Worldwide Assessment of the Mandibular First Molar Second Distal Root and Root Canal: A Cross-sectional Study with Meta-analysis.

INTRODUCTION: This study assessed the prevalence of radix entomolaris and 2 canals at the distal aspect of mandibular first molars among different geographic regions by means of cone-beam computed tomographic imaging. METHODS: Precalibrated observers from 23 worldwide geographic locations followed a standardized screening protocol to assess 5750 cone-beam computed tomographic images of mandibular first molars (250 per region), gathering demographic data and recording the presence of radix entomolaris and a second canal at the distal aspect of teeth. Intra- and interrater reliability tests were conducted and comparisons among groups were performed using proportions and odds ratio forest plots. The significance level was set at 5%. RESULTS: The results of intra- and interrater tests were above 0.79. The prevalence of radix entomolaris varied from 0.9% in Venezuela (95% confidence interval [CI], 0%-1.9%) to 22.4% in China (95% CI, 17.2%-27.6%). Regarding the proportion of a second distal canal, it ranged from 16.4% in Venezuela (95% CI, 11.8%-21.0%) to 60.0% in Egypt (95% CI, 53.9%-66.1%). The East Asia subgroup was associated with a significantly higher prevalence of an extra distolingual root, whereas the American subgroup, the American native ethnic group, and elderly patients were linked to significantly lower percentages of a second canal at the distal aspect of teeth. No significant differences were noted between male or female patients. CONCLUSIONS: The overall worldwide prevalence rates of radix entomolaris and a second canal at the distal aspect of the mandibular first molar were 5.6% and 36.9%, respectively. The East Asia geographic region and Asian ethnic group had a higher prevalence of a second distal root.

Worldwide Prevalence of a Lingual Canal in Mandibular Premolars: A Multicenter Cross-sectional Study with Meta-analysis.

INTRODUCTION: The presence of multiple root canals is an important morphologic aspect of mandibular premolars. This study aimed to perform a worldwide analysis on the prevalence of a lingual canal in mandibular premolars and to evaluate its influence on patients' demographics in 23 countries using cone-beam computed tomographic images. METHODS: Observers from 23 countries were instructed to evaluate cone-beam computed tomographic images of 300 first and 300 second premolars (13,800 teeth) regarding the presence of a lingual canal, canal configuration, and data related to patients' ethnicity, age, and sex following a standardized screening methodology. Intra- and interrater evaluations were performed using the Cohen kappa test and intraclass correlation coefficient. Proportion and odds ratio forest plots were calculated in order to compare groups. Statistical significance was set at 5%. RESULTS: Both kappa and intraclass correlation coefficient values were above 0.60, and the percentage of agreement was 94.9% (first premolar) and 97.8% (second premolar). A significant statistical difference was observed between the worldwide proportion of a lingual canal in mandibular first (23.8%; range, 12.0%-32.7%) and second (5.3%; range, 1.0%-15.3%) premolars (P < .05). Asians and patients over 60 years old were associated with the lowest proportions of a lingual canal (P < .05), whereas Africans and younger groups were associated with the highest proportions (P < .05). The prevalence of a lingual canal in males (27.9%) was higher than females (20.0%) for the first premolar only (P < .05). Males were associated with 1.533 and 1.597 higher odds of presenting a lingual root canal in the first and second premolars, respectively. CONCLUSIONS: The worldwide proportion of a lingual root canal was 23.6% and 5.3% for the first and second premolars, respectively. Ethnicity, geographic region, age, and sex had an influence on the outcomes.

Worldwide Analyses of Maxillary First Molar Second Mesiobuccal Prevalence: A Multicenter Cone-beam Computed Tomographic Study.

INTRODUCTION: Maxillary first molar second mesiobuccal (MB2) root canal prevalence may change among different populations. The aim of this study was to analyze the worldwide prevalence of the MB2 root canal and understand its possible relation with sex, age, side, and root configuration using in vivo cone-beam computed tomographic (CBCT) assessment. METHODS: Observers from 21 regions were calibrated to achieve a similar CBCT assessment methodology and instructed to collect data from 250 maxillary first molars in previously existing examinations. Intra- and interrater reliability tests were performed. The sample size included 5250 molars and was defined by way of a preliminary trial. Data collected included MB2 presence, sex, age, side, number of roots per tooth, and mesiobuccal root configuration. The z test for proportions in independent groups was used to analyze the differences among subgroups. P < .05 was considered significant. RESULTS: The worldwide CBCT-assessed MB2 prevalence was 73.8%, ranging from 48.0% in Venezuela to 97.6% in Belgium. The prevalence in males and females was 76.3% and 71.8%, respectively (P < .05). Significantly higher MB2 proportions were found in younger patients and 3-rooted molar configurations. The group intraclass correlation coefficient and the percentage of agreement for the MB2 presence were 0.95 and 0.91, respectively. The intrarater Cohen kappa value was above 0.61 for all observers. CONCLUSIONS: MB2 prevalence in the analyzed regions varied widely. The differences may be associated with specificities within each region but also patient demographics. Males, younger patients, and 3-rooted configurations were associated with higher MB2 proportions.

Intracanal Cryotherapy Reduces Postoperative Pain in Teeth with Symptomatic Apical Periodontitis: A Randomized Multicenter Clinical Trial.

INTRODUCTION: A prospective, multicentered, randomized clinical trial was designed to assess if controlled irrigation with cold saline could result in less incidence and intensity of postoperative pain in patients presenting with pulp necrosis and symptomatic apical periodontitis. METHODS: A total of 210 patients (presenting with necrotic uniradicular teeth with a diagnosis of symptomatic apical periodontitis and a preoperative visual analog scale (VAS) score higher than 7) were randomly allocated in the control or experimental group after the completion of shaping and cleaning procedures. The experimental group received a final irrigation with 20 mL sterile cold (2.5°C) saline solution delivered to the working length with a sterile, cold (2.5°C) Endovac microcannula (Kerr Endo, Orange Country, CA) for 5 minutes. The same protocol was used in the control group with room temperature saline solution. Patients were instructed to record the presence, duration and level of postoperative pain, and analgesic medication intake. A logistic regression was used to compare the incidence of postoperative pain and the need for painkillers between groups. Differences in general pain intensity between groups were analyzed using the ordinal (linear) chi-square test. Postoperative pain after 6, 24, and 72 hours (recorded in a VAS scale) and the need for analgesic medication intake between the 2 groups were assessed using the Mann-Whitney U test. RESULTS: Patients in the control group presented a significantly higher incidence of postoperative pain, intensity, and need for medication intake (P < .05). CONCLUSIONS: Cryotherapy reduced the incidence of postoperative pain and the need for medication intake in patients presenting with a diagnosis of necrotic pulp and symptomatic apical periodontitis.