The use of resin restorative materials became predominant with the growing
demand for tooth conservation procedures. The development of self adhesive resin composite has simplified their application method. The addition of remineralising and antibacterial agents may further improve the longevity of these restorations by sealing gaps and cracks when applied on caries affected dentine layer. Therefore, it is essential to evaluate the effect of adding these agents on the stability of the experimental composites chemical, physical and mechanical properties.

AIMS:
The aim was to investigate the effect of MCPM and PLS on the polymerisation stability and paste shelf life of experimental composite formulations, and also evaluate the depth of cure of the experimental formulations and two commercially available restorative materials. In addition, the polymerisation shrinkage, subsequent water sorption-induced mass changes, expansion and hydrogen ion release from four experimental resin-composite formulations were evaluated. The simulated wear resistance of five experimental resincomposite formulations and two commercial restorative materials was also investigated. Furthermore, the aim was to assess the effects of the storage container, time of high-temperature paste aging, sample depth and curing on colour of four experimental resin-composite formulations.

MATERIALS AND METHODS:
Resin-composite formulations containing PLS (0, 3, 4, 6 or 8 wt%) & double
these levels of MCPM and three commercial self-adhesive restorative
materials were evaluated. The polymerisation kinetics and paste shelf life
were evaluated by using FTIR spectroscopy. Delay times, maximum reaction
rate, 50% reaction time (t0.5) and final degree of conversion (%DC) were
determined. Resin-composite pastes were stored at room temperature (7
months), 60oC (18 days or 9 months) and at 4oC (9 months). The aged
formulations were compared to experimental formulations stored at 4oC and
room temperature. Percentage mass and volume change upon water storage
were determined gravimetrically regularly up to 11 weeks by using
Archimedes Principle and the polymerisation shrinkage was measured using
ISO 17304:2013. Storage solution acidity was evaluated at each time point
and dried solid content was analysed after 3 months and 1 year using SEM,
FTIR and EDX. The wear resistance was evaluated after 3 months and 1 year
by using a dual axis-chewing simulator. L*a* b* values for pastes and
composite discs were assessed using a spectrophotometer. Pastes samples
were stored in sealed brown glass containers at 4oC, 60oC, or 80oC and
studied before and after cure. Results were compared with previous data
(Pitsillou, 2019) for paste stored in compules.

RESULTS:
Experimental resin-composite formulations were only mildly affected by
additive addition or high-temperature aging. Average experimental composite
delay times were 4.9, 7.7 and 24.5s, at 1mm, 2mm and 4mm depths,
respectively. The maximum rates of reaction were on average 5, 4 and 2%/s,
at 1mm, 2mm and 4mm depth, respectively. The 50% reaction times were 12,
16 and 41s, at 1mm, 2mm and 4mm depth, respectively. At 1mm and 2 mm
depth, %DC of 74% and 72% could be achieved with 20s light exposure. 40s
light was required to gain an average of 64%DC at 4 mm depth. Experimental
formulations delay times and rates of reaction showed major differences when compared to Activa (2, 1 and 11s and 3, 2 and 0.67%/s) and Vertise flow (2, 4 and 10s and 5, 4 and 1%/s) at 1mm, 2mm and 4mm depth, respectively. The polymerisation shrinkage ranged between 3.0 and 4.0%. PLS significantly influenced subsequent initial rate of mass change versus square root of time (p