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Aim. The aim of this review is to get a comprehensive description of the factors that may influence the attractive force of the dental magnetic attachment. Background. Dental magnetic attachment is a term for a magnet used as an overdenture retainer. Magnets that are widely used are permanent magnets such as neodymium iron boron (NdFeB) and samarium cobalt (SmCo). Theoretically, the magnetic attractive force in a permanent magnet has a constant retentive force, and the magnitude of the force will not decrease over time. However, several studies revealed that the magnetic attractive force can be decreased, resulting in the failure of overdenture retention. Some of the factors of reduced magnetic attraction that have been studied are corrosion and temperature. There are no articles that specifically review the factors that can influence magnetic attraction. Review Results. A total of 25,880 articles were obtained during a search on 3 journal databases: PubMed (2,647), ScienceDirect (23,184), and Scopus (229). From those publications, 15 articles reported relevant outcome data that were then extracted. Magnetic attractive force can be influenced by temperature, corrosion, keeper surface morphology, type of magnet, keeper-assembly size combination, inclination, insertion-removal cycle, gliding/loading cycle, number of magnets, crosshead speed, and force direction. Conclusion. Many factors can affect the magnetic attraction force of the dental magnetic attachment. Corrosion is the most likely factor to occur because the dental magnetic attachment is always in the oral environment which contains corrosive saliva and is susceptible to damage due to mastication forces.

Dental magnetic attachments used as a retainer for overdentures are encapsulated with a corrosion resistant casing to prevent corrosion of magnets. However, some studies reported that the casing still has a risk of corrosion. This study aims to determine the effect of acid solutions on magnetic attractive force, dissolving metal ions and corrosion of magnetic attachment surfaces. The dental magnetic attachment material used is Magfit DX 600 (Aichi, Japan). It consists of assembly and keeper. The assembly and keeper immersed in acid solutions with a pH of 3.8 and 5.8 for 7 and 14 days. After immersion, the assembly and keeper were analyzed using SEM, universal testing machine, and the atomic absorption spectrophotometry to determine the surface corrosion, the magnetic attractive force, and dissolved metal ions, respectively. It is found that all assemblies showed signs of corrosion and reduction of magnetic attractive force after immersed in acid solutions with a pH of 3.8 and 5.8 for 7 and 14 days. A greater decrease in magnetic attraction was obtained at 14 days immersion in an acid solution with a pH of 3.8. Fe ion dissolution in the assembly and keeper was found to increase at 14 days of immersion. The lower the pH of the acid solution and the longer the immersion time, the signs of corrosion on the surface of dental magnetic attachment are clearly observed. The magnetic attraction force also decreased with decreasing the value of pH as well as the increase of the content of Fe ion in immersed solution.

Recently Indonesia is conducting Underground Coal Gasification (UCG) project in South Sumatra for power generation.The potential of negative impacts from UCG on groundwater and the broader environment can not be ignored since past similar projects were often confronted with pollution isues of BTEX and PAHs due to condensation of tar-loaded gas. This study focuses on finding indigenous microorganisms capable of BTEX degradation and evaluate their biodegradability. Several microorganisms were successfully isolated and screened. Pseudomonas putida and Bacillus cereus were chosen for this bioremediation study since the bacteria were predominant and highly viable on the screening test. The BTEX degradation has been studied in single component using single and mixed bacterial cultures in the concentration range of 250-500 ppm. The experimental results show that biodegradation of BTEX by P. putida ranged from 61.4-70.2% and by B.cereus ranging 63.9-74.7 % at initial BTEX concentration of 500 ppm.Meanwhile, consortium of both isolates has the highest percentage of BTEX biodegradation (67.8-79,8%) during 14 days of retention time.The findings reveal that indigenous bacteria of P. putida dan B. cereus exhibit the potential to be used for decontamination of BTEX as an anticipated mitigation for potential pollution coming from the UCG project.