Peter Parashos

Factors Influencing Defects of Rotary Nickel-Titanium Endodontic Instruments After Clinical Use

This study examined used, discarded rotary nickel-titanium instruments obtained from 14 endodontists in four countries, and identified factors that may influence defects produced during clinical use. A total of 7,159 instruments were examined for the presence of defects. Unwinding occurred in 12% of instruments and fractures in 5% (1.5% torsional, 3.5% flexural). The defect rates varied significantly among endodontists. Instrument design factors also influenced defect rate, but to a lesser extent. The mean number of uses of instruments with and without defects was 3.3 +/- 1.8 (range: 1-10), and 4.5 +/- 2.0 (range: 1-16), respectively. The most important influence on defect rates was the operator, which may be related to clinical skill or a conscious decision to use instruments a specified number of times or until defects were evident.

Treatment of tooth discoloration after the use of white mineral trioxide aggregate.

INTRODUCTION A number of vital pulp therapy techniques have been recommended to preserve pulp vitality in teeth with complicated crown fractures, especially in young patients. Calcium hydroxide has been the gold standard as a pulp capping material, but recently mineral trioxide aggregate (MTA) has been recommended. This case report describes the treatment of tooth discoloration caused by white MTA (WMTA) used for the management of a complicated crown fracture. METHODS A partial pulpotomy was performed with the use of WMTA after a complicated crown fracture of the upper right central incisor. Seventeen months later, the WMTA was removed because of tooth discoloration, and internal bleaching was performed. RESULTS Upon access, the WMTA was completely discolored. After it was removed, a significant color change was observed in the tooth crown, which was further improved with internal bleaching. The tooth remained vital, and a dentin bridge was confirmed clinically and radiographically. CONCLUSIONS The recommendation to use WMTA for vital pulp therapy in the esthetic zone may need to be reconsidered. Should discoloration occur with the use of WMTA, the technique described may be used to improve the esthetics.

Coronal Tooth Discoloration and White Mineral Trioxide Aggregate

INTRODUCTION This study assessed and characterized discoloration when white MTA (wMTA) was placed in the coronal aspect of the root canal ex vivo and the influence of red blood cells on this discoloration. METHODS Canals were prepared from the apical aspect and restored with either wMTA + saline (n = 18), wMTA + blood (n = 18), or controls (n = 4 + 4) (blood or saline alone). Color was assessed according to the CIE L*a*b* color space using standardized digital photographs at 3 time points: baseline, day 1, and day 35. Statistical analysis was performed by using 1-way analysis of variance and a 2-sample t test with P < .05. RESULTS All teeth discolored when restored with wMTA, which was most prominent in the cervical third of the crown. The presence of blood within the canal adjacent to the setting wMTA exacerbated the discoloration (P = .03). CONCLUSIONS wMTA induces the gray discoloration of the tooth crown, and the effect is compounded in the presence of blood.

Evaluation of an Ultrasonic Technique to Remove Fractured Rotary Nickel-Titanium Endodontic Instruments from Root Canals: Clinical Cases

The removal of fractured rotary nickel-titanium instruments from small, curved root canals is one of the most complex operative procedures in endodontics. There have been many different devices and techniques developed to remove fractured instruments, but none are consistently successful and all show a high incidence of canal damage such as perforation. A technique using a staging platform and the use of modern ultrasonic tips with direct visualization through a dental operating microscope has recently been evaluated. The use of this technique in clinical practice is described in 24 cases and illustrated by 3 cases.

The effect of ultrasonically activated irrigation on reduction of Enterococcus faecalis in experimentally infected root canals

AIM To investigate the ability of an ultrasonically activated irrigating system to eliminate bacteria from the canal wall and dentinal tubules of extracted teeth. METHODOLOGY One hundred and thirty roots of intact human teeth were inoculated with Enterococcus faecalis for 4 weeks. The straight roots were randomly allocated to a baseline group (n=25) or subjected to routine cleaning and shaping procedures (n=105). Two sub-groups of prepared canals were then additionally exposed either to ultrasonic irrigation with 1% sodium hypochlorite (NaOCl) for 1 min (n=35) or to 1 week of intracanal medication with calcium hydroxide [Ca(OH)(2)] (n=35). All roots were processed for light microscopy (Brown and Brenn stain) (n=28) or scanning electron microscopy (n=7). Triplicate histological sections from each of the apical, middle and coronal thirds were scored for bacterial presence using pre-defined criteria. RESULTS Baseline bacterial penetration resulted in an average depth of tubule invasion of 151 μm. Routine canal preparation failed to eliminate bacteria consistently from either the canal wall or within tubules. Ultrasonic irrigation and medication with Ca(OH)(2) consistently eliminated bacteria from the canal wall (P<0.001) compared with baseline and routine treatment, and more frequently from dentinal tubules than routine canal preparation alone (P<0.01). Ultrasonic irrigation was as effective in bacterial reduction as 1 week of intracanal medication with Ca(OH)(2), but neither led to complete bacterial elimination in all roots. CONCLUSIONS Ultrasonically activated irrigation for 1 min with 1% NaOCl after canal preparation in straight root canals is potentially an effective supplementary step in microbial control.

A Comparative Investigation of Cone-beam Computed Tomography and Periapical Radiography in the Diagnosis of a Healthy Periapex

INTRODUCTION This research aimed to compare the appearance of healthy periapical tissues on cone-beam computed tomography (CBCT) with periapical radiography and to measure the periodontal ligament (PDL) space on CBCT for teeth with healthy and necrotic pulps. METHODS Patient records from specialist endodontic practices were examined for teeth that had a high-resolution (0.08-mm voxel) and small field-of-view CBCT scan, a periapical radiograph, and clinical pulp tests (CO2 and electric pulp testing). The periapical regions of the CBCT scans and radiographs were scored individually by 2 calibrated, blinded examiners by using a modified CBCT-periapical index (CBCT-PAI) for both and represented as CBCT-PAI and PAI, respectively. The Fisher exact and χ(2) statistics tested the relationships between CBCT-PAI, PAI, and pulp status. RESULTS Of 200 teeth included in the study, 166 showed clinical signs of pulpal health, and the CBCT-PAI score was greater than the PAI in 72% (119 of 166), with a vital pulp likely to have a radiographic PDL space widening of 0-1 mm (P < .001). Although 2 healthy teeth showed radiolucencies 2-4 mm on CBCT scan when the periapical radiograph showed none, a PDL space of greater than 1-2 mm was indicative of a necrotic pulp (P < .001). CONCLUSIONS Teeth with necrotic pulps were more likely to have PDL widening, but the PDL space of a healthy tooth demonstrated significant variation when examined by CBCT. The radiographic interpretation of health and disease on CBCT must be further investigated before usage in outcome or epidemiologic investigations. This research questions the traditional radiographic interpretation of the PDL space.

Articaine: a review of the literature

Articaine is one of the most recent local anaesthetic drugs made available to dentists worldwide. Anecdotal reports advocate its superiority over other common local anaesthetic agents and controversy exists concerning its clinical safety. This article reviews the current literature on articaine use in dentistry specifically addressing the issues of efficacy and safety.

Australian endodontists’ perceptions of single and multiple visit root canal treatment

AIM To ascertain endodontists point of view (treatment philosophy, rationale and preference) regarding single- and multiple-visit root canal treatment. To identify the basis on which the choice is made and how the information necessary for the choice is acquired. METHODOLOGY Endodontists registered with the dental practice board of every state in Australia were contacted, and if they agreed to participate, they were interviewed either face to face or by telephone. The following topics were addressed in an interview lasting 15 to 20 min: demographics, current clinical procedures, treatment rationales and preference. A hypothetical scenario was posed to investigate which treatment regimen they would prefer to deliver if biological concerns were eliminated from consideration. RESULTS Fifty-two endodontists (71% of all Australian endodontists) agreed to participate in the study. Almost all (51/52) participants had performed single-visit root canal treatment, but very few routinely performed it. A majority of participants were willing to provide single-visit treatment where patients had time constraints, and in vital cases (including elective endodontics). The most powerful factor of influencing practice change was interpersonal contact with colleagues. Publications in academic journals have a weak influence in practice change. CONCLUSIONS Australian endodontists strongly prefer multiple-visit over single-visit root canal treatment even in cases where biological concerns are not an issue. Operator preference rather than biological or patient considerations appear to be the primary determinant of treatment choice.

Bonding of Resin-based Sealers to Root Dentin

This study compared the microshear bond strength of three resin-based sealers to root dentin and assessed whether sealer cements behave differently in thin and thick films. Extracted maxillary premolars were sectioned buccolingually, and 45 root halves were randomly allocated for microshear bond testing with the three resin sealers in thin and thick films. The microshear bond strength was then calculated in MPa. Failure modes were examined under light and scanning electron microscopy. Data were analyzed by using analysis of variance, with significance set at p < 0.05. Overall, the epoxy resin-based sealers had the highest microshear bond strength to root dentin compared with urethane dimethacrylate-based sealers (p < 0.001). Bond strengths for the thick sealer group were significantly higher than the thin sealer group (p < 0.001) and may reflect different patterns of behavior when the sealer is present as a thin layer.

Root canal debridement efficacy of different final irrigation protocols

AIM To compare the smear layer and debris removal effectiveness of four root canal irrigation protocols as well as their effectiveness in removing remaining soft tissues in curved root canals. METHODOLOGY The mesiobuccal and mesial root canals of 107 extracted human maxillary and mandibular molars were instrumented using Mtwo rotary NiTi instruments then randomly divided into four groups according to a final rinse protocol: Group 1 (n = 28) - manual agitation of 1% NaOCl and 15% EDTA; Group 2 (n = 26) - CanalBrush agitation of 1% NaOCl and 15% EDTA; Group 3 (n = 26) - 3% H(2) O(2) alternated with 1% NaOCl; Group 4 (n = 27) - passive ultrasonic agitation of 1% NaOCl and 15% EDTA. All irrigation protocols were performed in a closed system. Eleven roots per group were prepared and histologically stained (H&E) to assess percentage of remaining pulpal tissues in the apical thirds. The remaining specimens were split longitudinally and examined under scanning electron microscope at ×2000 magnification to assess smear layer and debris removal. Image Pro Plus 6.0 software was used to analyse smear layer and remaining pulp tissue. Debris presence was scored by two blinded investigators using a five-point scale. Data were analysed using Univariate analysis of variance (GenStat 13, α = 0.05). RESULTS CanalBrush and passive ultrasonic irrigation were equally effective with significantly less smear layer and debris than manual agitation and H(2) O(2) alternated with NaOCl (P < 0.05). The H(2) O(2) alternated with NaOCl protocol was significantly more effective in removing pulp tissue remnants in the apical level than manual agitation (P = 0.009) and passive ultrasonic irrigation (P = 0.01). CONCLUSIONS CanalBrush was as effective as passive ultrasonic irrigation in smear layer and debris removal. Alternating H(2) O(2) with NaOCl was effective in removing soft tissues from root canal complexities. Further studies are required to evaluate effectiveness of this regimen taking into account irrigant volume differences and effect of root canal system configuration.