Shigemi Goto

Effects of Propranolol on Bone Metabolism in Spontaneously Hypertensive Rats

The effects of propranolol (PRO), a nonselective β-adrenergic receptor (β-AR) antagonist with membrane-stabilizing action on bone metabolism, were examined in spontaneously hypertensive rats (SHR) showing osteoporosis with hyperactivity of the sympathetic nervous system. Treatment of SHR with PRO at 1 and 5 mg/kg p.o. for 12 weeks increased bone mass of the lumbar vertebra and proximal tibia without affecting blood pressure, but PRO at 50 and 100 mg/kg with hypotensive action did not increase bone mass. Next, the effects of PRO at 0.1, 1, and 10 mg/kg on bone status were examined in more detail. Compared with the SHR control, not only bone mass but also biomechanical parameters of strength and toughness of the lumbar vertebrae were increased in SHR treated with PRO at 0.1 and 1 mg/kg, suggesting antiosteoporotic action. PRO at 1 mg/kg statistically increased histomorphometry indices of bone formation, whereas PRO at doses of 0.1, 1, and 10 mg/kg decreased those of bone resorption. Antiosteoporotic effect of PRO is attenuated at 10 mg/kg compared with 0.1 and 1 mg/kg. In addition, treatment with timolol, a nonselective β-AR antagonist without membrane-stabilizing action, or butoxamine, a selective β2-AR antagonist, at 1 mg/kg increased bone mass in SHR. These results suggested that treatment of SHR with β-blockers at low dose improved bone loss and bone fragility. This antiosteoporotic effect of β-blockers seems to be caused by the blocking action of β2-AR, regardless of the membrane-stabilizing action.

Reproducibility of maxillofacial anatomic landmarks on 3-dimensional computed tomographic images determined with the 95% confidence ellipse method.

OBJECTIVE To assess the plotting reproducibility of landmarks on 3-dimensional computed tomography (3D-CT) images through use of the 95% confidence ellipse in order to propose sufficiently stable coordinate systems for 3D-CT measurements. MATERIALS AND METHODS Six dentists plotted 19 landmarks twice on 3D-CT images. Scatterplots and the 95% ellipses were produced 3-dimensionally, and the areas of the ellipses were calculated for evaluating the reproducibility of landmarks. RESULTS The plotting reproducibility of each landmark showed characteristic features. Among five landmarks (the sella [S], nasion [N], basion [Ba], orbitale [Or], and true porion [Po]) that are frequently used as reference points on cephalograms, Ba showed the smallest areas for all three coordinate axes, indicating high reproducibility. The coronoid process (CP) and the tooth-related landmarks showed relatively high reproducibility. CONCLUSION Sufficiently stable coordinate axes could be proposed for different treatments and studies.

Can Cephalometric Indices and Subjective Evaluation Be Consistent for Facial Asymmetry

The purpose of this study was to investigate the relationship between the subjective evaluation of facial asymmetry and seven cephalometric indices. Ten orthodontists subjectively evaluated the frontal photographs of 100 subjects and categorized them into three categories, ie, category I--symmetrical view; category II--a little asymmetry not requiring treatment; and category III--marked asymmetry requiring treatment. Seven indices that were used to evaluate facial asymmetry were determined using frontal cephalographs of these patients. Interobserver agreement was assessed using Cohens kappa statistic. Agreement among the observers for category III was higher than for categories I and II. To define the characteristics of each category, the cephalometric indices, which at least eight observers agreed on, were compared between the categories. No differences were found in any of the indices between categories I and II. Five indices showed differences between category III and the other categories. Among them, the distance of Me from the vertical reference line was the most relevant index for the subjective evaluation of facial asymmetry. When a discrepancy is found between skeletal measurements and a subjective evaluation, the influence of soft tissue structures should be considered in facial asymmetry.

Accurate pre-surgical determination for self-drilling miniscrew implant placement using surgical guides and cone-beam computed tomography

Miniscrew implants have proven to be effective in providing absolute orthodontic anchorage. However, as self-drilling miniscrew implants have become more popular, a problem has emerged, i.e. root contact, which can lead to perforation and other root injuries. To avoid possible root damage, a surgical guide was fabricated and cone-beam computed tomography (CBCT) was used to incorporate guide tubes drilled in accordance with the planned direction of the implants. Eighteen patients (5 males and 13 females; mean age 23.8 years; minimum 10.7, maximum 45.5) were included in the study. Forty-four self-drilling miniscrew implants (diameter 1.6, and length 8 mm) were placed in interradicular bone using a surgical guide procedure, the majority in the maxillary molar area. To determine the success rates, statistical analysis was undertaken using Fishers exact probability test. CBCT images of post-surgical self-drilling miniscrew implant placement showed no root contact (0/44). However, based on CBCT evaluation, it was necessary to change the location or angle of 52.3 per cent (23/44) of the guide tubes prior to surgery in order to obtain optimal placement. If orthodontic force could be applied to the screw until completion of orthodontic treatment, screw anchorage was recorded as successful. The total success rate of all miniscrews was 90.9 per cent (40/44). Orthodontic self-drilling miniscrew implants must be inserted carefully, particularly in the case of blind placement, since even guide tubes made on casts frequently require repositioning to avoid the roots of the teeth. The use of surgical guides, fabricated using CBCT images, appears to be a promising technique for placement of orthodontic self-drilling miniscrew implants adjacent to the dental roots and maxillary sinuses.

Experimental tooth movement-induced osteoclast activation is regulated by sympathetic signaling.

Experimental tooth movement (ETM) changes the distribution of sensory nerve fibers in periodontal ligament and the bone architecture through the stimulation of bone remodeling. As the sympathetic nervous system is involved in bone remodeling, we examined whether ETM is controlled by sympathetic signaling or not. In male mice, elastic rubber was inserted between upper left first molar (M1) and second molar (M2) for 3 or 5 days. Nerve fibers immunoreactive for not only sensory neuromarkers, such as calcitonin gene-related peptide (CGRP), but also sympathetic neuromarkers, such as tyrosine hydroxylase (TH) and neuropeptide Y (NPY) were increased in the periodontal ligament during ETM. To elucidate the effect of the sympathetic signal mediated by ETM, mice were intraperitoneally injected with a β-antagonist, propranolol (PRO: 20 μg/g/day), or a β-agonist, isoproterenol (ISO: 5 μg/g/day) from 7 days before ETM. PRO treatment suppressed the amount of tooth movement by 12.9% in 3-day ETM and by 32.2% in 5-day ETM compared with vehicle treatment. On the other hand, ISO treatment increased it. Furthermore, ETM remarkably increased the osteoclast number on the bone surface (alveolar socket) (Oc.N/BS) in all drug treatments. PRO treatment suppressed Oc.N/BS by 39.4% in 3-day ETM, while ISO treatment increased it by 32.1% in 3-day ETM compared with vehicle treatment. Chemical sympathectomy using 6-hydroxydopamine (6-OHDA: 250 μg/g) showed results similar to those for PRO treatment in terms of both the amount of tooth movement and osteoclast parameters. Our data showed that blockade of sympathetic signaling inhibited the tooth movement and osteoclast increase induced by ETM, and stimulation of sympathetic signaling accelerated these responses. These data suggest that the mechano-adaptive response induced by ETM is controlled by sympathetic signaling through osteoclast activation.

Case Report: Nonsurgical treatment of an adult with severe anterior open bite

A malocclusion characterized by open bite and vertical maxillary excess can be one of the most difficult problems to correct through orthodontic treatment because of the difficulty in permanently changing the morphological disharmony and/or functional disorder associated with open bite. However, in some patients with less severe skeletal impairment it may be possible to orthodontically correct the occlusal disharmony so that the new relationship of the dental arches becomes compatible with normal function of the oral environment. Stability may be enhanced if mechanics are used which do not extrude posterior teeth.

Reproducibility of landmark identification in the jaw and teeth on 3-dimensional cone-beam computed tomography images.

OBJECTIVE To compare the reproducibility of landmark identification on three-dimensional (3D) cone-beam computed tomography (CBCT) images between procedures based on traditional cephalometric definitions (procedure 1) and those tentatively proposed for 3D images (procedure 2). MATERIALS AND METHODS A phantom with embedded dried human skull was scanned using CBCT. The acquired volume data were transferred to a personal computer, and 3D images were reconstructed. Eighteen dentists plotted nine landmarks related to the jaws and teeth four times: menton (Me), pogonion (Po), upper-1 (U1), lower-1 (L1), left upper-6 (U6), left lower-6 (L6), gonion (Go), condyle (Cd), and coronoid process (Cp). The plotting reliabilities of the two procedures were compared by calculating standard deviations (SDs) in three components (x, y, and z) of coordinates and volumes of 95% confidence ellipsoid. RESULTS All 27 SDs for procedure 2 were less than 1 mm, and only five of them exceeded 0.5 mm. The variations were significantly different between the two procedures, and the SDs of procedure 2 were smaller than those of procedure 1 in 21 components of coordinates. The ellipsoid volumes were also smaller for procedure 2 than procedure 1, although a significant difference was not found. CONCLUSIONS Definitions determined strictly on each three sectional images, such as for procedure 2, were required for sufficient reliability in identifying the landmark related to the jaws and teeth.

IGF2 modulates the microenvironment for osteoclastogenesis.

We previously reported that hypoxic stress enhanced osteoclast differentiation via increasing insulin-like growth factor 2 (IGF2) production. However, the mechanisms underlying IGF2 stimulation remains unknown. In this study, we investigated the molecular mechanisms of osteoclastogenesis by IGF2 treatment. Primary mouse bone marrow cells were cultured with IGF2. Total RNAs were applied to a DNA microarray analysis, and quantitative RT-PCR was then used to confirm the microarray data and clarify which cells expressed the relative genes. The most interesting findings were the upregulations of CXC chemokine ligand 7 (CXCL7) expression in stromal cells and stromal cell-derived factor 1 (SDF1) expression in osteoblastic cells with IGF2 treatment. The addition of exogenous SDF1 to CXCL7 increased the number of osteoclasts and promoted the formation of giant osteoclasts. These results suggest that IGF2 modulates the microenvironment around osteoclast precursor cells. SDF1 together with CXCL7 may promote the formation of giant osteoclasts.

Movement of the mandibular condyle and activity of the masseter and lateral pterygoid muscles during masticatory-like jaw movements induced by electrical stimulation of the cortical masticatory area of rabbits

We examined the functional role of the lateral pterygoid muscle (LP) and the masseter muscle (MS) in the movement of the mandibular condyle in masticatory-like jaw movements induced by electrical stimulation of the cortical masticatory area of urethane-anaesthetised rabbits. EMGs of the LP and MS were recorded along with video images of the mandibular condyle movement filmed with a high-speed CCD camera at a time resolution of 8 ms. The time required for the contractile force of the MS and LP to emerge as bite force or jaw movement was determined by direct electrical stimulation to respective muscles: 32.8+/-1.5 ms for the MS and 34.3+/-2.9 ms for the LP. The LP on the working side showed biphasic activity not only in the jaw-opening phase but also in the middle occlusal phase. It is assumed that the MS on the working side begins to exert actually the maximum mechanical influence on the bite force 32.8 ms after its EMG peak in the early occlusal phase. Such development of the mechanical effect of the MS during middle occlusal phase is appeared to be involved in stabilization of the condyle in the middle occlusal phase. Approximately 25 ms (25.1+/-2.5 ms) after the peak of mechanical influence of the MS, the mechanical influence of the working-side LP activity reached maximum in the late stage of the occlusal phase. This LP mechanical influence seems to be functionally associated with an antero-inferior movement of the working side condyle in the late stage of the occlusal phase that is coincident with a movement of the incisal point towards the balancing side across the midline.

Differential diagnosis of obstructive sleep apnea syndrome patients and snorers using cephalograms

Abstract Severe snoring is thought by many to be an early stage of obstructive sleep apnea syndrome (OSAS), but the anatomical relation between snoring and OSAS, if any, has remained unclear. To compare the morphology of the airway between snorers and OSAS patients for possible similarities, we conducted a cephalometric analysis of Japanese OSAS patients (n = 10), habitual snorers (n = 10), and non‐snoring controls (n = 50). There was no significant difference in SNB (the angle formed by the sella, nasion and point B) between OSAS patients and the control subjects. Obstructive sleep apnea syndrome patients tended to have an anteriorly positioned maxilla, and an anteroposterior misalignment between the maxilla and mandible. There was also a tendency toward skeletal openbite. Both OSAS patients and snorers had large tongues and large soft palates, thus causing constriction of the airway with resultant smaller airway diameter and smaller airway surface area. Significant differences between OSAS patients and snorers were found in thickness and length of soft palate surface area, and thickness, length, and position of the hyoid bone. These results suggest that cephalographic measurements may be of considerable use in determining the seriousness of a patients condition.