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牵张成骨(distraction osteogenesis,DO)技术是指通过牵张装置对切开后的骨组织施加缓慢而稳定的牵张或扩张力,激活有关细胞的增殖与合成功能,促进骨及相关组织的再生,从而达到增加新骨、矫治骨骼发育不足或修复骨缺损的效果[1].     

口腔种植体体内生物学评价方法的研究进展

口腔种植体的体内生物学评价主要是通过动物实验获得种植体的生物安全性、骨结合效能及稳定性等相关生物学指标,为种植体表面处理改进、结构设计优化、缩短负重时机等提供科学依据。目前,鲜有报道,本文对有关口腔种植体的体内生物学评价方法进行综述。     

Ti-Ni shape memory alloy for dental use. Trial production of prefabricated straight-slit type posts by electric discharge machining

The possibility of dental application of Ti-Ni shape memory alloys was examined. To determine whether this material which is difficult to be machined could be processed by the electric discharge machining method (E.D.M.), the E.D.M. characteristics of this material were investigated. Trial straight-slit type posts were made by this material under an appropriate electric condition. The term of yield strength, retention force after cementing, and pressure of post when into a root canal filled unset cement were investigated. Ti-Ni shape memory alloy could be processed without a loss of shape memory effect by E.D.M. Hardenning layer in the machined surface was observed by both Ram-type and Wire-type E.D.M., but a thinner hardening layer was observed by the latter method. The retention force after cementing of the trial straight-slit type post were the same or stronger than those of posts on the market. Especially, the dependence for the post's length on this strength was not strong in the trial posts. The pressure produced by inserting the trial post into the root canal filled with unset cement was very low compared with those of post on the market. The trial straight-slit type posts made of Ti-Ni shape memory alloy may be useful for dental application.     

Short-term evaluation of dental implants in a diabetic population: an in vivo study

PURPOSE

The study was conducted to evaluate the efficacy of implant supported tooth replacement in diabetic patients.

MATERIALS AND METHODS

The study involved placement of implants (UNITI implants, Equinox Medical Technologies, Zeist, Holland, diameter of 3.7 mm and length 13 mm) in five diabetic patients (three females and two males) of age ranging from 35-65 years with acceptable metabolic control of plasma glucose. All patients included in the study were indicated for single tooth maxillary central incisor replacement, with the adjacent teeth intact. The survival of the restored implants was assessed for a period of three months by measurement of crestal bone heights, bleeding on probing and micro flora predominance. Paired t-test was done to find out the difference in the microbial colonization, bleeding on probing and crestal bone loss. P values of less than 0.05 were taken to indicate statistical significance.

RESULTS

Results indicated that there was a significant reduction in bleeding on probing and colonization at the end of three months and the bone loss was not statistically significant.

CONCLUSION

The study explores the hypothesis that patients with diabetes are appropriate candidates for implants and justifies the continued evaluation of the impact of diabetes on implant success and complications.     

An evaluation of the effects of collagen implants on new bone formation in vivo

Certain polypeptides have been shown to accelerate the formation of hydroxapatite crystals in virto. This investigation was designed to evaluate this phenomenon in vivo. Ox bone citrate-soluble collagen, by itself and pepsin treated, was implanted into small artifically produced defects in the maxillae of 35 rats. An indication of subsequent new bone formation was obtained by measuring the uptake of tetracycline by the defects at definite intervals after implantation. By the end of 14 days, tetracycline uptake by defects filled with untreated collagen reached a maximum of 17 times that of unimplanted controls. By 10 days, pepsin treated collagen accelerated tetracycline uptake 18 times control values. The tetracycline content in both the experimental and control defects was essentially the same after 35 days. From this experiment it is concluded that citrate-soluble collagen accelerated bone mineral deposition.     

Micro-CT活体观察大鼠牙齿移动及复发过程的实验研究

目的:Micro-CT活体扫描连续观察不同矫治力引起的牙齿移动及复发的规律。方法:选择10周龄SD大鼠15只随机分成3组。对大鼠左侧上颌第一磨牙分别施加20 g、50 g、100 g的矫治力,持续加载14 d后卸载。在加力后的0、3、7、10、14 d和停止加力后3、7、10、14、28、42 d用Micro-CT对大鼠进行活体扫描,测量每个时间点牙齿移动的距离。结果:在加力后的0～3 d各组的磨牙都发生明显的近中移动,第3～10天,牙移动缓慢,第10天时20 g和100 g组移动距离快速增加。20 g组在矫治力去除后的0～3 d复发最多,50 g和100 g组在0～7 d复发最多,28 d几乎完全复发。结论:加载矫治力后牙齿呈现快速、缓慢、快速的移动规律,且轻力引起的牙移动更多。拆除加力装置的初期复发的最快,牙齿移动距离越大,复发越快。     

An in vitro and in vivo evaluation of bioactive titanium implants following sodium removal treatment

ObjectiveThe aim of this study was to evaluate the effect of dilute HCl as a sodium removal treatment of grit blasted/NaOH/heat treated cp titanium implants on the in vitro bioactivity and the in vivo interface shear resistance at different healing periods.MethodsCylindrical implants were machined from cp titanium bars. Half of the implants were blasted by AL₂O₃ particles followed NaOH/heat treatment. The other half received similar treatment except, dilute HCl was additionally used as a sodium removal treatment. Implants surfaces topography was characterized by AFM before and after immersion in simulated body fluid (SBF) for 3 and 7 days. The implants resistance to interfacial shear force was evaluated at 2, 4, and 8 weeks implantation periods in experimental rabbits.ResultsSodium removal treatment significantly increased surface roughness (Sa parameter), valley fluid retention index and surface area before and after immersion in SBF, however, it significantly decreased core fluid retention index. Calcium and phosphorus containing surface deposits, of larger surface area, were precipitated on implants received the sodium removal treatment after 3 and 7 days in SBF. The implant–bone interface resistance to shear force was significantly increased at 2 weeks healing period after the use of the sodium removal treatment.SignificanceThe sodium removal treatment showed to be effective in improving the early bone–implant interface resistance to shear force. Topographical changes, after dilute HCl etching, seem to contribute to the different in vitro and/or in vivo responses observed.     

Micro-CT observation of rat dental pulp healing after pulpotomy in in vivo study

We report the newly developed Micro-CT, which allows us to observe the individual animal over a long experimental period and to compare changes in pulp tissue in relation to growth and aging without considering individual differences. Further, we used pathological examination to prove similar the result observing from Micro-CT. We have examined wound healing of teeth after pulpotomy in rats, and could clearly observe histopathological changes in the affected teeth and the absorption of temporary filling material and pulp capping agents. In cases with breakage of the dental crown, the CT images agreed with the pathological observations, and it was possible to estimate the time of breakage. In vivo Micro-CT is possible to apply in continuous recording of small experimental animals, such as rats, under anesthesia and the result is sufficiently high. High-quality image was obtained in of the entire head region of the rat. It was suggested that this method can be used for long-term continuous observation of changes in the teeth conditions after pulpotomy in experimental animals. We report the newly developed Micro-CT, which allows us to observe the individual animal over a long experimental period and to compare changes in pulp tissue in relation to growth and aging without considering individual differences.     

Placement of implants in distraction osteogenesis: a pilot study in dogs

This study investigated the possibility of achieving osseointegration of implants placed in a distracted site during the consolidation period. Four healthy male mongrel dogs were used in this experiment. A subperiosteal corticotomy around the mandible was performed between the left mandibular premolar and first molar. After a 7-day latency period for soft tissue healing, the distraction was performed at the rate of 1 mm per day for 14 consecutive days to allow for 14 mm of elongation, using an extraoral distraction device. Three weeks after the completion of distraction, screw-type implants were placed in the distracted site. Twenty-four weeks after placement of the implants, they were stable, and osseointegration had been achieved physically, radiographically, and histologically. These results suggest the possibility of shortening the period of implant treatment by using the distraction osteogenesis technique.     

OPG缺失后小鼠下颌骨微结构增龄性变化的Micro-CT评价

目的:基于Micro-CT评价骨保护素基因敲除(Opg-knockout,Opg-KO)型小鼠与野生型(wild type,WT)小鼠的下颌骨微结构增龄性变化,以便更好了解小鼠下颌骨的增龄性骨质改建情况。方法:分别采集6周、12月龄Opg-KO小鼠和WT小鼠各6只,采用Micro-CT扫描观察小鼠下颌骨三维结构,对感兴趣区域根分叉部位松质骨及前牙颏孔前缘区皮质骨骨微结构进行定量分析。结果:与WT小鼠相比,Opg-KO小鼠6周时第一磨牙根分叉处松质骨、髁突颈部、下颌角处、前牙颏孔前缘区均出现了明显的坑凹状吸收;12月时,这些区域破坏愈发严重,甚至出现穿孔;根分叉松质骨区域骨小梁平均厚度、骨密度、骨体积分数明显降低(P<0.05),骨小梁分离度明显升高(P<0.05);前牙颏孔前缘区皮质骨骨密度及骨体积分数明显降低(P<0.05)。结论:OPG缺失引起小鼠下颌骨发生严重的骨质破坏,随着年龄增加骨质破坏程度越发严重,并且松质骨骨微结构改变更显著。     

Clinical evaluation of dental implants with surfaces roughened by anodic oxidation, dual acid-etched implants, and machined implants

PURPOSE: The purpose of this study was the clinical and radiographic comparison of dental implants with surfaces roughened by anodic oxidation (TiUnite), dual acid-etched implants (Osseotite), and machined implants. MATERIALS AND METHODS: Seventy-four patients (mean age, 52.8 +/- 14.2 years; range, 23 to 80 years; 41 men and 33 women) received 198 dental implants-58 TiUnite implants (25 patients), 52 Osseotite implants (27 patients), and 88 machined implants (22 patients). Clinical measurements and radiographs were evaluated at the time of surgery, at the restorative phase, and 2 years postloading. To account for statistical correlation among multiple implants in the same subject, a "per patient" mode of analysis was conducted. A 1-way analysis of variance of bone loss was conducted by type of implant as well by area of the mouth. In addition, differences in mean bone loss were tested for bone density category, gender, and smoking status using Student t tests. RESULTS: Eighteen TiUnite implants (31.0%) were placed in the maxilla and 40 (69.0%) in the mandible. The Osseotite group included 29 maxillary implants (55.8%) and 23 mandibular implants (44.2%). The machined group included 49 maxillary implants (55.7%) and 39 mandibular implants (44.3%). All 198 implants were considered radiographically and clinically successful. No mobility, signs of infection, or inflammation were detected. DISCUSSION: Implant size, location, bone quality, gender, age, and smoking did not influence the comparative clinical outcomes of the 3 groups (P > .05). A trend toward greater coronal bone loss in the TiUnite group was detected. CONCLUSION: Within the limitations of the present study, TiUnite, Osseotite, and machined dental implants had similar short-term clinical outcomes. No statistically significant differences in bone loss could be detected among implant groups or among the different regions of the oral cavity. The present data underlined the significance of surgical and prosthetic treatment planning.     

Surface and elemental alterations of dental alloys induced by electro discharge machining (EDM).

OBJECTIVES: To evaluate the surface and elemental alterations induced by electro discharge machining (EDM) on the surface of dental cast alloys used for the fabrication of implant retained meso- and super-structures. METHODS: A completed cast model of an arch that received dental implants was used for the preparation of six wax patterns which were divided into three groups (Au, Co and Ti). The wax patterns of the Au and Co groups were invested with conventional phosphate-bonded silica-based investment material and the Ti group with magnesia-based investment material. The investment rings of the Au and Co groups were cast with an Au-Ag alloy (Stabilor G) and a Co-Cr base alloy (Okta C), respectively, while the investment rings of group Ti were cast with cp Ti (Biotan). One casting of each group was subjected to electro discharge machining (EDM); the other was conventionally ground and polished. The surface morphology and the elemental compositions of conventionally and EDM-finished surfaces were studied by SEM/X-ray EDS analysis. Six spectra were collected from each surface employing the area scan mode and the mean value of each element between conventionally and EDM-finished surfaces was statistically analyzed by t-test (a=0.05). Then the specimens of each group were cut perpendicular to their longitudinal axis and after metallographic grinding and polishing the cross-sections studied under the SEM. RESULTS: The EDM surfaces showed a significant increase in C due to the decomposition of the dielectric fluid during spark erosion. Moreover, a significant Cu uptake was noted on these surfaces from the decomposition of the Cu electrodes used for EDM. Cross-sectional analysis showed that all alloys developed a superficial zone (recast layer) varying from 2 microm for Au-Ag to 10 microm for Co-Cr alloy. SIGNIFICANCE: The elemental composition of dental alloy surfaces is significantly altered after EDM treatment.     

Long-term evaluation of the stability of reconstructed condyles by transport distraction osteogenesis

This retrospective longitudinal study evaluated the long-term stability of reconstructed condyles by transport distraction osteogenesis of the mandibular ramus in patients with unilateral temporomandibular joint (TMJ) ankylosis. 7 patients were followed up for 16–92 months (mean 39.4 months). The mean age of the patients at the time of distraction was 22.9 years (range 7–44 years). Maximal mouth opening and panoramic radiographs were recorded preoperatively, at the time of device removal and several years after removal of distraction device. At follow-up, cone beam CT images of the TMJ were obtained to confirm the changes of the reconstructed condyle. Absolute height (Co–Inc) and relative height (Co–Inc/Co–Go) of the reconstructed condyle and the asymmetric difference ratio (AR) were examined to assess the changes of condylar height and mandibular symmetry. The mean maximal mouth opening was stable during the period of follow-up. The mean absolute height and relative height of the reconstructed condyle decreased significantly (P < 0.05). Although no significant difference was found, the mandibular asymmetry difference ratio increased by 16.7%. These results suggested that the heights of reconstructed condyles were not stable in the long-term, and the mandible tended to be asymmetrical.     

An in vitro evaluation of distractors used for osteogenesis

Objective. The objective of this investigation was to evaluate and compare the mechanical behaviors of distractors used for osteogenesis under various conditions by means of common engineering standards.Study design. Five groups of 5 synthetic mandibles were used in this study (N = 25). The first portion of the investigation compared mandibles without intervention (group A [controls]; n = 5), mandibles that had uniform osteotomies stabilized with an external distractor (group B; n = 5), and mandibles that had simulated sagittal osteotomies rigidly fixated with 3 positional screws (group C; n = 5). The second portion of the investigation compared uniform osteotomies (group B; n = 5) and uniform corticotomies (group D; n = 5) that were stabilized with the same external distractor. The last portion of the investigation compared osteotomies stabilized with an external distractor (group B; n = 5) and osteotomies stabilized with an internal distractor (group E; n = 5). Each construct was subjected to vertical loads on a mechanical testing unit. Common engineering standards, including yield load, yield displacement, maximum load, displacement at maximum load, and stiffness, were measured, recorded, and compared by means of a 1-way analysis of variance and a Scheffé multiple comparison test or independent-samples t test. The means between groups were considered significant for P < .05. A polynomial best-fit curve was calculated for the load/displacement data for each group.Results. During the first portion of the investigation, no significant differences were noted between the control, rigidly fixated sagittal osteotomy, and external distractor with osteotomy groups for displacement at maximum load (P = .19). Significant differences were noted between groups for yield displacement (P = .009), yield load (P < .001), maximum load (P < .001), and stiffness (P < .007). Failures occurred in the control and rigidly fixated groups with fractures of the synthetic mandibles. Failures occurred in the external distractor group with permanent deformation or torsion of the pins. During the second portion of the experiment, no statistically significant differences were noted between the corticotomy and osteotomy groups in stiffness (P = .363), maximum load (P = .207), or yield displacement (P = .940). Statistically significant differences were noted between groups for yield load (P = .036) and displacement at maximum load (P = .010). Failures occurred in both groups with permanent deformation or torsion of the pins. During the last portion of the investigation, statistically significant differences were noted between the external distractor and internal distractor groups in yield load (P < .001), yield displacement (P < .001), maximum load (P = .001), and displacement at maximum load (P = .01); no significant differences were noted in stiffness (P = .71). Failures occurred in the external distractor group with permanent deformation or torsion of the pins. Failures occurred in the internal distractor group with fracture of the model or displacement beyond 30.0 mm.Conclusions. Different patterns of mechanical behavior were found between the control and rigidly fixated sagittal osteotomy groups and the external distractor group, between the corticotomy and osteotomy groups, and between the internal and external distractor groups.     

In vivo expression of proteases and protease inhibitor,a serpin,by periodontal pathogens at teeth and implants

Porphyromonas gingivalis and Tannerella forsythia secrete proteases, gingipains and KLIKK‐proteases. In addition, T. forsythia produces a serpin (miropin) with broad inhibitory spectrum. The aim of this pilot study was to determine the level of expression of miropin and individual proteases in vivo in periodontal and peri‐implant health and disease conditions. Biofilm and gingival crevicular fluid (GCF)/ peri‐implant sulcular fluid (PISF) samples were taken from healthy tooth and implant sites (n = 10), gingivitis and mucositis sites (n = 12), and periodontitis and peri‐implantitis sites (n = 10). Concentration of interleukin‐8 (IL‐8), IL‐1β and IL‐10 in GCF was determined by enzyme‐linked immunosorbent assay. Loads of P. gingivalis and T. forsythia and the presence of proteases and miropin genes were assessed in biofilm by quantitative PCR, whereas gene expression was estimated by quantitative RT‐PCR. The presence of P. gingivalis and T. forsythia, as well as the level of IL‐8 and IL‐1β, were associated with disease severity in the periodontal and peri‐implant tissues. In biofilm samples harboring T. forsythia, genes encoding proteases were found to be present at 72.4% for karilysin and 100% for other KLIKK‐protease genes and miropin. At the same time, detectable mRNA expression of individual genes ranged from 20.7% to 58.6% of samples (for forsylisin and miropsin‐1, respectively). In comparison with the T. forsythia proteases, miropin and the gingipains were highly expressed. The level of expression of gingipains was associated with those of miropin and certain T. forsythia proteases around teeth but not implants. Cumulatively, KLIKK‐proteases and especially miropin, might play a role in pathogenesis of both periodontal and peri‐implant diseases.