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Int Poster J Dent Oral Med 6 (2004), No. 1     15. Mar. 2004

Int Poster J Dent Oral Med 2004, Vol 6 No 01, Poster 207

Tensile bond strength of dentin adhesives on irradiated and nonirradiated dentin

Language: English

Authors:
Dr. Christian R. Gernhardt, Department of Operative Dentistry and Periodontology, Martin-Luther-University Halle-Wittenberg
Prof. Dr. Andrej M. Kielbassa, Department of Operative Dentistry and Periodontology, Free University of Berlin
Prof. Dr. Hans-Guenter Schaller, Department of Operative Dentistry and Periodontology, Martin-Luther-University Halle-Wittenberg

Date/Event/Venue:
May 11th - 13th, 2000
Conseuro 2000
Bologna/Italy

Introduction

"Radiation caries", a rapidly developing and highly destructive form of tooth decay, is a well-known consequence of radiotherapy. This is due to several effects of radiotherapy concerning even the dental hard tissues1. The irradiation damage of collagen fibers2 could result in an impaired bond strength between composite and dentin, as has been described recently after high-dose irradiation3.

Objectives

Since the effects of fractionally applied irradiation on adhesion of composites to dentin have not been described in the dental literature, the aim of the present study was to evaluate the influence of radiotherapy on the tensile bond strength of four different dentin adhesives on human dentin.

Material and Methods

One hundred and twenty caries-free freshly extracted human third molars were used in this study. Sixty teeth were irradiated with a total dose of 60 Gy (fractionally applied in doses of 2 Gy, five days weekly, over a period of six weeks). Specimens were prepared according to a special procedure described recently. Thus, simulation of intrapulpal pressure and dentin perfusion was allowed. The pressure was adjusted to 30 cm H2O (Fig. 1 and 2).

Fig. 1: Mounted dentin specimen on the perfused chamber. Fig. 2: Experimental apparatus designed to test tensile bond strength of composite resin on dry and perfused dentin specimen.

Both, the 60 irradiated specimen and the 60 nonirradiated specimen were divided at random into four experimental groups each. These groups were assigned to one dentin bonding agent used as recommended by the manufacturers (Table 1). A standardized metal ring was filled with the composite material (Tetric) in small increments. These were polymerized for 60 seconds. After polymerization, tensile bond strength was tested using an Instron Universal testing machine. The maximum tensile bond strength was recorded from a personal computer and graphically expressed. Bond strength was calculated. For each subgroup mean tensile bond strengths and standard deviations were calculated. Differences between irradiated and nonirradiated groups were calculated by using Wilcoxon test. Closed test procedure (based on the Kruskal Wallis test) was used to calculate differences between the different material groups.

Group Material Manufacturer Composition
A ScotchbondTM 1 3M Dental products, Loughborough, Great Britain Ethanol, 2-hydroxyethylmethacrylate, bisphenol-A-diglycidyl-ehter-dimethacylat, urethandimethacylate, water
B Solobond Plus® VOCO,Cuxhaven, Germany Primer: water, aceton, maleic acid, acid-functionalized, methacrylates, fluorides Adhesive: aceton, dimethacrylate, hydroxymethacrylate
C Prime&BondTM 2.1 DeTrey Dentsply, Dreieich, Germany Dipentaerythritole-pentacrylate-phosphoric acid ester, urethandimethacrylate, bisphenol-A-dimethacrylate, butylhydroxytoluole, camphoroquinone, 4-ethyl-dimethyl-aminobenzoate, aceton, cetylaminhydrofluoride
D Syntac® Vivadent, Schaan, Liechtenstein Primer: Tetraethylenglycolmethacrylate, maleic acid, dimethylketone, water
Adhesive: Polyethyleneglycoldimethacrylate, maleid acid, glutaraldehyde, water
Table 1: Used dentin adhesive systems and their composition.

Results

Irradiation itself did not show any significant influence on adhesion of composite to dentin (P > 0.05; ANOVA). Regarding the adhesive systems, ANOVA revealed a significant influence on the tensile bond strength of both irradiated and nonirradiated dentin (P = 0.0001). Closed test procedure based on Kruskal-Wallis test showed that the tensile bond strength for the nonirradiated groups treated with ScotchbondTM 1 was significantly higher if compared to Solobond Plus® and Prime&BondTM 2.1 (P < 0.05; compare Table 2 and 3). In the case of irradiated groups statistical analysis revealed a significant differences between ScotchbondTM 1 and Solobond Plus® (p<0.05) and between Solobond Plus® and Prime&BondTM 2.1 (p<0.05).

Airradiated X      
Birradiated P<0,005 X    
Cirradiated NS P<0,05 X  
Dirradiated NS NS NS X
Group Airradiated Birradiated Cirradiated Dirradiated
 
Acontrol X      
Bcontrol P<0,05 X    
Ccontrol P<0,05 NS X  
Dcontrol NS NS NS X
Group Acontrol Bcontrol Ccontrol Dcontrol
Table 2 and 3: Statistical results (closed test procedure based on Kruskal-Wallis test) for the nonirradiated groups.
Fig. 3: Mean tensile bond strength and correlation within the different groups.

Discussion and Conclusions

In contrast to a recent publication by Pioch (1998), who described a reduced dentin bond strength after irradiation, this study did not reveal any significant differences between the irradiated and nonirradiated groups. Thus the described changes in dental hard tissues after irradiation obviously does not influence the bond strength of dentin adhesives4,5. The evaluated tensile bond strength of the used dentin bonding system was lower than described by other investigations. However, it should be kept in mind that most studies examined the bond strength without simulation of the dentin perfusion. Previous papers using the same experimental design have shown similar results6. The comparison (ANOVA) of the four dentin adhesives used in this investigation showed a significantly higher tensile bond strength for ScotchbondTM 1. The more sensitively closed test procedure could not completely prove these findings.
Regarding the dentin adhesive systems tested in this study, no significant differences could be observed between the irradiated and nonirradiated specimens. Thus the use of adhesive techniques to restore caries lesions in patients after irradiation can be recommended.

Bibliography

  1. Kielbassa, A.M., Beetz, I., Schendera, A. & Hellwig, E. (1997b) Irradiation effects on microhardness of fluoridated and non-fluoridated bovine dentin. European Journal of Oral Science, 105, 444-447.
  2. Cheung, D.T., Perelman, N., Tong, D. & Nimni, M.E. (1990) The effect of gamma-irradiation on collagen molecules, isolated alpha- chains, and crosslinked native fibers. Journal of Biomedical Material Research, 24, 581-589.
  3. Pioch, T. (1998) Studies on radiation-induced changes in dental hard tissues. Postdoctoral thesis, Heidelberg.
  4. Kielbassa, A.M., Schaller, H.-G. & Hellwig, E. (1998) Qualitative observations of in situ caries in irradiated dentin. A combined SEM and TMR study. Acta Medicinae Dentium Helvetica, 3, 161-169.
  5. Pioch, T., Golfels, D. & Staehle, H.J. (1992) An experimental study of the stability of irradiated teeth in the region of the dentinoenamel junction. Endod Dent Traumatol, 8, 241-244.
  6. Paul, S.J. & Schärer, P. (1993) The shear strength of dentin-bonding agents under intrapulpal pressure and temperature change. An in-vitro study. Schweizer Monatsschrift für Zahnmedizin, 103, 709-714.

This Poster was submitted by Dr. Christian Gernhardt.

Correspondence address:
Dr. Christian Gernhardt
Martin-Luther-University Halle-Wittenberg
University School of Dental Medicine
Department of Operative Dentistry and Periodontology
Grosse Steinstrasse 19
D-06108 Halle/Saale
Germany