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     

Resonance frequency measurements in vivo and related surface properties of magnesium-incorporated, micropatterned and magnesium-incorporated TiUnite®, Osseotite®, SLA® and TiOblast® implants

Objective: To investigate implant stability using resonance frequency measurements of topographically changed and/or surface chemistry‐modified implants in rabbit bone. Material and methods: Six groups of microstructured, screw‐shaped titanium implants: two oxidized, cation‐incorporated experimental implants [Mg implants and MgMp implants with micropatterned thread flanges (80–150 μm wide and 60–70 μm deep)] and four commercially available clinical implants (TiUnite^®, Osseotite^®, SLA^®, and TiOblast^®) were installed in 10 rabbit tibia for 6 weeks. The surface properties of the implants were characterized in detail using several analytical techniques. Implant stability was measured using a resonance frequency analyzer (Osstell^?). Results: Surface characterization of the implants revealed microstructured, moderately rough implant surfaces varying 0.7–1.4 μm in S_a (mean height deviation), but with clear differences in surface chemistry. After 6 weeks, all implants showed statistically significantly higher increases in implant stability. When compared with one another, MgMp implants showed the most significant mean implant stability quotient (ISQ) value relative to the others (P≤0.016). In terms of increment (ΔISQ) in implant stability, MgMp implants showed a significantly greater value as compared with Osseotite^® (P≤0.005), TiOblast^® (P≤0.005), TiUnite^® (P≤0.005), SLA^® (P≤0.007), and Mg implants (P≤0.012). In addition, transducer direction dependence of resonance frequency analysis (RFA) measurements was observed such that the differences in the mean ISQ values between longitudinal and perpendicular measurements were significant at implant placement (P≤0.004) and after 6 weeks (P≤0). Conclusion: The present study found that implant surface properties influence RFA measurements of implant stability. Surface chemistry‐modified titanium implants showed higher mean ISQ values than did topographically changed implants. In particular, cation (magnesium)‐incorporated micropatterns in MgMp implants may play a primary role in ΔISQ.     

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-implant contact at calcium phosphate-coated and porous titanium oxide (TiUnite)-modified oral implants

BACKGROUND: Calcium phosphate (CP)-coated implants are usually referred to as having osteoconductive properties, whereas titanium implants with a native oxide layer are considered less osteoconductive. Often smooth titanium oxides (TOs) are compared to relatively rough CP structures. The objective of this study was to evaluate osteoconduction by comparing bone-implant contact at a relatively smooth, highly crystalline CP coating with a structured, porous TO (TiUnite)-modified surface. MATERIAL AND METHODS: Ten adult Hound Labrador mongrel dogs were used. Four titanium implants (Nobel Biocare) with CP-coated (2) or TO-modified (2) surfaces were installed 12 weeks following mandibular premolar and molar teeth extraction. The implants were alternated within and between jaw quadrants in consecutive animals. Mucosal flaps were advanced and sutured leaving the implants in a submerged position. The animals were injected with fluorescent bone labels at 3 and 4 weeks postsurgery, and pre-euthanasia to monitor progress of bone formation. The animals were euthanized at 8 weeks postsurgery and block biopsies were prepared for histologic and histometric analysis. RESULTS: There were no remarkable differences in bone formation and apparent bone-implant contact comparing the TO-modified and CP-coated surfaces. However, the measured average bone-implant contact was 71% and 57% (P=0.027) for TO-modified and CP-coated implants, respectively. CONCLUSIONS: We conclude that the TO surface exhibits osteoconductive properties exceeding that of the CP surface. One or several of the chemical and physical properties of the TO surface may result in the remarkable bone formation along its surface. This study indicated that crystallinity and/or chemistry may be important.     

A removal torque and histomorphometric study of commercially pure niobium and titanium implants in rabbit bone

Screw-shaped commercially pure (c.p.) niobium and c.p. titanium implants were inserted in rabbit bone. After a healing period of 3 months, a significantly higher removal torque was demonstrated to unscrew the niobium implants (average 32.9 Ncm) compared to the c.p. titanium implants (average 25.3 Ncm). In the histomorphometric part of the study, there were no significant differences in bone-to-metal contact between the 2 implant materials. An average of 41.1% bony contact was demonstrated for the niobium screws compared to an average of 37.2% for the c.p. titanium ones. Our removal torque findings could be related to the differences that we observed between the 2 implant surfaces as indicated by SEM. Since niobium implants showed a more irregular surface topography and niobium is a softer metal than c.p. titanium, this seems the most probable reason for the differences observed in removal torque between the 2 metals. Hypothetically, a more "positive biocompatibility" of the c.p. niobium in comparison to the c.p. titanium remains as another possible reason for the observed differences. However, against such a difference in biocompatibility between c.p. niobium and c.p. titanium, there is the very similar amount of bony contact registered in the histomorphometric analysis.     

Bone reactions adjacent to titanium implants with different surface characteristics subjected to static load. A study in the dog (II)

The purpose of the present study was to compare bone reactions adjacent to titanium implants with either a titanium plasma-sprayed (TPS) or a machined surface subjected to lateral static loading induced by an expansion force. In 3 labrador dogs, the 2nd, 3rd and 4th mandibular premolars were extracted bilaterally. 12 weeks later, 2 implants with a TPS surface were placed in one side and 2 implants with a machined surface were placed in the contralateral side. Twelve weeks after implant installation, crowns, connected in pairs with orthodontic expansion screws, were fitted to the implants and a 0.6 mm wide expansion was initiated. Clinical registrations, standardized radiographs and fluorochrome labeling were carried out during a 24-week period of loading. Biopsies with the implants in situ were harvested and processed for ground sectioning. The sections were subjected to histologic and histometric examination. A higher marginal bone level was observed around implants with a TPS surface compared to machined implants. Furthermore, the values describing the amount of bone-to-implant contact at the bone/implant interface as well as the density of the peri-implant bone were lower at the machined than at the TPS implants.     

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.     

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     

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.     

Effect of FK‐506 (tacrolimus) therapy on bone healing of titanium implants: a histometric and biomechanical study in mice

Immunosuppressive agents have been recognized as a factor affecting bone metabolism. The aim of the present study was to evaluate the influence of FK‐506 administration on the healing of bone around titanium implants. Thirty‐two male mice were randomly allocated to two groups: the FK‐506 group (n = 16 mice), which received subcutaneous administration of FK‐506 (1 mg kg^?1 d^?1); and the control group (n = 16 mice), which received saline solution by the same route of administration. After 2 wk, one titanium implant with sandblasted/acid‐etched surface was placed in the femur. The therapy continued until the mice were killed 2 and 4 wk after surgery. The femurs with implants were evaluated by biomechanical testing and histologic analysis. The bone–implant contact (BIC) and bone volume (BV/TV) within a 100‐μm‐wide circumferential zone lateral to the implant surface were histomorphometrically analyzed. Compared with the control group, the FK‐506 group showed significantly lower BIC and BV/TV at both 2 and 4 wk. Biomechanical tests showed that FK‐506 significantly impaired the strength of bone–implant integration at both 2 and 4 wk postoperatively. Our data indicate that immunosuppressive therapy with FK‐506 negatively affects the fixation of titanium implants.     

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     

Bone reactions adjacent to titanium implants subjected to static load of different duration. A study in the dog (III)

The aim of the present experiment was to study the effect of a long-standing lateral static load on the peri-implant bone. Three beagle dogs were used. The mandibular premolars were extracted and 12 weeks later 3 titanium implants (ITI(R) Dental Implant System) were installed in each quadrant. Crowns were fitted to all implants 12 weeks after the installation procedure. The anterior and central crowns were fused and connected to the posterior crown by an expansion screw. In the right side of the mandible, the expansion screws were activated every 2 weeks during a 46-week period. During the last 10 weeks of this period, an expansion force similar to that of the right side was applied in the left. The animals were sacrificed and block biopsies of each implant site harvested and prepared for histological analysis. Sites subjected to 10 weeks or 46 weeks of lateral load had a similar (i) distribution of bone markers (ii) proportion of bone density and (iii) degree of bone-to-implant contact. The proportion of fluorochromes was higher at sites subjected to 10 weeks of loading than at sites subjected to 46 weeks of loading.     

Osseointegration enhanced by chemical etching of the titanium surface. A torque removal study in the rabbit.

Roughened implant surfaces are thought to enhance osseointegration. Torque removal forces have been used as a biomechanical measure of anchorage or osseointegration in which the greater forces required to remove implants may be interpreted as an increase in the strength of osseointegration. The purpose of this study was to compare the torque resistance to removal of screw shaped titanium implants having an acid etched (HCl/H₂SO₄) surface (Osseotite®) with implants having a machined surface. Two custom screw shaped implants, 1 acid etched and the other machined, were placed into the distal femurs of 10 adult New Zealand White rabbits. These implants were 3.25 mm in diameter x 4.00 mm in length without holes, grooves or slots to resist rotation. Following a 2 month healing period, the implants were removed under reverse torque rotation with a digital torque measuring device. Two implants with the machined surface preparation failed to achieve osseointegration. All other implants were found to be anchored to bone. Resistance to torque removal was found to be 4 x greater for the implants with the acid etched surface as compared to the implants with the machined surface. The mean torque values were 20.50 ± 6.59 N cm and 4.95 ± 1.61 N cm for the acid etched and machined surfaces respectively. The results of this study suggest that chemical etching of the titanium implant surface significantly increases the strength of osseointegration as determined by resistance to reverse torque rotation.