The Influence Of Different Fabrication And Impression .
J Bagh College DentistryVol. 29(4), December 2017The InfluenceamongThe Influence of Different Fabrication and ImpressionTechniques on the Marginal Adaptation of LithiumDisilicate Crowns (A comparative in vitro study)Shatha Saadallah, B.D.S (1)Abdul Kareem J. Al-Azzawi, B.D.S., M.Sc. (2)ABSTRACTBackground: The marginal adaptation has a key role in the success and longevity of the fixed dental restoration,which is affected by the impression and the fabrication techniques .The objective of this in vitro study was toevaluate and compare the marginal fitness of lithium disilicate crowns using two different digital impressiontechniques (direct and indirect techniques) and two different fabrication techniques (CAD/CAM and Presstechniques).Materials and Methods: Thirty two sound upper first premolar teeth of comparable size extracted for orthodonticreason were selected in this study .Standardized preparation of all teeth samples were carried out with modifieddental surveyor to receive all ceramic crown restoration with 1 mm deep chamfer finishing line, 4 mm axial lengthand 6 degree convergence angle. Half of the teeth were duplicated and poured in type IV dental stone to havesixteen dies and then these dies and the remaining teeth divided in to two groups according to the type of digitalimpression techniques (n 16) as follow: Group A: Indirect digital impression technique scanned by inEos X5 camera;Group B: Direct digital impression technique scanned by CEREC AC Omnicam camera. Each group was subdividedaccording to the technique of fabrication into two subgroups (n 8): Press technique using IPS e-max press (A1, B1);CAD/CAM technique using IPS e-max CAD (A2, B2).Marginal gaps were evaluated on the prepared teeth at fourdefined points on each aspect using digital microscope at a magnification of (280X). One way ANOVA and LSD testswere used to identify and localize the source of difference among the groups.Results: The results showed that indirect digital impression with IPS e-max CAD/CAM group A2 revealed the poorestmarginal integrity with (55.93 μm 3.300). Group B2 and group A1 were next in line with(44.49 μm 6.840 and 37.74μm 5.433) respectively, while in the first group of restorations, the result of 29.9 μm 5.534 obtained with directdigital impression with pressable ceramic was clearly better.Conclusions: All the tested digital impression techniques showed clinically acceptable accuracy and intraoralscanning with pressable ceramic significantly enhanced the marginal fitKey words: Marginal fitness, CAD/CAM system, Digital impression, Press technique. (J Bagh Coll Dentistry 2017;29(4):20-26)INTRODUCTIONMarginal fit is an important predictor of theclinical success and longevity of dental prosthesis(1). Marginal discrepancy can be defined as thevertical distance from the finish line of thepreparation to the cervical margin of therestoration (2). Poor marginal adaptation increasesplaque accumulation, recurrent caries and causingperiodontal diseases (3).Increasing patients demand for esthetic dentalrestoration have made metal-free, all-ceramicsystem more widely distributed due to theirenamel-like color, light transmission andimproved reproduction of the translucency ofnatural teeth (4,5). Several ceramic systems whichmay differ in composition or fabrication techniqueare available; lithium disilicate is one of them.Lithium disilicate is a glassy ceramic that has70% crystalline phase and claim to have optimumesthetics, natural light refraction and high flexuralstrength in the range of 360-400 MPa (6).It can be made using either lost-wax hot pressingtechniques (IPS E.max Press) or (CAD/CAM)milling procedures (IPS E.max CAD) (7).Impressions made with elastomers materials,also known as conventional impressions,represent a commonly used procedure in generaldental practice. Low reproduction of thepreparation margins, tearing of the impressionmaterial and an undistinguishable margin on thestone dies are frequently encountered problems (8).There are several reasons for these problems,including the knowledge and skill level of thepractitioner (9). However, there are potentialsources of error are not practitioner-relatedinclude the disinfection procedures, total or partialseparation of the impression material from thetray and transportation to the dental laboratoryunder different climatic conditions (10,11). Toeliminate the need for the traditional impressiontaking, model-pouring and laboratory-shippingsteps of fabricating crowns, CAD/CAM systemsintroduced in the dental field (12). DigitalComputer Aided Design and Computer AidedManufacturing (CAD/CAM) is a 3-dimensional(1) Master Student, Department of conservative, college ofdentistry, University of Baghdad.(2) Professor, Department of conservative, college of dentistry,University of Baghdad.Restorative Dentistry20
J Bagh College DentistryVol. 29(4), December 2017scanning technology being utilized in dentistry toincrease productivity, patient satisfaction andoptimize the quality of the restoration as well asthe efficiency of the workflow (13).The InfluenceamongFigure 1: Tooth preparation with modifieddental surveyor.MATERIALS AND METHODSTeeth preparation: Thirty two sound recentlyextracted maxillary 1st premolar were collectedfor this study, the root of each tooth wasembedded in an individual block of acrylic toabout (2mm) below the CEJ by the aid ofsurveyor. Each specimen was prepared to receiveall ceramic crown using high speed turbine handpiece with water coolant that was adapted to thevertical arm of the modified dental surveyor insuch a way that the long axis of the clinical crownkept parallel to that of the bur all the way duringtooth preparation procedure to ensure the sameconvergence angle for all specimens (Fig.1). Eachspecimen was prepared with the followingpreparation features; a planar (anatomical)occlusal reduction, 1.0 mm depth deep chamferfinishing line, 6 degree convergence angle and 4mm height (Fig.2).Figure 2: Finished prepared tooth.Impression proceduresImpression was taken for sixteen teeth by onestep impression technique using addition siliconeheavy and light body viscosity. The heavyimpression material (Express XT Penta H) wasautomatically mixed by Pentamix Lite automaticmixing machine (3M ESPE, Germany), while thelight body material (Express XT) was mixed anddispensed using a garant dispenser (3M ESPE,Germany). The heavy body was injected into thespecial tray and the light body material wascarefully injected on the prepared tooth until thetooth was completely covered then the special trayloaded with heavy body was seated on thespecimen by a dental surveyor under a 500 g loaduntil the three guided pines completely engagedthe holes in the acrylic base of the specimen (Fig.3).This procedure was continued sixteen times toget sixteen impression. Impressions were thenpoured by type IV dental die stone; all theprocedure was done according to themanufacturer's instructions.(A)(B)Restorative Dentistry21
J Bagh College DentistryVol. 29(4), December 2017center of the preheated pressing furnace(programat EP3000; Ivoclar Vivadent Schaan,Liechtenstein) at 920ºC (Fig. 4).Figure 3: Impression taking with dentalsurveyor.Samples groupingThe prepared teeth specimens and the workingdies are divided into two groups according to thetechnique of digital impression:Group A: Indirect digital impression technique.Group B: Direct digital impression technique.Each group was then subdivided into twosubgroups according to the fabrication techniquesas follow: A1: Indirect digital impression wastaken for eight dies using CEREC inEos X5scanner for the fabrication of eight IPS e-maxPress crowns. A2: Indirect digital impression wastaken for eight dies using CEREC inEos X5scanner for the fabrication of eight IPS e-maxCAD/CAM crowns. B1: Direct digital impressionwas taken for eight prepared teeth using intraoralCEREC AC Omnicam camera for the fabricationof eight IPS e-max Press crowns. B2: Directdigital impression was taken for eight preparedteeth using intraoral CEREC AC Omnicamcamera for the fabrication of eight IPS e-maxCAD/CAM crowns.Crowns fabricationinLab MC X5 (Sirona Dental Systems,Bensheim, Germany) was used to fabricate thefull ceramic crowns and the wax patterns usingCEREC in-Lab (version 15.2) software.CAD/CAM Crowns fabrication (A2, B2): IPS emax CAD (LT A2, Ivoclar Vivadent, Schaan,Liechtenstein) block was used to constructceramic crowns for these groups. The crownswere designed using the biogeneric softwareaccording to the recommended parameters (80 μmcement spacer and 100 μm marginal thickness)then crystallized in a short 25 minutes firing cyclein a ceramic firing furnace (Programat P310,Ivoclar Vivadent/technical, Schaan, Liechtenstein)at 840ºC according to the manufacturer’sinstructions.Pressing fabrication technique (A1, B1): Thesame procedure used for the fabrication of IPS emax cad crowns was followed here in order tofabricate a digital wax patterns using blueCAD/CAM wax blank (BiLKiM, Izmir, Turkey).The sixteen wax patterns were sprued andinvested into the investment ring. The investmentring was then preheated in a burn out furnace at(850ºC) for 45 min. After that, the ring wasremoved from the preheated furnace and a coldIPS e.max press (LT A2, Ivoclar Vivadent,Schaan, Liechtenstein) ingots were placed insidethe investment ring followed by placement of coldIPS Alox Plunger and then transferred into theRestorative DentistryThe Influenceamong(A)(B)(C)(D)22
J Bagh College DentistryVol. 29(4), December 2017The Influenceamong(E)Figure 4: Steps of press crown fabrication.Measurement of the marginal gapThe marginal fit of the crown was calculatedby measuring the vertical gap between the marginof the tooth and that of the ceramic crown.A specially designed holding device was usedto apply a static load of (50 N) on the testedcrowns to ensure the accuracy of their seating andto hold them in place during the examination (14).With a Dino-lite digital microscope at amagnification of 280X the measurements wereperformed on four points on each tooth surface(two on both sides of the indentation): first pointwas determined on the edge of the indentationwhereas the second one was (1mm) from the firstpoint, a total of 16 marginal adaptation evaluationsites for each tooth (15) (Fig. 5). The digital imageswere captured by (Dino capture software) andthen analyzed with image analysis software(Image J, 1.50i, U.S. National Institutes of Health,Bethesda, MA, USA) which was used to measurethe vertical marginal gap by drawing a linebetween the margin of the tooth and that of thecrown. Calibration for magnification was made bytaking an image of a millimeter ruler at the samemagnification (280 X) and input into (Image J)and converted the readings from pixels to (μm)(Fig.6).Figure 6: Image of one millimeter at 280Xmagnification.Statistical analysesData were collected and analyzed using SPSS(statistical package of social science) softwareversion 18.The following statistics were used:A- Descriptive statistic: including mean, standarddeviation, statistical tables and graphicalpresentation by bar charts.B- Inferential statisticsI. One way analysis of variance test (ANOVA)was used to see if there were any significantdifferences among the means of subgroups.II. LSD (least significant difference) test wascarried out to examine the source of differencesamong the four subgroups.RESULTSTotal of (512) measurements of verticalmarginal gap from four subgroups were recorded,with 16 measurements for each crown.Table (1) showed that the highest mean of verticalmarginal gap was recorded in group A2 (55.93 μm 3.300).While the lowest mean marginal gapwas recorded in group B1 (29.91 μm 5.534) andthis clearly explained in (Fig.7) while Table (2)and Table (3) showed that there is a highlysignificant difference in vertical marginal gapamong the four subgroups.Figure 5: Points of measurement.Table 1: Descriptive statistics of vertical marginal gap for all groups in (μm) .Digital techniqueGroupsNIndirect digital techniqueADirect digital techniqueBRestorative .431Descriptive StatisticsMaxMeanMax.Mean Std.47.78837.74 5.43362.16955.93 3.30042.27629.91 5.53459.66144.49 6.840
J Bagh College DentistryTable 2: ANOVA test among the groups.Sum of SquaresdfMean 1Between GroupsWithin GroupsTotalHS: P 0.01GroupsA1B2Vol. 29(4), December 2017The InfluenceamongF160.833Sig.0.000(HS)Table 3: LSD test for comparison of significance between subgroups.Mean DifferencesP- (HS)B114.580.000(HS)HS: P e 7: Bar-chart showing the mean values of the marginal gap in (μm) for all subgroups.camera) do not require disinfection, landtransportation or fabrication of a gypsum cast.Thus, the potential for dimensional inaccuraciescould be eliminated, or at least dramaticallyreduced (17).The results of this study agree with Jonthan etal. (2014) (19) and Khdaier and Ibraheem (2016) (20)who founded that crowns fabricated with directdigital impressions showed more accuratemarginal adaptation. However, this finding is incontract with Salem et al. (2016) (21) whoconcluded that the conventional impressions aresignificantly more accurate. Such disagreementcould be due to the difference in the methodologyused.Effect of the fabrication technique: Accordingto the results of this study, crowns fabricated withCAD/CAM technique showed higher marginalgap than crowns fabricated with press technique.This may be due to the shrinkage of the materialduring crystallization process causing distortionof the margins.DISCUSSIONResults obtained from the current studyshowed that the marginal gap of the four groupswas within the clinically acceptable range becausethe mean marginal gap with the range of 120 μmhave been proposed as being clinically acceptablewith regard to the longevity of restorations(16).Effect of digital impression technique: Theresults of this study revealed that indirect digitaltechnique groups had significantly highermarginal gap than the direct digital groups.The higher inaccuracy of the indirect way isalways present from the first steps of the processuntil completion of the definitive restoration dueto the fact that conventional impression techniquerequires numerous steps such as impressionmaterials selection, tray selection, use ofadhesives, disinfection, transportation, pouringand since every step in a workflow contributes tothe risk of overall failure, the elimination of theconventional impression and its inherent risks,results in higher accuracy (17,18). On the otherhand, direct digital impressions (OmnicamRestorative Dentistry24
J Bagh College DentistryVol. 29(4), December 2017At the time of milling, IPS e-max CAD blockis partially crystallized (lithium metasilicate) andthe size of particles generally ranges between 0.2μm and 1.0 μm with a flexural strength of 130MPa. After crystallization at 840 C for 25minutes in a furnace, the size of the particlesincreases under control to 5 μm. Through suchmodification processes, the flexural strength ofthe restoration increases to 360 MPa, an increaseof 170% (22, 23). The crystal spacing becomesdenser and the proportion of fine lithium disilicatecrystals within the glassy matrix increases from40% to 70% after complete crystallization. Suchchanges was not fully controllable and causes0.2% linear shrinkage which affect the overall fitof the dental prosthesis, increasing marginal gaps(24,25,26). In pressed ceramics, sintering shrinkageduring firing may be avoided because it isfabricated by a combination of the lost-wax andheat pressed techniques. In this technique, thecomplete contour wax pattern is invested and aceramic ingot is pressed into the resultantinvestment mold to the full extent of the waxpattern (27).The result of this study was coinciding withMously et al. (2014) (28) and Neves et al. (2014)(29) who found that lithium disilicate restorationfabricated with the press technique hadsignificantly smaller marginal gap than thosefabricated with CAD technique.However, the finding of this study is disagreewith study done by Jonthan et al. (2014) (19) whofound that E-max CAD restoration hadsignificantly smaller marginal gap than E-maxpress restoration; such disagreement could be dueto the difference in the methodology . Hamza TA, Ezzat HA, El-Hossary MM, Katamish HA,Shokry TE, Rosenstiel SF. Accuracy of ceramicrestorations made with two CAD/CAM systems. JProsthet Dent 2013; 109(2): 83-87.2. Holmes JR, Bayne SC, Holland GA, Sulik WD.Considerations in measurement of marginal fit. JProsthodont Dent 1989; 62(4): 405-408.3. Maritilo, Gjerdet NR, Tvinnereim HM. The firingprocedure influences properties of a zirconia coreceramic. J Dent Mater 2008; 24: 471-475.4. Christensen GJ. Esthetic dentistry-2008. J Alpha Omega2008; 101: 69-70.5. Fasbinder D, Dennison J, Heys D, Neiva G. A clinicalevaluation of chairside lithium disilicate CAD/CAMcrowns: a two-year report. J Am Dent Assoc 2010; 141:105-114.6. Tysowsky G. The science behind lithium disilicate:today’s surprisingly versatile, esthetic and durablemetal-free alternative. J Oral Health 2009.7. Anadioti E, Aquilino S, Gratton D, Holloway J, Denry I,Thomas G, Qian F. 3D and 2D marginal fit of pressedand CAD/CAM lithium disilicate crowns made fromRestorative Dentistry20.21.22.23.24.25.25The Influenceamongdigital and conventional impressions. J Prosthodont2014; 23: 610-617.Christensen GJ. Laboratories want better impressions. JAm Dent Assoc 2007; 138(4): 527-529Christensen GJ. The state of fixed prosthodonticimpressions. Room for improvement. J Am Dent Assoc2005; 136: 343-346.Al-Bakri IA, Hussey D, Al-Omari WM. Thedimensional accuracy of four impression techniqueswith the use of addition silicone impression materials. JClin Dent 2007; 18(2): 29-33.Touchstone A, Nieting T, Ulmer N. Digital transition:the collaboration between dentists and laboratorytechnicians on CAD/CAM restorations. J Am DentAssoc 2010; 141(2): 15S-19S.Tan PL, Gratton DG, Diaz-Arnold AM, Holmes DC. Anin vitro comparison of vertical marginal gaps ofCAD/CAM titanium and conventional cast restorations.J Prosthodontics 2008; 17(5): 378-383.Beuer F, Schweiger J, Edelhoff D. Digital dentistry: anoverview of recent developments for CAD/CAMgenerated restorations. Br J Dent 2008; 204(9): 505-511.Beuer F, Aggstaller H, Edelhoff D, Gernet W, SorensenJ. Marginal and internal fits of fixed dental prostheseszirconia retainers. Dent Mater J 2009; 25: 94-102.Lombardas P, Carbunaru A, Mcalarney ME, ToothakerRW. Dimensional accuracy of castings produced withringless and metal ring investment systems. J ProsthetDent 2000; 84(1): 27-31.Mclean JW, Vonfraunhofer JA. The estimation ofcement film thickness by an in vivo techique. Br Dent J1971; 131(3): 107-111.Syrek A, Reich G, Ranftl D, Klein C, Cerny B,Brodesser J. Clinical evaluation of all-ceramic crownsfabricated from digital impressions based on theprinciple of active wavefront sampling. J Dent 2010;38(7): 553-559.Burgess JO, Lawson NC, Robles A. Comparing Digitaland Conventional Impressions and Assessing theaccuracy, efficiency, and value of today’s systems. Jinside Dentistry 2013; 9(11).Jonathan NG, Ruse D, Wyatt C. A comparison of themarginal fit of crowns fabricated with digital andconventional methods. J Prosthet Dent 2014; 112(3):555-560.Khdaier RM, Ibraheem AF. Marginal fitness ofCAD/CAM all ceramic crowns constructed by direct andindirect digital impression techniques: An in vitro study.J Bagh coll Dentistry 2016; 28(2): 30-33.Salem NM, Abdel Kader SH, Al Abbassy F, Azer AS.Evaluation of fit accuracy of compute raideddesign/computer-aided manufacturing crowns fabricatedby three different digital impression techniques usingcone-beam computerized tomography. Eur J Prosthodont2016; 4(2): 32-36.Giordano
Figure 3: Impression taking with dental surveyor. Samples grouping The prepared teeth specimens and the working dies are divided into two groups according to the technique of digital impression: Group A: Indirect digital impression technique. Group B: Direct digital impression technique. Each group was then subdivided into two
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