Abstract
Orthodontic treatment is a lengthy process determined primarily by rate of tooth movement, which is controlled by the biological response to orthodontic force. An understanding of the clinical parameters and biological processes underlying orthodontic tooth movement (OTM) is an important foundation for investigations of orthodontic treatment time.This thesis has systematically reviewed the evidence on rate of OTM and duration of treatment during the alignment and canine retraction phases of orthodontic treatment with fixed appliances; characterised the salivary peptidome and protease profile during the alignment stage of orthodontic treatment with fixed appliances; investigated the effect of adipokines on inflammation and extracellular matrix (ECM) remodelling biomarkers in compressed human periodontal and gingival fibroblasts in the presence or absence of inflammation; and assessed the effect of appointment interval (2 weeks versus 8 weeks) on duration and rate of orthodontic tooth alignment.
The systematic review and meta-analysis demonstrated that pooled duration for complete alignment of the mandibular dentition was 263.0 days, initial alignment of the mandibular incisor teeth was 100.7 days, and pooled average incisor irregularity changes were 2.9 mm (month 1), 1.5 mm (months 1-2), 0.7 mm (months 2-3), 0.3 mm (months 3-4), 0.3 mm (months 4-5), and 0.2 mm (months 5-6). These data were obtained from 35 randomised controlled trials (RCTs). Moreover, the estimated average pooled duration to achieve canine retraction was 4.98 months, pooled average canine retraction was 0.97 mm at months 0-1, 1.83 mm at months 0-2, 2.44 mm at months 0-3, 3.49 mm at months 0-4, and 4.25 mm at months 0-5. The data were obtained from 50 RCTs.
In the retrospective study, a total of 2852 naturally-occurring peptides were detected, deriving from 436 different proteins. Proteasix predicted 73 proteases potentially involved in generating these peptides, including metalloproteinases, cathepsins, and calpains. The tissue culture study demonstrated that leptin showed pro-inflammatory properties by selectively enhancing IL-1α-induced expression of IL-6, IL-8, MMP-1, MMP-3, and MMP-8 in human periodontal and gingival fibroblasts in the presence or absence of compressive force. However, AdipoRon exhibited anti-inflammatory properties by attenuating these biomarkers under similar conditions.
The prospective RCT showed that patients reviewed every 2 weeks needed a mean of 168.5 days less than the 8-week group to achieve complete alignment. Moreover, a faster rate of OTM was observed within the 2-week group, with an overall rate of 0.07 mm per day compared to 0.03 mm per day in the 8-week group.
Patient- and treatment-related characteristics were associated with the reported rates of OTM. Surgically-assisted orthodontics was associated with a reduced duration of initial alignment and greater canine retraction. In addition, shorter intervals between appointments significantly reduced the time required to achieve complete alignment. Moreover, the rate of OTM depends on the extent of periodontal and gingival fibroblast-mediated ECM remodelling, which relies, in part, on the combination of orthodontic forces and inflammation. Finally, protease prediction from peptidome data demonstrates a potential tool for identifying novel biomarkers and discriminating between different approaches proposed to accelerate OTM.
| Date of Award | 1 Jul 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Martyn Cobourne (Supervisor) & Guy Carpenter (Supervisor) |