Micro-CT assessment of the shaping ability of four root canal instrumentation systems in oval-shaped canals.

AIM: To compare the shaping ability of four root canal instrumentation systems in oval-shaped canals using micro-computed tomographic analysis. METHODOLOGY: Forty anatomically matched mandibular incisors were scanned and assigned to four groups (n = 10), according to the canal preparation protocol: BioRace, Reciproc, Self-Adjusting File (SAF) and TRUShape systems. After canal instrumentation, the specimens were rescanned, and the registered pre- and postoperative datasets were examined to evaluate the percentages of accumulated hard-tissue debris, untouched canal walls and dentine removed. Kruskal-Wallis and Mann-Whitney U-tests with Bonferroni correction were used to compare the variables in the groups (α = 5%). RESULTS: The preparation techniques did not affect the percentage of accumulated hard-tissue debris (P = 0.126). The percentage of untouched canal areas was significantly higher for BioRace (32.38%)compared to Reciproc (18.95%) and SAF (16.08%) systems (P < 0.05). Reciproc removed significantly more dentine (4.18%) than BioRace (2.21%) and SAF (2.56%) (P < 0.05). The TRUShape system had intermediate results for both untouched canal walls (19.20%) and dentine removed (3.77%), with no significant difference compared to BioRace, Reciproc and SAF systems. CONCLUSIONS: The preparation techniques resulted in the same level of accumulated hard-tissue debris. Compared to the other tested systems, BioRace was associated with more untouched canal walls and Reciproc produced the greatest amount of removed dentine. Although it touched more of the root canal walls, the SAF system removed less dentine, whereas TRUShape had intermediate results for these same parameters. None of the systems tested were able to provide optimal shaping ability in oval-shaped canals.

Efficacy of reciprocating and rotary techniques for removing filling material during root canal retreatment.

AIM: To compare the efficacy of reciprocating and rotary techniques with that of hand files for removing gutta-percha and sealer from root canals. METHODOLOGY: The root canals of fifty-four human extracted maxillary central incisors were cleaned and shaped using a crown-down technique to a size 40 and filled with gutta-percha and a zinc oxide-eugenol-based sealer using a lateral compaction technique. Teeth were divided into three groups according to the technique used for removing the root filling material: group I - Gates-Glidden burs and stainless steel hand files up to size 50; group II - rotary technique with NiTi Mtwo R files and additional Mtwo files to size 50, 0.04 taper; group III - reciprocating technique with the Reciproc instrument R50, size 50, 0.05 taper. Chloroform was used as a solvent in all groups. Teeth were then split longitudinally and photographed under 8× magnification. The images were transferred to a computer, and the total canal space and remaining filling material were quantified. The ratio of remaining filling material to root canal periphery was computed with the aid of Image Tool 3.0 software. The mean percentages of remaining filling material and time required to remove it were compared using the Kruskal-Wallis and Mann-Whitney tests (P < 0.05). RESULTS: The mean percentage of remaining filling material was significantly higher (P < 0.05) in group II, with Mtwo rotary files (12.17%), than in group I, with the hand file technique (7.19%), and group III, with Reciproc instruments (4.57%), which were statistically similar (P > 0.05). The time required to remove filling material was significantly shorter (P < 0.05) in group III (194 s), followed by group II (365 s) and group I (725 s) (P < 0.05). CONCLUSION: Remaining endodontic filling material was observed on the canal walls of all teeth regardless of the technique used. Hand files combined with Gates-Glidden burs (group I) and the reciprocating technique (group III) removed more filling material from the canal walls than the Mtwo R files. The reciprocating technique was the most rapid method for removing gutta-percha and sealer, followed by the rotary technique and the hand file technique.

Identification of GM3 as a marker of therapy-resistant periradicular lesions.

The purpose of this study was to analyze the profile of glycosphingolipids (GSLs) in periradicular lesions refractory to endodontic treatment. Sixteen periapical lesions were removed surgically from patients (experimental group) and compared with 10 samples of periodontal ligament removed from extracted intact third molars (control group). After the GSLs extraction and purification procedures were performed the neutral and acidic GSL fractions were analyzed by high-performance thin-layer chromatography and quantified by densitometry. Data reported herein show that: (i) tissues in the experimental group presented about twice as much GSLs as the control group; (ii) lesion tissues express lactoneotetraosylceramide, and lactofucopentaosyl (IV) ceramide, whereas these neutral GSLs are absent in normal tissues; and (iii) normal tissues express GT1b, whereas lesions cells do not express this ganglioside. In contrast lesion tissues express GM3, which is conspicuously absent in normal tissues.

Orifice locating with a microscope.

The purpose of this study was to determine whether the use of the dental operating microscope (DOM) could increase the number of root canal orifices located in mandibular molars. Ninety-three first and 111 second extracted mandibular molars were used. With the naked eye, all access cavities were prepared and the number of canals in each root was recorded. Using a DOM with x8-x13 magnification, all teeth had the access cavity preparations again examined. With the naked eye, a total of 641 canals were seen in all teeth. After the DOM examination, 50 more canals could be visualized, representing a 7.8% increase in the total number of located canals. From these canals, 35 were located in the first molars and 15 in the second molars. The use of the DOM increases the number of root canal orifices located.

Prognosis in periradicular surgery: a clinical prospective study.

AIM: The purpose of this prospective study was to evaluate the prognosis of periradicular surgery using well-defined case selection and a rigorous surgical protocol. METHODOLOGY: Teeth to be treated surgically demonstrated a periradicular lesion of strictly endodontic origin with or without clinical signs and symptoms of inflammation. A total of 114 teeth were treated. Following the reflection of a full mucoperiosteal tissue flap, residual soft tissues were curetted, root ends were resected with a fine high-speed diamond bur, root-end cavities were prepared ultrasonically with diamond tips, and IRM root-end fillings were placed. Cases were followed clinically and radiographically for a period ranging from 1 to 4 years. RESULTS: The results of this study showed 91.2% success out of a total of 102 teeth available for follow-up, based on accepted parameters of evaluation. Cases were considered successful if there were no clinical signs or symptoms present and there was radiographic evidence of complete or incomplete healing (scar tissue). Factors related to case selection, parameters of healing and surgical technique are discussed in relation to the success rate identified in this prospective study. CONCLUSIONS: Adherence to a strict endodontic surgical protocol and the use of contemporary techniques and materials will result in a predictably successful outcome in a wide range of teeth.

Ultrasonic root-end preparation with smooth and diamond-coated tips.

The purpose of this study was to compare the effects of smooth and diamond-coated ultrasonic retrotips on the external and internal surfaces of root-end preparations with the aid of a scanning electron microscope (SEM). Forty-four mesial roots of human mandibular molars were selected. The canals were cleaned, shaped and obturated using gutta-percha and sealer. The apical portions were resected at a 45 degrees-angle bevel exposing both mesial canals and the isthmus area. The roots were then divided into two groups according to the type of root-end preparation: Group A--performed with smooth retrotips (S) and Group B--performed with diamond-coated retrotips (DC). The specimens were coded and prepared for SEM evaluation. Observations of the external surface preparation showed that the S and DC retrotips produced very well-centered cavities involving both canals and isthmus area with minimal deviations and no perforative defects. When the internal surface of the root-end preparations was evaluated, it was evident that the use of S retrotips resulted in clean canal walls with little superficial debris and smear layer. Internal canal surfaces done with DC retrotips were irregular showing patent grooves, in contrast with the more uniform, regular and smoother surfaces when S retrotips were employed.

Sealing ability of composite resin placed over calcium hydroxide and calcium sulphate plugs in the repair of furcation perforations in mandibular molars: a study in vitro.

The purpose of this study was to evaluate in vitro the sealing ability of various materials in the repair of furcation perforations in mandibular molars by measuring coronal microleakage with Indian ink. Ninety extracted mandibular molars were embedded individually into a plaster of Paris block, with the roots surrounded by a simulated periodontal ligament of silicone. Subsequently, a standard coronal access opening was prepared, the root canal orifices were located and a perforation was made with a size 012 round bur in a water-cooled high-speed handpiece directly into the centre of the floor of the pulp chamber. The perforations were repaired with amalgam, composite resin, calcium sulphate under composite resin and calcium hydroxide under composite resin. The teeth were coated with two layers of nail polish, leaving the access opening area uncovered, and immersed in Indian ink for 4 days at 37 degrees C. The teeth were sectioned longitudinally and dye penetration measured from the coronal level of the repair material to the apical end of the perforation. All experimental groups revealed dye penetration in varying degrees, but there was no significant difference amongst them (Kruskal-Wallis test P < 0.05). Calcium sulphate and calcium hydroxide prevented overextrusion of composite resin when used under this repair material.

Instrument deterioration with usage: nickel-titanium versus stainless steel.

Nickel-titanium instruments purportedly resist deformation and loss of sharpness better than do stainless steel instruments but may be more susceptible to breakage. The processes of wear and breakage of nickel-titanium and stainless steel instruments were examined. Sixty files of five types (12 each) and three manufacturers were used. All were used repeatedly in curved canals until failure or for a maximum of 22 minutes. Each instrument was examined with scanning electron microscopy both new (control) and at spaced intervals for evidence of wear and fatigue. All new instruments were of good quality. Stainless steel instrument tended to wear the most rapidly, and next were nickel-titanium rotary instruments; the most resistant to wear were nickel-titanium hand instruments. There were few instrument separations. In general, nickel-titanium (particularly hand) instruments resisted deterioration better than did stainless steel. Nickel-titanium rotary instruments (2 of 12) had the most breakage.

Bacterial penetration through temporary restorative materials in root-canal-treated teeth in vitro.

Seventy extracted single-rooted mandibular premolars were used in this study to determine the length of time needed for bacteria present in natural human saliva to penetrate through three commonly used temporary restorative materials and through the entire root canal system obturated with the lateral condensation technique. Five intact teeth with no decay were used in the negative control group and five teeth with extensive decay in communication with the canal, in the positive control group. The 60 teeth used in the experimental group were divided into three groups. In Group 1, the access cavities of 20 teeth were temporarily restored with gutta percha, in Group 2 with IRM and in Group 3 with Cavit-G. All 70 teeth were mounted individually where the crown was placed in contact with human saliva. All five teeth in the positive control group caused broth turbidity within 24 h. In contrast, broth in the negative control group remained clear throughout the entire experimental period. In the experimental group, the average time for broth contamination of access cavities closed with gutta percha, IRM and Cavit-G was 7.85, 12.95 and 9.80 days, respectively. The Kruskal-Wallis nonparametric test showed significant differences among the groups, while the multiple comparison test showed that the IRM group was statistically better than the gutta percha group when the average lengths of time for contamination were compared (P < 0.05).

Effectiveness of the Canal Finder and hand instrumentation in removal of gutta-percha root fillings during root canal retreatment.

The purpose of this study was to quantify the amount of remaining gutta-percha/sealer on the canal walls when the Canal Finder system, hand instrumentation and a combination of both (hybrid technique) were used to remove these materials. The amount of apically-extruded debris and the time required for removal were also recorded. Sixty extracted maxillary anterior teeth were prepared using a stepback technique and obturated with gutta-percha. Reinstrumentation of all groups was done in conjunction with a solvent, chloroform. The teeth were split longitudinally and photographed, and the total area of the root canal and the area of the debris were traced and quantified using a computerized image analysis system. The ratio of remaining obturation material to root canal surface was derived and analysed statistically. Hand instrumentation resulted in less debris remaining than did the other two techniques (P < 0.05). The differences in the amount of apically extruded debris were not significant among the techniques (P > 0.05). The hybrid technique required significantly less time for filling material removal. The Canal Finder system alone was not superior to hand instrumentation.

Factors associated with endodontic flare-ups: a prospective study.

The purpose of this prospective study was to assess the incidence of flare-ups (a severe problem requiring an unscheduled visit and treatment) among patients who received endodontic treatment by the two authors in their respective practices during a period of one year, and also to examine the correlation with pre-operative and operative variables. The results showed an incidence of 1.58% for flare-ups from 1012 endodontically treated teeth. Statistical analysis using the chi-square test (P<0.05) indicated that flare-ups were found to be positively correlated with multiple appointments, retreatment cases, periradicular pain prior to treatment, presence of radiolucent lesions, and patients taking analgesic or anti-inflammatory drugs. In contrast, there was no correlation between flare-up, and age, sex, different arch/tooth groups and the status of the pulp.

Guided bone regeneration in the treatment of a large periapical lesion: a case report.

A large (19 mm x 24 mm) periapical lesion associated with tooth #10, perforating both the labial and palatal cortical plates, was treated with decalcified freeze-dried bone allograft and guided bone regeneration. The membranes were removed after a seven-month healing period. Complete osseous reconstruction of the cortical plates was noted. Biopsies demonstrated healing with mature bone and hemopoietic marrow. Few particles of decalcified freeze-dried bone could be observed. Graft particles that remained were surrounded by new bone. The learning objective of this article is to present the regeneration procedure utilized along with the histologic biopsy results to the clinician.

Ridge augmentation following extraction of replanted central incisor.

Regeneration of bone defects remains a clinically important problem in many instances. This paper reports on the use of membrane technique combined with decalcified freeze-dried bone allograft to promote bone formation after extraction of a replanted central incisor with extensive root resorption. The procedure prevented ridge reduction, both buccolingually and apicocoronally, and will facilitate prosthetic replacement of the lost tooth without esthetic problems.

Endodontic retreatment of thermafil or lateral condensation obturations in post space prepared teeth.

The purpose of this study was to quantify the amount of remaining gutta-percha/sealer after retreatment of post space prepared teeth obturated with a lateral condensation technique or with Thermafil with plastic and metallic carrier. The time required for retreatment was also recorded. Forty-five extracted mandibular premolars were prepared using a step-back flared technique and obturated. The post space was prepared and a 5-mm obturation was left in the canal. Retreatment of all groups was done using a solvent technique. The teeth were split longitudinally and photographed. The total area of the canal and the area of gutta-percha/sealer were traced on white paper. Both areas were quantified using a computerized image analysis system and the ratio of remaining obturation material to root canal periphery was derived and statistically analyzed. Statistical analysis (analysis of variance, p = 0.01) showed no differences among the techniques when the average percentage of remaining gutta-percha/sealer was compared. Results revealed that the Thermafil metallic retreatment group consumed significantly more time than the others (analysis of variance, Scheffe p = 0.01). The metallic carriers were not easily removed from the canals, six metal carriers could not be retrieved during the retreatment routine.

Comparison of endodontic retreatment of laterally condensed gutta-percha and Thermafil with plastic carriers.

The purpose of this study was to evaluate canal wall cleanliness in cases of retreatment using laterally condensed gutta-percha and Thermafil with plastic carriers. Forty extracted mandibular canines were prepared using a step-back flared technique and divided into two groups: group A, obturated with lateral condensation and group B, obturated with Thermafil. AH26 was the sealer used in both groups. Retreatment of all teeth was done using Gates Glidden burs and a solvent. The teeth were then split longitudinally, photographed, and projected onto a screen at x10 magnification. The total area of the canal and the area of gutta-percha/sealer were then traced on white paper. Both areas were accurately quantified using a computerized image analysis system and the ratio of remaining obturation material to root canal periphery was derived and statistically analyzed. Results showed that the average percentage of the remaining gutta-percha/sealer was 14.23 for the lateral condensation group and 15.70 for the Thermafil group with no statistically significant difference (Student's t test, p = 0.01). The plastic carrier was easily removed from the canals.

Canal Master files: scanning electron microscopic evaluation of new instruments and their wear with clinical usage.

Canal Master instruments have a short, fluted cutting area and a small flexible shaft; they may be predisposed to rapid wear and breakage. This study examined new and used files as to tip, flute, and shaft design when new and with increasing time of canal preparation. One hundred files prepared 140 curved canals. Sizes #20, #40, and #60 files were examined unused and after 1, 3, 5, and 7 min of use. Evaluation was for uniformity when new and for deterioration and breakage with usage. The smaller sizes (#20 and #40) had some inconsistencies when new and were most predisposed to wear and breakage with time. Findings suggest that smaller files could have had improved quality control by the manufacturer. Also, they should be used with caution and discarded after short times of use in small, curved canals. This should minimize instrument separation and maximize cutting efficiency.

Histologic evaluation of three endodontic instrument/preparation techniques.

33 curved canals were prepared to quantify both the increase in canal area and predentin removal in the apical region. Compared were three different file designs/instrumentation techniques, that is "stepback" with K-flex file, "balanced force" with Flex-R file, and the Canal Master system. Following canal preparation and histological processing, cross-sections at 1 and 3 mm levels were examined using the Bioquant image analysis system. Results showed that, at the 3 mm leve, the mean increase in canal area and predentin removal showed no statistically significant difference (p > 0.05) between the techniques. At 1 mm, the step-back technique (with K-flex files) resulted in a significant increase in canal area and greater predentin removal than did the "balanced forces" (with Flex-R files) or the Canal Master system. However, although there were statistical differences, the actual differences were small; these may not translate to clinically significant differences in the 3 techniques.