Effects of Tooth Coating Material and Finishing Agent on Bleached Enamel Surfaces by KTP Laser.

OBJECTIVE: The purpose of this study was to evaluate the effect of tooth coating material and finishing agent on bleached enamel surfaces after using KTP laser with 27% hydrogen peroxide. BACKGROUND DATA: There have been few reports on the effects of tooth coating materials and finishing agents after bleaching. METHODS: After 40 crowns of human extracted maxillary incisors were bleached by KTP laser, bleached enamels were finished with fluoride only or both of fluoride and nano-hydroxyapatite as a finishing agent. After application(s) of fluoride and/or finishing agent, the enamel surfaces were divided into 2 groups, which were covered with the coating material or without coating material. After application of coating materials, all specimens were kept for 2 weeks at 37°C of 100% humidity. After removing the coating material, color changing was measured and enamel surfaces were examined by scanning electron microscopy (SEM). RESULTS: SEM observation of enamel surfaces treated the fluoride gel, finishing agent and coating material showed the most flattered surface compared to other groups. By measuring the color changing, few color changing was observed on the enamel surfaces treated the fluoride gel, finishing agents and coating material. CONCLUSION: These results suggested that applications of fluoride gel, finishing agent and coating material made the enamel-surfaces flattered and kept effects of bleaching, could prevent the re-coloration. After applications of fluoride gel and finishing agent, covering the bleached-enamel surfaces with the coating material enhanced the keeping whiteness. It would give the patients satisfaction of whiteness.

In vitro guidance of dental pulp cells by Nd:YAG laser-irradiated endothelial cells.

OBJECTIVE: After endothelial cells were ablated by neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation, we investigated the response of pulp cells by examining the expression of transforming growth factor beta-1 (TGF-ß1). BACKGROUND DATA: The reaction of stimulated blood vessels is related to the initiation of dentinogenesis. After artificial injury of endothelial cells, pulp cells migrate to the site of the injured endothelial cells. MATERIALS AND METHODS: Rat aortic endothelial cells were cultured in the lower compartment of the experimental assembly, and a pulsed Nd:YAG laser was used to ablate these cells. Pulp cells were fluorescence labeled and cultured in the upper compartment. After 7-14 days of laser irradiation, total RNA was extracted from the cells in the lower chamber, and RT-PCR was performed to examine the expression of TGF-ß1 and osteocalcin mRNA. TGF-ß1 was also examined with immunohistochemistry. RESULTS: Seven days after laser irradiation, migrating pulp cells that expressed TGF-ß1 were observed in the lower compartment, and the expression of TGF-ß1 mRNA and osteocalcin mRNA was altered. Without laser irradiation, few migrating pulp cells were observed, and the expression of TGF-ß1 mRNA and osteocalcin mRNA was weak. These results suggested that TGF-ß1 mRNA expression is detected earlier in pulp cells rather than in endothelial cells following injury to endothelial cells. CONCLUSIONS: Using the Nd:YAG laser as an ablative stimulant, this study model was useful for investigating pulp-endothelial cell interactions in reparative dentinogenesis.

Adhesiveness of various glass ionomer cements in cavities treated with Carisolv.

OBJECTIVE: The purpose of this study was to investigate the adhesion of glass ionomer cements to dentin and the effect of pretreatment using Carisolv. STUDY DESIGN: Forty extracted permanent teeth with caries were used for this study. All lesions were removed using the Carisolv system and teeth were divided into eight groups. Groups 1 to 4 were filled with three types of conventional glass ionomer cements and a resin modified glass ionomer cement. Group 8 was restored with composite resin. In the remaining three groups (Groups 5 to 7), several pretreatment procedures, including EDTA and dentin primer application and a combination of these, were performed before restoring with resin modified glass ionomer cement. All restorations were thermocycled, and microleakage tests were performed on all teeth. RESULTS: There were no statistical differences among Groups 1, 2 and 3 or between Groups 4 and 8. However Groups 1 to 3 had higher microleakage levels than Groups 4 and 8. Groups 5 to 7 showed similar leakage levels as Group 4. CONCLUSION: Pretreatment with EDTA or dentin primer did not improve bonding ability. Combination of caries removal using Carisolv and a resin modified glass ionomer cement restoration without pretreatment seems to be an acceptable method for caries treatment.

Removal of organic debris with Er:YAG laser irradiation and microleakage of fissures sealants in vitro.

The current study was conducted to improve fissure sealing by pre-treatment with Er:YAG laser irradiation in order to remove organic debris. The surface morphology, surface roughness of fissure cavities, and the degree of microleakage after laser treatment were compared with those after bristle brush treatment in vitro. Sixty extracted human teeth were used in this study. The teeth were randomly divided into two groups of 30 each. Artificial fissures were prepared in all teeth into which artificial organic debris was placed. The debris in 30 teeth of one group was removed by means of Er:YAG laser system and the remaining 30 teeth were cleaned using a bristle brush with prophylaxis paste. Surface morphology and surface roughness of were analyzed in ten samples from each group by color laser three-dimensional (3D) microscopy and by scanning electron microscopic examination. The remaining samples were then filled with sealant and subjected to a microleakage test under thermocycling. Statistical analysis was performed using the Mann-Whitney U test; a value of p < 0.05 was considered significant. Morphologically, most of the debris was removed by Er:YAG laser treatment, whereas some fissures were not cleaned by bristle brush. However, microleakage test of both laser and etched brush methods showed similar results. Laser technique might facilitate good adaptation of resin sealant to enamel, because of an increase in surface roughness and favorable surface characteristics.

Histological examination of experimentally infected root canals after preparation by Er:YAG laser irradiation.

The influence of Er:YAG laser irradiation on periodontal tissues along the root surface and apical region during root canal preparation was histologically evaluated using experimentally infected root canals of rats. Eighty experimentally mesial infected root canals of mandibular first molars in rats were divided into four groups. In three groups, root canals were irradiated using an Er:YAG laser at 2 Hz with 34, 68, or 102 mJ/pulse for 30 s. Non-irradiated canals served as controls. The influence of laser irradiation on periodontal tissues along the root surface and apical area was evaluated histologically under light microscopy at 0 (immediately after), 1, 2, 4, and 8 weeks after irradiation. At all periods, no inflammation or resorption on the root surfaces caused by laser irradiation was observed in any cases in the control or 34 mJ/pulse-irradiated groups. However, mild to severe inflammation with resorption of root surfaces was observed in some cases in the 68- and 102-mJ/pulse-irradiated groups. No significant difference was apparent between control and laser-irradiated groups at the apical area for all experimental periods (p > 0.05). These results suggest that thermal influences on periodontal tissues of experimentally infected root canals during root canal preparation by Er:YAG laser irradiation are minimal if appropriate parameters are selected. Er:YAG laser irradiation is thus a potential therapy for human infected root canals.

Removal of organic debris from occlusal fissures: advantage of Carisolv system over sodium hypochlorite.

OBJECTIVE: The purpose of this in vitro study was to evaluate and compare the removal of artificial debris from pits and fissures using the Carisolv system and sodium hypochlorite. STUDY DESIGN: Forty artificial fissures prepared on extracted human teeth were filled with artificial organic debris. Debris was removed using either Carisolv or 10% sodium hypochlorite gel. After stereoscopic observation, samples were filled with a sealant and subjected to microleakage test. RESULTS: Both Carisolv and sodium hypochlorite demonstrated adequate cleaning ability and prevention of microleakage. Although both Carisolv and 10% sodium hypochlorite are effective at removing debris from fissures, Carisolv presents greater advantages in terms of safety and antibacterial properties. CONCLUSION: Fissure cleaning using Carisolv might be an effective approach to improve the retention of fissure sealants.

Effect of glypican-1 gene on the pulp cells during the reparative dentine process.

GPC-1 (glypican-1) is a cell surface heparan sulfate proteoglycan that acts as a co-receptor for heparin-binding growth factors and members of the TGF-ß (transforming growth factor beta-1) family. The function of cell-surface proteoglycans in the reparative dentine process has been under investigation. Gpc-1 was detected with similar frequency as tgf-ß1 in the cDNA library using mRNA from the odontoblast-like cell-enriched pulp of rat incisors. The aim of this study was to test our hypothesis that gpc-1 may be related to reparative dentine formation. We examined the expression of this gene during the reparative dentine process, as well as the effect of gpc-1 on odontoblast-like cell differentiation using siRNA (small interfering RNA) to down-regulate gpc-1 expression. Immunohistological examination showed that GPC-1 was expressed in pulp cells entrapped by fibrodentine and odontoblast-like cells as well as TGF-ß1. The mRNAs for gpc-1, -3 and -4, except for gpc-2, were expressed during odontoblast-like cell differentiation in pulp cells. The relative levels of gpc-1 mRNA were increased prior to the differentiation stages and were decreased during the secretory and maturation stages of pulp cells. Down-regulation of gpc-1 expression resulted in a 3.9-fold increase in tgf-ß1 expression in pulp cells and a 0.3-fold decrease in dspp (dentine sialophosphoprotein) expression compared with control. These results suggested that gpc-1 and tgfß-1 expression are necessary for the onset of differentiation, but should be down-regulated before other molecules are implicated in the formation of reparative dentine. In conclusion, gpc-1 expression in odontoblast-like cells is associated with the early differentiation but not with the formation of reparative dentine.

Effects of mineral trioxide aggregate on the differentiation of rat dental pulp cells.

The effect of mineral trioxide aggregate (MTA) on the odontoblast-like differentiation of pulp cells was evaluated using heat-shock protein 25 (hsp25) as a marker for odontoblast differentiation. The cells were cultured with tooth-colored MTA or calcium hydroxide-containing cement (Dycal). The effects of the materials on the pulp cells were observed using a confocal laser scanning microscope. The cells were labelled immunocytochemically using polyclonal antibodies against hsp25 and actin. The mRNA expression of hsp25 and dspp in the pulp cells at 2 days were examined by quantitative reverse transcription-polymerase chain reaction (RT-PCR). Most of the cells cultured with MTA showed an intense immunolabelling for hsp25 and the mRNA expressions of hsp25 and dspp at 2 days were higher than those cultured with Dycal. These findings indicate that MTA is an effective pulp capping material and is able to induce the differentiation of odontoblast-like cells and the formation of reparative tertiary dentin with minimum apoptosis.

Basic study of the use of laser on detection of vertical root fracture.

OBJECTIVE: Many methods are used to detect vertical root fractures, but most are not adequate for identification of incomplete fractures or cracks. The purpose of this study was to evaluate the effects of three detergents on detection of vertical root fractures by DIAGNOdent with methylene blue (MB) solution. METHODS: Vertical incomplete fractures were artificially created on the roots of extracted human teeth, the DIAGNOdent values (D values) recorded in the presence or absence of MB solution, and the effects of detergents on D values examined. The effects of 20% ethanol on enhancing detergent action were also investigated. Statistical analysis was performed using the Mann-Whitney U-test; a value of p<0.01 was considered significant. RESULTS: D values increased significantly when MB solution was used with 0.1% or 1.0% polyoxyethylene (10) octylphenyl ether compared to MB solution only. CONCLUSION: These findings suggest that 0.1% or 1.0% polyoxyethylene (10) octylphenyl ether could be used as an enhancer for detection of vertical root fractures by DIAGNOdent using MB solution.

Analysis of surface roughness and microleakage of fissure sealants following organic debris removal with Carisolv.

OBJECTIVE: The objective of the present study was to improve fissure sealing by pre-treatment with Carisolv in order to remove organic debris. The surface morphology and roughness of fissure cavities and the degree of microleakage after Carisolv application were compared with those after bristle brush treatment in vitro. METHODS: Fifty extracted human teeth were used in this study. The teeth were randomly divided into two groups of 25 each. Artificial fissures were prepared in all teeth into which artificial organic debris was placed. The debris in 25 teeth of one group was removed using Carisolv applied for 30s and excavation was performed with a dental explorer until the gel was clear. The remaining 25 teeth were then cleaned using bristle brush with prophylaxis paste. Surface roughness was analyzed in five samples from each group by color laser three-dimensional (3D) microscopy and by scanning electron microscopic examination. The remaining samples were filled with sealant and subjected to a microleakage test under thermocycling. Statistical analysis was performed using the Mann-Whitney U-test; a value of p<0.05 was considered significant. RESULTS: Morphologically, most of the debris in the fissures was removed by Carisolv treatment, whereas some fissures were not cleaned by bristle brush. Carisolv-treatment with acid-etching resulted in removal of debris-like smear layer leaving enamel prisms open, and 3D laser microscopy demonstrated that the roughness values increased after acid-etching. However, microleakage test of both Carisolv and brush methods showed similar results. CONCLUSIONS: Carisolv-treated surfaces especially when subjected to acid-etching might facilitate good adaptation of sealant to enamel, because of an increase in surface roughness and favorable surface characteristics.

Artificial plaque removal with Carisolv system: a clinical approach.

In the present study, removal of artifcial plaque in pits and fissures with the Carisolv system was compared with that of conventional bristle brush methoda in vitro. The results indicate that in the dental clinic, complete plaque removal with the Carisolv is possible, and in addition to acid etching, treated cavity was almost free of debris which might increase sealant retention.

Basic study of morphological changes and surface roughness of cavities prepared by TEA CO2 laser irradiation.

OBJECTIVE: The purpose of this study was to investigate the morphological change of dental hard tissue and surface roughness of cavities prepared by transversely excited, atmospheric pressure (TEA) CO2 laser irradiation. BACKGROUND DATA: It has been reported that dental hard tissues and bone can be removed by a long-pulse of TEA CO2 laser irradiation with minimal thermal damage. However, there are few reports on the surface roughness of lased teeth. METHODS: The TEA CO2 laser was irradiated on the enamel and dentin surfaces of extracted human teeth under the following conditions: wavelength, 10.6 microm; output, 95 mJ/pulse; pulse repetition rate, 1 Hz; irradiation time, 7.5 microsec/shot; and energy density, 7.9 J/cm2. Morphological studies were performed by histological and scanning electron microscopic (SEM) examination. Surface roughness of prepared cavities was measured by three-dimensional laser microscopy. RESULTS: Irradiated dentin produced a deeper defect (705 +/- 11 microm) than the enamel (501 +/- 10 microm). Histological appearance showed a basophilic line at the margin of lased dentin. SEM observation noted that the surfaces of the enamel cavity seem to be melted, and dentinal tubules were sealed. The surface roughness of the enamel cavity wall and dentin floor were 175 +/- 5 microm and 170 +/- 6 microm, respectively. CONCLUSION: These findings suggest that it is possible to remove carious dental hard tissue or cavity preparation with the TEA CO2 laser irradiation. Lased dental hard tissue can facilitate caries prevention, and surface roughness of the cavities might improve the bond strength of restorative dental materials.

Functional basis for the overlap in ligand interactions and substrate specificities of matrix metalloproteinases-9 and -2.

The MMPs (matrix metalloproteinases) MMP-9 and -2 each possess a unique CBD (collagen-binding domain) containing three fibronectin type II-like modules. The present experiments investigated whether the contributions to ligand interactions and enzymatic activities by the CBD of MMP-9 (CBD-9) corresponded to those of CBD in MMP-2 (CBD-2). The interactions of recombinant CBD-9 with a series of collagen types and extracellular matrix molecules were characterized by protein-protein binding assays. CBD-9 bound native and denatured type I, II, III, IV and V collagen, as well as Matrigel and laminin, with apparent K(d) values of (0.1-6.8)x10(-7) M, which were similar to the K(d) values for CBD-2 [(0.2-3.7)x10(-7) M]. However, CBD-9 bound neither native nor denatured type VI collagen. We also generated two modified MMPs, MMP-9(E402A) and MMP-2(E404A), by site-specific mutations in the active sites to obtain enzymes with intact ligand binding, but abrogated catalytic properties. In subsequent competitive binding assays, CBD-9 and MMP-9(E402A) inhibited the interactions of MMP-2(E404A) and, conversely, CBD-2 and MMP-2(E404A) competed with MMP-9(E402A) binding to native and denatured type I collagens, pointing to shared binding sites. Importantly, the capacity of CBD-9 to disrupt the MMP-9 and MMP-2 binding of collagen translated to inhibition of the gelatinolytic activity of the enzymes. Collectively, these results emphasize the essential contribution of CBD-9 to MMP-9 substrate binding and gelatinolysis, and demonstrate that the CBDs of MMP-9 and MMP-2 bind the same or closely positioned sites on type I collagen.

Caries removal with Carisolv system: criteria evaluation and microleakage test.

In the present study, cavities prepared by Carisolv were verified as being caries-free by two methods; by conventional visual and tactile criteria, and by DIAGNOdent. The results indicate that in the dental clinic, the efficiency of complete carious dentin removal with Carisolv is no longer difficult when a proper clinical guide is used. Furthermore, treatment of dentin surfaces with Carisolv is capable of decreasing marginal microleakage after composite resin restorations.

Dentinal composition and Knoop hardness measurements of cavity floor following carious dentin removal with Carisolv.

This study evaluated the dentinal composition and Knoop hardness measurements of the cavity floor following the removal of carious dentin by the Carisolv chemo-mechanical caries removal system, in vitro. The carious dentin of 25 extracted human teeth was removed by using Carisolv for one minute with instruments and excavation that was performed until the gel was clear. Caries removal with a sharp explorer was verified according to the color and hardness of the lesion, then, by means of DIAGNOdent. Atomic analysis of treated cavities was performed by energy dispersive x-ray spectroscopy (SEM-EDX) and the Knoop hardness number (KHN) of the cavity floor was determined. Surface characteristics were observed by the scanning electron microscope (SEM). Adjacent sound dentin was used as a control reference. No significant differences were found between the quantities of calcium content (Ca weight %), phosphorus content (P weight %) and the Ca/P weight ratio of Carisolv cavities with that of the adjacent, sound dentin (p<0.01). KHN of the Carisolv cavity floor was almost similar to that of the adjacent sound dentin. SEM analysis revealed an extremely rough or irregular surface, and there remained a minimal debris-like smear layer; most of the dentinal tubules were opened. The results indicated that Carisolv does not produce any adverse side effects on dentinal compositions of the treated cavities. The possibility of remaining residual softened dentin was also minimal in this study.

A comparative study on compositional changes and Knoop hardness measurement of the cavity floor prepared by Er:YAG laser irradiation and mechanical bur cavity.

OBJECTIVE: This present study was performed to compare the compositional changes of human dentin and, Knoop hardness of the cavity floor prepared by Er:YAG laser irradiation with that of the conventional bur cavity. BACKGROUND DATA: There are still no reports on the compositional changes of dental hard tissues and microhardness of the cavity floor prepared by Er:YAG laser irradiation. MATERIALS AND METHODS: Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and Knoop hardness testing. Statistical analyses were performed using the Mann-Whitney U test; a value of p < 0.01 was considered significant. Cross sections of the remaining five laser and five bur cavities were examined by light microscopy and then by SEM. RESULTS: The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavities, but no significant differences were found between the Ca/P ratio and Knoop hardness number of laser and bur cavities. The results of SEM observation revealed that the lased cavity surface was irregular, and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed. CONCLUSION: Er:YAG laser device produces minimal thermal induced changes of dental hard tissue compositions; Ca/P ratio and Knoop hardness of the lased cavity floor was almost similar to the bur cavities.

Compositional and structural changes of human dentin following caries removal by Er,Cr:YSGG laser irradiation in primary teeth.

In this in vitro study, the compositional and structural changes of human dentin, and knoop harness of cavity floor following the removal of dental caries by Er,Cr:YSGG laser irradiation in primary teeth was compared with that of the conventional bur cavity. The results confirmed that laser irradiation revealed minimal thermal damage to the surrounding tissues, minimal thermal induced changes of dental hard tissue compositions, and favorable surface characteristic.

Microleakage of composite resin restoration in cavities prepared by Er,Cr:YSGG laser irradiation and etched bur cavities in primary teeth.

In this in vitro study, the surface alterations of enamel and dentin in cavities prepared by Er,Cr:YSGG laser irradiation was investigated by scanning electron microscopy and compared to the microleakage degree after composite resin restoration with etched bur cavities in human primary teeth. The results confirmed that laser cavity surface facilitated a good adhesion with the restorative materials; the acid etch step can be easily avoided with the laser treatment.

Acquired acid resistance of enamel and dentin by CO2 laser irradiation with sodium fluoride solution.

OBJECTIVE: The purpose of this study was to investigate the caries-preventive effect of CO2 laser irradiation with or without sodium fluoride (NaF) solution at human dental enamel and dentin in vitro. BACKGROUND DATA: The capability of caries prevention with CO2 laser irradiation has been reported in many previous studies, but few studies have been performed with regard to the combined effect of fluoride and laser. MATERIALS AND METHODS: Forty extracted human incisor teeth were used for the enamel study, and 40 molar teeth were used for the dentin study. Samples were then divided into four categories: control (no treatment); CO2 laser irradiation only; NaF treatment only; and NaF treatment followed by CO2 laser irradiation. Each sample was immersed in 2 mL of lactic acid (0.1 M, pH 4.8) solution for 24 h at 37 degrees C in 100% humidity. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometry. The samples were also observed by stereoscopy and scanning electron microscopy (SEM). RESULTS: The lowest mean Ca2+ ppm was recorded at the enamel or dentin samples treated with NaF and laser. Statistical analysis of the data was considered significant (p < 0.01). SEM observation showed that surfaces were changed to melted, smooth, and mirror-like appearances when CO2 laser irradiation was applied with NaF solution. CONCLUSION: It can be concluded that CO2 laser irradiation with NaF solution has more caries-preventive effect than CO2 laser irradiation only at the enamel and dentin surfaces.