IADR Abstract Archives
Adhesive Application in Class II Composite Restorations Before/After Matrix Positioning
Objectives: Resin-based composite (RBC) restorations are characterized by excellent performances, yet their application is critical at the cervical margin of class II restorations. A clinical protocol suggests applying the adhesive system before positioning of interproximal matrices, to achieve better control.
This study aimed to morphologically investigate the effect of adhesive placement prior, or subsequent, to matrix positioning in direct-bonded Class II RBC restorations. Additional aim was to evaluate possible differences when using a two-step (CSE, Clearfil SE Bond2) or a one-step adhesive system (CU, Clearfil Universal Bond Quick).
Methods: Standardized mesio-occlusal and disto-occlusal cavities were prepared on twenty human molars. Teeth were randomly assigned to two groups according to (n=10) contoured sectional metal matrices positioned before adhesive application (M->A), or (n=10) after adhesive application (A->M). Both adhesive systems were additioned with crystal violet dye (CV, 10 vol%). Specimen sections (0.5 mm thickness) were prepared and assessed with optical and scanning electron microscopy (SEM). Bond strength of the CV-additioned adhesives was tested by microshear bond test on enamel and dentin of 12 additional molars.
Results: M->A produced a layer of adhesive both on tooth surfaces inside the restoration box and on external restoration surfaces in contact with the matrix. A->M produced a thin layer of adhesive on external tooth surfaces, well beyond cavity margins and end of RBC restoration. In all restorations, excess RBC material with uneven margins was observed over cervical margin (Figure 1). Shear bond strengths: CV addition significantly reduced adhesion forces on dentine (p=0.0015). When CU+CV was used on dentine, adhesion forces showed a 10-fold reduction.
Conclusions: Both M->A and A>-M protocols showed pros and cons, expressing adhesive layers in a hard to reach area, with the risk of being poorly polymerized. To improve longevity, all cervical margins of RBC restorations should be carefully finished, no matter the clinical protocol adopted.
This study aimed to morphologically investigate the effect of adhesive placement prior, or subsequent, to matrix positioning in direct-bonded Class II RBC restorations. Additional aim was to evaluate possible differences when using a two-step (CSE, Clearfil SE Bond2) or a one-step adhesive system (CU, Clearfil Universal Bond Quick).
Methods: Standardized mesio-occlusal and disto-occlusal cavities were prepared on twenty human molars. Teeth were randomly assigned to two groups according to (n=10) contoured sectional metal matrices positioned before adhesive application (M->A), or (n=10) after adhesive application (A->M). Both adhesive systems were additioned with crystal violet dye (CV, 10 vol%). Specimen sections (0.5 mm thickness) were prepared and assessed with optical and scanning electron microscopy (SEM). Bond strength of the CV-additioned adhesives was tested by microshear bond test on enamel and dentin of 12 additional molars.
Results: M->A produced a layer of adhesive both on tooth surfaces inside the restoration box and on external restoration surfaces in contact with the matrix. A->M produced a thin layer of adhesive on external tooth surfaces, well beyond cavity margins and end of RBC restoration. In all restorations, excess RBC material with uneven margins was observed over cervical margin (Figure 1). Shear bond strengths: CV addition significantly reduced adhesion forces on dentine (p=0.0015). When CU+CV was used on dentine, adhesion forces showed a 10-fold reduction.
Conclusions: Both M->A and A>-M protocols showed pros and cons, expressing adhesive layers in a hard to reach area, with the risk of being poorly polymerized. To improve longevity, all cervical margins of RBC restorations should be carefully finished, no matter the clinical protocol adopted.
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