Fatigue bond strength of dental adhesive systems: Historical background of test methodology, clinical considerations and future perspectives

Abstract

Numerous laboratory evaluations have been conducted since Dr. Rafael Bowen introduced a method for determining the bond strengths of adhesive systems to dental substrates in 1965. Most of the past studies have been conducted using static bond strength tests, such as shear and tensile bond strength testing with either macro or micro sized specimens. These static bond strength tests are conducted using a monotonically increasing load in which stress is applied continuously until failure occurs. Although the type of stress that develops in static bond strength tests is not typically encountered in clinical situations, over the years clinicians have based their choice of adhesive systems for use in daily practice on the results of such tests. However, some well-known researchers have reported that the results obtained from static bond strength testing may have limited clinical relevance and should not be used only by themselves to make recommendations for clinical use. In clinical situations, restorations undergo cyclic stress during mastication at stress levels well below the breaking stress used in static bond strength tests. Thus, dynamic bond strength tests, using cyclic loading, should be more clinically relevant than static bond strength tests. Over 15 years, a testing method designed to assess fatigue bond strengths of dental adhesive systems has been developed through inter-collegial and international collaborative efforts. This review discusses the development of fatigue bond strength testing methodology, provides both a historical perspective and current information regarding available testing data for all categories of adhesive systems to enamel and dentin and perspectives on the future development of both adhesive systems and testing methods.

Keywords: Bond strength; Dentin; Enamel; Fatigue; Light-curing dental adhesives.

Fig. 1

Fatigue bond strength testing set-up with ACTA Fatigue Tester (Academic Center for Dentistry Amsterdam, Amsterdam, Netherlands).

Fig. 2

Fatigue bond strength testing set-up with Four-station Fatigue Cycler (Proto-tech, Portland, OR, USA).

Fig. 3

Fatigue bond strength testing set-up with MTS 858 Mini Bionix II Servo Hydraulic System (MTS Systems Corporation, Eden Prairie, MN, USA).

Fig. 4

Fatigue bond strength testing set-up with ElectroPuls E1000 (Instron, Norwood, MA, USA).

Fig. 5

The results for fatigue bond strength of 3- and 2-step etch-and-rinse (E&R) adhesive systems and universal adhesives in E&R mode to enamel and dentin.

Fig. 6

Categorization of available etch-and-rinse (E&R) adhesive systems.

Fig. 7

Categorization of available self-etch adhesive systems.

Fig. 8

The results for fatigue bond strength of 2- and 1-step self-etch adhesive systems and universal adhesives in self-etch mode to enamel and dentin.

Fig. 9

Scanning electron microscopy (SEM) observations of enamel-adhesive interfaces for 3- and 2-step etch-and-rinse (E&R) adhesive systems and universal adhesive in E&R mode. A: adhesive; E: enamel; R: resin composite.

Fig. 10

Atomic force microscopy (AFM) and scanning electron microscopy (SEM) observations of ground and phosphoric acid etched enamel.

Fig. 11

Scanning electron microscopy (SEM) observations of enamel-adhesive interfaces for 2- and 1-step self-etch adhesive systems and universal adhesives in self-etch mode. A: adhesive; E: enamel; R: resin composite.

Fig. 12

Scanning electron microscopy (SEM) observations of dentin-adhesive interfaces for 3- and 2-step etch-and-rinse (E&R) adhesive systems and universal adhesive in E&R mode. A: adhesive; D: dentin; R: resin composite.

Fig. 13

Scanning electron microscopy (SEM) observations of dentin-adhesive interfaces for 3- and 2-step etch-and-rinse (E&R) adhesive systems and universal adhesive in E&R mode after acid-base treatment. A: adhesive; D: dentin; RT: resin tag.

Fig. 14

Scanning electron microscopy (SEM) observations of hybrid layer for 3- and 2-step etch-and-rinse (E&R) adhesive systems and universal adhesive in E&R mode. D: dentin; HL: hybrid layer.

Fig. 15

Scanning electron microscopy (SEM) observations of transition zone (TZ) and nano interaction zone (NZ) for 2- and 1-step self-etch adhesive systems and universal adhesives in self-etch mode.