The non-linear FEM analysis of different connection lengths of internal connection abutment

Purpose: This study is aimed to assess changes of stress distribution dependent on different connection lengths and placement of the fixture top relative to the ridge crest. Materials and methods: The internal-conical connection implant which has a hexagonal anti-rotation index was used for FEM analysis on stress distribution in accordance with connection length of fixture-abutment. Different connection lengths of 2.5 mm, 3.5 mm, and 4.5 mm were designed respectively with the top of the fixture flush with residual ridge crest level, or 2 mm above. Therefore, a total of 6 models were made for the FEM analysis. The load was 170 N and 30-degree tilted. Results: In all cases, the maximum von Mises stress was located adjacent to the top portion of the fixture and ridge crest in the bone. The longer the connection length was, the lower the maximum von Mises stress was in the fixture, abutment, screw and bone. The reduction rate of the maximum von Mises stress depending on increased connection length was greater in the case of the fixture top at 2 mm above the ridge crest versus flush with the ridge crest. Conclusion: It was found that the longer the connection length, the lower the maximum von Mises stress appears. Furthermore, it will help prevent mechanical or biological complications of implants.ope

Titanium-zirconium alloy narrow-diameter implants for the rehabilitation of horizontally deficient mandibular posterior edentulous ridges

In case of the insufficient horizontal bone loss, a regular diameter implant is not possible without lateral bone augmentation. In this situation, narrow diameter implants (NDIs) could be the alternative to lateral bone augmentation procedures. However, complication generally expected with the NDI is implant fracture. Recently, the survival rate and success rate of NDI in the posterior region are similar to that of standard-diameter implants (SDIs). These 3 case reports demonstrate the incorporation of NDI to replace missing mandibular posterior teeth. So far, the follow-up examination period was maintained and no unusual complications were presented for more than four years. Long term follow-up clinical data are needed to confirm the excellent clinical performance of these implants.ope

Investigation of Pathogenic Genes in Peri-Implantitis from Implant Clustering Failure Patients: A Whole-Exome Sequencing Pilot Study

Peri-implantitis is a frequently occurring gum disease linked to multi-factorial traits with various environmental and genetic causalities and no known concrete pathogenesis. The varying severity of peri-implantitis among patients with relatively similar environments suggests a genetic aspect which needs to be investigated to understand and regulate the pathogenesis of the disease. Six unrelated individuals with multiple clusterization implant failure due to severe peri-implantitis were chosen for this study. These six individuals had relatively healthy lifestyles, with minimal environmental causalities affecting peri-implantitis. Research was undertaken to investigate pathogenic genes in peri-implantitis albeit with a small number of subjects and incomplete elimination of environmental causalities. Whole-exome sequencing was performed on collected saliva samples via self DNA collection kit. Common variants with minor allele frequencies (MAF) > = 0.05 from all control datasets were eliminated and variants having high and moderate impact and loss of function were used for comparison. Gene set enrichment analysis was performed to reveal functional groups associated with the genetic variants. 2,022 genes were left after filtering against dbSNP, the 1000 Genomes East Asian population, and healthy Korean randomized subsample data (GSK project). 175 (p-value <0.05) out of 927 gene sets were obtained via GSEA (DAVID). The top 10 was chosen (p-value <0.05) from cluster enrichment showing significance of cytoskeleton, cell adhesion, and metal ion binding. Network analysis was applied to find relationships between functional clusters. Among the functional groups, ion metal binding was located in the center of all clusters, indicating dysfunction of regulation in metal ion concentration might affect cell morphology or cell adhesion, resulting in implant failure. This result may demonstrate the feasibility of and provide pilot data for a larger research project aimed at discovering biomarkers for early diagnosis of peri-implantitis.ope

Clinical application of implant assisted removable partial denture to patient who underwent mandibular resection with oral cancer:A case report

Mandible defects could be caused by congenital malformations, trauma, osteomyelitis, tumor resection. If large areas are included for reconstruction, those are primarily due to tumor resection defects. The large jaw defect results in a problem about mastication, swallowing, occlusion and phonetics, and poor esthetics causes a lot of inconvenience in daily life. It is almost impossible to be a part underwent mandibular resection completely reproduced, should be rebuilt artificially. This case is of a patient who was diagnosed with squamous cell carcinoma pT1N0M0, stage I in February 2004 and received surgery (combined mandibulectomy and neck dissection operation (COMMANDO) in oromaxillofacial surgery) in March 2004, by implant assisted removable partial denture. We could obtain good retention and stability through sufficient coverage and implant holding. Follow up period was about four years. Mandibular left third molar regions have been observed to have resorption of surrounding bone, and periodic check-ups are necessary conditions.ope

Marginal tissue response to different Implant neck design

STATEMENT OF PROBLEM: Loss of the marginal bone to the first thread have been accepted but continuous effort have been made to reduce this bone loss by varying implant design and surface texture. PURPOSE: This animal study has examined the histomorphometric variations between implants with micro-thread, micro-grooved and turned surfaced neck designs. MATERIAL AND METHODS: Four mongrel dogs have been used the premolars removed and left to heal for three months. One of each implant systems with turned neck, micro-thread and micro-grooved were placed according to the manufacturers' protocol and left submerged for 8 and 12 weeks. These were then harvested for histological examination. RESULTS: The histologically all samples were successfully ossointegrated and active bone remodelling adjacent to implants. With the micro-grooved implants 0.40 mm and 0.26 mm of the marginal bone level changes were observed at 8 and 12 weeks respectively. The micro-threaded implants had changes of 0.79 mm and 0.56 mm at 8 and 12 weeks respectably. The turned neck designed implants had marginal bone level changes of 1.61 mm and 1.63 mm in 8 and 12 weeks specimens. A complex soft tissue arrangement could be observed against micro-threaded and micro-grooved implant surfaces. CONCLUSION: Within the limitations of this study, it could be concluded that implants with micro-grooved had the least and the turned neck designed implants had the most changes in the marginal bone level. The textured implant surfaces affect soft tissue responses.ope

Genetic investigation of bisphosphonate-related osteonecrosis of jaw (BRONJ) via whole exome sequencing and bioinformatics

Complications associated with the use of bisphosphonate (BP) have risen over the years due to an increase in the prescription of BP. BP-related osteonecrosis of jaw (BRONJ), one of the complications linked to the consumption of BP, greatly affects patients with minor dental trauma, incurring a long healing period. While BRONJ afflicts only a minority of patients prescribed with BP, BRONJ is a multigenic disease affected both by environmental and genetic factors having a distinctive phenotype. This study aims to discover genetic biomarkers associated with BRONJ via whole exome sequencing (WES) followed by statistical analysis. Sixteen individuals who had been prescribed with bisphosphonate medication and diagnosed as BRONJ were chosen and each individual's saliva sample was collected for WES. 126 randomized subsamples from the GSK project representing 109 male and 17 female Koreans were used as a control data set. Fisher's exact test was carried out to assess the significance of genetic variants in BRONJ patients. Gene set enrichment analysis (GSEA) (DAVID Bioinformatics Resource 6.7) was used to perform a cluster analysis of variants found from Fisher's exact test. The results from this study suggest that BRONJ-inducing factors are genetically associated and BRONJ occurs due to the malfunctioning of post-translational modification in osteoclast leading to the impairment of cell morphology and adhesion.ope

Impact of immediate and non-immediate provisionalization on the soft tissue esthetics of final restorations on immediately placed implants

STATEMENT OF PROBLEM: Interpoximal papilla could be re-established without immeidate support with a provisional resotration following an immdiate implant placement. PURPOSE: Successful esthetic outcomes were reported utilizing immediate provisionalization following immediate implant placements. The aim of this study was to evaluate the soft tissue esthetics around immediately placed single tooth implant restorations with or without immediate provisional restorations. METHODS: A total of ten patients, who had a hopeless maxillary anterior tooth, were enrolled in this study. Screw retained provisional restorations were delivered to the randomly chosen 5 patients (immediate provisionalization group) on the day of immediate implant placement and maintained for about 5 months. For the remaining five patients (non-immediate provisionalization group), healing abutments were delivered on the day of surgery, replaced with screw retained provisional restorations approximately 3 months afterwards, and the provisional restorations were maintained for about 3 months. Digital photographs were taken at the delivery of final restorations in order to assess following variables; mesial papilla, distal papilla, soft tissue level, soft tissue contour and facial soft tissue prominence. The variables were compared to those of the contralateral natural tooth and scored by prosthodontists, periodontists, orthodontists and dental students. RESULTS: The immediate provisionalization group marked significantly higher scores on the following variables; soft tissue level and facial soft tissue prominence. In evaluating each variable, there were no notable differences in opinion between four dentist groups. CONCLUSION: Immediate provisionalization can be a treatment option to achieve superior soft tissue esthetics around immediately placed single implant restorations rather than non-immediate provisionalization approachesope

Morphometric analysis of maxillary alveolar regions for immediate implantation

PURPOSE: The purpose of this study was to provide an actual guideline in determining the shape, diameter, and position of the implant in immediate implantation by the measurement of the thickness of facial and palatal plate, the thickness of cortical bone on the facial and palatal plate, the diameter of the root, and the distance between the roots in the cadavers. MATERIALS AND METHODS: The horizontal sections of 20 maxillae were measured and analyzed to obtain the average values. Resin blocks were produced and cut serially at 1 mm intervals from the cervical line to the root apex. Images of each section were obtained and the following measurements were performed: The thickness of the facial and palatal residual bone at each root surface, the thickness of the facial and palatal cortical bone at the interdental region, the diameter of all roots of each section on the faciopalatal and mesiodistal diameter, and the interroot distance. Three specimens with measurements close to the average values were chosen and 3-dimensional images were reconstructed. RESULTS: The thickness of the facial and palatal cortical bone at the interdental region in the maxilla, the buccal cortical bone was thicker in the posterior region compared to the anterior region. The interroot distance of the alveolar bone thickness between the roots increased from anterior to posterior region and from coronal to apical in the maxilla. CONCLUSION: In this study, the limited results of the morphometric analysis of the alveolar ridge using the sections of maxilla in the cadavers may offer the useful information when planning and selecting optimal implant for immediate implantation in the maxilla.ope

(A) study of photoelastic stress patterns produced by abutment retainer designs fot tooth-supported dentures

치의학과/박사[한글] 소수의 치아만이 잔존해있는 경우 잔존치아와 지지조직의 건강을 유지하고 기능적으로 유리한보철물을 제작하기 위해서 지대치의 유지장치 설계에 다양한 의견과 논란이 계속되어 왔다. 저자는 하악 좌우 견치만 잔존된 경우, 11가지의 서로 다른 유지장치를 설계하여 지대치 주위조직 및 잔존치조제로의 응력 분포 및 정도를 광탄성학적으로 관찰하여 다음과 같은 결론을 얻었다. 1. Short coping을 설계한 경우, 지대치로의 응력 집중이 가장 적었고 long coping을 설계한 경우 가장 컸다. 2. Rest를 설치하지 않은 wrought-wire clasp를 설계했을 때, 후방 잔존치조제로의 응력분산 효과를 얻을 수 있었으나 지대치에 torquing force가 컸다. 3. Bona-ball anchor attachment를 설계시 응력분포 및 크기는 bar type attachment의 경우와 차이가 거의 없었다. 4. Bar type attachment중 Hader bar가 지대치에 torquing force를 가장 적게 주었고 Ceka tissue bar가 가장 컸다. 5. 수직 성분의 완압장치를 가진 attachment가 비완압형 attachment보다 지대치 부위에 응력 집중이 적었고, 후방 잔존치조제에 보다 많이 분포되었다. [영문] When only a few teeth remained, most teeth ale unacceptable as abutments for conventional restorations. In the selection of an abutment design, the clinician has to choose the one that provides the most equitable distribution of the forces of mastication. The purpose of this study was to compare the transfer of tories from the dentures to the supporting structures of the abutment teeth and the posterior edentulous ridges by eleven abutment designs for tooth-supported dentures, including short coping, long coping, Bona-ball anchor, bar type attachments and wrought-wire clasp partial denture without rest. The following conclusions are based on the investigation utilizing photoelastic models to provide more thorough guidelines for abutment design, selection, and potential clinical use: 1. The short coping design produced least stress concentration on the abutment teeth and the long coping design produced most stress concentration. 2. The wrought-wire clasp partial denture without rest appeared to share the forces of occlusion between abutments and the posterior edentulous regions, but produced higher torquing forces on the abutment teeth. 3. The Bona-ball anchor attachment produced similar stress distribution and concentration with the bar type attachments. 4. Of the bar type attachments tested, the Hader bar produced least torquing forces and the Ceka tissue bar produced most torquing forces on the abutment teeth. 5. The vertical resilient type attachments produced less stress concentration to the abutment teeth, and distributed more stress to the posterior regions than the nonresilient type attachments.restrictio

(An) experimental study of marginal distortion related to various alloys in ceramo-metal restorations

치의학과/석사[한글] 도재 용착시에 야기되는 금속관의 변형은 결국 도재용착주조금관이 완성된 후 치아에 적합성을 불량하게 한다. 이와같은 변형을 방지하기 위해서는 금속관의 강성의 개선이 필요하다. 본 연구의 목적은 물리적 성질이 상이한 금 합금, 은-팔라듐 합금 및 두 종류의 니켈-크로뮴 합금 4종류를 선택하여 도재 용착시 금속관의 치경부 변연에서 야기되는 변형의 양을 비교하고자 하였다. 이에 저자는 각 합금 종류에 따라 5개씩의 도재용착주조금관을 위한 금속관을 주조한 후, 치경부 변연에서 순설측과 근원심측으로의 거리를 Universal measuring microscope를 사용하여 측정한 것을 기준으로 하여 degassing후 및 도재 용착 후에 각기 재측정하여 치경부 변연에서의 변형량을 합금 종류에 따라 비교했고, 니켈-크로뮴합금 경우에는 금속관의 금속 두께를 0.5mm 이외에 0.2mm로 감소시켜 제작하여 0.5mm두께로 제작한 군과 변형량을 비교한 결과 다음과 같은 결론을 얻었다. 1. 모든 금속관은 도재 용착 후, 치경부 변연의 변형을 초래했고, 순설측 및 근원심측에서의 변형은 모두 수축하는 경향을 보였다. 2. 금속관의 veneered area의 금속 두께를 0.5mm로 제작했을때, 도재 용착 후 순설측에서의 수축 변형은 Degudent G에 비해 JP92, Verabond와 RexilliumⅢ가 적은 양으로 나타났으며, Verabond와 RexilliumⅢ의 두께를 0.2nm로 하였을 때는 Degudent G의 변형량과 비교시 별차이가 없었다. 3. 도재 용착 후 JP92. Verabond와 RexilliumⅢ에서 근원심측의 수축 변형량은 Degudent G에 비해 변형량이 적었다. AN EXPERIMENTAL STUDY OF MARGINAL DISTORTION RELATED TO VARIOUS ALLOYS IN CERAMO- METAL RESTORATIONS Dong Hoo Han, D.D.S. Dept. of Dental Science, The Graduate School, Yonsei University. (Directed by Associate Prof. Ho Yong Lee, D.D.S., M.S.D., Ph.D.) Although castings suitable for veneering with porcelain can be made with the same precision as any other, baking the porcelain veneer presents additional distortion in the final restoration. So, it does not always fit as well after the application of the porcelain veneer. To ensure resistance to such a distortion, it is necessary to improve the rigidity of the metal coping. The purpose of this study was to compare the susceptibility to marginal distotion of each of the various ceramo-metal alloys. Materials used in this experiment were four kinds of precious, semi-precious, and non-precious ceramo-metal alloys, and Ceramco vaccum-fired porcelain. The author made five metal copings in each alloy and the porcelain was fired on each metal coping by the method to be recommended by the manufacturers. In addition to that, metal thickness of the veneered area decreased to 0.2mm in case of metal copings made of two kinds of nonprecious alloy. Measurements were made labiolingual diameter and mesiodistal diameter with Universal measuring microscope and recorded at 3 stages; (1) before any firing procedures, (2) following degassing,(3) following final glazing. The obtained result could be summarized in the followings ; 1. On all metal copings evaluated in this study, distortion of cervical margin was shown after porcelain was fired, and there was a tendency to decrease the labiolingual and mesiodistal diameters. 2. In case of metal thickness of the veneered area was 0.5mm, metal copings made of JP 92, Verabond, and Rexillium Ⅲ exhibited significantly less marginal distortion than Degudent G, and with 0.2mm in thickness, distortion of Verabond, and Rexillium Ⅲ were similar to Degudent G in labiolingual diameter after porcelain was fired. 3. Metal copings made of JP 92, Verabond, and Rexillium Ⅲ exhibited significantly less marginal distortion than Degudent G in mesiodistal diameter after porcelain was fired. [영문] Although castings suitable for veneering with porcelain can be made with the same precision as any other, baking the porcelain veneer presents additional distortion in the final restoration. So, it does not always fit as well after the application of the porcelain veneer. To ensure resistance to such a distortion, it is necessary to improve the rigidity of the metal coping. The purpose of this study was to compare the susceptibility to marginal distotion of each of the various ceramo-metal alloys. Materials used in this experiment were four kinds of precious, semi-precious, and non-precious ceramo-metal alloys, and Ceramco vaccum-fired porcelain. The author made five metal copings in each alloy and the porcelain was fired on each metal coping by the method to be recommended by the manufacturers. In addition to that, metal thickness of the veneered area decreased to 0.2mm in case of metal copings made of two kinds of nonprecious alloy. Measurements were made labiolingual diameter and mesiodistal diameter with Universal measuring microscope and recorded at 3 stages; (1) before any firing procedures, (2) following degassing,(3) following final glazing. The obtained result could be summarized in the followings ; 1. On all metal copings evaluated in this study, distortion of cervical margin was shown after porcelain was fired, and there was a tendency to decrease the labiolingual and mesiodistal diameters. 2. In case of metal thickness of the veneered area was 0.5mm, metal copings made of JP 92, Verabond, and Rexillium Ⅲ exhibited significantly less marginal distortion than Degudent G, and with 0.2mm in thickness, distortion of Verabond, and Rexillium Ⅲ were similar to Degudent G in labiolingual diameter after porcelain was fired. 3. Metal copings made of JP 92, Verabond, and Rexillium Ⅲ exhibited significantly less marginal distortion than Degudent G in mesiodistal diameter after porcelain was fired.restrictio