Ultrasonic Prong Welding for Broken Root Canal File Extraction

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Solution Overview

Problem

Broken endodontic files can become wedged in root canals during treatment, leading to treatment failures and requiring effective removal methods that avoid asymmetric loading, direct heat, and static friction.

Innovation Solution

A device with a flexible shaft and multi-pronged tip is used to surround the file fragment, applying ultrasonic vibrations for local melting and welding, followed by torque for extraction, utilizing a concentric shaft to ensure contact and deformation of prongs for secure attachment and rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional mechanical extraction methods are used to remove broken file fragments, then the extraction force can be applied directly, but asymmetric loading and static friction cause incomplete removal or further fragmentation

Engineering Contradiction:

Improveextraction completenessVSAvoidasymmetric loading

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies ultrasonic vibrations to the extraction device that contacts the broken file fragment. These high-frequency vibrations reduce static friction between the fragment and canal walls, enable symmetric loading during extraction, and prevent further fragmentation by maintaining controlled contact forces throughout the removal process.

Inventive Principle:

Principle #18Mechanical vibration

2Reliability

If direct heat is applied to melt and remove the file fragment, then removal can be achieved, but direct heating causes thermal damage to surrounding dental tissues

Engineering Contradiction:

Improvefragment removalVSAvoidthermal damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of direct heating, the patent uses ultrasonic mechanical vibrations to facilitate fragment removal. The vibrations create micro-motion and reduce friction at the contact interface between the extraction device and file fragment, enabling removal without thermal effects that could damage surrounding dental tissues.

Inventive Principle:

Principle #18Mechanical vibration

3Reliability

If high extraction force is applied to remove the wedged file fragment, then removal can be achieved, but the force causes further fragmentation or damage to the root canal structure

Engineering Contradiction:

Improveextraction effectivenessVSAvoidcanal structure integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The ultrasonic vibrations provide continuous micro-motion during extraction, reducing static friction and enabling the use of lower overall extraction forces. This prevents further fragmentation of the broken file and avoids damage to the delicate root canal structure while maintaining effective removal capability.

Inventive Principle:

Principle #18Mechanical vibration

4Force

If the extraction device makes rigid contact with the file fragment, then secure grip can be achieved, but static friction prevents rotation and extraction

Engineering Contradiction:

Improvegrip strengthVSAvoidstatic friction

Core Design Contradiction:

ForceVSObject-generated harmful factors

Solution Approach 1:

The patent applies ultrasonic vibrations to the contact interface between the extraction device and file fragment. These vibrations continuously reduce static friction, allowing the device to maintain secure grip through dynamic contact while enabling rotation and extraction that would otherwise be prevented by static friction forces.

Inventive Principle:

Principle #18Mechanical vibration

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The method effectively removes broken file fragments without asymmetric loading or direct heat, overcoming static friction through controlled vibrations and torque, enhancing the success rate of endodontic treatments.

Implementation Method 1

a device to create and deliver vibrations at an intensity configured to cause local melting of the plurality of prongs in contact with the file fragment, and welding of each of the prongs to the file fragment

Methodology Applied

Scientific EffectUltrasonic vibration: Ultrasonic Vibration

Implementation Method 2

welding of each of the prongs to the file fragment

Methodology Applied

Scientific EffectFriction welding: Friction Welding

Implementation Method 3

a torque for rotating the file fragment during application of an axial force for its extraction from the root canal

Methodology Applied

Scientific EffectTorque: Torque

Implementation Method 4

application of an axial force for its extraction from the root canal

Methodology Applied

Scientific EffectMechanical force: Mechanical Force

Data Source

PatentUS10813719B1Method and extraction device for removal of broken root canal file fragment

Publication Date: 2020.10.27 RADWAN SHERIF

AI summary

A device for removing a file fragment lodged within a root canal of a tooth may include: a flexible shaft configured for insertion into the root canal; a plurality of prongs extending from the distal end of the flexible shaft; a concentric shaft slidable upon the flexible shaft and configured to contact and move the prongs into contact with the file fragment; and a device to create and deliver vibrations at an intensity configured to cause local melting of the plurality of prongs in contact with the fragment, for welding of each of the prongs to the fragment. Counter-rotation of the shaft and fragment may cause it to be dislodged from the canal. Prior to using the device, the root canal may generally be enlarged using a drill, and an umbrella drill is used to form an opening around the coronal end of the fragment to expose a portion thereof.