J. LEMONS’s research while affiliated with University of Alabama at Birmingham and other places

A program operated since 1970 is now transitioning to an evidenced-based education (EBE) format and is utilizing examples of medical device retrieval and analysis (DRA) to introduce basic and applied concepts on the compatibility and longevity of device and host interactions. This paper provides an approach to EBE utilizing principles from the physical and biological sciences, which could be useful to other programs. The requirements of DRA include compliance with all regulations for confidentiality and safety. Explanations of identifying, processing, analyzing, and reporting on revision explants and en bloc postmortem donor specimens have provided the details of how initial observations and hypotheses can lead to establishing mechanism-based cause-effect relationships. Examples of surface interactions along total hip arthroplasty articulations and porous regions for biological fixation have been provided. DRA studies on human applications of surgical implant devices have provided quantitative data to accept hypotheses about reduced magnitudes of wear over time (0-20 yr) along metal on metal articulations of one device design and biomaterial. Also, the magnitude of ongrowth and ingrowth of bone into a specific rough/porous metallic surface (bone to implant contact) and the biomechanical properties of the bone within and away from the fixation have led to detailed discussions of osseous integration of joint prosthesis, and conditions of a stable fixation. Experience has shown the value of device retrieval and analysis study results as a component of evidence-based education within a sub-discipline area associated with medical treatments including surgical implant devices.

Objective: Prior research reports successful bone integration along implant regions initially implanted with Hydroxyapatite (HA) coatings and particulates. This study focused on analyzing structural and elemental properties of bone-implant interfaces from 3 post-mortem samples that included HA-coated mandibular custom osseous implants composed of cobalt-chromium. The hypothesis was that dental implant surfaces coated with HA when analyzed after >10years of functional bone remodeling, would exhibit osseous-integration along a chemically modified metallic-oxide substrate. Method: Bone-implant regions were sectioned using a non-decalcified process to produce multiple blocks per specimen. Micro-fracture was induced at the time of surface evaluations to minimize atmospheric contamination of the samples. Sections were then immediately arranged with fracture faces exposed to analyze surface structure and composition. Micro-topographical structure was evaluated by Scanning Electron Microscopy (SEM) and subsequently by optical light microscopy (Keyence). Energy Dispersive Spectroscopy (EDS) was utilized for chemical characterization of the specimen. Lower magnitudes of electron acceleration voltage allowed emphasis of surface conditions. Result: Keyence and SEM images of freshly fractured implants revealed an irregular micro-topography, including multimodal fractures along the interface and through the bone. EDS analysis revealed cobalt, chromium, and molybdenum plus calcium on the implant fracture surfaces. Residual areas of HA-coating consisted of calcium and phosphorus with much larger amounts of carbon and oxygen. Consistent with this finding, opposing bone surfaces revealed high levels of calcium and phosphorus with small amounts of carbon and oxygen plus chromium and cobalt. Conclusion: From prior research, bone integration was found along the micro-topography of the implant surface. However, current EDS analyses of fractures revealed residual calcium on the implant and metallic elements on bone surfaces. These results were consistent with dissolution of the coating during osteoclastic remodeling, shown with enzymatic staining in the same sections, and including the formation of a complex oxide-chemistry at the bone-implant interface.

Polymerization shrinkage is a primary concern when placing composite restorations. Strain produced during polymerization shrinkage may initiate failure at the composite-tooth interface producing marginal gaps, post-operative sensitivity, micro-leakage and caries. Objectives: To measure and compare polymerization shrinkage strain of commercially available composite resin materials. Method: Z100 composite blocks (7mmx7mmx10mm) with a rectangular (2mmx4mmx4mm) cavity preparation were mounted in acrylic in brass rings and stored (37˚C/24-hours). Strain gauges (Vishay) were attached to the specimen using M-Bond200 (Vishay) and connected to a Model 5100 Analog to Digital Scanner. The cavity was treated with aluminum oxide (50u/45psi/15sec) followed by Rocatec Soft (3M ESPE) (30u/45psi/15sec). Then silane (RelyX/3M ESPE) was applied to the preparation surfaces and dried. Adper Single Bond Plus bonding agent (3M ESPE) was applied and composite resin placed in the preparation and light cured (Bluephase20i/Ivoclar/1010mW/cm2) according to manufacturer's instructions. The strain on the composite surface was recorded (strain units/StrainSmart), as a graph showing peak strain (positive) and residual strain (negative) after 15-min. Data were analyzed using one-way ANOVA. Tukey's test was used for pairwise group comparisons (p=.05). Results: (MeanSD). Same letters are not statistically different (p>.05). Material Strain(strain units) Peak Residual Total/(Peak-Residual) Filtek Bulk Fill/3M ESPE 187.039.5 -156.443.5a 343.447.6 Venus Bulk Fill/Heraeus Dental 167.942.1 -222.092.1a,b 389.984.7 SureFil Posterior/Dentsply 215.436.0 -175.884.1a,b 391.290.8 Sonic Fill/Kerr 10043.4 -192.365.1a,b 292.364.1 Quixx/Dentsply 62.127.0 -229.874.6a,b 291.957.2 SureFil SDR flow/Dentsply 182.432.3 -155.355.8a 337.752.0 Z100/3M ESPE 25.328.5 -251.570.2b 276.867.4 Conclusion: Tukey HSD test showed that the residual strain was significantly lower for Filtek Bulk Fill and SureFil SDR flow (p<.05). The residual strain for Z100 was significantly higher than all other materials (p<.05). This model shows significant promise for evaluating shrinkage strain in composite resins and can be used as a method to rank order materials. Study supported in part by a grant from 3M ESPE.

Objective: To evaluate bone response around Co-alloy custom implants (HA plasma coating) and HA (hydroxyapatite) particulates from 3 post mortem human donors. Methods: Three individual mandibular custom osseous integrated implant devices at 10-11 years of function were processed (six transverse locations) to obtain non-decalcified ground sections (60–80µm) (n=36).They were stained with methylene blue/basic fuchsin and evaluated for histologic and histomorphometric properties by optical microscopy. Eight sections with a region of interest along the perimeter of the implant were selected based on cellular activity. Histomorphometric analysis was performed by digital optical microscopy (Keyence/VHX-600) at 100X magnification, examining 1 mm around implant component circumferences. Statistical analysis of HA particulates/HA implant coating utilized paired t-tests and regression analysis with a significance level 0.05. Results: The results were 8/36 sections showed changes along bone to implant interfaces supports dynamic condition of function. The percentage of HA coated regions replacement were 60.4±19.5 including 36.5±11.3 sites of significant cellular activity. These results support a cell mediated mechanism of bone/coating remodeling. Continuing studies include enzymatic staining for unique identification of multinucleated cell and extension to the bone/particulates interfaces. Conclusions: Histological and histomorphologic analysis of human post mortem sections along bone to implant interface showed (1) functional condition after 10 years, (2) regions of coating/remodeling supporting a multinucleated cellular mechanism .IRB # X050823001 and thanks to donors and Dr. Martin.

Objective: This study focuses on analyzing the microscopic structure and chemical properties of bone-implant interfaces of samples obtained from hydroxyapatite coated mandibular cobalt alloy custom implants after roughly eleven years in function. The hypothesis was that the plasma sprayed coating, which was present at implant delivery, would be mostly resorbed leaving bone integrated directly to the metallic implant surface. Method: Four bone-implant samples were selected from three post mortem specimens from a previous study (Roberson et al, AADR, 2011) which had sectioned the bone integrated implant structure into roughly 4mm2 pieces. These pieces had been microtensile tested, thus exposing the previously joined bone and implant surfaces. These pieces were processed to remove possible contaminants and arranged with fractured faces exposed, so they could be viewed initially using a Keyence optical microscope where images showed the microscopic topographical structure. Scanning Electron Microscopy (SEM) provided higher resolution of the implant microstructure and Energy Dispersive Spectroscopy (EDS) spectra provided surface chemical analyses. Result: Both Keyence and SEM images revealed boney microstructure that mirrored the implant’s roughened surface. The EDS spectrum of the implant alloy surfaces showed the presence of cobalt, chromium, and molybdenum along with calcium and phosphorous along bone sites. The boney surface EDS showed calcium and phosphorous, plus carbon and oxygen. Overall, the spectral analyses supported a complex chromium oxide surface on the alloy at the osseous interface region. Conclusion: We were unable to determine if the hydroxyapatite coating was totally resorbed; however, the bone had grown into the microscopic irregularities of the implant surface, providing the first report of bone integration along dental implant cobalt alloy surfaces after 11 years of human in vivo function. Future studies are planned to further analyze the chemical structure of these surfaces through ion milling, selected area diffraction, and related EM procedures.

Objective: The relative stabilities of calcium phosphate (CaP) biomaterial multiphasic coating (plasma sprayed) and particulates (polycrystalline CaP) during bone remodeling were evaluated for longer-term ( >10 year) dental implants. The hypothesis was that the kinetics and mechanisms of osteoclastic interactions would be significantly different. Methods: Three individual post mortem mandibular custom osseous integrated implant devices were processed non decalcified at six transverse locations (18x) to produce multiple (>54) slides. Slides were evaluated by histologic and histomorphometric optical microscopy methods in consultation with a pathologist to select 8 slides for bone-implant interface reactions focused on cells identified by staining. Results: Prior AADR/IADR abstracts and papers have shown conditions of osseous integration, interface biomechanical properties of nano-hardness and -modulus, and microtensile strength. Current analyses show uniquely different interactions where environment and osteoclasts at the bone interface: (1) removes the CaP coating followed by bone deposition along the exposed alloy (Co-Cr-Mo) surfaces with direct bone contact; (2) partially removes (roughens) the surfaces of the polycrystalline CaP particulates with continued osseous integration; and (3) overall opinions from histomorphometric characteristics supporting opportunities for longer-term clinical function. Conclusions: Analyses of bone-implant interfaces and osteoclasts from non decalcified sections of three (>10 year) post mortem custom dental implants showed very different interactions where CaP coatings were being replaced, particulate CaP were partially replaced, and osseous integration and clinical function were maintained. IRB #X050823001 CMBD Core NIH P30-AR403 Special recognition: D. Martin, DMD and Donors

Objectives: To determine nanoproperties of bone adjacent to regions of compression and shear in loaded root-form and plate-form implants retrieved after >1yr of in vivo function in primates. The differences in functional force transfer were of central focus based on geometry and in vivo sample ligation. Methods: Sample preparation via Exact machine with 1200, 1500, 2000-grit, sonication(10min-DIH20), 3um, 1/4um diamond paste polishing, alumina slurry polishing and sonication(10min-DIH20). Keyence imaging system, surface-roughness profiling system and the MTS-G200 Nano-machine were utilized for testing. Nanoindentation was standardized to 11 regions per sample: <100um from the implant interface in upper-left(UL), lower-left(LL), base, lower-right(LR), upper-right(UR), ~250um from interface(UL250, LL250, base250, LR250, UR250), and ~2000-3000um from interface for the control. Region distance from coronal bone loss and base of implants standardized at ~500um. Boney ridges were tested in each region via ~5 independent data points. Silica block was used to verify nano-testing accuracy(Modulus=69.6+/-1.7GPa,Hardness=9.3+/-0.4GPa). Statistical analysis based on 6 group comparisons: [plate-form-ligated(PL) vs plate-form-non-ligated(PN), root-form-non-ligated(TN), and root-form-ligated(TL), all plate-form(AP) vs root-form(AT), all ligated(AL) vs non-ligated(AN), and all bases vs controls]. Samples(n=8): PL(n=3), TL(n=1), PN(n=2), TN(n=2). Results: Mean, standard-deviation, paired t-test(α≤0.05), control omitted in first 5 comparisons. PL vs PN PL vs TN PL vs TL AP vs AT AL vs AN Bases vs Controls Modulus(Gpa) 14.8+/-3.2, 16.7+/-4.6 14.8+/-3.2, 11.9+/-3.2 14.8+/-3.2, 12.0+/-1.8 15.8+/-3.9, 12.0+/-2.5 13.4+/-2.5, 14.3+/-3.9 40.0+/-6.6, 15.1+/-2.5 Hardness(Gpa) 0.43+/-0.16, 0.57+/-0.21 p=0.005 0.43+/-0.16, 0.30+/-0.12 0.43+/-0.16, 0.39+/-0.09 0.50+/-0.19, 0.34+/-0.10 0.41+/-0.13, 0.43+/-0.17 1.6+/-0.55, 0.31+/-0.08 p=0.04 Conclusions: The nanoindentation results showed that PN had higher hardness when compared to PL(p=0.005). The bases had significantly higher hardness values(p=0.04) when compared to controls. Trending data considered important was that AP showed considerably higher modulus and hardness compared to AT, possibly demonstrating a higher functional force transfer to the bone due to implant geometry. Support: NIDCRT32-DE017607 DART Short-term Training for Dental Students, Grant#EB001715, Grant#P30-AR4603.

Objectives: The objective of this research was to test the microtensile strength of the bone-implant interface of a subperiosteal implant after approximately eleven years of function. The hypothesis was that the microtensile strength of those interfaces coated with calcium phosphate would be greater than that of uncoated regions. Methods: The mandible in which the implant was placed was removed postmortem and sectioned faciolingually using an Exakt band saw producing sections which were ground to thicknesses ranging from 1.31mm 2.05mm. Due to the design of the subperiosteal implant, each section of mandible contained multiple bone-implant interfaces. Each faciolingual section was then sectioned further, using a diamond bladed Bueler saw, in an attempt to produce samples which contained only the bone-implant interface. Samples were fixed to an Instron slide apparatus using cyanoacrylate and loaded at a rate of 3mm/min until failure. Five bone-implant interfaces were tested along both buccal and lingual surfaces, excluding one sample that fractured during sectioning giving a total of nine surfaces tested. Results: A mean maximum load of 26Newtons was determined across an average area of 5.52mm^2 producing an average change in length of 310m and a mean maximum tensile stress of 4.83MPa. Conclusions: The area of the bone-implant interface was directly proportional to the maximum load needed for fracture. There was a direct correlation between the area of the bone-implant interface and the maximum load needed for fracture, further analysis in planned to determine if increases in microtensile strength was due to calcium phosphate incorporation into osseointegration. Support: IRB#X050823001; T35 HL007473, Dale J. Benos-PI.

In vivo composite wear is a significant problem in large posterior restorations. To develop more wear resistant composite resin materials, wear machines that accurately predict in vivo wear are necessary. OBJECTIVE: To measure and compare the volumetric wear loss of in vitro specimens and in vivo restorations of a highly filled BisGMA nano-hybrid composite resin system (EsthetX HD/Caulk/Milford/DE) using a 3-D non-contact surface profilometer. METHODS: Fifty class II composite resin restorations were placed in a clinical trial using a standardized placement technique. Impressions and improved stone casts were made at baseline and one year recalls. Twenty-one of these restorations were evaluated. Casts were scanned (PROSCAN2000) and images of the baseline and 1 year restorations were superimposed (PROFORM-Software). Wear volume values were obtained for each restoration. For the in vitro wear testing, sixteen specimens of EsthetX HD were prepared in an elastomeric mold, cured, separated, embedded with acrylic resin in brass holders and polished using a series of polishing disks and pastes. The specimens were subjected to 200,000 or 400,000 cycles (n=8) in the Alabama Wear Testing Device. The specimens were scanned (PROSCAN 2000) before and after wear testing and the images superimposed using the PROFORM Software to determine volume wear loss of the EsthetX HD. Clinical wear data were analyzed with ANOVA for tooth type, arch, face side, and restoration type. In vitro volume wear loss was compared using t-tests. RESULTS: Volume Loss(mm3) Mean(SD) In Vivo1 year recall 1.791.7583 In Vitro200,000 cycles 0.011.0019 In Vitro400,000 cycles 0.017.0025 CONCLUSIONS: In vitro and in vivo wear results were not similar due to the confounding variables present in the clinical study. Better standardization of future clinical trials (bite force measurement, dominant side of mastication, occlusion, number of teeth) should improve comparisons between in vitro testing and in vivo test results.