Paulo G Coelho

Publications of Paulo G Coelho

• Assessment of a chair-side argon-based non-thermal plasma treatment on the surface characteristics and integration of dental implants with textured surfaces.

  Authors: Hellen S Teixeira, Charles Marin, Lukasz Witek, Amilcar Freitas, Nelson R F Silva, Thomas Lilin, Nick Tovar, Malvin N Janal, Paulo G Coelho

  Journal of the mechanical behavior of biomedical materials. 05/2012; 9:45-9.

  The biomechanical effects of a non-thermal plasma (NTP) treatment, suitable for use in a dental office, on the surface character and integration of a textured dental implant surface in a beagle dogThe biomechanical effects of a non-thermal plasma (NTP) treatment, suitable for use in a dental office, on the surface character and integration of a textured dental implant surface in a beagle dog model were evaluated. The experiment compared a control treatment, which presented an alumina-blasted/acid-etched (AB/AE) surface, to two experimental treatments, in which the same AB/AE surface also received NTP treatment for a period of 20 or 60 s per implant quadrant (PLASMA 20' and PLASMA 60' groups, respectively). The surface of each specimen was characterized by electron microscopy and optical interferometry, and surface energy and surface chemistry were determined prior to and after plasma treatment. Two implants of each type were then placed at six bilateral locations in 6 dogs, and allowed to heal for 2 or 4 weeks. Following sacrifice, removal torque was evaluated as a function of animal, implant surface and time in vivo in a mixed model ANOVA. Compared to the CONTROL group, PLASMA 20' and 60' groups presented substantially higher surface energy levels, lower amounts of adsorbed C species and significantly higher torque levels (p=.001). Result indicated that the NTP treatment increased the surface energy and the biomechanical fixation of textured-surface dental implants at early times in vivo.

• Argon-based atmospheric pressure plasma enhances early bone response to rough titanium surfaces.

  Authors: Paulo G Coelho, Gabriela Giro, Hellen S Teixeira, Charles Marin, Lukas Witek, Van P Thompson, Nick Tovar, Nelson R F A Silva

  Journal of biomedical materials research. Part A. 04/2012;

  This study investigated the effect of an Argon-based atmospheric pressure plasma (APP) surface treatment operated chairside at atmospheric pressure conditions applied immediately prior to dentalThis study investigated the effect of an Argon-based atmospheric pressure plasma (APP) surface treatment operated chairside at atmospheric pressure conditions applied immediately prior to dental implant placement in a canine model. Surfaces investigated comprised: rough titanium surface (Ti) and rough titanium surface + Argon-based APP (Ti-Plasma). Surface energy was characterized by the Owens-Wendt-Rabel-Kaelble method and chemistry by X-ray photoelectron spectroscopy (XPS). Six adult beagles dogs received two plateau-root form implants (n = 1 each surface) in each radii, providing implants that remained 1 and 3 weeks in vivo. Histometric parameters assessed were bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Statistical analysis was performed by Kruskall-Wallis (95% level of significance) and Dunn's post-hoc test. The XPS analysis showed peaks of Ti, C, and O for the Ti and Ti- Plasma surfaces. Both surfaces presented carbon primarily as hydrocarbon (CC, CH) with lower levels of oxidized carbon forms. The Ti-Plasma presented large increase in the Ti (+11%) and O (+16%) elements for the Ti- Plasma group along with a decrease of 23% in surface-adsorbed C content. At 1 week no difference was found in histometric parameters between groups. At 3 weeks significantly higher BIC (>300%) and mean BAFO (>30%) were observed for Ti-Plasma treated surfaces. From a morphologic standpoint, improved interaction between connective tissue was observed at 1 week, likely leading to more uniform and higher bone formation at 3 weeks for the Ti-Plasma treated implants was observed. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 2012.

• Reliability and failure modes of internal conical dental implant connections.

  Authors: Amilcar C Freitas-Júnior, Erika O Almeida, Estevam A Bonfante, Nelson R F A Silva, Paulo G Coelho

  Clinical oral implants research. 03/2012;

  OBJECTIVE: Biological and mechanical implant-abutment connection complications and failures are still present in clinical practice, frequently compromising oral function. The purpose of this studyOBJECTIVE: Biological and mechanical implant-abutment connection complications and failures are still present in clinical practice, frequently compromising oral function. The purpose of this study was to evaluate the reliability and failure modes of anterior single-unit restorations in internal conical interface (ICI) implants using step-stress accelerated life testing (SSALT). MATERIALS AND METHODS: Forty-two ICI implants were distributed in two groups (n = 21 each): group AT-OsseoSpeed(™) TX (Astra Tech, Waltham, MA, USA); group SV-Duocon System Line, Morse Taper (Signo Vinces Ltda., Campo Largo, PR, Brazil). The corresponding abutments were screwed to the implants and standardized maxillary central incisor metal crowns were cemented and subjected to SSALT in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N were calculated. Differences between groups were assessed by Kruskal-Wallis along with Bonferroni's post-hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta (β) value derived from use level probability Weibull calculation was 1.62 (1.01-2.58) for group AT and 2.56 (1.76-3.74) for group SV, indicating that fatigue was an accelerating factor for failure of both groups. The reliability for group AT was 0.95 and for group SV was 0.88. Kruskal-Wallis along with Bonferroni's post-hoc tests showed no significant difference between the groups tested (P > 0.27). In all specimens of both groups, the chief failure mode was abutment fracture at the conical joint region and screw fracture at neck's region. CONCLUSIONS: Reliability was not different between investigated ICI connections supporting maxillary incisor crowns. Failure modes were similar.

• Effect of microthread presence and restoration design (screw versus cemented) in dental implant reliability and failure modes.

  Authors: Erika O Almeida, Amilcar C Freitas Júnior, Estevam A Bonfante, Eduardo Passos Rocha, Nelson R F A Silva, Paulo G Coelho

  Clinical oral implants research. 03/2012;

  OBJECTIVES: This study evaluated the reliability and failure modes of implants with a microthreaded or smooth design at the crestal region, restored with screwed or cemented crowns. The postulatedOBJECTIVES: This study evaluated the reliability and failure modes of implants with a microthreaded or smooth design at the crestal region, restored with screwed or cemented crowns. The postulated null hypothesis was that the presence of microthreads in the implant cervical region would not result in different reliability and strength to failure than smooth design, regardless of fixation method, when subjected to step-stress accelerated life-testing (SSALT) in water. MATERIALS AND METHODS: Eighty four dental implants (3.3 × 10 mm) were divided into four groups (n = 21) according to implant macrogeometric design at the crestal region and crown fixation method: Microthreads Screwed (MS); Smooth Screwed (SS); Microthreads Cemented (MC), and Smooth Cemented (SC). The abutments were torqued to the implants and standardized maxillary central incisor metallic crowns were cemented (MC, SC) or screwed (MS, SS) and subjected to SSALT in water. The probability of failure versus cycles (90% two-sided confidence intervals) was calculated and plotted using a power law relationship for damage accumulation. Reliability for a mission of 50,000 cycles at 150 N (90% 2-sided confidence intervals) was calculated. Differences between final failure loads during fatigue for each group were assessed by Kruskal-Wallis along with Benferroni's post hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta (β) value (confidence interval range) derived from use level probability Weibull calculation of 1.30 (0.76-2.22), 1.17 (0.70-1.96), 1.12 (0.71-1.76), and 0.52 (0.30-0.89) for groups MC, SC, MS, and SS respectively, indicated that fatigue was an accelerating factor for all groups, except for SS. The calculated reliability was higher for SC (99%) compared to MC (87%). No difference was observed between screwed restorations (MS - 29%, SS - 43%). Failure involved abutment screw fracture for all groups. The cemented groups (MC, SC) presented more abutment and implant fractures. Significantly higher load to fracture values were observed for SC and MC relative to MS and SS (P < 0.001). CONCLUSION: Since reliability and strength to failure was higher for SC than for MC, our postulated null hypothesis was rejected.

• Fatigue reliability of 3 single-unit implant-abutment designs.

  Authors: Leandro M Martins, Estevam A Bonfante, Ricardo A Zavanelli, Amilcar C Freitas, Nelson R F A Silva, Leonard Marotta, Paulo G Coelho

  Implant dentistry. 02/2012; 21(1):67-71.

  Because the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of differentBecause the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of different implant-abutment systems used as single-unit crowns and their failure modes. Sixty-three Ti-6Al-4V implants were divided in 3 groups: Replace Select (RS); IC-IMP Osseotite; and Unitite were restored with their respective abutments. Anatomically correct central incisor metal crowns were cemented and subjected to separate single load to failure tests and step-stress accelerated life testing (n = 18). A master Weibull curve and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. The load at failure mean values during step-stress accelerated life testing were 348.14 N for RS, 324.07 N for Osseotite, and 321.29 N for the Unitite systems. No differences in reliability levels were detected between systems, and only the RS system mechanical failures were shown to be accelerated by damage accumulation. Failure modes differed between systems. The 3 evaluated systems did not present significantly different reliability; however, failure modes were different.

• Effect of drilling dimension on implant placement torque and early osseointegration stages: an experimental study in dogs.

  Authors: Felipe E Campos, Julio B Gomes, Charles Marin, Hellen S Teixeira, Marcelo Suzuki, Lukasz Witek, Darceny Zanetta-Barbosa, Paulo G Coelho

  Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 01/2012; 70(1):e43-50.

  Primary stability has been regarded as a key factor to ensure uneventful osseointegration of dental implants. Such stability is often achieved by placing implants in undersized drilled bone. ThePrimary stability has been regarded as a key factor to ensure uneventful osseointegration of dental implants. Such stability is often achieved by placing implants in undersized drilled bone. The present study evaluated the effect of drilling dimensions in insertion torque and early implant osseointegration stages in a beagle dog model. Six beagle dogs were acquired and subjected to bilateral surgeries in the radii 1 and 3 weeks before death. During surgery, 3 implants, 4 mm in diameter by 10 mm in length, were placed in bone sites drilled to 3.2 mm, 3.5 mm, and 3.8 mm in diameter. The insertion torque was recorded for all samples. After death, the implants in bone were nondecalcified processed and morphologically and morphometrically (bone-to-implant contact and bone area fraction occupancy) evaluated. Statistical analyses were performed using the Kruskal-Wallis test followed by Dunn's post hoc test for multiple comparisons at the 95% level of significance. The insertion torque levels obtained were inversely proportional to the drilling dimension, with a significant difference detected between the 3.2-mm and 3.8-mm groups (P = .003). Despite a significant increase in the bone-to-implant contact over time in vivo for all groups (P = .007), no effect for the drilling dimension was observed. Additionally, no effect of the drilling dimension and time was observed for the bone area fraction occupancy parameter (P = .31). The initial healing pathways differed between implants placed in bone drilled to different dimensions. Although different degrees of torque were observed with different drilling dimensions and these resulted in different healing patterns, no differences in the histometrically evaluated parameters were observed.

• Evaluation of surface roughness as a function of multiple blasting processing variables.

  Authors: Guilherme B Valverde, Ryo Jimbo, Hellen S Teixeira, Estevam A Bonfante, Malvin N Janal, Paulo G Coelho

  Clinical oral implants research. 12/2011;

  OBJECTIVES: This study evaluated the effect of implant surface blasting variables, such as blasting media size, velocity, and surface coverage and their two- and three-way interaction in surfaceOBJECTIVES: This study evaluated the effect of implant surface blasting variables, such as blasting media size, velocity, and surface coverage and their two- and three-way interaction in surface roughness parameters. MATERIAL AND METHODS: Machined, grade IV titanium-alloy implants (n = 180) had their surfaces treated by a combination of 36 different blasting protocols according to the following variables: aluminum oxide blasting media particle size (50, 100, and 150 μm); velocity (75, 100, 125, and 150 m/s), and surface coverage (5, 15, 25 g/in.(2) ) (n = 5 per blasting protocol). A single 0.46 inch nozzle of the blaster was pointed at the threaded area and spaced 0.050 inches away. Surface topography (n = 5 measurements per implant) was assessed by scanning electron microscopy. Roughness parameters Sa, Sq, Sdr, and Sds were evaluated by optical interferometry. A GLM statistical model evaluated the effects of blasting variables on the surface parameters, and their two- and three-way interaction (P < 0.05). Statistical inferences for Sa and Sq were performed after a log(10) transformation to correct for data skewness. RESULTS: Prior to the log(10) transformation, Sa and Sq values for all processing groups ranged from ~0.5 to ~2.6 μm and from ~0.75 to 4 μm, respectively. Statistical inferences showed that Sa, Sq, and Sdr values were significantly dependent on blasting media, velocity, and surface coverage (all P < 0.001). Media × velocity, media × coverage, and media × velocity × coverage also significantly affected Sa, Sq, and Sdr values (P < 0.002). The highest levels were obtained with 100 μm blasting media, coverage for 5 g/in.(2) , and velocity of 100 m/s. No significant differences were observed for Sds (P > 0.15). CONCLUSIONS: The blasting variables produced different surface topography features and knowledge of their interaction could be used to tailor a desired implant surface configuration.

• Alveolar buccal bone maintenance after immediate implantation with a surgical flap approach: a study in dogs.

  Authors: Paulo G Coelho, Charles Marin, Rodrigo Granato, Estevam A Bonfante, Cirilo P Lima, Sergio Oliveira, David M Dohan Ehrenfest, Mercelo Suzuki

  The International journal of periodontics & restorative dentistry. 11/2011; 31(6):e80-6.

  This study evaluated buccal bone maintenance after implantation with a surgical flap approach immediately following tooth extraction in a dog model. Mandibular premolars of six dogs were extracted,This study evaluated buccal bone maintenance after implantation with a surgical flap approach immediately following tooth extraction in a dog model. Mandibular premolars of six dogs were extracted, and threaded implants of 4-mm diameter and 8-mm length with as-machined and dual acid-etched surfaces were placed through balanced procedures in the distal root extraction sockets with a full-thickness flap design. Submerged healing was allowed for 4 weeks, and following euthanization, bone-to-implant contact and buccal and lingual bone loss were evaluated. None of the parameters evaluated were indicative of an effect of implant surface in hindering bone loss around immediately placed implants.

• The effect of different implant macrogeometries and surface treatment in early biomechanical fixation: an experimental study in dogs.

  Authors: Paulo G Coelho, Rodrigo Granato, Charles Marin, Hellen S Teixeira, Marcelo Suzuki, Guilherme B Valverde, Malvin N Janal, Tomas Lilin, Estevam A Bonfante

  Journal of the mechanical behavior of biomedical materials. 11/2011; 4(8):1974-81.

  Implant surface characterization and biomechanical testing were made to evaluate the effect of different surface treatments along with different implant bulk configurations expressed as biomechanicalImplant surface characterization and biomechanical testing were made to evaluate the effect of different surface treatments along with different implant bulk configurations expressed as biomechanical fixation at early implantation times. Three implant surfaces, namely bioactive ceramic electrodeposition (ED), alumina-blasted/acid etched (AB/AE), and resorbable blasting media (RBM) were fabricated in three implant macrogeometries (cylindrical, small chamber, and large chamber). All combinations between surface and bulk configurations were placed in the radii of beagle dogs (n=18), which were euthanized 14 and 40 days after surgery (n=9 animals per time in vivo). The implants were subjected to torque to interface fracture. Effects of time, surface, and macrogeometry on torque to interface fracture were evaluated by a GLM at 95% level of significance. The results showed a significant increase in torque as time elapsed in vivo (p<0.001), and that the ED surface presented significantly higher values compared to AB/AE and RBM (p<0.001) at both times. The small chamber only presented a significantly higher biomechanical fixation compared to other geometries at 40 days in vivo (p=0.02). Biomechanical fixation at 14 and 40 days was affected by implant surface treatment, whereas implant design only affected results at 40 days in vivo.

• Influence of implant design on the biomechanical environment of immediately placed implants: computed tomography-based nonlinear three-dimensional finite element analysis.

  Authors: Roberto S Pessoa, Paulo G Coelho, Luiza Muraru, Elcio Marcantonio, Luis Geraldo Vaz, Jos Vander Sloten, Siegfried V N Jaecques

  The International journal of oral & maxillofacial implants. 11/2011; 26(6):1279-87.

  To evaluate the influence of different implant designs on the biomechanical environment of immediately placed implants. Computed tomography (CT)-based finite element models comprising a maxillaryTo evaluate the influence of different implant designs on the biomechanical environment of immediately placed implants. Computed tomography (CT)-based finite element models comprising a maxillary central incisor socket and four commercially available internal-connection implants (SIN SW, 3i Certain, Nobel Replace, and ITI Standard) of comparable diameters and lengths were constructed. Biomechanical scenarios of immediate placement, immediate loading, and delayed loading protocols were simulated. Analysis of variance at the 95% confidence level was used to evaluate peak equivalent strain (EQV strain) in bone and bone-to-implant relative displacement. Loading magnitude (77.6%) and the clinical situation (15.0%) (ie, presence or absence of an extraction socket defect, condition of the bone-to-implant interface) presented the highest relative contributions to the results. Implant design contributed significantly to strains and displacements in the immediate placement protocol. Whereas a greater contribution of implant design was observed for strain values and distributions for immediately placed and immediately loaded protocols, a smaller contribution was observed in the delayed loading scenario. Implant design contributes significantly to changing biomechanical scenarios for immediately placed implants. The results also suggest that avoiding implant overloading and ensuring high primary implant stability are critical in encouraging the load-bearing capability of immediately placed implants.

• Reliability testing of indirect composites as single implant restorations.

  Authors: Marcelo Suzuki, Estevam Bonfante, Nelson Rfa Silva, Paulo G Coelho

  Journal of prosthodontics : official journal of the American College of Prosthodontists. 10/2011; 20(7):528-34.

  To investigate the reliability and failure modes of indirect composites as single-unit implant crowns. Thirty-eight custom-milled titanium alloy locking-taper abutments were divided into two groupsTo investigate the reliability and failure modes of indirect composites as single-unit implant crowns. Thirty-eight custom-milled titanium alloy locking-taper abutments were divided into two groups (n = 19 each), and crown build-up of a mandibular molar was accomplished using two indirect composite systems (Ceramage, Shofu, Kyoto, Japan; Diamond Crown, DRM, Branford, CT). Three crowns of each material were loaded until failure for determination of the step-stress profiles. Reliability testing started at a load 30% of the mean load to failure and used three profiles with increasing fatigue loading (step stress). Weibull curves with 300 N stress and 90% confidence intervals were calculated and plotted using a power-law relationship. Weibull modulus "Beta" and characteristic strength "Eta" were identified, and a contour plot was used (Beta vs. Eta) for examining differences between groups. Specimens were inspected in polarized light and scanning electron microscope for fracture analysis. Use level Weibull probability showed fatigue being a damage factor only for the Ceramage group (β= 3.39) but not for the Diamond Crown group (β= 0.40). Overlap in the confidence bounds resulted in no statistical difference. Irrespective of composite system, fracture initiated in the region immediately below the contact between the indenter and the cusp, with the crack propagating toward the margins of cohesive failure. No significant differences were observed in life and Weibull probability calculations for Ceramage and Diamond Crown veneered onto Ti alloy abutments. Failure modes comprised composite veneer chippings.

• Reliability and failure modes of anterior single-unit implant-supported restorations.

  Authors: Amilcar C Freitas, Estevam A Bonfante, Leandro M Martins, Nelson R F A Silva, Leonard Marotta, Paulo G Coelho

  Clinical oral implants research. 08/2011;

  PURPOSE: Failures of implant-abutment connections have been observed clinically, especially in single-tooth replacements. This study sought to evaluate the reliability and failure modes ofPURPOSE: Failures of implant-abutment connections have been observed clinically, especially in single-tooth replacements. This study sought to evaluate the reliability and failure modes of implant-supported anterior crowns restored with different implant systems. MATERIALS AND METHODS: Forty-two Ti-6Al-4V dental implants (~4 mm diameter) were used for single anterior crown replacement and divided into two groups according to tested system: (NB) Replace Select system, Nobel Biocare (n = 21); and (IL) Internal connection system, Intra-Lock International (n = 21). Proprietary abutments were screwed to the implants and anatomically correct maxillary central incisor metal crowns were cemented and subjected to step-stress-accelerated life testing in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N (95% 2-sided confidence intervals) were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The Beta values for NB and IL (2.09 and 2.05, respectively) indicated that fatigue accelerated the failure of both groups. The calculated reliability for the NB system (0.81) was lower than for the IL system (0.96), but no significant difference was observed between groups. Screw and abutment fracture was the chief failure mode in group NB, while screw fracture was most representative in specimens of group IL. CONCLUSIONS: Reliability of implant-supported maxillary central incisor crowns was not significantly different between NB and IL abutments. Failure modes differed between implant systems.

• Effect of implant-abutment connection design on reliability of crowns: regular vs. horizontal mismatched platform.

  Authors: Amilcar C Freitas Júnior, Estevam A Bonfante, Nelson R F A Silva, Leonard Marotta, Paulo G Coelho

  Clinical oral implants research. 08/2011;

  OBJECTIVES: To evaluate the reliability and failure modes of regular and horizontal mismatched platforms for implant-abutment connection varying the implant diameter. MATERIAL AND METHODS: RegularOBJECTIVES: To evaluate the reliability and failure modes of regular and horizontal mismatched platforms for implant-abutment connection varying the implant diameter. MATERIAL AND METHODS: Regular (REG, n = 21, 4.0-mm-diameter implant) and horizontal mismatched (HM, n = 21, 4.6-mm-diameter implant) platform Ti-6Al-4V implants were restored with proprietary identical Ti-6Al-4V abutments and metal crowns (cobalt-chrome, Wirobond(®) 280, BEGO, Bremen, Germany) cemented. Mechanical testing comprised step-stress accelerated-life testing, where crowns were distributed in three loading profiles for fatigue in water, producing timely and clinically relevant fractures. The probability of failure vs. cycles (95% two-sided confidence intervals) was calculated and plotted using a powerlaw relationship for damage accumulation, Weibull modulus (95% two-sided confidence intervals) and then the reliability for a mission of 50,000 cycles at 125 N load (95% two-sided confidence interval) were calculated. Fractography was performed in the scanning electron microscope. RESULTS: The β-value for group REG (β = 1.37) indicated that fatigue was a factor accelerating the failure, whereas load alone dictated the failure for group HM (β = 0.71). The Weibull parameter contour plot showed no significantly different Weibull modulus for REG (10.24) compared to HM (10.20) and characteristic strength of 162.6 and 166.8 N, respectively (P > 0.91). The calculated reliability for a mission of 50,000 cycles at 125 N load was not significantly different (0.71 for REG and 0.73 for HM). Abutment screw failure was the chief failure mode. CONCLUSIONS: Reliability was not significantly different between groups and failure modes were similar.

• Effect of implant connection and restoration design (screwed vs. cemented) in reliability and failure modes of anterior crowns.

  Authors: Amilcar C Freitas, Estevam A Bonfante, Eduardo P Rocha, Nelson R F A Silva, Leonard Marotta, Paulo G Coelho

  European journal of oral sciences. 08/2011; 119(4):323-30.

  The mechanical performance of cemented or screw-retained implant-supported crowns with an internal or external configuration is yet to be understood. This in vitro study evaluated the effect ofThe mechanical performance of cemented or screw-retained implant-supported crowns with an internal or external configuration is yet to be understood. This in vitro study evaluated the effect of screw-retained and cement-retained prostheses on internal and external implant-abutment connections. Thereby, the reliability and failure modes of crowns were investigated. Eighty-four implants (Emfils; Colosso Evolution system) were divided into four groups (n=21 each): screw-retained and internal connection (Si), screw-retained and external connection (Se), cement-retained and internal connection (Ci), and cement-retained and external connection (Ce). Ti-6Al-4V abutments were torqued (30 Ncm) to the implants, and maxillary central incisor metal crowns were torqued (30 Ncm) or cemented (Rely X Unicem; 3M-ESPE) and subjected to accelerated life-testing in water. Use-level probability Weibull curves and reliability for 50,000 cycles at 150 N were calculated. The β values for Si (1.72), Se (1.50), Ci (1.34), and Ce (1.77) groups indicated that fatigue/damage accumulation accelerated their failure. The Ci group presented the highest reliability, the Se group presented the lowest reliability, and Si and Ce groups presented intermediate reliability. Screw-retained restorations presented mainly abutment fracture. Cement-retained restorations resulted in failures of the screw in the Ce group, but implant/screw fracture in the Ci group.

• Histological and three-dimensional evaluation of osseointegration to nanostructured calcium phosphate-coated implants.

  Authors: Ryo Jimbo, Paulo G Coelho, Stefan Vandeweghe, Humberto Osvaldo Schwartz-Filho, Mariko Hayashi, Daisuke Ono, Martin Andersson, Ann Wennerberg

  Acta biomaterialia. 07/2011; 7(12):4229-34.

  Nanostructures on implant surfaces have been shown to enhance osseointegration; however, commonly used evaluation techniques are probably not sufficiently sensitive to fully determine the effects ofNanostructures on implant surfaces have been shown to enhance osseointegration; however, commonly used evaluation techniques are probably not sufficiently sensitive to fully determine the effects of this process. This study aimed to observe the osseointegration properties of nanostructured calcium phosphate (CaP)-coated implants, by using a combination of three-dimensional imaging and conventional histology. Titanium implants were coated with stable CaP nanoparticles using an immersion technique followed by heat treatment. Uncoated implants were used as the control. After topographical and chemical characterizations, implants were inserted into the rabbit femur. After 2 and 4weeks, the samples were retrieved for micro-computed tomography and histomorphometric evaluation. Scanning electron microscopy evaluation indicated that the implant surface was modified at the nanoscale by CaP to obtain surface textured with rod-shaped structures. Relative to the control, the bone-to-implant contact for the CaP-coated implant was significantly higher at 4weeks after the implant surgery. Further, corresponding 3-D images showed active bone formation surrounding the implant. 3-D quantification and 2-D histology demonstrated statistical correlation; moreover, 3-D quantification indicated a statistical decrease in bone density in the non-coated control implant group between 2 and 4weeks after the surgery. The application of 3-D evaluation further clarified the temporal characteristics and biological reaction of implants in bone.

• Reimplantation of Dental Implants following Ligature-Induced Peri-Implantitis: A Pilot Study in Dogs.

  Authors: Liran Levin, Hadar Zigdon, Paulo G Coelho, Marcelo Suzuki, Eli E Machtei

  Clinical implant dentistry and related research. 07/2011;

  Objectives: This preliminary investigation aimed to evaluate the potential of contaminated implants to reosseointegrate into pristine sites and, in addition, to assess the potential ofObjectives: This preliminary investigation aimed to evaluate the potential of contaminated implants to reosseointegrate into pristine sites and, in addition, to assess the potential of osseointegration of new implants in peri-implantitis sockets in a canine model. Methods: All mandibular premolars were bilaterally extracted from two mongrel dogs. Following 12 weeks of healing, two dental implants were inserted on each hemiarch. Forty-five days following implant placement, a silk ligature secured with cyanoacrylate was placed around the implants' cervical region in order to induce peri-implantitis. After another 45 days from ligature placement, the implants were mechanically removed using counter rotation with a ratchet and were reimplanted without any decontamination (neither rinsing nor chemical or mechanical cleaning) in adjacent pristine zones. In sites where implants were removed, new, wider-diameter implants were placed in the infected sockets. Forty-five days following reimplantation surgery, the dogs were sacrificed; nondecalcified specimens were processed and toluidine blue stained for morphologic and morphometric (bone-to-implant contact [BIC]) assessment under an optical microscope. Results: In dog 1 all the implants (both in the pristine and in the infected sites) survived and osseointegrated while in dog 2, six out of eight implants failed to osseointegrate and exfoliated. Overall, the mean BIC of all implants was 51.08% (SD 20.54). The mean BIC for the infected implants placed into pristine sites was 51.48% ± 26.29% (SD) and the mean BIC for the new implants in peri-implantitis socket was 50.58% ± 14.27% (SD). Conclusions: Within the limitations of this preliminary investigation, especially the small number of animals, osseointegration seems to be achievable both in infected sites and around contaminated implant surfaces.

• Influence of estrogen deficiency on bone around osseointegrated dental implants: an experimental study in the rat jaw model.

  Authors: Gabriela Giro, Paulo G Coelho, Roberto Sales-Pessoa, Rosa Maria Rodrigues Pereira, Toshihisa Kawai, Silvana Regina Perez Orrico

  Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 07/2011; 69(7):1911-8.

  The aim of this study was to evaluate the influence of estrogen deficiency on bone around osseointegrated dental implants in a rat jaw model. This study used 16 female rats that had the first molarsThe aim of this study was to evaluate the influence of estrogen deficiency on bone around osseointegrated dental implants in a rat jaw model. This study used 16 female rats that had the first molars bilaterally extracted and were allowed to heal for 30 days before implant placement. Sixty days after implant placement, the animals were randomly subjected to sham surgery or ovariectomy (OVX). The animals were euthanized 90 days after OVX. Bone-to-implant contact, bone area fraction occupancy between implant threads, mineral density, turnover markers, and cells positive for tartrate-resistant acid phosphatase were assessed for the 2 groups. The results showed that OVX group presented a decrease of systemic bone density, alterations in bone turnover markers, and an increase of cells positive for tartrate-resistant acid phosphatase compared with the sham-surgery group. However, no difference relative to bone-to-implant contact and bone area fraction occupancy was observed between groups. The findings of this study demonstrate that estrogen deficiency may not be considered a risk factor for osseointegrated implant failure in jaw bone.

• Surface characterization of Ti and Y-TZP following non-thermal plasma exposure.

  Authors: Nelson R F A Silva, Paulo G Coelho, Guilherme B Valverde, Kurt Becker, Roland Ihrke, Antje Quade, Van P Thompson

  Journal of biomedical materials research. Part B, Applied biomaterials. 06/2011; 99(1):199-206.

  Novel non-thermal plasma (NTP) technology has the potential to address the bonding issues of Y-TZP and Ti surfaces. This study aims to chemically characterize and evaluate the surface energy (SE) ofNovel non-thermal plasma (NTP) technology has the potential to address the bonding issues of Y-TZP and Ti surfaces. This study aims to chemically characterize and evaluate the surface energy (SE) of Y-TZP and Ti surfaces after NTP application. Y-TZP and Ti discs were treated with a hand-held NTP device followed by SE evaluation. Spectra of Y-TZP 3d and Ti 2p regions, survey scans, and quantification of the elements were performed via X-ray photoelectron Spectroscopy (XPS) prior and after NTP. Separate Y-TZP and Ti discs were NTP treated for contact angle readings using (10-methacryloyloxydecyl dihydrogenphosphate) MDP primer. Significant augmentation of SE values was observed in all NTP treated groups. XPS detected a large increase in the O element fraction on both Y-TZP and Ti surfaces. Reduction of contact angle reading was obtained when the MDP primer was placed on NTP treated Y-TZP. Ti surface showed high SE before and after NTP application on Ti surfaces. NTP decreased C and increased O on both surfaces independently of application protocol. Wettability of MDP primer on Y-TZP was significantly increased after NTP. The high polarity obtained on Y-TZP and Ti surfaces after NTP applications appear promising to enhance bonds.

• Effect of drilling technique on the early integration of plateau root form endosteal implants: an experimental study in dogs.

  Authors: Gabriela Giro, Charles Marin, Rodrigo Granato, Estevam A Bonfante, Marcelo Suzuki, Malvin N Janal, Paulo G Coelho

  Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 04/2011; 69(8):2158-63.

  This study tested the hypothesis that early integration of plateau root form endosseous implants is significantly affected by surgical drilling technique. Sixty-four implants were bilaterally placedThis study tested the hypothesis that early integration of plateau root form endosseous implants is significantly affected by surgical drilling technique. Sixty-four implants were bilaterally placed in the diaphysial radius of 8 beagles and remained 2 and 4 weeks in vivo. Half the implants had an alumina-blasted/acid-etched surface and the other half a surface coated with calcium phosphate. Half the implants with the 2 surface types were drilled at 50 rpm without saline irrigation and the other half were drilled at 900 rpm under abundant irrigation. After euthanasia, the implants in bone were nondecalcified and referred for histologic analysis. Bone-to-implant contact, bone area fraction occupancy, and the distance from the tip of the plateau to pristine cortical bone were measured. Statistical analyses were performed by analysis of variance at a 95% level of significance considering implant surface, time in vivo, and drilling speed as independent variables and bone-to-implant contact, bone area fraction occupancy, and distance from the tip of the plateau to pristine cortical bone as dependent variables. The results showed that both techniques led to implant integration and intimate contact between bone and the 2 implant surfaces. A significant increase in bone-to-implant contact and bone area fraction occupancy was observed as time elapsed at 2 and 4 weeks and for the calcium phosphate-coated implant surface compared with the alumina-blasted/acid-etched surface. Because the surgical drilling technique did not affect the early integration of plateau root form implants, the hypothesis was refuted.

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

  Authors: Charles Marin, Rodrigo Granato, Estevam A Bonfante, Marcelo Suzuki, Malvin N Janal, Paulo G Coelho

  Clinical oral implants research. 04/2011; 23(1):119-24.

  This study compared the biomechanical fixation and bone-to-implant contact (BIC) of implants with different surfaces treatment (experimental - resorbable blasting media-processed nanometer roughnessThis 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. 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. 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. The experimental surface resulted in enhanced biomechanical fixation but comparable BIC relative to control, suggesting higher bone mechanical properties around the experimental implants.