An Automated Measurement Method for the Endodontic Working Width of Lower Molars by Means of Parametric Models Using Cone-beam Computed Tomographcy and Micro-Computed Tomography

INTRODUCTION

A new method for the approximation of the root canal's cross-sectional shape and its working width using cone-beam computed tomographic (CBCT) or micro-computed tomographic (micro-CT) imaging was introduced.

METHODS

Scanned data from 29 extracted human mandibular first and second molar distal root canals without instrumentation were reconstructed and analyzed with a self-developed measurement algorithm. The 3-dimensional volume models were sliced perpendicular to the vertical axis. Using different 2-dimensional parametric models, the contour of each root canal slice was approximated and used to determine the canal's cross-sectional dimensions. The measurements of minor width, major width, and the root canal's conicity were statistically analyzed using analysis of variance.

RESULTS

The measured minor and major widths of the investigated root canals were significantly higher (probability value P < .05) when evaluated by CBCT images than the results obtained from micro-CT data. Both dimensions increased starting from the apical foramen (P < .01). The narrowest measured canal widths were 0.19-0.24 mm for CBCT imaging and 0.09-0.21 mm for micro-CT imaging in the apical part. The maximum values for conicity were between 13% and 17% in the cervical third.

CONCLUSIONS

The 3-dimensional imaging data from CBCT and micro-CT imaging enabled a valuable anatomic assessment of the root canal's cross-sectional working width along the canal up to the physiological foramen in order to determine an adequate apical diameter as well as the correct measured taper in the cervical and medial part.

Influence of Apical Preparation Size on Effective Conventional Irrigation in the Apical Third: A Scanning Electron Microscopic Study

Objective

This study aimed to investigate the relationship between final apical preparation size and smear layer removal in the apical third using conventional irrigation in mandibular bicuspids.

Methods

A total of 66 extracted human mandibular bicuspids with comparable root canal morphology were equally divided into five experimental groups and a control group (n=11). Based on their experimental group, samples were instrumented up to size 25, 30, 35, 40, or 45 with 0.04 taper using 2.5% sodium hypochlorite (NaOCl) as the irrigant. Final irrigation was performed with 17% EDTA followed by 2.5% NaOCl. The control group was instrumented up to size 45/.04, and was irrigated with distilled water. Samples were sectioned buc-colingually, and they were qualitatively evaluated under scanning electron microscope for efficacy in smear layer removal. The Kruskal-Wallis and Mann-Whitney U tests were employed for statistical analysis.

Results

Statistical analysis revealed comparable removal of smear layer in the coronal and middle thirds of all experimental samples regardless of grouping. When using file size larger than 35, removal of smear layer in the apical third significantly improved (p<0.05). No significant difference was observed between 40/.04 and 45/.04.

Conclusion

Under the conditions of this study, using conventional irrigation, apical enlargement more than size 35/.04 is essential to enhance removal of smear layer at the apical third.

Effect of Diode Laser on Bacteria Beyond the Apex in Relation to the Size of the Apical Preparation - An In-Vitro Study

INTRODUCTION

Microorganisms causing periapical infection are usually difficult to eradicate after conventional endodontic treatment or even in retreatment resulting in poor outcomes. So the purpose of the study was to assess whether disinfection of root canal with laser had any effect on bacteria in the periapex region.

AIM

The aim of the present study was to evaluate the effects of a diode laser when activated in root canals with varying apical diameters, on the bacteria present beyond the apex of the teeth.

MATERIALS AND METHODS

Total 30 intact single rooted teeth were taken and decoronated to standardize the root to a length of 12mm. They were divided into three groups depending on last file size used for instrumentation at apex i.e., size 30, 40 and 50 respectively. The samples were then mounted on test tubes such that roots of teeth were in contact with fresh broth of Escherichia coli (ATCC 25922) and left for incubation. Later a diode laser (Ezlase 940, Biolase) was used for disinfection of root canals of the samples. Following this the bacterial inoculums from each test tube were cultured and CFU were obtained from which the mean log values were obtained. Statistical analysis was done using Kruskal Wallis ANOVA test to compare mean CFU in three groups. Mann-Whitney U test with Bonferroni correction was used to compare inter-group differences.

RESULTS

There was statistically significant difference in mean log values of CFU in all the three study groups. Inter-group comparisons showed that, Group A had significantly lower mean CFUs than Group B and C respectively.

CONCLUSION

The study showed that intracanal irradiation with diode laser had an effect on the bacteria present beyond the apex, and it was influenced by the size of the apical preparation i.e., smaller apical size led to a greater reduction in the bacterial count.

Micro-Computed Tomography Analysis of the Root Canal Morphology of Palatal Roots of Maxillary First Molars

INTRODUCTION

A thorough knowledge of root canal anatomy is critical for successful root canal treatments. This study evaluated the internal anatomy of the palatal roots of maxillary first molars with micro-computed tomography (microCT).

METHODS

The palatal roots of extracted maxillary first molars (n = 169) were scanned with microCT to determine several anatomic parameters, including main canal classification, lateral canal occurrence and location, degree of curvature, main foramen position, apical constriction presence, diameters 1 and 2 mm from the apex and 1 mm from the foramen, minor dentin thickness in those regions, canal volume, surface area, and convexity.

RESULTS

All canals were classified as Vertucci type I. The cross sections were oval in 61% of the canals. Lateral canals were found in 25% of the samples. The main foramen did not coincide with the root apex in 95% of the cases. Only 8% of the canals were classified as straight. Apical constriction was identified in 38% of the roots. The minor and major canal diameters and minor dentin thickness were decreased near the apex. The minor dentin thickness 1 mm from the foramen was 0.82 mm. The palatal canals exhibited a volume of 6.91 mm(3) and surface area of 55.31 mm(2) and were rod-shaped.

CONCLUSIONS

The root canals of the palatal roots were classified as type I. However, some factors need to be considered during the treatment of these roots, including the frequent ocurrence of moderate/severe curvatures, oval-shaped cross-sections, and lateral canals, noncoincidence of the apical foramen with the root apex, and absence of apical constriction in most cases.

Morphology of the Physiological Apical Foramen in Maxillary and Mandibular First Molars

Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40× magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.