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Effect of Tri-strontium Phosphate Fillers on Monomer Conversion, Adhesion, Mechanical and Antibacterial Properties of Propylene-based Dental Composites

Objectives: Assess the effect of varying levels of tri-strontium phosphate fillers on monomer conversion, compressive strength, shear-bond strength and antibacterial properties of propylene-based dental composites
Methods: Tri-ethylene-glycol-dimethacrylate, polypropylene-dimethacrylate, camphorquinone and n-tolylglycine-dimethacrylate were mixed to get light curable stock-monomer.Stock-monomer was then mixed with varying levels of tri-strontium-phosphate-fillers(TSP)(0,10,20 and 40 wt%) along with silane-treated-glass-particles to obtained formulations TSP0, TSP10, TSP20, and TSP40 respectively. Z250™was used as a commercial control. Monomer conversion was assessed at 1mm,2mm,3mm and 4mm (20s light cure) using FTIR. Compressive strength was assessed after 1 and 28 days in simulated body fluid(SBF) at 37C. Shear bond strength was measured using ivory dentine following ISO 29022:2013. The anti-biofilm activity was assessed through quantitative assessment of biofilm formation on discs surfaces after three days in the growth-medium. Bioactivity was assessed in SBF using ISO 23317:2014. P-value set at 0.01 (SPSS v25)
Results: Monomer conversion decreased with the increase in increments level from 1mm to 4mm(Fig1).Furthermore, the monomer conversion of all experimental formulations decreased with an increased in TSP fillers especially at 3mm and 4mm(p<0.01).However,shear bond strength increased with an increased level of STP fillers(p<0.01).Compressive strength decreased with an increase in STP filler levels(Tab-1).Strontium fillers had no significant effect on bacteria growth in suspension, however bacterial attachment on discs decreased significantly with the increase in STP filler levels(p<0.01)(Fig2).Apatite layer was only formed on STP40 after 28days in SBF(Fig3)
Conclusions: Newly-developed tri-strontium phosphate fillers addition showed optimum degree of monomer conversion compared to Z250. Furthermore, it enhances the adhesive property of the composite compared to Z250. STP-added composites showed reduce biofilm formation which could decrease the chances of microbial failure at interface. STP fillers also enhances the apatite formation at the interface, which could be beneficial for a stronger bond between the tooth and composite. Hence, these materials could potentially solve the problem of future micro-leakage
Division: IADR/AADR/CADR General Session
Meeting: 2020 IADR/AADR/CADR General Session (Washington, D.C., USA)
Location: Washington, D.C., USA
Year: 2020
Final Presentation ID: 0668
Abstract Category|Abstract Category(s): Cariology Research-Demineralization/Remineralization
Authors
  • Khan, Muhammad  ( khyber medical university , Peshawar , Pakistan ;  Khyber College of Dentistry , Peshawar , Pakistan ;  University College London , Peshawar , Pakistan )
  • Young, Anne  ( UCL Eastman Institute , London , United Kingdom )
    • Financial Interest Disclosure: none
    SESSION INFORMATION
    Poster Session
    Demineralization/Remineralization I
    TABLES
    Compressive and shear bond strength of commercial Z250™ and experimental formulations. TSP0, TSP10, TSP20, TSP40 indicates 0, 10, 20, and 40 wt% tri-strontium phosphate in the fillers phase. Compressive strength decreased significantly after 28 days in SBF (n=8, 95%-CI).
    FormulationsCompressive Strength Day 1
    (MPa) (95%-CI)    		Compressive Strength Day 28
    (MPa) (95%-CI)    		Shear Bond Strength
    (MPa) (95%-CI)
    Z250™220 ±6180 ±75 ±3
    STP0218 ±5181 ±54 ±3
    STP10190 ±4140 ±67 ±3
    STP20170 ±6125 ±720 ±4
    STP40118 ±775 ±923 ±4

    IMAGES
    Fig-1 (a) shows the monomer conversion of experimental and commercial dental composites at 1mm, 2mm , 3mm and 4 mm with 20 second blue light exposure (depth of cure). The red line indicates the minimum requirement according to the <i>ISO</i>29022:2013 standards. p<0.01=* significant, p<0.001=** significant, p<0.0001 = ***(Error bars: 95% confidence interval with <i>n</i> = 4).
    3328114_File000000.jpg
    Fig-2 shows the Log Colony Forming Unit / ml for a commercial and four experimental formulations. Initial inoculum was ~ 5 x 105 cells/ ml (<i>Streptococcus Mutans</i>). CFU was calculated via serial dilution method. CFU/ml in the suspension was calculated at 24 hours after inoculation. biofilm formation on the discs was assessed by removing the adherend bacteria on the disc surface after 4 days in growth medium (TSB). serial dilution was done to assess the bacterial CFU on the disc specimens. *= p<0.01, ** = p<0.001 (Error bars: 95% confidence interval with <i>n </i>= 9)
    3328114_File000001.jpg
    Fig-3 shows SEM images of Z250 and STP40 after 28 days in SBF. Potential apatite precipitation is seen on the surface of disc STP40 after 28 days in simulated body fluid as confirmed by EDX. Commercial Z250 showed no apatite formation on its surface (<i>n</i> = 3).<br />
    3328114_File000002.jpg