Assessing the application of knowledge in clinical problem-solving: The structured professional reasoning exercise.

INTRODUCTION: Clinical reasoning is a fundamental and core clinical competence of healthcare professionals. The study aimed to investigate the utility of the Structured Professional Reasoning Exercise (SPRE), a new competence assessment method designed to measure dental students' clinical reasoning in simulated scenarios, covering the clinical areas of Oral Disease, Primary Dental Care and Restorative Dentistry, Child Dental Health and Dental Practice and Clinical Governance. MATERIALS AND METHODS: A total of 313 year-5 students sat for the assessment. Students spent 45 minutes assimilating the scenarios, before rotating through four pairs of 39 trained examiners who each independently assessed a single scenario over a ten-minute period, using a structured marking sheet. After the assessment, all students and examiners were invited to complete an anonymous perception questionnaire of the exercise. These questionnaires and the examination scores were statistically analysed. RESULTS AND DISCUSSION: Oral Disease showed the lowest scores; Dental Practice and Governance the highest. The overall Intraclass Correlation Coefficient (ICC) was 0.770, whilst examiner training helped to increase the ICC from 0.716 in 2013 to 0.835 in 2014. Exploratory factor analysis revealed one major factor with an eigenvalue of 2.75 (68.8% of total variance). The Generalizability coefficient was consistent at 0.806. A total of 295 students and 32 examiners completed the perception questionnaire. Students' lowest examination perceptions were an "Unpleasant" and "Unenjoyable" experience, whilst the highest were "Interesting", "Valuable" and "Important". The majority of students and examiners reported the assessment as acceptable, fair and valid. CONCLUSION: The SPRE offers a reliable, valid and acceptable assessment method, provided it comprises at least four scenarios with two independently marking and trained assessors. 3.

Analysis of dental students' written peer feedback from a prospective peer assessment protocol.

INTRODUCTION: Peer assessment and feedback is encouraged to enhance students' learning. The aim of this study was to quantitatively and qualitatively analyse pre-clinical and clinical dental students' written peer feedback provided as part of a continuous, formative and structured peer assessment protocol. MATERIALS AND METHODS: A total of 309 Year-2 and Year-5 dental students were invited to participate in a peer assessment and peer feedback protocol. Consenting volunteer students were trained to observe each other whilst working in the skills laboratory (Year-2) and in the dental clinic (Year-5). Subsequently, they followed a structured protocol of peer assessment and peer feedback using specially designed work-based forms during a complete academic year. The content of their written feedback was coded according to the UK General Dental Council domain, sign (positive or negative), specificity (task specific or general), and grouped into themes. RESULTS: A total of 108 participants (40 Year-2 and 68 Year-5) completed 1169 peer assessment work-based forms (516 pre-clinical and 653 clinical); 94% contained written feedback. The large majority (82%) of Year-2 feedback represented the clinical domain, 89% were positive, 77% were task specific, and they were grouped into 14 themes. Year-5 feedback was related mostly to Management and Leadership (37%) and Communication (32%), 64% were positive, 75% task specific, and they were clustered into 24 themes. DISCUSSION: The content of the feedback showed notable differences between Year-2 and Year-5 students. Senior students focused more on Communication and Management and Leadership skills, whilst juniors were more concerned with clinical skills. Year-5 students provided 13% negative feedback compared to only 2% from Year-2. Regulatory focus theory is discussed to explain these differences. Both groups provided peer feedback on a wide and different range of themes. However, four themes emerged in both groups: efficiency, infection control, time management and working speed. CONCLUSION: A structured peer assessment framework can be used to guide pre-clinical and clinical students to provide peer feedback focused on different domains, and on contrasting signs and specificities. It can also present an opportunity to complement tutors' feedback.

Outreach clinical dental education: the Portsmouth experience - a 4-year follow-up study.

BACKGROUND: The Portsmouth Dental Academy (UPDA) was opened in September 2010 and was a development from the highly successful School of Professionals Complementary to Dentistry (2004-2010). The aim of the Academy was to provide integrated team education for all dental professionals in a primary care setting. The dental students are on outreach from King's College London, and the dental care professional students are registered at the University of Portsmouth. OBJECTIVES: To evaluate the dental students response to the residential outreach educational experience at the UPDA. METHODS: A 49-item questionnaire divided into nine domains that provided both qualitative data and quantitative data were administered at the end of the longitudinal 10-week placement, to four successive cohorts of students in 2010-2014. RESULTS: A 95% return rate was achieved. Students valued highly the quality of the clinical teaching. Through their experience, they felt they understood fully the role of the dentist in care planning in primary care and felt well prepared for dental foundation training. This educational success is unpinned with successful maintenance factors including a well-organised induction period and giving the students a sense of belongingness, empowerment and autonomy for their personal development as new graduates. CONCLUSION: Within the limitations of the questionnaire study over the 4-year period, the students were very positive about all the aspects of this residential outreach education at the UPDA but particularly valued the immersion in clinical dentistry and the bridging from dental school to their dental foundation training.

Dental students' reflective habits: is there a relation with their academic achievements?

INTRODUCTION: Reflection is regarded as an important and essential component of healthcare professionals' education and practice. This cross-sectional study aimed to explore the levels of reflection habits of dental students and clinical and PhD postgraduate trainees and to establish the relationship between students' reflection and their academic performance. MATERIALS AND METHODS: A total of 324 subjects (208 females, 56% ≥23 years of age) from King's College London Dental Institute, consisting of 281 undergraduate and 43 postgraduate trainees, responded to the invitation to participate and completed an online self-reported Reflection Questionnaire; this assesses two levels of non-reflective actions (Habitual Action and Understanding) and two levels of reflective actions (Reflection and Critical Reflection). Reflection results were compared amongst different cohorts and correlated with students' academic performance. RESULTS: Reflection Questionnaire mean scores were 10.7 for Habitual Action, 17.3 for Understanding, 17.0 for Reflection and 14.4 for Critical Reflection, with significant differences between cohorts of undergraduate students, clinical postgraduates and PhD trainees. Reflection and Critical Reflection mean scores were higher as students climbed courses. Further, those ≥24 years of age and those with previous university degrees demonstrated higher reflective habits, whilst there was no gender difference. Additionally, the assessment programme methods correlated differently to the Reflection Questionnaire scores. DISCUSSION: The Reflection Questionnaire's internal reliability was acceptable. The most common approaches used by both students and trainees were Understanding and Reflection, whilst those with high Understanding scores also tended to have good Reflective scores. Further, multiple choice questions encouraged students to 'understand', whilst ill-defined problems, such as those from essays to clinical reasoning cases, increased this to the reflection scale. CONCLUSION: To foster reflective thinking, tutoring should primarily be focused on younger students (≤23 years old) and those without a previous university degree. Further, a wide variety of assessment methods is suggested to stimulate different reflective constructs.

Dental students' peer assessment: a prospective pilot study.

INTRODUCTION: Peer assessment is increasingly used in health education. The aims of this study were to evaluate the reliability, accuracy, educational impact and student's perceptions of undergraduate pre-clinical and clinical dental students' structured and prospective Peer assessment and peer feedback protocol. MATERIALS AND METHODS: Two Direct Observation of Procedural Skills (DOPS) forms were modified for use in pre-clinical and clinical peer assessment. Ten year two dental students working in a phantom-heads skills laboratory and 16-year five dental students attending a comprehensive care clinic piloted both peer DOPS forms. After training, pairs of students observed, assessed and provided immediate feedback to each other using their respective peer DOPS forms as frameworks. At the end of the 3-month study period, students anonymously provided their perceptions of the protocol. RESULTS: Year 2 and year 5 students completed 57 and 104 peer DOPS forms, respectively. The generalizability coefficient was 0.62 for year 2 (six encounters) and 0.67 for year 5 (seven encounters). Both groups were able to differentiate amongst peer-assessed domains and so detect improvement in peers' performance over time. Peer DOPS scores of both groups showed a positive correlation with their mean end-of-year examination marks (r ≥ 0.505, P ≥ 0.051) although this was not statistically significant. There was no difference (P ≥ 0.094) between the end-of-year examination marks of the participating students and the rest of their respective classes. The vast majority of both groups expressed positive perceptions of the piloted protocol. DISCUSSION: There are no data in the literature on the prospective use of peer assessment in the dental undergraduate setting. In the current study, both pre-clinical and clinical students demonstrated the ability to identify those domains where peers performed better, as well as those which needed improvement. Despite no observable educational impact, most students reported positive perceptions of the peer DOPS protocol. CONCLUSIONS: The results of this pilot study support the need for and the potential benefit of a larger- and longer-term follow-up study utilising the protocol.

The impact of integrated team care taught using a live NHS contract on the educational experience of final year dental students.

OBJECTIVE: To investigate the responses of the dental student body in the first three years of outreach education (2010-13) at the University of Portsmouth Dental Academy in the areas of integrated team work and use of a current NHS contact. METHODS: Use of a questionnaire to allow both quantitative and qualitative data to be obtained, administered to the three cohorts of students at the end of their longitudinal attendance at the Academy in their final year of education at King's College London Dental Institute. RESULTS: Data were obtained from 227 students which represented a 95% return rate. Sixty-four percent of students strongly agreed with both statements: 'I am confident with working with a dental nurse' and 'I now understand properly the scope of practice of dental hygiene-therapists'. Sixty-seven percent strongly agreed with the statement 'I have had useful experience of working in NHS primary care during the final year'. Eighty percent either strongly agreed or agreed with the statement 'My experience of real Units of Dental Activity and Key Performance Indicators has encouraged me to positively consider NHS high street dentistry as a career option'. CONCLUSIONS: Within the limitations of this study the dental students reported having gained useful experience of working in integrated team care dentistry. They expressed strong support for the education that is being delivered in an outreach environment and, most importantly, the student body was looking forward to entering general dental practice in the UK.

Levels of agreement between student and staff assessments of clinical skills in performing cavity preparation in artificial teeth.

OBJECTIVE: To determine the level of agreement between staff and students' assessment of clinical skills in performing tasks related to cavity preparation on a traditional dental manikin. METHODS: Two studies were conducted with two successive student cohorts: Study 1-138 year 1 BDS students in a 2009/10 cohort and Study 2-135 students in a 2010/11 cohort. Staff members and students rated the students' performance in preparing a cavity on a traditional dental manikin using artificial teeth: hand-held (Study 1) and located in a lower jaw (Study 2). A 5-item criterion-related scoring rubric was developed. The rubric assessed students' abilities to hold the instrument correctly, determine the angle of entry to the tooth, remove the caries, conserve healthy tissues and avoid pulp exposure. RESULTS: Agreement between the students' self-assessment and the staff's assessment was high for three of the five criteria (i.e. removal of artificial caries on the cavity wall, removal of artificial caries from the cavity floor and avoidance of pulp exposure). Levels of agreement for the remaining two criteria were moderate. A change in task difficulty affected the levels of agreement between staff and students, such that the more difficult the task, the greater the discrepancy in ratings. CONCLUSIONS: Students tend to overrate the quality of their performance when compared with staff ratings. Task difficulty has an impact on levels of agreement.

Threshold concepts in dental education.

The paper presents a conceptual framework to inform dental education. Drawing from a vast body of research into student learning, the simple model presented here has an explanatory value in describing what is currently observed to happen and a predictive value in guiding future teaching practices. We introduce to dental education the application of threshold concepts that have a transformative role in offering a new vision of the curriculum that helps to move away from the medieval transmission model of higher education towards a dual processing model that better reflects the way in which professionals operate within the discipline. Threshold concepts give a role for the student voice in offering a novice perspective which is paradoxically something that is out of reach of the subject expert. Finally, the application of threshold concepts highlights some of the weaknesses in the competency-based training model of clinical teaching.

Three-year clinical evaluation of two ceramic crown systems: a preliminary study.

STATEMENT OF PROBLEM: The clinical performance and failure mechanisms of recently introduced ceramic crown systems used to restore posterior teeth have not been adequately examined. PURPOSE: The purpose of this prospective clinical study was to evaluate and compare the clinical performance of 2 new ceramic crown systems with that of metal ceramic crowns using modified United States Public Health Services (USPHS) criteria. MATERIAL AND METHODS: Ninety posterior teeth requiring crown restorations in 48 patients were randomized into 3 equal groups (n=30) for which different crown systems were used: an experimental hot-pressed glass ceramic based on a modified lithium disilicate ceramic (IPS e.max Press), an alumina-coping-based ceramic (Procera AllCeram), and a metal ceramic (Simidur S 2 veneered with IPS Classic Porcelain). The crowns were assessed over 3 years using the modified USPHS criteria. Crowns that developed visible cracks were sectioned and removed, and the surfaces were analyzed using a scanning electron microscope (SEM). The data were analyzed using the Kruskal-Wallis nonparametric statistical test, followed by the Mann-Whitney test with Bonferroni correction (alpha=.05). RESULTS: USPHS evaluation showed that the IPS e.max Press and metal ceramic crowns experienced fewer clinical changes than Procera AllCeram. Visible roughness, wear, and deformity were noticed in occlusal contact areas of Procera AllCeram crowns. SEM images showed well defined wear facets in both ceramic crown systems. Kruskal-Wallis tests showed a significant difference (P<.05) in Alpha scores among the 3 crown systems. Mann-Whitney tests showed significant differences among groups. CONCLUSIONS: IPS e.max Press crowns demonstrated clinical behavior comparable to Procera AllCeram and metal ceramic crowns, but the wear resistance of this crown type was superior to the Procera AllCeram crowns, according to modified USPHS criteria.

Molecular typing of Streptococcus uberis strains isolated from cases of bovine mastitis.

The discriminatory power of two polymerase chain reaction-based DNA fingerprinting methods, random amplified polymorphic DNA and repetitive extragenic palindrome were compared by subtyping 128 isolates of Streptococcus uberis cultured from cows in six different dairy herds in New Zealand. The typing results demonstrated that the majority of isolates possessed unique fingerprint profiles except on occasions where multiple isolates were obtained from individual cows. On these occasions, individual quarters of the mammary gland were generally, but not exclusively, infected by the same strain of bacteria. Both random amplified polymorphic DNA and repetitive extragenic palindromic typing assays were simple to perform, relatively inexpensive ($11.00 per reaction), and provided reliable and reproducible results. Furthermore, when these assays were used in conjunction with each other, they provided a means of confirmation of the specific DNA fingerprint patterns obtained.

Treatment of dentin with polyacrylic acid--a retrospective observational study of the effect upon the durability of glass ionomer restorations.

This paper reports on the results of a material specific, retrospective observational study. It sought to determine the consequence of pretreatment of cavity margins with the conventional glass polyalkenoate Chemfil II prior to restoration with Tooth Cleanser on restoration durability. All restorations were placed and varnished by senior dental students under the supervision of a staff member. Manufacturer recommendations were followed. Data on each restoration was collected and entered into a relational computer database. Data included details of cavity morphology and the use or non-use of Tooth Cleanser. Six years following the study start a manual search of all records was carried out to determine, for those patients continuing to attend the Dental Hospital, the number of failed and surviving restorations. This yielded a dataset of 149 restorations, of which 41 had been placed with the aid of Tooth Cleanser and 108 without. The number of failed restorations was 20 and 62, respectively. Survival analysis by the Kaplan-Meier method revealed median survival times of 2,094 days, when Tooth Cleanser was used and 1,748 days when not. Although 80% survival times of 1111.0 (SE = 6.3) (With Tooth Cleanser) and 285.0 (SE = 3.8) (Without Tooth Cleanser) days were observed, together with a Hazard Ratio of 1.49 (95% Confidence Intervals 0.92 & 2.31), a Logrank test revealed no statistically significant difference between the survival curves (p = 0.12). It was concluded that although there was a trend for the application of Tooth Cleanser to improve the chances of obtaining a dependable restoration, this effect was not statistically significant.

Effect of localised antibiotic infusions applied to the teat-canal and teat sinus at drying-off on mastitis in the dry-period and at calving.

An experiment using three New Zealand herds and a total of 632 cows, examined the effect of localised prophylactic treatments with antibiotic at drying-off on the incidence of new intramammary infection during the dry period and at calving. Antibiotic was infused either into the teat canal (0.22 g of dry-cow formulation) or the teat sinus (3.1 g of lactating-cow formulation) of uninfected quarters to eliminate any bacteria present in these locations at the last milking of lactation. These treatments were compared with a negative control (nil treatment) and a positive antibiotic control (infusion of 3.6 g of dry-cow formulation). All antibiotic formulations used the same active ingredient, sodium cloxacillin. No significant reduction in new dry period clinical mastitis was observed for the two localised treatments whereas the positive control treatment achieved 100% reduction in new clinical mastitis compared with untreated control quarters. A 41% reduction (P < 0.05) in new Streptococcus uberis infections at calving was associated with the teat canal antibiotic treatment, compared with an 82% reduction (P < 0.001) for the positive antibiotic control. Both localised treatments showed a reduced incidence of new intramammary infection (P < 0.001) when pooled across periods and pathogens. Teats receiving either the teat canal antibiotic treatment or a full infusion of long acting dry-cow antibiotic had a lower incidence of open teat canals (P < 0.05) at 3 weeks after drying-off.

Effects of yeast expressed recombinant interleukin-2 and interferon-gamma on physiological changes in bovine mammary glands and on bactericidal activity of neutrophils.

The physiological effects of intramammary infusions of recombinant bovine cytokines in six lactating dairy cows on the quality and yield of milk and the bactericidal activity of milk neutrophils were investigated. Recombinant bovine interleukin-2 (rboIL-2) and interferon-gamma (rboIFN-gamma) were produced in the yeast Pichia pastoris. Two animals were given rboIL-2 (2 x 10(5) units) in two quarters, two animals were given rboIFN-gamma (6.5 x 10(5) units) in two quarters, and the other two cows received a dose of rboIL-2 in one quarter and rboIFN-gamma in a second quarter. In addition, each animal was given phosphate-buffered saline (PBS) in the other two quarters as a control. Somatic cell counts and conductivity of the fore milk were monitored before and after infusion. Neutrophils were isolated from quarter milk samples 36 h after infusion of cytokine or PBS and their bactericidal activities against Staphylococcus aureus were measured in vitro with a colorimetric assay. Quarters infused with rboIL-2 or rboIFN-gamma showed significant but transitory increases in both milk somatic cell counts and conductivity when compared with preinfusion values and with control quarters. There were minimal effects on daily milk yield. Neutrophils isolated from milk from quarters infused with rboIL-2 showed enhanced bactericidal activity against Staph. aureus. The bacterial killing from rboIL-2 treated quarters was significantly greater, with a mean of 63.5% compared with a mean of 5.4% for neutrophils taken from uninfected quarters to which PBS had been administered. The bactericidal activities for quarters treated with rboIFN-gamma and infected quarters treated with PBS were 15.0 and 30.0% respectively. The results indicate that intramammary infusions of rboIL-2 and rboIFN-gamma to lactating cows are well tolerated, and that rboIL-2 can activate milk neutrophils and augment their bactericidal activity.

Effect of milking frequency and pasture intake on milk yield and composition of late lactation cows.

Twenty-four monozygous twinsets in late lactation (> 210 d in milk) were used to examine the effects of feed restriction and milking frequency prior to drying off on milk yield and composition in a pastoral dairying system. Cows were assigned to one of four treatment groups for 26 d and were milked either twice or once daily and given either unrestricted or restricted access to feed. Dry matter intakes averaged 16 or 8 kg per cow per day, and diets comprised ryegrass and white clover pasture supplemented with 15% pasture silage. Feed restriction and once daily milking reduced milk yield and increased concentrations of milk fat and protein. Somatic cell count was increased by feed restriction only. Production losses caused by feed restriction were nearly threefold higher than were those for once daily milking. Yields of components that were mammary synthesized and serum derived were reduced by feed restriction, in accordance with milk volume reduction. Plasma lactose concentration increased with once daily milking only and indicated enhanced permeability of mammary tight junctions. Both feed restriction and once daily milking compromised milk quality, but increased leakage of serum components into milk via mammary tight junctions was deemed to occur only for once daily milking.

Changes in electrical conductivity and somatic cell count between milk fractions from quarters subclinically infected with particular mastitis pathogens.

Cows with subclinical intramammary infections were identified by milk bacteriology. The mastitis pathogens included Staphylococcus aureus (n = 9), Streptococcus uberis (n = 10) and coagulase-negative staphylococci (n = 10). Samples of first fore milk, main flow milk and strippings milk fractions were collected from each quarter and laboratory measurements were made of electrical conductivity, milk fat concentration and somatic cell count. Conductivity measurements were corrected for milk fat concentration and within-cow inter-quarter conductivity ratios calculated. Repeatability estimates of all measurements between days were calculated. In the case of infected quarters, all conductivity values decreased markedly (P < 0.05) from first fore milk to main flow milk fractions. Conductivity differences between quarters of infected cows were substantially lower during the main milk flow phase. For quarters infected with Staph. aureus an increase in conductivity was observed (P < 0.05) from main flow to strippings fractions. For uninfected quarters, conductivity declined as milk fat concentration increased with successive milk fractions. Variation, both within and between milk fractions, was greater for somatic cell count than for conductivity. Differences in conductivity between milk fractions from individual infected quarters were not accounted for by changes in fat concentration and may result from the mixing of milk from infected and uninfected regions of the gland. Localized infection may produce a decrease in conductivity between fore milk and mid-flow fractions while differential drainage from an infection site in the secretory tissue may additionally produce an increase in conductivity from mid-flow to strippings fractions. Such changes may thus provide information on the location and magnitude of an infection. The results clearly demonstrate the importance of the milk fraction when using conductivity as a diagnostic of intramammary infection, the highest diagnostic sensitivity being achieved by using first fore milk samples.

The prophylactic effect of a teat sealer on bovine mastitis during the dry period and the following lactation.

AIM: To determine the prophylactic efficacy of a teat sealer, administered at drying off, in reducing new intramammary infections in the dry period and the following lactation. METHODS: A total of 528 cows with late lactation somatic cell counts <2 00,000 cells/ml was identified in three commercial herds. Of these, bacteriological examination showed 482 cows were uninfected in all four quarters and 46 were infected in only one quarter. At drying off, uninfected quarters were randomly allocated to the following treatments: no infusion (negative controls), infusion with a bismuth subnitrate based teat sealer, infusion with teat sealer + antibiotic, or infusion with a cephalonium-based dry cow antibiotic (positive control). New infections were identified during the dry period by periodic udder palpations and at calving by bacteriological culture. RESULTS: All three infused treatments reduced the incidence of new intramammary infections due to Streptococcus uberis, both during the dry period and at calving, by about 90% (p <0.01). The majority of the infections were due to Streptococcus uberis. For all treatments, a 50% lower incidence of clinical mastitis over the first 5 months of the ensuing lactation was reported by farmers. X-ray imaging of 19 teats showed that the teat sealer material was retained, at least in part, in the lower teat sinus over about 100 days of the dry period. CONCLUSIONS: Closure of the teat canal from day one of the dry period as achieved by the teat sealer was as effective in reducing new dry period infections as the infusion of a long-acting dry cow antibiotic formulation. The lower incidence of new infections in the ensuing lactation among the infused quarters implies that fewer subclinical infections persisted from the dry period. Use of teat sealers at drying off appears to offer the same prophylactic efficacy as the dry cow antibiotic approach.

Influence of pulsationless milking on teat canal keratin growth and turnover.

In two separate experiments, the effects of pulsationless milking and milking vacuum on the rate of keratin removal from the teat canal were determined. Sixteen cows were milked with or without pulsation for either a single milking or for eight milkings. Milking without pulsation removed 10% of keratin present before milking, significantly less than milking with pulsation, which removed 32%. After eight milkings (4 d) without pulsation, up to 20% more keratin had accumulated within the teat canal but the rate of keratin regeneration reduced significantly upon return to pulsation milking. In a second experiment, ten cows were milked at 45 or 55 kPa and without pulsation. Only the absence of pulsation significantly reduced keratin loss during milking. Keratin loss during milking appears to be controlled by liner compression rather than by the rate of milk flowing through the teat canal. Pulsationless milking may increase penetrability of the teat canal to bacteria by reducing the natural rate of keratin removal during milking and reducing the rate of keratin regeneration.

The prevalence of mastitis in primiparous heifers in eleven Waikato dairy herds.

The objective of the study was to determine the prevalence of mastitis among primiparous heifers at calving and at drying off in 11 Waikato dairy herds during the 1993-94 dairy production season. Duplicate quarter milk samples were collected aseptically from 458 heifers within 5 days after calving for bacteriological analysis. Mastitis was diagnosed in at least one quarter in 35.6% of these heifers. Coagulase-negative staphylococci were isolated from 21.8% of the heifers. The prevalence of coagulase-negative staphylococci varied between herds from 4.3% to 44.8%. Environmental streptococci caused mastitis in 12.2% of heifers, ranging from 5.6% to 24.1% between herds. Streptococcus uberus was the pathogen identified most frequently at calving and accounted for more than 90% of the streptococcal isolates. Staphylococcus aureus and coliforms were isolated from less than 1% of samples. Clinical mastitis was observed in 8.1% of heifers at calving; environmental streptococci were isolated from 67.6% of these clinical clinical cases. Only 2.8% of heifers developed clinical mastitis during lactation and environmental streptococci were isolated from 38.5% of these cases. The prevalence of mastitis among 428 of the heifers at drying off was 64.7%; a 1.8 fold increase during lactation. Corynebactetium bovis was isolated from 43% of heifers at drying off even though it was not isolated from any heifers at calving. During the season, the prevalence of Staphylococcus aureus mastitis increased to 2.8% while mastitis caused by environmental streptococci declined to 2.8%. The prevalence of environmental mastitis pathogens decreased during lactation while contagious pathogens increased in each of the 11 herds. Ineffective post-milking teat sanitation probably contributed to the increase in mastitis caused by contagious pathogens. Specific factors were not determined that affected the variation in prevalence between herds.