Surface area analysis of dental implants using micro-computed tomography

Objectives: In this study, we present and evaluate a micro‐computed tomography (micro‐CT)‐based method for the calculation of the potential bone/implant contact area (p‐BICA) on the surface of dental implants. Material and methods: For seven commercially available implants (Ankylos? implant, Brånemark System^®, Frialit CELLplus?, Replace^® Select Tapered, Straumann Solid screw?, XiVE S CELLplus?, 3i Osseotite XP? Threaded Miniplant^®), the p‐BICA surface is determined by means of three‐dimensional X‐ray computed‐tomography and computer‐based data processing. Measurements were repeated two times, and the stability and repeatability of the measurement method were evaluated. Results: Our analysis revealed a p‐BICA of 118 mm² for the XiVE S CELLplus? implant, 134 mm² for the Ankylos?, 136 mm² for the Frialit CELLplus?, 138 mm² for the Brånemark System^®, 139 mm² for the Replace^®, 159 mm² for the 3i Osseotite XP? and 199 mm² for the Straumann Solid screw? implant. The measurement method proved to be stable and led to reproducible results. Conclusions: The micro‐ and macrostructure of dental implants define the surface and the p‐BICA. Precise determination of this parameter can be achieved by means of the micro‐CT‐based method as presented in this study. The value of p‐BICA lies in the predictability of industrial design before preclinical and clinical testing. Based on this method, dental implant properties become comparable even if geometrical details are not disclosed by the manufacturer.     

Bone microvascular pattern around loaded dental implants in a canine model

The vascularity of the implant bed is a very important parameter in both bone formation and maintenance after dental implants insertion. The relationship between bone and vessels network organization is still unknown. The aim of this study was to investigate the three-dimensional bone vascular canals of the peri-implant bone after loading. A total of ten implants with sandblasted and acid-etched surface were placed in the mandible of a beagle dog. Three months later, the implants were connected and loaded. The dog was killed after 12 months. The specimens were embedded and processed for scanning electron microscopy (SEM) analysis. After a 1-year loading period, a very intricate vessel network could be seen around the implants. The vessels, with neighbouring soft tissues, were round in shape and showed a lot of anastomoses with a mesh-like appearance. They ran circularly around the dental implant. In the bone, the majority of the vessels appeared to ran parallel to the mandibular canal. After a 1-year loading period, the peri-implant bone vasculature looked like a mesh that surrounded the implants. Nevertheless, the presence of many thick vessels inside the peri-implant crestal bone indicates a high metabolic need and also a different bone organization, as no osteons were noted. The crater-like bone loss around the marginal part of the implant could be related to the microvasculature “strain”. A high strain level could continuously activate the osteocyte–vessel syncytium, producing a net bone loss.     

Turned versus anodised dental implants: a meta‐analysis

The aim of this meta‐analysis was to test the null hypothesis of no difference in the implant failure rates, marginal bone loss (MBL)and post‐operative infection for patients being rehabilitated by turned versus anodised‐surface implants, against the alternative hypothesis of a difference. An electronic search without time or language restrictions was undertaken in November 2015. Eligibility criteria included clinical human studies, either randomised or not. Thirty‐eight publications were included. The results suggest a risk ratio of 2·82 (95% CI 1·95–4·06, P < 0·00001) for failure of turned implants, when compared to anodised‐surface implants. Sensitivity analyses showed similar results when only the studies inserting implants in maxillae or mandibles were pooled. There were no statistically significant effects of turned implants on the MBL (mean difference‐MD 0·02, 95%CI ?0·16–0·20; P = 0·82) in comparison to anodised implants. The results of a meta‐regression considering the follow‐up period as a covariate suggested an increase of the MD with the increase in the follow‐up time (MD increase 0·012 mm year^?1), however, without a statistical significance (P = 0·813). Due to lack of satisfactory information, meta‐analysis for the outcome ‘post‐operative infection’ was not performed. The results have to be interpreted with caution due to the presence of several confounding factors in the included studies.     

348枚牙种植体即刻种植的临床疗效及体会

目的:探讨即刻种植义齿修复牙缺失的外科植入方法,观察其临床疗效,评价其相关影响因素。方法:192例患者在拔牙同时即刻植入种植体348枚,前牙160枚,前磨牙80枚,磨牙108枚,3-9个月后行永久性修复,定期进行复诊和随访,观察6-84个月。结果:348枚种植体中,13枚因各种原因脱落、拔除,其余种植体骨结合好,取得了良好的临床效果,累积存留率96.26%。结论:即刻种植义齿具有自身优点,手术可行,在控制好适应证的情况下,可以取得良好的临床效果。     

改良喷砂表面处理对钛牙种植体骨结合的组织学作用

研究改良喷砂表面处理对钛牙种植体骨结合的影响。方法柱状纯钛种色植分两组（光滑表面和改良喷砂表面组）进行表面处理,植于狗后肢股骨内侧髁,分别于2、4、12周取材、固定、脱钙后常规HE染色,光镜观察。结果：改良喷砂表面组与光滑表面组的骨愈合过程,均为膜内成骨,并形成完全的骨结合。二者的差别主要表现在愈合的早期（割周）,改良喷砂表面组界面成骨较快,愈合中晚期差别不明显。结论：改良喷砂表面处理可以加快钛牙种植体的骨结合速度。     

The effect of internal versus external abutment connection modes on crestal bone changes around dental implants: a radiographic analysis

Background: To the best of our knowledge, the influence of external versus internal implant–abutment connections on crestal bone remodeling has not been reported. The aim of the present study is to investigate the influence of the abutment connection on peri‐implant crestal bone levels (CBLs) using radiographic recordings. Methods: Radiographic recordings from 40 single‐tooth implants (20 external and 20 internal octagonal connections; one implant/patient) in 40 patients (15 males and 25 females; mean age: 54.3 years) were selected for analyses. The radiographic evaluation included the following: 1) linear bone change (LBC); 2) dimensional change (DC); and 3) angle between the implant and adjacent bone (AIB). Differences in LBC, DC, and AIB between implant placement and 1 year after loading for each system were evaluated using a paired t test. Comparison of LBC, DC, and AIB between systems at 1 year after loading was done using analysis of covariance. The significance level was set at P ≤0.05. Results: Radiographic CBLs (LBCs) were reduced at 1 year after loading compared to those at implant placement to reach statistical significance for the external connection (P = 0.000) but not the internal connection (P = 0.939). CBL changes were significantly greater for the external compared to the internal connection (P = 0.000). Similarly, the DC for the external connection was significantly greater compared to that for the internal connection (P = 0.004). Conclusion: Within the limitations of this study, the implant–abutment connection technology appears to have a significant impact on peri‐implant CBLs, with the external connection paralleled by a significant reduction of CBLs.     

Survival of dental implants in irradiated head and neck cancer patients: a retrospective analysis

Purpose: To study the long‐term survival of dental implants placed in irradiated bone in subjects who received radiation for head and neck cancer. Materials and Method: A retrospective chart review was conducted for all patients who received dental implants following radiation treatment for head and neck cancer between May 1, 1987 through July 1, 2008. Only patients irradiated with a radiation dose of 50 Gy or greater and those who received dental implants in the irradiated field after head and neck radiation were included in the study. The associations between implant survival and patient/implant characteristics were estimated by fitting univariate marginal Cox proportional hazards models. Results: A total of 48 patients who had prior head and neck radiation had 271 dental implants placed during May 1987 to July 2008. The estimated survival at 1, 5, and 10 years was 98.9%, 89.9%, and 72.3%, respectively. Implants placed in the maxilla were more likely to fail than implants placed in the mandible (p = .002).There was also a tendency for implants placed in the posterior region to fail compared with those placed in the anterior region (p = .051). Conclusion: Dental implants placed in irradiated bone have a greater risk for failure. Survival is significantly influenced by the location of the implant (maxilla or mandible, anterior or posterior).     

骨质疏松状态下牙种植体骨髓整合改变的实验研究

目的:探索骨质疏松状态下牙种植体骨整合的变化机制,为提高骨质疏松状态下牙种植体成功率奠定基础。材料与方法:6月龄未交配SD雌性大鼠41只随机分为2组,即A:假去势手术组,20只,B:去势手术组,21只。将B组行卵巢切除术,术后1.5月对所有大鼠右股骨远中行牙种植手术,种植纯钛螺钉。分别于种植术后1.5月及3月,随机处死各组大鼠的一半。去势术前、种植术前及处死前分别测量大鼠腰椎3—5、左右股骨远中1/2骨密度。处死后,取右股骨对种植部位进行X线拍片,然后将右股骨沿种植体长轴剖成两半,做扫描电镜观察种植体与骨结合状况,进行骨接触率的测定。结果:1.骨密度:两组大鼠腰椎、左右股骨远中骨密度去势术前大致相同,无显著差异。种植手术前,A组基本保持不变,B组显著降低。1.5月及3月处死时,A组仍基本保持不变,B则持续显著降低。2.骨融合指数(OI):1.5月及3月处死时,A组大于B组,统计分析,差异显著。各组大鼠不同时期处死时,骨融合指数大致相同,统计分析无显著差异。结论:1.不同骨密度下骨整合状况不同,骨密度高,骨整合状况好。2.种植体-骨界面新骨形成后,在没有外界因素作用情况下,延长时间骨整合状况改善不明显。3.骨质疏松改变可使大鼠种植体—骨界面骨融合指数降低。     

钛膜引导骨再生在骨内种植体植入中的应用

目的：总结牙种植术后使用钛膜引导骨再生临床体会。方法：对30例47枚牙种植术中发现骨缺损、骨量不足的患者采用钛膜进行骨引导再生修复骨缺损及骨增量。术后定期观察，对新骨生长情况进行连续临床和X线的观察分析。结果：30例47枚牙种植术中，39枚种植体植入部位使用了钛膜。二期手术时种植体均已与骨组织形成理想的骨融合，顺利完成种植义齿修复。39枚种植体中有15枚种植体术后2个月的X线片可见到种植体封闭螺帽上方骨密度增高影。4月后二期手术切开牙龈时可见到新骨覆盖种植体表面，以骨凿等去除新骨后方可见到封闭螺帽。结论：医用钛膜在种植术中应用有较好的引导骨再生作用，有利于种植术后骨融合期新骨的形成。不可吸收性膜的一些固有缺陷可通过临床正确的设计关在术中严格按照操作要点进行手术，可获得理想的骨再生效果。     

Partial generation of periodontal ligament on endosseous dental implants in dogs

OBJECTIVES: The objective of this pilot study was to investigate the feasibility of periodontal ligament (PDL) generation on an implant surface by approximating a tooth-to-implant contact using orthodontics. METHODS: Maxillary second premolars of six beagle dogs were extracted bilaterally. After 2 weeks of healing, hydroxyapatite (HA) coated titanium implants, 5 mm in length and 3.3 mm in diameter, were placed in the extraction sites. One side of the arch was used as control. Orthodontic tooth movement was initiated following implant placement to tip the first premolar roots into contact with the implant. This was achieved in 4-6 weeks as confirmed radiographically. Tooth-to-implant contact was maintained for further 6 weeks after which time, teeth were separated from implant contact orthodontically. After further 2 weeks of stabilization, the animals were sacrificed. Samples were analyzed by Faxitron radiographs before histology. Histology samples were prepared with Stevenel's Blue and Van Gieson stain and were subjected to polarized light microscopy. RESULTS: Histologic analysis revealed transfer and formation of PDL-like structure with formation of cellular cementum on the implant surfaces, in four out of six animals, where tooth-to-implant contact had been achieved. Direct bone-to-implant contact was noted in the areas coronal to the PDL-like tissue, an important sign to distinguish between PDL-like tissue and connective tissue that could originate from the coronal portion of a failing implant. Additionally, at the site of contact, the implant surface revealed some resorption of the HA coating. CONCLUSION: An animal model was established in which the proximity of tooth-to-implant contact lead to partial generation of PDL on a bioactive implant surface in four out of six animals.     

密质骨厚度影响牙种植体稳定性的有限元固有频率分析

目的：用有限元方法研究密质骨厚度对牙种植体初期稳定性的影响。方法：建立牙种植体、局部下颌骨块三维有限元模型,利用ABAQUS有限元软件,分析不同密质骨厚度对种植体颊舌向、轴向一阶振动固有频率的影响。结果：随着密质骨厚度由缺如逐渐增加至3．0mm,种植体颊舌向、轴向振动的固有频率值均逐渐增加,其中颊舌向固有频率最大增幅达97．61％,而轴向固有频率最大值仅增加了11．06％。结论：种植体周密质骨厚度主要增加了种植体颊舌向稳定性,而对种植体轴向稳定性的增加有限。     

Plaque formation on surface modified dental implants

Bacterial adhesion on titanium implant surfaces has a strong influence on healing and long-term outcome of dental implants. Parameters like surface roughness and chemical composition of the implant surface were found to have a significant impact on plaque formation. The purpose of this study was to evaluate the influence of two physical hard coatings on bacterial adhesion in comparison with control surfaces of equivalent roughness. Two members of the oral microflora, Streptococcus mutans and Streptococcus sanguis were used. Commercially pure titanium discs were modified using four different surface treatments: physical vapour deposition (PVD) with either titanium nitride (TiN) or zirconium nitride (ZrN), thermal oxidation and structuring with laser radiation. Polished titanium surfaces were used as controls. Surface topography was examined by SEM and estimation of surface roughness was done using a contact stylus profilometer. Contact angle measurements were carried out to calculate surface energy. Titanium discs were incubated in the respective bacterial cell suspension for one hour and single colonies formed by adhering bacteria were counted by fluorescence microscopy. Contact angle measurements showed no significant differences between the surface modifications. The surface roughness (Ra) of all surfaces examined was between 0.14 and 1.00 microm. A significant reduction of the number of adherent bacteria was observed on inherently stable titanium hard materials such as TiN and ZrN and thermically oxidated titanium surfaces compared to polished titanium. In conclusion, physical modification of titanium implant surfaces such as coating with TiN or ZrN may reduce bacterial adherence and hence improve clinical results.     

Equicrestal and subcrestal dental implants: a histologic and histomorphometric evaluation of nine retrieved human implants

Background: Stability of peri‐implant crestal bone plays a relevant role relative to the presence or absence of interdental papilla. Several factors can contribute to the crestal bone resorption observed around two‐piece implants, such as the presence of a microgap at the level of the implant–abutment junction, the type of connection between implant and prosthetic components, the implant positioning relative to the alveolar crest, and the interimplant distance. Subcrestal positioning of dental implants has been proposed to decrease the risk of exposure of the metal of the top of the implant or of the abutment margin, and to get enough space in a vertical dimension to create a harmoniously esthetic emergence profile. Methods: The present retrospective histologic study was performed to evaluate dental implants retrieved from human jaws that had been inserted in an equicrestal or subcrestal position. A total of nine implants were evaluated: five of these had been inserted in an equicrestal position, whereas the other four had been positioned subcrestally (1 to 3 mm). Results: In all subcrestally placed implants, preexisting and newly formed bone was found over the implant shoulder. In the equicrestal implants, crestal bone resorption (0.5 to 1.5 mm) was present around all implants. Conclusion: The subcrestal position of the implants resulted in bone located above the implant shoulder.     

纳米级钛颗粒对牙周组织细胞的影响

目的通过研究纳米级钛颗粒对牙周膜细胞和牙槽骨细胞增值、分化的影响,探讨种植体脱落纳米级钛颗粒在种植体周围炎的发生、发展过程中的作用与机理。方法 利用透射电子显微镜观察实验所用纳米级钛颗粒的大小与表面形貌;分离培养12月龄 SPF级大鼠下颌第一磨牙牙周膜细胞和牙槽骨细胞,加入5×10 6粒/ml纳米级钛颗粒处理细胞,取该培养液为条件培养基,未加入纳米级钛颗粒的细胞和培养液作为对照组。培养2、4、6、8天后,倒置显微镜下观察细胞形态并计数;利用real-time PCR检测细胞培养24h后TNF-α和IL-1基因表达情况;当培养细胞发生接触抑制时,更换培养液并进行von Kossa染色后,观测钙化基质的沉积;利用real-time PCR 检测细胞成骨标志基因的表达。分离大鼠胫骨和腓骨骨髓单核细胞,阳性对照加入20ng/ml MCSF和50ng/ml RANKL处理,实验组加入纳米级钛颗粒处理的或未处理的条件培养基,培养1周后,进行TRAP染色并计破骨细胞数。结果 透射电子显微镜下,纳米级钛颗粒大小均一,直径约50~100nm,表面光滑;纳米级钛颗粒对牙周膜细胞和牙槽骨细胞增值具有微弱抑制作用,但无统计学差异( P ﹥0.05);Real-time PCR结果显示,细胞培养24h后,实验组牙周膜细胞和牙槽骨细胞TNF-α和IL-1基因表达明显增高;von Kossa染色可见,纳米级钛颗粒处理的实验组牙周膜细胞和牙槽骨细胞成骨分化能力低于对照组;纳米级钛颗粒促进牙周膜细胞和牙槽骨细胞分泌RANKL( P< 0.05),其中牙周膜细胞分泌较为显著;用含纳米级钛颗粒的条件培养基来处理大鼠骨髓单核细胞时,破骨细胞生成增多。结论 纳米级钛颗粒对体外培养牙周膜细胞和牙槽骨细胞增值无明显作用,但是对其成骨分化有明显的抑制作用;同时促进牙周膜细胞和牙周骨细胞TNF-α、IL-1及RANKL的分泌;并可促进单核细胞分化为破骨细胞。     

Mechanical complications of dental implants

Adverse occlusal forces can result in mechanical complications of implant components. While unacceptably high incidences of mechanical failures have been reported for the two-stage external hex screw-type implant systems, the standard-diameter ITI solid-screw implant does not seem to be vulnerable to these problems. The 8 degrees Morse taper has eliminated abutment screw loosening and fracture. The incidence of prosthetic screw loosening has been minimized by the 45 degrees bevel on the implant shoulder and by the 1.5 mm vertical abutment walls. The design of the standard-diameter solid-screw ITI implant and the material used in its fabrication (cold worked type IV cp titanium) have eliminated fixture fracture. However, because there have been some reported instances of fractures involving reduced-diameter and hollow implants, these designs should be used with caution.