Assessment of the Prevalence of Radix Entomolaris and Distolingual Canal in Mandibular First Molars in 15 Countries: A Multinational Cross-sectional Study with Meta-analysis.

AIM: The aim of this study was two-folded: i) to assess the prevalence of Distolingual Canal (DLC) and Radix Entomolaris (RE) in Mandibular First Molars (M1Ms), using Cone Beam Computed Tomography (CBCT) images and ii) to assess the impact of sociodemographic factors on the prevalence of these conditions worldwide. METHODS: CBCT images were scanned retrospectively and the ones including bilateral M1Ms were included in the study. The evaluation was performed by 1 researcher in each country, trained with CBCT technology. A written and video instruction program explaining the protocol to be followed step-by-step was provided to all observers to calibrate them. The CBCT imaging screening procedure consisted of evaluating axial sections from coronal to apical. The presence of DLC and RE in M1Ms (yes/no) was identified and recorded. RESULTS: Six thousand three hundred four CBCTs, representing 12,608 M1Ms, were evaluated. A significant difference was found between countries regarding the prevalence of both RE and DLC (P < .05). The prevalence of DLC ranged from 3% to 50%, and the overall prevalence was 22% (95% CI: 15%-29%). RE prevalence ranged from 0% to 12%, and the overall prevalence was 3% (95% CI: 2%-5%). There were no significant differences between left and right M1Ms or between genders for either DLC or RE (P > .05). CONCLUSION: The overall prevalence of RE and DLC in M1Ms was 3% and 22%. Additionally, both RE and DLC showed substantial bilaterally. These variations should be considered by endodontic clinicians during endodontic procedures in order to avoid potential complications.

Assessment of the Prevalence of Middle Mesial Canal in Mandibular First Molar: A Multinational Cross-sectional Study with Meta-analysis.

BACKGROUND: An additional canal found in the mandibular first molar (M1M) is the middle mesial canal (MMC), which is often missed during root canal treatment. In this study, the prevalence of MMC in M1M on cone-beam computed tomography (CBCT) images was evaluated in 15 countries, along with the effect of some demographic factors on its prevalence. METHODS: Deidentified CBCT images were scanned retrospectively, and the ones including bilateral M1Ms were included in the study. A written and video instruction program explaining the protocol to be followed step-by-step was provided to all observers to calibrate them. The CBCT imaging screening procedure consisted of evaluating three planes (coronal, sagittal, and axial) after a 3-dimensional alignment of the long axis of the root(s). The presence of an MMC in M1Ms (yes/no) was identified and recorded. RESULTS: In total, 6304 CBCTs, representing 12,608 M1Ms, were evaluated. A significant difference was found between countries (P < .05). MMC prevalence ranged from 1% to 23%, and the overall prevalence was 7% (95% confidence interval [CI]: 5%-9%). No significant differences were found between the left and right M1M (odds ratio = 1.09, 95% CI: 0.93, 1.27; P > .05) or between genders (odds ratio= 1.07, 95% CI: 0.91, 1.27; P > .05). As for the age groups, no significant differences were found (P > .05). CONCLUSIONS: The prevalence of MMC varies by ethnicity, but it is generally estimated at 7% worldwide. Physicians must pay close attention to the presence of MMC in M1M, especially for opposite M1Ms, due to the prevalence of MMC being significantly bilateral.

Study of Morphological Changes in Rat Liver Caused by Occlusion of Inferior Vena Cava.

Background/objectives: Up to date, there are no reports on animal survival rate and morphological changes in the liver caused by the impairment of blood outflow from the liver and its time dependence. Moreover, the impact of duration and degree of occlusion of inferior vena cava on pathological changes was not investigated yet. This study aimed at the assessment of the survival rate and morphological changes in the liver with varying degrees of occlusion of inferior vena cava. The exact timing of the reversibility of pathological processes was determined. Methods: Rats (n = 160) were randomly divided into five groups: I - control group (CG) (n = 20); II - sham group (SG) (n = 20); III - intervention group (IG-1) (narrowing of the lumen of the inferior vena cava by 25%) (n = 40); IV intervention group (IG-2) (narrowing by 50%) (n = 40); and intervention group V (IG-3) (narrowing by 75%) (n = 40). The level of postoperative pain, the body and liver weight of the animals, histological examination, morphometry, and macroscopic evaluation of abdominal organs were carried out on the 1, 3, 7, 14, and 30 days following the surgical intervention. The survival rate of animals was assessed using the Kaplan-Meier method. Results: On the 30th day, the rat grimace scale indices in the IG-1 (P ≤ 0.05), IG-2, and IG-3 (P ≤ 0.001) groups were higher. By body weight, this indicator on the 30th day was lower in the IG-1 (P ≤ 0.05), IG-2, and IG-3 (P ≤ 0.001) groups compared to the CG and SG groups. In the IG1 and IG2 groups, the survival rates were 72.5% and 65.0%, respectively. The lowest survival rate was observed in the IG3 group (22.5%). Conclusions: Compression of the inferior vena cava by 75% led to an increase in animal mortality and the development of persistent morphological changes in the liver. At the same time, the survival rate of animals and the extent of changes in the liver with narrowing of the inferior vena cava by 25% and 50% had similar results. The results acquired possess scientific and practical importance.