• The Journal of Advanced Prosthodontics
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• v.8 no.5
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• pp.363-371
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• 2016

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.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.2
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• pp.139-155
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• 2009

Objective : To assess the biological stability of immediate transmucosal placement of tapered implants into tooth extraction sockets. Material and methods : Following tooth extraction, tapered implants were immediately placed into the sockets. Teeth with evidence of acute periapical pathology were excluded. After implant placement, sutured allowing a non-submerged, transmucosal healing. Standardized radiographs were obtained every visiting from baseline to 32 weeks after implant placment. Changes in depth of the distance from the implant shoulder (IS) and from the alveolar crest (AC) to the bottom of the defect (BD) were assessed. Results : Thirteen patients (10 males and 3 females) were enrolled and followed. They contributed with 15 tapered implants. extraction iste displayed sufficient residual bone volume to allow primary stability of all implants. The mean surgery time was $41{\pm}10.0$ mins. All implants healed uneventfully yielding a survival rate of 100%. Mean ISQ values were relatively stable. Interproximal crestal bone decreased $1.69{\pm}1.2mm$ (mesial), $1.65{\pm}1.2mm$ (distal) from baseline to 32-week follow-up. No statistically significant changes with respect to FMPS, FMBS, PPD and width of KG were observed. Conclusions: Immediate transmucosal implant placement represented a predictable treatment option for the replacement of teeth lost due to reasons including fractures, endodontic failures and caries.

• Journal of Periodontal and Implant Science
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• v.46 no.3
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• pp.152-165
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• 2016

Purpose: This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions. Methods: A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment. Results: The maximum extent of micromotion was approximately $100{\mu}m$ in the low-density cancellous bone models, whereas it was under $30{\mu}m$ in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness. Conclusions: Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.1
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• pp.90-94
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• 2008

The purpose of this study was to investigate the effects of immediate non-functional loading by analyzing histomorphology around the implant tissues in dogs. Five eight- to nine-month-old full-grown dogs weighing around 12 kg were used in the study. Group I (control group) comprised those in which delayed loading was applied to the right side of the mandible, and Group II (experimental group) consisted of dogs in which immediate loading was performed on the left side of the mandible. Resorbable blast media (RBM)-treated double-threaded US III implants measuring 3.5 mm in diameter and 11 mm long were used in the study. Each animal received four implants in each group, for a total of 40 implants. Cemented type abutments were used after implantation. An 8-week period was allowed for bone healing and an abutment was placed after exposing the periosteum for loading. An implant sample was obtained from bone blocks taken when the dogs were killed at 16 weeks after loading. A Mann-Whitney U-test was performed to evaluate statistical significance. Student's t-test was used for the histological evaluation. The bone formation ratio in Groups 1 and 2 was 88.23 and 86.41%, respectively. No significant difference in new bone formation was observed in the two groups. As no significant difference was seen in new bone formation between the delayed and immediate loading groups, early loading might be possible after implant placement.

• Journal of the Korean Society of Radiology
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• v.82 no.3
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• pp.600-612
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• 2021

Purpose To evaluate the long-term radiologic and clinical outcomes of stent-graft placement for the treatment of post-pancreaticoduodenectomy arterial hemorrhage (PPAH) based on the imaging findings of stent-graft patency and results of liver function tests. Materials and Methods We retrospectively reviewed the medical records of nine consecutive patients who underwent stent-graft placement for PPAH between June 2012 and May 2017. We analyzed the immediate technical and clinical outcomes and liver function test results. Stent-graft patency was evaluated using serial CT angiography images. Results All stent-grafts were deployed in the intended position for the immediate cessation of arterial hemorrhage and preservation of hepatic arterial blood flow. Technical success was achieved in all nine patients. Eight patients survived after discharge, and one patient died on postoperative day 28. The median follow-up duration was 781 days (range: 28-1766 days). Follow-up CT angiography revealed stent-graft occlusion in all patients. However, serum aspartate aminotransferase or alanine aminotransferase levels in all patients were well below those observed in hepatic infarction cases. Conclusion Stent-graft placement is a safe and effective treatment method for acute life-threatening PPAH. Liver function and distal hepatic arterial blood flow were maintained postoperatively despite the high incidence of stent-graft occlusion observed on follow-up CT.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.3
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• pp.246-252
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• 2014

$Br{\aa}nemark^{\prime}s$ original protocol required 4 to 6 months for implant osseointegration before placement of the definitive prosthesis. Although this approach gave very predictable results, it had certain drawbacks. The main disadvantages of this approach were prolonged treatment time, two surgical procedures, placement of a removable prosthesis that required modifications during the course of treatment, and a greater number of appointments. Immediate implant loading is a viable treatment method for selected cases. One of the greatest advantages of this method is the virtual surgery, which precedes the actual clinical treatment and eliminates any need for last minute decisions. The actual surgery time is decreased, since all steps are predetermined. These advantages aren't only more useful for normal patients but also for the mental retardation patients whose cooperation is difficult. This article presents a clinical approach made possible due to the guided implant surgery and CAD/CAM technique.

• Imaging Science in Dentistry
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• v.52 no.2
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• pp.197-207
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• 2022

Purpose: This study evaluated the associations of the dental arch form, age-sex groups, and sagittal root position (SRP) with alveolar bone thickness of the maxillary central incisors using cone-beam computed tomography (CBCT) images. Materials and Methods: CBCT images of 280 patients were categorized based on the dental arch form and age-sex groups. From these patients, 560 sagittal CBCT images of the maxillary central incisors were examined to measure the labial and palatal bone thickness at the apex level and the palatal bone at the mid-root level, according to the SRP classification. The chi-square test, Kruskal-Wallis test, and multiple linear regression were used for statistical analyses. Results: Significant differences were found in alveolar bone thickness depending on the arch form and SRP at the apex level. The square dental arch form and class I SRP showed the highest bone thickness at both levels of the palatal aspect. The taper dental arch form and class II SRP presented the highest bone thickness at the apex level of the labial aspect. No association was found between the dental arch form and SRP. Elderly women showed a significant association with thinner alveolar bone. Age-sex group, the dental arch form, and SRP had significant associations with alveolar bone thickness at the apex level. Conclusion: The patient's age-sex group, dental arch form, and SRP were associated with alveolar bone thickness around the maxillary central incisors with varying magnitudes. Therefore, clinicians should take these factors into account when planning immediate implant placement.

• Journal of Periodontal and Implant Science
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• v.53 no.6
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• pp.453-466
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• 2023

Purpose: This study aimed to quantify alveolar bone morphology, demonstrate the relationship between tooth angulation and alveolar bone thickness, and introduce a new classification for anterior mandibular teeth related to immediate implant placement (IIP). Methods: Cone-beam computed tomography (CBCT) images of 211 anterior mandibular teeth were analyzed in sagittal slices to measure the thickness of the facial alveolar bone crest (FAB1) and apex (FAB2), and the lingual alveolar bone crest (LAB1) and apex (LAB2). Tooth angulation was classified as 1°-10°, 11°-20°, and >20° according to the tooth's long axis and alveolar bone wall. Spearman correlation coefficients were used to evaluate correlations between the variables. Results: FAB1 and LAB1 were predominantly thin (<1 mm) (84.4% and 73.4%, respectively), with the lateral incisors being thinnest. At the apical level, FAB2 and LAB2 were thick in 99.5% and 99.1% of cases, respectively. Significant differences were documented in FAB2 (P=0.004), LAB1 (P=0.001), and LAB2 (P=0.001) of all mandibular teeth. At all apical levels of the inspected teeth, a significant negative correlation existed between TA and FAB2. Meanwhile, TA showed a significant positive correlation with LAB2 of the lateral incisors and canines. These patterns were then divided into class I (thick facial and lingual alveolar bone), class II (facially inclined teeth) with subtype A (1°-10°) and subtype B (11°-20°), and class III (lingually inclined teeth) with subtype A (1°-10°) and subtype B (11°-20°). Conclusions: Mandibular anterior teeth have predominantly thin facial and lingual crests, making the lingual bone apical thickness crucial for IIP. Although anchorage can be obtained from lingual bone, tooth angulation and tooth types had an impact on IIP planning. Hence, the new classification based on TA and alveolar bone wall may enable rational clinical planning for IIP treatment.

• The Journal of the Korean dental association
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• v.47 no.11
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• pp.758-768
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• 2009

Purpose : Schulte introduced immediate implant cases in 1970s, since then many patients have been treated by immediate implants. The aim of this study was to evaluate the cumulative survival rate of immediate implant and to analyze various factors associated with survival of immediate implant in a 8-year period retrospectively. Materials and methods : From May, 2000 to October, 2007, 77 implants were placed in 63 patients immediately after tooth extraction at Department of Periodontology, Yonsei University Hospital. The implant survival rate was analyzed using a life-table analysis. After delivery of prosthesis, along 1 year of observation period, all implants were evaluated clinically and radiographically. Results : Among 77 implants, 59 were placed in maxilla and 18 in mandible. The most common site of the implantation was Mx anterior (65%). The overall survival rate was 94.8% over a mean follow-up period of $44.2{\pm}21$ months and the 8-year cumulative survival rate was 94.6%. Failure occurred in 4 implants, all of which were due to early failures. None of the following factors were significantly associated with the survival of immediate implants: advanced surgical technique including bone graft and guided bone regeneration, the types of implants, causes of tooth loss, and types of prosthesis. Conclusion : On the basis of 8-year life time analysis, immediate implant placement can be considered a safe and predictable treatment mordality.

• Journal of Periodontal and Implant Science
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• v.38 no.4
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• pp.603-610
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• 2008

Purpose: The guided bone regeneration (GBR) technique is widely used in periradicular surgery. However, there is still some controversy regarding the effectiveness of GBR in promoting bone healing after periradicular surgery. The purpose of this study was to evaluate the resorbable membrane on the osteointegration of immediate implants in sites with periradicular lesion that had been removed by periradicular surgery. Materials and methods: Six roots of lower second premolars and 15 roots of lower third and fourth premolars of dogs were used as control and experimental teeth, respectively. Periradicular lesions were induced only in the experimental teeth. Twelve weeks later, the control and experimental teeth were extracted and implants were placed immediately. Periradicular lesions were removed with osteotomy, curettage and saline irrigation. Resorbable membranes were used in experimental group 1 but not in experimental group 2. After 12 week of healing period, the implants were clinically not mobile and showed no signs of infection. Data obtained by histomorphometric analysis were analyzed by Kruskal-Wallis test. Results: The control group showed a significantly higher bone to implant contact (BIC) ($74.14{\pm}16.18$) than experimental group 1 ($40.28{\pm}15.96$) and 2 ($48.70{\pm}17.75$)(p<0.05). However, there was no significant difference between experimental group 1 and 2. Conclusion: Although BIC in experimental groups were lower than in control group, immediate implant can be successfully placed at extraction socket with periradicular lesion and osseous defect. However, the use of resorbable membrane in bony defect created during periradicular surgery was questioned.