Effects of Gates-Glidden, LA Axxess and orifice shaper burs on the cervical dentin thickness and root canal area of mandibular molars

Abstract

This study evaluated the increase of the instrumented area and dentin thickness in the mesial and distal aspects of mesial canals of mandibular molars after the use of Gates Glidden (GG), LA Axxess (LA) and Orifice Shaper (OS) instruments. A total of 53 canals from 27 mandibular molars were embedded in resin and divided into 3 groups. The roots were sectioned 3 mm below the cementoenamel junction and the images were captured before and after instrumentation. The increase of the instrumented area in terms of percentages and the remaining dentin thickness, in mm, at the mesial and furcal aspects were calculated using the Image tools software. Data were analyzed using the Kruskal-Wallis and Dunn's test. The significance level was set at 5%. All instruments promoted cervical flaring with different amounts of dentin removal at the mesial and distal aspects of the root canals. Statistically significant difference (p<0.05) was found between LA and all other instruments after using the first instrument. Regarding dentin thickness, no significant difference (p>0.05) was found between the mesial and distal walls in all groups. It may be concluded that LA 35.06 and GG 3 burs produced the thinnest dentin walls, and thus their use in mesial canals of mandibular molars should be done with caution.

The dentin thickness remaining in the risk zone of mandibular molars after cervical preflaring with four methods

“…The present study found similar rates of dentin removal compared to previous studies 4,[9][10][11][12][13][14][15]24 .…”

“…The wearing results caused by the instruments may be linked to the vector effect that leads the GG drills to the furcal direction, since as shown by Wu et al 4 , the anticurvature movement does not reduce the perforation risk by these drills, in addition, in this study, the LA Axxess and GG were powered at 20.000 rpm, increasing the cutting action, while Easy ProDesign was used at 750 rpm, as shown in previous studies comparing the GG and nickel-titanium rotating systems 22,24 .…”

“…Thus, this work aimed to determine, through CBCT, the variation of the cervical dentin thickness after preparation with different systems. This non-destructive method allows the evaluation of pre and post-instrumented samples 3,24 , but can also be performed by computed microtomography, which is a slow and expensive process that is not always readily available 24 .…”

“…Still, the literature considers that, due to the alloy and design features of instruments made of nickel-titanium, the centralization in the canal long axis is maintained, allowing proportional wear of dentin in risk area since the instrument does not tend towards the area of risk 4,19,21,23,24 .…”

Computed tomography evaluation of residual root thickness after pre-flaring using gates Glidden drills: The sequence effect

“…One problem due to use of the instruments for pre-flaring is whether they could create an increased risk for perforations, especially in mesial canals of mandibular molars. [1] One of the iatrogenic factors in different methods of root canal preparation is the residual root thickness, which is an indicator of the future fracture resistance of the root. [2] The mesial canals of mandibular first molars are not located in the center of the root and the areas between the canals and also between the canals and the furcation area have thin walls and are therefore called danger zones.…”