Peri-implant bone organization under immediate loading state. Circularly polarized light analyses: a minipig study

BACKGROUND: Immediate loading of dental implants is currently one of the most examined topics in implant dentistry. Using screw implants with a microstructured surface and bone-quality-adapted insertion procedures, osseointegration is achieved when implants are initially stable and when splinted with the superstructure. Despite reported success, there is a shortage of information relating to remodeling and peri-implant bone formation with immediately loaded implants. METHODS: Four to six immediately loaded and unloaded dental implants with a microstructured surface were placed in the mandible and the maxilla in seven minipigs. A total of 85 implants were placed. After a 4-month healing period, all implants were retrieved. Histomorphometry was performed using a light microscope in transmitted polarized light connected to a high-resolution video camera interfaced to a monitor and personal computer. This optical system was associated with a digitizing pad and a histomorphometry software package with image capturing capabilities. RESULTS: Implants showed osseointegration if the average insertion torque of the implants within one bridge was >35 Ncm. If the primary stability of the bridge was <35 Ncm, all implants in the quadrant were lost after 4 months. The multivariate discriminant analysis showed the highest correlation for implant stability by bridge insertion torque (BIT), localization (mandible or maxilla), and implant insertion torque (IIT) as success parameters. The loaded implants displayed collagen fibers, which were oriented in a more transverse way. In addition, a higher quantity of secondary osteons was present. In comparison, the unloaded implants had collagen fibers with a more parallel orientation, and a higher quantity of marrow spaces was present. CONCLUSIONS: When observed after 4 months, immediately loaded implants showed a higher degree of bone formation and remodeling in comparison to unloaded implants. Immediately loaded implants also demonstrated a prevalence of transversely oriented collagen fibers in the peri-implant bone. In this animal model, an average insertion torque of the implants within one bridge>35 Ncm was associated with the most successful implants.     

Influence of cyclosporin A on quality of bone around integrated dental implants: a radiographic study in rabbits

OBJECTIVES: To evaluate the influence of cyclosporin A (CsA) administration on bone around integrated dental implants assessed by a bone quality index and by quantitative subtraction radiography. MATERIAL AND METHODS: A total of 36 machine surface commercial implants were placed in 18 adult rabbits. After a 3-month healing period without any disturbance, the animals were randomly divided into three groups of six animals each. Group A was sacrificed at this time. CsA was injected subcutaneously in an immunosuppressive dose of 10 mg/kg/day in a test group (Group T), and a Group B served as a control, receiving only vehicle. After 3 months of cyclosporin administration, the animals of both Groups B and T were sacrificed. Radiographs were obtained at implant surgery and at the day of sacrifice with a CMOS sensor. Bone quality around the implants was compared between the groups using a bone quality index and quantitative subtraction radiography. RESULTS: The bone analysis showed that in Group T, the bone quality changed dramatically from a dense cortical to a loose trabecular bone structure (P<0.0001, chi(2) test) while in Groups A and B there were no significant differences. Quantitative digital subtraction radiography showed significantly (P<0.05) lower gray shade values (radiographic density) in a region of bone formation around the implants in Group T (118+/-12) than in Groups A (161+/-6) and B (186+/-10). CONCLUSION: Within the limits of this study, CsA administration has a negative effect on the quality of bone around integrated dental implant.     

热刺激取出骨结合种植体动物模型的建立

目的:研究热刺激取出骨结合牙种植体的条件,建立热刺激微创取出骨结合牙种植体的动物模型。方法:选用4只1~2岁杂种犬为实验动物,拔除双侧下颌第三或第四前磨牙,2个月后常规植入牙种植体,3个月后经临床及放射学检查,确定骨结合形成,随机选取右侧为实验侧,组成实验组,分别以(48±1) ℃持续1 min (简称A因素)、(53±1) ℃持续2.5 min(B)、(59±1) ℃持续3.5 min(C)刺激实验侧种植体,于每次热刺激前及刺激后4周测量种植体稳定性系数(ISQ),改良菌斑指数(modified plaque index ,mPLI),探诊深度( probing depth ,PD),观察影像学表现以及能否用扭矩扳手取出种植体,左侧为对照侧,组成对照组,不施加任何热刺激,测量项目同实验组。采用SPSS22.0统计软件对实验数据进行统计分析。结果:A、B因素刺激前和刺激后4周,实验组与对照组相比, ISQ 、mPLI,PD无显著性差异,影像学无明显变化,无法用扭矩扳手取出种植体。C因素刺激后4周与对照组相比,实验组ISQ明显下降,差异具有显著性(P<0.05),根尖X片显示种植体周围出现线形低密度影,低密度影外侧骨密度略有增高,但mPLI,PD实验组和对照组无显著性差异,实验组采用50 Ncm的扭矩可以取出种植体,对照组无法取出。种植体取出术后2个月,实验组牙槽骨基本愈合,与取出术前相比,牙槽嵴宽度和高度无显著性变化。 结论:动物实验显示,已完成骨结合的种植体在(59±1) ℃持续3.5 min热刺激条件下可使其周围骨质出现有限破坏,从而破坏其骨结合,达到微创取出种植体的目的,成功建立了热刺激取出骨结合牙种植体动物模型。     

Effect of bisphosphonates on anodized and heat-treated titanium surfaces: an animal experimental study

Background: Recent investigations reported that osseointegration of titanium implants can be significantly reinforced with a nanostructure treated with anodic oxidation and heat treatment. This experimental study investigates the effect of bisphosphonates on the nanotubular implant surface in rats. Methods: Thirty‐six titanium implants were divided into three groups: 1) machine‐turned (MT), 2) anodized and heat‐treated (AH), and 3) anodized and heat‐ and bisphosphonate‐treated (AHB) groups. The 36 implants were randomly placed in both tibias of 18 male Wistar rats. After 2 and 4 weeks, the levels of osseointegration of the implants were evaluated by a removal torque test and microcomputerized tomography (μCT). Peri‐implant bone tissue on the extracted region was examined for the expression of type I collagen and osteocalcin. Results: The AHB group showed the highest removal torque at 2 and 4 weeks (13.92 ± 1.51 Ncm and 18.10 ± 2.15 Ncm, respectively) followed, in order, by the AH group (11.63 ± 1.58 Ncm at 2 weeks and 14.80 ± 2.34 Ncm at 4 weeks) and MT group (4.30 ± 0.76 Ncm at 2 weeks and 6.20 ± 1.33 Ncm at 4 weeks) with statistically significant differences between the MT and other two groups at both time points. μCT images also revealed a denser appearance around implants in the AHB group than in the other groups. Levels of type I collagen and osteocalcin expression were similar between the MT and AH groups; however, the values were significantly higher in the AHB group compared to the other groups, which were 220.85% ± 71.09% and 363.04% ± 100.21%, respectively (P <0.05). Conclusion: Within the limits of this experiment, it was concluded that surface loading with bisphosphonates significantly improved the degree of osseointegration of titanium implants with a nanostructure.     

Influence of cyclosporin A therapy on bone healing around titanium implants: a histometric and biomechanic study in rabbits

BACKGROUND: Immunosuppressive agents may induce severe changes on bone metabolism. The purpose of the present study was to evaluate the influence of the administration of cyclosporin A (CsA) on the bone tissue around titanium implants. METHODS: Eighteen New Zealand rabbits were randomly divided into 2 groups of 9 each. The test group (CsA) received daily subcutaneous injection of CsA (10 mg/kg body weight) and the control group (CTL) received saline solution by the same administration route. Three days after therapy began, 2 implants (7.0 mm long and 3.75 mm in diameter) were inserted bilaterally at the region of the tibial methaphysis. After 4, 8, and 12 weeks the animals were sacrificed and biomechanical tests and histometrical procedures, consisting of the determination of the percentages of bone-implant contact and bone area within the limits of the implant threads, were performed. RESULTS: Intergroup analysis showed that the removal torque and the percentage of bone contact with the implant surface for CsA group were significantly lower than those of the CTL group at 12 weeks (28.5 and 39.2 N cm, P = 0.01; 7.76% and 18.52%, P = 0.02, respectively). CONCLUSION: The data from the present study suggest that long-term administration of cyclosporin A may negatively influence bone healing around dental implants.     

The influence of diabetes mellitus and insulin therapy on biomechanical retention around dental implants: a study in rabbits

The oral rehabilitation by dental implants in patients with diabetes remains a controversial issue. The aim of this study was to evaluate the influence of diabetes mellitus and insulin therapy on the bone healing around dental implants using torque removal. Twenty-seven rabbits were randomly divided into 3 groups with 9 animals each: control (C) group, induced diabetic (D) group, and insulin-treated diabetic (ITD) group (10 U/day). After 1 week, one implant was inserted at the tibial metaphysis of the animals. The glucose levels were periodically evaluated through the glucose-oxidase enzymatic method. The animals were killed at 4, 8, and 12 weeks after surgery and the biomechanical test was performed using a torque manometer. Statistically significant differences regarding the removal torque of the implant could not be found at 4 weeks (P = 0.2) among groups. Group C showed statistically higher values than groups D and ITD at the experimental periods of 8 (P = 0.0001 and P = 0.0002, respectively) and 12 weeks (P = 0.0053 and P = 0.001, respectively). There were no statistical differences between D and ITD groups in any of the experimental periods. Diabetes mellitus has negatively influenced the mechanical retention of implants placed at the tibial metaphysis of rabbits. Therapy with insulin did not induce any changes.     

Effect of 17beta-estradiol and alendronate on the removal torque of osseointegrated titanium implants in ovariectomized rats

BACKGROUND: This study investigated the influence of estrogen deficiency and its treatment with estrogen and alendronate on the removal torque of osseointegrated titanium implants. METHODS: Fifty-eight female Wistar rats received a titanium implant in the tibia metaphysis. After 60 days, which was needed for implant osseointegration, the animals were randomly divided into five groups: control (CTLE; N = 10), sham surgery (SHAM; N = 12), ovariectomy (OVX; N = 12), ovariectomy followed by hormone replacement (EST; N = 12), and ovariectomy followed by treatment with alendronate (ALE; N = 12). The CTLE group was sacrificed to confirm osseointegration, whereas the remaining groups were submitted to sham surgery or ovariectomy according to their designations. After 90 days, these animals were also sacrificed. Densitometry of femur and lumbar vertebrae was performed by dual-energy x-ray absorptiometry (DXA) to confirm systemic impairment of the animals. All implants were subjected to removal torque. RESULTS: Densitometric analysis of the femur and lumbar vertebrae confirmed a systemic impairment of the animals, disclosing lower values of bone mineral density for OVX. Analysis of the removal torque of the implants showed statistically lower values (P <0.05) for the OVX group in relation to the other groups. However, the group treated with alendronate (ALE group) presented significantly higher torque values compared to the others. CONCLUSION: According to this study, estrogen deficiency was observed to have a negative influence on the removal torque of osseointegrated implants, whereas treatment with alendronate increased the torque needed to remove the implants.     

Clinical Outcome of Dental Implants Placed with High Insertion Torques (Up to 176 Ncm)

Background: Primary stability can be improved by using a tapered implant in a slightly underprepared implant site. This may lead to high compression forces and elevated insertion torques. It has been postulated that disturbance of the local microcirculation may occur, leading to necrosis of the osteocytes and bone resorption. Purpose: Report on the clinical outcome of 42 implants placed with an insertion torque equal or greater than 70 Ncm and evaluate bone levels around these implants. Materials and Methods: This prospective study included 48 patients treated with 66 4.5 mm diameter Tapered Screw‐Vent implants (Zimmer Dental®, Carlsbad, CA, USA). Maximum insertion torque (MIT) was recorded with an electronic torque measuring device (Tohnichi® STC200CN, Hitachi, Tokyo, Japan). Nine implants (control group) presented MIT between 30 and 50 Ncm (mean = 37.1 Ncm) and 42 implants (experimental group) MIT greater than 70 Ncm (mean = 110.6 Ncm, range: 70.8–176 Ncm). Marginal bone levels were recorded at the time of loading and 1 year later for the two groups. Results: After 2–3 months of non‐sumerged healing, all implants were clinically stable. Mean marginal bone resorption was 1.03 mm (SD = 0.44) for the control group (low torque) and 0.72 mm (SD = 0.56) for the experimental group (high torque) at time of loading, and 1.09 (SD = 0.62) and 1.24 mm (SD = 0.75), respectively, after 1 year. There were no significant differences between the two groups for bone stability and implant success rate. Conclusions: The use of high insertion torques (up to 176 Ncm) did not prevent osseointegration. Marginal bone levels in the control and experimental groups were similar both at the time of loading and 1 year later.     

Effect of alendronate on endosseous implant integration: an in vivo study in rabbits.

PURPOSE: Alendronate sodium (Fosamax; Merck, Whitehouse Station, NJ) is a second-generation bisphosphonate used widely in osteopenic individuals for decreasing bone resorption and increasing bone density. The ability of alendronate to affect systemic bone remodeling raises natural questions about the drug's influence on dental implant osseointegration. Current knowledge regarding the effect of systemic bisphosphonates, specifically alendronate, on all 3 phrases of osseointegration is incomplete and only a few studies have started to investigate peri-implant bone responses to alendronate-coated implants. The purpose of this study was to determine the effect of systemic alendronate therapy on osseointegration of dental implants based on torque-removal values in rabbits. MATERIALS AND METHODS: Identical titanium dental implants were placed using a standardized surgical protocol in the bilateral distal femur and proximal tibia of 20 New Zealand white rabbits (79 implants total). One week before implant placement, 10 rabbits were given doses of alendronate and continued on weekly dosing for 5 weeks until euthanized. The other 10 rabbits were untreated controls. Torque-removal values were determined using a Tohinichi 15-BTG torque wrench (Tohinichi Mfg Co, Ltd, Tokyo, Japan) for all implants. RESULTS: Analysis of torque data showed no statistical differences between the alendronate and control groups in both femur and tibia sites. A statistically significant difference, however, was noted in torque removal values between femur and tibia sites regardless of drug or non-drug groups. CONCLUSIONS: In summary, orally dosed alendronate administration in rabbits had no significant effect on dental implant torque-removal values 6 weeks after endosseous placement in femur and tibia.     

Osseointegration of anodized titanium implants coated with fibroblast growth factor-fibronectin (FGF-FN) fusion protein

PURPOSE: The synergistic effect of fibroblast growth factor (FGF) and human fibronectin fragment (hFNIII9-10) on osteoblast cell adhesion has been demonstrated in vitro. The purpose of this study was to evaluate the bone response around anodized titanium implants treated with FGF-FN fusion protein using the histomorphometric analysis and the removal torque test. MATERIALS AND METHODS: Threaded implants were manufactured by machining a commercially pure titanium (grade 4). Two different groups of samples were prepared: Group 1 samples were anodized under a constant voltage of 300 V, and group 2 samples were anodized under a constant voltage of 300 V and then soaked in a solution containing fusion protein (65 microg/mL) for 24 hours. Ten implants from each group were placed in rabbit tibiae (1 implant per group per rabbit; each rabbit served as its own control). After a 3-month healing period, the animals were sacrificed. Removal torque testing and histomorphometric analysis was then carried out. RESULTS: The mean removal torque value of group 2 (44.8 Ncm) was greater than that of group 1 (37.6 Ncm). The percentages of bone-implant contact of the best 3 consecutive threads were 76.37% for group 1 and 88.02% for group 2. The percentage of bone-implant contact for the total length of the implant was higher for group 2 (36.91%) than for group 1 (29.47%). However, the percentage of the area inside the threads that consisted of bone did not differ significantly for the 2 groups. DISCUSSION AND CONCLUSION: This study demonstrated that the FGF-FN fusion protein coating on anodized implants may enhance osseointegration. However, the influence of fibronectin- and FGF-treated rough surfaces on long-term prognosis and the propagation of inflammation are subjects for further study.     

Removal torque of immediately loaded transitional endosseous implants in human subjects

PURPOSE: Transitional implants were designed to support provisional restorations and to allow for load-free osseointegration of conventional implants while a patient was provided with immediate esthetics and function. The purpose of this study was to evaluate the removal torque values of immediately loaded transitional implants in human subjects. MATERIALS AND METHODS: Thirty-one 1.8-mm-diameter transitional implants were placed in 4 patients to support provisional restorations and were subjected to immediate loading. Removal torque values were recorded using a modified ITI torque driver, which was calibrated on an Instron test machine. Torque values were subjected to analysis of variance and post hoc comparisons of means (P < .05). RESULTS: Twenty-six implants were removed intact with torque values between 10.5 and 22.9 Ncm, while 5 fractured at the bone crest at values between 27.1 and 35.4 Ncm. Mean torque values increased with time in function. These values were significantly lower in the maxilla (16.1 +/- 4.8 Ncm) than in the mandible (24.0 +/- 7.3 Ncm). DISCUSSION: Results suggest that these transitional implants may be safely removed from the maxilla after 7 to 15 months, but there is a risk of implant fracture during removal from the mandible after 10 months. CONCLUSION: Removal torque levels for these implants indicate varying degrees of integration even though they were subjected to immediate loading.     

Evaluation of the primary stability in dental implants placed in low density bone with a new drilling technique,Osseodensification: an in vitro study

Background Primary stability is an important key determinant of implant osseointegration. We investigated approaches to improve primary implant stability using a new drilling technique termed osseodensification (OD), which was compared with the conventional under-drilling (UD) method utilized for low-density bones. Material and Methods We placed 55 conical internal connection implants in each group, in 30 low-density sections of pig tibia. The implants were placed using twist drill bits in both groups; groups Under Drilling (UD) and Osseodensification (OD) included bone sections subjected to conventional UD and OD drilling, respectively. Before placing the implants, we randomized the bone sections that were to receive these implants to avoid sample bias. We evaluated various primary stability parameters, such as implant insertion torque and resonance frequency analysis (RFA) measurements. Results The results showed that compared with implants placed using the UD technique, those placed using the OD technique were associated with significantly higher primary stability. The mean insertion torque of the implants was 8.87±6.17 Ncm in group 1 (UD) and 21.72±17.14 Ncm in group 2 (OD). The mean RFA was 65.16±7.45 ISQ in group 1 (UD) and 69.75±6.79 ISQ in group 2 (OD). Conclusions The implant insertion torque and RFA values were significantly higher in OD group than in UD. Therefore, compared with UD, OD improves primary stability in low-density bones (based on torque and RFA measurements). Key words:Osseodensification, primary stability, low density bone, RFA.     

Evaluation of a New Titanium‐Zirconium Dental Implant: A Biomechanical and Histological Comparative Study in the Mini Pig

Background: Titanium zirconium alloy with 13–17% zirconium (TiZr1317) shows significantly better mechanical attributes than pure Ti with respect to elongation and fatigue strength. This material may be suitable for thin implants and implant components exposed to high mechanical constraints. Purpose: The aim of this study was to test the hypothesis that TiZr1317 and Ti implants show comparable osseointegration and stability. Materials and Methods: The mandibular premolars (P1, P2, P3) and the first molar (M1) in 12 adult miniature pigs were extracted 3 months prior to the study. Six specially designed implants made from Ti (commercially pure, Grade 4) or TiZr1317 (Roxolid®, Institut Straumann AG, Basel, Switzerland) with a hydrophilic sandblasted and acid‐etched (SLActive, Institut Straumann AG, Basel, Switzerland) surface were placed in each mandible; three standard implants modified for evaluation of removal torque (RT) in one side and three bone‐chamber implants for histologic observations in the contralateral side. RT tests were performed after 4 weeks when also the bone chamber implants and surrounding tissue were biopsied for histologic analyses in ground sections. Results: The RT results indicated significantly higher stability (p = 0.013) for TiZr1317 (230.9 ± 22.4 Ncm) than for Ti implants (204.7 ± 24.0 Ncm). The histology showed similar osteoconductive properties for both implant types. Histomorphometric measurements showed a statistically significant higher (p = 0.023) bone area within the chamber for the TiZr1317 implants (45.5 ± 13.2%) than did the Ti implants (40.2 ± 15.2%). No difference was observed concerning the bone to implant contact between the groups with 72.3 ± 20.5% for Ti and 70.2 ± 17.3% for TiZr1317 implants. Conclusion: It is concluded that the TiZr1317 implant with a hydrophilic sandblasted and acid‐etched surface showed similar or even stronger bone tissue responses than the Ti control implant     

3D打印和CAD/CAM氧化锆种植体骨结合性能的动物实验评价

目的　比较3D打印和计算机辅助设计与制造（computer aided design-computer assomated manufacture CAD/CAM）氧化锆种植体与纯钛种植体在动物体内的骨结合和成骨效果的差异,评价氧化锆种植体骨结合性能。方法　分别将3D打印氧化锆、CAD/CAM种植体和钛种植体各20枚随机植入6只Beagle犬的胫骨内,8周后观察氧化锆种植体的成功率和骨结合能力,并与钛种植体进行比较,观察指标为种植体的成功率、反向扭矩值、骨接触率和种植体周围骨密度。采用SPSS17.0软件包对数据进行统计学分析。结果　3组种植体的成功率均为100%。CAD/CAM氧化锆种植体组的反向转矩值均大于35 N;3D打印氧化锆种植体组的反向转矩值均大于35 N;钛种植体组中2颗种植体的反向转矩值为20～35 N,8颗种植体的反向转矩值大于35 N。组织学观察：3D打印氧化锆种植体、CAD/CAM氧化锆种植体和纯钛种植体的不含骨髓腔骨结合率、分别为（66.35±6.64%）、（61.32±10.41%）和（58.88±25.10%）,3D打印氧化锆种植体、CAD/CAM氧化锆种植体和纯钛种植体的含骨髓腔骨结合率分别为（49.57±5.04%）、（42.21±18.58%）和（38.45±23.27%）,3D打印氧化锆种植体、CAD/CAM氧化锆种植体和纯钛种植体的平均骨结合率分别为（58.94±6.31%）、（53.56±8.77%）和（48.31±20.76%）,3D打印氧化锆种植体、CAD/CAM氧化锆种植体和纯钛种植体的种植体周围骨密度分别为（60.59±7.31%）、（58.50±6.36%）和（58.18±14.80%）,差异无显著性（P＞0.05）。结论　氧化锆种植体与纯     

Histological and biomechanical evaluation of phosphorylcholine-coated titanium implants

Objective: Compounds considered for drug delivery from oral implant surfaces in support of local bone formation might themselves influence osseointegration. Phosphorylcholine (PC) polymers have been shown to enhance the biocompatibility of medical devices and to serve as drug delivery systems. The objective of this study was to evaluate local bone formation and osseointegration at PC and positively charged PC (PC+)‐coated endosseous implants in an established rabbit model. Material and Methods: Sixteen adult female New Zealand White rabbits were used. Eight animals received PC‐coated and control titanium porous oxide surface implants placed in the left and right distal femural condyle (trabecular bone) and proximal tibial metaphysis (cortical bone) using aseptic routines. The remaining eight animals similarly received PC+ and control implants. One implant was placed in each femural condyle and two implants in each tibial metaphysis. Experimental and control implants were alternated between the left and right hind legs. Fascia and skin were closed in layers. The animals were euthanized following a 6‐week healing interval for biomechanical (removal torque) and histometric analyses. Results: Peri‐implant bone density was considerably greater at tibial compared with femoral sites within as well as immediately outside the implant threads. However, there were no significant differences in bone density among PC, PC+, and control implants. Nevertheless, bone–implant contact was significantly lower at PC compared with PC+ and control implants in cortical bone (p<0.05). Numerical differences in trabecular bone did not reach statistical significance. The removal torque evaluation revealed significantly lower values for PC compared with PC+ and control sites (p<0.05). Conclusion: The histometric and biomechanical analyses suggest that PC coating may influence biological processes and ultimately osseointegration of endosseous implants. Apparently, incorporation of cationic charges may reverse or compensate for this scenario. Nevertheless, both PC coatings exhibited clinically acceptable osseointegration. In perspective, PC technology appears to be a viable candidate delivery system for agents in support of local bone formation at endosseous implant surfaces.     

A mechanical evaluation of implants placed with different surgical techniques into the trabecular bone of goats

The aim of the study was to assess the effects of surgical technique and implant surface roughness on implant fixation. A total of 48 screw implants with machined or etched surface topographies were placed into the femoral condyles of goats. The implant sites were prepared by a conventional technique, by undersized preparation, or by the osteotome technique. Bone tissue responses were evaluated after 12 weeks of healing by removal torque testing and histologic analysis using scanning electron microscope. The cumulative removal torque value of the etched implants placed with the undersized technique (98 +/- 29 Ncm) was higher (50 +/- 35 Ncm) to a level of statistical significance than machined surface implants placed by the osteotome technique. Scanning electron microscope evaluation indicated that all implants showed interfacial bone contact. The torque test resulted in fracture at the bone-implant interface for all experimental conditions. Installation of etched implants using an undersized preparation of the implant bed resulted in superior bonding strength with the surrounding bone at 12 weeks after surgery. Evidently, the undersized preparation technique improved the early fixation of oral implants in this study.     

Biomedical Ti–Mo Alloys with Surface Machined and Modified by Laser Beam: Biomechanical,Histological, and Histometric Analysis in Rabbits

Purpose: In vivo bone response was assessed by removal torque, hystological and histometrical analysis on a recently developed biomedical Ti‐15Mo alloy, after surface modification by laser beam irradiation, installed in the tibia of rabbits. Materials and Methods: A total of 32 wide cylindrical Ti‐15Mo dental implants were obtained (10 mm × 3.75 mm). The implants were divided into two groups: 1) control samples (Machined surface – MS) and 2) implants with their surface modified by Laser beam‐irradiation (Test samples – LS). Six implants of each surface were used for removal torque test and 10 of each surface for histological and histometrical analysis. The implants were placed in the tibial metaphyses of rabbits. Results: Average removal torque was 51.5 Ncm to MS and >90 Ncm to LS. Bone‐to‐implant‐contact percentage was significantly higher for LS implants both in the cortical and marrow regions. Conclusions: The present study demonstrated that laser treated Ti‐15Mo alloys are promising materials for biomedical application.     

Correlation between placement torque and survival of single-tooth implants

PURPOSE: This study evaluated the survival parameters of single-tooth implants through clinical and radiographic analysis. MATERIALS AND METHODS: Implants were restored within a 24-hour period with a provisional crown designed to receive an occlusal masticatory load. This approach was compared to implants restored after a healing period (the control group). Forty-six implants were placed in 23 patients who were each treated with 2 Frialit-2 implants placed in sites between the second premolar in the maxilla or mandible. The manufacturer's recommended formal surgical procedure was followed, and primary stability was standardized with a minimum insertion torque of 20 Ncm. The sites were randomly selected, and the clinical and radiographic parameters were standardized with individual templates. RESULTS: Data were collected at 24 h, and at 1, 3, 6, 12, 18, and 24 months. The experimental group included 10 failed implants; 9 of the failed implants had been placed with an insertion torque of 20 Ncm. One implant from the control group failed during the 24-month follow-up period. The survival rate was independent of implant length, site position, and bone quality and quantity. Relative risk for implant failure was associated with insertion torque (relative risk 0.79 [CI: 0.66-0.930]; Cox regression) (P < or = .007), in the experimental group but was not significant for those in the control group (ie, implants placed after a healing period; relative risk 0.78 [CI: 0.34-1.78]; Cox regression) (P < or = .057). To achieve osseointegration, it was found that an insertion torque above 32 Ncm was necessary (chi2= 15.68; P < or = .004). DISCUSSION: A careful evaluation is necessary for a better understanding of the survival rates of immediately loaded implants. In this study, insertion torque was associated with the potential for risk, which can be decreased by 20% per 9.8 Ncm added. CONCLUSION: Given these results, and considering the number of patients treated, immediate provisional crowns should only be proposed with early loading if an appropriate initial insertion torque has been applied.     

Early Healing of Hydroxyapatite‐Coated Implants in Grafted Bone of Zoledronic Acid–Treated Osteoporotic Rabbits

Background: Resorption of grafted bone and delayed osseointegration of implants are main problems associated with alveolar bone augmentation in dental implantology, especially for patients with osteoporosis. The aim of this study is to investigate the early healing response of implants to systemic treatment of zoledronic acid (ZA) in autogenous grafted iliac bone of osteoporotic rabbits. Methods: Ovariectomy (OVX) or sham operation was performed in 46 rabbits, and osteoporotic changes were verified in animals receiving OVX 3 months later. The remaining animals were divided into three groups (n = 12): sham, OVX, and OVX with ZA treatment (ZA group). Autogenous iliac bone grafting was performed in bilateral tibiae, and hydroxyapatite‐coated titanium implants were simultaneously placed into the grafted bone. The animals were sacrificed 2 and 8 weeks later for examination. Results: At both time points, systemic treatment of ZA efficiently promoted bone healing of implants in grafted bone, and all histologic and microcomputed tomography bone indices, including mineralized bone volume, implant–bone contact ratio, connectivity density, trabecular thickness, and trabecular number, were significantly increased in the ZA group compared with the OVX‐only group (P <0.01); implant–bone contact rates in the ZA group were even restored to levels similar to those of sham‐operated animals (P >0.05). Furthermore, biomechanical testing demonstrated that removal torque of implants was significantly increased in the ZA group compared with the OVX group (P <0.01). Conclusion: Systemic treatment with ZA could efficiently promote early bone healing of implants in autogenous grafted bone of osteoporotic rabbits by increasing early osseointegration and fixation of implants.     

Solcoseryl,a tissue respiration stimulating agent,significantly enhances the effect of capacitively coupled electric field on the promotion of bone formation around dental implants

In the present study we examined the combined effect of application of a capacitively coupled electric field (CCEF) and the tissue respiration stimulating agent, Solcoseryl, on the promotion of bone formation around dental implants histologically and mechanically. After a dental implant was inserted into each femur of Japanese white rabbits, Solcoseryl (2 ml/kg) was administered intravenously in the ear vein and a CCEF was applied for 4 h per day for 14 days. The degree of bone formation on microscopic observation, bone contact ratio, bone surface area ratio, and the level of removal torque of the implant in the Solcoseryl- and CCEF-treated group were significantly higher than the respective value in the control group, which had not been treated with Solcoseryl nor CCEF. Thus, the combination of CCEF stimulation and Solcoseryl effectively promoted the formation of new bone. It is suggested that the clinical use of a combination of CCEF stimulation and Solcoseryl for dental implants promotes osseointegration.