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Wireless Security: With the increasing use of wireless technology,security is becoming more important than ever

Genetic basis of cancer: insights from genome-wide associationstudies

The Latest Breakthroughs in Cancer Treatment

Fighting Cancer: A Comprehensive Guide

The aim of this study was to present a concise summary of the oral health policies and oral healthcare schemes for older adult populations in a number of selected countries around the world. In this paper, the current and planned national/regional oral health policies and oral healthcare schemes of nine countries (Australia, Brazil, China including Hong Kong, India, Japan, Switzerland, Thailand, the United Kingdom, and the United States) are reported. Barriers and challenges in oral health promotion in terms of devising oral health policies, implementing oral health schemes, and educating the future dental workforce are discussed. In response to the aging of population, individual countries have initiated or reformed their healthcare systems and developed innovative approaches to deliver oral health services for older adults. There is a global shortage of dentists trained in geriatric dentistry. In many countries, geriatric dentistry is not formally recognized as a specialty. Education and training in geriatric dentistry is needed to produce responsive and competent dental professionals to serve the increasing number of older adults. It is expected that oral health policies and oral healthcare services will be changing and reforming in the coming decades to tackle the enduring oral health challenges of aging societies worldwide.

A simple experimental setup based on a polarizing optical technique is designed to find the thickness of free standing thin film of Biphenyl (E7). Monochromatic light is passed through a liquid crystal thin film in two different modes of placement. In each mode approximately 10 mg of Biphenyl is used. The films of varying area were used in this study. The thin films were highly stable and could survive more than one day. The intensity of transmitted monochromatic radiation is measured using this technique by placing thin film in horizontal and vertical modes. Using Beer-Lambert’s Law the thickness of thin film is also measured using polarizing optical technique. In both the modes (horizontal and vertical) different behaviors of thickness of thin film are observed..

Background: Oral hygiene maintenance is crucial for prevention of various oral diseases. Oral hygiene practices across the country vary largely and people in peri-urban and rural areas use traditional methods of oral hygiene like powders, bark, oil and salt etc. Their effect on oral soft and hard tissues need to be studied to understand their beneficial and/ or harmful effects on maintenance of oral hygiene and prevention or causation of oral diseases. Objectives: This study aimed to assess the plaque-cleaning efficacy, gingival bleeding, recession and tooth wear with different traditional oral hygiene methods as compared to use of toothpaste-toothbrush, the most accepted method of oral hygiene practice. Study Design: Hospital based cross sectional analytical study. Results: Total 1062 traditional oral hygiene method users were compared with same number of toothpaste-brush users. The maximum number in the former group used tooth powder (76%) as compared to other indigenous methods, such as use of bark of trees etc and out of tooth powder users; almost 75% reported using red toothpowder. The plaque scores and gingival bleeding & recession were found to be more in traditional oral hygiene method users. The toothwear was also more severe among the toothpowder users. Conclusions: Traditional methods were found to be inferior in plaque control as was documented by increased bleeding and gingival recession. Its effect on hard tissues of teeth was very damaging with higher tooth wear scores on all surfaces.

Background: Age estimation in living individuals is imperative to amicably settle civil and criminal disputes. A biochemical method based on amino acid racemization was evaluated for age estimation of living Indian individuals. Design: Caries-free maxillary/mandibular premolar teeth (n = 90) were collected from participants with age proof documents and divided into predefined nine age groups. Materials and Methods: Dentine biopsy from the labial aspect of the tooth crown was taken with an indigenously developed microtrephine. The samples were processed and subjected to gas chromatography. Dextrorotatory:levorotatory ratios were calculated, and a regression equation was formulated. Results: Across all age groups, an error of 0 ± 4 years between protein racemization age and chronological age was observed. Conclusion: Aspartic acid racemization from dentine biopsy samples could be a viable and accurate technique for age estimation of living individuals who have attained a state of skeletal maturity.

Magnesium oxide (MgO) nanoparticles are synthesized by a simple coprecipitation method. XRD studies reveal that nanoparticles are predominantly (100) textured with an average crystallite size of 19 nm.The relative peak intensities for (100) and (110) textured grains i.e., I(100)/I(110) is found to be ~ 2. Scanning electron microscope (SEM) pictures of our samples indicate that our synthesized nanoparticles are spherically shaped. Due to excellent electron tunneling features of (100) textured MgO nanoparticles, our synthesis method is suitable for cost effective and simple synthesis of pure MgO nanoparticles for applications involving electron tunneling.

Aims and Objectives: The study aims at determining pulp response of two high fluoride releasing materials silver diamine fluoride (SDF) and Type VII glass ionomer cement (GIC) when used as indirect pulp treatment (IPT) materials. Materials and Methods: Deep Class V cavities were made on four first premolars indicated for extraction for orthodontic reasons. SDF, Type VII GIC, and calcium hydroxide base are given in three premolars, and one is kept control. Premolars were extracted 6 weeks after the procedure and subjected to histopathological examination to determine the pulp response. The results were analyzed using Chi-square test. Results: No inflammatory changes were observed in any of the groups. Significantly more number of specimens in SDF and Type VII GIC groups showed tertiary dentin deposition (TDD) when compared to control group. No significant difference was seen in TDD when intergroup comparison was made. Odontoblasts were seen as short cuboidal cells with dense basophilic nucleus in SDF and Type VII GIC group. Conclusion: The study demonstrated TDD inducing ability of SDF and Type VII GIC and also established the biocompatibility when used as IPT materials.

Loss of pulp vitality in an immature permanent tooth arrests root development. This leads to tooth with open apex and weak lateral dentinal walls. Management of such necrotic teeth with immature roots poses several treatment challenges. The documented study was performed to evaluate and compare apexogenesis induced by revascularization, with and without platelet rich plasma (PRP) in non-vital, immature anterior teeth. Three patients having bilateral, non-vital, immature maxillary central incisors with apical periodontitis were recruited after institutional ethical clearance. Subsequent to chemo-mechanical preparation, revascularization with and without PRP was randomly induced in either of the tooth. The cases were followed-up clinically and radiographically at 6 and 12 months. There was a marked difference in periapical healing, apical closure and dentinal wall thickening of teeth treated by revascularization with PRP.

Aim: This study aims to compare the periapical healing of teeth with asymptomatic apical periodontitis treated either by conventional apical preparation (CAP) or apical clearing technique (ACT). Materials and Methods: Twenty subjects with bilateral nonvital similar teeth exhibiting comparable periapical index (PAI) score were enrolled and randomly allocated. Group I (CAP, n = 20): Apical preparation three sizes greater (master apical file [MAF]) than the first binding file at the established working length. Group II (ACT, n = 20): Apical preparation three sizes greater than the MAF that was followed by dry reaming. Root canal therapy was accomplished in single-visit for all the teeth. They were pursued radiographically at 3, 6, 9 and 12 months. Pre- and post-treatment PAI scores were compared. To ascertain the proportion of healed teeth between the two groups, McNemar Chi-square test was applied. Results: At 3, 6, and 9 months’ time interval the proportion of healed teeth for Group II (ACT) was greater in comparison to Group I (CAP) (P < 0.05). However, at 12 months follow-up period this difference was not significant (P = 0.08). Conclusion: ACT enhanced the healing kinetics. However, the long-term (12 months) radiographic outcome was similar for either technique.

Introduction: Prevention of oral diseases can be achieved by preventive measures. There is an educational component associated to the preventive aspect. Health education is a cornerstone to the success of a preventive programme. Health education has always been regarded as a primary tool in imparting awareness, bringing changes in healthy behaviors and improved life. Aim: To assess the effectiveness of an Educational Video in improving oral health knowledge of subjects in a hospital setting. Methodology: The study was conducted in Outpatient Department, CDER, AIIMS. This was a cross sectional interventional study. In the present study a total of 109 subjects were considered those who completed pre and post intervention questionnaire. In order to assess baseline oral health knowledge, a-14 itemed questionnaire was specially designed, based on the contents of video and was pre-tested on 10 patients. Pre-intervention knowledge was assessed and then the 30-minute video was shown. Following this, post-exposure knowledge was assessed using the same questionnaire. Change in the knowledge score amongst the subjects was assessed pre and post-intervention (showing the video film). Results: Paired t- test was used to analyze the data. Pre-intervention mean knowledge score was 9.49±2.09 which increased to 11.55±1.60 post-intervention; the difference was statistically significant (P < 0.001). Conclusions: It was found that increase in knowledge score was statistically significant after exposure to an educational video film in a hospital setting. Incorporation of video in imparting oral health education can be an effective tool in improving oral health knowledge, which can impact the oral health behavior of people and community.

Statement of Problem: Change in color and loss of marginal adaptation of tooth colored restorative materials is not acceptable. Bleaching is commonly used for treating discolored teeth. However, the literature is scanty regarding its effect on color and marginal adaptation of direct and indirect composite laminate veneers (CLVs) under in vivo conditions. Purpose: Purpose of the study was to determine the effect of bleaching on color change and marginal adaptation of direct and indirect CLVs over a period of time when exposed to the oral environment. Materials and Methods: For this purpose, a total of 14 subjects irrespective of age and sex indicated for CLV restorations on maxillary anterior teeth were selected following the inclusion and exclusion criteria. For each subject, indirect CLVs were fabricated and looted in the first quadrant (Group 1) and direct CLV′s (Group 2), were given in the second quadrant. Color change was assessed clinically using intra-oral digital spectrophotometer and marginal adaptation was assessed on epoxy resin replica of the tooth-restoration interface under scanning electron microscope. After 6 months, the subjects underwent a home bleaching regimen for 14 days using 10% carbamide peroxide. The assessment of color change and marginal adaptation was done at 6 months after veneering (0-180 days), immediately after the bleaching regimen (0-194 days) and 3 months after the bleaching regimen (0-284 days). Results: The difference in median color change (ΔE) between the groups was tested using Wilcoxon rank sum test while the median color change with time within the groups was tested using Wilcoxon signed rank test. The difference in the rates of marginal adaptation was tested between the groups using Chi-square/Fisher′s exact test. Bleaching led to statistically significant color change at cervical (CE), middle and incisal (IE) regions when direct and indirect composites were compared (P < 0.05). During intra-group comparison, direct CLV′s showed significant color change at CE and IE regions when ΔE was compared at 180 days and 284 days (CE 10 vs. CE 30, P = 0.008, IE 10 vs. IE 30, P = 0.003). No significant differences were found when within group comparison was made for indirect laminates. Intergroup comparison between the groups showed significant difference in marginal adaptation at CE margin at all-time points (at baseline, P = 0.005; at 180 days, P = 0.007; 194 days, P = 0.025; at 284 days, P = 0.067). Conclusion: After bleaching, indirect CLVs performed better in terms of color stability whereas direct CLVs performed better in terms of marginal adaptation. Clinical Significance: Indirect composites should be preferred to direct composites as veneering materials as they have better color stability. Special attention should be given to their marginal adaptation especially in the CE region. Bleaching should be avoided in patients with composite restorations in the mouth.

Aim : Indirect pulp capping (IPC) preserves the pulp vitality by disinfecting and remineralizing remaining carious dentin. In the present study, glass ionomer (GC, FUJI VII) and silver diamine fluoride (SDF) were tested and compared to calcium hydroxide for their antimicrobial efficacy and remineralizing potential. Materials and Methods : Dentin disks prepared from 45 freshly extracted first premolars were divided into three groups (n = 15). Each disk was cut into two equal parts, in which one half formed the control. Thirty dentin samples were used for ion estimation and the other 15 for microhardness testing. Atomic absorption spectrophotometry, colorimetric and potentiometric titration analyses were performed for calcium, phosphate and fluoride ion detection, respectively. The antimicrobial efficacy was analyzed using pure culture of Streptococcus mutans and mixed flora. Results : Increase in the levels of calcium and phosphate ions was the highest in calcium hydroxide group. Both SDF and GC VII groups showed significant increase in fluoride ion levels. Samples treated with GC VII showed maximum increase in micro hardness. The highest zone of bacterial inhibition was found with SDF group. Conclusions : This in vitro study documented the remineralizing, re-hardening and antimicrobial efficacy of both SDF and GC VII and hence can act as effective IPC materials.

It is important for the clinician not only to gather as much information about a case as possible, but also to be able to correctly interpret the data to arrive at an accurate diagnosis. Occasionally, a case presents with symptoms that might be suggestive of a condition; however, the final diagnosis may be totally different. This paper reports on an interesting case of a true vertical root fracture, in an intact maxillary molar in a 55-year-old man. The case was misdiagnosed and treated as a periodontal defect for over two months. The paper discusses the various causes and diagnostic dilemmas of root fractures.

Dentistry has witnessed tremendous advances in all its branches over the past three decades. With these advances, the need for more precise diagnostic tools, specially imaging methods, have become mandatory. From the simple intra-oral periapical X-rays, advanced imaging techniques like computed tomography, cone beam computed tomography, magnetic resonance imaging and ultrasound have also found place in modern dentistry. Changing from analogue to digital radiography has not only made the process simpler and faster but also made image storage, manipulation (brightness/contrast, image cropping, etc.) and retrieval easier. The three-dimensional imaging has made the complex cranio-facial structures more accessible for examination and early and accurate diagnosis of deep seated lesions. This paper is to review current advances in imaging technology and their uses in different disciplines of dentistry.

To use mineral trioxide aggregate (MTA) in prophylactic management of talon cusp. Talon cusp is an endodontic oddity that possesses a treatment challenge to the clinician, especially when it causes esthetic and functional problems. Management ranges from periodic gradual reduction to radical removal followed by vital pulp/endodontic therapy. MTA has replaced calcium hydroxide as pulp capping material because of its superior properties. A 12-year-old boy reported with a complaint of irregular teeth. Clinical and radiographic examination revealed talon cusp on maxillary left central incisor. Radical removal of talon cusp and MTA pulpotomy was performed. The 4-year follow-up showed the positive pulp vitality test without any radiographic changes, emphasizing the use of MTA pulpotomy in successful management of talon cusp.

An oral health survey was conducted in 829 individuals in different age groups in Ballabhgarh, Haryana, India, to estimate the prevalence of Dental caries and Periodontal diseases. A survey tool was modified from WHO's STEPwise approach to surveillance and Oral Health Assessment form 2013 from recently released WHO Oral Health Survey: Basic Methods (5th Edition) keeping in mind the South East Asian region. Out of 28 villages, six villages were randomly selected. A random list of study participants (Age-sex specific) was generated from the pooled list of these 6 villages. Local health workes helped in inviting the specific subjects to one centralized location within each village/ locality. The subjects were examined by trained dental surgeons and recordings were done by trained assistants. The prevalence of dental caries in 5-7 year, 12-15 year, 35-44 year and 65-74 year was 33.2%, 31.3%, 64.9% and 50.1% respectively. The prevalence of Periodontal Disease in 35-44 year and 65-74 year found to be 65.2% and 90.4% respectively. Only 37 participants had mucosal lesions, of which leukoplakia and tobacco pouch keratosis was seen in majority. Using the adopted tool, the prevalence of dental caries was found to be highest in 35-44 year (64.9%) age group and the prevalence of periodontal disease was found to be high in 35-44 year (65.2%) age group and highest in 65-74 year (90.4%) age group. Oral health promotion efforts are required to prevent oro-dental diseases in the studied population.

The purpose of the study was to determine the effect of apical clearing and apical foramen widening in reducing apical ramifications and bacterial load in the apical third of root canals. The mesio-buccal roots of 21 maxillary first molar teeth were inoculated with Enterococcus faecalis suspension using a sterile pipette. Samples were incubated at 37°C for 72 hrs and divided into 3 groups: Group A, control group (n=5), no preparation; Group B (n=8) conventional preparation alone; and Group C (n=8), apical clearing and foramen widening in addition to conventional preparation. Bacterial counts were semi-quantitatively analyzed pre- and post-preparation. Samples were demineralized with 5% nitric acid after injection of India ink. Cross sections were obtained at every 0.5 mm from the apex to 3 mm of the root using a vibratome and viewed under a stereomicroscope at 64×magnification to locate any debris or apical ramifications. The Kruskal-Wallis and Mann-Whitney U tests were used for the statistical analysis. A statistically significant difference was observed (p value 0.006) in the number of ramifications among the 3 groups. Group C had a lower average number of ramifications (1) than Group B (2.5) or A (4). The debris score was analyzed at each level (0.5-3 mm). A statistically significant difference was observed at 0.5 mm and 1 mm between Group A and C (p=0.0041) and Group B and C (p=0.0050), whereas no difference was found between Group A and B (p>0.05). These results indicate that there was less debris and fewer apical ramifications in Group C. The microbiological study revealed a lower number of colony forming units (10(2) -10(3)) in Group B or C than in Group A (>10(5)). These results suggest that apical widening and clearing facilitates removal of apical ramifications and bacterial load within root canals.

An overview of the demographics and oral health status of the elderly population of India is presented. India is a vast country with a population of one billion people. Of this, people older than 60 years constitute 7.6%, which in actual number is 76 million. There are several factors that affect the oral health of elderly. The dentist:population ratio is 1:27,000 in urban areas and 1:300,000 in rural areas, whereas 80% of the elderly population reside in rural India. Forty per cent of the elderly live below the poverty line and 73% are illiterate. Ninety per cent of the elderly have no social security and the dependency ratio is 12.26. Incidence of oral cancer, which is considered an old-age disease, is highest in India, 13.5% of all body cancers are oral cancers. Preventive dental care is almost nonexistent to the rural masses and very limited in urban areas. Above all, there is no orientation of dental graduates towards the special needs of the geriatric population. Recommendations include: the establishment of Continuing Dental Education programmes on geriatric oral care; inclusion of a geriatric component in undergraduate and postgraduate curricula; initiation of a diploma, certificate and degree courses in geriatric dentistry; research on various aspects of ageing and age-related oral health problems; provision of preventive and curative treatment for various oral diseases to the elderly.

Thorough debridement is the key to the success of nonsurgical endodontic treatment in teeth with periapical lesions. Missed canals harbor bacteria which lead to treatment failure. This case report presents an unusual case of two rooted maxillary lateral incisors with the periapical lesion and emphasizes the importance of knowledge of the variability of root canal morphology. The tooth was treated with nonsurgical endodontic therapy. The patient was asymptomatic and bony healing was evident on radiograph at 12 and 18 months follow-up.

Aim: To evaluate the effect of prepolymerized custom-made composite megafiller and configuration factors (C-factor) on marginal adaptation of resin composite restorations. Materials and Methods: Forty extracted human mandibular molars were divided into four experimental groups consisting of 10 samples each. In groups I and III, class V (configuration factor 5) and in groups II and IV, class II box-shaped cavities (configuration factor 2) were prepared. Groups I and II were restored with a nanofilled composite (Filtek™ Z350 3M ESPE, St Paul, MN, USA) placed in horizontal increments. In groups III and IV, preformed composite megafiller was placed and cavities were restored with nanofilled composite Z-350. After curing, the samples were finished and prepared for examination under low vacuum scanning electron microscope. The data were analyzed with one-way analysis of variance. The significance between the individual groups was calculated by Post hoc test using the Holm-Sidak method ( P≤0.05). Results: The marginal gap values in groups III and IV were significantly lower than in groups I and II, respectively ( P≤0.05). Minimum gap values were seen in group IV. Conclusion: Use of prepolymerized composite megafiller and a lower C-factor decreased the marginal gaps between the tooth and composite restorations.

This study was conducted to determine the effect of 15% carbamide peroxide bleaching agent on color change and surface topography of different composite veneering materials (Filtek Z350 (3M ESPE), Esthet X (Dentsply India), and Admira (Voco, Germany).Methods. 30 samples were fabricated for evaluation of color change using CIELAB color system and Gonioreflectometer (GK 311/M, ZEISS). 45 disc-shaped specimens were made for evaluation of surface topography after bleaching (Nupro White Gold; Dentsply) using SEM.Statistical analysis. One way ANOVA and Multiple comparison tests were used to analyze the data. Statistical significance was declared if thePvalue was .05 or less.Results and conclusion. All the specimens showed significant discoloration (ΔE>3.3) after their immersion in solutions representing food and beverages. The total color change after bleaching as compared to baseline color was significant in Filtek Z350 (P=.000) and Esthet X (P=.002), while it was insignificant for Admira (P=.18). Esthet X showed maximum surface roughness followed by Admira and Filtek Z350. Bleaching was effective in reducing the discoloration to a clinically acceptable value in all the three groups (ΔE<3.3).

OBJECTIVE: To examine the relation between the quality of physicians and migration among alumni of All India Institute of Medical Sciences (AIIMS), New Delhi, India over the period 1989-2000. METHODS: In a retrospective cohort study, data on graduates of AIIMS were collected from entrance exam qualifier lists, the AIIMS alumni directory, convocation records, the American Medical Association and informal alumni networks. The data were analysed by use of 2x2 contingency tables and logistic regression models. FINDINGS: Nearly 54% of AIIMS graduates during 1989-2000 now reside outside India. Students admitted under the general category are twice as likely to reside abroad (95% confidence interval: 1.53-2.99) as students admitted under the affirmative-action category. Recipients of multiple academic awards were 35% more likely to emigrate than non-recipients of awards (95% confidence interval: 1.04-1.76). Multivariate analyses do not change these basic conclusions. CONCLUSION: Graduates from higher quality institutions account for a disproportionately large share of emigrating physicians. Even within high-end institutions, such as AIIMS, better physicians are more likely to emigrate. Interventions should focus on the highly trained individuals in the top institutions that contribute disproportionately to the loss of human resources for health. Our findings suggest that affirmative-action programmes may have an unintended benefit in that they may help retain a subset of such personnel.

Report from the west suggest an association of infections and inflammation with atherosclerotic coronary artery disease (CAD). Entire microbial burden from several simultaneous chronic infections could be more important than a single infection in promoting atherosclerosis. No study has been done in Indian population, investigating the association of various chronic infections with CAD. We therefore evaluated the presence of markers of chronic infections in CAD patients having no conventional risk factors and healthy individuals in a tertiary care hospital in north India.Seropositivity to IgG antibodies was investigated for Chlamydia pneumoniae, Mycoplasma pneumoniae, and Helicobacter pylori in 30 CAD patients with no conventional risk factors scheduled for coronary artery bypass surgery and in healthy blood donors. Periodontal pathogens were isolated by aerobic and anaerobic culture.All patients except one were55 yr of age and six were younger than 40 yr. Seropositivity to C. pneumoniae was significantly higher in CAD patients than healthy controls (63.3 vs. 23.3%, P0.01). Combined seropositivity to both C. pneumoniae and M. pneumoniae was significantly higher in CAD patients with myocardial infarction (MI) than those without MI (61.5 vs. 11.8%, P0.05). Aerobic and anaerobic cultures for the isolation of periodontal pathogens were positive in seven patients and five healthy blood donors.C. pneumoniae seropositivity was significantly higher (P0.001) in CAD patients without any of the conventional risk factors for CAD. Combined seropositivity to C. pneumoniae and M. pneumoniae was significantly higher (P0.05) in CAD patients with MI than in those without MI. Possibly CAD in young is not (or less) governed by conventional risk factors, and infectious agents can be potential risk factors for the development of atherosclerosis and CAD in this subset of patients.

Introduction: The main objective of a root canal sealer is to provide a fluid tight seal. The purpose of this systematic meta-analysis was to determine the relative toxicity of commonly used root canal sealers like zinc oxide eugenol, calcium hydroxide, and resin-based sealers. Materials and Methods: An online search was conducted in peer-reviewed journals listed in PubMed, Cochrane, EBSCO, and IndMed databases between 2000 and 2012). Statistical analysis was carried out by using analysis of variance (ANOVA) followed by post-hoc comparison by Bonferroni method. The comparison between toxicity at 24 h and between 3 and 7 days was done by using paired t-test for each sealer. Results: At 24 h, the relative biotoxicity of the three sealers reported was insignificant (P- value 0.29), but the difference in toxicity was found significant (P < 0.001) after 3 days. Conclusion: Calcium hydroxide sealer and zinc oxide eugenol were found to be significantly biotoxic as compared to resin-based sealers after 3 days.

Malignant osteopetrosis generally begins in utero and often results in stillbirth. Besides, failure to thrive, increased bone fragility resulting in frequent fractures and recurrent bone infections are the other characteristic features. Infections after tooth extraction and fracture of the sclerotic bone following mild trauma are serious complications, as these ordinarily common problems are very difficult to treat in such patients. Poor bone vascularisation and reduced local defences prolong the defensive response. A rare case of malignant osteopetrosis in a 19-year-old girl, who presented with the complication of osteomyelitis of the mandible following tooth extraction, is presented. The case is of interest for two reasons: it is very rare for a case of malignant osteopetrosis to survive until adulthood and to be aware of the potential dental and oral complications of the disorder.

Rad51 can promote extensive strand exchange in vitro in the absence of ATP hydrolysis, and the Rad51-K191R mutant protein, which can bind but poorly hydrolyze ATP, also promotes strand exchange. A haploid strain expressing the rad51-K191R allele showed an equivalent sensitivity at low doses of ionizing radiation to rad51-K191A or rad51 null mutants and was defective in spontaneous and double-strand break-induced mitotic recombination. However, the rad51-K191R/rad51-K191R diploid sporulated and the haploid spores showed high viability, indicating no apparent defect in meiotic recombination. The DNA repair defect caused by the rad51-K191R allele was suppressed in diploids and by mating-type heterozygosity in haploids. RAD54 expressed from a high-copy-number plasmid also suppressed the gamma-ray sensitivity of rad51-K191R haploids. The suppression by mating-type heterozygosity of the DNA repair defect conferred by the rad51-K191R allele could occur by elevated expression of factors that act to stabilize, or promote catalysis, by the partially functional Rad51-K191R protein.