Back to the glide path

Nicolas Coomber: National Account & Marketing Manager

The endodontic glide path is a smooth radicular passage from the coronal orifice of the root canal to its physiological terminus. Creating a consistent glide path reduces the incidence of biomechanical preparation failures, such as canal transportation or ledge formation. Among other advantages, it reduces the need for a pecking motion to achieve working length. Glide paths also reduce immediate postoperative pain and improve cutting ability.

The glide path is now considered to be an essential foundation for successful endodontic treatment, however, methods and instrument choices considered optimal may vary from case to case, or clinician to clinician.

Since the introduction of the Nickel Titanium (Ni-Ti) alloy in endodontics, there have been significant advancements in root canal instrumentation. Properly establishing a glide path can extend the lifespan of these instruments, as well as optimise the endodontic procedure. A well-executed glide path enhances the quality of chemo-mechanical debridement, and ensures complete obturation. While the use of manual instruments in canal shaping is still an important skill, options available for the mechanical preparation of a glide path are now increasingly predictable.

A brief history

When they were developed over thirty years ago, Ni-Ti rotary instruments revolutionised shaping procedures by both preparing a well-tapered preparation and reducing fatigue. They have a lower modulus of elasticity than stainless steel files, and exert less force on dentinal walls in curved canals. However, there was a concern about the taper lock effect in narrow canals, leading to procedural risks, such as ledge formation, perforation or file separation. The glide path came about to reduce the risk of cyclic flexural fatigue or torsional failure.

Cyclic fatigue occurs when an instrument experiences repeated tension and compression cycles as it rotates and meets resistance within the narrow space of the root canal. Torsional failure occurs when the tip or body of a file becomes locked in the canal while the shank continues to rotate. When the torque applied by the handpiece surpasses the elastic limit of the metal, the file will inevitably fracture.

Initially, it was advocated that a safe glide path was only achievable through the manual use of a K-file. However, rotary Ni-Ti instruments have evolved to reduce the risk of these complications. While both methods offer a number of advantages when creating a glide path, both can present disadvantages, without appropriate consideration of materials and methods.

Advantages and disadvantages of manual versus rotary glide path preparation

The use of manual K-files is still widespread for a number of good reasons. Some clinicians prefer them over rotary instruments due to the cues offered by direct tactile contact. Small-sized pre–curved K-files can effectively register any possible multiplanar curvatures within the root canal system, and the clinician can use touch to help with pathfinding, navigating calcifications and obstructions.

However, especially in complex cases, the operator must apply consistent pressure for extended periods, which over time can contribute to repetitive strain. Forceful pinching, associated with many dental procedures, can lead to work-related musculoskeletal disorders. Additionally, manual files are associated with more alterations to the root morphology than Ni-Ti rotary instruments.

There is evidence that as well as enabling the preservation of more dental tissue, there is also a lower risk of iatrogenic mishaps when using Ni-Ti rotary files. Preparing a glide path with NiTi rotary instruments additionally reduces the risk of operator fatigue.With ample irrigation, the majority of the latest NiTi rotary instruments extrudes less debris into the periapical tissues through the apical foramen compa\red to manual stainless steel K-files. This is thought to be a key reason that patients report less postoperative discomfort when rotary files have been used to create a glide path.

Optimising the advantages of NiTi rotary instruments

To harness their advantages, reducing the risk of fracture associated with rotary instruments has been the goal of manufacturers, and material science has evolved to enable engineers to enhance their flexibility and resistance to stress, while also ensuring they are more durable.

The HyFlex EDM OGSF file sequence from COLTENE is an excellent solution for mechanically opening the canal, and then creating an optimal glide path. The sequence is completed with appropriate files to shape and finish the process easily and predictably. Durability and stress-resistance is enhanced through the innovative Electric Discharge Machining (EDM) manufacturing process. HyFlex files are manufactured from nickel-titanium alloy with Controlled Memory (CM) heat treatment.

Preparing a perfect glide path should be a tailored treatment that benefits the clinical outcome, the comfort and safety of the patient, as well as the health and wellbeing of the clinician. It is in everyone’s interests that the materials and methods used achieve these goals.