SciELO - Scientific Electronic Library Online

 
vol.22 número2Antagonistic action of indigenous Streptococcus mutans strainsClinical and microbiological characteristics in predicting dentine caries progression índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados

Revista

Articulo

Indicadores

  • No hay articulos citadosCitado por SciELO

Links relacionados

  • No hay articulos similaresSimilares en SciELO

Compartir


Acta Odontológica Latinoamericana

versión On-line ISSN 1852-4834

Acta odontol. latinoam. vol.22 no.2 Buenos Aires set. 2009

 

ARTÍCULOS ORIGINALES

Marginal fit analysis of premachined and castable UCLA abutments

 

João L. Bondan1, Hugo M.S. Oshima2, Regênio M.H. Segundo1, Rosemary S.A. Shinkai2, Eduardo G. Mota3, Kléber R.M. Meyer4

1 Graduate program students of Pontifical Catholic University of Rio Grande do Sul, Brazil.
2 Assistant Professor, Department of Prosthodontics, Pontifical University of Rio Grande do Sul, Brazil.
3 Assistant Professor, Clinical Department, Pontifical University of Rio Grande do Sul, Brazil.
4 Professor, Department of Prosthodontics, Pontifical University of Rio Grande do Sul, Brazil.


ABSTRACT

This study evaluated the fit between implants and premachined and castable UCLA abutments. All plastic specimens were cast using the conventional technique in accordance with the manufacturer’s instructions. Five specimens of each experimental group were measured for vertical and horizontal gaps by scanning electronic microscopy (Phillips XL 30 model, Holland). Gold UCLA (vertical gap: 2.15 μm, horizontal gap: 11.30 μm) and castable rotational UCLA (vertical gap: 14.91 μm, horizontal gap: 59.41 μm) groups showed the lowest and highest mean values, respectively (Neodent, Curitiba, Parana, Brazil). In general, the castable UCLA abutments showed poorer marginal fit than the premachined abutments.

Key words: Dental implants; Abutments; Marginal fit.

RESUMO

Análise da adaptação marginal de pilares UCLA fundidos e usinados

Esse estudo avaliou a adaptacao entre implantes pilares UCLA usinados e fundidos. Todos os corpos de prova de plastico foram fundidos usando tecnica de fundicao convencional de acordo com o fabricante. Cinco corpos de prova foram avaliados em relacao a desadaptacao vertical e horizontal utilizando um Microscopio Eletronico de Varredura. Os grupos UCLA Ouro (desadaptacao vertical: 2.15 μm, horizontal : 11.30 μm) e UCLA rotacional fundido (desadaptacao vertical: 14.91 μm, horizontal: 59.41 μm) mostraram as medias mais baixas e mais altas, respectivamente. De uma maneira geral, os pilares UCLA fundidos mostraram adaptacao menor do que os pilares UCLA usinados.

Palabras-chave: Implantes dentarios; Pilares; Adaptacao marginal.


 

INTRODUCTION

Castable abutments were introduced as an alternative to the premachined abutments to allow prosthetic restoration of poorly fitting fixtures with little interocclusal space, in as well as to simplify restoration. In 1988, Beumer and Lewis developed a castable abutment, which would be connected directly to the implant, after casting. However when this castable abutment is cast, distortions inherent to the casting process occur. These distortions can cause a greater crown misfit, leading to peri-implantitis1,2. To reduce the distortion in abutment casting, UCLA type abutments were developed with premachined bases of noble or semi-noble alloys. These abutments are overcast with a metal alloy compatible with that of the abutment base, thus not altering the premachined base3. Therefore, marginal fit could be improved, since the passive fit of prosthetic components on implants is affected by the material and its manufacturing process4. Moreover, the imprecise fit of combined components could influence the prognosis of implant success, as lack of precise and passive fit can generate stresses that may lead to mechanical and biological complications, such as loss of screws, loosening, and eventually, implant fractures5,6. When fit is close to ideal, it generates greater stability of the screwed denture system, maintaining the torque and fit for a longer time, preventing early loss of preload, guaranteeing not only the micromechanical stability of the system but also peri-implant tissue health and osseointegration7-10.
The concept of fit in implant supported prosthesis is a controversial subject. There is still no consensus about the acceptable value of vertical gap and horizontal discrepancy, and the best method for verifying this misfit and its clinical implication11. In the literature an acceptable standard for misfit with values around 10 micrometers is mentioned1. For clinical evaluation of marginal gaps, radiography is the most used method; however, this analysis may lead to a very subjective interpretation due to the difficulties involved in obtaining a standard image12. Therefore, the aim of the present study was to evaluate the vertical and horizontal marginal fit of premachined and castable UCLA type abutments on implants of the same system, using scanning electron microscopy (SEM). This study uses a null hypothesis: the use of premachined or castable UCLA type abutments does not modify the marginal gap measurements.

MATERIALS AND METHODS

For this study implants and abutments of a commercial implant system (Neodent, Curitiba, Parana, Brazil), with external hexagon 3.75 mm in diameter and platform of 4.1mm were used. For each experimental group five specimens of each type of abutment were used: UCLA castable abutments, rotational, UCLA castable abutments, rotational with internal rectification, UCLA castable abutments, anti-rotation, UCLA premachined titanium abutments, UCLA type abutments with premachined Tilite base, UCLA Noble abutments, and custommade stub type abutments. The castable abutments were cast by the conventional lost-wax technique13 in Nickel-Chrome (Verabond II, AALBA Dent Inc, Cordelia, CA, USA) in accordance with the manufacturer’s recommendations. After casting, the specimens were cleaned internally; followed by airborne particle abrasion with aluminum oxide granulation of 100 micrometers under pressure of 5 kg/cm2, protecting the abutment cervicals with implant analogs. All the components were cleaned ultrasonically in an acetone bath before marginal fit assessment.

Marginal fit measurement
Marginal fit was evaluated by measuring the vertical gap and horizontal discrepancy (in micrometers) between implant and abutment, using SEM (Phillips XL 30 model, Holland)14 (Fig. 1).


Fig. 1
: Analysis of horizontal discrepancy in UCLA cast antirotational abutment.

The UCLA abutment was connected to the implant with a titanium screw under toque of 10N 15 with a manual torque meter (Neodent S.A., Curitiba, Parana, Brazil). The vertical gap of each set was measured at three points: two points at the extremity and one central point. Four opposite implant faces were assessed and marked to obtain 12 standard measurements. Horizontal discrepancy was measured at two points of each of the four faces evaluated, originating eight measurements per component evaluated. Arithmetic means of the vertical gap and horizontal discrepancy values were obtained for each specimen. The group of UCLA cast rotational abutments was analyzed first, soon after they were cast, and conventionally finished. Next, the internal surfaces of the abutments were rectified. Standardized rotational movements were made six times with a rectifier appliance (Conexao Sistemas de Proteses, Sao Paulo, SP, Brazil), alternating 10 clockwise movements with 10 anticlockwise movements. After rectification, the abutments were again connected to the implant to measure marginal fit. The vertical gap and horizontal discrepancy data in micrometers were evaluated by the ANOVA and Tukey tests at a 5% level of significance.

RESULTS

Comparison of the mean vertical gap and horizontal discrepancy values among the experimental groups is shown in Table 1 and Fig. 2. The highest values were found in the group of UCLA type castable abutments, both for vertical gap and horizontal discrepancy. Rectification of the rotational castable abutment reduced the vertical gap, but not the horizontal discrepancy. The lowest vertical gap and horizontal discrepancy values were observed with UCLA Gold and UCLA Tilite abutments. (Table 1, 2 and 3, Fig. 2).

Table 1: Vertical and horizontal gap mean values (μm) for each experimental group.

Table 2: Results of 1-way analysis of variance for Vertical Misfit.

Table 3: Results of 1-way analysis of variance for Horizontal Misfit.


Fig. 2
: Vertical and horizontal gaps (μm) of the experimental groups.

DISCUSSION

The success and popularity of the implant system desig ned by Branemark16-19, encouraged the appearance of alternative implant systems, which are compatible and interchangeable with the original Branemark system19. These implants and components are an attractive clinical alternative, as they have a lower cost, a larger range of restorative options and components are readily available commercially. With regard to the UCLA type abutments, alterations were introduced in the technical laboratory protocol of the castable UCLA pillars with premachined bases of noble or semi-noble alloys to improve fit between the implant and abutment. This study showed that the experimental groups presented significant differences in vertical gap and horizontal discrepancy. The components with premachined bases, UCLA Noble, UCLA Tilite, Custom-made Stub and UCLA Titanium, presented better fit with regard to vertical gap, corroborating previous findings21. The Custom-made Stub and UCLA Titanium groups did not differ, but presented worse fit than the UCLA Noble and Tilite groups.
The cast UCLA castable abutments presented the highest vertical gap and horizontal discrepancy values. Components whose complete structure is exposed to the casting process tend to be more technique-laboratory sensitive: casting shrinkage, inclusion technique, casting method, type of lining used and type of dental alloy used22. The internal rectification procedure was shown to improve the fit of completely castable components. However, the UCLA Noble and Tilite components were shown to be a superior alternative with regard to the pattern of fit. The better fit of the UCLA Titanium component in comparison with the completely castable groups is noteworthy, as the main indication of the UCLA Titanium component is for the provisional stage of implant work, while the completely castable components are indicated for definitive work. Noble alloy-based materials thus showed that not only do they provide better fit of components on implants, but as a result of this superior compatibility, they also maintain the long term integrity of peri-implant tissues and osseointegration4. The in vitro nature of this study precludes the extrapolation of results directly to the clinical field. It is therefore suggested that future longitudinal clinical studies be conducted on these components to confirm their clinical applicability, material longevity and health of the peri-implant tissue.

CONCLUSION

Within the limitations of this study, it could be concluded that:
1. The null hypothesis was rejected;
2. The components with premachined bases presented better fit than the cast components;
3. Internal rectification of the cast abutments produced a partial improvement in the fit of components;
4. The UCLA Tilite component showed fit values close to those of UCLA Noble, demonstrating that it was an alternative that promotes a more favorable connection in comparison with the completely castable components, whose compatibility and pattern of fit were shown to be inferior.

REFERENCES

1. Lewis SG. An Esthetic Titanium Abutment: report of technique. Int J Oral Maxillofac Implants 1991;6:195-201.         [ Links ]

2. Lewis SG, Llamas D, Avera S.The UCLA abutment: a four-year review. J Prosthet Dent 1992;67:509-515.         [ Links ]

3. Kano SC, Bonfante G, Hussne R, Siqueira AF. Use of base metal casting alloys for implant framework: marginal accuracy analysis. J Appl Oral Sci 2004;12:337-343.         [ Links ]

4. Karl M; Rosch S; Graef F; Taylor TD; Heckmann SM. Static Implant Loading Caused by as-cast Metal and Ceramic-Veneered Superstructures. J Prosthet. Dent 2005;93:324- 330.         [ Links ]

5. P Binon, F Sutter, K Beaty, J Brumski, H Gulbransen and R Weiner, The role of screws in implant systems: osseointegration ten years in private practice conference, Int J Oral Maxillofac Implant 9 (1994), pp. 48-63. (Panel Discussion)        [ Links ]

6. Naert I, Quirynen M, Van Steenberghe D, Darvis P. A study of 589 consecutive implants supporting complete fixed prostheses. Part II: prosthetic aspects. J Prosthet Dent 1992;68:949-956.         [ Links ]

7. Vidigal GM Jr, Novaes AB Jr, Chevitarese O, de Avillez RR, Groisman M. Evaluation of the Implant-connection Interface Using Scanning Electron microscopy. Braz Dent 1995;6:17-23.         [ Links ]

8. Patterson EA, Johns RB. Theoretical Analysis of the Fatigue Life of Fixture Screws in Osseointegrated Dental Implants. Int J Oral Maxilofac Implants 1992;7:26-34.         [ Links ]

9. Gross M, Abramovich I, Weiss EI. Microleakage at the abutmentimplant interface of osseointegrated implants: a Comparative Study. Int J Oral Maxilofac Implants 1999;14:94-100.         [ Links ]

10. Guindy JS, Schiel H, Schmidli F, Wirz J. Corrosion at the marginal gap of implant-supported superstructures and implant failure. Int J Oral Maxilofac Implants 2004;19:826-831.         [ Links ]

11. Carr AB, Gerard DA, Larsen PE. The response of Bone in Primates Around Unloaded Dental Implants Supporting Prostheses with Different levels of Fit. J Prosthet Dent 1996;76:500-509.         [ Links ]

12. Begona Ormaechea M, Millstein P, Hirayama H. The Angulation Effect on Radiographic Analysis of the Implant- Abutment Interface. Int J Oral Maxilofac Implants 1999;14:77-85.         [ Links ]

13. Kano, SC, Binon P, Bonfante G, Curtis DA. Effect of Casting Procedures on Screw Loosening in UCLA-Type Abutments. J Prosthodont 2006;15:77-81.         [ Links ]

14. Alonso FR, Triches DF, Teixeira ER, Hirakata LM. Marginal fit of implant- supported fixed prosthesis frameworks with prefabricated and calcinable cylinders. Rev Odonto Cienc 2008; 23:320-324.         [ Links ]

15. Cho SC, Small PN, Elian N, Tarnow D. Screw Loosening for Standard and Wide Diameter Implants in Partially Edentulous Cases: 3 - to 7- year Longitudinal Data. Implant Dent 2004;13:245-250.         [ Links ]

16. Branemark PI. Osseointegration and its experimental background. J Prosthet Dent 1983;50:399-410.         [ Links ]

17. Adell R, Ericksson B, Lekholm U, Branemark PI, Jemt T. A long term follow up study of osseointegrated implants in the treatment of totally edentulous jaws. Int J Oral Maxillofac Implants 1990;5:347-359.         [ Links ]

18. Scheller H, Urgell JP, Kultje C, Klineberg I, Goldberg PV, Stevenson-Moore P, Alonso JM, Schaller M, Corria RM, Engquist B, Toreskog S, Kastenbaum F, Smith CR. A 5-year Multicenter Study on Implant-Supported Single Crown Restorations. Int J Oral Maxilofac Implants 1998;13:212-218.         [ Links ]

19. Kourtis SG, Sotiriadou S, Voliotis S, Challas A. Private Practice Results of Dental Implants. Part I: Survival and Evaluation of Risk. Factors- Part II: Surgical and Prosthetic Complications. Implant Dent 2004;13:373-385.         [ Links ]

20. Dellow AG, Driessen CH, Nel HJ. Scanning electron microscopy evaluation of the interfacial fit of interchanged components of four dental implant systems. Int J Prosthodont. 1997;10:216-221.         [ Links ]

21. Byrne D, Houston F, Cleary R, Claffey N. The Fit of Cast and Premachined Implant Abutment. J Prosthet Dent 1998;80:184-192.         [ Links ]

22. Vigolo P, Majzoub Z, Cordioli G. Measurement of the dimensions and abutment rotational freedom of goldmachined 3i UCLA-type abutments in the as-received condition, after casting with a noble metal alloy and porcelain firing. J Prosthet Dent 2000;84:548-553.         [ Links ]

Creative Commons License Todo el contenido de esta revista, excepto dónde está identificado, está bajo una Licencia Creative Commons