The replacement of missing teeth, especially in the anterior region, is an essential part of dental practice. Fiber-reinforced composite resin bridges are a conservative alternative to conventional fixed dental prostheses or implants. It is a minimally invasive, reversible technique that can be completed in a single visit. The two cases presented herein exemplify the treatment of root-fractured anterior teeth with a natural pontic immediately after extraction.

This is a case report of chronic maxillary sinusitis caused by root canal overfilling of Calcipex II (Techno-Dent). A 60 year-old male complained of dull pain in the right maxillary molar area after complicated endodontic treatment using Calcipex II paste and was finally diagnosed with a chronic maxillary sinusitis through a clinical and radiological observation. In the biopsy examination, the periapical granuloma contained a lot of dark and translucent Calcipex II granules which were not stained with hematoxylin and eosin. They were usually engulfed by macrophages but rarely resorbed, resulting in scattering and migrating into antral mucosa. Most of the Calcipex II granules were also accumulated in the cytoplasms of secretory columnar epithelial cells, and small amount of Calcipex II granules were gradually secreted into sinus lumen by exocytosis. However, chronic granulomatous inflammation occurred without the additional recruitment of polymorphonuclear leukocytes (PMNs) and lymphocytes, and many macrophages which engulfed the Calcipex II granules were finally destroyed in the processes of cellular apoptosis. It is presumed that Calcipex II granules are likely to have a causative role to induce the granulomatous foreign body inflammation in the periapical region, and subsequently to exacerbate the chronic maxillary sinusitis in this study.

The purpose of this study was to compare radiopacity and radiographic discriminability of various FRC-Posts.

Six FRC-Posts were investigated ; 1) FRC Postec Plus (Ivoclar Vivadent AG, Schaan, Liechtenstein), 2) Snowlight (Carbotech, Lewis center, OH, USA), 3) Dentin Post (Komet Brasseler, Lamgo, Germany), 4) Rely-X Fiber Post (3M ESPE, St.paul, MN, USA), 5) D.T.-Light Post (BISCO, Schaumburg, IL,USA), 6) Luxapost (DMG, Hamburg, Germany)

The radiographs of each post with a reference 1 mm / 2 mm aluminum step-wedge was taken using digital sensor. The optical density were calculated by gray value of 10 × 10 pixel and compared in mm Al equivalent at five points.

Six maxillary incisors of similar radiopacity were used. Radiographs of posts in Mx. incisors of lingual side of dry mandible were taken.

We showed radiographs and asked the questionnaire to 3 radiologists, 3 endodontists, 3 general practitioners. The questionnaire was comprised of choices of the highest, lowest radiopaque individual post and the choices of best discriminable post at apical, coronal area.

The following results were obtained.

Each post system showed various radiopacity.

Although each post showed various radiopacity, the difference of radiopacity did not affect on discriminability.

The purpose of this study was to compare the different canal irrigation methods to prevent the formation of precipitate between sodium hypochlorite (NaOCl) and chlorhexidine (CHX).

Extracted 50 human single-rooted teeth were used. The root canals were instrumented using NiTi rotary file (Profile .04/#40) with 2.5% NaOCl and 17% EDTA as irrigants. Teeth were randomly divided into four experimental groups and one control group as follows; Control group: 2.5% NaOCl only, Group 1: 2.5% NaOCl + 2% CHX, Group 2: 2.5% NaOCl + paper points + 2% CHX, Group 3: 2.5% NaOCl + preparation with one large sized-file + 2% CHX, Group 4: 2.5% NaOCl +95% alcohol+ 2% CHX.

The teeth were split in bucco-lingual aspect and the specimens were observed using Field Emission Scanning Electron Microscope. The percentages of remaining debris and patent dentinal tubules were determined. Statistical analysis was performed with one-way analysis of variance (ANOVA). Energy Dispersive x-ray Spectroscopy was used for analyzing the occluded materials in dentinal tubule for elementary analysis.

There were no significant differences in percentage of remaining debris and patent tubules between all experimental groups at all levels (p > .05).

In elementary analysis, the most occluded materials in dentinal tubule were dentin debris. NaOCl/CHX precipitate was detected in one tooth specimen of Group 1.

In conclusion, there were no significant precipitate on root canal, but suspected material was detected on Group 1. The irrigation system used in this study could be prevent the precipitate formation.

Mouthguards were used to protect boxers from lip lacerations and other soft tissue injuries in the late 19th century. Now they are used various parts of dental treatment, which are sports protective aid, bleaching tray, orthodontic retainer, implant insertion guide tray, splint and so on.

Repeated dislodgement of Class V restoration due to habitual clenching stress should be restored with stress control. Mouthguard can be used as stress relief device.

This case describes methods that can relieve occlusal force to teeth by using mouthguard.

Satisfactory results can be obtained by using mouthguard for retention of repeated dislodgement Class V restorations.

If patients suffered from repeated restorations of Class V due to clenching, mouthguard can be used additional device to relieve the occlusal stress in conservative dentistry.

The purposes of this study were to compare the efficacy of irrigation systems by removing a calcium hydroxide (Ca(OH)₂) paste from the apical third of the root canal and the effect of the patency file. Sixty single rooted human teeth were used in this study. The canals were instrumented by a crown-down manner with .04 taper ProFile to ISO #35. Ca(OH)2 and distilled water were mixed and placed inside the root canals. The teeth were divided into 6 groups according to the root canal irrigation system and the use of patency file as follows: group 1 - conventional method; group 2 - EndoActivator^®; group 3 - EndoVac^®; group 4 - conventional method, patency; group 4 - EndoActivator^®, patency; group 6 - EndoVac^®, patency. All teeth were irrigated with sodium hypochlorite. After the root canal irrigation, the teeth were split in bucco-lingual aspect. Percentage of the root canal surface coverage with residual Ca(OH)2 until 3 mm from working length was analyzed using Image Pro Plus ver. 4.0. Statistical analysis was performed using the One-way ANOVA, t-test and Scheffe's post-hoc test. Conventional groups had significantly more Ca(OH)2 debris than EndoActivator^®, EndoVac^® groups. There was no significant difference between EndoActivator^® and EndoVac^® groups. Groups with patency file showed more effective in removing Ca(OH)₂ paste than no patency groups, but, it was no significant difference. This study showed that EndoActivator^® and EndoVac^® systems were more effective in removing Ca(OH)2 paste from the apical third of the root canal than conventional method.

The aim of this study was to evaluate endodontic irrigation methods with EndoVac^® and EndoActivator^® in the elimination of Enterococcus faecalis from the root canals. Extracted 70 human single-rooted teeth were used. The canals were instrumented by a crown-down technique with .04 taper ProFile to ISO size 40. After the teeth were autoclaved, the canals were inoculated with E. faecalis and incubated for 48 h. The teeth were randomly divided into three experimental groups of 20 teeth each according to canal irrigation methods and two control groups as follows: group 1 - EndoVac^®; group 2 - EndoActivator^®; group 3 - Conventional needle irrigation method. After canal irrigation using 2.5% NaOCl, first samples (S1) were taken using sterile paper point. And the canals were filled with sterile brain heart infusion (BHI) broth and incubated for 24 h, then second samples (S2) were taken. The samples were cultured on BHI agar plate to determine the numbers of colony forming units (CFU). In first sampling (S1), only one canal of conventional method among the all experimental groups was positive cultured. In second sampling (S2), EndoVac^® group showed the least positive culture numbers of E. faecalis. There was statistically significant difference between the EndoVac^® and conventional needle irrigation methods in the mean value of Log CFU. According to the results of this study, EndoVac^® showed better efficacy than conventional needle irrigation method in the elimination of E. faecalis from the root canal.

There are a number of situations where the oral mucosa can be sucked or pressed to produce relatively banal but clinical distinctive changes. The labial and buccal mucosa and tongue may develop protuberances in areas where a tooth is missing or extra space is present. The mucosa is pressed and sucked into these spaces, thus leading to the development of a fibrous hyperplasia.

This case report describes the management of fibrous hyperplasia in oral mucosa.

Fibrous hyperplasia can be formed by habitual pressure or suction in oral mucosa. Treatment of fibrous hyperplasia consists of simple excision and, if feasible, elimination of the cause. And habit control is a important factor for preventing recurrence.

The purpose of this study was to evaluate the physical properties of different self-adhesive resin cements and their shear bond strength on dentin and lithium disilicate ceramic and compare these result with that of conventional resin cement. For this study, four self-adhesive resin cements (Rely-X Unicem, Embrace Wetbond, Mexcem, BisCem), one conventional resin cement (Rely-X ARC) and one restorative resin composite (Z-350) were used. In order to evaluate the physical properties, compressive strength, diametral tensile strength and flexural strength were measured. To evaluate the shear bond strength on dentin, each cement was adhered to buccal dentinal surface of extracted human lower molars. Dentin bonding agent was applied after acid etching for groups of Rely-X ARC and Z-350. In order to evaluate the shear bond strength on ceramic, lithium disilicate glass ceramic (IPS Empress 2) disks were prepared. Only Rely-X ARC and Z-350 groups were pretreated with hydrofluoric acid and silane. And then each resin cement was adhered to ceramic surface in 2 mm diameter. Physical properties and shear bond strengths were measured using a universal testing machine.

Results were as follows

1. BisCem showed the lowest compressive strength, diametral tensile strength and flexural strength. (P<0.05)

2. Self-adhesive resin cements showed significantly lower shear bond strength on the dentin and lithium disilicate ceramic than Rely-X ARC and Z-350 (P<0.05)

In conclusion, self-adhesive resin cements represent the lower physical properties and shear bond strength than a conventional resin cement.

The purpose of this study was to compare the tensile bond strength of several self-adhesive resin cements bonded to dentin surfaces with different wet conditions.

Three self-adhesive resin cements; Rely-X Unicem (3M ESPE, St. Paul, MN, USA), Embrace Wetbond (Pulpdent, Oakland, MA, USA), Maxcem (Kerr, Orange, CA, USA) were used. Extracted sixty human molars were used. Each self-adhesive resin cement was adhered to the dentin specimens (two rectangular sticks from each molar) in different wet conditions.

Tensile bond strength were measured using universal testing machine (EZ Test, Shimadzu corporation, Kyoto, Japan) at a crosshead speed of 1.0mm/min. After the testing, bonding failures of specimens were observed by Operative microscope (OPMI pro, Carl Zeiss, Oberkochen, Germany). T-test was used to evaluate the effect of dentin surface wetness. One-way ANOVA test was used to evaluate the tensile bond strength of self-adhesive resin cements in the same condition. Scheffe's test was used for statistical analyzing at the 95% level of confidence.

The result showed that wetness of dentin surface didn't affect tensile bond strength of self-adhesive resin cements and Maxcem showed the lowest tensile bond strength.

The aim of this study was to evaluate the influence of light energy on the tooth whitening effect of bleaching agent in vitro. Extracted human mandibular molars were sectioned to 2 fragments(mesial, distal) and lingual portions of crown were used in this study. All specimens were stained using a red wine for 24 hours and immersed in artificial saliva. Specimens divided into four groups, group 1 and 2 light-activated by LumaCool (LED, LumaLite, Inc., Spring Valley, USA), group 3 and 4 light-activated by FlipoWhite2 (Plasma acr lamp, Lokki, Australia). Group 1 and 3 bleached with LumaWhite(LumaLite, Inc., Spring Valley, USA), group 2 and 4 bleached with Polaoffice(SDI, Victoria, Australia). Bleaching treatment performed during 10 minutes every 24 hours and repeated 6 times. During bleaching treatment , distal fragments was light-activated(L) but mesial fragments was not(NL). Shade assessment employed before and after bleaching treatment using spectrophotometer. The results of the change in shade was compared and analysed between NL and L by using paired-sample T test with 95% level of confidence.

There were no significant differences between NL and L with a few exceptions. In group 2, a^* value more change in L, in group 3, b^* value more change in L, in group 4, a^* value less change in L. After bleaching, L^* value and ΔE increased in all groups and the value of a^* and b^* decreased in all groups.

Within the limitation of this test conditions, the results of this study indicate that the light energy has no obvious improving impact on the tooth whitening effect of a bleaching agent.

When we use the total-etch dentin adhesive system for composite resin restorations, gel or liquid acid etchant such as 37% phosphoric acid is commonly used. Thirty seven percentage phosphoric acid is very powerful erosive agent, and can cause severe harmful effects when it contacts with an oral mucosa and facial skin.

This case describes iatrogenic chemical burn on facial skin caused by phosphoric acid which was happened during composite resin restorative procedure.

Chemical burn by acid etchant can be evoked by careless handling of remnant and syringe. In order to prevent these iatrogenic injuries, we should check the complete removal of the etching agent both in intra and extra-oral environments after etching and rinsing procedure and it is necessary to use of the rubber dam or isolation instruments.

If accidental burn were occurred, immediate wash with copious water. And bring the patient to the dermatologist as soon as possible.

The purpose of this study was to compare the apical microleakage in root canal filled with Resilon by methacrylate-based root canal sealer or 2 different self-adhesive resin cements. Seventy single-rooted extracted human teeth were sectioned at the CEJ perpendicular to the long axis of the roots with diamond disk. Canal preparation was performed with crown-down technique using Profile NiTi rotary instruments and GG drill. Each canal was prepared to ISO size 40, .04 taper and 1 mm short from the apex. The prepared roots were randomly divided into 4 experimental groups of 15 roots each and 5 roots each for positive and negative control group. The root canals were filled by lateral condensation as follows. Group 1: Guttapercha with AH-26, Group 2: Resilon with RealSeal primer & sealer, Group 3: Resilon with Rely-X Unicem, Group 4: Resilon with BisCem. After stored in 37℃, 100% humidity chamber for 7 days, the roots were coated with 2 layers of nail varnish except apical 3 mm. The roots were then immersed in 1% methylene blue dye for 7 days. Apical microleakage was measured by a maximum length of linear dye penetration after roots were separated longitudinally. One way ANOVA and Scheffe's post-hoc test were performed for statistical analysis. Group 1 showed the least apical leakage and there was no statistical significance between Group 2, 3, 4. According to the results, the self adhesive resin cement is possible to use as sealer instead of primer & sealant when root canal filled by Resilon.

The purpose of this study was to compare the apical microleakage in root canal filled with Resilon by several self-etching primers and methacrylate-based root canal sealer. Seventy single-rooted human teeth were used in this study. The canals were instrumented by a crown-down manner with Gate-Glidden drills and .04 Taper Profile to ISO #40. The teeth were randomly divided into four experimental groups of 15 teeth each according to root canal filling material and self-etching primers and two control groups (positive and negative) of 5 teeth each as follows: group 1 - gutta percha and AH26® sealer; group 2 - Resilon, RealSeal™ primer and RealSeal™ sealer; group 3 - Resilon, Clearfil SE Bond® primer and RealSeal™ sealer group 4 - Resilon, AdheSe® primer and RealSeal™ sealer. Apical leakage was measured by a maximum length of linear dye penetration of roots sectioned longitudinally by diamond disk. Statistical analysis was performed using the One-way ANOVA followed by Scheffe's test. There were no statistical differences in the mean apical dye penetration among the groups 2, 3 and 4 of self-etching primers. And group 1, 2 and 3 had also no statistical difference in apical dye penetration. But, there was statistical difference between group 1 and 4 (p < 0.05). The group 1 showed the least dye penetration. According to the results of this study, Resilon with self-etching primer was not sealed root canal better than gutta precha with AH26® at sealing root canals. And there was no significant difference in apical leakage among the three self-etching primers.

The purpose of this study was to assess the antibacterial effect of sodium dichloroisocyanurate (NaDCC), sodium hypochlorite (NaOCl), and chlorhexidine (CHX) on Enterococcus faecalis and to evaluate and to compare the time-dependant antimicrobial effect of NaDCC with NaOCl and CHX in the root canal in vitro before and after instrumentation.

Extracted human single teeth were prepared by serial instrumentation technique. The samples were autoclaved and contaminated for 3 days with E. faecalis monocultures. The teeth were then divided into 4 groups. Each group was irrigated and inserted with 2% NaOCl, 2% NaDCC, 2% CHX and sterilized saline. After 6, 12, 24, 72h, and 1 week incubation, sterilized paper point was inserted into the root canal. Paper points containing root canal contents were then placed on the agar plate. And then each root canal was prepared with #4 and #5 GG (Gates-Glidden) drill. The debris were collected in the sterilized microtube and the plates were incubated at 37℃ in an increased CO₂ atmosphere. After 24h incubation the growth of bacteria around the paper points were measured.

NaOCl and NaDCC solution shows similar antimicrobial effect for E. faecalis at 6, 12, 24, 72h and 1 week. In control group, irrigated with sterilized saline, no antimicrobial effect was observed.

The results are in agreement with other investigators, who have shown the bactericidal property and possibility of NaDCC as a root canal irrigation solution. Thus it seems that NaDCC solutions can be clinically applied into the root canal within 1 week after dilution.

The purpose of this study was to compare the effect of exponential curing method with conventional curing and soft start curing method on polymerization shrinkage of composite resins.

Three brands of composite resins (Synergy Duo Shade, Z250, Filtek Supreme) and three brands of light curing units (Spectrum 800, Elipar Highlight, Elipar Trilight) were used. 40 seconds curing time was given. The shrinkage was measured using linometer for 90 seconds.

The effect of time on polymerization shrinkage was analysed by one-way ANOVA and the effect of curing modes and materials on polymerization shrinkage at the time of 90s were analysed by two-way ANOVA. The shrinkage ratios at the time of 20s to 90s were taken and analysed the same way. The results were as follows:

1. All the groups except Supreme shrank almost within 20s. Supreme cured by soft start and exponential curing had no further shrinkage after 30s (p < 0.05).

2. Statistical analysis revealed that polymerization shrinkage varied among materials (p = 0.000) and curing modes (p = 0.003). There was no significant interaction between material and curing mode.

3. The groups cured by exponential curing showed the statistically lower polymerization shrinkage at 90s than the groups cured by conventional curing and soft start curing (p < 0.05).

4. The initial shrinkage ratios of soft start and exponential curing were statistically lower than conventional curing (p < 0.05).

From this study, the use of low initial light intensities may reduce the polymerization rate and, as a result, reduce the stress of polymerization shrinkage.

The objective of this in situ study was to evaluate the effects of whitening strip (Claren, LG Household & Health Care Ltd, 2.6% hydrogen peroxide) and gel (Opalescence, Ultradent, 10% carbamide peroxide) on microhardness of enamel in comparison with untreated control. Extracted twenty human upper incisors were disinfected, cleaned, and labial side of each incisor sectioned into 3 fragments by 2 × 2 mm size. After sectioning, labial sides of fragments were flattened and fixed to orthodontic bracket using flowable composite resin. Specimens prepared from each tooth were attached to the labial side of upper incisors of twenty volunteers one by one and treated by three different methods: (1) untreated control (2) treated with whitening strip for 14 days (3) treated with whitening gel for 14 days.

Microhardness (Microhardness tester, Zwick) of each specimen was measured at the baseline of pre-treatment, immediate after bleaching treatment, 14 days after bleaching treatment and Knoop Hardness Number was determined. Microhardness changes of experimental groups were compared.

The results show that tooth whitening strip and gel used in this study does not effect the micro-hardness of enamel during bleaching procedure.

During root canal preparation procedures, the potential for instrument separation is always present. Files, a lentulo, a Gates-Glidden (GG) bur or any manufactured obstruction can be left behind in the canal. Nickel-titanium (NiTi) rotary files are in common usage in these days. Despite their undeniable advantages, there is a potential risk of separation within the canals. It is very rapid, unpredictable, and creates a great deal of stress for the practitioner.

When an endodontic instrument separates, the best option is to remove it. Ultrasonic instruments and microscopes have improved the success rate for removing separated instruments. But it is difficult and not always possible. Therefore prevention is the key.

In this case report, several management methods of separated file in the canal are presented.

This study investigated the effect of anticurvature filing method on preparation of the curved root canal using ProFile.

Thirty six resin blocks were divided equally into three groups by instrumentation motions: anticurvature filing motion, circumferential filing motion and straight up-and-down motion. Each resin block was sectioned at 8 mm level from the apex and at the greatest curvature of the canal and reassembled in metal mold by a modified Bramante technique. All groups were instrumented with the ProFile system. At each levels, image of sectioned surface were taken using CCD camera under a stereomicroscope at ×40 magnification and stored. Distances of transportation at the inner and outer area of curvature and the centering ratio were determined and compared by statistical analysis, along with the assessment of the increase of root canal cross-sectional area.

The results were as follows;

1. In all groups, there was no statistical difference in the mean increase of root canal cross-sectional area, the centering ratio, and the mean distances of transportation at the inner area of curvature at each level.

2. At 8 mm level from the apex, the mean distances of transportation at the outer area of curvature decreases in following order anticurvature filing motion, circumferential filing motion, straight up-and-down motion but, no significant difference at the greatest curvature of the canal among three groups.

Effect of anticurvature filing motion using ProFile does not seem to be different from other instrumentation motions at the inner area of curvature in curved root canal.

Intracanal separation of the rotary files is a serious concern in modern endodontic practice. The objective of this study was to compare the life span and fracture patterns of three NiTi rotary files in molar teeth.

Mesiobuccal roots of upper molar (n = 150) and mesial roots of lower molar (n = 150) were divided into three groups and each group was prepared with Profile, ProTaper, and K3 respectively. Every file was used until separation and/or deterioration of the cutting blade was happened, and then the number of canals to separation and/or unwinding were recorded. Radiographs and Scanning electon microscope (SEM) photographs were taken to evaluate the patterns of separation.

The results were as follows :

1. There were no significant differences in numbers of canals to separation and/or unwinding among the groups.

2. Comparing between flaring files, K3 showed significant lower numbers of canals to separation and/or unwinding (p < 0.05), and there was no significant difference between shaping files

3. Separations of instruments were occurred at the midpoint of curvatures within the canals.

4. In SEM observations, ductile fractures were seen in most of cases, characterized by shallow dimples.

Additional researches is needed to provide a new guideline that informs the appropriate number of times to use NiTi files.

It is common for clinicians to encounter endodontically treated teeth that contain posts within their roots. If endodontic treatment is failed, these posts must be removed to facilitate successful nonsurgical retreatment.

There have been many techniques such as ultrasonic instrument, Ruddle post removal system, Eggler post remover and Masserann kit developed to facilitate removal of posts from the root canal space. But these methods may be disadvantageous because long length of time required for post removal and fracture of post or teeth. In now days new post removal technique using ATD automatic bridge remover was introduced. Advantages of this method are simple and short time consuming compare to others.

This article served as a successful case report of post removal using ATD automatic bridge remover.

Straight access cavity design allows the operator to locate all canals, helps in proper cleaning and shaping, ultimately facilitates the obturation of the canal system. However, change in the fracture strength according to the access cavity designs was not clearly demonstrated yet. The purpose of this study was to determine the influence of different access cavity designs on the fracture strength in endodontically treated mandibular anterior teeth.

Recently extracted mandibular anterior teeth that have no caries, cervical abrasion, and fracture were divided into three groups (Group 1 : conventional lingual access cavity, Group 2 : straight access cavity, Group 3 : extended straight access cavity) according to the cavity designs. After conventional endodontic treatment, cavities were filled with resin core material. Compressive loads parallel to the long axis of the teeth were applied at a crosshead speed of 2mm/min until the fracture occurred. The fracture strength analyzed with ANOVA and the Scheffe test at the 95% confidence level.

The results of this study were as follows :

1. The mean fracture strength decrease in following sequence Group 1 (558.90 ± 77.40 N), Group 2 (494.07 ± 123.98 N) and Group 3 (267.33 ± 27.02 N).

Considering advantage of direct access to apical third and results of this study, straight access cavity is recommended for access cavity form of the mandibular anterior teeth.

This study evaluated the microshear bond strength of composte resin to teeth bleached with commercial whitening strips and compared with those bleached with home bleaching gel. Twelve extracted human central incisors were cut into pieces and central four segments were chosen from each tooth and embedded in acrylic resin. Four blocks with 12 tooth segments embedded in acrylic resin were acquired and numbered from group one to group four. Group 1 was bleached with Crest Whitestrips, group 2 with Claren, group 3 with Opalescence tooth whitening gel (10% carbamide peroxide). Group 4 was used as control. The bleaching procedure was conducted for 14 days according to the manufacturer's instructions; the bleaching strips twice a day for 30 min and the bleaching gel once a day for 2 hr. After bleaching, composite resin (Filtek Supreme) was bonded to the enamel surfaces with a self-etching adhesive (Adper Prompt L-Pop) using Tygon tube. Microshear bond strength was tested with a universal testing machine (EZ-test). The data were statistically analysed by one-way ANOVA. The study resulted in no statistical differences in microshear bond strength between the tooth segments bleached with 2 different whitening strips and bleaching gel. It can be concluded that the effect of bleaching with either commercial whitening strips or bleaching gel on enamel is minimal in bonding with self-etching adhesive to composite resin.

Ormocer has organic-inorganic compound polymers. One of advantages of ormocer is reduced polymerization shrinkage. The purpose of this study was to compare the amount of contraction shrinkage of composite resins and ormocers. Additionally, the time of each material when there is no further change of contraction shrinkage was analysed.

Four brands of composite resins (P-60, Surefil, Z-250 and Denfil) and two brands of ormocers (Definite and Admira) were used. 20 seconds, 40 seconds and 60 seconds of curing times were given. Contraction shrinkage of them were measured using a linometer for 80 seconds.

The effect of material and curing time to contraction shrinkage at the time of 80 seconds was analysed by two-way ANOVA. The effect of time to contraction shrinkage was analysed by one-way ANOVA, and the time when there was no further change of the contraction shrinkage was analysed. The results are as follows :

P-60, Definite, Z-250 and Denfil had no further change of contraction shrinkage from the time of 20 seconds, and Surefil and Admira had no further change of contraction shrinkage from the time of 10 seconds.

The purpose of this study is to evaluate the polymerization ability of three different light sources by microhardness test. Stainless steel molds of 1, 2, 3, 4 and 5 mm in thickness of 7 mm in diameter were prepared. The hybrid composite Z100 was packed into the hole of the mold and curing light was activated for designated time. Three different light sources, conventional halogen, light emitting diode, and plasma arc, were used for curing of composite. Two different curing times applied; one is to follow the manufacturer's recommendation and the other is to extend the curing time of LED and plasma arc for balancing the light energy with halogen. Immediately after curing, the Vickers hardness was measured at the bottom of specimen.

The results were as follows.

The composite cured with LED showed equal to higher microhardnesss than halogen.

In conclusion, this study suggested that plasma arc needs properly extended curing time.

There are increasing usage of Nickel-Titanium rotary files in modern clinical endodontic treatment because it is effective and faster than hand filing due to reduced step.

This study was conducted to evaluate the effect of canal preparations using 3 different rotary Nickel-Titanium files that has different cross sectional shape and taper on the maintenance of canal curvature. Simulated resin block were instrumented with Profile(Dentsply, USA), GT rotary files(Dentsply, USA), Hero 642(Micro-Mega, France), and Pro-Taper(Dentsply, USA).

The image of Pre-instrumentation and Post-instrumentation were acquired using digital camera and overspreaded in the computer. Then the total differences of canal diameter, deviation at the outer portion of curvature, deviation at the inner portion of curvature, movement of center of the canal and the centering ratio at the pre-determined level from the apex were measured.

Results were statistically analyzed by means of ANOVA, followed by Scheffe test at a significance level of 0.05.

The results were as follows;

1. Deviation at the outer portion of curvature, deviation at the inner portion of curvature were showed largest in Pro-Taper, so also did in the total differences of canal diameter(p<0.05).

2. All the groups showed movements of center. Profile combined with GT rotary files and Hero 642 has no difference but Pro-Taper showed the most deviation(p<0.05).

3. At the 1, 2, 3mm level from the apex movements of center directed toward the outer portion of curvature, but in 4, 5 mm level directed toward the inner portion of curvature(p<0.05).

As a results of this study, it could be concluded that combined use of other Nickel-Titanium rotary files is strongly recommended when use Pro-Taper file because it could be remove too much canal structure and also made more deviation of canal curvature than others.

The aim of this study is to compare the adaptability of thermoplasticized injectable gutta-percha technique to the canal walls in ribbon-shaped canals.

Thirty resin models simulated ribbon-shape canals were instrumented to #40 using .06 taper Profile systems. Three groups of each 10 resin models were obturated by the lateral condensation technique(LC) and the two thermoplasticized injectable gutta-percha technique; Ultrafil Endoset+Obtura II(EO) and Ultrafil Firmset(UF), respectively.

After resin model were kept at room temperature for 4 days, they were resected horizontally with microtome at 1, 2, 3, 4 and 5mm levels from apex. At each levels, image of resected surface were taken using CCD camera under a stereomicroscope at ×40 magnification and stored. Ratio of the area of gutta-percha was obtained by calculating area of gutta-percha cone to the total area of canal using digitized image-analyzing program. The data were collected then analyzed statistically using One-way ANOVA.

The results were as follows.

1. At 1mm levels, there was no statistically significant difference in the mean ratio of gutta-percha among the groups.

2. At 2mm level, EO showed the highest mean ratio of gutta-percha (p<0.05) and there was no significant difference between LC and UF.

3. At 3, 4, 5mm levels, EO and UF had significantly greater mean ratio of gutta-percha than LC(p<0.05) and there was no significant difference between EO and UF.

In conclusion, the thermoplasticized injectable gutta-percha techniques demonstrated relatively favorable adaptability to canal walls than lateral condensation technique in ribbon-shaped canals except for 1mm level.

The purpose of this study is to evaluate the two warm gutta-percha filling techniques by measuring the weight changes of resin blocks before and after canal filling in ribbon shaped canal. Simulated ribbon shaped root canals in 30 transparent resin blocks were instrumented to #40 using .06 taper Profile. 15 resin blocks were obturated with gutta-percha using cold lateral condensation. Warm lateral condensation using the Endotec II was then accomplished on the same 15 blocks. Another 15 resin blocks were obturated using the System B. All canals were obturated without sealer. The resin blocks were weighed after canal preparation and after each subsequent obturation, and then weight changes of the resin blocks were calculated.

The results were as follows.

1. Warm lateral condensation using Endotec II and continuous wave of condensation using System B produced a denser obturation of gutta-percha compared with conventional cold lateral condensation (p<0.01).

2. There was no significant difference between warm lateral condensation and continuous wave condensation.

In conclusion, the warm gutta-percha condensation techniques like warm lateral condensation and continuous wave condensation can be expected to bring favorable canal obturation results in ribbon shaped canals.