Physical properties of root cementum: Part 28. Effects of high and low water fluoridation on orthodontic root resorption: A microcomputed tomography study.

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.

Effects of rapid and slow maxillary expansion on root resorption: a micro-computed tomography study.

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 » turn twice a day for 20 days in the RME group and » 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.

In vitro evaluation of a ceramic bracket with a laser-structured base.

BACKGROUND: The purpose of this study was the assessment of shear bond strength (SBS), adhesive remnant characteristics, integrity of the enamel, integrity of Discovery Pearl as well as the integrity of Fascination 2 ceramic brackets following SBS testing. METHODS: Sixty maxillary first premolars were randomly assigned into two groups. These groups were bonded with their respective brackets. The samples underwent thermocycling (1000 cycles), SBS testing and assessment of the residual adhesive. The statistical analyses used were the independent samples t-test, the Weibull analysis and the chi-square test. RESULTS: The independent samples t-test for the comparison of the mean SBS resulted in significant differences between Fascination 2 (10.50 ± 2.61 MPa) and Pearl (13.01 ± 2.50 MPa) brackets (p = 0.0003). The results of the chi-square test for ARI demonstrated a significant difference (p = 0.000) between the groups. A higher frequency of ARI scores of 2 and 3 for Pearl brackets existed. Enamel damage and bracket fracturing was not observed. CONCLUSIONS: The mean bond strength value, the adhesive remnant characteristics, the integrity of the enamel and the ceramic brackets as well as the Weibull analyses outcomes were highly encouraging during this in vitro screening. The way is paved for an in vivo investigation with the Pearl ceramic bracket.

Big toenail and hair samples as biomarkers for fluoride exposure - a pilot study.

BACKGROUND: Biomarkers can aid in detecting and preventing clinical disease through the recognition of change in biological samples. The objective of this case-control study was to further the knowledge on the use of big toenail and hair samples as biomarkers for fluoride exposure. METHODS: A total of 48 participants from an endemic (IC) and a non-endemic (SC) fluorosis region were included. Big toenail and hair samples were collected from each participant and the fluoride concentration was determined. The results of 42 participants were reported: 21 participants (11 males and 10 females, mean age 15.66 + 2.61 years) from IC and 21 participants (11 males and 10 females, mean age 15.06 + 0.79 years) from SC. RESULTS: The mean fluoride concentration of big toenail (2.34 ± 0.26 mg/kg) and hair (0.24 ± 0.04 mg/kg) in the endemic region was significantly higher than the mean fluoride concentration of big toenail (0.98 ± 0.08 mg/kg) and hair (0.14 ± 0.02 mg/kg) in the non-endemic region (p < 0.001 and p = 0.004, respectively). The Receiver Operating Characteristic (ROC) analysis showed that the Area Under the Curve (AUC) value was 0.889 for big toenail (p < 0.001) and 0.762 for hair (p = 0.004) samples. The fluoride assay for big toenails exhibits greater observed accuracy than does the fluoride assay for hair. CONCLUSION: Nail and hair samples can serve as biomarkers to detect biological fluoride exposure according to the data of this pilot study. Nevertheless, hair is less sensitive and specific as a biomarker when AUC values of big toenail and hair samples were compared.

The extent of root resorption and tooth movement following the application of ascending and descending magnetic forces: a prospective split mouth, microcomputed-tomography study.

OBJECTIVE: Various factors have been examined in the literature in an attempt to reduce the incidence and severity of root resorption. The purpose of the present investigation is to test the null hypothesis that there is no difference in relation to force level using gradually increasing (ascending) and decreasing (descending) orthodontic force generated by magnets on the severity of Orthodontically Induced Inflammatory Iatrogenic Root Resorption (OIIRR) and amount of tooth movement. METHODS: Twenty maxillary first premolars from 10 patients were subjected to ascending (25-225 g, magnets in attraction) and descending (225 to 25 g, magnets in repulsion) buccal forces using a split mouth design over an 8-week period. Polyvinyl siloxane impressions were taken at week 0, 4, and 8 to record the tooth movement. After 8 weeks, the teeth were extracted, scanned, with micro-CT in 16.9 µm resolution, and the root resorption craters were localized circumferentially and quantified at each level of the root. RESULTS: The total volume of OIIRR with ascending force was 1.20 mm3, and with descending force was 1.25 mm3, and there was no statistically significant difference between them. OIIRR on the palatal surface (0.012 mm3) was significantly less than on the buccal surface (0.057 mm3) and than on the mesial surface (0.035 mm3). There is no statistically significant difference in the degree of OIIRR between different level of the root (cervical, middle, and apical) at different surfaces. Moreover, the amount of tooth movement, at 0-, 4-, and 8-week interval, secondary to an ascending and descending force application was not statistically significant. CONCLUSIONS: There is no short-term (8 weeks) statistically significant difference between orthodontic ascending and descending forces, from 25 to 225 g and from 225 to 25 g, respectively, in term of severity and location of OIIRR as well as the amount of tooth movement. The buccal surface of the root showed highest degree of OIIRR compared to other root's surfaces.

Physical properties of root cementum: Part 25. Extent of root resorption after the application of light and heavy buccopalatal jiggling forces for 12 weeks: A microcomputed tomography study.

INTRODUCTION: The aims of this study were to evaluate with microcomputed tomography the orthodontically induced inflammatory root resorption in premolars caused by buccopalatal jiggling movement with light and heavy forces and to compare it with the resorption caused by equivalent but continuous buccal forces. METHODS: The sample consisted of 60 maxillary first premolars collected from 30 patients (15 girls, 15 boys; ages, 13-18 years) who required orthodontic treatment with extractions. They were divided into 3 groups of 10 patients. Light (25 g) or heavy (225 g) buccal tipping orthodontic forces were randomly assigned on the maxillary right or left quadrant with either continuous buccal (positive controls) or buccopalatal jiggling forces for 12 weeks. At the end of the experimental period, the teeth were carefully extracted and processed for 3-dimensional imaging and volumetric evaluations of resorption craters. Data were analyzed with Wilcoxon signed rank tests. RESULTS: There was no statistically significant difference between positive control light (P = 0.0173) and heavy (P = 0.0173) continuous forces and jiggling forces for both force magnitudes. However, statistically significant differences were observed between heavy and light jiggling forces (P = 0.038), with heavy jiggling forces causing greater total root resorption than light jiggling forces. CONCLUSIONS: Light and heavy jiggling forces in the buccopalatal direction did not cause significantly different amounts of root resorption when compared with continuous forces of the same magnitude. On the other hand, light jiggling forces resulted in less root resorption than heavy jiggling forces.

Physical properties of root cementum: part 24. Root resorption of the first premolars after 4 weeks of occlusal trauma.

INTRODUCTION: In orthodontics, adding restorative materials on occlusal or lingual surfaces is a common method to create a mini-biteplane to increase patients' vertical dimension temporarily to facilitate several treatment procedures. However, this method transmits excessive occlusal forces through the periodontal ligament and causes trauma. In this prospective randomized clinical trial, we measured and compared quantitatively the volumes of root resorption after 4 weeks of occlusal trauma. METHODS: Forty-eight maxillary and mandibular first premolars of 12 patients (6 girls, 6 boys) comprised the sample for this study. One side of each patient was randomly selected as the control. On the contralateral side, a light-cured glass ionomer cement (Transbond Plus Light Cure Band Adhesive; 3M Unitek, Monrovia, Calif) was bonded onto the occlusal surface of the mandibular first premolar so that the cement was in contact with the maxillary first premolar. After 4 weeks, both first premolars were extracted. Each sample was imaged using a microcomputed tomography system (1172; SkyScan, Aartselaar, Belgium) and analyzed with specially designed software for volumetric measurements of resorption craters. Furthermore, pain was evaluated with a visual analog scale for 7 days. RESULTS: There were significant differences in the amounts of root resorption between the control and the experimentally traumatized teeth. No significant difference among the buccal, lingual, mesial, and distal surfaces was found in either jaw. Furthermore, no significant difference existed in the amount of root resorption among the cervical, middle, and apical thirds of both jaws. There was no correlation between age, sex, volume of the root resorption craters, and pain. CONCLUSIONS: Restorative buildups, used to increase the vertical dimension by 2 mm for 4 weeks, caused root resorption along the sides of the teeth during the active bite-increase period.

Awareness about the orthodontic specialty: A survey study.

BACKGROUND: This study aimed to examine how well patients can differentiate between orthodontists and dentists. METHODS: Four hundred patients who applied to the Ondokuz Mayis University Faculty of Dentistry, Department of Oral and Maxillofacial Radiology between March and November of 2022 were queried regarding the difference between an orthodontist and a dentist via a face-to-face survey. The respondents were separated into the following two study groups: patients who had previously undergone orthodontic treatment and those who had not. Demographic data of the patients, such as age, sex, educational status, and monthly income, were also collected, and the effects of these factors on their doctor preferences were analyzed. RESULTS: The vast majority of respondents (>85%) thought that a dentist should be an orthodontic specialist to provide orthodontic treatment. Seven percent of patients chose to receive orthodontic treatment from a dentist. Patients who chose an orthodontist for their treatment were predominantly female and had a high income and a higher level of education. Patients who had a history of orthodontic treatment were better aware of the profession of orthodontics than those who did not. CONCLUSIONS: The results indicated that the respondents did not fully understand the clear distinction between an orthodontist and a dentist. This outcome suggests that education concerning this issue is required.

Evaluation of the Flash-Free Adhesive System for a 6-month Period: A Split-Mouth Trial.

Objective: To compare the adhesive pre-coated (APC) flash-free (FF) appliance system (3M Unitek) with an operator-coated (OC) system (Transbond XT Light Cure Adhesive Paste; 3M Unitek) in terms of bond failure, bracket survival, and chair time. Methods: This single-center study was planned with 30 non-extraction patients, 22 females and 8 males with an average age of 17 years and 5 months. A split-mouth design was used, and bonding time, failed brackets, reasons for failure, and adhesive remnant index (ARI) scores were noted. The data were analyzed with the chi-square, Kaplan-Meier, log-rank, and Mann-Whitney U tests. Results: OC and FF adhesive-coated brackets demonstrated bond failure rates of 0.7% and 3.0%, respectively. Failure rates and survival rates presented a statistically significant difference (p=0.033). Although higher bond failure for the lower arch along with higher bond failure for the incisor teeth compared with the premolar teeth were found, these findings were not statistically significant (p=0.128; p=0.261, respectively). The effect of gender on the bond failure rate (p=0.463) and survival rate (p=0.473) was not statistically significant. A significant difference was obtained for the ARI scores (p=0.011). The bonding time for each bracket type (64.43 seconds for FF versus 98.97 seconds for OC) demonstrated a significant difference (p=0.174). Conclusion: The bond failure rate was higher for the FF APC brackets, but the chair time reduction during bonding was recorded. Therefore, it seems that FF APC brackets are promising. Trial registration: ISRCTNand ISRCTN26731749. Registered October 7, 2020-Retrospectively registered, https://doi.org/10.1186/ISRCTN26731749.

Physical properties of root cementum: part 23. Effects of 2 or 3 weekly reactivated continuous or intermittent orthodontic forces on root resorption and tooth movement: a microcomputed tomography study.

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.

Comparison of surface roughness of root cementum and orthodontically induced root resorption craters from high- and low-fluoridation areas: a 3D confocal microscopy study.

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.

Physical properties of root cementum: Part 19. Comparison of the amounts of root resorption between the right and left first premolars after application of buccally directed heavy orthodontic tipping forces.

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.

Physical properties of root cementum: Part 16. Comparisons of root resorption and resorption craters after the application of light and heavy continuous and controlled orthodontic forces for 4, 8, and 12 weeks.

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.

Physical properties of root cementum: Part 17. Root resorption after the application of 2.5° and 15° of buccal root torque for 4 weeks: a microcomputed tomography study.

INTRODUCTION: Root resorption is an undesirable consequence of orthodontic tooth movement. The severity is unpredictable, and, despite extensive research, the etiology remains unknown. Torque has been acknowledged as a risk factor for root resorption. The aims of the study were to evaluate and quantify the extent of root resorption after the application of 2.5° and 15° of buccal root torque for 4 weeks. METHODS: Fifteen patients requiring bilateral extraction of their maxillary first premolars for orthodontic treatment were recruited to the study. By using a standardized experimental protocol, the right and left premolars were randomly subjected to either 2.5° or 15° of buccal root torque. At the end of the 4-week experimental period, the premolars were extracted. A volumetric analysis of root resorption was performed by using microcomputed tomography and measured with specially designed software. RESULTS: Overall, the amounts of root resorption were comparable after the application of 2.5° or 15° of buccal root torque (P = 0.59). There was a significant difference between the 2 force levels only at the apical region (P = 0.034). More root resorption occurred in areas of compression than in areas of tension. The variables of age and sex were not statistically significant. CONCLUSIONS: Root resorption was evident after 4 weeks of buccal root torque application. More root resorption was seen at the apical region than at the middle and cervical regions. Higher magnitudes of torque might cause more root resorption, particularly in the apical region. As shown in previous studies, the etiology of root resorption is multi-factorial and cannot be explained by mechanical factors alone.

Physical properties of root cementum: part 21. Extent of root resorption after the application of 2.5° and 15° tips for 4 weeks: a microcomputed tomography study.

INTRODUCTION: Microcomputed tomography offers a unique opportunity to accurately examine orthodontically induced inflammatory root resorption. The aims of this study were to quantify, in 3 dimensions, the amount of root resorption caused by placing heavy and light distal root tipping forces on premolars and to compare the prevalence of root resorption in different areas of the tooth. METHODS: Thirty maxillary first premolars from 15 patients who were to have these teeth extracted as part of their orthodontic treatment were selected for this study. Each tooth in the same patient was randomly chosen to have either a 2.5° or a 15° distal root tipping bend placed for 4 weeks. After the experimental period, the teeth were extracted according to a strict protocol to prevent damage to the root. They were then imaged by a microcomputed tomography scan x-ray system (SkyScan 1172, SkyScan, Aartselaar, Belgium) and analyzed by software designed for volumetric measurements. RESULTS: A significant difference was found in the amount of total root resorption between light and heavy forces (P = .021). The mean cube root volumes of the resorption craters in the 15° tip-bend group were greater than in the 2.5° tip-bend group. This significance was lost when the tooth was divided into vertical thirds, although a trend was still present. When the areas of expected compression in the periodontal ligament were compared with the areas of expected tension, significance was seen in the apical and cervical thirds only. CONCLUSIONS: Based on this experiment, one can conclude that a 15° distal root tip bend causes more orthodontically induced inflammatory root resorption than a 2.5° distal root tip bend. Furthermore, greater root resorption was found in areas under pressure when compared with areas under tension.

Physical properties of root cementum: Part 18. The extent of root resorption after the application of light and heavy controlled rotational orthodontic forces for 4 weeks: a microcomputed tomography study.

INTRODUCTION: The aim of this prospective randomized clinical trial was to quantitatively measure and compare the locations, dimensions, and volume of root resorption craters in human premolars after the application of controlled light and heavy rotational orthodontic forces over a 28-day (4-week) period. METHODS: Fifteen patients requiring bilateral extraction of maxillary first premolars as part of their orthodontic treatment were recruited for this study. Each patient received a heavy (225 g) rotational force on 1 premolar and a light (25 g) rotational force on the contralateral premolar. Orthodontic rotational forces were applied over 28 days with buccal and palatal cantilever springs; 0.016-inch beta-titanium molybdenum alloys were used to apply the light force and 0.018-inch stainless steel was used for the heavy force. After the 28-day experimental period, the upper first premolars were extracted under stringent protocols to prevent root surface damage. The samples were then scanned using a microcomputed tomography (micro-CT) scan x-ray system (SkyScan 1072, Skyscan, Aartselaar, Belgium), and analyzed using convex hull algorithm (CHULL2D; University of Sydney, Sydney, Australia) software to obtain direct volumetric measurements. RESULTS: The mean volume of resorption craters was 0.42 in the light force group and 0.51 in the heavy force group (P = 0.013). When separated at the root level, the difference in volume of root resorption craters between the 2 groups was significantly different only at the midlevel (P = 0.001). Root resorption craters were consistently detected at the boundaries between the buccal and distal surfaces and the mesial and lingual surfaces. The result supports our hypothesis that positive areas develop significantly more root resorption craters at all 3 levels, as compared with minimal areas (paired t test <0.001). CONCLUSIONS: Heavy rotational forces caused more root resorption than light rotational forces and compression areas (buccal-distal and lingual-mesial surfaces in this study) showed significantly higher root resorption than other areas at all levels of the root.

Physical properties of root cementum: part 20. Effect of fluoride on orthodontically induced root resorption with light and heavy orthodontic forces for 4 weeks: a microcomputed tomography study.

INTRODUCTION: The major side effect of orthodontic treatment is orthodontically induced inflammatory root resorption. Fluoride was previously shown to reduce the volume of the root resorption craters in rats. However, the effect of fluoride on orthodontically induced inflammatory root resorption in humans has not yet been investigated. The aim of this study was to investigate the effect of high and low amounts of fluoride intake from birth on orthodontically induced inflammatory root resorption under light (25 g) and heavy (225 g) force applications. METHODS: Forty-eight patients who required maxillary premolar extractions as part of their orthodontic treatment were selected from 2 cities in Turkey with high and low fluoride concentrations in the public water of ≥ 2 and ≤ 0.05 ppm, respectively. The patients were randomly separated into 4 groups of 12 each: group 1, high fluoride intake and heavy force; group 2, low fluoride intake and heavy force; group 3, high fluoride intake and light force; and group 4, low fluoride intake and light force. Light or heavy buccal tipping orthodontic forces were applied on the maxillary first premolars for 28 days. At day 28, the teeth were extracted, and the samples were analyzed with microcomputed tomography. RESULTS: Fluoride reduced the volume of root resorption craters in all groups; however, this effect was significantly different with high force application (P = 0.015). It was also found that light forces caused less root resorption than heavy forces. There was no statistical difference in the amount of root resorption observed on root surfaces (buccal, lingual, mesial, and distal) in all groups. However, the middle third of the roots showed the least root resorption. With high fluoride intake and heavy force application, less root resorption was found in all root surfaces and root thirds. CONCLUSIONS: Fluoride may reduce the volume of root resorption craters. This effect is significant with heavy force applications (P <0.05). The cervical and apical thirds of the root showed significantly greater root resorption after the application of buccal tipping force for 4 weeks.

Effects of fluorosis on the shear bond strength of orthodontic brackets bonded with a self-etching primer.

The aim of this study was to compare the shear bond strength (SBS) of brackets bonded to fluorosed and non-fluorosed teeth with self-etching primer (SEP) and phosphoric acid (PA). The study involved 40 mildly fluorosed [Thylstrup-Fejerskov (TFT) Index = 1-3] and 40 non-fluorosed human premolar teeth. The fluorosed and non-fluorosed teeth were randomly divided into two subgroups. In the first subgroup, 37 per cent PA was applied for 30 seconds and in the second, a SEP (Transbond Plus) was used. The brackets were bonded with light-cure adhesive paste (Transbond XT) and cured for 20 seconds. The SBSs were measured after 1000 thermocyclies. Two-way analysis of variance, Tukey's multiple comparison test, and Weibull analysis were used for the evaluation of SBS values. Bond failure locations were determined with the adhesive remnant index (ARI) and were compared with the Kruskal-Wallis and Mann-Whitney U-tests. The mean SBS was 9.01 MPa for the fluorosed teeth bonded with SEP. This value was significantly different from those of fluorosed teeth etched with PA (15.22 MPa) and non-fluorosed teeth conditioned with SEP (12.95 MPa) and PA (15.37 MPa). The ARI scores of the fluorosed teeth conditioned with SEP were significantly lower than those of non-fluorosed teeth conditioned with SEP or PA. The results of this in vitro study suggest that there are no differences in the SBS of orthodontic brackets between mildly fluorosed and non-fluorosed enamel etched with 37 per cent PA for 30 seconds. The SEP showed lower SBS values for orthodontic brackets bonded to mildly fluorosed enamel. The findings provide some evidence that routine clinical use of a SEP to bond brackets to mildly fluorosed teeth cannot be supported.

Effects of surface-conditioning methods on shear bond strength of brackets bonded to different all-ceramic materials.

The aims of this study were to investigate the effects of two surface-conditioning methods on the shear bond strength (SBS) of metal brackets bonded to three different all-ceramic materials, and to evaluate the mode of failure after debonding. Twenty feldspathic, 20 fluoro-apatite, and 20 leucite-reinforced ceramic specimens were examined following two surface-conditioning methods: air-particle abrasion (APA) with 25 µm Al(2)O(3) and silica coating with 30 µm Al(2)O(3) particles modified by silica. After silane application, metal brackets were bonded with light cure composite and then stored in distilled water for 1 week and thermocycled (×1000 at 5-55°C for 30 seconds). The SBS of the brackets was measured on a universal testing machine. The ceramic surfaces were examined with a stereomicroscope to determine the amount of composite resin remaining using the adhesive remnant index. Two-way analysis of variance, Tukey's multiple comparison test, and Weibull analysis were used for evaluation of SBS. The lowest SBS was with APA for the fluoro-apatite ceramic (11.82 MPa), which was not significantly different from APA for the feldspathic ceramic (13.58 MPa). The SBS for the fluoro-apatite ceramic was significantly lower than that of leucite-reinforced ceramic with APA (14.82 MPa). The highest SBS value was obtained with silica coating of the leucite-reinforced ceramic (24.17 MPa), but this was not significantly different from the SBS for feldspathic and fluoro-apatite ceramic (23.51 and 22.18 MPa, respectively). The SBS values with silica coating showed significant differences from those of APA. For all samples, the adhesive failures were between the ceramic and composite resin. No ceramic fractures or cracks were observed. Chairside tribochemical silica coating significantly increased the mean bond strength values.

The effect of fluoride on orthodontic tooth movement in humans. A two- and three-dimensional evaluation.

AIMS: The aim of the present study was to determine whether high and low fluoride concentrations in drinking water affected the early stages of tooth movement when heavy and light orthodontic forces were applied for 4 weeks. A further aim was to compare and evaluate the resulting two-dimensional (2-D) and three-dimensional (3-D) orthodontic tooth movement. METHODS: The sample consisted of 96 maxillary upper first premolars from 48 patients who required premolar extractions as part of their orthodontic treatment. Patients were selected from two different cities in Turkey with low and high fluoride concentrations of 0.05 and 2 ppm, respectively. The patient sample was divided into four groups according to the magnitude of force applied to the first premolars and the concentration of fluoride in the public water supply; Group 1, High fluoride intake (> or = 2 ppm)-Heavy force (225 g); Group 2, Low fluoride intake (< or = 0.05 ppm)-Heavy force; Group 3, High fluoride intake-Light force (25 g); and Group 4, Low fluoride intake-Light force. A light or heavy buccal tipping orthodontic force was applied to the upper first premolars for 4 weeks. The first three palatal rugae were used for the superimposition of patient casts in a 2-D and 3-D evaluation of generated movements. RESULTS: It was found that heavy force application and fluoride intake increased the average rate of tooth movement. It was further shown that age was negatively correlated with tooth movement in the 2-D and 3-D measurements. CONCLUSIONS: The average rate of tooth movement was found to be greater in the heavy force and high fluoride intake group (Group 1HH). Age was negatively correlated with orthodontic tooth movement. Two- and three-dimensional methods were accurate for the assessment of tooth movement after four weeks of buccal tipping force application when the palatal rugae were used for superimposition.