DELAYED TOOTH REPLANTATION AFTER ROOT SURFACE TREATMENT WITH SODIUM HYPOCHLORITE AND SODIUM FLUORIDE: HISTOMORPHOMETRIC ANALYSIS IN RATS

In cases of delayed tooth replantation, non-vital periodontal ligament remnants have been removed with sodium hypochlorite in an attempt to control root resorption. Nevertheless, reports of its irritating potential in contact with the alveolar connective tissue have been described. Therefore, this study evaluated the healing process on delayed replantation of rat teeth, after periodontal ligament removal by different treatment modalities. Twenty-four rats, assigned to 3 groups (n=8), had their upper right incisor extracted and left on the workbench for desiccation during 60 min. Afterwards, the teeth in group I were immersed in saline for 2 min. In group II, root surfaces were scrubbed with gauze soaked in saline for 2 min; and in group III, scrubbing was done with gauze soaked in 1% sodium hypochlorite solution. Thereafter, root surfaces were etched with 37% phosphoric acid and immersed in 2% acidulate-phosphate sodium fluoride solution, at pH 5.5. Root canals were filled with a calcium hydroxide-based paste and the teeth were replanted. The animals were sacrificed 60 days postoperatively and the pieces containing the replanted teeth were processed and paraffin-embedded. Semi-serial transversally sections were obtained from the middle third of the root and stained with hematoxylin and eosin for histomorphometric analysis. Data were analyzed statistically using Kruskal-Wallis and Dunn''s tests. The results showed that root structure and cementum extension were more affected by resorption in group III (p<0.05). All groups were affected by root resorption but the treatment performed in group III was the least effective for its control. The treatment accomplished in groups I and II yielded similar results to each other.     

EVALUATION OF THE APICAL INFILTRATION AFTER ROOT CANAL DISRUPTION AND OBTURATION

The aim of this study was to evaluate two root canal filling techniques used in teeth that had their apical foramen disrupted and compare the apical infiltration with an ideal clinical situation. Twenty-seven freshly extracted single-rooted teeth were selected and radiographed to confirm the existence of a single and straight root canal. The crowns were removed at a mean distance of 11 mm from the apex. The teeth had the root canals instrumented and were randomly assigned to 3 groups (n=9): ND group - root canals were filled using the lateral compaction technique and no disruption was performed; DRF group - the apical constriction was disrupted by advancing a #40 K-file 1 mm beyond the original working length, the canals were reinstrumented to create an apical ledge at 1 mm from the apical foramen and were obturated with a master gutta-percha cone with same size as the last file used for reinstrumentation; DF group - the teeth had the apical constriction disrupted and the canals were obturated with a master gutta-percha cone that fit at 1 mm from the apex. The teeth were submitted to dye leakage test with Rhodamine B for 7 days, using vaccum on the initial 5 min. The teeth were sectioned longitudinally and the leakage was measured in a linear fashion from apex to crown. There was no statistically significant difference (p>0.05) between the groups that had the apical foramen disrupted (DF, DRF), but significant difference was found between the disrupted groups and the non-disrupted one (p<0.01). In conclusion, none of the evaluated techniques was able to prevent apical infiltration, so working length so the working length determination has to be established and maintained carefully.     

HISTOMICROBIOLOGIC ASPECTS OF THE ROOT CANAL SYSTEM AND PERIAPICAL LESIONS IN DOGS' TEETH AFTER ROTARY INSTRUMENTATION AND INTRACANAL DRESSING WITH Ca(OH)2 PASTES

OBJECTIVE:

The purpose of this study was to evaluate the distribution of microorganisms in the root canal system (RCS) and periapical lesions of dogs'' teeth after rotary instrumentation and placement of different calcium hydroxide [Ca(OHy-based intracanal dressings.

MATERIALS AND METHODS:

Chronic periapical lesions were experimentally induced in 80 premolar roots of four dogs. Instrumentation was undertaken using the ProFile rotary system and irrigation with 5.25% sodium hypochlorite. The following Ca(OH)₂-based pastes were applied for 21 days: group 1 - Calen (n=18); group 2 - Calen+CPMC (n=20); group 3 - Ca(OH₂ p.a. + anaesthetic solution (n=16) and group 4 - Ca(OH₂ p.a.+ 2% chlorhexidine digluconate (n=18). Eight root canals without endodontic treatment constituted the control group. Histological sections were obtained and stained with Brown & Brenn staining technique to evaluate the presence of microorganisms in the main root canal, ramifications of the apical delta and secondary canals, apical cementoplasts, dentinal tubules, areas of cemental resorption and periapical lesions. The results were analyzed statistically by the Mann-Whitney U test (p<0.05).

RESULTS:

The control group showed the highest prevalence of microorganisms in all sites evaluated. Gram-positive cocci, bacilli and filaments were the most frequent morphotypes. Similar microbial distribution patterns in the RCS and areas of cementum resorption were observed in all groups (p>0.05). The percentage of RCS sites containing microorganisms in groups 1, 2, 3, 4 and control were: 67.6%, 62.5%, 78.2%, 62.0% and 87.6%, respectively.

CONCLUSION:

In conclusion, the histomicrobiological analysis showed that the rotary instrumentation and the different calcium hydroxide pastes employed did not effectively eliminate the infection from the RCS and periapical lesions. However, several bacteria seen in the histological sections were probably dead or were inactivated by the biomechanical preparation and calcium hydroxide-based intracanal dressing.     

A SCANNING ELECTRON MICROSCOPIC STUDY OF THE PATTERNS OF EXTERNAL ROOT RESORPTION UNDER DIFFERENT CONDITIONS

Objective:

The aim of this study was to examine if there are qualitative differences in the appearance of external root resorption patterns of primary teeth undergoing physiologic resorption and permanent teeth undergoing pathological root resorption in different conditions.

Material and Methods:

A total of 40 teeth undergoing external root resorption in different conditions were divided into 4 groups and prepared for examination under scanning electron microscopy at magnifications ranging from 20x to 1000x. Group I: 10 primary molars exfoliated due to physiologic root resorption; Group II: 10 permanent teeth with periapical granulomas showing signs of resorption; Group III:10 permanent teeth therapeutically extracted during the course of orthodontic therapy with evidence of resorption, and Group IV: 10 permanent teeth associated with odontogenic tumors that showed evidence of resorption.

Results:

In Group I, the primary teeth undergoing resorption showed smooth extensive and predominantly regular areas reflecting the slow ongoing physiologic process. In Group II, the teeth with periapical granulomas showed the resorption was localized to apex with a funnel shaped appearance in most cases. Teeth in Group III, which had been subjected to a short period of light orthodontic force, showed the presence of numerous resorption craters with adjoining areas of cemental repair in some cases. Teeth associated with odontogenic tumors in Group IV showed many variations in the patterns of resorption with extensive loss of root length and a sharp cut appearance of the root in most cases.

Conclusion:

Differences were observed in the patterns of external root resorption among the studied groups of primary and permanent teeth under physiologic and pathological conditions.     

IN VITRO EVALUATION OF ROOT CANAL PREPARATION USING OSCILLATORY AND ROTARY SYSTEMS IN FLATTENED ROOT CANALS

Objective:

The aim of this study was to evaluate the biomechanical preparation of flattened root canals using the following systems: Endo-Eze AET stainless steel oscillatory instruments (Ultradent) and RaCe rotary NiTi instruments (FKG Dentaire).

Materials and Methods:

Twenty extracted human mandibular incisors were randomly assigned to two groups: Group 1 - Instrumentation with oscillatory Endo-Eze AET files (oscillatory technique); Group 2 - Instrumentation with rotary NiTi RaCe files (rotary technique). The teeth were decoronated, had their apices and coronal openingssealed with sticky wax and were embedded in crystal-clear orthophtalic polyester resin. The roots were sectioned transversally with diamond discs at 10 mm (middle third) and 5 mm (apical third) from the apex and the segments were reassembled for instrumentation. The sections were photographed before and after root canal instrumentation and evaluated with respect to whether the original root canal shape was modified by instrumentation. To evaluate the differences in the root canal shape before and after biomechanical preparation, scores were given regarding the instruments touch on the intracanal walls.

Results:

In middle third of the root canals instrumented with the rotary system, there was a change in the original canal anatomy (p<0.05), with formation of a protuberance in the mesiodistal direction. This protuberance did not occur when the oscillatory instrumentation was used. The oscillatory system had better results in the middle and apical thirds as evaluated by Dunn’s multiple-comparison test (p>0.05).

Conclusion:

Under the tested conditions, Endo-Eze oscillatory system yielded the instrumentation of all flattened root canal walls, maintaining the canal original shape throughout the biomechanical preparation, and was more effective than RaCe rotary system.     

COMPARISON OF THE CLEANING EFFICACY OF THE FKG RACE SYSTEM AND HAND INSTRUMENT IN MOLAR ROOT CANAL

Introduction and objective:

The aim of this study was to evaluate the ability of root canal cleaning of the RaCe rotary instrumentation system (FKG Dentaire – La-Cheaux-de Fonds – Switzerland), compared to manual filing with Stainless Steel K-files (Maillefer Instruments – Ballaigues – Switzerland).

Material and Method:

Twenty extracted human teeth (maxillary molars) were selected and their pulp tissue was removed after coronal access. The root canals were filled with a dye (India ink) and allowed to dry for 48 hours, followed by establishment of the working length of the mesiobuccal root; then, half of the specimens were instrumented by the modified Oregon technique and the other half were instrumented by crown-down sequence of the RaCe system. After preparation, the teeth were longitudinally sectioned and evaluated according to the amount of remaining dye.

Results:

Data obtained were registered as numerical scores, and the arithmetic means were compared between groups using the Mann Whitney test. Both techniques were unable to completely clean the interior of the root canals, with a better performance of the manual technique only at the middle third.

Conclusion:

It could be concluded that the RaCe system was able to provide satisfactory cleaning, similar to that obtained by the manual instrumentation technique.     

MORPHOLOGIC AND MORPHOMETRIC ANALYSIS OF THE ROOT CANAL APICAL THIRD CLEANING AFTER BIOMECHANICAL PREPARATION USING 3.3% RICINUS COMMUNIS DETERGENT AND 1% NaOCL AS IRRIGATING SOLUTIONS

This study evaluated, by morphologic and morphometric analyses, the cleaning of apical third of root canals instrumented with nickel-titanium rotary files using different irrigating solutions. Twenty-seven single-rooted mandibular premolars were assigned to three groups (n=9), according to the irrigating solution used: Group I, distilled and deionized water; Group II, 1% NaOCl; and Group III, 3.3% Ricinus communis detergent. Biomechanical preparation was performed with Protaper Plusâ nickel-titanium files as follows: S1, SX and S2 at the cervical and middle thirds, and 25/02, 25/04, 25/06, 30/02, 30/04 and 30/06 to complete the instrumentation, operating at 1 mm from the root apex. Irrigation was done at each file change with 2 mL of irrigating solution, totalizing 20 mL for each tooth. After biomechanical preparation, the apical thirds were serially sectioned and histologically processed. The cross-sections were examined by an optical microscope (X40) connected to a computer. The images were captured and analyzed using a computer software and submitted to morphometric analysis with aid of a grid. The percentage of debris remaining at the apical third was calculated. Data were submitted to statistical analysis by ANOVA and Tukey test. The results showed no statistically significant difference (p>0.01) between the groups irrigated with 1% NaOCl and 3.3% Ricinus communis detergent, which presented the lowest percentage of debris at the apical third, 8.49% and 10.11%, respectively. The group irrigated with distilled and deionized water had the highest percentage of debris (15.58%) and was statistically different from the other groups (p<0.01). It may be concluded that 3.3% Ricinus communis detergent and 1% NaOCl had similar cleaning effectiveness on removal of debris from root canals.     

MICROBIAL LEAKAGE AND APICAL INFLAMMATORY RESPONSE IN DOG’S TEETH AFTER ROOT CANAL FILLING WITH DIFFERENT SEALERS,POST SPACE PREPARATION AND EXPOSURE TO THE ORAL ENVIRONMENT

Coronal leakage is an important factor affecting the outcome of endodontic therapy. This study evaluated the microbial leakage (ML) and the apical inflammatory response (AIR) in dog’s teeth after root canal filling with three endodontic sealers, post preparation and exposure to the oral environment, testing the hypothesis that there is a positive correlation between these two histological parameters (ML and AIR). Sixty-four root canals of 8 mongrel dogs were cleaned, shaped and randomly distributed into groups according to the sealer to be used: Sealer 26 (n=18); AH Plus (n=18); RoekoSeal (n=19); no sealer – control group (n=9). Root canals were filled by the lateral condensation technique. Post space preparation left 4 mm of filling material in the apical root third, and specimens were exposed to the oral environment for 90 days. The dogs were killed and jaw blocks were histologically processed using Brown & Brenn and HE staining techniques. ML and AIR were scored from 1 to 4. Results were analyzed statistically using ANOVA, Duncan’s post-hoc test and Spearman’s correlation. ML and AIR score means were: Sealer 26 - 2.44±0.98 and 2.50±0.70; AH Plus - 2.50±0.78 and 2.22±0.54; RoekoSeal - 1.84±0.95 and 2.63±0.83; Control - 2.56±1.23 and 3.11±0.60. Statistically significant differences in AIR scores were found between the AH Plus and control groups (p<0.05). Although RoekoSeal had the lowest ML means, and AH Plus, the lowest AIR means after 90-day exposure to the oral environment, no statistically significant differences were found between the three sealers under study, and no correlation was found between ML and AIR.     

IN VIVO EVALUATION OF THE SEALING ABILITY OF TWO ENDODONTIC SEALERS IN ROOT CANALS EXPOSED TO THE ORAL ENVIRONMENT FOR 45 AND 90 DAYS

This in vivo study evaluated the sealing ability of a resin-based sealer (AH Plus) and a zinc oxide-eugenol sealer (Endofill) in dogs'' teeth, exposed to the oral environment for 45 and 90 days. Forty eight lower incisors from 8 dogs were endodonticaly treated. A stratified randomization determined the sealer use in each root canal. All canals were filled using the lateral condensation technique. The excess filling material at the cervical portion of the root canal was sectioned, leaving a 10-mm obturation length inside the canal. Teeth were provisionally sealed with glass ionomer cement for 24 h and the canals were exposed to the oral environment for either 45 or 90 days. Therefore, the experimental groups were as follows: A45- AH Plus for 45 days; A90- AH Plus for 90 days; E45- Endofill for 45 days; and E90- Endofill for 90 days (n=12). After the experimental period, the dogs were killed and the lower jaw was removed. The incisors were extracted and the roots were covered with two coats of nail varnish. The teeth were immersed in India ink for 96 h and submitted to diaphanization. Dye leakage (in mm) was measured using stereomicroscopy (10x magnification). The results were statistically analyzed using two-way ANOVA and Tukey test for multiple comparisons (á = 0.05). Group E90 (2.03±0.94) showed significantly higher mean leakage value than all other groups (p<0.001). None of the sealers, in both study conditions, were able to prevent dye leakage.     

IN VITRO STUDY OF THE EFFECT OF ER:YAG LASER IRRADIATION ON THE APICAL SEALING OF DIFFERENT ROOT CANAL SEALERS

Objectives:

The aim of this study was to determine the effect of Er:YAG laser irradiation used to clean dentinal walls on the apical sealing of root canals filled with different types of sealers.

Background Data:

Laser application to the dentinal walls removed debris, rendering the root canals free of smear layers and leaving the dentinal canaliculi open.

Methods:

Sixty-four maxillary canines obtained from laboratory files were instrumented with K-files (Dentsply, Maillefer, Ballaigues, Switzerland) using the crown-down technique, and irrigated with a 0.5% sodium hypochlorite solution. The specimens were divided into two groups of 32 teeth each. In group I, the teeth were instrumented and irrigated with sodium hypochlorite solution, and divided into four subgroups to be sealed with the different materials (Endofill, N-Rickert, Sealapex and Sealer 26). In group II, the root canals were subjected to Er:YAG laser irradiation (200 mJ, 7 Hz and 60 J total energy), followed by root canal sealing as in group I.

Results:

The data showed lower levels of apical microleakage in the teeth filled with N-Rickert, Sealapex and Sealer 26 cements than in those sealed with Endofill (p < 0.01). No significant difference in microleakage was observed between teeth irrigated only with 0.5% sodium hypochlorite and those submitted to Er:YAG laser application (p > 0.05).

Conclusions:

The Er:YAG laser irradiation applied to the root canal walls was not able to prevent apical microleakage.     

CLEANING ABILITY OF CHLORHEXIDINE GEL AND SODIUM HYPOCHLORITE ASSOCIATED OR NOT WITH EDTA AS ROOT CANAL IRRIGANTS: A SCANNING ELECTRON MICROSCOPY STUDY

The aim of this study was to evaluate the cleaning efficacy of 2% chlorhexidine gluconate gel (CHX) compared to 2.5% sodium hypochlorite solution (NaOCl) associated or not with 17% EDTA used as irrigants during the biomechanical preparation. Fifty freshly extracted single-rooted human teeth with complete apex formation were randomly divided into five groups: G1 - sterile saline, G2 - 2.5% NaOCl, G3 - 2% CHX, G4 - 2.5% NaOCl + EDTA and G5 - 2% CHX + EDTA. The specimens of G1 were subdivided into two control groups. The teeth were decoronated and the coronal and middle root thirds were prepared with Gates-Glidden burs, and the apical third was reserved to manual instrumentation. All procedures were performed by a single operator. In all groups, 2 mL of irrigant was delivered between each file change. The teeth were sectioned and prepared for analyses under scanning electron microscopy (SEM). SEM micrographs were graded according to a score scale by two examiners. Data were analyzed statistically by Kruskal-Wallis and Dunn tests at 1% significance level. The best results were obtained in the groups in which the irrigant was used followed by the chelating agent. No statistically significant difference was observed among G4, G5 and the positive control group (p<0.01). The groups G2 and G3 were significantly different from the others, presenting the worst cleaning capacity. In conclusion, the use of the chelating agent is necessary to obtain clean canal walls, with open tubules and no heavy debris. The use of 2% chlorhexidine gluconate gel alone is not able to remove the smear layer.     

ORAL MYOFUNCTIONAL AND ELECTROMYOGRAPHIC EVALUATION OF THE ANTERIOR SUPRAHYOID MUSCLES AND TONGUE THRUST IN PATIENTS WITH CLASS II/1 MALOCCLUSION SUBMITTED TO FIRST PREMOLAR EXTRACTION

Objective:

The aim of this study was to assess the existence of myofunctional alterations before and after first premolar extraction in Class II/1 malocclusion patients that could endanger the long-term dental arch stability.

Materials and Methods:

The study was performed by means of morphological, functional and electromyographic analyses in 17 Class II/1 malocclusion patients (group T) and 17 Class I malocclusion patients (group C), both groups with 12-30-year age range (mean age: 20.93 ± 4.94 years).

Results:

Data analyzed statistically by Student’s t-test showed a significant decrease in the maxillary and mandibular dental arch perimeters after orthodontic treatment (p<0.05). The Kruskal-Wallis test analyzed data from tongue posture at rest and during swallowing, not showing significant differences after treatment (groups Tb and Ta) (p>0.05). However, group T differed significantly from group C (p<0.05). The electromyographic data showed that the anterior right and left suprahyoid muscles acted synergistically in both groups, while having a lower myoelectric activity in group T during swallowing.

Conclusions:

Myofunctional alterations observed after the orthodontic treatment in Class II/1 malocclusion seemed to jeopardize the long-term orthodontic stability, making recurrence possible. Further research should be conducted to compare electromyographic data before and after orthodontic treatment in order to corroborate the results of the present investigation.