Evaluation of four instruments with different working motion using artificial plastic model with C-shaped single canal.

The purpose of this study was to evaluate four instruments with different working motion for preparation of a C-shaped single canal wall using the same artificial plastic models reproduced from a human tooth. One tooth with root canal morphology C1 (the shape is an uninterrupted "C" with no separation or division) was selected among three-dimensional micro-computed tomography (micro-CT) imaging data of extracted human teeth. Imaging data were then converted into STL form data, and twenty-four C-shaped root canal model blocks were manufactured using this STL form data. These blocks were randomly divided into four groups of six blocks each and instrumented as follows: stainless steel K-files (SSK), Self-Adjusting File (SAF), ProTaper NEXT (PTN) and RECIPROC (REC). Micro-CT images taken before and after canal preparation were superimposed, and instrumented canal area, percentage of instrumented canal area, part of instrumented canal area, volume of instrumented canal and time taken for instrumentation were evaluated for each group. The greatest instrumented canal area, percentage of instrumented canal area and volume of instrumented canal were as follows (in decreasing order): SSK > SAF > PTN > REC (P < 0.05). The longest time taken for instrumentation was as follows (in decreasing order): SAF > SSK > PTN > REC (P < 0.05). The conscious shaping of SSK and the lattice structure of SAF were instrumented all root canal walls equally. PTN and REC required less time taken for instrumentation, but showed unequal instrumentation.

Removal of root canal filling materials using Er:YAG laser irradiation.

The purpose of this study was to examine the ability of Er:YAG laser to remove root canal filling materials. The root canals of 21 extracted human anterior teeth were enlarged, and then obturated with gutta-percha points and sealer by lateral condensation. Filling materials were removed from root canals using Er:YAG laser irradiation at three energy output levels (30, 40, and 50 mJ/ pulse), and the corresponding time required for material removal at each energy output level was recorded. The amount of remaining filling material and the degree of dentin ablation in the canal wall were assessed using microfocus X-ray CT before and after removal. At 30 mJ, the time required for root canal filling material removal was significantly longer than at energy outputs of 40 and 50 mJ (p<0.01). On filling material remnants and the degree of dentin ablation, these parameters were not significantly different among the three energy outputs. In conclusion, these results suggested that Er:YAG laser irradiation is capable of removing root canal filling materials.

Energy output reduction and surface alteration of quartz and sapphire tips following Er:YAG laser contact irradiation for tooth enamel ablation.

BACKGROUND: Despite the recent increase in application of Er:YAG laser for various dental treatments, limited information is available regarding the contact tips. This study examined the changes in energy output and surface condition of quartz and sapphire contact tips after Er:YAG laser contact irradiation for tooth enamel ablation. MATERIALS AND METHODS: Ten sets of unused quartz or sapphire contact tips were employed for contact irradiation to sound enamel of extracted teeth. The teeth were irradiated with Er:YAG laser at approximately 75 J/cm(2)/pulse and 20 Hz under water spray for 60 minutes. The energy output was measured before and every 5 minutes after irradiation, and the changes in morphology and chemical composition of the contact surface were analyzed. RESULTS: The energy output significantly decreased with time in both tips. The energy output from the sapphire tips was generally higher on average than that of the quartz. The contact surfaces of all the used quartz tips were concave and irregular. Most of the sapphire tips also appeared rough with crater formation and fractures, except for a few tips in which a high energy output and the original smooth surface were maintained. Spots of melted tooth substances were seen attached to the surface of both tips. CONCLUSION: In contact enamel ablation, the sapphire tip appeared to be more resistant than the quartz tip. The quartz tips showed similar patterns of energy reduction and surface alteration, whereas the sapphire tips revealed a wider and more characteristic variation among tips. Lasers Surg. Med. 41:595-604, 2009. (c) 2009 Wiley-Liss, Inc.

Clinical investigation of patients who develop neuropathic tooth pain after endodontic procedures.

INTRODUCTION: This study aimed to determine the characteristics of patients with neuropathic tooth pain (NTP) who were selected from a group of patients who developed persistent pain after undergoing endodontic procedures. METHODS: Of 271 patients who had chronic persistent pain that did not respond to previous endodontic procedures and were referred to the Endodontic Team of the Nippon Dental University Hospital, 16 patients (5.9%; mean age, 46.8 years; 13 women) who fulfilled the diagnostic criteria for NTP were recruited. The inclusion criteria for the patients were the presence of chronic persistent pain and other pain-related symptoms, despite the absence of major pathology. RESULTS: Pain predominantly occurred in the maxilla (14 patients). In 10 patients (62.5%), NTP developed after retreatment. Daily application of tricyclic antidepressants produced pain relief in 11 patients (68.8%). CONCLUSIONS: These results indicated that NTP is a rare type of chronic intractable endodontic pain and that careful diagnosis of NTP is important.

Setting properties and sealing ability of hydraulic temporary sealing materials.

This study sought to investigate the setting progress and sealing ability of hydraulic temporary sealing materials used in endodontic treatment: Lumicon, Caviton, and HY-Seal. To evaluate setting progress, the materials were filled into glass tubes with one end sealed and immersed in water. After immersion, a measurement apparatus was inserted from the non-immersed end and the set area was determined by subtracting the unset area from the sample thickness. To evaluate sealing ability, materials were filled into glass tubes and divided into four groups based on different immersion times. Thermal cycling and dye penetration were performed. At 7 days, the setting depths of HY-Seal and Caviton were almost equivalent to full sample thickness, while that of Lumicon was only half of full sample thickness (p < 0.01). On sealing ability, Lumicon ranked the highest followed by Caviton, whereas HY-Seal was unstable (p < 0.01). These results suggested that there was no correlation between setting progress and sealing ability.

Association of odor from infected root canal analyzed by an electronic nose with isolated bacteria.

Infected root canals usually cause foul odor. On sensory testing, objective evaluation of the odor is difficult because of the subjectivity of the examiner. In this study, the odor of the canal content was analyzed by an electronic nose. Moreover, association of the odor with culturable bacteria isolated from the root canal was examined. The median of the odor index (indicating odor quantity) in nonvital teeth group was significantly higher than that in vital teeth. When Prevotella, Porphyromonas, Fusobacterium, or Bacteroides was detected, the value of the odor index and the strength of smell representation (indicating odor quality) for hydrogen sulfide and ammonia were higher than when these bacteria were not present. Relationship between odor analysis data, clinical symptoms, and isolated bacterial species was seen, thus suggesting that the electronic nose is useful for objective evaluation of root canal odor.

Tooth-pulp-evoked rostral spinal trigeminal neuronal excitation is attenuated by the activation of 5-HT3 receptors via GABAergic interneurons in the rat.

The effect of iontophoretic application of the 5-HT3 receptor agonist, phenylbiguanide (PBG), on the excitation of the trigeminal spinal nucleus oralis (TSNO) neurons to tooth-pulp (TP) stimulation was examined. The PBG application inhibited the TP-evoked TSNO neuronal excitation, and this inhibition was completely blocked by co-application of a GABAA receptor antagonist, bicuculline. The results suggest that the activation of 5-HT3 receptors elicits GABA release in the TSNO.

Differential expression and localization of WNTs in an animal model of skin wound healing.

Wound healing is a dynamic process, and a variety of growth factors have a significant impact on the process. Although the WNT family has a multitude of effects on the state of various physiological pathways, the expression and role of WNT in wounded tissue have remained an enigma. The aim of this study was to assess the expression and localization of WNTs in a murine model of wound healing. RNA isolated from full-thickness cutaneous wounds from day 1 to day 21 postwounding were subjected to reverse transcription-polymerase chain reaction, and expression of WNT3, 4, 5a, and 10b were observed. Immunohistochemistry localized WNT10b to regenerating epithelial cells on day 1 and 3, and WNT4 on day 3 and 5. WNT4 also reacted with fibroblast-like cells beneath the epithelium. The cytoplasmic staining of beta-catenin, a WNT signaling molecule, in the epithelial cells indicates an activation of the WNT signaling pathway. Among target genes downstream of the pathway, matrix metalloproteinases (MMPs) degrade and remodel the extracellular matrix during wound healing. Gelatin zymography showed that MMP9 was expressed from day 1 to day 5. MMP-2 was continuously expressed, but maximally up-regulated at day 5. Activation of MMP-2 coincided with expression of membrane-type 1 MMP, suggesting an involvement of WNTs in this proteolytic cascade. Therefore, WNTs may contribute to the process of wound healing in a spatiotemporal manner.

Tooth-pulp-evoked rostral spinal trigeminal nucleus neuron activity is inhibited by conditioning sciatic nerve stimulation in the rat: possible role of 5-HT3 receptor mediated GABAergic inhibition.

The purpose of the present study was to determine whether modulation of the trigeminal spinal nucleus oralis (TSNO) neurons related to tooth-pulp (TP)-evoked jaw-opening reflex (JOR) after electrical stimulation of the sciatic nerve (SN) is mediated by the descending serotonergic (5-HT(3)) inhibitory system activated by inhibitory GABAergic interneurons. In 30 anesthetized rats, the activity of TSNO neurons (87.5%, 35/40) and all digastric muscle electromyograms (dEMG, n=30) in response to TP stimulation (at an intensity of 3.5 times the threshold for JOR) were inhibited by conditioning stimulation of the SN (5.0 mA x 0.5 ms, 1 Hz, conditioning-test intervals; 50 ms). The inhibitory effects were significantly attenuated after intravenous administration of the 5-HT(3) receptor antagonist ICS 205-930 (n=6). Using multibarrel electrodes, iontophoretic application of ICS 205-930 into the TSNO significantly reduced the SN stimulation-induced inhibition of TP-evoked TSNO neuronal excitation (n=6), and in the same neurons, iontophoretic application of the GABA(A) receptor antagonist bicuculline into the TSNO greatly inhibited their effect. On the other hand, we found the expression of 5-HT(3) receptor immunoreactive neurons in the TSNO. These results suggest that SN stimulation may activate the descending serotonergic (5-HT(3)) inhibitory system through activation of inhibitory GABAergic interneurons, which inhibit excitatory responses of the TSNO neurons to TP stimulation.

Electron probe micro-analysis of a contact probe after Er:YAG laser tooth ablation.

The purpose of this study was to investigate the contact probes of Er:YAG laser before and after tooth ablation. Three kinds of contact probe were prepared. The first was an unused probe (NE). The second was used to prepare 10 cervical cavities (KP). The third was a probe that was judged for an exchange by three dentists who had expertise with Er:YAG laser (EX). The surface observation and mapping analysis were performed. The contact surface of NE was a flat and smooth surface, only Si was observed. KP demonstrated an uneven surface, Si was observed throughout, with scattered indications of Ca and P. EX displayed regions of fracture along the edge and a surface exhibiting dissolved adherents in parts. It was suggested that micro-explosions have effects on not only the tooth substance, but also the contact surface of the probe.

Adhesion of Er:YAG laser-irradiated dentin and composite resins: application of various treatments on irradiated surface.

BACKGROUND AND OBJECTIVES: The investigation of adhesion between an Er:YAG laser-irradiated surface and composite resin is very important to ensure the best clinical results. The purpose of this investigation is to determine if the application of various treatments on Er:YAG laser-irradiated dentin surface affects the tensile bond strength between dentin and composite resins. STUDY DESIGN/MATERIALS AND METHODS: In this investigation, the application of phosphoric acid, ultrasonic scaler, air-scaler, and air-powder polisher were tested as techniques to increase the bond strength of composite resins to Er:YAG laser-irradiated dentin surface. RESULTS: The tensile bond strength of the air-powder polished group was highest, at 18.45 +/- 3.72 MPa, and the lowest value was that of the only laser-irradiated group, at 12.56 +/- 4.38 MPa. CONCLUSIONS: The bond strengths in treated with air-powder polished group and phosphoric acid etched group were significantly higher than that of the group in laser irradiation alone.