[Single file endodontic treatment: a new era?].

Root canal shaping is one of the key stages of endodontic treatment, when performed properly, it is a predictive factor for the outcome of the treatment. It is critical for an adequate disinfection, which is more effective at the completion of a proper shaping procedure. The introduction of NiTi instruments into endodontic greatly improved the root canal shaping and decreased the time required for a full mechanical preparation. Over the last 2 decades, numerous attempts have been made to further improve the procedure with a wide range of rotary NiTi endodontic file systems. All these systems require several subsequent files. Recently, three different concepts of single-file systems have been introduced: 1. The single file reciprocating working motion: it consists of a reciprocating counterclockwise and a clockwise motion. This reciprocal motion reduces torsional loads thus, allows safer instrumentation with less working time. 2. Single-file instrumentation using full 360 degrees rotational movement to be used in a full clockwise rotation. Some of these files also have an Anti Breakage Control (ABC) which protects from catastrophic procedural malfunction by unwinding of these file before breakage. 3. The Self-Adjusting File (SAF) which is a thin-walled, pointed cylinder, hollow nickel-titanium endodontic file that is elastically compressible into a root canal that has been previously negotiated using a #20 hand file and can widened inside it, facilitating removal of debris and dentin from the canal wall. The file conforms to the canal shape and permits irrigant flow through the file. The SAF works in a combined vibrating and partial rotational motions, and circumferentially simultaneously enlarging and irrigating the canal. The objectives of these new approaches is to reduce the working time and cost and improve safety of the shaping procedure, and suggest to have a lower procedural errors incidents. Few studies, conducted in the recent years, using these new instruments demonstrated an excellent shaping and centering ability of these new systems. They produce smooth tapered canal preparations with reproducible results, even when performed by less experienced practitioners. As mentioned above, these new techniques appeared to be promising, but further fundamental clinical and laboratory studies are needed to confirm their abilities.

The use of the erbium yttrium aluminium garnet (2,940 nm) in a laser-assisted apicectomy procedure.

If conventional endodontic treatment is not possible or not successful, apical endodontic surgery may be indicated. New techniques, materials and technologies have been used to increase the already high success rate of root canal treatment. The purpose of this article is to describe the use of the Erbium:YAG (2,940 nm) laser in treatment of apicectomy as a central tool, with the advantages of enhanced patient comfort, better bactericidal and decontamination effects.

Acid-etched and erbium:yttrium aluminium garnet laser-treated enamel for fissure sealants: a comparison of microleakage.

OBJECTIVES: A pilot study aimed to compare the microleakage of pit and fissure sealants in acid-etched and Erbium:Yttrium Aluminium Garnet (Er:YAG)-treated enamel. METHODS: Forty permanent noncarious young molars and premolars, which were extracted for orthodontic reasons, were selected. The teeth were divided into four groups, with five molars and five premolars in each group. The groups were treated as follows: (1) group A--laser irradiation of the enamel of the occlusal surface without contact and in scanning mode was carried out using an Er:YAG laser, placement of sealant material, light curing, and thermocycling between 6 degrees and 55 degrees C; (2) group B--the same as group A, but with no thermocycling; (3) group C--acid etching of the enamel surface, placement of sealant material, light curing and thermocycling; and (4) group D--the same as group C, but with no thermocycling. After being immersed in 1% methylene blue solution, all teeth were sectioned in the mesio-distal dimension into four slices. Images of the slices were then scanned to a Macintosh G3 computer and examined for marginal leakage. Leakage was measured by the degree of dye penetration. Three independent examiners evaluated the dye penetration. RESULTS: No penetration of dye material was observed in any of the slices in any of the four groups by any of the examiners. CONCLUSIONS: No difference in microleakage was seen between lasing or acid etching, and therefore, the results of the present study would suggest that the technique may be efficacious.

[New treatment protocols for avulsed teeth].

Traumatized teeth present a clinical challenge with regard to their diagnosis, treatment plan and prognosis. The injuries to the permanent dentition include crown and root fractures, subluxations, luxations and tooth avulsion. Common complications are pulp necrosis, periapical pathosis and root resorption. This article will describe new clinical modalities for the treatment of avulsed teeth and discuss the rational for their use.

[Platelet rich plasma (PRP) as adjuvant tool for bone augmentation].

New bone formation requires sufficient number of osteogenic progenitors capable of forming the bone desired. The site of engraftment must be filled with a matrix that facilitates attachment, migration and differentiation of osteoblastic progenitors. It is also necessary that the cells receive stimuli by growth factors that allow them to progress toward a bone phenotype. Another critical step in new tissue formation is the construction of new blood vessels--angiogenesis. Platelets contain growth factors that induce osteoinductive stimuli and accelerate angiogenesis. One strategy for harnessing this benefit is to apply platelet rich plasma (PRP) to bone graft site. The present article review platelets and growth factors physiology. We discuss the interaction between growth factors, thrombin and cells that form bone and blood vessels: osteoblasts, mesenchimal stem cells and endothelial cells. Methods and defaults of PRP preparation and safety issues are presented. The knowledge of platelet physiology and the mechanism by which growth factors effect cell proliferation and differentiation allow the dental surgeon to properly use this treatment modality and to achieve the ultimate goal of durable and effectively functioning bone.

Apex locators: update and prospects for the future.

The accuracy of working length determination in root canal treatment plays a crucial role in the treatment and prevention of periapical disease. Since the introduction of the first apex locator by Sunada in 1961, new and more accurate devices have been developed. Electronic apex locators reduce the number of radiographs required and may detect root canal perforations and fractures. Third and fourth generation apex locators can operate in the presence of intact or necrotic tissue, blood, inflammatory exudates, and various irrigants. The Raypex 4 and the Apex NRG novel apex locators are discussed in detail.

[Lasers in dentistry. Part A--Development, characteristics, structure, principles of operation and types of lasers].

Laser technology is developing very quickly. New Lasers with a wide range of characteristics are available today and are being used in the various fields of dentistry. The search for new devices and technologies for dental procedures was always challenging and in the last two decades much experience and knowledge has been gained. The purpose of this series of articles published in the journal of the Israel Dental Association in three parts is to present the Israeli dentist a comprehensive and contemporary overview which will assist him in understanding the potential of the use of laser technology for clinical applications in dentistry. The first part will describe the history and development of lasers in dentistry, the characteristics and structure of lasers as well as their principles of operation. A description of the different types of lasers used today in dentistry will be presented in the first part. The second part will describe the interaction of lasers with biological tissues and their effect on the soft and hard tissues of the oral cavity as well as on the dental pulp. Laser safety in the dental practice will also be discussed. The third part will focus on clinical applications of Lasers in Dentistry: pits and fissures sealing, dentin desensitization, cavity preparations, composite curing, surgical procedures and tooth whitening. Current status of using lasers in periodontics, endodontics and dental implantology will be discussed and possible future clinical applications of lasers in dentistry will be presented.

[Lasers in dentistry. Part B--Interaction with biological tissues and the effect on the soft tissues of the oral cavity, the hard tissues of the tooth and the dental pulp].

The interaction of laser energy with target tissue is mainly determined by two non operator-dependent factors: the specific wavelength of the laser and the optical properties of the target tissues. Power density, energy density, pulse repetition rate, pulse duration and the mode of energy transferring to the tissue are dictated by the clinician. Combination of these factors enables to control optimal response for the clinical application. Four responses are described when the laser beam hits the target tissue: reflection, absorption, transmission and scattering. Three main mechanisms of interaction between the laser and the biological tissues exist: photothermic, photoacoustic and photochemical. The effect of lasers on the soft tissues of the oral cavity is based on transformation of light energy into thermal energy which, in turn heats the target tissue to produce the desirable effect. In comparison to the scalpel used in surgical procedures, the laser beam is characterized by tissue natural sterility and by minimum bleeding during the surgical procedures due to blood vessels welding. The various effects achieved by the temperature elevation during the laser application on the soft tissue are: I. coagulation and hemostasis II. tissue sterilization III. tissue welding IV. incision and excision V. ablation and vaporization Ablation and melting are the two basic modalities by which the effect of lasers on the hard tissues of the tooth is produced. When discussing the effect of laser on dental hard tissues, the energy absorption in the hydroxyapatite plays a major role in addition to its absorption in water. When laser energy is absorbed in the water of the hard tissues, a rapid volume expansion of the evaporating water occurs as a result of a substantial temperature elevation in the interaction site. Microexplosions are produced causing hard tissue disintegration. If pulp temperatures are raised beyond 5 degrees C level, damage to the dental pulp is irreversible. Histologically, after laser ablation, presence of odontoblastic nuclei is important. Consistency and composition of the intracellular tissue is another factor influencing cell viability. If heat is intensive and exists for an extended time, the consistency of the intracellular ground substance may not be preserved. Accordingly, the application of excessive energy densities has been shown to result in significant damage to pulp tissue and in particular to odontoblasts. Studies showed that the use of Er:YAG laser to treat dental hard tissues is both safe and effective for caries removal, cavity preparation and enamel etching.

Effect of gutta-percha solvents on surface microhardness of IRM fillings.

Eighty identical samples of IRM were prepared and embedded in acrylic resin. The samples were polished, rinsed, and divided into experimental groups and controls, 10 specimens each. Each experimental group was treated for 1 or 5 min with one of the following gutta-percha solvents: chloroform, xylene, or halothane. Sterile saline was used as a control. Treatment consisted of pipetting each solvent onto the external IRM surface. The specimens were then sealed in plastic assay tubes for the corresponding exposure periods. At each time period, surface microhardness of the samples was measured using a mini-load hardness tester with a 500 g load for 20 s. It was found that xylene and halothane caused significant reduction in surface microhardness of IRM after 5 min (p < 0.01). Chloroform caused significant reduction in surface microhardness of IRM after 1 min of treatment (p < 0.01). Chloroform caused total dissolution after 5 min of treatment. Saline caused only minor and nonsignificant changes in surface microhardness of IRM.

Bacterial leakage versus dye leakage in obturated root canals.

AIM: The aim of this study was to compare in vitro bacterial and dye leakage tests, commonly used to determine the seal of root canal fillings. METHODOLOGY: Ninety-six single-rooted teeth had their crowns removed at the cemento-enamel junction and their roots instrumented to ISO size 60 within 1 mm of the apex. Three groups of 30 roots were obturated by lateral condensation using gutta-percha and one or other of the sealers. AH26, Ketac Endo, or Roth's 801 sealer. Three roots were used as negative controls and three roots as positive controls. The roots were then exposed at their coronal end first for 38 days to soy broth containing Staphylococcus epidermidis and thereafter for 48 h to basic fuchsin. Bacterial leakage was recorded when the challenging organism could be recovered from the apical end. Dye leakage was checked by microscopy of transverse sections of the apical tip at the end of the experiment. RESULTS: For the bacterial experiment, there was no significant difference amongst the three sealer groups. The dye experiment showed significantly greater leakage in the AH26 compared to the Ketac Endo group. No correlation between the results of the two tests could be seen. CONCLUSIONS: The results of this study suggest that the molecular size of the penetrating agent may not be the relevant parameter when attempting to determine an appropriate test for the sealability of root canal fillings.

Effect of chloroform, xylene, and halothane on enamel and dentin microhardness of human teeth.

OBJECTIVE: The purpose of this study was to assess in vitro the effect of commonly used gutta-percha solvents on the microhardness of human enamel and dentin. STUDY DESIGN: Crowns of human teeth were cut and treated with chloroform, xylene, and halothane. Treatment consisted of exposing the specimens for 5 or 15 minutes to the test solvents. Acid-treated and saline-treated specimens served as controls. After each treatment period, the specimens were rinsed, dried, and prepared for Vicker's microhardness analysis. Vicker's microhardness values for each specimen were recorded before and after treatment, and the differences were statistically compared. RESULTS: A statistically significant decrease in enamel and dentin microhardness was found in most solvent-treated groups; the amount of the decrease was directly related to the exposure time. CONCLUSIONS: Chloroform, xylene, and halothane may cause a significant softening effect on both enamel and dentin. This softening is already apparent after 5 minutes of treatment.

Dental anxiety among patients undergoing endodontic treatment.

The purpose of this study was to evaluate the dental anxiety expressed among patients undergoing endodontic treatment with respect to some social and dental parameters. The dental records of 98 patients, 42 men and 56 women who were referred for root canal treatment to an endodontist, were examined. Patients completed a Dental Anxiety Scale (DAS). Dental experience, time of last visit to the dentist, and symptoms of tooth were recorded. The mean DAS scores were higher than scores reported in other countries (9.4 +/- 3.3). Women demonstrated higher dental anxiety than men. Patients with higher education demonstrated lower dental anxiety. No difference was found between patients experienced in endodontic treatment and those who were not, patients who suffered previous pain in the treated tooth and patients who did not. Women in their mid-thirties to mid-forties and men in their twenties expressed the highest DAS scores.

Endodontic therapy for a fused mandibular molar.

Variations in tooth morphology present a clinical challenge when endodontic treatment is required. A case of conservative endodontic therapy for a fused mandibular second and third molar is presented.

Pulpal response to cavity preparation with the Er:YAG and Mark III free electron lasers.

OBJECTIVE: The purpose of this investigation was to evaluate the pulp response to class V cavity preparation with the use of the Er:YAG laser and free electron laser. STUDY DESIGN: Class V cavities were prepared in 133 teeth of four beagle dogs by one of three methods: (1) Er:YAG laser, (2) free electron laser, (3) high-speed handpiece. Treatment occurred at 1 hour, 1 day, 7 days, and 28 days. The teeth were removed and the pulp evaluated. Histologically, the data were evaluated with Mantel-Haenszel analysis. RESULTS: The Er:YAG laser, free electron laser, and handpiece treatment groups resulted in specimens with normal or mild pulp reactions in 36, 46, and 42 teeth, respectively; moderate or severe reactions were observed in 7, 1, and 1 teeth, respectively. No statistically significant difference in the pulp response to the three treatment modalities was observed. CONCLUSION: The pulp response to Er:YAG laser and free electron laser application would appear to be similar to the response from high-speed handpiece application.

Effect of carbamide peroxide and hydrogen peroxide on the surface morphology and zinc oxide levels of IRM fillings.

The effect of 10% carbamide peroxide or 10% hydrogen peroxide on the surface morphology and zinc oxide levels of IRM fillings was tested. Ninety IRM samples were treated with either 10% carbamide peroxide, 10% hydrogen peroxide or phosphate buffer which served as control. Treatment consisted of placing the samples in a dry incubator at 37 degrees C for 1, 3 or 7 days. At each time point, the samples were removed from the test solutions, dried and prepared for surface scanning electron microscopy and energy dispersive spectrometric analysis. After 3 days, 10% carbamide peroxide significantly reduced the zinc oxide levels as compared to the 10% hydrogen peroxide group (<0.01) and the controls (p<0.01). 10% hydrogen peroxide reduced the zinc oxide levels similarly to the control. No significant changes in the zinc oxide levels were found between 3 and 7 days in any of the groups tested. Microscopy examination of the carbamide peroxide group revealed granular surface with well defined crystalline areas. In the hydrogen peroxide group, numerous cracks with multiple sun burst-like areas were found. At the macroscopic level, the samples of this group appeared cracked and more swollen, as compared to controls and samples treated with carbamide peroxide. In conclusion, both 10% carbamide peroxide and 10% hydrogen peroxide altered the surface morphology and the zinc oxide levels of IRM fillings, but their modes of action differed.

Nd:YAG laser irradiation in root canal disinfection.

The purpose of this study was to assess the efficacy of Nd:YAG laser irradiation in disinfecting the root canal system. Seventy-five teeth were uniformly instrumented and sterilized, and their root canals were infected for 60 min with an overnight culture of Enterococcus faecalis in Tryptic Soy Broth. The teeth were divided into 6 groups: 1--non-infected controls; 2--infected controls; 3--infected, laser treated; 4--infected, laser dummy (dye only); 5--infected, laser dummy (dye and air-water spray); 6--infected, NaOCl-treated (reference group). After treatment, the root canals were dried and dentinal shavings removed for a post-treatment culture. Quantitative analysis of bacteria surviving the various treatments were performed and the bacterial counts for each group were compared. SEM analysis of teeth split longitudinally was used to illustrate the effect of treatment on the smear layer and on surface bacteria. Nd:YAG laser irradiation (group 3) significantly reduced the number of bacteria while NaOCl irrigation (group 6) effectively disinfected the canals.

Short vs. long-term calcium hydroxide treatment of established inflammatory root resorption in replanted dog teeth.

This study examined, histologically, the healing of intentionally produced inflammatory root resorption of replanted teeth in beagle dogs, treated with short- or long-term placement of calcium hydroxide. Thirty beagle dog incisors were randomly divided into four groups. In group 1 (negative control), uninfected incisors were extracted, the roots were longitudinally grooved and the teeth were replanted within 2 min. In group 2 the root canals were artificially infected followed by extraction, longitudinal grooving, and replantation as in group 1. Radiographs were taken biweekly and at the first signs of inflammatory root resorption or at 4 weeks, the root canals were fully instrumented and medicated with calcium hydroxide. In group 2, the root canals were permanently obturated with gutta-percha and sealer after 1 week of calcium hydroxide. The teeth in group 3 were treated as described in group 2 but after 1 wk the calcium hydroxide dressing was repacked for the duration of the study. In group 4 (positive control) the teeth were treated as described in groups 2 and 3 but no endodontic treatment was performed. Twelve weeks after the initiation of the endodontic treatment, sacrifice and histological preparation were carried out. In group 1, complete cemental repair was seen in all teeth. In group 2, five of ten teeth showed complete cemental repair whereas in group 3 complete cemental repair was seen in nine of ten teeth. None of the teeth in group 4 showed cemental repair. It was concluded that long-term may be more effective than short-term calcium hydroxide treatment of established inflammatory root resorption.

Efficacy of XeCl 308-nm excimer laser in reducing dye penetration through coronal dentinal tubules.

The efficacy of XeCl excimer laser irradiation in reducing dye penetration through human coronal dentinal tubules was studied. The roots of 20 freshly extracted human molars were resected, and the apical aspect of the crowns was ground until the pulp chamber was completely exposed. Following total removal of the pulp chamber and further grinding of the occlusal and apical surfaces up to the intact dentin, the teeth were randomly divided into experimental and control groups of 10 each. The teeth in the experimental group were completely coated with nail polish and then irradiated with XeCl 308-nm excimer laser at a fluence of 0.7 J/cm2 to form an elliptical lased area. The teeth in the control group were also coated with nail polish, but with a similar elliptical spot of exposed dentin corresponding to the irradiated spot created in the lased teeth left uncoated. All specimens were placed in 0.5% methylene blue dye for 48 h, rinsed, and air-dried. The specimens were then ground to reach the experimental area in order and photographed. The total area of penetrated dye was determined by three independent evaluators and then measured with a computerized planimeter. The mean total areas (mm2) measured in the lased specimens were significantly smaller than those in the controls (p = 0.012).

Efficacy of argon laser irradiation in removing intracanal debris.

Endodontic instrumentation, irrigation, or intracanal medication are unable to totally remove intracanal debris. The purpose of this study was to evaluate the efficacy of argon laser irradiation in removing debris from the root canal system. After cleaning and shaping, 12 single rooted teeth were randomly divided into two groups of six teeth each. The first group, which served as the control, was not lased. In the second group, a 300 microns argon laser fiber optic was introduced into the root canal of each tooth, to its working length. Fifteen pulses of 100 msec each with an energy of 2 watts were delivered for 5 seconds at the apex. The lasing procedure was repeated at 1 mm intervals along the root canal, and the fiber tip was retrieved from the apex to the orifice. Computerized scanning electron microscopy analysis revealed that the amount of debris in the lased group was significantly lower than that in the control (p = 0.0001). On the basis of these results, it appeared that intracanal argon laser irradiation was an efficient mean of removing intracanal debris.

Retreatment efficacy 3 months after obturation using glass ionomer cement, zinc oxide-eugenol, and epoxy resin sealers.

The efficacy of ultrasonic retreatment, 3 months after obturation, in conjunction with Ketac-Endo, Roth's 801, and AH26 sealers was evaluated. Seventy-two root canals were prepared and obturated with gutta-percha and one of the sealers mentioned above. After 90 days, the canals were retreated by an ultrasonic technique and the retreatment time was recorded. The roots were split and the amount of debris that remained on the canal walls in three separate levels was scored. Compared by one-way and two-way analysis of variance, the mean scores of remaining debris at the different canal levels for the three sealer groups, as well as for each group, were not significantly different. The only significant difference was found in retreatment time for which Ketac-Endo was significantly slower to retreat than the other two sealers (p < 0.002). Thus, the results of this study showed that the amount of debris remaining on the root canal walls following retreatment 3 months after obturation is similar for Ketac-Endo, Roth's 801, and AH26 sealers, but the retreatment time for Ketac-Endo is significantly longer.