Mario Luis Zuolo

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.

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.

Success Rates for Removing or Bypassing Fractured Instruments: A Prospective Clinical Study

INTRODUCTION The objective of this study was to evaluate the success rates of standardized techniques for removing or bypassing fractured instruments from root canals and determine whether visualization of the fractured instrument with the aid of an operating microscope has any impact on the success rates. METHODS In this prospective study, attempts were made to visualize 112 fractured instruments under a dental operating microscope after creating a straight-line access to the fragment. By using ultrasonic tips alone or associated with bypassing, the Ruddle technique was attempted to remove the 68 visible instruments. Bypassing was performed for the 44 nonvisible fragments. The χ(2) test was performed to assess whether any significant difference occurred between the success rates observed for the visible and nonvisible fractured instrument groups. RESULTS The overall success rate (removal and bypassing) was 70.5% (n = 79). In the visible fragment group, the success rate was 85.3% (n = 58), and in the nonvisible fragment group it was 47.7% (n = 21). Success rates were significantly higher when the fragment was visible (P = .0009). CONCLUSIONS The standardized techniques used in this study for removing or bypassing fractured instruments were effective, and approximately 2 times greater success rate was obtained when the fragment was visible inside the root canal compared with when it was nonvisible.

Comparison of the Incidence of Postoperative Pain after Using 2 Reciprocating Systems and a Continuous Rotary System: A Prospective Randomized Clinical Trial.

INTRODUCTION The objective of the present study was to clinically compare the incidence of postoperative pain and the intake of analgesic medication (frequency and quantity) after endodontic treatment of posterior teeth using 2 reciprocating systems and a continuous rotary system. METHODS In a prospective randomized clinical study, 210 patients with vital teeth indicated for conventional endodontic treatment were treated by 5 specialists according to a pre-established protocol. The teeth were randomly assigned to 1 of 3 groups (n = 70) according to the instrumentation system used: ProTaper Next (Dentsply Tulsa Dental Specialties, Johnson City, TN), WaveOne (Dentsply Tulsa Dental Specialties), or Reciproc (VDW, Munich, Germany). Treatments were performed in a single visit. After the visit, the patients were given a prescription for ibuprofen 400 mg to be taken every 6 hours if they experienced pain. Participants were asked to rate the intensity of the postoperative pain on a visual analog scale according to 4 classes (no pain, mild pain, moderate pain, and severe pain) after 24 hours, 48 hours, 72 hours, and 7 days. Patients were also asked to record the number of prescribed analgesic medication tablets taken at these time points. RESULTS No statistically significant difference was found among the 3 groups in relation to postoperative pain or analgesic medication intake at the 4 time points assessed (P > .05, Kruskal-Wallis test). CONCLUSIONS The reciprocating systems and the continuous rotary system were found to be equivalent in regard to the incidence of postoperative pain and intake of analgesic medication at the time points assessed.

Retreatment efficacy of gutta-percha removal using a clinical microscope and ultrasonic instruments: Part I—an ex vivo study

OBJECTIVE This study compared the efficacy of gutta-percha/sealer removal from endodontically treated extracted human teeth with and without the aid of a clinical operating microscope/ultrasonic instruments. STUDY DESIGN Forty human extracted maxillary central incisors were prepared using a modified crown-down technique and filled with lateral compactation. Teeth were divided into 2 groups: group I, re-treated using a conventional technique with burs and solvent; and group II, re-treated using a conventional technique with burs and solvent plus clinical operating microscope/ultrasonic tips. Teeth were split longitudinally and photographed, and coded photos transfered to a computer workstation. Total canal space and remaining gutta-percha/sealer were quantified, and ratio of remaining filling material and root canal periphery was computed. Mean percentage of remaining gutta-percha/sealer in each group was compared using analysis of variance. RESULTS The average percentage of remaining gutta-percha/sealer was 25.21% in group I and 9.31% in group II, showing a statistically significant difference (P = .05). CONCLUSION The use of the dental operating microscope and ultrasonic tips removed the filling material from root canal walls better, but all examined teeth, in both groups, had remaining filling material on canal walls.

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.

Evaluation of the Efficacy of TRUShape and Reciproc File Systems in the Removal of Root Filling Material: An Ex Vivo Micro-Computed Tomographic Study.

INTRODUCTION The purpose of this study was to evaluate the efficacy of TRUShape (Dentsply Tulsa Dental Specialties, Tulsa, OK) compared with the Reciproc file (VDW, Munich, Germany) in the removal of filling material from oval canals filled with 2 different sealers and differences in the working time. METHODS Sixty-four mandibular canines with oval canals were prepared and divided into 4 groups (n = 16). Half of the specimens were filled with gutta-percha and pulp canal sealer (PCS), and the remainders were filled with gutta-percha and bioceramic sealer (BCS). The specimens were retreated using either the Reciproc or TRUShape files. A micro-computed tomographic scanner was used to assess filling material removal, and the time taken for removal was also recorded. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. RESULTS The mean volume of the remaining filling material was similar when comparing both files (P ≥ .05). However, in the groups filled with BCS, the percentage of remaining filling material was higher than in the groups filled with PCS (P < .05). The reciprocating file allowed for faster filling removal than the TRUShape files (P < .05). Retreatment was faster in the groups that were filled with PCS compared with those filled with BCS (P < .05). CONCLUSIONS There was no difference regarding the percentage of remaining filling material when comparing both files system; however, Reciproc was faster than TRUShape. BCS groups exhibited significantly more remaining filling material in the canals and required more time for retreatment. Remaining filling material was observed in all samples regardless of the technique or sealer used.

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 (Students t test, p = 0.01). The plastic carrier was easily removed from the canals.

Micro–computed Tomography Assessment of Dentinal Micro-cracks after Root Canal Preparation with TRUShape and Self-adjusting File Systems

Introduction The aim of the present study was to evaluate the percentage frequency of dentinal micro‐cracks observed after root canal preparation with TRUShape and Self‐Adjusting File (SAF) systems by means of micro–computed tomography imaging analysis. A conventional full‐sequence rotary system (BioRace) and a single‐file reciprocation system (Reciproc) were used as reference techniques for comparison because of their known assertive cutting efficiency. Methods Forty anatomically matched mandibular incisors were selected, scanned at a resolution of 14.25 &mgr;m, and assigned to 4 experimental groups (n = 10), according to the preparation protocol: TRUShape, SAF, BioRace, and Reciproc systems. After the experimental procedures, the specimens were scanned again, and the registered preoperative and postoperative cross‐section images of the roots (n = 70,030) were screened to identify the presence of dentinal micro‐cracks. Results Overall, dentinal defects were observed in 28,790 cross‐section images (41.11%). In the TRUShape, SAF, BioRace, and Reciproc groups, dentinal micro‐cracks were visualized in 56.47% (n = 9842), 42.38% (n = 7450), 32.90% (n = 5826), and 32.77% (n = 5672) of the slices, respectively. All dentinal defects observed in the postoperative data sets were already present in the corresponding preoperative images. Conclusions None of the preparation systems induced the formation of new dentinal micro‐cracks. HighlightsThe frequency of dentinal micro‐cracks was evaluated after canal preparation with TRUShape and Self‐Adjusting File systems using micro‐CT analysis.Micro‐CT nondestructive technology provides the possibility to examine the dentinal tissue before any root canal procedure.Dentinal micro‐cracks were visualized in 56.47%, 42.38%, 32.90%, and 32.77% of the slices in the TRUShape, SAF, BioRace, and Reciproc groups, respectively.All dentinal defects observed in the postoperative data sets were already present in the corresponding preoperative images.None of the preparation systems induced the formation of new dentinal micro‐cracks.

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.