PurposeThe aim was to assess monomer conversion, dimensional stability, flexural strength / modulus, surface apatite precipitation and wear of mono / tri calcium phosphate (CaP) and polylysine (PLS)—containing dental composites. These were formulated using a new, high molecular weight, fluid monomer phase that requires no polymerisation activator.Materials and methodsUrethane and Polypropylene Glycol Dimethacrylates were combined with low levels of an adhesion promoting monomer and a light activated initiator. This liquid was mixed with a hybrid glass containing either 10 wt% CaP and 1 wt% PLS (F1) or 20 wt% CaP and 2 wt% PLS (F2). Powder to liquid mass ratio was 5:1. Commercial controls included Gradia Direct Posterior (GD) and Filtek Z250 (FZ). Monomer conversion and polymerisation shrinkage were calculated using Fourier Transform Infrared (FTIR). Subsequent volume increases in water over 7 weeks were determined using gravimetric studies. Biaxial flexural strength (BFS) / modulus (BFM) reduction and surface apatite precipitation upon 1 and 4 weeks immersion in water versus simulated body fluid (SBF) were assessed using a mechanical testing frame and scanning electron microscope (SEM). Mass / volume loss and surface roughness (Ra) following 7 weeks water immersion and subsequent accelerated tooth-brush abrasion were examined using gravimetric studies and profilometer.ResultsF1 and F2 exhibited much higher monomer conversion (72%) than FZ (54%) and low calculated polymerization shrinkage (2.2 vol%). Final hygroscopic expansions decreased in the order; F2 (3.5 vol%) > F1 (1.8 vol%) ~ Z250 (1.6 vol%) > Gradia (1.0 vol%). BFS and BFM were unaffected by storage medium type. Average BFS / BFM upon 4 weeks immersion reduced from 144 MPa / 8 GPa to 107 MPa / 5 GPa for F1 and 105 MPa / 6 GPa to 82 MPa / 4 GPa for F2. Much of this change was observed in the first week of immersion when water sorption rate was high. Surface apatite layers were incomplete at 1 week, but around 2 and 15 micron thick for F1 and F2 respectively following 4 weeks in SBF. Mass and volume loss following wear were equal. Average results for F1 (0.5%), F2 (0.7%), and FZ (0.5%) were comparable but lower than that of GD (1%). Ra, however, decreased in the order; F1 (15 μm) > F2 (11 μm) > GD (9 μm) > FZ (5 μm).ConclusionsHigh monomer conversion in combination with large monomer size and lack of amine activator should improve cytocompatibility of the new composites. High monomer molecular weight and powder content enables low polymerisation shrinkage despite high conversion. Increasing active filler provides enhanced swelling to balance shrinkage, which, in combination with greater surface apatite precipitation, may help seal gaps and reduce bacterial microleakage. High monomer conversion also ensures competitive mechanical / wear characteristics despite enhanced water sorption. Furthermore, increased active filler could help reduce surface roughness upon wear.
Calcium phosphate compounds are one of the biomaterials that are widely used for bone reconstruction because they are biocompatible and have a chemical composition that is close to the inorganic components present in the bone. Two types of calcium phosphate that are widely applied to the bone reconstruction process are hydroxyapatite (Ca10 (PO4) 6 (OH) 2) and β-Tricalcium Phosphate (Ca3 (PO4)2). This research develops the manufacture of β-Tricalcium Phosphate by reacting calcium compounds derived from chicken eggshells and phosphate sources derived from dinatrium phosphate (Na2HPO4) using precipitation method which is carried out with variations in sintering temperature 600 to 1000 °C and sintering time of 1 to 5 h. The results of X-Ray fluorescence (XRF) analysis showed that the Ca / P ratio obtained was 1.74, at the sintering temperature of 1000 °C and the sintering time for 5 h. These results have approached a standard where the ratio of Ca / P on Tricalcium Phosphate is 1.5. While based on the results of X-Ray Diffraction (XRD) analysis that in the sample formed two types of Calcium Phosphate namely β-Tricalcium Phosphate and Hydroxyapatite so that it can be said that the product produced is Biphase Calcium Phosphate. The high percentage of β-Tricalcium Phosphate is 81.9% with the 3 highest peaks, namely at the angle 2θ of 27.83; 31.03; 34.42 is obtained at the sintering temperature of 1000 °C and at the sintering time is 5 h.
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