Replica-based inspection of enamel wear microfeatures.

BACKGROUND: Surface replication is a nondestructive evaluation technique applied in examining surface wear by recording surface irregularities, especially in conditions when surfaces of interest cannot be further manipulated to fit directly under a microscope to be examined. Enamel is the outermost protective layer of the human teeth and is constantly stressed by mastication forces which results in enamel wear. OBJECTIVE: To date, a procedure combining the clinical and microscopic examination of enamel surfaces is absent, which hinders the early diagnosis and comprehension of the wear process. METHODS: This study investigated the role of replication sheets in registering microscopic wear on human enamel surfaces by both negative and positive replication techniques. RESULTS: The sheets replicated wear features successfully. Sheets were compatible to use with multiple microscopes, with proper preparation, including high resolution microscopes such as the scanning electron microscope and transmitting electron microscope.

Fenretinide, Tocilizumab, and Reparixin Provide Multifaceted Disruption of Oral Squamous Cell Carcinoma Stem Cell Properties: Implications for Tertiary Chemoprevention.

Locoregional recurrence of oral squamous cell carcinoma (OSCC) dramatically reduces patient survival. Further, as many OSCC recurrences are inoperable, radiotherapy and chemotherapy with or without biological adjuncts are the remaining treatment options. Although the tumors may initially respond, radiotherapy- and chemotherapy-resistant cancer stem cells (CSC) can readily repopulate OSCC tumors. Currently, following the initial OSCC treatment, patients are closely monitored until a recurrence or a second primary is detected. Identification of agents with complementary mechanisms to suppress CSC tumorigenic functions could change this passive approach. The goals of this study were twofold: (1) develop and validate CSC-enriched (CSCE) OSCC cell lines and (2) identify chemopreventive agents that obstruct multiple CSCE protumorigenic pathways. CSCE cultures, which were created by paclitaxel treatment followed by three tumorsphere passes, demonstrated CSC characteristics, including increased expression of stem cell and inflammatory genes, increased aldehyde dehydrogenase (ALDH) activity, and enhanced in vitro/in vivo proliferation and invasion. Three chemopreventives, fenretinide, tocilizumab, and reparixin, were selected due to their distinct and complementary CSC-disruptive mechanisms. The CSCE selection process modulated the cells' intermediate filaments resulting in an epithelial-predominant (enhanced cytokeratin, proliferation, IL6 release) line and a mesenchymal-predominant (upregulated vimentin, invasive, IL8 release) line. Our results confirm that 4HPR binds with appreciably higher affinity than Wnt at the Frizzled binding site and significantly inhibits CSC-enabling Wnt-ß-catenin downstream signaling. Notably, combination fenretinide-tocilizumab-reparixin treatment significantly suppressed IL6 and IL8 release, stem cell gene expression, and invasion in these diverse CSCE populations. These promising multiagent in vitro data provide the basis for our upcoming in vivo CSCE tertiary chemoprevention studies.

The application of cellulose acetate replication sheets in enamel wear investigations.

Surface replication is a nondestructive evaluation technique applied in examining surfaces' cracks/wear. This is quite valuable when the surface of interest cannot be further manipulated by cutting or polishing to fit directly under a microscope. Replication by acetate sheets is one of the techniques applied in industrial, metallographic and anthropological wear/examination. Enamel is the outermost protective layer of human teeth and is subjected to mechanical stresses due to the masticatory function; thus, wear is inevitable in human teeth. This relatively inert hard tissue has been reported to possess some properties of both metals and glasses due to its unique delicate microstructure. This study investigated the applicability of replication sheets in registering wear induced features on human enamel surfaces. The sheets replicated wear features successfully with compatibility to use with multiple microscopes. Acetate sheets have a potential in enamel wear replication.

Peri-implant mucosal dehiscence coverage with a modified semilunar coronary positioned flap in posterior maxilla: a case report.

Soft tissue dehiscence around dental implant has frequently been observed and it may lead to poor oral hygiene, especially around crowns that exhibit contours with prominent convexity. The present case demonstrates a peri-implant mucosal dehiscence coverage with modified semilunar coronary positioned flap (CPF) in #15 and 16. A semilunar partial-thickness incision was performed 7-10 mm apical from the facial gingival margin. Then, intrasulcular partial-thickness incision was tunneled to the semilunar incision. The tunnel preparation was extended interproximally under each papilla due to improvement of flap extension. Then, the tunneled flap was coronary positioned with a coronary-anchored suturing technique. Sub-epithelial connective tissue graft (SCTG) from the palate was inserted from the semilunar incision to the inside of the coronary positioned flap and sutured to stabilize the SCTG and supplemental site. Significant mucosal gain was achieved without any complication. The soft tissue volume was maintained at 9 months post-surgery, and the cleanability was improved. This technique has the potential in improving the graft survival and mucosa gain around implants.

Palatal window osteotomy technique improves maxillary sinus augmentation in previously insufficient augmentation case.

INTRODUCTION: Perforation of the Schneiderian membrane is the most common complication in sinus floor augmentation (SFA). When volume of grafting is qualified to prevent enlargement of the membrane perforation, lack of bone volume may occur in optimal site. CASE PRESENTATION: SFA was performed in sites #24 to 26 in a 63-year-old male. However, a 10-mm size perforation of the Schneiderian membrane occurred in site #26. Although the sinus cavity was grafted with deproteinized bovine bone mineral (DBBM) after repair of membrane perforation, insufficient bone formation was observed on palatal and distal aspects of site #26 at 5 months after SFA. Although additional SFA was required for implant placement, it seemed to be difficult to elevate the membrane by a conventional lateral approach in the palatal aspect of the sinus floor (site #26). Considering the configuration of new bone formation, it was decided to perform the palatal antrostomy approach. The Schneiderian membrane was elevated without perforation, and the sinus cavity was grafted with DBBM mixed with venous blood. Two 12-mm long, 4.1-mm diameter implants were placed in sites #14 and 16. Four months after implant placement, abutment-connection surgery was successfully performed. The radiographic image indicated improved radiopacity, without obvious bone resorption in site #26. CONCLUSION: The palatal window osteotomy technique could be considered as an alternative method for augmentation of maxillary sinus in cases where difficulty is encountered to elevate a membrane by a conventional approach (e.g., in cases in which buccal bone height is long).

Microbicidal activities of low frequency atmospheric pressure plasma jets on oral pathogens.

Research using low frequency atmospheric pressure plasma jets (LF jet) is becoming increasingly more common. We carried out experiments to evaluate the sterilizing effects of this technology on oral pathogenic microorganisms (S.mutans, C.albicans and E. faecalis) and to determine its potential for clinical application. We performed the direct exposure test on a solid surface, indirect exposure test on a liquid phase, and ROS (reactive oxygen species) inhibitory test. The results showed the LF jet had microbicidal effects on oral pathogens, and that the ROS influenced this sterilization effect. The experiments of this study revealed that LF jet had a sterilizing effect on oral pathogenic microorganisms present in both the solid and liquid phases. The sterilizing mechanism was considered to be related to the effect of superoxide anion radicals. These results indicate that LF jets may represent a novel technology that can be applied to the field of clinical dentistry.

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

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

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.

Thermographical and morphological studies of Er,Cr:YSGG laser irradiation on root canal walls.

OBJECTIVE: This study was performed to investigate the temperature rises on root surfaces and morphological changes on root canal walls of extracted human teeth after irradiation by erbium, chromium: yttrium, scandium, gallium, garnet (Er, Cr:YSGG) laser and to evaluate the efficiency in removing smear layer and debris from the prepared root canal walls in vitro. BACKGROUND DATA: No report on Er, Cr:YSGG laser effects under various conditions and specific tips for endodontic treatments has been reported. METHODS: Sixty extracted human teeth with single and straight root were used in this study. The teeth were prepared at 1 mm short of the apical foramen by a conventional technique using K-files. Fifty-four specimens were irradiated by Er, Cr:YSGG laser at the output powers of 2 W, 3 W, and 5 W for 7 sec with three fiber tips (200, 320, and 400 microm diameters). Temperature changes were recorded thermographically. All teeth were examined by light microscopy or scanning electron microscopy (SEM). RESULTS: Thermographic study showed that the average temperature rises on root surfaces were less than 8 degrees C. Observation by light microscopy revealed the ablation at the apical stop, and that by SEM indicated that laser irradiation at 5 W using a fiber tip with 400 microm diameter was efficient for removing smear layer and debris without carbonization or melting. CONCLUSIONS: The results of this study suggested that the temperature rises during Er, Cr:YSGG laser irradiation at the parameters used in this study are minimal to cause the damage on periodontal and bone tissues. Moreover, it was suggested that it is efficient to remove smear layer and debris without causing any carbonization and melting.

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.

Clinical application of Er:YAG laser for cavity preparation in children.

OBJECTIVE: The purpose of this study was to determine the clinical usefulness of Er:YAG laser for cavity preparation in children. BACKGROUND DATA: The conventional methods for cavity preparation instill fear and discomfort in pediatric patients. The Er:YAG laser is a new tool developed for cavity preparation; however, there are few reports of its clinical application. MATERIALS AND METHODS: A clinical evaluation using an Er:YAG laser was carried out using 32 subjects (with 16 deciduous and 19 permanent teeth) with ages ranging from 2 to 12 years. All cavities were restored with light-cured composite resin following the application of bonding agent, but without acid etching or primer conditioning. RESULTS: During laser treatment, the pediatric patients were very cooperative and hardly complained of any pain, and no tooth showed undesirable effects during the 3-year period of observation. CONCLUSION: It can be concluded from the results of this study that an Er:YAG laser would be a useful alternative method for cavity preparation for composite resin restoration in children.

Prevention of dental caries in partially erupted permanent teeth with a CO2 laser.

OBJECTIVE: The purpose of this study was to determine the effect of CO2 laser irradiation in the prevention of pit and fissure caries in immature molars with covering opercula. BACKGROUND DATA: In pediatric dentistry, it is not unusual to find partially erupted immature permanent teeth, especially with opercula. Conventional dental caries prevention is not effective in these cases because of the immaturity of tooth substance and the presence of the opercula, which accumulate a substantial amount of plaque. MATERIALS AND METHODS: The CO2 laser was used on 22 immature erupting molars with opercula. In each case, we first cut the operculum with a CO2 laser in a 2- or 3-watt continuous mode. Then, the occlusal surface was irradiated spot by spot along the pits and fissures of the molar using a CO2 laser in a 2-watt pulsed mode with 0.2 sec of irradiation time (average power, 0.3 watt; pulse width, 10 msec; repetition time, 15 Hz; energy density, 15 J/cm2). Each of the studied teeth was clinically examined for dental caries for 3 years. RESULTS: It took less than 2 min to cut the operculum, and there was no bleeding. The irradiation imparted acid resistance to the teeth without any discomfort to the patients. The patients did not complain of any pain after the procedure. Only two of the studied teeth developed dental caries during the observation period. CONCLUSION: We conclude that a CO2 laser might be an effective mode of treatment in the prevention of pit and fissure caries in partially erupted permanent molars covered with opercula.

[Application of a CO2 laser for oral soft tissue surgery in children in Sri Lanka--introduction of a laser through activities of aid to a developing country].

The objective of this study was to clarify the effect of CO2 laser irradiation on oral tissue problems in children in Sri Lanka, through the activities of aid to a developing country by the Japan International Cooperation Agency. This study took about six months, during two times periods: from November 2000 to February 2001, and from July 2001 to October 2001, in the paedodontic clinic of the Faculty of Dental Science, University of Peradeniya, in Sri Lanka. A CO2 laser was used on 48 subjects (51 cases), aged between 1 and 15 years, having main indications for labial frenectomy, frenectomy in ankyloglossia, and excision of mucocele. The results indicated that the CO2 laser had the following advantages. 1. Soft tissue cutting was efficient, with no bleeding, giving a clear operative field during operation. 2. There was no need to use sutures. 3. The surgery itself was simple and less time-consuming. Hence, there was no need for general anesthesia for such cases as tongue tie operation in small children. 4. There was no postsurgical infection. As a result, there was no need for analgesics or antibiotics, as post-surgical pain and infection were prevented. 5. Wound contraction and scarring were decreased or eliminated. Considering the above advantages, the use of a CO2 laser proved to be very safe and effective for soft tissue surgery, especially for children in developing countries such as Sri Lanka.