Aim; The purpose of this study was to evaluate the sealing ability of a newly introduced adhesive root canal sealer (MetaSEAL™, Parkell, USA) and other root canal filling materials. Materials and methods; Thirty-two single-rooted human mandibular premolars were used. The crowns were removed and the root lengths were standardized to 12mm. Four teeth were used as controls: two teeth were used as negative controls and the other two as positive controls. The remaining 28 teeth were randomly divided into 4 groups of 7 teeth each and filled with one of the following methods: Group A: Resilon™ (Pentron, USA)+Epiphany™ sealer (Pentron) using lateral condensation Group B: Gutta-percha point (GC)+Sealapex sealer (SybronEndo, USA) using lateral condensation Group C: Gutta-percha point+Superbond sealer (SunMedical) using single-cone technique Group D: Gutta-percha point+MetaSEAL™ using single-cone technique After the canal sealers set, a polypropylene tube that contained 0.06% methylene blue dye solution was attached to the coronal portion of each root. Two millimeters of the apical portion was immersed in distilled water within a glass bottle. The amount of dye emerging through the root into the water was measured with a spectrophotometer at 1, 4, 8, 15 and 30 days after the immersion. Data obtained were statistically analyzed using ANOVA and Tukey-Kramer at the 5% significance level. Results; There were significant differences among the groups and experimental time intervals (p<0.05; 2-way ANOVA). Statistical analysis revealed that the amount of leaked dye in the MetaSEAL™ group on the 30th day was significantly less than that in the other three groups (p<0.05). Conclusions; Under the conditions of this study, the sealing ability of MetaSEAL™ was significantly better than that of the other three different types of sealers.

View full abstract

Clinical practice and research focusing on quality of life have become increasingly important in health-care. Traditionally, in the treatment of periodontal diseases, much emphasis has been placed on patients' biomedical data, but little effort has been made to assess their quality of life. In order to provide patient-centered and comprehensive periodontal care, it is essential to understand the psycho-social behavioral aspects of each patient. The present study aimed to assess the perceived quality of life of patients with periodontitis, utilizing an instrument based on the dental hygiene model of oral health-related quality of life (OHRQL), and to discuss its significance. Thirty-one patients with clinical diagnoses of chronic periodontitis (average age: 54.1 years, 10 males and 21 females) were assessed for their perceptions of oral health by using a Japanese version of an instrument developed based on the OHRQL, before commencement of initial periodontal therapy. Opinions of dentists and dental hygienists regarding the introduction of the OHRQL assessment were also sought by a survey questionnaire. The total mean OHRQL score of the periodontal patients was statistically significantly higher than that of healthy volunteers, indicating that the patients' perceived quality of life was compromised. A comparison of mean scores for OHRQL domains revealed that domains such as "pain", "eating and chewing", and "psychological function" were especially compromised. Multiple regression analysis revealed that the OHRQL score was significantly associated with percentage of sites with probing depth&ge;4mm. As for "health perception", approximately 60% of respondents rated their oral health as "bad" when compared to others in the same age group. Through the process of OHRQL assessment, the dentists and dental hygienists felt that introduction of OHRQL is beneficial in clinical practice and education. Within the limitations of the present study, the results suggested that periodontal patients' perception of their quality of life can be objectively assessed by the OHRQL instrument. Planning and implementing interventions to address compromised domains of OHRQL may afford provision of periodontal care that focuses on the quality of life.

View full abstract

Recently, one- or two-step self-etching adhesives that reduce the number of application steps have been widely used. To evaluate the adhesive properties of these systems, bond strength tests of the tooth structure have been done. It is well known that many factors affect the results of the bond strength test. ISO/TS11405: 2003 (E) has been proposed as an international standard for testing adhesion to the tooth structure. According to this standard, the procedure of resin composites filling methods is defined, but the types of resin composites are not established. The purpose of this study was to evaluate the influence of types of resin composites on the shear bond strength of self-etching systems. The shear bond strength test, flexural strength test and scanning electron microscopic (SEM) observation were performed, and the results were as follows: 1. The types of resin composites affected the shear bond strength. 2. Adhesive failure was predominantly observed in the debonded almost enamel specimens. There was a tendency toward differences in failure mode among the specimens with dentin. 3. There was a significant difference in flexural strength and elastic modulus between Clearfil AP-X (Kuraray Medical) and Solare (GC). The resin composite that possesses good mechanical properties showed high bond strength. 4. From the SEM observation, the morphological features of debonded specimens depended on the adhesive system.

View full abstract

We recently investigated, by using real-time PCR analysis, the expression levels of mRNAs for some antigen presentation-related molecules and toll-like receptor 4 (TLR4) in different regions of the normal periodontal ligament of rat molars, and demonstrated that the levels were the highest in the furcal region. In order to further examine the early immunopathogenesis of pulp infection-induced furcal inflammation, in this study we induced furcal inflammation in rat molars by making unsealed pulp exposures for 1 day. Real-time PCR analyses of MHC class II, CD83 (predicted), CD86, TLR4, TLR2 and IFN-γ mRNAs were then performed for the furcal region of the inflamed periodontal ligament. Those from normal teeth served as controls. The results demonstrated that expression levels of all the mRNAs except for IFN-γ mRNA showed significant increases in the inflamed furcal region compared with controls. These findings suggest that maturation and/or activation of antigen-presenting cells residing in the furcal region may occur as an early event in response to pulpally-derived bacterial challenges.

View full abstract

To study the bond strength of the silica-resin interface, the treatment effect of 3-methacryloyloxypro-pyltrimethoxysilane (3-MPS) containing acetic and phosphoric acid, and ammonia water as catalysts was examined. The tensile bond strength of the resin composite and the contact angles of a monomer mixture (50% Bis-GMA, 50% TEGDMA) to the glass plates modified with 50mmol/l ethanol solution of 3-MPS added to the catalysts were measured. When the acid and base solution including 5.0vol% phosphoric acid or 5.0vol% ammonia water were added to 3-MPS ethanol solution to 10.0vol%, the tensile bond strengths were significantly higher than those of the control group (non-catalyst group), and the strength of each group after thermal stress showed no significant decrease compared with water immersion for 7 days. The contact angles of the monomer to the glass plates modified with the coupling solution including the acids and base were significantly lower than those of the control group. The 3-MPS solution including 5.0vol% phosphoric acid aqueous solution showed the highest coupling effect among the catalysts.

View full abstract

Dentists are often exposed to patients' blood or body fluid during dental treatment, and they are also at risk of needlestick injuries due to the use of needles and sharp instruments. To prevent needlestick injuries, which may cause blood-borne infection, we need to analyze the accidents at hospitals and to evaluate the effectiveness of the safety guidelines. The Infection Control Team (ICT) of Fukuoka Dental College Medical and Dental Hospital analyzed the needlestick injuries in this hospital, discussed prevention methods, and evaluated their effectiveness. The analysis was performed based on the infectious accident reports in our hospital from 2002 to 2007. A total of 80 accidents were reported in these 6 years, and we first analyzed the tendency of needlestick injuries. The biggest numbers of accidents were reported in November in a year, and the accidents often occurred on a Tuesday. Many accidents occurred from 11 to 12 in the morning. The needlestick injuries were mainly associated with injection needles, suture needles, scalar chips, and preparation bars. The accidents were mostly reported by doctors and dentists, but considerable numbers of accidents were reported by the junior college and dental school students who were undergoing on-the-job-training. The accidents often occurred when the staff were clearing and cleaning the instruments, and may have been partly because the students were also doing these jobs. To prevent needlestick injuries, we reviewed the infection control manual and are giving lectures on medical safety. From 2005, the handling of injection needles was restricted to faculty members, and the students were isolated from injection needles. As a result of these efforts, needlestick injuries decreased from 2006 to 2007. On the other hand, there is a possibility that not all accidents were reported, so we need to advise the medical staff to report needlestick injuries as soon as they occur. Since human error is inevitable, safety devices may be necessary in dental treatment.

View full abstract

Objective: We previously reported that physiological mechanical stress and periodontal bacteria induced cytokine production in human periodontal ligament (hPDL) cells and that these cytokines influenced both local inflammation of the periodontal ligament and occlusal trauma. In this study, we examined the production of cytokines in hPDL cells induced by Porphyromonas gingivalis and mechanical stress or non-physiological mechanical stress. Methods: The hPDL cells were obtained from a healthy erupted maxillary third molar. After the third to fourth passage, cells were exposed to various levels of mechanical stress (1MPa, 6MPa, 10MPa and 50MPa); mechanical stress group. A subset of the mechanically stressed cells was also stimulated with P. gingivalis (1×10⁷CFU/ml) for 24 hours; mechanical stress and P. gingivalis group. Total RNA was extracted and the cytokine mRNA expressions were determined by RT-PCR. We then analyzed the mRNA expressions of interleukin (IL) -1β, IL-6, IL-8 and tumor necrosis factor (TNF)-α. Cytokines in the culture supernatants were assessed by ELISA, and morphologic changes of hPDL cells were observed using an inverted optical microscope. This experimental procedure was approved by the Ethics Committee, Kyoto Prefectural University of Medicine. Results: IL-6, IL-8 and TNF-α mRNA were expressed in the mechanical stress group. Expressions of all inflammatory cytokines were detected in the mechanical stress and P. gingivalis group and the amounts of IL-6 and IL-8 in the mechanical stress group increased with mechanical stress. Moreover, the amounts of IL-6 and IL-8 in the mechanical stress and P. gingivalis group were higher than those in the mechanical stress group. The morphology of hPDL cells did not change after exposure to 6MPa or 10MPa, but hPDL cells were partly detached from the petri dish after exposure to 50MPa.

View full abstract

The purpose of this study was to evaluate a newly developed, higher filler content, non-fluoride-containing flowable resin composite UniFil MI Flow (GC), in terms of surface morphology and roughness after immersion in orange juice, wine and whisky. The tested products were UniFil MI Flow (MIF), Estelite Flow Quick (EFQ, Tokuyama Dental), Clearfil Majesty LV (MJLV, Kuraray Medical), UniFil LoFlo Plus (ULP, GC) and Clearfil Majesty (MJP, Kuraray Medical). Specimens were shaped into a disk form with a diameter of 10mm and thickness of 1mm (20 disks per material). All specimen surfaces were ground to 1200 grit and kept in deionized water for 24 hours at 37℃. Specimen surfaces at this stage of the experiment were regarded as standard specimen surfaces. The specimens were then immersed in orange juice, wine and whisky for 14 days, and the surface morphology was observed with a scanning electron microscope (SEM). The surface roughness profiles of each specimen were also taken using a confocal laser scanning microscope. SEM analysis of standard specimens showed a smooth surface in all of the test materials. After exposure to the drinks, the surface profile of MIF was similar to that of the standard specimen, although immersion in whisky caused a slight degree of erosion. On the other hand, ULP exhibited obvious structural defects characterized by the presence of voids suggestive of filler detachment. EQF and MJLV showed a slight degree of erosion and void formation. Significant differences of the surface roughness (Ra) were detected between MIF and ULP that were immersed in the drinks (p<0.05). It is concluded that, in comparison with ULP, MIF shows improved resistance to surface degradation after exposure to acidic and alcoholic drinks.

View full abstract

In some case of large defects, such as those with Class III or IV cavities, even when a composite resin is selected to match the tooth color, the background color sometimes shows through the resin and the restoration in the mouth appears darker than the natural teeth. The layering technique is effective to block the background color, but there have been few basic studies on it in composite resin restorations. In a preceding study, we reported the usefulness of the layering technique by developing a basic experimental system similar to those used in clinics, using the Vitapan Classical shade guide for the direct application of nano filler composite resin to experimental teeth with standardized cavities. In the present study, we objectively assessed some layering techniques using color modified nano filler high-cured composite resin: Filtek™ supreme DL universal restorative (3M ESPE) in the same color as the Vitapan Classical shade guide. Standardized cavities were prepared in the experimental teeth of the Vitapan Classical shade guide, and layerings were applied with opaque shade composite resin and body shade composite resin. Then, a colorimeter was used to measure CIE1976L*a*b*, XYZ values and then calculate ΔE*ab, contrast ratios and TP values. The results were as follows: 1. According to the ΔE*ab, when the tooth color was A2, the layering technique with OA3+A2 was effective. When the tooth color was A3, the layering technique with OA3+A3 or OA4+A3 was effective. When the tooth color was A4, no significant difference was observed between the OA4+A4 layering technique and A4 single-layer filling. 2. The TP values and contrast ratios suggested that the transparency may increase with a single-layer filling only using the body shade, allowing the penetration of the background color. 3. Compared to the nano filler composite resin used in the previous experiment, the color modified nano filler composite resin showed better compatibility. Therefore, when a layering technique is used in composite resin restorations, an esthetically favorable restoration can be achieved by selecting an opaque shade which is similar with or slightly darker than the natural tooth color and then applying a body shade in a color similar with the tooth to be restored. In addition, it was suggested that the colors may not match when the value of the tooth is low and an opaque shade of greater value is selected.

View full abstract

In the last decade, new toothbrushes that generate acoustical energy have been developed, and ultrasonic toothbrushes are now used widely. Although there have been reports on the clinical usefulness of ultrasonic toothbrushes, there has been almost no research on the influence on periodontal-pathogenic bacteria in periodontal pockets. The tested ultrasonic toothbrush (DENT.EX systema ultrasonic®, Lion Dentistry Material) is characterized by ultrasonic oscillation of 1.6MHz and extremely tapered end bristles. It was designed using the Bass method to remove plaque in periodontal pockets. The purpose of this research was to consider the influence of an ultrasonic toothbrush on bacteria on chronic periodontitis. The subjects were 14 chronic periodontal patients (5 males and 9 females, average age 48.6±12.4, age range 35 to 69) who visited the Department of Periodontics, Meikai University Hospital. As for the exanimate tooth, one or more of 56 premolars and molars were chosen for pockets of 4mm or more by Probing Pocket Depth (PPD); the ultrasonic toothbrush was used on the experiment side, and a manual brush (DENT.EX 44M® Lion Dentistry Material) was used on the control side. Subjects were instructed to perform brushing 2 to 3 times per day using the Bass method. (1) Plaque Index (P1I: Silness & Loe), (2) Bleeding on Probing (BOP), (3) Gingival Index (GI: Loe & Silness), (4) PPD and (5) the amount of Gingival Crevicular Fluids (GCF) were used as clinical parameters, and (1) the number of microorganism copies by the real-time PCR method and (2) the total number of periodontal-pathogenic bacteria (Actinobacillas actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, and Tannerella forsythia) copies were used as clinical parameters. As for BOP and GI, there was an improvement in the two groups with time. However, there was no significant difference among both groups. According to a comparison restricted to P1I (Mesiodistal) of 4w of the experiment group, improvement was shown (p<0.05). The number of periodontal-pathogenic bacteria in the gums of the experiment group showed a decreasing tendency with time. GCF decreased significantly in the experiment group of 4w (p<0.05). It is suggested that the 1.6MHz ultrasonic toothbrush affects the bacteria in periodontal pockets of chronic periodontitis patients.

View full abstract

Low concentration hydrogen peroxide (HP) bleaching agent containing titanium dioxide (TiO₂) as a photocatalyst is considered to be a new office bleaching agent that is safe and has good bleaching performance. In this study, Pyrenees®, a 3.5% HP bleaching agent containing TiO_2 photo-catalyst (Mitsubishi Gas Chemical, "PY") and Shofu HiLite™(Shofu, "HL"), a conventional 35% HP office bleaching agent, were applied to extracted human teeth or vital teeth to compare the changes in tooth color. PY and HL were used as bleaching agents. Of 69 extracted human teeth, 40 were used to measure tooth color. The micro-Vickers hardness of each of 10 teeth, bleached with PY and HL, was measured before and after bleaching. Nine teeth were divided into three groups (control, PY and HL group) for SEM examination, and the surface properties were compared at the magnification of 5,000. The wavelengths of 11 curing units (three halogen curing units, three xenon, three LED, and two multi arch irradiation units) were measured. The curing units used for measuring wavelength were also used for measuring temperature elevation during irradiation. To examine the bleaching effect of PY on vital teeth in a clinic, the maxillary anterior teeth of 15 volunteers were treated with PY and ZOOM! (Discus Dental, USA). Color changes of extracted human teeth, the highest result being ΔE*ab of 13.1, were obtained from PY with a high intensity halogen unit and irradiation from a distance of approximately 1mm. No differences were found between PY and HL in micro-Vickers hardness and SEM observations before and after bleaching. The wavelength of Hyper-Lightel (Morita) and ZOOM! generated visible light at around 400nm. The pH values were 6.13 with PY and 3.91 with HL. No temperature elevation higher than 40℃ was caused during irradiation. Color changes of the vital teeth were ΔE^*ab=4.9 at the third visit of bleaching treatment, and after 1 year the ΔE^*ab value was 4.0. PY was less invasive to tooth enamel and soft tissue and more effective than HL at the specific conditions used, i.e. wavelength irradiation of approximately 400nm. These findings suggest that PY is a safe and effective office bleaching agent.

View full abstract

In this study, supragingival irrigation with a pulsating waterjet device was performed on subgingival plaque, and then the changes in clinical parameters and bacterial flora were evaluated in comparison to tooth brushing. The test group used a waterjet device once a day. Plaque index (P1I), plaque control record (PCR), gingival index (GI), bleeding on probing (BOP), and probing depth (PD) were measured. Porphyromonas gingivalis was detected in the subgingival plaque by polymerase chain reaction. The clinical findings were superior for P1I and PCR in the group treated with tooth brushing. The test group detected only a slight amount of P. gingivalis. These findings indicate that this pulsating waterjet device may be a useful therapy for periodontal disease.

View full abstract