William G. Schindler

The Sealing Ability and Retention Characteristics of Mineral Trioxide Aggregate in a Model of Apexification

Treatment of the immature pulpless tooth presents both an endodontic and restorative challenge. A more favorable long-term prognosis may be achieved with a mineral trioxide aggregate (MTA) apexification procedure followed by an internal bonding technique. We investigated the efficacy of this treatment option by testing the sealing ability and retention characteristics of MTA when placed as an apical barrier in a standardized in vitro open apex model. MTA was placed as an apical barrier at a thickness of 1 mm or 4 mm, with and without prior calcium hydroxide medication. The barriers were challenged with bacteria exposure within a leakage model and displacement forces on an Instron machine. In the leakage study, 100% of the MTA apical barriers showed bacterial penetration by day 70, compared with 20% of MTA root-end fillings used as controls. The displacement study demonstrated a statistically significant greater resistance to force with a 4-mm thickness of MTA, regardless of calcium hydroxide use. We concluded that it was the intracanal delivery technique and not the MTA that contributed to the leakage observed. MTA shows promise in our proposed treatment option of immature pulpless teeth if the sealing ability can be enhanced by improving the delivery technique.

Epidemiological Evaluation of the Outcomes of Nonsurgical Root Canal Treatment in a Large Cohort of Insured Dental Patients

Selected outcomes following initial nonsurgical root canal treatment (NSRCT) procedures were retrospectively assessed using an insurance company database of 110,766 nonsurgical root canal procedures that were completed by endodontists and their referring general dentists. A subset of 44,613 cases, with a minimum required follow-up time of 2 yr, showed incidences of extraction, retreatment and periradicular surgery equal to 5.56%, 2.47%, and 1.41%, respectively. The incidence of subsequent extraction increased with patient age. Teeth that were not restored after root canal therapy were significantly more likely to undergo extraction than restored teeth. Although the practice pattern for endodontists consisted of a significantly higher proportion of molars (48% more; p < 0.001) and a smaller proportion of anterior teeth (43% less; p < 0.001) than general dentists, both groups of providers had comparable rates of untoward events. These data strongly support the hypothesis that the specialist practice provides similar rates of clinical success compared with other providers, even when treating significantly more complex NSRCT cases. Overall, 94.44% of nonsurgical root canal treated teeth remained functional over an average follow-up time of 3.5 yr. These results are an important indication of the benefits of endodontic treatment when provided in an integrated health care delivery system of endodontists and their referring general dentists.

Clinical Outcomes of Artificial Root-end Barriers with Mineral Trioxide Aggregate in Teeth with Immature Apices

The purpose of this retrospective study was to evaluate the clinical outcomes of ProRoot mineral trioxide aggregate used as an artificial apical barrier in teeth with immature apices. Twenty teeth from 19 patients were included in this study. A healed diagnosis was based on periapical index scores of 1 or 2 and no clinical signs or symptoms at recall examinations. Eighty-five percent (17/20) of these teeth were healed, and improvements in periapical index scores at recall appointments were shown to be statistically significant (P < .001, Wilcoxon signed-rank test). Chi-square test indicated that age, gender, primary treatment versus retreatment, presence of preoperative lesion, and differences in recall times did not significantly influence healing outcome. Overall, these results indicated that the mineral trioxide aggregate apical barrier technique is a successful method for obturating teeth with immature apices.

Evaluation of Ultrasonically Placed MTA and Fracture Resistance with Intracanal Composite Resin in a Model of Apexification

The purpose of this study was to evaluate whether intracoronal delivery of an apical barrier of mineral trioxide aggregate (MTA) placed ultrasonically, non-ultrasonically, or ultrasonically with the addition of an intracanal composite resin provided a better seal against bacterial leakage. A second purpose was to determine whether intracanal composite resin or gutta-percha and sealer placed against an apical barrier of MTA provided greater resistance to root fracture. In a standardized in vitro open apex model, MTA was placed as an apical barrier at a thickness of 4 mm, with and without ultrasonic vibration. The barriers were challenged with bacteria exposure within a leakage model, and fracture resistance was assessed with increasing forces applied via an Instron machine. After 45 days, the addition of ultrasonics significantly improved the MTA seal, compared with the non-ultrasonics treatment (Kruskal Wallis nonparametric ANOVA with Dunn multiple comparison test p < 0.05). Bacterial leakage occurred in 6 (33%) of 18 in the non-ultrasonic MTA group, 2 (11%) of 18 in the ultrasonic MTA group, and 1 (6%) of 18 in the ultrasonic MTA-composite group. There were no significant differences at 90 days. A 4-mm thickness of MTA followed with an intracanal composite resin demonstrated a significantly greater resistance to root fracture than MTA followed with gutta-percha and sealer (one-way ANOVA with Newman-Keuls multiple comparison test, p < 0.01). The MTA-gutta-percha group was not significantly different than the MTA unrestored positive control.

An In Vitro Evaluation of the Accuracy of the Root ZX in the Presence of Various Irrigants

The purpose of this study was to evaluate the accuracy of the Root ZX in vitro in the presence of a variety of endodontic irrigants. The in vitro model, described by Donnelly, consisted of refrigerated gelatin made with 0.9% sodium chloride instead of water. The following irrigants were tested: 2% lidocaine with 1:100,000 epinephrine, 5.25% sodium hypochlorite, RC Prep, liquid EDTA, 3% hydrogen peroxide, and Peridex. A total of 30 extracted, single-rooted teeth were used. The experimental measurements in the presence of the various irrigants were compared with the actual canal lengths. The present data indicate that the Root ZX electronic apex locator reliably measured canal lengths to within 0.31 mm and that there was virtually no difference in the length determination as a function of the seven irrigants used. These results strongly support the concept that the Root ZX is a useful, versatile, and accurate device for the determination of canal lengths over a wide range of irrigants commonly used in the practice of endodontics.

An Evaluation of Canal Morphology at Different Levels of Root Resection in Mandibular Incisors

One hundred randomly selected mandibular incisors were examined to assess the prevalence and location of two canals and to describe the canal anatomy that may be encountered during apical surgery. Sections of the root were cut at 1, 2, and 3 mm from the apex, simulating a 20-degree beveled surgical resection. The sections were digitally imaged at x 50 magnification, and canal dimensions were measured using imaging software. The prevalence of two canals was 2% at 1 mm, 0% at 2 mm, and 1% at 3 mm. At these levels in the roots, the canal was rarely divided by hard tooth structure. An isthmus of tissue was present 20% of the time at 1 mm, 30% at 2 mm, and 55% at 3 mm. Four distinct canal types were noted: (i) round, (ii) oval, (iii) long oval, and (iv) ribbon. In 75% of the teeth, the canal shapes varied from one level to the next. The more coronally the root-end resection was made, the more elongated the canal tended to become.

A Retrospective Study Comparing Clinical Outcomes after Obturation with Resilon/Epiphany or Gutta-Percha/Kerr Sealer

The purpose of this retrospective study was to evaluate the treatment outcome of root canal systems obturated with gutta-percha and Kerr Pulp Canal Sealer compared with Resilon and Epiphany sealer. One hundred three teeth treated in a private endodontic practice were included in the study. Clinical outcomes (healed versus nonhealed) were assessed by using the Periapical Index determination and clinical evaluation at recall appointments. The magnitude of the association between obturation materials used and outcome measured was evaluated with univariate and multivariate logistic regression analysis. Univariate analysis indicated that pulpal vitality, presence of a preoperative lesion, and length of recall times were statistically significant in predicting the outcome. Logistic regression analysis showed that age, tooth position, and length of recall times were statistically significant in predicting the outcome. Root canal systems obturated with gutta-percha and Kerr Pulp Canal Sealer or Resilon and Epiphany sealer had statistically indistinguishable differences in clinical outcome.

A mandibular first molar with a C-shaped root configuration

A case report of C-shape root and canal morphology in a mandibular first molar was presented. The clinical impression of a C-shape canal system formulated during treatment was eventually verified following the extraction and serial sectioning of this tooth. The vertical crown root fracture that necessitated extraction of this molar was discussed and the incorporation of “Why?” into the diagnostic thought process was encouraged.

Effect of Ultrasonic Vibration and Various Sealer and Cement Combinations on Titanium Post Removal

The purpose of this study was to determine the effect of ultrasonic vibration on the force required to remove prefabricated posts. Ninety-six extracted human canines were divided into eight groups, which were prepared and obturated with gutta-percha and either a eugenol-containing (Roths 801 Elite) or eugenol-free (AH26) sealer. Titanium #6 Parapost XH posts were cemented with either zinc phosphate or Panavia 21 resin cement. One half of the sample was subjected to ultrasonic vibration for 16 min at the post-dentin interface, whereas the other half received no vibration (controls). Each combination of sealer, cement, and vibration status was subjected to tensile load to failure using an Instron testing machine. Posts cemented in teeth obturated with gutta-percha and AH26 sealer demonstrated significantly greater resistance to dislodgement, compared with teeth obturated with gutta-percha and Roths 801 Elite sealer. There was no statistical difference in retention of posts cemented with either zinc phosphate or Panavia 21, regardless of the sealer used. Additionally ultrasonic vibration increased post retention for both cements.

A comparison of amounts of apically extruded debris using handpiece-driven nickel-titanium instrument systems

One hundred single-rooted teeth were instrumented with Lightspeed, Profile .04 Taper Series 29, and NT McXIM instruments according to the recommendations of the manufacturers, and Flex-R files using the balanced force technique. Groups were comparable with respect to average curvature, canal length, and major and minor foramen size. A standard amount of irrigant was used for each tooth. Apically extruded debris and irrigant were collected and weighed. Debris was desiccated before being weighed. There were no statistically significant differences among the four groups with respect to total extruded debris. The amount of extruded debris was positively correlated with the amount of irrigant extruded. Factors such as canal length, curvature, and foramen size did not affect the amount of debris extruded.