Adhesion strength testing – An improved approach

Hassan Elnadif Mohammed, Hesham (2025). Adhesion strength testing – An improved approach. University of Birmingham. Ph.D.

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Abstract

Background:

Generally, the bonding of one material to another is important for function, and especially with so-called ‘adhesive dentistry’. A test with discriminatory power that mimics the clinical failure mode i.e., the failure of that bond in peel mode, has not emerged.
Objective: Develop and validate a test protocol based on 4-point bending that may be used to examine the bonding of various dental materials to a range of substrates, taking dentine, stainless steel and aluminium alloy as examples.

Methods:

An improved approach for static flexural strength of ‘adhesive’ bond to dentine based on 4-point bend was developed. Slices of coronal dentine from extracted molars (larger and more squared teeth) were prepared using a diamond blade. Bonded interface specimens were prepared by shaping the material within the respective manufacturers’ (3M ESPE, Shofu, Ivoclar Vivadent, GC Europe, DE Healthcare, Dentsply DeTrey, Septodont) stated working time using a stainless steel split mould. The support span-depth ratio for the beam was chosen to minimise shear effects and to enable failures to occur in the maximum tension surface due to bending moments only. The new method was used to measure quantitatively the adhesive bond potential of various systems, i.e., zinc phosphate cement, zinc polycarboxylate cement, glass ionomer cement, calcium silicate cement, total-etch resin systems, and a self-adhesive resin cement. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to examine fracture surfaces, identify failure origins, and confirm failure mode.

Results:

Symmetrical 4-point bending was found to be a valid approach, compared with currently employed test methods, for the characterization of ‘adhesive’ and cohesive strengths. The test set up employed a relevant mode of loading with a subsequent failure pattern initiating at the tooth-restoration interface.

Conclusion:

With reproducibility, discriminatory power, economy with regard to substrates, and a straightforward robust process, the method is adaptable to many systems.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):