Optimum glide path motion is safer than continuous rotation of files in glide path preparation

Glide Path in Endodontics: A Literature Review of Current Knowledge

The introduction of nickel-titanium rotary instruments revolutionized shaping procedures as they were able to produce a well-tapered preparation while reducing operator fatigue. The major drawback of rotary instruments was the high risk of fracture due to bending and torsional stress. Thus, the creation of a glide path has been advocated and recommended by most rotary instrument manufacturers. The aim of the present review is to summarize existing knowledge on glide path preparation and identify areas where further research is needed. The primary goal is to provide a comprehensive overview of the techniques and instruments used in glide path preparation, highlighting their advantages and limitations. The secondary goal is to explore the effect of glide path creation on the overall success of endodontic treatment, particularly in terms of reducing procedural errors and improving treatment outcomes. An online search on PubMed, ScienceDirect, UCLA, and Scopus databases was conducted, and 116 articles were identified. Eligible articles were divided into nine categories based on what they researched and compared. The categories included centering ability and/or root canal transportation, cyclic fatigue resistance, glide path and shaping time, tortional stress resistance, apical extrusion of debris and/or bacteria, defects in dentine walls, file separation, postoperative pain assessment, and scouting ability and performance. Establishing a glide path reduces root canal transportation, especially with rotary methods. Reciprocating and heat-treated files offer higher fatigue resistance and shorter preparation time. Instruments with shorter pitch lengths have greater torsional strength. Preparation and coronal preflaring reduce apical debris and bacteria. Glide paths do not affect dentine microcracks, file separation, or defects but reduce immediate postoperative pain and improve cutting ability. Randomized trials are needed to assess their impact on treatment outcomes.

Impact of kinematics on the efficiency and safety of an engine-driven file for glide path preparation in MB2 canals of maxillary molars

AIM

To evaluate the influence of different kinematics on the efficiency and safety of an engine-driven file for glide path preparation in second mesiobuccal canals (MB2) of maxillary molars. In addition, the torsional resistance of the file was assessed after use.

METHODOLOGY

Thirty-six maxillary first and second molars with two canals in the mesiobuccal root were selected and the anatomy of the canals was verified by micro-CT. The teeth were divided into 4 groups (n = 9) according to the kinematics used for glide path preparation: continuous rotation (CR), 30°/150° reciprocation (REC 30°/150°), 30°/90° reciprocation (REC 30°/90°), and 90° optimum glide path motion (OGP 90°). The duration of the procedure, number of canals in which the file reached the full working length (RFWL), canal volume before and after the procedure, rate of file fracture, and file torsional strength after use were evaluated. The ANOVA and Tukey tests or Kruskal-Wallis and Dunn tests were used for statistical analysis.

RESULTS

No significant differences among the groups were found for procedure duration, success at reaching the FWL, distance from the file to apex, and number of fractured files (P > 0.05). The CR group showed a significant decrease in rotation angle compared with REC 90° and OGP 90° groups (P < 0.05). There was no significant difference in canal volume among the groups (P > 0.05).

CONCLUSION

The type of kinematics used did not affect the efficiency, success rate, and shaping ability of the file during glide path preparation. CR seems to induce more torsional stress than the other kinematics.

CLINICAL RELEVANCE

The glide path preparation of narrow canals such as the MB2 is difficult and accidents such as file fracture may occur. This study showed that reciprocation with different file angulations can be safer during this challenging stage.

Influence of temperature on the torsional properties of two thermally treated NiTi rotary instruments

This study aimed to evaluate the influence of temperature on torsional strength and angular deflection of two experimental NiTi rotary instruments manufactured from Blue and Gold thermal treatments and with identical cross-sections. A total of 40 experimental NiTi instruments 25.06 and with a triangular cross-section and manufactured from Blue and Gold thermal treatments were used (n=20). The torsional test was performed in the 3 mm from the tip of the instrument according to ISO 3630-1. The torsional test evaluated the torsional strength and angular deflection to failure at room temperature (21°C ± 1° C) and body temperature (36°C ±1°C). The fractured surface of each fragment was observed by using scanning electron microscopy (SEM). Data were analyzed using an unpaired t test for inter and intra-group comparison and the level of significance was set at 5%. The results showed that the body temperature did not affect the torsional strength and angular deflection of the instruments when compared with room temperature (P>0.05). However, at body temperature, the Blue NiTi instruments presented significantly lower angular deflection in comparison with Gold NiTi instruments (P<0.05). There was no significant difference regarding the torsional strength of the instruments at body temperature (P>0.05). The temperature did not affect the torsional strength of the instruments manufactured from Blue and Gold technology. However, the Blue NiTi instruments presented significantly lower angular deflection than Gold instruments at 36°C temperature.