Current Opinion in Molecular Pathology of Ameloblastoma: A Literature Review

Ameloblastoma is the most representative epithelial odontogenic tumor in the craniofacial region. Through several studies on Ameloblastoma that have been conducted so far, we have been able to get closer to the reality of Ameloblastoma. However, groundbreaking insight into the pathophysiology of Ameloblastoma has not yet been provided.This review assessed three aspects of five recently published papers on Ameloblastoma: cancer stem cells, calcium signaling, and tumor microenvironment, and compared them with previous studies on tumor physiology, including cancer. In addition, the characteristics of Ameloblastoma revealed by the experimental methods presented in the currently published five papers provide the possibility of Ameloblastoma as a study model in general tumor or cancer studies. Furthermore, the mechanisms of action of the chemicals identified in the studies support their potential as candidates for the second-line treatment of Ameloblastoma.

Development of a mouse model for pulp-dentin complex regeneration research: a preliminary study

OBJECTIVES: To achieve pulp-dentin complex regeneration with tissue engineering, treatment efficacies and safeties should be evaluated using in vivo orthotopic transplantation in a sufficient number of animals. Mice have been a species of choice in which to study stem cell biology in mammals. However, most pulp-dentin complex regeneration studies have used large animals because the mouse tooth is too small. The purpose of this study was to demonstrate the utility of the mouse tooth as a transplantation model for pulp-dentin complex regeneration research. MATERIALS AND METHODS: Experiments were performed using 7-week-old male Institute of Cancer Research (ICR) mice; a total of 35 mice had their pulp exposed, and 5 mice each were sacrificed at 1, 2, 4, 7, 9, 12 and 14 days after pulp exposure. After decalcification in 5% ethylenediaminetetraacetic acid, the samples were embedded and cut with a microtome and then stained with hematoxylin and eosin. Slides were observed under a high-magnification light microscope. RESULTS: Until 1 week postoperatively, the tissue below the pulp chamber orifice appeared normal. The remaining coronal portion of the pulp tissue was inflammatory and necrotic. After 1 week postoperatively, inflammation and necrosis were apparent in the root canals inferior to the orifices. The specimens obtained after experimental day 14 showed necrosis of all tissue in the root canals. CONCLUSIONS: This study could provide opportunities for researchers performing in vivo orthotopic transplantation experiments with mice.

Postoperative irradiation after implant placement: A pilot study for prosthetic reconstruction

PURPOSE: On maxillofacial tumor patients, oral implant placement prior to postoperative radiotherapy can shorten the period of prosthetic reconstruction. There is still lack of research on effects of post-implant radiotherapy such as healing process or loading time, which is important for prosthodontic treatment planning. Therefore, this study evaluated the effects of post-implant local irradiation on the osseointegration of implants during different healing stages. MATERIALS AND METHODS: Custom-made implants were placed bilaterally on maxillary posterior edentulous area 4 weeks after extraction of the maxillary first molars in Forty-eight Sprague-Dawley rats. Experimental group (exp.) received radiation after implant surgery and the other group (control) didn't. Each group was divided into three sub-groups according to the healing time (2, 4, and 8 week) from implant placement. The exp. group 1, 2 received 15-Gy radiation 1 day after implant placement (immediate irradiation). The exp. group 3 received 15-Gy radiation 4 weeks after implant placement (delayed irradiation). RESULTS: The bone mineral density (BMD) was significantly lower in the immediate irradiation groups. BMD was similar in the delayed irradiation group and the control group. The irradiated groups exhibited a lower bone-to-implant contact ratio, although the difference was not statistically significant. The irradiated groups also exhibited a significantly lower bone volume and higher empty lacuna count than the control groups. No implant failure due to local irradiation was found in this study. CONCLUSION: Within the limits of this study, the timing of local irradiation critically influences the bone healing mechanism, which is related to loading time of prostheses.

Temporal and Spatial Expression Patterns of miR-302 and miR-367 During Early Embryonic Chick Development

The microRNAs (miRNAs) are small, non-coding RNAs that modulate protein expression by interfering with target mRNA translation or stability. miRNAs play crucial roles in various functions such as cellular, developmental, and physiological processes. The spatial expression patterns of miRNAs are very essential for identifying their functions. The expressions of miR-302 and miR-367 are critical in maintaining stemness of pluripotent stem cells, including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) but their functions in early development are not fully elucidated. So, we used Locked Nucleic Acid (LNA) probes to perform in situ hybridization and confirmed the temporal and spatial distribution patterns during early chick development. As a result, we found that miR-302 and miR-367 were expressed in various tissues such as primitive steak, neural ectoderm, neural plate, neural fold, neural tube, notochord, and oral cavity. Specially, we confirmed that miR-302 and miR-367 were strongly expressed in neural folds in HH8 to HH10. miR-302 was expressed on dorsal part of the neural tube but miR-367 was expressed on lateral and ventral parts of the neural tube. And also we performed quantitative stem-loop real-time PCR to analyze global expression level of miR-302 and miR-367. miR-302 and miR-367 expression was sustained before Hamburger and Hamilton stage (HH) 14. Thus, the temporal and spatial expression patterns of miR-302 and miR-367 may provide us information of the role of these miRNAs on tissue formation during early chick development.

Biologic stability of plasma ion-implanted miniscrews / 대한치과교정학회지

OBJECTIVE: To gain basic information regarding the biologic stability of plasma ion-implanted miniscrews and their potential clinical applications. METHODS: Sixteen plasma ion-implanted and 16 sandblasted and acid-etched (SLA) miniscrews were bilaterally inserted in the mandibles of 4 beagles (2 miniscrews of each type per quadrant). Then, 250 - 300 gm of force from Ni-Ti coil springs was applied for 2 different periods: 12 weeks on one side and 3 weeks contralaterally. Thereafter, the animals were sacrificed and mandibular specimens including the miniscrews were collected. The insertion torque and mobility were compared between the groups. The bone-implant contact and bone volume ratio were calculated within 800 microm of the miniscrews and compared between the loading periods. The number of osteoblasts was also quantified. The measurements were expressed as percentages and analyzed by independent t-tests (p < 0.05). RESULTS: No significant differences in any of the analyzed parameters were noted between the groups. CONCLUSIONS: The preliminary findings indicate that plasma ion-implanted miniscrews have similar biologic characteristics to SLA miniscrews in terms of insertion torque, mobility, bone-implant contact rate, and bone volume rate.

Effect of alendronate on bone remodeling around implant in the rat

PURPOSE: The purpose of this study was to evaluate the effect of alendronates on bone remodeling around titanium implant in the maxilla of rats. MATERIALS AND METHODS: The maxillary first molars were extracted and customized-titanium implants were placed immediately in thirty male Sprague-Dawley rats. The rats were divided into experimental (bisphosphonate) group and control group. At 4 weeks after implantation, the rats in the bisphosphonate group were subcutaneously injected with alendronate three times a week for 6 weeks where as the rats in control group were injected with saline. The rats were sacrificed at 1, 2, 3, 4, or 6 weeks after starting of injection and maxillary bones were collected subsequently. Alveolar bone remodeling around the implants were evaluated by radiographic and histologic analysis. Microarray analysis and immunohistomorphologic analysis were also performed on one rat, sacrificed at 6 weeks after starting of injection, from each group. Statistical analysis was performed using repeated measures analysis of variance and independent t test at a significance level of 5%. RESULTS: There was no statistically significant difference in the bone area (%) around implant between the bisphosphonate group and the control group. However, the amount of empty lacuna was significantly increased in the bisphosphonate group, especially in the rats sacrificed at 4 weeks after starting of injection compared to that of the corresponding control group. The bisphosphonate group showed the same level of TRAP positive cell count, osteocalcin and angiopoietin 1 as the control group. CONCLUSION: Alendronate may not decrease the amount of osteoclast. However, the significantly increased amount of empty lacuna in the bisphosphonate group may explain the suppression of bone remodeling in the bisphosphonate group.

Expression Patterns of Ki-67, Cyclin A, and Cyclin D1 during Tooth Development / 체질인류학회지

Dental epithelial and mesenchymal cells that form the teeth undergo dynamic changes in cell cycle during tooth development and morphogenesis. Although proliferation has been known as a key event during odontogenesis, the cell cycle phases and their relations with the complicated molecular mechanisms of tooth development are not fully understood yet. This study comparatively examined the expression patterns of Ki-67, cyclin A, and cyclin D1 during tooth development in the mouse incisor and molar in order to identify the cell-cycle characteristics during odontogenesis. We found that Ki-67 and cyclin A were expressed in the proliferating cells in the dental epithelial and mesenchymal tissues at the bud, cap and bell stages. Cycln D1 showed distinct expression in the incisor odontoblast region and the enamel knot, in which Ki-67 nor cyclin A was expressed. Our results provide specific information on the cell cycle phases during tooth development that may provide clues to relate them with the complex odontogenic mechanisms. Furthermore, we suggest that our findings enlightened the previous studies on the incisor odontoblasts and the enamel knot during tooth development.

The Role of Microtubule in the Regulation of Endochondral Bone Formation in the Developing Mouse Cranial Base / 체질인류학회지

Endochondral bone formation of the developing cranial base is a complex process. This mechanism requires precise orchestration of many cellular events and cartilage matrix metabolism, such as proliferation, becoming round in shape, termination of proliferation, hypertrophic size-increase, and finally programmed cell death. Active formation and degradation of cartilage matrix take place, in which microtubules are involved for intracellular events; bone apposition follows these events. However, the involvement of microtubules during these changes in the developing cranial base has not been identified yet. Thus, we investigated the involvement of microtubules in the regulation of endochondral bone formation during cranial base development. Using tubulin-binding drug nocodazole, we examined the effects of altering the structure and function of microtubules during in vivo organ culture of the mouse cranial base. Cultured specimens were analyzed with HE staining, immunohistochemistry, and cell counting in order to study the morphological and molecular changes that occurred in the tissues. Disruption of the microtubular array by nocodazole reduced cells expressing proliferation marker Ki67, osteogenic marker BSP, and BMP4 within the sphenooccipital synchondrosis region; chondrocyte hypertrophy was ceased in the hypertrophic zone; degeneration of cartilage matrix and bone matrix apposition was inhibited in the ossification center of the basooccipital cranial base. Our data demonstrated that disruption of microtubules by nocodazole have multiple inhibitory effects on the sequential changes that occur during endochondral bone formation, suggesting the importance of normal microtubule-polymerization in cranial base development.

An Immune-compromised Method for Tooth Transplantation Using Adult Bone Marrow Stromal Cells and Embryonic Tooth Germ / 체질인류학회지

Tooth transplantation using autogenic adult teeth or embryonic tooth germs is the one of best treatments for replacement of missing teeth, but there are limitations in the accessibility. Isogenic or xenogenic tooth transplantation has been failed because of the immune rejection response occurring in the periodontal ligament of transplanted tooth. In this study, by utilizing the recombination between mouse embryonic tooth germ and mouse adult bone marrow stromal cells, we tried to replace the periodontal tissues such as periodontal ligament and alveolar bone with adult bone marrow stromal cells. At four weeks after the transplantation of the recombinant into a kidney, adult bone marrow-derived cells cells were observed in the periodontal ligament and alveolar bone. This result indicates that adult bone marrow stromal cells can participate in the formation of periodontal tissues. If these tooth and periodontal tissues are transplanted into host who donates adult bone marrow stromal cells, adult bone marrow-derived cells will be regarded as host cells, and immune rejection response will not occur in these cells. Therefore, it is suggested that recombination between adult bone marrow stromal cells and embryonic tooth germ is a good candidate method using xenogenic tooth germ for replacement of missing teeth in human by replacing cells in periodontal tissues with human adult bone marrow stromal cells.

Effects of hyaluronan on carrageenan-induced synovitis in rat TMJ / 대한해부학회지

Nitric oxide is one of many proinflammatory mediators that are involved in temporomandibular joint (TMJ) inflammatory disorder and is synthesized by inducible nitric oxide synthase (iNOS). iNOS is transcriptionally regulated by nuclear factor-kappaB (NF-kappaB) in cases of inflammation, proliferation, and apoptosis. It has also been reported that nitric oxide is positively regulated by carrageenan and negatively regulated by hyaluronan in the knee joint. The aim of this study was to histologically evaluate how inflammation and cell proliferation of the synovial membrane are affected by the exogenous administration of carrageenan and hyaluronan in the rat TMJ by investigating iNOS, NF-kappaB, and anti proliferating cell nuclear antigen (PCNA) immunoreactivity. As results, immunoreactive cells to iNOS, NF-kappaB, and PCNA were normally localized only in the synovial membrane of wild type TMJs. The numbers of immunoreactive cells were extensively larger in the carrageenan-injected synovial membranes exhibiting excessive folding, and smaller in the hyaluronan-injected synovial membranes showing a few folds. These results indicate that a carrageenan injection induced inflammation and cell proliferation especially in the synovial membrane and that hyaluronan relieved the inflammation by decreasing inflammatory molecules in the synovial membrane.

Comparison of viability of oral epithelial cells stored by different freezing methods / 대한치과보존학회지

This study examined the influence of the storage methods on the viability of oral epithelial cells using conventional cell freezing storage, slow freezing preservation, rapid freezing preservation, and slow freezing preservation with a pressure of 2 Mpa or 3 Mpa. The cell viability was evaluated by cell counting, WST-1 and the clonogenic capacity after 6 days of freezing storage. After 6 days, the frozen cells were thawed rapidly, and the cell counting, WST-1, and clonogenic capacity values were measured and compared. 1. The results from cell counting demonstrated that conventional cryopreservation, slow freezing under a 2 Mpa pressure and slow freezing under a 3 Mpa pressure showed significantly higher values than slow freezing preservation and rapid freezing preservation (p<0.05). 2. The results from the optical density by WST-1 demonstrated that slow freezing under a 2 Mpa pressure showed significantly higher values than slow freezing preservation and rapid freezing preservation (p<0.05). 3. The clonogenic capacity demonstrated that slow freezing under a 2 Mpa pressure showed significantly higher values than slow freezing preservation and rapid freezing preservation (p<0.05).

Localization Patterns of Cytokeratin 1, 14 and PAX 9 in Mouse Embryonic Tongue Development / 체질인류학회지

Epithelial differentiation and morphogenesis in skin and oral mucosa were elucidated using various experimental tools. However, tongue epithelial differentiation has not been examined properly yet. In this study, we identified the relationship between morphological changes and localizations of differentiation markers, such as cytokeratins and PAX 9 in mice embryonic tongue development. Protective barrier formation and localization pattern of cytokeratins in tongue epithelium were examined with toluidine blue staining and immunohistochemistry respectively. Localization patterns of PAX 9 and Cytokeratin 14 were coincided during tongue epithelium development. In addition, compared with Ki67 localizations, marker for cell proliferation, localization patterns of PAX 9 and Cytokeratin 14 would suggest that these factors would involve in tongue barrier formation through cell proliferation. Based on these results, tongue epithelial differentiation would begin at E14 with the specific localizations of PAX 9 and Cytokeratin 14 prior to protective barrier formation then Cytokeratin 1, keratinization marker, would involve in protective barrier and filiform papillae formations.

Point Mutation of Hoxd12 in Mice

PURPOSE: Genes of the HoxD cluster play a major role in vertebrate limb development, and changes that modify the Hoxd12 locus affect other genes also, suggesting that HoxD function is coordinated by a control mechanism involving multiple genes during limb morphogenesis. In this study, mutant phenotypes were produced by treatment of mice with a chemical mutagen, N-ethyl-N-nitrosourea (ENU). We analyzed mutant mice exhibiting the specific microdactyly phenotype and examined the genes affected. MATERIALS AND METHODS: We focused on phenotype characteristics including size, bone formation, and digit morphology of ENU-induced microdactyly mice. The expressions of several molecules were analyzed by genome-wide screening and quantitative real-time PCR to define the affected genes. RESULTS: We report on limb phenotypes of an ENU-induced A-to-C mutation in the Hoxd12 gene, resulting in alanine-to-serine conversion. Microdactyly mice exhibited growth defects in the zeugopod and autopod, shortening of digits, a missing tip of digit I, limb growth affected, and dramatic increases in the expressions of Fgf4 and Lmx1b. However, the expression level of Shh was not changed in Hoxd12 point mutated mice. CONCLUSION: These results suggest that point mutation rather than the entire deletion of Hoxd12, such as in knockout and transgenic mice, causes the abnormal limb phenotype in microdactyly mice. The precise nature of the spectrum of differences requires further investigation.

Location of the Modiolous and the Morphologic Variations of the Risorius and Zygomaticus Major Muscle Related to the Facial Expression in Koreans / 체질인류학회지

Location of the modiolous and morphological variations of the risorius and zygomaticus major muscles are related to the facial expression. The zygomaticus major, levator labii superioris, depressor labii inferioris, depressor anguli oris, risorius, orbicularis oris, buccinator and levator anguli oris muscles insert on the lateral border of the lip, forming the modiolus and mutually associating each other for functioning. The knowledge of the location of the modiolus and surrounding structures are essential to anatomy, prosthodontics, linguistic, physiology and computer simulation based on facial expressions. The authors examined the location of the modiolus, the morphological variations and anatomical relationship of risorius and zygomaticus major muscle to understand the features of the smile of Korean by dissecting 39 cadavers. The location of the modiolus can be showed as three types, according to their height related to the intercheilion horizontal line. Type A that modiolus locate at the intercheilion line was shown in 20 sides (26.0%), type B that modiolus locate above the intercheilion line was shown in 12 sides (15.6%), then type C that modiolus locate under the intercheilion line was shown in 45 sides (58.4%). Most modioli located at 10 ~20 mm lateral to the mouth corner and 0 ~10 mm below the intercheilion line. The risorius muscle was classified into five types by directions of muscle fibers. The depressor anguli oris -risorius type (type I) was observed in 31 sides (40.2%), the platisma -risorius type (type II) was observed in 30 sides (39.0%). Previously, it has been known that zygomaticus major muscle attaches to the modiolus mainly as one bundle. However, the results were clearly shown that two bundles of the zygomaticus major muscle attaches to the modiolus and the position of the mouth edge in 18 sides (23.4%). To sum it up, facial expression is of fundamental importance concerning the morphological variations and these results also can be considered for the facial reconstruction surgery and computer animation department.

A Variation of the Musculocutaneous Nerve Absent

A variation of the brachial plexus, characterized by the absence of the musculocutaneous nerve on the left arm, was found during the dissection of a 28-year old male cadaver. The whole lateral cord was joined to the median nerve, which it met in two points. One was a typical junction of both roots of the median nerve at the level of the coracoid process. The other was a junction of the remaining lateral cord and the median nerve, which was 92 mm away from the typical junction. This case provided some evidence about the absence of the musculocutaneous nerve, rather than a complete fusion of the median and musculocutaneous nerves. As the nerves are named due to their course or innervation, and not from their origin, it is reasonable to assume that the combined nerve was actually the median nerve, and that the musculocutaneous nerve did not exist.

A Variation of the Musculocutaneous Nerve Absent

A variation of the brachial plexus, characterized by the absence of the musculocutaneous nerve on the left arm, was found during the dissection of a 28-year old male cadaver. The whole lateral cord was joined to the median nerve, which it met in two points. One was a typical junction of both roots of the median nerve at the level of the coracoid process. The other was a junction of the remaining lateral cord and the median nerve, which was 92 mm away from the typical junction. This case provided some evidence about the absence of the musculocutaneous nerve, rather than a complete fusion of the median and musculocutaneous nerves. As the nerves are named due to their course or innervation, and not from their origin, it is reasonable to assume that the combined nerve was actually the median nerve, and that the musculocutaneous nerve did not exist.

Quality and Morphology on cortico-cancellous bone in Korean mandibular symphysis area / 대한치주과학회지

In performing implant procedures in the anterior portion of the maxilla, many difficulties exist because of anatomical reasons, such as the proximity of the nasal floor, lateral extension of the incisive canal, and labial concavity. On the other hand, in the posterior region of the maxilla, there is often insufficient recipient bone between the maxillary sinus and alveolar ridge due to alveolar ridge resorption and pneumatization of the maxillary sinus. In order to perform implants in such regions, ridge augmentation procedures such as onlay bone graft, guided bone regeneration, and maxillary sinus grafting are performed. In studies of Caucasians, use of autograft from mandibular symphysis has been reported to be highly successful in maxillary sinus grafting. However, in a clinical study of Koreans, autograft of mandibular symphysis has been reported to have significantly low success rate. It has been hypothesized that this is because of insufficient cancellous bone due to thick cortical bone. In order to test this hypothesis, bone quality and morphology of Koreans can be compared with those of Caucasians. In this study, the bone density and morphology of the cortical bone and cancellous bone in the mandibular symphysis of 35 Korean cadavers were evaluated. The following results were obtained: 1. In terms of bone density, type I, type II, and type III consisted of 1.4%(3/213), 72.3%(154/213), and 26.3%(56/213) of the cross-sectioned specimens, respectively. In general, the bone density tended to change from type II to type III, as cross-sectioned specimens were evaluated from the midline to the canine. Type IV wasn't observed in this study. 2. The distance between the root apex and the lower border of the cancellous bone was 18.34mm-20.59mm. Considering that the bone has to be cut 5mm below the root apex during the procedure, autografts with about 15mm of vertical thickness can be obtained. 3. The thickness of cortical bone on the labial side increased from the root apex to the lower border of the mandible. The average values ranged from 1.43mm to 2.36mm. 4. The labio-lingual thickness of cancellous bone ranged from 3.43mm to 6.51mm. The thickness tended to increase from the apex to the lower border of the mandible and decrease around the lower border of cancellous bone. From the above results, the anatomic factors of the mandibular symphysis (bone density, thickness, quantity and length of the cortical bone and cancellous bone) didn't show any difference from Caucasians, and it cannot be viewed as the cause of failure in autografts in the maxillary sinus for implants.