The effect of 4,4'-bis(N,N-diethylamino) benzophenone on the degree of conversion in liquid photopolymer for dental 3D printing

PURPOSE: The purpose of this preliminary study was to investigate the effects of adding 4,4'-bis(N,N-diethylamino) benzophenone (DEABP) as a co-initiator to a binary photoinitiating system (camphorquinone-amine) to analyze on the degree of conversion (DC) of a light-cured resin for dental 3D printing. MATERIALS AND METHODS: Cylindrical specimens (N=60, n=30 per group, o5 mm x 1 mm) were fabricated using bisphenol A glycerolate dimethacrylate (BisGMA) both with and without DEABP. The freshly mixed resins were exposed to light in a custom-made closed chamber with nine light-emitting diode lamps (wavelength: 405 nm; power: 840 mW/cm2) for polymerization at each incidence of light-irradiation at 10, 30, 60, 180, and 300 seconds, while five specimens at a time were evaluated at each given irradiation point. Fourier-transform infrared (FTIR) spectroscopy was used to measure the DC values of the resins. Two-way analysis of variance and the Duncan post hoc test were used to analyze statistically significant differences between the groups and given times (alpha=.05). RESULTS: In the DEABP-containing resin, the DC values were significantly higher at all points in time (P<.001), and also the initial polymerization velocity was faster than in the DEABP-free resin. CONCLUSION: The addition of DEABP significantly enhanced the DC values and, thus, could potentially become an efficient photoinitiator when combined with a camphorquinone-amine system and may be utilized as a more advanced photopolymerization system for dental 3D printing.

Histochemical Muscle Fiber Types of Autopsied Human Gastrocnemius, Soleus, Peroneus longus and Tibialis anterior Muscles

This study was designed for the evaluation of the mean proportions and range of individual difference of muscle fiber types in human Gastrocneminus, Soleus, Peroneus longus and Tibialis anterior muscles, respectively. Flash-frozen muscle sections obtained from 15 cadavers were stained for H&E, trichrome, PAS, regular & reversed myosin ATPase, succinic dehydrogenase (SDH), acid phosphatase (Ac-Pase) and alkaline phosphatase (Alk-Pase). The results obtained were as follows. 1) Differentiation of muscle fiber types was not evident in H&E and trichrome stained specimen. Three types of muscle fibers were, however, evident in PAS-stained sections according to the degree of positivity in observed skeletal muscles. 2) Two fiber types (Types I and II) were only differentiated and the predominant muscle fiber type was type I by regular myosin ATPase reaction in Gastrocnemius, Soleus, Peroneus longus and Tibialis anterior muscles. 3) Three muscle fiber types (Type I, IIa and IIb) were, however, differentiated and the predominant muscle fiber type was type IIa, contrary to patterns of regular myosin ATPase in skeletal muscles except for Soleus muscle by reversed myosin ATPase stains. Only two muscle fiber types (Type I and II) and predominant type I fibers were shown in Soleus muscle. 4) SDH stains showed three types of muscle fiber except Soleus muscle. The mean proportions(%) of type 1 fibers were 48.0% in Gastrocnemius, 62.3% in Soleus, 40.8% in Peroneus longus, and 39.8% in Tibialis anterior muscles, respectively. 5) The mean proportions (%) of muscle fiber types in human skeletal muscles were markedly different, according to individuals and various enzyme histochemical stains. 6) The size of muscle fibers was relatevely small in type I fibers compared with type IIb. 7) Evaluation for the combination patterns of various enzyme histochemical activities showed that the common muscle fiber types (Type I, IIa and IIb) were markedly reduced in the mean proportions and unusual rare muscle fibers predominant. This predominance of unusual muscle fiber types and marked discrepancy in muscle fiber types between regular and reversed myosin ATPase seemed to be ascribed to decreased muscle enzyme activities following postmortem period.

A Study on the Myelography with Water Soluble Medium, Metrizamide (Amipaque) / 대한정형외과학회잡지

A total 48 cases of myelography using Metrizamide were performed between August 1981 and July 1983 at the department of Orthopedic Surgery, Kwangju Christian Hospital. Of these cases, H.N.P was 26, tuberculous spondylitis 16, spondylolisthesis 4, and multiple sclero-sis 2 cases. The advantages of this study were as folows: 1. Complications were minimal in most of the cases except a slight headache. 2. Large amount of infusion was possible. 3. Rootlet was clearly seen. 4. Removal of dye was not necessary. 5. It gave a good contrast for the radiologic study.

The Treatment of Tuberculous Spondylitis of the Lumbosacral Junction by Transperitoneal Approach / 대한정형외과학회잡지

A total seven cases of tuberculous spondylitis of the lumbosacral junction were treated by transperitoneal anterior vertebral interbody fusion. The postoperative course was unevenful with minimal complications in all cases. There was no evidence of recurrence of infection, low back pain, or sciatica during follow-up periods of seven to sixty months. The clinical experience gained in this study leads us to conclude that the transperitoneal approach for tuberculous spondylitis of the lumbo-sacral junction is advantageous in that, the lesion is exposed under direct vision, so adequate curettage and the bone graft can be carried out accurately and easily.