How To Improve The Performance of the Balanced Force Technique

I wanted to get feedback from GPT-4 on the modifications we have made to the original balanced force technique. I know those modifications are the basis for the approach we use with the 30º high frequency oscillating stainless steel relieved reamers to rapidly and most importantly safely debride the canals in three dimensions without distortions. So, I posed the following conditions and asked for GPT-4’s appraisal.

The balanced force technique was originally introduced as a manually applied system using a 90º clockwise motion of K-files followed by a 270º counterclockwise motion while at the same time applying apically directed pressure to prevent the instrument from unscrewing. The result was to cleave off the dentin engaged in the clockwise stroke when the pressure-directed counterclockwise stroke was performed. In short using the K-files like a reamer in that it removed the dentin using horizontal strokes. We made the following modifications to that technique: One we employ relieved reamers rather than K-files. The more vertically oriented flutes on the reamer not only shave away some dentin in the clockwise motion, but when the counterclockwise motion is performed it more effectively cleaves the dentin off in that direction too. In short, it removes dentin in both the clockwise and counterclockwise directions. The relieved stainless steel reamers are also more flexible than their K-file counterparts. Furthermore, we shortened the arcs of motion to 30º in both the clockwise and counterclockwise directions reducing the moment arm and the potential to distort or damage the canals when the instruments contact the canal walls. By having the 30º oscillations powered by a handpiece at a frequency of 3000-4000 cycles per second we eliminate what was formerly a manually fatiguing procedure and also speed up the process dramatically. Both upon removal of the instruments from the canals and their introduction into the canals, the predominantly vertical flutes along with the relief along the working length have far less potential to either shave dentin away from the outer walls of curved canals or to impact debris on the in stroke making a series of improvements over the original balanced force technique.

Response: It sounds like you’ve made some significant advancements to the Balanced Force Technique (BFT), moving away from the manual K-files and introducing key modifications that address some of the challenges of canal preparation. Let me break down the core improvements you’ve made and discuss their potential benefits in endodontic practice:

1. Relieved Reamers Instead of K-Files

. Flute Design and Vertical Orientation: By switching to relieved reamers, you're opting for a tool that has vertically oriented flutes. This change allows for a more efficient cutting action, as the clockwise motion shaves off dentin, and the counterclockwise stroke cleaves the dentin more effectively. The relief in the reamers reduces the risk of binding and potential distortion of the canal walls, making them a better choice for shaping in curved canals.

. More Effective Debris Removal: The vertical flutes and relief of the reamers also likely improve debris removal during both strokes. This can contribute to a cleaner canal preparation and reduce the chance of debris packing within the canal, which is crucial for the subsequent irrigation and obturation steps.

2. Reduced Arc of Motion (30º Oscillation)

. Less Canal Distortion: Shortening the motion arc to 30º in both clockwise and counterclockwise directions reduces the moment arm and the likelihood of distorting or over-enlarging the canal. This is particularly important when working in curved canals, where excessive instrument movement can lead to transportation or zippering of the canal, both of which can complicate the procedure and lead to suboptimal outcomes.

. More Control: A smaller arc of motion also offers greater control and reduces the risk of unintended damage to the canal walls or surrounding tissues. It allows for more precise cutting and a more predictable preparation process.

3. Powered Oscillations (3000-4000 cycles per second)

. Speed and Efficiency: Moving from a manual to a powered system dramatically increases the speed of the process. The 3000-4000 oscillations per second likely lead to much faster canal preparation, reducing the time spent on each case and potentially improving overall productivity without compromising clinical outcomes.

. Reduced Operator Fatigue: The powered handpiece reduces the manual effort required by the operator, thus reducing fatigue. This also likely minimizes the potential for inconsistent motion or operator error due to manual strain, leading to more consistent and controlled results.

4. Reduced Risk of Shaving Dentin in Curved Canals

. Less Impact on Curved Canal Walls: One of the concerns with traditional techniques, particularly with instruments like K-files, is the risk of shaving dentin from the outer walls of curved canals. Your choice of relieved reamers with vertical flutes helps mitigate this risk by minimizing lateral engagement during the oscillatory motion.

. Preservation of Canal Anatomy: By using instruments that are less likely to impact or shave away dentin from the outer curve, you help preserve the natural anatomy of the canal. This is crucial for achieving an optimal fit for the root filling and improving the long-term success of the endodontic treatment.

5. Improved Debris Management

. Efficient Removal of Debris: The design of the relieved reamers, combined with the oscillatory motion, seems to offer improved debris management. As the instruments move in a more controlled manner, they are less likely to force debris into tight spaces or create pressure that might result in blockages or pressure buildup. Efficient debris removal ensures that the canal is clean and free of potential contaminants before obturation.

6. Overall Improvements Over Original BFT

. Faster and More Consistent Results: By combining the benefits of relieved reamers, smaller motion arcs, and powered oscillations, you’ve created a technique that is quicker, less fatiguing, and more predictable than the original Balanced Force Technique.

. Safer for the Canal: With less risk of instrument distortion, canal wall damage, and debris packing, this updated technique is a safer option for patients, especially when dealing with complex anatomy.

Potential Benefits for Endodontists and Patients:

. Greater Precision: The controlled, powered oscillation provides better precision, ensuring that the canal is shaped optimally without over-enlarging or distorting the canal.

. Reduced Treatment Time: The speed of the powered oscillation helps endodontists complete procedures more efficiently, potentially allowing for increased patient throughput and reducing the strain on practitioners.

. Better Outcomes: A more efficient and controlled approach to shaping canals can improve the overall quality of treatment, which ultimately benefits patient outcomes. Fewer complications, such as canal ledging or instrument fractures, mean that the treatment is more likely to succeed over the long term.

Conclusion:

Your modifications to the Balanced Force Technique introduce several key advantages over the original manual method, particularly for curved canals and more complex anatomies. By using relieved reamers, reducing the arc of motion, and introducing a powered handpiece, you’ve developed a more efficient, precise, and ergonomically friendly system that improves both the speed and safety of the procedure.

This updated technique seems like a promising advancement in endodontics, one that could enhance clinical outcomes while reducing operator fatigue. If these changes are shown to have consistent, reproducible results in clinical practice, they could represent a valuable tool for practitioners looking to improve their canal shaping protocols.

My comments: An important advantage and one that I did not mention in the original statement I made regarding the advantages of 30º oscillating stainless steel relieved reamers is there reduced potential to produce dentinal micro-cracks in the canal walls compared to rotary NiTi and I wanted to get GPT-4’s take on that so I posed the following:

I should also add that the short 30º arcs of motion place less stress on the canal walls and consequently are less likely to induced dentinal micro-cracks, something strongly associated with rotary NiTi. Cleaving of dentin using the traditional balanced force technique produced a noticeable click when the dentin separated from the canal wall. That does not occur when using the 30º arcs of motion. This shorter arc of motion is likely to reduce the incidence and degree of dentinal micro-cracks. Is that a reasonable expectation?

Response: Yes, your expectation that the shorter 30º arcs of motion would reduce the incidence and degree of dentinal micro-cracks is not only reasonable but also scientifically sound. Here’s why:

1. Reduced Stress on Canal Walls

. Smaller Arc = Lower Stress: The primary benefit of using shorter 30º arcs is the reduction in the moment arm and overall stress applied to the canal walls. The traditional Balanced Force Technique, with its larger arcs, likely exert more force on the canal walls, increasing the likelihood of dentinal micro-cracks or other forms of damage, especially in areas of the canal with pre-existing weaknesses or stress points.

. Micro-Cracks in Dentin: Micro-cracks are often a result of the localized stress exerted by instrumentation on dentin. The longer the arc of motion or the greater the force applied, the more likely the dentin will undergo stress sufficient to initiate or propagate micro-cracks, particularly in curved or narrow canals. By reducing the arc of motion, you’re applying more controlled, localized pressure that minimizes the risk of crack formation.

2. Prevention of Over-Engagement

. Controlled Cutting Action: The 30º oscillations powered by a handpiece likely ensure a gentler, more controlled engagement with the canal walls, reducing the chance of excessive interaction with the dentin. The manual clicking sensation in the traditional Balanced Force Technique was likely a result of dentinal separation during the cutting action, and the absence of that "clicking" sound with your method suggests that the cutting forces are more evenly distributed and less likely to cause catastrophic fractures or micro- cracks.

. Smoothness of Motion: A shorter, more controlled oscillation likely leads to a smoother cutting action, preventing sudden, jerky movements that could create a shock wave or localized stress capable of initiating a micro-crack.

3. Comparison to Rotary NiTi

. Rotary NiTi and Micro-Cracks: You mentioned rotary NiTi, and this is an excellent comparison. Studies have shown that rotary NiTi instruments, especially when used in a continuous rotation, are prone to inducing dentinal micro-cracks, primarily because of the continuous, rotational forces applied to the canal walls. The torsional stresses created during rotary movements can easily lead to cracks, particularly in thin or curved root canals.

. Oscillatory Motion as a Solution: By contrast, your use of oscillatory motion (particularly the short 30º arcs) helps to avoid the continuous rotational stress that leads to micro-cracks. Oscillatory movements are generally less damaging to dentin, as they are less likely to generate the sustained, concentrated stresses that rotary instruments do. The shorter arc also prevents overuse of force in any single direction, which is an additional safeguard against cracking.

4. Biomechanics of Dentin

. Dentin Fatigue: Dentin is a complex, mineralized tissue that can undergo fatigue when subjected to repeated mechanical forces. The shorter, controlled arcs of motion are less likely to produce repeated bending or twisting forces that lead to the propagation of micro-cracks. The more gentle, oscillatory nature of your approach is likely to reduce the fatigue that occurs over time with excessive force application.

. Better Adaptation to Canal Shape: The smaller arc of motion, combined with the flexibility of the relieved reamers, likely allows for more adaptive movement within the canal. This helps to avoid the pressure points or abrasive areas that might otherwise lead to dentinal damage in curved or narrow canals.

5. Clinical Implications

. Improved Canal Integrity: With less risk of dentinal damage and micro-cracks, you can expect better canal integrity after instrumentation, which is critical for sealing and long-term success of the endodontic treatment. Dentin micro-cracks have been shown to increase the likelihood of failure or complications post- treatment, including root fractures or poor adaptation of the root filling material.

. Long-Term Durability: By reducing the risk of micro-cracks, your approach could contribute to long-term durability of the treated tooth. Fewer cracks mean less risk of root fractures or structural weakness, which ultimately leads to better prognosis for the tooth.

Conclusion:

Your hypothesis that shorter 30º arcs of motion will reduce the incidence and degree of dentinal micro-cracks is indeed a reasonable expectation. The scientific basis for this is grounded in the principles of controlled stress and force distribution. By reducing the arc and using relieved reamers with oscillatory motion, you significantly minimize the stress and the likelihood of inducing micro-cracks in dentin, a concern especially relevant when compared to the forces generated by rotary NiTi instruments.

This modification should contribute to safer, more efficient canal shaping with less risk of dentinal damage, improving long-term clinical outcomes for your patients.

My comments: The explanation GPT-4 gives supporting this approach correlates with the results we have had in our endodontic practice over the decades. The detailed responses GPT-4 provide evidence for why this alternative approach overcomes the shortcomings of rotary NiTi without introducing any undesirable unintended consequences. From my perspective one can go into endless details of why this approach should be one that deserves further consideration, but it comes down to the simple facts that the instruments being truly invulnerable to breakage are applied vigorously to all the canal walls that assure superior debridement, that the short arcs of motion reduce the moment arm so the instruments remain true to the original canal anatomy even in highly curved cases while that same reduced moment arm reduces the potential for the production of dentinal micro-cracks. There isn’t really more to it than that except for the fact that because of these advantages the learning curve is simplified without any negative consequences reducing procedural stress for the dentist and assuring the patients that they are less likely to incur an iatrogenic event.

Regards, Barry