Friedrich Lampert

Bactericidal Effect of a 980-nm Diode Laser in the Root Canal Wall Dentin of Bovine Teeth

OBJECTIVE The aim of this in vitro study was to investigate the antibacterial depth effect of continuous wave laser irradiation with a wavelength of 980 nm in the root canal wall dentin of bovine teeth. BACKGROUND DATA The long-term success of an endodontic therapy often fails due to remaining bacteria in the root canal or dentin tubules, which cannot be sufficiently eliminated through the classical root canal preparation technique nor through rinsing solutions. MATERIALS AND METHODS A total of 102 slices of bovine root dentin of different thicknesses (100, 300 and 500 micro m) were prepared. The samples were inoculated from one side with 5 micro L of an enterococcus faecalis suspension of defined concentration. Four slices per slice thickness served as a control group; the rest of the 30 slices per thickness were subjected to laser irradiation - 10 each of these slices were irradiated with distal outputs of 1.75, 2.3, and 2.8 Watts (W). After drying them for 30 sec, the back of the inoculated dentin slice was irradiated for 32 seconds with a 200- micro m fiber optical waveguide under constant movement of the fibers. The remaining bacteria were then detached in NaCl under vibration. The eluate produced by this was - taking account of the degree of dilution - plated out on sheep blood agar plates. After 24 h of incubation, the grown bacterial colonies were able to be counted out and evaluated. By doing so, they were compared with the non-irradiated, but otherwise identically treated control group. RESULTS With a slice thickness of 100 micro m, the 980-nm diode laser achieved a maximum bacterial reduction of 95% at 1.75 W, 96% at 2.3 W, and 97% at 2.8 W. With a slice thickness of 300 micro m, a maximum of 77% of the bacteria was destroyed at 1.75 W, 87% at 2.3 W, and 89% at 2.8 W. The maximum bacterial reduction with a slice thickness of 500 micro m was 57% at 1.75 W, 66% at 2.3 W, and 86% at 2.8 W. CONCLUSION The results of this research show that the 980-nm diode laser can eliminate bacteria that have immigrated deep into the dentin, thus being able to increase the success rate in endodontic therapy.

Influence of the water content in dental enamel and dentin on ablation with erbium YAG and erbium YSGG lasers

The theory of the ablation of dental hard tissue with erbium lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The abrupt evaporation of the water is the cause of tissue fragments being blasted out of the tooth structure. The aim of this study is to examine the effect of the water contained in dental hard tissues on the efficiency of ablation. 192 specimens of both bovine dental enamel and bovine dentin are irradiated with an Er:YAG and an Er,Cr:YSGG laser. Half of the specimens are dehydrated beforehand. Irradiation is carried out in subgroups: without water spray and with water spray at flow rates of 0.8 and 3 mls. The ablated volume is determined following histological preparation. Only in dentin, and then only with irradiation with the Er:YAG laser, is the water contained in the tissue found to have a significant influence (p < 0.0001) on the ablated volume. The water content has no effect on the efficiency of laser ablation in any of the other test groups. In contrast, the externally supplied water always has a significant influence on the effectiveness of the ablation process.

Human leukocyte antigen polymorphism in chronic and aggressive periodontitis among Caucasians: a meta‐analysis

AIM Multiple studies have reported associations between periodontitis and particular human leukocyte antigens (HLA). Because associations are inconsistent, we conducted a systematic literature review and a meta-analysis focusing on Caucasian case-control studies. MATERIAL AND METHODS A literature search reporting on the distribution of HLA class I and II phenotypes in Caucasian patients with chronic periodontitis (CP) and aggressive periodontitis (AP) was performed. Data sources included electronic databases and bibliographies of published articles. Screening and data abstraction were conducted independently by different reviewers. RESULTS Out of 174 publications, 12 studies were considered to be suitable for meta-analysis. In patients with CP, no significant HLA associations were found. Patients with AP showed a positive association with HLA-A9 [odds ratio=2.59 (95% confidence interval 1.36-4.83), p=0.004] and HLA-B15 [1.90 (1.15-3.16), p=0.01] as well as a negative association with HLA-A2 [0.72 (0.56-0.94), p=0.01] and -B5 [0.49 (0.30-0.79), p=0.004]. On grouping all patients into one periodontitis group (AP+CP), the same deviations were confirmed with higher statistical significance. For HLA-A9 and -B15, significant heterogeneity was found between the studies. No significant associations were found with HLA class II antigens. CONCLUSIONS HLA-A9 and -B15 seem to represent susceptibility factors for AP whereas HLA-A2 and -B5 are potential protective factors against periodontitis among Caucasians.

Rehardening of acid-softened enamel and prevention of enamel softening through CO2 laser irradiation

OBJECTIVES The aims of the present study were to investigate whether irradiation with a CO(2) laser could prevent surface softening (i) in sound and (ii) in already softened enamel in vitro. METHODS 130 human enamel samples were obtained and polished with silicon carbide papers. They were divided into 10 groups (n = 13) receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C); and submitted to 2 different procedures: half of the groups was acid-softened before surface treatment and the other half after. Immersion in 1% citric acid was the acid challenge. Surface microhardness (SMH) was measured at baseline, after softening and after treatment. Additionally, fluoride uptake in the enamel was quantified. The data were statistically analysed by two-way repeated measurements ANOVA and post hoc comparisons at 5% significance level. RESULTS When softening was performed either before or after laser treatment, the L group presented at the end of the experiments SMH means that were not significantly different from baseline (p = 0.8432, p = 0.4620). Treatment after softening resulted for all laser groups in statistically significant increase in SMH means as compared to values after softening (p < 0.0001). Enamel fluoride uptake was significantly higher for combined laser-fluoride treatment than in control (p<0.0001). CONCLUSION Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5 μs, 226 Hz) not only significantly decreased erosive mineral loss (97%) but also rehardened previously softened enamel in vitro.

Penetration of etching agents and its influence on sealer penetration into fissures in vitro

OBJECTIVES This study was designed to assess: 1) the ability of several commercially available and laboratory-made acid etchants to penetrate occlusal fissures when used for pit and fissure sealing, and 2) the influence of adding a surfactant to the etchant on penetration of the sealer. Viscosity, surface tension and contact angle to enamel of the etchants were determined for each treatment, and these properties were related to the etchants ability to penetrate fissures. METHODS Penetration was assessed in an acrylic fissure model having a deep-narrow fissure using a microscope and a chronometer. Penetration depth was expressed as percentage of total fissure depth and was measured in intervals up to 90 s. Commercially available etching agents with different viscosities and two solutions of phosphoric acid (37%), one with and one without a surfactant, were tested. The etch pattern obtained on the fissure wall enamel of extracted teeth with some of these products was evaluated using scanning electron microscopy. Eventually, the penetration depths of a composite sealer in fissures treated with a conventional etchant were compared to those after application of a surfactant-containing etchant on sections of extracted teeth. RESULTS None of the commercially available etchants studied were able to penetrate farther than 17% of the total fissure depth in the fissure model. The surfactant-containing etchant showed complete penetration within about 1 min and had a significantly lower surface tension and contact angle than the other products tested. Only the surfactant-containing etchant could produce a retentive pattern on the entire wall enamel of the fissure with the exception of locations blocked by debris and plaque. Fissures treated with this product prior to sealing showed a significantly deeper penetration of the sealer in deep-marrow fissures. SIGNIFICANCE Surfactant-containing etchants with a low viscosity can penetrate completely into fissures and can produce an increased retentive and wettable surface which significantly increased sealant penetration into deep fissures.

Prevention of toothbrushing abrasion of acid-softened enamel by CO2 laser irradiation

OBJECTIVE The aim of the present study was to evaluate the effect of CO(2) laser irradiation (10.6μm) at 0.3J/cm(2) (0.5μs; 226Hz) on the resistance of softened enamel to toothbrushing abrasion, in vitro. METHODS Sixty human enamel samples were obtained, polished with silicon carbide papers and randomly divided into five groups (n=12), receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C). After surface treatment they were submitted to a 25-day erosive-abrasive cycle in 100ml sprite light (90s) and brushed twice daily with an electric toothbrush. Between the demineralization periods samples were immersed in supersaturated mineral solution. At the end of the experiments enamel surface loss was determined using a contact profilometer and morphological analysis was performed using scanning electron microscopy (SEM). For SEM analysis of demineralization pattern, cross-sectional cuts of cycled samples were prepared. The data were statistically analysed by one-way ANOVA model with subsequent pairwise comparison of treatments. RESULTS Abrasive surface loss was significantly lower in all laser groups compared to both control and fluoride groups (p<0.0001 in all cases). Amongst the laser groups no significant difference was observed. Softened enamel layer underneath lesions was less pronounced in laser-irradiated samples. CONCLUSION Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5μs, 226Hz) either alone or in combination with amine fluoride gel significantly decreases toothbrushing abrasion of softened-enamel, in vitro.

Effects of Nd:YAG-laser irradiation on monolayer cell cultures

The clinical applications of Nd:YAG lasers on oral soft tissues include a wide field of surgical and periodontal procedures. This in vitro study focuses on the histological effects of Nd:YAG‐laser irradiation on a fibroblast monolayer cell culture especially with regard to thermal damage and cell necrosis. The results of this basic research study provide us with clear power settings for a safe soft tissue laser treatment.

Dentine caries inhibition through CO2 laser (10.6 μm) irradiation and fluoride application, in vitro

OBJECTIVE The purpose of the study was to investigate whether dentine irradiation with a pulsed CO(2) laser (10.6μm) emitting pulses of 10 ms is capable of reducing dentine calcium and phosphorus losses in an artificial caries model. DESIGN The 90 dentine slabs obtained from bovine teeth were randomly divided into six groups (n=15): negative control group (GC); positive control group, treated with fluoride 1.23% (GF); and laser groups irradiated with 8 J/cm(2) (L8); irradiated as in L8+fluoride 1.23% (L8F); irradiated with 11 J/cm(2) (L11); irradiated as in L11+fluoride 1.23% (L11F). After laser irradiation the samples were submitted to a pH-cycling model for 9 days. The calcium and phosphorous contents in the de- and remineralization solutions were measured by means of inductively coupled plasma optical emission spectrometer--ICP-OES. Additionally intrapulpal temperature measurements were performed. The obtained data were analysed by means of ANOVA and Tukeys test (α=0.05). RESULTS In the demineralization solutions the groups L11F and GF presented significantly lower means of calcium and phosphorous losses than the control group; and in L11F means were significantly lower than in the fluoride group. Both irradiation parameters tested caused intrapulpal temperature increase below 2°C. CONCLUSION It can be concluded that under the conditions of this study, CO(2) laser irradiation (10.6 μm) with 11 J/cm(2) (540 mJ and 10 Hz) of fluoride treated dentine surfaces decreases the loss of calcium and phosphorous in the demineralization process and does not cause excessive temperature increase inside the pulp chamber.

Conditioning of Enamel with Nd:YAG and CO2 Dental Laser Systems and with Phosphoric Acid An In-Vitro Comparison of the Tensile Bond Strength and the Morphology of the Enamel Surface

AbstractMaterial and Method 1: The first stage of a three-stage in-vitro investigation used 146 maxillary incisors to identify optimum setting parameters for two CO2 and Nd:YAG standard laser systems applied in enamel conditioning for bracket bonding. Results: 31 of the 75 parameter combinations investigated for the Nd:YAG laser and nine of the 71 investigated for the CO2 laser proved appropriate for further investigation of tensile strength. Material and Method 2: In a second stage, tensile bond strength for the selected laser settings was determined in comparison to the conventional acid-etch technique for a further 210 teeth as the control group. Results: The highest average tensile strength for the Nd:YAG laser was 4.1 MPa, with comparable values of 3.3 MPa for the CO2 laser and 4.9 MPa for the acid-etch technique. Material and Method 3: The third stage of the investigation involved comparative scanning electron microscopy of enamel surface morphology following laser application and acid-etching. Results: The CO2 laser was found to produce craters of various dimensions, while the Nd:YAG laser produced honeycomb structures regionally similar to enamel samples from the acid-etch technique. Conclusion: The CO2 and Nd:YAG dental lasers tested produce enamel conditioning and tensile bond strength sufficient to meet the requirements of bracket bonding.ZusammenfassungMaterial und Methode 1: In einer dreiteiligen In-vitro-Studie wurden zunächst die optimalen Einstellungsparameter zur Schmelzkonditionierung im Rahmen der Bracketadhäsivtechnik für zwei handelsübliche CO2- und Nd:YAG-Lasersysteme an 146 Oberkieferschneidezähnen ermittelt. Ergebnisse: Für den Nd:YAG-Laser empfahlen sich 31 der 75 untersuchten Parameterkombinationen und für den CO2-Laser neun der 71 Parameterkombinationen zu einer weitergehenden Untersuchung der Abzugskräfte. Material und Methode 2: Im zweiten Teil wurde die Zugfestigkeit für die ausgewählten Lasereinstellungen im Vergleich zur konventionellen Säureätztechnik als Kontrollgruppe an weiteren 210 Zähnen bestimmt. Ergebnisse: Die höchste durchschnittliche Zugfestigkeit lag für den Nd:YAG-Laser bei 4,1 MPa, für den CO2-Laser bei 3,3 MPa und für die Säureätztechnik bei 4,9 MPa. Material und Methode 3: Im dritten Teil der Studie wurde die Schmelzmorphologie nach Laserapplikation und Säureätztechnik rasterelektronenmikroskopisch vergleichend analysiert. Ergebnisse: Beim CO2-Laser waren Krater unterschiedlicher Dimension und für den Nd:YAG-Laser Wabenstrukturen mit regionaler Ähnlichkeit zum Schmelzmuster der Säureätztechnik nachzuweisen. Schlussfolgerung: Die untersuchten CO2- und ND:YAG-Dentallaser erlauben eine ausreichende Schmelzkonditionierung und Zugfestigkeit für die Bracketadhäsivtechnik.

Screening of CO2 Laser (10.6 μm) Parameters for Prevention of Enamel Erosion

OBJECTIVE The aim of this study was to screen CO(2) laser (10.6 μm) parameters to increase enamel resistance to a continuous-flow erosive challenge. BACKGROUND DATA A new clinical CO(2) laser providing pulses of hundreds of microseconds, a range known to increase tooth acid-resistance, has been introduced in the market. METHODS Different laser parameters were tested in 12 groups (n=20) with varying fluences from 0.1 to 0.9 J/cm(2), pulse durations from 80 to 400 μs and repetition rates from 180 to 700 Hz. Non-lased samples (n=30) served as controls. All samples were eroded by exposure to hydrochloric acid (pH 2.6) under continuous acid flow (60 μL/min). Calcium and phosphate release into acid was monitored colorimetrically at 30 sec intervals up to 5 min and at 1 min intervals up to a total erosion time of 15 min. Scanning electron microscopic (SEM) analysis was performed in lased samples (n=3). Data were statistically analysed by one-way ANOVA (p<0.05) and Dunnetts post-hoc tests. RESULTS Calcium and phosphate release were significantly reduced by a maximum of 20% over time in samples irradiated with 0.4 J/cm(2) (200μs) at 450 Hz. Short-time reduction of calcium loss (≤1.5 min) could be also achieved by irradiation with 0.7 J/cm(2) (300μs) at 200 and 300 Hz. Both parameters revealed surface modification. CONCLUSIONS A set of CO(2) laser parameters was found that could significantly reduce enamel mineral loss (20%) under in vitro erosive conditions. However, as all parameters also caused surface cracking, they are not recommended for clinical use.