Root resorption after leveling with super-elastic and conventional steel arch wires: a prospective study.

BACKGROUND: The aim of this prospective study was to compare root resorption after the leveling phase of treatment, performed by either super-elastic or conventional multi-stranded stainless steel arch wires. METHODS: From a total of 156 future orthodontic patients in a private clinic, 82 were included in the study after excluding those who earlier had orthodontic or endodontic treatment or signs of resorption. Patients were equally arbitrary allocated into two groups, where leveling was performed either with super-elastic heat-activated or conventional multi-stranded stainless steel arch wires. Root length loss was calculated using pre-treatment and post-leveling periapical radiographs. RESULTS: The use of super-elastic arch wires did not significantly increase the severity of root resorption, except for tooth 31, while it reduced leveling time compared to conventional stainless steel wires. Crossbite of maxillary lateral incisors seemed to be a risk factor for resorption. CONCLUSION: Incisor root resorption after leveling did not differ significantly between patients treated with super-elastic and conventional stainless steel arch wires, except for a mandibular incisor.

Effect of compressive force on human osteoblast-like cells and bone remodelling: an in vitro study.

OBJECTIVE: The aim of this study was to determine the effect of continuous compressive force (CF) on expression by human alveolar bone-derived osteoblasts (HOBs) of some specific molecules involved in bone remodelling. DESIGN: HOBs were cultured with or without CF (control, 2.0, 4.0gcm(-2)) for 1, 3 and 7 days. Expression of alkaline phosphatase (ALP), type I collagen (Col I), osteopontin (OPN), osteocalcin (OCN), transcription factor Runx2, receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG) and prostaglandin E2 (PGE2) was analysed by real-time-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and/or immunostaining. RESULTS: The results revealed that CF upregulated ALP and Col I expression at both messenger RNA (mRNA) and protein levels but did not affect expression of OPN and OCN mRNA. Runx2 mRNA was inhibited by CF, which also altered the expression of molecules involved in osteoclastogenesis, by enhancing RANKL expression and suppressing OPG expression. At 4.0gcm(-2) of CF, the expression of RANKL and PGE2 was significantly upregulated. CONCLUSION: The results suggest that initial application of CF on HOBs can simultaneously affect expression of markers related to both osteogenesis and osteoclastogenesis.

Periodontal tissue reaction during orthodontic relapse in rat molars.

Relapse after orthodontic tooth movement (OTM) is an undesirable outcome that involves a number of factors. This study investigated the remodelling of the alveolar bone and related periodontal structures during orthodontic relapse in rat molars. The maxillary right first molars of 35 Wistar rats were moved mesially by a fixed orthodontic appliance for 10 days and the contralateral molars served as controls. The appliances were removed and six animals killed. The molars were allowed to relapse, and the remaining animals were sacrificed at 1, 3, 5, 7, 14, and 21 days. The jaws were sectioned and stained with haematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP). One day after appliance removal, the molars relapsed to a mean 62.5 per cent of the achieved OTM and then steadily relapsed to 86.1 per cent at 21 days. The number of osteoclasts situated along the alveolar bone of the first molars was highest at the end of active treatment and significantly decreased during the relapse period. In the OTM group, osteoclasts were most numerous in the pressure side of the periodontal ligament (PDL). As the molars relapsed over time, the osteoclast distribution shifted, and after 7 days of relapse, TRAP-positive cells were registered in previous pressure and tension sides of the first molars. After 21 days, these cells were concentrated in the distal parts of the PDL of all three maxillary right molars. These results indicate that orthodontic relapse in the rat model occurs rapidly and remodelling of the alveolar bone and PDL plays a central role in the relapse processes of both actively moved and adjacent teeth.

Initial responses of osteoblasts derived from human alveolar bone to various compressive forces.

Mechanical stress generated by orthodontic force is recognized as a major factor in the modulation of alveolar bone remodeling. During this process, osteoblasts play a crucial role, not only by participating in bone formation but also by promoting osteoclastogenesis. The aim of this study was to investigate how continuous compressive force (CF) affects human primary osteoblasts (HOBs) in terms of cell proliferation, apoptosis, and expression of interleukin-6 (IL-6) and chemokine CXC ligand 8 (CXCL8). Human primary osteoblasts, isolated from human mandibular bone pieces, were cultured with or without CF (1-4 g cm(-2)) for up to 72 h. Cell viability and proliferation were evaluated using the MTT assay. RT-PCR was used to determine the levels of expression of KI67 (a proliferation marker), BAX (a pro-apoptotic marker), BCL2 (an apoptotic inhibitor), IL6, and CXCL8 mRNAs, while a multiplexed bead immunoassay was used to measure the release of IL-6 and CXCL8. The results revealed that CF decreased cell viability and proliferation in a time- and force-dependent manner. After applying CF for 24 h, the mRNA expression of KI67 was markedly inhibited, whereas the mRNA expression of BAX and BCL2 was unaltered. In addition, CF enhanced the levels of IL6 and CXCL8 mRNAs in a force-dependent manner, whereas the levels of the corresponding proteins were reduced in the compressed HOBs.

Apical root resorption of incisors after orthodontic treatment of impacted maxillary canines: a radiographic study.

INTRODUCTION: The purpose of the study was to evaluate impacted maxillary canines as risk factor for orthodontic apical root resorption. METHODS: The sample comprised 66 patients treated with fixed appliances. Thirty-two patients with a unilateral impacted maxillary canine, which was distanced from the roots of the incisors at a preliminary phase of treatment before bonding, formed the impaction group, and 34 patients without impactions served as the controls. Root shortening was calculated by using pretreatment and posttreatment intraoral radiographs. Inclination of the eruption path of the impacted canine relative to the midline, axis of the lateral incisor, and nasal line, root development, and the medial and vertical positions of the impacted tooth were recorded on orthopantomograms and lateral cephalometric films. The follicle/tooth ratio was evaluated by using periapical radiographs. RESULTS: No significant difference in apical resorption of the maxillary incisors was detected between the impaction and control groups, or between the incisors of the impacted and contralateral sides in the same subject. Likewise, no difference in the severity of root resorption was found between the incisors of impacted side alone and the incisors of the control group. Mesial and vertical inclinations of the impacted canines were negatively related to a lateral incisor's root resorption. No correlations were found between resorption and medial or vertical position of the crown of the canine. The follicle/tooth ratio was significantly related to the mesial inclination of the impacted canine, but not to root resorption. CONCLUSIONS: An impacted maxillary canine, after being distanced from the incisor roots, does not seem to be a risk factor for apical root resorption during orthodontic treatment.

Discriminative ability of the generic and condition-specific Child-Oral Impacts on Daily Performances (Child-OIDP) by the Limpopo-Arusha School Health (LASH) project: a cross-sectional study.

BACKGROUND: Generic and condition-specific (CS) oral-health-related quality-of-life (OHRQoL) instruments assess the impacts of general oral conditions and specific oral diseases. Focusing schoolchildren from Arusha and Dar es Salaam, in Tanzania, this study compared the discriminative ability of the generic Child OIDP with respect to dental caries and periodontal problems across the study sites. Secondly, the discriminative ability of the generic-and the CS Child OIDP attributed to dental caries, periodontal problems and malocclusion was compared with respect to various oral conditions as part of a construct validation. METHODS: In Arusha, 1077 school children (mean age 14.9 years, range 12-17 years) and 1601 school children in Dar es Salaam (mean age 13.0 years, range 12-14 years) underwent oral clinical examinations and completed the Kiswahili version of the generic and CS Child-OIDP inventories. The discriminative ability was assessed as differences in overall mean and prevalence scores between groups, corresponding effect sizes and odd ratios, OR. RESULTS: The differences in the prevalence scores and the overall mean generic Child-OIDP scores were significant between the groups with (DMFT > 0) and without (DMFT = 0) caries experience and with (simplified oral hygiene index [OHI-S] > 1) and without periodontal problems (OHI-S ≤ 1) in Arusha and Dar es Salaam. In Dar es Salaam, differences in the generic and CS Child-OIDP scores were observed between the groups with and without dental caries, differences in the generic Child-OIDP scores were observed between the groups with and without periodontal problems, and differences in the CS Child-OIDP scores were observed between malocclusion groups. The adjusted OR for the association between dental caries and the CS Child-OIDP score attributed to dental caries was 5.4. The adjusted OR for the association between malocclusion and CS Child-OIDP attributed to malocclusion varied from 8.8 to 2.5. CONCLUSION: The generic Child-OIDP discriminated equally well between children with and without dental caries and periodontal problems across socio-culturally different study sites. Compared with its generic form, the CS Child-OIDP discriminated most strongly between children with and without dental caries and malocclusion. The CS Child OIDP attributed to dental caries and malocclusion seems to be better suited to support clinical indicators when estimating oral health needs among school children in Tanzania.

Experimental orthodontic tooth movement and extensive root resorption: periodontal and pulpal changes.

Previous studies have reported changes both in dental pulp and in periodontal ligament (PDL) following orthodontic tooth movement. However, pulpal changes following extensive root resorption after orthodontic tooth movement have not been studied in detail. The aim of this study was therefore to evaluate inflammatory changes, both in the dental pulp and in the compressed PDL, after experimentally induced extensive root resorption. Extensive root resorption was induced in rats by the activation and re-activation of orthodontic force, with a short intervening period of no force application. The distribution of immune cells, nerve fibres and blood vessels was studied immunohistochemically using antibodies against CD68-immunoreactive (IR) cells, major histocompatibility complex (MHC) class II Ia-expressing cells, CD43-IR cells, protein gene product 9.5 (PGP 9.5), and laminin. In the compressed PDL of experimental first molars, significantly increased density of CD68-IR cells and MHC class II Ia-expressing cells were found, whereas the density of CD43-IR cells were unchanged when compared with control second molars. In the compressed PDL, there was an increased density of blood vessels, but no sprouting of nerve fibres. In the dental pulp, however, no increased density of immune cells or sprouting of nerve fibres was recorded. In conclusion, inflammation after extensive root resorption was confined to the compressed PDL, whereas the dental pulp was unaffected.

Effectiveness of interceptive orthodontic treatment in reducing malocclusions.

INTRODUCTION: In this retrospective cohort study of the effectiveness of interceptive orthodontic treatment, we compared patients receiving interceptive orthodontic treatment with untreated control subjects. METHODS: Models were scored by using the index of complexity, outcome and need (ICON). Control models (n = 113) were archival and were selected based on malocclusion in the early mixed dentition and no orthodontic treatment during the subsequent 2 years. The patients (n = 133) were in the mixed dentition and consecutively treated in the University of Bergen orthodontic clinic. Initial ages were 9.4 years (+ or - 1.4) for the treated group and 9.3 years (+ or - 0.8) for the control group. The treatment took a mean of 27.2 months (+ or - 16.3) for the patients; the control group was observed for a mean of 24.4 months (+ or - 3.6). Subject Groups were matched for age, need, complexity, duration, and all ICON components except spacing (P <0.006) and crossbite (P <0.000). RESULTS: ICON scores decreased after treatment by 38.8% (P <0.0001) from 54.9 (+ or - 16.6) to 33.6 (+ or - 16.1). The controls were unchanged, with ICON scores of 54.0 (+ or - 14.8) and 54.2 (+ or - 16.9). Improvement grades were different (P <0.0001), with most controls categorized as "not improved or worse" (89.4%), whereas only 36.1% of the treated group were in that category. However, there were increases in the "minimal," "moderate," and "substantial" improvement categories for the treated subjects (22.6%, 21.1%, and 17.3%, respectively). The controls did not change in any ICON component and worsened in crowding (P <0.007), whereas the patients improved in esthetics, crowding, crossbite, and overbite (P <0.007). CONCLUSIONS: These results indicate that interceptive orthodontic treatment is effective for improving malocclusion but does not produce finished-quality results.

Prevalence of malocclusion and its relationship with socio-demographic factors, dental caries, and oral hygiene in 12- to 14-year-old Tanzanian schoolchildren.

The aim of this study was to assess the prevalence of malocclusion and its association with socio-demographic characteristics, caries experience, and level of oral hygiene in 12- to 14-year-old schoolchildren residing in two socio-economically different districts of Tanzania. A total of 1601 children (mean age 13 years, 60.5 per cent girls) attending 16 primary schools in Kinondoni and Temeke districts participated in a clinical examination and were interviewed in school settings. Chi-square and multiple logistic regression models were used to test for statistically significant differences between different groups. The results showed that 63.8 per cent (62.6 per cent in Kinondoni and 66.0 per cent in Temeke) of the subjects had at least one type of anomaly, with a midline shift (22.5 per cent), spacing of at least 2 mm (21.9 per cent), and an open bite (16.1 per cent) being the most frequently recorded. The majority (93.6 per cent) of the children showed a Class I molar relationship. Class II and Class III malocclusions were registered in 4.4 and 2.0 per cent, respectively. Multiple logistic regression analyses, controlling for socio-demographic factors, showed that the odds ratio for having an open bite was 1.8 if residing in a less socio-economically privileged district. Subjects with decayed, missing, and filled teeth (DNFT) (>0) were 1.7, 2.1, 2.4, and 1.7, respectively, more likely to be diagnosed with a malocclusion, a midline shift, Angle Class II and III, and an open bite. Schoolchildren with fair/poor oral hygiene were less likely than their counterparts with good oral hygiene to be diagnosed with a midline shift. Malocclusions were prevalent in the Tanzanian children investigated and were associated with environmental factors in terms of caries experience and residing in a less affluent district. Preventive programmes to combat the prevalence of malocclusion are recommended.

Malocclusion, psycho-social impacts and treatment need: A cross-sectional study of Tanzanian primary school-children.

BACKGROUND: studies on the relationship between children's malocclusion and its psycho-social impacts are so far largely unexplored in low-income countries. This study aimed to assess the prevalence of malocclusion, reported dental problems and dissatisfaction with dental appearance among primary school children in Tanzania. The relationship of dissatisfaction with socio-demographic characteristics, clinically defined malocclusion and psychosocial impacts of dental anomalies was investigated. Orthodontic treatment need was estimated using an integrated socio-dental approach. METHOD: One thousand six hundred and one children (mean age 13 yr) attending primary schools in the districts of Kinondoni and Temeke completed face to face interviews and a full mouth clinical examination. The survey instrument was designed to measure a Kiswahili translated and culturally adapted Child Oral Impact on Daily Performance (Child-OIDP) frequency score, reported dental problems, dissatisfaction with dental appearance/function and socio-demographic characteristics. RESULTS: The prevalence of malocclusion varied from 0.9% (deep bite) to 22.5% (midline shift) with a total of 63.8% having at least one type of anomaly. Moderate proportions of children admitted dental problems; ranging from 7% (space position) to 20% (pain). The odds ratio of having problems with teeth position, spaces, pain and swallowing if having any malocclusion were, respectively 6.7, 3.9, 1.4 and 6.8. A total of 23.3% children were dissatisfied with dental appearance/function. Children dissatisfied with their dental appearance were less likely to be Temeke residents (OR = 0.5) and having parents of higher education (OR = 0.6) and more likely to reporting problem with teeth position (OR = 4.3) and having oral impacts (OR = 2.7). The socio-dental treatment need of 12% was five times lower than the normative need assessment of 63.8%. CONCLUSION: Compared to the high prevalence of malocclusion, psycho social impacts and dissatisfaction with appearance/function was not frequent among Tanzanian schoolchildren. Subjects with malocclusion reported problems most frequently and malocclusion together with other psycho-social impact scores determined children's satisfaction with teeth appearance- and function.

Interleukin-1alpha and tumor necrosis factor-alpha expression during the early phases of orthodontic tooth movement in rats.

Remodelling of the periodontium after application of mechanical forces constitutes the basis of clinical orthodontics and various immunoregulatory molecules are involved in this process. The aim of this study was to investigate the expression of the cytokines interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) in dental tissues during the early phases of orthodontic tooth movement. Eightteen male Wistar rats were used. All maxillary right first molars were moved orthodontically, with a force of 0.5 N, for 3 h, 1 d, and 3 d. The contralateral sides served as untreated controls. Parasagittal sections of the maxillary molars and the surrounding tissues were subjected to immunohistochemical staining for IL-1alpha or TNF-alpha, and were evaluated with light microscopy. IL-1alpha and TNF-alpha were expressed in the bone and periodontal ligament (PDL) along the roots of the orthodontically moved molars and in the gingiva. Increased expression of both cytokines was observed in the aforementioned areas after 1 and 3 d of tooth movement. The pulp tissue exhibited only minor changes in cytokine expression during tooth movement. The results suggest that mechanical stress results in almost immediate inflammatory reactions in various dental tissues.

Is mild dental invagination a risk factor for apical root resorption in orthodontic patients?

The purpose of this retrospective study was to assess if dental invagination is a risk factor for root resorption during orthodontic treatment. The sample consisted of 91 patients (32 males, 59 females) with a mean age of 13.1 years (range 9.3-32.1 years) with complete orthodontic records, including periapical radiographs of the maxillary incisors before and after treatment. Forty-nine patients had at least one maxillary incisor invaginated, whilst the remaining 42 patients were free of dental invaginations. Variables recorded for each patient included gender, age, Angle classification, extraction or non-extraction therapy, ANB angle, overjet, overbite, trauma, habits, agenesis, tooth exfoliation, treatment duration, Class II elastics, body-build, general factors, impacted canines, and root form deviation. Crown and root length of the maxillary incisors were measured on pre- and post-treatment long cone periapical radiographs corrected for image distortion. The percentage of root shortening and root length loss in millimetres was then calculated. Most of the invaginated teeth were minor type 1. Statistical analysis revealed no significant difference in the severity of apical root resorption between invaginated and non-invaginated incisors in patients without dental invaginations, nor was the extent of dental invagination related to the severity of apical root resorption. However, invaginated teeth had malformed roots more often than non-invaginated teeth. Dental invagination, and particularly type 1, cannot be considered a risk factor for apical root resorption during orthodontic tooth movement.

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.

Early root alterations after orthodontic force application studied by light and scanning electron microscopy.

The purpose of the study was to characterize root surface alterations in orthodontically moved teeth. Thirty-six 40-50-day-old male Wistar rats were used. The maxillary right first molar was mesialized by means of a fixed appliance, exerting 50 g of force upon insertion. One, 2 and 4 days after force application the animals were sacrificed (nine animals per observation period) and block sections processed for analysis. Nine animals served as untreated controls. In total, 20 specimens were prepared for examination of the mesial aspect of the mesiobuccal root by scanning electron microscopy (SEM). The remaining specimens were processed for light microscopy. Three morphologically distinct types of resorption defect were observed: isolated small lacunae, wide shallow resorption bays, and deep resorption lacunae. The area occupied by each resorption type varied significantly (P < 0.05) with time. Isolated small lacunae were the earliest to be observed, sometimes found in continuity with wide shallow resorption bays. Mononucleated macrophage-like cells were associated with both resorption types. Deeper lacunae extending into the dentine were found at the 4 day observation period. These always occurred within shallow resorption bays and appeared to be created by multinucleated cells. From the sequence of the different root surface defects and associated cell types observed during the development of orthodontically induced root resorption, it may be concluded that different cell types, with different resorptive potential but functionally interrelated, are involved in the successive phases of the process, and that each cell type leaves a characteristic resorption pattern on the root surface.

CD40-CD40L expression during orthodontic tooth movement in rats.

The aim of this study was to investigate the expression of the costimulatory molecules CD40 and CD40L in periodontal and bone cells in orthodontically treated and untreated teeth using immunohistochemistry. The upper first molars were moved mesially by a fixed appliance. In the experimental group, CD40+ cells were detected at both the tension and the resorption sides in fibroblast-, macrophage-, and dendritic-like cells. The staining was more pronounced on the resorption side. The strongest expression was observed on day 3, decreased on day 7, and reached a low level on day 10 after application of orthodontic force. In contrast, in the treated animals CD40 ligand was expressed on day 3, the expression was enhanced on day 7, and was more pronounced on day 10. CD40L-expressing cells were found predominantly around hyalinized tissue in the resorption zone and the tension areas of the distal root. CD40L was expressed in the bone marrow cells in the pressure zone. In the tension side, some cells of the cellular cementum expressed CD40L. The expression of CD40 and CD40L was low in untreated teeth. These results suggest that CD40-CD40L interaction appears to be an active process during orthodontic tooth movement and that orthodontic force induces T-cell activation. Such activation may be involved in the induction of inflammatory mediators and subsequent bone remodeling. In addition, this may lead to the generation of anti-inflammatory mediators that support defense mechanisms against root resorption, which depend on the type of immune response that is induced regarding CD40-CD40L expression.

Sympathectomy causes increased root resorption after orthodontic tooth movement in rats: immunohistochemical study.

Accumulating evidence suggests that the sympathetic nervous system modulates inflammatory responses and bone remodeling. We have studied the effects of sympathectomy and orthodontic tooth movement (OTM) on root resorption, immunocompetent cell recruitment, neuropeptide, neurokinin-1 receptor (NK1-R), and interleukin 6 (IL-6) expression. Experimental rats (n=8) had the right superior cervical ganglion surgically removed, whereas control rats (n=6) underwent sham surgery. Three days later, all rats had the right maxillary first molar moved mesially by an orthodontic appliance. The rats were perfused 13 days later, and the right maxillae were processed for immunohistochemistry by using primary antibodies directed against ED1 antigen, CD43, substance P (SP), NK1-R, neuropeptide Y (NPY), and IL-6. Following OTM, sympathectomized (SCGx) rats had significantly more root resorption (P<0.01) and SP-immunoreactive (IR) fibers (P=0.01) in the compressed periodontal ligament (PDL) compared with control rats. There was a significant decrease in recruitment of CD43+ cells in the pulp after OTM in SCGx rats compared with control rats (P=0.02). An upregulation of NK1-R immunoreactivity was observed surrounding the hyalinized tissue, and an increase in the number of NK1-R IR cells and density of SP-IR fibers was present in first molar pulp of all rats. NPY-IR fibers were absent in the compressed PDL of SCGx and control rats. Thus, OTM induces remodeling not only around the periodontal tissues, but also in the dental pulp. The sympathetic nerves have an inhibitory effect on hard tissue resorption and a stimulatory effect on CD43+ cell recruitment after OTM.