Advances in Orthodontic Tooth Movement: Gene Therapy and Molecular Biology Aspect

Abstract

Accelerated orthodontic tooth movement has been recently the topic of interest for ortho- dontic practitioners. Increased numbers of both clinical and research articles associated with the accelerated orthodontic treatment have been published in peer-reviewed journals in the last couple of years. Biochemical approaches such as administration of drugs, vitamins, and proteins and/or physical approaches such as surgery, vibration, and photobiomodulation have been widely reported and demonstrated the predicted outcome; however, the results are controversial. Very few reports addressed on genetic background of patients or utiliza- tion of molecular biological approach on the accelerated orthodontic treatment. In this chapter, we will discuss about biology of tooth movement and how the advances in gene therapy and molecular biology technology would shape the future of orthodontic treatment. transfer approach using a hemagglutinating virus of Japan (HVJ) envelope vector carrying mouse OPG messenger RNA (mRNA) was performed in rats for 21 days of tooth movement. The vector solution was administered into rat ’ s palatal gingiva by infiltration injection. The result showed that local OPG gene transfer reduced the number of osteoclasts and decreased tooth movement by 50% in rats in the experimental group compared to the ones in the control group. The effect of OPG gene transfer was local and did not affect bone mineral density of tibia of the animals [105]. The same group of investigators performed another experiment using the same system to transfer mouse RANKL mRNA to periodontal tissue to activate osteoclastogenesis and accelerate tooth movement in rats. The results showed that local RANKL gene transfer induced increased numbers of osteoclasts and accelerated tooth movement by approximately 150% in the rats in the experimental group compared to the control group. The effect of RANKL gene transfer was local and did not elicit any systemic effects. Interestingly, the number of osteoclasts was reduced time dependently after gene transfer [104]. Another group of investigators compared corticotomy with gene therapy using a hemagglutinating virus of Japan envelope vector containing mouse RANKL mRNA in rats for 32 days. The results showed increased level of RANKL protein 3 folds in the gene therapy group and 2 folds in the corticotomy group after 10 days; however, the level