二单位式与四单位式种植牙周骨界面应力分布规律差异的三维有限元分析

为了探讨人工种植牙的数目、上部结构对种植牙周骨界面应力分布的影响，本实验应用三维有限元分析方法，对二单位和四单位式杆式覆盖种植义齿种植牙周骨界面的应力分布规律进行了探讨。结果表明：最大压应力、最大拉应力二单位式与四单位式均位于颈周密质骨，二单位式大于四单位式，两者有显著差异性，（Ｐ＜０．００１）。四单位式最大拉、压应力，远中种植牙要大于近中种植牙。最大位移运动二单位式小于四单位式，四单位式近中种植牙大于远中种植牙。二单位式与四单位式位、压应力主要集中于颈部，其它部位与颈部相比有非常显著的差异性，（Ｐ＜０．０００１）。结论：种植牙数目的增加，可以减小种植牙周颈部密质骨内的最大应力值。四单位式种植义齿颈周骨内应力要小于二单位式种植牙，从这点上看，四单位式种植义齿要优于二单位式种植义齿。多个种植牙种植时，杆的连接，改变了种植牙周骨内的应力分布规律，其应力主要由种植牙颈周密质骨来承担     

Long-lasting osseointegration of immediately loaded, bar-connected TPS screws after 12 years of function: a histologic case report of a 95-year-old patient.

The present case report provides histologic findings on four titanium plasma-sprayed screw implants after 12 years of incorporation and functional load in a 95-year-old patient. At the time of implant placement, the four implants were immediately connected with a bar and functionally loaded with a bar-supported overdenture. The histologic analysis demonstrated excellent osseointegration in either cortical or cancellous bone for all implants. The histomorphometric analysis showed direct bone-implant contact of approximately 70% to 80% at the interface. Close to the implant surface, signs of ongoing bone remodeling activities were present. The present histologic case report confirms the validity of the applied treatment concept--to immediately load titanium implants with a titanium plasma-sprayed surface in the anterior region of the mandible--if a minimum of four implants can be inserted and if the four implants are splinted with a bar.     

Computer-guided flapless placement and immediate loading of four conical screw-type implants in the edentulous mandible

AIM: The aim of this prospective study was to evaluate the outcome of computer-guided flapless placement and immediate loading of four conical screw-type implants in the interforaminal region. PATIENTS AND METHODS: From May to August 2003, 25 consecutive patients (m : f=16 : 9) with edentulous mandibles were included in the study. After transmucosal drilling with computer-assisted navigation, four implants were placed in the interforaminal region. The lower dentures were converted and implants immediately loaded. RESULTS: One-hundred implants were successfully placed. In two patients, all implants had to be submerged because of insufficient primary stability of one of the implants; another patient declined to receive immediate loading of implants after surgery and was lost to follow-up. During follow-up of the remaining 22 patients with 88 immediately loaded implants, loosening of four implants (4.5%) was seen in three patients. In these cases, immediate loading was terminated and all implants submerged; subsequently, two implants were lost in one patient, while the other two implants re-osseointegrated. The cumulative survival and success rates of immediately loaded implants were 97.7% after 2 years. Prosthetic success was 100%. CONCLUSION: Transmucosal computer-assisted placement and immediate loading of mandibular implants is a high-end approach to edentulism that provides excellent results while being minimally invasive.     

A systematic review of implant-supported maxillary overdentures after a mean observation period of at least 1 year

Aim: The aim of the present systematic review of implant-supported maxillary overdentures was to assess the survival of implants, survival of maxillary overdentures and the condition of surrounding hard and soft tissues after a mean observation period of at least 1 year.
Material and methods: MEDLINE (1950–August 2009), EMBASE (1966–August 2009) and CENTRAL (1800–August 2009) were searched to identify eligible studies. Two reviewers independently assessed the articles.
Results: Out of 147 primarily selected articles, 31 studies fulfilled the inclusion criteria. A meta-analysis showed an implant survival rate (SR) of 98.2% per year in case of six implants and a bar anchorage. In case of four implants and a bar anchorage, the implant SR was 96.3% per person. In case of four implants and a ball anchorage, the implant SR was 95.2% per year.
Conclusion: In all three treatment options, the SR of the implants is more than 95%. The studies included reveal that a maxillary overdenture supported by six dental implants, which are connected with a bar, is the most successful treatment regarding survival of both the implants and overdenture. Second in line is the treatment option with four implants and a bar. The treatment option with four or less implants and a ball attachment system is the least successful.     

基于有限元分区式多孔种植体设计研究

目的:根据现有普通种植体的几何参数,设计分区式多孔结构种植体进行拓扑优化,并通过有限元方法分析有无多孔、不同孔形以及不同位置的种植体在下颌骨模型中的应力分布,比较其优劣势。方法:通过“六维齿科牙种植设计软件”确定几何参数并UG建模;在有限元软件中模拟咬合力加载,分析4种种植体在最大力、适合力下的应力分布。结果:4种不同种植体的应力分布有较大差异,正菱形交错排布多孔种植体应力分布明显小于其它3组。结论:对于种植体修复,合适的多孔结构种植体在力学性能上比现有的普通实心种植体更具优势。     

新型种植体涂层材料rhBMP-2/PDLLA诱导成骨作用的观察

目的：观察rhBMP-2/PDLLA涂层诱导钛种植体周围新骨形成情况。方法：选取8只比格犬,在其双侧胫骨随机植入PDLLA/rhBMP-2、PDLLA、rhBMP-2涂层和空白种植体,术后2、4、8、12周进行生物力学测定和骨形态计量学分析,比较各组新骨形成和骨结合情况。结果：rhBMP-2/PDLLA涂层种植体周围新骨形成早于其他组;4周时rhBMP-2/PDLLA涂层种植体骨结合明显优于PDLLA组、空白组（P〈0.05）,8周和12周时PDLLA/rhBMP-2涂层种植体骨结合优于PDLLA组,并有大于其他两组的趋势。结论：新型涂层材料PDLLA/rhBMP-2具有促进新骨形成和提高骨结合率的双重作用。     

Standardized radiographs of the alveolar crest around implants in the mandible.

The techniques currently used for standardized longitudinal radiographic evaluation of the supporting bone around dental implants are not suitable for general application. An aiming device is described for intraoral radiography used to evaluate the crestal bone height around dental implants used as retention for overdentures. This aiming device has been tested on four different implant systems by four dentists. Error analysis of serial radiographs indicates small deviations in reproducibility. It is concluded that this method is suitable for routine evaluation of dental implants.     

二或四枚种植体支持的Locator覆盖义齿修复五年回顾

目的:比较下颌牙列缺失患者分别采用2枚或者4枚种植体支持的Locator覆盖义齿,修复5年后的临床效果。方法:选取采用2枚种植体(A组)和4枚种植体(B组)支持Locator覆盖义齿患者分别为20例、15例。评估2组患者满意度(整体满意度、咀嚼能力、说话适合性、固位和稳定性、舒适度),并检测咀嚼效率和边缘骨吸收值。结果:两组病人在整体满意度、咀嚼能力、说话适合性、固位和稳定性、舒适度及咀嚼效率、边缘骨吸收方面均无显著性差异(P>0.05)。结论:Locator种植覆盖义齿无论是采用2枚还是4枚种植体,5年后均能获得很好的临床效果,患者满意度高,但对其远期临床效果还有待观察。对于有可能出现义齿旋转的患者建议种植4枚种植体。     

Quadruple zygomatic implant support for retreatment of resorbed iliac crest bone graft transplant

PURPOSE: The purpose of this report is to present a reliable surgical and prosthodontic protocol for the treatment of the atrophic maxilla by placing four zygomatic implants. MATERIALS AND METHODS: The surgical and prosthodontic procedures are described for the retreatment of a 63-year-old woman who had previously undergone an iliac crest bone graft transplant, which had resorbed. RESULTS: It is possible to place double zygomatic implants bilaterally, in addition to conventional implants in the anterior maxilla. Bone grafting procedures can be avoided, resulting in a fixed implant-supported maxillary prosthesis. CONCLUSION: A logical treatment solution is four zygomatic implants for the atrophic maxilla, especially because the previous iliac crest bone graft had resorbed.     

Histomorphometric analyses of hydroxyapatite-coated and uncoated titanium dental implants in rabbit cortical bone

In this article, we report the results of analyses of bone healing around four types of dental implants. Five implants of each type were inserted into the proximal tibia metaphysis of adult New Zealand rabbits and were analyzed using computerized histomorphometry 12 weeks after implantation. Hydroxyapatite-coated implants showed more direct bone contact and more lamellar bone in the threads than the titanium implants. There was a significant correlation between an increase in the percentage of mineralized tissue in the threads of metallic implants and cellular density around the implant, indicating less lamellar bone in contact with metallic implants.     

Comparison of silastic and proplast implants in the temporomandibular joint after condylectomy for osteoarthritis

This study was undertaken to compare the long-term stability of Silastic and Proplast when used as alloplastic implants following high condylectomy. Twelve patients with osteoarthritis of the temporomandibular joint (TMJ) were treated either unilaterally or bilaterally. The follow-up period ranged from one to four years. In all ten TMJs that received Silastic implants and in ten that received Proplast implants, there were no discernible differences relative to comfort, masticatory function, or TMJ mobility. Although Silastic and Proplast had similar functional characteristics, Proplast implants had better long-term stability than the Silastic implants.     

Enhanced bone integration of implants with increased surface roughness: a long term study in the sheep

OBJECTIVES: This study evaluated the quality and the remodeling of bone around commercially pure titanium implants after 3, 6, 12 and 18 month implantation periods in the sheep. METHODS: Twelve animals were implanted in the cortico-trabecular areas of both femurs. Each femur received four implants with a rough surface (type 1) in the right femur and four with a smooth surface (type 2) in the left one. Bone blocks containing the implants were studied by histomorphometry on undecalcified specimens. The amount of bone around implants was measured (bone volume, fractional woven bone volume, bone thickness, contact interface) together with osteoblastic activity (mineral apposition rates, bone formation rates) and resorption activity (eroded surfaces). RESULTS: No significant differences could be observed for the two types of implants between 3 and 6 months. At 12 and 18 months, bone volume and contact interface were still increasing and there was always a tendency for type 1 implants to be associated with higher values. On the contrary, mineral apposition rate, bone formation rates and eroded surfaces decreased in the referent area in contact with the implant; this phenomenon of 'return to the normal' was more evident with type 1 implants. The remodeling process appears to increase bone quality and bone-titanium interface around implants in long term periods. CONCLUSIONS: The net bone quantity necessary to immobilize implants is obtained rapidly but the adapting process to mechanical strength can lead to a small but persistent increase in bone volume around implants. Although the differences between type 1 and type 2 implants were often small or statistically insignificant, the rougher type 1 implants seemed to be associated with stronger bone response.     

Assessment of adjunctive flurbiprofen therapy in root-form implant healing with digital subtraction radiography

The goals of these case reports were to (1) apply digital subtraction radiography to the assessment of the healing of root-form implants so that small changes in bone height and density could be detected and (2) to compare the bony support around root-form implants in patients prescribed the non-steroidal anti-inflammatory drug, flurbiprofen, with support in patients who did not receive the flurbiprofen as adjunctive therapy. Titanium root-form implants were surgically placed in four patients who were randomly assigned to receive either 100 mg flurbiprofen twice a day for three months or no flurbiprofen (as controls). Radiographs were taken immediately post-operatively and at four months. Digital subtraction radiography was used to detect sites of bone gain, loss, or unchanged bone around the implant. This four-month pilot study suggests that the non-steroidal anti-inflammatory drug, flurbiprofen, appears to be associated with increased bone density surrounding dental implants, and that digital subtraction radiography may be useful for the evaluation of bone density changes around dental implants.     

Rehabilitation of totally atrophied maxilla by means of four zygomatic implants and fixed prosthesis: a 6–40-month follow-up

The zygomatic implant is an alternative to bone grafting in extremely resorbed maxilla. This study evaluates the results of a consecutive cohort of 20 patients (mean age 56 years) with extremely resorbed maxillas provided with four zygomatic implants. The first 10 patients had a two-stage procedure, the next 10 next patients benefited from a one-stage surgical procedure and one of them had flapless guided surgery with Nobelguide^® in development and immediate function. The same surgical drilling protocol, according to Branemark's procedure, was applied to all the patients. Except for one patient who lost three implants, 18 patients received a fixed Procera^® implant bridge and another an overdenture retained by a screwed bar fixed on the four zygomatic implants. The cumulative survival rate after 40 months is 96%. Although bone augmenting procedures such as onlay grafts and sinus grafts are popular and well-documented, the four zygomatic implants procedure results in less morbidity, shorter delays between anatomical reconstruction and functional rehabilitation and can provide immediate or early loading with immediate function. Four zygomatic implants and a fixed bridge seem to be a valuable technique for the rehabilitation of extremely resorbed maxillas.     

Histological and clinical comparisons of guided tissue regeneration on dehisced hydroxylapatite-coated and titanium endosseous implant surfaces: a pilot study.

Fifty-six endosseous cylindrical implants were placed in dog mandibles 12 weeks after the extraction of all mandibular premolars and first molars. Eight implants, four coated with 50 microns of hydroxylapatite (HA) and four grit-blasted and titanium-surfaced, were placed in each dog. Ideal implant placement sites were modified by creating standardized 3 x 5-mm facial dehiscence defects. Half the dehiscences were treated with a modified expanded polytetrafluoroethylene (PTFE) membrane; the remainder served as controls. After 8 weeks of healing, the animals were sacrificed and measurements made to determine the percentage of dehiscence repair. The HA-coated implants had a mean defect fill of 95.17% and the grit-blasted implants had a percent fill of 82.8% in the guided tissue regeneration (GTR) test group; the control implants demonstrated a mean fill of 55% and 39% in the HA-coated and grit-blasted implants, respectively. Significant differences (P less than .05) were noted between both test groups and the titanium control group, and between the HA test and HA control groups. Histologic evaluation showed significantly greater repair associated with HA-coated implants, as well as significant bone loss associated with clinically exposed membranes. It was concluded that within the limitations of this study, guided tissue regeneration is a viable option in treating defects associated with dental implants.     

糖尿病与正常大鼠人工植入种植体的生物力学性能比较

目的:评价糖尿病大鼠与正常大鼠进行种植体植入后的生物力学性能。方法:建立糖尿病大鼠实验动物模型,分别在正常和糖尿病大鼠(每组各10只)的胫骨近骺端种植纯钛种植体,分别于植入后1、4周处死动物,进行植入种植体处的抗拉力及抗扭转力测试。结果:糖尿病大鼠种植体的抗拉力及抗扭转力测试结果明显小于正常大鼠组,种植体的抗拉力随时间增加而增大。结论:糖尿病影响种植体植入后的生物学性能,对于糖尿病患者的口腔种植修复应慎重。     

Immediate loading of dental implants placed in severely resorbed edentulous mandibles reconstructed with autogenous calvarial grafts

OBJECTIVE: The aim of this prospective study was to present the clinical outcome of immediately loaded dental implants placed in edentulous, severely atrophied mandibles, after reconstruction with autogenous multilayered calvarial grafts. MATERIALS AND METHODS: Six patients, two males and four females, aged 40-67 years (mean: 56 years) presenting with severely atrophied edentulous mandibles (Cawood and Howell class VI), were reconstructed with multilayered calvarial bone grafts placed in the intraforaminal area of the mandible. Five to 8 months afterwards, 23 dental implants were placed in the reconstructed areas (three to four implants per patient) and immediately loaded with implant-supported overdentures. Patients were followed with clinical and radiographic controls annually. RESULTS: Recovery after the reconstruction was uneventful in all patients. All 23 implants were osseointegrated 1-3 years after the start of immediate loading. The survival and success rates of implants were 100% and 95.7%, respectively. CONCLUSION: Results from this study showed that immediate loading of dental implants placed in severely atrophied edentulous mandibles reconstructed with calvarial bone grafts is a predictable procedure, which permits a successful dental rehabilitation with a shortening of treatment times.     

Critical soft tissue parameters of the zygomatic implant

AIM: Zygomatic implants have been introduced for the rehabilitation of patients with severe bone defects of the maxilla. The soft tissue aspects of the palatal emergence situation have not been described yet. The aim of this study was to evaluate the incidence and clinical impact of possible periimplant alterations of zygomatic implants. MATERIALS AND METHODS: From 1998 to 2001 all patients with zygomatic implants were included into this study (24 patients, 37 zygomatic implants). One implant was lost in the loading phase giving a survival rate of 97%. Fourteen patients with 20 zygomatic implants fulfilled the inclusion criteria and were all available for the recall examination. Thirteen zygomatic implants were inserted in cases of severe maxillary atrophy, seven in cases of tumour-resection of the maxilla. Clinical examination and microbial analysis using a DNA probe was performed. The implants had a mean time in situ of 598 days (min: 326, max: 914). RESULTS: Colonisation with periodontal pathogens was found at four of the 20 implants. A positive microbiologic result of the periimplant pocket and the maximum pocket probing depth were not statistically related. Nine of the 20 implants showed bleeding on probing, four of these had positive microbiologic results. At sites without bleeding on probing only negative microbiologic samples were found (p=0.026). The mean palatal and mesial probing depth was 1 mm deeper than at the vestibular and distal aspect. Thus at nine out of the 20 implants both, bleeding on probing and pocket probing depth >/=5 mm indicated soft tissue problems resulting in a success rate of only 55%. The patient's history (tumor versus atrophy) or smoking habits seemed not to have influence the situation. CONCLUSION: These soft tissue problems should be taken into account if zygomatic implants are considered as an alternative therapy option in the maxilla.     

修复上颌无牙颌不同种植体位置和数目的应力分析

目的：在前端种植体固定桥和后端冠外弹性附着体义齿联合修复上颌无牙颌的修复设计中，比较不同种植体位置和数目的3个有限元模型的应力分布，选择一种更合理的修复设计。方法：建立4个种植体在双侧侧切牙和尖牙的三维有限元模型Ⅰ，通过局部修改，建立2个种植体在双侧尖牙的模型Ⅱ，4个种植体在双侧尖牙和中切牙的模型Ⅲ。应力垂直加载于上颌右侧第一磨牙，加力300N，用MSC软件进行静态应力分析。结果：模型II中23种植体处的应力大约是模型Ⅰ的3倍。模型Ⅲ的附着体、23种植体和13种植体的应力比模型Ⅰ和模型Ⅱ明显高。然而，模型Ⅲ中21种植体和11种植体的应力比模型Ⅰ中22种植体和12种植体处的应力低。在模型Ⅲ中，4个种植体的应力相差很大。结论：在3个模型中，4个种植体在双侧侧切牙和尖牙的模型Ⅰ在生物力学方面是最合理的。     

Clinical outcome of implants placed immediately after implant removal

BACKGROUND: The purpose of this study was to evaluate the clinical success of implants placed immediately after the explantation of failed implants due to fracture at 12 months. METHODS: Nine immediate implants were placed in nine patients following explantation of nine fractured implants. Five experimental implants did not require any regenerative procedures; the remaining four immediate implants were grafted with deproteinized porcine bone particles and covered with bioabsorbable membranes. All implants were restored with fixed prostheses. The follow-up period was 12 months. RESULTS: No residual bone defects were observed or probed around any implant at the second-stage surgery, and all implants were asymptomatic and stable. All the implants were successful after prosthetic rehabilitation showing no mobility, pain, suppuration, or absence of peri-implant radiolucency. The radiographic measurements showed no significant bone loss pattern at the 12-month follow-up visit. CONCLUSION: The findings of this study suggested that implants placed immediately after implant explantation due to biomechanical fracture could be performed with results that are similar to results obtained with implants placed immediately after tooth extraction.