Subcutaneous emphysema in patients undergoing root canal treatment: a systematic review of the factors affecting its development and management.

BACKGROUND: Subcutaneous emphysema is an infrequent mishap during root canal treatment which, in rare cases, can lead to severe complications. AIM: To systematically review the literature on the factors affecting the development of subcutaneous emphysema during root canal treatment, and on its management. DATA SOURCES: An electronic search was conducted in EMBASE (1947-2018), LILACS (1982-2018), PubMed (1950-2018), SciELO (1997-2018), Scopus (1970-2018), Web of Science (1900-2018) and two grey literature databases. Moreover, all issues of nine journals and four endodontic textbooks were hand-searched. STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, INTERVENTIONS: The retrieved studies were screened by two reviewers to select clinical studies, case reports or case series describing subcutaneous emphysema that developed during or immediately after root canal treatment in adult patients. STUDY APPRAISAL AND SYNTHESIS METHODS: Included studies were critically appraised according to a custom list of quality requirements. The extracted data were arranged in tables, and combined through a narrative synthesis. RESULTS: The search retrieved 99 unique articles. Thirty six case reports and 15 case series describing a total of 65 cases of subcutaneous emphysema were included in this review. The methodological quality was medium. Reported cases of emphysema more often involved females and maxillary teeth. Drying of the root canal system with air under pressure, inadvertent extrusion of hydrogen peroxide through the apical foramen, the air-water spray produced by handpieces or laser devices, and the use of ozone gas were the most commonly suspected causes. Its management involved prescription of antibiotics and NSAIDs/analgesics, local application of ice packs or compresses and hospitalization. The signs and symptoms resolved completely within 1-17 days. LIMITATIONS: Case reports and case series are a low level of evidence. CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS: Subcutaneous emphysema can develop during both nonsurgical and surgical root canal treatment. Pressurized air streams or air-water sprays should not be directed towards the root canals or areas with mucosal discontinuity. None of the management approaches were clearly related to expedited recovery. Guidelines should be developed in order to avoid unnecessary or potentially harmful interventions.

Effect of curing conditions on physical and chemical properties of MTA.

AIM: To evaluate setting time, pH, solubility and surface roughness of MTA+ and ProRoot MTA and characterize their hydration under several curing conditions. METHODOLOGY: Specimens were prepared to evaluate setting time (n = 6 for each group, specimen dimensions 10 × 8 × 5 mm), solubility (n = 6 for each group, specimen dimension 20 mm in diameter and 1.5 mm thick) after 1 and 28 days, pH (n = 10 for each group, specimen dimensions 10 mm in diameter and 1 mm thick) after 1, 7, 14, 21 and 28 days and surface roughness (n = 10 for each group, specimen dimensions 4 mm in diameter and 3 mm high) after 28 days when cements were cured at 95% humidity or immersed in saline or HBSS at 37 °C. The powder and liquid were mechanically mixed by an amalgamator. The set materials were characterized using X-ray diffraction analysis, scanning electron microscopy and X-ray energy-dispersive analysis. Statistical comparisons were employed using one-way anova. The level of significance was set at P = 0.05. RESULTS: Setting time was significantly shorter when cements were cured at 95% humidity compared to those in saline (P < 0.001) and HBSS (P < 0.001). Setting time of MTA+ was significantly shorter than that of ProRoot MTA (P < 0.001), which had a significantly higher pH than MTA+ (P < 0.05) for all periods and immersion liquids. After immersion in saline, MTA+ was significantly less soluble than ProRoot MTA (P < 0.001); when immersed in HBSS, no significant difference was found (P = 1.00). The surface roughness of both cements was affected when exposed to HBSS (P < 0.001 for both cements) and saline (P < 0.001 for both cements). Storage in HBSS created a homogenous surface; incubation in saline or humidity created a biphasic surface. The main crystalline phases in both cements were tricalcium silicate, bismuth oxide and calcium hydroxide. CONCLUSIONS: MTA+ had a shorter setting time than ProRoot MTA, promoted lower pH and had lower solubility in saline. Curing conditions affected the surface roughness and microstructure of the cements.

Skin reactions amongst Greek endodontists: a national questionnaire survey.

AIM: To investigate amongst Greek endodontists in the past 5 years the prevalence, aetiologic factors, severity and treatment for skin reactions. METHODOLOGY: One hundred and 47 endodontists met the inclusion criteria and were invited to participate in the survey. Participants were asked for personal/professional data, prevalence, aetiologic factors, symptoms, severity and treatment for skin reactions in the past 5 years. The type of gloves used and frequency of hand washing as well as information on history of atopy and eczema were also recorded. Data were analysed using chi-square test and independent samples t-test. The level of significance was set at P = 0.05. RESULTS: The response rate was 84%. Skin reactions were reported by 32.5% of participants. Hands were the body part most frequently affected (66% of cases); glove powder accounted for 73% of skin reactions. Medical care was sought by 28.2% of the affected participants. Endodontists with a history of atopy (P < 0.001) and dermal eczema (P < 0.001) as well as females (P = 0.023) were more likely to report skin reactions. Replacement of powdered latex gloves with powder-free or vinyl/nitrile gloves, avoidance of potential allergens and use of pharmaceutical ointments were adopted by 48.7%, 23.1% and 2.6% of the affected endodontists, respectively, to manage skin reactions. CONCLUSIONS: Approximately one-third of participants reported skin reactions. History of atopy and dermal eczema as well as gender was significantly associated with such reactions. The use of powder-free latex gloves instead of powdered ones was the measure most frequently adopted to manage reactions.

Musculoskeletal disorders amongst Greek endodontists: a national questionnaire survey.

AIM: To investigate amongst Greek endodontists the prevalence and characteristics of musculoskeletal disorders (MSDs) in the past 12 months, the treatment followed, their postures during practice and the adoption of ergonomic standards. METHODOLOGY: One hundred and forty-seven endodontists met the inclusion criteria and were invited to participate in the survey. Participants were asked for personal/professional data, prevalence, characteristics and treatment for MDSs in the past 12 months. Endodontists' postures during practice as well as ergonomic factors were also recorded. Data were analysed using chi-square test, independent samples t-test and logistic regression. The level of significance was set at P = 0.05. RESULTS: The response rate was 84%. MSDs were reported by 61% of the participants. Of them, 69% reported pain to more than one body part. The prevalence of disorders was highest in the lower back (30%) and neck (30%). Medical care was applied in 53% of the disorders. A sitting position was always used by 83% of endodontists. Awkward postures during practice (OR:4.561, 95% CI:1.341-15.512), regular stretching exercises (OR:0.032, 95% CI:0.010-0.110) and number of patients day(-1) (OR:3.524, 95% CI:1.686-18.100) were significant predictors for MSDs. Properly adjusted stools, sufficient lighting and space in the operating room were reported by 71%, 96% and 93% of participants, respectively. CONCLUSIONS: A high percentage of endodontists reported MSDs. Adoption of correct/neutral postures, regular performance of stretching exercises and reduced number of patients/day were associated with a low prevalence of disorders. The majority of endodontists had adopted ergonomic innovations/standards to control disorders.

Formation and removal of apical vapor lock during syringe irrigation: a combined experimental and Computational Fluid Dynamics approach.

AIM: (i) To evaluate the effect of needle type and insertion depth, root canal size and irrigant flow rate on the entrapment of air bubbles in the apical part of a root canal (apical vapor lock) during syringe irrigation using experiments and a Computational Fluid Dynamics (CFD) model, (ii) to investigate whether the irrigant contact angle affects bubble entrapment, (iii) to examine if an established vapor lock can be removed by syringe irrigation. METHODOLOGY: Bubble entrapment during irrigation of straight artificial root canals of size 35 or 50 was evaluated by real-time visualizations. The irrigant was delivered by a closed-ended or an open-ended needle positioned at 1 or 3 mm short of working length (WL) and at a flow rate of 0.033-0.260 mL s(-1) . Results were analysed by nonparametric tests at 0.05 significance. Selected cases were also simulated by a two-phase CFD model. RESULTS: A vapor lock was observed in 48% of the cases investigated experimentally. Increasing the apical size, using an open-ended needle, positioning the needle closer to WL and delivering the irrigant at higher flow rate resulted in significantly smaller vapor lock. An increased contact angle resulted in the entrapment of a larger bubble when a low flow rate was used. Both brief insertion of the needle to WL whilst irrigating at a flow rate of 0.083 mL s(-1) and delivering the irrigant at 0.260 mL s(-1) without changing the needle position were capable of removing an established vapor lock. CONCLUSIONS: Apical vapor lock may occur under certain conditions, but appears to be easily prevented or removed by syringe irrigation.

Crown discoloration induced by endodontic sealers: spectrophotometric measurement of Commission International de I'Eclairage's L*, a*, b* chromatic parameters.

Despite the improvement of endodontic materials, crown discoloration induced by root canal sealers remains a concerning clinical issue. The aim of this study is the measurement of the alterations in CIE L*, a*, b* chromatic parameters of tooth crowns after placement of commonly used and new-generation endodontic sealers in pulp chambers. Eighty intact, fully developed third mandibular molars were randomly assigned in five groups. Crowns were cross-sectioned from the root complex 1 mm below the cement-enamel junction. The internal axial walls of the pulp chambers were debrided and coated with endodontic sealers (Roth-811, AH-26, Guttaflow, Epiphany SE). The apical access was sealed with glass-ionomer cement. The control group was only debrided. Crowns were stored in individually marked vials in standard conditions (100% humidity, 37°C). The spectral reflectance lines were recorded with a UV-Vis spectrophotometer in the visual spectrum. The CIE L*a*b* parameters were obtained by a linked computer software before sealer placement (baseline), after one week, one, three, and six months, respectively. Statistical analysis was performed with two-way mixed ANOVA models. The level of statistical significance was set at p<0.05. With the exception of the control group, experimental groups presented varying chromatic alterations. Among all experimental groups, Roth-811 sealer induced the most severe alterations in CIE L*, a*, b* chromatic parameters, during all observation periods. After root canal obturation, the clinician should be aware of the presence of remaining root canal filling materials. Thorough debridement of the pulp chamber is essential for the prevention of sealer-induced discoloration.

Occupational ocular accidents amongst Greek endodontists: a national questionnaire survey.

AIM: To investigate amongst Greek endodontists, the incidence of ocular accidents during practice, the circumstances associated with them, the therapeutic measures taken after the accidents, their compliance with the use of eye protection and their eye care behaviour. METHODOLOGY: One hundred and forty-seven endodontists met the inclusion criteria and were invited to participate in the survey. Data were gathered through interviews based on a questionnaire. Participants were asked for personal/professional data, information on ocular accidents in the past 5 years, post-accident actions and the type of eye protection used. Their eyesight status and frequency of ocular examination were also recorded. Data were analysed using chi-square test, independent samples t-test and logistic regression. The level of significance was set at P = 0.05. RESULTS: The response rate was 84%. Ocular accidents were reported by 73% of the participants. Amalgam and NaOCl were the foreign bodies most frequently associated with ocular accidents. Medical assistance was sought in 16% of the most recent accidents. No permanent eye damage was reported. Regular use of magnification (OR:0.305, 95%CI:0.123-0.754) and years of clinical experience (OR:0.191, 95%CI:0.066-0.551) were significant predictors for the incidence of ocular accidents. Adequate eye protection was utilized by 82% of endodontists. Endodontists with eyesight deficiencies attended more frequently for ocular examination (P = 0.018). CONCLUSION: A high percentage of endodontists experienced ocular accidents. Regular use of magnification and increasing years in practice were associated with a reduced risk of ocular accidents. The majority of endodontists reported using adequate eye protection.

Percutaneous injuries amongst Greek endodontists: a national questionnaire survey.

AIM: To investigate amongst Greek endodontists the incidence of percutaneous injuries, the circumstances associated with them, the therapeutic measures taken after the injuries and their compliance with infection control measures. METHODOLOGY: One hundred and forty-seven endodontists met the inclusion criteria and were invited to participate in the survey. Personal and professional data, information on percutaneous injuries in the past 5 years and on infection control practices were gathered through interviews based on a questionnaire. Data were analysed using chi-square test, independent samples t-test, one-way anova and Pearson's correlation coefficient. The level of significance was set at P = 0.05. RESULTS: The response rate was 84%. The injury rate was estimated at 1.35 per endodontist per year. Endodontic files were associated with 37% of the injuries and fingers were injured in 75% of the most recent cases. Medical assistance was sought in 36% of the most recent injuries. Endodontists who always or usually practiced 4-handed endodontics (P = 0.007) as well as those not performing surgical endodontics (P = 0.007) reported significantly fewer injuries. In 91% of the participants, a complete hepatitis B virus vaccination was reported. Gloves, masks, rubber dam isolation and puncture-resistant containers for disposal of sharp instruments were always used by 98%, 94%, 100% and 81% of the respondents, respectively. CONCLUSIONS: The injury rate was low. The practice of four-handed endodontics was associated with a reduced number of percutaneous injuries; the performance of surgical endodontics increased their incidence. Greek endodontists showed a high level of compliance with infection control measures.

Effect of root canal curvature on the failure incidence of ProFile rotary Ni-Ti endodontic instruments.

AIM: To investigate the effect of root canal curvature on the failure incidence and fracture mechanism of ProFile rotary Ni-Ti endodontic instruments. METHODOLOGY: Three hundred mesial root canals of mandibular molars were instrumented using the ProFile system in a crown-down technique up to size 25 0.06 taper. Root canals were classified according to the angle and radius of curvature to: straight (group A: 0 + 10°, radius 0 mm), moderately curved (group B: 30 ± 10°, radius 2 ± 1 mm) and severely curved (group C: 60 ± 10°, radius 2 ± 1 mm). After each use, instruments were cleaned ultrasonically and autoclaved. Instruments that prepared 20 root canals, fractured or were plastically deformed without fracture were retrieved and substituted. Kaplan-Meier estimator was used for survival analysis and post hoc test for determination of significant differences (a=0.05). All fractured instruments were subjected to fractographic analysis under SEM, and all used instruments were viewed under the metallographic microscope. RESULTS: Regardless of the size of instrument, fracture and overall failure were significantly more frequent (P<0.05) in group C. SEM examination of the fracture surfaces revealed mainly the characteristic pattern of ductile failure, whereas examination under the metallographic microscope revealed no sign of cracks. CONCLUSIONS: The abruptness of root canal curvature negatively affected the failure rate of ProFile rotary Ni-Ti instruments. The fractographic results confirmed that failure of Ni-Ti files was caused by a single overload during chemomechanical preparation.

Irrigant flow within a prepared root canal using various flow rates: a Computational Fluid Dynamics study.

AIM: To study using computer simulation the effect of irrigant flow rate on the flow pattern within a prepared root canal, during final irrigation with a syringe and needle. METHODOLOGY: Geometrical characteristics of a side-vented endodontic needle and clinically realistic flow rate values were obtained from previous and preliminary studies. A Computational Fluid Dynamics (CFD) model was created using FLUENT 6.2 software. Calculations were carried out for five selected flow rates (0.02-0.79 mL sec(-1)) and velocity and turbulence quantities along the domain were evaluated. RESULTS: Irrigant replacement was limited to 1-1.5 mm apical to the needle tip for all flow rates tested. Low-Reynolds number turbulent flow was detected near the needle outlet. Irrigant flow rate affected significantly the flow pattern within the root canal. CONCLUSIONS: Irrigation needles should be placed to within 1 mm from working length to ensure fluid exchange. Turbulent flow of irrigant leads to more efficient irrigant replacement. CFD represents a powerful tool for the study of irrigation.

An unusual case of root perforation caused by surgical trephination.

AIM: To present the diagnosis and management of an unusual case of root perforation caused by surgical trephination. SUMMARY: A root perforation caused by surgical trephination on a maxillary lateral incisor with diagnosis of symptomatic chronic periradicular periodontitis was managed with standard root canal preparation and filling with thermoplasticized gutta-percha. Recall radiographs up to 1 year revealed healing of the periapical lesion. *During surgical trephination, there is risk of damaging anatomical structures surrounding the tooth as well as the tooth itself. *Root perforation caused by trephination was successfully managed by standard canal preparation and filling with thermoplasticized gutta-percha.

Clinical relevance of standardization of endodontic irrigation needle dimensions according to the ISO 9,626:1991 and 9,626:1991/Amd 1:2001 specification.

AIM: To examine the current status of standardization of endodontic irrigation needles produced by different manufacturers. METHODOLOGY: Measurements of needle internal and external diameter were conducted under scanning electron microscopy and stereoscopic microscopy to determine the incidence and degree of deviation from ISO 9,626:1991 and ISO 9,626:1991/Amd 1:2001 specification. RESULTS: None of the needles examined complied with the ISO nominal size. All SS needles were within the ISO tolerance limits. A Ni-Ti needle, which is not included in the specification, was found to exceed ISO external diameter limits. CONCLUSIONS: Exact knowledge of the tip's external diameter is crucial for the selection of the appropriate size irrigation probe during endodontic treatment. Units of the widely used 'gauge' system cannot be directly extrapolated to clinical practice. Adoption of millimetre as the standard metric unit, already recommended by ISO, should be accelerated. A colour-coding of needles corresponding to endodontic instruments would also be beneficial.

Measurement of pressure and flow rates during irrigation of a root canal ex vivo with three endodontic needles.

AIM: To monitor ex vivo intra-canal irrigation with three endodontic needles (25, 27 and 30 gauge) and compare them in terms of irrigant flow rate, intra-barrel pressure, duration of irrigation and volume of irrigant delivered. METHODOLOGY: A testing system was constructed to allow measurement of selected variables with pressure and displacement transducers during ex vivo intra-canal irrigation with a syringe and three different needles (groups A, B, C) into a prepared root canal. Ten specialist endodontists performed the irrigation procedure. Each operator performed ten procedures with each needle. Data recorded by the transducers were analysed using Friedman's test, Wilcoxon Signed Rank test, Mann-Whitney U-test and Kendall's T(b) test. The level of significance was set to 95%. RESULTS: Significant differences were detected among the three needles for most variables. Duration of delivery and flow rates significantly decreased as the needle diameter increased, whilst pressure increased up to 400-550 kPa. Gender of the operator had a significant impact on the results. Experience of the operators (years) were negatively correlated to volume of irrigant (all groups), to the duration of delivery (groups A, B) and to the average flow rate (group A). CONCLUSIONS: Finer diameter needles require increased effort to deliver the irrigant and result in higher intra-barrel pressure. The syringe and needles used tolerated the pressure developed. Irrigant flow rate should be considered as a factor directly influencing flow beyond the needle. Wide variations of flow rate were observed among operators. Syringe irrigation appears difficult to standardize and control.

Ex vivo study of the efficacy of H-files and rotary Ni-Ti instruments to remove gutta-percha and four types of sealer.

AIM: To compare the efficacy of ProFile rotary Nickel-Titanium (Ni-Ti) instruments and Hedstroem-files (H-files) combined with Gates-Glidden (GG) drills during removal of gutta-percha root fillings used in combination with one of the four representative sealers. METHODOLOGY: Forty-eight single-rooted human teeth, with fully formed apices and straight root canals were used. The root canals were accessed and instrumented using a stepback technique with H-files. They were randomly assigned to four groups and subsequently filled with a combination of lateral and vertical condensation of gutta-percha and one of the following sealers: Roth 811, AH26, Endion and Roekoseal. The root fillings were removed 1 year later, using either H-files in combination with GG drills or the ProFile Ni-Ti system. Teeth were then grooved longitudinally and split. The amount of gutta-percha and sealer remaining on the root canal walls was traced and scored visually with the aid of a stereomicroscope. The scores were analysed and statistically compared with the Kruskal-Wallis test between the ProFile and H-file groups, as well as among the four sealer subgroups. Two samples from each group were studied under the scanning electron microscope to enhance inspection of canal walls and remaining material. RESULTS: Sealer remnants were observed with both techniques mainly in the middle and apical third of the root canal. The ProFile system and the H-files were associated with similar amounts of remaining filling material (P > 0.05). In the cervical third of the root canal all sealer remnants were removed with both techniques. In the middle and apical third AH26 was associated with a statistically significant greater quantity of remnants on the root canal walls with both removal techniques (P < 0.05). Endion, Roth 811 and Roekoseal were associated with approximately the same amount of filling material in the middle third of the root canal (P > 0.05), whereas in the apical third Endion was associated with significantly more remnants of filling material than the other two sealers with either ProFile or H-files (P < 0.05). CONCLUSIONS: None of the methods used for the removal of root fillings was totally effective, especially in the apical third of the root canal.

Removal efficacy of various calcium hydroxide/chlorhexidine medicaments from the root canal.

AIM: To compare the efficiency of removing calcium hydroxide [Ca(OH)(2)]/chlorhexidine (CHX) (gel), Ca(OH)(2)/CHX (solution) and Ca(OH)(2)/saline pastes with the use of instrumentation and irrigation with sodium hypochlorite and ethylene diamine tetraacetic acid (EDTA) solutions. Moreover the role of the patency file in the cleanliness of the apical third of the root canal was evaluated. METHODOLOGY: Sixty-four human single-rooted teeth with straight canals were used. Root canal preparation was performed with a stepback technique using Hedström (H) files. Teeth were randomly assigned to three groups and subsequently filled with one of the pastes: Ca(OH)(2)/CHX (gel), Ca(OH)(2)/CHX (solution) and Ca(OH)(2)/saline paste. The medicaments were removed 10 days later using instrumentation and irrigation with 1% sodium hypochlorite and 17% EDTA, with or without obtaining patency of the apical foramen with a size 10 H-file. The crowns were removed at the cemento-enamel junction and the roots were grooved longitudinally and split into halves. Images of all halves were acquired with the use of a flatbed scanner. A scoring system of 1 to 4 was used to assess the amount of residue on the cervical, middle and apical third of the canal. Data were subjected to statistical analysis using Kruskal-Wallis and Mann-Whitney tests, with Bonferroni correction, at 95% confidence level (P < 0.05). RESULTS: Remnants of medicament were found in all experimental teeth regardless of the experimental material used and the use of the patency file. When examining the root canal as a whole, Ca(OH)(2)/CHX (gel) paste was associated with significantly larger amount of residue, whereas the Ca(OH)(2)/CHX (solution) paste was associated with less amount (P < 0.05) than the other two medicaments with or without the use of a patency file. CONCLUSIONS: None of the techniques used in this study removed the inter-appointment root canal medicaments effectively; the use of the patency file facilitated removal of more of the medicament in the apical third of those straight canals.

Technical quality of root canal treatment and detection of iatrogenic errors in an undergraduate dental clinic.

AIM: To evaluate the technical quality of root canal treatment (RCT) and detect iatrogenic errors in an undergraduate dental clinic. METHODOLOGY: Three-hundred and eighty-eight root-filled teeth from the records of the Department of Endodontology at the Aristotle University of Thessaloniki, Greece were evaluated. Evaluation of root-filled teeth was based on two variables: length and presence of voids within the root filling. The technical standard of root fillings was categorized as: < or = 2 mm from the apex with no voids (acceptable); >2 mm from the apex with no voids; overfilling with no voids; < or = 2 mm from the apex with voids; >2 mm from the apex with voids and overfilling with voids. Iatrogenic errors that were detected included ledges, root perforations, furcation perforations, strip perforations and presence of fractured instruments. Chi-squared analysis was used to determine statistically significant differences between frequencies of root fillings between each tooth type. Significant differences were also determined between frequencies of ledges and root perforations according to tooth type and separately in molars according to tooth number, canal location and root canal curvature. Results Three-hundred and forty-three out of 620 root canals (55.3%) had a root filling that was classified as 'acceptable'. The frequency of root canals with an 'acceptable' filling was significantly greater in the anterior teeth (72.1%) than in pre-molars (55.2%) (P < 005) or in molars (46.7%) (P < 0.001). One-hundred and fifty-four (24.8%) root canals had ledges and 17 (2.7%) had a root perforation. The frequency of ledged root canals was significantly greater (P < 0.001) in molars than in anterior teeth. In molars, 105 out of 270 root canals (38.9%) had been ledged. Mesiobuccal, mesiolingual and distobuccal root canals were the most frequently ledged. Canal curvature was found to be the most important factor associated with ledges and root perforations. Conclusions Technical quality was found to be acceptable more often in anterior teeth. Ledges were identified more often in curved canals in molar teeth.

Healing of a radiolucent periradicular lesion with periradicular radiopacity.

Periradicular radiopacities that reveal the existence of sclerotic bone are less common than periradicular radiolucencies. Replacement of a radiolucent periradicular area by sclerotic bone after endodontic treatment is not very often reported and may be confused with condensing osteitis. An unusual case is presented of sclerotic bone formation after endodontic treatment of a first mandibular molar with initial diagnosis of apical periodontitis.

Clinical relevance of standardization of endodontic files dimensions according to the ISO 3630-1 specification.

The aim of this study was to examine the current status of standardization of endodontic instruments. Measurements of instrument dimensions were conducted on stainless steel H- and K-files (sizes 08-40), as well as on rotary-driven nickel titanium (NiTi) files (sizes 15-40), to determine the incidence and degree of deviation from ISO 3630-1, 1992 specification. In addition, the dimensions of sets of H- and K-files (sizes 08-25) were measured to identify discrepancies in dimensions among instruments within the same size per manufacturer. The percentage of difference in width were used to determine the graduation from each size to the next. None of the files tested complied with the ISO nominal size. All files were within the ISO tolerance limits. However, under such tolerance limits, there is a high possibility of either sizes overlapping or of great differences between two sequential sizes. These results may explain the clinical difficulty found in negotiating narrow and curved canals and may establish the need for a more comprehensive approach on the evaluation methods used in root-canal instrument dimension specifications.

Effect of calcium hydroxide as a supplementary barrier in the radicular penetration of hydrogen peroxide during intracoronal bleaching in vitro.

AIM: To examine pH changes in the cervical external root surface, when calcium hydroxide was used as a supplementary barrier to the protective base material during intracoronal bleaching. METHODOLOGY: Twenty-eight single-rooted human premolars extracted for orthodontic reasons were instrumented with K-Flex files, obturated with gutta-percha and subjected to thermocatalytic bleaching. The teeth were divided into four groups. In group A, a glass-ionomer cement barrier was placed at the cemento-enamel junction (CEJ) level and in group C, the barrier was placed 1 mm apical to the CEJ. In groups B and D, Ca(OH)2 was placed in contact and apical to the glass-ionomer cement at the CEJ and 1 mm apical to the CEJ, respectively. The teeth were placed in vials containing distilled water and the pH values of the medium surrounding the teeth were recorded after 1, 2, 4, 10 and 15 days, following renewal of the medium. RESULTS: The pH in the medium became acidic in all groups. No statistically significant differences existed between groups for all the experimental days (P = 0.790). CONCLUSION: The placement of Ca(OH)2 as a supplementary barrier during intracoronal bleaching did not have a significant effect in reversing the acidic pH created at the external root surface in vitro. Its potential effect during these procedures in vivo needs to be further investigated.

The effect of maintaining apical patency on periapical extrusion.

Thirty-three human maxillary incisors were secured in the openings of a glass vial. Root canals were instrumented to the apical constriction with a step-back technique and a patency file was not used throughout the root canal preparation. The irrigant, 1% NaOCl, was delivered by means of a plastic syringe with a 23-gauge needle and the overflow was suctioned with an aspirator. The total volume of irrigant used was 10 ml. Apically extruded debris and NaOCl were measured. The apical constriction was then deliberately enlarged. With a step-back technique a new 'apical constriction' was created, coronally to the original one. A patency file was again not used, and irrigation was identical to the that used during the initial root canal preparation. Extruded debris and NaOCl in each bottle were again measured. Results indicated that there was significant difference in the amounts of extruded material before and after the enlargement of the apical constriction with greater extrusion when the constriction remained intact.