Evaluation of two different root-end cavity preparation techniques: A scanning electron microscope study

Is There a Relationship between Laser Therapy and Root Canal Cracks Formation? A Systematic Review

Introduction

Crack formation has become an important issue for endodontists, as it can be decisive for the long-term prognosis of the endodontically treated tooth. Since the applicability of laser in endodontics has become frequent, this systematic review aimed to evaluate the association between laser therapy and the formation of cracks in the dentinal structure of the root canal.

Materials and Methods

A search was performed in PubMed, Scopus, Web of Science, and Virtual Health Library, as well as in the gray literature, on September 24, 2021. Studies that evaluated the formation of cracks in human root dentin due to different types of lasers were included. The risk of bias was assessed following the modified version of the Consolidated Standards of Reporting Trials (CONSORT) checklist tool. A meta-analysis was performed to evaluate (i) the total number of crack incidences; (ii) complete crack formation; (iii) incomplete crack formation; (iv) intra-dentinal crack formation between ultrasonic tips and laser use. The mean difference was calculated with a 95% confidence interval in a fixed-effect model, the heterogeneity was tested using the I² index with level of significance of 5%.

Results

Of the 22 studies included in this review, 15 have shown that lasers can form cracks in root dentin, including those that performed baseline assessment of samples. The meta-analysis confirmed no difference in crack formation between ultrasonic tips and laser devices.

Conclusions

Laser therapy has been gaining prominence in endodontics and that irradiation can form and propagate cracks in the dentinal structure of the root canal assessed by in vitro studies. This is a critical concern for endodontists as it affects the strength and longevity of the tooth. Future research is encouraged to seek the standardization of good methodological practices and achieve establishing parameters to minimize harmful effects of laser on dentin.

Comparison of crack formation induced by ultrasonic tips and burs during root-end preparation: a systematic review and meta-analysis

Introduction The main objective of root canal treatment is to achieve apical seal. Crack formation during root-end preparation promotes bacterial penetration, thereby leading to failure. This systematic review aims to examine the literature and summarise studies that compare the crack formation induced by ultrasonic tips and burs during root-end preparation.Methods This systematic review and meta-analysis were reported and conducted according to the PRISMA guidelines. The online databases PubMed, Scopus, and Google Scholar were used for data search. In vitro and ex vivo studies conducted up to March 2021 in the English language were included in the review. The risk of bias in the present study was assessed using a customised tool. A random-effects model was used for meta-analysis, χ² values and I² values were used to assess statistical heterogeneity. Meta-analysis was performed using RevMan software Version 5.4.Results A total of 317 records were found from all of the databases and one article was added following hand-searching. Twelve articles were included in the study after the application of the eligibility criteria of which ten articles were included for the meta-analysis. Nine studies showed a medium risk of bias while three studies showed a high risk of bias. The analysis of the crack formation showed a statistically significant difference between the ultrasonic tip and the bur (P = 0.0002). The odds ratio was 2.72 (1.60, 4.65) with a confidence interval of 95% suggesting higher odds of crack formation in the ultrasonic group.Conclusion This review concludes that ultrasonic root-end preparation resulted in higher crack formation than burs.

Sealing ability of two root-end filling materials at different retro-preparation lengths

PURPOSE

The aim of the present study was to evaluate the sealing performance, expressed as microleakage (ML), of two root-end filling materials when used at different retro-preparation lengths.

METHODS

Fifty single-rooted human teeth were collected for the study. The teeth were cut at the cement-enamel junction and endodontic treatment was performed. Each root was cut at 3 mm from the apex and then stored in wet condition. The teeth were divided into three groups according to the retro-preparation length: control group (no retro-preparation); group 1 (retro-preparation of 3 mm); group 2 (retro-preparation of 9 mm). The teeth were equally allocated to either Biodentine or Super EBA treatment group. The teeth were immersed in 3% methylene blue dye solution for 24 h. The samples were split longitudinally and the depth of dye penetration was examined through light microscopy.

RESULTS

No significant statistical differences were found at different retro-preparation lengths (P > 0.05). Differences were found between materials (P > 0.05).

CONCLUSION

Biodentine showed significantly lower ML when compared to Super-EBA and no statistical significative differences were observed when samples were retro-prepared at 3 mm or 9 mm.

Comparison of microcomputed tomography, cone beam tomography, stereomicroscopy, and scanning electron microscopy techniques for detection of microcracks on root dentin and effect of different apical sizes on microcrack formation

The aim of the study was to compare different imaging methods in the diagnosis of microcracks on root dentin and to evaluate the frequency of dentinal microcracks observed after root canal preparation using the ProTaper Universal (PTU) system of different sizes. A total of 30 mandibular molars' mesial roots were scanned with microcomputed tomography (micro-CT) and cone beam computed tomography (CBCT) imaging methods before instrumentation. Root canal instrumentation was performed up to PTU F2 and F4 files. After instrumentation stages, the roots were scanned again with micro-CT and then with CBCT in same parameters. All roots were sectioned horizontally at 2, 4, 6, 8, and 10 mm from the apices of the specimens. The sections were imaged under a stereomicroscope. Finally, imaging of the sections was done by scanning electron microscopy (SEM). Statistical data analysis of instrumentation steps was performed using Friedman and Wilcoxon tests, and the data of imaging methods were analyzed using Kruskal-Wallis and Mann-Whitney U tests (p = .05). Instrumentation with the PTU system up to F2 and F4 files significantly increased the number of microcracks compared with preoperative samples according to micro-CT imaging (p < .05). For detecting microcracks on the root dentin, there were no statistically significant differences between micro-CT (43.9%) and stereomicroscopy (45.8%) (p < .05). SEM showed significantly higher percentage of microcracks (88.3%) (p > .05). No microcrack was observed using the CBCT method. There were no statistically differences between micro-CT and stereomicroscopy. SEM showed more dentinal microcracks while no microcrack was observed with CBCT.

Cracked tooth diagnosis and treatment: An alternative paradigm

This article reviews the diagnosis and treatment of cracked teeth, and explores common clinical examples of cracked teeth, such as cusp fractures, fractures into tooth furcations, and root fractures. This article provides alternative definitions of terms such as cracked teeth, complete and incomplete fractures and crack lines, and explores the scientific rationale for dental terminology commonly used to describe cracked teeth, such as cracked tooth syndrome, structural versus nonstructural cracks, and vertical, horizontal, and oblique fractures. The article explains the advantages of high magnification loupes (×6-8 or greater), or the surgical operating microscope, combined with co-axial or head-mounted illumination, when observing teeth for microscopic crack lines or enamel craze lines. The article explores what biomechanical factors help to facilitate the development of cracks in teeth, and under what circumstances a full coverage crown may be indicated for preventing further propagation of a fracture plane. Articles on cracked tooth phenomena were located via a PubMed search using a variety of keywords, and via selective hand-searching of citations contained within located articles.