The purpose of this study was to measure the physical properties of enamel and cementum of permanent teeth and to determine the correlation between them. This study was conducted on 50 maxillary premolars that were collected from 26 orthodontic patients (10 males and 21 females, mean age: 19.51 years, range: 12-35 years). The hardness and elastic modulus of the enamel and cementum were measured at the surface of the crown and root at three locations (cervical third: CC, middle third: CM, and apical third: CA). There were individual differences in the hardness and elastic modulus of enamel and cementum. The hardness of the cementum decreased from the cervical to apical regions on the root surfaces in the moderate and soft groups (p<0.01). Individual variations were observed in the hardness and elastic modulus of the human first premolar cementum. A correlation was noted between the hardness and elastic modulus of the enamel and cementum in the CA group (hardness: r=0.551, p<0.01, elastic modulus: r=0.552, P<0.01). These results suggested that the physical properties of cementum may be involved in the occurrence of root resorption caused by orthodontic forces.
Articular cartilage is suffered from high mechanical loads under normal physiological conditions and articular chondrocytes regulate the composition of peri-cellular matrix (PCM), in response to mechanical signals. This study aims to investigate influence of cyclical dynamic compression on matrix metabolite and mechanical properties of chondrocytes cultured in alginate. Two months old New Zealand white rabbits were sacrificed by air embolism. Chondrocytes were taken from knee joints under aseptic conditions and cultured in alginate. The suspension was gelled in a shape of disc in CaCl2 solution and processed for intermittent compression by using Flexcell-5000 compression system kept under an uncompressed condition as a control. The gene regulation of aggrecan (Agg), collagen α! (Col-2), matrix metallo-proteinases 13 (MMP-13) and collagen X (Col-10) were determined by reverse transcription polymerase chain reaction (RT-PCR) at 7th, 14th and 21st day post loading. The alteration in mechanical properties of chondrocytes induced by compression was evaluated using micropipette aspiration technique combined with a half-space model. A significant up-regulation was observed in gene expression of Agg and Col-2 on 7th day or MMP-13 and Col-10 on 14th day respectively after loading of compression. In response to compression, chondrocytes exhibited viscoelastic solid creep behavior. Young’s modulus almost approximated to control group (0.65±0.42kPa). However, viscoelastic properties decreased gradually along with intermittent compression. Viscoelastic properties in experimental 21st day, including equilibrium modulus (E∞), the instantaneous modulus (E0) and apparent viscosity (μ) were significantly lower than experimental 7th day and 14th day (P<0.001), no significant difference was found between experimental 7th day and 14th day (P >0.05). In conclusion, chondrocytes cultured in alginate are stable of mechanical properties and suitable to construct seed cell of tissue engineering, and can keep phenotype and mechanical properties.
Excessive chemical and dynamic stimulation to a cell increases oxidative stress in the cell and causes cellular dysfunction. Osteoblast counts decrease under oxidative stress, and it is known that in the healing process after surgical treatment, bone regeneration treatment, bone fracture, and dental implant treatment, apoptosis is induced, and there is a decrease in bone tissue. In addition, hydrogen peroxide induces cell death via oxidative stress, and vitamin B is known to be involved as a coenzyme of the oxidation-reduction reaction. However, the effects of vitamin B on tissues and cells remain unclear. In this study, we investigated the effects of a vitamin B3, nicotinamide (NAm), on the cytotoxicity induced by hydrogen peroxide. In this study, osteoblasts-like cells derived from Sprague-Dawley rat marrow were cultured. NAm was added to the culture medium for pretreatment, and hydrogen peroxide was added for cytotoxic treatment. A phase contrast microscope was used to observe the morphology of the treated cells, and water-soluble tetrazolium salt-8-based colorimetry was used for evaluating the number of attached cells. Changes in cell shape and decreased cell attachment were observed after cytotoxic treatment with hydrogen peroxide. These changes were not observed in cells treated with only the NAm pretreatment. However, in cells treated with both the NAm pretreatment and the cytotoxic treatment, NAm pretreatment inhibited the changes in cell shape and the decrease in cell attachment. In conclusions, pretreatment with NAm inhibited the cytotoxic treatment-induced morphological changes and decrease in cell attachment. The results suggest that NAm might inhibit cytotoxicity, including apoptosis. As such, NAm may be a promising candidate adjuvant for bone regeneration treatments. However, in the NAm-pretreated cells, the cytotoxic effects of hydrogen peroxide on cell morphology were observed later, and they appeared to progress with time. From this, it appears that NAm affects the time progress of the cytotoxicity resulting from oxidative stress.
The aim of this study was to determine the most accurate position of the mental foramen in a sample of Bangladeshi dental patients. A retrospective study was performed using panoramic radiograph of 5923 patients, who ranged in age from 14 to 50 years old. All radiographs were obtained and analyzed for the most accurate position of the mental foramen by Planmeca Romexis® 3.0 software (Planmeca Oy, Helsinki, Finland). Pearson chi-square test was employed. The most common horizontal and vertical position of the mental foramen was in the line of long axis of 2nd premolar (P4- 58.4%) and below the root apex level (LC- 71.3%) respectively. Knowledge from this article could help the clinicians for safe surgeries and anthropologists to predict the position of the mental foramen to be symmetrical and in the line of long axis of 2nd premolar teeth below the root apex level.
The purpose of this study was to evaluate the dental arch relationship of non-syndromic Malay unilateral cleft lip and palate (UCLP) children and also assess the various congenital and postnatal treatment factors that affect dental arch relationship. Study models of 107 UCLP children were included in this study that was treated in Hospital Universiti Sains Malaysia over a period of 12 years (2000-2012). The mean age was 7.69± 2.46 (mean± SD). The dental arch relationship was assessed by GOSLON Yardstick which comprises five categories; named- 1: excellent; 2: good; 3: fair; 4: poor; 5: very poor. All the subjects were divided into two groups; favorable (category ratings 1-3) and unfavorable (category ratings 4 and 5) groups. Kappa statistics was used to evaluate the intra- and inter-examiner agreements and logistic regression analysis was used to explore the responsible factors that affect dental arch relationship. The mean GOSLON score was 3.15±0.9. Total 72 subjects (68% of all subjects) were categorized into favourable group (category rating 1, 2 and 3) using GOSLON Yardstick. Intra- and inter-examiner agreements were good to very good. Palatoplasty and cheiloplasty seemed to be correlated with favourable dental arch relationship using crude regression analysis but no significant associations were found. This multivariate study shows no significant association between various congenital and postnatal treatment factors and dental arch relationship.
Tetraspanin CD81, which is up-regulated in rheumatoid arthritis (RA) synoviocytes, is a molecule containing four transmembrane domains. We recently showed that small interfering RNA targeting CD81 (CD81 siRNA) ameliorated arthritis in rats. In that study, the expression of synoviolin was decreased in RA joints by CD81 siRNA. We also showed that CD81 siRNA decreased the expression of synoviolin and TNF-α in SW982 synovial sarcoma cells, suggesting that overexpression of CD81 in synovial cells induces the expression of both synoviolin and TNF-α in the same cells. Here we raised monoclonal antibodies (MAbs) against CD81 by immunization of the outer membrane region of CD81 (LEL) that was overexpressed as a recombinant protein. One of these MAbs stimulated CD81 on the membrane of SW982 and up-regulated the expression of synoviolin. We also defined the region of the synoviolin gene promoter that is essential for induction of synoviolin gene expression by using reporter gene system. This system might be useful for the screening of anti-RA medicine.
Previous studies have evaluated bisphosphonate-related osteonecrosis of the jaw (ONJ) after tooth extraction with concurrent administration of bisphosphonate zoledronic acid (ZOL) and steroids. However, details of jawbone changes after administration of ZOL and steroids without tooth extraction remain unclear. In this study, we administered ZOL and dexamethasone (DEX) in rats and compared changes in the jawbone with and without tooth extraction. The right maxillary first molar (M1) was extracted from 8-week-old rats treated with ZOL, ZOL+DEX or DEX. The right maxillary M1 region as the extraction sample and the left maxillary M1 region as the non-extraction sample were compared with macroscopic, radiological, histologic and immunohistochemical examinations. In the extraction samples, we detected incomplete mucosal closure macroscopically and found ONJ on histological examination. In addition, immunohistochemical and three-dimensional analysis of trabecular bone structure showed inhibition of remodeling and angiogenesis in the extraction samples. In the non-extraction samples, we observed inhibition of remodeling, reduced activity of osteoclasts and osteoblasts and suppression of angiogenesis. These findings demonstrate that ONJ can develop under the mucosa with ZOL and DEX treatment, even without invasive procedures. The data suggest that ZOL and DEX can induce ONJ in rats under both invasive and noninvasive conditions because ZOL suppresses osteoclast activity and DEX inhibits remodeling by suppressing osteoblast activity. The results also suggest that surgical stress, such as tooth extraction or bacterial infection, might lead to more severe bisphosphonate-related ONJ.
Low-intensity pulsed ultrasound stimulation (LIPUS) is used in orthopedics as a supplementary therapy to promote the healing of pathological and traumatic fractures, and has also been used in dental implant surgery. Little research exists on the effects of ultrasound on maxillary sinus augmentation, and the mechanisms involved in this process remain unclear. The purpose of the present study was to determine the optimal frequency for enhancing bone regeneration in sinus augmentation by measuring cell proliferation via bromodeoxyuridine (BrdU) analysis in a rabbit model. Forty male rabbits underwent bilateral sinus augmentation in the nasal bone. LIPUS was applied to the experimental sites at two different frequencies (1 and 3 MHz) daily for 1, 2, 4 and 8 weeks. Each histological area of the experimental and control sites was divided into an upper and lower portion from the parietal region to a depth of 5 mm. Immunoreactive nucleated cells were counted by BrdU analysis in each of the three measured areas (1 × 1 mm squares) in the experimental and control sites. The labeling index was defined as the number of BrdU-labeled nuclei divided by the total number of nuclei and was expressed as a percentage. At 1 and 2 weeks, the experimental sites in the 1 MHz group exhibited a significantly higher labeling index than the control sites in both the upper and lower portions. At 1, 2, 4 and 8 weeks, no differences were observed in the upper and lower portions between the experimental and control sites in the 3 MHz group. In conclusion, our results suggest that LIPUS enhances cell proliferation in relation to newly formed bone at 1 week following maxillary sinus augmentation; this effect is greater at a frequency of 1 MHz than at 3 MHz.
The aim of this study was to analyze sagittal and vertical occlusal cephalometric analyses of Pancherz among Malaysian Malay and Malaysian Chinese. Further comparisons of each area of interest are needed to know the differences between them. It was a cross sectional study and total 640 lateral cephalogram (Malay=407, Chinese=233) were randomly selected among orthodontic patients. All sagittal and vertical occlusal cephalometric parameters of Pancherz were measured digitally using Planmeca software. Descriptive statistics, gender and racial dimorphism were analyzed using IBM SPSS Statistics Version 22.0. Data were analyzed using independent t-test. Statistically significant disparities were found in the Malaysian Malay population between males and females for 3 of 10 in the vertical occlusal analysis but there were no significant disparities found in sagittal occlusal analysis. In the Malaysian Chinese population, significant disparities found between males and females for 1 of 11 in sagittal occlusal analysis and 6 of 10 vertical occlusal analysis. Statistically significant disparities were also found between Malaysian Malay and Malaysian Chinese population for 10 of 11 parameters in sagittal occlusal analysis and 5 of 10 parameters in vertical occlusal analysis. In conclusion, there were significant disparities between Malaysian Malay and Malaysian Chinese in general and also between genders of each race seen using cephalometric analyses of Pancherz.
The study aims to evaluate the biocompatibility of titanium produced by laser rapid forming. Ten laser rapid forming titanium (LRF Ti) discs and ten commercially pure titanium (CP Ti) discs were prepared; CP Ti discs were used as controls. Total surface energy was calculated by measuring the contact angle of the metallic surface, and calvaria of newborn Sprague-Dawley rats were used for the primary culture of osteoblasts to study adhesion, spreading, and proliferation of osteoblasts on the metallic surface. The dispersive component, polar component, and total surface energy of LRF Ti discs were larger than those of controls (P < 0.05). After 10 d of osteoblast culture, the cellular adhesive percentage and alkaline phosphatase activity of the LRF Ti group was significantly higher than those of controls (P < 0.05). With increasing culture time, more cells gradually attached to the LRF Ti metallic surface, which caused changes in cellular morphology. This study demonstrates that LRF Ti is highly compatible with bone similar to CP Ti and meets the biocompatibility requirements for implant materials.
The aim of this study was to clarify the relation between calcification and crystallization occurring in the immature bovine enamel and dentin. The calcification process was semi-quantified using monochromatic X-ray microradiography and expressed as pseudo-color mapping for the polished thin sections. The crystallographic properties for the thin sections were carried out using two micro X-ray diffraction methods; i) PSPC-type micro-diffractometer for the precise lattice parameters measurement and ii) IP-type micro-diffractometer for the crystal orientation analysis. The quantification analysis showed the clear calcification progress from the incisal to cervical regions in the immature enamel, whereas did not show the remarkable changes in the dentin. The obtained calcification patterns were in accordance with the reported data. The crystallographic data obtained by the micro-diffraction methods showed the differences in the crystal content, crystallization degree and crystallites orientation from part to part in the developing enamel but not in harmony with the calcification progress. These results indicated that the crystallization pattern in tooth enamel was independent apart from the calcification process, i.e., the calcification process was the accumulation of the inorganic materials and the crystallization process was really the crystallizing of the accumulated inorganic materials.
When performing mandibular reconstruction following mandibular segmentectomy, the surgical method that we have been using involves creating a surgical guide plate using a three dimensions model for bending the mandible reconstruction plate. It has been reported that the current method results in an excellent suitability of the graft into the mandible, which allows for a highly esthetic recovery. The purpose of the present study was to evaluate how well the current surgical method enables the grafted bone to suitability within the mandibular defect in terms of esthetics and functionality by measuring masticatory performance using a gummy score method. We enrolled 11 patients who had undergone mandibular reconstruction using the current method following mandibular tumorectomy at Osaka Medical College Hospital. Among them, 6 evaluable patients were examined using the gummy score method and occlusal force measurement two months after the operation. Gummy score evaluations were performed while masticating on a whole and then a half-portion gummy jelly, taking into account the decline in occlusal force. The results revealed a declining tendency in masticatory performance and occlusal force; however, adequate masticatory performance was obtained with the half-portion gummy jelly. We believe that the gummy score method using a test gummy jelly is a useful tool in evaluating whether a functionally good suitability between the grafted bone and the mandible has been achieved after mandibular reconstruction using the current method.
Mandibular fractures occur frequently and account for more than half of all maxillofacial fractures. The mandible is then subject to complications after treatment. The aim of this study is to assess the function of the masticatory muscles in patients who have been treated for mandibular fractures in Hospital Universiti Sains Malaysia (HUSM) in relation to quality of life, clinical findings and surface electromyography (sEMG) findings of the masseter and temporalis muscles. Subject group refer to patients who underwent treatment for mandibular fracture in HUSM. Subjects were interviewed using a quality of life questionnaire adapted from the University of Washington Quality of Life Scale-Version 4 and then assessed clinically. The functions of the masticatory muscles were then assessed using sEMG and the results compared to that of the control group of patients who never had mandibular fracture. Statistical analysis of the parameters showed significant difference (p<0.05) for both masseter and temporalis muscles during rest, chewing and clenching except for the right masseter muscle during rest. In conclusion, the function of the masticatory muscles was significantly affected even after treatments have been given post mandibular fracture in relation to their quality of life, clinical findings and sEMG results.
Osseous dysplasia (OD), which is subdivided into four subtypes (focal cement-osseous dysplasia, florid osseous dysplasia, periapical cemental dysplasia, and familial gigantiform cementoma), is an idiopathic process located in the periapical region of the tooth-bearing jaw areas, characterized by a replacement of normal bone by fibrous tissue and metaplastic bone. Unless accompanied by bulging or secondary infection of the jawbone, treatment is not necessary. However, treatment for extirpation is required when a secondary infection is present. Consequently, occlusion reconstruction becomes difficult because of large bone defect. Herein, we report the surgical technique to maintain the alveolar ridge form after resecting the lesion and for the case of an infected alveolar bone in a patient with OD. The loss of the buccal cortical bone was inevitable after removal of the infected area. For postoperative occlusal reconstruction, we performed a bone graft to maintain the alveolar ridge form at the same time as the tumor extirpation. Deficient buccal cortical bone was rebuilt with bone taken from the mandibular ramus and a bioactive resorbable plate. We describe the management of OD and the surgical technique for alveolar ridge form management by resecting the lesion and infected alveolar bone.
Fractures of the mandibular condyle still account for a significant proportion of all mandibular fractures, and open reduction and internal rigid fixation of subcondylar fractures has become the standard treatment for this condition. The preference for this approach rests on the considerable technical progress made in this domain, especially in hardware development (e.g., three-dimensional anatomically specifically shaped and biomechanically stable locking subcondylar plate systems), as well as on an improved understanding of the osteobiology and osteophysiology of fracture healing. However, in the present case, the postoperative complication of unexpected fatigue plate fracture in a 68-year-old male patient after open treatment of a subcondylar fracture of the mandible could not be averted despite application of a mechanically stiff enough locking plate and anatomically accurate fracture reduction. This unusual case highlights the need for further osteophysiobiological research and for possible modification of the hardware system in view of the biomechanically complex nature of mandibular subcondylar fracture surgical treatment.
In 2014, the American Association of Oral and Maxillofacial Surgery recommended surgical treatment for medication-related osteonecrosis of the jaw (MRONJ) patients classified as stage 3 or those with mobile segments of bony sequestrum. However, there is limited information regarding the healing mechanism in MRONJ surgical treatments. This study aimed to retrospectively elucidate clinical outcomes of the surgical treatment of MRONJ patients. This study included 26 patients (7 men, 19 women; age: 42–92 years; mean ± standard deviation, 75.3 ± 11.7 years) who were classified as stage 3 or had mobile segments of bony sequestrum, and intake of the offending drug was ceased. The sequestrum was removed with surrounding vital bone, and segmental resection was performed in one patient with a pathological mandibular fracture. The outcome was classified into one of the following three categories: “Healing,” “Improvement,” “Unchanged.” and “Exacerbation.” The mean postoperative follow-up period was 16.6 months (3.0 –57.9 months), and complete healing was observed in 21 patients (80.8%), improvement of the lesion was observed in four patients (15.4%), and the outcome of one patient was unchanged (3.8%). The procedure described here may be recommended with relatively high clinical success rate for the patients with MRONJ requiring surgical treatment.
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