Validation of an experimental polyurethane model for biomechanical studies on implant-supported prosthesis – compression tests
Identifieur interne : 000619 ( Pmc/Corpus ); précédent : 000618; suivant : 000620Validation of an experimental polyurethane model for biomechanical studies on implant-supported prosthesis – compression tests
Auteurs : Rafael Tobias Moretti Neto ; Daniel Afonso Hiramatsu ; Valdey Suedam ; Paulo César Rodrigues Conti ; José Henrique RuboSource :
- Journal of Applied Oral Science [ 1678-7757 ] ; 2011.
Abstract
The complexity and heterogeneity of human bone, as well as ethical issues, most
always hinder the performance of clinical trials. Thus,
In this study, fast-curing polyurethane (F16 polyurethane, Axson) was used to build 40 specimens that were divided into five groups. The following reagent ratios (part A/part B) were used: Group A (0.5/1.0), Group B (0.8/1.0), Group C (1.0/1.0), Group D (1.2/1.0), and Group E (1.5/1.0). A universal testing machine (Kratos model K – 2000 MP) was used to measure modulus of elasticity values by compression.
Mean modulus of elasticity values were: Group A – 389.72 MPa, Group B – 529.19 MPa, Group C – 571.11 MPa, Group D – 470.35 MPa, Group E – 437.36 MPa.
The best mechanical characteristics and modulus of elasticity value comparable to that of human trabecular bone were obtained when A/B ratio was 1:1.
Url:
DOI: 10.1590/S1678-77572011000100010
PubMed: 21437469
PubMed Central: 4245863
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PMC:4245863Le document en format XML
<record><TEI><teiHeader><fileDesc><titleStmt><title xml:lang="en"> Validation of an experimental polyurethane model for biomechanical
studies on implant-supported prosthesis – compression tests</title><author><name sortKey="Moretti Neto, Rafael Tobias" sort="Moretti Neto, Rafael Tobias" uniqKey="Moretti Neto R" first="Rafael Tobias" last="Moretti Neto">Rafael Tobias Moretti Neto</name><affiliation><nlm:aff id="aff01"> DDs, MSc, PhD, Department of Clinics and Surgery, Dental School, Federal University of Alfenas, Alfenas, MG, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Hiramatsu, Daniel Afonso" sort="Hiramatsu, Daniel Afonso" uniqKey="Hiramatsu D" first="Daniel Afonso" last="Hiramatsu">Daniel Afonso Hiramatsu</name><affiliation><nlm:aff id="aff02"> DDs, MSc, Private Practice, Santos, SP, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Suedam, Valdey" sort="Suedam, Valdey" uniqKey="Suedam V" first="Valdey" last="Suedam">Valdey Suedam</name><affiliation><nlm:aff id="aff03"> DDs, MSc, PhD, Private Practice, Bauru, SP, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Conti, Paulo Cesar Rodrigues" sort="Conti, Paulo Cesar Rodrigues" uniqKey="Conti P" first="Paulo César Rodrigues" last="Conti">Paulo César Rodrigues Conti</name><affiliation><nlm:aff id="aff04"> DDs, MSc, PhD, Associate Professor, Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Rubo, Jose Henrique" sort="Rubo, Jose Henrique" uniqKey="Rubo J" first="José Henrique" last="Rubo">José Henrique Rubo</name><affiliation><nlm:aff id="aff04"> DDs, MSc, PhD, Associate Professor, Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.</nlm:aff></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">PMC</idno><idno type="pmid">21437469</idno><idno type="pmc">4245863</idno><idno type="url">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4245863</idno><idno type="RBID">PMC:4245863</idno><idno type="doi">10.1590/S1678-77572011000100010</idno><date when="2011">2011</date><idno type="wicri:Area/Pmc/Corpus">000619</idno><idno type="wicri:explorRef" wicri:stream="Pmc" wicri:step="Corpus" wicri:corpus="PMC">000619</idno></publicationStmt><sourceDesc><biblStruct><analytic><title xml:lang="en" level="a" type="main"> Validation of an experimental polyurethane model for biomechanical
studies on implant-supported prosthesis – compression tests</title><author><name sortKey="Moretti Neto, Rafael Tobias" sort="Moretti Neto, Rafael Tobias" uniqKey="Moretti Neto R" first="Rafael Tobias" last="Moretti Neto">Rafael Tobias Moretti Neto</name><affiliation><nlm:aff id="aff01"> DDs, MSc, PhD, Department of Clinics and Surgery, Dental School, Federal University of Alfenas, Alfenas, MG, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Hiramatsu, Daniel Afonso" sort="Hiramatsu, Daniel Afonso" uniqKey="Hiramatsu D" first="Daniel Afonso" last="Hiramatsu">Daniel Afonso Hiramatsu</name><affiliation><nlm:aff id="aff02"> DDs, MSc, Private Practice, Santos, SP, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Suedam, Valdey" sort="Suedam, Valdey" uniqKey="Suedam V" first="Valdey" last="Suedam">Valdey Suedam</name><affiliation><nlm:aff id="aff03"> DDs, MSc, PhD, Private Practice, Bauru, SP, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Conti, Paulo Cesar Rodrigues" sort="Conti, Paulo Cesar Rodrigues" uniqKey="Conti P" first="Paulo César Rodrigues" last="Conti">Paulo César Rodrigues Conti</name><affiliation><nlm:aff id="aff04"> DDs, MSc, PhD, Associate Professor, Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.</nlm:aff></affiliation></author><author><name sortKey="Rubo, Jose Henrique" sort="Rubo, Jose Henrique" uniqKey="Rubo J" first="José Henrique" last="Rubo">José Henrique Rubo</name><affiliation><nlm:aff id="aff04"> DDs, MSc, PhD, Associate Professor, Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.</nlm:aff></affiliation></author></analytic><series><title level="j">Journal of Applied Oral Science</title><idno type="ISSN">1678-7757</idno><idno type="eISSN">1678-7765</idno><imprint><date when="2011">2011</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en"><sec><title>Objectives</title><p>The complexity and heterogeneity of human bone, as well as ethical issues, most
always hinder the performance of clinical trials. Thus, <italic>in vitro</italic>studies become an important source of information for the understanding of
biomechanical events on implantsupported prostheses, although study results cannot
be considered reliable unless validation studies are conducted. The purpose of
this work was to validate an artificial experimental model based on its modulus of
elasticity, to simulate the performance of human bone <italic>in vivo</italic> in
biomechanical studies of implant-supported prostheses.</p></sec><sec><title>Material and Methods</title><p>In this study, fast-curing polyurethane (F16 polyurethane, Axson) was used to
build 40 specimens that were divided into five groups. The following reagent
ratios (part A/part B) were used: Group A (0.5/1.0), Group B (0.8/1.0), Group C
(1.0/1.0), Group D (1.2/1.0), and Group E (1.5/1.0). A universal testing machine
(Kratos model K – 2000 MP) was used to measure modulus of elasticity values by
compression.</p></sec><sec><title>Results</title><p>Mean modulus of elasticity values were: Group A – 389.72 MPa, Group B – 529.19
MPa, Group C – 571.11 MPa, Group D – 470.35 MPa, Group E – 437.36 MPa.</p></sec><sec><title>Conclusion</title><p>The best mechanical characteristics and modulus of elasticity value comparable to
that of human trabecular bone were obtained when A/B ratio was 1:1.</p></sec></div></front><back><div1 type="bibliography"><listBibl><biblStruct><analytic><author><name sortKey="Cook, Sd" uniqKey="Cook S">SD Cook</name></author><author><name sortKey="Klawitter, Jj" uniqKey="Klawitter J">JJ Klawitter</name></author><author><name sortKey="Weinstein, Am" uniqKey="Weinstein A">AM Weinstein</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Giesen, Eb" uniqKey="Giesen E">EB Giesen</name></author><author><name sortKey="Ding, M" uniqKey="Ding M">M Ding</name></author><author><name sortKey="Dalstra, M" uniqKey="Dalstra M">M Dalstra</name></author><author><name sortKey="Van Eijden, Tm" uniqKey="Van Eijden T">TM Van Eijden</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Iplikcioglu, H" uniqKey="Iplikcioglu H">H Iplikçioglu</name></author><author><name sortKey="Akca, K" uniqKey="Akca K">K Akça</name></author><author><name sortKey="Cehrelli, Mc" uniqKey="Cehrelli M">MC Cehrelli</name></author><author><name sortKey="Sahin, S" uniqKey="Sahin S">S Sahin</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Klemetti, E" uniqKey="Klemetti E">E Klemetti</name></author><author><name sortKey="Vainio, P" uniqKey="Vainio P">P Vainio</name></author><author><name sortKey="Lassila, V" uniqKey="Lassila V">V Lassila</name></author><author><name sortKey="Alhava, E" uniqKey="Alhava E">E Alhava</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Lindh, C" uniqKey="Lindh C">C Lindh</name></author><author><name sortKey="Petersson, A" uniqKey="Petersson A">A Petersson</name></author><author><name sortKey="Klinge, B" uniqKey="Klinge B">B Klinge</name></author><author><name sortKey="Nilsson, M" uniqKey="Nilsson M">M Nilsson</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Mish, Ce" uniqKey="Mish C">CE Mish</name></author><author><name sortKey="Qu, Z" uniqKey="Qu Z">Z Qu</name></author><author><name sortKey="Bidez, Mw" uniqKey="Bidez M">MW Bidez</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="O Mahony, Am" uniqKey="O Mahony A">AM O'Mahony</name></author><author><name sortKey="Willians, Jl" uniqKey="Willians J">JL Willians</name></author><author><name sortKey="Katz, Jo" uniqKey="Katz J">JO Katz</name></author><author><name sortKey="Spencer, P" uniqKey="Spencer P">P Spencer</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Oyen, Ml" uniqKey="Oyen M">ML Oyen</name></author><author><name sortKey="Ferguson, Vl" uniqKey="Ferguson V">VL Ferguson</name></author><author><name sortKey="Bembey, Ak" uniqKey="Bembey A">AK Bembey</name></author><author><name sortKey="Bushby, Aj" uniqKey="Bushby A">AJ Bushby</name></author><author><name sortKey="Boyde, A" uniqKey="Boyde A">A Boyde</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Seong, Wj" uniqKey="Seong W">WJ Seong</name></author><author><name sortKey="Kim, Uk" uniqKey="Kim U">UK Kim</name></author><author><name sortKey="Swift, Jq" uniqKey="Swift J">JQ Swift</name></author><author><name sortKey="Heo, Yc" uniqKey="Heo Y">YC Heo</name></author><author><name sortKey="Hodges, Js" uniqKey="Hodges J">JS Hodges</name></author><author><name sortKey="Ko, Cc" uniqKey="Ko C">CC Ko</name></author></analytic></biblStruct><biblStruct><analytic><author><name sortKey="Tomatsu, Y" uniqKey="Tomatsu Y">Y Tomatsu</name></author><author><name sortKey="Kaimoto, K" uniqKey="Kaimoto K">K Kaimoto</name></author><author><name sortKey="Arai, M" uniqKey="Arai M">M Arai</name></author><author><name sortKey="Ide, Y" uniqKey="Ide Y">Y Ide</name></author></analytic></biblStruct></listBibl></div1></back></TEI><pmc article-type="research-article"><pmc-dir>properties open_access</pmc-dir>
<front><journal-meta><journal-id journal-id-type="nlm-ta">J Appl Oral Sci</journal-id><journal-id journal-id-type="iso-abbrev">J Appl Oral Sci</journal-id><journal-title-group><journal-title>Journal of Applied Oral Science</journal-title></journal-title-group><issn pub-type="ppub">1678-7757</issn><issn pub-type="epub">1678-7765</issn><publisher><publisher-name>Faculdade de Odontologia de Bauru da Universidade de São
Paulo</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="pmid">21437469</article-id><article-id pub-id-type="pmc">4245863</article-id><article-id pub-id-type="doi">10.1590/S1678-77572011000100010</article-id><article-categories><subj-group subj-group-type="heading"><subject>Original Articles</subject></subj-group></article-categories><title-group><article-title> Validation of an experimental polyurethane model for biomechanical
studies on implant-supported prosthesis – compression tests</article-title></title-group><contrib-group><contrib contrib-type="author"><name><surname>MORETTI NETO</surname><given-names>Rafael Tobias</given-names></name><xref ref-type="aff" rid="aff01">1</xref></contrib><contrib contrib-type="author"><name><surname>HIRAMATSU</surname><given-names>Daniel Afonso</given-names></name><xref ref-type="aff" rid="aff02">2</xref></contrib><contrib contrib-type="author"><name><surname>SUEDAM</surname><given-names>Valdey</given-names></name><xref ref-type="aff" rid="aff03">3</xref></contrib><contrib contrib-type="author"><name><surname>CONTI</surname><given-names>Paulo César Rodrigues</given-names></name><xref ref-type="aff" rid="aff04">4</xref></contrib><contrib contrib-type="author"><name><surname>RUBO</surname><given-names>José Henrique</given-names></name><xref ref-type="aff" rid="aff04">4</xref><xref ref-type="corresp" rid="c01"></xref></contrib></contrib-group><aff id="aff01"><label>1</label> DDs, MSc, PhD, Department of Clinics and Surgery, Dental School, Federal University of Alfenas, Alfenas, MG, Brazil.</aff><aff id="aff02"><label>2</label> DDs, MSc, Private Practice, Santos, SP, Brazil.</aff><aff id="aff03"><label>3</label> DDs, MSc, PhD, Private Practice, Bauru, SP, Brazil.</aff><aff id="aff04"><label>4</label> DDs, MSc, PhD, Associate Professor, Department of Prosthodontics, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.</aff><author-notes><corresp id="c01"><bold>Corresponding address:</bold> José Henrique Rubo -
Faculdade de Odontologia de Bauru - USP - Departamento de Prótese - Al. Dr.
Octávio Pinheiro Brisolla, 9-75 - Bauru, SP - Brasil - 17012-901 - e-mail:
<email>jrubo@fob.usp.br</email> - Phone/fax: 55 14 3235 8277</corresp></author-notes><pub-date pub-type="epub-ppub"><season>Jan-Feb</season><year>2011</year></pub-date><pmc-comment>Fake ppub date generated by PMC from publisher
pub-date/@pub-type='epub-ppub' </pmc-comment>
<pub-date pub-type="ppub"><season>Jan-Feb</season><year>2011</year></pub-date><volume>19</volume><issue>1</issue><fpage>47</fpage><lpage>51</lpage><history><date date-type="received"><day>19</day><month>5</month><year>2009</year></date><date date-type="rev-recd"><day>09</day><month>4</month><year>2010</year></date><date date-type="accepted"><day>27</day><month>4</month><year>2010</year></date></history><permissions><license license-type="open-access" xlink:href="http://creativecommons.org/licenses/by-nc/3.0/"><license-p>This is an Open Access article distributed under the terms of the Creative
Commons Attribution Non-Commercial License which permits unrestricted
non-commercial use, distribution, and reproduction in any medium, provided the
original work is properly cited.</license-p></license></permissions><abstract><sec><title>Objectives</title><p>The complexity and heterogeneity of human bone, as well as ethical issues, most
always hinder the performance of clinical trials. Thus, <italic>in vitro</italic>studies become an important source of information for the understanding of
biomechanical events on implantsupported prostheses, although study results cannot
be considered reliable unless validation studies are conducted. The purpose of
this work was to validate an artificial experimental model based on its modulus of
elasticity, to simulate the performance of human bone <italic>in vivo</italic> in
biomechanical studies of implant-supported prostheses.</p></sec><sec><title>Material and Methods</title><p>In this study, fast-curing polyurethane (F16 polyurethane, Axson) was used to
build 40 specimens that were divided into five groups. The following reagent
ratios (part A/part B) were used: Group A (0.5/1.0), Group B (0.8/1.0), Group C
(1.0/1.0), Group D (1.2/1.0), and Group E (1.5/1.0). A universal testing machine
(Kratos model K – 2000 MP) was used to measure modulus of elasticity values by
compression.</p></sec><sec><title>Results</title><p>Mean modulus of elasticity values were: Group A – 389.72 MPa, Group B – 529.19
MPa, Group C – 571.11 MPa, Group D – 470.35 MPa, Group E – 437.36 MPa.</p></sec><sec><title>Conclusion</title><p>The best mechanical characteristics and modulus of elasticity value comparable to
that of human trabecular bone were obtained when A/B ratio was 1:1.</p></sec></abstract><kwd-group><kwd>Polyurethanes</kwd><kwd>Validation studies</kwd><kwd>Dental implants</kwd></kwd-group><funding-group><award-group><funding-source>FAPESP</funding-source><award-id>2006/57414-8</award-id></award-group></funding-group></article-meta></front><body><sec sec-type="intro"><title>INTRODUCTION</title><p>Peri-implant bone resorption has been implicated in the success/failure of
osseointegrated implants, as well as in the maintenance of osseointegration after the
application of functional forces. Despite the high success rates reported, failures are
likely to occur. It is well established in the literature that late implant failures are
related to biomechanical complications, and that limited understanding on implant
biomechanics is the primary cause of these failures. Controlling the forces acting on
implants is essential for long-term success, and the adequate qualification and
quantification of these forces are crucial for treatment outcome. Measuring and
assessing these forces are a complex problem and a challenge to be solved<sup><xref rid="r03" ref-type="bibr">3</xref></sup>.</p><p>In humans, bone is not homogenous. Its physical properties vary greatly according to
species, age, gender, type (e.g. femoral, mandibular, cortical, and trabecular), and
even according to the location of sample harvesting. This heterogeneity hinders efforts
to model bone in finite element analysis and photoelastic studies<sup><xref rid="r07" ref-type="bibr">7</xref></sup>. Dental implant stability and functional
longevity are largely dependent on the supporting bone<sup><xref rid="r01" ref-type="bibr">1</xref></sup>. Implant failure has been reported to be greater in poor
quality bone. Given that bone implants are often placed in contact with trabecular bone,
knowledge of the mechanical properties of the trabecular bone in different areas of the
human mandible and maxilla may provide the understanding of the cause of higher failure
rates in poor quality bone<sup><xref rid="r06" ref-type="bibr">6</xref></sup>.</p><p>The modulus of elasticity is a material property of bone that may be affected by the
processes of apposition and alveolar resorption that occur following tooth loss. The
modulus of elasticity is a measure of the material rigidity and varies as a function of
both the density and microstructure of the bone. Tomatsu, et al.<sup><xref rid="r10" ref-type="bibr">10</xref></sup> (1996), assessed the modulus of
elasticity in small bone specimens from four adult male dried mandibles and concluded
that the modulus of elasticity of the mandible varied with bone site and orientation,
and that the mandibular bone showed anisotropic characteristics, reflecting the
complexity of its structure<sup><xref rid="r02" ref-type="bibr">2</xref>,<xref rid="r05" ref-type="bibr">5</xref></sup>. Same result was reported by Misch, Qu
and Bidez<sup><xref rid="r06" ref-type="bibr">6</xref></sup> (1999) who tested
compression in bone specimens and observed that the modulus of elasticity ranged from
24.9 to 240.0 MPa (mean value of 96.2 MPa) with cortical plates present, and from 3.5 to
125.6 MPa (mean value of 56.0 MPa) without cortical plates.</p><p>In order to obtain reliable data in experiments assessing the forces that are applied on
implants and transferred to the supporting bone, the use of strain gauges has been
recommended. However, <italic>in vivo</italic> strain gauge studies cannot be easily
conducted due to the difficulty in attaching the sensors to the oral cavity. Ideally,
the material used in this type of experiment, should have isotropic elastic
characteristics as well as physical and mechanical characteristics similar to those
found in the target bone region. Furthermore, it should be suitable for use in
<italic>in vitro</italic> studies of the distribution of the forces generated by
implant-supported prostheses.</p><p>Based on these grounds, it seems necessary to validate a homogeneous, artificial
experimental model with isotropic elastic properties, and modulus of elasticity and
density, similar to those found in the human medullar bone that could simulate human
bone performance in biomechanical studies of implant-supported prostheses. For such,
five groups of polyurethane specimens, differing in their composition by the reagents
content, were formed to test the null hypothesis that none of them can present a modulus
of elasticity compatible to bone to be used as bone model in biomechanical bench
tests.</p></sec><sec sec-type="materials|methods"><title>MATERIAL AND METHODS</title><sec><title>Specimens</title><p>Test specimens were made of fast-curing F16 polyurethane (Axson, Cergy, France),
usually used for casting molds and prototype models. Its major characteristics
include quick demolding, good temperature resistance after cure and low viscosity. It
is formed by two reagents: Polyol (part A) and Isocyanate (part B), and reaches 1.05
g/ cm<sup><xref rid="r03" ref-type="bibr">3</xref></sup> in density after
polymerization, according to the manufacturer.</p><p>Craft silicone rubber (Grau Industrial; São Paulo, SP, Brazil) was used,
according to the manufacturer’s instructions, to build a male/ female mold. This mold
allowed the shaping of 10 specimens measuring 9.53x7.73x7.73 mm (height x width x
depth) each (<xref ref-type="fig" rid="f01">Figure 1 A</xref> and <xref ref-type="fig" rid="f01">B</xref>).</p><fig id="f01" orientation="portrait" position="float"><label>Figure 1 A and B</label><caption><p>Specimen standardization measure 9.53x7.73x7.73 mm (height x width x depth)</p></caption><graphic xlink:href="jaos-19-01-0047-g01"></graphic></fig><p>Polyurethane specimens were obtained by using two 10-ml pipettes (one for Part A and
the other for part B) so that material contamination could be avoided. Both reagents
were placed in a glass container and mixed for 60 s for complete homogenization. The
mixture was then injected into the silicone mold. After 30 min, final curing was
achieved and specimens were demolded. The A/B ratios used in each study group are
shown in <xref ref-type="table" rid="t01">Table 1</xref>.</p><table-wrap id="t01" orientation="portrait" position="float"><label>Table 1</label><caption><p>Study groups according to A/B ratio</p></caption><table frame="hsides" rules="groups"><thead><tr style="background-color:#dcdcde"><th align="center" rowspan="1" colspan="1"><bold>Groups</bold></th><th align="center" rowspan="1" colspan="1"><bold>Number of specimens</bold></th><th align="center" rowspan="1" colspan="1"><bold>A/B ratio</bold></th></tr></thead><tbody><tr><td align="center" rowspan="1" colspan="1">A</td><td align="center" rowspan="1" colspan="1">8</td><td align="center" rowspan="1" colspan="1">0.5/1.0</td></tr><tr style="background-color:#dcdcde"><td align="center" rowspan="1" colspan="1">B</td><td align="center" rowspan="1" colspan="1">8</td><td align="center" rowspan="1" colspan="1">0.8/1.0</td></tr><tr><td align="center" rowspan="1" colspan="1">C</td><td align="center" rowspan="1" colspan="1">8</td><td align="center" rowspan="1" colspan="1">1.0/1.0</td></tr><tr style="background-color:#dcdcde"><td align="center" rowspan="1" colspan="1">D</td><td align="center" rowspan="1" colspan="1">8</td><td align="center" rowspan="1" colspan="1">1.2/1.0</td></tr><tr><td align="center" rowspan="1" colspan="1">E</td><td align="center" rowspan="1" colspan="1">8</td><td align="center" rowspan="1" colspan="1">1.5/1.0</td></tr></tbody></table></table-wrap></sec><sec><title>Testing</title><p>Eight specimens from each study group were put to compression testing in a universal
testing machine (Kratos Model K – 2000 MP; Kratos equipamentos Industriais Ltda.,
São Paulo, SP, Brazil) (<xref ref-type="fig" rid="f02">Figure 2</xref>).</p><fig id="f02" orientation="portrait" position="float"><label>Figure 2</label><caption><p>Compression test in Kratos Machine model K 2000 MP</p></caption><graphic xlink:href="jaos-19-01-0047-g02"></graphic></fig><p>The test machine was configured with a 500-kgf load cell, crosshead speed of 0.50
mm/min, at a constant temperature of 25ºC and relative humidity of 50%. The
compression results were recorded and a final report was generated. One-Way ANOVA and
Tukey’s test were performed to determine statistically significant differences among
groups at a significance level of 0.05.</p><p>Generated compression was calculated as follows:</p><mml:math id="e01"><mml:mstyle mathcolor="#000000" mathsize="12.0pt" mathvariant="normal"><mml:mi mathvariant="normal">T</mml:mi><mml:mspace width="0.33em"></mml:mspace><mml:mo>=</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mstyle mathsize="12.0pt"><mml:mfrac><mml:mi mathvariant="normal">P</mml:mi><mml:mi mathvariant="italic">So</mml:mi></mml:mfrac></mml:mstyle></mml:mstyle></mml:math><list list-type="simple"><list-item><p>Where: T=compression [Pa];</p></list-item><list-item><p> P=load [N];</p></list-item><list-item><p>So=original cross section [m].</p></list-item></list><p>Deformation was calculated as follows:</p><mml:math id="e02"><mml:mstyle mathcolor="#000000" mathsize="12.0pt" mathvariant="normal"><mml:mo mathvariant="normal">ɛ</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mo>=</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mstyle mathsize="12.0pt"><mml:mfrac><mml:mrow><mml:mi mathvariant="normal">(</mml:mi><mml:mi mathvariant="italic">L</mml:mi><mml:mo mathvariant="italic">−</mml:mo><mml:mi mathvariant="italic">Lo</mml:mi><mml:mi mathvariant="normal">)</mml:mi></mml:mrow><mml:mi mathvariant="italic">Lo</mml:mi></mml:mfrac></mml:mstyle><mml:mspace width="0.33em"></mml:mspace><mml:mo>=</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mstyle mathsize="12.0pt"><mml:mfrac><mml:mrow><mml:mo>Δ</mml:mo><mml:mi mathvariant="italic">L</mml:mi></mml:mrow><mml:mi mathvariant="italic">Lo</mml:mi></mml:mfrac></mml:mstyle></mml:mstyle></mml:math><list list-type="simple"><list-item><p>where: ε=deformation [non dimensional];</p></list-item><list-item><p>Lo=reference initial length (load zero) [m];</p></list-item><list-item><p>L=reference length for load <italic>P</italic> [m].</p></list-item></list><p>Finally, the modulus of elasticity was calculated as follows:</p><mml:math id="e03"><mml:mstyle mathcolor="#000000" mathsize="12.0pt" mathvariant="normal"><mml:mi mathvariant="normal">E</mml:mi><mml:mspace width="0.33em"></mml:mspace><mml:mo>=</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mstyle mathsize="12.0pt"><mml:mfrac><mml:mi mathvariant="normal">T</mml:mi><mml:mo mathvariant="normal">ɛ</mml:mo></mml:mfrac></mml:mstyle><mml:mspace width="0.33em"></mml:mspace><mml:mo>=</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mstyle mathsize="12.0pt"><mml:mfrac><mml:mrow><mml:mi mathvariant="normal">(</mml:mi><mml:mi mathvariant="normal">P</mml:mi><mml:mspace width="0.33em"></mml:mspace><mml:mo mathvariant="normal">×</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mi mathvariant="italic">Lo</mml:mi><mml:mi mathvariant="normal">)</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">(</mml:mi><mml:mi mathvariant="italic">So</mml:mi><mml:mspace width="0.33em"></mml:mspace><mml:mo mathvariant="normal">×</mml:mo><mml:mspace width="0.33em"></mml:mspace><mml:mo>Δ</mml:mo><mml:mi mathvariant="italic">L</mml:mi><mml:mi mathvariant="normal">)</mml:mi></mml:mrow></mml:mfrac></mml:mstyle></mml:mstyle></mml:math><p>where: Ε =modulus of elasticity [Pa].</p><p>The values of P and ΔL were calculated according to the elastic deformation of the
polyurethane specimen, represented in <xref ref-type="fig" rid="f03">Figure 3</xref>by the curve of compression versus linear deformation of the specimen during the
test.</p><fig id="f03" orientation="portrait" position="float"><label>Figure 3</label><caption><p>Compression versus linear deformation curve of the specimen after tension
test</p></caption><graphic xlink:href="jaos-19-01-0047-g03"></graphic></fig></sec></sec><sec sec-type="results"><title>RESULTS</title><p>Modulus of elasticity values clearly varied according to A/B ratio. Maximum compression
forces showed within-group variations; the mean values observed for groups A, B, C, D
and e were 2040.30±20.39 N, 2410.51±30.60 N, 2430.15±60.84 N,
2200.84±90.55 N, and 1900.33±30.22 N, respectively.</p><p>Modulus of elasticity values (389.72±18.58 MPa, 529.19±61.91 MPa,
571.11±58.17 MPa, 470.35±32.81, and 437.36±44.69 for groups A, B,
C, D, and e, respectively) differed among groups according to A/B ratio. <xref ref-type="table" rid="t02">Table 2</xref> shows the modulus of elasticity value
recorded in each specimen, the mean values and the statistically significant differences
found between groups as evidenced by the Tukey test at p=0.05.</p><table-wrap id="t02" orientation="portrait" position="float"><label>Table 2</label><caption><p>Mean modulus of elasticity (MPa) found for groups A, B, C, D and E</p></caption><table frame="hsides" rules="groups"><thead><tr style="background-color:#dcdcde"><th colspan="10" align="center" rowspan="1"><bold>Specimen</bold></th></tr></thead><tbody><tr><td align="center" rowspan="1" colspan="1"><bold>Group</bold></td><td align="center" rowspan="1" colspan="1">1</td><td align="center" rowspan="1" colspan="1">2</td><td align="center" rowspan="1" colspan="1">3</td><td align="center" rowspan="1" colspan="1">4</td><td align="center" rowspan="1" colspan="1">5</td><td align="center" rowspan="1" colspan="1">6</td><td align="center" rowspan="1" colspan="1">7</td><td align="center" rowspan="1" colspan="1">8</td><td align="center" rowspan="1" colspan="1">Mean</td></tr><tr style="background-color:#dcdcde"><td align="center" rowspan="1" colspan="1">A</td><td align="center" rowspan="1" colspan="1">361.17</td><td align="center" rowspan="1" colspan="1">379.23</td><td align="center" rowspan="1" colspan="1">379.23</td><td align="center" rowspan="1" colspan="1">399.19</td><td align="center" rowspan="1" colspan="1">379.23</td><td align="center" rowspan="1" colspan="1">399.19</td><td align="center" rowspan="1" colspan="1">421.37</td><td align="center" rowspan="1" colspan="1">399.19</td><td align="center" rowspan="1" colspan="1">389.72<sup>a</sup></td></tr><tr><td align="center" rowspan="1" colspan="1">B</td><td align="center" rowspan="1" colspan="1">459.81</td><td align="center" rowspan="1" colspan="1">442.78</td><td align="center" rowspan="1" colspan="1">498.13</td><td align="center" rowspan="1" colspan="1">597.76</td><td align="center" rowspan="1" colspan="1">498.13</td><td align="center" rowspan="1" colspan="1">597.76</td><td align="center" rowspan="1" colspan="1">569.29</td><td align="center" rowspan="1" colspan="1">569.29</td><td align="center" rowspan="1" colspan="1">529.19<sup>bb</sup></td></tr><tr style="background-color:#dcdcde"><td align="center" rowspan="1" colspan="1">C</td><td align="center" rowspan="1" colspan="1">478.20</td><td align="center" rowspan="1" colspan="1">629.22</td><td align="center" rowspan="1" colspan="1">543.42</td><td align="center" rowspan="1" colspan="1">597.76</td><td align="center" rowspan="1" colspan="1">543.42</td><td align="center" rowspan="1" colspan="1">664.18</td><td align="center" rowspan="1" colspan="1">543.42</td><td align="center" rowspan="1" colspan="1">569.29</td><td align="center" rowspan="1" colspan="1">571.11<sup>cbc</sup></td></tr><tr><td align="center" rowspan="1" colspan="1">D</td><td align="center" rowspan="1" colspan="1">497.73</td><td align="center" rowspan="1" colspan="1">442.43</td><td align="center" rowspan="1" colspan="1">519.37</td><td align="center" rowspan="1" colspan="1">442.43</td><td align="center" rowspan="1" colspan="1">477.02</td><td align="center" rowspan="1" colspan="1">459.44</td><td align="center" rowspan="1" colspan="1">426.63</td><td align="center" rowspan="1" colspan="1">497.73</td><td align="center" rowspan="1" colspan="1">470.35<sup>dbdd</sup></td></tr><tr style="background-color:#dcdcde"><td align="center" rowspan="1" colspan="1">E</td><td align="center" rowspan="1" colspan="1">446.15</td><td align="center" rowspan="1" colspan="1">474.04</td><td align="center" rowspan="1" colspan="1">399.19</td><td align="center" rowspan="1" colspan="1">474.04</td><td align="center" rowspan="1" colspan="1">421.37</td><td align="center" rowspan="1" colspan="1">399.19</td><td align="center" rowspan="1" colspan="1">505.64</td><td align="center" rowspan="1" colspan="1">379.23</td><td align="center" rowspan="1" colspan="1">437.36<sup>acdd</sup></td></tr></tbody></table><table-wrap-foot><fn><p>Different letters in columns indicate statistically significant difference at
5%.</p></fn></table-wrap-foot></table-wrap><p>One-Way ANOVA revealed statistically significant differences among groups.</p></sec><sec sec-type="discussion"><title>DISCUSSION</title><p>Polyurethane foam systems usually consist of two components. One of the components is
isocyanate and the other contains at least one polyol. In this study, fast-curing
polyurethane (F16 polyurethane, Axson) was used as it is easy to handle, providing
appropriate pot life and fast curing time. Its mechanical properties reflect the
response of this material to external mechanical influences manifested by its capacity
to develop reversible and irreversible deformations and to resist fracture. These
characteristics are often assessed by tests that investigate stress-deformation
relations.</p><p>Compression resistance tests are used to determine the amount and the speed of the force
required for the compression or rupture of a specimen placed between two parallel
plates. Based on this test, the modulus of elasticity is defined as the ratio of the
applied stress to the resulting deformation within the elastic limit at which
deformation is totally reversible and proportional to stress.</p><p>The modulus of elasticity is crucial for the validation of materials used in
experimental models because the comparison between the values obtained with those
reported in the literature for the trabecular bone is the basis for building a
reproducible, easy-to-handle model with isotropic characteristics. The A/B reagent ratio
of polyurethane recommended by the manufacturer to reach a mixture suitable for its
industrial purposes is 1:1. Nevertheless, bone properties are highly variable depending
on various aspects<sup><xref rid="r07" ref-type="bibr">7</xref></sup>. Therefore, it was
decided to introduce small variations in the mixing ratio of PU to verify whether it
would be possible to fabricate experimental models with varied moduli of elasticity.
Also, different mixing ratios were tested to determine in which group the modulus of
elasticity was closer to that of the human trabecular bone.</p><p>Our results show that, in group A specimens, curing time was greater than in the other
groups, with no sign of material expansion. A considerable heat release was also noted
for this group. The macroscopic characteristics of groups B, C and D were similar in
relation to curing time with no visible sign of material expansion or heat release. In
group E, a reduction in the final curing time was observed.</p><p>The modulus of elasticity ranged from 388.72 MPa in group A to 571.11 MPa in group C.
The Tukey test showed that group C significantly differed from groups A, D and e, but
not from group B. Moreover, the greatest modulus of elasticity value was observed in
group C specimens where A/B ratio was 1:1, that is, according to the manufacturer’s
instructions, also yields optimal structural characteristics. The maximum force applied
to the specimens was 2430.15 N, which allows the use of the specimens in biomechanical
studies as the forces acting on the mastication process do not exceed the values
found.</p><p>O’Mahony, et al.<sup><xref rid="r07" ref-type="bibr">7</xref></sup> (2000) found
different modulus of elasticity values in different mandibular regions (47 to 2283 MPa),
showing that bone is not homogeneous and that its physical properties may vary with
race, age, gender and the location from which the sample is taken. Klemetti, et
al.<sup><xref rid="r04" ref-type="bibr">4</xref></sup> (1993) using quantitative
computed tomography, found that mean trabecular bone mineral density was 1063
mg/cm<sup>3</sup> among 74 totally or nearly edentulous menopausal women. In
addition, bone mineral density was 1059 mg/cm<sup>3</sup> and 1067 mg/cm<sup>3</sup> in
dentate and edentate individuals, respectively. These results are consistent with the
mean density value after final hardening informed by the polyurethane manufacturer (1053
mg/ cm<sup>3</sup>). Mineral volume fraction also influences bone mechanical performance
and is directly proportional to its modulus of elasticity<sup><xref rid="r08" ref-type="bibr">8</xref></sup>.</p><p>Misch, Qu and Bidez<sup><xref rid="r06" ref-type="bibr">6</xref></sup> (1999) sought to
establish the relationships among bone density, modulus of elasticity, and ultimate
compressive strength of trabecular bone in the human mandible. They found that the
density of mandibular trabecular specimens ranged from 0.85 to 1.53 g/cm<sup>3</sup>,
with a mean value of 1.14 g/cm<sup>3</sup>. With the cortical plates present, the
modulus of elasticity ranged from 24.9 to 240.0 MPa (mean value of 96.2 MPa). Without
the cortical plates present, the modulus of elasticity ranged from 3.5 to 125.6 MPa
(mean value of 56.0 MPa). The ultimate compressive strength of the trabecular bone
ranged from 0.22 to 10.44 MPa (mean value of 3.9 MPa).</p><p>According to O’Mahony, et al.<sup><xref rid="r07" ref-type="bibr">7</xref></sup> (2000),
the modulus of elasticity of the mandibular bone may be affected by tooth loss and the
resorption of the alveolar process. In their work, these authors assessed apparent
density and modulus of elasticity values in several anatomic sites of the mandible.
Their results showed that apparent density ranged from 0.23 to 0.96 g/cm<sup> 3</sup>while modulus of elasticity values varied from 47 to 2283 MPa in the mandibular regions
evaluated. These data are in accordance with those obtained with polyurethane. In this
study, the modulus of elasticity found in specimens with a reagent ratio of 1:1 was
463.47±31.66 MPa. According to the manufacturer, this ratio yields a density of
1.05 g/cm<sup>3</sup> after cure. Seong, et al.<sup><xref rid="r09" ref-type="bibr">9</xref></sup> (2009) found a bone apparent density of 1.18 g/ cm<sup>3</sup>,
but with a considerably higher modulus of elasticity - 18.3GPa.</p><p>The results reported above show that bone quality within a same mandible is extremely
variable. This gives us more freedom to develop a reliable experimental model to be used
in biomechanical studies of implant-supported prostheses. Polyurethane with a reagent
ratio of 1:1 allows the building of experimental models with the desired characteristics
of isotropy, modulus of elasticity compatible to that reported in the literature, and
reproducibility.</p></sec><sec sec-type="conclusions"><title>CONCLUSIONS</title><p>Taking into consideration the limitations of the data obtained in this study, it seems
valid to conclude that:</p><p>1 – Final modulus of elasticity values varied according to A/B ratio.</p><p>2 – A/B ratio 1:1 yielded the best mechanical characteristics and a modulus of
elasticity value similar to that of the trabecular bone.</p><p>3 – A polyurethane experimental model build in a 1:1 ratio present an appropriate
modulus of elasticity to simulate bone in <italic>in vitro</italic> tests with strain
gauges.</p></sec></body><back><ack><title>ACKNOWLEDGEMENTS</title><p>This investigation was supported by FAPESP (The State of São Paulo Research
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