The effects of three dry-field techniques on intraoral temperature and relative humidity.

BACKGROUND: The authors evaluated the effects of three dry-field techniques (rubber dam, Isolite i2 [Isolite Systems, Santa Barbara, Calif.] and Coolex [APT, Osaka, Japan]) on intraoral temperature and relative humidity (RH), compared with the effects of a nonisolated control on intraoral temperature and RH. METHODS: The authors measured the room's temperature and RH and then placed dry-field devices in five participants' mouths and measured the intraoral temperature and RH for 20 minutes. They then removed the devices or turned off the vacuum system and measured intraoral temperature for an additional five minutes. RESULTS: The authors found no significant differences in either intraoral temperature or RH at any time during the measurement period in the isolated control group (P > .05); the intraoral temperature was more than 30°C and RH was more than 95 percent. On the other hand, the use of dry-field techniques significantly reduced both intraoral temperature and RH when the rubber dam was in place or the vacuums were turned on (P > .05). The intraoral temperature and RH gradually increased after the authors removed the rubber dam or turned off the vacuums. CONCLUSIONS: The results of this study revealed that all three dry-field techniques could reduce both temperature and RH effectively. CLINICAL IMPLICATIONS: Both Isolite i2 and Coolex could provide environments similar to the room conditions used during in vitro specimen preparation for investigating the mechanical properties of dental restorative materials.

Bactericidal effects of 2.94 µm and 1.67 µm laser.

The bactericidal effects of lasers with wavelengths of 1.67 and 2.94 µm on cariogenic Streptococcus mutans were investigated. Temperature during irradiation was also measured to determine the mechanism underlying the bactericidal effects of the lasers. An aliquot of 2 µl cell suspension of S. mutans JC-2 strain was placed on anhydrous quartz or dentin plate, covering an area of approximately 5.0 mm in diameter to a depth of approximately 0.1 mm. Cell suspension was then irradiated at a power of 0.8 W (3.1 J/cm²) at a rate of 40 pps for 30 sec. After irradiation, the plate was put into a bottle containing PBS and vigorously voltated. Solution was serially diluted and inoculated on MS agar. After incubation anaerobically for 72 hr, colony forming units on the agar were counted. The experimental group, the number of bacteria decreased significantly compared to the control group under all conditions. No significant differences were observed in effect of wavelength or plate on bactericidal activity. In conclusion, laser irradiation at a wavelength of 1.67 µm for 30 sec showed a bactericidal effect on S. mutans, suggesting that this wavelength is more useful than 2.94 µm due to greater tissue penetration.

Microtensile bond strength of indirect resin composite to resin-coated dentin: interaction between diamond bur roughness and coating material.

This aim of this study was to determine the effect of type of bur and resin-coating material on microtensile bond strength (microTBS) of indirect composite to dentin. Dentin surfaces were first ground with two types of diamond bur and resin-coated using UniFil Bond (UB) or Adper Single Bond (SB), and then bonded to a resin composite disc for indirect restoration with adhesive resin cement. After storage for 24 hr in distilled water at 37 degrees C, microTBS was measured (crosshead speed 1 mm/min). When UB was applied to dentin prepared using the regular-grit diamond bur, microTBS was significantly lower than that in dentin prepared using the superfine-grit bur. In contrast, no significant difference was found between regular-grit and superfine-grit bur with SB. However, more than half of the superfine-grit specimens failed before microTBS testing. These results indicate that selection of bur type is important in improving the bond strength of adhesive resin cement between indirect resin composite and resin-coated dentin.

Tensile bond strength of single-step self-etch adhesives to Er:YAG laser-irradiated dentin.

OBJECTIVE: The purpose of this study was to evaluate the influence of Er:YAG laser irradiation on the bond strength to dentine of three single-step adhesives (AQ Bond Plus, G-Bond, and Clearfil Tri-S Bond), and one two-step self-etch adhesive (Clearfil Megabond) as a control. BACKGROUND DATA: The vast majority of the numerous reports on resin bonding to Er:YAG-lased dentine have concluded that Er:YAG laser irradiation is less effective in terms of bond strength, because of the sub-surface damage it produces. However, its effect in combination with single-step adhesives on bonding to dentine remains to be clarified. METHODS: Eighty bovine incisors were ground with silicon carbide paper to obtain a flat dentine surface, which 40 were irradiated with an Er:YAG laser. Both lased and unlased dentine was bonded to a resin composite with each adhesive. Tensile bond strength was determined after 24 h of storage in water at 37 degrees C. Failure patterns after tensile bond testing was analyzed by scanning electron microscopy. RESULTS: The two-step self-etch adhesive (Clearfil Megabond) showed the highest bond strength to unlased dentine, but was significantly less effective on lased dentine than the three single-step adhesives. On the other hand, AQ Bond Plus produced an effective bond strength to both lased and unlased dentine, perhaps due to its low viscosity. CONCLUSION: The single-step adhesives tested in this study were as effective in combination with Er:YAG-lased dentine as the two-step self-etch adhesive.

Effect of dentin hardness on ablation rate with Er:YAG laser.

OBJECTIVE: This study used artificially demineralized bovine dentin to ascertain the effect of hardness of demineralized dentin on ablation rate with the Er:YAG laser. BACKGROUND DATA: Before restoration of carious teeth, it is necessary to ablate any infected dentin that cannot be remineralized due to softening by the invading caries. A correlation has been suggested between the ablation efficiency of the Er:YAG laser and the progression of caries in dentin. To the best of our knowledge, no studies have investigated the relationship between degree of demineralization by dentinal caries and ablation rate with the Er:YAG laser. MATERIALS AND METHODS: Bovine mandibular anterior tooth roots were used as dentin samples. Each sample was soaked in a demineralizing solution (2 M lactic acid, pH 4.0) for 3 d to obtain demineralized dentin (DD) samples. Another group of samples were prepared without demineralization as a sound dentin (SD) group for comparison. After determining the Knoop hardness number (KHN) of each sample, the dentin surface was ablated with an Er:YAG laser. Tip output and pulse rate were set at 50 mJ and 20 pulses per second (pps), respectively, and the water spray was set at 3.5 mL/min. Ablation width, depth, and volume were measured following irradiation. RESULTS: In the DD group, dentin hardness was 10.4 +/- 1.6 KHN at 100 microm from the surface. In the sound dentin group, Knoop hardness was 51.0 +/- 1.6 KHN cross-sectionally throughout. No differences were observed from the surface to a depth of 2000 microm. In the DD group, dentin ablation volume at the superficial demineralized layer was 2888 +/- 272 x 10(4) microm. In the SD group, dentin ablation volume was 1298 +/- 219 microm(3). The relationship between ablation volume and Knoop hardness was defined as Y = -40.699x + 3350, revealing a marked negative correlation. CONCLUSION: The results demonstrate that the ablation volume for demineralized dentin was greater than that for sound dentin. The results suggest that the Er:YAG laser is capable of ablating infected dentin without damaging sound dentin by adjustment of tip output and pulse rate.

Influence of finishing/polishing procedures on the surface texture of two resin composites.

This study compared surface roughness and gloss produced by different finishing/polishing procedures for two resin composites, Clearfil AP-X (AP-X) and Estelite Sigma (ES). A total of 70 composite discs (n=35 for each resin composite) were prepared and divided at random into seven finishing/polishing groups (n=5): glass-pressed control; using a super-fine-grit diamond bur (SF); using CompoMaster (CM) after SF-finishing (SF+CM); using White Point (WP) after SF-finishing (SF+WP); using CM after SF+WP-finishing (SF+WP+CM); using Stainbuster (SB) after SF-finishing (SF+SB); and using CM after SF+SB-finishing (SF+SB+CM). After the finishing/polishing procedures, average surface roughness (R(a)) and surface gloss (Gs(60( degrees ))) of all specimens were assessed with a surface profilometer and specimen gloss meter, respectively. Glass-pressed controls for both AP-X and ES composites showed the best surface finish in terms of both R(a) and Gs(60( degrees )). SF-finishing produced the roughest surface and led to almost complete loss of gloss. While additional polishing with CM reduced R(a) and increased Gs(60( degrees )), the additional finishing effect of WP or SB between SF-finishing and CM-polishing was not found for either AP-X or ES.

Influence of free-hand vs uniform irradiation on tensile bond strength in Er:YAG-lased dentin.

PURPOSE: To compare effects of free-hand and mechanically applied uniform irradiation on tensile bond strength of 4-META/MMA-TBB resin to Er:YAG laser-irradiated dentin using an X-Y moving stage. MATERIALS AND METHODS: Three different laser conditions were evaluated: 1.0 W, 100 mJ/pulse, 10 pps; 1.0 W, 50 mJ/pulse, 20 pps; 1.0 W, 33 mJ/pulse, 30 pps. Samples of bovine dentin were set on a moving stage and mechanically irradiated with an Er:YAG laser at a scanning speed of 1.0 mm/s or subjected to free-hand irradiation. The lased dentin surfaces were acid conditioned with 10% citric acid/3% ferric chloride for 15 s, rinsed, and dried. The surfaces were bonded to PMMA rods with 4-META/MMA-TBB resin, and mini-dumbbell-shaped bonded specimens were prepared. Tensile bond strength was measured and compared with the results for free-hand irradiated samples obtained under the same conditions in an earlier study. SEM observations of fractured surfaces after tensile bond testing were also performed. RESULTS: A significant difference was found in tensile bond strength among the 3 laser settings in both free-hand and mechanically uniform irradiations. A comparison of free-hand laser irradiation and mechanically performed uniform laser irradiation revealed no significant difference under either laser condition (p > 0.05). SEM observation of the fractured surfaces showed no difference between the two irradiation methods under all laser conditions. CONCLUSION: No significant difference was found in tensile bond strength between free-hand and mechanically irradiated dentin. Significant differences were found, however, with changes in laser setting in both groups.

Tensile bond strength of one-step self-etch adhesives to Er:YAG laser-irradiated and non-irradiated enamel.

This study determined the bond strengths to Er:YAG laser-irradiated and non-irradiated bovine enamel of three one-step self-etch adhesives (AQ Bond Plus (AQP), G-Bond (GB), and Clearfil Tri-S Bond (TS)) and one two-step self-etch adhesive (Clearfil Megabond (MB)). Eighty SiC paper-ground bovine enamel surfaces were used, of which half were laser-irradiated. The enamel surfaces were bonded to a resin composite with each adhesive, and tensile bond strengths were determined after 24 hours. For non-irradiated enamel groups, MB achieved greater bond strength to enamel than GB and TS (p < 0.05), but no significant difference was found between MB and AQP (p > 0.05). For laser-irradiated enamel groups, no significant differences were found among the four adhesives (p > 0.05). Additionally, for each adhesive, no significant differences were found between laser-irradiated and non-irradiated enamel. It was thus concluded that Er: YAG laser irradiation of enamel did not affect the tensile bond strength of one-step and two-step self-etch adhesives.

Influence of output energy and pulse repetition rate of the Er:YAG laser on dentin ablation.

OBJECTIVE: We sought to improve the efficiency of dentin ablation with the Er:YAG laser by investigating the effects of output energy and pulse repetition rate on ablation. BACKGROUND DATA: The Er:YAG laser is superior to other lasers in ablating dental hard tissues. However, the factors affecting the efficiency of ablation with an Er:YAG laser remain unclear. METHODS: Fifty bovine root dentin plates were irradiated with an Er:YAG laser at an output power of 1.0 W, 1.5 W, or 2.0 W under a water spray while moving the plate at 1 mm/sec. After irradiation, the depth and volume of each ablated site were measured by laser microscopy and the ablated surfaces were examined by scanning electron microscopy. RESULTS: The output power showed a strong positive correlation with the depth and volume of ablation. The output energy had much more pronounced effects on the depth and volume of ablation compared to the pulse repetition rate. The shape of the ablated site varied with the output power, and no cracking or vitrification was observed under the irradiated dentin. The most effective parameters for dentin ablation were an output power of 2.0 W, with an output energy of 80 mJ/pulse at 25 pulses per second (pps) or 100 mJ/pulse at 20 pps. CONCLUSION: These findings suggest that the output energy is the main factor affecting the efficiency of dentin ablation with an Er:YAG laser. We propose that the efficiency of dentin ablation can be improved by choosing an optimal combination of output energy and repetition rate.

Nano-hardness of adhesive interface between Er:YAG laser-irradiated dentin and 4-META/MMA-TBB resin.

OBJECTIVE: The purpose of this study was to evaluate the hardness of the adhesive interface between resin and Er:YAG laser-irradiated bovine dentin by nano-indentation. BACKGROUND DATA: It has been reported that laser output energy and pulse repetition rate affect the tensile bond strength in Er:YAG laser-irradiated dentin. MATERIALS AND METHODS: Three laser settings were evaluated at the same total energy level (approximately 1.0 W): 100 mJ/pulse-10 pps (100-10), 50 mJ/pulse-20 pps (50-20), and 33 mJ/pulse-30 pps (33-30). Laser-irradiated dentin in each group was conditioned with 10% citric acid solution containing 3% ferric chloride for 15 sec, rinsed with distilled water for 30 sec, and bonded to PMMA rods with 4-META/MMA-TBB resin. The bonded specimens were sectioned vertically, embedded in epoxy resin, and their nano-hardness measured. A non-irradiated control group was also investigated. RESULTS: The adhesive resin interface in the controls showed the lowest level of hardness, which gradually increased from the top of the hybrid layer (0 microm) through the bottom of the hybrid layer (5 microm) and into the underlying dentin ( approximately 10 microm). Significant differences in hardness were observed between the 5 microm point in the controls, the 10 microm and 15 microm points in the 100-10 group, and the 10 microm point in the 50-20 and 33-30 groups. CONCLUSION: The results suggest that laser settings affect hybrid layer thickness, even when the total energy level is constant.

An experimental pathologic study of gingivectomy using dual-wavelength laser equipment with OPO.

BACKGROUND AND OBJECTIVES: This study was conducted to evaluate how soft tissues respond to treatment by a tunable laser with an optical parametric oscillating (OPO) mechanism capable of simultaneously emitting two wavelengths. MATERIALS AND METHODS: Marginal gingiva of dogs was incised by a prototype laser oscillator. The oscillator was set at two wavelengths known to effectively incise tissue and arrest hemorrhage with minimal invasiveness. Four laser irradiation conditions were set based on different combinations of the 1.67 and 2.94 microm wavelengths. The animals were sacrificed immediately after surgery, 7 days after surgery, and 28 days after surgery for histological examination. RESULTS: When irradiation at 1.67 and 2.94 microm wavelengths was simultaneously applied, the former conferred an observable hemostatic effect and the latter incised the tissue. Wound healing was similar to that in conventional methods and no serious inflammation was observed. CONCLUSION: Simultaneous irradiation at wavelengths of 1.67 and 2.94 microm can be an effective method in soft tissue surgery.

Resin bonding to dentin irradiated by high repetition rate Er:YAG laser.

OBJECTIVE: This study evaluated the influence of laser irradiation with a high pulse repetition rate on dentin bonding. BACKGROUND DATA: Although resin bonding to erbium:yttrium-aluminium-garnet (Er:YAG) laserirradiated dentin has frequently been investigated, the effects of a high pulse repetition rate have not yet been sufficiently investigated. METHODS: Four groups treated under different laser conditions were evaluated in this study: 100 mJ/pulse-10 pulses per second [pps], 50 mJ/pulse-20 pps, 33 mJ/pulse-30 pps, and the unlased condition as a control. The total energy used to irradiate each group was adjusted to 1.0 W. After bovine dentin specimens were irradiated by an Er:YAG laser, acid conditioners (10% citric acid/3% ferric chloride) were applied to the lased surface. Thereafter, a PMMA rod was bonded to the lased dentin using 4- META/MMA-TBB resin, and mini-dumbbell-shaped specimens were prepared. These specimens were then tested under tensile mode and fractured surfaces were observed under scanning electron microscopy (SEM). RESULTS: The bond strength of the unlased control was significantly higher than those of the three lased groups. Among the three lased groups, irradiation with higher output energy and lower pulse repetition rate tended to affect the higher bond strength. Upon SEM observation of the fractured surface, the lased groups showed the mixture of failure in the hybrid layer in almost part. There was no significant difference among the three lased groups. CONCLUSION: It can be concluded from the results of this study that a higher pulse repetition rate is not effective for resin bonding to laser-irradiated dentin.

Criteria for a diagnosis of caries through the DIAGNOdent.

OBJECTIVE: The aim of this study was to investigate the correlation between the demineralization depth measured by dental computed tomography (CT) and the measured value from a non-destructive dental caries diagnosis with a laser. METHODS: Optimal cut-off points were obtained for enamel and dentin caries, from the measured levels from a dental caries diagnosis with a laser, to investigate the clinical usefulness of a diagnosis using a laser. Using human teeth, the demineralization depth was measured and the caries were diagnosed by a dental caries diagnosis with a laser. RESULTS: The optimal cut-off point was investigated for accuracy, sensibility, and specificity, which were calculated from the results. These results demonstrated the correlation between the measured values and demineralization depth in both the pit and fissure caries and smooth surface caries. The optimal cut-off points were found to be 16-21 in the fissure caries and 9-11 in the smooth surface caries.

Pathological study of pulp treated with chemicals after Er:YAG laser preparation.

OBJECTIVE: The aim of this study was to clarify pulp reaction following cavity preparation with an Er:YAG laser and subsequent treatment with topically applied chemicals to achieve a high resin bond strength. BACKGROUND DATA: The application of chemicals has been found to effectively remove or reform the denatured layer produced by Er:YAG laser irradiation and has been proposed as a new strategy for improving resin bond strength. However, very little is known about pulp reaction to chemical procedures. METHODS: Class 5 dentin cavities were prepared with an Er:YAG laser in 128 teeth in nine adult dogs. The teeth were then coated with glutaraldehyde (GA group), or phosphoric acid and sodium hypochlorite (PA group) to reform or remove the denatured layer. All the cavities were then restored with composite resin. In the control group, no chemical application was carried out prior to restoration. The animals were sacrificed immediately after, and at 7 and 90 days following treatment. The treated teeth were then extracted for histopathological examination of the pulp. RESULTS: Pathological evaluation of the pulp indicated a good condition in each group at each of the three observation time points. No bacterial growth was observed on the cavity walls or bacterial invasion into the dentinal tubules or pulp chambers in any of the groups at any of the observation periods. CONCLUSION: Our findings suggest that the application of chemicals to remove or reform denatured layers is effective in obtaining better composite resin restoration with no pulp damage.

Comparison of short-term in vitro fluoride release and recharge from four different types of pit-and-fissure sealants.

OBJECTIVE: The purpose of this in vitro study was to assess the effects of four commercial fluoride-containing pit-and-fissure sealants on caries prevention. MATERIALS AND METHODS: Four sealants containing fluoride, Fuji III, Fuji III LC (GC Co., Tokyo), Teethmate F-1 (Kuraray Medical Co., Osaka) and Helioseal F (Vivadent Co., Liechtenstein) were used to investigate fluoride release and recharge. Disk-shaped specimens prepared from each material were immersed in distilled water at a temperature of 37 degrees C. After seven days, acidulated phosphate fluoride solution (APF) was applied to each specimen, and it was then again immersed in distilled water for 14 days. We then determined how much fluoride had been released into the immersing water. Fuji III LC was used with APF solution to investigate the fluoride uptake. RESULTS: Fuji III had the highest fluoride release, and Fuji III LC had the highest fluoride recharge. Helioseal F and Teethmate F-1 had almost no fluoride recharge. Fuji III LC/APF had a higher fluoride uptake to enamel than Fuji III LC. CONCLUSIONS: These results suggest that GIC-sealants in the oral cavity can serve as a fluoride reservoir and contribute to retaining a low fluoride level in oral fluids, thereby preventing caries.

Adhesion of 4-META/MMA-TBB resin to heated dentin: effects of pre-treatments with FeCl3 and/or HEMA.

The purpose of this study was to compare the tensile bond strengths (TBSs) and failure mode of 4-META/MMA-TBB resin to 60 degrees C-heated and unheated bovine dentin, especially to investigate the influence of ferric chloride contained in citric acid pre-conditioning. In addition, the effect of HEMA priming for heated dentin was also evaluated. The TBSs to heated dentin were significantly lower than those to unheated dentin. Adhesive failures were observed in most specimens of the heated and HEMA-non primed group. HEMA application to heated dentin significantly increased the TBSs in each acid conditioning, which were also significantly higher than those of the unheated and ferric chloride-contained citric acid-conditioned group. It was clarified that heating dentin decreased the bond strength without HEMA priming even if the dentin surfaces were acid conditioned with 10-3, while HEMA priming after acid conditioning recovered the bond strength.

Fluoride release from newly developed dental adhesives.

This study compared fluoride release from three fluoride-releasing dental adhesives (Trial KBF Bond, One-up Bond F, Reactmer Bond) and one conventional dental adhesive (Clearfil SE Bond) for 70 days in vitro. From each material, five disk-shaped specimens (diameter: 9.0 mm, height: 1.5 mm) were prepared and immersed in 5 ml of 10 mM phosphate buffered solution (pH 7.0). After 1, 3, 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70 days, the samples were transferred into new solutions. The fluoride content was determined with a combined fluoride sensitive electrode attached to an ion analyzer. Data were statistically analyzed with ANOVA, followed by Scheffé's test. Reactmer Bond showed the greatest fluoride release over 70 days (280.2 +/- 10.1 micrograms/cm2) among the materials tested. The values for One-up Bond F and Trial KBF Bond were 83.4 +/- 5.3 micrograms/cm2 and 58.6 +/- 1.5 micrograms/cm2, respectively. The values were significantly different among the four groups (p < 0.0001). Clearfil SE Bond showed almost no fluoride release over 70 days.