不同愈合期施加载荷对正畸微种植体稳定性影响的研究

目的 探讨微种植体在不同愈合时间施加载荷的生物力学性能和稳定性。方法 将64枚微种植体以（12±1） N·cm扭力植入在8只Beagle犬的下颌牙槽骨上,实验组微种植体于植入后即刻及愈合1、3、8周时施加载荷0.98 N,持续10周,对照组不施加载荷,分别于植入后1、3、8、10周取材。测量两组微种植体的最大旋出扭力,以评价微种植体-骨界面结合强度,旋出微种植体用扫描电子显微镜观察微种植体-骨界面的形态。结果 实验组即刻载荷及愈合1、3、8周载荷的微种植体平均最大旋出扭力分别为4.10、4.25、2.42、4.42 N·cm,其中愈合3周的旋出扭力明显低于其他组（P<0.05）;对照组愈合3周的旋出扭力亦明显低于其他组。实验组愈合3周微种植体的表面为编织骨样结构;而其他愈合时间施加载荷后,其表面多为板层骨样结构。结论 微种植体植入后3周左右为稳定性危险期,此时施加载荷不利于微种植体的稳定。临床应选择微种植体的功能愈合期,即植入后即刻,或愈合1、8周后进行适度加载。     

Bone response to unloaded titanium implants in the fibula, iliac crest, and scapula: an animal study in the Yorkshire pig

The reconstruction of extended maxillary and mandibular defects with prefabricated free flaps is a two stage procedure, that allows immediate function with implant supported dentures. The appropriate delay between prefabrication and reconstruction depends on the interfacial strength of the bone-implant surface. The purpose of this animal study was to evaluate the removal torque of unloaded titanium implants in the fibula, the scapula and the iliac crest. Ninety implants with a sandblasted and acid-etched (SLA) surface were tested after healing periods of 3, 6, and 12 weeks, respectively. Removal torque values (RTV) were collected using a computerized counterclockwise torque driver. The bicortical anchored 8mm implants in the fibula revealed values of 63.73 Ncm, 91.50 Ncm, and 101.83 Ncm at 3, 6, and 12 weeks, respectively. The monocortical anchorage in the iliac crest showed values of 71.40 Ncm, 63.14 Ncm, and 61.59 Ncm with 12 mm implants at the corresponding times. The monocortical anchorage in the scapula demonstrated mean RTV of 62.28 Ncm, 97.63 Ncm, and 99.7 Ncm with 12 mm implants at 3, 6, and 12 weeks, respectively. The study showed an increase of removal torque with increasing healing time. The interfacial strength for bicortical anchored 8mm implants in the fibula was comparable to monocortical anchored 12 mm implants in the iliac crest and the scapula at the corresponding times. The resistance to shear seemed to be determined by the type of anchorage (monocortical vs. bicortical) and the length of the implant with greater amount of bone-implant interface.     

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.     

Biomechanical and histomorphometric comparison between zirconia implants with varying surface textures and a titanium implant in the maxilla of miniature pigs

BACKGROUND: Mechanical properties and biocompatibility make zirconia ceramics suitable implant material. The characteristics of tooth-color like, the ability to be machined and the low plaque affinity make zirconia especially suitable as a dental implant material. The influence of surface modification on the osseointegration of this material has not been extensively investigated. PURPOSE: Long-term investigations with titanium implants have shown superior biomechanical results with the sandblasted acid-etched (SLA) surface, demonstrating a high bone-implant interaction. The objective of this study was to compare two different zirconia surface topographies biomechanically and histologically with the well-documented titanium SLA surface. MATERIAL AND METHODS: Zirconia implants with either a machined (ZrO2m) or a sandblasted (rough, ZrO2r) surface were manufactured with the exact same cylindrical shape with a standard ITI thread configuration as the SLA titanium implants. The incisors 2 and 3 were removed from both sides of the maxillae of 13 adult miniature pigs and the tissues left to heal for 6 months. After this time period the animals received a total of 78 implants using a randomized scheme, with the titanium SLA implant used as an only individual reference. After healing periods of 4, 8, and 12 weeks 20, 24, and 25 implants, respectively, were subjected to removal torque tests (RTQ) as the main biomechanical analysis of the of the study. A fewer number was resected on bloc, embedded in methylmethacrylat and analyzed for their direct bone apposition under a light microscope. RESULTS: Surface analysis revealed the highest surface roughness for the SLA-implant, followed by ZrO2r and ZrO2m. The turned ZrO2m implants showed statistically significant lower RTQ values than the other two implants types after 8 and 12 weeks, while the SLA implant showed significantly higher RTQs values than ZrO2r surface after 8 weeks. Differences in the bone apposition were observed in the histomorphometric analysis using light microscopy for all surfaces at any time point. CONCLUSION: The findings suggest that ZrO2r implants can achieve a higher stability in bone than ZrO2m implants. Roughening the turned zirconia implants enhances bone apposition and has a beneficial effect on the interfacial shear strength.     

The effect of hydroxyapatite nanocrystals on early bone formation surrounding dental implants

The knowledge of how nanostructures might affect early bone healing and osseointegration is limited. The aim of this study was to investigate if nanometer thick coatings of hydroxyapatite nanocrystals applied on a moderately rough surface might enhance early bone healing on screw-shaped dental implants and to evaluate if the thickness of the coat influences healing. Sandblasted and acid etched titanium implants coated with two different thicknesses of hydroxyapatite (test implants) and sandblasted and acid etched titanium implants (control implants), were inserted in rabbit tibia. After a healing time of 2, 4 and 9 weeks, a removal torque analysis and a histological evaluation were performed. The results from the removal torque analysis showed a tendency for higher values for the double coated hydroxyapatite after 4 weeks and for both the coated surfaces after 9 weeks of healing. The histological evaluations indicated slightly more new bone formation with the coated implants compared with the control; the differences did not reach statistical significance. The present study could not support the importance of nanometer thick coatings of hydroxyapatite nanocrystals in early bone healing, at least not when applied on a blasted and etched surface and placed in a cortical bone.     

The influence of cyclosporin a on mechanical retention of dental implants previously integrated to the bone: a study in rabbits

BACKGROUND: Immunosuppressive agents may induce severe changes on bone metabolism and may impair the osseointegration process during the implant healing. No data are available concerning the influence of cyclosporin A on dental implants previously integrated to the bone. The aim of this study was to evaluate the influence of cyclosporin A administration on the mechanical retention of bone previously integrated to dental implants. METHODS: Eighteen female New Zealand rabbits were submitted to an implant surgery. Each animal received one commercial dental implant of 10 x 3.75 mm. After 12 weeks of an undisturbed healing period, six animals were randomly sacrificed and the removal torque test was performed (group A). In addition, six animals were submitted to a daily injection of cyclosporin A in a dosage of 10 mg/kg (group C), and six animals received saline solution as a control (group B). After 12 weeks of cyclosporin A administration, groups B and C were sacrificed and submitted to a removal torque test in which higher values can be interpreted as higher mechanical bone retention to the implant surface or higher osseointegration. RESULTS: The removal torque results were 30.5 (+/-9.8) Ncm for group A, 50.17 (+/-17.5) Ncm for group B, and 26 (+/-7.8) Ncm for group C. The statistical analysis showed significant differences between groups A and B (P <0.05) and groups B and C (P <0.01). CONCLUSION: Cyclosporin A administration may impair the mechanical retention of dental implants previously integrated to the bone.     

Biomechanical evaluation of a titanium implant surface conditioned by a hydroxide ion solution

Two groups of titanium dental implants, identical in geometry but different in the treatment of their surfaces, were tested in an in vivo minipig model of the mandible. The surfaces that were tested were, first, sandblasted and acid-etched; and secondly, sandblasted, acid-etched, and conditioned. The removal torque was assessed at 2, 4, and 8 weeks after implantation (n=6 animals in each healing period). The interfacial stiffness was also evaluated. All dental implants were well-integrated at the time of death. Removal torque values increased significantly over the course of 8 weeks. Removal torque and interfacial stiffness were increased for conditioned surfaces after 2 weeks, but there were no significant differences between the two surfaces. The sandblasted and acid-etched implants are the standard, and conditioning of the surface showed a tendency to increase early peri-implant formation of bone.     

Effects of a calcium phosphate coating on the osseointegration of endosseous implants in a rabbit model

Objectives: The aim of the present study was to evaluate a Ca–P coated implant surface in a rabbit model. The Ca–P surface (test) was compared to the titanium porous oxide surface (control) in terms of bone‐to‐implant contact (BIC) and removal torque value. Materials and methods: Two hundred and sixteen dental implants were inserted in the tibia and in the femur of 36 rabbits. One hundred and eight were represented by Ca–P oxidized surface implant and other 108 were titanium porous oxide surface modified implants. Each rabbit received six implants. Animals were sacrificed after 2, 4 and 9 weeks of healing. Each group included 12 rabbits. The femoral implant and the proximal implant of the tibia of each animal were subjected to the histologic analysis and the distal implants of the tibia underwent removal torque test (RTQ). Results: Histological analysis in terms of BIC and RTQ did not revealed any significant difference between the Ca–P oxidized surface and the oxidized surface at 2 and 4 weeks. At 9 weeks, the oxidized surface demonstrated better results in terms of RTQ in the tibia. Conclusion: In conclusion, findings from the present study suggested that the Ca–P coating had no beneficial effect in improving bonding strength at the bone–implant interface either at 2, 4 and 9 weeks. To cite this article:
Fontana F, Rocchietta I, Addis A, Schupbach P, Zanotti G, Simion M. Effects of a calcium phosphate coating on the osseointegration of endosseous implants in a rabbit model
Clin. Oral Impl. Res. 22 , 2011; 760–766
doi: 10.1111/j.1600‐0501.2010.02056.x     

The effect of calcium ion concentration on the bone response to oxidized titanium implants

Aim: To investigate the effect of calcium concentration on the bone tissue response to Ca‐incorporated titanium implants Materials and methods: Two titanium surfaces containing 4.2% and 6.6% calcium were prepared using the micro‐arc oxidation process. The implants were inserted in the tibia of nine New Zealand White rabbits. After 6 weeks of healing, the bone response to the implants was quantitatively compared by biomechanical and histomorphometrical measurements. Results: Ca 4.2% and Ca 6.6% containing implants revealed no distinctive differences in their qualitative surface chemistry; chemical bonding state of Ca in titanium oxide was mainly calcium titanates. No significant differences were observed between two implants in peak removal torque and shear strength comparisons (P>0.05). Histomorphometrical analyses presented no significant differences in bone–metal contact, bone area and newly formed bone measurements between two implants (P>0.05). Conclusions: From biomechanical and histomorphometrical measurements, the two calcium concentrations in this study did not differ significantly with respect to their influence on the bone tissue response. This similar bone response in rabbit tibiae may be explained by the similarity of the qualitative Ca chemistry in titanium surfaces.     

Importance of Ca(2+) modifications for osseointegration of smooth and moderately rough anodized titanium implants - a removal torque and histological evaluation in rabbit

Background: Incorporation of Ca²⁺ into the titania of anodized titanium surfaces has been found to enhance osseointegration. It provides a stable surface when the ions are incorporated into the oxide layer during the anodizing process. The Ca²⁺ may suggestively be prominent sites for mineral induction, attract proteins, and catalyze intracellular cascades. Purpose: The aim of the present study was to evaluate the osseointegration of smooth (S_a < 0.5 µm) and moderately rough (S_a 1.0–2.0 µm) commercially pure titanium implants, with and without Ca²⁺, in order to reflect on the importance of surface chemistry in relation to topography. Materials and Methods: Anodized implants with (OxCa) or without Ca²⁺ (Ox), blasted implants (Bl), and blasted anodized implants, with (BlOxCa) or without Ca²⁺ (BlOx), were inserted in rabbit femur and tibia. The implant surfaces were characterized using interferometry, scanning electron microscopy, and X‐ray photoelectron spectroscopy prior to implant installation. Removal torque (RTQ) measurements were executed on all implants after a healing period of 12 weeks. The implants were, thereafter, removed en bloc with surrounding tissues and prepared for histological evaluations. Results: RTQ measurements of tibial implants revealed significantly higher values for BlOxCa implants (90.7 ± 23.3 Ncm) compared to OxCa (64.6 ± 18.2 Ncm) and BlOx implants (69.7 ± 17.5 Ncm) (p = 0.029). Ca²⁺ modification of smooth implants placed in the femur did not reveal any differences. Conclusion: Ca²⁺ modification of smooth implants resulted in similar interfacial shear strength as moderately rough implants and Ca²⁺ modification of moderately rough implants demonstrated the significantly strongest interfacial shear strength when placed in rabbit tibia. This possibly demonstrated surface chemistry compensating for lesser roughness.     

A mechanical evaluation of TiO2-gritblasted and Ca-P magnetron sputter coated implants placed into the trabecular bone of the goat: Part 1

The influence of Ca-P magnetron sputter coated implants on the mechanical anchorage was evaluated in a goat model. Therefore, uncoated and coated screw designed commercially pure titanium TiO2-blasted implants were inserted into the trabecular bone of the femoral condyles of 12 goats. The thicknesses of the coatings were 0.1 micron (CaP-0.1), 1.0 micron (CaP-1) and 4.0 microns (CaP-4). In addition, uncoated TiO2-blasted implants (Ti) were used as control. Evaluation of the interface strength and appearance, using torque test and scanning electron microscopy, was done at implantation periods of 6 and 12 weeks. Although, especially at 6 weeks of implantation, the Ca-P coated implants showed higher failure torque values than the TiO2 blasted implants, the observed differences for type of implant and evaluation period were not significant (P > 0.1). SEM evaluation showed that all implants with failure values of more than 100 N conducted bone growth into their screw threads. In addition, we observed that the fracture plane for the CaP-4 implants was situated at the coating-implant interface or inside the coating. For the CaP-1 and CaP-0.1 the fracture line could not be determined definitely. For the Ti implants, the fracture torque testing resulted in failure at the bone-implant interface. Therefore, we conclude that all implants resulted in a good bonding strength with the surrounding bone. The sputtered Ca-P coatings seemed to improve the initial fixation of the TiO2 blasted implants.     

A Comparison Study of the Osseointegration of Zirconia and Titanium Dental Implants. A Biomechanical Evaluation in the Maxilla of Pigs

Objectives: The purpose of the present study was to investigate the osseointegration of microstructured zirconia implants in comparison with sandblasted and acid‐etched (SLA) titanium implants in a biomechanical study. Materials: Zirconia implants (4.1 mm in diameter, 10 mm in length) were produced using a new low pressure injection molding technique. After that the implants were acid‐etched with hydrofluoric acid. Standard Ti‐SLA implants of the exact same shape served as controls. Six months after extraction of incisors 2 and 3, 16 adult pigs received a total of 64 implants in the maxillae. After 4, 8, and 12 weeks the animals were sacrificed, and 59 implants could be analyzed to removal torque (RTQ) testing. Results: The mean RTQ values for zirconia implants were 42.4 Ncm at 4 weeks, 69.6 Ncm at 8 weeks, and 69.3 Ncm at 12 weeks of healing, whereas RTQ values for the Ti‐SLA implants were 42.1 Ncm, 75.0 Ncm, and 73.1 Ncm at corresponding time intervals. There is no statistical difference in RTQ values between Ti‐SLA and zirconia implants at 8 weeks. Conclusions: Within the limits of the present study it was concluded that acid‐etching of zirconia implants enhances bone apposition resulting in RTQ values which were equivalent to that of Ti‐SLA.     

Surface-modified zirconia implants: tissue response in rabbits

Aim: To evaluate the bone tissue response to zirconia implants with three different surface modifications in comparison with the oxidized titanium surface with the goal to optimize osseointegration in terms of strength and speed.
Materials and methods: A total of 18 rabbits with 143 implants were used. One hundred and twenty-three were threaded zirconia ceramic implants with three different surface topographies and 20 modified titanium oxide implants were controls. Each rabbit received eight implants and sacrificed after 3 weeks. The removal torque test (RTQ) and histology were performed.
Results: Sixteen out of 18 rabbits completed the study with a total of 110 implants. No statistical significance was observed between the chemical modification implants compared with the topographically modified zirconia implant in terms of interfacial shear strength proven by the RTQ applied. No statistical significance was also observed in the bone-to-implant contact between the zirconia implants and the control oxidized implants.
Conclusions: The findings suggest that additional specific chemical modifications of the topographically modified zirconia implants do not seem to enhance the bone-to-implant contact and appear not to increase the interfacial shear strength.     

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.     

Primary stability of turned and acid-etched screw-type implants: a removal torque and histomorphometric study in rabbits

PURPOSE: This study evaluated the effect of primary stability on the osseointegration of turned and acid-etched screw implants in a rabbit model. MATERIALS AND METHODS: One pair of turned and acid-etched implants (3.75 in diameter, 5.5 mm long) was placed in each tibia of 15 rabbits. In the right tibial metaphysis the implants were inserted according to a standard surgical protocol. In the left tibia, the osteotomy sites were enlarged using a sequence of drills, and 2 implants were placed with reduction of primary stability. Animals were sacrificed 9 weeks after surgery. Histomorphometric and removal torque analyses were performed to evaluate bone-implant contact and strength of osseointegration. RESULTS: Surface texture had a significant effect on percentage of bone-implant contact (P = .001). Acid-etched implants with high primary stability showed the highest percentage of bone-implant contact (77%), followed by acid-etched implants with low primary stability (61%), turned implants with low primary stability (56%), and turned implants with high primary stability (46%). For removal torque, acid-etched implants had higher peak mean values than turned implant groups (P < .001). Reduction of primary stability was not significant to either percentage of bone-implant contact (P = .645) or removal torque values (P = .214). CONCLUSION: Acid-etched implants had higher bone response and implant fixation than turned implants, regardless of primary stability.     

Osseointegration of anodized titanium implants under different current voltages: a rabbit study

The oxide layer that covers a titanium surface is extremely stable and appears to have excellent biocompatibility, which can result in successful osseointegration. The aim of this study was to analyse the characteristics of an oxide layer formed by anodic oxidation (anodization), and to evaluate the extent of bone healing around the anodized implant. The screw-type implants were made of commercially pure titanium (Grade 2). The Group 1 samples had a turned surface, and three other types of experimental specimens were anodized under constant voltages of 190 V (Group 2), 230 V (Group 3) and 270 V (Group 4). The surface characteristics of each sample type were inspected. Removal torque was measured after a 4-week healing period and the histomorphometric analysis was performed 6 weeks after implantation in rabbit tibiae. There was an increase in both the size and number of pores as the anodizing voltage increased. The Ra value of the Group 4 samples was higher than those in the Group 1 and 2 samples (P < 0.05). Group 3 showed a difference compared with Group 1 (P < 0.05). A thicker oxide layer, which contained crystalline (anatase) TiO(2) with the inclusion of some electrolytes (Ca, P), was formed at the higher anodizing voltage. Group 4 had higher removal torque values and percentages of bone-to-implant contact than the other groups (P < 0.05). The anodized titanium implants showed more intimate and stronger connections with peri-implant bone during early osseointegration than the turned titanium implants in this experimental model.     

Effects of a novel calcium titanate coating on the osseointegration of blasted endosseous implants in rabbit tibiae

OBJECTIVE: The purpose of this study was to investigate the effects of a nanostructured calcium coating on the surfaces of blasted Ti implants on peri-implant bone formation in the rabbit tibiae. MATERIAL AND METHODS: Threaded implants (3.75 mm in diameter, 6 mm in length) were roughened by hydroxyapatite (HA) blasting (control; blasted implants). The implants were then hydrothermally treated in a Ca-containing solution for 24 h to prepare Ca-incorporated Ti surfaces (experimental; blasted/Ca implants). Surface characterizations were performed by scanning electron microscopy and stylus profilometry before and after Ca coating. Forty-two implants (21 control and 21 experimental) were placed in the proximal tibiae of seven New Zealand White rabbits. Each rabbit received six implants. To evaluate the effects of the nanostructured Ca coating on the peri-implant bone-healing response, removal torque tests and histomorphometric analyses were performed 6 weeks after surgery. RESULTS: The Ca coating did not significantly change the surface properties produced by blasting at the micron level. Histologically, active bone apposition was observed in the blasted/Ca implants in the marrow space. Compared with the blasted implants, the blasted/Ca implants showed significantly increased bone-to-implant contact over the total implant length (P<0.01) and greater mean removal torque values (P<0.05). DISCUSSION AND CONCLUSION: The nanostructured, Ca-incorporated surface significantly enhanced the peri-implant bone-healing response of HA-blasted Ti implants. It may be concluded that the use of nanostructured, Ca-coated surfaces may have synergic effects in enhancing osseointegration of blasted Ti implants due to their micron-scaled surface properties and biologically active surface chemistry.     

Biological responses of anodized titanium implants under different current voltages

The oxide layer of a titanium surface is very stable, and seems to result in excellent biocompatibility and successful osseointegration. The purpose of this study was to investigate the effects of high anodic oxidation voltages on the surface characteristics of titanium implants and the biologic response of rabbit tibiae. Bone tissue responses were evaluated by removal torque tests and histomorphometric analysis. Screw-shaped implants with microthreads were made of commercially pure titanium (Grade II). We prepared anodized implants under 300 V (group I), 400 V (group II), 500 V (group III) and 550 V (group IV). The surface characteristics of specimens were inspected according to three categories: surface morphology, surface roughness and oxide layer thickness. The screw-shaped implants were installed in rabbit tibiae. The removal torque values were measured and histomorphometric analysis was done after 1- and 3-month healing periods. Data indicate that as anodic oxidation voltage increased above 300 V, oxide layer thickness increased rapidly and pore size also increased. The roughness values of the implants increased with voltage up to 500 V, but decreased at 550 V. In the removal torque test, group III showed higher values than groups I and II at a statistically significant level (P < 0.05) after a 1-month healing period. In histomorphometric analysis, groups III and IV, after a 3-month healing period, showed greater bone to implant contact ratios for the total implant surface than did group I (P < 0.05).     

Is the osseointegration of immediately and delayed loaded implants the same?—comparison of the implant stability during a 3‐month healing period in a prospective study

Objectives: The objectives of the present study were (1) to compare the stability of delayed loaded (DL) and immediately loaded (IL) ITI SLA implants during the first 3 months of the healing period using resonance frequency analysis (RFA) and (2) to determine the factors that affect implant stability during the healing period.
Materials and methods: To compare implant stability, RFA was performed on two groups of patients (12 patients received 25 IL implants and 47 patients received 79 DL implants) with a total 104 ITI SLA implants. Implant stability was measured directly by RFA at implant placement and consecutively once a week for 12 weeks. Statistical analyses were carried out to study implant stability differences between IL and DL groups.
Results: One of the 25 implants in the IL group failed, and no implant was lost in the DL group. Implant stability between the IL and DL groups showed a statistically significant difference ( P <0.05). The mean implant stability quotient of all measured implants from implant insertion to 12 weeks was 72.88 ± 5.39 for the DL and 75.86 ± 3.60 for the IL types. The lowest stability was at 4 weeks for DL implants (mean: 71.58 ± 5.11) and 2 weeks for IL implants (mean: 71.33 ± 2.97). In both groups, bone types I and II showed higher implant stability than bone type III ( P <0.05).
Conclusions: The findings of this study indicate that differences in osseointegration between IL and DL implants may be predicted according to differential implant stability.     

Interface of unloaded titanium implants in the iliac crest, fibula, and scapula: a histomorphometric and biomechanical study in the pig

PURPOSE: Prefabrication of free vascularized fibular flaps is a 2-stage procedure for the reconstruction of maxillary and mandibular defects. The delay between prefabrication and flap transfer is 6 weeks and depends on biomechanical stability and osseointegration of the implants. The purpose of this animal study was to evaluate implant stability by measuring the removal torque values (RTVs) at 3, 6, and 12 weeks and to compare the results with interface strength of the bone-implant surface in the fibula, the scapula, and the iliac crest under unloaded conditions. MATERIALS AND METHODS: ITI implants (n = 108) with a sandblasted and acid-etched surface were placed in the fibula, the scapula, and the iliac crest of 6 Yorkshire pigs. Biomechanical, histologic, and histomorphometric results were collected at 3, 6, and 12 weeks, respectively. RESULTS: Bicortical anchored 8-mm implants in the fibula (63.7 to 101.8 Ncm) showed RTVs similar to those of monocortical anchored 12-mm implants in the scapula (62.3 to 99.7 Ncm). The RTVs of monocortical anchored 8-mm and 10-mm implants in the iliac crest (19.1 to 44.3 Ncm) and the scapula (27.2 to 55.3 Ncm) were significantly lower. The bone-to-implant contact in the fibula at 3, 6, and 12 weeks (35.2%, 44.4%, and 46.8%, respectively) was similar to that in the iliac crest (24.2%, 44.2%, and 52.5%, respectively), but significantly lower than in the scapula (63.7%, 73.8%, and 74.2%, respectively). DISCUSSION AND CONCLUSION: Bicortical anchorage determined implant stability in the fibula, whereas interfacial strength seemed to define stability in the scapula. The quality and type of bone determined the bone's response in terms of biomechanical press fit or biologic interface strength.