Dental enamel, an avascular, irreparable, outermost and protective layer of the human clinical crown has a potential to withstand the physico-chemical effects and forces. These properties are being regulated by a unique association among elements occurring in the crystallites setup of human dental enamel. Calcium and phosphate are the major components (hydroxyapatite) in addition to some trace elements which have a profound effect on enamel. The current review was planned to determine the aptitude of various trace elements to substitute and their influence on human dental enamel in terms of physical and chemical properties.
This in vivo study revealed that porous hydroxyapatite (PHA) and dense hydroxyapatite (DHA) are good implant materials that can accelerate bone healing and resorbed in acceptable time. But there were differences in the mechanism of the resorption of DHA and PHA due to variability in the physical properties and osteogenicity.
Various blend ratios of high-density polyethylene (HDPE) and ultra high molecular weight polyethylene (UHMWPE) were prepared with the objective of determining their suitability as biomaterials. In the unfilled state, a blend of 50/50 (HDPE/UHMWPE) ratio by weight was found to yield optimum properties in terms of processability and mechanical properties. Hydroxyapatite (HA) was compounded with the optimum blend ratio. The effects of HA loading, varied from 0 to 50wt% for both filled and unfilled blends were tested for mechanical properties. It was found that the inclusion of HA in the blend led to a remarkable improvement of mechanical properties compared to the unfilled blend. In order to improve the bonding between the polymer blend and the filler, the HA used was chemically treated with a coupling agent known as 3-(trimethoxysiyl) propyl methacrylate and the treated HA was mixed into the blend. The effect of mixing the blend with silane-treated HA also led to an overall improvement of mechanical properties.
The paper presents the effect of sintering temperature on the physical properties of porous hydroxyapatite (HAp In this study, the HAp was prepared using polymeric sponge techniques with different binder concentrations. The sintering process was carried out in air for temperature ranging from 1200 degrees C to 1600 degrees C. Different physical properties namely density and porosity were observed at different sintering temperatures. The HAp prepared with higher PVP binder showed a slightly decreased in apparent density with increasing sintering temperature, while those HAp prepared with lower PVP showed a slightly increase in apparent density with increasing sintering temperature. The total porosity was found to be approximately constant in the whole sintering temperature range. However, closed porosity decreases with increasing sintering temperature for HAp prepared by lower binder concentration. On the other hand, the HAp prepared by higher binder concentrations showed increasing closed porosity with increasing sintering temperature. Other features such as the influence of sintering temperatures on grain and strut would also be presented in this paper.
The paper presents a method of producing synthetic Hydroxyapatite (HA) Ca10(PO4)6(OH)2 and other apatites for biological use by solid-state reaction. The solid-state reaction involves mix-grinding dry powders of beta-tricalcium phosphate powder (TCP) and either calcium hydroxide (Ca(OH)2) or calcium carbonate (CaCO3) or combination thereof, from pure commercial chemicals or derived from natural limestone or from seashells, of total calcium/phosphorus molar ratio between 1.5 to 2.0, to particle size of less than 10 microns, and firing the resultant powder to temperature between 600 degrees C - 1250 degrees C in atmosphere or in controlled atmospheric condition. The resultant apatites formed were characterised using XRD, SEM-EDX and FTIR. The presented reaction process was found to be much simpler compared to conventional methods of producing synthetic apatites since it involves only dry mix-grinding of the reactants before firing at high temperatures based on the required levels of purity. It can also produce synthetic apatites with good reproducibility in a shorter time. Thus the presented method has a great industrial value.
Hydroxyapatite, (HA; Ca1O(PO4)6(OH)2) has been successfully applied in medical and dental applications for several years due to its excellent biocompatibility. The usage of HA in Malaysia, however, is limited due to the lack of availability. Therefore the aim of this work is to produce HA materials from both pure chemicals and from Malaysian natural limestone precursors, and to compare their bulk properties. However, parts of Malaysian natural limestone deposits actually consist of a combination of Ca(OH)2 and CaCO3. In order to utilise the limestone to produce HA material, the combination of these commercially pure chemicals as HA precursors should still work. In order to test this hypothesis, two HAs were produced by wet synthesis technique utilising (a) combination of Ca(OH)2 + CaCO3 from pure commercial chemicals [WCC] and (b) a local natural limestone [WL] precursors. The HAs produced; WCC and WL, were compacted into discs and sintered at 1250 degrees C. The characterisations and evaluations conducted were XRD, SEM-EDX, FTIR and shrinkage factor. The results indicate that WL gives slightly better bulk properties compared to WCC.
This study presents a novel tool to predict temperature-exposure of incinerated pig teeth as a proxy for understanding impacts of fire on human teeth. Previous studies on the estimation of temperature-exposure of skeletal elements have been limited to that of heat-exposed bone. This predictive tool was developed using a multinomial regression model of colourimetric and hydroxyapatite crystal size variables using data obtained from unheated pig teeth and teeth incinerated at 300 °C, 600 °C, 800 °C and 1000 °C. An additional variable based on the observed appearance of the tooth was included in the tool. This enables the tooth to be classified as definitely burnt (600 °C-1000 °C) or uncertain (27 °C/300 °C). As a result, the model predicting the temperature-exposure of the incinerated teeth had an accuracy of 95%. This tool is a holistic, robust and reliable approach to estimate temperature of heat-exposed pig teeth, with high accuracy, and may act as a valuable proxy to estimate heat exposure for human teeth in forensic casework.
A mixture with different compositions of HA and TCP were synthesize in this work by precipitation method using Ca(NO3)2 4H2 and (NH4)2HPO4 as the starting materials. A mixture with HA and TCP phases in different ratios were produced. The powders were sintered from 1000 degrees C to 1250 degrees C. The phase compositions of the mixtures were then studied via XRD. This work shows that the pH value determines the different phase compositions of the HA-TCP mixture. Chemical analyses were carried out by FTIR. The microstructure was observed under SEM.