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Objective: This study evaluated the dentinal and marginal permeability of the cut surface after apicoectomy, treatment and retrocavity preparation with Er:YAG and Nd:YAG lasers. Furthermore, scanning electron microscopy (SEM) analysed the morphological alteration of dentin caused by laser irradiation through an optical fiber., Background Data: Numerous studies have shown the beneficial effects of laser treatment upon sealing dental apex, avoiding the changes of organic fluids, microorganisms and their by-products between the root canal system and periapex., Materials and Methods: Twenty-four extracted and endodontically treated teeth were divided into three groups: GI, apices were resected with Er:YAG laser (350 mJ; 4 Hz) treatment of cut dentinal surface and retrocavity were lased with this same laser (120 mJ; 4 Hz; bur 2051) using the optical fiber 50/10; GII, apicoectomy was performed similar to GI, however the cut dentinal surface was treated with Nd:YAG laser through optical fiber, as well as the retrocavity preparation (100 mJ; 15 Hz; 1.5 W); and GIII (control group), high speed burs were used., Results: Analysis of methylene blue dye penetration into dentin demonstrated that the specimens of the groups irradiated with laser showed to have lower infiltration indices than the control group. These results were compatible with structural and morphological injuries, evidenced by SEM., Conclusion: Under the conditions of the present study, apicoectomy using Er:YAG laser, followed by dentinal surface irradiation and retrocavity preparation with Nd:YAG laser, showed to be an alternative clinical tool able to reduce the dentinal permeability.

The electron paramagnetic resonance (EPR) response of tooth enamel in a monenergetic neutron beam of 14 MeV was studied, with the aim to evaluate the relative neutron to (60)Co sensitivity. Three samples of tooth enamel powder were irradiated in air. A whole tooth and a powdered sample were irradiated in a geometrical PMMA phantom, in order to simulate the real exposure of a tooth inside a human head. The measured dose in enamel was compared to the dose calculated by Monte Carlo simulation. The relative neutron to (60)Co sensitivity using different reference materials (air, water and enamel) was evaluated as well. Large differences in sensitivity values were found depending on the reference material: the obtained relative neutron to (60)Co sensitivity was 0.47+/-0.09 for enamel and 0.15+/-0.03 for water. A comparison with results in fast neutron fields is reported.

Sequences of picosecond pulses of 1.06-microm Nd:YAG laser radiation with a total energy of approximately 2 mJ are transmitted through a hollow-core photonic-crystal fiber with a core diameter of approximately 14 microm and are focused onto a tooth's surface in vitro to ablate dental tissue. The hollow-core photonic-crystal fiber is shown to support the single-fundamental-mode regime for 1.06-microm laser radiation, serving as a spatial filter and allowing the laser beam's quality to be substantially improved. The same fiber is used to transmit emission from plasmas produced by laser pulses onto the tooth's surface in the backward direction for detection and optical diagnostics.

Background and Objectives: This study aimed to assess in vitro the influence of Er:YAG laser energy on the shear bond strength of a total-etch adhesive to lased dentin of primary teeth, and observe under SEM the morphological appearance of laser-ablated dentin surfaces., Study Design/materials and Methods: For SBS, specimens were irradiated with the energies 60 mJ/2 Hz (G2), 80 mJ/2 Hz (G3), 100 mJ/2 Hz (G4). Control (G1) was not irradiated. Dentin surfaces were acid-etched, Single Bond adhesive (3 M) was applied, and resin cylinders were fabricated from Z250 resin (3 M). Bond strength was tested in shear (0.5 mm/min). For morphological analysis, specimens were irradiated using the same energies, either or not acid-etched, and observed by SEM., Results and Conclusions: SBS means, in MPa, were: G1-17.89(+/-4.75); G2-12.34(+/-4.85); G3-10.30(+/-3.67); G4-10.41(+/-4.20). Overall, Er:YAG laser irradiation of primary teeth dentin, prior to the adhesive protocol, adversely affected bond strength. Furthermore, it was noticed that even though there was no significant difference among the Er:YAG laser-treated groups, the increase of laser energy resulted in increasingly cratered surfaces, regardless of acid-etching association., (Copyright 2004 Wiley-Liss, Inc.)

Objective: The purpose of this study was to evaluate the morphological changes of Er, Cr: YSGG laser irradiated dental hard tissues by scanning electron microscopy (SEM)., Methods: 12 freshly extracted premolars were treated with fissure bur, Er, Cr: YSGG laser at 4 watt, Er, Cr: YSGG laser at 6 watt, respectively, and then bisected transversally and longitudinally. The tooth slice were prepared with conventional methods and observed by SEM., Results: Compared with fissure bur, laser treatment resulted in a rather scaly and rough surface. The sections were free of smear layer, with open dentinal tubules. No carbonization and thermal damages were observed. The laser at 6 watt appeared rougher than at 4 watt, occasionally caused micro-cracks., Conclusion: The utilizing of Er, Cr: YSGG laser can contribute to enhance the bond strength between restorative materials and dental hard tissues. It suggests that higher energy could be applied in cutting enamel, whereas the lower energy in dentin.

Human teeth have been considered as dosimeters for decades. Methods include the in vivo measurement of 90Sr/90Y in teeth with a tooth-beta counter, the radiochemical determination of 90Sr in whole teeth, and the measurement of dose in teeth by use of electron paramagnetic resonance. Presented in this paper are results of 2,514 tooth-beta counter measurements, 334 radiochemical measurements, and 218 electron paramagnetic resonance measurements for residents living in settlements along the Techa River. All three kinds of measurements indicate a sharp peak that corresponds to the uptake of 90Sr by tooth tissue. The results can be interpreted in terms of an intake function for 90Sr only if the period of calcification of each individual tooth is considered--such detail on a tooth-by-tooth basis is presented in this paper. The conclusion is reached that the tooth-beta counter data are the most reliable in terms of reconstruction of 90Sr intake; this is due in part to the fact that the tooth-beta counter measures four teeth (all at position 1) with essentially the same time periods of mineralization and because there are a large number of tooth-beta counter measurements. The main utility of electron paramagnetic resonance measurements is considered to be the validation of estimates of external dose; but for this purpose teeth with 90Sr taken up into enamel must be avoided.

The presently available evidence about the magnitude of doses received by members of the public living in villages in the vicinity of Semipalatinsk nuclear test in Kazakhstan, particularly with respect to external radiation, while preliminary, is conflicting. The village of Dolon, in particular, has been identified for many years as the most highly exposed location in the vicinity of the test site. Previous publications cited external doses of more than 2 Gy to residents of Dolon while an expert group assembled by the WHO in 1997 estimated that external doses were likely to have been less than 0.5 Gy. In 2001, a larger expert group workshop was held in Helsinki jointly by the WHO, the National Cancer Institute of the United States, and the Radiation and Nuclear Safety Authority of Finland, with the expressed purpose to acquire data to evaluate the state of knowledge concerning doses received in Kazakhstan. This paper summarizes evidence presented at that workshop. External dose estimates from calculations based on sparse physical measurements and bio-dosimetric estimates based on chromosome abnormalities and electron paramagnetic resonance from a relatively small sample of teeth do not agree well. The physical dose estimates are generally higher than the biodosimetric estimates (1 Gy or more compared to 0.5 Gy or less). When viewed in its entirety, the present body of evidence does not appear to support external doses greater than 0.5 Gy; however, research is continuing to try and resolve the difference in dose estimates from the different methods. Thyroid doses from internal irradiation, which can only be estimated via calculation, are expected to have been several times greater than the doses from external irradiation, especially where received by small children.

In the present study, the compositional changes and knoop hardness of the cavity floor prepared by Er,Cr:YSGG laser irradiation was compared with that of the conventional bur cavity. Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and knoop hardness test. Statistical analyses were performed using the Mann-Whitney U-test; a value of P < 0.01 was considered significant. Surface characteristics of the prepared cavities were also investigated by light microscopy and scanning electron microscopy (SEM). The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavity floor but no significant differences were found between the Ca/P ratio and knoop hardness number of laser and bur cavities. The SEM observation revealed that the lased cavity surface was irregular and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed. Er,Cr:YSGG laser device is considered as one of the most effective and safe devices for cavity preparation because of its many advantages. This includes easy delivery system, minimal thermal damage to the surrounding tissues, minimal thermal-induced changes of dental hard tissue compositions, and favourable surface characteristic.

Purpose: To describe potential effects of multimodality therapy on dental and facial development in long-term survivors of head and neck rhabdomyosarcoma., Patients and Methods: The medical records of all patients aged 20 years or less presenting between 1985 and 1996 with a diagnosis of rhabdomyosarcoma and treated by protocol were reviewed. Head and neck rhabdomyosarcoma patients who were followed in the Dental Service and were alive and free of disease with at least a 5-year follow-up were included in the review. Ten patients satisfied the inclusion criteria and form the basis of this report. The median age at diagnosis of the 10 patients was 4.3 years (range 10 months to 19.5 years). All patients were treated with chemotherapy, two patients underwent surgery, and all but one patient received external beam radiation therapy., Results: Clinical or radiographic dentofacial abnormalities were observed in 8 of the 10 (80%) patients. Abnormalities included enamel defects, bony hypoplasia/facial asymmetry, trismus, velopharyngeal incompetency, tooth/root agenesis, and disturbance in root development. Bony hypoplasia and disturbance in root formation were the most common findings., Conclusions: Multimodality therapy for head and neck rhabdomyosarcoma can result in dentofacial abnormalities that affect the patient's quality of life. The care of the long-term survivor requires a multidisciplinary approach, including early involvement of the dental team.

Objective: This present study was performed to compare the compositional changes of human dentin and, Knoop hardness of the cavity floor prepared by Er:YAG laser irradiation with that of the conventional bur cavity., Background Data: There are still no reports on the compositional changes of dental hard tissues and microhardness of the cavity floor prepared by Er:YAG laser irradiation., Materials and Methods: Fifteen laser and 15 bur cavities were cross-sectioned, and subjected to atomic analysis by SEM-EDX and Knoop hardness testing. Statistical analyses were performed using the Mann-Whitney U test; a value of p < 0.01 was considered significant. Cross sections of the remaining five laser and five bur cavities were examined by light microscopy and then by SEM., Results: The results showed that the quantities of Ca (Ca weight %) and P (P weight %) were increased significantly in the laser cavities, but no significant differences were found between the Ca/P ratio and Knoop hardness number of laser and bur cavities. The results of SEM observation revealed that the lased cavity surface was irregular, and there was also the absence of a smear layer; the orifice of dentinal tubules was exposed., Conclusion: Er:YAG laser device produces minimal thermal induced changes of dental hard tissue compositions; Ca/P ratio and Knoop hardness of the lased cavity floor was almost similar to the bur cavities.

The risk of oral exposure to uranium potentially involves the population at large. Tooth eruption and development are ongoing processes that begin during fetal development and continue until the age of 18 y. Since one of the mechanisms involved in tooth eruption is bone formation and it is well documented that uranium inhibits bone formation, the aim of the present work was to study the effect of oral administration of uranyl nitrate (UN) on tooth eruption and development. Wistar rats aged 1 and 7 d were orally administered a single dose of 90 mg kg(-1) body weight of uranyl nitrate. Two age matched groups received an equal volume of saline and served as controls. The animals were killed at 7 and 14 d of age, respectively. Mandibles were resected and processed to obtain bucco-lingual sections oriented at the level of the mesial root of the first mandibular molar, and histomorphometric studies were performed. Results showed that an acute high dose of uranyl nitrate delays both tooth eruption and development, probably due to its effect on target cells.

This paper reports the first attempt to use L-band spectroscopy for estimating the sensitivity of whole teeth to fast neutrons and gamma-rays. Three teeth were successively irradiated first with fast neutrons with a wide energy spectrum (mean energy around 30 MeV) up to approximately 160 Gy and then with gamma-rays up to approximately 14 Gy. After each irradiation, L-band (approximately 1 GHz) EPR spectra of each whole tooth surrounded by the surface-coil resonator were recorded, yielding a single composite line principally due to CO2- and native radicals. The sensitivities are estimated by the slopes of the linear dose response curves of the dosimetric CO2- radicals. The ratios of the gamma/neutron sensitivities were found to be in the range 8-9 (+/- 2) for the three teeth., (c2002 Elsevier Science Ltd. All rights reserved.)

Dose distribution in the oral region of a medical physicist who received occupational radiation exposure for almost 40 y was determined retrospectively by electron spin resonance measurements of 24 tooth enamel samples using a calibration curve method. The result is considered to agree well with the value estimated from the record of his occupational exposure, including the measured values of personnel monitors. Doses to twelve of the above samples were determined by the additive re-irradiation method. The measured values obtained by the two methods agreed with the exception of one sample.

The problem of retrospectively measuring radiation doses to humans having both external and internal exposures is addressed. A simplified theoretical model is presented by which the internal exposure from a bone seeking radionuclide can be measured and distinguished from an external gamma-ray dose. The model also provides a means of estimating initial acute uptakes of 90Sr.

The use of thin-layer alpha-Al2O3:C thermoluminescent detectors (TLDs) for the assessment of current beta dose rate in human teeth due to 90Sr intake is investigated. The teeth used in this study were collected from members of the Techa river population who were exposed to radiation as a result of releases of the Mayak plutonium production facilities (Southern Urals-Russia) between 1949 and 1956. The beta dose rates from different parts of the tooth (enamel, crown dentine, and root) were determined by storing the detectors over the samples in a shielded environment. The cumulative dose measured by electron paramagnetic resonance (EPR) in different dental tissues is found to be proportional to current dose rate obtained from alpha-Al2O3:C thermoluminescence dosemeters. The retention of 90Sr in various parts of the teeth is discussed.

Background and Objectives: The effects of Er:YAG laser irradiation on dentin have not been sufficiently investigated. The purpose of this study was to investigate the effects of Er:YAG laser irradiation on dentin., Study Design/materials and Methods: After cavities were prepared using Er:YAG laser irradiation or rotary cutting instruments, histological observations of cavity-floor dentin utilizing polarizing microscopy, microradiography and light microscopy, and analysis of composition of cavity-floor dentin using Fourier-transformed (FT-IR) spectrometry were conducted., Results: In the laser-treated side, a deeply stained basophilic layer was observed. The number of odontoblastic processes present was obviously less in the laser-treated side than in the bur-treated side. FT-IR analysis revealed that compared to the bur-treated side, a broad background peak at around 1,600 cm(-1) was present., Conclusions: Er:YAG laser irradiation might have denatured the organic materials of dentin., (Copyright 2002 Wiley-Liss, Inc.)

Regarding in vivo L-band dosimetry with human teeth, a number of preliminary experiments were carried out that were linked to the resonators response and the relative contribution of enamel to the EPR signal intensity of irradiated whole teeth. The sensitivity of the extended loop resonator varies in the antenna plane, but this variation tends to vanish when the sample is moved away from this plane. When the loop antenna is placed just above the highly irradiated molar, around 88% of the dosimetric signal is due to the crown enamel. The sensitivity inside a birdcage cavity is approximately equal over the volume of a molar; only 30% of the molar's total dosimetric signal results from enamel. Some decrease in the intensity of the dosimetric signal from enamel is observed after irradiation. At room temperature, the signal is reduced by about 20% within 90 days and approaches a plateau with a time constant of about 35 days.

The back-scattered spectrum of ultrashort laser pulses (800 nm, 0.2 ps) was studied in human dental and other hard tissues in vitro below the ablation threshold. Frequency doubled radiation (SHG), frequency tripled radiation and two-photon fluorescence were detected. The relative yield for these processes was measured for various pulse energies. The dependence of the SHG signal on probe thickness was determined in forward and back scattering geometry. SHG is sensitive to linear polarization of the incident laser radiation. SHG in human teeth was studied in vitro showing larger signals in dentin than in cementum and enamel. In carious areas no SHG signal could be detected. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed.

Objective: The purpose of this study was to verify if the application of the Nd:YAG laser following pretreatment of dentin with adhesive systems that were not light cured in class V cavities and were prepared with Er:YAG laser would promote better sealing of the gingival margins when compared to cavities prepared the conventional way., Background Data: Previous studies had shown that the pretreatment of dentin with laser irradiation after the application of an adhesive system is efficient in achieving higher shear bond and tensile bond strength., Materials and Methods: Er:YAG laser (Kavo-Key, Germany) with 350 mJ, 4 Hz, and 116.7 J/cm2 was used for cavity preparation. The conventional preparation was made with diamond bur mounted in high-speed turbine. Dentin treatment was accomplished using an Nd:YAG laser (Pulse Master 1000, ADT. USA) at 60 mJ, 10 Hz, and 74.65/cm2 following application of the adhesive system. The cavities were stored with Single Bond/Z100 and Prime & Bond NT/TPH. Eighty bovine incisors were used, and class V preparations were done at buccal and lingual surfaces divided into eight groups: (1) Er:YAG preparation + Prime & Bond NT + TPH; (2) Er:YAG preparation + Single Bond + Z100; (3) Er:YAG preparation + Single Bond + Nd:YAG + Z100; (4) Er:YAG preparation + Prime & Bond NT + Nd:YAG + TPH; (5) conventional preparation + Prime & Bond NT + TPH; (6) conventional preparation + Single Bond + Z100; (7) conventional preparation + Single Bond + Nd:YAG + Z100; (8) conventional preparation + Prime & Bond NT + Nd:YAG + TPH. All specimens were thermocycled for 300 full cycles between 5 degrees C+/-2 degrees C and 55 degrees C+/-2 degrees C (dwell time of 30 sec), and stored in 50% silver nitrate solution for 24 h soaked in photodeveloping solution and exposed to fluorescent light for 6 h. After this procedure, the specimens were sectioned longitudinally in 3 portions and the extension of microleakage at the gingival wall was determined following a criteria ranging from 0 to 4 using scanning electron microscopy (SEM). The medium portion sectioned of each specimen was polished and prepared for nanoleakage avaliation by SEM., Results: Kruskall-Wallis and Miller statistical tests determined that group 3 presented less microleakage and nanoleakage., Conclusion: Application of the Nd:YAG laser following pretreatment of dentin with adhesive Single Bond non-photocured Single Bond adhesive in cavities prepared with Er:YAG promote better sealing of the gingival margins.

A mathematical model for calculation of the 90Sr absorbed doses in dental tissues is presented. The results of the Monte-Carlo calculations are compared to the data obtained by EPR measurements of dental tissues. Radiometric measurements of the 90Sr concentrations. TLD and EPR dosimetry investigations were performed in animal (dog) study. The importance of the irregular 90Sr distribution in the dentine for absorbed dose formation has been shown. The dominant dose formation factors (main source-tissues) were identified for the crown dentine and enamel. The model has shown agreement with experimental data which allows to determine further directions of the human tooth model development.

The radiation dose on tooth enamel of children living close to Chernobyl has been evaluated by EPR. The sample preparation was reduced to a minimum of mechanical steps to remove a piece of enamel. A standard X-ray tube at low energy was used for additive irradiation. The filtration effect of facial soft tissue was taken into account. The radiation dose for a group of teeth slightly exceeds the annual dose, whereas for another group the dose very much exceeds the annual dose. Since the higher dose is found in teeth whose enamel have much lower EPR sensitivity to the radiation, it can be suggested that for these teeth the native signal could alter the evaluation of the smaller radiation signal.

Objectives: Since the first description of rapid destruction of dental hard tissues following head and neck radiotherapy 80 years ago, "radiation caries" is an established clinical finding. The internationally accepted clinical evaluation score RTOG/EORTC however is lacking a classification of this frequent radiogenic alteration., Material and Methods: Medical records, data and images of radiation effects on the teeth of more than 1,500 patients, who underwent periradiotherapeutic care, were analyzed. Macroscopic alterations regarding the grade of late lesions of tooth crowns were used for a classification into 4 grades according to the RTOG/EORTC guidelines., Results: No early radiation effects were found by macroscopic inspection. In the first 90 days following radiotherapy 1/3 of the patients complained of reversible hypersensitivity, which may be related to a temporary hyperemia of the pulp. It was possible to classify radiation caries as a late radiation effect on a graded scale as known from RTOG/EORTC for other organ systems. This is a prerequisite for the integration of radiation caries into the international nomenclature of the RTOG/EORTC classification., Conclusions: The documentation of early radiation effects on dental hard tissues seems to be neglectable. On the other hand the documentation of Late radiation effects has a high clinical impact. The identification of an initial lesion at the high-risk areas of the neck and incisal part of the tooth can lead to a successful therapy as a major prerequisite for orofacial rehabilitation. An internationally standardized documentation is a basis for the evaluation of the side effects of radiooncotic therapy as well as the effectiveness of protective and supportive procedures.

An analysis of doses to tooth enamel and to organs was carried out to develop a method that can predict the organ doses and the effective dose by electron spin resonance (ESR) dosimetry using tooth samples for external photon exposure. Absorbed dose to tooth enamel and organ doses were obtained by Monte Carlo calculations using the EGS4 code in combination with a mathematical human model with a newly defined teeth part. The calculations gave quantitative relations between tooth enamel dose and organ doses for some cases of external photon exposure. It was also found that tooth enamel dose depends more significantly on energy of incident photons than the other organ dose or the effective dose. The obtained data are to be useful for the assessment of individual dose in past exposure events by the ESR dosimetry using tooth enamel.

Between 1986 and 1991 approximately 6500 Latvian inhabitants were recruited for clean-up work at the Chernobyl nuclear power plant. Their absorbed doses are usually unknown, because less than half of them had their external exposure officially documented. Clinical investigations show a high morbidity rate for these clean-up workers when compared with that of the general population. In order to understand the causes of their diseases and the impact of ionising radiation, electron spin resonance (ESR) has been used to measure the absorbed doses in human tooth enamel. The doses estimated by ESR were between two and three times higher than previously documented and are in accord with the results of immunological and biological tests. The results may be explained by considering the effects of irradiation caused by long-lived incorporated radionuclides.

Ultrasound transmission velocity (UTV) in isotropic material as a measure for the modulus of elasticity was correlated to mechanical properties. Changes in micromechanical properties of radiated teeth and influence of the oral cavity were to be evaluated nondestructively. UTV was measured in extracted teeth after 36 Gy and 62 Gy of in situ (enorally, with no contact to the oral cavity) and in vitro irradiation. Relative to controls, teeth subjected to 62 Gy in vivo showed higher UTV values for dentine and enamel. Sound teeth irradiated with 60 Gy in situ also showed higher UTV values for enamel, whereas dentine values were not significantly different from those of control. The mechanical properties of teeth irradiated in vitro were affected only after high experimental doses of up to 500 Gy. The difference between in vivo and in vitro mechanical properties may be due to radioxerostomia-induced damages as well as the status of dentine vitality. This supports the concept of direct radiation-induced damage in synergy with radioxerostomia-induced caries.

People living on the banks of the Techa river were exposed to 90Sr in the early 1950s. Data obtained by radiochemical measurements of extracted permanent teeth, 90Sr autopsy measurements in bone and tooth samples, in vivo measurements of surface beta activity of the anterior teeth and whole-body counter (WBC) measurements of 90Sr in the skeleton have been analyzed. Surface beta activity measurements indicate a biological half-life of 90Sr of about 35 years in enamel. The WBC measurements have been performed since 1974 and a model for the age-dependent strontium retention in human bone has been used to extrapolate to previous time periods when the other measurement results were obtained. For the first decade after the intake, the ratio of the 90Sr concentrations in teeth and bones were found to decrease with age at the time of major intake, from about 10 for 1-year-old children to about 0.3 for adults. There was a considerable variability of individual data within each age group. For adults, the correlation between 90Sr in skeleton and teeth was not high at 0.47 according to radiochemical data for posterior teeth (molars and premolars) and 0.43 according to measurements of surface beta activity for anterior teeth. For children and adolescents there was no correlation between individual measurements in the skeleton and teeth. The absorbed dose in enamel due to 90Sr in dentine has been calculated by Monte Carlo simulations of the electron transport. The results are in agreement with EPR measurements of the absorbed dose in the enamel of persons exposed, mainly due to 90Sr ingestion.

A pre-molar of a Toxodon platensis (sp), a large mammal that inhabited the forests of Southeast Brazil during quaternary times, was dated by electron spin resonance (ESR). Enamel and dentine were separated giving, the following archeological doses (AD): (4.0+/-0.8) and (11+/-2) Gy, respectively. This difference was explained by the higher content of Uranium in dentine (25.1+/-0.3) ppm as compared to enamel (0.37+/-0.03) ppm. Taking account of the internal dose contribution to the AD, the age obtained is (6.7+/-1.3) ky BP for dentine and (5.0+/-1.6) ky BP for enamel.

Low frequency electron paramagnetic resonance (EPR) provides the potential advantage of making accurate and sensitive measurements of absorbed radiation dose in teeth in situ, i.e. without removing the teeth from the potential victim. The potential limiting factors for making such measurements are: (1) whether low frequency EPR is sufficiently sensitive to detect radiation-induced signal in human teeth; (2) whether sufficient sensitivity can be maintained under in vivo conditions. In this manuscript, we summarize results indicating that this approach is feasible. Using 1.2 GHz EPR spectroscopy, we found that the lower limit for these measurements in isolated human teeth is 0.2 Gy or lower. Measurements of radiation-induced EPR signals in the teeth of living rats were achieved with sufficient sensitivity to indicate that, when taking into consideration the larger mass of human teeth, similar measurements in human teeth in situ would provide sensitivity in the dose range for potential accidental exposures. We estimate that the current lower limit for detecting radiation doses in human teeth in situ (in vivo) is 0.5-1.0 Gy; this would be sufficient for determining if a person has been exposed to potentially life threatening doses of ionizing radiation. The limiting factor for sensitivity appears to be background signals rather than signal/noise, and there are feasible means to overcome this problem and further increase sensitivity. The additional instrumental developments required to make an effective in vivo EPR dosimetric spectrometer for the measurements in teeth in human subjects in situ, seem quite achievable.

Nearly 25 years ago, Motoji Ikeya demonstrated the potential of ESR dating. From a single substance (stalagmitic carbonate) and a single site (Akiyoshi Cavern), the field has grown to include materials from all over the world and time periods from a few thousand years ago to several million years ago. A vigorous program of instrumentation development has increased the precision of measurements as well as opening up new ways of collecting and interpreting spectra. Yet there are still references to ESR dating as an 'experimental' technique, one which cannot be trusted to produce dates that are accurate or precise. This paper discusses areas for which this is true and suggests what should be done to convince skeptics. Other areas for which the evidence suggests that ESR is at least as reliable as 'standard' methods will also be covered.

Electron spin resonance (ESR) spectroscopy is used to assess absorbed doses of six teeth belonging to victims of the highly irradiated group of Goiânia accident. The influence of the broad background signal at g = 2.0040 as well as of the unstable fraction of CO2- radicals was taken into account in dose estimates. Three victims teeth showed absorbed doses comparable to those estimated by chromosomal analysis. For the other three teeth, the doses were higher by a factor of 1.3, 1.8 and 2.2.

Malignant lymphoma is one of the most common hematological diseases of children. The prognosis is fairly good with multimodal cancer therapy. We reported a boy with Burkitt's lymphoma in the nasal cavity who received chemotherapy and irradiation of the head and neck area at four years of age. During seven years of follow-up, we studied the developmental effects of cancer therapy, including general growth, maxillofacial bones, and dentition. Compared with boys of matching age, the development of his entire body and maxillofacial bones was delayed. In the irradiated areas, the roots of teeth were short or poorly developed and the root apices showed premature closure. After the patient was in remission from the tumor in his early childhood, the long-term effects of cancer therapy on dental and maxillofacial development are worth our further evaluation and follow-up.

A total of 27 teeth were examined in those subjects having been exposed to ionizing radiation in doses between 0.5 and 2.0 Gy, together with ten teeth of essentially healthy individuals. The enamel, dentine and cement mineral and protein contents were studied versus control with the aid of infrared spectroscopy techniques. It has been ascertained that in the teeth of patients presenting with dose loads there take place changes in the organic matrix. Amide I: amide II ratio tends to diminish toward contribution of Amide I. The mineral composition of the enamel reveals practically no changes under exposure to radiation. The dentine and cement display clear-cut changes in the mineral component. There appear absorption bands that belong to more soluble forms of calcium phosphate, which fact suggests an active destructive process in underlying hard tissues of the teeth, that gets intensified under exposure to ionizing radiation.

Objectives: To estimate the radiation-related risk associated with twelve imaging programs available on the Orthophos (Siemens, Erlangen, Germany) dental panoramic radiography unit., Methods: Organ absorbed doses for each program were measured using a Rando anthropomorphic phantom loaded with thermoluminescent dosemeters. Effective dose (E) was calculated in two ways; first, using the method recommended by the International Commission on Radiological Protection, which excludes the salivary glands (designated Eexc), and second, with its inclusion (designated Einc). Organ and effective doses were both used to compare the various imaging programs., Results: In 11 of the 12 programs studied the salivary glands received the highest individual organ dose, and Einc was found to be up to double Eexc. When the image was restricted to the dentition (program 2) organ doses were lower than for the complete jaws (program 1) by up to 85%, and Eexc and Einc reduced by about one half. When programs 2 and 6 (to image the temporomandibular joints) are used in place of program 1, the former combination provides more image information at an equivalent risk., Conclusions: The value of E in panoramic radiography depends on the inclusion of the salivary glands in the calculation and the magnitude of the dose.

Objective: The purposes of this study were to determine the degree of apical leakage using a dye penetration method after argon, pulsed Nd:YAG with or without black ink, or Er:YAG laser treatment and obturation, and to compare the results of three types of laser irradiation in vitro., Summary Background Data: There have been only a few reports of the laser effect on apical leakage after laser treatment and obturation., Methods: Seventy-five human extracted single root teeth were divided into five groups of 15 teeth each and prepared up to a #60 K-file size. One group served as the control and was not irradiated. The other four groups were irradiated with an argon laser at 0.3 W for 3 seconds at continuous mode, pulsed Nd:YAG laser at 2 W and 20 Hz for 4 seconds with or without black ink, and Er:YAG laser at 50 mJ per pulse and 4 Hz for 5 seconds. In each group, ten teeth for the apical leakage study were obturated and immersed in rhodamine B solution for 48 hours at 37 degrees C, and the others were used for the observation by scanning electron microscopy (SEM). All teeth were longitudinally bisected and observed by stereoscopy or SEM., Results: After pulsed Nd:YAG laser treatment with black ink and obturation, the apical leakage degree (mean score: 0) was reduced compared to that in the control (mean score: 1.2) significantly (p < 0.05). SEM findings showed that specimens irradiated by pulsed Nd:YAG laser with black ink presented clean root canal walls with debris and smear layer evaporated, melted, fused, and recrystallized in most cases., Conclusion: These results suggest that pulsed Nd:YAG laser irradiation with black ink at the apical stop is useful for the reduction of apical leakage after obturation.

Objective: This study was conducted to establish the operating parameters of the argon laser without thermal damage to the pulp tissue for clinical applications., Summary Background Data: Previous studies have mainly compared the temperature modifications of the pulp chamber in a very limited situation, where a complete view of the thermal history cannot be obtained nor even extrapolated to new applications., Methods: We used samples of molar and premolar tooth where a class V cavity was prepared and illuminated with an argon laser at different power levels, fixing the exposition area for all cases. Situations including open cavity and teeth restoration were analyzed. High-precision thermistors were placed in four different positions, one of which was inside the pulp chamber. The temperature evolution was monitored continuously by an interfaced computer during all laser exposure. Special attention was paid to the intrapulpal temperature variation because it is considered the most vulnerable thermal region. The temperature time evolution allowed the determination of the operating conditions (power-time-temperature variation) in which the use of the argon laser causes no pulpal damage. As a function of temperature variation, we divided the whole parameter space (power-time-temperature) into zones and the optimum zone of operation was determined., Conclusions: We created a diagram called power-time-temperature (PTT) where zones of temperature increased under laser irradiation allow the verification of which condition is safe for clinical laser application. The results have a broad use when this type of analysis is applicable.

Objective: This investigation was performed to evaluate the effect of CO2 laser irradiation on the acquired acid resistance of dental hard tissues to artificial caries-like formation and the ultrastructure of lased areas was morphologically investigated in vitro., Summary Background Data: In recent years, many studies have been carried out to evaluate the effect of the CO2 laser on the enhanced resistance to artificial caries formation of enamel. However, a limited number of papers concerning its effect on dentin have been published., Methods: A CO2 laser of 10.6 microns wavelength was used to irradiate human enamel and dentin samples from 20 extracted human molar teeth, and samples were subjected to 2 microliters of 0.1 M lactic acid solution (pH 4.8) for 24 h at 36 degrees C. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometry and the morphological changes were investigated by scanning electron microscopy (SEM)., Results: The lowest mean Ca2+ ppm was recorded in the samples irradiated at 3 W, followed by 2 W, 1 W, and unlased samples. SEM observation showed that the lased areas were melting with solidification of the smear layer. Even after acid demineralization, the lased surfaces were almost unchanged., Conclusions: The results of this study suggested that CO2 laser irradiation could sufficiently melt and solidify the enamel and dentin surfaces and thus enhance resistance to artificial caries-like formation.

Background: This review of children and adolescents with nonorbital soft-tissue sarcoma of the head and neck was undertaken to describe late sequelae of treatment, as manifested primarily by problems with statural growth, facial and nuchal symmetry, dentition, vision and hearing, and school performance., Procedure: Four hundred sixty-nine patients entered the IRS-II and -III protocols with localized, nonorbital soft-tissue sarcomas of the head and neck from 1978 through 1987. Their overall survival rate was 53% (250/469) at 5 years. Two hundred thirteen patients were surviving relapse-free 5 or more years after diagnosis, for whom there were serial height measurements at 2 or more years after initiation of therapy. Their median age at diagnosis was 5 years; the median length of follow-up was 7 years. All received multiple-agent chemotherapy, and all but 3 received irradiation to the primary tumor volume. Sixty-eight percent of the tumors arose in cranial parameningeal sites, 22% in nonparameningeal sites, and 10% in the neck. We reviewed flow sheets submitted to the IRS Group Statistical Office to ascertain which late sequelae were recorded., Results: One hundred sixty-four patients (77%) had one or more problems recorded. One hundred ninety of the two hundred thirteen patients (89%) were under 15 years of age at study entry, and at follow-up 92 (48%) had failed to maintain their initial height velocity, which had decreased by more than 25 percentile points from the original value. Thirty-six of the one hundred ninety patients (19%) were receiving growth hormone injections. Hypoplasia or asymmetry of tissues in the primary tumor site was reported in 74 patients, and 13 underwent reconstructive surgery. Poor dentition or malformed teeth were noted in 61 patients. Impaired vision developed in 37 patients, owing primarily to cataracts, corneal changes, and optic atrophy. Thirty-six patients had decreased hearing acuity, and 9 were fitted with hearing aids; 5 of these 9 had received cisplatin. Thirty-five patients were noted to have problems learning in school. Four patients developed a second malignancy (two sarcomas, one carcinoma, one leukemia)., Conclusions: Late sequelae affected the majority of these patients treated for soft-tissue sarcoma of the head and neck on IRS-II and -III. The potential impact of certain sequelae could be reduced by specific measures, such as surgical reconstruction and hormonal therapy. Late sequelae must be taken into account in designing future curative treatments., (Copyright 1999 Wiley-Liss, Inc.)

Stationary and dynamic characteristics of autofluorescence in human dentine were examined with a nanosecond time-resolved fluorescence microphotometer. With ageing, the intensity of the fluorescence increased whereas the decay time decreased. There were no differences in fluorescence intensity, decay time or spectral profile among tooth types taken from the same individuals or from individuals of the same age. Fluorescence intensity was enhanced after the application of heat (37 and 50 degrees C), but remained unchanged when specimens were kept at 4 degrees C. These results suggest that the increase in fluorescence intensity was partially due to a temperature-dependent physicochemical mechanism.

Doses of radiation estimated from ESR analysis of tooth enamel were compared with activities of alpha- and beta-emitters in enamel and in bone tissue of mandibles of 77 reindeer from populations with different levels of radiation contamination. Contribution of the radionuclides incorporated into bone (or bone-seeking radionuclides in food) to ESR-evaluated doses was substantial and the contribution of the radionuclides incorporated into enamel itself proved to be relatively small.

Objective: The purpose of this study was to evaluate the success and failure of root canal treatment performed in areas of previous irradiation and to examine any cases of osteoradionecrosis associated with such treatment., Study Design: A retrospective analysis was done on 22 teeth that had root canal treatment after radiation therapy. Strict radiographic and clinical criteria were used to determine success and failure., Results: There was a mean follow-up period of 19 months. Of 22 cases, 20 (91%) were considered successful. Both failures occurred with a diagnosis of pulpal necrosis. There were no occurrences of osteoradionecrosis., Conclusions: Our study showed that root canal treatment in previously irradiated patients may be successful. In addition, treatment approaches, as well as the criteria for success and failure, should be the same for irradiated patients as for those who have not received radiation treatment.

There has been an explosion in research, articles and case reports about laser therapy during recent years. The future is promising and the literature is exciting, but sometimes conflicting in findings. A review of the literature reveals that lasers have many uses in medicine, often allowing procedures to be performed that would not have been feasible through other means. Lasers would seem to have a much greater role in the future than is now realized. Each laser has its own unique features, advantages and disadvantages. While one laser may be suitable for some procedures, it will be unsuitable for others. Some reviewers have expressed concerns about safety and cost/benefit.

The authors describe the side-effects and complications occurring in the oral cavity during the irradiation treatment of head and neck tumours. They stress the necessity of dental therapy before, during and after irradiation so that occasional subsequent grave complications (for instance osteoradionecrosis) could be prevented. They emphasize the importance of basic radiological knowledge of dental surgeons and dentists and their cooperation with the irradiation therapists.

Aim: In spite of a great number of relevant studies the etiology of radiation induced caries still is discussed in controversy: The assumption of direct radiation induced lesions in the hard tissue is in contrast to an indirect pathogenesis mediated via radio-xerostomia., Methods: A systematic study is presented, comparing teeth with a manifest radiation caries (group 1, about 60 Gy, long interval to the extraction) and clinically caries free teeth (group 2, about 30 Gy, short interval) with tooth specimens after an experimental enoral (in situ) irradiation (60 Gy, group 3) and after in vitro irradiation (500 to 2,500 Gy, group 4). 60Co was the irradiation source. Sound teeth were used as a standard (group 5). For non destructive visualisation of subsurface histotomograms by confocal laser scanning microscopy (CLSM) teeth were either used as fresh sections or as Technovit embedded thin slices (sawing grinding technique)., Results: Tooth samples from radiotherapy patients (cancer therapeutic doses, long interval before extraction; group 1) showed three characteristic changes: 1, rarefcation of the branching (ramification) of odontoblast processes near the junction, 2. dentine tubules end in front of the interface to the hard tissue and 3, in dentine the interface is characterised by an zone (about 10 microns wide) of low intensity of the remitted light., Conclusions: The obliteration of the dentine tubules, preceded by a degeneration of the odontoblast processes, is obviously the result of a direct radiogenic cell damage with hampered vascularisation and metabolism particularly in the area of the terminations of the odontoblast processes. The deficit in metabolism combined with a latent damage of the parenchyma (hypo-remitting zone) is evidence for the functional symptoms (subsurface caries). The prerequisite for the micromorphological manifestation of this direct irradiation damage is a vital tooth and in consequence cannot be simulated in situ or in vivo.

Despite more than 30 years of experience with low level laser therapy (LLLT) or 'biostimulation' in dentistry, concerns remain as to its effectiveness as a treatment modality. Controlled clinical studies have demonstrated that while LLLT is effective for some specific applications, it is not a panacea. This paper provides an outline of the biological basis of LLLT and summarizes the findings of controlled clinical studies of the use of LLLT for specific soft tissue applications in dentistry. Areas of controversy where there is a pressing need for further research are identified.

The authors examine the dental and skeletal alterations consequent to the use of radiotherapy as the elective method of treating retinoblastoma, an endobulbar neuroectodermal tumour typical of early infancy. The authors revise the basic concepts of radiobiology and the modifications induced by radiation in developing tissues with reference to both alterations at a microscopic (histological) level and those at a macroscopic level, namely of a morphological and structural nature. In the first part of the study the authors examine the damage to dental structures relating to both developing tissues and damage to mature tissue. The second part of the paper analyses radiation damage on cartilage and bone tissues in the process of formation and the authors present their documentation in the form of iconographic and radiographic material together with an esthetic face analysis performed using Ricketts' [correction of Rickettz's] method in three cases referred to their attention.

Objective: Infection control concerns regarding the handling of teeth for research purposes have prompted investigators to evaluate the effects of disinfection/sterilization on extracted teeth. The objectives of this literature review were to assess the reported findings of the effect of disinfection or sterilization on teeth used for in vitro bonding studies and make recommendations on their use., Methods: A search of the literature was performed to obtain background information on infection control guidelines and current findings regarding disinfection or sterilization of extracted teeth. Published articles addressing the effects of different disinfection and sterilizing procedures on the tooth, such as structural changes of dentin and dentin permeability or effect on bond strengths, were examined and compared for agreement or disagreement of findings. The review was organized by the type of disinfection or sterilization method utilized by the investigators. These methods were evaluated in an attempt to address whether disinfection/sterilization of extracted teeth can be recommended or if the procedure simply produces another variable., Results: Formalin, chemical heat sterilization (Chemiclave), autoclave, ethylene oxide and gamma radiation methods of disinfection/sterilization have been investigated for their effects on extracted teeth. When the effect of formalin storage on dentin bond strengths was examined, investigator results were extremely varied. Autoclave and chemical sterilization were found to produce comparable dentin bond results when compared to controls. Gamma radiation did not produce structural changes in the dentin but it currently has not been investigated for its effect on dentin bond strength. And while ethylene oxide produced similar dentin bond strength results when compared to controls, its use as a sterilant was determined to be ineffective., Significance: Investigators have found formalin storage to be effective for infection control purposes. It cannot, however, be recommended as a storage medium for dentin bonding studies due to the variability in dentin bond strengths resulting from its use. Ethylene oxide is also not recommended due to its inability to effectively sterilize teeth. Chemical heat and autoclave sterilization methods are recommended for preventing cross-contamination during in vitro dentin bonding research. This recommendation is based on current research findings which examined the effect of these sterilization methods on dentin and dentin bond strengths.