- Email: [email protected]
CAM zirconia copings
In vitro evaluation of the internal and marginal misfit of CAD/CAM zirconia copings Leonardo Lins, DDS,a Vinícius Bemfica, PhD,b Celso Queiroz, PhD,c and Antonio Canabarro, PhDd Veiga de Almeida University (UVA), Rio de Janeiro, Brazil; Federal University of Rio de Janeiro, Rio de Janeiro, Brazil Statement of problem. The constant updating of computer-aided design/computer-aided manufacture (CAD/CAM) systems and the introduction of new systems confirm the need for scientific evidence on internal and marginal adaptation. Purpose. The purpose of this in vitro study was to measure and compare the degree of internal and marginal misfits of zirconia single-unit copings made by using 3 different CAD/CAM systems (Ceramill, Lava 3M, and Neoshape). Material and methods. Twenty-four anatomic prefabricated abutments (Neodent) were used to fabricate zirconia copings in Ceramill (n¼ 8), Lava (n¼ 8), and Neoshape (n¼ 8). All copings were cemented and cut with a precision cutting machine to obtain 5 surfaces (mesial, distal, buccal, palatal, and incisal) and angle regions (internal axiogingival and axioincisal angles). Measurements were obtained from images at a magnification of 100 and 200 made with a digital camera attached to an optical microscope and adapted with a measuring device. The data were statistically analyzed with the 2-way ANOVA and Tukey honestly significant difference tests (a¼.05). Results. In the internal misfit evaluation, the mean values observed for Ceramill, Lava, and Neoshape were palatal surface 76.5, 65.5, and 77.7 mm (P¼.003); angle regions 69.4, 68.6, and 74.5 mm (P¼.010); incisal surface 127.7, 97.2, and 182.2 mm (P<.001); and overall mean 72.1, 69.4, and 76.4 mm (P¼.003). Significant differences were not found for mesial, distal, or buccal surfaces (P>.05). In the evaluation of marginal misfit (marginal discrepancy and absolute marginal discrepancy), the mean values found were 40.9 and 65.8 mm for Ceramill, 34.2 and 70.0 mm for Lava, and 39.3 and 74.5 mm for Neoshape. No significant differences were found among the 3 systems (P>.05). Conclusions. Although the Lava system showed a significantly lower value of internal misfit than the Neoshape system, all systems showed clinically acceptable marginal misfit values. (J Prosthet Dent 2014;-:---)
Clinical Implications Zirconia copings fabricated with CAD/CAM technology have been considered a good choice for restorations because of their excellent esthetics. The standardization of manufacturing processes may also produce copings with acceptable internal and marginal fit.
Computer-aided design/computeraided manufacture (CAD/CAM) has been used in dentistry since the 1980s, mainly to automate manual processes. Some authors claim that this system results in high-quality materials, standardization of manufacturing
a
processes, and reduction of production costs for prosthetic appliances.1-8 The development of different metal alloys and precise melting systems has contributed to the success of metalbased restorations. However, a need for materials with improved esthetic
Master of Science student, Department of Oral Rehabilitation, Veiga de Almeida University. Postdoctoral student, Department of Material Science, Federal University of Rio de Janeiro. c Full Professor, Department of Oral Rehabilitation, Veiga de Almeida University. d Full Professor, Department of Oral Rehabilitation, Veiga de Almeida University. b
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and biological properties has increased the requests for ceramic restorations. New zirconia restorations, for example, have helped to answer this demand.3 Internal and marginal adaptation are key criteria for the long-term clinical performance of fixed prostheses,
2
Volume including implant-supported restorations which have been the object of study by several authors.9-19 Studies have included the ideal internal and marginal thickness of the cement line20,21 and the correlation of the cement line and the mechanical22,23 and biological24-26 properties. The CAD/CAM technique, ceramic type, and their interaction have been found to have a statistically significant effect on the mean marginal fit.27 Studies have been undertaken to standardize methods of evaluating these adaptation criteria.10,11,28-37 However, in a systematic review of the internal and marginal adaptations of prosthetic elements fabricated with CAD/CAM systems, only 15 articles met the inclusion criteria, and only 9 systems were evaluated.32 These data reveal not only the lack of standardization of these studies but also the shortage of studies that evaluate new systems and new materials. Therefore, the aim of this study was to evaluate the internal and marginal adaptation of zirconia copings made on cone Morse (CM) anatomic abutments (Neodent), in Ceramill (AmannGirrbach), Lava (3M ESPE), and Neoshape (Neodent) CAD/CAM systems. Because of its esthetic advantage, zirconia copings have been considered a good choice for restorations in anterior teeth,38 although they do not affect marginal and internal adaptation.
MATERIAL AND METHODS Twenty-four CM anatomic exact titanium abutments (Neodent) and 9 cone Morse titanium implant analogs (Neodent) were obtained from the manufacturer. The analogs were attached with the aid of a dental surveyor (Delineador B2; Bio-Art Dental Equipment) in order to maintain them in the same position. A CM implant analog (Neodent) was fixed with liquid epoxy resin (Aradur HY 951; Aral Barco Material Trading Ltd) to a metal part to standardize the position of the CM anatomic abutments. Eight cone Morse titanium implant analogs (Neodent) were included with Type IV dental stone
(Vigodent) in plastic parts (Monta Tudo; Elka Plastics Ltda) to simulate the abutments sent to a laboratory for the fabrication of zirconia copings. Twenty-four zirconia copings were divided equally into 3 groups and made by using 3 different CAD/CAM systems: Ceramill system (C-G) (n¼8), Lava 3M system (L-G) (n¼8), and Neoshape system (N-G) (n¼8). The sample size was determined by a pilot study with 3 specimens of each system. The mean value found for the internal misfit was 72 mm, with a standard deviation of 4.5 mm. The reference value of 76 mm was based on the values of a previous study.33 On the basis of these values, for a power of .80 with a¼.05, the sample size was calculated as 8. The copings were made in 3 different laboratories that followed the recommended requirements of each system and were certified by the manufacturers. They were fabricated in tetragonal polycrystalline zirconia stabilized with 0.6 mm thick (Y-TZP) presynthesized yttrium and were inspected with a stereomicroscope (Stemi DV4; Carl Zeiss) at 8 magnification to detect any possible fabrication defect. The zirconia copings were cemented on the CM anatomic abutments with zinc phosphate cement (SS White) because it is considered the gold standard against which all other luting agents are compared.39 The specimens were submitted to a 50-N load in a universal testing machine (Emic DL 2000; Emic) for the 5-minute period recommended by the zinc phosphate cement manufacturer. Any excess cement was removed with a scalpel (Solidor). After 24 hours, the specimens were embedded in liquid epoxy resin (Aradur HY 951; Aral Barco Material Trading Ltd) in custom metal molds to standardize their position and to prevent displacement during the cutting and polishing procedures. The embedded specimens were sectioned across their long axis to obtain buccal (or facial) and palatal (or lingual) surfaces with a low concentration diamond blade (Extec Corp;
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Enfield) in a low-speed precision cutting machine (Isomet; Buehler Ltd). They were polished with a wet abrasive paper (3M Brazil) in a polishing machine (Arotec S/A Industry and Trade) following a sequence of 400, 600, 1200, and 2500 grits. A polishing cloth (Struers DP-Mol and DP-Nap; Struers Scientific Instruments) with 6, 3, and 1 mm diamond paste (Struers Scientific Instruments) was used for the finishing. The specimens were then examined with an optical microscope (Olympus BX60M; Olympus Corp), and photographs were made. Then the specimens were reembedded in liquid epoxy resin and cut across their long axis to obtain the mesial and distal surfaces. To evaluate the internal and marginal misfits, an optical microscope (Olympus BX60M; Olympus Corp) was used in association with a digital camera (Canon 5D Mark III; Canon Inc) adapted with a measuring device (Multifunction Target Max Levy; Max Levy Autograph Inc). Digital photographs with 100 and 200 magnification were standardized to a 57603840 pixel resolution in the RAW format. They were then transferred to an image management program (Adobe Photoshop CS5 Extended; Adobe Systems Inc), and the logic length was converted in pixel length with the program measurement tools. Digital photographs were made to evaluate the internal misfit of the cement line of the 11 buccal and palatal cuts (BP). Six were used for the buccal surface and incisal-buccal border, and 5 were used for the palatal surface and incisalpalatal border. Eight photographs were made of the mesial-distal cut. Four were used for the mesial surface and for the mesial and incisal border and 4 for the distal surface and distal-incisal border. The photographs were made every 1.7 mm along the cement-abutment interface (Figs. 1, 2). To evaluate the internal misfit, measurements were initially made in the angle regions (internal axiogingival angle, n¼3; axioincisal angle, n¼3) for a more accurate measurement. The first point of reference corresponds to the
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1 Anatomic titanium abutment and coping cemented to 2 Coping cemented to abutment sectioned in mesial-distal abutment sectioned in buccal-palatal direction (buccal sur- direction (mesial surface at top, distal surface at bottom); original magnification, 5. face at top, palatal surface at bottom); original magnification, 5.
3 Standardization used to measure internal misfit. Note that initial Point 1 is based in center of curve, on internal surface of cement line. Points 2 and 3 stand at points 200 mm equidistant from initial point. Scale bars, 0.1 and 0.5 mm; original magnification, 100. central point of the angle (Fig. 3). The 2 subsequent points were located 200 mm equidistant from this central point (Fig. 3). Lines were drawn perpendicular to those points passing through the cement line and were measured with a microrule (Max Levy Inc). Seven lines were also drawn and measured along each surface: mesial, distal, buccal, palatal, and incisal (Figs. 1, 2). To measure the marginal discrepancy and absolute marginal discrepancy of the buccal-palatal (B-P) and mesialdistal (M-D) cuts, digital photographs were made in the cervical regions, 1 for each surface, at 200 magnification. Two measurements were made for each
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4 Standardization used to measure marginal discrepancy (top measurement) and absolute marginal discrepancy (bottom measurement). Scale bars, 0.1 and 0.5 mm; original magnification, 100.
region photographed: one to measure the marginal discrepancy and the other to measure the absolute marginal discrepancy according to the classification of Holmes et al37 (Fig. 4). Briefly, marginal discrepancy was measured along a perpendicular line from the internal surface of the coping to the axial wall of the abutment in the cervical region (Fig 4, line on the top), and absolute marginal discrepancy was measured from the margin of the coping surface to the cavosurface angle of the abutment (Fig. 4, line on the bottom). Internal misfit was considered the primary outcome. All other evaluated parameters were secondary outcomes. In
the evaluation of the internal and marginal misfit, the Levene test was performed to assess the equality of variances. Subsequently, the 2-way ANOVA was performed (a¼.05). The Tukey multiple comparison (honestly significant difference) test was used for the variable independent systems whenever significant statistical differences occurred. The statistical software program used was SPSS Statistics v21 (IBM Corp).
RESULTS The mean internal misfit values for each system are shown in Table I and Figure 5.
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Table I.
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Internal misfit by location and systems (mm) (n¼8)
Location
Ceramill
Lava
Neoshape
F
P
Mesial
76.3 (7.05)
71.7 (10.1)
78.4 (8.15)
1.258
.305
Distal
68.7 (10.8)
68.6 (8.41)
75.3 (7.97)
1.383
.273
Buccal
71.5 (5.13)
71.7 (4.87)
74.5 (5.14)
.901
.421
Palatal
76.5 (5.91)
65.5 (5.78)
77.7 (8.20)
8.074
.003*
Angle regions
69.4 (3.92)
68.6 (2.49)
74.5 (4.63)
5.723
.010*
Incisal
127.7(13.0)
97.2 (10.3)
182.2(32.3)
Overall mean
72.1 (4.05)
69.4 (3.10)
76.4 (3.42)
<.001*
33.53 7.899
.003*
Data are presented as mean (standard deviation). *Mean difference is significant at P<.05 (2-way ANOVA).
179
250
** **
System Ceramill Lava Neoshape
200
**
150
Gap (µm)
A significant statistical difference was found for the palatal surface between the Ceramill and Lava systems (P¼.009) and between the Lava and Neoshape systems (P¼.004). For the angle regions, significant differences were found between Ceramill and Neoshape (P¼.033) and for Lava and Neoshape (P¼.014). For the incisal surface, significant differences were also found between Ceramill and Lava (P¼.022), Ceramill and Neoshape (P<.001), and Lava and Neoshape (P<.001). No statistical difference was found among the other surfaces (P>.05). When mean values were compared with each other, a significant difference was found between Lava and Neoshape (P¼.002). No statistical difference was found between Ceramill and Neoshape or between Ceramill and Lava (P>.05). In the marginal misfit evaluation, a mean value was made for each zirconia coping. The results of the buccal, palatal, mesial, and distal surfaces are shown in Table II and Figure 6. No significant statistical difference was found for marginal discrepancy between the Ceramill and Lava (P¼.147), the Ceramill and Neoshape (P¼.878), or the Lava and Neoshape (P¼.321). For absolute marginal discrepancy, no significant statistical difference was found between the Ceramill and Lava (P¼.860), between the Ceramill and Neoshape (P¼.534), or the Lava and Neoshape (P¼.842) systems.
-
100 **
76
** **
**
** 167
95
191
103 186 154
92
50
68
DISCUSSION This study evaluated the internal and marginal misfits of 3 CAD/CAM systems (Ceramill, Lava, and Neoshape). The internal misfit evaluation showed that Lava values were lower than those of Neoshape (P¼.004). However, the mean value obtained for the 3 systems was 72.6 mm, corroborating the values found in the study by Beuer et al,12 who presented the following results: 65.8 mm for the Etkon system and 77.2 mm for the Cerec in Lab system. In another study performed
0
Mesial
Distal
Buccal
Palatal
Angle Incisal Regions
Overall Mean
Location 5 Box-plot diagrams for internal misfit gap (mm) by system and location. Significant differences are indicated by horizontal bars. **P<.05.
by Beuer et al33 evaluating the Lava and Procera systems, the mean values obtained were 89.5 and 76 mm, compatible with those found in the present study.
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In a systematic review of the internal and marginal misfit of prosthetic elements fabricated with CAD/CAM systems, Abduo et al32 described their difficulty in classifying the marginal
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5 Marginal misfit by location and systems (mm) (n¼ 8)
Table II. Location
Ceramill
Lava
Neoshape
F
P
Marginal discrepancy
40.9 (8.44)
34.2 (5.92)
39.3 (5.67)
2.113
.146
Absolute marginal discrepancy
65.8 (7.62)
70.0 (15.9)
74.5 (6.80)
0.661
.527
Data are presented as mean (standard deviation). Mean difference is significant at P<.05 (2-way ANOVA).
100
Gap (µm)
80
System Ceramill Lava Neoshape
11
60
40
20
0
Marginal Discrepancy
Absolute Marginal Discrepancy
Location 6 Box-plot diagrams for marginal misfit gap (mm) by system and location. adaptation of CAD/CAM systems currently available because of the variations in the methodologies used by the different studies. They also described a significant variation among values obtained in these studies, including those that evaluated the same systems. Among other variables, some studies used different cements, whereas others did not use any cement to attach the prosthetic element.39 In this study, marginal discrepancy and absolute marginal discrepancy were used to evaluate marginal misfit, according to the classification proposed by Holmes et al.37 A cementation technique was used to attach all prosthetic elements,10,33-35 and then all specimens were cut and examined under an optical microscope with a digital camera at 200 magnification.11 In the marginal discrepancy evaluation, the statistical analysis showed no difference among the CAD/CAM systems evaluated. In the multiple comparisons analysis, Ceramill and Lava systems did
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not present a significant statistical difference (P¼.144). The same occurred with the Ceramill and Neoshape and the Lava and Neoshape systems (P¼.878 and P¼.318). The mean value obtained in the 3 systems was 38.1 mm, corroborating the values found in the studies undertaken by Vigolo and Fonzi19 (56.9 mm) and Tinschert et al17 (45.5 mm). In absolute marginal discrepancy, the statistical analysis showed no difference among the Ceramill, Neoshape, and Lava systems. The mean value obtained in the 3 systems was 70.1 mm, corroborating the result found in the systematic review carried out by Abduo et al,32 in which the absolute marginal discrepancy mean for all systems was 73.8 mm. Martinez-Rus et al36 evaluated the marginal misfit of zirconia copings manufactured in the In-Ceram, Cercon, and Procera systems. These authors followed the classification proposed by Holmes et al37 to evaluate absolute
marginal discrepancy. The mean values reported in that study are lower than the ones found in the present study. The authors assumed that the values found were lower than the average ones obtained in similar studies and attributed this result to the evolution of the systems. However, the present study used contemporary systems and obtained much higher mean values. Thus, these differences may be attributed to differences in the method. In the work of Martinez-Rus et al,36 the specimens were not cemented, and the measurements were made directly under the microscope without sectioning the specimens. According to McLean and von Fraunhofer,40 the ideal marginal misfit should be less than 120 mm for clinical success. However, despite the lack of consensus in terms of method and evaluation regions, several authors cite the McLean and von Fraunhofer study.10,11,14,16,35,36 In terms of internal misfit, some authors claim that the gap should be between 50 and 100 mm,15 and in several articles published on prosthesis fabricated in CAD/CAM systems, these internal misfit values have been reached.11,18,33-36 A systematic review suggested that the success rate of the clinical performance of single units fabricated with CAD/CAM systems is comparable with restorations made with traditional methods.41 If laboratory studies are within clinically acceptable levels in terms of internal and marginal misfit, clinical studies prove the success of these prostheses, increasing the scientific evidence that shows the efficiency of this new technology in relation to the parameter misfit. Grenade et al35 evaluated the marginal and internal misfit
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Volume of 2 CAD/CAM systems (Procera and Ceramill). This study followed a method similar in many ways to the present study, with results compatible with those found for both internal and marginal misfit. A significant characteristic of that study is a lower result for incisor teeth. This contrasts with the anatomic abutment design chosen for the present study. Bindl and Mörmann34 evaluated the marginal and internal adaptation of zirconia copings manufactured in 4 CAD/CAM systems (Cerec inLab, DCS, Decim, and Procera). In the present study, the mean values of marginal discrepancy obtained for Ceramill, Lava, and Neoshape systems are in accordance with those found in the Bindl and Mörmann study of Cerec inLab and DCS systems. Although the present study used different cement, the methodologies had several points in common. Komine et al15 evaluated the internal and marginal misfit of zirconia copings manufactured by using the CAD/CAM system (Cercon) with 3 different margin designs: shoulder, rounded shoulder, and chamfer. In the present study, the values found in the internal and marginal misfit for the different systems evaluated are in agreement with those values found for the rounded shoulder and chamfer in the study undertaken by Komine et al. Over the last 10 years, a significant improvement in dental CAD/CAM systems has taken place. The results found in the present study show equivalence between the systems studied, thus being in line with those found in other studies. There were some limitations to the present study. The copings were made in different laboratories by different technicians, and the internal space necessary for the fabrication of copings was determined by each system. Furthermore, they were tested under laboratory conditions, which may not reflect clinical conditions.
CONCLUSIONS Within the limits of this study, although the Lava system showed a
smaller overall internal misfit than the Neoshape system, the values found for all 3 systems, both for internal and marginal misfit, were within clinically acceptable levels.
REFERENCES 1. Beuer F, Schweiger J, Edelhoff D. Digital dentistry: an overview of recent developments for CAD/CAM generated restorations. Br Dent J 2008;204:505-11. 2. Davidowitz G, Kotick PG. The use of CAD/ CAM in dentistry. Dent Clin North Am 2011;55:559-70. 3. Miyazaki T, Hotta Y. CAD/CAM systems available for the fabrication of crown and bridge restorations. Aust Dent J 2011;56(suppl 1):97-106. 4. Miyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. A review of dental CAD/CAM: current status and future perspectives from 20 years of experience. Dent Mater J 2009;28: 44-56. 5. Sjogren G, Molin M, van Dijken JW. A 10year prospective evaluation of CAD/CAM manufactured (Cerec) ceramic inlays cemented with a chemically cured or dualcured resin composite. Int J Prosthodont 2004;17:241-6. 6. Strub JR, Rekow ED, Witkowski S. Computeraided design and fabrication of dental restorations: current systems and future possibilities. J Am Dent Assoc 2006;137:1289-96. 7. Bindl A. Rapid progress in digital dentistry thanks to computer technology. Int J Comput Dent 2012;15:3-5. 8. Duret F, Preston JD. CAD/CAM imaging in dentistry. Curr Opin Dent 1991;1:150-4. 9. Conrad HJ, Seong WJ, Pesun IJ. Current ceramic materials and systems with clinical recommendations: a systematic review. J Prosthet Dent 2007;98:389-404. 10. Aboushelib MN, Elmahy WA, Ghazy MH. Internal adaptation, marginal accuracy and microleakage of a pressable versus a machinable ceramic laminate veneers. J Dent 2012;40:670-7. 11. Baig MR, Tan KB, Nicholls JI. Evaluation of the marginal fit of a zirconia ceramic computer aided machined (CAM) crown system. J Prosthet Dent 2010;104:216-27. 12. Beuer F, Neumeier P, Naumann M. Marginal fit of 14-unit zirconia fixed dental prosthesis retainers. J Oral Rehabil 2009;36:142-9. 13. Colpani JT, Borba M, Della Bona A. Evaluation of marginal and internal fit of ceramic crown copings. Dent Mater 2013;29:174-80. 14. Kokubo Y, Nagayama Y, Tsumita M, Ohkubo C, Fukushima S, Vult von Steyern P. Clinical marginal and internal gaps of InCeram crowns fabricated using the GN-I system. J Oral Rehabil 2005;32:753-8. 15. Komine F, Iwai T, Kobayashi K, Matsumura H. Marginal and internal adaptation of zirconium dioxide ceramic copings and crowns with different finish line designs. Dent Mater J 2007;26:659-64.
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16. Rinke S, Fornefett D, Gersdorff N, Lange K, Roediger M. Multifactorial analysis of the impact of different manufacturing processes on the marginal fit of zirconia copings. Dent Mater J 2012;31:601-9. 17. Tinschert J, Natt G, Mautsch W, Spiekermann H, Anusavice KJ. Marginal fit of alumina-and zirconia-based fixed partial dentures produced by a CAD/CAM system. Oper Dent 2001;26:367-74. 18. Witkowski S, Komine F, Gerds T. Marginal accuracy of titanium copings fabricated by casting and CAD/CAM techniques. J Prosthet Dent 2006;96:47-52. 19. Vigolo P, Fonzi F. An in vitro evaluation of fit of zirconium-oxide-based ceramic four-unit fixed partial dentures, generated with three different CAD/CAM systems, before and after porcelain firing cycles and after glaze cycles. J Prosthodont 2008;17:621-6. 20. Holmes JR, Sulik WD, Holland GA, Bayne SC. Marginal fit of castable ceramic crowns. J Prosthet Dent 1992;67:594-9. 21. Molin MK, Karlsson SL, Kristiansen MS. Influence of film thickness on joint bend strength of a ceramic/resin composite joint. Dent Mater 1996;12:245-9. 22. Prakki A, Cilli R, Da Costa AU, Goncalves SE, Mondelli RF, Pereira JC. Effect of resin luting film thickness on fracture resistance of a ceramic cemented to dentin. J Prosthodont 2007;16:172-8. 23. Tuntiprawon M, Wilson PR. The effect of cement thickness on the fracture strength of all ceramic crowns. Aust Dent J 1995;40:17-21. 24. Felton DA, Kanoy BE, Bayne SC, Wirthman GP. Effect of in vivo crown margin discrepancies on periodontal health. J Prosthet Dent 1991;65:357-64. 25. Kosyfaki P, del Pilar Pinilla Martin M, Strub JR. Relationship between crowns and the periodontium: a literature update. Quintessence Int 2010;41:109-26. 26. Lang NP, Kiel RA, Anderhalden K. Clinical and microbiological effects of subgingival restorations with overhanging or clinically perfect margins. J Clin Periodontol 1983;10: 563-78. 27. Hamza TA, Ezzat HA, El-Hossary MM, Katamish HA, Shokry TE, Rosenstiel SF. Accuracy of ceramic restorations made with two CAD/CAM systems. J Prosthet Dent 2013;109:83-7. 28. Att W, Komine F, Gerds T, Strub JR. Marginal adaptation of three different zirconium dioxide three-unit fixed dental prostheses. J Prosthet Dent 2009;101:239-47. 29. Han HS, Yang HS, Lim HP, Park YJ. Marginal accuracy and internal fit of machine-milled and cast titanium crowns. J Prosthet Dent 2011;106:191-7. 30. Hmaidouch R, Neumann P, Mueller WD. Influence of preparation form, luting space setting and cement type on the marginal and internal fit of CAD/CAM crown copings. Int J Comput Dent 2011;14:219-26. 31. Renne W, McGill ST, Forshee KV, DeFee MR, Mennito AS. Predicting marginal fit of CAD/ CAM crowns based on the presence or absence of common preparation errors. J Prosthet Dent 2012;108:310-5.
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32. Abduo J, Lyons K, Swain M. Fit of zirconia fixed partial denture: a systematic review. J Oral Rehabil 2010;37:866-76. 33. Beuer F, Aggstaller H, Edelhoff D, Gernet W, Sorensen J. Marginal and internal fits of fixed dental prostheses zirconia retainers. Dent Mater 2009;25:94-102. 34. Bindl A, Mörmann WH. Marginal and internal fit of all-ceramic CAD/CAM crowncopings on chamfer preparations. J Oral Rehabil 2005;32:441-7. 35. Grenade C, Mainjot A, Vanheusden A. Fit of single tooth zirconia copings: comparison between various manufacturing processes. J Prosthet Dent 2011;105:249-55.
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7 36. Martinez-Rus F, Suarez MJ, Rivera B, Pradies G. Evaluation of the absolute marginal discrepancy of zirconia-based ceramic copings. J Prosthet Dent 2011;105:108-14. 37. Holmes JR, Bayne SC, Holland GA, Sulik WD. Considerations in measurement of marginal fit. J Prosthet Dent 1989;62:405-8. 38. Contrepois M, Soenen A, Bartala M, Laviole O. Marginal adaptation of ceramic crowns: a systematic review. J Prosthet Dent 2013;110:447-54. 39. Jivraj SA, Kim TH, Donovan TE. Selection of luting agents, part 1. J Calif Dent Assoc 2006;34:149-60. 40. McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J 1971;131:107-11.
41. Wittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical performance of CAD/CAM singletooth restorations. Int J Prosthodont 2009;22:466-71. Corresponding author: Dr Antonio Canabarro Veiga de Almeida University (UVA) Rua Ibituruna 108, casa 3, sala 201 Tijuca. Rio de Janeiro, RJ 20271-020 BRAZIL E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
Clinical Implications Zirconia copings fabricated with CAD/CAM technology have been considered a good choice for restorations because of their excellent esthetics. The standardization of manufacturing processes may also produce copings with acceptable internal and marginal fit.
Computer-aided design/computeraided manufacture (CAD/CAM) has been used in dentistry since the 1980s, mainly to automate manual processes. Some authors claim that this system results in high-quality materials, standardization of manufacturing
a
processes, and reduction of production costs for prosthetic appliances.1-8 The development of different metal alloys and precise melting systems has contributed to the success of metalbased restorations. However, a need for materials with improved esthetic
Master of Science student, Department of Oral Rehabilitation, Veiga de Almeida University. Postdoctoral student, Department of Material Science, Federal University of Rio de Janeiro. c Full Professor, Department of Oral Rehabilitation, Veiga de Almeida University. d Full Professor, Department of Oral Rehabilitation, Veiga de Almeida University. b
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and biological properties has increased the requests for ceramic restorations. New zirconia restorations, for example, have helped to answer this demand.3 Internal and marginal adaptation are key criteria for the long-term clinical performance of fixed prostheses,
2
Volume including implant-supported restorations which have been the object of study by several authors.9-19 Studies have included the ideal internal and marginal thickness of the cement line20,21 and the correlation of the cement line and the mechanical22,23 and biological24-26 properties. The CAD/CAM technique, ceramic type, and their interaction have been found to have a statistically significant effect on the mean marginal fit.27 Studies have been undertaken to standardize methods of evaluating these adaptation criteria.10,11,28-37 However, in a systematic review of the internal and marginal adaptations of prosthetic elements fabricated with CAD/CAM systems, only 15 articles met the inclusion criteria, and only 9 systems were evaluated.32 These data reveal not only the lack of standardization of these studies but also the shortage of studies that evaluate new systems and new materials. Therefore, the aim of this study was to evaluate the internal and marginal adaptation of zirconia copings made on cone Morse (CM) anatomic abutments (Neodent), in Ceramill (AmannGirrbach), Lava (3M ESPE), and Neoshape (Neodent) CAD/CAM systems. Because of its esthetic advantage, zirconia copings have been considered a good choice for restorations in anterior teeth,38 although they do not affect marginal and internal adaptation.
MATERIAL AND METHODS Twenty-four CM anatomic exact titanium abutments (Neodent) and 9 cone Morse titanium implant analogs (Neodent) were obtained from the manufacturer. The analogs were attached with the aid of a dental surveyor (Delineador B2; Bio-Art Dental Equipment) in order to maintain them in the same position. A CM implant analog (Neodent) was fixed with liquid epoxy resin (Aradur HY 951; Aral Barco Material Trading Ltd) to a metal part to standardize the position of the CM anatomic abutments. Eight cone Morse titanium implant analogs (Neodent) were included with Type IV dental stone
(Vigodent) in plastic parts (Monta Tudo; Elka Plastics Ltda) to simulate the abutments sent to a laboratory for the fabrication of zirconia copings. Twenty-four zirconia copings were divided equally into 3 groups and made by using 3 different CAD/CAM systems: Ceramill system (C-G) (n¼8), Lava 3M system (L-G) (n¼8), and Neoshape system (N-G) (n¼8). The sample size was determined by a pilot study with 3 specimens of each system. The mean value found for the internal misfit was 72 mm, with a standard deviation of 4.5 mm. The reference value of 76 mm was based on the values of a previous study.33 On the basis of these values, for a power of .80 with a¼.05, the sample size was calculated as 8. The copings were made in 3 different laboratories that followed the recommended requirements of each system and were certified by the manufacturers. They were fabricated in tetragonal polycrystalline zirconia stabilized with 0.6 mm thick (Y-TZP) presynthesized yttrium and were inspected with a stereomicroscope (Stemi DV4; Carl Zeiss) at 8 magnification to detect any possible fabrication defect. The zirconia copings were cemented on the CM anatomic abutments with zinc phosphate cement (SS White) because it is considered the gold standard against which all other luting agents are compared.39 The specimens were submitted to a 50-N load in a universal testing machine (Emic DL 2000; Emic) for the 5-minute period recommended by the zinc phosphate cement manufacturer. Any excess cement was removed with a scalpel (Solidor). After 24 hours, the specimens were embedded in liquid epoxy resin (Aradur HY 951; Aral Barco Material Trading Ltd) in custom metal molds to standardize their position and to prevent displacement during the cutting and polishing procedures. The embedded specimens were sectioned across their long axis to obtain buccal (or facial) and palatal (or lingual) surfaces with a low concentration diamond blade (Extec Corp;
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Enfield) in a low-speed precision cutting machine (Isomet; Buehler Ltd). They were polished with a wet abrasive paper (3M Brazil) in a polishing machine (Arotec S/A Industry and Trade) following a sequence of 400, 600, 1200, and 2500 grits. A polishing cloth (Struers DP-Mol and DP-Nap; Struers Scientific Instruments) with 6, 3, and 1 mm diamond paste (Struers Scientific Instruments) was used for the finishing. The specimens were then examined with an optical microscope (Olympus BX60M; Olympus Corp), and photographs were made. Then the specimens were reembedded in liquid epoxy resin and cut across their long axis to obtain the mesial and distal surfaces. To evaluate the internal and marginal misfits, an optical microscope (Olympus BX60M; Olympus Corp) was used in association with a digital camera (Canon 5D Mark III; Canon Inc) adapted with a measuring device (Multifunction Target Max Levy; Max Levy Autograph Inc). Digital photographs with 100 and 200 magnification were standardized to a 57603840 pixel resolution in the RAW format. They were then transferred to an image management program (Adobe Photoshop CS5 Extended; Adobe Systems Inc), and the logic length was converted in pixel length with the program measurement tools. Digital photographs were made to evaluate the internal misfit of the cement line of the 11 buccal and palatal cuts (BP). Six were used for the buccal surface and incisal-buccal border, and 5 were used for the palatal surface and incisalpalatal border. Eight photographs were made of the mesial-distal cut. Four were used for the mesial surface and for the mesial and incisal border and 4 for the distal surface and distal-incisal border. The photographs were made every 1.7 mm along the cement-abutment interface (Figs. 1, 2). To evaluate the internal misfit, measurements were initially made in the angle regions (internal axiogingival angle, n¼3; axioincisal angle, n¼3) for a more accurate measurement. The first point of reference corresponds to the
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1 Anatomic titanium abutment and coping cemented to 2 Coping cemented to abutment sectioned in mesial-distal abutment sectioned in buccal-palatal direction (buccal sur- direction (mesial surface at top, distal surface at bottom); original magnification, 5. face at top, palatal surface at bottom); original magnification, 5.
3 Standardization used to measure internal misfit. Note that initial Point 1 is based in center of curve, on internal surface of cement line. Points 2 and 3 stand at points 200 mm equidistant from initial point. Scale bars, 0.1 and 0.5 mm; original magnification, 100. central point of the angle (Fig. 3). The 2 subsequent points were located 200 mm equidistant from this central point (Fig. 3). Lines were drawn perpendicular to those points passing through the cement line and were measured with a microrule (Max Levy Inc). Seven lines were also drawn and measured along each surface: mesial, distal, buccal, palatal, and incisal (Figs. 1, 2). To measure the marginal discrepancy and absolute marginal discrepancy of the buccal-palatal (B-P) and mesialdistal (M-D) cuts, digital photographs were made in the cervical regions, 1 for each surface, at 200 magnification. Two measurements were made for each
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4 Standardization used to measure marginal discrepancy (top measurement) and absolute marginal discrepancy (bottom measurement). Scale bars, 0.1 and 0.5 mm; original magnification, 100.
region photographed: one to measure the marginal discrepancy and the other to measure the absolute marginal discrepancy according to the classification of Holmes et al37 (Fig. 4). Briefly, marginal discrepancy was measured along a perpendicular line from the internal surface of the coping to the axial wall of the abutment in the cervical region (Fig 4, line on the top), and absolute marginal discrepancy was measured from the margin of the coping surface to the cavosurface angle of the abutment (Fig. 4, line on the bottom). Internal misfit was considered the primary outcome. All other evaluated parameters were secondary outcomes. In
the evaluation of the internal and marginal misfit, the Levene test was performed to assess the equality of variances. Subsequently, the 2-way ANOVA was performed (a¼.05). The Tukey multiple comparison (honestly significant difference) test was used for the variable independent systems whenever significant statistical differences occurred. The statistical software program used was SPSS Statistics v21 (IBM Corp).
RESULTS The mean internal misfit values for each system are shown in Table I and Figure 5.
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Table I.
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Internal misfit by location and systems (mm) (n¼8)
Location
Ceramill
Lava
Neoshape
F
P
Mesial
76.3 (7.05)
71.7 (10.1)
78.4 (8.15)
1.258
.305
Distal
68.7 (10.8)
68.6 (8.41)
75.3 (7.97)
1.383
.273
Buccal
71.5 (5.13)
71.7 (4.87)
74.5 (5.14)
.901
.421
Palatal
76.5 (5.91)
65.5 (5.78)
77.7 (8.20)
8.074
.003*
Angle regions
69.4 (3.92)
68.6 (2.49)
74.5 (4.63)
5.723
.010*
Incisal
127.7(13.0)
97.2 (10.3)
182.2(32.3)
Overall mean
72.1 (4.05)
69.4 (3.10)
76.4 (3.42)
<.001*
33.53 7.899
.003*
Data are presented as mean (standard deviation). *Mean difference is significant at P<.05 (2-way ANOVA).
179
250
** **
System Ceramill Lava Neoshape
200
**
150
Gap (µm)
A significant statistical difference was found for the palatal surface between the Ceramill and Lava systems (P¼.009) and between the Lava and Neoshape systems (P¼.004). For the angle regions, significant differences were found between Ceramill and Neoshape (P¼.033) and for Lava and Neoshape (P¼.014). For the incisal surface, significant differences were also found between Ceramill and Lava (P¼.022), Ceramill and Neoshape (P<.001), and Lava and Neoshape (P<.001). No statistical difference was found among the other surfaces (P>.05). When mean values were compared with each other, a significant difference was found between Lava and Neoshape (P¼.002). No statistical difference was found between Ceramill and Neoshape or between Ceramill and Lava (P>.05). In the marginal misfit evaluation, a mean value was made for each zirconia coping. The results of the buccal, palatal, mesial, and distal surfaces are shown in Table II and Figure 6. No significant statistical difference was found for marginal discrepancy between the Ceramill and Lava (P¼.147), the Ceramill and Neoshape (P¼.878), or the Lava and Neoshape (P¼.321). For absolute marginal discrepancy, no significant statistical difference was found between the Ceramill and Lava (P¼.860), between the Ceramill and Neoshape (P¼.534), or the Lava and Neoshape (P¼.842) systems.
-
100 **
76
** **
**
** 167
95
191
103 186 154
92
50
68
DISCUSSION This study evaluated the internal and marginal misfits of 3 CAD/CAM systems (Ceramill, Lava, and Neoshape). The internal misfit evaluation showed that Lava values were lower than those of Neoshape (P¼.004). However, the mean value obtained for the 3 systems was 72.6 mm, corroborating the values found in the study by Beuer et al,12 who presented the following results: 65.8 mm for the Etkon system and 77.2 mm for the Cerec in Lab system. In another study performed
0
Mesial
Distal
Buccal
Palatal
Angle Incisal Regions
Overall Mean
Location 5 Box-plot diagrams for internal misfit gap (mm) by system and location. Significant differences are indicated by horizontal bars. **P<.05.
by Beuer et al33 evaluating the Lava and Procera systems, the mean values obtained were 89.5 and 76 mm, compatible with those found in the present study.
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In a systematic review of the internal and marginal misfit of prosthetic elements fabricated with CAD/CAM systems, Abduo et al32 described their difficulty in classifying the marginal
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5 Marginal misfit by location and systems (mm) (n¼ 8)
Table II. Location
Ceramill
Lava
Neoshape
F
P
Marginal discrepancy
40.9 (8.44)
34.2 (5.92)
39.3 (5.67)
2.113
.146
Absolute marginal discrepancy
65.8 (7.62)
70.0 (15.9)
74.5 (6.80)
0.661
.527
Data are presented as mean (standard deviation). Mean difference is significant at P<.05 (2-way ANOVA).
100
Gap (µm)
80
System Ceramill Lava Neoshape
11
60
40
20
0
Marginal Discrepancy
Absolute Marginal Discrepancy
Location 6 Box-plot diagrams for marginal misfit gap (mm) by system and location. adaptation of CAD/CAM systems currently available because of the variations in the methodologies used by the different studies. They also described a significant variation among values obtained in these studies, including those that evaluated the same systems. Among other variables, some studies used different cements, whereas others did not use any cement to attach the prosthetic element.39 In this study, marginal discrepancy and absolute marginal discrepancy were used to evaluate marginal misfit, according to the classification proposed by Holmes et al.37 A cementation technique was used to attach all prosthetic elements,10,33-35 and then all specimens were cut and examined under an optical microscope with a digital camera at 200 magnification.11 In the marginal discrepancy evaluation, the statistical analysis showed no difference among the CAD/CAM systems evaluated. In the multiple comparisons analysis, Ceramill and Lava systems did
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not present a significant statistical difference (P¼.144). The same occurred with the Ceramill and Neoshape and the Lava and Neoshape systems (P¼.878 and P¼.318). The mean value obtained in the 3 systems was 38.1 mm, corroborating the values found in the studies undertaken by Vigolo and Fonzi19 (56.9 mm) and Tinschert et al17 (45.5 mm). In absolute marginal discrepancy, the statistical analysis showed no difference among the Ceramill, Neoshape, and Lava systems. The mean value obtained in the 3 systems was 70.1 mm, corroborating the result found in the systematic review carried out by Abduo et al,32 in which the absolute marginal discrepancy mean for all systems was 73.8 mm. Martinez-Rus et al36 evaluated the marginal misfit of zirconia copings manufactured in the In-Ceram, Cercon, and Procera systems. These authors followed the classification proposed by Holmes et al37 to evaluate absolute
marginal discrepancy. The mean values reported in that study are lower than the ones found in the present study. The authors assumed that the values found were lower than the average ones obtained in similar studies and attributed this result to the evolution of the systems. However, the present study used contemporary systems and obtained much higher mean values. Thus, these differences may be attributed to differences in the method. In the work of Martinez-Rus et al,36 the specimens were not cemented, and the measurements were made directly under the microscope without sectioning the specimens. According to McLean and von Fraunhofer,40 the ideal marginal misfit should be less than 120 mm for clinical success. However, despite the lack of consensus in terms of method and evaluation regions, several authors cite the McLean and von Fraunhofer study.10,11,14,16,35,36 In terms of internal misfit, some authors claim that the gap should be between 50 and 100 mm,15 and in several articles published on prosthesis fabricated in CAD/CAM systems, these internal misfit values have been reached.11,18,33-36 A systematic review suggested that the success rate of the clinical performance of single units fabricated with CAD/CAM systems is comparable with restorations made with traditional methods.41 If laboratory studies are within clinically acceptable levels in terms of internal and marginal misfit, clinical studies prove the success of these prostheses, increasing the scientific evidence that shows the efficiency of this new technology in relation to the parameter misfit. Grenade et al35 evaluated the marginal and internal misfit
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Volume of 2 CAD/CAM systems (Procera and Ceramill). This study followed a method similar in many ways to the present study, with results compatible with those found for both internal and marginal misfit. A significant characteristic of that study is a lower result for incisor teeth. This contrasts with the anatomic abutment design chosen for the present study. Bindl and Mörmann34 evaluated the marginal and internal adaptation of zirconia copings manufactured in 4 CAD/CAM systems (Cerec inLab, DCS, Decim, and Procera). In the present study, the mean values of marginal discrepancy obtained for Ceramill, Lava, and Neoshape systems are in accordance with those found in the Bindl and Mörmann study of Cerec inLab and DCS systems. Although the present study used different cement, the methodologies had several points in common. Komine et al15 evaluated the internal and marginal misfit of zirconia copings manufactured by using the CAD/CAM system (Cercon) with 3 different margin designs: shoulder, rounded shoulder, and chamfer. In the present study, the values found in the internal and marginal misfit for the different systems evaluated are in agreement with those values found for the rounded shoulder and chamfer in the study undertaken by Komine et al. Over the last 10 years, a significant improvement in dental CAD/CAM systems has taken place. The results found in the present study show equivalence between the systems studied, thus being in line with those found in other studies. There were some limitations to the present study. The copings were made in different laboratories by different technicians, and the internal space necessary for the fabrication of copings was determined by each system. Furthermore, they were tested under laboratory conditions, which may not reflect clinical conditions.
CONCLUSIONS Within the limits of this study, although the Lava system showed a
smaller overall internal misfit than the Neoshape system, the values found for all 3 systems, both for internal and marginal misfit, were within clinically acceptable levels.
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41. Wittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical performance of CAD/CAM singletooth restorations. Int J Prosthodont 2009;22:466-71. Corresponding author: Dr Antonio Canabarro Veiga de Almeida University (UVA) Rua Ibituruna 108, casa 3, sala 201 Tijuca. Rio de Janeiro, RJ 20271-020 BRAZIL E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.