Cementoblast response to low- and high-intensity ultrasound.

OBJECTIVE: It has been shown that ultrasound stimulation accelerates repair of orthodontically induced root resorption. However, the mechanism of such adaptive change is still unclear. The purpose of this study was to evaluate pulsed ultrasound on the differentiation-potential and cementoblast-mediated osteoclastogenesis using a cementoblastic cell line. DESIGN: Cultured cementoblasts (murine cementoblastic cell line, OCCM-30) were subjected to ultrasound exposure (frequency = 1 MHz; pulsed 1:4; spatial average temporal average intensities=30 or 150 mW/cm(2)) or sham exposure for 15 min per day. Expression levels of alkaline phosphatase (ALP), type I collagen (COL-I), osteoprotegerin (OPG) and receptor activator of nuclear factor small ka, CyrillicB ligand (RANKL) mRNAs were analysed by a real-time PCR analysis. Furthermore, ALP activity, collagen synthesis, and protein levels of OPG and RANKL were examined after 6-day ultrasound exposure. RESULTS: Real-time PCR analysis indicated that, irrespective of the intensity, single ultrasound exposure increased the expression of transcripts for COL-I and ALP after 24h; the expression of OPG and RANKL also increased after 1 and 4h, respectively. Cultured cementoblasts receiving ultrasound stimulation for 6 days showed a significant (p<0.05 or 0.01) increase in cell number and collagen synthesis. ALP activity and OPG synthesis were also significantly (p<0.05) upregulated by ultrasound stimulation with 150 mW/cm(2). CONCLUSIONS: These results demonstrated that ultrasound stimulation especially with 150 mW/cm(2) might be a better candidate as a medical remedy to protect against root resorption and/or accelerate its repair.

Dynamic shear properties of the porcine molar periodontal ligament.

The role of the periodontal ligament (PDL) is to support the tooth during function and resist external forces applied to it. The dominant vertical component of these forces is associated with shear in the PDL. Little information, however, is available on the dynamic behavior of the PDL in shear. Therefore, the present study was designed to determine the dynamic shear properties of the PDL in the porcine molar (n=10). From dissected mandibles transverse sections of the mesial root of the first molar were obtained at the apical and coronal levels and used for dynamic shear tests. Shear strain (0.5%, 1.0%, and 1.5%) was applied in superoinferior direction parallel to the root axis with a wide range of frequencies (0.01-100 Hz). The dynamic complex and storage moduli increased significantly with the loading frequency, the dynamic loss modulus showed only a small increase. The dynamic elasticity was significantly larger in the coronal region than in the apical region although the dynamic viscosity was similar in both regions. The present results suggest that non-linearities, compression/shear coupling, and intrinsic viscoelasticity affect the shear material behavior of the PDL, which might have important implications for load transmission from tooth to bone and vice versa.

Effects of ultrasound on cementoblast metabolism in vitro.

Ultrasound (US) has been shown to alter cell/tissue functions. However the effects of US on cementoblasts are not known. The aim of the present study was to evaluate the effect of US exposure on proliferation and metabolism of cementoblast (murine cementoblastic cell line [OCCM-30]) in vitro. Cultured cementoblasts received US exposure (frequency = 1 MHz; pulsed 1:4; spatial-average intensities (I(SA)) = 100, 150 or 400mW/cm(2)) or sham exposure for 15 min per d for 4 d. They were then assayed for calcium content and cell proliferation. Furthermore, expression levels of osteocalcin, bone-sialoprotein, alkaline phosphatase and osteopontin were analyzed by real time polymerase chain reaction. Calcium content was statistically increased (p < 0.05) after US exposure at 100 or 150 mW/cm2. Alkaline phosphatase mRNA levels were (p < 0.05) increased significantly by US stimulation with 150 mW/cm2. These results demonstrate that US affects cementoblasts by regulation of some genes-related protein in vitro and, although more studies are necessary, it may be important to consider in designing in vivo US therapies targeted at the oral cavity.

Platelet-derived growth factor enhances proliferation and matrix synthesis of temporomandibular joint disc-derived cells.

Platelet-derived growth factor (PDGF) is an essential signaling molecule for wound healing and tissue repair. This study was aimed at evaluating the effect of PDGF on the proliferation of temporomandibular joint (TMJ) disc-derived cells and extracellular matrix synthesis. The number of cultured cells were counted by COULTER Z1. The assay for collagen synthesis was performed using a sircol soluble collagen assay. Hyaluronic acid (HA) synthesis was analyzed by a high performance liquid chromatography. The expression of collagens, matrix metalloproteinases (MMPs), and the tissue inhibitors of metalloproteinases (TIMPs) were examined using SYBR Green in terms of the RNA levels. PDGF treatment significantly (P < .01) increased the proliferation rate of the disc-derived cells as compared with the controls when the dose was 5 ng/ mL or greater. Treatment with more than 5 ng/mL PDGF resulted in an amount of collagen synthesis significantly (P < .01) higher than the controls. HA synthesis was maximal with 5 ng/mL PDGF treatment. Quantitative real-time polymerase chain reaction analyses showed that treatment with 5 ng/mL of PDGF-BB upregulated the mitochondrial RNA levels of type I and II collagens, MMPs, and TIMPs within 6 hours. It is concluded that PDGF, if its concentration is optimal, enhanced proliferation and matrix synthesis of TMJ disc-derived cells, indicating that PDGF may be effective for use in tissue engineering of the TMJ disc.

Severe crowding and a dilacerated maxillary central incisor in an adolescent.

This study reports the treatment of an adolescent patient with dilacerated maxillary incisor. She complained of severe crowding with a high-positioned left upper canine. Her left central incisor had been impacted and moved to proper position at the age of eight years, resulting in a severe root dilaceration. To avoid any progression of root dilacerations and resorption in the maxillary incisor, maxillary lateral expansion and molar distalization plus multibracket appliance were selected as the best nonextraction treatment plan. The maxillary expansion and molar distalization should provide adequate space for the correction of the severe crowding, and treatment with a multibracket appliance was initiated. After a 17-month treatment with a multibracket appliance, an acceptable occlusion was achieved with a Class I molar relationship. An acceptable occlusion was maintained without recurrence of the crowding and impairment of the dilacerated root in the maxillary incisor during three years of retention. It is emphasized that careful planning is required to avoid any progression of the root dilaceration and resorption through orthodontic treatment. A shortening of the period of applying orthodontic force on the dilacerated incisor and avoidance of tooth extraction will minimize the risk factors.

The effect of experimental cartilage damage and impairment and restoration of synovial lubrication on friction in the temporomandibular joint.

AIMS: To evaluate how the frictional coefficient of the porcine temporomandibular joint (TMJ) is affected by an impairment of the synovial lubrication produced by an experimental abrasion of the articular cartilage and the application of hyaluronic acid (HA) with different molecular weights to the abraded cartilage surfaces. METHODS: Erosion of the articular cartilage was produced by scouring it with sandpaper. Impairment and restoration of synovial lubrication were modeled by washing the joint space with phosphate-buffered saline (PBS) and by the application of HA with different molecular weights. After measuring the frictional coefficients in the intact TMJs (n = 10), the effects of washing with PBS, sandpaper scouring, and the application of HA were subsequently examined. RESULTS: The mean frictional coefficient in the intact joint was 0.0154 (SD 0.0043). After PBS washing and sandpaper scouring, it increased significantly to 0.0235 (SD 0.0052) and 0.0520 (SD 0.0088), respectively. Subsequent application of HA resulted in a significant decrease (43% to 56%) of the frictional coefficient. Observations by scanning electron microscopy showed that after sandpaper scouring, the superficial cartilage layer was disrupted and inner layer was exposed, creating an irregular surface. CONCLUSION: Joint friction may increase by approximately 350% following an experimental scouring of the cartilage surface and impairment of synovial lubrication. Lubrication by means of HA decreased joint friction by approximately 50%.

Longitudinal measurements of tooth mobility during orthodontic treatment using a periotest.

The present study was designed to investigate the alteration of tooth mobility through orthodontic treatment using a Periotest. Eighty-three crowding cases without severe skeletal discrepancies were used as subjects. For each subject, the mobility of the central and lateral incisors on both arches (U1, U2, L1, and L2) was measured immediately before and after orthodontic treatment (T1 and T2 stages) and after retention (T3 stage) by use of a Periotest. No significant differences of all the measurements were found between the left and right sides. At T1 stage, the mean values were 10.8, 10.4, 9.3, and 7.4 for U1, U2, L1, and L2, respectively. At T2 stage, the Periotest values for all the teeth increased in comparison with those at T1 stage, and significantly decreased at T3 stage compared with those at T2 stage. Negative correlations were found between the Periotest value and age, which imply that tooth mobility decreases with age. The durations of treatment and retention had low correlation with the change of tooth mobility for all the teeth. It is suggested that the tooth mobility before treatment and after retention may be one of the useful indicators for determination of the retention period.

An adult case of skeletal open bite with a large lower anterior facial height.

Control of the height of posterior dentoalveolar regions is of great importance for the correction of skeletal open bite. Traditionally, second premolar extraction facilitates the closure of open bite by inducing a counterclockwise mandibular rotation without molar intrusion. This article reports treatment for a 24-year six-month-old female patient with an open bite and large anterior facial height. She complained of occlusal disturbances and difficulty of lip closure because of the open bite. Overjet and overbite were +3.0 mm and -3.0 mm, respectively. To correct open bite and crowding, the bilateral extraction of the maxillary and mandibular second premolars plus multibracket appliances for mesial movement of the molars was selected as the treatment plan. After a two-year treatment, an acceptable occlusion was achieved, the lower anterior facial height was decreased, and the lips showed less tension in a lip closure. An acceptable occlusion was maintained without recurrence of the open bite during a three-year retention period, indicating a long-term stability of the occlusion. The results of this treatment indicated that the correction of open bite with no or less molar intrusion or incisor extrusion is of great importance for achieving stable occlusion and avoiding the relapse of open bite.

Unilateral ear fullness and temporary hearing loss diagnosed and successfully managed as a temporomandibular disorder: a case report.

BACKGROUND AND OVERVIEW: A 73-year-old woman had a 4-month history of debilitating left-sided otic fullness, hearing loss, and a watery sensation in her ear without obvious cause. She had consulted with an otolaryngologist who cleared the ear of all middle ear pathology and then placed ventilation tubes in the tympanic membrane to relieve her symptoms of ear fullness. The ventilation tubes did not produce long-lasting relief so she was referred to the dental clinic. CASE DESCRIPTION: The patient did not have substantial symptoms of jaw dysfunction or jaw pain and was clearly bothered more by her ear symptoms; she exhibited the following signs and symptoms: limited mandibular range of motion (37 millimeters), crepitation in the left temporomandibular joint (TMJ), active trigger points in the left superficial masseter, and severe pain on palpation in the left TMJ (lateral and dorsal). A panoramic radiograph and maxillary computed tomography scan revealed moderate degenerative changes observed bilaterally in the TMJs. A diagnosis of localized osteoarthritis (OA) of the TMJ (TMJ-OA) and masticatory myofascial pain was given. The authors provided 3 months of treatment that included self-applied physical therapy (stretch and thermal packs), full-arch stabilization splint, trigger point injection, and a TMJ injection using triamcinolone acetonide (20 milligrams). RESULTS: The patient reported a 90% improvement in her TMJ and ear-related symptoms as a result of the treatments. The authors speculated that TMJ-OA and myofascial muscle disorders are potentially contributory to a tensor tympani muscle dysfunction, which could explain her ear fullness and hypoacusis. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Diagnosis and management of TMJ dysfunction (pain on palpation, OA, and limitation of motion) should be considered when patients have symptoms of unexplained ear fullness and have been cleared for ear infection or other ear-related pathology.

Age-associated changes in viscoelastic properties of the bovine temporomandibular joint disc.

To test the hypothesis that compressive properties of the temporomandibular joint (TMJ) disc change with age, we investigated its viscoelastic properties and stress-relaxation behavior under compression. Compressive stress-relaxation tests were performed in different regions of bovine discs of various ages. For each disc, specimens were derived from three different regions (anterior, central, and posterior). For four strain levels (5, 10, 15, and 20%), a stress-relaxation test was conducted over a 5-min period. Values of the instantaneous modulus, E(0), appeared to be larger in the anterior than in the posterior region of the disc, irrespective of age. The E(0) value increased with age, especially in the central region. Values of the relaxed modulus, E(R), also increased significantly with age. There were no regional differences in values of the relaxed modulus. Under stress-relaxation, the relaxation time became longer with age, especially in the posterior region. The results suggest that the compressive properties, instantaneous and relaxed moduli, increase with age, while the relaxation time becomes longer. This implies that the TMJ disc becomes harder with age. Furthermore, the compressive properties of the TMJ disc are region-specific. As a result of the harder disc, it is likely that the TMJ becomes more vulnerable to secondary damage, such as fracture and tissue degradation.

The effect of removal of the disc on the friction in the temporomandibular joint.

PURPOSE: The amount of friction in the temporomandibular joint (TMJ) is dependent on the joint components, including the synovial fluid, disc, and articular surface cartilage. As friction in the TMJ is less than in other (discless) joints, we hypothesized that this is caused by the presence of the disc. MATERIALS AND METHODS: The frictional coefficient of the TMJ was first measured in the intact porcine joint (n = 10). After the disc was removed the measurement of frictional coefficient was conducted again. Furthermore, the subsequent effects of loading duration and the application of hyaluronic acid (HA) were examined. RESULTS: The mean frictional coefficient in the intact joint was 0.0177 (SD 0.0021). After disc resection it became 0.0361 (SD 0.0063). The frictional coefficient increased with the length of the preceding loading duration and exceeded 0.0635 (SD 0.0085) after 30 minutes. Subsequent application of HA resulted in a slight decrease of the frictional coefficient. CONCLUSIONS: The presence of the disc reduces the amount of friction in the TMJ. This reduction is likely due to the role of the disc in reducing the amount of incongruity between the articular surfaces and in increasing synovial fluid lubrication.

Fibroblast growth factor-2 augments recombinant human bone morphogenetic protein-2-induced osteoinductive activity.

The osteoinductive activity induced by recombinant human BMP-2 (rhBMP-2) blunts proportionately as the recipient ages. In order to compensate for this bluntness administration of fibroblast growth factor-2 (FGF-2) has been considered. The aim of this study was to determine whether FGF-2 administration augments osteoinductive activity caused by rhBMP-2 and to evaluate the effect of aging on bone formation induced by coadministration of rhBMP-2 and FGF-2. Sixty-four Wistar strain male rats of 8-week-old (prepubertal) and 16-week-old (postpubertal) received bone defects bilaterally in the parietal bone and the defects were filled by a polylactic acid polyglycolic acid copolymer/gelatin sponge (PGS) impregnated with rhBMP-2 plus 0 ng, 25 ng, and 250 ng FGF-2 (n=10 in each). At 2 weeks after grafting, the new bone volume seemed to be larger in the rhBMP-2+FGF-2 groups than in the rhBMP-2 alone group. At 4 weeks, the new bone formation was linked to the adjacent original bone. In the prepubertal rats, all newly formed bone was similarly calcified. In the postpubertal rats, only the rhBMP-2+25 ng FGF-2 group showed this higher degree of calcification. At 2 weeks, alkaline phosphatase (ALP) activity in the rhBMP-2+25 ng FGF-2 group was significantly (p<0.05) larger than that in the rhBMP-2 group in both prepubertal and postpubertal rats. This result shows that low-dose administration of FGF-2 enhanced the degree of calcification and ALP activity in the rhBMP-2 grafting site especially in the postpubertal rats. Therefore, FGF-2 would be a candidate to compensate for the reduction of osteoinductive activity of rhBMP-2 with aging.

Tratamento ortognático de um paciente com assimetria mandibular severa e disfunção dos músculos mastigatórios: relato de um caso clínico / An orthognathic treatment of patient with severe mandibular asymmetry and masticatory muscles dysfunction: a case report

Pacientes com maloclusão assimétrica geralmente apresentam disfunção dos músculos mastigatórios. A correção de mandíbulas assimétricas possibilita a retomada harmoniosa da função estomatognática. Este artigo apresenta o relato de um caso de um paciente adulto, sexo masculino, assimetria mandibular severa, mordida cruzada unilateral e disfunção muscular. Para avaliação da função muscular mastigatória, foram realizados os exames de eletromiograma (EMG) e Dental Prescale System (sistema de medição de pressões) antes e após o tratamento. No estágio inicial, as forças oclusais apresentavam-se relativamente baixas (312.6 N) durante a mordida máxima dos dentes e a área de contato oclusal era pequena (7.5 mm²). A resolução do problema foi feita através de tratamento ortodôntico com aparelho fixo e cirurgia ortognática da mandíbula. Após 15 meses de tratamento, foi estabelecida uma oclusão adequada. No estágio final, a força oclusal apresentou-se aumentada (579.9 N). A área de contato oclusal durante a mordida máxima dos dentes também obteve um aumento (9.9 mm²), se comparado ao estágio inicial. Após 2 anos de contenção, a oclusão manteve-se estável e sem recorrência da assimetria mandibular, indicando uma estabilidade oclusal de longo prazo

Cisto ósseo traumático: revisäo da literatura e relato de um caso / Traumatic bone cyst: a review of the literature and report of case

Este trabalho apresenta o caso clínico de uma paciente jovem que após se submeter a realizaçäo de uma radiografia panorâmica foi descoberta acidentalmente a presença de uma lesäo radiolúcida, cujas características radiográficas em nada faziam pensar na hipótese de um cisto ósseo traumático. No entanto, este foi o diagnóstico estabelecido após a intervençäo cirúrgica e posterior exame histopatológico