Van T. Himel

Evaluation of repair of mechanical perforations of the pulp chamber floor using biodegradable tricalcium phosphate or calcium hydroxide

The effects of three materials on the biological repair of a defect created by perforating the pulp chamber floor of mandibular posterior teeth in dogs was studied clinically and histologically. The three materials used were tricalcium phosphate, calcium hydroxide, or Teflon discs. The calcium hydroxide caused a more destructive reaction than did the Teflon or tricalcium phosphate groups. The size of the tooth in relation to the size of the perforation was directly proportional to the prognosis; larger teeth had the best results.

The Sealing Ability of Injection-molded Thermoplasticized Gutta-percha with and without the Use of Sealers

This in vitro study evaluated the need for verticalcompaction and the need for sealer when using an injection-molded thermoplasticized gutta-percha technique in straight canals. Seventy-two extracted maxillary anteriors were treated, placed into a fluorescent dye for 24 h, and cross-sectioned at 1, 3, 5, and 7 mm. After recording the presence or absence of dye at each level, a significant difference was found between the groups with sealer and those without sealer, the sealer group having the least amount of leakage.

Treatment of the endodontic emergency: A decade later

A questionnaire was sent to diplomates of the American Board of Endodontics to determine changing trends in the treatment of endodontic emergencies since Dorns survey 10 yr ago. There is a definitely greater trend toward complete instrumentation of the root canals to the apex regardless of the emergency condition than there was a decade ago. The number of respondents who leave teeth open when the pulp is nonvital has dropped dramatically in the past decade. When there is no periapical involvement, over one third of the respondents are completing treatment in one visit. A decrease in the use of classic phenolic medicaments was noted with a corresponding increase in calcium hydroxide or no medication at all.

Torsional properties of nickel-titanium versus stainless steel endodontic files

The purpose of this study was to evaluate and compare the torsional properties of stainless steel K-type .02 taper and nickel-titanium U-type .02 and .04 taper instruments. Torsion tests were performed on all three designs of instruments according to ANSI/ADA specification number 28. For each design, 20 instruments of each of three sizes (15, 25, and 35) were tested. The three parameters measured were maximum torque, torque at failure, and angular deflection. Stainless steel K-type .02 taper and nickel-titanium U-type .02 and .04 taper instruments met or exceeded specification standards for maximum torque. They also satisfied and far exceeded the standards for angular deflection at the failure point. The stainless steel instruments showed no significant difference between maximum torque and torque at failure, whereas both of the nickel-titanium instruments showed a significant differential between maximum torque and torque at failure.

Evaluation of pigmented intraorifice barriers in endodontically treated teeth

The purpose of this study was to evaluate the effectiveness of three pigmented glass ionomer cements used as intraorifice barriers to prevent coronal microleakage. One hundred ten extracted mandibular human premolars were divided into four experimental groups of 25 teeth each and two control groups of 5 teeth each. The experimental teeth were instrumented and obturated using thermoplasticized gutta-percha and AH26 sealer. Group 1 teeth received no further treatment. Teeth in groups 2 through 4 had 1 of 3 pigmented glass ionomers (Vitrebond, GC America, and Ketac-Bond) placed as an intraorifice barrier. Positive control teeth were instrumented but not obturated. The negative control teeth were instrumented, obturated, and externally sealed with epoxy resin. The coronal 3 mm of each root was sealed into the lumen of an 18-mm segment of latex surgical tubing. After the apparatus was sterilized, 2.0 ml of a 24 h growth of Proteus vulgaris in trypticase soy broth (TSB) was placed in the coronal reservoir of the tooth. The inoculated apparatus was placed into a presterilized test tube containing 1.5 ml of TSB and incubated for 90 days at 37 degrees C. The TSB in the lower reservoir was observed daily for turbidity, which would indicate leakage along the full length of the obturated root canal. To determine if differences in microbial leakage occurred among the four experimental groups, Pearsons chi 2 and Fishers exact tests were performed. The confidence level was set at 95%. The positive and negative controls validated the microbial testing method. The teeth without an intraorifice barrier leaked significantly more than teeth with Vitrebond intraorifice barriers (p < 0.05). The difference in leakage among the experimental glass ionomer barriers was not significant (p > 0.05).

An in vitro evaluation of plaster of paris barriers used under amalgam and glass ionomer to repair furcation perforations

Furcation perforations were created in the pulpal floor of 60 teeth and were repaired with amalgam alone, plaster of Paris under amalgam, light-cured glass ionomer alone, and plaster of Paris under light-cured glass ionomer. After the access openings were filled with composite resin, the teeth were immersed in 2% erythrocin B dye solution for 2 wk, sectioned longitudinally, and dye penetration was measured. The light-cured glass ionomer group provided the least amount of leakage, followed by the group of plaster of Paris under glass ionomer. The groups using amalgam alone and plaster of Paris under amalgam showed the most leakage. The plaster of Paris barrier prevented the overextension of the repair materials when used under amalgam and glass ionomer.

Thermafil retreatment using a new “system B” technique or a solvent

The solid plastic carrier in the Thermafil obturation system must be removed to facilitate retreatment. The purpose of this study was to compare the efficacy and time required to retreat canals obturated with Thermafil with plastic carriers using a new technique based on the System B HeatSource or a solvent. Fifty-two extracted human mandibular premolars with single canals were instrumented and then obturated with Thermafil with plastic carriers. After 2 wk storage at 22 degrees C and 100% humidity, they were randomly divided into 2 groups of 26 teeth each. Group 1 teeth were retreated using chloroform and hand files, whereas teeth in group 2 were retreated with a new technique using the System B HeatSource. The end point of retreatment was defined as complete removal of the plastic carrier. The time required for retreatment was recorded. Then, the apical 5 mm segment of each root was sectioned horizontally at 1 mm intervals and each section digitally imaged. The total area of the canal and the area of the canal occupied by gutta-percha and sealer were measured using NIH image software. Data were analyzed using an unpaired t test. The mean time for retrieval of the plastic carrier was significantly less for the System B technique (1.8 min) than for the solvent technique (3.6 min) (p < 0.001). The difference between the two groups in the amount of filling material (carrier, gutta-percha, and sealer) removed was not significant (p > 0.05).

Effect of dentin preparation and acid etching on the sealing ability of glass ionomer and composite resin when used to repair furcation perforations over plaster of Paris barriers.

Access openings and furcation perforations were prepared in 60 human extracted teeth and randomly divided into four equal groups. Plaster of Paris barriers were created in all perforations. The defects were obturated using either glass ionomer or composite resin with or without acid etching of the dentin. The pulp chambers and access openings were filled with composite resin. After immersion in 2% methylene blue solution for 2 weeks, the teeth were sectioned longitudinally and dye penetration was measured under a stereomicroscope using the NIH Image 1.47 Macintosh program. The results indicated that light-cured glass ionomer provided a significantly better seal than did the light-cured composite resin with or without dentin preparation and acid etching. The glass ionomer allowed significantly less dye penetration when used on etched dentin than it did on nonetched dentin.

Periapical response to an apical plug of dentin filings intentionally placed after root canal overinstrumentation

A comparison of periapical response following endodontic overinstrumentation of 24 baboon roots was made between the use of an apical plug of dentin fillings to aid obturation and obturation with gutta-percha and sealer alone. After six months, the groups were evaluated radiographically and histologically. Under the conditions of this study, the following conclusions were made: the presence of an apical plug of dentin filings between the periapical tissues and gutta-percha and sealer filling does not promote a more rapid and favorable healing response than is produced by a gutta-percha and sealer filling without the presence of a dentin plug. At the time intervals selected, a plug of dentin chips promotes a significantly more severe periapical inflammatory response than a gutta-percha and sealer filling without an apical dentin plug. A dentin plug appears to inhibit the deposition of cementum and bone when placed at the apical foramen of an overinstrumented root canal.

Comparison of autoclaving effects on torsional deformation and fracture resistance of three innovative endodontic file systems.

INTRODUCTION Recent innovative manufacturing techniques have produced nickel-titanium (NiTi) rotary instruments with reports of superior properties compared with standard NiTi files. These include Profile Vortex made from M-Wire (PV), Twisted Files (TF), and 10 Series files made from CM Wire (CM). Sterilization is recommended before use and is repeated if files are reused and/or carried forward between cases. The purpose for this study was to compare the effects of multiple autoclaving cycles on the torsional load resistance of these 3 new rotary endodontic files. METHODS PV, TF, and CM files (n = 100; size 25/.04) were divided into 5 groups (n = 20). Files were steam autoclaved for 1, 2, 3, and 7 sterilization cycles. A control group was not subjected to autoclaving. Files were tested in a torsiometer in general accordance with ISO 3630-1 standards. Torsional load and degrees of rotation to failure were recorded. Mean data were analyzed by using Kruskal-Wallace/Dunn post hoc tests (P < .05). RESULTS Autoclave cycles had no significant overall effect on file performance for any of the instrument systems tested. PV and CM displayed significantly greater resistance to torsional load than TF (P < .001) but were not different from each other (P > .05). Angular deflection values for TF and CM were significantly higher than for PV (P < .001), with TF demonstrating greater rotational distortion than CM (P < .05). CONCLUSIONS Under the conditions of this study, repeated steam autoclaving did not affect torsional resistance for unused files of the systems evaluated. In addition, CM Wire files might have a combined advantage of greater torsional strength and high deformation before failure.