The Journal of Indian Prosthodontic Society

RESEARCH
Year
: 2022  |  Volume : 22  |  Issue : 3  |  Page : 225--232

Evaluation of customized cobalt-chromium abutments fabricated with different manufacturing process versus titanium stock abutments on the marginal misfit -An in vitro study


Writuraj Sutradhar1, Sunil Kumar Mishra2, Ramesh Chowdhary1,  
1 Department of Prosthodontics, Rajarajeswari Dental College and Hospital, Bengaluru, Karnataka, India
2 Department of Prosthodontics, Rama Dental College, Hospital and Research Centre, Kanpur, Uttar Pradesh, India

Correspondence Address:
Ramesh Chowdhary
Department of Prosthodontics, Rajarajeswari Dental College and Hospital, Bengaluru - 560 098, Karnataka
India

Abstract

Aim: Accurate fit of the abutment to the implant is required for the uniform load distribution throughout the assembly. The study aims to compare the marginal misfit of titanium stock abutments with the cobalt-chromium (CoCr) customized abutments fabricated with the different manufacturing processes in internal hex implant-abutment connection using an appropriate scanning technique. Setting and Design: In vitro comparative study. Materials and Methods: A total of 40 abutments were included in the study. Ten titanium stock abutments were used as control (Group CN) and 30 CoCr abutments were fabricated and taken as the test group. Stock abutments were scanned and from obtained images test group abutments were fabricated as follows: Ten cast abutments (Group CA), 10 sintered abutments (Group SA), and 10 milled abutments (Group MA). Endosseous implanst having internal hex connections were matched with 10 stock abutments and 30 customized CoCr abutments. Implants were mounted in a clear epoxy resin block and the abutments were then fitted onto the implants with a torque of 30Ncm. The marginal discrepancy at implant-abutment connections was measured with confocal laser scanning microscope. Statistical Analysis Used: One-way ANOVA and Tukey's post hoc test was done for statistical analysis. Results: One-way ANOVA revealed a significant difference in marginal misfit of abutments. The mean marginal misfit was lowest for stock abutments (0.35 ± 0.009 μm). Among the customized abutments, the mean marginal misfit was highest for cast abutments (2.44 ± 0.445 μm) followed by sintered abutments (1.67 ± 0.232 μm) and least for milled abutments (0.65 ± 0.041 μm). A significant difference was found in marginal misfit with cast abutments and sintered abutments when compared to stock abutments (P < 0.001). The difference in marginal misfit was insignificant between stock abutments and milled abutments (P = 0.052). Conclusion: Difference in marginal misfit exists between the titanium stock abutments and customized CoCr abutments. Among the customized abutments, milled CoCr abutments have the least marginal discrepancy and cast CoCr abutments have a maximum marginal discrepancy. Milled CoCr abutments can be used as an alternative to titanium stock abutments.



How to cite this article:
Sutradhar W, Mishra SK, Chowdhary R. Evaluation of customized cobalt-chromium abutments fabricated with different manufacturing process versus titanium stock abutments on the marginal misfit -An in vitro study.J Indian Prosthodont Soc 2022;22:225-232


How to cite this URL:
Sutradhar W, Mishra SK, Chowdhary R. Evaluation of customized cobalt-chromium abutments fabricated with different manufacturing process versus titanium stock abutments on the marginal misfit -An in vitro study. J Indian Prosthodont Soc [serial online] 2022 [cited 2022 Aug 9 ];22:225-232
Available from: https://www.j-ips.org/text.asp?2022/22/3/225/351281


Full Text



 Introduction



Dental implant abutments are of two types: stock abutments supplied by the manufacturers, which matches the respective implant systems; and custom-made abutments made with (computer-aided design and computer-aided manufacturing [CAD/CAM]). The custom-made abutments contoured the soft tissues well around the restorations during the healing stage.[1] These abutments provide a natural emergence profile to the implant prosthesis. Crown margin depth can be customized for better hygiene and esthetics.[2]

The implant-abutment assembly attached with a screw produces an interface between the abutment-implant junction.[3],[4] There should not be any vertical misfit between the abutment and implant, a key requirement to secure function and the esthetic requirements for long-term implant success.[5],[6],[7] The gap usually created between the abutment and the implant may result in the microleakage of bacteria and their metabolic products causing inflammation of the peri-implant tissues with successive bone loss.[8],[9]

The presence of the microgap sometimes causes micromovements and transfers the stresses from the abutment to the implant leading to screw loosening, fracture of the screw, or the abutment with the reduction in the prosthetic screw preload.[10],[11] Internal hex abutment-implant interface has been introduced with an attempt to reduce the mechanical drawbacks related to external connection with long-term stability, less screw loosening, and fracture, better aesthetics, and reduced crestal bone loss.[12],[13],[14],[15]

Titanium and zirconia are widely used as implant abutments;[16],[17],[18],[19] however, the use of cobalt-chromium alloy (CoCr) as abutments is sparse.[19],[20],[21] Previously published literature has studied the microgap at the abutment-implant interface using scanning electron microscopy (SEM) and optical microscope. However, these microscopic techniques are not very suitable for accurate measurement of the misfit between the components fabricated with different manufacturing processes.[22],[23],[24] Baschong et al.[25] stated that a Confocal microscope helps in getting better three-dimensional (3D) images as compared to SEM and it also does not require any additional preparation of the sample to be recorded. This microscope has been already in use for evaluating the surface topography and biofilm formation on dental tissues and implants.[26]

The marginal fit has a key role in the osseointegration and success of dental implants. The manufacturing process for the fabrication of abutment can affect the precision of marginal fit of the abutment with the implant.[21] Hence, the present in-vitro research was done to compare the marginal misfit of titanium tock abutments with CoCr customized abutments fabricated with different manufacturing processes (cast, sintered, and milled) in an internal hex implant-abutment connection using an appropriate scanning technique. The null hypothesis was that no difference exists in the marginal misfit of titanium stock abutments and CoCr customized abutments fabricated using different manufacturing processes.

 Materials and Methods



In this study, a power analysis was established by G * power, version 3.0.1 (Franz Faul universitat, Kiel, Germany). A sample size of 40 samples (10 in each group) which yield 80% power to detect significant differences, with effect size of 0.57 and a significance level at 0.05 were needed. Based on the power analysis, 40 abutments were included in the study. Ten titanium stock abutments were used as control [Group CN, [Figure 1]a], and 30 CoCr abutments were fabricated and taken as a test group [Figure 1]b, [Figure 1]c, [Figure 1]d. Stock abutments were scanned [Figure 2]a and from obtained images test group abutments were fabricated as follows: 10 cast abutments (Group CA), 10 sintered abutments (Group SA), and 10 milled abutments (Group MA). The cast abutments were fabricated from CoCr alloy with the help of milled polymethyl methacrylate patterns [Figure 2]b obtained from the scanned data utilizing the lost wax casting technique. Cobalt chromium sintered abutments were fabricated using the laser beam, in which powdered raw material was placed in a tray (HBD 100D, Guangdong Hanbang 3D Tech Co. Ltd, China) [Figure 2]c. A laser beam was spotted over the working tray to increase the temperature of the powder and make the particles bind together layer by layer to obtain the desired shape. Cobalt chromium abutments of the milled group were fabricated utilizing the milling procedure (Ceramill, Amann Girrbach, Austria) where the cutting tools remove the excess material gradually and shape the component [Figure 2]d.[19]{Figure 1}{Figure 2}

Endosseous dental implants (5.0 mm diameter × 10 mm length) with internal hex connection (Alpha Bio Tec, Israel) were matched with 10 titanium stock abutments and 30 CoCr abutments. Clear epoxy resin blocks of 20 mm × 20 mm × 20 mm in dimension were made. A central borehole of 5 mm length × 5 mm diameter was made to place half of the length of an implant as required for scanning.[18],[21] The implant was placed in the borehole and fixed with epoxy resin. The abutments were then fitted onto the implant with an abutment screw with a torque of 30Ncm [Figure 3]a, [Figure 3]b, [Figure 3]c, [Figure 3]d.{Figure 3}

Implant-abutment connections were evaluated under SEM for the marginal discrepancy.[21] When the samples were scanned under the SEM, the images obtained could not record the marginal depth because of the curvature of the abutment with that of the implant. The implant used in the study was an internal hex due to which the margins of the implant covered the seated abutment. Hence, it was decided that the samples need to be scanned by an alternative scanner, which can record this curvature.

A confocal laser scanning microscopy (CLSM) (FV1000; Olympus, Finland) was selected for this and after a few initial trial scans, it was found that a CLSM was an appropriate tool for measuring the marginal discrepancy in this situation and so used in the study. This microscope removes the signals which are out-of-focus, with illumination at a single point at a slower speed. With the CLSM technique, the optical resolution and contrast of the micrographs were increased.[27],[28],[29],[30]

The analysis was performed with statistical software (IBM Corp. Released 2019. IBM SPSS Statistics for Windows, Version 26.0. Armonk, NY, USA: IBM Corp). One-way ANOVA and Tukey's post hoc test was done to find significant (P < 0.05) difference in between the groups.

 Results



Comparison of mean marginal misfit at the implant-abutment junction of the stock abutment, cast abutment, sintered abutment, and milled abutment is presented in [Table 1], [Graph 1]. The marginal misfit at the implant-abutment junction was compared using One-way ANOVA which revealed a significant difference in the marginal misfit of abutments (P < 0.001). The mean marginal misfit was lowest for stock abutments (0.35 ± 0.009 μm) [Figure 4]a, [Figure 4]b, [Figure 4]c, [Figure 4]d, [Figure 4]e, [Figure 4]f. Among the customized abutments, marginal misfit was highest for cast abutments (2.44 ± 0.445 μm) [Figure 5]a, [Figure 5]b, [Figure 5]c, [Figure 5]d, [Figure 5]e, [Figure 5]f followed by sintered abutments (1.67 ± 0.232 μm) [Figure 6]a, [Figure 6]b, [Figure 6]c, [Figure 6]d, [Figure 6]e, [Figure 6]f and least for milled abutments (0.65 ± 0.041 μm) [Figure 7]a, [Figure 7]b, [Figure 7]c, [Figure 7]d, [Figure 7]e, [Figure 7]f.{Table 1}[INLINE:1]{Figure 4}{Figure 5}{Figure 6}{Figure 7}

Pairwise comparison of mean marginal misfit at the implant-abutment junction was done using Tukey's post hoc analysis to find the difference between the stock abutment, cast abutment, sintered abutment, and milled abutment [Table 2] Pairwise comparison showed a significant difference in the marginal misfit with cast abutments and sintered abutments when compared to stock abutments (P < 0.001). The difference in marginal misfit was insignificant between stock abutments and milled abutments (P = 0.052).{Table 2}

 Discussion



The null hypothesis was rejected as differences exist in the marginal fit of stock implant abutments and customized implant abutments fabricated using different manufacturing processes.

In the majority of the implant systems, due to marginal discrepancies, microgaps may present at the implant-abutment connection. The implant platform which is usually presents at the crest level of the alveolar bone causes exposure at the bone-implant connection and leads to the colonization of microbes.[31],[32] These cause the passage of fluid at the interface and may lead to potential implant failure.[33],[34],[35],[36],[37]

Stock abutments work well for the posterior teeth, which are away from the esthetic zone. However, these abutments cannot control the marginal fit of the crown in a well-précised fashion due to the abutment height and implant depth. This lack of precision might lead to failure of the dental implant due to peri-implantitis.[1],[2] Abutments that lack proper surface proximity can also lead to screw loosening. Custom abutments fabricated with CAD/CAM on the other hand are very well customized and specific for the patients. These abutments can be accurately milled to fit the crest of the dental implant and the soft tissue to give a better fit and also improve esthetics.[10]

The roughness at the surface of the abutment usually creates a microgap at the implant-abutment connection and inhibits in obtaining a passive fit.[38],[39],[40],[41] Fernández et al.[19] in an in-vitro study compared the misfit of CoCr custom-made implant abutments with the external hexagonal connection using three different techniques (casting, laser sintering, and milling). They found that the abutments manufactured by the milling process showed the least microgap (0.73 μm), followed by sintered abutments (11.30 μm) and cast abutments (9.09 μm) in the mating surface of the implant-abutment area. Although no significant difference was found between sintered and cast abutment (P = 0.26). In the present study, a statistically significant difference was found for the misfit of CoCr custom-made implant abutments with the internal hexagonal connection among all the groups. Milled abutments showed the least marginal discrepancy (0.65 μm), followed by sintered abutments (1.67 μm) and cast abutments (2.44 μm). Milled abutment surface provides a better fit at the implant mating surface with more number of contacts and seals the microgap in a better way.[42],[43] Cast abutments had a high degree of marginal discrepancy which might be due to the expansion of investment products used which causes increased misfit.[10],[19]

Gonzalo et al.[21] compared the misfit among milled titanium versus laser sintered CoCr abutment at the implant-abutment interface with internal hexagon connection design. Regardless of the implant system the mean marginal misfit for the milled titanium abutments was less (0.75 ± 1.27 μm) compared to the CoCr laser sintered abutments (11.83 ± 13.21 μm). Although in the present study CoCr abutments were used for fabrication of both milled and Sintered abutments, still the obtained result was similar with less marginal discrepancy with Milled abutments (0.65 ± 0.041 μm) compared to the sintered abutments (1.67 ± 0.232 μm). Alonso-Pérez et al.[20] in an SEM study compared the marginal accuracy of titanium Stock abutments with custom-made CoCr laser sintered abutment and found that marginal accuracy was best for stock abutments with no measurable gap. A mean marginal gap of 2.5 ± 1.0 μm was found in laser sintered abutments. They stated that the difference in result may be due to the composition of the material, as titanium stock abutments were used in the study and not by the manufacturing process. In the present study also a similar result was obtained with titanium Stock abutments having the least marginal discrepancy. CoCr material was used for fabrication of customized abutments and among that laser sintered abutments had a more mean marginal gap (1.67 ± 0.232 μm) compared to the milled abutment (0.65 ± 0.041 μm).

Reported literature states that laser sintering causes distortion, porosity, and delamination and produces a rough connection between abutment and implant. This creates a microgap and inhibits achieving a passive fit.[19],[44],[45],[46] The present study with its finding supports that the migrogap created at the implant-abutment connection is not only due to abutment material and type of connection, but it is also due to the different manufacturing process.

In the present study, the CLSM imaging technique was used, as the resolution obtained is best compared to SEM In CLSM, true 3D images can be obtained by suppressing any signal coming from out-of-focus planes. Atomic force microscopy or scanning tunneling microscope produces the image with scanning by a fine tip over a surface, whereas CLSM does not require a probe to be placed close to the surface.[30] Illumination in CLSM is by a point laser in a 3D diffraction fashion.[28],[29],[47]

The use of CoCr alloy as an abutment is sparse. This material is used as an abutment would reduce the cost of implant-supported fixed restorations, so this study was done to find a marginal gap at the implant-abutment interface to find its suitability as an abutment with the different manufacturing processes. The findings of the present study also support that the marginal misfit was insignificant (P = 0.052) when CoCr milled abutments were compared with titanium stock abutments. The limitations of the study are that its an in-vitro study and only CoCr abutments with internal hexagonal implant connection were evaluated. Further in-vivo research is needed to be evaluated with different abutment materials to find the clinical relevance.

 Conclusion



The difference in marginal misfit exists between the titanium stock abutments and customized CoCr abutments. Among the customized abutments, Milled CoCr abutments have the least marginal discrepancy and Cast CoCr abutments have a maximum marginal discrepancy. Milled CoCr abutments can be used as an alternative to titanium stock abutments.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1Sailer I, Zembic A, Jung RE, Hämmerle CH, Mattiola A. Single-tooth implant reconstructions: Esthetic factors influencing the decision between titanium and zirconia abutments in anterior regions. Eur J Esthet Dent 2007;2:296-310.
2Brodbeck U. The ZiReal post: A new ceramic implant abutment. J Esthet Restor Dent 2003;15:10-23.
3do Nascimento C, Barbosa RE, Issa JP, Watanabe E, Ito IY, Albuquerque RF Jr. Bacterial leakage along the implant-abutment interface of premachined or cast components. Int J Oral Maxillofac Surg 2008;37:177-80.
4Kanneganti KC, Vinnakota DN, Pottem SR, Pulagam M. Comparative effect of implant-abutment connections, abutment angulations, and screw lengths on preloaded abutment screw using three-dimensional finite element analysis: An in vitro study. J Indian Prosthodont Soc 2018;18:161-7.
5Sahoo PK. Implant abutment junction: Demystified. J Indian Prosthodont Soc 2020;20 Suppl S1:39.
6Mobilio N, Fasiol A, Franceschetti G, Catapano S. Marginal vertical fit along the implant-abutment interface: A microscope qualitative analysis. Dent J (Basel) 2016;4:31.
7Butignon LE, de Almeida Basilio M, Sgavioli Santo J, Arioli Filho JN. Vertical misfit of single-implant abutments made from different materials under cycling loading. Int J Oral Maxillofac Implant 2016;31:1017-22.
8Tallarico M, Canullo L, Caneva M, Özcan M. Microbial colonization at the implant-abutment interface and its possible influence on periimplantitis: A systematic review and meta-analysis. J Prosthodont Res 2017;61:233-41.
9Park SD, Lee Y, Kim YL, Yu SH, Bae JM, Cho HW. Microleakage of different sealing materials in access holes of internal connection implant systems. J Prosthet Dent 2012;108:173-80.
10Byrne D, Houston F, Cleary R, Claffey N. The fit of cast and premachined implant abutments. J Prosthet Dent 1998;80:184-92.
11Sahin S, Cehreli MC. The significance of passive framework fit in implant prosthodontics: Current status. Implant Dent 2001;10:85-92.
12Caricasulo R, Malchiodi L, Ghensi P, Fantozzi G, Cucchi A. The influence of implant-abutment connection to peri-implant bone loss: A systematic review and meta-analysis. Clin Implant Dent Relat Res 2018;20:653-64.
13Siadat H, Beyabanaki E, Mousavi N, Alikhasi M. Comparison of fit accuracy and torque maintenance of zirconia and titanium abutments for internal tri-channel and external-hex implant connections. J Adv Prosthodont 2017;9:271-7.
14Kofron MD, Carstens M, Fu C, Wen HB. In vitro assessment of connection strength and stability of internal implant-abutment connections. Clin Biomech (Bristol, Avon) 2019;65:92-9.
15Mumcu E, Erdinç G. Implant abutment selection criteria. Acta Sci Dent Sci 2018;8:31-8.
16Vélez J, Peláez J, López-Suárez C, Agustín-Panadero R, Tobar C, Suárez MJ. Influence of implant connection, abutment design and screw insertion torque on implant-abutment misfit. J Clin Med 2020;9:2365.
17Şen N, Şermet IB, Gürler N. Sealing capability and marginal fit of titanium versus zirconia abutments with different connection designs. J Adv Prosthodont 2019;11:105-11.
18Baldassarri M, Hjerppe J, Romeo D, Fickl S, Thompson VP, Stappert CF. Marginal accuracy of three implant-ceramic abutment configurations. Int J Oral Maxillofac Implants 2012;27:537-43.
19Fernández M, Delgado L, Molmeneu M, García D, Rodríguez D. Analysis of the misfit of dental implant-supported prostheses made with three manufacturing processes. J Prosthet Dent 2014;111:116-23.
20Alonso-Pérez R, Bartolomé JF, Ferreiroa A, Salido MP, Pradíes G. Evaluation of the mechanical behavior and marginal accuracy of stock and laser-sintered implant abutments. Int J Prosthodont 2017;30:136-8.
21Gonzalo E, Vizoso B, Lopez-Suarez C, Diaz P, Pelaez J, Suarez MJ. Evaluation of milled titanium versus laser sintered Co-Cr abutments on the marginal misfit in internal implant-abutment connection. Materials (Basel) 2020;13:4873.
22Riedy SJ, Lang BR, Lang BE. Fit of implant frameworks fabricated by different techniques. J Prosthet Dent 1997;78:596-604.
23Koke U, Wolf A, Lenz P, Gilde H. In vitro investigation of marginal accuracy of implant-supported screw-retained partial dentures. J Oral Rehabil 2004;31:477-82.
24Kano SC, Binon PP, Bonfante G, Curtis DA. The effect of casting procedures on rotational misfit in castable abutments. Int J Oral Maxillofac Implants 2007;22:575-9.
25Baschong W, Suetterlin R, Hefti A, Schiel H. Confocal laser scanning microscopy and scanning electron microscopy of tissue Ti-implant interfaces. Micron 2001;32:33-41.
26Dige I, Nilsson H, Kilian M, Nyvad B. In situ identification of streptococci and other bacteria in initial dental biofilm by confocal laser scanning microscopy and fluorescence in situ hybridization. Eur J Oral Sci 2007;115:459-67.
27Art JJ, Goodman MB, editors. Cell Biological Applications of Confocal Microscopy. 1st ed. San Diego: Academic Press; 1993. p. 47-78.
28Webb RH. Confocal optical microscopy. Rep Prog Phys 1996;59:427-71.
29Lavrentovich OD. Fluorescence confocal polarizing microscopy: Three-dimensional imaging of the director. J Phys 2003;61:373-84.
30Lavrentovich OD. Confocal fluorescence microscopy. In: Kaufmann's Characterization of Materials. 2nd ed. River Street Hoboken NJ, United States: John Wiley & Sons, Inc; 2012. p. 1-15.
31Jansen VK, Conrads G, Richter EJ. Microbial leakage and marginal fit of the implant-abutment interface. Int J Oral Maxillofac Implants 1997;12:527-40.
32Gross M, Abramovich I, Weiss EI. Microleakage at the abutment-implant interface of osseointegrated implants: A comparative study. Int J Oral Maxillofac Implants 1999;14:94-100.
33Rismanchian M, Hatami M, Badrian H, Khalighinejad N, Goroohi H. Evaluation of microgap size and microbial leakage in the connection area of 4 abutments with straumann (ITI) implant. J Oral Implantol 2012;38:677-85.
34Piattelli A, Vrespa G, Petrone G, Iezzi G, Annibali S, Scarano A. Role of the microgap between implant and abutment: A retrospective histologic evaluation in monkeys. J Periodontol 2003;74:346-52.
35Nascimento CD, Pita MS, Fernandes FH, Pedrazzi V, de Albuquerque Junior RF, Ribeiro RF. Bacterial adhesion on the titanium and zirconia abutment surfaces. Clin Oral Implants Res 2014;25:337-43.
36Hermann JS, Schoolfield JD, Schenk RK, Buser D, Cochran DL. Influence of the size of the microgap on crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged implants in the canine mandible. J Periodontol 2001;72:1372-83.
37Duarte AR, Rossetti PH, Rossetti LM, Torres SA, Bonachela WC. In vitro sealing ability of two materials at five different implant-abutment surfaces. J Periodontol 2006;77:1828-32.
38Binon PP. The effect of implant/abutment hexagonal misfit on screw joint stability. Int J Prosthodont 1996;9:149-60.
39Hecker DM, Eckert SE. Cyclic loading of implant-supported prostheses: Changes in component fit over time. J Prosthet Dent 2003;89:346-51.
40Cibirka RM, Nelson SK, Lang BR, Rueggeberg FA. Examination of the implant-abutment interface after fatigue testing. J Prosthet Dent 2001;85:268-75.
41Khraisat A, Stegaroiu R, Nomura S, Miyakawa O. Fatigue resistance of two implant/abutment joint designs. J Prosthet Dent 2002;88:604-10.
42Guzaitis KL, Knoernschild KL, Viana MA. Effect of repeated screw joint closing and opening cycles on implant prosthetic screw reverse torque and implant and screw thread morphology. J Prosthet Dent 2011;106:159-69.
43Byrne D, Jacobs S, O'Connell B, Houston F, Claffey N. Preloads generated with repeated tightening in three types of screws used in dental implant assemblies. J Prosthodont 2006;15:164-71.
44Song B, Zhao X, Li S, Han C, Wei Q, Wen S, et al. Differences in microstructure and properties between selective laser melting and traditional manufacturing for fabrication of metal parts: A review. Front Mech Eng 2015;10:111-25.
45Hjalmarsson L, Örtorp A, Smedberg JI, Jemt T. Precision of fit to implants: A comparison of Cresco™ and Procera® implant bridge frameworks. Clin Implant Dent Relat Res 2010;12:271-80.
46Yap CY, Chua CK, Dong ZL, Liu ZH, Zhang DQ, Loh LE, et al. Review of selective laser melting: Materials and applications. Appl Phys Rev 2015;2:041101.
47Rashid H. Application of confocal laser scanning microscopy in dentistry. J Adv Microsc Res 2014;9:245-52.