• International Journal of Oral Biology
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• v.35 no.4
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• pp.145-151
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• 2010

Periodontitis is an inflammatory disorder of the periodontium and is characterized by destruction of the tooth supporting tissues, mediated by the upregulation of synthesis and release of a variety of pro-inflammatory factors. Inflammatory cytokines and prostaglandins upregulate RANKL and its subsequent binding to RANK stimulates osteoclast formation, resorption activity, and survival. In our present study, we investigated the effects of HP08-0111, composed of Coptis japonica (Thunb.) Makino, vitamin C and vitamin E, upon inflammatory responses, osteoclastogenesis and alveolar bone loss. HP08-0111 decreased the expression of IL-1$\beta$ and COX2 on LPS-induced RAW 264.7 cells and inhibited osteoclast-specific genes such as c-Fos, MMP-9, and TRAP. HP08-0111 also exhibited protective effects against alveolar bone loss in rats with ligature-induced periodontitis. Our results suggest that HP08-0111 is potentially an important therapeutic tool for the treatment of disorders associated with bone loss such as periodontitis.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.1-11
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• 1991

A two dimensional finite element method was used to analyze the changes in mechanical behavior of the supporting structures when a fixed prosthesis replaced a mandibular 1st molar. In the unrestored situation as the degree of bone resorption increased, there was a corresponding increase in stress in the periodontium. Tilting of the molar abutment induced the additional stress on the mesial side of the root. The presence of a fixed prosthesis markedly reduced the magnitude and distribution of stress in the periodontium. The mechanical advantage obtained by a fixed prosthesis was greater in the situation of a tilted 2nd molar with reduced bone support than with the higher bone levels.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.1
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• pp.59-72
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• 2000

This study was performed to investigate the effects of tooth mobility and design of the direct retainer on the stress of supporting tissues in distal extension removable partial denture. Tooth mobility was simulated and four different types of direct retainer such as Alters clasp, I-bar clasp, wrought wire clasp, and Dalbo attachment were designed and stress on the support-ing tissues were measured and analyzed with straingauge method. The following conclusions were drawn from this study. 1. The stress revealed at the lingual side of alveolar bone of the abutment tooth in edentulous area was the largest. 2. The stress at the lingual side of alveolar bone of the abutment tooth in edentulous area was increased according to the increase of tooth mobility in I-bar clasp and Dalbo attachment. 3. The stress at the residual ridge crest was the great in Dalbo attachment on mobility 0, in I-bar clasp on mobility 1, and in wrought wire clasp on mobility 2. 4. There was little changes of stress according to the increase of tooth mobility at buccal and lingual side of the residual ridge crest and around the abutment teeth in dentulous area.

• Journal of Periodontal and Implant Science
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• v.37 no.3
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• pp.543-551
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• 2007

When clinicians faced with an insufficient volume of supporting bone on ideally esthetic and bio-mechanical position for dental implantation, guided bone regeneration(GBR) was indicated. Although GBR has wide application at clinic, proper time of membrane removal remains qustionable in using non-resorbable membrane, such as non-expanded polytetrafluoroethylene(PTFE), The aim of this study was to compare the effect of maintenance period of PTFE membrane on bone regeneration in rabbit calvarial defects. Eight adult New Zealand white female rabbits were used in this study. Four defects were surgically made in their calvaria. Using a trephine bur, 4 'through and through' defects were created and classified into 3 groups, which were consisted of control group(no graft), experimental group 1(autogenous bone)and experimental group 2(deproteinized bovine bone; $OCS-B^{(R)}$). The defects were covered with PTFE membrane($Cytoplast^{(R)}$). Membranes were removed after 1, 2, 4 and 8 weeks post-GBR procedure in 2 rabbits repectively, All rabbits were sacrificed after 8 week post-GBR procedure. Specimens were harvested and observed histologically. The results were as follow; 1) The use of graft material and membrane was necessary in GBR procedure. 2) When PTFE membranes were removed early, the most favorable bone regeneration was revealed in experimental group T, followed by experimental group II and control group. 3) On GBR, it is recommended that membrane should maintain for 4 weeks with autogenous graft. As well, the use of xenograft need longer maintenance period than autogenous bone. Further evaluations will be needed, such as histomorphologic research, more species and different kinds of graft materials. And on the basis of these studies, clinical researches would be required.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.2
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• pp.116-126
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• 2009

The use of short implants has been accepted risky from biomechanical point of view. However, short implants appear to be a long term viable solution according to recent clinical reports. The purpose of this study was to investigate the effect of different diameter and length of implant size to the different type of bone on the load distribution pattern. Stress analysis was performed using 3-dimensional finite element analysis(3D-FEA). A three-dimensional linear elastic model was generated. All implants modeled were of the various diameter(${\phi}4.0$, 4.5, 5.0 and 6.0 mm) and varied in length, at 7.0, 8.5 and 10.0 mm. Each implant was modeled with a titanium abutment screw and abutment. The implants were seated in a supporting D2 and D4 bone structure consisting of cortical and cancellous bone. An amount of 100 N occlusal load of vertical and $30^{\circ}$ angle to axis of implant and to buccolingual plane were applied. As a result, the maximum equivalent stress of D2 and D4 bones has been concentrated upper region of cortical bone. As the width of implant is increased, the equivalent stress is decreased in cancellous bone and stress was more homogeneously distributed along the implants in all types of bone. The short implant of diameter 5.0mm, 6.0mm showed effective stress distribution in D2 and D4 bone. The oblique force of 100N generated more concentrated stress on the D2 cortical bone. Within the limitations of this study, the use of short implant may offer a predictable treatment method in the vertically restricted sites.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.5
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• pp.507-524
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• 2002

Load transfer of implant overdenture varies depending on anchorage systems that are the design of the superstructure and substructure and the choice of attachment. Overload by using improper anchorage system not only will cause fracture of the framework or screw but also may cause failure of osseointegration. Choosing anchorage system in making prosthesis, therefore, can be considered to be one of the most important factors that affect long-term success of implant treatment. In this study, in order to determine the effect of anchorage systems on load transfer in mandibular implant overdenture in which 4 implants were placed in the interforaminal region, patterns of stress distribution in implant supporting bone in case of unilateral vertical loading on mandibular left first molar were compared each other according to various types of anchorage system using three-dimensional photoelastic stress analysis. The five photoelastic overdenture models utilizing Hader bar without cantilever using clips(type 1), cantilevered Hader bar using clips(type 2), cantilevered Hader bar with milled surface using clips(type 3), cantilevered milled-bar using swivel-latchs and frictional pins(type 4), and Hader bar using clip and ERA attachments(type 5), and one cantilevered fixed-detachable prosthesis(type 6) model as control were fabricated. The following conclusions were drawn within the limitations of this study, 1. In all experimental models. the highest stress was concentrated on the most distal implant supporting bone on loaded side. 2. Maximum fringe orders on ipsilateral distal implant supporting bone in a ascending order is as follows: type 5, type 1, type 4, type 2 and type 3, and type 6. 3. Regardless of anchorage systems. more or less stresses were generated on the residual ridge under distal extension base of all overdenture models. To summarize the above mentioned results, in case of the patients with unfavorable biomechanical conditions such as not sufficient number of supporting implants, short length of the implant and unfavorable antero-posterior spread. selecting resilient type attachment or minimizing distal cantilever bar is considered to be appropriate methods to prevent overloading on implants by reducing cantilever effect and gaining more support from the distal residual ridge.

• Journal of Periodontal and Implant Science
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• v.38 no.3
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• pp.429-436
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• 2008

Purpose: The goal of periodontal regenerative therapy is to replace bone, cementum, and periodontal ligament on a previously diseased root surface, which has suffered the loss of these supporting structures. To accomplish the regeneration, a number of surgical procedures have been advocated throughout the years. There seems to be a potential for some spontaneous periodontal tissue regeneration in the bottom of periodontal defect following open flap debridement alone. The aim of this study was to analyse the radiographic bone changes over 2-year after flap operation. Material and Methods: Patients attending the department of periodontics of Kyungpook National University Hospital were studied. Patients had clinical and radiographic evidence of infrabony defect(s). forty two sites of 33 patients aged 26 to 65 (mean age 45.5) were treated by flap operation with or without osseous surgery. Baseline and over 2-year follow-up radiographs were collected and evaluated for this study. Radiographic assessment includes a bone fill, bone crest change, defect resolution, and % of defect resolution. Pre- and post-treatment differences between variables (maxilla and mandible, gender, defect depth, defect angle) using the paired t-test were examined. Result: We observed 0.74 mm of bone fill, 0.66 mm of crestal resorption, 1.40 mm of defect resolution, and 27% of percentage of defect resolution. Mandible, women, deeper initial defect depth, narrower initial defect angle showed greater bone fill, defect resolution, and % of defect resolution. Conclusion: The results of this study suggest that the use of flap operation did enhance the outcome in terms of radiographically detectable bone fill. Both treatment resulted in some loss of crestal bone height.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.257-268
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• 2003

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis according to position and direction of load, under vertical and inclined loading using FEA analysis. The finite element model was designed according to standard fixture (4.1mm restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric usp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant in both vertical and oblique loading but stresses in the cancellous bone were low in both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. 4. The relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 5. The magnitude of the stress in the supporting bone, fixture and abutment screw was greater with the outward oblique loading than with the inward oblique loading and was the greatest under loading at the centric cusp in a $30^{\circ}$ outward oblique direction. Conclusively, this study provides evidence that bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. But it seems to be more important that how long is the distance from center of rotation of the implant itself to the resultant line of force from occlusal contact(leverage). The goal of improving implants should be to avoid bending of the implant.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.632-649
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• 1996

The purpose of this study was to examine, by the method of 3-dimentional finite element analysis. how infraocclusion affected the stress distribution in surrounding bone and osseointegrated prosthesis. The 3-dimentional finite element mandibular models were made, in which the first and second molars were removed and the two osseointegrated implants were placed in the first and second molar sites and implant supported fixed prostheses were constructed. Analysis of equivalent stress and displacement induced by strong occlusion or infraocclusion was performed under vertical or inclined distributed loads. The results were as follows; 1. Under vertical load of 50N or 500N, the model in which infraocclusion had not been allowed showed greater stress on implants and the supporting bone than on natural teeth. 2. In the model in which infraocclusion of $30{\mu}m$ had been allowed, implant-prosthesis on the molars had no contact with opposing teeth under vertical load of 50N, However with the same allowed infraocclusion and the model under vertical load of 500N, implant prosthesis on the second molar had contact with opposing teeth, and stress distribution occured properly on natural teeth and implants. 3. Under $45^{\circ}$ inclined load, the model in which infraocclusion had not been allowed showed greater stress on implants and the supporting bone than on natural teeth. There was greater stress in the case of $45^{\circ}$ inclined load than in the case of vertical load. 4. Under $45^{\circ}$ inclined load of 50N or 500N, the model in which infraocclusion of $30{\mu}m$, had been allowed showed no occlusal contact on the implants and occlusal contact on the natural teeth. 5. In partially edentulous cases with implant supported prosthesis, we can prevent excessive load on implants by allowing infraocclusion.

• International Journal of Oral Biology
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• v.36 no.4
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• pp.187-194
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• 2011

Periodontitis is an inflammatory disorder of the periodontium, characterized by destruction of the tooth supporting tissues including alveolar bone and mediated by various pro-inflammatory mediators. Here, we demonstrated that HP08-0106, composed of four crude drugs-Gardenia jasminoides Grandiflora, Angelica gigas Nakai, Rehmannia glutinosa, and Schizonepeta tenuifolia in a weight ratio of 2:2:1:2, perturbs inflammatory responses, osteoclast formation in LPS-induced RAW 264.7 cells and alveolar bone resorption in ligature-induced periodontitis. HP08-0106 decreased the protein level of iNOS and COX2 as well as the secreted level of IL-$1{\beta}$, indicating that HP08-0106 has antiinflammatory effects. HP08-0106 also inhibited the expression of genes associated with osteoclastogenesis including c-Fos, MMP-9 and TRAP. Moreover, HP08-0106 exhibited a protective effect from alveolar bone loss in ligature-induced periodontitis animal models. Our results strongly suggest that HP08-0106 represent an important therapeutic tool to treat inflammatory disorders associated with bone loss such as periodontitis.