Muhammad Kaleem

Microwave-assisted synthesis and evaluation of type 1 collagen–apatite composites for dental tissue regeneration:

The aim was to develop an economical and biocompatible collagen-based bioactive composite for tooth regeneration. Acid-soluble collagen was extracted and purified from fish scales. The design was innovated to molecularly tailor the surface charge sites of the nano-apatite providing chemical bonds with the collagen matrix via microwave irradiation technique. The obtained collagen was identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, and scanning electron microscopy. MC3T3-E1 cell lines were used to assess the biological effects of these materials by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetra zolium bromide (MTT) assay. Indirect contact test was performed by extracting representative elutes in cell culture media and sulforhodamine B analysis was performed. Chorioallantoic membrane assay was conducted to define the new vessels formation behavior. The purity of collagen extracts was determined and showed two α-chains, i.e. the characteristic of type I collagen. Fourier transform infrared spectroscopy showed the characteristic peaks for amide I, I, III, and phosphate for collagen and composites. Scanning electron microscopy images showed three-dimensional mesh of collagen/apatite nano-fibers. Nontoxic behavior of composites was observed and there were graded and dose-related effects on experimental compounds. The angiogenesis and vessels formation behavior were observed in bioactive collagen composite. The obtained composites have potential to be used for tooth structure regeneration.

Comparative abrasive wear resistance and surface analysis of dental resin-based materials

Objective: The objective of this study was to assess the surface properties (microhardness and wear resistance) of various composites and compomer materials. In addition, the methodologies used for assessing wear resistance were compared. Materials and Methods: This study was conducted using restorative material (Filtek Z250, Filtek Z350, QuiXfil, SureFil SDR, and Dyract XP) to assess wear resistance. A custom-made toothbrush simulator was employed for wear testing. Before and after wear resistance, structural, surface, and physical properties were assessed using various techniques. Results: Structural changes and mass loss were observed after treatment, whereas no significant difference in terms of microhardness was observed. The correlation between atomic force microscopy (AFM) and profilometer and between wear resistance and filler volume was highly significant. The correlation between wear resistance and microhardness were insignificant. Conclusions: The AFM presented higher precision compared to optical profilometers at a nanoscale level, but both methods can be used in tandem for a more detailed and precise roughness analysis.

Effect of nano-bioceramics on monomer leaching and degree of conversion of resin-based composites

The aim of this laboratory study was to evaluate the monomer leaching and degree of conversion (DC) from experimental bioactive resin composites (RBCs) and to do comparison with commercial bulkfill and packable resin composites. Experimental dimethacrylatebased resin composites were reinforced with silanated nano-hydroxyapatite (30 and 45 wt%). The ion leaching and DC of these resin composites were compared and contrasted with SDR™ and Filtek P60™ by using the high performance liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR), respectively. A significant difference was found in elution of monomer between the resin composites. SDR™ showed significantly high monomer elution and structural changes compared to other resin composites. The DC of bioactive RBCs showed the highest conversion rate after polymerization. Resin composite with nano-hydroxyapatite with the presence of a bioactive component might provide biomimetic approach for the material. Moreover, a low concentration of nanohydroxyapatite nano-fillers have shown better properties than micro-fillers based resin composites.

Effect of filler particles morphology of resin-composites on cavity packing force for repeated condensation

Effect of variation in morphology and size of filler particles, temperature and increase in condensation speed on packability of resincomposites was investigated. Eight experimental light-cured resin-composites (RZDn series) were tested. Each material was placed in a cylindrical mould at 26 or 32ºC. A flat-ended stainless-steel probe (φ=6 mm) was mechanically lowered with two different speeds 2 and 8 mm/s onto and into at the surface of the unset sample until a compressive force of 1 N was reached. This was repeated for five cycles, and from each cycle Fp was calculated. All spherical and irregular filler particle resin-composites showed a decrease in Fp with increase in number of compressions. Increase in temperature also decreased Fp, but this effect was not very prominent in the case of irregular filler resin-composites. Filler particle morphology, increase in temperature and compression cycle speed has a prominent effect on packability of resin-composites.

Oral assessment of children with autism spectrum disorder in Rawalpindi, Pakistan:

Comparison of oral health status, dental needs and dietary habits of children with autism and their healthy siblings. In this cross-sectional study, oral hygiene measures, sugar consumption and dental examination of 58 Pakistani children with autism spectrum disorder were assessed and compared to 27 of their siblings without autism spectrum disorder. Questionnaires were distributed to their parents regarding oral hygiene measures, dietary habits and past dental experiences. Clinical examination for the presence of dental caries, periodontal disease or parafunctional habits was carried out and findings were associated with the mother’s education. Children with autism had a higher incidence of caries (50%) as compared to their healthy siblings (22.2%). Significant differences were observed between the groups regarding frequency of brushing and independent brushing. Dental plaque was observed on anterior teeth in 24% children with autism spectrum disorder as compared to 14% in the control group. Trauma due to self-injurious behaviour and bruxism was also recorded and compliance during clinical examination was noted in children with autism spectrum disorder. There was no significant difference in sugar consumption between children with autism spectrum disorder and their healthy siblings. Children with autism had greater dental needs and were more prone to developing dental problems as compared to their healthy siblings.

Stiffness of uncured resin-composites assessed via cavity-packing forces

OBJECTIVES To evaluate the stiffness and packability of unset resin-composites at different temperatures, taking into account the cavity wall effect. MATERIALS AND METHODS Six representative commercial resin-composites were selected. Each material was placed in mould of different sizes for example (φ=7, depth=5mm; or φ=3, depth=5mm) held at 26 or 37°C. Maximum packing force (Fp) of the resin-composite was measured. A flat-ended stainless-steel probe with a diameter of either 6mm or 3mm was mechanically lowered onto and into the surface of each unset sample with a speed of 0.50mm/s to a depth of 2mm, which was held constant for 10s. The compressive force produced on the probe by the unset resin-composites was plotted against time and the maximum value was identified (Fp). Peak stress Sp was calculated by dividing the Fp by area of the probe used. Data were analyzed by univariate ANOVA and multiple pair wise comparisons were performed using a Tukey post-hoc test to establish homogenous subsets (at p=0.05). RESULTS Sp was taken as potential measure of stiffness. It ranged from 0.12 to 4.21MPa and from 0.07 to 3.08MPa at 26 and 37°C, respectively. Univariate ANOVA showed significant influence of the plunger cavity ratios, temperature and materials on Sp (p<0.001). A strong interaction was also found between plunger cavity ratios, temperature and materials for Sp (p<0.05). CONCLUSION Peak stress Sp is a useful parameter for characterizing the stiffness of uncured resin-composite materials, additionally resin-composite formulation, temperature and wall effect did effect the packability of resin-composite.