Lumley PJ.

Journal: International Endodontic Journal, 33, 262—266, 2000.

Prepared by: Gary Altenburg

Purpose: To assess canal cleaning following shaping with hand files of greater taper.

M&M:

Thirty mesial canals and 30 distal canals in mandibular molars were prepared with .08 and .10 hand files of greater taper, respectively.
Following initial preparation, 0.02 instruments were used incrementally shorter in a step-back manner.
In half the canals instrumentation was performed to size 35 1 mm short of the canal terminus.
In the other half the series was continued through to size 60 using step-back increments of half to one millimeter as appropriate (foramen size was maintained at size 20 in all groups).
Sodium hypochlorite (4.5%) and REDTA (17%) were used as irrigants for all groups.
Cleaning efficacy was evaluated by scoring the amount of remaining debris using a light microscope and calibrated eyepiece micrometer.

Results: Canals stepped back through to a size 60 were significantly cleaner than those instrumented to a size 35 only.

Conclusions: Refining the apical region of canal preparation by stepping back through to a size 60 reduced remaining debris following shaping with files of greater taper. Irrigation is the positive factor in flared cases, and is likely responsible for the success of this experiment.

Title: Influence of calcium hydroxide intracanal dressings on the prognosis of teeth with endodontically induced periapical lesions

Author: Weiger et al.

Journal: International Endodontic Journal, 33, 219-226, 2000.

Prepared by: Tom Goebel

Purpose: To explore the influence of calcium used as an interappointment intracanal medicament on the healing process of periapical lesions associated with pulpless teeth. The prognosis after 2-visit RCT was compared with 1-visit tx.

M & M: 73 patients whom had not taken antibiotics 4 weeks prior to endodontic therapy were recruited for this trial. Necrotic teeth with lesions were treated. Caries & leaking restorations were removed. Teeth were accessed, rubber dam placed, rubber dam was disinfected with 1% sodium hypochlorite. Root canal therapy was performed using GG burs 1-4, WL determined to be 1 mm short of radiographic apex, instrumented with K-files with thorough irrigation of 1% sodium hypochlorite. Apical portion was prepared with the standardized technique to an apical size 40 or larger. Curved canals were prepared step-back technique to an apical size of 30. When the RCT was not completed in one visit, the calcium hydroxide was mixed with sterile physiological saline to a creamy consistency & placed with sterile paper points. The paste was packed in the root canal by step-by-step condensation. Access cavity was sealed with temporary dressing. Calcium hydroxide remained in the canals for 7 to 47 days (mean 22 days). At the 2^nd appointment, the calcium hydroxide was removed via irrigation with 1% sodium hypochlorite & filing the walls with the MAF. Root canals were obturated with GP & Sealapex via lateral condensation. Pulp chamber was sealed with GI or composite restoration. The following pre-operative & post-operative findings were recorded & compared: history of pain, swelling, fistula, percussion, perio pockets, mobility, size of radiographic lesion, apical extent of root filling. Cases were compared for success or failure. Complete healing included no symptoms & radiographically normal PDL space. Incomplete healing included no symptoms, radiographic reduction in size of lesion or no change within 4 years of treatment. No healing included symptoms, persisting lesion after 4 – 5 years, involvement of a previously uninvolved root of a multi-rooted tooth.

Results: 36 of the 67 teeth were treated with single-visit endodontics. The other 31 teeth were obturated at the 2^nd visit after treatment with calcium hydroxide. 52 teeth had complete healing. 11 teeth had incomplete healing. 4 teeth were failures. Time for complete apical healing was 4 to 58 months. Single visit endodontics was successful in 30 of 36 teeth. Two visit endodontics was successful in 22 of 31 cases. The 4 failed cases comprised of 3 single-visit and 1 two-visit endo. Statistically, the number of visits did not effect the success of treatment outcome while the pre-operative size of the apical lesion had a significant effect on the healing process.

Conclusion: One-visit RCT is an alternative to two-visit tx with calcium hydroxide as an interappointment dressing for pulpless teeth associated with endodontically induced lesions.

Title: Complications during Root Canal Irrigation- Literature Review and Case Reports

Author: Hulsmann and Hahn

Journal: Int End J 33: 186-193, 2000

Prepared by: Brian Frey

Purpose:

To review the etiology, symptomatology, and therapy of complications during root canal irrigation (whether it’s the use of NaOCl and H₂0₂ beyond root apices as illustrated in case reports or tissue emphysema by expression of air into periapical and soft tissues) along with clinical symptoms associated with these complications.
To review preventive and therapeutic considerations in patient management of such complications

Complications during root canal irrigation:

Damage to clothing- must protect patient’s clothing and assure that the irrigation needle and syringe are securely attached and will not separate during transfer of irrigation in order to prevent leakage over patient
Damage to eye- results in immediate pain, profuse watering, burning, and erythema. Tx- ocular irrigation with large amounts of tap water or sterile saline and refer pt to ophthalmologist for exam and tx
Injection of NaOCl beyond the apical foramen- causes immediate severe pain, rapid edema of soft tissues and spread into adjacent facial spaces, profuse bleeding from canal and interstitial bleeding –hemorrhage of skin and mucosa (ecchymosis), chlorine taste and throat irritation after expression into max sinus, possible secondary infection, and possible paraesthesia
Therapy after inadvertent injection of NaOCl into PA tissues- inform pt on cause and severity, use of pain controls (local anesthetics and analgesics), referral to hospital if severe, extraoral cold compresses for reduction of swelling (1^st 24 hours), warm compresses and warm mouth rinses 1 day later (for systemic circulation stimulation), daily recalls, antibiotics (if indicated), antihistamines (if possible allergic reaction), corticosteroids (controversial), and completion of endo therapy at later date (when acute symptoms are resolved) with saline or chlorhexidine as root canal irrigants
Air emphysema- happens when root canal is dried with compressed air that expresses through apical constriction into pa tissues; does not require antibiotics or any other therapy ; usually resolves after few days
Possible allergic reactions to solutions

Etiology of complications:

Incorrect working length, iatrogenic widening of apical foramen, lateral perforation, or wedging of irrigating needle

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Week of October 17, 2000

Title: Endodontic retreatment decisions: no consensus

Author: Aryanpour, S. et al.

Journal: International Endodontic Journal 33(3): 208-218, May 2000.

Prepared by: Lance Isaac

Purpose:

To determine whether or not there was a consensus among dental schools, students and their instructors managing the same clinical cases.
To determine the predominant proposed treatment option, and the influence of the ‘school effect’ on decision variations.
To analyze the relationship between technical complexity of retreatment and difficulty choosing a treatment option.

Materials and Methods:

Final year dental students, endodontic faculty members and instructors of 10 European dental schools surveyed as decision makers in 1995-1996.
14 different radiographic cases of endodontically-treated teeth presented with brief clinical Hx.
Decision makers from each university in one room, and individual data of each participant recorded.
For each case, decision makers required to: 1) choose from 9 proposed treatment options, 2) assess difficulty in making a decision, 3) evaluate technical complexity of retreatment procedure.
Cases divided into 4 categories according to presence of radiographic and clinical and/or subjective signs.
Treatment alternatives pooled into 4 groups (no retreatment, nonsurgical retreatment, surgical retreatment, extraction).
One way analysis of variance used to assess influence of country, university and specialization on the four kind of decisions.

Results:

Wide inter- and intra-school disagreements in clinical management of endo-treated teeth.
Main source of variation was the ‘school effect’, whereby therapeutic choices vary significantly amongst universities (accounting for the greatest amount of variance). Especially seen in final year students who decide not to decide, request more tests, adopt instructor’s or school’s method, due to lack of significant clinical experience.
Decision difficulty moderately correlated to technical complexity.

Conclusion: No clear consensus discernible amongst or within dental schools with regards to the 14 cases presented. Lack of consensus somewhat explained by school effect.

Title: Apparent periapical repair without operative intervention: a case report and discussion

Author: Whitworth, J.M.

Journal: International Endodontic Journal, 33, 286- 289, 2000

Classification: Case Report

Key Words: Apical pathosis, healing, host/parasite relationship, imaging

Reviewed by: Kimberly Pham, D.M.D

Purpose: This report describes an unusual case of apical periodontitis, in which significant bony healing appeared to take place without any operative intervention, and in the presence of long-term dental neglect and without antibiotic use.

Case report: A 35-year-old female Caucasian presented at Newcastle Dental Hospital complaining of pain on biting from tooth 36(FDI) (tooth 19, American system). Her medical history was non-contributory. Clinical examination revealed a large carious lesion with broken distal marginal ridge of tooth 36. Pulp testing with ethyl chloride and EPT yielded no response. There was no evidence of discharge through fistula, or through the intact periodontum. The tooth was moderately tender to percussion. A periapical radiograph shows the presence of large carious lesion involving the pulp, and 5 mm diameter radiolucencies affecting both mesial and distal roots. The tooth was diagnosed of pulp necrosis with an acute exacerbation of chronic apical periodontitis. For unmentioned reason patient did not have any root canal treatment even she expressed her design to save the tooth.

Patient returned to the Newcastle Dental Hospital 31 months later complaining of lingual discomfort from abrasion on the sharp lingual wall of tooth 36. She had received no dental care in the interim, and gave no history of antibiotic use. There was no discomfort from the tooth itself and the associated soft tissue appeared healthy. Periapical radiograph revealed caries affecting the whole crown and involving the root bifurcation. The periapical lesion affecting the distal root appeared to have completely healed with the reestablishment of a normal periodontal ligament shadow. The mesial lesion had also reduced in size radiographically. Tooth 36 was extracted.

Discussion:

A change in redox potential, or nutritional status within tooth 36 as it continued to be opened by caries may have created a selective pressure for a change in the microbial flora of the canal system to a less pathogenic one, incapable of sustaining chronic inflammatory change.
The host can mobilize defense factors against bacteria in root canals to an extent such factors may influence the host parasite relationship during the development of apical periodontitis.
Radiographic differentiation of periapical cysts and granulomas is difficult .The lesions were in fact periapical cysts, and that coronal breakdown and possible apical root resorption, may have open a free pathway for drainage and decompression. Radiographic signs of healing may have then followed epithelial disruption and breakdown, despite the continued presence of intracanal infection

The reliability of routine radiographs is questioned because cortical erosion or perforation is required for the detection of periapical lesions. Slight decompression and shrinkage of a perapical lesion and regeneration of cortical plate may have given the impression of repair in the presence of a still substantial lesion.

Title: A comparison of two nickel-titanium instrumentation techniques in teeth using microcomputed tomography.

Author: Rhodes et al.

Journal: Internat Endo Journal 33(3):279, May 2000.

Classification: Research Comparison Article

Key Words: microcomputed tomography, nickel-titanium, root canal preparation, three-dimensional imaging.

Reviewed by: Dr. Paul Slusarz

Purpose: To compare the shaping of root canals by two nickel-titanium instrumentation techniques using microcomputed tomography (MCT).

Materials and Methods:

The sample consisted of 10 human mandibular first molar teeth (30 canals) that were unrestored, had intact crowns, fully formed apices and allowed an ISO size 10 file to negotiate the full length of each root canal.
All samples were scanned using microcomputed tomography (MCT), and were divided into two groups of five teeth.
The first group were instrumented using NiTiFlex hand-files with a balanced force technique.
The teeth in the other group were instrumented using ProFile 0.04 taper rotary instruments.
The total area of dentin removed by instrumentation was calculated for each tooth at the predetermined levels using MCT area measurements; the two techniques were then compared.

Results:

The mean change in area for hand instrumentation exhibited a larger range at each level compared with rotary instrumentation. However, statistical analysis showed that there was no significant difference in the total volume change between the two methods of canal preparation.
The mean amount of dentin removed (both systems) accounted for a 28% enlargement of the root canals.
In all areas, there was no significant difference between the instrumentation types.
The mean time taken for rotary preparation was 15 min 9 sec, whilst that for hand instrumentation was 17 min 7 sec per tooth.

Discussion: MCT is a non-invasive modality which makes it possible to visualize the root canal before, during and after instrumentation without altering the sample. Statistical analysis of the results showed that there was no significant difference between NiTi hand- and machine- instrumented root canals, despite hand instrumentation appearing to produce a more variable shape. There was also no significant difference in centering between these two methods. There was little difference in the speed of preparation between hand instrumentation with balanced force and rotary NiTi instrumentation.

Conclusion: There was little difference between NiTiFlex hand files and Profile 0.04 taper files with respect to removal of dentin, centering, quality and speed.

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Week of October 24, 2000

Title: The effect of root canal preparation on microleakage within endodontically treated teeth: an in vitro study

Author: Von Fraunhofer, J. A, et al

Source: International Endodontic Journal, 33, 355-360, 2000

Reviewed by: Nima Dayani, DDS

Goal: To evaluate the effect of smear layer and canal instrumentation on leakage in root-filled teeth

Introduction:

Smear layer is important during instrumentation as it covers the instrumented dentin. It can preclude penetration of sealer and/or gutta percha into dentinal tubules. REDTA is thought to be the most effective agent in removal of the smear layer. Effective instrumentation is needed for delivery of the irrigant and condensation of root canal fillings which in turn to enhance the apical seal.

Although it is known that NiTi files have superiority over the traditional stainless steal files with regard to elasticity and torsional characteristic, it is not know their effect over the canal seal

This paper studies the effect of canal preparation and obturation on post-obturation microleakage.

Materials and Methods:

80 human, single-canal, freshly extracted premolar and canine teeth with closed apices were selected. They were randomly assigned to six groups. Electrochemical technique used to measure microleakage, as it offers a quantifiable data as well as the ability to make a longitudinal study.

Treatment/group	A	B	C	D	E	F
Instrumentation	Rotary	Rotary	Rotary	Rotary	Hand	Hand
Smear layer	Removed	Intact	Removed	Intact	Removed	Intact
Obturation	Multiphase	Multiphase	Lateral	Lateral	Lateral	-

Hand instrumented teeth were open to a master apical file size 35 and step-backed. Teeth in rotary groups were instrumented to size 35 MAF as well. 5.25% NaOCl was used as an irrigant. Each sample tooth was incorporated into an electric current circuit. The magnitude of current for each tooth was directly proportional to microleakage. Measurements were taken daily for 38 days with final measurement on 45th day

Results:

Statistically significant differences were noted only between groups A and the remaining groups through the length of the experiment with group A having less leakage. (Figure 2)

Discussion:

Previous studies have shown that all sealed root canals leaks. Time dependent increase in leakage only occurred in groups A, B, and C. The other groups showed no change in leakage behavior than the positive group after ten days. These findings suggest that hand instrumented canals and canals with intact smear layer exhibit less satisfactory leakage behavior. An accurately instrumented canal has fewer irregularities that facilitate a better seal. Based on the results, authors concluded that multiphase obturation is better than lateral condensation, (although, there is no statistically significant difference with some groups of specimens).

Conclusion:

Rotary provides superior preparation than hand instrument. Removing smear layer and multiphase obturation provide superior seal than lateral condensation.

Title: A comparison of the relative efficacies of four hand and rotary instrumentation techniques during endodontic retreatment.

Author: Imura, Z. et al.

Journal: Internt. Endo. Journal 33(4): 361, July 2000

Reviewer: Mark Wang, D.M.D.

Purpose: To examine the cleanliness of root canal walls after retreatment using two engine-driven instruments (Quantec & Profile)compared to two hand instruments (K-file & Hedstrom file). The parameters measured were: the amount of residual gutta-percha/sealer on the canal walls in the coronal, middle and apical levels: the volume of apically extruded debris; and the time required for gutta-percha/sealer removal.

Materials and Method:

100 extracted mandibular premolars were prepared using a modified step-back, flare technique and obturated with the lateral condensation technique.
After repreparation with the test instruments, the specimens were cut transversally at the cervical, middle, and apical thirds with steel discs and the three sections were split longitudinally.
The amount of residual debris on the canal walls in each section was examined using a stereomicroscope.

Results:

In all groups the cervical and middle 1/3 showed no debris. In the apical 1/3, obturating material was observed in some specimens.
No statistically significant difference was found between the two groups for incidence of debris, although the Hedstrom group showed a greater number of sample with remaining gutta-percha/sealer.
When analyzing dirty specimens only, there was a statistically significant difference between the four groups (P<0.01) with the Hedstrom group having significantly less length of canal wall with remaining obturation material than the Quantec group.
There was no significant difference amongst the groups for weight of extruded debris.
However, there was a significant difference amongst the groups for mean treatment time with the Hedstrom file group requiring significantly less time than the Quantec group (P<0.01); no significant differences were found between the other groups.
6 instruments fractured in the Quantec group, 4 in the Profile group, 2 in the Hedstrom group and 2 in the K-type group.

Conclusions:

The results showed that overall, all instruments may leave filling material inside the root canal.
During retreatment, there is a risk of instrument breakage, especially rotary instruments

Title: An in vitro comparison of canal preparation using two automated rotary nickel-titanium instrumentation techniques

Author: Jardine, SJ et al

Journal: Intern. Endo. J 33; 381-391, 2000

Reviewer: M.Oller

Purpose: To compare the efficacy of root canal preparation using two automated rotary nickel-titanium instrumentation techniques with a double flared balanced forces hand preparation technique using stainless steel files in extracted human teeth.

Materials and Methods: 60 root canals in extracted human teeth were matched for curvature, length, and diameter and divided evenly between three groups (further divided into groups of < 35 and > 35 degrees curvature):

Group 1= double flare using Flexofiles®, (the coronal portion of the canal was initially instrumented with a size 35 file and the instrumentation progressed in a stepdown fashion in 1mm increments until the W.L. was reached. The canal was enlarged to a size 30 file at WL. The taper of the canals was then refined by stepback in 1mm increments to size 55 file.

Group 2 = rotary nickel titanium using McXIM® instruments. McXIM files are a series of nickel-titanium rotary instrument available in five different tapers and four designs. The tapers are .03, .04, .045, .05, and .055, all with the identical tip size of 25. These files also have flattened radial land and non-cutting tips. There are four blade designs: U type, Hedstrom, .02 taper with equal radial lands and those with dissimilar helical lands throughout their length. (the canals were opened with a size 0.45, WL was gained with a small file or in a smaller to larger file sequence until the WL was gained. The files were used at 360 r.p.m.)

Group 3 = rotary nickel titanium using Profile® .04 Taper™ Series 29 instruments. These files have .04 taper and flutes with flat outer edges (radial lands) to prevent threading into the canal and bullet-nosed tips to prevent ledging, zipping and transportation. There is a constant 29% increase in tip diameter between sizes. (Initial crown down to ¾ of the canal length with a #4,3 files. A #8 K-flex file was use to obtain WL and the canal was enlarged by stepback to a size 4, .21mm)

-A standard radiographic technique using mercury as a contrast medium was used to evaluate the canal shape before and after preparation in the plane of maximum curvature.

-The pre- and postoperative radiographic images were compared against each other and with a predicted ‘ideal preparation’ calculated form a projection of the final instrument dimensions.

-The outcome measures were changes in canal dimension as quantified by measuring the changes in the position of the inner and outer walls at 1mm internals. Alteration in canal curvature could be inferred by comparison with the ideal preparation.

-A two way ANOVA test was done to detect significant differences b/t outcome measures.

Results:

The degree of curvature did not influence the effectiveness of any of the techniques.
The results showed no statistically significant differences in the outcome measures between the groups.
There was no significant differences in canal wall position changes at any level except the apical three 3mm, where significantly less change occurred in all groups.
Instruments fractured in three canals with acute curves in groups 2 and 3.

Conclusion: Canal curvatures are equally and well maintained following preparation in all groups.

Possible reasons for lower change in the apical 3mm are: the presence of safe ends on the instrument as was as inconstant length control or that rotary instruments remove relatively less tissue apically.
The authors observation regarding the lack of apical preparation is important to consider when instrumenting, perhaps careful attention to this area is need.

Title: An overview of nickel titanium alloys used in dentistry

Author: S.A. Thompson

Journal: International Endodontic Journal, 33, 297-310 (2000)

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

Purpose: To review NiTi alloy and its roles in dentistry in order for its unique characteristics to be appreciated.

Summary: Developed in the early 1960’s by metallurgist W.F. Buehler (NITINOL) NI = nickel, TI = titanium, NOL = naval ordinance lab.
Metallurgy:

56%(wt.) = Ni, 44%(wt.) = Ti
Alloy has inherent ability to alter its atomic bonding causing unique and significant changes in mechanical properties as a function of temp. and stress = Austenite/Martensite Transition
As a result of this transition the characteristics of shape memory and super elasticity are gained
NiTi has greater strength and a lower modulus of elasticity compared to stainless steel
Super elastic means that on unloading it returns to its original shape. In other words they are not permanently deformed as easy as stainless steel
The martensitic phase is the one of importance to us, giving it the unique characteristics.
The transition b/w phases can also occur as a result of stress, such as that encountered during root canal preparation
In most metals, when an external force exceeds a given amount, mechanical slip is induced within the lattice causing permanent deformation; however, with NiTi alloys a stress induced martensitic transformation occurs, rather than a slip = super elasticity and springback/shape memory

Manufacturing:

NiTi is more complex than stainless steel, as the files have to be machined rather than twisted
The super elasticity of the alloy means that it cannot maintain a spiral, as the alloy undergoes no permanent deformation. Attempts to twist conventionally would result in fracture
The instrument profile or design has to be ground into the NITINOL blanks as this process results in surface irregularities that may compromise their cutting ability and lead to corrosion

Usage:

Ortho arch wire
Crown and bridge castings
Implants
Bone plates for rigid fixation

Considerations:

Many discrepancies in studies on the effects of sterilization on NiTi and corrosion
Potential decrease in cutting ability due to wear
Problem with matching instruments to a consistent size

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Week of October 31, 2000

Title: Pulp revascularization of replanted immature dog teeth after different treatment methods.

Author: Yanpiset K, Trope M.

Journal: Endod Dent Traumatol. 16(5): 211-217. October 2000.

Prepared by: G. Altenburg

Purpose: To determine the effect of topical treatment with doxycycline and/or the application of unfilled resin to the anatomical crown on the occurrence of revascularization in reimplanted dog teeth.

Materials &Methods:

Ninety-six teeth in 4 young mongrel dogs were used. Eighty one teeth were atraumatically extracted and divided into four groups.
Group 1, 17 teeth were kept dry for 5 min and then replanted.
Group 2, 21 teeth were soaked with a freshly prepared solution of doxycycline (1 mg/ 20 ml saline) for 5 min before reimplantation.
Group 3, 23 teeth were soaked with the doxycycline solution for 5 min, and then replanted. The crowns were coated with 2 layers of light cured unfilled resin.
Group 4, 20 teeth were kept dry for 5 min, and then replanted. The crowns were treated as with the teeth in Group 3.

Results:

Three months after surgery, radiographic evaluation revealed that 27 teeth had continued root development and 32 teeth showed arrested root development with periradicular pathosis.
The remaining 17 teeth, which had arrested root development but no signs of periradicular pathosis, were all histologically evaluated for final assessment.
The occurrence of revascularization according to treatment group was 29.4%, 60%, 60%, 36.8% in Group 1, 2, 3, and 4, respectively.

Revascularization according to treatment group

Group	Treatment	# of teeth	Vital		Non-vital
Group	Treatment	# of teeth	#	%	#	%
1	Dry 5 min	17	5	29.4	12	70.6
2	Doxycycline 5 min	20	12	60	8	40
3	Doxycycline 5 min + resin	20	12	60	8	40
4	Dry 5 min + resin	19	7	36.8	12	63.2
Total		76	36	47.3	40	52.7

Conclusions: Soaking for 5 min in doxycycline significantly increased the revascularization rate while the addition of resin to the crown did not result in an increased incidence of pulp revascularization.

Title: Factors associated with root canal ledging during instrumentation.

Author: Kapalas, A. & T. Lambrianidis

Journal: Endodontics & Dental Traum., 16(5):229. October 2000

Prepared by: Barry Hoch

Purpose: To identify the presence of a ledge in cases treated by dental students and endodontists (private practice), and to identify the clinical factors associated with ledging.

Materials and Methods:

141 mand. and max. molars were treated by undergraduate dental students (no retreatments).
103 mand. molars were treated by endodontists (25 retreatments).
Radiographs were evaluated – working length, master cone, and final obturation.
All canals were instrumented with gates glidden drills and a step-back technique with K-files.
The parameters evaluated were canal location, tooth #, and root canal curvature (<5⁰ to >25⁰).
Ledging was diagnosed when the root filling was at least 1mm shorter than the initial working length or deviated from the original canal shape.

Results:

Dental students:

51.5% of canals were ledged (significantly different from endodontists).
Tooth #18 – most likely to be ledged.
Canal location – significant effect on ledging (MB, ML, DB were ledged more the D, P canals).
Canal curvature had the greatest effect on ledging (more curved the canal the more ledging).

Endodontists:

35% of canals were ledged (intact pulp cavities – 33.2%, retreatments – 40.6%).
The location of the molars did not seem to matter.
Canal location did have a significant effect (MB, DB canals were ledged most).
Canal curvature had a significant effect on canal ledging.

Discussion:

Endodontists, despite their higher clinical skills, still had a significant ledge rate, with even greater numbers in retreated teeth.
One question of this study was the definition of a ledge – "a root filling at least 1mm shorter than the working length." This may be due to debris or dentinal chips and not due to an alteration in canal shape.
As one might expect, canal curvature had the most significant effect of ledging, and the step-back technique did not perform as well as one would hope. A comparison with a crown down technique would be nice.

Title: Influence of Coronal Restorations on the Periapical Health of Endodontically Treated Teeth

Author: Tronstad, L. and et al

Journal: Endodontics and Dental Traumatology, 16(5): 218-221, October 2000

Prepared by: Andrew W. Chan, DDS

Purpose: To evaluate a possible relationship between the quality of the coronal restoration, the root canal obturation, and the periapical status of endodontically treated teeth.

Materials & Methods: Two examiners evaluated a total of 1,001 endodontically treated teeth restored with a permanent restoration independently. According to a predetermined set of radiographic criteria, the technical quality of the root filling of each tooth was scored as either good (GE) or poor (PE), and the technical quality of the coronal restoration was scored as good (GR) or poor (PR). The root and the surrounding structures were then evaluated and according to the periradicular findings, the treatment was categorized as success or failure.

Results: The success rate for all endodontically treated teeth was 67.4%. Teeth with root canal posts had a success rate of 70.7% and teeth without posts had a success rate of 63.6%. The two groups with technically good endodontics had the highest success rates. In combination with technically good restorations the success rate was 81% and combined with technically poor restorations the success rate was 71%. The two groups with technically poor endodontics combined with either good restorations or poor restorations had significantly lower success rates (56% and 57% respectively).

Discussion: The technical quality of the endodontic treatment as judged radiographically was significantly more important than the technical quality of the coronal restoration when the periapical status of endodontically treated teeth were evaluated. This was in clear contrast to the findings of Ray and Trope who concluded that the quality of the coronal restoration is significantly more important than the quality of the root filling in securing periapical health.

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Roy H. Stevens, DDS, MS; Wanda Gordon, D.M.D. - Comments to author:	wgordon@dental.temple.edu
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