In Vitro Comparison of Marginal Fit of All Metal, Porcelain Fused to Metal and All Ceramic Crowns

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1 INTERNATIONAL JOURNAL of BIOMEDICAL SCIENCE ORIGINAL ARTICLE In Vitro Comprison of Mrginl Fit of All Metl, Porcelin Fused to Metl nd All Cermic Crowns G. S. Amrnth 1, Ishit Jkhnwl 2, Hri Annth Prsd 3, Mohmmed Hill 4, T. Anupm 5, Mridul Ayush 6 1 Professor nd HOD, Deprtment of Prosthodontics including Crown nd Bridge nd Implntology, M R Ambedkr Dentl College nd Hospitl, Bengluru, Krntk, Indi; 2 Post-grdute student, Deprtment of Prosthodontics including Crown nd Bridge nd Implntology, M R Ambedkr Dentl College nd Hospitl, Bengluru, Krntk, Indi; 3 Reder, Deprtment of Prosthodontics including Crown nd Bridge nd Implntology, M R Ambedkr Dentl College nd Hospitl, Bengluru, Krntk, Indi; 4 Reder, Deprtment of Prosthodontics including Crown nd Bridge nd Implntology, M R Ambedkr Dentl College nd Hospitl, Bengluru, Krntk; 5 Post-grdute student, Deprtment of Prosthodontics including Crown nd Bridge nd Implntology, M R Ambedkr Dentl College nd Hospitl, Bengluru, Krntk, Indi; 6 Lecturer, Deprtment of Rdiodignosis nd Imging, D Y Ptil Medicl College nd Reserch Centre, Pimpri, Pune, Indi ABSTRACT PURPOSE: To compre the mrginl fit of ll metl, porcelin fused to metl nd ll cermic crowns fbricted using different mterils nd techniques commercilly vilble. MATERIALS AND METHODS: 80 freshly extrcted humn mndibulr first premolrs were divided into 8 groups of 10 ech which received Nickel-Chromium (Ni-Cr) ll metl (AM) crowns, Coblt-Chromium (Co-Cr) AM crowns, Ni-Cr three-qurter crowns, Co-Cr three qurter crowns, porcelin fused to metl (PFM) crowns with Ni-Cr copings, PFM crowns with Co-Cr copings, pressed ll cermic (AC) crowns nd CAD/CAM fbricted AC crowns respectively. Crowns were cemented nd specimen were sectioned buccolingully. The mrginl gp ws evluted under stereomicroscope. Lesser mrginl gp indicted better mrginl fit. RESULTS: The men mrginl gp ws mximum for Group 8 (222.3 µm) nd lest for Group 1 (85.5 µm). The men mrginl gps for ll metl crowns nd metl cermic crowns showed significntly lesser mrginl gps ( p<0.05) for Ni-Cr Groups thn Co-Cr Groups. When only ll cermic crowns were compred, significntly lesser mrginl gp ws found for pressed AC crowns (148.6 µm) thn CAD/CAM fbricted AC crowns (222.3 µm). CONCLUSION: Mrginl fit of AM crowns were significntly better thn PFM crowns nd AC crowns. Ni-Cr group lwys showed better mrginl fit thn Co-Cr group. A better mrginl fit of pressed AC crowns ws seen thn CAD/CAM fbricted AC crowns. Chmfer finish line showed significntly better mrginl fit thn shoulder finish line. (Int J Biomed Sci 2017; 13 (3): ) Keywords: Finish line; Mrginl fit; Mrginl gp Corresponding uthor: Ishit Jkhnwl, Deprtment of Prosthodontics including Crown nd Bridge nd Implntology, M R Ambedkr Dentl College nd Hospitl, Bengluru, Krntk, Indi. Tel: ; E-mil: ishitjkhnwl90@gmil.com. Received June 19, 2017; Accepted August 23, 2017 Copyright: 2017 G. S. Amrnth et l. This is n open-ccess rticle distributed under the terms of the Cretive Commons Attribution License ( which permits unrestricted use, distribution, nd reproduction in ny medium, provided the originl uthor nd source re credited. Int J Biomed Sci Vol. 13 No. 3 September

2 INTRODUCTION Restortion cn survive in the biologic environment of the orl cvity only if the mrgins re closely dpted to the finish line of the preprtion. The configurtion of the preprtion finish line dicttes the shpe nd bulk of restortive mteril in the mrgin of the restortion. It lso cn ffect both mrginl dpttion nd the degree of seting of the restortion. The mrginl fit of cstings bsiclly relies on perceptive tooth preprtion, ccurte impressions, precision cstings, nd creful finishing procedures (1, 2). Precise mrginl fit is essentil for successful cst restortion becuse introrl degrdtion of cements cn result in loss of mrginl sel nd promote retention of plque. Thus, mrginl fit of cstings is one fctor tht leds directly or indirectly to secondry cries, dverse pulpl rections, nd periodontl disese (2). Till this dte, there is no conclusive evidence of optimum fit of crowns. This topic is hevily investigted nd fit vlues reported re widely diverse nd rnge from 7.5 µm to 313 µm. Such vrition cn be minly ttributed to the lck of coherence bout the definition of fit, long with differences in methods employed to determine the fit, testing prmeters followed nd vrious mterils used for the fbriction of crowns (3, 4). This study ws done to compre nd evlute the mrginl fit of complete metl, porcelin fused to metl nd metl free cermic crowns fbricted with different types of mterils commercilly vilble, in which crowns were fbricted for mndibulr first premolrs nd cemented using resin cement. The cement thickness t the mrgins were mesured using stereomicroscope. This study thus imed to determine the best mrginl fit mongst the mentioned crowns bove. After removl of clculus nd soft tissue deposits, teeth were disinfected in 3% sodium hypochlorite solution nd embedded in stndrd MS (mild steel) cylinders (20 mm dimeter, 20 mm length) with self curing crylic resin (DPI, Indi) to within 2 mm of the cemento-enmel junction, with the long xis of the roots perpendiculr to the horizontl plne (Fig. 1). They were divided into eight groups of ten ech to receive the following groups of crowns: Group 1 - Nickel-Chromium (Ni-Cr) ll metl (AM) crowns; Group 2 - Coblt-Chromium (Co-Cr) AM crowns; Group 3 - Ni-Cr three-qurter crowns; Group 4 - Co-Cr three qurter crowns; Group 5 - porcelin fused to metl (PFM) crowns with Ni-Cr copings; Group 6 - PFM crowns with Co-Cr copings; Group 7 - pressed ll cermic (AC) crowns nd Group 8 - CAD/CAM fbricted AC crowns. Idel tooth preprtion ws done for ech group to receive ll metl, porcelin fused to metl nd ll cermic crowns. Group 1, 2, 3 nd 4 were given chmfer finish line ll round, group 5 nd 6 received buccl shoulder nd lingul chmfer finish lines while group 7 nd 8 were prepred with ll round shoulder. Impression ws mde for ech specimen using polyvinyl siloxne (PVS) (Fig. 2) nd impressions were poured in type IV die stone. Crown fbriction for Group 1, 2, 3 nd 4 Two lyers of die spcer ws pplied nd wx ptterns of full coverge restortion were mde for Group 1 nd 2. Group 1 specimen were csted in Ni-Cr lloy (Bego, Germny), wheres Group 2 specimen were csted in Co-Cr lloy (Bego, Germny). Similrly, wx ptterns for threequrter crowns were mde for Group 3 nd 4 nd Group 3 ptterns were csted in Ni-Cr lloy, wheres Group 4 ptterns were csted in Co-Cr lloy. MATERIALS AND METHODS Humn first mndibulr premolrs, eighty in number, extrcted for orthodontic purposes or periodontlly compromised teeth (indicted for extrction) were selected using the following inclusion criteri: 1. Absence of cries in the tooth; 2. Intct clinicl crown nd root; 3. Non hypoplstic teeth; 4. Tooth with miniml or no significnt ttrition, brsion or erosion; 5. Absence of visible frcture lines in the tooth; Completely formed pex. Figure 1. Tooth embedded in self cure crylic resin. 148 September 2017 Vol. 13 No. 3 Int J Biomed Sci

3 Figure 2. Impression mde for ech specimen using polyvinyl siloxne impression mteril. Crown fbriction for Group 5 nd 6 Two lyers of die spcer ws pplied nd full coverge wx ptterns were mde for Group 5 nd 6. Cut Bck of the wx ptterns were done for uniform lyering of the porcelin. Wx ptterns were then csted in Ni-Cr lloy for Group 5 nd in Co-Cr lloy for Group 6, thereby fbricting the respective metl copings. Lyering of the porcelin (VITA VMK Mster, Germny) ws done, followed by firing (t 650ºC for 15 minutes) nd glzing ccording to the mnufcturer s instructions. Crown fbriction for Group 7 Two lyers of die spcers were pplied over the dies nd wx ptterns with cut bck design were prepred for Group 7. Burn out of the wx ptterns were done fter which the investment ring ws trnsferred to the press mchine for the press procedure. The e-mx glss cermic ingots (IPS e.mx, Ivoclr Vivdent, Indi) plced in the mchine were softened t 920ºC nd were utomticlly pressed into the mould. After pressing nd cooling, crowns were divested, clened, dried nd brded with 50 µm glss bed prticles for 20 sec. Cermic lyering ws done over the copings nd then fired t 750ºC. This ws followed by glzing t temperture of 730ºC. Crown fbriction for Group 8 The restortion for Group 8 were fbricted using computer ided designing (CAD) nd computer ided mchining (CAM) by CERAMILL system. Dies prepred for the Group 6 were scnned nd the digitl models were constructed from them. Spcer thickness of 50 µm ws djusted in the system. Virtul designing of the coping ws then done in the CAD softwre of CERAMILL. After completion of designing, dt ws then fed into the milling unit to get the corresponding zirconium oxide copings (Amnn Girrbch). Copings obtined were then sintered t 1450ºC for 10 hours. Cermic lyering ws done over the copings nd then fired t 930ºC. This ws followed by glzing t 910ºC. The crowns fter fbriction were cemented to their respective dies with the rein cement (Mxcem Elite, Kerr Co., USA). Pink colour ws dded to the cement before cementtion for esy visuliztion under the microscope. A thin, even lyer of the mixed cements ws pplied to the fitting surfce of the crowns. The crowns were seted on their respective restortions nd n uniform lod of 50N ws pplied on ech crown for 2-3 minutes (Fig. 3). Finl curing ws done using ultr curing light for 10 sec. Curing ws s per mnufcturer s instructions. Excess cement ws removed from round the mrgins using shrp probe. The cemented crowns were sectioned using low speed dimond cutter (Model: Struers: Minitom) buccolingully (Fig. 4). The mrginl fit ws evluted by mesuring Figure 3. Crown cemented under uniform lod of 50 N. Figure 4. Cemented crown sectioned buccolingully using slow speed dimond cutter. Int J Biomed Sci Vol. 13 No. 3 September

4 the perpendiculr distnce from the internl surfce of the csting to the xil wll of the prepred tooth t the mrgin in stereomicroscope (Model: Crl Zeiss Discovery V20) under 40 mgnifiction, with n imging processing softwre (Fig. 5A, 5B). 6 redings were tken for ech specimen, 3 on the buccl mrgin nd 3 on the lingul mrgin. The first reding ws recorded t the edge of the buccl mrgin of the prepred tooth. The second nd the third redings were mde t distnce of 0.5 mm nd 1mm from the point of the first reding respectively. The 3 redings were then verged to obtin the buccl mrginl gp or discrepncy. 3 redings were tken on the lingul mrgin in similr wy nd they were verged to obtin the lingul mrginl gp or discrepncy for ech specimen. A Sttisticl Anlysis To compre the mrginl fit between the six groups, obtined results were sttisticlly nlyzed using SPSS softwre. The dt were described in Men, Stndrd Devition nd Rnge vlues. One wy ANOVA ws used for multiple group comprison followed by Independent smple t test to ssess ny significnt difference between the buccl nd lingul mrginl gp within ech group. In order to find out which pir of groups there existed significnt difference, Tukey test (post hoc test) ws pplied. RESULTS ANOVA test ws done to compre the men mrginl gp mongst different groups. Highest men mrginl gp ws obtined for Group 8 (222.3 µm) followed by Group 6 (194.4 µm), Group 7 (148.6 µm), Group 5 (143.9 µm), Group 4 (123.4 µm), Group 2 (117.1 µm), Group 3 (94.15 µm) nd Group 1 (85.5 µm) (Tble 1, Tble 2). In order to find out which pir of groups there exist significnt difference, Tukey test (post hoc test) ws pplied. B Figure 5. Evlution of mrginl fit under stereomicroscope under 40x mgnifiction. Tble 1. Men Vlue, Stndrd Devition nd Rnge (In µm) Of Mrginl Gps of Different Groups MEAN STANDARD DEVIATION RANGE Tble 2. Multiple Group Comprison: ANOVA Sum of Squres Df Men Squre F Sig. (P- Vlue) Between Groups Within Groups Totl Denotes significnt difference t 0.05 level. 150 September 2017 Vol. 13 No. 3 Int J Biomed Sci

5 When the men mrginl gps of ll metl crowns were compred, results showed tht Group 1 showed significntly lesser vlue thn Group 2 (P<0.05). Similrly, Group 3 showed significntly lesser mrginl gp compred to Group 4 (P<0.05). However, the men mrginl gp of Group 1 showed no significnt difference compred to Group 3 (P>0.05). Similrly, the men mrginl gp of Group 2 ws comprble with tht of Group 4 (P>0.05) (Tble 3). Compring the men mrginl gp between the two types of ll cermic crowns, the results showed significntly lesser mrginl gp in Group 7 thn Group 8 (P<0.05). When the men mrginl gp of metl cermic crowns were compred with ll metl crowns hving similr lloy types, Group 1 showed significntly lesser mrginl gp s compred to Group 5 (P<0.05). Similrly, Group 2 showed significntly lesser mrginl gp compred to Group 6 (P<0.05) (Tble 4). When compring the different ll metl crowns with ll cermic crowns, ll the ll metl groups (Group 1, Group 2, Group 3, Group 4) showed significntly lesser men mrginl gp compred to the ll cermic crowns groups (Groups 7, Group 8) (P<0.05) (Tble 5). When the different metl cermic crowns were compred with ll cermic crowns, there ws no sttisticlly significnt difference in the men mrginl gp of Group 5 nd Group 7 (P>0.05), however, Group 5 showed significntly lesser mrginl gp compred to Group 8 (P<0.05). Furthermore, results showed tht the men mrginl gp of Group 6 ws significntly lesser thn Group 7 nd group 8 (P<0.05) (Tble 6). To find out which group exhibited significnt difference between its buccl nd the lingul mrginl fit, Independent 2 smples t test ws performed. When the men mrginl gp between the buccl nd the lingul mrgins for ech group ws compred; Group 1, Group 2, Group 3, Group 4, group 6 nd Group 8 showed no significnt difference for either of the mrgins (P>0.05). However, for Group 5 nd Group 6, the men lingul mrginl gp ws significntly lesser thn the men buccl mrginl gp (P<0.05). DISCUSSION Mrginl dpttion is one of the most importnt criteri for determining the clinicl success of the dentl restortion. Poor fit of the crown cn led to deficient mrgins, nd this could led to tooth sensitivity in vitl teeth nd higher plque index nd thereby cusing cries nd inflmmtion of periodontl tissues (5). Tble 3. Compring the Men Mrginl Gps of Different All Metl Crowns : Tukey s Test P-Vlue Denotes significnt difference t 0.05 level. Tble 4. Compring The Men Mrginl Gps Of Different All Cermic Crowns : Tukey s Test P-Vlue * Tble 5. Compring the Men Mrginl Gps of Different All Metl Crowns nd All Cermic Crowns : Tukey s Test P-Vlue Denotes significnt difference t 0.05 level. Tble 6. Compring the Men Mrginl Gp of Different Metl Cermic Crowns nd All Cermic Crowns : Tukey s Test P-Vlue Denotes significnt difference t 0.05 level. Int J Biomed Sci Vol. 13 No. 3 September

6 A definition of mrginl fit vries from one study to nother, with ech study drwing conclusion bsed on its own definition. In this study, we defined perpendiculr distnce from the internl surfce of the csting to the xil wll of the prepred tooth t the mrgin s the mrginl discrepncy or the mrginl gp, tht cn be mesured only on sections of cemented crowns. In the cross-sectionl technique used in the present study, the smples must be scrificed nd lso it is more time-consuming. However, it hs greter precision in mesurements, s mesurement points re more ccurte nd repetble. Therefore this method ws chosen for mesuring the mrginl fit (6, 7). Humn mndibulr first premolrs extrcted for periodontl nd orthodontic resons were used s the test specimens for this study. The use of nturl teeth is cliniclly more relevnt compred to lterntive test specimens of metl dies of typhodont teeth tht hve been reported on previously. The true effect on the mrginl fit of the crowns my be compromised in the studies tht do not use nturl teeth (8). The dt supports the rejection of the null hypothesis tht the mrginl fit of ll metl, porcelin fused to metl nd ll cermic crowns re not significntly different (P<0.05). The results show tht the men mrginl gp ws lrgest for Group 8, i.e, Amnn Girrbch ll cermic crowns (222.3 µm), wheres the lest mrginl gp ws seen for group 1, i.e, Ni-Cr ll metl crowns (85.5 µm). Amongst the ll metl crowns, the men mrginl gp for Ni-Cr full coverge restortions were significntly lesser (85.5µm) thn for the Co-Cr full coverge restortions (117.1 µm). A similr study ws done by Ktt Sridhr Chowdhry, in 2011, who concluded tht Co-Cr lloy copings hd lesser mrginl fit when compred with copings of Ni-Cr lloy. The reson for the higher mrginl discrepncy for Co-Cr crowns cn be ttributed to its higher csting shrinkge (2.3%) thn tht of Ni-Cr crowns (2%). This in turn my be result of the higher melting temperture of Co-Cr lloy (1495ºc) thn Ni-Cr lloy (1400ºC) (9). This study lso reported significntly higher mrginl discrepncy of the porcelin fused to metl crowns thn the corresponding ll metl crowns. The reson for the incresed mrginl gp fter veneering ws due to the difference in therml contrction between the metl coping nd the lyering porcelin during cooling of the prosthesis from the firing temperture. The distortion of the lower metl core occured due to the difference in het expnsion coefficients of the lower metl nd the upper porcelin, difference in the degree of expnsion nd high temperture during the firing of the upper porcelin. Similr findings were reported by Buchnn et l (10). All-cermic restortions re in fst progression in properties nd usge. In situtions with high esthetic demnds, these mterils my be the mteril of choice for the restortion (11). In the present study, the men mrginl gp of IPS e mx, pressed glss cermic crowns ws µm nd for CAD/CAM fbricted zirconi crowns, it ws µm. Low shrinkge of het pressed cores my explin this difference. Furthermore, in het pressed cermics, which uses lost wx technique, 0.4% shrinkge of wx pttern nd 0.2% shrinkge of cermic coping cn be compensted by 0.3% setting nd 0.2% therml expnsion of investment mteril. Thus, becuse of inherent properties, lrge gps re not expected in the pressed copings. Similr results were noted by Frid et l. in their study (12). This lso explins the reson for the CAD/CAM fbricted zirconi crowns hving the lrgest mrginl discrepncy when compred to the other seven groups, s ll other groups except group 8 used the lost wx technique for the fbriction of the crowns. Moreover, CAD/CAM mchining of the pre-sintered Y-TZP blocks induce microcrcks t zirconi surfce which cnnot be completely eliminted by sintering. These microcrcks ct s stress concentrtion sites which together with those cused by (core veneer) CTEs mismtch re thought to contribute to the mrginl distortion developed during veneering of CAD/CAM frmeworks (13). Previous studies stte the mount distortion in the pressed cermic copings is less thn tht observed in the metl copings. The pressed cermic crowns hve better dpttion thn the metl cermic crowns even fter exposure to multiple high temperture firing cycles (7). However, no sttisticlly significnt difference between the mrginl fit of porcelin fused to metl crowns with Ni-Cr metl copings (146.7 µm) nd those of pressed ll cermic crowns (IPS e mx) (148.6 µm) in the present study could be ttributed to the difference in the mrgin designs for the two types of crowns. In this study, the specimen which received porcelin fused to metl crowns with Ni-Cr copings were prepred with lingul chmfer nd buccl shoulder finish line mrgin design, wheres specimen for the pressed ll cermic crowns (IPS e mx) were prepred with chmfer finish line mrgin design ll round. Porcelin firing cycles chnge the mrginl fit of shoulder copings more dversely compred with rounded chmfer copings. This phenomenon occurs becuse the chmfer finish line hs some length on xil wll of the preprtion, so the closing of mrgin is more probble long this length. On the other hnd, shoulder mrgin hs butt joint form, without ny length on the xil wll. This 152 September 2017 Vol. 13 No. 3 Int J Biomed Sci

7 is why if ny distortion hppens due to porcelin firing, it will ffect the whole mrginl gp. Per et l., evluted the mrginl dpttion of porcelin cermic crowns nd reported improved mrginl fit of In-Cerm crowns fbricted on chmfer compred with shoulder finish line (14). The result of the present study ws in ccordnce with the foresid studies, explining the reson for sttisticlly significnt difference between the mrginl discrepncies of the buccl nd the lingul mrgins in the porcelin fused to metl group. Similry, no significnt difference ws found between the buccl nd lingul mrginl gps within group 7 nd group 8 s they exhibited shoulder mrgin design ll round. CONCLUSION Moldovn et l. in his study, rted the vlues of 100 µm for mrginl misfit s good nd vlues of µm s cceptble (7). According to the bove, the mrginl misfit or discrepncy for the ll metl crowns noted in the present study ws within 100 µm nd thus, could be rted s good. For the porcelin-fused-to-metl crowns nd ll cermic crowns, the mrginl misfit or discrepncy obtined ws between µm which could be rted s cceptble. Within the limittions of the study, the mrginl fit of ll the types of crowns being within the cliniclly cceptble rnge, it ws concluded tht the mrginl fit of ll metl crowns were significntly better thn porcelin fused to metl or ll cermic restortions. Moreover, Ni-Cr crowns hd significntly better mrginl fit thn Co-Cr crowns. Porcelin fused to metl crowns showed better mrginl fit with Ni-Cr copings s compred to Co- Cr copings. The study lso concluded better mrginl fit of pressed ll cermic crowns thn CAD/CAM fbricted ll cermic crowns. When compred to porcelin fused to metl crowns, pressed ll cermic crowns showed lmost comprble mrginl fit with metl cermic crowns with Ni-Cr copings, however better mrginl fit thn metl cermic crowns with Co-Cr copings. No significnt difference ws found between the full coverge nd prtil coverge ll metl restortions. 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