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Introduction: Transient inflammatory surface resorption, referred to as orthodontic induced inflammatory root resorption (OIIRR), is an iatrogenic consequence of orthodontic tooth movement. Systemic fluoride has been associated with a reduction of OIIRR. This study aimed to investigate the effects of water fluoridation levels on OIIRR in a clinically applicable human orthodontic model., Methods: Twenty-eight patients who required bilateral maxillary first premolar extraction as part of orthodontic treatment were selected from 2 cities with high and low water fluoridation of ≥2 ppm and ≤0.05 ppm, respectively. Patients were separated into high fluoride (HF) and low fluoride (LF) groups on the basis of water fluoridation levels. Bilateral maxillary first premolar teeth were subjected to 150 g of buccal tipping forces for 12 weeks with reactivation every 4 weeks. Teeth were extracted at the end of 12 weeks. Root resorption crater volume was determined using microcomputed tomography and 3-dimensional reconstruction., Results: HF group showed significantly less mean root resorption volume on the palatal root surface when compared with the LF group (P = 0.025). This difference was specifically displayed at palatal apical regions (P = 0.041). When root resorption volumes from the zones of orthodontic pressure (buccal cervical, palatal apical) were combined, the mean difference between HF and LF groups was statistically significant (P = 0.045)., Conclusions: Findings of the present study indicated a positive correlation between water fluoridation and the reduction of OIIRR, especially at the zones of orthodontic pressure, using a clinically relevant human orthodontic model., (Copyright © 2022. Published by Elsevier Inc.)

Background: Fluoride has a major role in strengthening the structure of enamel against acids. Despite differences between caries and root resorption processes, both events inherently involve acidic dissolution of dental tissues. The aim of the present study was to investigate the effects of water fluoridation levels on the surface roughness of root cementum and resorption craters. The findings provided more insight into the influence of fluoride on the surfaces of intact cementum surface and resorption craters., Methods: Twenty-eight orthodontic patients were recruited from two cities in Turkey, with high (≥ 2 ppm) and low (≤ 0.05 ppm) water fluoridation. These patients needed bilateral maxillary first premolar extraction as part of their orthodontic treatment and were allocated into two study groups (n = 14 in each group) based on water fluoridation exposure level: the high-fluoride group (HF) and low-fluoride group (LF). 150 g of buccal tipping forces was applied to all maxillary first premolar teeth for 12 weeks with a beta-titanium spring which was reactivated every 4 weeks. All maxillary premolars were removed at the end of the experiment for surface roughness assessment using three-dimensional confocal microscopy and the associated software. The buccal root surface and the largest buccal resorption crater were investigated., Results: Resorption craters were significantly rougher in LF group compared to HF group (p = 0.002). Craters were rougher than the intact root surfaces (p = 0.000). Cervical and apical regions were significantly rougher than the middle region (p = 0.000 and p = 0.024, respectively)., Conclusions: Higher water fluoridation level of ≥ 2 ppm resulted in significantly smoother root resorption craters than low water fluoridation level of ≤ 0.05 ppm when the teeth were subjected to 150 g of buccal tipping force. Fluoride seems to have a protective role at the interface of root resorption, and further mineral or histological studies may shed light on the exact protective process against root resorption., (© 2022. The Author(s).)

Aim: To compare root resorption (RR) after rapid maxillary expansion (RME) and slow maxillary expansion (SME) through micro-computed tomography (micro-CT)., Subjects and Methods: Twenty-six subjects who required maxillary expansion and bilateral upper first premolar extraction were randomly assigned to RME (n = 13, mean age: 13.25 ± 0.88 years) or SME (n = 13, mean age: 13.53±1.28 years) group. A hyrax-type acrylic bonded expansion appliance was used. The Hyrax screw was activated ¼ turn twice a day for 20 days in the RME group and ¼ turn every second day for 80 days in the SME group. One randomly selected upper first premolar was extracted in each patient after active expansion. The appliance was left in situ for a 24-week retention period then the contralateral upper first premolar was extracted. Extracted teeth were scanned with micro-CT and the volume of the resorption craters was analysed with a specialized software. Transversal skeletal and dental widths were measured on posteroanterior radiographs taken before and after expansion and retention periods., Results: The resorption craters were concentrated mostly on the buccal surface and middle level in all samples. The total RR in the RME group was less post-expansion (P ≤ 0.05) and more post-retention (P > 0.05) than the SME group. During retention, there was a significant decrease in the total RR in the SME group (P > 0.05) and an increase in the RME group. Both RME and SME groups displayed a similar increase in skeletal transverse dimensions, but inter-molar width increased significantly more in the SME group during the whole experimental period., Conclusion: RME does not have an advantage over SME in terms of skeletal expansion and the amount of RR when a retention period of six months is followed., (© The Author(s) 2021. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objectives:: To compare the extent of root resorption and the amount of tooth movement between continuous orthodontic force and intermittent orthodontic force that was activated in a similar way to a 4-week orthodontic adjustment period., Materials and Methods:: Twenty-five patients who required the extraction of upper first premolars were recruited in this study. A buccally directed continuous force of 150 g was applied to the upper first premolar on one side for 15 weeks. A buccally directed intermittent force (28 days on, 7 days off) of the same magnitude was applied to the contralateral first premolar. The teeth were extracted at the end of the experimental period and processed for volumetric evaluations of resorption craters. The degree of tooth movement and rotation were measured on the study models., Results:: Continuous force application displayed significantly higher root resorption volume than the intermittent force application ( P < .05), particularly on the buccal and lingual surfaces (P < .05) and the middle third of the root ( P < .01). There was more tipping and rotational movement in the continuous force group., Conclusions:: In a 4-week orthodontic adjustment period, intermittent force significantly reduced the amount of root resorption compared with continuous force. Although there was less degree of tooth movement with intermittent force, unwanted rotational movement was avoided. This is crucial in patients who are predisposed to orthodontically induced inflammatory root resorption, and the use of this intermittent regimen should be considered.

Introduction: The force application period is a modifiable factor in root resorption. There is still ambiguity if the continuity of force application is advantageous in terms of root resorption and tooth movement. In this prospective randomized clinical trial, we compared the effects of 2 reactivation periods of controlled-intermittent and continuous forces on root resorption and tooth movement., Methods: Thirty-two patients were randomly divided into 2 groups: 2 weekly and 3 weekly reactivations. A split-mouth setup was used for the intermittent and continuous force comparisons. The intermittent force was designed with a pause of 3 days before each reactivation of the springs. A buccally directed tipping force (150 g) was generated with 0.017 × 0.025-in Beta III Titanium cantilever springs (3M Unitek, Monrovia, Calif). After the extractions, surface analysis was performed with microcomputed tomography (model 1172; SkyScan, Aartselaar, Belgium) and specially designed software (CHull2D) for direct volumetric analysis. Buccal premolar movement was also measured on the images of the study casts., Results: Continuous forces produced more resorption than intermittent forces on the total volumes in both groups. A significant difference was found for the 3-weekly group only (P <0.01) on the cervical-mesial (P <0.01) and cervical-buccal (P <0.05) compression regions. In the 2-weekly group, differences were evident in the middle-distal (P <0.05) and middle-lingual (P <0.05) tension regions. Continuous forces produced significantly more tooth movement than did the intermittent forces for both the 2-weekly (P <0.01) and the 3-weekly (P <0.001) regimens. Significant differences were not observed between the 2 intermittent force regimens regarding root resorption and tooth movement., Conclusions: Intermittent force causes less root resorption and tooth movement than continuous force. Root resorption decreases irrespective of the timing of reactivation, when a pause is given. On the other hand, timing of reactivation might have critical importance on continuous force applications, since 2 weekly reactivations produced faster tooth movement with similar root resorption when compared with intermittent force., (Copyright © 2012 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: Previous studies have used the right and left sides of the same jaw to compare different force levels, types of movement, and durations of forces. However, the amounts of root resorption have not been compared between the right and left sides after applying the same amount of force. The aims of the study were to quantitatively compare the volumes of the root resorption lacunae between the right and left first premolars to determine whether 1 side can serve as a control to the other and to compare the volumes of root resorption lacunae of the first premolars between the maxilla and the mandible., Methods: Forty-four first premolars, orthodontically indicated for extraction from 11 patients (left and right maxillary and mandibular first premolars from each) were moved buccally by using beta-titanium-molybdenum alloy 0.017 × 0.025-in cantilever springs with continuous heavy (225 g) force. After the experimental period, the teeth were extracted under a strict protocol to prevent root cementum damage and then analyzed by using a microcomputed tomography scan x-ray system (1172; SkyScan, Aartselaar, Belgium) and specially designed software (Convex Hull 2D, University of Sydney, Sydney, Australia) for direct volumetric measurements., Results: There were no statistically significant differences in the mean cube root volumes of root resorption craters between the right and left sides (P = 0.18) or between the maxillary and mandibular jaws (P = 0.10). There was also no statistical significance for the interception (P = 0.41), which indicated that the jaw and the side had independent effects., Conclusions: The amount of root resorption on the left and right sides of the jaw were similar in both the maxilla and the mandible. Therefore, for future root resorption studies, it is justifiable to use the split-mouth technique so that teeth from 1 side of the jaw can serve as the controls., (Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: Orthodontic force duration can affect the severity of root resorption. The aim of this clinical study was to investigate the amounts of root resorption volumetrically after the application of controlled light and heavy forces in the buccal direction for 4, 8, and 12 weeks., Methods: The sample consisted of 54 maxillary first premolars in 36 patients (mean age, 14.9 years; 21 girls, 15 boys) who required first premolar extractions as part of their orthodontic treatment. The teeth were allocated into 3 groups that varied in the duration of force application: 4, 8, or 12 weeks. The right or left first premolars were randomly selected to receive 2 levels of forces. A light buccally directed orthodontic force of 25 g was applied to the experimental tooth on 1 side, while a heavy orthodontic force of 225 g was applied on the contralateral premolar. At the end of the experimental period, the teeth were extracted and scanned with the microcomputed-tomography x-ray system. Resorption crater analysis was performed with specially designed software for direct volumetric measurements., Results: Significant differences in the extent of root resorption were found between 4, 8, and 12 weeks of force application (P <0.001), with substantially more severe resorption in the longer force duration groups. The light force produced significantly less root resorption than did the heavy force., Conclusions: After 4, 8, or 12 weeks of buccally directed orthodontic forces applied on the maxillary first premolars, the volumes of root resorption craters were found to be related to the duration and the magnitude of the forces., (Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: Root resorption resulting from orthodontic treatment is an unpredictable adverse effect. Literature examining the potential protective influence of tooth cementum minerals against orthodontically induced inflammatory root resorption has been sparse. Fluorine could have a role in minimizing the extent and severity of resorptive lesions. The purpose of this study was to examine the elemental content of tooth cementum in orthodontically induced inflammatory root resorption lesions and the effect of systemic fluoride., Methods: Twenty 7-week-old Wistar rats were divided into 2 groups of 10 and exposed to systemic fluoride (100 ppm) or nonfluoridated drinking water for 2 weeks. Orthodontic tooth movement was implemented with a nickel-titanitum closing coil with a force of 100 g. The molars were then extracted, dissected, and prepared for cross-sectioning through the largest mesial midroot crater. The samples were mounted and scanned by using the Commonwealth Scientific and Industrial Research Organisation and the Australian Research Council's National Key for Geochemical Evolution and Metallogeny of Continents Nuclear Microprobe (Melbourne, Victoria, Australia). Analysis of variance (ANOVA) was used for statistical comparison of the elements and to determine the effect of fluoride, and unaffected tooth structure compared with root resorption craters. The Student t test was used to compare root crater lengths and depths of the fluoride vs no-fluoride groups., Results: Root resorption lesions of the group exposed to fluoride were significantly reduced in length and depth (P <0.01). The mineral content of the root resorption craters of the fluoride group had higher concentrations of fluorine and zinc (P <0.01). There was less calcium in the craters of the no-fluoride group compared with the fluoride group (P <0.05)., Conclusions: Cementum quality (influenced by systemic fluoride exposure) might impact the extent of orthodontically induced resorptive defects., (Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: Repair of root resorption cavities has been studied under light microscopy, scanning electron microscopy, and transmission electron microscopy. The aim of this investigation was to demonstrate the use of microcomputed tomography (micro-CT) to assist in the identification of the region of interest for light microscopy preparation. This study also qualitatively illustrated the root resorption craters with 4 or 8 weeks of retention after 4 weeks of continuous light or heavy orthodontic force application., Methods: Four patients who required bilateral extractions of maxillary first premolars as part of their orthodontic treatment were divided into 2 groups (groups I and II) of 2. The maxillary left and right first premolars were loaded with light (25 g) or heavy (225 g) orthodontic force for 4 weeks. After 4 or 8 weeks of retention, the maxillary first premolars were extracted. The extracted teeth were investigated with micro-CT. By using 3-dimensional images created by the micro-CT, the largest resorption craters on the buccal and lingual sides were identified. Parasagittal sections of these resorption craters were studied histologically under hematoxylin and eosin staining., Results: The use of micro-CT improved the efficiency and accuracy of histologic techniques. Comparatively, less root resorption was repaired by new cementum after heavy orthodontic force application and short retention time. The reparative processes seemed to depend on time, with longer retention time yielding the most amount of repair. Reparative cementum was a mixture of acellular and cellular cementum. Reparative processes seemed to commence at the central part of the resorption cavity and expand to the periphery., Conclusions: Root resorption cavities have the potential to repair regardless of the orthodontic force magnitude. Correlative microscopy with micro-CT and conventional light microscopy adds a new dimension to current root resorption investigation techniques., (Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.)

Introduction: The reparative process of root absorption begins in the periodontium when orthodontic force is discontinued or reduced below a certain level. Our aim was to evaluate cementum repair at 4 and 8 weeks of retention after 4 weeks of continuous light and heavy orthodontic forces. The effects of age, tooth movement, and fluoride exposure were also investigated., Methods: Forty patients were recruited and divided into 4 groups of 10. The maxillary first premolars were loaded with either light (25 g) or heavy (225 g) orthodontic force. After 4 weeks of loading, the maxillary left first premolars were extracted as the positive control group, and the maxillary right first premolars were placed in retention for 4 or 8 more weeks before extraction; these were the experimental groups. The extracted teeth were studied with microcomputed tomography. To assess cementum repair, volumetric changes of the resorption craters were measured with specially designed computer software. Tooth movement was also measured on study casts taken before and after the extractions., Results: Root resorption continued for 4 weeks after orthodontic force ceased. The resorptive activity was more pronounced from heavy forces. Passive retention after 4 weeks of light force had the least root resorption crater volume (cube root scale). The total amount of the cementum repaired did not depend on magnitude of orthodontic force or retention time within our parameters (P >0.05). This might indicate concurrence of resorption and repair during passive retention. Most repair seemed to occur after 4 weeks of passive retention following the 4 weeks of heavy forces. The volume of root resorption craters positively depended on tooth movement (P = 0.02) and negatively correlated with chronologic age (P <0.01)., Conclusions: Although there was no significant difference in the amounts of repair between groups, root resorption continued for 4 weeks after orthodontic force stopped. Resorptive activity was more pronounced after the heavy forces. The reparative processes were different between the light and heavy forces, with marked individual variations. Repair seemed to become steady after 4 weeks of passive retention following 4 weeks of light force application, whereas most repair occurred after 4 weeks of passive retention following 4 weeks of heavy force application. Root resorption crater volume positively depended on tooth movement and negatively correlated with chronologic age.