Study on broken periodontal curetsOh-Jang Kwon, Jae-Kwan Lee, Beom-Seok Chang, Heung-Sik Um* Department of Periodontology, College of Dentistry, Kangnung National University ABSTRACT Purpose: The purpose of this study was to investigate the incidence of curet fracture and its contributing factors. Material and Methods: Fifty-eight periodontal curets which were broken during periodontal treatment in Kangnung National University Dental Hospital for 1 year were used as study materials. The blade thickness of new curets and broken ones was measured using a digital micrometer. Types of treatment procedures, clinical experience of operators, point of breakage, and method of removal of broken fragments were recorded for each broken curet. Results: The incidence of curet fracture in root planing (16.4 curets per 1,000 procedures) was higher than those in flap surgery (7.5) or supragingival scaling (2.7). No curet was broken during supportive periodontal treatment. The incidence of fracture did not seem to be related with clinical experience of operators. The most frequent breakage point of the curets were upper 1/3 of blades. Fifty-six of 58 broken fragments were removed by non-surgical methods. Two broken tips which could not removed non-surgically were left in the pockets, and proved to be removed spontaneously 1 week later. Conclusion: Root planing showed higher incidence of curet fracture than any other type of periodontal treatment. Most of the fractured fragments were removed by non-surgical method. Further study is needed to develop methods of removal of the fragments which can not be removed non-surgically. (J Korean Acad Periodontol 2008;38:23-30)

We experimentally investigated a simple and new technique for the fabrication of micro-ridge long-period gratings (MRLPGs) based on polarization-maintaining fibers (PMFs). The cladding region of the PMFs was etched periodically using a wet etching technique resulting in the periodic formation of micro-ridges on the surface of the PMF. The PMF-based MRLPGs has two resonant peaks because of the birefringence of the PMF. The extinction ratios of two resonant peaks of the PMF-based MRLPGs were effectively improved by increasing the applied strain because of the photoelastic effect.

Transmission characteristics of polarization-dependent refractometer based on a surface long-period grating (SLPG) inscribed in a D-shaped photonic crystal fiber (PCF) are investigated. The birefringence of SLPG produces the separation of transmission spectra for TE and TM polarization modes. We also measure the sensitivities of PCF-based SLPG to temperature and external refractive index change depending on the input polarization states. The SLPG-based sensor exhibits different temperature and ambient index sensitivities corresponding to TE and TM polarization modes. Therefore, the SLPG inscribed in D-shaped PCFs can effectively discriminate temperature and ambient index sensitivities.

A new fabrication technique for corrugated longperiod fiber gratings (CLPFGs) with periodic polymer microstructures is proposed. Transmission characteristics of CLPFGs are improved by changing the applied strain because of the control of the coupling strength. The sensitivities of strain, torsion and ambient refractive index were measured.

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