Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Clinical Dentistry

Program

Orthodontics

Supervisor

Dr. Douglas Hamilton

2nd Supervisor

Dr. Ali Tassi

Co-Supervisor

Abstract

The pressure-tension theory of orthodontic tooth movement (OTM) states that there are differences in microenvironment between the tension and compressions side within the periodontal ligament, leading to differential gene expression within those zones. Cementum protein 1 (CEMP-1) is a human-specific protein localized to the root of a tooth and may play a role in OTM. The first objective was to develop a protocol to apply tensile force to human PDL cells similar to that within the tension zone during OTM. For this, the FlexCell®FX-5000 Tension system was used and fluorescent microscopy was used to confirm validity of the protocol. The second objective was to evaluate expression of CEMP-1 in human PDL cells under tensile force using RTqPCR. Expression of CEMP-1 appeared to decrease over time regardless of amount of force application or time point. More research is required to further investigate CEMP-1 expression in human PDL cells.

Summary for Lay Audience

Orthodontics is the dental specialty that addresses the diagnosis, prevention and correction of malpositioned teeth and jaws. Tooth movement is just one of the tools used to address dental malocclusion. A specialized group of fibers, called the periodontal ligament (PDL), connects the tooth to the surrounding bone and is essential for tooth movement. When a tooth is moved through the bones of the jaw, one side of the PDL is compressed while the other side of the PDL is experiencing tension. Because the forces are different on either side of the tooth’s PDL, this can lead to differences in the microenvironments between the zones of compression and tension. Previous studies have shown that certain proteins – such as Periostin – are differentially expressed in the different zones and this suggests that other proteins might be differentially regulated as well. This study specifically wanted to look at how cementum protein 1 (CEMP- 1) was expressed in the zone of tension. CEMP-1 is only found in humans and as such there is not much known about this protein. It is thought that it may help generate or regulate components that help repair teeth during orthodontic tooth movement. In order to evaluate CEMP-1 expression in an environment as similar as possible to that found in humans, a protocol was developed using a specialized machine (FlexCell®FX-5000 Tension system) that could apply tension to human PDL cells isolated from extracted teeth in a 3- dimensional collagen gel. Using this protocol, it was determined that CEMP-1 expression decreased over time with or without tension applied. Additional research is required to more fully understand the role of CEMP-1 in orthodontic tooth movement.

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