Thermal cycling distortion of porcelain fused to metal fixed partial dentures
Identifieur interne : 006665 ( Istex/Corpus ); précédent : 006664; suivant : 006666Thermal cycling distortion of porcelain fused to metal fixed partial dentures
Auteurs : Deniz Gemalmaz ; Semih Berksun ; Hasan Necdet Alkumru ; Cigdem KasapogluSource :
- The Journal of Prosthetic Dentistry [ 0022-3913 ] ; 1998.
English descriptors
- KwdEn :
- Abutment, Alloy, Alloy type, Axial wall, Change values, Cycle alloy, Cycle alloy retainer, Cycle retainer, Cycling, Degassing, Dent, Dentistry, Denture, Distortion, Distortion values, Framework length, Gemalmaz, Inner surface, Internal surfaces, Marginal distortion, Marmara university, Master model, Metal conditioning, Metal framework, Metal sheets, Molar, Molar retainers, Partial dentures, Porcelain, Porcelain application, Porcelain veneering, Premolar, Prosthet, Prosthet dent, Prosthetic, Prosthetic dentistry, Resilience, Retainer, Significant differences, Single crowns, Thermal cycling distortion, Variance results.
- Teeft :
- Abutment, Alloy, Alloy type, Axial wall, Change values, Cycle alloy, Cycle alloy retainer, Cycle retainer, Cycling, Degassing, Dent, Dentistry, Denture, Distortion, Distortion values, Framework length, Gemalmaz, Inner surface, Internal surfaces, Marginal distortion, Marmara university, Master model, Metal conditioning, Metal framework, Metal sheets, Molar, Molar retainers, Partial dentures, Porcelain, Porcelain application, Porcelain veneering, Premolar, Prosthet, Prosthet dent, Prosthetic, Prosthetic dentistry, Resilience, Retainer, Significant differences, Single crowns, Thermal cycling distortion, Variance results.
Abstract
Abstract: Statement of problem. The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. Purpose. This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. Material and methods. A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. Results. Measured differences between the 2 firing stages ranged from –47 to 81.7 μm. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. Conclusions. A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal. (J Prosthet Dent 1998;80:654-60.)
Url:
DOI: 10.1016/S0022-3913(98)70051-4
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veneering</term><term>Premolar</term><term>Prosthet</term><term>Prosthet dent</term><term>Prosthetic</term><term>Prosthetic dentistry</term><term>Resilience</term><term>Retainer</term><term>Significant differences</term><term>Single crowns</term><term>Thermal cycling distortion</term><term>Variance results</term></keywords><keywords scheme="Teeft" xml:lang="en"><term>Abutment</term><term>Alloy</term><term>Alloy type</term><term>Axial wall</term><term>Change values</term><term>Cycle alloy</term><term>Cycle alloy retainer</term><term>Cycle retainer</term><term>Cycling</term><term>Degassing</term><term>Dent</term><term>Dentistry</term><term>Denture</term><term>Distortion</term><term>Distortion values</term><term>Framework length</term><term>Gemalmaz</term><term>Inner surface</term><term>Internal surfaces</term><term>Marginal distortion</term><term>Marmara university</term><term>Master model</term><term>Metal conditioning</term><term>Metal framework</term><term>Metal sheets</term><term>Molar</term><term>Molar retainers</term><term>Partial dentures</term><term>Porcelain</term><term>Porcelain application</term><term>Porcelain veneering</term><term>Premolar</term><term>Prosthet</term><term>Prosthet dent</term><term>Prosthetic</term><term>Prosthetic dentistry</term><term>Resilience</term><term>Retainer</term><term>Significant differences</term><term>Single crowns</term><term>Thermal cycling distortion</term><term>Variance results</term></keywords></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Abstract: Statement of problem. The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. Purpose. This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. Material and methods. A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. Results. Measured differences between the 2 firing stages ranged from –47 to 81.7 μm. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. Conclusions. A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal. 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The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. Purpose. This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. Material and methods. A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. Results. Measured differences between the 2 firing stages ranged from –47 to 81.7 μm. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. Conclusions. A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal. (J Prosthet Dent 1998;80:654-60.)</abstract><qualityIndicators><score>8.593</score><pdfWordCount>3593</pdfWordCount><pdfCharCount>23534</pdfCharCount><pdfVersion>1.3</pdfVersion><pdfPageCount>7</pdfPageCount><pdfPageSize>612 x 792 pts (letter)</pdfPageSize><refBibsNative>true</refBibsNative><abstractWordCount>273</abstractWordCount><abstractCharCount>1855</abstractCharCount><keywordCount>0</keywordCount></qualityIndicators><title>Thermal cycling distortion of porcelain fused to metal fixed partial dentures</title><pmid><json:string>9830069</json:string></pmid><pii><json:string>S0022-3913(98)70051-4</json:string></pii><genre><json:string>research-article</json:string></genre><host><title>The Journal of Prosthetic Dentistry</title><language><json:string>unknown</json:string></language><publicationDate>1998</publicationDate><issn><json:string>0022-3913</json:string></issn><pii><json:string>S0022-3913(05)X7059-7</json:string></pii><volume>80</volume><issue>6</issue><pages><first>654</first><last>660</last></pages><genre><json:string>journal</json:string></genre></host><namedEntities><unitex><date><json:string>1998</json:string></date><geogName></geogName><orgName><json:string>Turkey Statement</json:string><json:string>Ankara University</json:string><json:string>Department of Prosthodontics, Faculty of Dentistry, Ankara University</json:string><json:string>Department of Prosthodontics, Faculty of Dentistry, Marmara University</json:string></orgName><orgName_funder></orgName_funder><orgName_provider></orgName_provider><persName><json:string>Hasan Necdet</json:string><json:string>I. Analysis</json:string><json:string>Strating</json:string><json:string>AL Fig</json:string><json:string>Van Rensburg</json:string></persName><placeName><json:string>Paris</json:string><json:string>Germany</json:string><json:string>Bremen</json:string><json:string>Liechtenstein</json:string><json:string>Japan</json:string><json:string>Tokyo</json:string><json:string>France</json:string><json:string>Schaan</json:string></placeName><ref_url></ref_url><ref_bibl><json:string>Ando et al.</json:string><json:string>Buchanan et al.</json:string></ref_bibl><bibl></bibl></unitex></namedEntities><ark><json:string>ark:/67375/6H6-6374JRWZ-M</json:string></ark><categories><wos><json:string>1 - science</json:string><json:string>2 - dentistry, oral surgery & medicine</json:string></wos><scienceMetrix><json:string>1 - health sciences</json:string><json:string>2 - clinical medicine</json:string><json:string>3 - dentistry</json:string></scienceMetrix><scopus><json:string>1 - Health Sciences</json:string><json:string>2 - Dentistry</json:string><json:string>3 - Oral Surgery</json:string></scopus><inist><json:string>1 - sciences appliquees, technologies et medecines</json:string><json:string>2 - sciences biologiques et medicales</json:string><json:string>3 - sciences medicales</json:string></inist></categories><publicationDate>1998</publicationDate><copyrightDate>1998</copyrightDate><doi><json:string>10.1016/S0022-3913(98)70051-4</json:string></doi><id>CE77DD901A191752F1347AC78804F04273F0648E</id><score>1</score><fulltext><json:item><extension>pdf</extension><original>true</original><mimetype>application/pdf</mimetype><uri>https://api.istex.fr/document/CE77DD901A191752F1347AC78804F04273F0648E/fulltext/pdf</uri></json:item><json:item><extension>zip</extension><original>false</original><mimetype>application/zip</mimetype><uri>https://api.istex.fr/document/CE77DD901A191752F1347AC78804F04273F0648E/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/CE77DD901A191752F1347AC78804F04273F0648E/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a" type="main" xml:lang="en">Thermal cycling distortion of porcelain fused to metal fixed partial dentures</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>ELSEVIER</publisher><availability><p>©1998 Editorial Council of The Journal of Prosthetic Dentistry.</p></availability><date>1998</date></publicationStmt><notesStmt><note>a Associate Professor, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</note><note>b Professor, Department of Prosthodontics, Faculty of Dentistry, Ankara University.</note><note>c Professor, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</note><note>d Research assistant, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</note><note>Reprint requests to: Dr Deniz Gemalmaz, Marmara Universitesi, Dis Hekimligi Fakultesi,80200 Nisantasi, Istanbul, TURKEY</note><note>0022-3913/98/$5.00 + 0. 10/1/92982</note><note type="content">Table I: Analysis of variance results of mean changes in internal fit</note><note type="content">Table II: Analysis of variance results of mean changes in framework length</note></notesStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a" type="main" xml:lang="en">Thermal cycling distortion of porcelain fused to metal fixed partial dentures</title><author xml:id="author-0000"><persName><forename type="first">Deniz</forename><surname>Gemalmaz</surname></persName><roleName type="degree">DDS, PhDa</roleName><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation></author><author xml:id="author-0001"><persName><forename type="first">Semih</forename><surname>Berksun</surname></persName><roleName type="degree">DDS, PhDb</roleName><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation></author><author xml:id="author-0002"><persName><forename type="first">Hasan Necdet</forename><surname>Alkumru</surname></persName><roleName type="degree">DDS, PhDc</roleName><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation></author><author xml:id="author-0003"><persName><forename type="first">Cigdem</forename><surname>Kasapoglu</surname></persName><roleName type="degree">DDSd</roleName><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation></author><idno type="istex">CE77DD901A191752F1347AC78804F04273F0648E</idno><idno type="DOI">10.1016/S0022-3913(98)70051-4</idno><idno type="PII">S0022-3913(98)70051-4</idno></analytic><monogr><title level="j">The Journal of Prosthetic Dentistry</title><title level="j" type="abbrev">YMPR</title><idno type="pISSN">0022-3913</idno><idno type="PII">S0022-3913(05)X7059-7</idno><imprint><publisher>ELSEVIER</publisher><date type="published" when="1998"></date><biblScope unit="volume">80</biblScope><biblScope unit="issue">6</biblScope><biblScope unit="page" from="654">654</biblScope><biblScope unit="page" to="660">660</biblScope></imprint></monogr></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>1998</date></creation><langUsage><language ident="en">en</language></langUsage><abstract xml:lang="en"><p>Statement of problem. The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. Purpose. This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. Material and methods. A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. Results. Measured differences between the 2 firing stages ranged from –47 to 81.7 μm. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. Conclusions. A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal. (J Prosthet Dent 1998;80:654-60.)</p></abstract></profileDesc><revisionDesc><change when="1998">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><extension>txt</extension><original>false</original><mimetype>text/plain</mimetype><uri>https://api.istex.fr/document/CE77DD901A191752F1347AC78804F04273F0648E/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="Elsevier doc found" wicri:toSee="Elsevier, no converted or simple article"><istex:xmlDeclaration>version="1.0" encoding="utf-8"</istex:xmlDeclaration><istex:docType PUBLIC="-//ES//DTD journal article DTD version 5.0.1//EN//XML" URI="art501.dtd" name="istex:docType"><istex:entity SYSTEM="gr1" NDATA="IMAGE" name="gr1"></istex:entity><istex:entity SYSTEM="gr2" NDATA="IMAGE" name="gr2"></istex:entity><istex:entity SYSTEM="gr3" NDATA="IMAGE" name="gr3"></istex:entity><istex:entity SYSTEM="gr4" NDATA="IMAGE" name="gr4"></istex:entity><istex:entity SYSTEM="gr5" NDATA="IMAGE" name="gr5"></istex:entity><istex:entity SYSTEM="gr6" NDATA="IMAGE" name="gr6"></istex:entity><istex:entity SYSTEM="gr7" NDATA="IMAGE" name="gr7"></istex:entity></istex:docType><istex:document><article docsubtype="fla" xml:lang="en"><item-info><jid>YMPR</jid><aid>92982</aid><ce:pii>S0022-3913(98)70051-4</ce:pii><ce:doi>10.1016/S0022-3913(98)70051-4</ce:doi><ce:copyright type="other" year="1998">Editorial Council of The Journal of Prosthetic Dentistry.</ce:copyright></item-info><ce:floats><ce:table id="tab1" colsep="0" rowsep="0" frame="topbot"><ce:label>Table I</ce:label><ce:caption><ce:simple-para>Analysis of variance results of mean changes in internal fit</ce:simple-para></ce:caption><tgroup cols="6"><colspec colname="col1" colsep="0"></colspec><colspec colname="col2" colsep="0"></colspec><colspec colname="col3" colsep="0"></colspec><colspec colname="col4" colsep="0"></colspec><colspec colname="col5" colsep="0"></colspec><colspec colname="col6" colsep="0"></colspec><thead><row><entry>Source</entry><entry align="center">df</entry><entry align="center">Sum of squares</entry><entry align="center">Mean squares</entry><entry align="center">F-test</entry><entry align="center">P value</entry></row></thead><tbody><row><entry><ce:italic>Between-subjects effects</ce:italic></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry></row><row><entry>Alloy</entry><entry align="center">1</entry><entry align="center">33157</entry><entry align="center">33157</entry><entry align="center">3</entry><entry align="center">.1012</entry></row><row><entry>Retainer</entry><entry align="center">1</entry><entry align="center">118118</entry><entry align="center">118118</entry><entry align="center">10</entry><entry align="center">.0028*</entry></row><row><entry>Axial wall</entry><entry align="center">2</entry><entry align="center">2027146</entry><entry align="center">1013573</entry><entry align="center">85</entry><entry align="center">.0001*</entry></row><row><entry>Alloy × retainer</entry><entry align="center">1</entry><entry align="center">33</entry><entry align="center">33</entry><entry align="center">3E-3</entry><entry align="center">.9582</entry></row><row><entry>Alloy × axial wall</entry><entry align="center">2</entry><entry align="center">72694</entry><entry align="center">36347</entry><entry align="center">3</entry><entry align="center">.0561</entry></row><row><entry>Retainer × axial wall</entry><entry align="center">2</entry><entry align="center">254931</entry><entry align="center">127465</entry><entry align="center">11</entry><entry align="center">.0001*</entry></row><row><entry>Alloy × retainer × axial wall</entry><entry align="center">2</entry><entry align="center">13633</entry><entry align="center">6616</entry><entry align="center">1</entry><entry align="center">.5671</entry></row><row><entry>Residual</entry><entry align="center">48</entry><entry align="center">569953</entry><entry align="center">11874</entry><entry align="center"></entry><entry align="center"></entry></row><row><entry><ce:italic>Within-subjects effects</ce:italic></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry></row><row><entry>Firing cycle</entry><entry align="center">2</entry><entry align="center">14173</entry><entry align="center">7087</entry><entry align="center">6</entry><entry align="center">.0051*</entry></row><row><entry>Alloy × firing cycle</entry><entry align="center">2</entry><entry align="center">2874</entry><entry align="center">1437</entry><entry align="center">1</entry><entry align="center">.3271</entry></row><row><entry>Retainer × firing cycle</entry><entry align="center">2</entry><entry align="center">4686</entry><entry align="center">2343</entry><entry align="center">2</entry><entry align="center">.1638</entry></row><row><entry>Axial wall × firing cycle</entry><entry align="center">4</entry><entry align="center">21847</entry><entry align="center">5462</entry><entry align="center">4</entry><entry align="center">.0031*</entry></row><row><entry>Alloy × retainer × firing cycle</entry><entry align="center">2</entry><entry align="center">2423</entry><entry align="center">1212</entry><entry align="center">1</entry><entry align="center">.3891</entry></row><row><entry>Alloy × axial wall × firing cycle</entry><entry align="center">4</entry><entry align="center">2501</entry><entry align="center">625</entry><entry align="center">5E-1</entry><entry align="center">.7416</entry></row><row><entry>Retainer × axial wall × firing cycle</entry><entry align="center">4</entry><entry align="center">7725</entry><entry align="center">1931</entry><entry align="center">2</entry><entry align="center">.2026</entry></row><row><entry>Alloy × retainer × axial wall × firing cycle</entry><entry align="center">4</entry><entry align="center">4580</entry><entry align="center">1145</entry><entry align="center">1</entry><entry align="center">.4668</entry></row><row><entry>Residual</entry><entry align="center">96</entry><entry align="center">122019</entry><entry align="center">1271</entry><entry align="center"></entry><entry align="center"></entry></row><row><entry namest="col1" nameend="col6">*Statistically significant.</entry></row></tbody></tgroup></ce:table><ce:table id="tab2" colsep="0" rowsep="0" frame="topbot"><ce:label>Table II</ce:label><ce:caption><ce:simple-para>Analysis of variance results of mean changes in framework length</ce:simple-para></ce:caption><tgroup cols="6"><colspec colname="col1" colsep="0"></colspec><colspec colname="col2" colsep="0"></colspec><colspec colname="col3" colsep="0"></colspec><colspec colname="col4" colsep="0"></colspec><colspec colname="col5" colsep="0"></colspec><colspec colname="col6" colsep="0"></colspec><thead><row><entry>Source</entry><entry align="center">df</entry><entry align="center">Sum of squares</entry><entry align="center">Mean squares</entry><entry align="center">F-test</entry><entry align="center">P value</entry></row></thead><tbody><row><entry><ce:italic>Between-subjects effects</ce:italic></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry></row><row><entry>Alloy</entry><entry align="center">1</entry><entry align="center">172.8</entry><entry align="center">172.8</entry><entry align="center">3.1</entry><entry align="center">.1186</entry></row><row><entry>Residual</entry><entry align="center">8</entry><entry align="center">452.4</entry><entry align="center">56.6</entry><entry align="center"></entry><entry align="center"></entry></row><row><entry><ce:italic>Within-subjects effects</ce:italic></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry></row><row><entry>Firing cycle</entry><entry align="center">2</entry><entry align="center">375.2</entry><entry align="center">187.6</entry><entry align="center">8.3</entry><entry align="center">.0033*</entry></row><row><entry>Alloy × firing cycle</entry><entry align="center">2</entry><entry align="center">72.8</entry><entry align="center">36.4</entry><entry align="center">1.6</entry><entry align="center">.2292</entry></row><row><entry>Residual</entry><entry align="center">16</entry><entry align="center">360</entry><entry align="center">22.5</entry><entry align="center"></entry><entry align="center"></entry></row><row><entry namest="col1" nameend="col6"></entry></row></tbody></tgroup><ce:legend><ce:simple-para>Statistically significant.</ce:simple-para></ce:legend></ce:table></ce:floats><head><ce:article-footnote><ce:label>☆</ce:label><ce:note-para><ce:sup>a</ce:sup> Associate Professor, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</ce:note-para></ce:article-footnote><ce:article-footnote><ce:label>☆☆</ce:label><ce:note-para><ce:sup>b</ce:sup> Professor, Department of Prosthodontics, Faculty of Dentistry, Ankara University.</ce:note-para></ce:article-footnote><ce:article-footnote><ce:label>★</ce:label><ce:note-para><ce:sup>c</ce:sup> Professor, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</ce:note-para></ce:article-footnote><ce:article-footnote><ce:label>★★</ce:label><ce:note-para><ce:sup>d</ce:sup> Research assistant, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</ce:note-para></ce:article-footnote><ce:article-footnote><ce:label>♢</ce:label><ce:note-para>Reprint requests to: Dr Deniz Gemalmaz, Marmara Universitesi, Dis Hekimligi Fakultesi,80200 Nisantasi, Istanbul, TURKEY</ce:note-para></ce:article-footnote><ce:article-footnote><ce:label>♢♢</ce:label><ce:note-para>0022-3913/98/$5.00 + 0. <ce:bold>10/1/92982</ce:bold></ce:note-para></ce:article-footnote><ce:title>Thermal cycling distortion of porcelain fused to metal fixed partial dentures</ce:title><ce:author-group><ce:author><ce:given-name>Deniz</ce:given-name><ce:surname>Gemalmaz</ce:surname><ce:degrees>DDS, PhD<ce:sup>a</ce:sup></ce:degrees></ce:author><ce:author><ce:given-name>Semih</ce:given-name><ce:surname>Berksun</ce:surname><ce:degrees>DDS, PhD<ce:sup>b</ce:sup></ce:degrees></ce:author><ce:author><ce:given-name>Hasan Necdet</ce:given-name><ce:surname>Alkumru</ce:surname><ce:degrees>DDS, PhD<ce:sup>c</ce:sup></ce:degrees></ce:author><ce:author><ce:given-name>Cigdem</ce:given-name><ce:surname>Kasapoglu</ce:surname><ce:degrees>DDS<ce:sup>d</ce:sup></ce:degrees></ce:author><ce:affiliation><ce:textfn>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</ce:textfn></ce:affiliation></ce:author-group><ce:abstract><ce:section-title>Abstract</ce:section-title><ce:abstract-sec><ce:simple-para><ce:bold>Statement of problem.</ce:bold> The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. <ce:bold>Purpose.</ce:bold> This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. <ce:bold>Material and methods.</ce:bold> A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. <ce:bold>Results.</ce:bold> Measured differences between the 2 firing stages ranged from –47 to 81.7 μm. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. <ce:bold>Conclusions.</ce:bold> A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal. (J Prosthet Dent 1998;80:654-60.)</ce:simple-para></ce:abstract-sec></ce:abstract></head><body><ce:sections><ce:para><ce:display><ce:textbox><ce:textbox-body><ce:sections><ce:para><ce:bold><ce:italic>Thermal cycling distortion occurred in porcelain fused to metal fixed partial denture frameworks during porcelain application firing. Deterioration of fit, observed, resulted in poorer vertical fit of the framework that could be clinically unacceptable. In addition, thermal cycling distortion occurred regardless of the alloy type because comparison of nickel-chromium and palladium-copper alloys revealed no significant difference.</ce:italic></ce:bold></ce:para></ce:sections></ce:textbox-body></ce:textbox></ce:display></ce:para><ce:para>It has been widely observed that the as-cast fit of metal-ceramic restorations deteriorates during the high temperature firing cycles used for porcelain veneer application.<ce:cross-refs refid="bib1 bib2 bib3 bib4 bib5 bib6 bib7 bib8 bib9 bib10 bib11 bib12 bib13 bib14 bib15 bib16 bib17 bib18 bib19"><ce:sup>1-19</ce:sup></ce:cross-refs> The cause of this thermal cycling distortion has been contributed to various factors. However, there is a lack of agreement on the actual cause of the thermal cycling distortion of metal-ceramic frameworks.</ce:para><ce:para>On the basis of the results of the previous studies, a consensus can be made in 2 areas: (1) The timing of the deformation is such that most of the distortion occurs during the initial oxidation of the alloy and small changes continue during the subsequent heating and porcelain applications.<ce:cross-refs refid="bib1 bib3 bib4 bib5 bib7 bib12 bib15 bib16 bib17 bib18"><ce:sup>1,3-5,7,12,15-18</ce:sup></ce:cross-refs> (2) The metal framework shows a complex pattern of distortion due to its multiwalled configuration and it is hard to define a single pattern of distortion for all situations.<ce:cross-refs refid="bib13 bib18"><ce:sup>13,18</ce:sup></ce:cross-refs></ce:para><ce:para>Apart from the lack of consensus on the cause of the thermal cycling distortion, another problem existing with the related studies is that, most of the studies existing in the literature were made using single crown models. Ando et al.<ce:cross-ref refid="bib1"><ce:sup>1</ce:sup></ce:cross-ref> used open-ended castings cast from 5 different gold-based alloys to compare the deformation of gold alloys during porcelain firing cycle. Studies that followed examined the thermal cycling distortion of similar margin designs, in single crowns, using a scanning electron microscope technique.<ce:cross-refs refid="bib2 bib5 bib10 bib19"><ce:sup>2,5,10,19</ce:sup></ce:cross-refs> Buchanan et al.<ce:cross-ref refid="bib6"><ce:sup>6</ce:sup></ce:cross-ref> measured marginal distortion on repeated firings of 2 alloys by using a machined stainless steel die system to have standardized coping. The system of coping fabrication described by Buchanan et al.<ce:cross-ref refid="bib6"><ce:sup>6</ce:sup></ce:cross-ref> was also used by other investigators.<ce:cross-refs refid="bib12 bib16 bib20"><ce:sup>12,16,20</ce:sup></ce:cross-refs> Another study that was performed on single copings to evaluate marginal distortion was made by DeHoff and Anusavice<ce:cross-ref refid="bib9"><ce:sup>9</ce:sup></ce:cross-ref> with finite element analysis.</ce:para><ce:para>Campbell and Pelletier<ce:cross-ref refid="bib14"><ce:sup>14</ce:sup></ce:cross-ref> created an experimental design that was composed of a single axial wall casting, fitting on a machined die representing one wall of a full crown preparation. Their aim was to maximize the measuring sensitivity and to eliminate the casting variables to allow direct measurement of casting distortion. Bryant and Nicholls<ce:cross-ref refid="bib4"><ce:sup>4</ce:sup></ce:cross-ref> performed on an experimental model of a sectioned aluminum rod seems to be the earliest study about thermal cycling distortion of multiple unit castings. Few studies have then investigated the deformation of the fixed partial denture (FPD) frameworks on master models of prepared abutments.<ce:cross-refs refid="bib7 bib8 bib13"><ce:sup>7,8,13</ce:sup></ce:cross-refs> The number of studies that were performed on an FPD framework design is too limited, and it is apparent that there is a need for a multidimensional analysis of framework distortion on bridgework designed frameworks.</ce:para><ce:para>Therefore the purpose of this study was to evaluate the multidimensional thermal cycling distortion of 3-unit porcelain fused to metal framework at different firing stages.</ce:para><ce:section><ce:section-title>MATERIAL AND METHODS</ce:section-title><ce:para>A master model was designed to represent the 2 abutments of a 3-unit FPD that replaced a missing mandibular molar (Fig. 1).
<ce:display><ce:figure><ce:label>Fig. 1</ce:label><ce:caption><ce:simple-para>Experimental model.</ce:simple-para></ce:caption> <ce:link locator="gr1"></ce:link></ce:figure></ce:display>The model was cast in a base metal alloy. Abutments were machined to a height of 7 mm with a taper of 4 degrees and chamfer marginal design was constructed. Both of the abutments and the pontic were prepared to receive a porcelain fused to metal crown with full porcelain coverage.</ce:para><ce:para>To create a wax pattern of 0.4-mm uniform thickness, Adapta deep drawing system (Bego, Bremen, Germany) was used. To create uniform pontics, a master pontic was developed to the related edentulous space and by having a silicone mold, uniform pontics were duplicated. Ten individual castings were made by using the standardized techniques in a vacuum-pressure casting machine (Nautilus, Bego). Half of the copings were cast in a Ni-Cr alloy (Wiron 99, Bego) and the other half in a Pd-Cu alloy (Begopal, Bego).</ce:para><ce:para>Cooled castings were cleaned, adjusted to ensure complete seating on the master model and finished with aluminum oxide stones in preparation for porcelain application. The frameworks were subjected to metal-conditioning firing according to the manufacturer’s recommendations. All the castings were fired under air pressure at 960°C. Holding time for Begopal and Wiron 99 alloy were 3 and 10 minutes, respectively. Sandblasting procedure is recommended for Wiron 99 alloy to remove the excess oxide layer. However, to avoid possible metal loss during sandblasting, this procedure was eliminated. Ivoclar IPS porcelain (Ivoclar, Schaan, Liechtenstein) was used for both the opaque and the body porcelain applications according to the manufacturer’s recommendations. For application of body porcelain, a split mold was used to create a uniform contour (Fig. 2).
<ce:display><ce:figure><ce:label>Fig. 2</ce:label><ce:caption><ce:simple-para>Split mold for application of porcelain.</ce:simple-para></ce:caption> <ce:link locator="gr2"></ce:link></ce:figure></ce:display>Porcelain application involved 1 degassing firing, 2 opaque porcelain firings, 2 body porcelain firings, and 1 glaze firing.</ce:para><ce:section><ce:section-title>Inner fit change measurements</ce:section-title><ce:para>Distortion of the frameworks were measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. To measure the distance between the casting and the retainer walls, replicas were made of the intermediate space between the inner surface of the metal framework and the metal die surfaces. This was achieved by coating the inner surface of the metal framework with a thin layer of light body addition silicone material (Extrude, Kerr Mfg., Paris, France); after which the denture was placed onto the master model and a standard load of 5 kg was applied.<ce:cross-ref refid="bib21"><ce:sup>21</ce:sup></ce:cross-ref> After the impression material set, the framework was removed, adhering a thin film of light body material to the outer surfaces of the abutments, which represented the discrepancy between framework and retainers. For the purpose of stabilization, a heavy body silicone material (Extrude, Kerr Mfg.) was applied over the abutments with an acrylic resin index. This procedure made it possible to remove and handle the intermediate replica of the light body material. After these silicone materials were removed from the master model, a medium viscosity silicone material (Kerr Extrude, Kerr Division, France) that adhered with the light body film was injected into the abutment spaces.</ce:para><ce:para>The replica specimens were bisectioned with a scalpel in mesiodistal direction. To standardize the bisectioning procedure, fixed splits were made on mesial and distal sides of the outer acrylic resin index, and the silicone replicas were sectioned with the aid of these splits. A reflection microscope (Nikon, Tokyo, Japan), with a measuring accuracy of 1 μm, was used at ×100 magnification for measurements. Measurements of film thicknesses were performed along mesial, occlusal, and distal walls of each retainer with 1-mm intervals. Measurements were analyzed which determined average fit for each of the 3 axial walls of both premolar and molar retainers.</ce:para></ce:section><ce:section><ce:section-title>Horizontal measurements</ce:section-title><ce:para>An acrylic resin index was used to make certain reference marks that were placed to the midpoints of both the mesial finish line of premolar retainer and the distal finish line of molar retainer during wax pattern construction. The distance between these 2 reference marks, the total length of the framework, was measured with a digital micrometer with a measuring accuracy of 1 μm.</ce:para></ce:section><ce:section><ce:section-title>Vertical measurements</ce:section-title><ce:para>Vertical pins of 2 mm height were placed on the occlusal surfaces of both premolar and molar retainers during wax pattern fabrication, and they were used as certain reference marks for the assessment of vertical fit changes. Vertical fit of each retainer was recorded by using a vertical dial gauge with a measuring capability of 1.27 μm (Fig. 3)
<ce:display><ce:figure><ce:label>Fig. 3</ce:label><ce:caption><ce:simple-para>Measurement of vertical fit by using dial gauge.</ce:simple-para></ce:caption> <ce:link locator="gr3"></ce:link></ce:figure></ce:display>. Each measurement was repeated 3 times.</ce:para><ce:para>The measurements (inner fit, horizontal framework length, and vertical fit) were made (1) initially, (2) after degassing and, (3) after glaze firing. Differences between the initial measurements and the degassing measurements created the distortion values of the retainers for degassing firing. The distortion values of porcelain application were calculated by subtracting the measurements of degassing firing from the measurements of glaze firing.</ce:para><ce:para>The results obtained in 3 dimensions were compiled and a repeated measures analysis of variance (ANOVA) was performed at a significance level of 0.05 to detect statistically significant differences among the groups.</ce:para></ce:section></ce:section><ce:section><ce:section-title>RESULTS</ce:section-title><ce:para>Arithmetic means and standard deviations of the inner fit changes of premolar and molar retainers of Ni-Cr and Pd-Cu frameworks are illustrated in Figures 4 and 5, respectively.
<ce:display><ce:figure id="fig4"><ce:label>Fig. 4</ce:label><ce:caption><ce:simple-para>Mean inner fit changes observed for Ni-Cr alloy as function of retainer and axial wall. Numbers above bars indicate mean values.</ce:simple-para></ce:caption> <ce:link locator="gr4"></ce:link></ce:figure></ce:display><ce:display><ce:figure id="fig5"><ce:label>Fig. 5</ce:label><ce:caption><ce:simple-para>Mean inner fit changes observed for Pd-Cu alloy as function of retainer and axial wall. Numbers above bars indicate mean values.</ce:simple-para></ce:caption> <ce:link locator="gr5"></ce:link></ce:figure></ce:display>Bar graphs reflect the changes between the prefiring measurements and the various firing cycles; thus, they are not additive. Both positive and negative values were possible. Positive values imply an increase in gap and a poorer fit, whereas negative values indicate a decrease in gap and better adaptation of the axial wall. The mean differences between the initial inner adaptation and the fit after the firing cycles ranges from –47 to 81.7 μm.</ce:para><ce:para>Mean values of inner fit change for porcelain application firing were higher in magnitude than the values of metal conditioning firing; ANOVA results revealed that this difference was statistically significant (Table I).
<ce:float-anchor refid="tab1"></ce:float-anchor><ce:cross-ref refid="tab1">Table I</ce:cross-ref> presents the mean inner fit changes recorded for 2 alloys as a function of firing cycle, alloy, retainer, and axial wall. Comparison of 3 axial walls in combination with 2 retainers revealed statistically significant mean inner fit changes.</ce:para><ce:para>The mean horizontal change in framework length in relation to alloy type and firing procedure is presented in Figure 6.
<ce:display><ce:figure id="fig6"><ce:label>Fig. 6</ce:label><ce:caption><ce:simple-para>Mean changes in horizontal measurements as function of alloy type. Horizontal lines connect values that are not significantly different. Numbers above bars indicate mean values.</ce:simple-para></ce:caption> <ce:link locator="gr6"></ce:link></ce:figure></ce:display>The mean value of 6.2 μm recorded for Ni-Cr alloy for metal conditioning firing indicated that the mesial margin of the premolar abutment and the distal margin of the molar abutment were farther away from each other because of deterioration of these margins during firing. There was no significant difference in horizontal framework length change related to alloy type (Table II).
<ce:float-anchor refid="tab2"></ce:float-anchor>However, the firing stage had a significant effect on horizontal framework length change (<ce:cross-ref refid="tab2">Table II</ce:cross-ref>). The magnitude of change seen at metal conditioning firing was significantly greater than that observed after porcelain application firing (<ce:cross-ref refid="fig6">Fig. 6</ce:cross-ref>).</ce:para><ce:para>Changes in vertical fit of both premolar and molar retainers were measured by using certain reference marks after metal conditioning and porcelain application firings. The mean change values and standard deviations recorded are illustrated in Figure 7.
<ce:display><ce:figure id="fig7"><ce:label>Fig. 7</ce:label><ce:caption><ce:simple-para>Mean change values recorded for vertical measurements. Horizontal lines connect values that are not significantly different. Numbers above bars indicate mean values.</ce:simple-para></ce:caption> <ce:link locator="gr7"></ce:link></ce:figure></ce:display>Negative changes indicate better vertical fit of the retainer, whereas positive values show poorer vertical adaptation. The values –3.4 and –16.4 μm were recorded for the premolar and molar retainers of Ni-Cr alloy at metal conditioning firing, respectively. These values implied that both retainers had better vertical adaptation on their related abutments. However, at porcelain application firing, the same group had fit change values of 99.6 and 43.2 μm recorded for premolar and molar retainers, respectively. This revealed that both retainers had significantly poorer vertical fit after porcelain application firing (Table III).
<ce:display><ce:table colsep="0" rowsep="0" frame="topbot"><ce:label>Table III</ce:label><ce:caption><ce:simple-para>Analysis of variance results of mean changes in vertical measurements</ce:simple-para></ce:caption><tgroup cols="6"><colspec colname="col1" colsep="0"></colspec><colspec colname="col2" colsep="0"></colspec><colspec colname="col3" colsep="0"></colspec><colspec colname="col4" colsep="0"></colspec><colspec colname="col5" colsep="0"></colspec><colspec colname="col6" colsep="0"></colspec><thead><row><entry>Source</entry><entry align="center">df</entry><entry align="center">Sum of squares</entry><entry align="center">Mean squares</entry><entry align="center">F-test</entry><entry align="center">P value</entry></row></thead><tbody><row><entry><ce:italic>Between-subjects effects</ce:italic></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry></row><row><entry>Alloy</entry><entry align="center">1</entry><entry align="center">402620</entry><entry align="center">402620</entry><entry align="center">4E-1</entry><entry align="center">.5345</entry></row><row><entry>Retainer</entry><entry align="center">1</entry><entry align="center">2732800</entry><entry align="center">2732800</entry><entry align="center">3</entry><entry align="center">.1176</entry></row><row><entry>Alloy × retainer</entry><entry align="center">1</entry><entry align="center">844</entry><entry align="center">844</entry><entry align="center">8E-4</entry><entry align="center">.9772</entry></row><row><entry>Residual</entry><entry align="center">16</entry><entry align="center">15988597</entry><entry align="center">999162</entry><entry align="center"></entry><entry align="center"></entry></row><row><entry><ce:italic>Within-subjects effects</ce:italic></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry><entry align="center"></entry></row><row><entry>Firing cycle</entry><entry align="center">2</entry><entry align="center">53858</entry><entry align="center">26929</entry><entry align="center">50</entry><entry align="center">.0001*</entry></row><row><entry>Alloy × firing cycle</entry><entry align="center">2</entry><entry align="center">597</entry><entry align="center">299</entry><entry align="center">1</entry><entry align="center">.577</entry></row><row><entry>Retainer × firing cycle</entry><entry align="center">2</entry><entry align="center">13163</entry><entry align="center">6582</entry><entry align="center">12</entry><entry align="center">.0001*</entry></row><row><entry>Alloy × retainer × firing cycle</entry><entry align="center">2</entry><entry align="center">378</entry><entry align="center">189</entry><entry align="center">4E-1</entry><entry align="center">.7049</entry></row><row><entry>Residual</entry><entry align="center">32</entry><entry align="center">17083</entry><entry align="center">534</entry><entry align="center"></entry><entry align="center"></entry></row><row><entry namest="col1" nameend="col6">*Statistically significant.</entry></row></tbody></tgroup></ce:table></ce:display>The same relation was also observed between premolar and molar retainers of Pd-Cu alloy, at metal conditioning and porcelain application firing cycles (<ce:cross-ref refid="fig7">Fig. 7</ce:cross-ref>).</ce:para></ce:section><ce:section><ce:section-title>DISCUSSION</ce:section-title><ce:para>In this study, the application of porcelain caused an increase in internal gap between occlusal wall of both premolar and molar retainers and the abutments(<ce:cross-refs refid="fig4 fig5">Figs. 4 and 5</ce:cross-refs>). Thus, the vertical fit of the framework was poorer after porcelain application firing stages. This finding was also supported by the results of vertical fit measurements. After porcelain application vertical fit changes of 99.6 and 43.2 μm were observed for premolar and molar retainers of Ni-Cr alloy, respectively. The fit changes of 87.2 μm and 49.8 μm were recorded for premolar and molar retainers of Pd-Cu alloy. For both alloy groups, both premolar and molar retainers showed poorer vertical fit after porcelain application (<ce:cross-ref refid="fig7">Fig 7</ce:cross-ref>).</ce:para><ce:para>Many studies have investigated the distortion that results for metal frameworks after the various stages of the porcelain firing schedule. The investigators reported that timing of the deformation is such that most of it occurs during the initial oxidation of the alloy (before porcelain application) and small changes continue during the subsequent heating and porcelain applications.<ce:cross-refs refid="bib1 bib3 bib5 bib6 bib7 bib9 bib12 bib15 bib16 bib17 bib18"><ce:sup>1,3,5-7,9,12,15-18</ce:sup></ce:cross-refs> However, a few observed the reverse of this finding.<ce:cross-refs refid="bib7 bib8 bib11"><ce:sup>7,8,11</ce:sup></ce:cross-refs> Bridger and Nicholls<ce:cross-ref refid="bib7"><ce:sup>7</ce:sup></ce:cross-ref> measured 3-dimensional changes of a 6-unit maxillary anterior FPD framework during the firing stages and concluded that the greatest distortion changes occurred during the degassing stage and the final glaze stage of the porcelain firing cycle. They also demonstrated that distortion incurred by the application and firing of the porcelain was reversible. The fit was better when the porcelain was chemically removed from the framework. The authors attributed the distortion to thermal contraction mismatch stresses. However, Anusavice and Carroll<ce:cross-ref refid="bib11"><ce:sup>11</ce:sup></ce:cross-ref> showed that thermal contraction mismatch stresses did not cause distortion even in 0.1-mm thick metal copings. It is highly probable that the authors concluded with better fit after porcelain was removed, because the resilience of the metal framework was gained again and the contaminated porcelain particles were removed from the internal surfaces. The results of Van Rensburg and Strating<ce:cross-ref refid="bib8"><ce:sup>8</ce:sup></ce:cross-ref> are also in agreement with those of Bridger and Nicholls.<ce:cross-ref refid="bib7"><ce:sup>7</ce:sup></ce:cross-ref> The authors who investigated the effect of porcelain veneering on the marginal integrity and overall dimensional stability of a 3-unit FPD concluded that porcelain veneering enhanced distortion.</ce:para><ce:para>It is noted that the studies in which it was concluded that distortion occurred primarily before porcelain application<ce:cross-refs refid="bib1 bib3 bib6 bib9 bib12 bib15 bib16 bib17"><ce:sup>1,3,6,9,12,15-17</ce:sup></ce:cross-refs> were made on experimental models such as metal sheets or crown configurations. And the studies<ce:cross-refs refid="bib7 bib8 bib13"><ce:sup>7,8,13</ce:sup></ce:cross-refs> that resulted with distortion also in porcelain application firing were performed on FPD framework models. The controversy between the results of these studies is probably dependent on the variety in experimental models. Distortion of the metal-ceramic framework during porcelain application firing cycle can be attributed to factors such as thermal incompatibility stresses, contamination of the internal surfaces of the coping with porcelain, and reduction in the resilience of the metal because of the rigidity of porcelain. Anusavice and Carroll<ce:cross-ref refid="bib11"><ce:sup>11</ce:sup></ce:cross-ref> measured the marginal gap of 0.1-mm thick metal copings in a condition where thermal contraction mismatch between the metal and porcelain was exaggerated. However, they concluded in remarkably small gap changes, which indicated that the thermal contraction differences were not the primary cause of distortion.</ce:para><ce:para>The contamination of porcelain to the inner surfaces of the metal framework seems to be a minor factor; however, it has been shown to be unavoidable,<ce:cross-ref refid="bib16"><ce:sup>16</ce:sup></ce:cross-ref> and it may lead to poorer vertical fit of the framework that could be clinically unacceptable. The resilience of the metal framework was reduced after porcelain veneering as a result of the rigidity of porcelain. This became more apparent with multiple unit castings than single crowns. Contamination of porcelain in metal coping and reduction in resilience of metal become more effective in FPD frameworks than in single crown or metal sheets because of the increased number of retainers. Thus, the distortion seen in a greater magnitude, after porcelain veneering, for studies performed with FPD frameworks can be explained with the multiple effect of the mentioned factors.</ce:para><ce:para>The results of horizontal framework length changes revealed significant differences in relation to the firing procedure. The changes of 6.2 μm and 8.2 μm recorded at metal-conditioning firing for Ni-Cr and Pd-Cu frameworks was significantly greater than 3 μm and –3 μm recorded for the same groups after porcelain application. Main distortion occurred during metal conditioning when lateral changes were considered; this finding is in agreement with the results of other studies.<ce:cross-refs refid="bib1 bib3 bib5 bib6 bib7 bib9 bib12 bib15 bib16 bib17 bib18"><ce:sup>1,3,5-7,9,12,15-18</ce:sup></ce:cross-refs> The occurrence of horizontal distortion mainly in metal conditioning firing shows that the distortion in metal itself mainly occurs in metalconditioning firing as a result of the factor of relaxation of residual stresses. However, factors such as contamination of porcelain to the inner surface of the metal coping and reduction in resilience of metal affected vertical fit of the restoration in a negative way and resulted in a greater distortion after porcelain application.</ce:para><ce:para>Investigations of thermal cycling distortion performed on single crowns<ce:cross-refs refid="bib9 bib11 bib12 bib17 bib19 bib20"><ce:sup>9,11,12,17,19,20</ce:sup></ce:cross-refs> concluded that the mean value of distortion did not exceed 30 μm, and this value of marginal distortion was within clinical acceptability. However, distortion values recorded for metal-ceramic FPDs were clinically significant.<ce:cross-refs refid="bib4 bib7"><ce:sup>4,7</ce:sup></ce:cross-refs> The results of our study are in agreement with these earlier studies.<ce:cross-refs refid="bib4 bib7"><ce:sup>4,7</ce:sup></ce:cross-refs> The recorded average change values even reached to 99.6 μm, and this will lead to marginal gap values exceeding 39 μm optimal marginal gap reported by Christensen.<ce:cross-ref refid="bib22"><ce:sup>22</ce:sup></ce:cross-ref> In FPDs, multiple abutments are used that result in increase in distortion due to accumulation of fit changes for each retainer and the increased effect of loss of resilience of metal after porcelain application.</ce:para></ce:section><ce:section><ce:section-title>CONCLUSIONS</ce:section-title><ce:para>Within the limits of this study, the following conclusions were drawn:</ce:para><ce:para><ce:list><ce:list-item><ce:label>1.</ce:label><ce:para>Distortion was observed in metal-ceramic frameworks (both Ni-Cr and Pd-Cu) during metal conditioning firing and porcelain application firing cycles, and it caused deterioration in vertical fit of the retainers.</ce:para></ce:list-item><ce:list-item><ce:label>2.</ce:label><ce:para>Distortion in horizontal framework length occurred mainly after metal conditioning, which was attributed to relaxation of residual stresses during the first firing stage. In contrast, the magnitude of vertical fit change was greater during porcelain application firing. It was concluded that the vertical fit of retainers deteriorated after porcelain veneering as a result of contamination of the internal surfaces of the coping with porcelain and reduction in the resilience of the metal because of the rigidity of porcelain. 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fit of gold inlay castings</sb:maintitle></sb:title></sb:contribution><sb:host><sb:issue><sb:series><sb:title><sb:maintitle>J Prosthet Dent</sb:maintitle></sb:title><sb:volume-nr>16</sb:volume-nr></sb:series><sb:date>1966</sb:date></sb:issue><sb:pages><sb:first-page>297</sb:first-page><sb:last-page>305</sb:last-page></sb:pages></sb:host></sb:reference></ce:bib-reference></ce:bibliography-sec></ce:bibliography></tail></article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo lang="en"><title>Thermal cycling distortion of porcelain fused to metal fixed partial dentures</title></titleInfo><titleInfo type="alternative" lang="en" contentType="CDATA"><title>Thermal cycling distortion of porcelain fused to metal fixed partial dentures</title></titleInfo><name type="personal"><namePart type="given">Deniz</namePart><namePart type="family">Gemalmaz</namePart><namePart type="termsOfAddress">DDS, PhDa</namePart><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Semih</namePart><namePart type="family">Berksun</namePart><namePart type="termsOfAddress">DDS, PhDb</namePart><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Hasan Necdet</namePart><namePart type="family">Alkumru</namePart><namePart type="termsOfAddress">DDS, PhDc</namePart><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Cigdem</namePart><namePart type="family">Kasapoglu</namePart><namePart type="termsOfAddress">DDSd</namePart><affiliation>Faculty of Dentistry Marmara University Marmara , and Faculty of Dentistry, Ankara University Ankara, Turkey</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="research-article" displayLabel="Full-length article" authority="ISTEX" authorityURI="https://content-type.data.istex.fr" valueURI="https://content-type.data.istex.fr/ark:/67375/XTP-1JC4F85T-7">research-article</genre><originInfo><publisher>ELSEVIER</publisher><dateIssued encoding="w3cdtf">1998</dateIssued><copyrightDate encoding="w3cdtf">1998</copyrightDate></originInfo><language><languageTerm type="code" authority="iso639-2b">eng</languageTerm><languageTerm type="code" authority="rfc3066">en</languageTerm></language><abstract lang="en">Abstract: Statement of problem. The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. Purpose. This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. Material and methods. A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. Results. Measured differences between the 2 firing stages ranged from –47 to 81.7 μm. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. Conclusions. A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal. (J Prosthet Dent 1998;80:654-60.)</abstract><note>a Associate Professor, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</note><note>b Professor, Department of Prosthodontics, Faculty of Dentistry, Ankara University.</note><note>c Professor, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</note><note>d Research assistant, Department of Prosthodontics, Faculty of Dentistry, Marmara University.</note><note>Reprint requests to: Dr Deniz Gemalmaz, Marmara Universitesi, Dis Hekimligi Fakultesi,80200 Nisantasi, Istanbul, TURKEY</note><note>0022-3913/98/$5.00 + 0. 10/1/92982</note><note type="content">Table I: Analysis of variance results of mean changes in internal fit</note><note type="content">Table II: Analysis of variance results of mean changes in framework length</note><relatedItem type="host"><titleInfo><title>The Journal of Prosthetic Dentistry</title></titleInfo><titleInfo type="abbreviated"><title>YMPR</title></titleInfo><genre type="journal" authority="ISTEX" authorityURI="https://publication-type.data.istex.fr" valueURI="https://publication-type.data.istex.fr/ark:/67375/JMC-0GLKJH51-B">journal</genre><originInfo><publisher>ELSEVIER</publisher><dateIssued encoding="w3cdtf">199812</dateIssued></originInfo><identifier type="ISSN">0022-3913</identifier><identifier type="PII">S0022-3913(05)X7059-7</identifier><part><date>199812</date><detail type="volume"><number>80</number><caption>vol.</caption></detail><detail type="issue"><number>6</number><caption>no.</caption></detail><extent unit="issue-pages"><start>16</start><end>732</end></extent><extent unit="pages"><start>654</start><end>660</end></extent></part></relatedItem><identifier type="istex">CE77DD901A191752F1347AC78804F04273F0648E</identifier><identifier type="ark">ark:/67375/6H6-6374JRWZ-M</identifier><identifier type="DOI">10.1016/S0022-3913(98)70051-4</identifier><identifier type="PII">S0022-3913(98)70051-4</identifier><accessCondition type="use and reproduction" contentType="copyright">©1998 Editorial Council of The Journal of Prosthetic Dentistry.</accessCondition><recordInfo><recordContentSource authority="ISTEX" authorityURI="https://loaded-corpus.data.istex.fr" valueURI="https://loaded-corpus.data.istex.fr/ark:/67375/XBH-HKKZVM7B-M">elsevier</recordContentSource><recordOrigin>Editorial Council of The Journal of Prosthetic Dentistry., ©1998</recordOrigin></recordInfo></mods><json:item><extension>json</extension><original>false</original><mimetype>application/json</mimetype><uri>https://api.istex.fr/document/CE77DD901A191752F1347AC78804F04273F0648E/metadata/json</uri></json:item></metadata><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
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