Frequency doubled neodymium:yttrium-aluminum-garnet and diode laser-activated power bleaching--pH, environmental scanning electron microscopy, and colorimetric in vitro evaluations.

Corrosiveness of enamel surfaces of Smartbleach, Opus White, Opalescense Xtra Boost and a gel containing titanium dioxide (TiO(2)) particles, activated either by a frequency doubled neodymium: yttrium-aluminum-garnet (Nd:YAG) laser (532 nm) or a diode laser (810 nm) was evaluated by environmental scanning electron microscopy (ESEM). Changes in teeth color shades and the pH were also evaluated. Each bleaching agent was laser activated for 30 s and removed after 1 min or 10 min. This procedure was repeated up to four times, the bleaching agent receiving a maximum application time of 40 min, with total irradiation times of 0.5 min to 2 min of laser activation. The results of the pH measurements showed that only Smartbleach was in the alkaline pH range, whereas the other three were acidic. The surface effects were unrelated to the pH of the bleaching agents. With the exception of Opus White, no severe alterations on the enamel surface were detected. Although short application times were chosen, improved changes in brightness of up to ten steps on the Vitapan classical shade guide were detected.

Measuring the angular dependent energy distribution of backscattered electrons at variable geometry.

An aluminium semisphere system with 120 points of entry and eight detection areas, assembled on a meridian covering 0.0026 steradian each, was put over a solid bulk sample (e.g., aluminium), which was mounted in the eucentric point so that the incident electron beam could be varied by a polar rotation of the sphere in steps of 11.25 degrees. The complete angular distribution of the backscattered electrons became available by a rotation in steps of 11.25 degrees azimuthally. For this particular setup, the signals from the detection areas as well as the signal from the rest of the semisphere were amplified by operational amplifiers (Burr-Brown OPA128LM). However the signal of the semisphere was not available at that time. Specimen current measurements made the total amount of electrons accessible, providing a possibility for normalization of the results and comparison with total backscattering coefficients. By use of counter voltage variable up to 10 kV inside the detection assembly, it was possible to measure an energy resolution of the backscattered electrons for each detection area at the same time. Details of the construction and calibration procedures, possible errors, and sources of systematic deviations as well as first test results are discussed.

[Qualitative analysis of the binding of fibrin in organic tissue (author's transl)]. / Qualitative Analyse der Bindung von Fibrin in organischem Gewebe.

The binding energy (EB) of oxygen, sulphur and nitrogen was determined in highly concentrated fibrin, collagen, liver parenchyma and muscle tissue using photoelectron spectrometry. Fibrin was mixed with the collagen, liver or muscle homogenisate, with or without substitution of clotting factor XIII or additional inhibiton of fibrinolysis and the EB was determined again. Changes in the binding energy arise from an alteration in chemical binding. The present investigation showed that fibrin builds up new linkages in liver parenchyma and in collagen using nitrogen bonds and, additionally via a sulphur bond. After addition of fibrin stabilizing factor a new chemical link appeared between fibrin and collagen again through a nitrogen bond and, additionally via a sulphur bond. The inhibition of fibrinolysis produced a new oxygen linkage in all the examined substances (fibrin-tissue).

In vitro irradiation of infected root canals with a diode laser: results of microbiologic, infrared spectrometric, and stain penetration examinations.

This study aimed to examine the suitability of the diode laser with a wavelength of 810 nm for reducing bacteria in root canals. Forty-four extracted, endodontically prepared teeth were inoculated with Escherichia coli and Streptococcus faecalis. No bacterial growth was observed when the teeth were irradiated at an output power of 4 W and a pulse rate of 10 milliseconds, with breaks of 10 milliseconds between the irradiations. Exposure time was five times 5 seconds. Infrared spectroscopic examinations revealed that irradiation at 4 W under even circling movements resulted in a maximum rise in temperature of 6 degrees C on the root surface. Stain penetration tests and scanning electron microscopic examinations revealed complete closure of the dentinal tubules on the irradiated root canal walls.

[The stress transmission of prefabricated root canal posts]. / Kraftübertragung von vorgefertigten Wurzelkanalstiften.

Photoelastic stress analyses were done with nine prefabricated endodontic posts under axial and diagonal (26 degrees) burden with 5, 10, 15, 20, 25 kg. Stress presented itself in form of interference fringes, which became visible under polarized light. The tapered, grooved pins (Mooser and Unimetric) caused fringes along the shaft and apical as well. They worked at higher stress like a wedge. Cylindrical pins (Para Post Unity 5, Radix-anchor) showed relative strong fringes predominantly at the top. Cylindrically tapered pins (Tenax, CM, Pivomatic) and a conical pin with flat thread and grooves (Exatec-S) caused a more favourable stress distribution and the fringes at the top were clearly slighter.

The impact of an erbium, chromium:yttrium-scandium-gallium-garnet laser with radial-firing tips on endodontic treatment.

Radial-firing tips should allow a more homogeneous laser irradiation of root canal walls. The aim of the study was to assess the effects of erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation in conjunction with those newly designed tips. The investigation comprised bacteriology, morphological evaluations and temperature measurements. Root canals were inoculated with two test strains and laser irradiated with power settings of 0.6 W and 0.9 W and a repetition rate of 20 Hz. Subsequently, the samples were subjected to microbiological evaluation. The morphological changes of the canal walls were assessed by scanning electron microscopy. To reveal possible thermal side effects, we carried out temperature measurements. The bacteriological evaluation revealed a decisive disinfectant effect. Scanning electron microscopy showed the homogeneous removal of smear layer from the root canal walls. The temperature rise at the root surface during the irradiation was moderate, yielding 1.3 degrees C for the 0.6 W setting and 1.6 degrees C for the 0.9 W setting. The investigations indicated that the Er,Cr:YSGG laser, in conjunction with radial-firing tips, is a suitable tool for the elimination of bacteria in root canals and for the removal of smear layer.

[Heavy metal deposits in pathologically modified hard tissues. Clinical and experimental studies]. / Schwermetallablagerungen in pathologisch veränderten Hartgeweben. Klinische und experimentelle Untersuchungen.

Various studies have shown a relationship to exist between toxic heavy metal accumulation and pathologic processes in various tissues. In the present study pathologic processes were found to be associated with an increase in the concentrations of various elements including Hg, Cd, Pb, Zn, Cu and Mn. Our results suggest the accumulation of toxic heavy metals and the increase in the Zn concentration to be a secondary phenomenon. If the tissue damage becomes irreversible, the zinc concentration drops, while toxic heavy metals continue to accumulate. consequently, zinc could be an indicator of the biological reactivity of tissues.

[Ionomeric vitreous cement for retrograde root filling]. / Glasionomerzement als retrogrades Wurzelfüllmaterial.

In an in vitro study the sealing properties of materials commonly used for retrograde filling of apicectomized teeth were investigated in extracted teeth and compared with those of ionomeric vitreous cement. Materials tested included: --Heat-sealed guttapercha; --Guttapercha + phosphate cement; --Amalgam; --Standardized ceramic pins (Ulm system); and --Ionomeric vitreous cement. Sealing was established by methylene blue perfusion. Seals produced by heat-sealed guttapercha, guttapercha + phosphate cement and non-gamma-2 amalgam were found to be inferior to those obtained with ionomeric vitreous cement and standardized aluminium oxide ceramic pins.

Characterization of microblasted and reactive ion etched surfaces on the commercially pure metals niobium, tantalum and titanium.

In surface-roughened metallic implant materials, the topography, chemistry and energy of the surfaces play an important role for the cell and tissue attachment. The highly reactive commercially pure metals niobium, tantalum and titanium were analysed after microblasting (with Al2O3 powder and consecutive shot-peening with ZrSiO2), and after additional reactive ion etching (RIE, with CF4). Scanning electron microscopy in combination with energy-dispersive X-ray analysis and surface roughness measurements showed, for all microblasted surfaces, a heterogeneous roughening (Ra about 0.7 microm), and a contamination with blasting particles. RIE resulted in a further roughening (Ra about 1.1 microm), and a total cleaning from contaminations, except for traces of aluminium. Determination of surface energy by dynamic contact angle measurements showed an increase in surface energy after microblasting, which further increased after RIE, most pronounced for commercially pure niobium. In conjunction with superior electrochemical properties, this makes niobium and tantalum promising candidates for implant purposes, at least equal to the generally used titanium.

Alternatives in enamel conditioning: a comparison of conventional and innovative methods.

When composite restorative materials are used, conditioning of the enamel surface is necessary to achieve adequate retention of the composite material. Aside from conventional acid etching, laser treatment and pretreatment with kinetic cavity preparation technique are available. In our study, we compared the different methods using scanning electron microscopy and measurements of tensile strength. The results obtained using both laser treatments of Nd:YAG and Er:YAG lasers and kinetic cavity preparation were comparable to those obtained with the acid etching technique.

The advantage of CO2-treated dental necks, in comparison with a standard method: results of an in vivo study.

Various methods are used for treatment of hypersensitive dental necks. They all aim to seal exposed dentinal tubules, which are open toward the oral cavity and transmit stimuli to the sensitive nerve endings of the tooth pulp. The main sealing materials are fluoride preparations, strontium chloride, and hydroxyapatite. However, these materials must be applied periodically to achieve permanent freedom from pain. Since the introduction of laser technology into dentistry, efforts have been made to treat dentine hypersensitivity with the laser. An in vitro study revealed that CO2 laser irradiation results in almost complete closure of the dentinal tubules in the dental neck region. In the present in vivo study, the efficacy of laser treatment was examined in 72 patients with dentine hypersensitivity and 72 control patients over a period of 12 weeks. When success was defined as complete freedom from pain, the success rate in the laser group was 94.5%; when marked pain relief was included in the definition of treatment success, 98.6% of the patients were treated successfully. Treatment of the control group with conventional dental neck fluoridation resulted in no marked improvement. Laser Doppler measurements of pulpal blood flow immediately before and after treatment revealed no effects of laser irradiation on pulpal blood flow. Dentine samples were obtained from the dental necks 6 weeks after laser treatment and examined with atomic absorption spectroscopy (AAS). Tin was present in the samples, which suggests that the combined laser treatment and fluoridation result in permanent integration of fluoride in the dentine surface.

The carbon dioxide laser as an aid in apicoectomy: an in vitro study.

OBJECTIVE: To achieve the required goal of optimally sealing the apical section and the root-canal when performing an apicoectomy, the authors decided to use the CO2 laser as an additional aid. SUMMARY BACKGROUND DATA: The CO2 laser has previously shown to have an excellent sealing effect on dentin surfaces. METHODS: In this in vitro study, the authors examined the effects of CO2 laser application in apicoectomies with the help of color penetration tests and scanning electron microscopic (SEM) examinations. Sections and root canals were irradiated with low power (0.5 W) in continuous wave mode for totally 20 sec. The thermal stress for the adjacent tissues attaching thereto is moderate as shown by infrared-spectroscopy. RESULTS: A comparison with nonirradiated samples revealed that CO2 laser irradiation reduced color penetration at the section to a minimum. Also, irradiation of the root-canal wall resulted in satisfactory sealing of the surface. These findings were supported by the results of the SEM examinations. CONCLUSIONS: CO2 laser treatment optimally prepares the tooth for final intraoperative filling because of sealing of the dentinal tubules, the resultant elimination of niches for bacteria and the sterilizing effect of the laser.

Treatment of periodontal pockets with a diode laser.

BACKGROUND AND OBJECTIVE: The aim of this study is to examine the long-term effect of diode laser therapy on periodontal pockets with regard to its bactericidal abilities and the improvement of periodontal condition. STUDY DESIGN/MATERIALS AND METHODS: Fifty patients were randomly subdivided into two groups (laser-group and control-group) and microbiologic samples were collected. There have been six appointments for 6 months following an exact treatment scheme. After evaluating periodontal indices (bleeding on probing, Quigley-Hein) including pocket depths and instruction of patients in oral hygiene and scaling therapy of all patients, the deepest pockets of each quadrant of the laser-group's patients were microbiologically examined. Afterwards, all teeth were treated with the diode laser. The control-group received the same treatment but instead of laser therapy were rinsed with H2O2. Each appointment also included a hygienic check-up. After 6 months the final values of the periodontal indices and further microbiologic samples were measured. The total bacterial count as well as specific bacteria, such as Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Porphyromonas gingivalis, were assessed semiquantitatively. RESULTS: The bacterial reduction with diode laser therapy was significantly better than in the control group. The index of bleeding on probing improved in 96.9% in the laser-group, whereas only 66.7% in the control group. Pocket depths could be more reduced in the laser group than in the control group. CONCLUSION: The diode laser reveals a bactericidal effect and helps to reduce inflammation in the periodontal pockets in addition to scaling. The diode laser therapy, in combination with scaling, supports healing of the periodontal pockets through eliminating bacteria.

The bactericidal effect of Nd:YAG, Ho:YAG, and Er:YAG laser irradiation in the root canal: an in vitro comparison.

OBJECTIVE: The aim of this study was to compare the antibacterial effectiveness of the Nd:YAG, the Ho:YAG, and the Er:YAG laser in infected root canals. SUMMARY BACKGROUND DATA: Lasers are gaining increasing importance in the field of endodontics. Numerous studies have shown the beneficial effects of laser treatment in disinfecting root canals. METHODS: In our in vitro experimental setup, 40 extracted and endodontically treated teeth were inoculated with a suspension of Escherichia coli and Enterococcus faecalis and then irradiated at standardized power settings. The disinfecting efficacy of each laser was proved by classical microbiological examination. RESULTS: This article highlights that all three lasers substantially decreased the bacterial population with only minimal differences in their microbicidal efficacy. At 1.5 W, the best results were obtained by the Er:YAG laser achieving a mean bacterial elimination of 99.64%, followed by the Nd:YAG laser (99.16%), and the Ho:YAG laser (99.05%). CONCLUSION: Our findings indicate that all three lasers act as strongly effective microbicides without causing unfavorable temperature rises at the settings used. They can thus be considered a valuable tool for root canal treatment.

Long-term effects of CO2 laser irradiation on treatment of hypersensitive dental necks: results of an in Vivo study.

OBJECTIVE: The present in vivo study was performed to examine the long-term effects of combined CO2 laser treatment and fluoridation on hypersensitive dental necks. SUMMARY BACKGROUND DATA: Attempts have been made to treat dental hypersensitivity by sealing exposed dentinal tubules, primarily using fluoride preparations, strontium chloride, and hydroxyapatite. However, these treatment methods have the disadvantage that the preparation is effective only for a limited period of time and must be applied repeatedly, at short intervals. The CO2 laser has been shown to have an excellent sealing effect on hypersensitive dentinal surfaces. METHODS: Test subjects suffering from dentinal hypersensitivity were recruited from the patients of the Department of Conservative Dentistry, School of Dentistry of the University of Vienna, Austria and treated with combined laser irradiation and fluoridation with stannous fluoride gel. The patients were followed up for a period of 18 months. In vivo examinations were supplemented by atomic absorption spectroscopy (AAS) of tiny dentin samples obtained from the dental necks 6 weeks and 18 months after laser treatment and by scanning electron microscopy (SEM). RESULTS: Compared to conventional fluoridation, combined laser irradiation and fluoridation was shown to be effective in the treatment of hypersensitive dental necks. When success was defined as complete freedom from pain, the success rate in the laser group was 96.5%. Furthermore, examinations of irradiated teeth under the scanning electron microscope still revealed complete closure of the dentinal tubules four and six months after laser treatment. AAS showed that tin was present in the samples, which indicates that combined laser treatment and fluoridation result in permanent integration of fluoride in the dentin surface. CONCLUSIONS: Based on these results, the CO2 laser can be recommended as an ideal tool for desensitization of dental necks.

Procedures for enamel and dentin conditioning: a comparison of conventional and innovative methods.

Composite materials have become an integral part of the wide range of filling materials currently available. Conditioning is necessary to achieve adequate bonding of the composite material to enamel and dentin. Normally, this is done by applying acid preparations to the dental surfaces. These acids have an etching effect that causes surface roughening. The increasing application of lasers in dentistry has introduced another possibility. Laser irradiation can cause roughening of enamel and dentin surfaces. Another interesting alternative is the so-called kinetic cavity preparation technique. This method also results in distinct surface roughening. The purpose of the present study, was to compare the described methods. Tensile bond strength tests and shear bond tests were carried out to examine the adhesion of a composite material to surfaces treated with these methods. Laser irradiation with certain devices and the air-abrasive technique yielded results similar to those with acid etching.