THE EFFECT OF THE SUPERSATURATED SOLUTIONS CONTAINING HIGH CONCENTRATIONS OF FLUORIDE ON SEEDED CRYSTAL GROWTH

In biological systems, the mineral that forms hard tissue is of an apatitic nature, and hydroxyapatite($Ca_5OH(PO_4)_3$: HA) is generally considered as the prototype for such a mineral. Thus, the precipitation of HA, having biological implications, has been the subject of several investigations. Crystal growth studies using HA seeds in supersaturated solutions have enhanced our understanding of the process and mechanism involved in seeded crystal growth. From these studies, it has become apparent that the precipitation rate of HA onto the seed crystals depends on the various conditions, especially on the additives. The relation between the supersaturated solution containing fluoride and the process of HA crystal growth enhances the understanding of mechanism of HA crystal growth. Until recently, the studies have been on the crystal growth of enamel minerals and synthetic HA seeds in the supersaturated solution containing 1~2 ppm fluoride. The purpose of the present investigation is to study the effect that fluoride of high concentration has on the crystal growth kinetics of HA. In order to produce the composition found in the secretory enamel fluid, experimental solutions of 1mM Ca, 3mM P, and 100mM Tris as background electrolyte were used. Then this experimental solutions were added to 0, 2, 4, 6, 8, 10 ppm fluoride. The effect of fluoride at high concentrations on the precipitation was examined in a bench-top crystal growth model adopting a miniaturized reaction column. Chemical analysis was employed for characterization of working solutions before and after the experimentation. Remarkable findings were : 1) the amount of crystal growth was gradually accelerated as the fluoride concentration increased until 6 ppm, but decreased in 8 and 10 ppm fluoride; 2) the amount of fluoride ion consumed in crystal formation was constant despite the increase in fluoride concentration.ope

THE EFFECT OF PERIODONTAL REGENERATION AND ANTI-RESTORATION OF DEXAMETHASONE AND OP-1 FOLLOWING DELAYED REPLANTATION IN RAT MODEL

The purpose of this study was to observe the effect of dexamethasone and osteogenic protein-1(BMP-7) on bone, cementum and periodontal tissue regeneration. A total of 60 Sprague-Dawley white female mice were selected and beta-APN was used for five days to extract the maxillary first molar a traumatically. After the extraction of the teeth, the mesiobuccal root canal was filled with Caviton$^{\circledR}$. The teeth were etched with citric acid for 1 min and coated with one of four different experimental solutions : DEX(500nM/ml), DEX(1000nM/ml), OP-1(100㎍/ml) and OP-1(500㎍/ml) for three minutes depending on the group. All teeth were then replanted under microscope. All replantation procedures were done within 30 minutes. Teeth that were replanted after 30 minutes of bench dry only was used as positive control. All animals were sacrificed at 3 weeks following replantation and histologic observtion was done. The results were as follows ; 1. Active root resorption rate was decreased by the order of OP-1(500㎍/ml), DEX(1000nM/ml), OP-1(100㎍/ml), and DEX(500nM/ml). There was statistically less root resorption in OP-1 (500㎍/ml) and DEX(1000nM/ml) group(P<0.05). 2. The group with higher concentration of dexamethasone(1000nM/ml) had statistically more bone union compared to positive control group(P<0.05),but there were no significant differences among four experimental groups. 3. OP-1(500㎍/ml) and DEX(1000nM/ml) groups showed less degree of inflammation compared to the OP-1(100㎍/ml). DEX(500nM/ml), and positive control group (P<0.05). In conclusion, the group with higher concentration of OP-1 had the best results on root resorption, bone ankylosis and anti-inflammatory effects compared to the other experimental groups, but a long-term study is also necessary to evaluate the exact pharmacological effects of the drugs in the future.ope

COMPARISON OF SHAPING ABILITY OF NICKEL-TITANIUM ROTARY FILES WITH DIFFERENT TAPER IN SIMULATED RESIN CANALS

The aim of this study was to compare shaping ability of nickel-titanium rotary files with different taper in simulated resin canals. The instruments used in this study were GT with .04 taper ProFile with ISO-sized tip, .04 taper ProFile with ISO-sized tip alone, and .02 taper Naviflex file and all canals were prepared by crown-down technique. A total of 30 composite images were made from pre- and post-canal scanned images using Scanjet 4C scanner and Corel photopaint 8.0 and then, prevalence of canal aberrations was measured. The amount of coronal substance the instruments removed was also calculated two-dimensionally on digitized images with the Brain C software to compare the relative enlarging efficiency. Finally, the prepared internal canal form was evaluated three-dimensionally with impression technique. The results were as follows; 1. The incidence of zipping in Naviflex group was significantly high compared to the other two groups(P<.05). 2. The amount of coronal substance the GT combined group removed was significantly larger than the other two groups(P<.05). 3. The GT combined group produced canals with good taper and flow. Under the conditionas of this study, the combined use of larger tapered nickel-titanium rotary files prepared simulated canals safely, efficiently and with good three-dimensional form.ope

THE INHIBITORY EFFECT OF TAURINE AND ALENDRONATE ON THE OSTEOCLAST DIFFERENTIATION MEDIATED BY SONICATED EXTRACTS OF PORPHYROMONAS GINGIVALIS IN VITRO.

The objective of this study was to investigate the inhibitory effect of taurine and alendronate on the osteoclast differentiation. Osteoblasts and bone marrow cells from 1-2 day old mouse were co-cultured in 10% fetal bovine serum - minimal essential media (FBS-MEM). Osteoclast differentiation was induced by adding the sonicated extracts of Porphyromonas gingivalis (P.gingivalis). Osteoclasts were identified using tartrate resistant acid phosphotase staining (TRAP). Alendronate of 10^{-7}, 10^{-6}, 10^{-5}M and taurine of 500, 1000, 1500㎍/ml were added respectively. The cytotoxic effects of alendronate and taurine were examined using MTT(3-(4,5-dimethylthiazol -2-yl-2,5-diphenyltetrazo- lium bromide) method. After culturing with the sonicated extracts of P.gingivalis, the amounts of IL-6 in the culture supernatant were measured and compared using the ELISA method. The results were as follows : 1. Osteoclasts were differentiated at the concentration of 0.01~0.1㎍/ml sonicated extracts of P.gingivalis. (P<0.05). 2. Alendronate inhibited osteoclasts differentiation at the concentration of 10-5 M when the concentration of sonicated extracts of P.gingivalis was 0.01㎍/ml. 3. Taurine inhibited osteoclasts differentiation at the concentration of 1500㎍/ml when the concentration of sonicated extracts of P.gingivalis 0.01㎍/ml. 4. In cytotoxic test (MTT test), no cytotoxic effect was evident in all concentrations of alendronate and taurine. 5. Taurine (10-5M) and alendronate(1500㎍/ml) did not change the amounts of IL-6 induced by sonicated extracts of P.gingivalis significantly.ope

A COMPARISON OF THE APICAL SEAL PRODUCED BY EASY FILLING SYSTEM AND QUICK OBTURATION SYSTEM

The aim of this study was to compare the apical sealing ability of a new thermoplasticized gutta-percha filling technique, the Easy Filling and the Quick Obturation system with lateral condensation technique and Thermafil system to evaluate their clinical acceptabilities. Fifty-two extracted single-rooted teeth were instrumented to #35 using the .04 taper ProFile system. Four groups of 12 teeth were obturated by lateral condensation technique. Thermafil system and two new thermoplasticized gutta-percha techniques, the Easy Filling system and Quick Obturation system (Meta Dental co. Ltd. Korea), respectively. Four teeth served as controls. After the teeth were immersed in 2% methylene blue dye for 48 hours, they were resected horizontally at 1mm to 5mm level from the anatomical apex using a low-speed microtome. Each section was examined under a stereomicroscope at ×40 ×40 magnification and photographed. After each image was scanned, the leakage area was measured at each level using Brain 3 (Nosdia Tech., Korea) software. Leakage ratio was calculated for each group and was analyzed statistically to come up with the following results: 1. At 1mm level, the Quick Obturation system had the largest amount of apical leakage and it was statistically significant when compared with the lateral condensation group and the Thermafil group (p 0.05), and from 4mm level, no apical dye penetration was observed in all the groups. In conclusion, the apical seal produced by Easy Filling system and the Quick Obturation system was comparable to lateral condensation technique and Thermafil system except for the 1mm level. More improvement of the apical seal can be expected as the operator becomes skillful with the new techniques.ope

Minimizing the extra-oral time in autogeneous tooth transplantation: use of computer-aided rapid prototyping (CARP) as a duplicate model tooth

OBJECTIVES: The maintenance of the healthy periodontal ligament cells of the root surface of donor tooth and intimate surface contact between the donor tooth and the recipient bone are the key factors for successful tooth transplantation. In order to achieve these purposes, a duplicated donor tooth model can be utilized to reduce the extra-oral time using the computer-aided rapid prototyping (CARP) technique. MATERIALS AND METHODS: Briefly, a three-dimensional digital imaging and communication in medicine (DICOM) image with the real dimensions of the donor tooth was obtained from a computed tomography (CT), and a life-sized resin tooth model was fabricated. Dimensional errors between real tooth, 3D CT image model and CARP model were calculated. And extra-oral time was recorded during the autotransplantation of the teeth. RESULTS: The average extra-oral time was 7 min 25 sec with the range of immediate to 25 min in cases which extra-oral root canal treatments were not performed while it was 9 min 15 sec when extra-oral root canal treatments were performed. The average radiographic distance between the root surface and the alveolar bone was 1.17 mm and 1.35 mm at mesial cervix and apex; they were 0.98 mm and 1.26 mm at the distal cervix and apex. When the dimensional errors between real tooth, 3D CT image model and CARP model were measured in cadavers, the average of absolute error was 0.291 mm between real teeth and CARP model. CONCLUSIONS: These data indicate that CARP may be of value in minimizing the extra-oral time and the gap between the donor tooth and the recipient alveolar bone in tooth transplantation.ope

A study of ionic dissociation on various calcium hydroxide pastes using molecular sieving model

The purpose of this study was two-fold. First was to evaluate whether the molecular sieving model was appropriate for ionic dissociation experiment. Second was to compare the dissociation of calcium and hydroxyl ions from five types of calcium hydroxide pastes (Pure calcium hydroxide paste, DT temporary dressing®, Metapaste®, Chidopex®, Metapex®) in three vehicles (aqueous, viscous and oily) and the antibacterial effect. Each calcium hydroxide pastes was placed into 0.65ml tube with cap and then 15% polyacrylamide gel was placed onto calcium hydroxide pastes. After the gel was hardened, the tubes were filled with tridistilled water (pH 7.14) and closed with cap. The tubes were stored in 37℃, 100% incubator. The pH reading and the concentration of calcium ions were taken at 1, 4, 7, 10, and 14 days. The brain heart infusion agar plates with S. mutans and A. actinomycetemcomitans were used for antibacterial activity test. Middle of agar plate was filled with the calcium hydroxide pastes. The plates were incubated at 37℃ and observations were made to detect the zones of inhibition. These data were evaluated statistically by use of the analysis of variance and duncan test. The results were as follows. 1. In fresh mixing state, the pH of five types of calcium hydroxide pastes were measured between 12.5 and 12.8. 2. The pH was increased in all five types of calcium hydroxide pastes compared with control group. In 14 days, Pure calcium hydroxide paste (11.45) and DT temporary dressing® (11.33) showed highest pH, followed by Metapaste® (9.49), Chidopex® (8.37) and Metapex® (7.59). 3. Calcium was higher in all five types of calcium hydroxide pastes compared with control group. In 14 days, Pure calcium hydroxide paste (137.29 mg%) and DT temporary dressing® (124.6 mg%) showed highest value, followed by Metapaste® (116.74 mg%), Chidopex® (111.84 mg%) and Metapex® (60.22 mg%). 4. The zones of bacterial inhibition were seen around all five types of calcium hydroxide pastes. Chidopex® and Metapex® groups which include iodoform were observed significantly larger zone of inhibition in A. actinomycetemcomitans compared with the other calcium hydroxide groups (p<0.05). However, Metapex® showed the least antibacterial effect on S. mutans compared with other groups (p<0.05). The molecular sieving model was found to be acceptable in dissociation experiment of hydroxyl and calcium ions when compared with the previous tooth model study. But this model was not appropriate for the antibacterial test.ope

Comparison of linear polymerization shrinkage and microhardness between QTH-cured & LED-cured composites

This study evaluated the effectiveness of second generation light emitting diode (2ndLED) units in composite curing. In order to compare their effectiveness with that of conventional quartz tungsten halogen light curing units (QTH) and first generation LEDs (1stLED), the amount of linear polymerization shrinkage, polymerization speed and microhardness were measured. Linear polymerization shrinkage was measured every 0.5-0.55 seconds for 60 seconds when composite specimens (Z250, 3M ESPE Dental Products, St Paul, MN, USA) were light cured with five different light sources: XL 3000 (QTH, 3M ESPE Dental Products), Elipar FreeLight 2 (2ndLED, 3M ESPE Dental Products), Ultra-Lume LED2 (2ndLED, Ultradent Products, South Jordan, UT, USA), Elipar FreeLight (1stLED, 3M ESPE Dental Products) and experimental product X (1stLED, Biomedisys, Seoul, Korea). The amount of linear polymerization shrinkage in 60 seconds and the speed of polymerization shrinkage in the first 15 seconds were measured for the different lighting units. The amount of polymerization was compared with one-way ANOVA using Tukey at the 95% confidence level. In order to compare the speed of polymerization, the peak time (PT) showing the highest speed of polymerization and maximum speed of polymerization (Smax) were determined from the data and compared using one-way ANOVA with Tukey at the 95% confidence level for each material. For microhardness measurements, the microhardness of 2-mm composites, Z250, which had been light cured by XL 3000 (G1), FreeLight 2 (G2), Ultra-Lume LED2 (G3), FreeLight (G4) or experimental product X (G5) were compared on the upper and lower surface. The microhardness of each surface was compared between groups using two-way ANOVA with Tukey test at 95% levels of confidence. The amount of polymerization shrinkage at 60 seconds was G1, G2, G3> G4, G5 (p G3 >G4, G5 (p G3> G4, G5 (p<0.05). There was no difference in microhardness between the upper and lower surface in G1 and G2; whereas, microhardness of the lower surface was lower in G3, G4 and G5. It was concluded that 2ndLEDs and the conventional QTH unit cu red composites moreeffectively than 1stLEDs.ope

In vitro evaluation of the consistency of two electronic apex locators

The purpose of this study was to evaluate the consistency of two electronic apex locators in vitro model. Materials consisted of fifty two extracted premolars and two electronic apex locators; Root ZX (J. Morita, Osaka, Japan) and E-Magic Finder Deluxe (S-Denti. Cheonan, Korea). After access preparation, the teeth were embedded in a saline-mixed alginate model. Canal lengths of each tooth were measured at "0.5" and "Apex" mark of the apex locators, respectively so that each tooth had two measurements from 0.5 and Apex points. The file was fixed at final measurement using a glass ionomer cement. The apical 4 mm from the apex was exposed to measure the distance from the file tip to the major apical foramen of each tooth. Average distances and standard deviations were used to evaluate the consistency. Results showed that all measurements of both Root ZX and E-Magic Finder located the major foramen the range of ${\pm}0.5\;mm$ level. Both apex locators showed better consistency at Apex mark than at 0.5 mark. The average distance of file tip-major foramen was - 0.18 mm at 0.5 mark and - 0.07 mm at Apex mark in Root ZX, - 0.25 mm at 0.5 mark and - 0.02 mm at Apex mark in E-Magic Finder. Standard deviation was 0.21 at 0.5 mark and 0.12 at Apex mark in Root ZX, 0.12 at 0.5 mark and 0.09 at Apex mark in E-Magic Finderope

Partial pulp necrosis caused by excessive orthodontic force

As the dental pulp is encased with a rigid, noncompliant shell, changes in pulpal blood flow or vascular tissue pressure can have serious implication for the health of pulp. Numerous studies have demonstrated that orthodontic force application may influence both blood flow and cellular metabolism, leading degenerative and/or inflammatory responses in the dental pulp. The aim of this case report is to present a case about tooth with chronic periapical abscess which showed normal vital responses. Excessive orthodontic force is thought to be the prime cause of partial pulp necrosis. Owing to remaining vital tissue, wrong dianosis can be made, and tooth falsely diagnosed as vital may be left untreated, causing the necrotic tissue to destroy the supporting tissuses. Clinician should be able to utilize various diagnostic tools for the precise diagnosis, and be aware of the endodontic-orthodontic inter-relationshipope