Background: Molar Incisor Hypomineralisation (MIH) represents a prevalent enamel defect. While resin composites are often the treatment of choice, there is evidence indicating that resin composite has a weaker bond strength to MIH teeth when compared to sound enamel. Here, we investigate if pre-treatment of hypomineralised enamel of MIH teeth with CurodontTM Repair Self-Assembling Peptide (SAPs) P₁₁₋₄ improves the bond strength of resin composite restorations to MIH teeth.
Method: Enamel specimens were collected from 25 sound and 50 MIH teeth. Baseline analysis consisted of Laser Fluorescence to assess the mineral content of sound teeth and hypomineralised enamel in MIH teeth. Followed by digital photography, and colour measurements which were used to divide the MIH specimens into two distinct severity groups (mild/moderate and severe). Enamel specimens were divided into three groups: Sound (SE), hypomineralised enamel (MIH), and SAPs-pre-treated enamel (MIH+T), (n=25 each). To produce a smooth enamel surface, crowns were examined and sectioned into 3x3 mm enamel specimens which were then placed in resin blocks. Specimens were initially etched with 37% wt phosphoric acid for 20 s, and then, only group (MIH+T) surfaces were pretreated with P₁₁₋₄. All the groups were followed by applying Optibond Solo (Kerr Corporation), then light-cured using Demi Plus LED Light Curing System for 40s (Kerr). Resin composite cylinder Filtek Supreme Universal (3M Oral Care ESPE) was then attached to each enamel specimen as per ISO 29022. Specimens were stored in phosphate-buffered saline (PBS) storage media for 24 hours in 37 °C incubator before testing. Each group underwent ISO 29022- notch-shear bond strength (SBS) testing using an Universal Testing Machine (UTM) at a crosshead speed of 1 mm/min until failure. Further analysis was conducted on 15 representative specimens from the three groups (SE), (MIH), (MIH+T) (n=5 each), using Micro CT to measure the mineral density, 9 representative specimens (n=3 each) for Scan Electron Microscope (SEM) and Energy-dispersive X-ray (EDX) to understand the type of the failure. SPSS software version 28 was used to analyse the data.
Results: The mean SBS of composite to sound teeth in group (SE) was 15.87 MPa +/-12.87 (SD), and for group (MIH) teeth, the mean value was 1.69 MPa +/-0.81 (SD), and for the group (MIH+T) it was 4.5 MPa +/- 1.45 (SD). There was a significant difference between all three groups (SE), (MIH) and (MIH +T) P<0.001, with a significant difference between (SE) and (MIH) with P<0.001, (MIH) and (MIH+T) P<0.001, and (SE) and (MIH+T) P<0.001.Conclusion: P₁₁₋₄ enhanced the SBS of resin composites to MIH affected teeth in vitro when compared to MIH teeth without pre-treatment. However, this remained significantly lower than SBS to sound enamel.
