Bone density changes around teeth during orthodontic treatment. Clin Oral Investig. 2011;15:511-519. [PMID: 20393863 DOI: 10.1007/s00784-010-0410-1]

Menopause-related changes to maxillary trabecular bone micro-architecture

The number of midlife women seeking orthodontic treatment has significantly increased over the past 40 years. With this rise, orthodontists need to consider the potential impact of menopause on treatment planning. There have been no recent published studies on maxillary trabecular bone changes in humans related to menopause. This study aimed to explore the subject further. This cross-sectional cohort study was composed of qualifying participants with diagnostic maxillary CBCT images who were separated by self report into pre- (N = 21) and postmenopausal (N = 19) groups. The regions of interest were the trabecular bone of the incisive foramen and maxillary tuberosity. All scans were converted into binary images in order to draw all parametric and ratio raw data. The parameters of interest included trabecular bone volume fraction (BVF), trabecular thickness, trabecular number, and trabecular separation. In the incisive foramen subgroup, postmenopausal women showed a significant increase in trabecular separation (0.60 ± 0.25 to 0.84 ± 0.31 mm, P < 0.06). For the maxillary tuberosity subgroup, significant decreases in BV/TV (32.58 ± 15.85 to 17.63 ± 14.38 %, P <0.004), trabecular bone surface/tissue volume (2.66 ± 1.01 to 1.43 ± 1.09 %, P < 0.001) and trabecular separation (0.91 ± 0.39 to 1.58 ± 0.51 mm, P < 0.001) were observed. The findings reveal statistically significant differences in maxillary bone density at the level of the maxillary tuberosity and incisive foramen demonstrated in women who are of preversus post-menopausal status.

Association between obstructive sleep apnea syndrome and bone mineral density in adult orthodontic populations

OBJECTIVE

To determine the association between obstructive sleep apnea syndrome (OSAS) and predicted bone mineral density (BMD) in adults presenting for orthodontic treatment.

METHODS

This retrospective cross-sectional study included 38 adults divided into OSAS and non-OSAS groups. Using pre-treatment CBCT images, radiographic density (RD) of left and right lateral regions of the 1st cervical vertebrae and dens of the 2nd cervical vertebrae were measured as an indicator for BMD.

RESULTS

When controlling for age, sex, and BMI, the mean RD was significantly lower in the OSAS group compared to the non-OSAS group (left CV1: 36.69 ± 84.50 vs. 81.67 ± 93.25 Hounsfield Units [HU], respectively, p = 0.031; right CV1: 30.59 ± 81.18 vs. 74.26 ± 91.81 HU, p = 0.045; dens: 159.25 ± 115.96 vs. 223.94 ± 106.09 HU, p = 0.038).

CONCLUSION

Adults with OSAS have lower values for predicted BMD than those without OSAS.

The Effect of Heparin on Bone Metabolism and Orthodontic Tooth Movement in Rats

OBJECTIVES

Various attempts have been made to increase the rate of orthodontic tooth movement (OTM). The aim of this study was to determine the effect of different doses of heparin on OTM and paraclinical factors related to bone metabolism in rats.

METHODS AND MATERIALS

A total of 24 Sprague-Dawley rats were randomly divided into three groups of 8 animals each and injected with 0 (control), 3000, and 6000 U/Kg/d heparin sulfate for 4 weeks. Radiographs were obtained at the initiation and at the end of the study period. Orthodontic forces were applied on Day 14 and continued for the next 2 weeks, after which, OTM, optical density, parathyroid hormone (PTH) level, and histologic variables were assessed for each rat. The latter was performed on hematoxylin/eosin-stained sections of the mesial roots of the first molar and included calculation of the osteoclast number, and resorption lacunae depth and number. One-way analysis of variance, the Tukey test, and a paired-t-test were used for statistical analysis (p < 0.05).

RESULTS

A significant increase in OTM, the number of resorptive lacunae, and PTH secretion was observed in the group that received 6000 U/Kg/d compared with both the other groups. There was no significant difference in optical density, and, therefore, bone density, among the study groups (p > 0.05).

CONCLUSION

Heparin injection affects bone metabolism in rats, as shown by the increases in OTM and PTH and its impact on histologic parameters. These effects seem to be dose-dependent and may be a factor that should be taken into consideration during orthodontic treatment planning.

The Differential Impact of Clear Aligners and Fixed Orthodontic Appliances on Periodontal Health: A Systematic Review

BACKGROUND/OBJECTIVE

In orthodontic therapy, the periodontal ligament plays a critical role in the bone remodeling process by stimulating osteoblasts in tension zones and promoting bone resorption through osteoclasts in compression zones in response to mechanical stress. These processes are regulated by key cytokines, such as RANKL and IL-1, which are influenced by factors such as patient age and force application. This work evaluates the effectiveness of clear aligners versus traditional braces on periodontal health in patients with periodontitis, following PRISMA guidelines and utilizing specific inclusion and exclusion criteria.

METHODS

A systematic review of 1664 records was conducted, leading to the inclusion of eight studies that focus on the impact of orthodontic treatments on periodontal health. The review identifies various biases present in the literature.

RESULTS

The findings reveal that clear aligners, in contrast to fixed appliances, improve oral hygiene and reduce inflammation, leading to better periodontal outcomes. Fixed appliances, on the other hand, may exacerbate plaque accumulation and inflammation, which can worsen periodontal health.

CONCLUSIONS

Clear aligners offer advantages over fixed appliances in terms of enhancing periodontal health, improving patient compliance, and providing long-term benefits, particularly in patients with severe periodontitis. The effectiveness of clear aligners is linked to better management of periodontal complications and overall oral hygiene. Treatment decisions should be based on patient-specific criteria to optimize outcomes.

Use of CBCT in Orthodontics: A Scoping Review

Objectives: The present scoping review aims to provide a panoramic view of the current state of knowledge, highlighting the strengths, limitations, and future directions, on the use of CBCT in orthodontic practice. Methods: This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines to identify eligible studies from the following databases: PubMed, Scopus, and Web of Science. The research question was formulated as follows: "What is the scientific evidence concerning the preferential use of 3D CBCT over 2D radiography in orthodontics"? Results: Through database searching, 521 records were identified, and ultimately, 37 studies that compared 3D CBCT with 2D conventional radiography were included. Of these, 16 articles regarded the use of CBCT for cephalometric analysis, 5 papers analyzed the evaluation of root resorption, 10 studies evaluated the diagnostic accuracy of root angulation and determining tooth position, and the remaining 6 articles were conducted for miscellaneous applications: determining the size of the nasopharyngeal airway (n = 2), miniscrew positioning (n = 1), estimating cervical vertebrae maturity (n = 1), and evaluating the correctness of the root location when placing digital indirect brackets (n = 1). Conclusions: The choice between 3D CBCT or CBCT-generated radiography and conventional 2D radiography in orthodontics involves careful consideration of the specific clinical context, the complexity of the case, and the balance between the diagnostic advantages and the associated limitations. Future Directions: Future studies with a prospective design and standardized imaging protocols are encouraged to facilitate the development of a consensus on the best practices.

Optimal positions of clear aligner attachments to achieve lower canine tipping and bodily movement using finite element analysis

Background/purpose

Clear aligners are popular orthodontic tools because of their relatively aesthetic appearance and convenience of use. Nevertheless, bodily tooth movements still present challenges. This study evaluated various configurations of attachments placed on the mandibular canine in terms of the efficiency of canine bodily movement and correction of tipping.

Materials and methods

A finite element model of the mandible was constructed to investigate the effects of various attachment configurations on the overall bodily movement and undesirable tipping of a mandibular canine. Canine movements were categorized into four types, namely tipping and bodily movements in the mesial and distal directions. The size and shape of the attachments were fixed, but their placement and orientation were varied. Five and seven attachment configurations were evaluated for their influence on tipping and bodily movements, respectively.

Results

Attachment configuration significantly influenced mandibular canine tipping. The mesial occlusal-distal cervical and mesial occlusal-mesial cervical configurations had notable effects on mesial tipping, and the mesial occlusal-mesial cervical configuration excelled in distal tipping by increasing strain by 33.1%. The mesial occlusal-mesial cervical attachment configuration consistently had superior efficiency in facilitating both mesial and distal bodily movements of the canine.

Conclusion

The mesial occlusal-mesial cervical attachment configuration excelled in all four types of canine movement. Irrespective of the attachment configuration, canines tend to move overall with slight tipping due to skeletal resistance and their center of rotation. The attachment configuration is crucial to the success of clear aligner treatment and must be carefully considered in clinical practice.

Jamil F, M. AL-Anee A, Jassim Muhsen S. Relationship Between the Level of Vitamin D3 Deficiency and Successful Osseointegration: A Prospective Clinical Study

Purpose: This study aimed to evaluate the influence of vitamin D3 levels on bone density, primary dental implant stability, and successful osseointegration. Materials and Methods: Clinical and radiological examination with a standardized cone-beam computed tomography (CBCT) machine and laboratory investigation for serum levels of vitamin D3 were performed for all patients. Only patients in need of single or multiple straightforward dental implant surgery in either jaw with no history of systemic disease or condition that may interfere with bone healing were included in this study to receive the dental implant by the same oral and maxillofacial surgeon, which re-opened 4 months later to assess the osseointegration and to complete the prosthetic part. Results: One hundred twenty-eight dental implants were inserted into 108 patients. Most of the patients in the study had insufficient vitamin D3 levels. The prognosis of dental implants regarding successful osseointegration 4 months after implant placement had a weak positive association with the insertion torque and bone mineral density and a statistically significant positive correlation with the serum vitamin D3 level. Conclusion: Preoperatively, it is advisable to request the serum vitamin D3 level of the patients along with the standard clinical and radiological examination. Severe vitamin D3 deficiency could be associated with early dental implant failure despite the favorable bone density and primary dental implant stability achieved. Trial Registration: ClinicalTrials.gov identifier: TCTR20200304001.

Low-intensity pulsed ultrasound reduces alveolar bone resorption during orthodontic treatment via Lamin A/C-Yes-associated protein axis in stem cells

BACKGROUND

The bone remodeling during orthodontic treatment for malocclusion often requires a long duration of around two to three years, which also may lead to some complications such as alveolar bone resorption or tooth root resorption. Low-intensity pulsed ultrasound (LIPUS), a noninvasive physical therapy, has been shown to promote bone fracture healing. It is also reported that LIPUS could reduce the duration of orthodontic treatment; however, how LIPUS regulates the bone metabolism during the orthodontic treatment process is still unclear.

AIM

To investigate the effects of LIPUS on bone remodeling in an orthodontic tooth movement (OTM) model and explore the underlying mechanisms.

METHODS

A rat model of OTM was established, and alveolar bone remodeling and tooth movement rate were evaluated via micro-computed tomography and staining of tissue sections. In vitro, human bone marrow mesenchymal stem cells (hBMSCs) were isolated to detect their osteogenic differentiation potential under compression and LIPUS stimulation by quantitative reverse transcription-polymerase chain reaction, Western blot, alkaline phosphatase (ALP) staining, and Alizarin red staining. The expression of Yes-associated protein (YAP1), the actin cytoskeleton, and the Lamin A/C nucleoskeleton were detected with or without YAP1 small interfering RNA (siRNA) application via immunofluorescence.

RESULTS

The force treatment inhibited the osteogenic differentiation potential of hBMSCs; moreover, the expression of osteogenesis markers, such as type 1 collagen (COL1), runt-related transcription factor 2, ALP, and osteocalcin (OCN), decreased. LIPUS could rescue the osteogenic differentiation of hBMSCs with increased expression of osteogenic marker inhibited by force. Mechanically, the expression of LaminA/C, F-actin, and YAP1 was downregulated after force treatment, which could be rescued by LIPUS. Moreover, the osteogenic differentiation of hBMSCs increased by LIPUS could be attenuated by YAP siRNA treatment. Consistently, LIPUS increased alveolar bone density and decreased vertical bone absorption in vivo. The decreased expression of COL1, OCN, and YAP1 on the compression side of the alveolar bone was partially rescued by LIPUS.

CONCLUSION

LIPUS can accelerate tooth movement and reduce alveolar bone resorption by modulating the cytoskeleton-Lamin A/C-YAP axis, which may be a promising strategy to reduce the orthodontic treatment process.

Three-dimensional Analysis of Alveolar Bone With and Without Periodontitis

OBJECTIVE

The aim of this study was to investigate the alveolar bone density and thickness in Chinese participants with and without periodontitis.

METHODOLOGY

This study was retrospective and cross-sectional in nature and used cone-beam computed tomography (CBCT) to evaluate alveolar bone loss, bone density, and bone thickness around 668 mandibular molars (344 periodontally healthy teeth and 324 teeth with periodontitis). Comparative statistical tests were done related to the age, sex, tooth type, tooth side, and degree of bone loss. The significance level was set to be P < .05.

RESULTS

The alveolar bone density significantly differed between the healthy and periodontitis groups (mean difference = 24.4 Hounsfield units; P = .007). Similarly, the alveolar bone thickness of the healthy group was significantly higher than that of the periodontitis group (4.6 ± 1.8 mm compared to 4.2 ± 1.1 mm). Teeth in females demonstrated a significantly (P ˂ .001) higher bone density compared with males in both healthy and compromised groups. However, males showed a significantly (P ˂ .05) thicker bone of the teeth than females in relation to the healthy group. The alveolar bone density and thickness in both healthy and periodontitis groups significantly differed between the first and the second molars (P < .001). The alveolar bone thickness had a highly significant difference (P < .001) between the different degrees of bone loss.

CONCLUSIONS

Alveolar bone thickness and density were reduced at periodontally diseased teeth.

The effects of micro-osteoperforation on upper first molar root resorption and bone density after distalization by miniscrew-supported Fast Back appliance in adults: A CBCT randomized controlled trial

OBJECTIVE

To evaluate, primary the effects of Micro-osteoperforation (MOP) on orthodontically induced inflammatory root resorption (OIIRR) of maxillary first molars, and secondary, the density of surrounding alveolar bone during distalization phase with Fast Back distalizer.

MATERIALS AND METHODS

Female patients between 16-20 years of age (University of Mansoura), meeting the criteria, were included between March to September 2019. They were randomly, and equally allocated into control and MOP groups. Both of them underwent distalization with Fast Back distalizer. 3MOPs were applied in the intervention group, distal to the first molars using a 3D printed guide. CBCT images were obtained before and after distalization. Apical root resorption maxillary first molars' roots, and alveolar bone density surrounding them were evaluated using independent-samples t-test. Time of distalization phase was assessed using Mann-Whitney U test. Correlation and partial correlation tests were done between resorption of roots, bone density, and time.

RESULTS

Screening of 50 patients, and exclusion for 30 of them were done. Only 20 subjects underwent the trial to the end. In MOP group, OIIRR of mesiobuccal roots significantly increased (MD=-0.2 (-0.34 to -0.01), P<0.05), and significantly decreased for disto-buccal roots (MD=0.6 (0.45 to 0.72), P<0.001). The second and third layers of bone density decreased significantly in MOP group (MD=116.7 (50.8 to 182.5), MD=560.4 (327.9 to 792.7) respectively, P<0.001). Time for distalization phase was significantly reduced in MOP group (P<0.001).

CONCLUSIONS

MOP decreased OIIRR for nearby distobuccal roots by reduction in surrounding density of bone, and increased OIIRR for the far mesiobuccal roots.

The effect of orthodontic treatment on the periodontium and soft tissue esthetics in adult patients

OBJECTIVE

Most patients seek orthodontic treatment to achieve an esthetic outcome. Orthodontic treatment has possible negative sequelae. The aim of this study is to assess these possible effects on the periodontium and tissue esthetics.

METHODS

One hundred fifty-six patients who have completed orthodontic treatment at Jordan University of Science and Technology clinics were recruited. They were divided into extraction and nonextraction subgroups. Another 155 patients never undergoing orthodontic treatment were assessed. The height of papilla, width of keratinized gingiva, gingival recession, degree of tooth display, smile line, crestal bone level, and proximal caries were assessed. Chi- square test was used for categorical/discrete variables while independent t-test was used for continuous variables. The level of significance was set at (p ≤ 0.05).

RESULTS

The mean age was 22 years with no significant difference between the groups. There was a significant difference between "ortho" and "nonortho" groups in tooth display and keratinized gingiva (p = 0.006 and <0.001, respectively). The overall crestal bone level, smile line, recession, and papilla fill did not show any significant differences (p = 0.200, 0.067, 0.120, and 0.066, respectively). The crestal bone level in the upper and lower anterior segments was significantly lower in the "ortho" treated group compared to the "nonortho" treated group (p = 0.002 and 0.005, respectively). A significant difference between "extraction" and "nonextraction" groups was in the width of keratinized gingiva (p = 0.003) and the number of teeth displayed (p < 0.001). Despite reaching statistical significance these differences are not necessarily of clinical significance.

CONCLUSION

Orthodontic treatment clearly affects the periodontal tissues; however, the detrimental effects appear to be minimal. Patients with history of orthodontic treatment might have lower crestal bone levels at certain sites and this should not be confused with periodontal disease.

Effects of Injectable platelet rich fibrin (i-PRF) on reduction of relapse after orthodontic tooth movement: Rabbits model study

OBJECTIVES:

The objective of this study is to determine whether submucosal local injection of i-PRF may affect orthodontic relapse by increasing bone density, which further leads to reducing orthodontic relapse.

MATERIALS AND METHODS:

Forty-five adult male albino rabbits were randomly divided into three groups: group I (control) with 15 rabbits injected with 200 μl of phosphate-buffered saline (PBS), group II with 15 rabbits injected with 200 μl of i-PRF, and group III of 15 rabbits inject with 400 μl of i-PRF. The lower incisors of rabbits moved distally by a modified orthodontic appliance for 2 weeks; then, the appliance was maintained in position to retain the gaining space for 2 weeks. During the retention period, each group was injected with the specific drug every 7 days. After the retention period, teeth were allowed to relapse by removal of the orthodontic appliance. The results were evaluated by measuring the amount of orthodontic relapse and bone density. The statistical analysis performed by ANOVA and Duncan (P < 0.05 was considered significant).

RESULTS:

I-PRF groups showed a significant reduction in the amount of relapse at 10, 13, 17, and 20 days compared to the control group, indicated by the highest percentage of relapse for the control group at the end of the study (20 days); it was (90.4%) in compared to lowest percentage of relapse for i-PRF groups—they were 61.2% and 59.9%, respectively.

CONCLUSION:

Results indicated that i-PRF has the potential to enhance the stability of teeth after orthodontic tooth movement and could have the ability to reduce relapse, probably by increasing the alveolar bone density.

A Qualitative Assessment of Bone Mineral Density in Individuals With Hemifacial Microsomia: A Cone-Beam Computed Tomography Study

OBJECTIVE

The purpose of this study is to utilize cone-beam computed tomography (CBCT) to compare the bone mineral density (BMD) on the affected versus nonaffected side, among individuals with hemifacial microsomia (HFM).

METHODS

This retrospective study included 9 patients with HFM. Pretreatment CBCT volumes were imported into Invivo5 software, which was used to measure BMD through Hounsfield units (HU) in 3 regions of the mandible; inferior to the lower lateral incisors, inferior to the first molar and at the ramus inferior to the sigmoid notch. Each region was measured at the buccal cortical bone, lingual cortical bone, and cancellous bone. The densities on the right and left sides were compared by Wilcoxon signed-rank test.

RESULTS

Overall, the BMD on the affected side tended to show slightly lower values when compared with the nonaffected side. Differences ranged from 14 HU at the lingual cortical plate of the first molar region to 234 HU at the buccal cortical plate of the ramus region. Differences were only statistically significant at the ramus region for the buccal (P = .002) and lingual (P < .001) cortical plates and at the lower incisor region at the buccal cortical plate (P = .016) and cancellous bone (P = .044). The differences, however, did not seem to be clinically significant.

CONCLUSIONS

The current study shows that the quality of bone on the affected side may be slightly reduced but did not seem to be clinically significant. This should be accounted for during surgical and orthodontic planning for patients with HFM.

Osseous evidence behind micro-osteoperforation technique in accelerating orthodontic tooth movement: A 3-month study

INTRODUCTION

The study aimed to investigate the effects of micro-osteoperforations (MOPs) on the mandibular bone volume/tissue volume (BV/TV) ratio changes and the rate of orthodontic tooth movement using cone-beam computed tomography images. Another objective was to evaluate the effects of MOP frequency intervals (4 weeks, 8 weeks, and 12 weeks) on the BV/TV ratio and rate of tooth movement.

METHODS

In 24 participants, 140-200 g of force was applied for mandibular canine retraction. Three MOPs were made according to the scheduled intervals of the 3 different groups: group 1 (MOP 4 weeks), group 2 (MOP 8 weeks), and group 3 (MOP 12 weeks) directly at the mandibular buccal cortical bone of extracted first premolars sites. Cone-beam computed tomography scans were obtained at the 12th week after MOP application. Computed tomography Analyzer software (version 1.11.0.0; Skyscan, Kontich, Belgium) was used to compute the trabecular alveolar BV/TV ratio.

RESULTS

A significant difference was observed in the rate of canine movement between control and MOP. Paired t test analysis showed a significant difference (P = 0.001) in the mean BV/TV ratio between control and MOP sides in all the frequency intervals groups. However, the difference was significant only in group 1 (P = 0.014). A strong negative correlation (r = -0.86) was observed between the rate of canine tooth movement and the BV/TV ratio at the MOP side for group 1 and all frequency intervals together (r = -0.42).

CONCLUSIONS

The rate of orthodontic tooth movement can be accelerated by the MOP technique with frequently repeated MOPs throughout the treatment.

Standardization of a cone beam computed tomography machine in evaluating bone density: a novel approach

BACKGROUND

Advent of cone beam computed tomography (CBCT) in dentistry has brought us to a new era of precise imaging. Radiographic evaluation of a CBCT image is more informational when compared to CT. The density measurements in CBCT images are based on greyscale values, which are more accurate in CT and these values are inconsistent across various CBCT machines. Hence, we aim at standardizing a single CBCT scanner to evaluate or determine tissue density from the greyscale values.

METHODS

A total of 8 halves of undamaged, dry goat mandibles are included in the study. Scans of the bone are obtained using the KODAK CBCT unit and the PHILLIPS CT machine respectively. Densities are evaluated at 96 points on both the CT scans and the CBCT scans, respectively, using the Radiant Dicom viewer. The obtained data is entered into the excel spreadsheet and subjected to statistical analysis.

RESULTS

The greyscale values are obtained from each of the CBCT scans. Hounsfield units are calculated from CT images coinciding with the same points on CBCT scans. The collected data is subjected to linear regression analysis and an equation is derived to determine Hounsfield units (calculated HU units) from greyscale values of CBCT images. We found no significant difference between the mean original HU units and the mean calculated HU units, thus making the equation reliable for calculating HU units from CBCT greyscale values.

CONCLUSIONS

Our results conclude that the technique was effective in calculating the Original density of tissues using grey standards of CBCT scans.

Alveolar restoration following rapid maxillary expansion with and without corticotomy: A microcomputed tomography study in sheep

Objective

This study examined bone microstructure restoration after rapid maxillary expansion (RME) with and without corticotomy over multiple retention periods.

Methods

Eighteen male Dorper sheep were randomly distributed into three groups (n = 6 each group): group 1, RME with corticotomy on the buccal and palatal sides; group 2, conventional RME treatment; and group 3, no treatment. Post-RME, trabecular bone microstructure and new bone formation were evaluated by using microcomputed tomography (microCT) and histomorphometry after a 4- or 12-week retention period. Intergroup differences in bone quality and bone remodeling were analyzed by using two-way analysis of variance with Bonferroni post-hoc test.

Results

The bone volume fraction (bone volume [BV]/total volume [TV]) values relative to the control in groups 1 and 2 were 54.40% to 69.88% after the 4-week retention period and returned to approximately 80% after the 12-week retention period. The pooled BV/TV values of the banded teeth in groups 1 and 2 were significantly lower than those of the control after the 4-week retention period (p < 0.05). However, after the 12-week retention period, the pooled BV/TV values in group 2 were significantly lower than those in groups 1 and 3 (p < 0.05). Histomorphological analysis showed that the new bone formation area in group 1 was approximately two to three times of those in group 2 and control.

Conclusions

Corticotomy significantly enhanced the restoration of bone quality after the retention periods for banded teeth. This benefit might result from the increased new bone formation after corticotomy.

Effects of a self-ligating appliance for orthodontic treatment of severe adult periodontitis

This study was conducted to investigate the short-term effects of a self-ligating appliance for orthodontic treatment of severe adult periodontitis. Thirty patients diagnosed as severe periodontitis were recruited at Nanjing Stomatological Hospital, P. R.China, between January 2012 and January 2016. General clinical and demographic data were collected from the patients, all of whom were treated with a self-ligating appliance. Probing pocket depth (PPD), clinical attachment level (CAL), bleeding on probing (BOP) and plaque index (PI) were measured before appliance placement, and at 1 and 3 months after appliance placement, respectively. Results showed the rate of tooth loss, mean PPD, mean CAL and the BOP ratio were more favorable in healthy subjects than in the patients. Smokers accounted for a significantly higher proportion of the patients in comparison with the healthy subjects. Clinical outcomes revealed that both the mean PPD and mean CAL were significantly decreased compared with the baseline (P < 0.05). Furthermore, the percentage of BOP, PI and bone mineral density were also significantly decreased at 1 month after treatment (P < 0.05). The volume of gingival crevicular fluid, as well as the levels of alkaline phosphatase, aspartate aminotransferase and glutathione peroxidase, were significantly increased in the first month after treatment, being decreased at 2 months, and finally returning to normal in the third month. In summary, orthodontic treatment using a self-ligating appliance can apparently improve the periodontal condition of patients with severe adult periodontitis.

A Novel Analysis via Micro-CT Imaging Indicates That Chemically Modified Tetracycline-3 (CMT-3) Inhibits Tooth Relapse after Orthodontic Movement: A Pilot Experimental Study

Objective

To evaluate the effect of chemically modified tetracycline-3 (CMT-3) and simvastatin on tooth relapse after orthodontic movement in rats using a novel analysis method employing high-resolution micro-CT (Micro-CT) images. In addition, the correlation between bone density and orthodontic relapse was also evaluated for each experimental group.

Methods

Forty adult male Wistar rats had stainless steel springs installed on their left upper first molars in order to generate tooth movement for 18 days. After this initial period, the animals were divided into three groups: (1) 30 mg/kg of CMT-3; (2) 5 mg/kg of simvastatin; and (3) 0.5% carboxymethylcellulose, and each group was treated for 20 days. Micro-CT images were analyzed (conventional method and 3D reconstruction) on the 7th and 18th days following spring fixation and finally, 20 days after treatment either with CMT-3 or simvastatin (38th day). Bone mineral density (BMD) of the mesial and distal roots of the upper first molar was also analyzed.

Results

The difference was statistically significant between the groups as to recurrence (p=0.048), and the post hoc test identified the value of p=0.007 between the control group and the CMT-3 group. Simvastatin was not able to inhibit tooth relapse. The bone mineral densities of both the mesial and distal roots were different between the three groups, after the 20th day of drug use (p=0001 and p < 0001).

Conclusion

Our findings support the initial evidence that CMT-3 is able to prevent relapse after tooth movement. Future trials in humans should evaluate such treatment as a promising approach to preventing this common phenomenon.

Clinical Relevance

Considering the results obtained, CMT-3 can be used to avoid relapse after tooth movement.

Metformin as an add-on to insulin improves periodontal response during orthodontic tooth movement in type 1 diabetic rats

BACKGROUND

Type 1 diabetes (T1D) is associated with delayed tissue healing and bone loss. Periodontal tissues during tooth movement (OTM) in T1D and under diabetic treatment are poorly understood. We aimed to study the effect of metformin as an add-on to insulin therapy on periodontal structures during OTM in T1D rats.

METHODS

Rats were divided into normoglycemic (NG, n = 20) and streptozotocin-induced diabetic groups that were untreated (T1D, n = 20), treated with insulin (I-T1D, n = 20), or treated with insulin plus metformin (IM-T1D, n = 20). After 7 days of treatment, the first right upper molar (M1) was moved mesially. At days 0, 3, 7 and 14, the pattern of OTM and the periodontal tissues were analyzed by micro-CT, histomorphometry, and immunohistochemistry for TRAP.

RESULTS

In T1D, major osteoclastogenic activity and bone loss versus other groups were confirmed by a greater TRAP-positive cell number and reabsorption surface on both the pressure and tension sides for 14 days (p < 0.01). Additionally, we observed low bone volume density. Metformin plus insulin resulted in a daily insulin dose reduction and major glycemic control versus I-T1D. Although no significant differences were observed between I-T1D and IM-T1D, the tooth displacement and inclination, periodontal ligament thickness, and alveolar bone density on the pressure side in IM-T1D were similar to that of NG (p > 0.05).

CONCLUSION

Antidiabetic treatment reduces severe periodontal damage during applied orthodontic force in T1D untreated rats. Metformin as an add-on to insulin therapy resulted in glycemic control and a periodontal tissue response to orthodontic forces that was similar to that of normoglycemic rats.

Comparison of Early Implant Failure Rates Between Subjects With and Without Orthodontic Treatment Before Dental Implantation

The present study compared early dental implant failure rates between patients with and without orthodontic treatment before dental implantation. The data of adults who had undergone dental implantation between January 2007 and December 2016 were analyzed retrospectively. A total of 124 subjects with 255 implants were divided into a treatment group (46 subjects, 85 teeth) consisting of patients who had undergone implant surgery after orthodontic treatment and a control group of patients who had not undergone preimplant orthodontic treatment. Implants that failed before permanent crown fabrication were defined as failures. No significant differences in gender or age were found between the treatment group and controls. No significant differences were found in implant failure rates in either jaw between the treatment and control groups. However, the failure rate was still higher in the treatment group (14.81%) than in the control group (3.28%) for the maxilla. Results of this study demonstrate an increased implant failure rate only in the maxilla of patients who underwent orthodontic treatment before dental implantation, especially implant surgery combined with a sinus lift procedure. Further study with a larger sample size and longer follow-up period is necessary to confirm results of the present study and identify other confounding factors.

Efficacy of Cone-Beam Computed Tomography in Evaluating Bone Quality for Optimum Implant Treatment Planning

PURPOSE

This study examined (1) if cone-beam computed tomography (CBCT) can determine relative differences in bone mineral density distribution using clinical images of patients' mandibular bone and (2) if the relative differences can be used to detect the effects of sex and age on bone mineral density distribution.

MATERIALS AND METHODS

Sixty-six clinical CBCT images from patients (36 females and 30 males) of 3 age groups (40, 50, and 60 years) were identified. Alveolar (AB) and basal cortical bone (CB) regions were digitally isolated. A histogram of gray levels, which are proportional to degrees of bone mineralization, was obtained from each region. Mean, variability (SD and coefficient of variation), and percentage differences of gray level parameters between AB and basal CBs were computed.

RESULTS

Significant sex differences in gray level variability were observed within the postmenopausal age group (P < 0.042).

CONCLUSION

These findings suggest that clinical CBCT images can be a valuable tool in providing information on bone quality, which is an important criterion for optimum planning for dental implant placement.

Variations in bone density across the body of the immature human mandible

During growth the mandible accommodates increases in biomechanical loading resulting from changes in the function of structures of the oral cavity. Biomechanical loads are thought to play an intricate and vital role in the modelling and remodelling of bone, with site-specific effects on bone mineral density. It is anticipated that the effects of this loading on bone mineral density are intensified during the functional transition from prenatal to postnatal stages. The aim of this study was thus to evaluate changes in bone mineral density across the body of the immature human mandible during the early stages of dental development. The study sample included 45 human mandibles, subdivided into three age groups: prenatal (30 gestational weeks to birth; n = 15); early postnatal (birth to 12 months; n = 18); and late postnatal (1-5 years; n = 12). Mandibles were scanned using X-ray micro-computed tomography. Eight landmarks were selected along the buccal/labial and lingual surfaces of each dental crypt for evaluation of the bone mineral density. Bone mineral density values were calculated using a reference standard and analysed using multivariate statistics. The bone mineral density of the lingual surface was found to be significantly higher (P ≤ 0.000) than that of the buccal/labial surface. Furthermore, bone mineral density in the alveolar region of the buccal/labial surface of the deciduous central incisor (P ≤ 0.001), the deciduous first molar (P ≤ 0.013) and lingual alveolar area of the deciduous second molar (P ≤ 0.032) were significantly greater in the early postnatal period than in the prenatal period. While changes in bone mineral density across the lingual surface were consistent with the progression of development and the biomechanical demand of the tongue as previously demonstrated, changes observed across the buccal/labial surface of the mandible appeared to accompany the advancing dental development. Thus, changes in bone mineral density across the mandible appear to be reflective of the stage of dental development and the level of biomechanical loading.

Assessment of the changes in alveolar bone quality after fixed orthodontic therapy: A trabecular structure analysis

Background. Tooth displacement changes the periodontium. The aim of orthodontic treatment is desired tooth movement with minimum side effects on the alveolar bone quality. The aim of the present study was to assess changes of alveolar trabeculation in children, young adults and adults and the two genders.

Methods. In this cross-sectional study, 63 patients who had been treated in Department of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran, were chosen with convenient sampling method. They were divided into three groups based on their age. Their digitized panoramic radiographs (PRs) were evaluated at six interdental sites from the mesial aspect of the mandibular second molars to the distal aspect of the mandibular first premolars using a visual index. The trabeculation pattern was assigned as either dense (score 3), dense-sparse (score 2) or sparse (score 1). Data were imported to SPSS. Mean of the scores before treatment (score B) and mean of them after treatment (score A) were compared for each group with paired t-test. Changes between score B and sore A of the groups were compared using one-way ANOVA and post hoc tests.

Results. Mean score A was significantly higher than mean score B in children (P = 0.001). In contrast, mean score A was significantly lower than mean score B in young adults (P = 0.003).

Conclusion. Orthodontists should be cautious when treating young adults and adults regarding the probable, yet possibly temporary, negative effects of orthodontic therapy on the alveolar bone quality.

Comparison of Cone Beam Computed Tomography-Derived Alveolar Bone Density Between Subjects with and without Aggressive Periodontitis

INTRODUCTION

Understanding the changes in bone density of patients affected by aggressive periodontitis could be useful in early disease detection and proper treatment planning.

AIM

The aim of this study was to compare alveolar bone density in patients affected with aggressive periodontitis and periodontally healthy individuals using Cone Beam Computed Tomography (CBCT).

MATERIALS AND METHODS

This cross-sectional study was conducted on 20 patients with a confirmed diagnosis of aggressive periodontitis. Twenty periodontally healthy patients attending the dental clinics for implant placement or extraction of impacted third molars served as controls. Alveolar bone density was measured using CBCT scanning. Comparisons between aggressive periodontitis group and controls for age and alveolar bone density of the anterior and posterior regions were performed using an independent sample t-test. Multivariable linear regression models were also performed.

RESULTS

The differences between groups in regard to age, anterior and posterior alveolar bone density was not statistically significant (p<0.05). In the posterior region, the multivariable regression model showed that bone density was not associated with age, gender or the study groups. Whereas, in the anterior region, patient's age was found to be significantly associated with bone density, p=0.014.

CONCLUSION

Alveolar bone density as measured by CBCT in aggressive periodontitis patients was not different from periodontally healthy individuals. Further studies are needed to confirm these findings.

Does Orthodontic Treatment Affect the Alveolar Bone Density?

Few studies involving human participants have been conducted to investigate the effect of orthodontic treatment on alveolar bone density around the teeth. Our previous study revealed that patients who received 6 months of active orthodontic treatment exhibited an ∼24% decrease in alveolar bone density around the teeth. However, after an extensive retention period following orthodontic treatment, whether the bone density around the teeth can recover to its original state from before the treatment remains unclear, thus warranting further investigation.The purpose of this study was to assess the bone density changes around the teeth before, during, and after orthodontic treatment.Dental cone-beam computed tomography (CBCT) was used to measure the changes in bone density around 6 teeth in the anterior maxilla (maxilla central incisors, lateral incisors, and canines) of 8 patients before and after orthodontic treatment. Each patient underwent 3 dental CBCT scans: before treatment (T0); at the end of 7 months of active orthodontic treatment (T1); after several months (20-22 months) of retention (T2). The Friedman test was applied to evaluate the changes in the alveolar bone density around the teeth according to the 3 dental CBCT scans.From T0 to T1, a significant reduction in bone density was observed around the teeth (23.36 ± 10.33%); by contrast, a significant increase was observed from T1 to T2 (31.81 ± 23.80%). From the perspective of the overall orthodontic treatment, comparing the T0 and T2 scans revealed that the bone density around the teeth was relatively constant (a reduction of only 0.75 ± 19.85%). The results of the statistical test also confirmed that the difference in bone density between T0 and T2 was nonsignificant.During orthodontic tooth movement, the alveolar bone density around the teeth was reduced. However, after a period of bone recovery, the reduced bone density recovered to its previous state from before the orthodontic treatment. However, the bone density around ∼10% of the teeth in this region could not recover to 80% of its state from before the orthodontic treatment.

Quantification of dental prostheses on cone-beam CT images by the Taguchi method

The gray values accuracy of dental cone‐beam computed tomography (CBCT) is affected by dental metal prostheses. The distortion of dental CBCT gray values could lead to inaccuracies of orthodontic and implant treatment. The aim of this study was to quantify the effect of scanning parameters and dental metal prostheses on the accuracy of dental cone‐beam computed tomography (CBCT) gray values using the Taguchi method. Eight dental model casts of an upper jaw including prostheses, and a ninth prosthesis‐free dental model cast, were scanned by two dental CBCT devices. The mean gray value of the selected circular regions of interest (ROIs) were measured using dental CBCT images of eight dental model casts and were compared with those measured from CBCT images of the prosthesis‐free dental model cast. For each image set, four consecutive slices of gingiva were selected. The seven factors (CBCTs, occlusal plane canting, implant connection, prosthesis position, coping material, coping thickness, and types of dental restoration) were used to evaluate scanning parameter and dental prostheses effects. Statistical methods of signal to noise ratio (S/N) and analysis of variance (ANOVA) with 95% confidence were applied to quantify the effects of scanning parameters and dental prostheses on dental CBCT gray values accuracy. For ROIs surrounding dental prostheses, the accuracy of CBCT gray values were affected primarily by implant connection (42%), followed by type of restoration (29%), prostheses position (19%), coping material (4%), and coping thickness (4%). For a single crown prosthesis (without support of implants) placed in dental model casts, gray value differences for ROIs 1–9 were below 12% and gray value differences for ROIs 13–18 away from prostheses were below 10%. We found the gray value differences set to be between 7% and 8% for regions next to a single implant‐supported titanium prosthesis, and between 46% and 59% for regions between double implant‐supported, nickel‐chromium alloys (Ni‐Cr) prostheses. Quantification of the effect of prostheses and scanning parameters on dental CBCT gray values was assessed.

PACS numbers: 87.59.bd, 87.57Q

New quantitative classification of the anatomical relationship between impacted third molars and the inferior alveolar nerve

BACKGROUND

Before extracting impacted lower third molars, dentists must first identify the spatial relationship between the inferior alveolar nerve (IAN) and an impacted lower third molar to prevent nerve injury from the extraction. Nevertheless, the current method for describing the spatial relationship between the IAN and an impacted lower third molar is deficient. Therefore, the objectives of this study were to: (1) evaluate the relative position between impacted lower third molars and the IAN; and (2) investigate the relative position between impacted lower third molars and the IAN by using a cylindrical coordinate system.

METHODS

From the radiology department's database, we selected computed tomography images of 137 lower third molars (from 75 patients) requiring removal and applied a Cartesian coordinate system by using Mimics, a medical imaging software application, to measure the distribution between impacted mandibular third molars and the IAN. In addition, the orientation of the lower third molar to the IAN was also measured, but by using a cylindrical coordinate system with the IAN as the origin.

RESULTS

According to the Cartesian coordinate system, most of the IAN runs through the inferior side of the third molar (78.6 %), followed by the lingual side (11.8 %), and the buccal side (8.9 %); only 0.7 % is positioned between the roots. Unlike the Cartesian coordinate system, the cylindrical coordinate system clearly identified the relative position, r and θ, between the IAN and lower third molar.

CONCLUSIONS

Using the cylindrical coordinate system to present the relationship between the IAN and lower third molar as (r, θ) might provide clinical practitioners with a more explicit and objective description of the relative position of both sites. However, comprehensive research and cautious application of this system remain necessary.

The effect of simvastatin on relapse of tooth movement and bone mineral density in rats measured by a new method using microtomography

PURPOSE

To evaluate the effect of simvastatin on relapse of tooth movement in rats using microtomography (micro CT), as well as the correlation of bone density with the orthodontic relapse.

METHODS

Twenty-five adult male Wistar rats, divided into two groups, had stainless steel springs installed on left maxillary first molar. The molars were moved for 18 days, and after removing the springs, were applied by oral gavage, 5mg/kg of simvastatin in the experimental group for 20 days. Tooth relapse was assessed with a micro CT scanner, and the images chosen through the Data Viewer software 1.5.0.0 had their measurement guides made and checked by the software Image ProR plus 5.1, and compared by Mann-Whitney test. After rats were sacrificed, bone mineral density was evaluated by micro CT through the software CT Analyzer 1.13 and compared by independent T-test, as well as by Spearman correlation test.

RESULTS

Relapse and bone mineral density (BMD) was lower in the experimental group than in the control group, however without a statistically significant difference.

CONCLUSION

Simvastatin did not inhibit the relapse of tooth movement in rats, and there was no correlation between bone density and orthodontic relapse.

Hounsfield unit change in root and alveolar bone during canine retraction

INTRODUCTION

The objective of this study was to determine the Hounsfield unit (HU) changes in the alveolar bone and root surfaces during controlled canine retractions.

METHODS

Eighteen maxillary canine retraction patients were selected for this split-mouth design clinical trial. The canines in each patient were randomly assigned to receive either translation or controlled tipping treatment. Pretreatment and posttreatment cone-beam computed tomography scans of each patient were used to determine tooth movement direction and HU changes. The alveolar bone and root surface were divided into 108 divisions, respectively. The HUs in each division were measured. Mixed-model analysis of variance was applied to test the HU change distribution at the P <0.05 significance level.

RESULTS

The HU changes varied with the directions relative to the canine movement. The HU reductions occurred at the root surfaces. Larger reductions occurred in the divisions that were perpendicular to the moving direction. However, HUs decreased in the alveolar bone in the moving direction. The highest HU reduction was at the coronal level.

CONCLUSIONS

HU reduction occurs on the root surface in the direction perpendicular to tooth movement and in the alveolar bone in the direction of tooth movement when a canine is retracted.

Intrusion of supraerupted maxillary molar using a high interim restoration on the defective opposing tooth: a clinical report

Wear, extraction, or fracture of all or part of a mandibular first molar can lead to the supraeruption of the opposing maxillary molar, resulting in occlusal interference and lack of restoration space. This report describes a method to gain sufficient vertical space for permanent restoration. A direct composite resin restoration was placed on the occlusal surface of a lower molar, intentionally making the interim restoration high and intruding the maxillary molar. After 6 weeks, the extruded tooth returned to the desired position, and functional occlusion was restored, enabling a ceramic restoration on the mandibular molar. No marked adverse sensory reaction was reported in this therapeutic process, and no deleterious signs were detected in the teeth, periodontium, or temporomandibular joints. The simple treatment type was effective, noninvasive, and time saving, while also preserving maximum tooth structures.

Interradicular trabecular bone density of the lateral maxilla for temporary anchorage devices--a histomorphometric study

OBJECTIVE

To analyze the interradicular trabecular bone density of the lateral maxilla regarding the insertion of temporary anchorage devices (TADs).

MATERIAL AND METHODS

The material consisted of tissue blocks of autopsy material from 20 subjects (17 male, 3 female, 16 - 63y). The specimens comprised the dentated alveolar bone of the lateral maxilla. The interradicular areas (IRA) from canine to distally of the second molar (IRA 3-4, 4-5, 5-6, 6-7, 7d) were histomorphometrically measured with respect to the hard tissue fraction of the trabecular bone (HTFTB, %) and statistically analyzed.

RESULTS

Histomorphometric measurements showed the following results: Mean HTFTB of IRA 3-4 was 44.08%, of IRA 4-5 31.07%, of IRA 5-6 33.96%, of IRA 6-7 36.33% and of IRA 7d 25.40%. Only the difference between the HTFTB of IRA 3-4 and the other IRAs was statistically significant (p < 0.05). Regarding the minimum and maximum HTFTB value of each IRA, there was a great amount of difference, especially for IRA 3-4: minimum HTFTB was 17.20% and maximum 67.03%.

CONCLUSION

Apart from the IRA between canine and first premolar, the HTFTB in the IRAs of the lateral maxilla have to be classified as low or even moderate. IRA 3-4 should also be considered cautious regarding its minimum values. Thus, it seems that the interradicular trabecular bone density of the lateral maxilla is unfavorable to achieve a good primary stability of TADs.

Comparison of molar intrusion efficiency and bone density by CT in patients with different vertical facial morphology

The purpose of this study is to examine the relationship between molar intrusion efficiency and bone density in patients with different vertical facial morphology. Thirty-six female patients, with overerupted upper first molars, were divided into two groups according to mandiblular plane angle (FH-MP): hyperdivergent, FH-MP>30° (G1), hypodivergent, FH-MP<22° (G2). Mini-screw implants with elastic chains were used to intrude upper first molars. Spiral CT was used to measure the intrusion degree of upper first molar and bone density, and molar intrusion efficiency was calculated as amount/duration (mm month(-1) ). In addition, each tooth was divided into three portions (cervical, furcation and apical) to measure the bone density. It was found in this study that treatment duration was 3·13 and 4·71 months in G1 and G2 and that the intrusion efficiency was 1·57 and 0·81 in G1 and G2 with significant difference (P < 0·05). There were significant differences in cervical, furcation and apical bone density between two groups (P < 0·05). The bone density was significantly reduced after molar intrusion. In addition, the bone density change was greater in G1 than in G2 (P < 0·05). It was concluded that molars were more easily to be intruded in hyperdivergent than in hypodivergent patients. The difference of bone density and bone density changes during intrusion may account for the variation of molar intrusion efficiency.

Cervical vertebral bone mineral density changes in adolescents during orthodontic treatment

INTRODUCTION

The cervical vertebral maturation (CVM) stages have been used to estimate facial growth status. In this study, we examined whether cone-beam computed tomography images can be used to detect changes of CVM-related parameters and bone mineral density distribution in adolescents during orthodontic treatment.

METHODS

Eighty-two cone-beam computed tomography images were obtained from 41 patients before (14.47 ± 1.42 years) and after (16.15 ± 1.38 years) orthodontic treatment. Two cervical vertebral bodies (C2 and C3) were digitally isolated from each image, and their volumes, means, and standard deviations of gray-level histograms were measured. The CVM stages and mandibular lengths were also estimated after converting the cone-beam computed tomography images.

RESULTS

Significant changes for the examined variables were detected during the observation period (P ≤0.018) except for C3 vertebral body volume (P = 0.210). The changes of CVM stage had significant positive correlations with those of vertebral body volume (P ≤0.021). The change of the standard deviation of bone mineral density (variability) showed significant correlations with those of vertebral body volume and mandibular length for C2 (P ≤0.029).

CONCLUSIONS

The means and variability of the gray levels account for bone mineral density and active remodeling, respectively. Our results indicate that bone mineral density distribution and the volume of the cervical vertebral body changed because of active bone remodeling during maturation.

Bone mineral density in cone beam computed tomography: Only a few shades of gray

Cone beam computed tomography (CBCT) has often been used to determine the quality of craniofacial bone structures through the determination of mineral density, which is based on gray scales of the images obtained. However, there is no consensus regarding the accuracy of the determination of the gray scales in these exams. This study aims to provide a literature review concerning the reliability of CBCT to determine bone mineral density. The gray values obtained with CBCT show a linear relationship with the attenuation coefficients of the materials, Hounsfield Units values obtained with medical computed tomography, and density values from dual energy X-ray absorciometry. However, errors are expected when CBCT images are used to define the quality of the scanned structures because these images show inconsistencies and arbitrariness in the gray values, particularly when related to abrupt change in the density of the object, X-ray beam hardening effect, scattered radiation, projection data discontinuity-related effect, differences between CBCT devices, changes in the volume of the field of view (FOV), and changes in the relationships of size and position between the FOV and the object evaluated. A few methods of mathematical correction of the gray scales in CBCT have been proposed; however, they do not generate consistent values that are independent of the devices and their configurations or of the scanned objects. Thus, CBCT should not be considered the examination of choice for the determination of bone and soft tissue mineral density at the current stage, particularly when values obtained are to be compared to predetermined standard values. Comparisons between symmetrically positioned structures inside the FOV and in relation to the exomass of the object, as it occurs with the right and left sides of the skull, seem to be viable because the effects on the gray scale in the regions of interest are the same.

Can dental cone beam computed tomography assess bone mineral density?

Mineral density distribution of bone tissue is altered by active bone modeling and remodeling due to bone complications including bone disease and implantation surgery. Clinical cone beam computed tomography (CBCT) has been examined whether it can assess oral bone mineral density (BMD) in patient. It has been indicated that CBCT has disadvantages of higher noise and lower contrast than conventional medical computed tomography (CT) systems. On the other hand, it has advantages of a relatively lower cost and radiation dose but higher spatial resolution. However, the reliability of CBCT based mineral density measurement has not yet been fully validated. Thus, the objectives of this review are to discuss 1) why assessment of BMD distribution is important and 2) whether the clinical CBCT can be used as a potential tool to measure the BMD. Brief descriptions of image artefacts associated with assessment of gray value, which has been used to account for mineral density, in CBCT images are provided. Techniques to correct local and conversion errors in obtaining the gray values in CBCT images are also introduced. This review can be used as a quick reference for users who may encounter these errors during analysis of CBCT images.

Location of the mandibular canal and thickness of the occlusal cortical bone at dental implant sites in the lower second premolar and first molar

The objective of this study was to evaluate the location of the mandibular canal and the thickness of the occlusal cortical bone at dental implant sites in the lower second premolar and lower first molar by using dental cone-beam computed tomography (CBCT). Seventy-nine sites (47 second premolar and 32 first molar sites) were identified in the dental CBCT examinations of 47 patients. In this study, 4 parameters were measured: (1) MC—the distance from the mandibular canal to the upper border of the mandible; (2) CD—the distance from the mandibular canal to the buccal border of the mandible; (3) MD—the distance from the mandibular canal to the lingual border of the mandible; (4) TC—the thickness of the cortical bone at the occlusal side. A statistical analysis was employed to compare the size and differences between these 4 parameters at the lower second premolar and lower first molar. Regarding the MC and MD, the experimental results showed no statistical difference between the first molar and second premolar. However, the TC for the second premolar was greater than that of the first molar. Thus, careful consideration is necessary in choosing the size of and operation type for dental implants.

The role of orthodontic tooth movement in bone and root mineral density: a study of patients submitted and not submitted to orthodontic treatment

Background

Orthodontic force application to the teeth is responsible for a series of biological responses in the bone and dentin, which lead to some alterations of the mineral density of the tissues. Our objective was determine, through cone-beam computed tomography (CBCT), the mineral density of the apical third of the roots of the upper central incisors and of the periapical bone portion surrounding these teeth, in patients submitted to orthodontic treated and untreated individuals.

Material/Methods

30 untreated individuals and 15 treated ones (treatment cessation at least 1 year before the study) underwent CBCT. Mineral density was assessed in the apical third of the root of the upper central incisors and in the alveolar bone in the periapical region of these teeth. In order to reduce CBCT-related mineral density variability, we standardized the cone-beam tomography device, the image-acquisition settings and the field of view positioning and size. Student’s t test was used for the analyses.

Results

bone mineral density (BMD) and root mineral density (RMD), in Hounsfield Units, were 674.84 and 1282.26 for the untreated group and 630.28 and 1370.29 for the treated group, respectively. The differences between the group means were statistically significant for RMD (p<0.05).

Conclusions

untreated individuals had a significant lower mean RMD in comparison with those submitted to orthodontic treatment.

Apical root resorption: the dark side of the root

INTRODUCTION

The diagnosis of apical root resorption is usually based on routine radiographs. However, these methods are limited because the images reflect the superimposition of the whole root structure and can lead to underestimation of the extent of apical root resorption. In this study, we aimed to determine the lengths of the labial and lingual surfaces of incisors with apical root resorption and compare them with the longest radicular length obtained on sagittal images of cone-beam computed tomography, and to create a qualitative visual scale of the different patterns of apical root resorption.

METHODS

Eighty-two incisors with apical root resorption from 25 patients had their labial and lingual root surfaces and the longest radicular lengths determined in the sagittal plane and compared. Five orthodontists, at 2 times, classified the images of each incisor according to a visual scale developed by the authors.

RESULTS

There was no significant difference between the labial and lingual surfaces; however, the longest radicular length was significantly greater than the shortest surface length. The visual scale showed intraobserver agreement of 0.615 and interobserver agreements of 0.74 and 0.52 at both times, respectively.

CONCLUSIONS

The difference between the longest and shortest root lengths suggests that radiographic superimposition underestimates the extent of the resorption lesion. The proposed visual scale showed a frequency of agreement above 65% and a coefficient of reproducibility varying from moderate to substantial.

THE EFFECT OF CYCLIC STRETCHING SPEED ON THE FORCE DEGRADATION OF ORTHODONTIC ELASTIC BANDS

This study evaluated the effect of the cyclic stretching speed on the force degradation of orthodontic elastics. Forty-five natural rubber bands (3M Unitek™) were stretched at different speeds in three groups: (1) static stretching test, (2) cyclic stretching test at a speed of 80 mm/min, and (3) cyclic stretching at a speed of 160 mm/min. A material tester and customized strain gauge were used to measure the residual force of the elastics in 37°C artificial saliva at different times. One-way repeated-measure analysis of variance followed by Scheffe's post-hoc comparison and t-test were used for statistical analysis. In Group 1, the force of the elastics degraded with time, with two separate phases being observed — distinctive degradation after 15 min and stabilization after 120 min. The cyclic stretching in Group 2 produced a significant deviation in the residual force and the initial force from the first minute, and stabilization after 300 min. After 1,440 min, 60% of the bands had snapped. Under accelerated stretching, no areas of relative stability were observed between the start of stretching to the start of breaking. After 1,440 high-speed stretches, 87% of the elastics in Group 3 snapped. These results indicate that the stretching speed affects the stability of the residual force of elastics. Cyclic stretching at high speed immediately induces a rapid degradation of the elastic's force and increases its probability of breakage.

Predicting cortical bone strength from DXA and dental cone-beam CT

OBJECTIVE

This study compared the capabilities of dual-energy X-ray absorptiometry (DXA) and dental cone-beam computed tomography (CBCT) for predicting the cortical bone strength of rat femurs and tibias.

MATERIALS AND METHODS

Specimens of femurs and tibias obtained from 14 rats were first scanned with DXA to obtain the areal bone mineral density (BMD) of the midshaft cortical portion of the bones. The bones were then scanned using dental CBCT to measure the volumetric cortical bone mineral density (vCtBMD) and the cross-sectional moment of inertia (CSMI) for calculating the bone strength index (BSI). A three-point bending test was conducted to measure the fracture load of each femur and tibia. Bivariate linear Pearson analysis was used to calculate the correlation coefficients (r values) among the CBCT measurements, DXA measurements, and three-point bending parameters.

RESULTS

The correlation coefficients for the associations of the fracture load with areal BMD (measured using DXA), vCtBMD (measured using CBCT), CSMI (measured using CBCT), and BSI were 0.585 (p = 0.028) and 0.532 (p = 0.050) (for the femur and tibia, respectively), 0.638 (p = 0.014) and 0.762 (p = 0.002), 0.778 (p = 0.001) and 0.792 (p<0.001), and 0.822 (p<0.001) and 0.842 (p<0.001), respectively.

CONCLUSIONS

CBCT was found to be superior to DXA for predicting cortical bone fracture loads in rat femurs and tibias. The BSI, which is a combined index of densitometric and geometric parameters, was especially useful. Further clinical studies are needed to validate the predictive value of BSI obtained from CBCT and should include testing on human cadaver specimens.

Comparison of micro-CT and cone beam CT-based assessments for relative difference of grey level distribution in a human mandible

OBJECTIVES

The purpose of this study was to examine the ability of CT to assess the relative difference of degree of bone mineralization (grey level) parameters in a human mandible.

METHODS

Ten mandibular sections from cadavers (81.5 ± 12.1 years) were scanned using micro-CT with 27.2 μm voxel size and cone beam CT (CBCT) with 200 μm, 300 μm, and 400 μm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 ± 3.3 years) were identified. After segmentation of bone voxels, alveolar bone and basal cortical bone regions were digitally isolated. A histogram of grey level, which is equivalent to degree of bone mineralization, was obtained from each region of the CT images. Mean, standard deviation (SD), coefficient of variation (COV), fifth percentile low (Low(5)) and high (High(5)) of alveolar bone and basal cortical bone regions were obtained. Percentage differences of grey level parameters between alveolar and basal cortical bones were computed.

RESULTS

The alveolar bone region had significantly lower Mean, Low(5) and High(5) values but significantly higher SD and COV than the basal cortical bone region for all CT images (p < 0.05). All parameters were significantly lower for the old cadaver group than for the young patient group (p < 0.05).

CONCLUSIONS

CBCT and micro-CT provide comparable results in the assessment of relative difference in grey level distribution between alveolar and basal cortical bone regions in the human mandible. The percentage difference relative to an internal reference (basal cortical bone) can be a reliable method when assessing the degree of bone mineralization using CBCT images for both cross-sectional and longitudinal comparisons.