Preserving the roots and restoring a young smile: a challenge to the pedodontist

Early childhood caries is one of the most common chronic diseases seen in preschool children. It mainly affects maxillary primary anterior teeth and if untreated leads to pulpal involvement and destruction of coronal tooth structure. This results in decreased masticatory efficiency, difficulty in speech, compromised esthetics, development of abnormal tongue habits, subsequent malocclusion and psychological problems. The successful restoration of primary anterior teeth with severe loss of coronal structure is a challenging task for the dentists. The purpose of this case report is to describe the treatment of severely mutilated primary anterior teeth with a simple and efficient technique using omega wire extension and fiber post.

Arc Interference Behavior during Twin Wire Gas Metal Arc Welding Process

In order to study arc interference behavior during twin wire gas metal arc welding process, the synchronous acquisition system has been established to acquire instantaneous information of arc profile including dynamic arc length variation as well as relative voltage and current signals. The results show that after trailing arc (T-arc) is added to the middle arc (M-arc) in a stable welding process, the current of M arc remains unchanged while the agitation increases; the voltage of M arc has an obvious increase; the shape of M arc changes, with increasing width, length, and area; the transfer frequency of M arc droplet increases and the droplet itself becomes smaller. The wire extension length of twin arc turns out to be shorter than that of single arc welding.

The Effect of Square Wave AC Parameters on Weld Forming Performance

The effects of weld current, voltage, frequency and duty cycle on weld forming performance were investigated in SAW (Submerged Arc Welding) with square wave AC mode. The results showed that the penetration increased with the decrease of frequency and increase of duty cycle, but weld width showed the opposite change tendency. Furthermore, some experiments were implemented to analyze the effect of wire extension length and arc voltage on bead appearance. All of these experimental data could provide proper parameters for the lead arc and the trail arc in tandem SAW using square wave AC and also testified square wave AC was preferred over DC and traditional 50Hz AC. The square wave AC power source could be applied widely in tandem SAW.