Highlights • This study compared canal shaping with the rotary One Shape (nickel titanium), rotary ProTaper NEXT (M-Wire), and reciprocating Primary WaveOne Gold (Gold wire) after glide path preparation with K-Files, One G, and ProGlider. • No statistically significant difference in the mean centering ratios at the apical, midroot, and coronal levels of the various glide path groups in combination with the shaping instruments. • WaveOne Gold exhibited the lowest transportation values at all levels with ProGlider. • ProTaper NEXT exhibited the highest volume of dentin removed regardless of the glide path preparation technique used.

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The aim was to evaluate apical debris extrusion produced by a single-file system used in counter-clockwise reciprocation and compare it to rotary singlefile systems used in clockwise rotation and clockwise reciprocation. A total of 100 first mandibular molars were divided into five groups (n = 20): (i) WaveOne Gold Glider and Primary instrument in counter-clockwise reciprocation; (ii) One G and One Curve file in clockwise rotation; (iii) One G and One Curve file in clockwise reciprocation; (iv) TruNatomy Glider and Prime instrument in clockwise rotation; and (v) TruNatomy Glider and Prime instrument in clockwise reciprocation. Apical debris extruded was measured after glide path preparation and canal preparation. WaveOne Gold displayed significantly higher amounts of apical debris extrusion in all the groups (P < 0.05). The lowest mean values were recorded by clockwise reciprocation groups: TruNatomy Glider, One Curve and TruNatomy Glider and Prime combined value, for glide path, canal preparation and combined mean values, respectively.

One-G and ProGlider were significantly more centred at the apical, midroot and coronal levels than K-files. Apical canal transportation ratio values after glide path enlargement were significantly higher for K-files than for One-G and ProGlider. All groups resulted in similar canal volume changes.

Maintaining a smooth, reproducible, glide path when successive files are used is an important characteristic of proper root canal preparation. Glide path enlargement allows for safer, more effective canal shaping with increased prospects of successful treatment outcomes.

Calcific metamorphosis (CM) or pulp canal obliteration (Fig. 1A-C) is a common occurrence following concussion and subluxation injuries. 1,2 Although the exact mechanism by which the canal obliterates is unknown, it is believed to be related to neurovascular damage and deposition of hard tissue within the canal. 3,4 This calcification of the pulp canal space results in a loss of translucency leaving the crown with a yellow discolouration (Fig. 2 and 3). 5 CM can be clinically detected as early as three months after injury but remains undetected in most cases for up to a year after trauma. [6][7][8] Asymptomatic teeth presenting with CM do not initially require treatment other than annual review. 1,9 However, the pulp status within partially obliterated canals may eventually lead to apical pathology requiring treatment. [10][11][12][13][14] Treatment protocols and exact intervention times for the treatment of CM remains controversial and a challenge for even the skilled clinician. [15][16][17] CM is a common outcome of trauma frequently associated with anterior teeth of young adults and is characterised by partial or total obliteration of the root canal. 6,8,15

Chemo-mechanical preparation and the removal of infected dentine in order to eliminate microorganisms and avoid apical periodontitis remain the main objectives in endodontic treatment. Mechanical preparation of the root canal system not only provides the space for obturation but also facilitates disinfection of the root canal system through the use of irrigation solutions.