• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.4
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• pp.337-346
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• 2013

It is necessary to consider the median lingual foramen carefully to prevent the bleeding due to the damage of the sublingual artery for implant surgery. This study is to evaluate the frequency, location, diameter and the number of the Mandibular median lingual foramen regarding gender and age in the CBCT. Sixty two images of cone beam computed tomography (CBCT) whose visited the Chonnam National University Dental hospital from Sept. 2010 to Apr. 2011 were evaluated. Frequency, number, location and the diameter of Mandibular median lingual foramen shown in the CBCT image were evaluated. Sixty two patients (100%) had at least one median lingual foramen and fifty six patients (90.32%) had multiple foramens. Forty patients (66.13%) showed the median lingual foramen on the location between Mn. central incisors. The mean vertical position of the genial spine and the median lingual foramen was 24.21 mm and 14.52 mm, respectively. And the relative mean vertical dimension of median lingual foramen was 0.45. The mean diameter of the foramen was 0.93 mm. CBCT demonstrated the frequency, location, diameter and the number of median lingual foramen. It is necessary to take CBCT before implant placement to prevent the bleeding.

• Journal of Korean Dental Science
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• v.4 no.2
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• pp.46-51
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• 2011

Purpose: For aesthetic reasons, composite resin brackets are widely used. However, related studies are rare. This pilot study sought to compare the stress distributions in two commercially available composite resin brackets with metal slot. Materials and Methods: Two commercially available resin brackets -- full-metal slot resin bracket (fSRB) and partial-metal slot resin bracket (pSRB) with straight wire appliance dimension of $0.022{\times}0.028$ in -- were selected. In each bracket, 3-dimensional finite element models were constructed, and stress level was evaluated using finite element analysis. By loading the tipping force and torsion moment, which are similar to those applied by the stainless steel rectangular wire ($0.019{\times}0.025$ -in), stress distributions were calculated, and von Mises stress values were obtained. Results: In pSRB and fSRB, the stress value of the torque moment was much higher than that of the tipping force. The pSRB showed higher stress value than fSRB in both tipping force and torque moment because of the difference in size and configuration of the metal frame inserted into the slot. More stress was also found to be concentrated on the slot area than the wing area in fSRB. Conclusion: The slot form of fSRB was found to be more resistant to the stress of tipping and torque than the slot form of pSRB. In addition, the slot areas -- rather than the wing areas -- of the bracket showed breakage susceptibility. Therefore, resistance to the torque moment on the slot area should be considered in bracket design.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.385-396
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• 2006

For the regeneration of periodontal tissues, the microenvironment for new attachment of connective tissue fibers should be provided, At this point of view, cementum formation in root surface plays a key role for this new attachment. This study was performed to figure out which factor promotes differentiation of cementoblast Considering anatomical structure of tooth, we selected the cells which may affect the differentiation of cementoblast - Ameloblast, OD11&MDPC23 for odontoblasts, NIH3T3 for fibroblsts and MG63 for osteoblasts. And OCCM30 was selected for cementoblast cell line. Then, the cell lines were cultured respectively and transferred the conditioned media to OCCM30. To evaluate the result, Alizarin red S stain was proceeded for evaluation of mineralization. The subjected mRNA genes are bone sialoprotein(BSP), alkaline phosphate(ALP) , osteocalcin(OC), type I collagen(Col I), osteonectin(SPARC ; secreted protein acidic and rich in cysteine). Expression of the gene were analysed by RT-PCR, The results were as follows: 1. For alizarin red S staining, control OCCM30 didn't show any mineralized red nodules until 14 days. But red nodules started to appear from about 4 days in MDPC-OCCM30 & OD11-OCCM30. 2. For results of RT-PCR, ESP mRNAs of control-OCCM30 and others were expressed from 14 days, but in MDPC23-OCCM30 & OD11-OCCM30 from 4 days. Like this, the gene expression of MDPC23-OCCM30 & OD11-OCCM30 were detected much earlier than others. 3. For confirmation of odontoblast effect on cementoblast, conditioned media of osteoblasts(MG63) which is mineralized by producing matrix vesicles didn't affect on the mineralized nodule formation of cementoblasts(OCCM30). This suggest the possibility that cementoblast mineralization is regulated by specific factor in dentin matrix protein rather than matrix vesicles. Therefore, we proved that the dentin/odontoblast promotes differentiation/mineralization of cementoblasts. This new approach might hole promise as diverse possibilities for the regeneration of tissues after periodontal disease.

• Journal of Periodontal and Implant Science
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• v.36 no.2
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• pp.409-425
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• 2006

치주질환의 병원균은 세포벽의 항원에 의하여 조직내 존재하는 mononuclear phagocytes가 활성화되어 cytokine들이 생성됨 으로써 치주 결체조직의 파괴를 진행시킨다. 이런 관련된 cytokine들은 순차적으로 상주하는 치은세포 및 대식세포가 Matrix metalloproteinase 합성을 하도록 유도하여 조직파괴를 시작한다. 이들 Matrix metalloproteinase중 MMP-2, MMP-9 (Gelatinase A,B)는 type IV collagen 및 변성된 interstitial collagen을 파괴하며 치주환자의 치은 열구액, 치은조직, 타액 네에서 높게 보고 되어왔다. 당뇨병은 치주질환의 위험요소중 하나로 달뇨 환자에서는 치주질환의 유병율이 일반인에 비해 높고 치주질환의 중증도도 더 심하여 진행도 빠르다고 알려져 있다. 그 병리 기전 중 하나로는 당뇨 환자에서는 치은 열구액 내 중성구 유래의 Matrix metalloproteinase의 활성 증가 및$TNF-{\alpha}$ 의 활성 증가가 추정되고 있다. 본 실험에서는 제2형 당뇨병 환자와 비당뇨 환자들에서 만성 치주염 부위의 치은 및 건강한 치은에서 염증매개체 중 하나인 MMP-2, MMP-9 및 $TNF-{\alpha}$ 의 발현에 대해 상호 비교 분석함으로서 염증, 혈당이 미치는 영향을 밝히고 제 2형 당뇨병 환자에서 심한 치주조직 파괴의 기전을 연구하고자 하였다. 경북대학교병원 치주과 내원환자 중 제2형 당뇨병 환자와 비당뇨 환자들 및 치주질환이 없는 건강인 대조군을 대상으로 여러 가지 환자요소, 임상 치주상태를 기록하고, 전신적으로 건강한 환자의 건강한 부위(n=8,Group 1), 전신적으로 건강한 환자으 만성 치주염 부위(n=8, Group 2), 제2형 당뇨병 환자의 만성 치주염 부위 (n=8,Group 3)에서 각각 변연치은을 채득하고 액화질소에 급속 동결하였다. Western blotting을 이용하여 각 조직 내 MMP-2, MMP-9 및 $TNF-{\alpha}$ 의 발현을 관찰, densitometer를 이용하여 상대적 발현을 정량, 각 조직의${\beta}-actin$을 이용하여 표준화하여 실험군과 대조군들의 평균치를 비교하였다. 비당뇨 환자들의 만성 치주염 부위 및 제2형 당뇨병 환자의 만성 치주염 부위에서 모두 건강 대조군에 비해 MMP-2와 MMP-9 의 발현이 증가되었다. 또한 MMP-2와 MMP-9는 2형 당뇨 환자의 만성 치주염 부위가 비당뇨 환자의 만성 치주염 부위보다 증가된 발현양상을 보였으며, $TNF-{\alpha}$ 발현 비교시 각 군간 유의성 있는 변화는 없었으나 2형 당뇨환자군에서 MMP-2 및 MMP-9의 증가와 함께 다소 증가 양상을 보였다. 결론적으로 본 실험에서 MMP-2 및 MMP-9의 증가가 만성 치주염 및 2형 당뇨 환자에서의 만성치주염에서 비당뇨환자 보다 MMP-2, MMP-9의 증가양상을 보여 주었으며 $TNF-{\alpha}$ 가 2형 당뇨환자의 만성치주염 진행과정에 기여인자로써 역할을 하는 것으로 생각된다.

• The Journal of Advanced Prosthodontics
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• v.7 no.6
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• pp.468-474
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• 2015

PURPOSE. The aim of this study was to characterize and compare bacterial diversity on the removable partial denture (RPD) framework over time. MATERIALS AND METHODS. This descriptive pilot study included five women who were rehabilitated with free-end mandibular RPD. The biofilm on T-bar clasps were collected 1 week ($t_1$) and 4 months ($t_2$) after the RPD was inserted ($t_0$). Bacterial 16S rDNA was extracted and PCR amplified. Amplicons were cloned; clones were submitted to cycle sequencing, and sequences were compared with GenBank (98% similarity). RESULTS. A total of 180 sequences with more than 499 bp were obtained. Two phylogenetic trees with 84 ($t_1$) and 96 ($t_2$) clones represented the bacteria biofilm at the RPD. About 93% of the obtained phylotypes fell into 25 known species for $t_1$ and 17 for $t_2$, which were grouped in 5 phyla: Firmicutes ($t_1=82%$; $t_2=60%$), Actinobacteria ($t_1=5%$; $t_2=10%$), Bacteroidetes ($t_1=2%$; $t_2=6%$), Proteobacteria ($t_1=10%$; $t_2=15%$) and Fusobacteria ($t_1=1%$; $t_2=8%$). The libraries also include 3 novel phylotypes for $t_1$ and 11 for $t_2$. Library $t_2$ differs from $t_1$ (P=.004); $t_1$ is a subset of the $t_2$ (P=.052). Periodontal pathogens, such as F. nucleatum, were more prevalent in $t_2$. CONCLUSION. The biofilm composition of the RPD metal clasps changed along time after RPD wearing. The RPD framework may act as a reservoir for potentially pathogenic bacteria and the RPD wearers may benefit from regular follow-up visits and strategies on prosthesis-related oral health instructions.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.4
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• pp.349-357
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• 2012

The purpose of this study was to measure the thickness of the sinus lateral wall using cone-beam computed tomography (CBCT), and to find the most suitable vertical position for lateral window opening prior to sinus elevation. Fifty three patients requiring sinus elevation had CBCT scans acquired by CB MercuRay (Hitachi, Medico, Tokyo, Japan) from July, 2010 to June, 2012. The thickness of the sinus lateral wall was measured according to its vertical position against the sinus inferior border (SIB), and its mean was calculated through two repeated measurements. The thickness of the sinus lateral wall was more than 2 mm at 2 mm above the sinus inferior border (SIB+2), however, it was less than 2 mm at 3 mm above the sinus inferior border (SIB+3). In conclusion, it is recommended that the inferior border of lateral wall window be made 3 mm above the sinus inferior border during sinus elevation using the lateral approach considering the thickness of the sinus lateral wall.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.3
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• pp.176-182
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• 2020

Purpose: To evaluate the effects of load direction, number of implants, and alignment of implant position on stress distribution in implant, prosthesis, and bone tissue. Materials and Methods: Four 3D models were made to simulate posterior mandible bone block: two implants and 3-unit fixed dental prosthesis (FDP) with a pontic in the center (model M1), two implants and 3-unit FDP with a cantilever pontic at one end (model M2), FDP supported by three implants with straight line placement (model M3) and FDP supported by three implants with staggered implant configuration (model M4). The applied force was 120 N axially or 120 N obliquely. Results: Peak von Mises stresses caused by oblique occlusal force were 3.4 to 5.1 times higher in the implant and 3.5 to 8.3 times higher in the alveolar bone than those stresses caused by axial occlusal force. In model M2, the connector area of the distal cantilever in the prosthesis generated the highest von Mises stresses among all models. With the design of a large number of implants, low stresses were generated. When three implants were placed, there were no significant differences in the magnitude of stress between staggered arrangement and straight arrangement. Conclusion: The effect of staggering alignment on implant stress was negligible. However, the number of implants had a significant effect on stress magnitude.

• Molecules and Cells
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• v.42 no.11
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• pp.763-772
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• 2019

Periodontitis is characterized by the loss of periodontal tissues, especially alveolar bone. Common therapies cannot satisfactorily recover lost alveolar bone. Periodontal ligament stem cells (PDLSCs) possess the capacity of self-renewal and multilineage differentiation and are likely to recover lost alveolar bone. In addition, periodontitis is accompanied by hypoxia, and hypoxia-inducible $factor-1{\alpha}$ ($HIF-1{\alpha}$) is a master transcription factor in the response to hypoxia. Thus, we aimed to ascertain how hypoxia affects runt-related transcription factor 2 (RUNX2), a key osteogenic marker, in the osteogenesis of PDLSCs. In this study, we found that hypoxia enhanced the protein expression of $HIF-1{\alpha}$, vascular endothelial growth factor (VEGF), and RUNX2 ex vivo and in situ. VEGF is a target gene of $HIF-1{\alpha}$, and the increased expression of VEGF and RUNX2 proteins was enhanced by cobalt chloride ($CoCl_2$, $100{\mu}mol/L$), an agonist of $HIF-1{\alpha}$, and suppressed by 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1, $10{\mu}mol/L$), an antagonist of $HIF-1{\alpha}$. In addition, VEGF could regulate the expression of RUNX2, as RUNX2 expression was enhanced by human VEGF ($hVEGF_{165}$) and suppressed by VEGF siRNA. In addition, knocking down VEGF could decrease the expression of osteogenesis-related genes, i.e., RUNX2, alkaline phosphatase (ALP), and type I collagen (COL1), and hypoxia could enhance the expression of ALP, COL1, and osteocalcin (OCN) in the early stage of osteogenesis of PDLSCs. Taken together, our results showed that hypoxia could mediate the expression of RUNX2 in PDLSCs via $HIF-1{\alpha}$-induced VEGF and play a positive role in the early stage of osteogenesis of PDLSCs.

• Journal of Periodontal and Implant Science
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• v.51 no.4
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• pp.264-275
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• 2021

Purpose: Periodontitis is considered a local risk factor for medication-related osteonecrosis of the jaws (MRONJ). However, little is known about the progression of periodontitis in the presence of zoledronic acid (ZOL). The aim of this study was to evaluate the effects of the systemic use of ZOL on the progression of experimental periodontitis (EP) in rats, as ZOL could modulate the progression of periodontitis and concomitantly cause MRONJ in individuals with periodontitis. Methods: Forty-eight male Wistar rats were randomly distributed in 6 groups (n=8 each). To induce EP, ligatures were placed around the right first mandibular molars. Three groups were treated with ZOL (0.15 mg/kg/week, intraperitoneal), and 3 with 0.9% saline solution (controls). In the ZOL/Lig30 and ZOL/Lig 15 groups, after 4 weeks of treatment with ZOL, EP was induced and euthanasia was performed after 30 and 15 days of EP induction, respectively. In both groups, the animals continued to receive ZOL after EP until the end of the experiment. In the Lig/ZOL group, EP was induced first, and 15 days later, ZOL was administered for 8 weeks, with euthanasia 1 week after the last dose. After euthanasia, the mandibles were evaluated using micro-computed microtomography (micro-CT) and histomorphometry. Bone loss was measured, and the presence of osteonecrosis was evaluated histologically. The data were evaluated using the Student t-test and the Mann-Whitney test, with a significance level of 5%. Results: In the Lig/ZOL group, micro-CT revealed less alveolar bone resorption in the distal root (P<0.01) than in the control group (Lig/Con). Histomorphometric analysis confirmed less alveolar bone resorption in the Lig/ZOL group (P=0.001). Histologically, osteonecrosis was more common in the ZOL groups. Conclusion: ZOL decreased alveolar bone resorption in rats with EP. However, it presented a higher risk for MRONJ.

• Journal of Periodontal and Implant Science
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• v.49 no.3
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• pp.138-147
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• 2019

Purpose: Several studies have shown that the oral cavity is a secondary location for Helicobacter pylori colonization and that H. pylori is associated with the severity of periodontitis. This study investigated whether H. pylori had an effect on the periodontium. We established an invasion model of a standard strain of H. pylori in human periodontal ligament fibroblasts (hPDLFs), and evaluated the effects of H. pylori on cell proliferation and cell cycle progression. Methods: Different concentrations of H. pylori were used to infect hPDLFs, with 6 hours of co-culture. The multiplicity of infection in the low- and high-concentration groups was 10:1 and 100:1, respectively. The Cell Counting Kit-8 method and Ki-67 immunofluorescence were used to detect cell proliferation. Flow cytometry, quantitative real-time polymerase chain reaction, and western blots were used to detect cell cycle progression. In the high-concentration group, the invasion of H. pylori was observed by transmission electron microscopy. Results: It was found that H. pylori invaded the fibroblasts, with cytoplasmic localization. Analyses of cell proliferation and flow cytometry showed that H. pylori inhibited the proliferation of periodontal fibroblasts by causing G2 phase arrest. The inhibition of proliferation and G2 phase arrest were more obvious in the high-concentration group. In the low-concentration group, the G2 phase regulatory factors cyclin dependent kinase 1 (CDK1) and cell division cycle 25C (Cdc25C) were upregulated, while cyclin B1 was inhibited. However, in the high-concentration group, cyclin B1 was upregulated and CDK1 was inhibited. Furthermore, the deactivated states of tyrosine phosphorylation of CDK1 (CDK1-Y15) and serine phosphorylation of Cdc25C (Cdc25C-S216) were upregulated after H. pylori infection. Conclusions: In our model, H. pylori inhibited the proliferation of hPDLFs and exerted an invasive effect, causing G2 phase arrest via the Cdc25C/CDK1/cyclin B1 signaling cascade. Its inhibitory effect on proliferation was stronger in the high-concentration group.