Elimination of catastrophic optical mirror damage in continuous-wave high-power laser diodes using multi-section waveguides.

One of the persistent obstacles for high-power laser diodes (LDs) has been the catastrophic optical mirror damage (COMD), which limits the operating power level and lifetime of commercial high-power LDs. The output facet of LD reaches a critical temperature resulting in COMD, which is an irreversible device failure. Here, we fabricate multi-section LDs by tailoring the waveguide structure along the cavity that separates the output facet from the heat-generating lasing region. In this method, the LD waveguide is divided into electrically isolated laser and window sections along the cavity. The laser section is pumped at a high current to achieve high output power, and the window is biased at a low current with negligible heat generation. This design restricts the thermal impact of the laser section on the facet, and the window section allows lossless transport of the laser to the output facet. The lasers were operated continuous-wave up to the maximum achievable power. While standard LDs show COMD failures, the multi-section waveguide LDs are COMD-free. Our technique and results provide a pathway for high-reliability LDs, which would find diverse applications in semiconductor lasers.

Synthesis and Optical Properties of Novel Red-Emitting PbNb2O6: Eu(3+) Phosphors.

Undoped and PbNb2O6:Eu(3+) (1.0 ≤ x ≤ 6.0 mol%) phosphors were synthesized at 1100 °C for 3.5 h by the conventional solid state reaction method. Synthesized PbNb2O6:Eu(3+) phosphors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Photoluminescence (PL) analyses. The PL spectra showed series of excitation peaks between 350 and 430 nm due to the 4f-4f transitions of Eu(3+). For 395.0 nm excitation, emission spectra of Eu(3+) doped samples were observed at 591 nm (orange) and 614 nm (red) due to the (5)D0 â†’ (7)F1 transitions and (5)D0 â†’ (7)F2 transitions, respectively. PL analysis results also showed that the emission intensity increased by increasing Eu(3+) ion content. No concentration quenching effect was observed. The CIE chromaticity color coordinates (x,y) of the PbNb2O6:Eu(3+) phosphors were found to be in the red region of the chromaticity diagram.

Microcomputed tomography evaluation of white spot lesion remineralization with various procedures.

INTRODUCTION: The aim of this study was to use microcomputed tomography to evaluate the effects on white spot lesions of 3 remineralizing agents compared with artificial saliva (Inonu University, Malatya, Turkey). The agents were GC Tooth Mousse (GC International, Itabashi-ku, Tokyo, Japan), 50-ppm sodium fluoride solution (Inonu University, Malatya, Turkey), and Clinpro 5000 (3M ESPE Dental Products (St Paul, Minn). The experimental and control teeth were stored in artificial saliva. METHODS: Forty-four extracted premolars were divided into 4 groups of 11 teeth each (3 experimental groups and 1 control group). After white spot lesions were created on the teeth, a remineralizing agent was applied. Microcomputed tomography scanning was performed at the following times: T0 (sound enamel), T1 (day 0, when the white spot lesion was formed), T2 (day 15), and T3 (day 30). Volume, depth, surface area, and mineral density changes of the white spot lesions were evaluated at different time points using CTAn software (SkyScan; Bruker, Kontich, Belgium). RESULTS: GC Tooth Mousse and Clinpro 5000 improved all measurements after 30 days. However, Clinpro 5000 was not as effective in reducing lesion depth as it was in the other parameters. The artificial saliva group and the 50-ppm sodium fluoride solution did not show significant effects in the regression of the white spot lesions at the end of the 30-day experiment. CONCLUSIONS: GC Tooth Mousse and Clinpro 5000 were more effective in remineralization of white spot lesions than sodium fluoride solution and artificial saliva. They can be preferred for use clinically. Microcomputed tomography is a novel and effective method that shows promise in accurately evaluating white spot lesions and remineralization.

Effects of strontium ranelate on sutural bone formation: a histological and immunohistochemical study.

AIM: Rapid maxillary expansion is performed to correct a skeletal transverse deficiency of the maxilla, which is a frequently- encountered orthodontic anomaly. Strontium ranelate (SrR) is a novel agent that has a dual action, involving anti-resorptive and bone-forming effects. The aim of this study was to evaluate the effects of systemically applied SrR on osteoblastic bone formation after maxillary expansion on the mid-palatal suture of rats using histological and immunohistochemical tests. MATERIALS AND METHODS: A total of 24 Wistar rats were randomly divided into two equal groups. In all animals, five-day inter-premaxillary expansion was applied and maintained for a seven-day retention period, during which 625mg/kg/day SrR diluted with saline solution was administered orally to the experimental group. The rats were sacrificed and the tissues prepared for histological and immunohistochemical examinations after the retention period. RESULTS: Osteoblastic activity and the width of the blood vessels in the suture area were significantly increased in the SrR group compared with the control group (p < 0.051. Ossification was also observed to be active under light microscopy by staining with hematoxylin and eosin in the experimental group. Immunohistochemical labelling performed using osteonectin, osteocalcin, TGF-P and VEGF antibodies revealed significant immunoreactivity in the experimental group (p < 0.05). CONCLUSION: It may be concluded that SrR contributed to stimulatory osteogenesis in the expansion region. Therefore, a retention period may be shortened and relapse possibly reduced, following the application of SrR after the expansion.

Temperature increase during orthodontic bonding with different curing units using an infrared camera.

AIM: To evaluate the effects of different curing units and light-tip tooth surface distances on the temperature increase generated during orthodontic bonding, using an infrared camera (IR) and artificial neural networks (ANN). MATERIALS AND METHODS: Fifty-two freshly extracted human premolar teeth were used. Metallic orthodontic brackets were bonded to the buccal surfaces of the teeth and thermal records were taken using an IR camera and ANN. Brackets were cured with a light-emitting diode (LED) and high intensity halogen (HQTH). Teeth were divided into four groups according to the curing units (LED and HQTH) and curing distances (from tooth surface and 10 mm away from tooth surface). The results were analyzed with analysis of variance (ANOVA) and the Tukey HSD test. RESULTS: The ANOVA and Tukey HSD tests revealed that temperature changes were influenced by the type of light source and exposure times. All groups revealed significant differences between each other (p < 0.001). The highest surface temperature increase was gained from curing with a LED unit from the tooth surface (11.35°C ± 0.91°C). The lowest surface temperature increase was gained from curing with a HQTH unit 10 mm away from the tooth surface (2.57°C ± 0.6°C). CONCLUSION: The LED unit induced significantly higher temperature changes than did the HQTH. The temperature increase during orthodontic bonding was increased with long exposure time. A shorter light-tip tooth surface distance leads to greater increases in temperature.

The comparison of facial estethics between orthodontically treated patients and their parents.

Orthodontists emphasize the importance of facial esthetics while planning a treatment, and orthodontist state that orthodontics have more than expected effects on dentofacial esthetics. The facial esthetics of treated patients and their parents was analyzed and compared to define facial growth and to use in forensic sciences. Our study was applied to 45 orthodontic patients who were treated in our clinic and their untreated parents. The patients were divided into Classes I, II, and III groups according to their malocclusions. Pre- and posttreatment changes, pretreatment facial esthetics of the paitents and its accordance with their parents, and the calculation of heritability tests were performed. After the statistics, for pre- and posttreatment changes, all the groups except Class I revealed significant changes. There were significant correlations of patients for the heritability values and pretreatment esthetic in accordance with parents, but there were more correlations of fathers when compared to mothers. The facial esthetics in adolescences is related with so many factors, not only related with one factor. The facial esthetics in fact includes the aim of evaluation of facial properties partly or totally. Because orthodontic treatments affect facial esthetics, performing similar studies for the treatment outcomes, capabilities, and borders is important.

Single-mode quasi PT-symmetric laser with high power emission.

Large-area lasers are practical for generating high output powers. However, this often comes at the expense of lower beam quality due to the introduction of higher-order modes. Here, we experimentally demonstrate a new type of electrically pumped, large-area edge-emitting lasers that exhibit a high power emission (∼0.4 W) and a high-quality beam (M2∼1.25). These favorable operational characteristics are enabled by establishing a quasi PT-symmetry between the second-order mode of a large area two-mode laser cavity and that of a single-mode auxiliary partner cavity, i.e., by implementing a partial isospectrality between the two coupled cavities. This in turn enlarges the effective volume of the higher-order modes. As a result, a selective pump applied via current injection into the main laser cavity can provide a stronger modal gain to the fundamental mode, and thus lead to lasing in the single mode regime after filtering out higher order transverse modes. The reported experimental results confirm this intuitive picture and are in good agreement with both theoretical and numerical analysis. Above all, the employed material platform and fabrication process are compatible with the industrial standards of semiconductor lasers. This work provides the first clear demonstration, beyond previous proof-of-concept studies, of the utility of PT-symmetry in building laser geometries with enhanced performance and, at the same time, useful output power levels and emission characteristics.

Geometrically enhanced morphology-dependent resonances of a dielectric sphere.

The effect that geometrical resonances of orbiting internally reflecting rays have on the morphology-dependent resonances of microspheres is investigated heuristically and numerically using generalized Lorenz-Mie theory. Angularly resolved off-axis Gaussian beam elastic scattering spectra are presented. The results obtained show that the elastic scattering intensity of morphology-dependent resonances is noticeably enhanced in the vicinity of the geometrical resonance scattering angles.

Effects of thermocycling on the degree of cure of two lingual retainer composites.

The aim of this study was to evaluate the effects of thermocycling on the degree of cure (DC) and water sorption behavior of two lingual retainer composites. A total of 50 composite specimens, 5 mm diameter and 2 mm height, were prepared using Light Cure Retainer (LCR) (Reliance) and Transbond Lingual Retainer (TLR) (3M Unitek). After 40-second curing with a halogen light and after 24-hour water storage, the composite specimens were subjected to different thermocycling regimes. Absorbance peaks to monitor the DC were recorded using Fourier transform infrared (FTIR) spectroscopy, while water sorption was calculated in microg/mm(3). On DC, significant differences among the different thermocycling regimes were observed only for the TLR specimens (p<0.05). On water sorption behavior, an increase in the number of thermal cycles resulted in increased water sorption for both composites, but the statistical differences in these groups were not significant. On the effect of thermocycling up to 20,000 cycles, present findings showed that LCR was less affected than TLR. Further, LCR exhibited higher DC and lower water sorption values than TLR after thermal cycling.

Is transdermal nitroglycerin application effective in preventing and healing flap ischaemia after modified radical mastectomy?

OBJECTIVE: We evaluated the efficacy of local nitroglycerin application in preventing and treating flap complications after modified radical mastectomy in a large patient cohort. PATIENTS AND METHODS: Between 1993 and 2008, 6426 patients undergoing surgery for stage II breast cancer were enrolled in this prospective study. Patients were randomised into treatment and control groups. In the treatment group a nitroglycerin preparation (Nitroderm) was applied to the flap area. Major complications, recovery periods, menopausal status, additional diseases (diabetes mellitus, hypertension, atherosclerotic heart disease) and adverse effects related to nitroglycerin use were recorded. RESULTS: The recovery rate without major complications was statistically significantly higher in the nitroglycerin-treated group than in the controls (p < 0.001). CONCLUSION: Our results indicate that topical nitroglycerin reduces flap complications after breast surgery.

Angular photogrammetric analysis of the soft tissue facial profile of Turkish adults.

One of the most important components of orthodontic diagnosis and treatment planning is the evaluation of the patient's soft tissue profile. The aim of this study was to develop angular photogrammetric standards for Class I Anatolian Turkish males and females. A random sample of 100 Turkish individuals (46 males and 54 females; ages 19-25 years) was obtained. The photographic set-up consisted of a tripod that held a 35 mm camera and a primary flash. The camera was used in its manual position and photographic records were taken of the subjects in natural head posture. The photographic records, 35 mm slide format, were digitized and analyzed using the Quick Ceph Image software program for Windows. Twelve measurements were digitally analyzed on each photograph. For statistical evaluation a Student's t-test was performed and the reliability of the method was analyzed. The results were compared with reported norms of facial aesthetics. The nasofrontal (G-N-Prn), nasal (Cm-Sn/N-Prn), vertical nasal (N-Prn/TV), and nasal dorsum (N-Mn-Prn) angles showed statistically insignificant gender differences (P>0.05). The nasolabial angle (Cm-Sn-Ls) demonstrated large variability. Gender differences were present in the mentolabial (Li-Sm-Pg) and cervicomental (G-Pg/C-Me) angles. The mentolabial angle showed a high method error and large variability. Facial (G-Sn-Pg) and total facial (G-Prn-Pg) convexity angles were similar, while Cm-Sn-Ls angle range was larger compared with other angles. The mean values obtained from this sample can be used for comparison with records of subjects with the same characteristics and following the same photogrammetric technique. Angular photogrammetric profile analysis can provide the orthodontist with a way of determining problems associated with various soft tissue segments of the face.

Conventional and high intensity halogen light effects on water sorption and microhardness of orthodontic adhesives.

OBJECTIVE: To test the null hypothesis that when the equivalent total light energy is irradiated to three orthodontic adhesive resins, there is no difference between the microhardness and water sorption values regardless of the curing light sources. MATERIALS AND METHODS: Samples were divided into six groups according to the combination of three orthodontic adhesives (Kurasper F, Light-Bond, Transbond XT) and two light intensities (quartz tungsten halogen [QTH] and high intensity quartz tungsten halogen [HQTH]). One half of each of the 40 samples of three adhesive pastes was polymerized for 20 seconds by a QTH light source, and the other half was polymerized for 10 seconds by a HQTH light source. Water sorption was determined and Vickers hardness was established with three measurements per sample at the top, center, and bottom. Statistical analysis was performed using two-way analysis of variance (ANOVA) with multiple comparisons (Tukey-HSD). RESULTS: Statistically significant differences were found among all adhesives for water sorption and hardness values cured with QTH and HQTH. The HQTH curing unit resulted in higher values than did the QTH. The highest water sorption values were observed for Kurasper F cured with HQTH and the lowest value was observed for Transbond XT cured with QTH. For microhardness Light-Bond cured with HQTH produced the highest values, and Transbond XT cured with QTH produced the lowest. CONCLUSIONS: When the equivalent total light energy is irradiated to three orthodontic adhesive resins, there are significant differences between the microhardness and water sorption values cured with the QTH and HQTH light source. The null hypothesis is rejected.

Conventional and high-intensity halogen light effects on polymerization shrinkage of orthodontic adhesives.

The objectives of this study were to compare the polymerization shrinkage of three orthodontic adhesives. In addition we wanted to determine the effectiveness of the high-intensity quartz tungsten halogen (HQTH) in curing orthodontic adhesives on polymerization shrinkage with that of the quartz tungsten halogen (QTH). A total of 120 glass ring molds were prepared using a low-speed saw. The internal surface of the glass rings were roughened and etched. Adhesive pastes were placed into the glass molds, which were sandwiched between two glass slides. Samples were divided into six groups according to the combination of three orthodontic adhesives (Kurasper F, Light Bond, and Transbond XT) and two light intensities. One half of each 40 samples of three adhesive pastes was polymerized for 20 seconds by a QTH (Hilux 350), and the other half was polymerized for 10 seconds by a HQTH (Optilux 501). The volumetric polymerization shrinkage for each system was measured through the specific density method modified by Puckett and Smith. Statistical analysis was performed using two-way analysis of variance for intergroup comparisons. The HQTH-curing unit resulted in a more polymerization shrinkage than did the QTH for all investigated adhesives. However, no statistically significant differences were found. The highest shrinkage was observed for Light Bond cured with HQTH (1.59 +/- 0.82%), and the lowest value was observed for Transbond XT cured with QTH (1.23 +/- 0.60%). There are no significant differences in polymerization shrinkage of the three investigated orthodontic adhesives when polymerized with a QTH or a HQTH.

The association of occlusal factors with masticatory muscle tenderness in 10- to 19-year old Turkish subjects.

The aims of this study were (1) to investigate the relationship between occlusal factors and masticatory muscle tenderness among 10- to 19-year-old (mean 14 years eight months) Turkish subjects and (2) to identify possible sex differences between them. The sample consisted of 716 individuals (355 male and 361 female subjects). Tenderness with palpation of masseter and temporalis muscles and functional manipulation of lateral and medial pterygoid muscles was registered. The examiners recorded the Angle classification bilaterally for molars, presence of anterior and posterior crossbites, excessive overjet, open and deep bites, functional shift, and severity of anterior crowding. Associations between the occlusal factors and muscle tenderness according to sex were evaluated with chi-square analysis. Statistically significant associations were found between masticatory muscle tenderness and all the investigated occlusal factors except posterior crossbite and functional shift. Masseter, medial, and lateral pterygoid muscle tenderness was higher in female subjects. Medial and lateral pterygoid muscle tenderness in Class I cases and masseter and medial pterygoid muscle tenderness in Class II, division 1 malocclusion cases were higher in female subjects (P < .05). In open-bite cases, medial pterygoid muscle tenderness (P < .05), in deep-bite cases, masseter (P < .01) and medial pterygoid (P < .05) muscle tenderness, and in excessive overjet cases, masseter muscle tenderness (P < .05) were also higher in female subjects. These results suggest that greater masticatory muscle tenderness in female subjects may contribute to the greater prevalence of temporomandibular disorders in them.

Effects of chlorhexidine and povidone-iodine mouth rinses on the bond strength of an orthodontic composite.

The purpose of this study was to determine whether the application of two antibacterial mouth rinses to etched and unetched enamel affects the shear bond strength (SBS) of an orthodontic composite resin. Eighty-five lower human incisors were divided into five groups, ie, group 1: control group, no mouth rinse was used; groups 2 and 3: mouth rinses were applied to the intact enamel surface before etching; groups 4 and 5: mouth rinses were applied to the etched enamel. A bonding agent and a composite resin were applied to the teeth surface. For shear bond testing, the specimens were mounted in a universal testing machine, and an apparatus attached to a compression load cell was applied to each specimen until failure occurred. The data were analyzed using analysis of variance and Tukey honestly significance tests. Fracture modes were analyzed by Mann-Whitney U-test. There was no statistically significant difference between the SBS values of group 1 (31.64 +/- 3.62 MPa) and group 4-five experimental applications (P > or = .05). However, the SBS value of group 3 (36.56 +/- 5.95 MPa) was significantly larger than those of group 4 (30.00 +/- 4.97 MPa) and group 5 (30.26 +/- 7.30 MPa). In addition, no significant differences were observed between group 1 and groups 2 (34.33 +/- 7.26 MPa) and 3 (36.56 +/- 5.95 MPa) (P > or = .05). Because the application of chlorhexidine and povidone-iodine before acid etching did not cause any decrease in bond strength, it is advisable for use under the orthodontic resin composite to obtain an antibacterial effect or to prevent the risk of bacteremia.

Are the flowable composites suitable for orthodontic bracket bonding?

The study aims to determine the shear bond strength (SBS) values of different flowable composites (Pulpdent Flows-Rite, 3M Filtek Flow, and Heraeus Kulzer Flow Line) in comparison with a conventional orthodontic adhesive and the bond failure sites of these composites. Eighty extracted human premolars were divided into four groups of 20 teeth each. Brackets were bonded to the teeth in each test group with different composites, according to the manufacturer's instructions. SBS values of these brackets were recorded (in MPa) using a universal testing machine. Adhesive remnant index (ARI) scores were determined after the failure of brackets. Data were analyzed using analysis of variance (ANOVA), Tukey honestly significant difference, and chi-square tests. SBS values of groups 1 (Transbond XT), 2 (Flows-Rite), 3 (Flow), and 4 (Flow Line) were found to be 17.10 +/- 2.48 MPa, 6.60 +/- 3.2 MPa, 7.75 +/- 2.9 MPa, and 8.53 +/- 3.50 MPa, respectively. The results of this study demonstrate that the orthodontic adhesive (Transbond XT) had higher SBS values than the flowable composites. Results of ANOVA revealed statistically significant differences among the groups (P < .05). The SBS values were significantly lower in all flowable composite groups than the orthodontic adhesive. ARI scores were significantly different between the orthodontic adhesive and all the flowable groups investigated. The use of flowable composites is not advocated for orthodontic bracket bonding because of significantly lower SBS values achieved.

The relationship between bruxism and occlusal factors among seven- to 19-year-old Turkish children.

The aim of this study was (1) to investigate the relationship between occlusal factors and bruxism among 965 Turkish subjects (472 boys and 493 girls) with a mean age of 12.8 years (range, seven to 19 years); and (2) to identify possible sex differences between girls and boys. This sample was divided into two groups of bruxers or nonbruxers based on a clinical examination and self-reports. The examiner recorded the Angle molar classification bilaterally, severity of anterior crowding, existence of anterior and posterior crossbite, open and deep bite, functional shift, and excessive overjet. The relationships between occlusal factors and bruxism and sex differences between boys and girls were evaluated with chi-square analysis (chi2) using the SPSS software package. The results showed that bruxism was diagnosed in 12.6% of all subjects. The evaluation of the findings indicated that no statistically significant relationships were determined between bruxism and occlusal factors. No sex differences were found between occlusal factors in relation to bruxism. The prevalence of bruxism in boys and girls was similar, and no statistically significant differences were found. It is concluded that none of the occlusal factors seem to play a role in the development of bruxism. However, additional longitudinal studies with larger samples need to be conducted to determine if there is any relationship between occlusal factors and bruxism.

The influence of extraction treatment on Holdaway soft-tissue measurements.

The aims of this study were (1) to determine the changes in the soft-tissue measurements of orthodontic patients treated with four first premolars extractions as determined by the Holdaway Analysis, (2) to investigate the sexual differences between pre- and posttreatment values, and (3) to compare the Holdaway soft-tissue norms with findings in Anatolian Turkish adults. Pretreatment and posttreatment lateral cephalograms of 58 patients (26 boys and 32 girls) were evaluated. During treatment, the H angle, soft tissue subnasale to H line, and upper-lip strain decreased, and the upper-lip thickness, inferior sulcus to H line, and nose prominence increased. No statistically significant sex differences were found between the pre- and posttreatment values of the four premolar extraction cases. When the pretreatment values were compared with the Holdaway soft-tissue norms of Anatolian Turkish adults, seven variables showed statistically significant differences. When the posttreatment values were compared, six measurements showed statistically significant differences. It was determined that some measurements (H angle, inferior sulcus to H line, upper-lip thickness) moved closer to the Anatolian Turkish norms with extraction of four first premolars. However, upper-lip strain measurement changed in an undesirable direction during the treatment. In this study, the sample began treatment with greater facial imbalance, and the facial esthetics improved during treatment. It is necessary to investigate this difference in future studies using larger sample sizes.

The effect of tooth bleaching on the shear bond strength of orthodontic brackets using self-etching primer systems.

OBJECTIVE: The purpose of this study was to determine the effect of 10% carbamide peroxide and 38% hydrogen peroxide bleaching agents on the shear bond strength of orthodontic brackets using self-etching primer systems. METHODS: Forty five freshly extracted human premolar teeth were randomly divided into 3 groups of 15 teeth each: control (group 1), 10% carbamide peroxide at-home bleached (group 2), and 38% hydrogen peroxide in-office bleached (group 3). Three weeks later, all brackets were bonded using a self-etching primer system. The shear bond strength of these brackets was measured and recorded in MPa. Adhesive remnant index (ARI) scores were determined after the brackets failed. Data were analyzed using Kruskal- Wallis test, pairwise comparisons were made using the Mann-Whitney U test and ARI scores were analyzed using a chi-square test at a significance level of P<.05. RESULTS: The shear bond strengths of group 1 (mean: 17.7 ± 9.7 MPa) were significantly higher (P<.05) than those of group 3 (mean: 9.9 ± 5.4 MPa). No significant differences were found between group 2 (mean: 12.3 ± 4.7) and either group 1 or group 3 (P>.05). ARI scores did not differ significantly among the 3 groups. CONCLUSIONS: The use of 10% carbamide peroxide bleaching does not significantly reduce shear bond strength values. In contrast, use of 38% hydrogen peroxide bleaching significantly reduces these values.