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PubMed1996

The anterior alveolus: its importance in limiting orthodontic treatment and its influence on the occurrence of iatrogenic sequelae.

Delineating the limits of orthodontic treatment in nongrowing individuals is important when making treatment decisions, especially in borderline orthodontic-surgical cases. The labial and lingual cortical plates at the level of the incisor apex may represent the anatomic limits of tooth movement. Cephalometric films of 107 adults were measured to determine the width of alveolar bone anterior and posterior to the incisor apex in each arch. Thin alveolar widths were found both labial and lingual to the mandibular incisors in groups of Class I, II, and III individuals with high SN-MP angle and in a group of Class III average SN-MP individuals. Thin alveolar widths were also found lingual to the maxillary incisors in a Class II high angle group. Clinical cases are presented showing that orthodontic tooth movement may be limited in patients with narrow alveolar bone widths and that these patients are likely to experience increased iatrogenic sequelae.

Adult↗

PubMed2002

The difference in condylar position between centric relation and centric occlusion in pretreatment Japanese orthodontic patients.

This study investigates the differences in condylar position between centric relation (CR) and centric occlusion (CO) in Japanese orthodontic patients before treatment. We employed 150 consecutive cases (age range: 6-57 years) for the study. Dental casts were mounted on a Panadent articulator with a power centric CR bite record. The differences in condylar position between CR and CO in all three spatial planes were measured using the Panadent Condyle Position Indicator (CPI). The subjects were divided into groups by age, gender, mandibular plane angle or angle classification. No significant differences in the magnitude of CPI measurements were found among the groups. The three-dimensional distances of condylar displacement on both sides were almost identical, and the superoinferior displacement (S-I) was greater (P < .0001) than the anteroposterior displacement (A-P). The S-I was greater (P = .02) on the left side than on the right side, while the A-P displacement was smaller (P < .0001) on the left side than that on the right side. Significant condylar displacement (2.0 mm for S-I and A-P, 0.5 mm for the lateral displacement, L) was found frequently in L (31.3%), S-I, and A-P, in that order. Fifty-eight (38.7%) of the subjects had significant displacement in L, S-I, or A-P. Moreover, Angle Class III subjects tended to have significant condylar displacement toward the left side. The results suggest that orthodontists should be aware of a high incidence of condylar displacement in Japanese orthodontic patients and measure condylar displacement before the start of comprehensive orthodontic treatment to unmask real jaw relationships and avoid possible misdiagnoses.

Adolescent↗

PubMed2003

Evaluation of the validity of tooth size and arch width measurements using conventional and three-dimensional virtual orthodontic models.

Measurements and different analyses of dental casts are essential for precise diagnosis of an orthodontic case. At present, virtual computerized models, such as OrthoCAD, are available for clinicians, supplemented by dedicated software for performing needed measurements on them. The purpose of this study was to test the accuracy of measuring casts with the aid of calipers or OrthoCAD and compare these two techniques. Twenty setups using artificial teeth corresponding to various malocclusions were created. Impressions were taken of them, providing 20 plaster and 20 virtual orthodontic models. Measurements of mesiodistal tooth dimension as well as intercanine and intermolar width were made on both. Additionally, values of tooth size were calculated from the isolated artificial teeth removed from the setups and of arch width from the existing setups. The resulting values were compared by the use of nonparametric statistics, and methods' errors were also calculated. Results showed the methods being highly valid and reproducible for both tooth size and arch width. For the tested clinically applicable methods, measurement with digital calipers on plaster models showed the highest accuracy and reproducibility, closely followed by OrthoCAD. Digital calipers seem to be a more suitable instrument for scientific work. However, OrthoCAD's accuracy is clinically acceptable, and most likely, considering its present advantages and future possibilities, the examined or an equivalent 3D virtual models' procedure would become the standard for orthodontic clinical use.

Calibration↗

PubMed2004

Agenesis of third molar germs depends on sagittal maxillary jaw dimensions in orthodontic patients in Japan.

The aim of this study was to determine the correlation between congenitally missing third molar tooth germs and sagittal maxillomandibular jaw dimensions in orthodontic patients in Japan. The subjects were 391 patients from the orthodontic clinic of the Hokkaido University Dental Hospital who were less than 15 years of age. Assessments were made from panoramic radiographs and lateral cephalograms. The subjects were divided into a maxillary/mandibular third molar absent and an existent group. The ANB angle and the sagittal dimensions of the nasal floor (ANS-PNS), maxillary basal bone (Mx), mandibular corpus (Go-Pog), and mandibular basal bone (Mn) were measured. Logistic regression analysis was used to estimate associations between third molar agenesis and these measures. The following results were obtained: (1) The frequency of the maxillary third molar agenesis significantly increased with decreasing Mx (odds ratio = 0.559, 95% confidence interval = 0.377 - 0.829). The frequency of the mandibular third molar agenesis also increased with decreasing Mx (odds ratio = 0.532, 95% confidence interval = 0.330 - 0.856). (2) There were no significant correlations between Mn and mandibular third molar agenesis. These results suggest that agenesis of third molar germs does not depend on anteroposterior dimensions of the mandible but depends on anteroposterior dimensions of the maxilla in Japanese orthodontic patients.

Adolescent↗

PubMed1999

Temporomandibular disorders in saudi females seeking orthodontic treatment.

The aim of this study was to describe the prevalence of signs and symptoms of temporomandibular disorders (TMD) in a group of patients seeking orthodontic treatment. One hundred and ninety one consecutive prospective orthodontic female patients, divided into three age groups of 8, 14 and 18 years, were examined for TMD signs and symptoms and orthodontic treatment need (IOTN). The percentages of signs and symptoms found were 41 and 30%, respectively. No significant association was found between IOTN and TMD signs and symptoms. The youngest age group reported significantly less headache and temporomandibular joint (TMJ) noise. Headache was significantly associated with all TMD symptoms and with tenderness to palpation. In conclusion, the results indicate that malocclusion could not be considered as a primary aetiologic factor for TMD within the age range studied.

Adolescent↗

PubMed2000

The relationship between frontal facial morphology and occlusal force in orthodontic patients with temporomandibular disorder.

The aim of this study was to investigate the relation between frontal craniofacial morphology and the distribution of occlusal force in orthodontic patients with and without TMD. Experimental data were obtained from 45 female orthodontic patients (TMD-free group: 22 subjects; TMD group: 23 subjects) using the pressure-sensitive sheet. The following results were obtained: (1) There were significant differences in the gonial angle width and the mandibular deviation of the postero-anterior cephalogram between the two groups. (2) There were significant differences in occlusal force, occlusal contact area and average occlusal pressure between the two groups. (3) On the relation between the frontal craniofacial morphology and the occlusal data, the asymmetry indices of occlusal force and occlusal contact area showed significant positive correlations to the mandibular deviation and the ratios of maxillary and gonial angle widths in the TMD group. The TMD-free group showed the smaller mandibular deviation and the smaller asymmetry indices of occlusal force and occlusal contact area than those in the TMD group. It could be concluded that orthodontic patients with TMD may have not only the morphological disharmony but also the imbalance of occlusal force.

Adolescent↗

PubMed2000

Nonsteroidal anti-inflammatory drugs in orthodontic tooth movement: metalloproteinase activity and collagen synthesis by endothelial cells.

Orthodontic treatment is based on the biologic principle that prolonged pressure on teeth results in remodeling of periodontal structures, allowing for tooth movement. Periodontal remodeling is a complex process regulated in part by prostaglandins and adversely affected by the use of nonsteroidal anti-inflammatory drugs. We investigated the effects of indomethacin on collagenase activity and procollagen synthesis in rat endothelial cell cultures. Cyclooxygenase inhibition resulted in exacerbation of IL-1 beta-mediated collagenase B (MMP-9) production and activity, as well as attenuation of type IV procollagen synthesis levels by endothelial cells in vitro. Hence, the use of over-the-counter nonsteroidal anti-inflammatory drugs during tooth movement may result in aberrant remodeling of periodontal vasculature and other structures, ultimately affecting orthodontic treatment efficacy. Further studies are needed to establish novel pain relievers that do not interfere with orthodontic processes.

Analysis of Variance↗

PubMed2000

Effect of orthodontic therapy on the facial profile in long and short vertical facial patterns.

The purpose of the present study was to evaluate the effects of orthodontic treatment on the soft tissue facial profile of patients with long and short facial types. Orthodontic treatment records of 99 white long-faced and short-faced patients were analyzed to determine the effects of edgewise orthodontic treatment over an average period of 2.16 +/- 0.32 years. The average ages at the initiation and conclusion of treatment were 13.40 +/- 0.40 years and 15.61 +/- 0.29 years, respectively. A significant finding in this study was the large variability in soft tissue response to tooth movement. This variability was due to a wide dispersion of individual results between upper and lower lip change to maxillary and mandibular incisor movement anteriorly or posteriorly. Because of this soft tissue variability among individuals, definite differences between the long-faced and short-faced types could not be identified, nor was it possible to establish definite ratios for change in lip response to incisor movements.

Adolescent↗

PubMed2001

Orthodontic tooth movement and de novo synthesis of proinflammatory cytokines.

Interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) are proinflammatory cytokines that are thought to play a role in bone remodeling, bone resorption, and new bone deposition. In the present work, in situ hybridization was performed to measure the messenger RNA expression of IL-1beta, IL-6, and TNF-alpha at 3, 7, and 10 days after the application of orthodontic force on the maxillary first molars of 12 rats. The contralateral side and 3 untreated rats served as controls. Measurements of the messenger RNA expression were selected as the means to investigate the role of orthodontic force in de novo synthesis of proinflammatory cytokines. After the application of force, the induction of IL-1beta and IL-6 was observed to reach a maximum on day 3 and to decline thereafter. No messenger RNA induction of either cytokine was measured in the control teeth. The messenger RNA expression of TNF-alpha was not detected at any time point of this study in the experimental or contralateral sides or in the control animals. Our data support the hypothesis that these proinflammatory cytokines may play important roles in bone resorption after the application of orthodontic force.

Animals↗

PubMed2001

Orthodontic treatment for patients with Turner syndrome.

The purpose of this study was to review the distinctive characteristics of Turner syndrome and to illustrate how they influenced the orthodontic treatment of a 17-year-old patient with Turner syndrome. The rate and the timing of growth, the development of the craniofacial structures, and the somatic and dental morphology unique to Turner syndrome significantly influence orthodontic treatment. Modifications that might be required to orthodontic treatment plans include (1) antibiotic prophylaxis, (2) occlusal adjustments to account for altered dental morphology, (3) altered treatment timing because of major differences in growth and differences between chronological and skeletal ages, and (4) growth hormone therapy. Orthodontists must understand the characteristics of Turner syndrome and modify the patient's treatment plan accordingly.

Adolescent↗

PubMed2001

The influence of PDL principal fibers in a 3-dimensional analysis of orthodontic tooth movement.

The effects of mechanical loads on the tooth-alveolus complex are of particular concern in orthodontics. The concepts of center of resistance (CRes) and center of rotation (CRot) are used to characterize tooth responses to orthodontic loads. The mechanical environment (stresses and strains) associated with orthodontic tooth movement is a unique model in bone adaptation physiology. Numerous finite element models of varying complexity have been developed to calculate tooth movements and stress distributions within the alveolar bone and the periodontal ligament (PDL). In general, the PDL has been idealized as a homogeneous isotropic material. For this project, a 3-dimensional tooth/PDL/mandible/finite element model was developed in which, for the first time in such an analysis, the PDL's principal-fiber structure was also incorporated. Parametric analyses showed that the fiber orientation and the mechanical properties do not exert much influence on the locations of the CRes and the CRot and on the stress patterns within the bone and the PDL matrix. However, the absence of principal fibers produces not only different stress magnitudes, but also differences in stress patterns. Furthermore, the no-fiber-associated CRes and CRot are considerably separated from the cluster of fiber-influenced centers. It was concluded that it may be more realistic to incorporate "generic" principal fibers into finite element models than not to include them at all, despite the lack of reliable information about fibers.

Alveolar Process↗

PubMed2002

Numerical experiments on long-time orthodontic tooth movement.

In orthodontic treatment, teeth are moved by the use of specific force systems. The force system used depends on the patient's orthodontic situation characterized by the geometry of the tooth and the surrounding alveolar bone, which defines the position of the center of resistance. Therefore, the simulation of bone remodeling could be helpful for the treatment strategy. In this study, the optimal force system for bodily movement of a single-root tooth, with an orthodontic bracket attached, was determined. This was achieved by the use of the numerical finite element method, including a distinct mechanical bone-remodeling algorithm. This algorithm works with equilibrium iterations separated in 2 calculation steps. Furthermore, a parametric 3-dimensional finite element model, which allows modifications in the root length and its diameter, is described. For different geometries, the ideal moment-by-force ratios that induce a bodily movement were determined. The knowledge of root geometry is important in defining an optimal force system.

Algorithms↗

PubMed2000

Orthodontic movement induces high numbers of cells expressing IFN-gamma at mRNA and protein levels.

Cytokines are important signaling proteins that are liberated during immune challenges and exhibit many modulatory activities. However, their role in periodontal modeling during orthodontic tooth movement is not fully understood. The aim of this study was to analyze effects of mechanical force during orthodontic tooth movement, in the pressure zone, on the induction of interferon-gamma (IFN-gamma) as a proinflammatory cytokine of Th1 type and interleukin-4 (IL-4)/IL-10 as anti-inflammatory cytokines of Th2 type. In 12 Wistar rats 40-45 days old, the maxillary first molar was moved mesially by means of a closed coil spring for 3, 7, and 10 days. The contralateral side served as a control. IFN-gamma, IL-4, and IL-10 mRNA were determined by in situ, hybridization, and protein levels of IFN-gamma was measured by immunohistochemistry. Induction of IFN-gamma at both mRNA and protein levels was significantly higher on the experimental side than on the contralateral control side on day 3. The signal gradually became stronger on day 7 and remained high on day 10. Cytokines of the Th2 type (IL-4 and IL-10) were not detected at all examined time points in both pressure and contralateral control sides. Considering the potential immunoregulatory roles played by IFN-gamma, our data suggest that IFN-gamma may be involved in periodontium remodeling during orthodontic tooth movement.

Animals↗

PubMed1999

Chemokines are upregulated during orthodontic tooth movement.

In the early stage of orthodontic tooth movement, an acute inflammatory response characterized by the migration of leukocytes occurs. This response suggests the presence of specific chemotactic signals that may play a role in the mechanism of bone remodeling, in particular in resorption. The aim of the present study was to explore the induction of potential chemokines at the resorption side during orthodontic tooth movement. Monocyte chemoattractant protein-1 (MCP-1), regulated on activation normal T cell expressed and secreted (RANTES), and macrophage inflammatory protein-2 (MIP-2) were examined by in situ hybridization using radioactive synthetic oligoneucleotide probes. Mesial movement of the upper first molars was performed with a fixed appliance for 3, 7, and 10 days. The results demonstrated that MCP-1, RANTES, and MIP-2 were highly expressed during orthodontic movement. On day 3, MCP-1 showed maximum induction in the pressure zone, followed in intensity by RANTES and MIP-2, although not in the contralateral control side. The induction of these chemokines had declined on day 7 and reached low levels on day 10. Our data suggest that chemokines are induced early in the application of force, and such induction may contribute to the early inflammatory response that may be responsible in part for the ensuing bone remodeling.

Animals↗

PubMed2000

The rate and the type of orthodontic tooth movement is influenced by bone turnover in a rat model.

The influence of bone metabolism on both the rate and the type of orthodontic tooth movement was investigated. A rat model in which high (n = 16) and low (n = 17) bone turnover was pharmacologically induced was used. A non-pharmacologically treated group (n = 19) served as the control. A mesially directed constant single force of 25 cN was applied to the upper left first molar for a period of 3 weeks. The study was performed as a split-mouth design, the contralateral side of each animal serving as its control. The displacement of the molar crown was measured with an electronic calliper, while changes in inclination of the teeth were measured from micro-CT scans of the excised maxillae. The bone turnover significantly affected the rate of tooth movement. In the case of high turnover, the rate of tooth movement was increased while it was reduced in the case of low turnover. A controlled mesial tipping in all three groups was observed, but the actual location of the centre of rotation seemed to be influenced by the metabolic state of the bone. Based on the results it can be concluded that deviations in bone turnover influence the response to orthodontic forces, and should be taken into consideration when planning orthodontic treatment in patients with metabolic bone disease or those on chronic medication influencing bone metabolism.

Analysis of Variance↗

PubMed2001

Tooth movement and changes in periodontal tissue in response to orthodontic force in rats vary depending on the time of day the force is applied.

The purpose of this study was to investigate whether there are any differences in tooth movement or in the response of periodontal tissue to orthodontic force when the force is applied at different times of the day. One hundred 6-week-old male Wistar rats were divided into one control group without force application and three experimental groups based on the time of day the force was applied to the upper first molars. Animals in the whole-day group received force continuously throughout the experimental period, while animals in the light- and dark-period groups received force only during the light (07:00-19:00) or dark period (19:00-07:00), respectively. Tooth movement was measured using the occlusal view of a precise plaster model with a profile projector. Periodontal tissues were evaluated histologically. The time course of tooth movement varied among the groups. Tooth movement over 21 days in the whole-day and light-period groups was about twice that as in the dark-period group. The formation of new bone on the tension side in the whole-day and light-period groups was more than twice that as in the dark-period group. On the pressure side, more osteoclasts appeared on the alveolar bone in the whole-day and light-period groups than in the dark-period group. The light-period group showed less extensive hyalinization of the periodontal ligament (PDL) than the whole-day group. The area of root resorption on day 21 also varied among the groups. Interference by masticatory forces did not seem to be a principal cause of the decreased tooth movement in the dark-period group. These results indicate that there are considerable variations in tooth movement and in the response of periodontal tissue to orthodontic force when the force is applied at different times of the day in rats. The results suggest that diurnal rhythms in bone metabolism have important implications in orthodontic treatment.

Alveolar Process↗

PubMed2005

Attractiveness ratings of anterior open bites and reverse overjets using the aesthetic component of the Index of Orthodontic Treatment Need.

This study was carried out to determine the level of attractiveness of anterior open bites (AOB) and reverse overjets of varying severity. A sample of 180 non-dental students (101 females and 79 males; average age 20 +/- 0.75 years) and 45 dental professionals (12 females and 33 males; average age 35.5 +/- 5.07 years) was asked to complete a questionnaire to rate the level of attractiveness of AOB and reverse overjets of varying severity using the aesthetic component (AC) of the Index of Orthodontic Treatment Need (IOTN). Photographs of mild and severe AOB and reverse overjets were projected onto a white screen in a lecture theatre (15 seconds each with a 5 second interval between images). The participants were asked to record the AC grade at which they thought the projected picture of the AOB or reverse overjets had similar attractiveness. Dental awareness of non-dental students was determined by asking them their opinion on how important it was to have straight teeth (very unimportant, unimportant, important, very important), about their personal or close family members' orthodontic experiences and if they thought they were in need of any orthodontic treatment. A chi-square test was applied to record any differences between sexes and between the different groups. Backward stepwise linear regression analysis was used to determine the relationship between the students' ratings of the photographs and their dental awareness. The majority of non-dental students rated a mild AOB (93 per cent) and mild reverse overjet (96 per cent) to be aesthetically acceptable. A mild AOB and mild reverse overjet were found to be acceptable by 40 and 58 per cent of dental professionals, respectively. The differences in the ratings between dental professionals and non-dental students were significant at P < 0.001.A severe AOB was considered unattractive by both students and dental professionals. However, dental professionals rated it at the more unattractive end of the scale (P < 0.001). A severe reverse overjet was rated by the majority of the subjects as aesthetically unacceptable (85 per cent of the non-dental students and 78 per cent of the dental professionals).

Adult↗

PubMed2005

Orthodontically induced root and alveolar bone resorption: inhibitory effect of systemic doxycycline administration in rats.

The aim of the present study was to investigate the effect of systemic administration of low-dose doxycycline (DC) on orthodontic root resorption. The effect on alveolar bone, the cell population involved, and the amount of tooth movement were also evaluated.Fifty-six 40-50-day-old male Wistar rats were used. Six animals served as untreated controls. Six animals were only administered DC for 7 days, by means of a mini-osmotic pump implanted subcutaneously. In 44 animals the maxillary first molar was mesialized by a fixed orthodontic appliance exerting 50 g force upon insertion. In 28 of these animals DC was administered at the time of appliance insertion and throughout the experiment. The animals were sacrificed 7, 10 or 14 days after force application and block sections processed for analysis. An area including the mesial aspect of the distopalatal root and the adjacent inter-radicular alveolar bone was histomorphometrically evaluated. The root resorption area, absolute alveolar bone area, distance between first and second molars, number of odontoclasts, osteoclasts, mononuclear cells on the root, tartrate-resistant acid phosphatase (TRAP)-positive cells on the root, bone, and in the periodontal ligament (PDL) were compared between DC-treated and non-DC-treated animals. The results revealed a significant reduction in root resorption, the number of odontoclasts, osteoclasts, mononuclear cells on the root surface, and TRAP-positive cells on the root and bone for the DC-administered group. The absolute alveolar bone area was greater, whereas the distance between the first and second molars did not differ between groups. In conclusion, systemic administration of low-dose DC in rats may have an inhibitory effect on orthodontically induced resorptive activity.

Acid Phosphatase↗

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