Periodontal and root changes after orthodontic treatment in middle-aged adults are similar to those in young adults.

INTRODUCTION: The goal of this study was to compare the outcomes and amount of change in periodontal health of anterior teeth in young versus middle-aged adults, who were treated to improve anterior alignment and occlusion. METHODS: Pre- and posttreatment records including orthodontic casts, cephalograms, and standardized periapical radiographs were retrospectively collected from young adults (aged 19-30 years; n = 12) and middle-aged adults (aged ≥40 years; n = 27). Following the American Board of Orthodontics criteria, discrepancy index (DI), cast-radiograph evaluation (CRE), treatment duration (TD), marginal bone loss (MBL), and tooth length (TL) were measured, and with the use of periapical radiographs, changes in the level of marginal bone (MBC) and the amount of root resorption (RR) after orthodontic treatment were calculated. RESULTS: DI, MBL, and TD were significantly higher in the middle-aged adults than in the young adults (P < 0.05). However, CRE and MBC after treatment were similar between the 2 groups (P > 0.05). The mean amount of RR following treatment was -0.6 ± 0.44 mm and -1.0 ± 0.61 mm in young and middle-aged adults, respectively. The degree of RR after compensating for treatment complexity and TD was similar between the 2 groups (P > 0.05). CONCLUSIONS: Although the initial malocclusion and periodontal conditions were unfavorable for the middle-aged adults, the overall treatment and periodontal outcomes after orthodontic treatment of the anterior teeth were similar to those for young adults. It appears that older adults tolerate orthodontics to improve the appearance of the anterior teeth as well as younger adults, with no additional burden because of their increased age.

Retrospective study of 100 autotransplanted teeth with complete root formation and subsequent orthodontic treatment.

INTRODUCTION: Autotransplantation has become a major therapeutic option for replacing missing teeth in adult orthodontic patients. However, little systematic information is available about the long-term stability of autotransplanted teeth with complete root formation after the application of an orthodontic force. The objective of this study was to investigate the outcomes of autotransplanted teeth with complete root formation that underwent orthodontic treatment. METHODS: One hundred teeth, autotransplanted in 89 patients, were examined over a mean observation period of 5.8 years. Orthodontic force was applied with nickel-titanium wires 4 to 8 weeks after autotransplantation. Root resorption, ankylosis, mobility, pocket depth, and inflammation at the recipient site were investigated clinically and with radiographs. RESULTS: The survival rate of the autotransplanted teeth was 93.0%. Abnormal findings were found in 29 teeth, including 7 lost teeth, for a success rate of 71.0%. Donor tooth type and occlusal condition of the donor tooth before transplantation were associated with abnormal findings. CONCLUSIONS: The early application of orthodontic force may increase the success rate of autotransplanted teeth, and the type and presurgical occlusal condition of donor teeth affect the success rate.

Constitutively active PTH/PTHrP receptor specifically expressed in osteoblasts enhances bone formation induced by bone marrow ablation.

Bone is maintained by continuous bone formation by osteoblasts provided by proliferation and differentiation of osteoprogenitors. Parathyroid hormone (PTH) activates bone formation, but because of the complexity of cells in the osteoblast lineage, how these osteoprogenitors are regulated by PTH in vivo is incompletely understood. To elucidate how signals by PTH in differentiated osteoblasts regulate osteoprogenitors in vivo, we conducted bone marrow ablation using Col1a1-constitutively active PTH/PTHrP receptor (caPPR) transgenic mice. These mice express caPPR specifically in osteoblasts by using 2.3 kb Col1a1 promoter and showed higher trabecular bone volume under steady-state conditions. In contrast, after bone marrow ablation, stromal cells recruited from bone surface extensively proliferated in the marrow cavity in transgenic mice, compared to limited proliferation in wild-type mice. Whereas de novo bone formation was restricted to the ablated area in wild-type mice, the entire marrow cavity, including not only ablated area but also outside the ablated area, was filled with newly formed bone in transgenic mice. Bone mineral density was significantly increased after ablation in transgenic mice. Bone marrow cell culture in osteogenic medium revealed that alkaline phosphatase-positive area was markedly increased in the cells obtained from transgenic mice. Furthermore, mRNA expression of Wnt-signaling molecules such as LRP5, Wnt7b, and Wnt10b were upregulated after marrow ablation in bone marrow cells of transgenic mice. These results indicate that constitutive activation of PTH/PTHrP receptor in differentiated osteoblasts enhances bone marrow ablation-induced recruitment, proliferation, and differentiation of osteoprogenitors.

The effect of diabetes mellitus on rat mandibular bone formation and microarchitecture.

The aim of this study was to assess the effect of type 1 diabetes mellitus (DM) on the structure of mandibular bone and on the changes of alveolar/jaw bone formation. Experimental DM was induced in 3-wk-old male Wistar rats by a single dose of 60 mg/kg body weight of streptozotocin. All rats were injected with calcein on days 21 and 28. The rats were killed when 8 wk of age. Bone structure was analyzed by bone histomorphometry, microcomputed tomography (micro-CT), and histological section. Histomorphometric analysis showed that the mineral apposition and the bone formation rates in most of the mandibular regions were significantly decreased in the DM group compared with the control group. Micro-CT analysis showed significant deterioration of the bone quality in rats with DM. For a histometric measure of bone resorption, the number of osteoclasts along the distal surface of the alveolar wall was counted. The number of osteoclasts was significantly lower in the rats with DM than in the controls. These findings suggest that uncontrolled DM decreases mandibular bone formation, reduces the rate of bone turnover in the alveolar wall surrounding the root, and affects the quality of bone structure resulting in retardation of its skeletal development.

Clinical study of frontal chewing patterns in various crossbite malocclusions.

INTRODUCTION: The purpose of this study was to clarify the frontal chewing patterns of various crossbite malocclusions. METHODS: A mandibular kinesiograph was used to record the masticatory movements of 106 subjects (ages, 12-35 years) with crossbite malocclusion and 22 subjects (ages, 16-30 years) with normal occlusion. The chewing patterns were classified into 8 chewing types according to the cycle shape of the frontal incisor point movement. The crossbite subjects were divided into 5 groups by the anteroposterior position of the crossbite, and then the subjects with posterior crossbite were divided into 3 groups by the transverse position of the crossbite. The Mann-Whitney U test was used to compare the frequency of each chewing type between any crossbite group and the control group; and between the various crossbite groups. RESULTS: In the crossbite groups, normal chewing occurred much less often than in subjects with normal occlusion. In the posterior crossbite group, reverse chewing was greater (P = 0.002), and normal chewing was less frequent (P = 0.001) compared with the anterior crossbite group. When accompanied by mandibular shift, mandibular prognathism, arch crossbite, in the crossbite or shift side, reverse type, and reverse-crossing type occurred more often than in contralateral side. CONCLUSIONS: In the frontal plane, patients with posterior crossbite might have more abnormal chewing types than those with anterior crossbite, and posterior crossbite could contribute to the high frequency of reverse and reverse-crossing chewing types, especially when accompanied by mandibular shift, mandibular prognathism, or arch crossbite.

Changes in the distribution of nerve fibers immunoreactive to calcitonin gene-related peptide according to growth and aging in rat molar periodontal ligament.

OBJECTIVE: To analyze the age-dependent changes in nerve fibers immunoreactive to calcitonin gene-related peptide (CGRP-ir) in the periodontal ligaments of rats. MATERIALS AND METHODS: Thirty male Wistar-ST rats were divided into growing groups (5, 9, and 15 weeks of age) and aging groups (6, 12, and 24 months of age) (n = 5 in each group). Eight serial sagittal sections, 5 microm thick, were cut parallel to the distobuccal root of the maxillary right first molar. These tissues were stained with a rabbit monoclonal antibody against CGRP. The observation area was divided into three parts (mesial, apical, and distal) and observed using a light microscope. RESULTS: CGRP-ir nerve fibers were primarily distributed in the apical periodontal ligament in the growing group, with significantly more fibers than in the aging group. CONCLUSIONS: CGRP-ir nerve fibers in the periodontal ligament are dense during the growth period and decrease gradually with aging, indicating that CGRP may affect periodontal tissue with growth and aging.

Influence of occlusal stimuli on the microvasculature in rat dental pulp.

OBJECTIVE: To examine the influence of occlusal stimuli on the vasculature in the dental pulp, using an occlusal hypofunction model. MATERIALS AND METHODS: Twenty 7-week-old male Sprague-Dawley rats were divided into two groups. To produce occlusal hypofunction, the appliances were attached to the maxillary and mandibular incisors. Untreated rats served as controls. Serial horizontal paraffin sections of the mandibular first molar were processed by conventional methods. To evaluate the microvasculature in the dental pulp, sections of each specimen were stained with hematoxylin-eosin. RESULTS: In the experimental group, the arterioles in the tooth pulp tissue ran convergently, and their inside diameter was significantly smaller than that of the control group. CONCLUSION: This study suggests that occlusal stimuli influence the periodontal ligament throughout the microvasculature of the dental pulp.

Effects of occlusal contact and its area on gravity fluctuation.

OBJECTIVE: To examine changes in gravity fluctuation caused by experimentally altering the area of occlusal contact. MATERIALS AND METHODS: Subjects consisted of 15 adult Japanese males with normal stomatognathic function, no missing teeth except for the third molars, and equivalent occlusal contact in the anterior and bilateral posterior regions. Silicon biteplates fabricated for each subject to evaluate gravity fluctuation in relation to changes in occlusal contact area were as follows: RP(-)-OC(+) (entire occlusal surface covered in centric occlusion); RP(+)-OC(+) (entire occlusal surface covered with bite slightly raised); Ant or Pos/RP(+)-OC(+) (anterior or posterior region selectively covered); and RP(+)-OC(-) (only retromolar pads covered, no occlusal coverage). RESULTS: No significant differences in gravity fluctuation were noted between subjects wearing biteplates covering the entire occlusal surface. Subjects wearing biteplates with no occlusal contact showed greater gravity fluctuation than those with occlusal contact. In addition, gravity fluctuation for the Ant/RP(+)-OC(+) group (no occlusal contact in the posterior region) was greater than for RP(+)-OC(+) and Pos/RP(+)-OC(+). However, groups with unilateral occlusal contact in the posterior region exhibited large right and left sway amplitude. CONCLUSIONS: These results suggest that occlusal contact, especially posterior occlusal contact, affects gravity fluctuation, and that appropriate occlusion attained by maintaining even occlusal contact in the posterior region is crucial for gravity fluctuation.

Masticatory function and maturation of the jaw-opening reflex.

OBJECTIVE: To test the null hypothesis that alteration in masticatory function due to liquid-diet feeding during growth does not affect jaw-opening reflex (JOR) maturation. MATERIALS AND METHODS: Soon after weaning, 70 female Wistar rats were divided into two equal groups and fed either solid (control group) or liquid (experimental group) diets. At 5, 9, and 13 weeks, the rats were anesthetized and the JOR was recorded in the anterior belly of the digastric muscles as evoked by a low-intensity electrical stimulation of the left inferior alveolar nerve. RESULTS: There were similar tendencies at each recording age. Peak-to-peak amplitude of the JOR was significantly smaller, and the latency was significantly longer in the experimental group, although the duration was not significantly different between the two groups. CONCLUSIONS: These data suggest that long-term masticatory functional change due to liquid-diet feeding during growth may impede the learning for JOR maturation, and thus may affect the masticatory performance in the adult.

Functional changes of temporomandibular joint mechanoreceptors induced by reduced masseter muscle activity in growing rats.

OBJECTIVE: To determine the influence of masseter muscle activity during growth on the functional characteristics of temporomandibular joint (TMJ) mechanoreceptors. MATERIALS AND METHODS: Sixty-six 3-week-old male Wistar rats were divided into an experimental group, in which the masseter muscles were bilaterally resected at 3 weeks of age, and a control group. Single-unit activities of the TMJ mechanoreceptors were evoked by indirect stimulation of passive jaw movement. Electrophysiologic recordings of TMJ units were made at 5, 7, and 9 weeks of age. RESULTS: During this period, the firing threshold of the TMJ units was significantly lower and the maximum instantaneous frequency of the TMJ units was significantly higher in the experimental group than in the control group. CONCLUSION: Reduced masseter activity during the growth period alters the response properties of TMJ mechanoreceptors.

Relationship between occlusal force and mandibular condyle morphology. Evaluated by limited cone-beam computed tomography.

OBJECTIVE: To clarify the relationship between occlusal force and mandibular condyle morphology using clinical data. MATERIALS AND METHODS: The subjects were 40 female patients with malocclusion. The mandibular condyle morphology was assessed by using limited cone-beam CT imaging. The maximum occlusal force was calculated by using pressure-sensitive films. Maxillofacial morphologies were analyzed by using data from lateral cephalograms. RESULTS: Correlation analysis showed that the occlusal force was correlated with the lateral and posterior radii of the condyles, and with the mandibular plane angle to the Frankfort horizontal plane (FH). Moreover, condylar length was significantly correlated with the occlusal plane angle to the FH, the mandibular plane angle to the FH, the ramus inclination, and the posterior facial height (S-Go). Low-occlusal-force patients tended to have smaller mandibular condyles. This size-related difference was more remarkable on the lateral and posterior side. CONCLUSIONS: Occlusal force influences not only maxillofacial morphology but also mandibular condyle morphology.

Functional lateral shift of the mandible effects on the expression of ECM in rat temporomandibular cartilage.

OBJECTIVE: To test the hypothesis that the effects of mechanical stress from a functional lateral shift of the mandible have no effect on the expression of two main condylar cartilage extracellular matrix components, type II collagen and aggrecan, in rats from early puberty to young adulthood. MATERIALS AND METHODS: Functional lateral shift of the mandible was induced in experimental groups of 5-week-old male Wistar rats, using guiding appliances. The rats were sacrificed at 3, 7, 14, and 28 days post appliance attachment. The condyles were immunohistochemically evaluated for type II collagen and aggrecan (the immunoreactive areas were quantified). RESULTS: As compared with the control group, on the contralateral condyles, the immunoreactivity of the experimental groups was significantly increased from 7 to 14 days. While on the ipsilateral condyles, the immunoreactive areas were significantly decreased throughout the experimental period. CONCLUSION: A functional lateral shift of the mandible modulated the condylar cartilage extracellular matrix differently on each side of the condyle, which affected condylar morphology, growth, biomechanical properties, and even the susceptibility of the condylar cartilage to pathogenesis.

OPN deficiency suppresses appearance of odontoclastic cells and resorption of the tooth root induced by experimental force application.

Osteopontin (OPN) is a major non-collagenous bone matrix protein implicated in the regulation of cell function. Although OPN is rich in the cementum of the tooth, the significance of OPN in this tissue is not understood. Tooth root resorption is the most frequent complication of orthodontic tooth movement (TM). The objective of this study was to examine the pathophysiological role of OPN in cementum of the tooth root. For this purpose, the upper right first molar (M1) in OPN-deficient and wild-type (WT) mice was subjected to mechanical force via 10 gf NiTi coil spring while the left side molar was kept intact to serve as an internal control. Micro-CT section and the level of tartrate resistant acid phosphatase (TRAP)-positive cells on the tooth root surface defined as odontoclasts were quantified at the end of the force application. In WT mice, force application to the tooth caused appearance of odontoclasts around the mesial surface of the tooth root resulting in tooth root resorption. In contrast, OPN deficiency significantly suppressed the force-induced increase in the number of odontoclasts and suppressed root resorption. This force application also induced increase in the number of TRAP-positive cells in the alveolar bone on the pressure side defined as osteoclasts, while the levels of the increase in osteoclastic cell number in such alveolar bone were similar between the OPN-deficient and WT mice. These observations indicate that OPN deficiency suppresses specifically tooth root resorption in case of experimental force application.

Effect of experimental diabetes on craniofacial growth in rats.

OBJECTIVES: The goal of this study was to assess the effect of type 1 diabetes mellitus (T1DM) on the craniofacial growth and skeletal maturation using the STZ-DM rat model. DESIGN: Experimental T1DM was induced in 3-week-old male Wistar rats by a single dose of 60 mg/kg body weight of streptozotocin (STZ). Lateral and dorsoventral X-rays of the head were taken at the age of 7 weeks. The X-rays were scanned, digitised and selected linear distances were measured and analysed statistically. RESULTS: In STZ-DM statistical analysis of results revealed a reduction in growth of most of the linear measurements in the neurocranium and mandible by X-ray analysis, and all measurements were significantly lower in viscerocranium. CONCLUSIONS: Uncontrolled T1DM reduces craniofacial growth, resulting in retardation of skeletal development.

Expression of integrinalpha5beta1, focal adhesion kinase and integrin-linked kinase in rat condylar cartilage during mandibular lateral displacement.

Integrins are cell-surface mechanochemical sensors and transducers involved in various cellular processes in combination with extracellular ligands. The aim of this study was to investigate the effect of mechanical stress on the expression of integrinalpha5beta1 and its downstream kinases, focal adhesion kinase (FAK) and integrin-linked kinase (ILK), in condylar cartilage during mandible lateral shift in young rats. Sixty 4-week-old male Wistar rats were divided at random into five control groups and five experimental groups. All rats in the experimental groups were fitted with a resin plate to functionally displace the mandible 2mm to the left (ipsilateral side). The rats were killed 1, 3, 7, 14 and 28 days after attachment of the appliance. Serial 6-mum sagittal sections were cut through the condylar head and processed for immunostaining of integrinalpha5beta1, FAK and ILK. The results were quantified using an image analysing system. Integrinalpha5beta1 expression in the superior-posterior region of the condylar cartilage on the ipsilateral side increased from 3 to 14 days compared with the contralateral side, with an intermediate level of expression in the control groups. Expression of FAK and ILK was similar to integrinalpha5beta1 expression, and they were also upregulated on the ipsilateral side compared with the contralateral side at the early stages of the experiment. The different mechanical loading on the two sides of the condylar cartilage led to different expression patterns of integrinalpha5beta1, FAK and ILK, which may correlate with the different morphological and histological changes seen between sides during mandibular lateral shift.

The influence of occlusal stimuli on basic fibroblast growth factor expression in the periodontal healing of replanted teeth.

Occlusal stimuli and the periodontal healing of replanted teeth have been reported to be related. However, the mechanism for preventing dentoalveolar ankylosis remains unclear. Basic fibroblast growth factor (bFGF/FGF-2) is considered as a key factor in wound healing. The purpose of this study was to evaluate the relationship between occlusal stimuli, bFGF, and the periodontal healing after tooth replantation. Five-week-old male rats were divided into non-occluded, occluded, and recovery groups. The right maxillary first molars were replanted in all groups, and the left maxillary first molars in the 2-week occluded group without replantation were served as nontreated. An anterior bite plate was attached to the maxillary and mandibular incisors to produce occlusal hypofunction in the non-occluded group and was then removed after 1 week in the recovery group. Histological observations were performed after 1 and 2 weeks of the experimental period. After 2 weeks, the non-occluded group had detectable ankylosis and obvious periodontal tissue stricture. Meanwhile, the occluded and recovery groups showed enlarged and thickened periodontia without ankylosis. The number of bFGF-positive cells in the occluded and recovery groups significantly increased as compared to in the non-occluded group. These results suggest that occlusal stimuli enhance the production of bFGF in the periodontal healing of replanted teeth and prevent dentoalveolar ankylosis.

Treatment of severe Class II Division 1 deep overbite malocclusion without extractions in an adult.

This case report describes the orthodontic treatment and retention of an adult with severe Class II Division 1 deep overbite malocclusion; treatment was completed without premolar extractions. We used improved superelastic nickel-titanium alloy wire (L&H Titan, Tomy, Tokyo, Japan) with J-hook headgear for the combined intrusion of the anterior segment and the distalization of the maxillary posterior segments. The overbite was corrected from 6.0 to 2.0 mm by intrusion of the maxillary and mandibular incisors; the overjet was corrected from 13.0 to 2.0 mm. Although no premolars were extracted, good occlusion and facial esthetics were achieved. Follow-up records 2 years after active treatment show that the results were maintained.

Occlusal stimuli influence on the expression of IGF-1 and the IGF-1 receptor in the rat periodontal ligament.

OBJECTIVE: To test the hypothesis that hypofunction/recovered occlusal function has no effect on the changes in insulin-like growth factor-1 (IGF-1) and IGF-1 receptor expressions and cell proliferation of periodontal ligament (PDL) cells. MATERIALS AND METHODS: To produce occlusal hypofunction, the appliances were attached to the rats' maxillary and mandibular incisors. Subsequently, occlusal contact of the molar area was thoroughly recovered by removal of the appliances. RESULTS: In periodontal sections, localization of IGF-1, the IGF-1 receptor, and proliferating cell nuclear antigen (PCNA) immunoreactive cells was significantly more expressed in the control group compared with the hypofunctional group (P < .01). In addition, after the recovery of the occlusion, IGF-1, IGF-1 receptor, and PCNA were detected significantly much more than in the hypofunction group (P < .01). CONCLUSION: The hypothesis was rejected. This study suggests that occlusal stimuli induce cell proliferation of PDL cells by increasing IGF-1 and IGF-1 receptor expression.

Masseter muscular weakness affects temporomandibular synovitis induced by jaw opening in growing rats.

OBJECTIVE: To evaluate the influence of impaired masseter function during growth on the development of temporomandibular synovitis. MATERIALS AND METHODS: Sixteen 3-week-old male Wistar rats were classified into four groups. The first group served as control; and in the second group, jaw opening was forced for 3 hours when the rats were 9 weeks old. In the third and fourth groups, the masseter muscles were bilaterally resected at 3 weeks of age, and the rats in the fourth group were additionally forced to open their jaw at 9 weeks of age. All rats were sacrificed at 9 weeks. Temporomandibular joint (TMJ) tissue samples were processed for histology, and evaluated for cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions by immunohistochemistry to examine the inflammatory changes in the synovial membrane. RESULTS: The control group showed noninflammatory changes. In the jaw-opening group, vascular dilation and weak COX-2 immunoreactivity were induced by jaw opening in the synovium. In the masseter-resection group, the masseter-resected rats exhibited moderate synovial changes while in the resection with opening group, the masseter-resected rats revealed more significant inflammatory changes including synovial hyperplasia, dilated vasculature, fibrin deposits, and intense immunoreactivity for COX-2 and iNOS, all caused by jaw opening. CONCLUSIONS: These results suggest that masseter activity in the growth period is an important factor in the induction of temporomandibular synovitis.

Occlusal hypofunction induces atrophic changes in rat gingiva.

OBJECTIVE: To clarify the influence of occlusal hypofunction on the integrity of gingival tissue and gingival extracellular matrix biosynthesis. MATERIALS AND METHODS: Thirteen-week-old male Wistar rats were divided into two groups. To eliminate occlusal forces, all the right maxillary molars were extracted in the hypofunctional group. The control group was anesthetized but not subjected to surgery. The rats were killed at 2 and 4 weeks after the procedure, and the lower right second molars were prepared for histological analysis. To investigate the effect of occlusal hypofunction on collagen biosynthesis, the expression of connective tissue growth factor (CTGF) and lysyl oxidase (LOX) was determined by immunohistochemistry as well as histological examination by hematoxylin and eosin staining. RESULTS: Disorientation of the collagen fibers, proliferation of the connective tissue fibroblasts, and enlargement of epithelial intercellular gaps were observed in gingival tissue of rat molars with experimental occlusal hypofunction. Immunohistochemically, the expression of CTGF and LOX was increased significantly (P < .05) in the hypofunctional group. CONCLUSION: These results suggest that occlusal hypofunction can affect the structural integrity and the expression of CTGF and LOX in gingival tissue.