J Oral Maxillofac Surg 68:1631-1638, 2010

Effect of Surface Modifications on Early Bone Healing Around Plateau Root Form Implants: An Experimental Study in Rabbits Marcelo Suzuki, DDS,* Monica D. Calasans-Maia, DDS, PhD, MS,† Charles Marin, DDS, MS,‡ Rodrigo Granato, DDS, MS,§ Jose N. Gil, DDS, PhD, MS,储 Jose M. Granjeiro, DDS, PhD,¶ and Paulo G. Coelho, DDS, PhD# Purpose: The objective of the present study was to evaluate the biomechanical fixation and bone-to-

implant contact (BIC) of plateau root form implants of varied surfaces. Materials and Methods: Plateau root form implants, 3.5 mm in diameter, 8 mm in length, with 4 surfaces (n ⫽ 16 each)—machined, alumina-blasted/acid-etched, alumina-blasted/acid-etched plus nanothickness bioceramic coating, and plasma-sprayed calcium-phosphate—were used. They were bilaterally placed at the distal femur of 16 New Zealand rabbits and remained in place for 2 and 4 weeks in vivo. After euthanizing the rabbits, the implants were subjected to torque to interface fracture and were subsequently processed as nondecalcified ⬃30-␮m-thickness slides for histomorphologic analysis and BIC determination. Statistical analysis was performed using analysis of variance at the 95% level of significance, considering implantation time and implant surface as independent variables and the torque-to-interface fracture and BIC as dependent variables. Results: The torque-to-interface fracture was significantly affected by the implant surface (P ⬍ .001) but was not affected by the implantation time (P ⬎ .20). The implantation time and implant surface had significant effects on the BIC (P ⬍ .04 and P ⬍ .001, respectively). The greatest torque-to-interface fracture and BIC was observed for the plasma-sprayed calcium-phosphate. Conclusion: The implant surface significantly influenced early bone healing around plateau root form implants. © 2010 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg 68:1631-1638, 2010 Implant dentistry has become one of the most successful dental specialties, with success rates often reported at greater than 90%.1,2 However, although high success has been achieved through classic surgical and restorative protocols, in which several months are allowed between implant placement and *Assistant Professor, Department of Prosthodontics, Tufts University School of Dental Medicine, Boston, MA. †Adjunct Professor, Department of Oral and Maxillofacial Surgery, Universidade Federal Fluminense, Rio de Janeiro, Brazil. ‡Instructor, Department of Dentistry, Rio Grande do Sul Pontifical Catholic University, Porto Alegre, Brazil. §Instructor, Department of Dentistry, Universidade Federal de Santa Catarina, Florianopolis, Brazil. 储Professor, Department of Dentistry, Universidade Federal de Santa Catarina, Florianopolis, Brazil. ¶Adjunct Professor, Department of Cell and Molecular Biology, Universidade Federal Fluminense, Rio de Janeiro, Brazil.

restoration, decreasing the treatment periods is of interest for clinicians and patients.3 To decrease the interval between implant placement and restoration by increasing the host-to-implant early response, several implant design alterations have been attempted.4 Common implant design alterations include changes #Assistant Professor, Department of Biomaterials and Biomimetics, New York University, New York, NY. This study was partially supported by Bicon, LLC, Boston, MA, and the Department of Oral and Maxillofacial Surgery, Universidade Federal de Santa Catarina, Florianopolis, Brazil. Address correspondence and reprint requests to Dr Coelho: Department of Biomaterials and Biomimetics, New York University, 345 24th Street, Room 804s, New York NY 10010; e-mail: [email protected] © 2010 American Association of Oral and Maxillofacial Surgeons

0278-2391/10/6807-0026$36.00/0 doi:10.1016/j.joms.2009.07.064

1631

1632

EFFECTS OF SURFACE MODIFICATIONS ON EARLY BONE HEALING

in the macrogeometry and/or surgical instrumentation5-7 and surface texture and/or chemical alterations.3,4,8 Depending on the interaction between the implant design and its respective osteotomy dimensions, 2 different bone healing pathways will ultimately lead to implant integration with the bone.5,7 When an intimate surgical fit between bone and implant (typically observed in screw root form implants) occurs, a thin blood clot will be established, leading to the classic pathway to osseointegration.5,9-11 In contrast, if the interplay between the implant shape and its respective osteotomy allows large void spaces between the implant and the osteotomy wall (contactfree areas), an intramembranous-like formation of woven bone will rapidly fill the spaces previously filled with blood clot after implant placement.5-7 Regardless of the healing pathway, histomorphometric studies have shown that the integration rates are comparable at the early healing stages,7 and long-term stability is ensured by the bone modeling and remodeling processes.9 Although alterations in macrogeometry and/or surgical instrumentation have demonstrated significant effects at the early stages of bone healing around endosseous implants,3-8,12 a substantially smaller body of data has been developed on the topic compared with that of surface modifications.4,8 Surface modifications have been by far the most investigated implant design parameter in an attempt to change the host-to-implant response.3,4,8 A large number of studies have shown that increasing the implant surface texture by a variety of processes, such as acid etching and various forms of grit-blasting, positively affected early healing, leading to greater degrees of integration and biomechanical fixation.4 In addition to texture alterations, chemistry modifications, such as the incorporation of hydroxyapatite as a surface coating through a variety of processes, resulted in highly osseoconductive surfaces.13 However, weak interfaces between the coating and implant substrate, such as those found in plasma-sprayed hydroxyapatite (PSHA), raised concerns with respect to their long-term clinical performance.13 Thus, current research has concentrated on obtaining synergism between surface roughness and elemental chemistry (bioceramic coatings or depositions at the nanometer scale) and has shown encouraging results.4,12-21 However, although newly developed surfaces have been compared with rough surfaces and highly osseoconductive plasma-sprayed bioceramic coatings,13 most investigations considered an implant bulk design that allowed intimate contact with the osteotomy walls after placement. The objective of the present study was to test the hypothesis that biomechanical fixation and bone-toimplant contact (BIC) would be significantly affected

by the surface modifications on plateau root form implants.

Materials and Methods This study used plateau root form endosseous Ti6Al-4V implants 3.5 mm in diameter and 8 mm in length. The plateau root form dental implant differs from the commonly used screw root implant in that it has a series of separate circumferential fins spaced along the bone-interfacing portion of the implant. Such an implant design is not screwed into the osteotomy but tapped into an osteotomy of a diameter similar to the implant diameter.7 For mechanical testing purposes, an external hexagon was machined onto the top of the implants, and no retentive features were present along the implant experimental design, allowing rotation in either direction during subsequent torque testing. The implant groups used included the following surfaces: as-machined, alumina-blasted/acid-etched (AB/AE; Integra-TiTM, Bicon, Boston, MA), AB/AE plus nanothickness bioceramic-coated (Nano; Nanotite, Bicon), and plasma-sprayed calcium-phosphate (PSCaP; Integra-CP, Bicon) implants (Fig 1; n ⫽ 16 for each surface). After approval of the bioethics committee for animal experimentation at the Universidade Federal Fluminense (approval no. 10/08), Brazil, 16 New Zealand white rabbits weighing 2.5 to 3 kg and in good health were acquired for the study and kept in-house for 4 weeks before the experiment. The surgical region was the distal femur, and 2 implants were placed along each limb. The different implant surfaces were alternately placed at the proximal and distal sites at distances of 2 cm from each other along the central region of the bone. The distributions for the 2- and 4-week comparison for the various surfaces resulted in an equal number of implants per group (8 implants per surface and time in vivo, 8 rabbits per time in vivo). All surgical procedures were performed with the rabbits under general anesthesia. The preanesthetic procedure included an intramuscular administration of ketamine (20 mg/kg) and xylasin (1 mg/kg). General anesthesia was then achieved with 1% isofluorane by inhalation. After hair shaving, skin exposure, and antiseptic cleaning with iodine solution at the surgical and surrounding areas, a 5-cm incision at the skin level was performed followed by a muscle layer incision. Next, a flap was reflected, and the distal femur was exposed. Two osteotomies per limb were created at least 2 cm from each other from distal to proximal. The initial drilling was performed using a 2-mm-diameter pilot drill at 1,200 rpm under saline irrigation. Next,

1633

SUZUKI ET AL

FIGURE 1. Plateau root form endosseous Ti-6Al-4V implants, 3 mm in diameter and 8 mm in length fabricated with 4 different surface treatments. Scanning electron micrographs of A, as-machined, B, AB/AE, C, 300- to 500-nm thickness bioceramic deposition (Nano), and D, PSCaP. Suzuki et al. Effects of Surface Modifications on Early Bone Healing. J Oral Maxillofac Surg 2010.

slow speed sequential drilling with burs of 2.5, 3.0, and 3.5 mm was performed at 800 rpm under saline irrigation. The implants were then press fit into the osteotomy sites using manual pressure. To avoid any damage to the implant– bone interface due to removal of a callus overgrowth after limb retrieval, a customized cover screw was installed in each implant. Standard layered suture techniques were used for wound closure (4-0 Vicryl for the internal layers and 4-0 nylon for the skin). The postoperative medication included antibiotics (penicillin 20,000 UI/kg) and analgesics (ketoprophen 1 mL/5 kg) for a 48-hour period postoperatively. Euthanasia was performed using an anesthesia overdose. At necropsy, the limbs were retrieved by sharp dissection, the soft tissue was removed by surgical blades, and an initial clinical evaluation was performed to determine implant stability. For biomechanical testing, the bone blocks with the implants were adapted to an electronic torque machine equipped with a 200 Ncm torque load cell (Test Resources, Minneapolis, MN). Custom machined tooling was adapted to the implants’ external hexagons, and the retrieved bone was carefully positioned to minimize angulation during testing. The implants were torqued in a clockwise direction to interfacial fracture at a rate of ⬃0.19618 rad/second, and a torque versus displacement curve was recorded for

each specimen. The torque machine was set to automatically stop when a torque decrease of 10% from the greatest load was detected. The rationale for this procedure was to minimize interface damage before the histologic procedures.13,16 After biomechanical testing, the bone blocks were kept in 10% buffered formalin solution for 24 hours, washed in running water for 24 hours, and gradually dehydrated in a series of alcohol solutions ranging from 70% to 100% ethanol. After dehydration, the samples were embedded in a methacrylate-based resin (Technovit 9100; Heraeus Kulzer GmbH, Wehrheim, Germany) according to the manufacturer’s instructions. The blocks were then cut into slices (⬃300 ␮m thick) aiming for the center of the implant along its long axis with a precision diamond saw (Isomet 2000; Buehler, Lake Bluff, IL), glued to acrylic plates with an acrylatebased cement, and a 24-hour setting time was allowed before grinding and polishing. The sections were then reduced to a final thickness of ⬃30 ␮m using a series of SiC (Buehler) abrasive papers (400, 600, 800, 1,200, and 2,400) in a grinding/polishing machine (Metaserv 3000, Buehler) under water irrigation.22 The sections were then stained with toluidine blue and sent for optical microscopy evaluation. The BIC was determined at 50⫻ to 200⫻ magnification (Leica DM2500M, Leica Microsystems GmbH, Wetzlar, Germany) using a computer software pro-

1634

EFFECTS OF SURFACE MODIFICATIONS ON EARLY BONE HEALING

gram (Leica Application Suite, Leica Microsystems). The regions of BIC along the implant perimeter were subtracted from the total implant perimeter, and calculations were performed to determine the BIC. Statistical analyses were performed by analysis of variance, with implantation time and implant surface as independent variables and torque-to-interface fracture and BIC as dependent variables. Tukey’s post hoc test was used for multiple comparisons. Statistical significance was indicated by P less than .05.

Results The surgical procedure and follow-up data demonstrated no complications regarding procedural conditions, postoperative infection, or other clinical concerns. No implants were excluded from the study because of clinical instability immediately after euthanization. The analysis of variance results showed a significant effect of implant surface (P ⬍ .001) and no effect of implantation time (P ⬎ .20) on the torque-to-interface fracture. Significantly greater values were observed for PSCaP than for all other surfaces. Although the Nano group and AB/AE groups had greater mean values than the as-machined group, no significant differences were observed (Fig 2). The nondecalcified sample processing after controlled torque testing showed intimate bone contact with all implant surfaces at regions of cortical and trabecular bone. Greater magnification of the bone– implant interface region showed that the nondecalcified sections obtained after biomechanical testing had minimal morphologic distortion resulting from bone disruption from the mechanical testing (Figs 3-6).

FIGURE 3. Optical micrographs obtained at 100⫻ original magnification of as-machined group at A, 2 and B, 4 weeks of implantation time. Note, presence of woven bone formation as early as 2 weeks in vivo through intramembranous-like pathway in healing chamber region between plateaus. Slight bone microstructural evolution observed at 4 weeks, with primary osteonic structures indicating onset of remodeling after initial modeling healing stage. Toluidine blue stained. Suzuki et al. Effects of Surface Modifications on Early Bone Healing. J Oral Maxillofac Surg 2010.

FIGURE 2. Implant surface resulted in significantly different torqueto-interface fracture (P ⬍ .001), with mean ⫾ 95% confidence interval for PSCaP of 32.01 ⫾ 4.22 Ncm, for Nano of 20.59 ⫾ 3.81 Ncm, for as-machined of 17.44 ⫾ 3.82 Ncm, and for AB/AE of 23.09 ⫾ 3.81 Ncm. Number of asterisks denotes statistically homogenous groups. Suzuki et al. Effects of Surface Modifications on Early Bone Healing. J Oral Maxillofac Surg 2010.

Under 100⫻ magnification, the bone–implant interfaces were easily visualized and facilitated BIC determination (Figs 3-6). The wound healing pattern observed for all groups between the implant plateaus followed the intramembranous-type healing mode (Figs 3-6). In general, bone formation within the healing chambers (region between plateaus) presented with initial filling with woven bone at 2 weeks in vivo, irrespective of the implant surface. Bone microstructural evolution, with onset of remodeling, had occurred for all groups at 4 weeks (as evidenced by the lighter staining at regions of lamellar bone replacing the darker stained woven bone between plateaus). No qualitative temporal morphologic differences were observed among the groups.

SUZUKI ET AL

1635 central regions and regions in close proximity to the implant surface (Figs 4B, 5B, 6B). The as-machined group primarily showed woven bone replacement at the central region of the healing chamber (Fig 3B). General high-magnification light microscopy of the bone–implant interface showed evidence of an interface between the bone, PSCaP coating, and implant substrate (Fig 7). No evidence of the presence of a coating for the Nano group, which resembled the interface was observed between the bone and asmachined, and AB/AE surfaces. The analysis of variance results showed that the percentage of BIC was significantly affected by both implant surface (P ⬍ .04) and implantation time (P ⬍ .001; mean ⫾ 95% confidence interval, 2 weeks: 21.31% ⫾ 3.54%; 4 weeks: 29.25% ⫾ 3.37%). The Nano-coated implants had significantly greater degrees of BIC than did the as-machined group (Fig 7). Although greater mean BIC values were observed for the PSCaP and AB/AE group than for the as-machined

FIGURE 4. Optical micrographs obtained at 100⫻ original magnification of AB/AE group at A, 2 and B, 4 weeks’ implantation time. Note, presence of primary osteonic structures indicating onset of remodeling after initial modeling healing stage as early as 4 weeks in vivo. Suzuki et al. Effects of Surface Modifications on Early Bone Healing. J Oral Maxillofac Surg 2010.

At 2 weeks, woven bone formation had occurred at both central regions and at regions in close proximity to the implant surface for all groups (Figs 3A, 4A, 5A, 6A). However, woven bone formation occurred primarily at the central region of the healing chambers for the as-machined group. In contrast, the other groups presented with a more spread woven bone distribution, with woven bone present at regions in close contact with the implant surface (Figs 4A, 5A, 6A). At 4 weeks, the initial replacement of woven bone by lamellar bone (primary osteonic structures) was observed for all groups (Figs 3B, 4B, 5B, 6B). No qualitative morphologic differences were observed among the different implant surface groups at 4 weeks in vivo. Remodeling regions followed the qualitative spatial distribution observed at 2 weeks for all groups, with the AB/AE, Nano, and PSCaP groups presenting with woven bone replacement at both

FIGURE 5. Optical micrographs obtained at 100⫻ original magnification of Nano group at A, 2 and B, 4 weeks’ implantation time. Toluidine blue stained. Suzuki et al. Effects of Surface Modifications on Early Bone Healing. J Oral Maxillofac Surg 2010.

1636

EFFECTS OF SURFACE MODIFICATIONS ON EARLY BONE HEALING

FIGURE 6. Optical micrographs obtained at 100⫻ original magnification of PSCaP group at A, 2 and B, 4 weeks’ implantation time. Arrows indicate PSCaP coating. Toluidine blue stained. Suzuki et al. Effects of Surface Modifications on Early Bone Healing. J Oral Maxillofac Surg 2010.

group, the differences were not statistically significant (Fig 7).

tion effects on implants that allow healing chambers such as plateau root form implants. The present study tested the hypothesis that biomechanical fixation and BIC are significantly affected by the surface modifications on plateau root form implants. Over the years, endosseous implant surfaces have evolved from as-machined to the more osseoconductive moderately rough surfaces.3,4,8,23 The period in between also resulted in developments with respect to implant coating technology, with the introduction of the highly osseoconductive PSHA-coated implants. However, because of a potential weak interface between implant coating and substrate and the potential high susceptibility to peri-implant tissue disease, PSHA-coated implants fell from favor in clinical practice.4,6,24 Thus, from an informed design rationale standpoint, surfaces preset with moderately rough surfaces and chemistry components similar to PSHA were desirable, as long as the PSHA drawbacks were avoided. Such a rationale resulted in the incorporation of bioceramics in smaller domains onto moderately rough surfaces.4,12-16,21,25,26 Several studies have shown that sputtered coatings ranging from a few hundred nanometers to several micrometers onto rough surfaces were a feasible alternative to PSHA-coated implants.4,13-16,18,20,21 Recent reports have also shown promising results for both bioceramic discrete crystalline deposition onto acid-etched rough surfaces25,26 and molecular incorporations of calcium and phosphate within the implant titanium surface oxides.12 Considering the 4 surfaces evaluated in the present study, characterization investigation has shown that as-machined implants have titanium oxides in their surfaces and a smoother profile compared with moderately rough surfaces.8 Atomic force microscopybased texture analysis of the other 3 surfaces investigated in the present study has shown that the PSCaP

Discussion Because the surface is the first part of the implant to interact with the host, its texture and chemical configuration have been widely investigated.3,4,8 However, depending on the implant bulk design and its osteotomy counterpart, substantially different healing pathways will occur for endosseous implants.5,7 Thus, depending on the implant bulk design and osteotomy dimensions, the surface modifications could affect the early healing of implants differently. Although a substantial amount of research concerning the surface modifications of implants by shape and osteotomy dimensions that result in intimate contact between the implant surface and osteotomy walls (ie, screw root form implants) has been done, little has been published regarding the surface modifica-

FIGURE 7. Implant surface resulted in significantly different BIC values (P ⬍ .04). Number of asterisks denotes statistically homogenous groups; error bars represent 95% confidence intervals. Suzuki et al. Effects of Surface Modifications on Early Bone Healing. J Oral Maxillofac Surg 2010.

1637

SUZUKI ET AL

presented with significantly greater average roughness values compared with the AB/AE and Nano surfaces at 1.8 ⫾ 0.25, 0.48 ⫾ 0.10, and 0.66 ⫾ 0.10 ␮m, respectively.13 According to the published data,3,4 all textured surfaces evaluated in the present experiment were within the average roughness range of 0.5 to 2 ␮m, which favors early healing of implants compared with the smoother as-machined surfaces (average roughness values 0.2 to 0.4 ␮m).3,4 Previous detailed chemical analysis also showed that the Nano group surface had a 300 to 500-nm thickness, high calcium/ phosphorus stoichiometry, amorphous coating, and the PSCaP surface had a calcium- and phosphorusbased multicrystalline (primarily crystalline hydroxyapatite, high amorphous content) phase, 20- to 30-␮m thickness coating.13 Although the period in vivo did not influence the torque-to-interface fracture, the implant surface showed a significant effect, with PSCaP having the greatest values among all surfaces, indicating that the amount of calcium and phosphorus and its chemical structure played a significant role in the biomechanical fixation of endosseous implants presenting a space between the inner and outer diameter of the implant, also known as healing chambers. The low degree of mechanical disruption between the bone and implant observed on the histologic slides after mechanical testing was likely a result of the implant shape, proper specimen alignment, and slow torque rate. The implant geometric configuration, in which no vertical force component resulted during testing owing to the implant bulk configuration without retention features (pure plateaus), allowed free rotation under torque and precise stopping of the machine at a 10% decrease in the maximum load recorded.13,15,16 Thus, mechanical disruption was observed only in a few histologic sections, and the BIC determination was uneventful.13,15,16 The general observation of the histologic sections showed intimate bone contact with all implant surfaces, demonstrating their biocompatible and osseoconductive properties. Also, irrespective of the surface, the wound healing sequence and mode observed in our study was comparable to the previously described wound healing sequence for healing chamber models, in which osseointegration was relatively short for implants with large contact-free surfaces immediately after placement.5,7 However, qualitative histomorphologic evaluation showed a more even distribution of woven bone (at both central and peripheral regions of the healing chambers) for rough surfaces (AB/AE, Nano, and PSCaP) compared with the as-machined surface. Such an observation was likely because the as-machined surface decreased the ability of uniformly retaining the blood clot early after implantation compared with the other surfaces,8 po-

tentially changing the temporal blood clot spatial distribution and, thereby, the subsequent healing kinetics and woven bone location within the healing chamber. In agreement with previous studies, careful examination of the PSCaP-coated surface and bone revealed the presence of the remains of the coating.13 Although the Nano group coating presence could not be evaluated using optical microscopy resolution because of the reduced coating thickness, the mean torque-to-interfacial fracture values were comparable to those for the AB/AE group, suggesting that no weak link between the coating and metallic substrate was present.13,15,16 Statistical analysis showed a significant increase in the percentage of BIC with the time in vivo and a significant effect on the implant surface, in which the mean percentage of BIC for all rough surfaces was greater than for the as-machined surface (only the Nano group was significantly greater than the asmachined group, and the mean PSCaP and AB/AE values were slightly lower than those for the Nano group). Although it is intuitive that biomechanical fixation would be proportional to the amount of intimate contact between the implant and bone, the results obtained in the present investigation, and in other studies12,13,15,16 using endosseous implants with and without healing chamber models, have shown that the same degrees of BIC can lead to significantly different biomechanical fixation levels. This suggests that the interface characteristics and bone mechanical properties also play a role in biomechanical testing.16 A large number of published studies have reported the benefits of surface topographic and chemical modifications around screw type implants.8,12,21 In addition, recent studies have reported positive results concerning surface modifications in endosseous implants with healing chambers.16,27 Because different bulk designs can result in different wound healing pathways, controlled investigations considering similar surface modifications in implant designs with and without healing chambers are desirable. According to the results obtained in the present study, the hypothesis that surface modifications significantly affect early bone healing around plateau root form implants is confirmed.

References 1. Chuang SK, Tian L, Wei LJ, et al: Kaplan-Meier analysis of dental implant survival: A strategy for estimating survival with clustered observations. J Dent Res 80:2016, 2001 2. Chuang SK, Wei LJ, Douglass CW, et al: Risk factors for dental implant failure: A strategy for the analysis of clustered failuretime observations. J Dent Res 81:572, 2002

1638

EFFECTS OF SURFACE MODIFICATIONS ON EARLY BONE HEALING

3. Albrektsson T, Wennerberg A: Oral implant surfaces: Part 2: Review focusing on clinical knowledge of different surfaces. Int J Prosthodont 17:544, 2004 4. Coelho PG, Granjeiro JM, Romanos GE, et al: Basic research methods and current trends of dental implant surfaces. J Biomed Mater Res B Appl Biomater 88:579, 2009 5. Berglundh T, Abrahamsson I, Lang NP, et al: Novo alveolar bone formation adjacent to endosseous implants. Clin Oral Implants Res 14:251, 2003 6. Lemons JE: Biomaterials, biomechanics, tissue healing, and immediate-function dental implants. J Oral Implantol 30:318, 2004 7. Leonard G, Coelho PG, Polyzois I, et al: A study of the bone healing kinetics of plateau versus screw root design titanium dental implants. Clin Oral Implants Res 20:232, 2009 8. Albrektsson T, Wennerberg A: Oral implant surfaces: Part 1: Review focusing on topographic and chemical properties of different surfaces and in vivo responses to them. Int J Prosthodont 17:536, 2004 9. Davies JE: Understanding peri-implant endosseous healing. J Dent Educ 67:932, 2003 10. Albrektsson T, Branemark PI, Hansson HA, et al: Osseointegrated titanium implants: Requirements for ensuring a longlasting, direct bone-to-implant anchorage in man. Acta Orthop Scand 52:155, 1981 11. Branemark PI, Adell R, Breine U, et al: Intra-osseous anchorage of dental prostheses. I. Experimental studies. Scand J Plast Reconstr Surg 3:81, 1969 12. Marin C, Granato R, Suzuki M, et al: Removal torque and histomorphometric evaluation of bioceramic grit-blasted/acidetched and dual acid-etched implant surfaces: An experimental study in dogs. J Periodontol 79:1942, 2008 13. Coelho PG, Lemons JE: Physico/chemical characterization and in vivo evaluation of nanothickness bioceramic depositions on alumina-blasted/acid-etched Ti-6Al-4V implant surfaces. J Biomed Mater Res A 90A:351, 2009 14. Coelho PG, Cardaropoli G, Suzuki M, et al: Histomorphometric evaluation of a nanothickness bioceramic deposition on endosseous implants: A study in dogs. Clin Implant Dent Relat Res 11:292, 2009 15. Coelho PG, Cardaropoli G, Suzuki M, et al: Early healing of nanothickness bioceramic coatings on dental implants: An ex-

16.

17. 18.

19.

20.

21. 22. 23. 24. 25. 26.

27.

perimental study in dogs. J Biomed Mater Res B Appl Biomater 88:387, 2009 Granato R, Marin C, Suzuki M, et al: Biomechanical and histomorphometric evaluation of a thin ion beam bioceramic deposition on plateau root form implants: An experimental study in dogs. J Biomed Mater Res B Appl Biomater 90:396, 2009 Mendes VC, Moineddin R, Davies JE: The effect of discrete calcium phosphate nanocrystals on bone-bonding to titanium surfaces. Biomaterials 28:4748, 2007 Ong JL, Bessho K, Carnes DL: Bone response to plasma-sprayed hydroxyapatite and radiofrequency-sputtered calcium phosphate implants in vivo. Int J Oral Maxillofac Implants 17:581, 2002 Orsini G, Piatelli M, Scarano A, et al: Randomized, controlled histologic and histomorphomteric evaluation of implants with nanometer-scale calcium phosphate added to the dual acidetched surface in the human posterior maxilla. J Periodontol 77:1984, 2006 Park YS, Yi KY, Lee IS, et al: The effects of ion beam-assisted deposition of hydroxyapatite on the grit-blasted surface of endosseous implants in rabbit tibiae. Int J Oral Maxillofac Implants 20:31, 2005 Yang Y, Kim KH, Ong JL: A review on calcium phosphate coatings produced using a sputtering process—An alternative to plasma spraying. Biomaterials 26:327, 2005 Donath K, Breuner G: A method for the study of undecalcified bones and teeth with attached soft tissues: The Sage-Schliff (sawing and grinding) technique. J Oral Pathol 11:318, 1982 Butz F, Aita H, Wang CJ, et al: Harder and stiffer bone osseointegrated to roughened titanium. J Dent Res 85:560, 2006 Lemons J, Dietch-Misch F: Biomaterials for dental implants, in Misch CE (ed): Contemporary Implant Denstistry (ed 2). St Louis, Mosby, 1999, pp 271-302 Mendes VC, Moineddin R, Davies JE: The effect of discrete calcium phosphate nanocrystals on bone-bonding to titanium surfaces. Biomaterials 28:4748, 2007 Mendes VC, Moineddin R, Davies JE: Discrete calcium phosphate nanocrystalline deposition enhances osteoconduction on titanium-based implant surfaces. J Biomed Mater Res A 90A:577, 2009 Buser D, Broggini N, Wieland M, et al: Enhanced bone apposition to a chemically modified SLA titanium surface. J Dent Res 83:529, 2004