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.

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.

Effect of a novel Er:YAG laser in caries removal and cavity preparation: a clinical observation.

OBJECTIVE: We evaluated the applicability of a novel Er:YAG laser under clinical conditions. BACKGROUND DATA: The Er:YAG laser has been demonstrated to be a safe and effective alternative to the conventional turbine bur, but the relatively low cutting speed prevented the wide application of Er:YAG laser in clinical cavity preparation. METHODS: A Smart 2940 D laser developed by Deka Corporation was used for cavity preparation in 95 teeth of 45 patients. Parameters were as follows: wavelength 2.94 microm, pulse energy 700 mJ, repetition rate 8 Hz. Pain, discomfort, assessment during cavity preparation, prognosis factor, and overall clinical evaluation were assessed during or after treatment. RESULTS: No adverse reaction was observed in any tooth. No intraoperative pain or only slight intraoperative pain was described in 85 teeth (89.5%). Cavity preparation was completed with the laser system alone in 90 teeth (94.7%). Overall clinical evaluation showed no safety problems, with a very good or good rating in 86 teeth (90.5%). The overall operation time was 49 sec on average. CONCLUSION: The Smart 2940 D is an efficient, effective, safe, and suitable instrument for caries removal and for cavity preparation. It greatly shortens operation time.

Effects of KTP laser irradiation, diode laser, and LED on tooth bleaching: a comparative study.

OBJECTIVE: This in vitro study examines the whitening efficacy of a light-emitting diode (LED), a diode laser, and a KTP laser irradiation in dental bleaching by analyzing the change in color achieved from the treatment, the temperature increase induced in the pulpal cavity, as well as enamel microhardness measurement after treatment. BACKGROUND DATA: Bleaching techniques achieved significant advances with the use of coherent or incoherent radiation sources to activate the bleaching agents. METHODS: A hydrogen peroxide bleaching agent, Hi-Lite, was stimulated with an LED, a 980-nm diode laser at 0.8 W, or a 532-nm KTP laser at 1.0 W for 30 sec on 64 extracted human incisors. During irradiation, the temperature in the pulpal cavity was monitored. The color change was evaluated using the CIE L*a*b* color space measurement system, and Vikers enamel microhardness was tested after treatment. RESULTS: A mean total color difference value (DeltaE*) greater than 5.0 was obtained in each group. KTP-laser-induced bleaching gave a significantly higher DeltaL* (8.35) after treatment (p < 0.01). Neither LED nor the two lasers produced significant differences in the enamel microhardness after treatment (p > 0.01). Mean maximal pulpal temperature rise was 2.95 degrees C for LED, 3.76 degrees C for KTP laser, and 7.72 degrees C for diode laser, respectively. CONCLUSION: The results of this study suggest that KTP laser is effective at providing brighter teeth. According to the conditions used in this study, the LED and KTP laser induced a safer pulpal temperature increase when assisted with Hi-Lite bleaching gel.

Light intensity evaluation of laser-induced fluorescence after caries removal using an experimental caries staining agent.

OBJECTIVE: The purpose of this study was to evaluate the intensity of fluorescent light reflected from cavity wall dentin, after dentin stained by an experimental caries detecting liquid was removed. BACKGROUND DATA: The conventional caries detecting liquid tends to penetrate dentin too deeply. On the other hand, DIAGNOdent has gradually gained recognition and established itself as a caries detection device using a laser beam. METHOD: An experimental caries staining liquid or the conventional caries staining liquid was applied in the same cavity to observe for differences in dye penetration. Intensity of fluorescence reflected from treated dentin was measured by DIAGNOdent. RESULTS: The mean DIAGNOdent value after removing the tooth substance stained by the experimental liquid was 17.9+/-4.1, compared with 7.7+/-2.7 by conventional one. CONCLUSION: Light intensity evaluation of laser-induced fluorescence suggested that the experimental caries detecting liquid did not penetrate the dentin which should be preserved, hence avoiding overtreatment.

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.

Ultramorphological and histochemical changes after ER,CR:YSGG laser irradiation and two different irrigation regimes.

The purpose of this study was to evaluate the ultramorphological and chemical changes in Er,Cr:YSGG laser-treated radicular dentin in comparison with two different irrigation regimes. Extracted human premolars were assigned into three experimental groups. Group 1: After each file size, root canals were irrigated with 5.25% NaOCL, followed by a final irrigation with 5.25% NaOCL. Group 2: At each file size, biomechanical preparation was performed in conjunction with Rc-Prep, followed by 5.25% NaOCL irrigation; and 5.25% NaOCL for the final flush. Group 3: 5.25% NaOCL was used after each file size, followed by Er,Cr:YSGG laser irradiation; and a final flush with 5.25% NaOCL. Scanning electron microscopic (SEM) evaluations revealed failure of smear removal in NaOCL-irrigated specimens. RC-Prep + NaOCL-treated dentin revealed moderate-to-total presence of the smear layer with distinct areas of exposed collagen. Er,Cr:YSGG laser irradiation of radicular dentin also resulted in partial or total removal of the smear associated with a few small regions of thermal injury, including carbonization and partial melting. Energy dispersive X-ray analysis (SEM-EDX) showed no significant difference between the Ca/P ratios of the test groups, suggesting absence of changes at the molecular level.

Isolation and partial sequencing of cDNA clones from rat incisor after Nd:YAG laser irradiation in root canal.

OBJECTIVE: The purpose of this study was to identify the genes expressed in odontoblast-like cells and related to osteodentin production of pulp cells in vivo during the repair process. METHODS: A pulsed Nd:YAG laser was irradiated in mandibular incisors of rats at 2 W and 20 pulses/s for 5 s. We constructed a unidirectional cDNA library from the non-calcified portion of irradiated incisors, sequenced cDNA clones and classified their sequences by homology search through the GenBank database. RESULTS: Of the sequences determined, 26% represented sequences of new genes that were not related to any previously reported gene. 65.5% of the clones strongly matched genes and proteins in the databases. Among them, sequences found more than once were amelogenin, ameloblastin, amelin, collagen alpha1 type 1, osteonectin, nestin, enamelin and osteocalcin. Sequences detected only once were transforming growth factor beta-1 (TGF-beta1), growth hormone receptor (Ghr), glypican, enamelysin (Mmp20), amelin 2, integral membrane protein 2B, amelogenin precursor (Ame1), splicing factor 3b, insuline-like growth factor binding protein 5. CONCLUSION: This library reflects the gene expression during the dentin repair process in vivo including the odontoblast-like cell specific gene expression and osteodentin-production. Using this library, we indicate the candidate genes which might be related to odontoblast-differentiation and formation of osteodentin.

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.

Morphological study of the Er,Cr:YSGG laser for root canal preparation in mandibular incisors with curved root canals.

OBJECTIVE: The objectives of this study were to observe morphological changes of root canal walls and to evaluate the capability of Er,Cr:YSGG laser for preparation of curved mandibular incisor root canals in vitro. BACKGROUND DATA: There are no published reports on the use of Er,Cr:YSGG laser for curved root canal preparation. METHODS: Twenty curved mandibular incisor root canals (10 and 15 degrees) were prepared sequentially by laser irradiation at 20 Hz, 2 Wusing two different sizes of fine fiber tips (200 and 320 microm in diameters). After laser irradiation, the teeth were bisected longitudinally, and the specimens were observed by stereoscope and scanning electron microscope (SEM). RESULTS: Root canal walls of the irradiated areas showed step-like appearances and openings of dentinal tubules, and root canal preparation, having curvatures of less than 10 degrees, could be carried out by this laser irradiation. CONCLUSIONS: Er,Cr:YSGG laser irradiation is capable of preparing root canals having curvatures of less than 10 degrees.

Efficacy of root canal preparation by Er,Cr:YSGG laser irradiation with crown-down technique in vitro.

OBJECTIVE: The purpose of this study was to compare the efficacy of Er,Cr:YSGG laser in root canal preparation and its effectiveness in removing debris and smear layer with the efficacy of the conventional hand instrument, in vitro. BACKGROUND DATA: Recently, the use of the Er,Cr:YSGG laser device in root canal preparation has been excepted in the dental clinic. However, there have been no published reports on root canal preparation by using the Er,Cr:YSGG laser irradiation. MATERIALS AND METHODS: A total of 40 straight root canals were prepared by an Er,Cr:YSGG laser at a output power of 2 W, and 40 canals were shaped by using the K file under irrigation with NaOCl and H2O2 by using the crown-down technique (control). The achievement degree of root canal preparation and debris score was morphologically investigated. RESULTS: The results showed that great improvement in the cleanliness of the walls was found using the laser technique as compared with the control technique; a significant decrease in smear layer or debris was also recognized in laser-prepared canals (p < 0.01). But canal preparations with the laser device sometime result in ledge, zipped, perforation, or over-instrumentation. CONCLUSION: The results demonstrated that root canal preparations with the laser device were significantly worse than in the control group. Further development in laser device and technique are required to ensure its success in root canal preparation.

Effects of diode laser irradiation on smear layer removal from root canal walls and apical leakage after obturation.

OBJECTIVE: The objective of this study was to investigate the rise in temperature in root surfaces during and immediately after diode laser irradiation, to observe morphological changes of root canal wall after irradiation, and to evaluate the apical leakage after irradiation and obturation in vitro. BACKGROUND DATA: There have been very few reports on root canal treatment by 980-nm wavelength diode laser. METHODS: Sixty-six extracted human single-rooted teeth were instrumented up to size 60 K-file, and then randomly divided into three groups of 22 teeth each. Groups 1 and 2 were irradiated with a diode laser at 5 W for 7 sec using fibers of diameters 550 and 365 microm, respectively. Group 3 was not irradiated, and served as a control. The rise in temperature on root surfaces of the teeth in groups 1 and 2 were measured by thermography. Six teeth in each group were bisected longitudinally and observed morphologically. Other teeth were obturated and immersed in rhodamine B solution, and the degree of apical leakage was evaluated longitudinally and transversally. RESULTS: A maximum temperature rise of 8.1( degrees )C was recorded in group 1. The smear layer in the laser-treated groups was evaporated and removed, resulting in clean root canal walls, which was significantly superior to the control group (p < 0.05). After obturation, the laser-treated groups showed significantly less apical leakage than the control group (p < 0.05). CONCLUSIONS: These results indicate that the diode laser is useful for removing smear layer and debris from root canal walls, and reducing apical leakage after obturation in vitro, and suggest that it would be useful for root canal treatment in clinic.

Morphological comparative study on ablation of dental hard tissues at cavity preparation by Er:YAG and Er,Cr:YSGG lasers.

OBJECTIVE: The purpose of this study was to evaluate morphologically the dental hard tissue ablation at the class V cavity preparation by two types of laser devices: Er:YAG and Er,Cr:YSGG lasers in vitro. BACKGROUND DATA: There have been no reports on the comparative study of dental tissue ablation at cavity preparation by Er:YAG and Er,Cr:YSGG lasers. METHODS: Twenty-two extracted human mature molar teeth were used in this study and divided into two groups of 11 teeth each. The teeth of the Er:YAG laser-irradiated group were irradiated at the parameters of 250 mJ/pulse and 15 Hz with water spray, and those of the Er,Cr:YSGG laserirradiated group were irradiated at the parameters of 5 Wand 20 Hz with water spray. After cavity preparation, the teeth were dehydrated, coated with platinum, and examined by scanning electron microscopy. RESULTS: Both of the laser devices were capable of ablating dental hard tissues, but similar, irregular, and rugged surface aspects with different depths were observed. Open dentinal tubules at the cavities prepared by Er,Cr:YSGG laser were more clearly visible than those prepared by Er:YAG laser. Smaller width and stripped surfaces were observed on the cavities prepared by Er,Cr:YSGG laser. CONCLUSION: The results suggested that there is little difference between the two types of lasers-Er:YAG and Er,Cr:YSGG lasers-morphologically for class V cavity preparation, because both lasers were capable of preparing class V cavities, and the morphological features of the irradiated surfaces were very similar.

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.

Histopathological study of dental pulp tissue capped with enamel matrix derivative.

The purpose of this study was to examine the histopathological response of dental pulp tissue to enamel matrix derivative (EMD) used as a pulp capping material. Thirty-two teeth from two mongrel dogs were divided into four equal groups. One group served as controls, and the others were used for deep Class V cavity preparation followed by direct pulp capping with enamel matrix derivative. The treated teeth were extracted after 1, 4, and 8 weeks and prepared for histopathological examination by light microscopy. All teeth prepared after 4 and 8 weeks demonstrated an increase in tertiary dentin, suggesting that enamel matrix derivative exerts a considerable influence on odontoblasts and endothelial cells of capillaries in dental pulp tissue. These results imply that enamel matrix derivative used as a pulp capping material may play a role in the calcification of dental pulp tissue.

Root surface temperature increase during Er:YAG laser irradiation of root canals.

The authors measured the temperature of the root surface during root canal preparation using Er:YAG laser irradiation and evaluated the thermal effect on the periodontal region. Twenty extracted human teeth with single roots were divided into two groups of 10. These were irradiated using an Er: YAG laser at 2 Hz and 136 to 184 or 170 to 230 mJ/pulse for 1 min with a water spray. The temperature of the root surface was monitored using thermocouples throughout the procedure. The teeth were longitudinally bisected and observed by stereoscopy and scanning electron microscopy. The temperature on the root surface increased by less than 6 degrees C at the apical area and by less than 3 degrees C at the central area. A morphological evaluation revealed no carbonization or melting. These results suggest that the thermal effect on periodontal tissues during root canal preparation using an Er: YAG laser at less than 230 mJ/pulse for 1 min is minimal.

An immunohistochemical study of the effects of pulsed neodymium:yttrium-aluminium-garnet laser irradiation in root canals on the eruption of rat incisors.

The incisors of 21 Wistar rats were transected, pulp tissue was extirpated for 10mm from the level of the gingival margin and each canal was prepared with files. The fibre tip of a pulsed neodymium:yttrium-aluminium-garnet laser was inserted into the root canal for 10mm and laser irradiation delivered at 2 W and 20 pulses/s for 10s. After 6 weeks the mandibles were removed and sectioned. Sections were stained either with haematoxylin and eosin or immunohistochemically using polyclonal antibodies against keratin/cytokeratin, amelogenin and type I collagen. The inner epithelial cells on the labial side differentiated into ameloblasts in animals where eruption had recovered. The pulp cells differentiated into odontoblast-like cells and staining for type I collagen was evident in pulp cells, odontoblast-like cells and inside dentinal tubules. In animals where eruption had ceased, the inner epithelial cells on the labial side did not differentiate into ameloblasts. Staining for type I collagen was observed in the mineralized nodules and tubules of dentine-like hard tissues in the pulp cavity. These results suggest that differentiation of epithelial cells on the labial side into ameloblasts is involved in the re-eruption process.

A histochemical study of the regeneration process after injury by pulsed Nd:YAG laser irradiation of root canals.

Histological changes of rat dental pulp cells were followed after injury. The regeneration process after 3, 6 and 10 days was monitored. Mandibular incisors were irradiated with a pulsed Nd:YAG laser at 2 W and 20 pulses per sec (pps) for 5 sec and the pulp was examined histologically and immunohistochemically for TGF-beta1. Eruption of the developing tooth was disturbed for a short period only. Rapid formation of osteodentin was observed. After 3 days, a zone of fibrodentin matrix as well as newly formed vessels were found. Afterwards, regenerative dentin formation was observed accompanied by the formation of a layer of odontoblast-like cells in the damaged area. Immunohistochemical staining of TGF-beta1 showed that positivity was present in small tissue areas beneath the mantle dentin, the zone of fibrodentin matrix and odontoblast-like cells. These results indicate that pulsed Nd:YAG laser irradiation of rat incisor pulp induces formation of osteodentin, and TGF-beta1 plays a role during regeneration.

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.

Effects on periradicular periodontal tissues of root canal irradiation with Er:YAG laser in rats.

OBJECTIVE: The effects of Er:YAG laser irradiation on the periodontal region during root canal preparation were evaluated using rats histopathologically. BACKGROUND DATA: The effects on periodontal tissues along the root surface and apical area during root canal preparation using Er:YAG laser irradiation in vivo are not clear. METHODS: One hundred mesial root canals of mandibular first molars in rats were divided into four groups. In three of these groups, root canals were irradiated using an Er:YAG laser at 2 Hz and 34, 68, and 102 mJ/pulse for 30 sec. Non-irradiated canals served as controls. The effects of laser irradiation on the periodontal tissues along the root surface and apical area were evaluated at 0, 2 days, 1, 2, and 4 weeks after irradiation under light microscopy. RESULTS: At 4 weeks after treatment, no inflammation or resorption was observed in any cases in the control or 34 mJ/pulse-irradiated groups. However, moderate to severe inflammation with resorption of root surface was observed in four of five cases (80%) in the 102 mJ/pulse-irradiated group, which was significantly different from the control (p < 0.01). CONCLUSIONS: These results suggest that the effects on periodontal tissues during root canal preparation by Er:YAG laser irradiation after pulpectomy are minimal, if appropriate parameters are selected, and this is a potential therapy for human root canals of teeth.