Effect of cryogenic treatment on nickel-titanium endodontic instruments.

AIM: To investigate the effects of cryogenic treatment on nickel-titanium endodontic instruments. The null hypothesis was that cryogenic treatment would result in no changes in composition, microhardness or cutting efficiency of nickel-titanium instruments. METHODOLOGY: Microhardness was measured on 30 nickel-titanium K-files (ISO size 25) using a Vicker's indenter. Elemental composition was measured on two instruments using X-ray spectroscopy. A nickel-titanium bulk specimen was analysed for crystalline phase composition using X-ray diffraction. Half of the specimens to be used for each analysis were subjected to a cryogenic treatment in liquid nitrogen (-196 degrees C) for either 3 s (microhardness specimens) or 10 min (other specimens). Cutting efficiency was assessed by recording operator choice using 80 nickel-titanium rotary instruments (ProFile 20, .06) half of which had been cryogenically treated and had been distributed amongst 14 clinicians. After conditioning by preparing four corresponding canals, each pair of instruments were evaluated for cutting efficiency by a clinician during preparation of one canal system in vitro. A Student's t-test was used to analyse the microhardness data, and a binomial test was used to analyse the observer choice data. Composition data were analysed qualitatively. RESULTS: Cryogenically treated specimens had a significantly higher microhardness than the controls (P < 0.001; beta > 0.999). Observers showed a preference for cryogenically treated instruments (61%), but this was not significant (P = 0.21). Both treated and control specimens were composed of 56% Ni, 44% Ti, 0% N (by weight) with a majority in the austenite phase. CONCLUSIONS: Cryogenic treatment resulted in increased microhardness, but this increase was not detected clinically. There was no measurable change in elemental or crystalline phase composition.

The efficacy of pain control following nonsurgical root canal treatment using ibuprofen or a combination of ibuprofen and acetaminophen in a randomized, double-blind, placebo-controlled study.

AIM: To compare ibuprofen, to an ibuprofen/acetaminophen combination in managing postoperative pain following root canal treatment. It is hypothesized that the drug combination will provide more postoperative pain relief than the placebo or ibuprofen alone. METHODOLOGY: Patients presenting at the Texas A&M Baylor College of Dentistry's graduate endodontic clinic, experiencing moderate to severe pain, were considered potential candidates. Fifty-seven patients were included based on established criteria. Following administration of local anaesthesia, a pulpectomy was performed. The patients were administered a single dose of either: (i) placebo; (ii) 600 mg ibuprofen; or (iii) 600 mg ibuprofen and 1000 mg of acetaminophen. Patients recorded pain intensity following treatment on a visual analogue scale and a baseline four-point category pain scale as well as pain relief every hour for the first 4 h then every 2 h thereafter for a total of 8 h. A general linear model (GLM) analysis was used to analyse the outcome. RESULTS: Based upon the GLM analysis, there was a significant difference between the ibuprofen and the combination drug group, and between placebo and combination drug groups. There was no significant difference between the placebo and the ibuprofen. CONCLUSION: The results demonstrate that the combination of ibuprofen with acetaminophen may be more effective than ibuprofen alone for the management of postoperative endodontic pain.

Comparison of Diaket and MTA when used as root-end filling materials to support regeneration of the periradicular tissues.

AIM: The objective of this study was to evaluate on a comparative basis the potential for mineral trioxide aggregate (MTA) and Diaket to promote periradicular tissue regeneration when used as surgical root-end filling materials. METHODOLOGY: Seven dogs weighing between 15 and 25 kg were anesthetized prior to having the root canals of their mandibular premolars accessed, cleaned, shaped and obturated. Coronal access cavities were restored with IRM. Surgical access to the root ends was established and the root ends were resected and prepared with ultrasonic tips. Root-end fillings of either MTA or thickly mixed Diaket were randomly assigned to the preparations. Reflected tissues were repositioned and sutured with 4-0 vicryl sutures. Sixty days postsurgery, the animals were killed, perfused with 10% neutral buffered formalin and the third and fourth premolars removed in block sections. The specimens were demineralized and sectioned at 6-microm intervals for histological assessment. Sections were stained with either haematoxylin and eosin or Gomori's one step trichrome stain and examined under the light microscope. All evaluations were made by two calibrated examiners and gradings were scored based on established criteria. The raw data was evaluated statistically using anova after adjusting for the animal block effect. RESULTS: Statistical evaluation indicated that there were no statistical differences between the observed regenerative responses of the tissues to the two root-end filling materials. CONCLUSIONS: Both Diaket and MTA can support almost complete regeneration of the periradicular periodontium when used as root-end filling materials in periradicular surgery on noninfected teeth.

Role of angiography in the detection of aortic branch vessel injury after blunt thoracic trauma.

PURPOSE: The occurrence of aortic arch branch vessel injury as an isolated occurrence or in association with aortic injury after blunt chest trauma has not been emphasized in the literature. The imaging evaluation is also controversial. METHODS: We reviewed thoracic aortograms of 166 patients examined at our institution from May 1995 to May 1999 performed after blunt thoracic trauma. We evaluated the aortograms for aortic and arch branch vessel injuries. Twenty-four injuries were detected and all patients had either a wide mediastinum demonstrated on plain radiographs (22 patients) or mechanism of injury conducive to aortic injury. RESULTS: Of the 166 patients, 24 (14%; 16 men, 8 women; mean age, 50 years) had aortic or arch branch vessel injuries. Isolated aortic injury occurred in 15 (9%) of 166 patients. Branch vessel injury occurred in 9 (5%) of 166 patients; seven patients (10 branch vessels) had isolated branch vessel injury and two patients (three branch vessels) had branch vessel injury associated with aortic injury. The injured branch vessels were brachiocephalic artery (four), left common carotid artery (four), left subclavian artery (three), right internal mammary artery (one), and left vertebral artery (one). The types of branch vessel injuries included intimal tears (nine vessels; 69%), and transection causing a pseudoaneurysm (four vessels; 31%). Revised Trauma Scores in patients with branch vessel injuries were 12 in seven patients and 11 and 4 in one each. CONCLUSION: We emphasize the angiographic findings in these patients that can at times be quite subtle. Awareness of the incidence of such injuries either in isolation or associated with aortic injury has implications regarding evaluation of this patient population with less invasive techniques such as CT or transesophageal echocardiography.

A survey of interfacial forces used during endosonic instrumentation of root canals.

AIM: The aim of this in-vitro study was to measure interfacial forces acting between root canal dentine and ultrasonic files during endosonic instrumentation. METHODOLOGY: Single-rooted teeth were mounted on a cantilevered aluminium beam to which two pairs of single element strain gauges were joined in a half-bridge configuration mounted at right angles to each other. The strain gauges were connected to an analogue-to-digital converter fitted in a microcomputer via a conditioning amplifier. This enabled strains to be recorded as a function of interfacial forces over a period of time. Twenty operators instrumented root canals using sizes 15, 20 and 25 ultrasonically energized K-type files. The lateral forces generated were calculated. RESULTS: The mean interfacial forces used varied widely between operators and files, ranging from 18 g to 149 g, but there was a consistency in the relative magnitude for each operator. The average force used by the operators increased with file size; the differences between file sizes were significant (P < 0.05). CONCLUSIONS: The range of forces measured is broader than previously reported and may have a bearing on possible uncontrolled dentine removal, even during ultrasonically activated irrigation.

UDS induction by an array of standard carcinogens in human and rodent hepatocytes: effect of cryopreservation.

The UDS induction assay with primary hepatocytes as the target cells is a determinative assay for chemical carcinogens. This assay is, however, limited to the availability of freshly prepared liver cells. A cryopreservation technique for liver cells has recently been described. Frozen cells have been shown to retain a variety of enzyme activities essential for xenobiotic metabolism after being thawed. In the present investigation, 19 direct or indirect-acting carcinogens were tested with respect to their capacity to induce DNA repair in primary as well as cryopreserved human and rat hepatocytes. Cryopreserved cells yielded results that were essentially indistinguishable from fresh cells. Only marginal differences were observed between hepatocytes of rat or human origin. These results demonstrate the suitability of cryopreserved hepatocytes as indicator cells for the study of UDS induction to discover possible carcinogenicity in chemicals.

A survey of interfacial forces used during filing of root canals.

The pattern of dentine removal during endodontic instrumentation is influenced by many factors including the interfacial forces applied by the operator. The aim of this study was to investigate the influence of operators and different sizes and types of instruments on the magnitude of these interfacial forces. Single-rooted teeth were mounted on a cantilevered aluminium beam to which two pairs of single element strain gauges were joined in a half-bridge configuration and mounted at right angles to each other. The strain gauges were connected to an analogue-to-digital converter fitted in a micro-computer via conditioning amplifiers. This enabled strains to be recorded over a period of time. Twenty operators instrumented root canals using a series of hand instruments for 1 min each. The mean interfacial forces used by operators demonstrated a wide variation ranging from 9.06 g to 149.42 g (range of forces from 0-331 g) but there was a consistency in the relative magnitude for each operator. The 20 operators could be divided into 13 groups which were significantly different (alpha = 0.05) from each other. There were significant differences (alpha = 0.05) between the forces used for each of the K-Flex files (15, 25, 35, 45, and 70), the force increasing with the file size. There was also a significant difference (alpha = 0.05) in the forces used between the Flexofile (#25) and the #25 K-Flex and Hedström files. However, there was no significant difference between the K-Flex and Hedström files.

The influence of interfacial forces and duration of filing on root canal shaping.

The aim of this study was to investigate the possible relationship between interfacial forces, duration of instrumentation and effectiveness of root canal shaping by filing. All factors were standardised except the manner of manipulation of the files and the dependent variables (interfacial force and duration of filing). The outcome measured was the final prepared canal shape. The study tested the hypothesis that if interfacial forces and duration of filing had predictive value for effective canal shaping, a relationship between them should be apparent. If it was not, it could be inferred that the remaining uncontrollable variable, "manner of file manipulation" had a dominating influence. 18 operators used a standard filing technique to instrument a root canal each in single rooted teeth matched for anatomy. The teeth were mounted in a custom-made transducer designed to measure laterally applied interfacial forces between file and dentine. The length of time taken with each instrument in the series was measured giving a total duration of instrumentation. The final canal shape measured by standardised "before" and "after" radiographic images of the roots was judged against an "ideal" canal shape calculated from the size of instruments used and based on the preliminary canal shape. Although some trends were revealed, no obvious relationship was demonstrated between interfacial force, duration of filing and final canal shape. Operators clearly used a range of interfacial forces characteristic for each individual and for the different file sizes. Both light and heavy forces could produce a satisfactory canal shape. Use of light or heavy forces did not obviously affect speed of preparation. Tactile discrimination was not dependent on use of light or heavy forces. It was inferred that the "manner of file manipulation" remained undefined and was probably the dominant factor influencing outcome of canal shaping.

Response of periradicular tissues to growth factors introduced into the surgical site in the root-end filling material.

AIM: The objective of this study was to evaluate the healing of the periradicular tissues when exogenous growth factors were delivered to the respected root-end. The healing response was compared with that when Diaket was used as a control. METHODOLOGY: Non-surgical root canal treatment was performed on mandibular teeth in mongrel dogs. Surgical treatment followed and included root-end resection and root-end cavity preparation. Insulin-like growth factor in combination with platelet-derived growth factor, or fibroblast growth factor alone, were then placed in the root-end preparations on a polylactic acid carrier (Atrisorb) with or without the incorporation of the carrier tetracalcium phosphate. The healing was evaluated at 60 days with regard to presence of inflammatory response, bone regeneration, periodontal ligament formation and cementum formation. RESULTS: Osseous regeneration in the excisional would and periodontal formation were significantly greater when Diaket was used as the root-end filling material. Likewise, cementum deposition occurred significantly more frequently in the Diaket group (P < 0.05). The polylactic carrier Atrisorb remained in the surgical sites for the duration of the study. CONCLUSIONS: The use of specific growth factors, FGF and a combination of IGF/PDGF, delivered to the prepared root end in a collagen carrier did not initiate the desired periradicular tissue response of regeneration. Diaket, as used in this study, did stimulate a periradicular tissue response compatible with regeneration.

Rapid thrombectomy of superior sagittal sinus and transverse sinus thrombosis with a rheolytic catheter device.

Thrombosis of the dural venous sinuses is a potentially lethal condition that remains a diagnostic dilemma. Clinical outcome is typically dependent on the timeliness of diagnosis and definitive treatment. We report a case of successful rapid thrombectomy of extensive thrombus within the superior sagittal and transverse sinuses using a rheolytic catheter device. This appears to be a promising treatment option, particularly in those patients who do not respond to other, more established, forms of therapy.

Primary stenting of the extracranial internal carotid artery in a patient with multiple cervical dissections: technical case report.

OBJECTIVE AND IMPORTANCE: Spontaneous dissection of the extracranial internal carotid artery (ICA) and vertebral artery (VA) is a well-documented cause of stroke in young, previously healthy patients. The majority of patients with spontaneous dissection are successfully treated with antiplatelet or anticoagulation therapy, but a significant proportion of patients progress to suffer devastating morbidity and mortality. Surgical intervention has primarily consisted of proximal ligation, extracranial-intracranial bypass, or endarterectomy. Generally, these procedures are technically demanding and yield disappointing clinical results. CLINICAL PRESENTATION/INTERVENTION: A 36-year-old man without a significant medical history initially presented with a several-day history of episodic right upper extremity weakness and numbness and visual obscurations. Cerebral angiography revealed bilateral ICA long segment narrowing (95%), distal left VA high-grade (95%) stenosis compatible with dissections, and right VA proximal occlusion. While therapeutically anticoagulated on heparin, the patient continued to experience crescendo episodes of right upper extremity paresis and paresthesias as well as aphasia. The patient underwent primary stenting of the left ICA, using a series of six overlapping stents (three Gianturco-Roubin coronary stents and three Palmaz-Schatz coronary stents). The patient remained symptom-free without neurological complications, and subsequent angiography performed at the 9-month follow-up examination confirmed continued patency of the stented left ICA as well as recanalization of the right ICA and VA. CONCLUSION: Neurovascular stents offer a minimally invasive and potentially efficacious treatment for the prevention of cerebral ischemia in patients with spontaneous extracranial dissection who remain symptomatic despite therapeutic anticoagulation.

Infected renal artery pseudoaneurysm and mycotic aortic aneurysm after percutaneous transluminal renal artery angioplasty and stent placement in a patient with a solitary kidney.

Endovascular infections after percutaneous transluminal renal angioplasty with stenting (PTRAS) are rarely reported. Because strict longitudinal follow-up of patients undergoing PTRAS is lacking, the true incidence of such complications remains obscure. We report the first case of a patient with an infected renal artery pseudoaneurysm and de novo mycotic aortic aneurysm after PTRAS. This case serves to illustrate several important points, including (1) the retrieval of renal function in patients with renal artery occlusion, (2) the pathogenesis of infection after PTRAS, (3) the diagnosis and management of endovascular infection after percutaneous vascular intervention, and (4) recommendations for periprocedural antibiotic prophylaxis during PTRAS.

Update on interventional uroradiology.

From its humble beginnings as a method of expediently decompressing the obstructed kidney, the field of interventional uroradiology has evolved in the hands of urologists and interventional radiologists to a means of addressing myriad problems in the urinary tract and has changed the day-to-day practice of urology. The foundation of interventional uroradiology is the creation of an appropriate entry into the urinary system. After a review of this basic procedure, extensions of the technique and new applications of emerging technology are reviewed.

UVB DNA dosimeters analyzed by polymerase chain reactions.

Purified bacteriophage lambda DNA was dried on a UV-transparent polymer film and served as a UVB dosimeter for personal and ecological applications. Bacteriophage lambda DNA was chosen because it is commercially available and inexpensive, and its entire sequence is known. Each dosimeter contained two sets of DNA sandwiched between UV-transparent polymer films, one exposed to solar radiation (experimental) and another protected from UV radiation by black paper (control). The DNA dosimeter was then analyzed by a polymerase chain reaction (PCR) that amplifies a 500 base pair specific region of lambda DNA. Photoinduced damage in DNA blocks polymerase from synthesizing a new strand; therefore, the amount of amplified product in UV-exposed DNA was reduced from that found in control DNA. The average lesion frequency per 500 base pair per strand at 16 PCR cycles was approximately 1.22, 1.00, 0.70 and 0.50 for 30 ng, 50 ng, 100 ng and 150 ng of dried DNA, respectively, after a total dose of 60 kJ m(-2) delivered with a solar UVB simulator. Although the average lesion frequency increases linearly with increasing doses for four different amounts of template DNA, the lesion frequency seems to be averaged by the amplified products from the protected lambda DNA molecules below the top few layers. The average daily dose, equivalent to the UV dose applied with the solar UVB simulator was 10.2 +/- 0.4 kJ m(-2) with the 50 ng containing DNA dosimeter in September 1995 in Melbourne, FL. Both 50 ng and 150 ng containing DNA dosimeters produced the same average daily dose within experimental error in January 1996, which was 5.2 +/- 0.3 kJ m(-2) at the same location. The dried lambda DNA dosimeter is compact, robust, safe and transportable, stable over long storage times and provides the total UVB dose integrated over the exposure time.

Solar UVB dosimetry by amplification of short and long segments in phage lambda DNA.

DNA UVB dosimeters, consisting of minidots of dried bacteriophage DNA placed on a UV-transparent polymer film, were analyzed by polymerase chain reactions (PCR). Ultraviolet-B dosimetry obtained with amplification of phage lambda DNA of segments of 1.08 kilobase pairs (kbp) and 2.24 kbp was compared with that obtained with amplification of a 0.5 kbp segment (H. Yoshida and J. D. Regan, 66, 82-88, Photochem. Photobiol. 1997). The number of lesions in each segment induced by UV radiation is proportional to the size of the amplified segments; thus, the average lesion frequency per unit dose was greatest in the 2.24 kbp and least in the 0.5 kbp segment. The average lesion frequency per unit dose was approximately 3.5 x 10(-2) and approximately 11.9 x 10(-2) m2 kJ-1 for 1.08 kbp and 2.24 kbp, respectively, compared to that for 0.5 kbp of approximately 1.7 x 10(-2) m2 kJ-1 at 50 ng DNA. Dependability of DNA dosimeters, containing 50 ng and 100 ng, was tested by placing the DNA dosimeters for a time period of either 1 or 2 days outdoors on 8-12 January at Melbourne, FL. The daily dose was obtained directly with amplification of the 2.24 kbp segment and the 2 day continuous dose was obtained with amplification of the 1.08 kbp segment. Although the average lesion frequencies were different, both 50 ng and 100 ng DNA dosimeters provided about the same UVB dose, equivalent to the dose applied with a solar UVB simulator. The total UVB dose for 4 days obtained by amplification of the 1.08 and 2.24 kbp segments was 19.4-20.8 kJ m-2, which is within experimental error with the 4 day continuous dose obtained with 0.5 kbp segments. The average daily dose obtained by 0.5 kbp and 1.08 kbp agreed with the average daily dose directly obtained with 2.24 kbp.

The T cell receptor gene usage by simian immunodeficiency virus gag-specific cytotoxic T lymphocytes in rhesus monkeys.

MHC class I-restricted CTL play an important role in limiting the spread of HIV-1 in the infected individual. Elucidating the molecular interactions of CTL with the virus is, therefore, of central importance for characterizing the immune control of this infection. In exploring this CTL response, we have defined the TCR usage by SIVmac Gag-specific CTL in rhesus monkeys. Thirty-nine CTL clones were generated from PBL of three SIVmac-infected monkeys expressing the MHC class I Mamu-A*01 gene product, all of which were shown to recognize a single SIVmac Gag peptide in association with Mamu-A*01. Sixty-six percent of CTL clones derived from two monkeys early after infection expressed TCR genes of the V beta 13 family; 70% of these V beta 13+ CTL clones expressed a TCR heterodimer composed of V alpha 1 and V beta 13 gene products. In addition, there appeared to be a selection of a single conserved amino acid and restricted CDR3 lengths in junctional regions of TCR beta-chains expressed by the V beta 13+ CTL clones. These findings indicate significant structural constraints on the CTL-TCR interaction with the AIDS virus. Interestingly, 55% of the CTL clones derived from the third animal at a later time following infection employed genes of the V beta 6 family in their TCR. Despite the preferential use of TCR V family genes by the CTL clones, the SIVmac Gag-specific CTL response was clearly polyclonal; TCR expressed by these CTL clones displayed varied sequences in their CDR3 regions. Other V gene families, including V beta 23, V alpha 8, and V alpha 20, were used in TCR expressed by SIVmac Gag-specific CTL clones. These studies, therefore, indicate that the TCR repertoire of SIVmac Gag-specific CTL that share a peptide and MHC class I recognition specificity can be diverse. Such a broad CTL-TCR repertoire may be advantageous for the host in containing an AIDS virus infection.

DNA UVB dosimeters.

DNA can be used to establish and monitor solar UVB dose. Since the principal molecular site of UVB damage in living organisms is DNA, it is logical to quantitate biologically effective solar UVB in DNA dosimeters. In addition to their particular sensitivity to UVB, DNA dosimeters have the advantage of a 2 pi geometry for collecting diffuse UVB radiation from all vectors, low cost, small size and portability, and no moving parts. Both molecular (cyclobutane pyrimidine dimers) and biological (bacteriophage plaques) dosimeters can be quantitated as endpoints to yield the total dose. DNA dosimeters integrate the absorbed energy of all UVB wavelengths (290-320 nm), are highly sensitive to the differential biological effectiveness of these wavelengths, and also integrate over time in hours, days or weeks of exposure. Our experiments have focused on the demonstration of DNA solar dosimeters in the ocean at various depths, the application of the dosimeters to the terrestrial monitoring of solar UVB under various conditions, and the development of a mini-dosimeter which uses nanograms of DNA and is assayed by polymerase chain reaction.

An acutely lethal simian immunodeficiency virus stimulates expansion of V beta 7- and V beta 14-expressing T lymphocytes.

SIVsmmPBj14, a variant simian immunodeficiency virus isolated from a pig-tailed macaque, stimulates the proliferation of macaque T lymphocytes in vitro and induces an acutely lethal disease in macaques characterized, in part, by lymphadenopathy and splenomegaly. To determine whether SIVsmmPBj14 exhibits superantigen-like activity, in vitro and in vivo studies of T-cell receptor V beta repertoire were undertaken using PCR-based quantitative methods. Whereas in vitro phytohemagglutinin stimulation of macaque peripheral blood lymphocytes did not cause a perturbation of T-cell receptor V beta repertoire, SIVsmmPBj14 stimulated the expansion of both CD4+ and CD8+ T-lymphocyte subpopulations expressing the V beta 7 and V beta 14 gene families. Such V beta 7 and V beta 14 expansions could be confirmed by a multiple RNase protection assay. Furthermore, the expansion of the same lymphocyte subpopulations was also detected in peripheral blood lymphocytes and lymph node cells of virus-infected macaques. These observations suggest that SIVsmmPBj14-mediated V beta expansion may contribute to the induction of an acutely lethal disease in macaques.

DNA as a solar dosimeter in the ocean.

Stratospheric ozone depletion may result in increased solar UV-B radiation to the ocean's upper layers and may cause deleterious effects on marine organisms. The primary UV-B damage induced in biological systems is to DNA. While physical measurements of solar UV-B penetration into the sea have been made, the effective depth and magnitude of actual DNA damage have not been determined. In the experiments reported here, UV-B-induced photoproducts (cyclobutane pyrimidine dimers) have been quantified in DNA molecules exposed to solar UV at the surface and at various depths in clear, tropical marine waters off Lee Stocking Island (23 degrees 45' N, 76 degrees 0.7' W), Exuma Cays, Bahamas. (14C)thymidine-labeled DNA or unlabeled bacteriophage phi X174 DNA was placed in specially designed quartz tubes at various depths for up to five days. Following exposure, DNA samples were removed to the laboratory where UV-B-induced pyrimidine dimers were quantified using a radiochromatographic assay, and bacteriophage DNA inactivation by solar UV-B was assayed by plaque formation in spheroplasts of Escherichia coli. Pyrimidine dimer induction was linear with time but the accumulation of dimers in DNA with time varied greatly with depth. Attenuation of dimer formation with depth of water was exponential. DNA at 3 m depth had only 17% of the pyrimidine dimers found at the surface. Bacteriophage phi X174 DNA, while reduced 96% in plaque-forming ability by a one day exposure to solar UV at the surface of the water, showed no effect on plaque formation after a similar exposure at 3 m. The data collected at the water's surface showed a "surface-enhanced dose" in that DNA damages at the real surface were greater than at the imaginary surface, which was obtained by extrapolating the data at depth to the surface. These results show the sensitivity of both the biochemical (dimers) and biological (phage plaques) DNA dosimeters. DNA dosimeters offer a sensitive, convenient and relatively inexpensive monitoring system, having both biochemical and biological endpoints for monitoring the biologically effective UV-B flux in the marine environment. Unlike physical dosimeters, DNA dosimeters do not have to be adjusted for biological effectiveness since they are sensitive only to DNA-mediated biologically effective UV-B radiation. Results of pyrimidine dimer induction in DNA by solar UV accurately predicted UV doses to the phage DNA.