Introduction:
Tooth movement is caused by inflammatory and cellular reactions within the bone in response to applied orthodontic forces. Several attempts have been made to increase the rate of bone turnover in order to achieve accelerated tooth movement. These attempts can be classified into two categories: physical trauma (such as Alveolar Corticotomy "Wilckodontics", Piezopuncture, Laser and Resonance Vibrations) and application of drugs (such as the systemic and local application of Vitamin D, Prostaglandins and Corticosteroids) .
Some of these techniques showed inconsistent results such as laser; while others had undesired side effects(such as osteoporosis induced with the use of corticosteroids or headache associated with the use of a pain mediator as prostaglandin) that pose a challenge to their application in clinical practice. Even though the alveolar corticotomy procedure has had more consistent results, it remains an invasive surgical procedure that causes a tremendous amount of trauma. The unanswered question remains: Is there a mechanical system capable of delivering the lowest threshold of trauma that can cause accelerated tooth movement with minimal discomfort and invasion?
The aim of this study is to design a system that delivers trauma to the bone through the gingiva without raising a flap in order to accelerate the rate of tooth movement. It should be minimally invasive with tolerable forces. In addition, forces and frequency should be accurately and easily controlled by the operator, and the system should be autoclavable.
Material and methods:
Initial trials were conducted using three needles with varying thickness to qualitatively assess the force level needed to pierce a synthetic bone block of medium hardness. Further quantification of these force levels was done using the Instron machine. The needle length can be determined clinically using a periodontal probe and the needle material will be made of both surgical SS 316 & Titanium. A handpiece was designed containing a pressure gauge, a solenoid valve connected to a timer and a pneumatic piston. FEM analysis was performed on the external and needle design of the handpiece to ensure that a uniform thickness of 1mm and the selected needle thickness were sufficient to withstand the forces generated by this system. A prototype was made and it was tested on a pig jaw for the force calibration. Micro Ct scan was used to quantify bone trauma.
Results:
The forces that pierced the synthetic bone block were qualitatively assessed by two different examiners. It was found that the needle of 0.23 mm thickness at the apex and 0.4 mm at the base could penetrate the bone with trauma that could be easily tolerated by the patient. The Instron machine quantified these forces to range from 10-17 N. The assembled prototype, using the mechanical design described above, produced desired forces and pierced the synthetic bone block, and the operator was able to control the level of force.. Further trials on pig jaws proved that the system was able to pierce the gingival tissue with an adequate force to cause bone trauma. FEM study illustrated that a handpiece with 1 mm thick external casing (surgical SS 316 L), and a needle with thickness of 0.23 mm at the apex and 0.4 mm at the base (Surgical SS 316L and Titanium) could safely withstand the forces generated by this system.
Conclusion:
The corticopuncture system designed in this study provides a fully controlled, minimally invasive, effective and efficient technique of causing bone trauma. An external handpiece casing could be safely manufactured using surgical stainless steel 316 L with a uniform thickness of 1mm. A needle with a thickness of 0.23 mm at the apex and 0.4 mm at the base could cause adequate bone trauma at force levels that can be tolerated by patients.
