Three dimensional finite element analysis of the stress distribution around the mandibular posterior implant during non-working movement according to the amount of cantilever

PURPOSE: In case of large horizontal discrepancy of alveolar ridge due to severe resorption, cantilevered crown is usually an unavoidable treatment modality. The purpose of this study was to evaluate the clinical criteria for the placement of the aforementioned implant crown. MATERIALS AND METHODS: The mandible model with 2 mm thick cortical bone and cancellous bone was fabricated from CT cross-section image. An external connection type implant was installed and cantilevered crowns with increasing offset of 3, 4, 5, 6, and 7 mm were connected. Vertical load and 30degrees oblique load of 300 N was applied and stress around bone and implant component was analyzed. A total of 14 cases were modeled and finite element analysis was performed using COSMOS Works (Solid works Inc, USA). RESULTS: As for the location of the vertical load, the maximum stress generated on the lingual side of the implant became larger according to the increase of offset distance. When the oblique load was applied at 30degrees, the maximum stress was generated on the buccal side and its magnitude gradually decreased as the distance of the offset load increased to 5 mm. After that point, the magnitude of implant component's stress increased gradually. CONCLUSION: The results of this study suggest that for the patient with atrophied alveolar ridge following the loss of molar teeth, von-Mises stress on implant components was the lowest under the 30degrees oblique load at the 5 mm offset point. Further studies for the various crown height and numbers of occusal points are needed to generalize the conclusion of present study.

Changes of the Airway Space and the Position of Hyoid Bone after Mandibular Set Back Surgery Using Bilateral Sagittal Split Ramus Osteotomy Technique / 대한악안면성형재건외과학회지

PURPOSE: Although there have been several studies of reduced airway space after mandibular setback surgery using the sagittal split ramus osteotomy technique, research on the risk factors for changes of the airway space is lacking. Therefore, this study was performed to examine airway changes and the position of the hyoid bone after orthognathic surgery, and to assess possible risk factors. METHODS: In this retrospective study, 50 patients who underwent posterior displacement of the mandible by the bilateral sagittal split ramus osteotomy technique were included. Changes of the position of the hyoid bone and the airway space were analyzed over various follow-up periods, using cephalometric radiography taken preoperatively, immediately after surgery, eight weeks after surgery, six months after surgery, and one year after surgery. To identify risk factors, multiple regression analysis of age, gender, body mass index (BMI), posterior mandibular movement, and the presence of genioplasty was performed. RESULTS: Inferor and posterior movement of the hyoid bone was observed postoperatively, but subsequent observations showed regression towards the anterosuperior aspect. The airway space also significantly decreased after surgery (P<0.05), and increased slightly up until six months after surgery. The airway space significantly decreased (beta=0.47, P<0.01) as the amount of mandibular setback increased. However, age, sex, BMI, and presence of genioplasty were not associated with airway reduction. CONCLUSION: The amount of mandibular set back was significantly associated with postoperative reduction of airway space. It is necessary to establish a treatment plan considering this factor.

Modulation of osteoblastic/odontoblastic differentiation of adult mesenchymal stem cells through gene introduction: a brief review

Bone tissue engineering is one of the important therapeutic approaches to the regeneration of bones in the entire field of regeneration medicine. Mesenchymal stem cells (MSCs) are actively discussed as material for bone tissue engineering due to their ability to differentiate into autologous bone. MSCs are able to differentiate into different lineages: osteo/odontogenic, adipogenic, and neurogenic. The tissue of origin for MSCs defines them as bone marrow-derived stem cells, adipose tissue-derived stem cells, and, among many others, dental stem cells. According to the tissue of origin, DSCs are further stratified into dental pulp stem cells, periodontal ligament stem cells, stem cells from apical papilla, stem cells from human exfoliated deciduous teeth, dental follicle precursor cells, and dental papilla cells. There are numerous in vitro/in vivo reports suggesting successful mineralization potential or osteo/odontogenic ability of MSCs. Still, there is further need for the optimization of MSCs-based tissue engineering methods, and the introduction of genes related to osteo/odontogenic differentiation into MSCs might aid in the process. In this review, articles that reported enhanced osteo/odontogenic differentiation with gene introduction into MSCs will be discussed to provide a background for successful bone tissue engineering using MSCs with artificially introduced genes.

Self-inflating oral tissue expander for ridge augmentation in the severely atrophic mandible

In dentistry, tissue expanders have been used to obtain sufficient soft tissue for alveolar bone augmentation in the severely atrophic ridge. Herein, we review two cases of soft tissue augmentation using a self-inflating tissue expander in patients in the Department of Oral and Maxillofacial Surgery at Ewha Womans University Mokdong Hospital for bone graft and implant operations. The results of each patient were presented using pre-operative and post-operative radiographs and clinical exams. The results of our study indicate successful bone graft and implant surgery using a self-inflating tissue expander.

Self-inflating oral tissue expander for ridge augmentation in the severely atrophic mandible

In dentistry, tissue expanders have been used to obtain sufficient soft tissue for alveolar bone augmentation in the severely atrophic ridge. Herein, we review two cases of soft tissue augmentation using a self-inflating tissue expander in patients in the Department of Oral and Maxillofacial Surgery at Ewha Womans University Mokdong Hospital for bone graft and implant operations. The results of each patient were presented using pre-operative and post-operative radiographs and clinical exams. The results of our study indicate successful bone graft and implant surgery using a self-inflating tissue expander.

Cherubism: Review of 2 Cases

Clinical evaluation of temporomandibular joint disorder after orthognathic surgery in skeletal class II malocclusion patients

OBJECTIVES: This study was performed in order to evaluate the occurrence of temporomandibular joint disorder after surgical correction of skeletal class II malocclusion. MATERIALS AND METHODS: This study included 21 patients who underwent orthognathic surgery for the correction of dentofacial deformities by a single surgeon at Mokdong Hospital, Ewha Womans University from 2000 to 2010. They underwent bilateral sagittal split ramus osteotomy for the treatment of undesirable mandibular advancement. The temporomandibular disorder (TMD) symptoms prior to surgery were recorded and the radiographic evaluation (panorama, bone scan, and magnetic resonance imaging [MRI]) of the post-surgery temporomandibular joint (TMJ) were assessed in order to evaluate condylar resorption, remodeling and disc displacement. The minimum follow-up period, including orthodontic treatment, was 12 months. Orthognathic procedures included 1-jaw surgery (n=8 patients) and 2-jaw surgery (n=13 patients). The monocortical plate was used for bilateral sagittal split ramus osteotomy fixation. RESULTS: Among class II malocclusion patients with TMD symptom, clicking improved in 29.1%, and maximum mouth opening increased from 34.5+/-2.1 mm to 37.2+/-3.5 mm. The differences were not statistically significant, however. Radiographic changes in bone scan improved slightly based on the report by radiologist but not in TMJ dynamic MRI. CONCLUSION: No particular improvements were found in patients with joint sound only. Patients with limitation of mouth opening showed an increase in the degree of opening, but the difference was not statistically significant (P>0.05).

Customized abutment and screw-type implant prostheses after cementation based on the digital intra-oral impression technique / 대한치과보철학회지

Fixed dental prostheses such as inlay, onlay, crown, and bridge fabricated by CAD/CAM technique combined with digital impressions is getting popular due to the recent rapid progress of digital impression taking system. For the scope of implant prosthesis, however, digital intra-oral scan hasn't been actively utilized for the fabrication of superstructures. In this case report, 6 cases of titanium-milled custom abutment based on the iTero intra-oral scan data were introduced, five of them were restored with screw-type prosthesis after cementation (SCRP) and the clinical results were satisfactory on restoring the function and esthetics.

A Radiographic Evaluation of Graft Height Changes after Maxillary Sinus Augmentation according to Single-unit Implants and Multi-unit Implants / 이화의대지

OBJECTIVES: This study was performed to evaluate whether there is the difference of graft height changes in radiographic evaluation in single implants and multiple implants after maxillary sinus floor augmentation with an auto-xenograft mixture. METHODS: The study group comprised 29 patients (16 men, 13 women; mean age, 56.5+/-12.4 years; range, 27 to 87 years) treated at the implant clinic of the Ewha Womans University Mokdong Hospital. They were treated with the sinus floor augmentation of lateral window technique and simultaneous placement of dental implants. Their implants have been evaluated for 42.4+/-10.5 months. To evaluate the height of grafted material, the real implant length was compared with that of panoramic radiography evaluated by a digital caliper (PACS program), and then the real height of grafted material was assumed. SPSS 19.0 was used in statistical analysis. Wilcoxon singed rank test was utilized for P value and Mann-Whitney for statistical significance in the changes of grafted height between single implants and multiple implants. The level of statistical significance was defined as P0.001). CONCLUSION: There was no statistical significance of radiographic graft height after maxillary sinus floor augmentation between single implants and multiple implants.

The retrospective study of marginal bone loss around dental implants according to different autogenous bone grafts

INTRODUCTION: This study examined the cumulative resorption of implants placed in a severely atrophic mandible and analyzed the radiologic bone resorption in the marginal bone, after an autogenous bone graft including both block and particulates that had been harvested from the ramus and iliac crest. MATERIALS AND METHODS: A retrospective study was performed on patients who had bone grafts for augmentation followed by implant installation in the mandible area from 2003 to 2008. Twelve patients (6 men and 6 women) who received 34 implants in the augmented sites were evaluated. Cumulative radiologic resorption around the implants was measured immediately, 3 months, 6 months and 12 months after implant installation surgery. RESULTS: The installed implant in grafted bone showed 0.84 mm marginal bone resorption after 3 months and 50% total cumulative resorption after 1 year. The mean marginal bone resorption around the implant installed in the grafted bone was 0.44 mm after 3 months, 0.52 mm after 1 year, after which it stabilized. The implant survival rate was 97% (failed implant was 1/34). Marginal bone resorption of the installed implant in the autogenous onlay block bone grafts was 0.98 mm after 3 months, which was significantly higher than that of a particulated bone graft (0.74 mm) (P<0.05). CONCLUSION: An autogenous graft including block type and particulate type is a predictable procedure for the use of dental implants in a severely atrophic mandible. Implant placement in augmented areas show a relatively high survival and minimal bone loss, as revealed by a radiologic evaluation.

Comparative study on the estimated blood loss follwing to orthognathic surgeries

PURPOSE: The aim of this study was to compare the estimated blood loss and determine the change in hemoglobin depending on the combination of each orthognathic surgery. SUBJECTS AND METHODS: The subjects of this study were patients who underwent orthognathic surgery among those diagnosed with a dentofaical deformity in Mok-Dong hospital, Ewha Womans University from 2002 to 2009. One hundred patients (men - 36, women - 64, mean age of 24.5+/-4.6) participated in the study and were divided into four groups (group 1 - bilateral sagittal ramus osteotomy [BSSRO], group 2 - BSSRO+Genioplasty, group 3 - Lefort 1+BSSRO+genioplasty, group 4 - anterior segmental osteotomy on maxilla and mandible). A comparative study on the estimated blood loss (EBL), operation time, peri-operative changes in hemoglobin was performed using anesthesia records. The results were analyzed statistically using a Mann-Whitney U-test and Spearman's Rho test - SPSS 12.0 (SPSS Inc. Chicago, IL, USA). RESULTS: In group 1 (BSSRO), the mean EBL, operation time and change in hemoglobin was 394.43+/-52.69 ml, 184+/-42.33 minutes, and 1.43, respectively, In group 2 (BSSRO+genioplasty), it was 556.32+/-63.42 ml, 231+/-37.45 minutes, and 1.80, respectively. In group 3 (Lefort 1+BSSRO+Genioplasty), it was 820.55+/-105.54 ml, 320+/-15.41 minutes, and 2.73, respectively. In group 4 (segmental osteotomy), it was 1025.39+/-160.21 ml, 355+/-20.10 minutes, and 3.33, respectively. In particular, in group 3, significant differences were observed depending on the method of the orthognathic surgery. The mean EBL in a Lefort 1 osteotomy with advancement was only 687 ml, whereas Lefort 1 osteotomy with canting correction (992 ml), even impaction (764 ml), and posterior nasal spine impaction (100 ml) showed a much higher EBL. CONCLUSION: From these results, the EBL and peri-operation hemoglobin increased as treatment plans became more complicated and increasing operation time. Safe orthognathic surgery should be performed by applying proper autologous transfusion plans based on the average EBL of each orthognathic surgery type.

Maxillary distraction osteogenesis in the management of cleft lip and palate: report of 2 cases

This study is to evaluate the growth and development of the maxilla advanced by transoral distraction osteogenesis of cleft lip and palate children. Subjects are two patients diagnosed as maxillary hypoplasia with cleft lip and palate, and followed up over 5 years after distraction. At the age of 11.4 years (mean), the distraction had been rendered and periodically taken lateral cephalograms were analysed to trace the growth of the maxilla. This cephalometric study showed continuous growth and development of the distracted maxilla to be stable through long term follow-up.

The clinical study on the sedative effect and recovery in patients undergoing intravenous conscious sedation with midazolam for mandibular third molars extraction

INTRODUCTION: This study examined the depth of sedation and the usefulness of the monitoring tool in determining the level of sedation in patients undergoing third molars extraction under conscious sedation with midazolam. MATERIALS AND METHODS: Twenty two patients undergoing third molars extraction at the department of Oral and Maxillofacial surgery, Ewha Womans Mokdong Hospital from February 2010 to April 2010 were analyzed. All patients were classified as American Society of Anesthesiologist (ASA) class I and had no contraindications tosedation. The bispectral index was recorded continually during surgery using a bispectral monitor. The initial sedation was accomplished using a 3 mg bolus of midazolam followed by a 2 mg bolus of midazolam until the level of sedation, at which the patient's eyes were closed or the subject was responsive only to loud or repeated calling of their name, was reached. All subjects were surveyed with a postoperative questionnaire to evaluate the level of sedation. RESULTS: The bispectral index (BIS) decreased approximately 5 minutes after midazolam administration, but increased at the local anesthesia injection and odontomy procedure. The amnestic effect was shown effectively in the early stages of surgery. CONCLUSION: Conscious sedation with intravenous midazolam is effective in achieving the effect of anxiolysis, analgesia and amnesia. The BIS is an objective and useful means of assessing the depth of sedation.

A 3-dimensional finite element analysis of tapered internal connection implant system (Avana SS III(R)) on different abutment connections / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare the stress distribution characteristics of four different abutment connections on SS-III(R) fixture under occlusal loading, using 3-dimensional finite element method. MATERIALS AND METHODS: The fixture of SS-III(R) (Osstem, Korea) with 4 mm diameter and 11.5 mm length and 4 types of abutments were analyzed; Solid, Com-Octa, ComOcta Gold, and Octa abutment. The models were placed in the area of first molar in the mandible. The 4 loading conditions were; (1) the vertical loading of 100 N on the central fossa, (2) the vertical loading of 100 N on the buccal cusp, (3) the 30degreesinclined loading of 100 N to lingual side on the central fossa, and (4) the 30degrees inclined loading of 100 N to the lingual side on the buccal cusp. The 3G.Author program was used, the von-Mises stress was calculated and the stress contours were plotted on each part of the implant systems and the surrounding bone structures. RESULTS: Regardless of abutment types and loading conditions, higher stress concentration was observed at the cortical bone. In cancellous bone, the highest stress was observed at apical portion and the maximum stress occurred at the implant neck. The higher internal stress was observed in the fixtures than in the bone. The lowest stress was observed at loading condition 1 and the stress concentration was also lower than any other loading conditions. CONCLUSION: Within the limitation of the result of this study, it seems that the abutment connection type does not affect much on the stress distribution of bone structure.

The synovial chondromatosis of the temporomandibular joints: review of the 4 cases

Synovial condromatosis of the temporomandibular joint (TMJ) is characterized by the presence of loose bodies (joint mices). It can be confused with temporomandibular disorder clinically, and be with chondrosarcoma histologically. The purpose of this clinical report was to review the clinical, radiological, arthroscopic findings, histological feature and the results of surgical treatment of TMJ synovial chondromatosis. Four patients presented with pain of TMJ and limited mouth opening. The dynamic magnetic resonance imaging (MRI) disclosed a characteristic morphologic changes and displacement of the meniscus with limited translation of the condyle head. Bone scans showed progressive resorptive changes with hot-uptake of the radioisotope. The synovial loose bodies in the joint spaces were removed and sent to pathology for diagnosis as the synovial chondromatosis. The follow-up examination with computed tomography (CT) and MRI revealed no evidence of recurrence and good in function until postoperative 18 months. Diagnostically, the distension of the lateral capsule and fluid findings in the joint on the MRI are very suggestive tool for this synovial chondromatosis, but they are not always detected on the preoperative MRI. Arthroscopic approaches are very useful to inspect the joint spaces and to remove the loose bodies without interruption of the whole synovial membranes.

Effects of Polycaprolactone-Tricalcium Phosphate, Recombinant Human Bone Morphogenetic Protein-2 and Dog Mesenchymal Stem Cells on Bone Formation: Pilot Study in Dogs

PURPOSE: The aim of this study was to evaluate the survival, proliferation, and bone formation of dog mesenchymal stem cells (dMSCs) in the graft material by using Polycaprolactone-tricalcium phosphate (PCL-TCP), auto-fibrin glue (AFG), recombinant human bone morphogenetic protein-2 (rhBMP-2), and dMSCs after a transplantation to the scapula of adult beagle dogs. MATERIALS AND METHODS: The subjects were two beagle dogs. Total dose of rhBMP-2 on each block was 10 microg with 50 microg/mg concentration. The cortical bone of the scapula of the dog was removed which was the same size of PCL-TCP block (Osteopore International Pte, Singapore; 5.0x5.0x8.0 mm in size), and the following graft material then was fixed with orthodontic mini-implant, Dual-top(R) (Titanium alloy, Jeil Co. Seoul, Korea). Four experimental groups were prepared for this study, Group 1: PCL-TCP + aFG; Group 2: PCL-TCP + aFG + dMSCs; Group 3: PCL-TCP + aFG + dMSCs + rhBMP-2; Group 4: PCL-TCP + aFG + dMSCs + rhBMP-2 + PCL membrane. The survival or proliferation of dMSCs cells was identified with an extracted tissue through a fluorescence microscope, H-E staining and Von-Kossa staining in two weeks and four weeks after the transplantation. RESULTS: The survival and proliferation of dMSCs were identified through a fluorescence microscope from both Group 1 and Group 2 in two weeks and four weeks after the transplantation. Histological observation also found that the injected cells were proliferating well in the G2, G3, and G4 scaffolds. CONCLUSION: This study concluded that bone ingrowth occurred in PCL-TCP scaffold which was transplanted with rhBMP-2, and MSCs did not affect bone growth. More sufficient healing time would be needed to recognize effects of dMSCs on bone formation.

Complications of the implant-supported posterior mandibularsingle restorations with mesial cantilever

PURPOSE: This retrospective study was performed to analyze the relationship between complications of the posterior mandibular single crowns and distance from the adjacent teeth to the implant. SUBJECTS AND METHODS: Of the patients who presented Ewha Womans University Mokdong Hospital and Yonsei University Dental Hospital with missing of the posterior mandibular molar and restored with implant-supported 18 Single crowns between 1996 thru 2007, 115 patients had been followed after crown delivery. The subjects were divided into complication-followed group and a control without any problems. The distance from the most distal tooth to the implant were measured. The prosthetic and biologic complications were reviewed by the cantilever distance and analyzed by abutment type, age and gender statistically using SAS version 9.1 (SAS Inc., USA). RESULTS AND CONCLUSION The results were as follows; 1) The posterior mandibular single crown with cantilever showed higher incidence of follow-up complications upon logistic analysis (p<0.05). 2) The prosthetic and biologic complications are related with the cantilever distance with 2.1 odds ratio and 3.39 cut-off value of specificity and sensitivity by SPSS 12.0. 3) The complications are neither significant in abutment types nor age and gender.

A Retrospective study of the Cumulative Survival Rate and change of peri-implant marginal bone around implants associated with maxillary sinus augmentation / 대한치과보철학회지

STATEMENT OF PROBLEM: Insertion of endosseous implants in the atrophic maxilla is often complicated because of lack of supporting bone. Augmentation of the floor of the maxillary sinus with autogenous bone & bone substitute graft has been proven to be a reliable treatment modality, at least in the short term. The aim of this study is to evaluate the factors of implant survival rate associated with maxillary sinus lift with grafts. MATERIAL AND METHODS: The sinus floor was augmented with bone grafts derived from modified Caldwell-luctechnique (71 subject, 93 sinus, 180 implants), the autogenous bone or autogenous + Bio-oss. Before implant installation the width and height of the alveolar crest were increased in the first stage procedure in 10 patients while in the other 61 patients augmentation and implant installation could be performed simultaneously width and height of the alveolar crest > 4 mm) or delayed installation. RESULTS: In all case bone volume was sufficients for implant insertion. 14 of 180 inserted implants were lost during follow up and the healing period Patient received implant supported overdenture (5 patients) or fixed bridge (62 patients). CONCLUSION: Within the limit of the result of this study, we conclude that bone grafting of the floor of the maxillary sinus floor with bone for the insertion of implants might be a reliable treatment modality and the autogenous bone graft and delayed installation method might be the factors for good results.

A Retrospective Study of the Surgical Success and Vertical Bone Resorption Rate after Autogenous Block Onlay Graft in Posterior Maxilla

PURPOSE: The purpose of this study was to evaluate the surgical success of bone reconstruction of the severely atrophic maxilla using autogenous block bone onlay graft from the ramus and ilium prior to dental implantation. And we measured the amount of vertical height change MATERIAL AND METHODS: 26 partially edentulous patients(32 case) who needed block onlay bone graft before implant placement in posterior maxillary area from 2002 to 2009 were selected for this study. Patients consisted of 20 males &6 females and the average of their age was 54.2. Patients who were treated with ramal bone were 19 case and patients who were treated with iliac bone were 11 case. Digital panoramic X-ray was taken at the day of surgery, 3 months and 6 months later after the surgery. Vertical height change&resorption rate of grafted bone were measured with the same X-rays and compared RESULTS: Two out of 32 bone grafts had to be removed because of inflamation at the grafts area(97.3%). The mean of radiographic vertical height change(change rate) of post-op. 3 month was 0.54mm(8.5%)and 6 month was 0.99mm(15.9%). Compairing to intraoral donor site(ramus), iliac bone had more vertical height change(1.18mm) at 6 month after surgery. CONCLUSIONS: Within the limit of this study, autogenous block onlay grafts can be considered a promising treatment for severely atrophic maxilla.

Survival rate of the dental implants placed in posterior maxilla without sinus augmentation

PURPOSE : The purpose of this study is to evaluate 7-year survival rate of implants placed without bone graft in posterior maxilla and compare the survival rate by the age and gender of patient, length and diameter of implant, region of implant placement, bicortical engagement of fixture, and connection of prosthesis. MATERIAL AND METHODS : 78 patients (170 implants) who visited our institution from 2002 to 2007 and were followed up with panoramic view and medical records. Kaplan-Meier survival analysis and Log Rank (Mantel-Cox) test were used. RESULTS AND CONCLUSIONS : A 7-year cumulative survival rate for implants placed in posterior maxilla without sinus graft was 95.3%. The survival rate in men was 91.8%, significantly lower than 98.8% in woman.(p0.05), while the wide platform implant resulted in 85% survival rate which was statistically lower than 98.5% in regular platform. The posterior maxillary implants engaged bicortically showed 97.6% of 7-year Survival rate, comparing 88.6% in not engaged implants. The survival rate of the single implant was 91.2%, while 98.5% in splinted prosthesis. Therefore, the bicortical engagement of the fixtures and splinted prosthesis may be recommended to get a long-term survival rate in posterior maxilla.