Damping factor for monitoring the bone interface at dental implants

OBJECTIVES: The aim of this study is to investigate whether the damping of osseointegrated implants, as measured quantitatively with the Osstell equipment, is related to the fractal dimension of peri-implant bone. MATERIAL AND METHODS: Fifty-five maxillary implants in function for 3 years before the present study were investigated. Two Osstell measurements were obtained for each implant with the transducer oriented first palatally and then distally. Using the half-power bandwidth method, the damping was calculated from the frequency/amplitude plot obtained from the Osstell. Damping data were then related to the fractal dimension of peri-implant bone. Fractal dimensions were calculated using a box-counting algorithm on digitally processed intra-oral radiographs of the implants. A Spearman's test was used to verify the correlation between damping and fractal dimension values. RESULTS: All the implants were clinically stable and free from symptoms. The mean ISQ was 63 for the palatal orientation and 71 for the distal orientation. The mean fractal dimension was 1.47; the mean damping value for palatal orientation was 12.3%, while that for the distal orientation was 8.2%. No significant correlation was found. CONCLUSIONS: Damping values, measured at peri-implant bone, were found not to be related to a radiographic parameter of trabecular bone pattern like the fractal dimension. The clinical implication would be that Osstell graphs displaying distinct or more rounded peaks might both indicate a stable implant as long as the associated implant stability quotients are in the range of satisfactory values proposed in the literature.     

Biological and biomechanical evaluation of bone remodelling and implant stability after using an osteotome technique

The influence of the osteotome technique on the osseointegration and biomechanical behaviour of cylinder implants (SLA, ITI was compared with conventional preparation of the implant site in an animal model. A total of 56 implants were placed in the cranial and caudal tibia condyle of six Gottinger minipigs. The implant site was prepared either by the conventional technique with drills (control group A) or by the osteotome technique (experimental group B). Resonance frequency measurements (RFMs) were made on each implant at the time of fixture placement and at the time of scarification. Half of the minipigs were sacrificed 7 days and 28 days after implant placement and the implants were removed with the surrounding bone. Bone tissue responses were evaluated by histological analysis and removal torque testing. For histological evaluation 30-50 microm-thick ground sections were examined. Biomechanical testing revealed a significantly higher stability of implants in the control group (A) than in the experimental group (B) (P = 0.004) at day 7. After 28 days implant stability in the control group remained significant higher (47%) than those of group B (P > 0.001). RFM demonstrated no significant difference between both groups and during the experimental course. Histological analysis demonstrated fractured trabeculae in peri-implant bone in the experimental group at day 7, while they were not posed at day 28. We conclude that the decreased implant stability by using the osteotome technique is based on microfractures in peri-implant bone.     

Clinical and microbiological findings on newly inserted hydroxyapatite‐coated and pure‐ titanium human dental implants

The clinical and microbiologic features of 30 hydroxyapatite-coated root-form endosseous dental implants (Tri-Stage) were compared to 10 similar pure titanium implants without hydroxyapatite coatings. In 7 of 9 partially edentulous patients studied, pure titanium fixtures were placed adjacent to hydroxyapatite-coated implants. Implants in the maxilla were submerged beneath mucosal tissues after implant placement for a minimum of 6 months, and in the mandible for at least 4 months. All patients were prescribed short-term beta-lactam antibiotic therapy after fixture placement, and 8 of 9 used chlorhexidine mouthrinses after fixture exposure. Clinical and microbiological examination was carried out 7-10 months after fixed prosthetic loading of the implants. Clinical measurements included the gingival index, plaque index, bleeding on probing and peri-implant probing depths determined with the Florida Probe system. Subgingival microbial samples were collected with paper points and transported in VMGA III. Specimens were examined by direct phase-contrast microscopy and were plated onto nonselective and selective culture media for anaerobic and aerobic incubation. No significant mean clinical or microbiological differences were found between the implant types, although one hydroxyapatite-coated implant exhibited deep probing depths, bleeding on probing and marked radiographic crestal bone loss. Streptococcus sanguis and Streptococcus mitis were the most predominant organisms recovered from clinically stable implants, whereas high proportions of Fusobacterium species and Peptostreptococcus prevotii were isolated from the ailing hydroxyapatite-coated implant. One or more implants in 8 of the study subjects yielded enteric rods, pseudomonads, enterococci or staphylococci. The prognosis of implants with varying early microbiotas needs to be established in longitudinal studies.     

牙种植体挤压植入后早期骨界面的组织学变化

目的:了解种植体挤压植入后界面骨的早期组织学变化.方法:18颗Compress种植体挤压植入3头小型猪的下颌骨中,在植入4小时、3天、7天处死动物,切割含种植体的下颌骨,制作HE染色的脱钙骨组织切片,光镜观察.结果:3天时髓腔内大量纤维样间充质细胞增生,并部分替代凝血块,7天时在间充质细胞中及骨切剖面有新骨形成.结论:种植体挤压植入后的骨结合一周内已开始形成.     

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。     

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     

上颌窦冲顶提升术同期种植体植入的临床研究

目的 研究上颌窦冲顶提升术不植骨同期植入种植体的临床效果及种植特点。方法 43例患者,牙槽嵴顶距窦底骨高度为5～10mm。经上颌窦冲顶提升术不植骨植入56颗ITI种植体。结果 术后X片显示上颌窦底抬高(2.50±1.70)mm。所有患者未发生上颌窦炎的并发症,种植体稳固,X线片显示骨结合良好。所有种植体术后3～4个月均完成种植修复,可正常负重;种植体存留率100%。结论 在选择好适应证及良好的手术操作配合下,上颌窦冲顶提升术不植骨同期植入种植体可以获得很好的种植成功率。     

自攻型种植体在即刻种植中的生物学性能研究

目的　比较自攻型与非自攻型种植体在即刻种植方式中的初期稳定性,骨结合及新骨形成能力。为自攻型种植体临床应用提供依据。方法：选取健康雄性成年Beagle实验犬36只,微创拔牙后,行种植体即刻植入术。每只实验犬下颌植入骨水平自攻型种植体（BLE）,骨水平非自攻型种植体（BL）,软组织水平自攻型种植体（TLE）,软组织水平非自攻型种植体（TL）各一枚。分别在种植体植入后4,8,12周取材。记录并分析种植体植入时的旋入扭矩。应用种植体共振频率分析仪量化分析自攻型牙种植体的初期稳定性和长期稳定性。应用micro-CT观察并计算骨体积分数（骨体积/总体积, BV/TV, %）,骨小梁数量(Tb N,1/mm)、骨小梁间距(Tb. Sp, mm)分析植体周围骨改建情况。应用荧光标记物盐酸四环素进行骨改建情况示踪标记,利用激光共聚焦显微镜观察,分析比较自攻型种植体与非自攻型种植体新生骨面积。结果：对种植体植入时的植入扭矩和ISQ值进行分析,自攻组结果均优于非自攻组(p<0.05)。植入后4周,8周,12周的ISQ值,BLE组显著高于BL组(p<0.05),TLE组在植入后4周,8周显著高于TL组,在植入后12周与TL组基本一致。骨体积分数和新生骨面积均为自攻组优于非自攻组(p<0.05)。结论：在即刻种植中,自攻型种植体初期稳定性、骨结合强于非自攻型种植体,并且在新骨形成方面略强于非自攻型种植体。     

Short dental implants in patients with oral lichen planus: a long-term follow-up

Oral lichen planus is associated with the Koebner phenomenon, and trauma may exacerbate oral lesions. Short dental implants, as alternatives to bony augmentation, would reduce the number of interventions and their morbidity. However, we know of no studies that have analysed the long-term outcomes of short implants in patients with oral lichen planus. We have therefore designed a retrospective study of such patients treated with short implants (≤ 8.5 mm long), with survival of implants as the main outcome. The secondary outcomes were marginal bone loss and the development of complications. We calculated the implants’ survival and compared the outcomes statistically between erosive and reticular oral lichen planus. Sixty-six short implants were placed in 23 patients with a mean (SD) age of 58 (7)?years. The mean (SD) peri-implant bone loss was 0.96 (0.89)?mm mesially and 0.99 (1.1)?mm distally. Sixty-five of the 66 implants survived with a mean (SD) follow-up of 68 (32) months, and there were no significant differences between erosive and reticular disease. Stable long-term outcomes can be expected for short implants placed in patients with oral lichen planus, and graftless rehabilitation of missing teeth could be possible in these patients if short implants were used.     

Study of the osseointegration of dental implants placed with an adapted surgical technique

Objective: To study the osseointegration of dental implants placed with a modified surgical technique in Beagle dogs and to compare it with the conventional method. Materials and methods: Dental implants were placed bilaterally in the mandible of Beagle dogs using the press‐fit as well as undersized implant bed preparation technique. Micro computer tomography (micro‐CT) and histometric methods were used to analyze the bone implant contact and bone volume (BV) around the implants. Results: The bone‐to‐implant contact percentage (BIC: expressed as %), first BIC (1st BIC: expressed in mm), sulcus depth (SD: expressed in mm) and connective tissue thickness (CT: expressed in mm) were analyzed for both groups. The BIC percentage was significantly higher for the undersized installed implants (P=0.0118). Also, a significant difference existed between the undersized and press‐fit installed implants for the first screw thread showing bone contact (P=0.0145). There were no significant differences in mucosal response (SD and CT) for both installation procedures. Also, no significant difference was found in the BV, as measured using micro‐CT, between the implants placed with an undersized technique (59.3±4.6) compared with the press‐fit implants (56.6±4.3). Conclusion: From the observations of the study, it can be concluded that an undersized implant bed can enhance the implant–bone response. To cite this article:
Al‐Marshood MM, Junker R, Al‐Rasheed A, Al Farraj Aldosari A, Jansen JA, Anil S. Study of the osseointegration of dental implants placed with an adapted surgical technique
Clin. Oral Impl. Res. 22 , 2011; 753–759
doi: 10.1111/j.1600‐0501.2010.02055.x     

骨质疏松高危患者种牙区骨密度测定和手术对策

目的：观察后牙缺失患者缺牙区松质骨CT值对种植修复的影响。方法：我科2008年10月到2009年7月后牙缺失患者年龄26～69岁,平均年龄46.7岁。按照年龄和绝经与否分成骨质疏松高危组,绝经期女性和65岁以上老年男性,18例患者,24颗牙;骨质疏松低危组,非绝经期女性和64岁以下男性,23例患者,31颗牙。CT扫描后测定患者第三颈椎椎体和缺牙区松质骨的CT值作为该区的骨密度值,进行统计分析。将缺牙区骨密度低的患者进行手术设计,实施骨挤压种植手术。术后检查种植体初期稳定性,完成修复后做随访。结果：骨质疏松高危组患者第三颈椎椎体松质的密度与骨质疏松低危组差异无统计学意义（t=0.8403,p〉0.05）,骨质疏松高危组患者缺牙区松质骨的密度与骨质疏松低危组差异无统计学意义（t=0.5102,p〉0.05）,骨质疏松高危组患者缺牙区松质骨的密度与第三椎体松质骨的密度之间的差值和骨质疏松低危组相比差异也无统计学意义（t=0.4578,p〉0.05）。两组患者种植体初期稳定性均好,除骨质疏松高危组有2例失败病例外均成功完成Ⅱ期种植修复,并随访正常。结论：绝经期女性和65岁以上老年男性缺牙区松质骨的密度和其他人群无明显差异,种植手术时更应关注缺牙区的骨质情况,骨挤压和充分发挥骨皮质作用有利于增加骨密度低的患者种植义齿的初期稳定性。     

Peri-implant alveolar bone loss with respect to bone quality after use of the osteotome technique: results of a retrospective study

Knife-edge configurations or non space-maintaining defects of the alveolar ridge limit the indications for implant-prosthetic rehabilitation. If ridge expansion is required, bone splitting and bone spreading techniques may be applied. Summers introduced a modified approach for ridge expansion by osteotome technique. The principles of this nonablative implant bed preparation technique are lateral and apical bone relocation and condensation. The peri-implant alveolar bone loss after use of the osteotome technique was evaluated radiographically with respect to the bone quality in 22 patients with 22 implants. Differences between the alveolar crest and the implant shoulder in radiographs obtained immediately after implant insertion, after the end of unloaded healing period and after different periods of functional loading were calculated. The osteotome technique was used in bone quality classes 2 and 3, respectively, according to the Lekholm and Zarb classification. Two implants failed. Significant differences were found between the bone levels after implant insertion and at the end of the healing period as well as after functional loading (P = 0.028). The bone quality was significantly correlated (r = - 0.505; P = 0.023) with the change of the peri-implant marginal bone height level 6 months after the implant installation. The present data indicate the importance of bone quality evaluation before application of the osteotome technique.     

Pulsed electromagnetic fields promote bone formation around dental implants inserted into the femur of rabbits

The present study examined the effect of applying a pulsed electromagnetic field (PEMF) on bone formation around a rough-surfaced dental implant. A dental implant was inserted into the femur of Japanese white rabbits bilaterally. A PEMF with a pulse width of 25 microseconds and a pulse frequency of 100 Hz was applied. PEMF stimulation was applied for 4 h or 8 h per day, at a magnetic intensity of 0.2 mT, 0.3 mT or 0.8 mT. The animals were sacrificed 1, 2 or 4 weeks after implantation. After staining the resin sections with 2% basic fuchsin and 0.1% methylene blue, newly formed bone around the implant on tissue sections was evaluated by computer image analysis. The bone contact ratios of the PEMF-treated femurs were significantly larger than those of the control groups. Both the bone contact ratio and bone area ratio of the 0.2 mT- and 0.3 mT-treated femurs were significantly larger than the respective value of the 0.8 mT-treated femurs (P < 0.001). No significant difference in bone contact ratio or bone area ratio was observed whether PEMF was applied for 4 h/day or 8 h/day. Although a significantly greater amount of bone had formed around the implant of the 2-week treated femurs than the 1-week treated femurs, no significant difference was observed between the 2-week and 4-week treated femurs. These results suggest that PEMF stimulation may be useful for promoting bone formation around rough-surfaced dental implants. It is important to select the proper magnetic intensity, duration per day, and length of treatment.     

Histomorphometric assessment in human cadavers of the peri-implant bone density in maxillary tuberosity following implant placement using osteotome and conventional techniques

Objective: To evaluate and compare peri‐implant bone condensation in the maxillary tuberosity of human cadavers following the osteotome and standard drilling techniques, and to determine whether peri‐implant bone condensation following the osteotome technique is localized or homogeneous. Material and methods: Twenty‐four cylinder‐threaded titanium implants (12 on each side) were placed in the left (standard technique) and right (osteotome technique with tapered osteotomes for bone condensation, Straumann^®) maxillary tuberosities of 12 edentulous posterior maxillae of deceased people who had bequeathed their bodies to the University of Santiago de Compostela for medical‐scientific research. After surgery, the implants were removed with the surrounding bone, prepared using sawing and grinding technique and examined histomorphometrically. The bone density (bone area/analyzed area) of the entire, periapical (fifth apical) and pericylinder peri‐implant areas was calculated, statistically analyzed and compared with the bone density of the host cancellous maxillary bone. Results: The bone density of the entire peri‐implant area was statistically found to be greater with the osteotome technique (39.38 ± 9.67) than with conventional drilling technique (31.06 ± 5.9). This difference was greatest for the periapical zone (53.32 ± 12.26 vs. 34.18 ± 6.34). Nonetheless, in the pericylinder area no significant difference was found between the two techniques (32.30 ± 8.74 vs. 30.34 ± 7.2). Conclusion: Peri‐implant bone condensation following the osteotome technique is not homogeneously observed through the entire peri‐implant area. A greater bone density was achieved only in the fifth apical peri‐implant area.     

Plasminogen activator in human gingival tissue adjacent to dental implants

The installment of endosseous dental implants has become an accepted treatment procedure, and the long-term clinical results appear excellent. The composition of the soft tissue environment, however, is different from that around natural teeth. One characteristic of original junctional epithelium is its association with plasminogen activator (PA) activity. In 11 patients with a total of 30 ITI hollow-screw titanium dental implants, 16 biopsies were taken. Histologic cryostat sections were assayed for the presence of PA in the junctional epithelium. The results demonstrated that junctional epithelium around titanium implants yields PA activity in a manner very similar to that of natural teeth. The ability to produce this enzyme activity is not related to the developmental origin of the junctional cells, but to their position and function at the base of the gingival sulcus.