Effects of implant surface roughness and stiffness of grafted bone on an immediately loaded maxillary implant: a 3D numerical analysis

summary   This study investigated the effects of the stiffness of a maxillary sinus graft and the surface roughness of an immediately loaded implant using a non-linear three-dimensional finite element (FE) analysis (3D). Six FE models were created, including two stiffness values of grafted bone (345 and 3450 MPa of elastic modulus) and three conditions of implant–bone interfaces (Frictional coefficient of 0·3 for machined surface, 0·45 for rough implant surface and a bonded implant–bone interface for an osseointegrated implant). Computer tomographic images of a human skull were used to construct a posterior maxillary model. All implants were designed via the computer aided design software with a spiral threaded configuration. Three loading scenarios were investigated for each of the six models; axial loading and lateral loadings at 30° and 60°. The results showed that a 60° lateral loading has scored the highest level of bone stresses among the three loading conditions. Immediately loaded implants with 0·3 frictional coefficient have suffered the highest bone stresses which were higher than those with bonded interface by about 57%. Increasing the frictional coeffecient to 0·45, however, did not show any benefits in reducing the peak bone stress. Raising the stiffness of grafted bone diminished the bone stress by about 10% in both the immediately loaded and the osseointegrated implants. It was also noted that increasing graft stiffness and implant surface roughness reduced the sliding at the implant-bone interface which may improve the implant stability and long-term survival.     

Comparison of implant body designs and threaded designs of dental implants: a 3-dimensional finite element analysis

PURPOSE: Stress analysis was performed for various implant designs using 3-dimensional finite element analysis approaches. MATERIALS AND METHODS: Six implant designs were included: 3 parallel-sided implants (no thread, triangular thread, and squared thread), 2 stepped configurations (non-thread and triangular thread), and a tapered body of implant with squared thread. All threads had spiral characteristics. The mandibular model was constructed from computed tomographic (CT) images of a human mandible, and the material properties were anisotropic (different in different directions). A 100-N oblique force was applied at a 45-degree angle to the long axis of the implants at the buccal cusp as the loading condition. RESULTS: Compared with cylindric implants, threaded implants (either triangular or squared) demonstrated increased peak stress at the crestal bone. The bone stress of stepped implants was decreased in the cortical region but was increased in the trabecular region. However, both threaded and stepped designs showed decreased interfacial stresses of bone near the valleys of the threaded and stepped areas. The tapered design decreased stresses by up to 32% in the cortical region and 17% in the trabecular region. CONCLUSIONS: Although threaded implants could not decrease the peak stress at the crestal bone, both threaded and stepped designs show an ability to dissipate the interfacial stresses of bone. The use of tapered implants could reduce peak stress in both cortical and trabecular bone.     

支抗种植体外形影响骨界面应力分布的研究

目的探讨种植体外形差异对骨界面应力分布的影响，并筛选出最佳支抗种植体外形。方法应用三维有限元分析方法对刃状螺纹型、矩形螺纹型及光滑型种植体进行骨界面应力和位移分析。结果刃状螺纹型种植体做支抗体时其骨界面第一、第二及第三主应力分别为6.67MPa、1.47MPa及0.52MPa，并且VonMises应力为7.22MPa，在三种种植体中应力值最小。而3种种植体颈部牙槽骨的DMX位移值分别为0.11×10     

微型支抗种植钉加载时机的动物实验研究

目的 建立支抗种植钉的动物模型,分析不同愈合期加载对种植钉稳定性的影响。方法 于绵羊牙槽骨上植入微型支抗种植钉,建立颌骨-支抗种植钉的动物模型,随机分为4组（不加力为A组,即刻加力为B组,植入2周加力为C组,植入4周加力为D组）,截取带有种植钉的上、下颌骨组织标本;上颌骨块制作不脱钙的骨磨片,光镜下观察种植钉与骨组织界面的愈合情况,下颌骨块用材料性能试验机检测种植钉与骨组织松脱瞬间的最大剪切力值,并进行统计分析。结果1）4组种植钉的剪切力值总体上有差别,A、B组的剪切力低于C、D组。2）骨纵磨片显示：种植钉与周围组织界面的结合方式在种植钉的压力侧和张力侧无明显区别;横断磨片显示：4组界面既有纤维性结合,又有骨性结合,A、D组界面以骨性结合为主,B、C组界面以纤维性结合为主,C组种植钉周围可见新生的骨组织潜行生长。结论加载时机对支抗种植钉的稳定性有一定的影响。     

种植体颈部微螺纹结构对种植稳定性影响的三维有限元分析

目的：通过分析种植体颈部螺纹结构,以及Von-Mises应力和应变分布情况,为种植体结构设计提供生物力学实验数据和理论参考依据。方法：本文通过运用三维计算机辅助设计CAD软件,设计建立颈部有螺纹和无螺纹三维种植体模型,利用CT扫描数据重建下颌骨三维模型,牙齿咬合面与上颌骨长轴面形成的倾角为45。,沿此方向施加120N的力作用在牙冠顶部,以模拟实际咬合状态受力。利用有限元分析软件模拟即刻负荷（即骨一种植体之间摩擦系数0．3）和骨愈合后期（即骨一种植体之间为绑定接触）两种加载情况下种植体与周围骨组织之间Von-Mises应力和应变峰值大小及分布状况进行比较和分析。结果：在即刻负荷的条件下,Von-Mises应力、应变在颈部光滑的种植体与皮质骨之间分布均匀,峰值分别为28．654MPa、0．01334mm;而颈部有螺纹种植体与皮质骨之间的Von-Mises应力、应变峰值分别为52．630MPa、0．015864mm。在骨愈合后期,颈部光滑的种植体,在相同咬合力作用下,皮质骨Von-Mises应力、应变峰值分别为36．975MPa、0．010272mm;而具有颈部螺纹设计的种植体所引起的Von-Mises应力、应变峰值分别为35．857MPa、0．010234mm。在骨愈合后期,增加种植体颈部的螺纹设计使得皮质骨所受Von-Mises应力减小1．118MPa、应变峰值也有减小的趋势。结论：即刻负载种植时,增加种植体颈部螺纹结构,在种植体一骨愈合后期,颈部的微螺纹结构可使种植体一骨接触界面的Von-Mises应力和应变峰值有所减小,并且有效改善了接触界面的应力分布状况,有助于其长期稳定性及种植成功率的提高。     

Histologic evaluation of a provisional implant retrieved from man 7 months after placement in a sinus augmented with calcium sulphate: a case report

Little is known about the in vivo healing processes at the interface of implants placed in different grafting materials. For optimal sinus augmentation, a bone graft substitute that can regenerate high-quality bone and enable the osseointegration of load-bearing titanium implants is needed in clinical practice. Calcium sulphate (CaS) is one of the oldest biomaterials used in medicine, but few studies have addressed its use as a sinus augmentation material in conjunction with simultaneous implant placement. The aim of the present study was to histologically evaluate an immediately loaded provisional implant retrieved 7 months after simultaneous placement in a human sinus grafted with CaS. During retrieval bone detached partially from one of the implants which precluded its use for histologic analysis. The second implant was completely surrounded by native and newly formed bone, and it underwent histologic evaluation. Lamellar bone, with small osteocyte lacunae, was present and in contact with the implant surface. No gaps, epithelial cells, or connective tissues were present at the bone-implant interface. No residual CaS was present. Bone-implant contact percentage was 55% +/- 8%. Of this percentage, 40% was represented by native bone and 15% by newly formed bone. CaS showed complete resorption and new bone formation in the maxillary sinus; this bone was found to be in close contact with the implant surface after immediate loading.     

A descriptive study on retrieved non-threaded and threaded implant designs

Objectives: In the light microscope compare the amount of bone saucerization for non‐threaded cylindrical and threaded implant designs in retrieved samples from patients. Material and method: Consecutively received retrieved oral implants from 117 patients, whereof 85 non‐threaded cylindrical and 85 Brånemark implants, have been included in the study. For 75 non‐threaded cylindrical and 46 Brånemark implants was the entire implant length available for calculation. Undecalcified ground sections were investigated in the light microscope with calculation of percentage of implant length coronal to the first bone–implant contact and percentage of bone to implant contact. Results: Mean value for implant length coronal to first bone–implant contact was 65%, standard error of the mean (SEM) 3 (range 0–100%), for non‐threaded cylindrical implants and 43%, SEM 6 (range 0–100%) for Brånemark implants. Mean values of bone contact along the entire implant length was 23%, SEM 2 (range 0–65%), for the non‐threaded cylindrical implants and 33%, SEM 5 (range 0–93%) for the Brånemark implants. Conclusion: Within the limitations of this retrospective, retrieval study non‐threaded cylindrical implants demonstrated a greater bone saucerization when evaluated in the light microscope.     

Maxillary sinus floor augmentation using bioactive glass granules and autogenous bone with simultaneous implant placement. Clinical and histological findings

This clinical study was undertaken to: 1) evaluate the use of bioactive glass Biogran combined with autogenous bone as grafting material for maxillary sinus augmentation with simultaneous implant placement using radiography and histology; and 2) document the short-term post-loading success of implants inserted in sinus cavities augmented with this material. Unilateral or bilateral sinus augmentation was performed in 12 patients with 3-5 mm of alveolar crestal bone height in the posterior maxilla prior to grafting. The sinuses were grafted with bioactive glass mixed in a 4:1 ratio with autogenous bone. Simultaneously, 2-3 threaded titanium implants were inserted into the augmented sinuses. Second stage surgery was carried out 9 to 12 months post implantation. At abutment connection, 10 core biopsy specimens were taken from different grafted sites and evaluated histologically. All 27 implants were clinically stable at second stage surgery. A mean increase in mineralized tissue height of 7.1 +/- 1.6 mm was evident when comparing the pre-surgical CT scans with those performed 9-12 months following the sinus augmentation procedure. Evaluation of the cores yielded a mean of 30.6 +/- 5.7% of bone tissue in the grafted sites. One implant failed during the prosthetic phase while the remaining 26 implants were stable 12 months post loading. This study suggests that Biogran/autogenous bone graft combination used in one-stage sinus augmentation yields sufficient quality and volume of mineralized tissue for predictable simultaneous implant placement in patients with 3-5 mm of bone height prior to grafting.     

上颌窦外提升术在口腔种植术中的应用

目的:探讨上颌窦提升术在口腔种植术中的应用以扩大口腔种植术中的应用范围。方法:25例患者通过上颌窦提升术同期或延期植入种植体31枚,术中患者使用了Bio-Oss胶原质作为骨移植材料,采用非埋入式种植技术。结果:术后6个月,上颌窦底提高4-6mm,所有病例完成修复后,随访6-24各月,x线检查窦底骨质无明显吸收,种植体骨结合良好,无松动脱落,修复效果满意。结论:上颌窦提升术扩大了口腔种植术的应用范围。     

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys

The aim of this study was to evaluate clinically, histologically and histometrically the use of anorganic bovine bone matrix (i.e. Bio-oss®) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (i.e. Mucaca mulattu) the 1st 2nd and 3rd maxillary molars on one side of the jaws were extracted. The remaining bone between the alveolar crest and the bottom of the sinus was then reduced to 3–4 mm. After 3 months, maxillary sinus augmentation procedures were performed on one side of the jaws in each monkey and the sinuses were grafted with the bovine bone matrix. At that time, 2 IMZ pure titanium plasma coated implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into these previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received the same treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants-unloaded group and delayed implants-unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited significant bone formation with integration of the bovine bone matrix particles to the new bone. Direct mineralized bone-to-implant contact was greater for the delayed implant placement groups than for the implants installed simultaneously with the sinus augmentation. Furthermore, the percentage of direct mineralized bone-to-implant contact was greater in the residual bone than in the augmented area. It was concluded that the anorganic bovine bone matrix facilitated bone formation and implant osseointegration in the augmented sinuses and that the delayed implant placement in combination with the sinus augmentation procedure seemed to be preferable.     

Bone reformation and implant integration following maxillary sinus membrane elevation: an experimental study in primates

Background: Recent clinical studies have described maxillary sinus floor augmentation by simply elevating the maxillary sinus membrane without the use of adjunctive grafting materials. Purpose: This experimental study aimed at comparing the histologic outcomes of sinus membrane elevation and simultaneous placement of implants with and without adjunctive autogenous bone grafts. The purpose was also to investigate the role played by the implant surface in osseointegration under such circumstances. Materials and Methods: Four tufted capuchin primates had all upper premolars and the first molar extracted bilaterally. Four months later, the animals underwent maxillary sinus membrane elevation surgery using a replaceable bone window technique. The schneiderian membrane was kept elevated by insertion of two implants (turned and oxidized, Brånemark System®, Nobel Biocare AB, Göteborg, Sweden) in both sinuses. The right sinus was left with no additional treatment, whereas the left sinus was filled with autogenous bone graft. Implant stability was assessed through resonance frequency analysis (Osstell^TM, Integration Diagnostics AB, Göteborg, Sweden) at installation and at sacrifice. The pattern of bone formation in the experimental sites and related to the different implant surfaces was investigated using fluorochromes. The animals were sacrificed 6 months after the maxillary sinus floor augmentation procedure for histology and histomorphometry (bone‐implant contact, bone area in threads, and bone area in rectangle). Results: The results showed no differences between membrane‐elevated and grafted sites regarding implant stability, bone‐implant contacts, and bone area within and outside implant threads. The oxidized implants exhibited improved integration compared with turned ones as higher values of bone‐implant contact and bone area within threads were observed. Conclusions: The amount of augmented bone tissue in the maxillary sinus after sinus membrane elevation with or without adjunctive autogenous bone grafts does not differ after 6 months of healing. New bone is frequently deposited in contact with the schneiderian membrane in coagulum‐alone sites, indicating the osteoinductive potential of the membrane. Oxidized implants show a stronger bone tissue response than turned implants in sinus floor augmentation procedures.     

Ultimate masticatory force as a criterion in implant selection

Osseointegrated implants often fail because of excessive masticatory forces that cause extremely large stresses in bone tissue. We hypothesized that a proper dental implant could be selected by comparing the ultimate masticatory forces of a wide range of commercially available implants. We determined ultimate oblique masticatory forces for different cylindrical implants, taking into consideration the biomechanical correlation between implant dimensions and stresses in supporting bone. For this purpose, we used the finite element (FE) method and studied von Mises stresses in implant-bone interface areas to evaluate the influence of implant dimensions on stress concentration and on the value of an implant's ultimate masticatory load. Geometric models of a mandibular segment were generated from computed tomography (CT) images and were analyzed with osseointegrated cylindrical implants. Masticatory forces were applied in their natural direction. All materials were assumed to be linearly elastic and isotropic. Critical point in the peri-implant area of bone was determined. The ultimate value of the masticatory load, which generates ultimate stresses at the critical point, was calculated for each implant. These findings provide correct selection of implant dimensions in clinical cases, because corresponding ultimate values of masticatory force were used as a criterion for assessment of their load-carrying capacity and applicability.     

上颌窦提升术同期或延期牙种植的早期临床评价

目的对上颌窦提升术同期或延期牙种植进行早期临床评价。方法37例患者38侧上颌窦进行上颌窦提升同期或延期牙种植,种植体上部结构修复完成后6～36个月定期复查。结果观察期内同期牙种植27侧上颌窦共59颗种植体,松动、脱落1颗,成功率为98.3%。延期牙种植上颌窦11侧共23颗种植体,全部成功。除1颗失败种植体外,其余同期或延期植入的种植体均无松动或脱落,经X线片检查显示植入骨材料改建良好,种植体周围未见明显骨吸收阴影。结论上颌窦提升术同期或延期牙种植的早期临床效果无明显差异。     

All-on-Four技术在口腔种植领域中的应用进展

种植修复是恢复无牙颌患者咀嚼功能和美观的有效治疗方法,但因可用骨量的不足、上颌窦和下牙槽神经血管束等解剖问题而面临巨大挑战。对该类患者行种植体植入术时,常需要进行相关的骨增量手术。All?on?Four技术是指在无牙颌前牙区植入两颗轴向种植体,在远中端植入两颗角度种植体,并即刻负重,且在4～6个月后完成最终修复的新种植修复技术。该技术避免了人工骨粉植入术及上颌窦提升术等骨增量过程,患者心理反应及术后反应较轻,同时节省了患者的时间和金钱成本。这种联合应用倾斜种植体和直种植体来共同完成无牙颌患者的固定修复治疗被认为是一种可行的治疗方式。本文将就All?on?Four概念、常规技术、评价研究以及近年来提出的一些新的观点进行阐述。     

Maxillary sinus augmentation using different grafting materials and osseointegrated dental implants in monkeys. Part IV Evaluation of hydroxyapatite‐coated implants.

The aim of this study was to evaluate clinically, histologically and histometrically the use of hydroxyapatite-coated dental implants in conjunction with maxillary sinus augmentation procedures. In 4 adult male Rhesus monkeys (Mucaca muluttu) the 3 maxillary molars on 1 side of the jaws were extracted and the remaining bone between the alveolar crest and the floor of the sinus was reduced to 3–4 mm. After 3 months, maxillary sinus augmentation procedures were performed in each monkey and the sinuses were grafted with a porous hydroxyapatite bone graft (Interpore-200®). At the same time, 2 hydroxyapatite-coated cylinder implants (IMZ®) were immediately placed into the augmented sinuses (i.e. simultaneous-implants-loaded group). Four months later, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed-implants-loaded group). After 4 months, the abutment connection was performed, and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received the same treatment with the exception that removal of the maxillary molars was performed 7 months after those in the opposite side, and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous-implants-unloaded group and delayed-implants-unloaded group) were obtained. Clinically, all loaded and unloaded implants were stable the day of sacrifice. Histologically, the grafted sinuses exhibited a significant amount of new bone formation, with integration of the porous hydroxyapatite graft particles and hydroxyapatite-coat of the dental implants to the new bone. Histometric analysis indicated that on the loaded side the implants placed simultaneously with the sinus lift procedure exhibited greater direct mineralized bone-to-implant contact than the delayed placed implants. In addition, the percentage of direct mineralized bone-to-implant contact was significantly greater in the residual bone in comparison to the augmented area in all groups. Loading of the implants exhibited a positive effect on the percentage of direct mineralized bone-to-implant contact in the augmented area. It could be concluded that hydroxyapatite-coated implants may be of benefit when used in conjunction with sinus augmentation procedures.     

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Evaluation of autogenous bone combined with porous hydroxyapatite.

The aim of this study was to evaluate clinically, histologically, and histometrically the use of autogenous bone combined with porous hydroxyapatite (Interpore 200®) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted. After a healing period of 3 months. maxillary sinus augmentation procedures were performed in each monkey, and the sinuses were grafted with autogenous bone from the monkeys' tibia mixed in a 3:1 ratio with porous hydroxyapatite. At the same time. 2 pure titanium plasma-sprayed IMZB cylinder implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received similar treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants unloaded group and delayed implants unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited a significant amount of new bone formation. The porous hydroxyapatite granules appeared integrated with the newly formed bone. Histometric analyses revealed that delayed implant placement resulted in a greater amount of direct mineralized bone-to-implant contact in the augmented area than the simultaneous implant placement. Furthermore, the percentage of direct mineralized bone-to-implant contact was far more significant in the residual bone than in the augmented area. It was concluded that the autogenous bone/porous hydroxyapatite graft combination enhanced bone formation and mineralized bone-to-implant contact in the augmented sinuses and that the delayed implant placement may be favorable for sinus augmentation procedures.     

上颌窦外提升在口腔种植术中的应用

目地：探讨上颌窦外提升术在口腔种植手术中的应用,以扩大口腔种植术的适应证。方法：2007年5月-2012年12月对41例患者,通过上颌窦外提升术同期或延期植入86枚Itl种植体,使用Bio—Oss人工骨作为骨移植材料,采用非埋入式种植技术。结果：41例患者中2例发生上颌窦黏膜破裂,86枚种植体均完成种植修复,随访至2012年底,种植修复体无松动脱落,临床修复效果满意。结论：上颌窦外提升术可以扩大口腔种植的适应症。     

Simultaneous dental implant placement and endoscope-guided internal sinus floor elevation: 2-year post-loading outcomes

Aims: To determine whether endoscope‐guided sinus elevation procedures can be consistently used to create sufficient bone support for stable implant placement and long‐term implant success. Material and methods: Sixty‐two implants were surgically placed into 30 patients (14 men and 16 women) following internal sinus elevation without the use of graft material. Panoramic radiographs were made pre‐, post‐operative and after 24 months in order to evaluate the peri‐implant bone and maxillary sinuses. Resonance frequency analysis (RFA) was used to evaluate implant stability immediately upon placement and just before prosthesis delivery. Results: The average pre‐operative height of the maxillary alveolar bone was 8.4±2.2 mm at the premolar and 7.3±3.1 mm at the molar regions. The average bone gain was 3.5±1.8 and 4.5±1.9 mm in the premolar and molar sites, respectively. Clinical parameters and the RFA (4 and 12 weeks post‐operative) outcomes show sufficient stability (ISQ=60) of the inserted implants. Three implants failed during the healing period of 12 weeks. The overall implant success rate was 94%. After loading, no further implant failure was observed. The overall success rate after beginning of implant loading was 100%. Conclusions: Sinus floor elevation is a well‐established procedure for augmentation of the atrophic maxillary posterior region. The minimally invasive internal sinus floor elevation procedure visually guided by an endoscope helped to prevent, diagnose and manage complications such as sinus membrane perforation. The clinical outcomes of this study show that endoscope‐controlled internal sinus floor elevation combined with implant placement results in low intra operative trauma, good implant stability upon placement, low incidence of post‐operative symptoms and high success rates after 24 months of loading.     

Effects of exposing dental implant to the maxillary sinus cavity

The aim of this study was to evaluate the effects of exposing dental implants to the maxillary sinus cavity. This is a retrospective study. Thirteen patients with 18 implants that had radiographic evidence of implant exposure to the maxillary sinuses participated in this study. We evaluated the patient's radiographs immediately after implant insertion and 12 months after operation with the patient's clinical signs and symptoms due to sinusitis. Thirteen patients with 18 implants in the maxillary sinus had no signs and symptoms of sinusitis. Radiography showed thickening of the sinus membranes in 2 patients. All penetrated implants were successfully integrated, and there were no radiographic signs of bone loss or other complications.The exposure of implants to the maxillary sinuses caused no problems in the maxillary sinuses, and bone formation occurred in THE maxillary floor when penetration of maxillary sinuses occurred without tearing of the membrane.     

口腔种植中骨增量技术的应用进展

临床上,种植部位骨量不足是种植治疗常遇到的难题。为确保种植区符合种植条件,骨增量技术尤为重要。常用的骨增量技术包括骨移植术、引导骨再生技术、骨劈开术、骨挤压术、上颌窦底提升术及牵张成骨术等。本文就骨增量技术在口腔种植中的应用进展作一综述。