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Biomedical subjects

D Fried

Publications and source records attributed to D Fried.

At least 19 recordsLinked to original sources
PubMed2006

Imaging artificial caries on the occlusal surfaces with polarization-sensitive optical coherence tomography.

Polarization-sensitive optical coherence tomography (PS-OCT) is a nondestructive imaging system that can utilize near-infrared (IR) light to produce depth-resolved images of dental enamel and has the potential to monitor early enamel occlusal caries. The objective of this study was to investigate the relationship between the magnitude of backscattered light and depolarization recorded by PS-OCT with changes in the enamel mineral volume in an artificial caries model. Artificial lesions were created on a selected region on the occlusal surfaces of sound posterior teeth (n=10) using a well-characterized 14-day pH cycling model. An all-fiber-based PS-OCT system operating at 1,310 nm was used to collect serial images at day 0 and day 14 prior to tooth sectioning. The quantitative mineral content profile and relative mineral loss, DeltaZ (%volxmicrom), of the carious enamel samples were obtained from transverse sections using high-resolution digital microradiography (DM). Line profiles of PS-OCT and DM images were used to evaluate the artificial caries severity and depth. The integrated reflectivity of the perpendicular-axis PS-OCT image, quantifying lesion severity, was correlated to the DeltaZ of the caries lesions. There was also a strong correlation between the lesion depth calculated from both imaging modalities. PS-OCT can image and quantify artificial occlusal caries by measuring the increase in backscattering and depolarization of near-IR light. This optical method has promising applications for in vivo detection and monitoring of early enamel occlusal caries.

Analysis of Variance↗
PubMed2006

Remineralization of enamel caries can decrease optical reflectivity.

The remineralization of enamel caries can lead to distinct optical changes within a lesion. We hypothesized that the restoration of mineral volume would result in a measurable decrease in the depth-resolved reflectivity of polarized light from the lesion. To test this hypothesis, we measured optical changes in artificial caries undergoing remineralization as a function of depth, using Polarization-sensitive Optical Coherence Tomography (PS-OCT). Lesions were imaged non-destructively before and after exposure to a remineralization regimen. After imaging, microradiographs of histological thin sections indicated that the significant reflectivity reduction measured by PS-OCT accurately represented the increase in mineral content within a larger repaired surface zone. Mineral volume changes arising from remineralization can be measured on the basis of the optical reflectivity of the lesion.

Calcium Phosphates↗
PubMed2001

Comparison of Er:YAG and 9.6-microm TE CO(2) lasers for ablation of skull tissue.

BACKGROUND AND OBJECTIVE: Craniotomy by using a drill and saw frequently results in fragmentation of the skull plate. Lasers have the potential to remove the skull plate intact, simplifying the reconstructive surgery. STUDY DESIGN/MATERIALS AND METHODS: Transverse-excited CO(2) lasers operating at the peak absorption wavelength of bone (lambda = 9.6 microm) and with pulse durations of 5-8 microsec, approximately the thermal relaxation time in hard tissue, produced high ablation rates and minimal peripheral thermal damage. Both thick (2 mm) and thin (250 microm) bovine skull samples were perforated and the ablation rates calculated. Results were compared with Q-switched and free-running Er:YAG lasers (lambda = 2.94 microm, tau(p) = 0.5 microsec and 300 microsec). RESULTS: The CO(2) laser produced ablation rates of up to 60 and 15 microm per pulse for thin and thick sections, respectively, and perforated thin and thick sections with fluences of less than 1 J/cm(2) and 6 J/cm(2), respectively. There was no discernible thermal damage and no need for water irrigation during ablation. Pulse durations > or =20 microsec resulted in significant tissue charring, which increased with the pulse duration. Although the free-running Er:YAG laser produced ablation rates of up to 100 microm per pulse, fluences of 10 J/cm(2) and 30 J/cm(2) were required to perforate thin and thick samples, respectively, and peripheral thermal damage measured 25-40 microm. CONCLUSIONS: In summary, the novel 5- to 8-microsec pulse length of the TE CO(2) laser is long enough to avoid a marked reduction in the ablation rate due to plasma formation and short enough to avoid peripheral thermal damage through thermal diffusion during the laser pulse. Furthermore, in vivo animal studies with the TE CO(2) laser are warranted for potential clinical application in craniotomy and craniofacial procedures.

Animals↗
PubMed2001

Residual heat deposition in dental enamel during IR laser ablation at 2.79, 2.94, 9.6, and 10.6 microm.

BACKGROUND AND OBJECTIVE: The principal factor limiting the rate of laser ablation of dental hard tissue is the risk of excessive heat accumulation in the tooth. Excessive heat deposition or accumulation may result in unacceptable damage to the pulp. The objective of this study was to measure the residual heat deposition during the laser ablation of dental enamel at those IR laser wavelengths well suited for the removal of dental caries. Optimal laser ablation systems minimize the residual heat deposition in the tooth by efficiently transferring the deposited laser energy to kinetic and internal energy of ejected tissue components. STUDY DESIGN/MATERIALS AND METHODS: The residual heat deposition in dental enamel was measured at laser wavelengths of 2.79, 2.94, 9.6, and 10.6 microm and pulse widths of 150 nsec -150 microsec using bovine block "calorimeters." Water droplets were applied to the surface before ablation with 150 microsec Er:YAG laser pulses to determine the influence of an optically thick water layer on reducing heat deposition. RESULTS: The residual heat was at a minimum for fluences well above the ablation threshold where measured values ranged from 25-70% depending on pulse duration and wavelength for the systems investigated. The lowest values of the residual heat were measured for short (< 20 micros) CO(2) laser pulses at 9.6 microm and for Q-switched erbium laser pulses at 2.79 and 2.94 microm. Droplets of water applied to the surface before ablation significantly reduced the residual heat deposition during ablation with 150 microsec Er:YAG laser pulses. CONCLUSIONS: Residual heat deposition can be markedly reduced by using CO(2) laser pulses of less than 20 microsec duration and shorter Q-switched Er:YAG and Er:YSGG laser pulses for enamel ablation.

Animals↗
PubMed2001

Effect of CO2 laser on pulpal temperature and surface morphology: an in vitro study.

OBJECTIVES: The objective of this study was to evaluate the potential effects on underlying dental hard tissues of a high pulse rate carbon dioxide (CO2) laser that was designed for soft tissue surgery. METHODS: Eighteen extracted human teeth were sectioned longitudinally, cleaned, and varnished, leaving nine exposed windows on each: six on the coronal surface (enamel) and three on the root surface (cementum, dentin). The CO2 irradiation conditions used were: wave length 10.6 microm; 1.2-2.6J/cm(2) fluence per pulse; repetition rate 120-1000Hz; 100-200ms pulse duration; and cumulative fluences ranging from 14 to 2200J/cm(2). Each window was irradiated with a 0.3mm beam diameter at one of nine power settings for 0.1, 0.5, or 1.0s. The pulp chamber temperature was measured with a microthermocouple. The irradiated teeth were evaluated by Polarized Light Microscopy (PLM) and Scanning Electron Microscopy (SEM). RESULTS: The pulp chamber temperature rise ranged from 0.5 to 19 degrees C depending on the location of the window and distance to pulp chamber. SEM revealed crystal fusion in both enamel and dentin at all cumulative fluences. At cumulative fluences of 40J/cm(2), 200 pulses/second and higher, measurable tissue loss was observed with PLM both in dentin and enamel. CONCLUSIONS: These results indicate there are threshold conditions above which pulsed CO2 laser light used for soft tissue surgery may cause detrimental changes to underlying oral hard tissue and to the pulp.

Body Temperature↗
PubMed2001

Dental hard tissue modification and removal using sealed transverse excited atmospheric-pressure lasers operating at lambda=9.6 and 10.6 microm.

Pulsed CO(2) lasers have been shown to be effective for both removal and modification of dental hard tissue for the treatment of dental caries. In this study, sealed transverse excited atmospheric pressure (TEA) laser systems optimally tuned to the highly absorbed 9.6 microm wavelength were investigated for application on dental hard tissue. Conventional TEA lasers produce an initial high energy spike at the beginning of the laser pulse of submicrosecond duration followed by a long tail of about 1-4 micros. The pulse duration is well matched to the 1-2 micros thermal relaxation time of the deposited laser energy at 9.6 microm and effectively heats the enamel to the temperatures required for surface modification at absorbed fluences of less than 0.5 J/cm(2). Thus, the heat deposition in the tooth and the corresponding risk of pulpal necrosis from excessive heat accumulation is minimized. At higher fluences, the high peak power of the laser pulse rapidly initiates a plasma that markedly reduces the ablation rate and efficiency, severely limiting applicability for hard tissue ablation. By lengthening the laser pulse to reduce the energy distributed in the initial high energy spike, the plasma threshold can be raised sufficiently to increase the ablation rate by an order of magnitude. This results in a practical and efficient CO(2) laser system for caries ablation and surface modification.

Dental Caries↗
PubMed2000

Selective ablation of orthodontic composite by using sub-microsecond IR laser pulses with optical feedback.

BACKGROUND AND OBJECTIVE: Conventional methods of residual composite removal after debonding orthodontic brackets involve the use of abrasives that damage the underlying enamel. The objective of this study was to determine whether infrared pulsed lasers are suitable for the removal of composite through selective laser ablation. STUDY DESIGN/MATERIALS AND METHODS: Pulsed CO(2) and Er:YAG lasers were evaluated for their ability to selectively ablate orthodontic composites. Optical emission spectra of the luminous plasma produced during composite and enamel ablation were acquired to differentiate between enamel and composite ablation to minimize accidental removal of enamel. RESULTS: TEA CO(2) laser pulses at a wavelength of 10.6 microm were best suited for the selective ablation of composite. Spectral analysis of plume emission identified several calcium emission lines that can potentially be used to distinguish between enamel and composite ablation. CONCLUSION: TEA CO(2) lasers operating at 10.6 microm used in conjunction with optical feedback have the potential to selectively ablate residual dental composite and minimize inadvertent removal of enamel.

Carbon Dioxide↗
PubMed1999

Eyelid resurfacing.

BACKGROUND AND OBJECTIVE: Laser resurfacing of eyelids was examined in a series of experiments designed to measure beam parameters, surface temperatures, ablation characteristics, thermal damage, tissue responses and clinical outcomes. These data were collected for the purpose of developing a logical basis for clinical dosimetry. STUDY DESIGN: All experiments were conducted with similar short-pulse CO(2) lasers (TruPulse, Albuquerque, NM) where the beam had been carefully characterized and calibrated. The chronological sequence examined begins with the photophysical laser/tissue interactions during the first few microsec of irradiation and ends with an evaluation of the efficacy of wrinkle reduction nine months after treatment. RESULTS: Eyelid tissue removed by the first and second passes consisted mostly of epidermis with about 38 microm of thermal damage into the papillary dermis. Erythema resolved within four weeks and most patients experienced 70-100% wrinkle reduction by nine months. CONCLUSION: A layer of contracted dermal scar tissue that replaced the thermally challenged zone in the dermis is identified as the substrate for wrinkle reduction. The data support the following dosimetry for periorbital wrinkle reduction: One pass 4-6 J/cm(2) (350-500 mJ into a 3 x 3 mm spot). A second treatment after 9-12 months may be more beneficial than a second pass.

Animals↗
PubMed1999

Modeling the modification depth of carbon dioxide laser-treated dental enamel.

BACKGROUND AND OBJECTIVES: Many studies of laser-induced thermal decomposition of dental enamel have demonstrated a reduction in the rate of acid dissolution, size of artificial caries-like lesions, and acid reactivity. Additionally, studies have correlated the loss of carbonate from dental enamel with a reduction in acid dissolution. Dental mineral consists of hydroxyapatite with many substitutions, the major one being carbonate ( approximately 3-5% by weight), which markedly affects acid reactivity. The principle objective of the present work was to determine the precise depth of modification, i.e. , thermally induced decomposition of dental enamel (carbonate loss), at the predicted optimum laser irradiation parameters. STUDY DESIGN/ MATERIALS AND METHODS: Bovine enamel blocks were irradiated at lambda = 9.6 microm with 2-microsec and 100-microsec pulses and at lambda = 10.6 microm with 2-microsec pulses. Carbonate loss was calculated from infrared spectra as a function of depth and compared to numerical simulations of the maximum temperature rise. RESULTS: Carbonate loss was initiated at temperatures greater than 400 degrees C, but was complete only after repeated irradiation of the surface above the melting threshold. Carbonate loss of dental enamel irradiated at 9.6 microm with a 100-microsec pulse and at 10.6 microm with a 2-microsec pulse was greater than that of enamel irradiated at 9.6 microm with a 2-microsec pulse. The depth of carbonate loss in dental enamel irradiated with a 2-microsec pulse was greater for lambda = 10.6 microm than for lambda = 9.6 microm. CONCLUSION: The depth of modification is consistent with the presented model that incorporates the absorption depth and thermal relaxation time/pulse duration. However, repeated irradiation is required for complete removal of carbonate, depending on absorption depth and pulse duration.

Animals↗
PubMed1999

Artificial caries removal and inhibition of artificial secondary caries by pulsed CO2 laser irradiation.

PURPOSE: To investigate the inhibition of artifical secondary caries around restorations placed after removal of artificial caries by pulsed CO2 laser irradiation and by mechanical means. MATERIALS & METHODS: Beveled cavities were prepared mechanically on the facial surfaces of extracted human molars. Each cavity was subsequently exposed to an artificial caries (demineralizing) solution (pH 5.0) for 7 d to generate a demineralized zone approximately 100-200 microns thick on the cavity surface. The artificial carious/demineralized zones of the cavities were removed by a pulsed CO2 laser operating at a wavelength of 9.3 microns with pulse duration of 100 microseconds and an irradiation intensity of 5 J/cm2. Artificial control caries were removed mechanically with a carbide bur in a slow speed handpiece. The cavities were slightly undercut and restored with a resin-based composite without etching and bonding and the restored teeth were subjected to pH cycling solutions for 10 d as follows: Demineralization solution, pH 4.5 for 6 hrs, followed by remineralization solution, pH 7.0 for 18 hrs. Cycled teeth were sectioned through the restorations and the resulting lesions were analyzed in thin section using polarized light and Knoop microhardness. RESULTS: Mean microhardness delta Z values, indicating mineral loss were: 549 (SD 191) for control, and 140 (SD 127) N = 11. This difference is significant with t = 5.543 and P = 0.000 (Paired t-test). Caries penetration: Control side--231 microns (SD 71), Laser treated side: 123 microns (SD 79) N = 6. This difference is significant with t = 5.198 and P = 0.003 (Paired t-test). The results show that the laser treatment not only removed artificial caries, but also inhibited decalcification of the cavity wall in a subsequent artificial caries challenge by as much as 81% compared to control samples. No etching and bonding was used in this pilot study, which might have influenced the results. Future studies should address the inhibition effect of the laser treatment as compared to adhesive techniques, fluoride treatments and fluoride release restorative materials. CONCLUSION: Caries removal by a pulsed lambda = 9.3 microns CO2 laser produces a cavity surface morphology with marked resistance to artificial secondary caries as compared to mechanical removal.

Carbon Dioxide↗
PubMed1998

[Demonstration of the sentinel lymph node in axillary dissection for breast cancer].

OBJECTIVES: The sentinel node is defined as the first-line axillary lymphatic drainage node in breast cancer. If the sentinel node can be identified, during axillary dissection for breast cancer, resection could be limited reducing subsequent morbidity. However, before modifying the standard dissection procedure, it is important to prove that the sentinel node is representative of the metastatic status of other axillary nodes. PATIENTS AND METHODS: Between March and December 1996, 86 patients (mean age 58 years, range 32-82) underwent amputation (n = 20), tumorectomy with dissection (n = 56) or tumorectomy followed by secondary dissection (n = 10) for breast cancer. Ten ml of diluted patent blue was injected either into the peripheral portion of the tumor or the tumorectomy cavity. Node dissection was performed 10 to 20 minutes after injection. The blue sentinel node was identified prior to standard dissection. RESULTS: A mean 12 nodes were removed (range 4-21). Seventy-nine sentinel nodes were identified (91%) and in 7 cases (8%) a sentinel node could not be identified. In 7 other cases the sentinel node was a false negative, i.e. non malignant despite metastases in other dissected nodes. In all the other cases, the status of the sentinel node predicted the status of the other nodes, i.e. a non-metastatic sentinel node associated with other metastatic nodes. Finally, in 7 cases, the sentinel node was the only invaded node among the nodes dissected. During the last 3 months of the study, the sentinel node was identified in 100% of the cases and was representative of the overall dissection. CONCLUSION: Identifying the sentinel node is an alternative to standard axillary node dissection procedures. The method requires a training period and identification can be improved with radioimmunologic guidance. Patient selection within the framework of a rigorous multidisciplinary protocol is indispensable. A nationwide study is currently being conducted to validate these preliminary results.

Adult↗
PubMed1998

CO2 laser inhibitor of artificial caries-like lesion progression in dental enamel.

Several studies during the last 30 years have demonstrated the potential of laser pre-treatment of enamel or tooth roots to inhibit subsequent acid-induced dissolution or artificial caries-like challenge in the laboratory. The overall objective of ongoing studies in our laboratories is to determine, systematically, the optimum sets of parameters for carbon dioxide laser irradiation that will potentially effectively inhibit dental caries in enamel and tooth roots. The aim of the present study was to examine the roles of wavelength and fluence in the prevention of caries progression in vitro in enamel by means of a pH-cycling model. The hypothesis to be tested was that the highly absorbed 9.3- and 9.6-microm wavelengths would be efficiently converted to heat, creating a temperature sufficiently high to reduce the acid-reactivity of the mineral and inhibit caries-like lesion progression in dental enamel. One hundred and sixty caries-free tooth crowns were cleaned and varnished with acid-resistant varnish, leaving one exposed window of enamel. Twelve groups of 10 enamel samples were irradiated in their individual windows by one of the four wavelengths (9.3, 9.6, 10.3, or 10.6 microm) of a tunable CO2 laser. Energy per pulse was 25, 50, 100, 200, or 250 mJ (25 pulses). Repetition rate was 10 Hz, and beam diameter was 1.6 mm. Fluence conditions of 1 to 12.5 J/cm2 per pulse were produced. All teeth, including 40 non-irradiated controls, were subjected to pH-cycling to produce artificial caries-like lesions. Results were assessed by cross-sectional microhardness testing. Inhibition of caries progression of from 40% to 85% was achieved over the range of laser conditions tested. At 9.3 and 9.6 microm, 25 pulses at absorbed fluences of 1 to 3 J/cm2 produced inhibition on the order of 70% with minimal subsurface temperature elevation (< 1 degree C at 2 mm depth), comparable with inhibition produced in this model with daily fluoride dentifrice treatments. Safety and efficacy studies will be required in animals and humans before these promising laboratory results can be applied in clinical practice.

Absorption↗
PubMed1998

Caries prevention by CO2 laser treatment: dependency on the number of pulses used.

The aim of this study was to assess the caries-preventive potential of various carbon dioxide laser conditions and to explore the effect of the number of laser pulses used. The authors irradiated unerupted human molars at two wavelengths--10.6 or 9.6 micrometers--and at 1, 5, 25 or 100 pulses. All teeth were then subjected to pH cycling simulating the conditions for caries progression. Pulsed CO2 laser-preventive treatment inhibited caries-like lesion progression by up to 87 percent. This effect was dependent on the number of pulses used, but there was no correlation between caries resistance and enamel surface morphological changes.

Acetates↗
PubMed1997

Permanent and transient changes in the reflectance of CO2 laser-irradiated dental hard tissues at lambda = 9.3, 9.6, 10.3, and 10.6 microns and at fluences of 1-20 J/cm2.

BACKGROUND AND OBJECTIVE: Effective use of lasers for preventive dental treatments requires accurate knowledge of the amount and distribution of laser energy deposited during irradiation. At CO2 wavelengths, the reflection losses are considerable and reduce the laser energy absorbed by the tissue surface. STUDY DESIGN/MATERIALS AND METHODS: The specular and diffuse reflectance of enamel and dentin were measured at the 10.6-, 10.3-, 9.6-, and 9.3-microns wavelengths of the CO2 laser. Changes in reflectance during and after laser irradiation were investigated. RESULTS: The low-fluence reflectance (< 1 J/cm2) of calcified dental tissues at CO2 wavelengths varies between 9% and 50%. Permanent and transient changes in the reflectance are induced at higher irradiation intensities. CONCLUSION: These changes resulted in increased energy coupling during irradiation.

Animals↗
PubMed1996

[Carbon dioxide embolism during hysteroscopy followed by transient blindness].

A 43 year-old woman, with uterine bleeding and right ovary cyst, was scheduled for hysteroscopy-curettage and laparoscopy. Her history was unremarkable. After induction of general anaesthesia and tracheal intubation (propofol, fentanyl, vecuronium), anesthesia was maintained with N2O/O2 (60%/40%) and isoflurane 1 vol %. The patient was placed in the dorsal lithotomy position. Two minutes after the beginning of CO2 insufflation for hysteroscopy, a ventricular tachycardia with a circulatory arrest suddenly occurred. Insufflation was stopped, cardiopulmonary resuscitation started and lignocaine 100 mg iv administered. The haemodynamic status improved rapidly with a return to sinusal rhythm and stable blood pressure within two minutes. In the recovery room, the patient was restless and experienced blindness for 3 hours. Physical examination and all investigations (EEG, brain CT scan, carotid Doppler and transoesophageal echocardiography) were normal. The most probable diagnosis was a CO2 venous embolism associated with an arterial paradoxal embolism responsible for the temporary blindness.

Adult↗