RESEARCH AND EDUCATION

Materials donaAssistant PrbResearch AcResearch AsdProfessor an

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Comparison of fracture strength and failure mode of differentceramic implant abutments

Adham Elsayed, BDS,a Sebastian Wille, Dr rer nat,b Majed Al-Akhali, BDS,c

and Matthias Kern, Prof Dr med dent habild

ABSTRACTStatement of problem. The whitish color of zirconia (ZrO2) abutments offers favorable estheticscompared with the grayish color of titanium (Ti) abutments. Nonetheless, ZrO2 has greater opacity,making it difficult to achieve natural tooth color. Therefore, lithium disilicate (LaT) abutments havebeen suggested to replace metal abutments.

Purpose. The purpose of this in vitro study was to evaluate the fracture strength and failure modeof single-tooth implant restorations using ZrO2 and LaT abutments, and to compare them withtitanium (Ti) abutments.

Material and methods. Five different types of abutments, Ti; ZrO2 with no metal base; ZrO2 with ametal base (ZrT); LaT; and LaT combination abutment and crown (LcT) were assembled on 40 Tiimplants and restored with LaT crowns. Specimens were subjected to quasistatic loading using auniversal testing machine, until the implant-abutment connection failed. As bending of the metalwould be considered a clinical failure, the values of force (N) at which the plastic deformation of themetal occurred were calculated, and the rate of deformation was analyzed. Statistical analysis wasdone using the Mann-Whitney U test (a=.05).

Results. Group ZrO2 revealed the lowest resistance to failure with a mean of 202 ±33 N. Groups ZrT,LaT, and LaC withstood higher forces without fracture or debonding of the ceramic suprastructure,and failure was due to deformation of metal bases, with no statistically significant differencesbetween these groups regarding the bending behavior.

Conclusions. Within the limitations of this in vitro study, it was concluded that LaT abutments havethe potential to withstand the physiological occlusal forces that occur in the anterior region andthat ZrO2 abutments combined with Ti inserts have much higher fracture strength than pure ZrO2

abutments. (J Prosthet Dent 2017;117:499-506)

Dental implants have beensuccessfully used to restorecomplete and partially eden-tulous arches.1-3 Furthermore,many in vivo studies haveshown high success rates over5 to 10 years, ranging from 95%to 97% for single-implant res-torations.4-6 As a result of itswell-documented biomechan-ical properties,1,7,8 titanium (Ti)became the standard materialfor implant abutments. How-ever, metal components oftenshine through the mucosa giv-ing a grayish shade.9 In addi-tion, when Ti abutments arerestored with ceramic crowns,the underlying metal abutmentmay affect the color of therestoration.2,10-12

To meet the increased de-mands for highly esthetic re-sults, new generations of

ceramic abutments have been developed. Still, ceramicsare inherently brittle, making them susceptible to tensilestresses.13 This limits the widespread application of ce-ramics as implant abutments. Zirconia (ZrO2) ceramics,as a result of transformation toughening, exhibit highflexural strength (900 to 1200 MPa), compression

ated by FairImplant (Bönningstedt, Germany) and Ivoclar Vivadent AG (Scofessor, Department of Prosthodontics, Propaedeutics and Dental Materialssociate, Department of Prosthodontics, Propaedeutics and Dental Materiasociate, Department of Prosthodontics, Propaedeutics and Dental Materiad Chair, Department of Prosthodontics, Propaedeutics and Dental Materia

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strength (2000 MPa), and fracture toughness (6MPa$m0.5) as well as excellent biocompatibility andimproved esthetics.14-17

Zembic et al18 showed excellent survival rates forsingle-implant ceramic crowns supported by ZrO2

abutments and estimated 5-year survival and failure rates

haan, Liechtenstein).s, School of Dentistry, Christian-Albrechts University at Kiel, Kiel, Germany.ls, School of Dentistry, Christian-Albrechts University at Kiel, Kiel, Germany.ls, School of Dentistry, Christian-Albrechts University at Kiel, Kiel, Germany.ls, School of Dentistry, Christian-Albrechts University at Kiel, Kiel, Germany.

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Table 1.Overview of study outline and group codes

Group Abutment Crown

Ti Titaniuma Lithium disilicatec

ZrO2 Zirconia (no metal insert)b Lithium disilicatec

ZrT Zirconia (with metal insert)b Lithium disilicatec

LaT Lithium disilicate (with metal insert)c Lithium disilicatec

LcT Lithium disilicate combination abutment and crown (with metalinsert)c

aCopraTi-4: grade 4 Ti blanks (Whitepeaks; lot no. T4001). bWieland Zenostar (WielandDental; lot no. S23252). cIPS e.max CAD (Ivoclar Vivadent; lot no. T44702).

Clinical ImplicationsConventionally, titanium is the material of choice forimplant abutments, although the metal mightpresent esthetic problems. Zirconia and lithiumdisilicate ceramic abutments seem to providepromising treatment alternatives to metalabutments, especially in esthetically challengingsituations.

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comparable to metal abutments supporting metalceramic crowns. Conversely, ZrO2 aging and sensitivityto low-temperature degradation could reduce strengthand toughness.16,17

Excellent esthetics can be achieved by manufacturingabutments entirely of ZrO2, yet weak and fracture-pronepoints can develop at the connection, especially withinternal connection types.19,20 Moreover, the precision ofthe pure ZrO2 abutment connection interface has beenquestioned, as ceramics cannot be machined as preciselyas metals.21 Such inaccuracy can promote screw loos-ening and microbial infections, which may lead to mar-ginal bone loss.22

A Ti insert can overcome the brittleness of ZrO2 andimprove the fracture resistance of the abutment.23 In arecent study, when 5 different ZrO2 abutments weretested for fracture strength, ZrO2 abutments with Ti in-serts demonstrated a greater fracture resistance than pureZrO2 abutments.24

Glass ceramics have proven to be more esthetic thanZrO2, which has poor translucency and is unnaturallywhite and opaque.25-27 Lithium disilicate is the strongestand toughest of the glass ceramics available. It hasmoderate flexural strength (360 to 440 MPa)28 and frac-ture toughness (2.5 to 3 MPa$m0.5)29 and excellenttranslucency and shade matching.27,30 Higher trans-lucency was observed for lithium disilicate (LaT) than forZrO2-based ceramic systems.26,31

In esthetically challenging treatments, tooth-coloredLaT offers better and more natural esthetics than whiteZrO2 abutments. LaT abutments may be suitable as anesthetic alternative toZrO2 if proved tobe clinically reliable.

LaT abutments may be used as a combination abut-ment bonded to a Ti insert supporting a ceramic crown(lithium disilicate) or as a combination abutment andcrown, where the abutment and crown are fabricated in 1piece that will be bonded to a Ti insert and screwed to theimplant. The screw access hole is subsequently closedwith composite resin.32-34

Because cemented crowns are difficult to remove aftera complication, such as screw loosening, the combinationabutment crown allows easy access to the screw throughthe composite resin. Additionally, residual cement may

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lead to periimplant tissue inflammation.35,36 These haz-ards could be eliminated with the use of the combinationabutment crown.

The authors are aware of few articles or case reportsdescribing the use of LaT ceramic as an implant abutmentmaterial.32-34 Additionally, limited laboratory or clinicalstudies have compared the mechanical properties of ZrO2

abutments with ZrO2 abutments supported by a Ti insertusing internal conical connection and have shown betterresults for the ZrO2 abutments with inserts.19,24,37

Laboratory tests can be done in a short time and arereproducible, with the possibility of standardizing testparameters.38 Well-designed laboratory tests can beeffective indicators of the applicability and performance ofmaterials and their likely clinical success before wide-spread clinical use is recommended. The purpose of thisin vitro study was to (1) evaluate the fracture resistance ofsingle-tooth implant-supported ceramic restorations us-ing ZrO2 and LaT abutments and to compare them withconventional Ti abutments and to identify the mode offailure of the restorations; (2) evaluate the effect of a Tiinsert on the fracture strength of ZrO2 abutments; and (3)evaluate the differences in mechanical properties betweenthe 2 methods of using LaT as an abutment material.

The null hypothesis of the study was that no differ-ences would be found in resistance to fracture among thedifferent abutment materials or the different forms ofusing ZrO2 or LaT abutments.

MATERIAL AND METHODS

Forty Ti implants (FairTwo, grade 4 Ti, lot: 135395;FairImplant) with a diameter of 4.2 mm, a length of 11.5mm, and an internal conical connection and platform-switched design were used in this study. For randomi-zation, numbers were assigned to the implant specimens.Then, numbers were randomly drawn to distribute thespecimens into 5 groups of 8 implants each according tothe abutment material and type (Ti; pure ZrO2; ZrO2

with Ti insert [ZrT]; LaT; and LaT combination abutmentcrown [LcT]) as shown in Table 1 with their group codes.The implants were restored with 40 single implant-supported ceramic crowns made from lithium disilicateglass ceramic (IPS e.max CAD, lot: T44702; Ivoclar

Elsayed et al

Figure 1. Restoration components of groups ZrT, LaT, and LcT. GroupZrT: implant (a), Ti insert (b) bonded to ZrO2 suprastructure (c), andcrown (e) was cemented onto abutment. Group LaT: implant (a), Ti insert(b) bonded to LaT suprastructure (d), and crown (e) was cemented ontoabutment. Group LcT: implant (a), Ti insert (b) bonded to LaTcombination abutment and crown (f).

8.5

3.1

4.8

11

1.2

2.8

3.0

0.5

3.0

Figure 2. Dimensions (mm) of restorations: Ti insert (blue), abutment/suprastructure (orange), and crown (green).

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Vivadent AG), simulating a maxillary right central incisorof 11 mm in length and 8.5 mm in width. Figure 1 showsthe components of groups ZrT, LaT, and LcT.

The implants were embedded in a 3-component,autopolymerizing polyester resin (Technovit 4000, lot:010294; Heraeus Kulzer) to imitate the elastic reaction ofthe surrounding bone during loading.39 The resincovered the implant body up to the first thread. Brasstubes were used as molds and served to hold the spec-imen during testing.

All abutments were attached to the implants with Tiscrews (lot: 961209; FairImplant). The torque wrencheswere calibrated (Torque Tester; Crane Electronics), andthe screws were tightened to 25 Ncm. After 10 minutes,the screws were retightened to prevent screw loos-ening.40-42 The screw holes were filled with foam pelletsand gutta percha.

All abutments and crowns were custom-manufacturedaccording to a scanned modified Ti abutment and acrown wax pattern. For means of standardization, usingcomputer-aided design/computer-aided manufacture(CAD) technology, the scanned design was used to millall restorations. The dimensions of the crowns andabutments are shown in Figure 2. A minimum thicknessof 0.5 mm for the abutment was applied. A chamfer finishline with rounded internal angles was used to provideimproved mechanical retention43,44 and marginal fit.45,46

Elsayed et al

Before adhesive cementation of the restorations,proper surface treatment of each material was done ac-cording to the manufacturers’ instructions (Table 2).Subsequently, all surfaces were primed for at least 60seconds using a universal primer for ceramics and metal47

(Monobond Plus, lot: S14727; Ivoclar Vivadent AG).Ti inserts (grade 4 Ti inserts, lot: 399275; FairImplant)

were adhesively cemented to the ceramic suprastructures(ZrO2 in group ZrT and LaT in groups LaT and LcT),using an autopolymerizing luting composite resin (Mul-tilink Hybrid Abutment, lot: T35016; Ivoclar VivadentAG) under a constant load of 7.4 N. Excess cement wasremoved, and a glycerin gel (Liquid strip, lot: T29465;Ivoclar Vivadent AG) was applied to prevent the forma-tion of an oxygen-inhibited layer.

For adhesive cementation of the crowns to the abut-ments, a dual-polymerizing adhesive resin cement (Mul-tilink Automix, lot: T29844; Ivoclar Vivadent AG)was usedunder a constant load of 50 N. After excess cementwas removed, a glycerin gel (Liquid strip; Ivoclar VivadentAG) was applied to the abutment-crown interface. Lightpolymerization (Elipar 2500; 3M ESPE) was then appliedfor 20 seconds from the labial and palatal sides.

In group LcT, the screw hole was sealed with com-posite resin (Tetric EvoCeram, lot: T09635; Ivoclar Viva-dent AG), which was applied in increments, and each

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Table 2. Surface treatment of all materials used

Material Restoration Surface Treatment

Titanium Titanium abutments(group Ti)Titanium inserts (groupsZrT, LaT, LcT)

Airborne-particle abrasion with 50-mmalumina particles at 250 kPa until dullsurface was achieved*

Zirconia Zirconia abutments(group ZrO2)Zirconia suprastructure(group ZrT)

Airborne-particle abrasion with 50-mmalumina particles at 100 kPa, until blackmarker coating was completely removed*

Lithiumdisilicate

Abutments (group LaT)Combination abutmentand crown (group LcT)Crowns of groups (Ti,ZrO2, ZrT, LaT)

Etching for 20 s with 4.5% hydrofluoric acid(IPS Ceramic Etching Gel, lot: T40413; IvoclarVivadent AG)†

*After airborne-particle abrasion, parts ultrasonically cleaned in 99% isopropanol for3 minutes and dried. †After etching, parts cleaned with water spray and dried withoil-free air.

Figure 3. Specimen of control group (Ti) during quasistatic loading.Force applied at 30 degrees to implant axis.

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was light polymerized for 20 seconds. The restorationswere stored in distilled water at 37�C for 72 hours beforetesting to ensure that the resin cement had completelypolymerized.

Fracture strength measurements were carried outusing a universal testing machine (Z010; Zwick). Loadswere applied with an angle of 30 degrees to the long axisof the implants to simulate a clinical occlusal forceapplication48-50 representing a class I occlusion with a150-degree interincisal angle.51 The point of forceapplication was 3 mm below the incisal edge, using a 0.5-mm-thick tin foil (Zinnfolie; Dentaurum) to ensure evenstress distribution (Fig. 3). A compressive force was thenapplied using a preload of 5 N and a cross-head speed of2 mm/min until failure, which was perceived as thefracture, a sudden reduction in force, or deflection of 3mm. The failure loads were recorded with software(testXpert II V3.3; Zwick).

After failure, each specimen was examined visuallyand under an optical microscope (Carl Zeiss) to deter-mine the mode of failure. Radiographs were made of thespecimens that failed due to metal bending to observewhether the screw or the abutments had fractured.

To reveal differences in the bending behavior of metalbases, the deformation in each abutment was determinedfor forces equivalent to 100, 200, 300, and 400 N. Thedeflection of the specimens (in mm) for each 100-Nincrease in force was measured and analyzed. Normalitydistribution was tested using the Shapiro-Wilk test, whichrevealed that the data were not normally distributed.Therefore, statistical analyses of the test results weremadewith the Kruskal-Wallis test, followed by multiple pair-wise comparisons of the groups using the Mann-Whitney U test (a=.05). Significance levels were adjustedwith the Bonferroni-Holm correction for multiple testing.

RESULTS

The mean fracture load for 1-piece ZrO2 abutments was218.5 ±14.4 N. These abutments exhibited 1 type of

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failure that was fracture of the ceramic and was locatedpredominantly at or slightly above the level of theimplant shoulder (Fig. 4A).

A visual assessment of failed specimens of the Tiabutments (group Ti) and all abutments with Ti insert(groups ZrT, LaT, and LcT) showed a homogenous modeof failure. They presented bending at the screw andinternal connection of the Ti abutment or insert withoutceramic displacement or fracture. Figure 4B shows arepresentative LaT abutment. None of the abutments inthe 4 groups fractured or showed mobility after testing.However, radiographs (Fig. 4C, D) showed no fracture inthe screw or the metal. Figure 5 shows the measurementsused to determine the deformation of metal in these 4groups. The results of the deflection of the specimens foreach 100-N increase in force are given in Table 3. Asignificant difference was found between the Ti abut-ments and the 3 groups with Ti inserts, whereas the Tiabutments showed significantly higher deformation thanthe Ti inserts for all measurements (100 to 200 N, 200 to300 N, and 300 to 400 N). However, groups ZrT, LaT,and LcT with the Ti inserts did not show any significantlydifferent deformation behavior.

DISCUSSION

The null hypothesis was partially rejected, as no differ-ences were found between LaT abutments with the 2designs and the combination ZrO2 abutments. However,pure ZrO2 abutments showed lower resistance to fracturethan combination ZrO2 abutments. To eliminate otherpossible factors influencing the fracture strength, only thematerial of the abutment was varied, while all otherfactors such as crown and luting materials were keptconstant.

Maximal occlusal forces reported in the anteriorregion were in the range of 150 to 235 N with a mean of206 N.49 Such loads were tolerated by specimens from

Elsayed et al

Figure 4. A-D, Failure mode of specimens from groups Ti, ZrO2, ZrT, and LcT. A, Fracture specimen. Image shows fracture line slightly above implantshoulder, which is a typical fracture of ZrO2 abutments (original magnification ×40). B, Typical failure mode of specimens with LaT abutments (groupsLaT and LcT) bending of Ti insert to buccal direction. C, Radiographic image shows group Ti specimen after failure. D, Radiographic image shows groupZrT specimen after failure.

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groups Ti, ZrT, LaT, and LcT but not by specimens fromgroup ZrO2.

The pure ZrO2 abutments in this study had a mean±SD fracture resistance of 218.5 ±14.4 N. This value isconsidered to be in the range of the physiologicalmaximum occlusal forces in the anterior region, indi-cating a risk of failure when this type of abutment is usedclinically. The mode of failure of the pure ZrO2 abut-ments was fracture of the ceramic at the connection. Nofracture or bending of the implant or abutment screw

Elsayed et al

occurred. This is consistent with the results of otherstudies.39,52-55

In this study, Ti, combination ZrO2 and both types ofLaT abutments could bear loads more than the reportedphysiological occlusal forces in the anterior regions.Although they became deformed, combination ZrO2 andLaT abutments successfully resisted fracture and couldtolerate forces in the range of 900 N. Still, these valuescannot be stated as the definitive fracture strength of thematerials as there was reduction of force and the test was

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Figure 5. Force-deflection graph used to measure deflection (specimenfrom group LcT). Red lines indicate specimen deflection at 100, 200, 300,and 400 N.

Table 3. Traverse distance of deformation of metal at given forces (mm)and statistical differences

Group dL (100-200 N) dL (200-300 N) dL (300-400 N)

Ti (n=8) 512A 635A 853A

ZrT (n=8) 156B 182B 195B

LaT (n=8) 173B 142B 207B

LcT (n=8) 141B 164B 189B

Different superscript letters indicate significant differences between groups. Mann-WhitneyU tests (a=.05). Overall Kruskal-Wallis test (a=.001).

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stopped because of plastic deformation of the Ti inserts,which is deemed as failure. In addition, failure of com-bination ZrO2 and LaT because of fracture or debondingbetween the metal and ceramic did not occur in thisstudy. Thus, all specimens of these groups showed moreresistance to loading than the minimum required fractureresistance for anterior restorations.

The mean fracture strength of the LaT ceramics arereported to be lower than that of ZrO2,30,56 yet statisticalanalysis of this study revealed no significant differencebetween the use of both materials as combination abut-ments. The failure occurred as a result of deformation ofthe Ti inserts and screws, which are similar in both typesof abutments, whereas the ceramic suprastructureremained intact. The purpose of this study was to test thefailure of the abutments in respect to clinical situation. Asa result, testing was stopped after 3 mm of deformation ofthe abutments, even if ceramic fracture did not occur.However, if the loading tests had been continued, a dif-ference in the fracture resistance of ZrO2 and LaT mighthave been noticed. Similarly, no differences betweenabutments and combination abutment and crown madefrom LaT were observed, as again, the failure occurred atthe Ti inserts and not at the ceramic suprastructure. It canbe assumed that the adhesive cementation strengthenedthe connection between the abutment and the crown.

Clearly, the application of a secondary Ti insert posi-tively influences the performance of ZrO2 abutments byreplacing the brittle ZrO2 with metal at the weakest part.Furthermore, the difference between the fracture mode ofthe ZrO2 and ZrT groups was prominent. This resultcorresponds to that of previous studies.19,24,37 The Ti insert

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and the ZrO2 abutments were airborne-particle abraded,and both parts were adhesively bonded using a compositeresin, as recommended clinically and by some studies.23

The cervical region of the abutments is subjected tohigh stress concentrations; therefore, the implementationof a Ti insert is important to replace the brittle ceramicwith metal. Hence, the LaT abutments were exclusivelyassembled with Ti inserts. This also complies with themanufacturer’s instructions.

During screw tightening, some favorable degree ofelastic deformation occurs in the Ti,7 which is known asthe settling effect.8 Loads higher than the yield limit of theTi will cause plastic deformation of the abutment, whichmay result in fracture of the screw as it is the weakestcomponent of the implant-abutment connection.52 Thisexplains the deformation of the Ti abutment and Ti insertsin this study. The bending behavior of Ti inserts in spec-imens from the ZrT, LaT, and LcT groups was similar.However, the Ti abutments exhibited higher bending thanthe Ti inserts at the same load values. According to themanufacturer’s explanation, the Ti abutments used weremilled from blanks in a dental laboratory to produce thecustomized design of the abutment requested; mean-while, the Ti inserts were prefabricated in the factory withhigher precision equipment.

Several factors contribute to differences in the resultsand mode of failures between studies. Slight differencesin the composition of the Ti and the ZrO2 tested may bea reason for the different values between studies.19

Additionally, the load-bearing capacity of the implantrestorative system depends on the implant-abutmentconnection. The performance of Ti abutments, whenloaded, for systems with conical connections seems to beinferior to that of external hexagon connections.57,58

The specimens underwent no artificial aging withfatigue loading, which is a limitation of the study. Furtherstudies comparing data of the fatigue resistance of LaTabutments as well as ZrO2 with or without a Ti insert arerequired.

CONCLUSIONS

Within the limitations of this in vitro study, the followingconclusions were drawn:

1. LaT and ZrO2 abutments with metal inserts havethe potential to withstand physiological occlusal

Elsayed et al

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forces that occur in the anterior region and cantherefore be recommended as an esthetic alternativefor restoring single implants in the anterior region.

2. The fracture strength of LaT abutments is notinfluenced when they are used as a combinationabutment or as a combination abutment and crown.

3. ZrO2 abutments combined with Ti inserts havemuch higher fracture strength than pure ZrO2

abutments. Therefore, care must be taken whenusing pure ZrO2 abutments.

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54. Nothdurft FP, Doppler KE, Erdelt KJ, Knauber AW, Pospiech PR.Fracture behavior of straight or angulated zirconia implant abutmentssupporting anterior single crowns. Clin Oral Investig 2011;15:157-63.

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Noteworthy Abstracts of

Comparative accuracy of facial models fabric3D imaging techniques

Lincoln KP, Sun AYT, Prihoda TJ, Sutton AJ

J Prosthodontics 2016;25:207-215

Purpose. The purpose of this investigation was to compare thimpression methods to the three-dimensional printed (3DP)from cone beam computed tomography (CBCT) and 3D ster

Materials and Methods. A reference phantom model was fawith ten fiducial markers placed on common anthropometrigation control phantom model (CPM) using 3DP methods. Thcapture. Three CBCT and three 3D-SPG images of the CPM3dMD and three CBCT were imported to the 3DP, and six tdental stone were used to make three facial moulages of thegypsum dental stone. A coordinate measuring machine (CMMten fiducial markers. Each measurement was made using onsame measuring procedures were accomplished on all specimmens and the control. The data were analyzed using ANOVAand fiducial markers.

Results. The ANOVA multiple comparisons showed significFurther, the interaction of methods versus fiducial markers alsfacial moulage method showed the greatest accuracy.

Conclusion. 3DP models fabricated using 3D-SPG showed stusing the traditional method of facial moulage and 3DP modusing 3D-SPG were less accurate than the CPM and modelstechniques.

Reprinted with permission by the American College of Prost

THE JOURNAL OF PROSTHETIC DENTISTRY

Corresponding author:Dr Adham ElsayedDepartment of Prosthodontics, Propaedeutics and Dental MaterialsSchool of DentistryChristian-Albrechts University at KielArnold-Heller-Strasse 16, 24105 KielGERMANYEmail: aelsayed@proth.uni-kiel.de

AcknowledgmentsHamburger Fräsmanufaktur (Bönningstedt, Germany) for technical assistance.

Copyright © 2016 by the Editorial Council for The Journal of Prosthetic Dentistry.

the Current Literature

ated using traditional and

e accuracy of facial models fabricated using facial moulagefabrication methods using soft tissue images obtainedeophotogrammetry (3D-SPG) scans.

bricated using a 3D-SPG image of a human control formc landmarks. This image was converted into the investi-e CPM was attached to a camera tripod for ease of imagewere captured. The DICOM and STL files from the threeesting models were made. Reversible hydrocolloid andCPM, and the impressions/casts were poured in type IV) was used to measure the distances between each of the

e point as a static reference to the other nine points. Theens. All measurements were compared between speci-and Tukey pairwise comparison of the raters, methods,

ant difference among the three methods (p < 0.05).o showed significant difference (p < 0.05). The CBCT and

atistical difference in comparison to the models fabricatedels fabricated from CBCT imaging. 3DP models fabricatedfabricated using facial moulage and CBCT imaging

hodontists.

Elsayed et al