Butyrate induces reactive oxygen species production and affects cell cycle progression in human gingival fibroblasts.

BACKGROUND AND OBJECTIVE: Short-chain fatty acids, such as butyric acid and propionic acid, are metabolic by-products generated by periodontal microflora such as Porphyromonas gingivalis, and contribute to the pathogenesis of periodontitis. However, the effects of butyrate on the biological activities of gingival fibroblasts (GFs) are not well elucidated. MATERIAL AND METHODS: Human GFs were exposed to various concentrations of butyrate (0.5-16 mm) for 24 h. Viable cells that excluded trypan blue were counted. Cell cycle distribution of GFs was analyzed by propidium iodide-staining flow cytometry. Cellular reactive oxygen species (ROS) production was measured by flow cytometry using 2',7'-dichlorofluorescein (DCF). Total RNA and protein lysates were isolated and subjected to RT-PCR using specific primers or to western blotting using specific antibodies, respectively. RESULTS: Butyrate inhibited the growth of GFs, as indicated by a decrease in the number of viable cells. This event was associated with an induction of G0/G1 and G2/M cell cycle arrest by butyrate (4-16 mm) in GFs. However, no marked apoptosis of GFs was noted in this experimental condition. Butyrate (> 2 mm) inhibited the expression of cdc2, cdc25C and cyclinB1 mRNAs and reduced the levels of Cdc2, Cdc25C and cyclinB1 proteins in GFs, as determined using RT-PCR and western blotting, respectively. This toxic effect of butyrate was associated with the production of ROS. CONCLUSION: These results suggest that butyrate generated by periodontal pathogens may be involved in the pathogenesis of periodontal diseases via the induction of ROS production and the impairment of cell growth, cell cycle progression and expression of cell cycle-related genes in GFs. These events are important in the initiation and prolongation of inflammatory processes in periodontal diseases.

Effects of EDTA on the hydration mechanism of mineral trioxide aggregate.

Ethylenediaminetetraacetic acid (EDTA) is commonly used during the preparation of obstructed root canals that face a high risk of root perforation. Such perforations may be repaired with mineral trioxide aggregate (MTA). Due to EDTA's ability to chelate calcium ions, we hypothesized that EDTA may disrupt the hydration of MTA. Using scanning electron microscopy and energy-dispersive x-ray spectroscopy, we found that MTA specimens stored in an EDTA solution had no crystalline structure and a Ca/Si molar ratio considerably lower than those obtained for specimens stored in distilled water and normal saline. Poor cell adhesion in EDTA-treated MTA was also noted. X-ray diffraction indicated that the peak corresponding to portlandite, which is normally present in hydrated MTA, was not shown in the EDTA group. The microhardness of EDTA-treated specimens was also significantly reduced (p < 0.0001). These findings suggest that EDTA interferes with the hydration of MTA, resulting in decreased hardness and poor biocompatibility.

Cytokine-induced prostaglandin E2 production and cyclooxygenase-2 expression in dental pulp cells: downstream calcium signalling via activation of prostaglandin EP receptor.

AIM: To determine whether (i) proinflammatory cytokines stimulate prostaglandin E(2) (PGE(2)) production and cyclooxygenase (COX) gene expression in dental pulp cells, and (ii) pulp cells that express different prostaglandin E(2) receptor (EP) isoforms and their activation by PGE(2) leads to downstream Ca(2+) signalling. METHODOLOGY: Cultured human dental pulp cells were exposed to interleukin (IL)-1beta and tumour necrotic factor-alpha (TNF-alpha). The expression of COX-1 and COX-2 was measured with reverse transcriptase-polymerase chain reaction (RT-PCR). The production of PGE(2) was measured using an enzyme-linked immunosorbent assay. Expression of prostaglandin EP receptor isoforms was studied by RT-PCR, whereas fura-2 fluorescence was used to measure calcium mobilization. The Kruskal-Wallis test and Wilcoxon sum rank test with Bonferroni correction were used for statistical analysis. RESULTS: Interleukin-1beta and TNF-alpha stimulate PGE(2) production of human dental pulp cells (P < 0.05). IL-1beta stimulated the COX-2 but not COX-1 mRNA expression. Pulp cells express mainly EP2, EP3 and EP1 receptors as analysed by RT-PCR. PGE(2) (0.25-2 micromol L(-1)) stimulated the Ca(2+) mobilization as indicated by increase in fura-2 fluorescence. CONCLUSIONS: Interleukin-1beta and TNF-alpha may stimulate PGE(2) production in dental pulp cells. Activation of prostaglandin EP receptors in dental pulp cells by PGE(2) may induce Ca(2+) signalling to regulate cellular biological activity during inflammation.

Effects of TGF-beta s on the growth, collagen synthesis and collagen lattice contraction of human dental pulp fibroblasts in vitro.

Transforming growth factor-beta (TGF-beta) is important in regulating the repair and regeneration of damaged dental pulp. For further elucidating the roles of different isoforms of TGF-beta in the healing and inflammatory processes of human dental pulp, we found that TGF-beta1, TGF-beta2 and TGF-beta3 inhibited the growth of two human dental pulp cell strains in vitro by 19-29, 18-25 and 23-26%, respectively, at a concentration of 0.5 ng/ml. TGF-beta also differentially stimulated the collagen synthesis of pulp cells. Collagen synthesis increased by 1 ng/ml of TGF-beta1 and TGF-beta2 by 42 and 51%, respectively. TGF-beta3 (0.1-1 ng/ml) lacked of stimulatory effect on collagen synthesis of pulp cells. Pulp cells have the intrinsic capacity to contract collagen lattice, leading to decreasing of lattice diameter. An 8 h exposure to TGF-beta1 and TGF-beta2 enhanced the pulp cell-populated collagen lattice contraction at concentrations ranging from 0.2 to 3 ng/ml. At similar concentrations, TGF-beta3 lacked of this stimulatory effect. When collagen lattice were detached after 24 h of exposure, TGF-beta1 and TGF-beta2 (0.6-3 ng/ml) induced the pulp cells-populated collagen lattice contraction within 4-8h of gel detachment. These results indicate that TGF-beta-induced collagen lattice contraction is a late cellular event. These in vitro results indicate that effects of TGF-beta isoforms on the growth, collagen synthesis and collagen lattice contraction of pulp cells may play crucial roles in the pathobiological processes of dental pulp.

Scavenging property of three cresol isomers against H2O2, hypochlorite, superoxide and hydroxyl radicals.

Formocresol has long been used for pulpotomy of primary teeth and as an intracanal medicament. Little is known, however, about the pharmacological effect of tricresols. This study showed that three cresol isomers, o-cresol, m-cresol and p-cresol, are H2O2 scavengers with a 50% inhibitory concentration (IC50) of 502, 6.7 and 10.16 microM, respectively. o-, m- and p-cresol were also shown to be effective scavengers of superoxide radicals generated by xanthine/xanthine oxidase with an IC50 of 282, 153 and > 4000 microM, respectively, as analyzed by luminometer. o-, m- and p-cresol showed protective effects on the DNA breaks generated by H2O2/FeCl2 and FeCl3/ascorbate/H2O2 systems at concentrations ranging from 70 microM to 1.43 mM, o-, m- and p-cresol also showed differential protective effects against DNA breaks induced by 0.17% NaOCl with 100% inhibitory concentration (IC100) of about 10, 1 and 10 mM, respectively. In addition, reaction with 3% H2O2 and 0.17% NaOCl completely prevented NaOCl-induced DNA breaks. The results indicate that the three cresol isomers are effective ROS scavengers and may prevent ROS induced damage when used as pulpotomy agents or as intracanal medicaments. Owing to the difference in the position of the functional hydroxyl group in the three cresol isomers, m-cresol is the most effective ROS scavenger. Concomitant use of H2O2 for root canal irrigation may diminish both the tissue dissolving capacity of NaOCl and NaOCl-induced DNA damage.

Characteristics of organic precursors and their relationship with disinfection by-products.

The molecular weight distribution and chemical composition of precursors and their relationship with disinfection by-products (DBPs) were investigated. Most of the organic matter responsible for the major DBP precursors in the Pan-Hsin water are small compounds with a molecular weight less than 1 kDa. The hydrophobic acids display the greatest ability to produce DBP. Therefore, effective removal of small molecules or hydrophobic acidic organics prior to disinfection process will significantly reduce the DBP concentration in the finished water. Although the coagulation process is effective in removing large organic precursors and the removal efficiencies of CHCl3 formation potential and organic carbon increase proportionally to the molecular weight of the precursors, the conventional treatment methods have limited efficiency in eliminating small precursors, which have high DBP formation potential.

Phase, compositional, and morphological changes of human dentin after Nd:YAG laser treatment.

Although techniques for repairing root fracture have been proposed, the prognosis is generally poor. If the fusion of a root fracture by laser is possible, it will offer an alternative to extraction. Our group has attempted to use lasers to fuse a low melting-point bioactive glass to fractured dentin. This report is focused on the phase, compositional, and morphological changes observed by means of X-ray diffractometer, Fourier transforming infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy in human dentin after exposure to Nd:YAG laser. The irradiation energies were from 150 mJ/ pulse-10 pps-4 s to 150 mJ/pulse-30 pps-4 s. After exposure to Nd:YAG laser, dentin showed four peaks on the X-ray diffractometer that corresponding to a-tricalcium phosphate (TCP) and beta-TCP at 20 = 30.78 degrees/34.21 degrees and 32.47 degrees/33.05 degrees, respectively. The peaks of a-TCP and beta-TCP gradually increased in intensity with the elevation of irradiation energy. In Fourier transforming infrared analysis, two absorption bands at 2200 cm(-1) and 2015 cm(-1) could be traced on dentin treated by Nd:YAG laser with the irradiation energies beyond 150 mJ/pulse-10 pps-4 s. The energy dispersive X-ray results showed that the calcium/phosphorus ratios of the irradiated area proportionally increased with the elevation of irradiation energy. The laser energies of 150 mJ/ pulse-30 pps-4 s and 150 mJ/pulse-20 pps-4 s could result in the a-TCP formation and collagen breakdown. However, the formation of glass-like melted substances without a-TCP at the irradiated site was induced by the energy output of 150 mJ/ pulse-10 pps-4 s. Scanning electron micrographs also revealed that the laser energy of 150 mJ/ pulse-10 pps-4 s was sufficient to prompt melting and recrystallization of dentin crystals without cracking. Therefore, we suggest that the irradiation energy of Nd:YAG laser used to fuse a low melting-point bioactive glass to dentin is 150 mJ/ pulse-10 pps-4 s.

Induction of dental pulp fibroblast matrix metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 gene expression by interleukin-1alpha and tumor necrosis factor-alpha through a prostaglandin-dependent pathway.

Matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) are involved in the degradation of extracellular matrix in many inflammatory diseases. Little is known regarding the expression of these mediators in dental pulp fibroblasts. The effects of proinflammatory cytokines (interleukin (IL)-1alpha and tumor necrosis factor-alpha (TNF-alpha)) and prostaglandin E2 (PGE2) on pulp fibroblast MMP-1 and TIMP-1 gene expression were investigated. Northern hybridization showed that IL-1alpha and TNF-alpha induced significant MMP-1 gene expression, with only little effect on TIMP-1 gene. Exogenous PGE2, however, upregulated TIMP-1 mRNA synthesis but not MMP-1. Concomitant addition of IL-1alpha and PGE2 or TNF-alpha and PGE2 suppressed MMP-1 mRNA production, compared with the groups treated with IL-1alpha or TNF-alpha alone. In contrast, PGE2 enhanced the upregulatory effects of TIMP-1 mRNA by IL-1alpha or TNF-alpha. Furthermore, cytokine stimulation of MMP-1 and TIMP-1 gene expressions can be enhanced or blocked by indomethacin, respectively, and reversed by exogenous PGE2. These results suggested that cytokine-stimulated MMP-1 and TIMP-1 gene expression in dental pulp fibroblasts was mediated, at least in part, by a prostaglandin-dependent pathway. The differential regulation of IL-1alpha or TNF-alpha-induced MMP-1 and TIMP-1 mRNA synthesis, as well as the direct upregulation of TIMP-1 gene expression by PGE2, also implied that prostaglandin may serve as a protective mechanism from excessive tissue breakdown during pulpitis.

Synergistic effect of Nd:YAG laser combined with fluoride varnish on inhibition of caries formation in dental pits and fissures in vitro.

BACKGROUND AND PURPOSE: Although the effectiveness of neodymium yttrium aluminum garnet (Nd:YAG) laser and fluoride anticaries treatment has been established, most previous studies focused on smooth tooth surfaces. We evaluated the anticaries effects of Nd:YAG laser combined with fluoride varnish (Duraphat) on caries-susceptible pit and fissure areas. METHODS: A total of 36 noncarious molars were treated with either a Nd:YAG laser (2.5 W, 6 sec) followed by fluoride varnish, Nd:YAG laser only, fluoride varnish only, or no treatment (control). Artificial carious lesions were created to assess the acid resistance of enamel after treatment. Undecalcified successive tooth slices were made. Percentage lesion formation, lesion length, and lesion depth were evaluated using polarized light microscopy. RESULTS: The Nd:YAG laser enhanced the resistance of dental enamel to acid challenge. However, Nd:YAG laser alone was not as effective as the Nd:YAG laser combined with fluoride varnish, especially for the treatment of pits and fissures. Nd:YAG laser treatment combined with fluoride varnish inhibited 43% of lesions at pits and fissures and 80% of lesions on smooth surfaces compared to no treatment. Carious lesions had shallower depth and shorter length. No carious lesion extended beyond the dentinoenamel junction in either laser-treatment group. CONCLUSIONS: A synergistic effect on dental caries prevention in pit and fissure areas and on the smooth surfaces of the tooth can be achieved by applying Nd:YAG laser followed by fluoride varnish.

Thrombin-stimulated growth, clustering, and collagen lattice contraction of human gingival fibroblasts is associated with its protease activity.

BACKGROUND: Thrombin is a serine protease produced following gingival tissue injury or inflammation. It regulates the functional behavior of injury-neighboring cells via the activation of specific protease-activated receptors (PAR). Thrombin's role in gingival tissue healing and inflammatory response processes is not yet well understood. METHODS: We investigated the effects of thrombin on gingival fibroblast (GF) growth [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay], collagen lattice contraction, and associated morphological changes. RESULTS: Thrombin (>1 U/ml), but not thrombin receptor (PAR-1) agonist peptide (SFLLRN, single letter amino acid code, abbreviated as TRAP, 1 to 50 microg/ml), stimulated the growth and clustering of cultured human GF in vitro. Growth-stimulatory effects of thrombin were inhibited by D-Phe-Pro-ArgCH2Cl (PPACK), a serine protease inhibitor. By contrast, trypsin (>10 microg/ml), a PAR-2 activator, suppressed the growth of GF. Thrombin (>0.2 U/ml) and TRAP (10 to 25 microg/ml), but not trypsin, prostaglandin E2 (0.01 to 0.5 microg/ml), or bovine serum albumin (BSA) (1 to 80 microg/ml), induced the GF-populated collagen lattice contraction within 30 to 60 minutes of exposure. The thrombin-induced collagen lattice contraction was inhibited by PPACK (20 microg/ml) and an actin filament polymerization inhibitor, cytochalasin B (1 microg/ml). The collagen lattice contraction induced by TRAP was also inhibited by cytochalasin B, but not by PPACK. Using a reverse-transcriptase polymerase chain reaction (RT-PCR), the expression of PAR-1, and to a lesser extent PAR-3, was observed for human GF, although little PAR-2 and PAR-4 expression was noted. CONCLUSIONS: These results indicate that thrombin is important in periodontal wound healing and inflammatory processes by promoting the growth and contraction of GF. The stimulatory effects of thrombin are associated with its protease activation of thrombin receptors.

Treatment of tooth fracture by medium-energy CO2 laser and DP-bioactive glass paste: the interaction of enamel and DP-bioactive glass paste during irradiation by CO2 laser.

Acute trauma or trauma associated with occlusal disturbance can produce tooth crack or fracture. Although several methods are proposed to treat the defect, however, the prognosis is generally poor. If the fusion of a tooth fracture by laser is possible, it will offer an alternative to extraction or at least serve as an adjunctive treatment in the reconstruction. We have tried to use a continuous-wave CO2 laser and a newly developed DP-bioactive glass paste (DPGP) to fuse or bridge tooth crack or fracture lines. Both the DP-bioactive glass paste and tooth enamel have strong absorption bands at the wavelength of 10.6 microm. Therefore, under CO2 laser, DPGP and enamel should have an effective absorption and melt together. The interface between DPGP and enamel could be regarded as a mixture of DPGP and enamel (DPG-E). The study focused on the phase transformation, microstructure, functional group and thermal behavior of DPG-E with or without CO2 laser irradiation, by the analytical techniques of XRD, FTIR, DTA/TGA, and SEM. The results of XRD showed that the main crystal phase in the DPG-E was dicalcium phosphate dihydrate (CaHPO4.2H2O). It changed into CaHPO4, gamma-Ca2P2O7, beta-Ca2P2O7 and finally alpha-Ca2P2O7 with increasing temperature. In the FTIR analysis, the 720 cm(-1) absorption band ascribed to the P-O-P linkage in pyrophosphate rose up and the intensities of the OH- bands reduced after laser irradiation. In regard to the results of DTA/TGA after irradiation, the weight loss decreased due to the removal of part of absorption water and crystallization water by the CO2 laser. SEM micrographs revealed that the melted masses and the plate-like crystals formed a tight chemical bond between the enamel and DPGP. We expect that DPGP with the help of CO2 laser can be an alternative to the treatment of tooth crack or fracture.

Effects of Nd:YAG laser irradiation on cultured human gingival fibroblasts.

BACKGROUND AND OBJECTIVE: The Nd:YAG laser has been proposed to apply in minor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG laser on gingival fibroblasts, which play an important role in the early healing processes of periodontal repair. STUDY DESIGN/MATERIALS AND METHODS: Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from healthy human gingiva by an explant method. The size of laser diode was 400 microm in diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of irradiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vitality was also examined with the help of MTT staining. RESULTS: The area of laser damage on cell culture was circular in shape, with diameter beyond the size of laser diode. By scanning electron microscopy, we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased power settings. The cytomorphologic changes ranged from disappearance of cellular boundary, loss of identifiable cellular nucleus, and finally cell contraction and vacuolization. Significant decrease in cellular vitality (14% approximately 44%) after laser treatment with irradiation distance of nearly contact was noted. However, 2 mm defocusing irradiation with the same power settings did not significantly decrease cellular vitality. CONCLUSION: Our study demonstrated the cell damaging effects of Nd:YAG laser, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to understand the potential hazard of laser application in periodontal treatment. If the energy output is enough for the clinical purposes, Nd:YAG laser with lower pulse energy and corresponding pulse rate should be selected to minimize the damage on adjacent soft tissue.

Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: compositional, structural, and phase changes of DP-bioglass paste after irradiation by CO2 laser.

Nowadays, fractured teeth are difficult to treat effectively. Currently, root fractures are usually treated by root amputation, hemisection or tooth extraction. If the fusion of tooth fracture by laser were possible, it would offer a different therapy to repair fracture teeth. We tried to use a developed DP-bioactive glass paste to fuse or bridge the tooth crack line by a medium energy continuous-wave CO2 laser. The study is divided into three parts: (1) The compositional and structure changes in tooth enamel and dentin after laser treatment; (2) The phase transformation and recrystallization of DP-bioactive paste during exposure to the CO2 laser; (3) The thermal interactions and bridge mechanism between DP-bioactive glass paste and enamel/dentin when they are subjected to CO2 laser. The present report will focus on the second part that will examine the changes of laser-exposed DP-bioactive glass paste by means of X-ray diffractometer (XRD), Fourier transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). From the study, we could find that the temperature increase due to laser irradiation is greater than 900 degrees C and that the DP-bioactive glass paste could be melted in a short period of time after irradiation. In the study, we successfully developed a DP-bioactive glass paste which could form a melting glass within seconds after exposure to a medium energy density continuous-wave CO2 laser. The paste will be used in the near future to bridge the enamel or dentin surface crack by the continuous-wave CO2 laser.

A comparison of the morphological changes after Nd-YAG and CO2 laser irradiation of dentin surfaces.

The purpose of this study was to compare the morphological changes after Nd-YAG and CO2 laser irradiation on dentin surfaces with or without the smear layer. Eighty-one 3-mm-thick dentin specimens collected from the middle third of molar crowns were used. The dentin surfaces were ground to #320, #400, and #600 grit in series to create a smear layer. Half of the specimens were treated with 14% EDTA for 2 min to remove the smear layers. The lasers were applied on each specimen perpendicularly with 1-mm focus distance to the dentin surface for 4 s. The parameters for the Nd-YAG laser were 50 mJ, 100 mJ, and 150 mJ at 10 pps, 20 pps, and 30 pps, and for the CO2 laser were 2 W, 3 W, and 4 W at 5 ms x 20 pps, 10 ms x 10 pps, 20 ms x 20 pps, 50 ms x 2 pps, 100 ms x 2 pps, and 200 ms x 2 pps. The results showed that the Nd-YAG laser caused crater and melting of the dentin surface, especially in dentin specimens with smear layers. The CO2 laser produced extensive cracking lines on dentin surfaces with a smear layer, whereas surface erosion and crater formation were found on specimens without a smear layer. In conclusion, both the laser types and smear layer have a significant influence on the morphological changes of dentin surfaces irradiated by lasers.

Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: thermal behavior and phase transformation of human tooth enamel and dentin after irradiation by CO2 laser.

Acute trauma or trauma associated with occlusal disharmony can produce tooth crack or fracture. Although several methods are proposed to treat the defect, however, the prognosis is generally poor. If the fusion of a tooth fracture by laser is possible it will offer an alternative to extraction or at least serve as an adjunctive treatment in the reconstruction. The responses of soft tissues to lasers of different wavelengths are fairly well known, but the reactions of hard tissues are still to be understood. The purpose of this research was to study the feasibility of using a medium energy continuous-wave CO(2) laser and a low melting-point bioactive glass to fuse or bridge tooth fractures. The present report is focused on the first part of the research, the analysis of changes in laser-irradiated human tooth enamel/dentin by means of X-ray diffractometer (XRD), Fourier-transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). After CO(2) laser irradiation, there were no marked changes in the X-ray diffraction pattern of the enamel when compared to that before laser treatment. However, a small peak belonging to alpha-TCP appeared at the position of 2theta=30.78 degrees C. After being treated with CO(2) laser, the dentin showed much sharper peaks on the diffraction patterns because of grain growth and better crystallinity. alpha-TCP and beta-TCP were identified after laser treatment. In the FTIR analysis, an HPO(4)(-2) absorption band was noted before laser treatment disappeared after the irradiation. No significant change in the absorption band of HPO(4)(-2) was found on the FTIR curves of enamel after laser treatment. The results of DTA/TGA indicated that loss of water and organic materials occurred in both enamel and dentin after laser treatment. Under SEM, melting and resolidification occurred in both enamel and dentin by medium energy of CO(2) laser. This implies that using a continuous-wave CO(2) laser of medium energy density to fuse a low melting-point bioactive glass to the enamel/dentin is possible. We believe these phase changes and thermal data can make a useful guide for future studies on the thermal interaction and bridging mechanism between the bioactive glass and enamel/dentin under CO(2) laser irradiation.

Comparison of Nd:YAG laser versus scaling and root planing in periodontal therapy.

BACKGROUND: The Nd:YAG laser has recently been used in the treatment of periodontal disease. However, although a clinical reduction of probing depth and gingival inflammation to this new approach has been reported, it has not been fully evaluated. Interleukin-1 beta (IL- 1beta), a potent stimulator of bone resorption, has been identified in gingival crevicular fluid (GCF), which is closely associated with periodontal destruction. The aim of this study was to compare the effects of Nd:YAG laser treatment versus scaling/root planing (SRP) treatment on crevicular IL-1beta levels in 52 sampled sites obtained from 8 periodontitis patients. METHODS: One or 2 periodontitis-affected sites with a 4 to 6 mm probing depth and horizontal bone loss from 3 adjacent single-root teeth in each of 4 separate quadrants were selected from patients for clinical documentation and IL-1beta assay. Sampling site(s) from each diseased quadrant was randomly assigned to one of the following groups: 1) subgingival laser treatment (20 pps, 150 mJ) only; 2) SRP only; 3) laser treatment first, followed by SRP 6 weeks later; or 4) SRP first, followed by laser therapy 6 weeks later. The GCF was collected and the amount of IL-1beta was assayed by enzyme-linked immunosorbent assay (ELISA). Clinical parameters and GCF were measured at baseline and biweekly after therapy for 12 weeks. RESULTS: An obvious clinical improvement (marked decrease in the number of diseased sites with gingival index > or =2) and reduction of crevicular IL- 1beta were found in all groups. The level of IL- 1beta was significantly lower in the SRP group (P = 0.035) than in the laser therapy group for the duration of the 12 weeks. The laser combined SRP therapy group showed a further reduction of IL- 1beta (6 to 12 weeks after treatment) than either laser therapy alone or SRP combined laser therapy. CONCLUSIONS: Our data suggest that laser therapy appeared to be less effective than traditional SRP treatment. Of the 4 treatment modalities, inclusion of SRP was found to have a superior IL- 1beta response, when compared to other therapies without it. In addition, no additional benefit was found when laser treatment was used secondary to traditional SRP therapy.

The combined occluding effect of sodium fluoride varnish and Nd:YAG laser irradiation on human dentinal tubules.

Various methods and materials used in the treatment of dentin hypersensitivity are thought to achieve a therapeutic benefit by tubule occlusion. The aim of the present study was to evaluate the combined occluding effect of sodium fluoride varnish and Nd:YAG laser irradiation on human dentinal tubules. Thirty-six dentin specimens with exposed dentinal tubule orifices were used in this study. The samples were randomly divided into four groups. Groups A, B, and C were varnished by sodium fluoride, whereas group D served as a control. Then, group C was lased by 30 mJ of Nd:YAG laser, 10 pulses/s for 2 min by light painting. Three hours later, groups B and C were brushed by an electrical toothbrush for 30 min. Under SEM observation, the control group showed numerous exposed dentinal tubule orifices, and the sodium fluoride varnished specimens showed closure of exposed dentinal tubule orifices. After electrical toothbrushing, most of the sodium fluoride varnish was brushed away, except in the specimens that were irradiated by Nd:YAG laser. Over 90% of the dentinal tubule orifices were occluded by sodium fluoride varnish combined with Nd:YAG laser irradiation.

The effects of extracellular citric acid acidosis on the viability, cellular adhesion capacity and protein synthesis of cultured human gingival fibroblasts.

Root surface demineralization is widely used as an adjunct to periodontal treatment. To clarify the influence of citric acid root conditioning on periodontal wound healing, the effects of citric acid and associated extracellular acidosis on the viability (MTT assay), attachment and protein synthesis ([3H]-proline incorporation into trichloroacetic acid-precipitated proteins) of human gingival fibroblasts (GF) were investigated. A concentration of 47.6 mmol/L of citric acid (pH 2.3) in water led to total cell death within three minutes of incubation. Media containing 23.8 mmol/L and 47.6 mmol/L of citric acid exerted strong cytotoxicity (47 to 90 per cent of cell death) and inhibited protein synthesis (IC50 = 0.28 per cent) of GF within three hours of incubation. Incubation of cells in a medium containing 11.9 mmol/L of citric acid also suppressed the attachment and spreading of fibroblasts on culture plates and Type I collagen, with 58 per cent and 22 per cent of inhibition, respectively. Culture medium supplemented with 11.9, 23.8 and 47.6 mmol/L of citric acid also led to extracellular acidosis by decreasing the pH value from 7.5 to 6.3, 5.2 and 3.8, respectively. In addition, it was confirmed that the toxic effect of media containing citric acid was due to their acidity rather than the citrate content. Most of the citric acid-induced cell death could be prevented by adjusting the pH value of the culture medium to pH 7.5. Sodium citrate, at a concentration of 47.6 mmol/L, also exerted little cytotoxicity. The results suggested that toxicity of citric acid in specific stages of the healing process must be considered prior to its clinical application. Careful management of citric acid in order to avoid contact with tissue or the development of other demineralizing agents is important in enhancing periodontal wound healing.

Ultrastructural changes of the tooth root surface by Nd:YAG laser irradiation followed by citric acid and tetracycline.

The neodymium:yttrium-aluminum-garnet (Nd:YAG) laser has been used for treatment of dentinal hypersensitivity, eradicating periodontal pathogens, and facilitating calculus removal. However, Nd:YAG laser irradiation exerts potentially harmful effects on the tooth root surface. The purpose of this study was to examine the ultrastructural changes of the tooth root surface caused by Nd:YAG laser irradiation, and to determine whether chemical and mechanical preparations can correct these ultrastructural changes. Eighteen tooth specimens (3 x 3 x 0.5 mm) with healthy root surfaces were prepared and irradiated with an Nd:YAG laser at various power densities. Root surfaces were irradiated at 100 mJ at 20 pulses per second (pps) for 2 seconds followed by the application of citric acid (pH 1.2) or tetracycline solution (100 mg/mL) for 3 and 5 minutes, respectively, or ultrasonic scaling for 5 strokes of 3 seconds per stroke. As observed with low-vacuum scanning electron microscopy, (Wet-SEM), Nd:YAG laser irradiation at 70 to 100 mJ, 20 pps for 2 seconds caused surface cratering, areas of porosity, pitting, fissures, and lava-like structures in an area 140 to 280 microns in diameter. Irradiation of 50 mJ, 20 pps for 2 seconds, led to only mild surface charring. No evidence of morphologic changes was found when root surfaces were irradiated with the Nd:YAG laser at 20 mJ, 20 pps for 2 seconds or at 50 mJ, 10 pps for 8 seconds. The laser-induced lava-like structures were partially detached by citric acid (pH 1.2) etching and ultrasonic scaling, but not by tetracycline (100 mg/mL). These results indicate that chemical and mechanical preparations can be used effectively in conjunction with Nd:YAG laser irradiation for root surface preparation during both nonsurgical and surgical periodontal treatments.

Temperature elevation on the root surface during Nd:YAG laser irradiation in the root canal.

Nd:YAG lasers have been suggested as a potential tool in endodontic therapy because of their sterilizing and sealing effects on the dentinal tubules. However, the generation of heat in the root canal by laser irradiation may produce potentially harmful effects on adjacent tissues. The purpose of this study was to evaluate the temperature elevation on the root surface when Nd:YAG laser was irradiated in the root canal. The apical third area of 90 single-rooted teeth were irradiated with normal pulsed Nd:YAG laser (50, 80, 100, 150, and 200 mJ/pulse; 20, 25, and 30 pulses/s). The temperature elevation was measured and recorded on the root surface simultaneously. The temperature elevation did not exceed 10 degrees C only when the laser energy output was below 100 mJ/pulse and under 20 pulses/s.