Sample size considerations for split-mouth design

Split-mouth designs are frequently used in dental clinical research, where a mouth is divided into two or more experimental segments that are randomly assigned to different treatments. It has the distinct advantage of removing a lot of inter-subject variability from the estimated treatment effect. Methods of statistical analyses for split-mouth design have been well developed. However, little work is available on sample size consideration at the design phase of a split-mouth trial, although many researchers pointed out that the split-mouth design can only be more efficient than a parallel-group design when within-subject correlation coefficient is substantial. In this paper, we propose to use the generalized estimating equation (GEE) approach to assess treatment effect in split-mouth trials, accounting for correlations among observations. Closed-form sample size formulas are introduced for the split-mouth design with continuous and binary outcomes, assuming exchangeable and "nested exchangeable" correlation structures for outcomes from the same subject. The statistical inference is based on the large sample approximation under the GEE approach. Simulation studies are conducted to investigate the finite-sample performance of the GEE sample size formulas. A dental clinical trial example is presented for illustration.

Creation and Initial Outcomes of a Selective Four-Year Research Program for Predoctoral Dental Students

Educators agree that dental students' involvement in research plays an important role in their development and contributes to the future of dental education. However, dental schools are challenged to provide the time and support necessary to nurture their students in undertaking research activities. The aim of this study was to examine student participation in a predoctoral student research program at one U.S. dental school and to track participants' outcomes both before and after introduction of an additional, highly selective research scholarship program. Research participation was recorded for all predoctoral dental students in the graduating classes of 2005-15. The number of years of participation was also tracked for each student who participated in research. The results showed that, since the inception of the research honors scholarship in 2005, there has been a more than threefold increase in the number of dental students participating in research each year. The number of students who do multiple years of research has tripled, and the number of students' poster presentations at national academic meetings has risen tenfold in those ten years. The introduction of a competitive award that recognizes exceptional research by students has added to the research profile of the school and has shown success in encouraging students to become involved in research throughout their four years in dental school.

Statistical Power for Analyses of Changes in Randomized Controlled Trials

Randomized controlled trials (RCTs) are widely recommended as the most useful study design to generate reliable evidence and guidance to daily practices in medicine and dentistry. However, it is not well-known in dental research that different statistical methods of data analysis can yield substantial differences in study power. In this study, computer simulations are used to explore how using different univariate and multivariate statistical methods of analyzing change in continuous outcome variables affects study power, and the sample size required for RCTs. Results show that, in general, analysis of covariance (ANCOVA) yields greater power than other statistical methods in testing the superiority of one treatment over another, or in testing the equivalence between two treatments. Therefore, ANCOVA should be used in preference to change score or percentage change score to reduce type II error rates.

Frailty Approach for the Analysis of Clustered Failure Time Observations in Dental Research

Because dental implant failure patterns tend to cluster within subjects, we hypothesized that the risk of implant failure varies among subjects. To address this hypothesis in the setting of clustered, correlated observations, we considered a retrospective cohort study where we identified a cohort having at least one implant placed. The cohort was composed of 677 patients who had 2349 implants placed. To test the hypothesis, we applied an innovative analytic method, i.e., the Cox proportional hazards model with frailty, to account for correlation within subjects and the heterogeneity of risk, i.e., frailty, among subjects for implant failure. Consistent with our hypothesis, risk for implant failure among subjects varied to a statistically significantly degree (p = 0.041). In addition, the risk for implant failure is significantly associated with several factors, including tobacco use, implant length, immediate implant placement, staging, well size, and proximity of adjacent implants or teeth.

Factors affecting scientific productivity of German oral-maxillofacial surgery training centers: a retrospective cohort study

PURPOSE

To identify factors associated with scientific productivity (SP) of German oral-maxillofacial surgery (OMFS) training centers.

MATERIALS AND METHODS

This retrospective cohort study was composed of a set of data from German OMFS training centers. A total of eight predictor variables were grouped into demographic, structural, and personal categories. The outcome variables were average publications in 2013 per senior staff, and percentage of OMFS trainees with >1 publications. Descriptive and univariate statistics were computed using P < 0.05.

RESULTS

The sample included outputs from 62 OMFS departments (34 [54.8 %] university-based; 46 [74.2 %] in large cities). Average publications were 2.4 ± 3 per senior staff (range, 0-27), and 160 trainees (31.7 %) published >1 papers. The number of publications and productive trainees was not linked to department name and number of female senior staffs, but publication count was significantly increased when the hospital was in a metropolis (P = 0.018) or university-based (P < 0.0001), the OMFS' chairperson and >3 staffs within the department had a postdoctoral degree (German "Habilitation") (P = 0.013 and <0.0001), and the chairperson had h-index >10 or the first/last authorship in 2013 (P < 0.0001). Female senior surgeons were less scientifically productive than the male ones (P = 0.01).

CONCLUSION

SP of German OMFS training centers is greatly different across the country and influenced by city size, university base, educational backgrounds, and research activities of chairpersons and senior staffs. This helps students, trainees, and young surgeons to reach the career choice that is personally appropriate. The involved organizations may need to encourage research output of less productive surgeons/centers. Increasing postdoctoral-qualified staffs will increase SP of the department.

Methodological challenges when performing a systematic review

Well-conducted systematic reviews can provide a foundation upon which to base educational curricula, practice guidelines and healthcare policy. We aim to provide an overview of important methodological issues that need to be addressed during the five phases of performing a systematic review. 1. The specific problems to be addressed by the systematic review need to be formulated as clear, unambiguous and structured question/s. 2. Literature from multiple resources should be searched to avoid publication biases, as positive outcomes are more likely to be published than null/negative results. 3. The quality of selected articles should be assessed using a checklist, while the reliability of graders, as well as the quality of the checklist, needs to be established a priori. 4. Statistical heterogeneity needs to be assessed to determine if a meta-analysis is appropriate to pool the data. If not, a narrative synthesis of the evidence/overall findings needs to be performed within a clinical context.

Concordance between responses to questionnaire scenarios and actual treatment to repair or replace dental restorations in the National Dental PBRN

OBJECTIVE

To quantify the agreement between treatment recommended during hypothetical clinical scenarios and actual treatment provided in comparable clinical circumstances.

METHODS

A total of 193 practitioners in the National Dental Practice-Based Research Network participated in both a questionnaire and a clinical study. The questionnaire included three hypothetical scenarios about treatment of existing restorations. Clinicians then participated in a clinical study about repair or replacement of existing restorations. We quantified the overall concordance between their questionnaire responses and what they did in actual clinical treatment.

RESULTS

Practitioners who recommended repair (instead of replacement) of more scenario restorations also had higher repair percentages in clinical practice. Additionally, for each of the three hypothetical scenario restorations, practitioners who recommended repair had higher repair percentages in clinical practice.

CONCLUSIONS

The questionnaire scenarios were a valid measure of clinicians' tendency to repair or replace restorations in actual clinical practice.

CLINICAL IMPLICATIONS

Although there was substantial variation in practitioners' tendency to repair or replace restorations, responses to questionnaire scenarios by individual practitioners were concordant with what they did in actual clinical practice.

The statistical reporting quality of articles published in 2010 in five dental journals

OBJECTIVES

Statistical methods play an important role in medical and dental research. In earlier studies it has been observed that current use of methods and reporting of statistics are responsible for some of the errors in the interpretation of results. The aim of this study was to investigate the quality of statistical reporting in dental research articles.

METHODS

A total of 200 articles published in 2010 were analysed covering five dental journals: Journal of Dental Research, Caries Research, Community Dentistry and Oral Epidemiology, Journal of Dentistry and Acta Odontologica Scandinavica. Each paper underwent careful scrutiny for the use of statistical methods and reporting. A paper with at least one poor reporting item has been classified as 'problems with reporting statistics' and a paper without any poor reporting item as 'acceptable'.

RESULTS

The investigation showed that 18 (9%) papers were acceptable and 182 (91%) papers contained at least one poor reporting item.

CONCLUSIONS

The proportion of at least one poor reporting item in this survey was high (91%). The authors of dental journals should be encouraged to improve the statistical section of their research articles and to present the results in such a way that it is in line with the policy and presentation of the leading dental journals.

Reporting of statistical results in prosthodontic and implantology journals: p values or confidence intervals?

PURPOSE

Confidence intervals (CIs) are integral to the interpretation of the precision and clinical relevance of research findings. The aim of this study was to ascertain the frequency of reporting of CIs in leading prosthodontic and dental implantology journals and to explore possible factors associated with improved reporting.

MATERIALS AND METHODS

Thirty issues of nine journals in prosthodontics and implant dentistry were accessed, covering the years 2005 to 2012: The Journal of Prosthetic Dentistry, Journal of Oral Rehabilitation, The International Journal of Prosthodontics, The International Journal of Periodontics & Restorative Dentistry, Clinical Oral Implants Research, Clinical Implant Dentistry and Related Research, The International Journal of Oral & Maxillofacial Implants, Implant Dentistry, and Journal of Dentistry. Articles were screened and the reporting of CIs and P values recorded. Other information including study design, region of authorship, involvement of methodologists, and ethical approval was also obtained. Univariable and multivariable logistic regression was used to identify characteristics associated with reporting of CIs.

RESULTS

Interrater agreement for the data extraction performed was excellent (kappa = 0.88; 95% CI: 0.87 to 0.89). CI reporting was limited, with mean reporting across journals of 14%. CI reporting was associated with journal type, study design, and involvement of a methodologist or statistician.

CONCLUSIONS

Reporting of CI in implant dentistry and prosthodontic journals requires improvement. Improved reporting will aid appraisal of the clinical relevance of research findings by providing a range of values within which the effect size lies, thus giving the end user the opportunity to interpret the results in relation to clinical practice.

Dental school vacant budgeted faculty positions, academic years 2008-09 to 2010-11

The annual turnover of dental school faculty creates a varying number of vacant budgeted positions from year to year. The American Dental Education Association (ADEA) conducts an annual survey to determine the status and characteristics of these vacant faculty positions. The number of vacant budgeted faculty positions in U.S. dental schools increased throughout the 1990s, with a peak of 417 positions in 2005-06. Since that time, there has been a decrease in the number of estimated vacancies, falling to 227 in 2010-11. The 2008-09 to 2010-11 faculty vacancy surveys explored these decreases, along with information relevant to the number and characteristics of dental faculty vacancies, including data on the distribution of full-time, part-time, and volunteer faculty, reasons for faculty separations, and sources of new faculty.

How to report reliability in orthodontic research: Part 2

Proper statistical analysis is an absolutely essential tool for both clinicians and researchers attempting to implement evidence-based decisions. When analyzing reliability, statistical graphic representation is the best method. Other previously published error studies of 2-dimensional measurements, such as cephalometric landmarks, have inappropriately applied 1-dimensional approaches, such as linear or angular measurements. The aim of this article is to illustrate a graphic presentation method that can be applied to 2-dimensional data sets. We propose that this technique can show errors in both the x-axis and the y-axis simultaneously and should be used when reporting the reliability of a 2-dimensional data set. Our prediction error analysis of soft-tissue changes after orthognathic surgery will be presented as an example. By using different colors in each ellipse, this method can also identify any between-group differences.

Measuring the international spreading of the knowledge produced by French dental master theses

We estimated the international spreading of the knowledge produced by French dental master theses by searching for corresponding publications, either as articles in Medline-indexed journals or abstracts of IADR meetings published in the Journal of Dental Research. From the 634 theses defended in 2010 in the 16 French odontology faculties, we found only one article, in a journal without impact factor, and six abstracts, over a 3-year period (2009-2011). This corresponds to a spreading rate of 0.6%. The participation rate of French odontology faculties at IADR meetings varies from 37.5% to 81.3% depending on the year. Although there are very few studies available on the matter, it appears that this international spreading rate is much lower than both the one found by Nieminen for odontology in Finland (8.2%) and typical spreading rates of medical theses (from 6% to 41% depending on the country). This great discrepancy could be explained by the lack of specific training provided to the students; the low awareness and little engagement of the students themselves, usually more concerned with their own private practice work; and the inadequate involvement of their supervisors. To tackle the lack of appropriate training, we suggest that a specific course on scientific writing should be offered to the students in the last year of their dental master studies.

Examiner alignment and assessment in clinical periodontal research

Periodontal research typically relies on clinical examiners to assess variables such as gingival inflammation, plaque scores or probing depths as a means of determining treatment outcomes or for performing group comparisons. The quality of the gathered information is dependent, to a large extent, on the skills of the examiner(s) and on the validity of the assessment methods that are used. Attempts have been made to increase the objectivity of periodontal assessments, for example by introducing scoring systems for gingival inflammation, but within these systems there is often considerable scope for variation when interpreting the scoring criteria, leading to subjectivity when assigning scores to individual periodontal sites. This has led to an awareness of the importance of examiner alignment and assessment to improve the data quality by standardizing techniques and improving examiner reliability. Examiner alignment and assessment is used in preference to the term 'examiner calibration' because calibration implies comparison with an accurate or 'gold' standard, which is not available in periodontal research. In this review, we consider the historical perspective that led to the development of clinical scoring systems for periodontal research using gingival inflammation as an example. A clinical protocol for undertaking examiner alignment and assessment is presented, and we review the common sources of error and bias that can lead to difficulties in aligning examiners, and consider how they can be eliminated. It is particularly important that subjects who are recruited to the examiner alignment and assessment study present with a comparable level of disease to the subjects who will ultimately be recruited to the planned clinical trial. Another challenge in examiner alignment and assessment is applying appropriate statistical tests to assess the outcome of the alignment exercise. In the periodontal literature, the statistic kappa is frequently used to confirm an adequate degree of examiner agreement, but kappa is bound to significant restrictions when applied for this purpose. Through the use of case studies, we present different approaches to data analysis from calibration studies, focusing on continuous variables (such as probing depths and attachment levels) or ordinal data (such as gingival or plaque indices), to enable a correct, although frequently conservative, interpretation of data generated during examiner alignment and assessment studies.

Key statistical and analytical issues for evaluating treatment effects in periodontal research

Statistics is an indispensible tool for evaluating treatment effects in clinical research. Due to the complexities of periodontal disease progression and data collection, statistical analyses for periodontal research have been a great challenge for both clinicians and statisticians. The aim of this article is to provide an overview of several basic, but important, statistical issues related to the evaluation of treatment effects and to clarify some common statistical misconceptions. Some of these issues are general, concerning many disciplines, and some are unique to periodontal research. We first discuss several statistical concepts that have sometimes been overlooked or misunderstood by periodontal researchers. For instance, decisions about whether to use the t-test or analysis of covariance, or whether to use parametric tests such as the t-test or its non-parametric counterpart, the Mann-Whitney U-test, have perplexed many periodontal researchers. We also describe more advanced methodological issues that have sometimes been overlooked by researchers. For instance, the phenomenon of regression to the mean is a fundamental issue to be considered when evaluating treatment effects, and collinearity amongst covariates is a conundrum that must be resolved when explaining and predicting treatment effects. Quick and easy solutions to these methodological and analytical issues are not always available in the literature, and careful statistical thinking is paramount when conducting useful and meaningful research.

Critical issues in clinical periodontal research

As periodontal researchers and clinicians, we are challenged every day to make decisions relating to the clinical management of our patients and about how best to conduct clinical periodontal research. This volume of Periodontology 2000 addresses some of the critical issues in contemporary clinical periodontics and periodontal research that are of direct relevance to clinicians, researchers, teachers and students. The 11 review articles in this volume of Periodontology 2000 focus on aspects of periodontal research methodology and clinical periodontology. In terms of research methodology, the articles aim to inform the reader on topics relating to randomized controlled trials in periodontal research, evidence-based dentistry, calibration of clinical examiners and statistics relevant to periodontal research. The clinical periodontology articles address issues relating to decisions on retaining periodontally compromised teeth or replacing them with implants, periodontal management in the patient with osteoporosis, surgical approaches for root coverage and the emerging science of advanced regenerative technologies, including the use of stem cells, for periodontal regeneration. It is hoped that these critical reviews will address many of the dilemmas that confront us on a regular basis and provide practical guidance to those engaged in both clinical periodontology and clinical periodontal research.

Level of oral health impacts among patients participating in PEARL: a dental practice-based research network

OBJECTIVES

To determine whether participants of a dental practice-based research network (PBRN) differ in their level of oral health impact as measured by the Oral Health Impact Profile (OHIP) questionnaire.

METHODS

A total of 2410 patients contributed 2432 OHIP measurements (median age = 43 years; interquartile range = 28) were enrolled in four dental studies. All participants completed the Oral Health Impact Profile (OHIP-14) during a baseline visit. The main outcome of this study was the level of oral health impact, defined as follows: no impact ('Never' reported on all items); low ('Occasionally' or 'Hardly ever' as the greatest frequency score reported on any item); and high ('Fairly often' or 'Very often' as the greatest frequency reported on any item). Polychotomous logistic regression was used to develop a predictive model for the level of oral health impact considering the following predictors: patient's age, gender, race, practice location, type of dentist, and number of years the enrolling dentist has been practicing.

RESULTS

A high level of oral health impacts was reported in 8% of the sample; almost a third (29%) of the sample reported a low level of impacts, and 63% had no oral health impacts. The prevalence of impacts differed significantly across protocols (P < 0.001). Women were more likely to be in the high oral impact group than in the no impact group compared to men (OR = 1.46; 95% CI = 1.06-1.99). African Americans were more likely to report high oral impacts when compared to other racial/ethnic groups (OR = 2.11; 95% CI = 1.26-3.55). Protective effects for being in the high or in the low-impact groups were observed among patients enrolled by a solo practice (P < 0.001) or by more experienced dentists (P = 0.01). A small but highly significant statistical association was obtained for patient age (P < 0.001). In the multivariate model, patient's age, practice size, and gender were found to jointly be significant predictors of oral health impact level.

CONCLUSIONS

Patients' subjective report of oral health impact in the clinical setting is of importance for their health. In the context of a dental PBRN, the report of oral health-related quality of life (OHRQoL) was different across four dental studies. The observed findings validate the differential impact that oral health has on the patients' perception of OHRQoL particularly among specific groups. Similar investigations to elucidate the factors associated with patient's report of quality of life are warranted.

An introduction to research for primary dental care clinicians part 8: stage 9. Analysing the data

This paper, the eighth in the series, will address the ninth stage of a research project suggested in the first paper. The ten suggested stages are: 1. The initial idea (asking a research question). 2. Searching the literature. 3. Refining the research question. 4. Planning the study. 5. Writing a protocol. 6. Obtaining ethics approval and funding. 7. Piloting the project and project management. 8. Collecting data. 9. Analysing the data. 10. Writing up and disseminating the results. The previous paper outlined how to collect data during a research project. The next stage is to analyse the data that have been collected. This paper briefly introduces readers to data analysis and basic statistics. It updates the Faculty of General Dental Practice (UK) research advice sheets: Introduction to Statistics, Statistics for Research, Testing for Statistical Significance.

Trends in funding, internationalization, and types of study for original articles published in five implant-related journals between 2005 and 2009

PURPOSE

The aims of this study were to evaluate the trends in funding, geographic origin, and study types of original articles in the dental implant literature and to investigate the relationships among these factors.

MATERIALS AND METHODS

Articles published in Clinical Oral Implants Research, The International Journal of Oral and Maxillofacial Implants, Clinical Implant Dentistry and Related Research, Implant Dentistry, and Journal of Oral Implantology from 2005 to 2009 were reviewed. Nonoriginal articles were excluded. For each article included, extramural funding source, geographic origin, and study type were recorded. Descriptive and analytic analyses (α = .05), including a logistic regression analysis, and chi-square test were used where appropriate.

RESULTS

Of a total of 2,085 articles published, 1,503 met the inclusion criteria. The most common source of funding was from industry (32.4%). The proportion of studies that reported funding increased significantly over time. Europe represented the highest percentage (55.8%) of published articles. Most of the articles reported on clinical studies (49.9%), followed by animal studies (25.9%). Articles from Asia and South America and animal and in vitro studies were significantly more likely to be funded.

CONCLUSION

Almost half of the original dental implant articles were funded. The trend toward internationalization of authorship was evident. A strong association was observed between funding and geographic origin and between funding and study type. Most studies in North America and Europe were clinical studies and supported by industry, whereas a greater proportion of studies in Asia and South America were in vitro or animal studies funded through government resources.

Research in prosthodontics: a 10-year observation of trends in topics, collaboration, and funding

PURPOSE

The objectives of this study were to investigate the nature of recently published prosthodontic literature, to investigate the types of collaboration and funding as well as their relationship, and to analyze the associations between collaboration and extramural funding.

MATERIALS AND METHODS

Three peer-reviewed prosthodontic journals were used for the analysis of articles published in 1998, 2003, and 2008. The articles were analyzed based on associations between the type of article, type of original research, collaboration, and funding. The chi-square test and logistic regression were used for data analysis (a = .05).

RESULTS

From 998 articles, a significant decrease in reviews (P < .001) and an increase in case reports (P = .001) were observed. Articles regarding dental materials ranged from 53% to 58% of the total original research, and the amount of collaboration among disciplines (P = .012), institutions (P < .001), and countries (P = .014) increased from 1998 to 2008. Most studies (77.5%) did not report funding, and articles related to dental materials had the most collaboration and funding. Dental materials (48%), clinical care (37%), and education/public health research (7%) were supported by private companies, and biomedical and translational studies were mostly supported by a university (13%) or the government (7%). A strong association was noted between collaboration (P = .010), extramural funding, and original research, especially related to education/public health (P < .001), clinical care (P = .013), and dental materials (P = .004).

CONCLUSION

An increase in original research and collaboration was observed from 1998 to 2008. Studies that reported funding remained constant. A strong association with collaboration and funding was observed, along with studies involving clinical care, education, public health, and dental materials.

Inter-examiner reliability of salivary diagnostic tests in a practice-based research network

PURPOSE

Patient salivary characteristics are being measured as part of the Northwest PRECEDENT (Practice-based REsearch Collaborative in Evidence-based DENTistry) study on caries risk assessment. Prior to the implementation of these salivary diagnostic tests in a practice-based cohort study, inter-examiner reliability was assessed for resting salivary pH, stimulated salivary flow rate, pH and buffering capacity.

METHODS

An initial evaluation of inter-examiner reliability of the 4 salivary tests was conducted among 6 dental auxiliary examiners using a convenience sample of 40 dental students. An in complete block design was used to assign samples to examiners (3 examiners per sample and 20 samples per examiner). Inter-examiner reliability testing was conducted on a patient population representative of the practice-based network in 4 member practices. Two dental assistants per practice independently conducted the salivary tests on samples provided by a random selection of 20 to 25 patients. A separate analysis was performed for each study. For each test, an inter-examiner reliability index was computed.

RESULTS

Results from two studies are reported. In the first, stimulated salivary flow rate demonstrated excellent inter-examiner reliability, and resting salivary pH showed high inter-examiner reliability, while buffering capacity and stimulated salivary pH had moderate and very low inter-examiner reliability, respectively. In the second, inter-examiner reliability was excellent for the stimulated salivary flow rate and the resting salivary pH. The inter-examiner reliability for the stimulated salivary pH was also high and the stimulated salivary buffering capacity test had moderate reliability.

CONCLUSION

The small variance in stimulated salivary pH and buffering capacity in dental students may have artificially made the reliability appear low in the first attempt at inter-examiner reliability testing. In the second study, all 4 tests had an accept able performance.

Factors influencing publication rates of abstracts presented at the ADEA annual session & exhibition

Factors related to the path of abstracts from presentation at a conference to publication as a full article have been analyzed in the medical field, but only a few studies have been performed in dentistry. This study investigated the rate of publication of articles based on abstracts presented at the American Dental Education Association (ADEA) Annual Session & Exhibition in 2002 and 2003 and the time lag to publication. This study also aimed to characterize the abstracts and subsequent articles and determine if there were any significant factors related to expansion of an abstract into a full manuscript. A total of 370 abstracts met the inclusion criteria and were examined for this study. Subsequent published articles were located using a standard PubMed search. Descriptive statistics and bivariate analyses were used to analyze the data collected (α=0.05). Results suggest that there was a low (19 percent) publication rate for articles based on abstracts presented at the meetings studied. The median time between abstract presentation and article publication was ten months. Factors that showed significant correlation to likelihood of article publication were multiple affiliations, presence of analytical statistics, and, to a lesser extent, funding. We suggest that presenters at these meetings should expand their abstracts into full manuscripts and seek to publish them in peer-reviewed journals for the benefit of the profession.

How effective is that treatment? The number needed to treat

The Number Needed to Treat (NNT) is a tool useful for comparing the relative effectiveness of two or more therapeutic or preventive interventions. The NNT may be presented by authors of a clinical research article, or, if not provided, may be calculated by the reader if the authors have reported outcomes as positive or negative per research subject. The NNT is simply calculated as the inverse of the absolute risk reduction. The NNT is most meaningful when reported within a confidence interval and when describing clinical trials of higher validity such as randomized controlled trials and meta-analyses of such trials. Several example NNTs from the dental and medical literature are reported.

Alternative careers in pediatric dentistry: a survey of pediatric dental residents

Pediatric dentistry has enjoyed growing popularity in recent years, yet there remains a need for leadership in academe, research, and public health. In November 2008, the first Maternal and Child Health Bureau-sponsored regional Leadership in Pediatric Dentistry convocation was held at the Columbia University College of Dental Medicine. Seventy-two pediatric dentistry trainees from thirteen programs in the New York City area participated in interactive presentations and exercises. Of the sixty- seven participants who completed a pre-event survey, 93 percent stated they would likely or very likely pursue careers that involved, at least in part, private practice, 55 percent in care of children in Medicaid, 51 percent academics, 36 percent dental public health, and 12 percent research. Barriers related to finances, competence, or work environment/location were perceived by 83 percent for careers involving research, 73 percent for dental public health, 66 percent for providing care to children in Medicaid, 46 percent for academics, and 9 percent for private practice. Results of a pair of pre-event and post-event surveys completed by sixty-three attendees showed no change in reported likelihood to pursue a career alternative except for an increase in the likelihood of working in a practice that accepts Medicaid. The challenge before dental educators is to provide consistent and meaningful opportunities throughout training that encourage residents to consider all career options and to discover how their individual interests mesh with their clinical learning.

Gender trends in dental leadership and academics: a twenty-two-year observation

The purpose of this study was to examine gender disparities in dental leadership and academics in the United States. Nine journals that represent the dental specialties and high published impact factors were selected to analyze the percentage of female dentists' first and senior authorship for the years 1986, 1990, 1995, 2000, 2005, and 2008. Data on appointment status and female deanship were collected from the American Dental Association (ADA) survey, and the trends were studied. The proportion of female presidents in ADA-recognized specialty organizations was also calculated. Overall, the increase in first female authorship was not statistically significant, but the increase of last female authorship was statistically significant in a linear trend over the years. The percentage of tenured female faculty members and female deans in U.S. dental schools increased by factors of 1.7 and 9, respectively, during the study period. However, female involvement in professional organizations was limited. Findings from this study indicate that female participation in authorship and leadership has increased over time. Nevertheless, females are still a minority in dental academics and leadership.

A guide to the appraisal of research: 2. What's in a number?

This review explores the nature of numbers in dental research, their importance and, at a basic level, how these are handled. This includes the important numbers that practitioners should look at when appraising research and discussion of some commonly found statistical terms.

CLINICAL RELEVANCE

In order to apply evidence-based dentistry in clinical practice, dentists should have an understanding of the basic numbers reported in dental research, and an appreciation of this should allow them to identify which papers are most valuable to inform their clinical practice.

Dental research in Iran: a bibliometric analysis of electronically available literature

PURPOSE

To carry out a bibliometric analysis of all electronically available dental literature in Iran from 1983 to 2006, in order to study availability and examine trends.

MATERIALS AND METHODS

Accessing all electronically available Iranian dental articles published in domestic journals, and comparing the results with Iranian dental articles published in Pubmed. The following data were collected from each article: name of journal, year of publication, number of authors, gender of corresponding author, academic levels of authors, main language of article, language of abstract, study environment, population studied, field of dentistry, type of article, design strategy, design of study, and analysis design.

RESULTS

In terms of publications in domestic journals, a total of 1,994 dental articles were electronically available, published in six different dental journals in Iran. Majority of articles, 84.5%, were original studies. In terms of design strategy, 49.7% of studies were cross-sectional, 35.5% were prospective, and 14.8% were retrospective studies. The main language of 99.3% of articles was Farsi, and 0.7% was English. Majority of articles, 38.7%, were written by two authors. Gender of corresponding author in 66.7% of articles was male, and in 33.3% of articles was female. There was an increasing trend in percentage of original studies, clinical trials and female corresponding authors. In terms of publications in Pubmed, a total of 75 dental articles from Iran were electronically available. Significant differences were revealed in terms of number of authors, study types and design strategies when compared to publications in domestic journals.

CONCLUSION

A number of encouraging trends were identified, which is a reflection of improvements in quality of domestic electronic dental literature. However, as the majority of articles are written in Farsi, availability of research evidence to the international community is limited. Overall, results of this study indicate the need for future bibliometric analyses which can be used to construct a comprehensive database that will assist in evidence-based clinical decision making.

Dental traumatology: an orphan in pediatric dentistry?

Traumatic dental injuries are very frequent during childhood and adolescence. In fact, 2 out of 3 children have suffered a traumatic dental injury before adulthood. This fact links dental traumatology to pediatric dentistry. Unfortunately, this is not reflected by active participation by pediatric dentists in acute treatment, follow-up, and research. To examine the status of pediatric dentistry in relation to dental trauma, a publication analysis was undertaken in 1980, 1990, 2000, and 2007 about trauma articles published in 4 pediatric journals: journal of Dentistry for Children, Pediatric Dentistry, The journal of Pedodontics, and the International journal of Pediatric Dentistry. This study shows an average publication rate of trauma articles of approximately 3 percent of all articles published and with no improvement in later decennia. If only clinical studies are considered (leaving out case reports), the publication rate is less than 1 percent--completely out of proportion to the size of the problem dental trauma impose in children.

Research productivity of members of IADR Behavioral Sciences and Health Services Research Group: relationship to professional and personal factors

This report describes the research productivity of the members of the International Association for Dental Research (IADR) Behavioral Sciences and Health Services Research Group and examines personal and professional factors related to greater productivity. The findings from previous studies suggested there might be gender discrimination in opportunities for women faculty. Members on the active membership list for this IADR group were surveyed by email. Most were dentists, and three-quarters had external funding for their research. The primary outcome measure was the number of self-reported published articles in PubMed in the preceding twenty-four months. The mean number of these publications was 4.9 (SD=5.1). Gender and time in research were the best predictors of research productivity of this population. There was no difference in time for research between the men and women in this study. Controlling for gender, the best single predictor of research productivity remained percent time spent in research. Overall, the members of the IADR group spent almost three times as much time in research and were more than twice as productive as faculty members as a whole as described in earlier studies. In view of the current emphasis in many countries on addressing the social and behavioral determinants of oral health disparities, the productivity of this area of dental research is very important. Trends toward clinically oriented, non-research-intensive dental schools in the United States and reductions in time and funding available to conduct research should be of concern.

Peer-reviewed publication output from South African dental schools 1990-2005

INTRODUCTION

A study published in 1996 suggested that a limit had been reached for peer-reviewed publication output from South African dental schools.

AIMS AND OBJECTIVES

This study was to examine recent trends in publication output from five South African dental schools to compare with the earlier study.

METHODS

A PubMed on-line search coupled with a manual search was done for peer-reviewed publications appearing in 1995-2005 from the five dental schools.

RESULTS

The literature search identified 610 listings--595 actual publications six of which were listed for two dental schools. Overall there was a slight reduction in number of articles as well as an increase in articles published in South African journals. Within the schools there was also a decline in output. Disciplines producing the publications varied within the schools with dental materials being the most common, There was little difference in the quality of articles indicated by mean CJM scores between the schools.

CONCLUSIONS

This study shows that research output has declined beyond the limit speculated in 1996.

Participation of dental researchers at annual SA IADR Conferences (1967-2004): drivers and passengers

A descriptive study of SA IADR Conference participation 1967-2004 showed that both membership numbers and conference presentations have declined by half over the past 20 years. Of the total of 3 259 presentations, from mainly the six Schools of Oral Health Sciences (SOHS), the majority were from SOHS 1, followed by the SOHS 2, 3, 5, 4 and 6. Productivity of individual SOHS has changed over the years. Number of annual presentations per school has varied according to the organising school and the distance of the school from the conference venue. Research prizes are well supported. Research active "drivers" have high personal research productivity but do not significantly influence (P > 0.05) the number of conference presentations of their respective schools.

DRI productivity and participation at the SA IADR (1967-2004)

This analysis describes the scientific research productivity and participation of the Dental Research Institute (DRI) in the South African Division of the International Association for Dental Research (1967-2004). A total of 438 presentations were delivered by the 257 individuals conducting research under the auspices of the DRI. Presenters were mainly DRI staff (45%); from the associated Dental School 26% and private practitioners 22%. Most the presentations were produced by a minority of researchers. Postgraduates had 150 presentations linked to research for their higher degrees. While the numbers of DRI presentations has declined with time, staff presentation productivity has increased. There has been a slight change in abstract descriptors with a recent falling away of animal studies. Sixty eight percent of oral presentations were ultimately published with between 1 to 4 oral presentations contributing towards a journal publication. Most of the current presenters have reached retirement age and their SA IADR activity will cease.

Reported methodological quality of split-mouth studies

BACKGROUND/AIM

Hujoel & Moulton previously questioned the reported quality of split-mouth studies. Since then, there has been little enquiry into the methodology of this study design. The aim was to conduct a systematic review of the reported methodology of clinical studies using a split-mouth design published in dental journals over a 1-year period (2004).

MATERIAL AND METHODS

An extension of the CONSORT guidelines for cluster-randomized designs was used to evaluate quality. We evaluated the methods used and quality of reporting split-mouth studies.

RESULTS

Thirty-four studies were eligible for this review. The results showed that many papers lack essential qualities of good reporting, e.g. five of 34 papers gave the rationale for choosing a split-mouth design, 19 of 34 (56%) used appropriate analytical statistical methods and only one of 34 presented an appropriate sample size calculation. Of the five studies that used survival analysis, none of them used a paired approach.

CONCLUSIONS

Despite some progress in statistical analysis, if the reporting of studies represents the actual methodology of the trial, this review has identified important aspects of split-mouth study design and analysis that would benefit from development.

Supporting the emergence of dental informatics with an online community

Dental Informatics (DI) is the application of computer and information science to improve dental practice, research, education, and program administration. As an emerging field, dental informatics faces many challenges and barriers to establishing itself as a full-fledged discipline; these include the small number of geographically dispersed DI researchers as well as the lack of DI professional societies and DI-specific journals. E-communities have the potential to overcome these obstacles by bringing researchers together at a resources hub and giving them the ability to share information, discuss topics, and find collaborators. In this paper, we discuss our assessment of the information needs of individuals interested in DI and discuss their expectations for an e-community so that we can design an optimal electronic infrastructure for the Dental Informatics Online Community (DIOC). The 256 survey respondents indicated they prefer electronic resources over traditional print material to satisfy their information needs. The most frequently expected benefits from participation in the DIOC were general information (85% of respondents), peer networking (31.1%), and identification of potential collaborators and/or research opportunities (23.2%). We are currently building the DIOC electronic infrastructure: a searchable publication archive and the learning center have been created, and the people directory is underway. Readers are encouraged to access the DIOC Website at www.dentalinformatics.com and initiate a discussion with the authors of this paper.

A Study on Variances in Multivariate Analyses of Oral Implant Outcome

BACKGROUND

Elaborate studies have shown that interdependency exists between implants being placed in the same patient/jaw. Therefore, interdependency ought to be an important aspect to address, whenever performing statistical analyses of oral implant outcomes. A Jackknife method could be an option when conducting statistical evaluations of oral implant failure prognoses.

PURPOSE

The aim of this study was to evaluate whether a statistical difference can be detected by using the Jackknife method in conjunction with life table analyses and/or a log rank test of four different combinations of jaw density and quantity.

MATERIALS AND METHODS

Four multicenter studies were pooled and adjusted in order to create a research database consisting of 486 patients and 1,737 implants in preparation for the Jackknife resampling method. Combinations of jaw shapes and bone qualities were constructed to select at-risk patients.

STATISTICAL METHODS

Life tables with confidence intervals were calculated and a log rank test was used to determine whether a statistical difference between the combinations could be established.

RESULTS

Both statistical analyses, after the Jackknife resampling method, showed that patients with poor bone quality and resorbed jaws (combination IV) had a statistically higher risk of implant failure.

CONCLUSION

By rearranging data using the Jackknife method, standardized statistical tests seem to work well even when the study population tested was affected by interdependency.

Statistical Aspects of Design and Analysis of Clinical Trials for the Prevention of Caries

This paper considers the methods used in design and analysis of recent clinical trials of topical fluoride interventions designed to prevent the development of dental caries in children, with particular consideration given to issues related to cluster-randomized trials. Studies which met the inclusion criteria were recent clinical trials of topical fluoride interventions published since 1990, conducted in children under 16 years of age, with caries as the outcome variable. Papers not published in English were translated. Information was extracted from the published trial reports on the units of randomization and analysis. The papers were also studied to assess if reporting allowed the assessment of potential consent bias in cluster-randomized trials and the reproduction of sample size calculations. Fifteen trials published since 1990 were included, of which five were cluster randomized. Only 1 of the 5 accounted for the clustering in the analysis. For the other four trials, it was possible to calculate that values from 0.002 (for DMFS) and 0.08 (for being caries free) for the intracluster correlation coefficient within schools could result in statistically non-significant findings. 3 of the 5 cluster-randomized trials did not report the consenting procedure in enough detail to judge whether consent bias could be present. Only 1 of the total 15 trials reported a sample size calculation. In summary, researchers should be aware of the importance of correctly analyzing cluster-randomized data and thorough reporting of clinical trials according to the CONSORT guidelines.

World dental research production: an ISI database approach (1999-2003)

The objective of this study was to obtain a geographic world map of scientific production in dentistry by analysing published papers. Articles and reviews in the Dentistry, Oral Surgery & Medicine category published from 1999 to 2003 were accessed through the ISI database. The data were analyzed quantitatively (number of documents, number of researchers, productivity, interannual variation rate and relative specialization index), qualitatively (weighted impact factor, relative impact factor, citation rate per document and top 5 publications) and socioeconomically (number of documents per inhabitant and per dentist and in relation to the country's GDP). The USA, UK, Japan and Scandinavian countries were found to be the most productive countries (number of publications). Publications from Scandinavian countries were also of high quality as measured by Impact Factor and Citation Rate, while the UK had one of the highest productivity rates (number of documents per researcher).