The purpose of this article is to introduce Optiflex (TM), the first non-metal archwire in orthodontics. This clear archwire is comprised of three layers : a silicone dioxide core, a silicon resin middle layer and a stain-resistant nylon outer layer. It is available in two sizes : 0.017″ and 0.021″. Optiflex was compared to three other flexible archwires (Niti, Respond and Nitinol) by means of tensile, bending and time-dependent effects tests. The results showed that : 1. The tensile strength of Optiflex was significantly lower than that of metal archwires. 2. The force delivered by Optiflex was much lighter and more constant than those delivered by other archwires. 3. The force of Optiflex was less than half the force delivered by at “Respond” archwire of similar size. 4. Time-dependent effects of Optiflex were almost identical to those of nickel-titanium. These mechanical advantages, along with its esthetic properties and stain resistance, make Optiflex a unique addition to orthodontic archwires currently available. The new archwire is highly effective in the alignment of crowding in most orthodontic cases, particularly adults with special esthetic considerations.
Various-shaped and sized defects of human coronal enamel were illustrated by scanning electron microscopy. Small Tomes' process pits (TPP) and larger focal holes (FH) were usually present in the enamel surfaces. On the other hand, FH-like defects were often scattered in the regions adjacent to large enamel defects. Some TPP contained a smaller punched-out deep pit (POP). In the natural surfaces of hypoplastic enamel, keyhole-shaped prism structures (KHP) were observed. Some KHP also contained a POP. That is, the center of enamel prisms occasionally mineralized later than the other prism regions. Small deep holes, roughly equal to FH in diameter, were relatively rarely observed. In rare cases, large shallow and deep defects were observed, while minor irregular oval or slit-shaped defects with a depth up to 15 ym were scattered in the supracervical zones. In addition, the rows of conic-shaped defects running longitudinally or transversely were found in the supracervical zones. The floors of the large defects showed TPP, KHP, or afibrillar cementum-like structures as well as smooth enamel surfaces. FH and TPP occasionally with a smaller POP, which are usually present along the perikymatas, are formed by the final stage of normal amelogenesis, while the remaining pits and defects must have been caused by some hypoplastic enamel.
The adaptation accuracy of a commercially available non-computer-aided ceramic system (CELAY system) to the MOD inlay model specified by the ADA was investigated by measuring the discrepancy between the top surface of the master die and the resin pattern or the ceramic inlay. Even when the resin pattern was prepared directly on the stainless master model, the ceramic inlay could not to be seated exactly on the master model. The discrepancy between the resin pattern and the master die (0.083 ±0.028 mm) was not significantly greater than that between the ceramic inlay and the master die (0.118±0.052 mm). However, this discrepancy was significantly decreased when the resin pattern was prepared in a stone model that had been coated with a resinous die spacer at a thickness of approximately 30 pm. However, it was still difficult to obtain a ceramic inlay which exactly fit the master model. These results suggest that greater effort should be devoted to improving the accuracy of resin pattern preparation and the milling apparatus itself.
The purpose of this study was to determine whether the application of pulsed electromagnetic fields (PEMFs) could accelerate bone formation in the midpalatal suture after rapid maxillary expansion. Nine adult male dogs were divided into three groups. Group 1 (N=1) was kept as a sham operation control. Group 2 (N=4) was treated for 2 weeks and then separated into a non-PEMF and a PEMF-stimulated subgroup. Group 3 (N=4) was also separated as group 2 was but treated for 3 weeks. The maxilla was rapidly expanded for 1 week and left for retention of 1 or 2 weeks. The experimental groups were stimulated by PEMFs for 10 hours daily. The PEMF appliance was set to produce the specific asymmetrical repetitive 200 its pulses in burst of 4.8 ms repeated at a 15 Hz rate. Tetracycline and calcein were intramuscularly injected at intervals according to the experimental schedule. Soft X-ray photographs were taken and frontal sections of undecalcified and decalcified tissues were prepared. Contact microradiographs were then taken and bone histomorphometry was applied to quantify the areas of new bone formation. After 2 or 3 weeks of PEMF stimulation, the bone formation rate and mineral apposition rate, including total new bone volume, in the experimental groups were significantly increased. The results suggested that PEMFs enhanced acceleration of bone formation rate in midpalatal suture after rapidly maxillary expansion treatment and should be considered for clinical orthodontic application in the near future.
Antibacterial activity of filler powder (designated Apacider) was examined by in vitro growth inhibition assay of Streptococcus mutans IFO 13955. Apacider powder itself showed the growth inhibition effect against S. mutans. The Apacider also exhibited an effective inhibition even when it was mixed into a resin composite. The maximum inhibition activity was obtained at the filler concentration of 10 wt %. At the concentration of 15 to 40 wt % filler, those activities were the same as that of 10 wt % filler. Five wt % of the filler also showed the effect, but its activity was weaker than that of 10%. It took about 7 days to observe the effective inhibition activity at any filler concentrations. Color of Apacider-containing composite resin did not change and it has been keeping antibacterial activity even when those materials were exposed into an artificial saliva for 7 days. Direct tensile and compressive strength of the resin containing various concentrations of Apacider decreased slightly as compared with the composite resin without Apacider. But those values were still effective for clinical use. These results indicated that the composite resin containing Apacider could be useful as an antibacterial agent in the field of clinical dentistry.