The effect of two different types of forces on possible root resorption in relation to dentin phosphoprotein levels: a single-blind, split-mouth, randomized controlled trial

Background The purpose of this 2-arm-parallel split-mouth trial was to evaluate and compare the extent of possible root resorption using dentin phosphoprotein levels in gingival crevicular fluid between controlled continuous and intermittent orthodontic force groups. Materials and methods A sample of 16 maxillary first premolars from 8 patients requiring bilateral extractions of the upper first premolars as part of their orthodontic treatment were recruited. A buccally directed continuous force of 150 g, reactivated after 28 days, was applied to the upper first premolar on one side for 8 weeks. On the contralateral first premolar, a buccally directed intermittent force (21 days on, 7 days off) of the same magnitude was applied for the same period. Gingival crevicular fluid samples were collected at the beginning of the study, 1st, 3rd, 4th and 5th week, and at the end of the study to quantify and compare dentin phosphoprotein levels in both groups. Results Dentin phosphoprotein levels showed a higher concentration in the continuous force group than the intermittent force group in week 4 and 8 of sample collection; where the differences were statistically significant (95% CI 0.007–0.14; P < .04) and (95% CI 0.02–0.17; P < .04) respectively. No harm was observed. Conclusions Dentin phosphoprotein was found to be a useful early biomarker to detect and monitor root resorption, showing that the application of an intermittent orthodontic force caused less root resorption than a continuous force. Trial registration NCT04825665 ClinicalTrials.gov. Registered 1 April 2021—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04825665.

Impact of the prefabricated forms of NiTi archwires on orthodontic forces delivered to the mandibular dental arch

Background Although preformed archwires with a variety of arch forms are currently commercially available, the effects of variation in the shape of these archwires on the orthodontic force at each tooth are not well understood. Therefore, we evaluated the forces delivered by various types of commercially available preformed nickel–titanium alloy (NiTi) archwires in a simulated mandibular dental arch. Methods Sixty-three types of 0.019 × 0.025-inch preformed NiTi archwires from 15 manufactures were selected for analysis. The intercanine width (ICW) and intermolar width (IMW) of each archwire were measured at the mean canine and first molar depths of 30 untreated subjects with normal occlusions. Each archwire was placed in a multi-sensor measurement system simulating the mandibular dental arch of subjects with normal occlusions, and orthodontic forces in the facial-lingual direction at the central incisors, canines, and first molars were measured. Correlations between the ICW, IMW, and ICW/IMW ratio of archwires and the delivered forces were analyzed. The archwires were classified into the following four groups according to the ICW and IMW: Control group, ICW and IMW are within the means ± standard deviations of the normal ranges; Ovoid group, narrow ICW and IMW; Tapered group, narrow ICW; and Square group, narrow IMW. The forces were compared among these groups for each tooth. Results Significant correlations between the measured archwire width and force to each tooth were found, except between IMW and forces at the central incisors and canines. Significant differences in the forces were found among all groups, except between the Ovoid and Tapered groups at all teeth and between the Ovoid/Tapered and Control groups at the first molar. Significantly greater orthodontic forces in the facial direction were delivered at the central incisors by the archwires in the Ovoid and Tapered groups when compared with the archwires in the other groups. Conclusion These findings suggest that there is a possible risk of a clinically significant level of unfavorable orthodontic force being delivered to the mandibular incisors in labial inclination when using a preformed archwire with an ICW that is narrower than the dental arch.

The Balance between Orthodontic Force and Radiation in the Jawbone: Microstructural, Histological, and Molecular Study in a Rat Model

Irradiation of facial bones is associated with a lifelong risk of osteonecrosis. In a rat model, maxillae were exposed to a single 5 Gy dose of external beam radiation and orthodontic force was applied for 2 weeks on the first maxillary molar; control rats were treated identically without radiation. Tooth movement in irradiated jaws was 30% less than in controls, representing radiation-related damage. Micro-CT, histological, and molecular outcomes of orthodontic tooth movement were studied. Microstructurally, bone parameters (trabecular thickness, bone volume fraction, bone mineral density) were significantly affected by orthodontic force but not by radiation. Histological parameters were influenced only by orthodontic force, especially by an increase in osteoclasts. A molecular study revealed a differential distribution of cells expressing pre-osteoclast markers (RANK+—majority, CD11b+, CD14+—minority), with changes being influenced by orthodontic force (increased CD11b+ and CD14+ cells) and also by radiation (decreased RANK+ cells). The activation status of osteoclasts (TRAP staining) showed an orthodontic-force-related increase, which probably could not fully compensate for the radiation-associated impairment. The overall balance showed that orthodontic force had elicited a substantial microstructural, histological, and functional normalization process in irradiated maxillae but a radiation-induced impact was still conspicuous. Additional studies are needed to validate these findings.

FINITE ELEMENT ANALYSIS OF ROOT RESORPTION ASSOCIATED WITH TOOTH MOVEMENT: A SYSTEMATIC REVIEW”

Background: The purpose of this systematic review was to examine the available evidence of root resorption during orthodontic treatment with different force systems using nite element analysis. Methods: The following electronic databases were searched for literature till June 2021 : Pro-Quest Dissertation Abstracts and Thesis database, Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, Google Scholar, Embase, US National Library of Medicine, and National Research Register. Root resorption studied under orthodontic forces, which simulated under various technique of nite element method (3D FEM) models were included in the study. The selected studies were assessed for the risk of bias using the Cochrane Collaboration risk of bias tool. The “trafc plot” and “weighted plot” risk of bias distribution were designed using the ROBVIS tool. The authors extracted and analyzed the data. Results: Fourteen studies fullled the inclusion criteria. The risks of biases were high for all studies.Data on quantity and direction of force applied, different type of root morphology and its various surface inuence on root resorption were extracted. The outcomes of the included studies were heterogeneous. Conclusion: Based on the current available literature, for reducing root resorption the excessive force may accelerate root resorption when it exceeds the typical human capillary blood pressure. Root resorption occurs more when extrusion/intrusion and tipping occur than when teeth actually move. A tooth with little or no orthodontic force load hardly shows any root resorption compared to one that has orthodontic force.