A shear bond strength of resin cement bonded to human uncut enamel, cut enamel, and dentin in vitro / 대한치과보철학회지

STATEMENT OF PROBLEM: Adhesives in dentistry play a major role in the success of restorative treatments. In the treatment of all ceramic restoration it is needed to find the adequate bond strength between enamel and dentin. PURPOSE: The purpose of this study was to evaluate shear bond strength of resin cement bonded to extracted human uncut enamel, cut enamel, and dentin in vitro. MATERIAL AND METHODS: Ten freshly extracted anterior teeth without any previous restorative treatments were chosen. The extracted teeth were embedded in PMMA cold acrylic in the shape of a cylinder, 25 mm in diameter by 25 mm in height. The bonding system used was as follow: Uni-Etch (32 % phosphoric acid), One-Step adhesive, Duolink resin cement. The specimens were acid etched and rinsed with water. Two layers of One-Step adhesive were coated with a disposable brush on the uncut enamel. VIP curing light at 500 mV/cm2 was used to cure the adhesive. For cut enamel shear bond test, the specimen used for uncut enamel was further reduced approximately 0.3 - 0.5 mm using a laminate preparation diamond bur (0.3 mm in depth). The specimens were subsequently treated with 320-grit SiC paper followed by 600-grit SiC paper and cleaned with distilled water. The bonding procedure on the cut enamel was same as uncut enamel bonding procedure. For dentin bonding test, the specimen used for cut enamel was further reduced approximately 0.5 mm ~ 1.0 mm using a laminate preparation diamond bur (0.5 mm in depth of diamond cutting). The amount of reduction was evaluated with the silicone mold. The specimens were subsequently treated with 320-grit SiC paper followed by 600-grit silicon carbon paper and cleaned in distilled water. The bonding procedure on the dentin was same as uncut enamel bonding procedure. All samples were mounted and secured on the Ultradent shear bond test sample holder, and Ultradent restricted shear bond testing device was used with Universal Instron machine until fracture. Analysis of variance (ANOVA) test was performed comparing the result at P<0.05. Multiple comparison (Tukey) was used to compare each groups. RESULT: The result showed that the mean value in shear bond strength of resin cement bonded to uncut enamel, cut enamel and dentin were 27.04 Mpa, 30.25 Mpa and 26.39 Mpa with respect. CONCLUSION: Within the limitation of this study, the mean value of the shear bond strength of cut enamel was higher than those of uncut enamel or dentin. However there existed no statistical differences between three different human dentition substrates due to increased adhesive characteristics.

A shear bond strength of resin cements bonded to pressable porcelain with various surface treatments / 대한치과보철학회지

STATEMENT OF PROBLEM: Resin cements are widely used in adhesive dentistry specially on all ceramic restorations. It is needed to find out adequate bonding strength between different porcelain surface treatments, commercially available porcelains, and different resin cement systems. PURPOSE: The purpose of this study was to evaluate shear bond strength of resin cements bonded to porcelains in three different modalities; 5 different porcelain surface treatments, 3 different resin cement systems and 3 different commercially available pressable porcelains. MATERIAL AND METHOD: This study consisted of 3 parts. Part I examined the effect of five different surface treatments on the pressable porcelain. Fifty discs (5 mm in diameter and 3 mm in height) of Authentic porcelain were randomly divided into 5 groups (n = 10). The specimens were sanded with 320 grit SiC paper followed by 600 grit SiC paper. The specimens were treated as follow: Group 1-Sandblasting (aluminum oxide) only, Group 2 - sandblasting/silane, Group - sandblasting/acid etching/silane, Group 4 - acid etching only, Group 5 - acid etching/silane. Part II examined the shear bond strength of 3 different resin cement systems (Duolink, Variolink II, Rely X ARC) on acid etching/ silane treated Authentic pressable porcelain. Part 3 examined the shear bond strength of Duolink resin cement on 3 different pressable porcelains (Authentic, Empress I, Finesse). All cemented specimens were stored in distilled water for 2 hours and tested with Ultradent shear bond strength test jig under Universal Instron machine until fracture. An analysis of variance(ANOVA) test was used to evaluate differences in shear bond strength. RESULT: The shear bond strength test resulted in the following: (1) Acid etched porcelains recorded greater shear bond strength values to the sandblasted porcelains. (2) Silane treated porcelains recorded greater shear bond strength values to non-silane treated porcelains. (3) There was no significant difference between sandblasting/acid etching/silane teated and acid etching/silane treated porcelains. However those values were much higher than other three groups. (4) The shear bond strength with Variolink II was lower than the value of Duolink or Rely X ARC. (5) The shear bond strength of Finesse was lower than the value of Authentic or Empress I.

The study on the removal torque of the diamond like carbon coated titanium abutment screws / 대한치과보철학회지

STATEMENT OF PROBLEM: Implant screw loosening remains a problem in implant prosthodontics. Some abutment screws with treated surfaces were introduced to prevent screw loosening and to increase preload. DLC(Diamond Like Carbon) film has similar properties on hardness, wear resistance, chemical stability, biocompatibility as real diamond materials. PURPOSE: The purpose of this study was to investigate the effect of lubricant layer on abutment screw and to discriminate more effective method between soft lubricant and hard lubricant to prevent screw loosening. MATERIAL AND METHOD: In this study, 1mum thickness DLC was used as protective, lubricating layer of titanium screws and 3 times removal torque was measured on the abutment screws to investigate the difference in 10 coated and 10 non-coated abutment screws. RESULTS: The results indicated that the implants with DLC coating group were not more resistant to the applied force in screw loosening. At 32Ncm, the 3 times removal torque in DLC group were 27.7+/-2.89, 25.85+/-2.35 and 26.2+/-2.57. The removal torque in no-coated abutment screws were 27.85+/-4.23, 27.35+/-2.81 and 27.9+/-2.31, respectively. CONCLUSION: The lubricant layer used in this study was Diamond Like Carbon(DLC) and it have a properties of hard and stable layer. The DLC coating layer was hard enough to prevent distortion of screws in the repeated unscrewing procedure in clinical situation. The reduced friction coefficient in hard DLC layer was not effective to prevent screw loosening.

Fat Myringoplasty in Graft Failures / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Fat myringoplasty has been used for closure of small tympanic membrane perforations. It is fast, safe and efficient method on ambulatory basis. The performance of this study is to investigate the results of fat myringoplasty in graft failure patient after conventional tympanoplasty with temporalis muscle fascia. METHOD:Fat myringoplasty were performed on 21 ears in 18 patients. RESULTS: We found that in 21 ear success rate was 71% (15/21), but in patient basis success rate was 83% (15/18). CONCLUSIONS: We believe that due to significant operational advantage, fat myringoplasty can be suggested for reparing perforation in graft failure patient.

Congenital Epiglottic Cysts / 대한이비인후과학회지

Epiglottic cyst are relatively uncommon and account for about five percent of benign laryngeal lesions. The most common location is the epiglottis. We experienced two cases of congenital epiglottic cysts, one in an infant who showed dyspnea at birth and was incubated and the other in a 1-month-old infant with increasing stridor during the first month of life. In both cases, each cysts were completely removed under suspension laryngoscopy under general anesthesia with satisfactory results. We reviewed the clinical characteristics, diagnostic modalities, treatments, and prognosis of the epiglottic cyst.

Test / Retest Reliability of DPOAE and TEOAE / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Otoacoustic emissions (OAEs) are the objective and noninvasive methods to assess cochlear function. The purpose of the present study is to determine the short-term and long-term test/retest reliability of the distortion-product otoacoustic emissions (DPOAEs) and transient-evoked otoacoustic emissions (TEOAEs). MATHODS: The short-and long-term reliability of DPOAE and TEOAE were examined in 11 normally hearing adults. DPOAE were collected in two basic forms consisting of audiograms and input/output (I/O) functions and reliabilities for TEOAE level, reproducibility index and peak stimulus level were calculated. RESULTS: The result of this study showed that the reliability of DPOAE and TEOAE was generally excellent. CONCLUSIONS: The DPOAE and TEOAE are highly reliable and useful tests to monitor the cochlear function for the purpose of study or clinical use in combination with other standard tests of audiometric function.