Peripheral quantitative computer tomographic,histomorphometric, and removal torque analyses of two different non‐coated implants in a rabbit model

Objective: The objectives of this study were (1) to investigate the bone–tissue response to zirconia and titanium implants at the implant‐to‐bone interface and at the periosteal level and (2) to quantitatively measure the mineral density of the peri‐implant bone using peripheral quantitative computer tomography (pQCT). Material and methods: Ten 3.5 mm × 6.6 mm screw‐shaped threaded implants fabricated from titanium and zirconia were inserted into the mid‐tibial diaphysis of five male New Zealand white rabbits. Calcein green was administered at 4 weeks post‐implantation. The animals were sacrificed after 6 weeks and implants were retrieved and analyzed in terms of bone‐to‐implant contact (BIC), bone area (BA), mineralized surface (MS) percentage, inter‐thread calcein labels, removal torque (RT) values, as well as pQCT measurements. Findings: No statistically significant differences were detected between the zirconia and titanium implants in terms of BIC, RT, and pQCT. However, statistically significant higher BA and MS levels were found in the titanium group, while the higher amount of calcein labels occupying the threads were found in the zirconium group. Significant differences were also found in the quantity and the composition of bone at the bone–implant interfacial area vs. the region 1.5 mm away from the bone–implant interface, irrespective of the implant type. Conclusion: Zirconia implants demonstrated a lower bone remodeling activity in the periosteal region. The bone at the bone–implant interface shows a significantly lower cortical bone density, a higher trabecular density, and trabecular mineral content. Finally, zirconia and titanium implants showed similar bone–implant responses in terms of BIC and RT. To cite this article:
Shin D, Blanchard SB, Ito M, Chu T‐MG. Peripheral quantitative computer tomographic, histomorphometric, and removal torque analyses of two different non‐coated implants in a rabbit model.
Clin. Oral Impl. Res. 22 , 2011; 242–250.
doi: 10.1111/j.1600‐0501.2010.01980.x     

Effect of a macroscopic groove on bone response and implant stability

Objectives: The aim of this study was to investigate the effect of a macroscopic groove on bone response and implant stability during the early stages of healing using a rabbit tibia model. Materials and methods: Anodized titanium implants with (n=24) and without (n=24) macroscopic grooves were prepared. A total of 12 rabbits were used and each received four implants: six rabbits with implants with macroscopic grooves (test group) and six rabbits with implants without macroscopic groves (control group). Histomorphometry, resonance frequency, and removal torque value were evaluated 2 and 6 weeks post‐implant‐insertion. Results: At 2 and 6 weeks, there was no significant difference between the two groups in the percentage of bone‐to‐implant contact (P>0.05). At 6 weeks, the test group had significantly higher implant stability quotient values than the control group (P<0.05). At 2 and 6 weeks, implants with grooves showed a significantly greater resistance to reverse torque than control implants (P<0.05). Conclusion: The groove on the oxidized titanium surface may increase both resistance to shear load and adhesion at the bone–implant interface. A geometric feature such as a macroscopic groove may facilitate osseointegration and increase implant stability in various clinical conditions. Further studies are required to confirm whether the improvement in implant stability will enhance treatment success in humans. To cite this article:
Yoon H‐I, Yeo I‐S, Yang J‐H. Effect of a macroscopic groove on bone response and implant stability.
Clin. Oral Impl. Res. 21 , 2010; 1379–1385.
doi: 10.1111/j.1600‐0501.2010.01960.x     

Enhanced implant integration with hierarchically structured implants: a pilot study in rabbits

Aim: To investigate bone‐to‐implant bonding for some novel surface modifications with a hierarchic structure and to correlate the in vivo results with surface roughness parameters. Materials and methods: Newly developed implants surfaces were tested in rabbits and compared with the commercially available OsseoSpeed^? (OS) implant. The blasted test samples were subjected to treatment in oxalic acid (AT‐II), followed by subsequent etching in hydrofluoric acid (AT‐I). Scanning electron microscopy and X‐ray photoelectron spectroscopy were used to characterize the surface topography and chemical composition of the implants. Biomechanical testing after 6 weeks of healing was complemented with the quantification of fluorochromes and the results were subjected to a multivariate statistical analysis. Results: The results show, both with biomechanical‐ and with histomorphometrical tests, that the AT‐I implants with different surface roughness at the micro (blasting), submicro (shallow cavities) and nanolevels (precipitates) have a greater bone tissue integration compared with the AT‐II‐ and OS implants. The 2D bone‐to‐implant contact (BIC) data were in accordance with the 3D removal torque (RTQ) results even if the former were deduced from implants located in spongeous‐type bone and the latter in cortical bone. The increase in RTQ values for the test samples AT‐I and AT‐II compared with the reference complies with the slightly higher S_a values for these surfaces. Conclusions: Using a combination of conventional methods with novel quantification of florochrome and multivariate analysis, the influence of surface roughness on different levels could be discriminated. The RTQ and BIC values show that the most hierarchical structure with submicro cavities and nanoscale precipitates possesses the most favourable osseointegration properties. To cite this article:
Johansson CB, Gretzer C, Jimbo R, Mattisson I, Ahlberg E. Enhanced implant integration with hierarchically structured implants: a pilot study in rabbits
Clin. Oral Impl. Res. 23 , 2012; 943–953
doi: 10.1111/j.1600‐0501.2011.02233.x     

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.     

Osseointegration of commercial microstructured titanium implants incorporating magnesium: a histomorphometric study in rabbit cancellous bone

Objective: Recent studies have suggested that magnesium (Mg) ions exert a beneficial effect on implant osseointegration. This study assessed the osseointegration of nanoporous titanium (Ti) surface incorporating the Mg produced by hydrothermal treatment in rabbit cancellous bone to determine whether this surface would further enhance bone healing of moderately rough‐surfaced implants in cancellous bone, and compared the result with commercially available micro‐arc oxidized Mg‐incorporated implants. Material and methods: The Mg‐incorporated Ti surfaces (RBM/Mg) were obtained by hydrothermal treatment using an alkaline Mg‐containing solution on grit‐blasted moderately rough (RBM) implants. Untreated RBM and recently introduced Mg‐incorporated microporous Ti implants produced by micro‐arc oxidation (M) were used controls in this study. The surface characteristics were evaluated by scanning electron microscopy, X‐ray photoelectron spectroscopy and optical profilometry. Twenty‐four threaded implants with a length of 10 mm (eight RBM implants, eight RBM/Mg implants and eight M implants) were placed in the femoral condyles of 12 New Zealand White rabbits. Histomorphometric analysis was performed 4 weeks after implantation. Results: Hydrothermally treated and untreated grit‐blasted implants displayed almost identical surface morphologies and R_a values at the micron‐scale. The RBM/Mg implants exhibited morphological differences compared with the RBM implants at the nano‐scale, which displayed nanoporous surface structures. The Mg‐incorporated implants (RBM/Mg and M) exhibited more continuous bone apposition and a higher degree of bone‐to‐implant contact (BIC) than the untreated RBM implants in rabbit cancellous bone. The RBM/Mg implants displayed significantly greater BIC% than untreated RBM implants, both in terms of the all threads region and the total lateral length of implants (P<0.05), but no statistical differences were found between the RBM/Mg and M implants except BIC% values in total lateral length. Conclusion: These results indicate that a nanoporous Mg‐incorporated surface may be effective in enhancing the osseointegration of moderately rough grit‐blasted implants by increasing the degree of bone?implant contact in areas of cancellous bone. To cite this article :
Park J‐W, An C‐H, Jeong S‐H, Suh J‐Y. Osseointegration of commercial microstructured titanium implants incorporating magnesium: a histomorphometric study in rabbit cancellous bone.
Clin. Oral Impl. Res. 23 , 2012; 294–300.
doi: 10.1111/j.1600‐0501.2010.02144.x     

Increased bone apposition on a titanium oxide surface incorporating phosphate and strontium

Objective: This study investigated the osteoconductivity of titanium (Ti) implants with a phosphate (P)‐ and strontium (Sr) ion‐incorporated oxide surface, produced by hydrothermal treatment in the rabbit cortical and cancellous bone, for future biomedical applications as a biocompatible endosseous implant surface. Material and methods: The P‐ and Sr ion‐incorporated Ti implants (P/Sr implant) were produced by hydrothermal treatment using a P‐ and Sr‐containing solution. The surface characteristics were evaluated by scanning electron microscopy, thin‐film X‐ray diffractometry, X‐ray photoelectron spectroscopy and optical profilometry. Forty screw implants (20 control and 20 experimental) were placed in the tibiae and femoral condyles of 10 New Zealand White rabbits. The surface in vivo osteoconductivity of the P/Sr implants was compared with micro‐arc oxidized (TO) implants with surface calcium and P chemistry by histomorphometric analysis in the cortical and cancellous bone after 4 weeks of implantation. Results: The P/Sr implants showed moderately rough surface features and had lower R_a values than the TO implants. Histologically, more direct bone apposition was observed on the surface of the P/Sr implants. The P/Sr implants displayed significantly higher bone‐to‐implant contact percentages compared with the TO implant in both the tibiae and the femoral condyles (P<0.01). Conclusion: The results indicate that the hydrothermally produced P‐ and Sr ion‐incorporated Ti oxide surface may be effective in improving implant osseointegration in both cortical and cancellous bone by increasing bone apposition, due to its surface properties combining micro‐topography, P/Sr chemistry and superior wettability. To cite this article:
Park J‐W. Increased bone apposition on a titanium oxide surface incorporating phosphate and strontium.
Clin. Oral Impl. Res. 22 , 2011; 230–234.
doi: 10.1111/j.1600‐0501.2010.01974.x     

Bone response of Mg ion‐implanted clinical implants with the plasma source ion implantation method

Objectives: This study examined the bone response of magnesium (Mg) ion‐implanted implants produced using a plasma source ion implantation method. Materials and methods: The surface characteristics were evaluated by scanning electron microscopy, Auger electron spectroscopy, X‐ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. The screw‐type titanium implants were treated with resorbable blasting media (RBM) and divided into one control group (RBM implants) and three test groups (Mg ion‐implanted implants with different retained Mg doses). Twenty‐four implants from each group were placed into the tibiae of 24 New Zealand white rabbits. After allowing 6 weeks for healing, the removal torque (RTQ) was measured and the implants were subjected to histomorphometric analysis. Results: The surface roughness and surface morphology of the test groups were similar. The Mg ion‐implanted implants with a 2.3 × 10¹⁵ ions/cm² retained dose showed a significantly higher RTQ than the other implants. Histomorphometric analysis indicated that the bone contact of this group was superior to the other groups. Conclusion: The bone response of Mg ion‐implanted implant showed results superior or similar to an RBM‐treated implant. The optimal Mg ion concentration that induced the strongest osseointegration was approximately 9%. To cite this article:
Cho L‐R, Kim D‐G, Kim J‐H, Byon E‐S, Jeong Y‐S, Park C‐J. Bone response of Mg ion‐implanted clinical implants with plasma source ion implantation method.
Clin. Oral Impl. Res. 21 , 2010; 848–856.
doi: 10.1111/j.1600‐0501.2009.01862.x     

Osseointegration of one‐piece zirconia implants compared with a titanium implant of identical design: a histomorphometric study in the dog

Objective: The aim of this study was to evaluate osseointegration of one‐piece zirconia vs. titanium implants depending on their insertion depth by histomorphometry. Material and methods: Four one‐piece implants of identical geometry were inserted on each side of six mongrel dogs: (1) an uncoated zirconia implant, (2) a zirconia implant coated with a calcium‐liberating titanium oxide coating, (3) a titanium implant and (4) an experimental implant made of a synthetic material (polyetheretherketone). In a split‐mouth manner they were inserted in submerged and non‐submerged gingival healing modes. After 4 months, dissected blocks were stained with toluidine blue in order to histologically assess the bone‐to‐implant contact (BIC) rates and the bone levels (BL) of the implants. Results: All 48 implants were osseointegrated clinically and histologically. Histomorphometrically, BL in the crestal implant part did not differ significantly with regard to material type or healing modality. The submerged coated zirconia implants tended to offer the most stable crestal BL. The histometric results reflected the different healing modes by establishing different BL. The median BIC of the apical implant part of the zirconia and titanium group amounted to 59.2% for uncoated zirconia, 58.3% for coated zirconia, 26.8% for the synthetic material and 41.2% for titanium implants. Conclusions: Within the limits of this animal study, it is concluded that zirconia implants are capable of establishing close BIC rates similar to what is known from the osseointegration behaviour of titanium implants with the same surface modification and roughness. To cite this article:
Koch FP, Weng D, Krämer S, Biesterfeld S, Jahn‐Eimermacher A, Wagner W. Osseointegration of one‐piece zirconia implants compared with a titanium implant of identical design: a histomorphometric study in the dog.
Clin. Oral Impl. Res. 21 , 2010; 350–356.
doi: 10.1111/j.1600‐0501.2009.01832.x     

In vivo performance of zirconia and titanium implants: a histomorphometric study in mini pig maxillae

Objectives: To compare the bone tissue response to surface‐modified zirconia (ZrO₂) and titanium implants. Methods: Cylindrical low‐pressure injection moulded zirconia (ZrO₂) implants were produced with an acid‐etched surface. Titanium implants with identical shape, sandblasted and acid‐etched surface (SLA) served as controls. Eighteen adult miniature pigs received both implant types in the maxilla 6 months after extraction of the canines and incisors. The animals were euthanized after 4, 8 and 12 weeks and 16 zirconia and 18 titanium implants with the surrounding tissue were retrieved, embedded in methylmethacrylate and stained with Giemsa–Eosin. The stained sections were digitized and histomorphometrically analysed with regard to peri‐implant bone density (bone volume/total volume) and bone–implant contact (BIC) ratio. Statistical analysis was performed using Mann–Whitney' U‐test. Results: Histomorphometrical analysis showed direct osseous integration for both materials. ZrO₂ implants revealed mean peri‐implant bone density values of 60.4% (SD ± 9.9) at 4 weeks, 65.4% (SD ± 13.8) at 8 weeks, and 63.3% (SD ± 21.5) at 12 weeks after implantation, whereas Ti‐SLA implants demonstrated mean values of 61.1% (SD ± 6.2), 63.6% (SD ± 6.8) and 68.2% (SD ± 5.8) at corresponding time intervals. Concerning the BIC ratio, the mean values for ZrO₂ ranged between 67.1% (SD ± 21.1) and 70% (SD ± 14.5) and for Ti‐SLA between 64.7% (SD ± 9.4) and 83.7% (SD ± 10.3). For the two parameters investigated, no significant differences between both types of implants could be detected at any time point. Conclusion: The results indicate that there was no difference in osseointegration between ZrO₂ implants and Ti‐SLA controls regarding peri‐implant bone density and BIC ratio. To cite this article :
Gahlert M, Roehling S, Sprecher CM, Kniha H, Milz S, Bormann K. In vivo performance of zirconia and titanium implants: a histomorphometric study in mini pig maxillae.
Clin. Oral Impl. Res. 23 , 2012; 281–286.
doi: 10.1111/j.1600‐0501.2011.02157.x     

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.     

The effect of water pyrolysis on the removal torque of titanium implant inserted in rabbit tibias

Objective: The aim of this study is to examine the effect of oxidation with water pyrolysis (OWP) method on titanium (Ti) implants by comparing the bonding strength between bone and Ti implants that were inserted in the proximal tibia metaphysic of a rabbit for 12 weeks. The removal torque was measured to evaluate the bonding strength for different Ti implants with and without the OWP method. Material and methods: Nine sets of threaded Ti implants (ASTM grade 2) of diameter 3.75 mm and length 5 mm were prepared for the experiment. Each set was composed of four specimens; one was machine‐prepared (group D) and the other three were threaded followed by the OWP method at 300°C (group A), 600°C (group B), and 800°C (group C) for 10 min, respectively. Each set was used for each adult rabbit. To eliminate the effect of the sites or the legs, each rabbit received all four implants, two in the left and two in the right leg, inserted in the proximal tibia metaphyses of the left leg, using a fixed block randomization. After 12 weeks, removal torque tests were carried out. Results: The mean removal torque for the control group D was 16.19 N cm, while the mean removal torque values for the OWP groups A, B, and C were 26.75, 31.51, and 41.05 N cm, respectively. The removal torques obtained from the OWP groups B and C (showing the rutile oxide structure) were significantly greater than that for the control group by Bonferroni's‐corrected Wilcoxon's signed‐rank test (P<0.05). Conclusion: The strongest bonding between bone and group C (OWP method at 800°C) was confirmed by the comparison of removal torques. To cite this article:
S‐H Park, WB Song, KH Kim, DJ Soe, S‐A Cho. The effect of water pyrolysis on the removal torque of titanium implant inserted in rabbit tibias.
Clin. Oral Impl. Res. 22 , 2011; 157–164.
doi: 10.1111/j.1600‐0501.2010.01971.x     

Evaluation of a nanometer roughness scale resorbable media-processed surface: a study in dogs

Objectives: This study compared the biomechanical fixation and bone‐to‐implant contact (BIC) of implants with different surfaces treatment (experimental – resorbable blasting media‐processed nanometer roughness scale surface, and control – dual acid‐etched) in a dog model. Material and methods: Surface characterization was made in six implants by means of scanning electron microscopic imaging, atomic force microscopy to evaluate roughness parameters, and X‐ray photoelectron spectroscopy (XPS) for chemical assessment. The animal model comprised the bilateral placement of control (n=24) and experimental surface (n=24) implants along the proximal tibiae of six mongrel dogs, which remained in place for 2 or 4 weeks. Half of the specimens were biomechanically tested (torque), and the other half was subjected to histomorphologic/morphometric evaluation. BIC and resistance to failure measures were each evaluated as a function of time and surface treatment in a mixed model ANOVA. Results: Surface texturing was significantly higher for the experimental compared with the control surface. The survey XPS spectra detected O, C, Al, and Ti at the control group, and Ca (～0.2– 0.9%) and P (～1.7– 4.1%) besides O, C, Al, and Ti at experimental surfaces. While no statistical difference in BIC was found between experimental and control surfaces or between 2 and 4 weeks in vivo, both longer time and use of experimental surface significantly increased resistance to failure. Conclusions: The experimental surface resulted in enhanced biomechanical fixation but comparable BIC relative to control, suggesting higher bone mechanical properties around the experimental implants. To cite this article :
Marin C, Granato R, Bonfante EA, Suzuki M, Janal MN, Coelho PG. Evaluation of a nanometer roughness scale resorbable media‐processed surface: a study in dogs.
Clin. Oral Impl. Res. 23 , 2012; 119–124.
doi: 10.1111/j.1600‐0501.2010.02155.x     

Biofunctionalization of titanium implants with a biomimetic active peptide (P‐15) promotes early osseointegration

Objectives: The early stages of peri‐implant bone formation play an essential role in the osseointegration and long‐term success of dental implants. By incorporating bioactive coatings, this biofunctionalization of implant surfaces may enhance the attachment of the implant to the surrounding bone and stimulate bone regeneration. Material and methods: To demonstrate faster osseointegration, the surfaces of dental implants were grit‐blasted and acid‐etched. They were then coated with hydroxyapatite (HA) and experimental implants were further coated with a biomimetic active peptide (P‐15) in one of two concentrations. These biofunctionalized samples and controls with no peptide were placed in the forehead region of 12 adult pigs. Six animals were evaluated for a period of 14 or 30 days. Results: Histomorphometric analysis demonstrated that the implants with the high concentration of P‐15 had significantly higher percentage of bone‐to‐implant contact (BIC) at 14 (P=0.018) and 30 (P=0.015) days compared with the other groups. Both concentrations of P‐15 showed increased peri‐implant bone density compared to the control group at 30 days. Conclusion: Biofunctionalization of the implant surface with a biomimetic active peptide leads to significantly increased BIC rates at 14 and 30 days and higher peri‐implant bone density at 30 days. To cite this article:
Lutz R, Srour S, Nonhoff J, Weisel T, Damien CJ, Schlegel KA. Biofunctionalization of titanium implants with a biomimetic active peptide (P‐15) promotes early osseointegration.
Clin. Oral Impl. Res. 21 , 2010; 726–734.
doi: 10.1111/j.1600‐0501.2009.01904.x     

Effect of Si addition on Ca- and P-impregnated implant surfaces with nanometer-scale roughness: an experimental study in dogs

Objectives: To investigate the effect of Si addition on a nanometer‐scale roughness Ca and P implant surfaces in a canine tibia model by biomechanical and histomorphometric evaluations. Material and methods: The implant surfaces comprised a resorbable media CaP microblasted (control) and a CaP resorbable media+silica‐boost microblasted (experimental) surfaces. Surfaces were characterized by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and optical interferometry (IFM) down to the nanometric level. The animal model involved the bilateral placement of control (n=24) and experimental surface (n=24) implants along the proximal tibiae of six dogs, remaining in vivo for 2 or 4 weeks. After euthanization, half of the specimens were torqued‐to‐interface failure, and the other half was subjected to histomorphologic and bone‐to‐implant contact (BIC) evaluation. Torque and BIC statistical evaluation was performed by the Friedman test at 95% level of significance, and comparisons between groups was performed by the Dunn test. Results: IFM and SEM observations depicted comparable roughness parameters for both implant surfaces on the micrometer and nanometer scales. XPS analysis revealed similar chemical composition, except for the addition of Si on the experimental group. Torque‐to‐interface failure and BIC mean values showed no significant differences (P=0.25 and 0.51, respectively) at both 2‐ and 4‐week evaluation points for experimental and control groups. Early bone healing histomorphologic events were similar between groups. Conclusions: The experimental surface resulted in not significantly different biomechanical fixation and BIC relative to control. Both surfaces were biocompatible and osseoconductive. To cite this article:
Coelho PG, Granato R, Marin C, Jimbo R, Lin S, Witek L, Suzuki M, Bonfante EA. Effect of Si addition on Ca‐ and P‐impregnated implant surfaces with nanometer‐scale roughness: an experimental study in dogs. Clin. Oral Impl. Res. 23 , 2012; 373–378.
doi: 10.1111/j.1600‐0501.2010.02150.x     

Effect of immediate or delayed loading following immediate placement of implants with a modified surface

Objective: To evaluate the effect of the timing of loading on bone‐to‐implant contact (BIC) following immediate placement of implants with a hydrophilic sandblasted, large‐grit and acid‐etched surface (modSLA) into fresh extraction sockets in a minipig model. Material and methods: Six minipigs were used in this study. In each hemi‐mandible, two conical shape implants (TE, Straumann implants) with a hydrophilic surface (modSLA) were placed in fresh extraction sockets. In one side of the mandible (control), two implants were immediately placed in fresh extraction sockets. The implants were loaded after 4 weeks of healing. At the contralateral side (test), two implants were immediately placed and loaded. After 8 weeks of healing, the animals were sacrificed and histologically analysed. Results: During the experimental period, no implants were lost and all of them presented to be osseointegrated. The percentage of BIC was similar in both groups: 66.1% and 65.1% for the control and test group, respectively. Furthermore, the distance from the shoulder of the implant to bone crest and the distance from the shoulder to the first BIC were similar in both groups. Conclusion: Immediate implant placement and loading showed similar BIC with immediate placement and delayed loading when implants with a modSLA surface were used. Both procedures showed similar buccal bone crest levels, which presented some resorption irrespective of the treatment modality. To cite this article:
Liñares A, Mardas N, Dard M, Donos N. Effect of immediate or delayed loading following immediate placement of implants with a modified surface.
Clin. Oral Impl. Res. 22 , 2011; 38–46.
doi: 10.1111/j.1600‐0501.2010.01988.x     

Which surface properties enhance bone response to implants? Comparison of oxidized magnesium, TiUnite, and Osseotite implant surfaces

PURPOSE: This study compared the speed and strength of osseointegration and osteoconductivity between an oxidized experimental magnesium (Mg) implant, an oxidized commercially available TiUnite implant, and a dual acid-etched surface Osseotite implant. The aim was to investigate which surface properties enhance bone response to implants, and thereby to test a biochemical bonding theory. MATERIALS AND METHODS: A total of 60 screw implants (20 of each design) were inserted through 1 cortex into the tibiae of 10 rabbits. Surface chemistry, oxide thickness, morphology, crystal structure, and surface roughness were evaluated. After healing times of 3 and 6 weeks, all bone implants were unscrewed with removal torque (RTQ) devices, and the bone specimens were subjected to histomorphometry. RESULTS: RTQ values for Mg, TiUnite, and Osseotite implants were 27.1, 21.3, and 15.4 Ncm, with new bone formation values of 29%, 18%, and 15%, respectively, at 3 weeks. At 6 weeks the RTQ values were 37.5, 36.4, and 21.5 Ncm, with new bone formation values of 39%, 31%, and 26%, respectively. Discussion: Mg implants demonstrated significantly greater RTQ values (P = .008 and P = .0001) and more new bone formation (P = .031 and P = .030) than Osseotite at 3 and 6 weeks, respectively. Mg implants also showed higher RTQ values at 3 weeks and new bone formation at 6 weeks than TiUnite, but neither were significant (P > .05). TiUnite showed significantly higher RTQ values than Osseotite at 6 weeks (P = .001), but was not significant at 3 weeks (P > .05). Osseointegration rate (deltaRTQ/deltaweeks) was significantly faster for Mg (P = .011) and TiUnite (P = .001) implants between 3 and 6 weeks of healing time, but was not significant for Osseotite. CONCLUSIONS: The results indicate that surface chemistry facilitated more rapid and stronger osseointegration of the Mg implants despite their minimal roughness compared to the moderately roughened TiUnite. This suggests potential advantages of Mg implants for reducing high implant failure rates in the early postimplantation stage and in compromised bone, making it possible to shorten bone healing time from surgery to functional loading, and enhancing the possibility of immediate/early loading.     

Ex Vivo and In Vivo Biomechanical Test of Implant Attachment to Various Materials: Introduction of a New User‐Friendly Removal Torque Equipment

Objective: The removal torque (RTQ) analysis is commonly used for biomechanical evaluation of osseointegration. The overall aim of this study was to verify results obtained with a newly developed equipment for biomechanical testing of osseointegration. Methods: Verification of the new equipment for biomechanical tests involved three experiments: Part I, comparison of RTQ between implants placed in four different types of dental synthetic plasters. Part II, comparison of RTQ between custom made, experimentally used implants to self‐tapping, commercially available implants molded in the same type of dental plaster. Part III, comparison of RTQ between commercially pure titanium implants to Ti6Al4V implants placed in rabbit bone, 6 weeks after insertion. Briefly, for all experiments, the peak RTQ values and the removal process were recorded every 0.01 seconds up to 10 seconds. After the measurements, peak RTQ values were converted to shear strength. Results: The developed equipment sensitively responded to the changes of properties related to the molding plasters, implant topographies, and materials. The monitored graphs corresponded well to the expected properties of the different implants and tested materials. Conclusion: The new RTQ equipment proved to be accurate and could add new knowledge in understanding the biomechanical aspects of osseointegration.     

Biomechanical and histologic evaluation of non-washed resorbable blasting media and alumina-blasted/acid-etched surfaces

Objectives: To compare the biomechanical fixation and histomorphometric parameters between two implant surfaces: non‐washed resorbable blasting media (NWRBM) and alumina‐blasted/acid‐etched (AB/AE), in a dog model. Material and methods: The surface topography was assessed by scanning electron microscopy, optical interferometry and chemistry by X‐ray photoelectron spectroscopy (XPS). Six beagle dogs of ～1.5 years of age were utilized and each animal received one implant of each surface per limb (distal radii sites). After a healing period of 3 weeks, the animals were euthanized and half of the implants were biomechanically tested (removal torque) and the other half was referred to nondecalcified histology processing. Histomorphometric analysis considered bone‐to‐implant contact (BIC) and bone area fraction occupancy (BAFO). Following data normality check with the Kolmogorov–Smirnov test, statistical analysis was performed by paired t‐tests at 95% level of significance. Results: Surface roughness parameters S_a (average surface roughness) and S_q (mean root square of the surface) were significantly lower for the NWRBM compared with AB/AE. The XPS spectra revealed the presence of Ca and P in the NWRBM. While no significant differences were observed for both BIC and BAFO parameters (P>0.35 and P>0.11, respectively), a significantly higher level of torque was observed for the NWRBM group (P=0.01). Bone morphology was similar between groups, which presented newly formed woven bone in proximity with the implant surfaces. Conclusion: A significant increase in early biomechanical fixation was observed for implants presenting the NWRBM surface. To cite this article:
Coelho PG, Marin C, Granato R, Giro G, Suzuki M, Bonfante EA. Biomechanical and histologic evaluation of non‐washed resorbable blasting media and alumina‐blasted/acid‐etched surfaces.
Clin. Oral Impl. Res. 23 , 2012; 132–135.
doi: 10.1111/j.1600‐0501.2010.02147.x     

The effect of combined delivery of recombinant human bone morphogenetic protein-2 and recombinant human vascular endothelial growth factor 165 from biomimetic calcium-phosphate-coated implants on osseointegration

Objectives: The delivery of growth factors for enhanced osseointegration depends on the effectiveness of the carrier systems at the bone–implant interface. This study evaluated the effect of solo and dual delivery of recombinant human bone morphogenetic protein‐2 (rhBMP‐2) and recombinant human vascular endothelial growth factor (rhVEGF₁₆₅) from biomimetically octacalcium phosphate‐coated implants on osseointegration. Materials and methods: Biomimetic implants, bearing either a single growth factor (BMP or VEGF) or their combination (BMP+VEGF), were established, and compared with acid‐etched (AE, control) and biomimetic implants without growth factor (CAP). Implants were placed into frontal skulls of nine domestic pigs. The quality of osseointegration was evaluated using microradiographic and histomorphometric analysis of bone formation inside four defined bone chambers of the experimental implant at 1, 2 and 4 weeks. Results: Biomimetic implants, either with or without growth factor, showed enhanced bone volume density (BVD) values after 2 and 4 weeks. This enhancement was significant for the BMP and BMP+VEGF group compared with the control AE group after 2 weeks (P<0.05). All biomimetic calcium‐phosphate (Ca‐P) coatings exhibited significantly enhanced bone–implant contact (BIC) rates compared with the uncoated control surface after 2 weeks (P<0.05). However, the combined delivery of BMP‐2 and VEGF did not significantly enhance BIC at the final observation period. Conclusion: It was concluded that the combined delivery of BMP‐2 and VEGF enhances BVD around implants, but not BIC. Therefore, it may be assumed that changes in the surface characteristics should be considered when designing growth factor‐delivering surfaces. To cite this article:
Ramazanoglu M, Lutz R, Ergun C, von Wilmowsky C, Nkenke E, Schlegel K A. The effect of combined delivery of recombinant human bone morphogenetic protein‐2 and recombinant human vascular endothelial growth factor 165 from biomimetic calcium‐phosphatecoated implants on osseointegration.
Clin. Oral Impl. Res. xx , 2011; 000–000.
doi: 10.1111/j.1600‐0501.2010.02133.x