Renewal MI Dental Composite Etch and Seal Properties

Abstract

This study's aim was to assess whether the Renewal MI composite can self-etch enamel, seal sound cavities, and stabilize demineralized dentine. Etching was assessed using scanning electron microscopy (SEM). Cavity sealing was quantified using the ISO-11405 dye microleakage test. Demineralized dentine stabilization was evaluated by visualizing resin tag formation, enzyme activity and mineral precipitation at the adhesion interface. Renewal MI provided a mild etching of sound enamel in comparison with 37% phosphoric acid. It provided a comparable seal of sound cavities to Z250/Scotchbond Universal adhesive and a superior seal to Activa, Fuji IX and Fuji II LC. With demineralized dentine, Renewal MI formed 300-400 µm resin tags covering 63% of the adhesion interface compared with 55 and 39% for Z250/Scotchbond and Activa. Fuji IX and Fuji II LC formed no resin tags. A higher tag percentage correlated with lower surface enzyme activity. Unlike Activa and Fuji II LC, Renewal MI promoted mineral precipitation from simulated body fluid, occluding adjacent dentinal tubules within 6 months. These novel etching and sealing properties may facilitate Renewal MI's application in minimally invasive dentistry.

Keywords: dental composite; dentine sealing; enzymatic degradation; microleakage; minimally invasive dentistry; remineralization.

Figure 1

Representative SEM images of the enamel surface upon applying Renewal MI or phosphoric acid gel 37% for different times followed by rinsing with acetone and/or water.

Figure 2

Blue dye microleakage following immersion in water for 24 h at 37 °C. The labels on the bars indicate the numbers of cavities. The y axis indicates this number as a percentage of the total group sample number. The cavosurface was either enamel (E) or dentine (D). The darker the column, the more extensive the dye penetration, and the worse the cavity sealing.

Figure 3

SEM images of resin tags formed within demineralized dentine by Renewal MI, Z250 and Activa (Fuji II LC and Fuji IX gave no tags).

Figure 4

Tag coverage area at the adhesion interface with the demineralized dentine using Renewal MI, Z250, Activa, Fuji IX or Fuji II LC. * indicates a significant difference from all other groups, while the blue bars indicate a significant difference within groups. Error bars are 95% CI (n = 3).

Figure 5

CLSM images of resin tags formation within demineralized dentine by Renewal MI, Z250, Fuji IX or Fuji II LC. All images are of areas 204 µm × 204 µm.

Figure 6

Representative CLSM images (204 × 204 µm) demonstrating MMP activity (in green) after 1 day and 14 days at the adhesion interface between Renewal MI, Z250 with bonding agent, Activa, Fuji IX or Fuji II LC and demineralized dentine. Non-restored demineralized dentine was used as a negative control.

Figure 7

Green fluorescence area as a percentage of CLSM images of enzyme activity. This indicates the relative level of interface MMP activity on demineralized dentine restored with different materials (1 or 14 days). * indicates significant difference from all other groups. Sharing the same letter (a or b) means no significant difference between these groups. Error bars are 95% CI (n = 3).

Figure 8

Example SEM images of the collagen mesh discs following their contact with pre-cured Activa, Fuji II LC and Renewal MI discs (n = 3 per material). Samples were incubated at 37 °C in SBF for 6 months. Activa and Fuji II LC shows widely opened dentinal tubules. Conversely, Renewal MI caused formation of a layer of minerals that covered the whole surface (n = 3).