Our Essential and Endangered Dentist-Scientist Workforce.

Future advances in dental medicine rely on a robust and stable pipeline of dentist-scientists who are dedicated to research inspired by the patients' condition. The biomedical research community faces external and internal pressures that have been building over years. This is now threatening the current and future status of basic, translational and patient-oriented research by dentist-scientists who study dental, oral and craniofacial diseases, population sciences, and prevention. The dental academic, research and practicing communities can no longer ignore the warning signs of a system that is under considerable stress. Here, the authors report findings of the Physician-Scientist Workforce Working Group, charged by the National Institutes of Health (NIH) Director, to perform quantitative and qualitative analyses on dentist-scientists by addressing the size, composition and activities of the group, relative to other health professions. From 1999 to 2012, trends in the numbers of grant applications and awards to dentist-scientists point to an overall decline. Disturbing are the low numbers of new investigators who apply for Early Career NIH Programs. While more seasoned dentist researchers enjoy greater success, the average age of first-time funded dentists is 52.7 y for females and 54.6 y for males, with a relatively low number of applications submitted and funded. These new data led the panel to stress the need to expand the capacity of the dentist-scientist workforce to leverage technologies and research opportunities that benefit the profession at-large. Suggestions were made to invest in developing clinical research faculty, including those with foreign degrees, through new training mechanisms. The creation of new alliances between national organizations like the American Association for Dental Research, the American Dental Education Association and the American Dental Association will undoubtedly lead to bold and concerted actions that must be pursued with a sense of urgency. A more supportive culture within dental schools and universities for dentist-scientists is needed, as their success is critical to the future career choices of their mentees. Knowledge Transfer Statement: Advances in dental medicine rely on a pipeline of dentist-scientists who are dedicated to research inspired by the patients' condition. Despite the recent advancement in technology and innovation, the dental community can no longer ignore the various pressures that threaten the future of the dentist-scientist profession. Here, the authors report findings of the Physician-Scientist Workforce Working Group of NIH that were published in 2014, and draw attention to the key issues threatening the NIH-funded pool of dentist-scientists.

Dental hygiene work in a clinical trial.

UNLABELLED: Dental hygiene activities were developed as part of a randomized clinical trial designed to assess the safety of low-level mercury exposure from dental amalgam restorations. Along with dental-hygiene clinical work, a community programme was implemented after investigators noticed the poor oral hygiene habits of participants, and the need for urgent action to minimize oral health problems in the study population. OBJECTIVES: Clinical and community activity goal was to promote oral health and prevent new disease. Community activities involved participants and their fellow students and were aimed at providing education on oral health in a school environment. METHODS: Dental hygienists developed clinical work with prophylaxis, sealants application and topical fluoride and implemented the community programme with in-class sessions on oral health themes. Twice a month fluoride mouthrinses and bi-annual tooth brushing instructional activity took place. Participation at dental-hygiene activities, sealed teeth with no need of restoration and dental-plaque-index were measures used to evaluate success of the programme for the participants. RESULTS: Improvement in dental hygiene is shown by the decrease in dental plaque index scores (P < 0.0001); also sealants integrity is achieved in 86.3% of teeth. 888 (13.7%) teeth with sealants had to be restored or were lost. Children participated actively on dental hygiene activities. Teachers became aware of the problem and included oral-health in school curricula. CONCLUSION: Dental hygiene activities have shown to be helpful to promote dental hygiene, promote oral health and to provide school-age children with education on habits that will be important for their future good health.

A randomized clinical trial of chlorhexidine in the maintenance of oral candidiasis-free period in HIV infection.

OBJECTIVE: To determine if chlorhexidine can be used as an intervention to prolong the time to relapse of oral candidiasis. SUBJECTS AND METHODS: A double-blinded randomized clinical trial was performed in 75 HIV/AIDS subjects with oral candidiasis. Clotrimazole troche was prescribed, and the subjects were re-examined every 2 weeks until the lesions were completely eradicated. The subjects were then randomly divided into two groups; 0.12% chlorhexidine (n = 37, aged 22-52 years, mean 34 years) and 0.9% normal saline (n = 38, aged 22-55 years, mean 38 years). They were re-examined every 2 weeks until the next episode was observed. RESULTS: The time to recurrence of oral candidiasis between the chlorhexidine and the saline group was not statistically significant (P > 0.05). The following variables were significantly associated with the time of recurrence; frequency of antifungal therapy (P = 0.011), total lymphocyte (P = 0.017), alcohol consumption (P = 0.043), and candidiasis on gingiva (P = 0.048). The subjects with lower lymphocyte showed shorter oral candidiasis-free periods (P = 0.034). CONCLUSIONS: Chlorhexidine showed a small but not statistically significant effect in maintenance of oral candidiasis-free period. This lack of significance may be due to the small sample size. Further study should be performed to better assess the size of the effect, or to confirm our findings.

Evaluation of a 7-year school-based community dental hygiene programme in Portugal by high school teachers.

OBJECTIVES: To obtain high school teachers evaluation of a Community Dental Hygiene programme, developed as part of a clinical trial designed to assess the safety of low-level mercury exposure from amalgam restorations. METHODS: A questionnaire to assess programme evaluation, personal opinion on programme relevance and satisfaction with activities was distributed among teachers. It had a total of 22 questions organized into three groups. RESULTS: A total of 25 questionnaires were obtained from teachers who participated in the programme. Ninety-two per cent of the respondents had a positive opinion concerning the existence of the programme. Eighty-eight per cent of the teachers believed that the programme changed student's knowledge about dental hygiene. Ninety-two per cent of teachers supported the existence of the programme and 88% of them disagreed with a statement that participation in the programme was a waste of time. Teachers who did not collaborate actively with dental hygiene activities indicated belief that the programme affected school activities (P = 0.003). Teachers who actively participated in the programme believe that dental hygiene activities were important for students (P = 0.005). CONCLUSIONS: Teacher evaluations of this kind of programme are critical for the development of school-based Dental Hygiene Education programmes. Teachers believe that Dental Hygiene Education is crucial for students' well-being.

Efficiency issues among statistical methods for demonstrating efficacy of caries prevention.

Although repeated tooth-surface-specific information is commonly collected during a longitudinal caries clinical trial, traditional methods often make limited use of the repeated measures. Newer methods of analysis, such as methods based on time-to-event and methods for longitudinal or clustered data, have the potential to increase the efficiency of the statistical analysis. We compare a range of analytical methods from the traditional analysis based only on the number of caries onsets to newer methods that incorporate time at risk and surface-specific information, such as Poisson regression methods for clustered data, with respect to the efficiency of treatment comparisons. Under most circumstances, the greatest gain in efficiency associated with time-to-event methods will be due to the ability of subjects to contribute caries onsets to the analysis until they are lost from the study. Incorporating the number of surfaces at risk, the surface time at risk, and surface-specific characteristics will typically produce only a modest gain in efficiency.

Bias induced by self-reported smoking on periodontitis-systemic disease associations.

Non-causal associations between periodontitis and systemic diseases may be spuriously induced by smoking because of its strong relationship to both. The goal of this study was to evaluate whether adjustment for self-reported smoking removes tobacco-related confounding and eliminated such spurious confounding. Using NHANES III data, we evaluated associations between attachment loss and serum cotinine after adjustment by self-reported number of cigarettes smoked. Cotinine, a metabolite of nicotine, should not be related to attachment loss, if self-reported smoking captures the effect of tobacco on attachment levels. Adjustment for self-reported cigarette smoking did not completely remove the correlation between attachment loss and serum-cotinine level (r = 0.075, n= 1507, p = 0.003). Simulation studies indicated similar results for time-to-event data. These findings demonstrate the difficulty in distinguishing the effects of periodontitis from those of smoking with respect to a smoking-related outcome. Future studies should report results of analyses on separate subcohorts of never-smokers and smokers.

A hidden periodontitis epidemic during the 20th century?

OBJECTIVES: Increasing evidence suggests a strong causal link between smoking and periodontitis. The goal of this study was to impute how the secular changes in smoking prevalence during the 20th century impacted the advanced periodontitis incidence in the US. METHODS: Epidemiological analyses based on US prevalence data of advanced periodontitis and smoking, and predictions of future smoking prevalence. RESULTS: Assuming other risk factors for periodontitis remained constant, we estimated that the incidence of advanced periodontitis decreased by 31% between 1955 and 2000. The changes in smoking habits, and consequently the changes in periodontitis incidence, depended strongly on education and gender. Between 1966 and 1998, we estimated a 43% decreased periodontitis incidence among college-educated individuals versus only an 8% decrease among individuals with less than a high school education. Between 1955 and 1999, we estimated a 41% decrease among males versus a 14% decrease among females. By the year 2020, the incidence of advanced periodontitis may decrease 43% from its level in 1955. CONCLUSIONS: A periodontitis epidemic fueled by smoking remained hidden for most of the 20th century. Because this epidemic was hidden, it distorted our understanding of the treatment and etiology of periodontitis. The socioeconomic polarization of this epidemic will dictate alterations in patterns of periodontal care.

Pre-existing cardiovascular disease and periodontitis: a follow-up study.

Periodontal infections in individuals with pre-existing heart disease are believed to increase the risk for future coronary heart disease (CHD) events. The goal of this study was to search for an association between periodontitis and CHD events among individuals with pre-existing heart disease, reported in the First National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. Dentate adults (n = 636) with a history of pre-existing cardiovascular disease were followed for CHD events. The presence of periodontitis and gingivitis did not increase CHD risk among these at-risk individuals (hazard ratio [HR], 0.97, and 95% confidence interval [CI], 0.72-1.31; and HR, 1.09, and 95% CI, 0.79-1.50, respectively). When limited to individuals with a self-reported prior heart attack, periodontitis was associated with a 34% decreased CHD risk (HR, 0.66; 95% CI, 0.42-1.05). It is concluded that periodontitis or gingivitis does not elevate CHD risk among individuals with a prior heart attack or self-reported pre-existing cardiovascular disease.

Examining the link between coronary heart disease and the elimination of chronic dental infections.

BACKGROUND: While it has been suggested that periodontal disease may be associated with coronary heart disease, or CHD, there are no data to suggest that the elimination of chronic dental infections actually lowers the risk of developing chronic CHD. The goal of this study was to determine whether people with a definitive elimination of all potential dental infections--edentulous people, who are at the optimum endpoint of dental infection elimination from a CHD perspective--lower their CHD risk over time when compared with people who have a specific dental infection, periodontitis. METHODS: The authors examined data from a prospective cohort of 4,027 people who participated in the First National Health and Nutrition Examination Survey, or NHANES I, Epidemiologic Follow-up Study. The primary outcome measure was the first CHD event. RESULTS: During a mean follow-up of 17 years, there were 1,238 CHD events (538 fatal). The confirmed elimination of chronic dental infections did not lead to a decreased risk of experiencing a CHD event (relative risk, 1.02; 95 percent confidence interval, 0.86-1.21). The CHD risk among people with and without chronic dental infections remained constant over time with respect to each other (test for increasing or decreasing trend over time: not significant, chi2(1) = 0.48; P = .93). CONCLUSIONS: People who had a complete, definitive and long-term elimination of all potential dental infections through extraction of all teeth did not have lower CHD risk when compared with people with diagnosed periodontitis. CLINICAL IMPLICATIONS: Until evidence is found to the contrary, the authors suggest that prevention of CHD should not be used as the basis for recommending treatment to eliminate chronic dental infections.

A covariance estimator for GEE with improved small-sample properties.

In this paper, we propose an alternative covariance estimator to the robust covariance estimator of generalized estimating equations (GEE). Hypothesis tests using the robust covariance estimator can have inflated size when the number of independent clusters is small. Resampling methods, such as the jackknife and bootstrap, have been suggested for covariance estimation when the number of clusters is small. A drawback of the resampling methods when the response is binary is that the methods can break down when the number of subjects is small due to zero or near-zero cell counts caused by resampling. We propose a bias-corrected covariance estimator that avoids this problem. In a small simulation study, we compare the bias-corrected covariance estimator to the robust and jackknife covariance estimators for binary responses for situations involving 10-40 subjects with equal and unequal cluster sizes of 16-64 observations. The bias-corrected covariance estimator gave tests with sizes close to the nominal level even when the number of subjects was 10 and cluster sizes were unequal, whereas the robust and jackknife covariance estimators gave tests with sizes that could be 2-3 times the nominal level. The methods are illustrated using data from a randomized clinical trial on treatment for bone loss in subjects with periodontal disease.

Between-subject and within-subject statistical information in dental research.

The evaluation of risk factors in dental research frequently uses observations at multiple sites in the same patient. For this reason, statistical methods that accommodate correlated data are generally used to assess the significance of the risk factors (e.g., generalized estimating equations, generalized linear mixed models). In applications of these methods, it is typically assumed (implicitly, if not explicitly) that between-subject and within-subject comparisons will produce the same estimated effect of the risk factor. When between- and within-subject comparisons conflict, the statistical methods can give biased estimates or results that are difficult to interpret. For illustration, we present two examples from periodontal disease studies in which different statistical methods give different estimates and significance levels for a risk factor. Statistical analyses in dental research should assess whether different sources of information give similar conclusions about risk factors or treatments.

Periodontal disease and coronary heart disease risk.

CONTEXT: Research has suggested a relationship between periodontal disease and coronary heart disease (CHD), but data on the association between these 2 common conditions are inconclusive due to the possibility of confounding. OBJECTIVE: To evaluate the risk of CHD in persons with periodontitis, gingivitis, or no periodontal disease. DESIGN: Prospective cohort study. SETTING: The First National Health and Nutrition Examination Survey Epidemiologic Follow-up Study, conducted in 1982-1984, 1986, 1987, and 1992. PARTICIPANTS: A total of 8032 dentate adults aged 25 to 74 years with no reported history of cardiovascular disease, including 1859 individuals with periodontitis, 2421 with gingivitis, and 3752 with healthy periodontal tissues. MAIN OUTCOME MEASURE: First occurrence of death from CHD or hospitalization due to CHD, or revascularization procedures, obtained from death certificates and medical records, by baseline periodontal status. RESULTS: During follow-up, 1265 individuals had at least 1 CHD event, including CHD fatality (n = 468) or at least 1 hospitalization with a diagnosis of CHD (n = 1022), including coronary revascularization procedures (n = 155). After adjustment for known cardiovascular risk factors, gingivitis was not associated with CHD (hazard ratio, 1.05; 95% confidence interval, 0.88-1.26), while periodontitis was associated with a nonsignificant increased risk for CHD event (hazard ratio, 1. 14; 95% confidence interval, 0.96-1.36). CONCLUSION: This study did not find convincing evidence of a causal association between periodontal disease and CHD risk. JAMA. 2000;284:1406-1410.

Association of oral spirochetes from periodontally healthy sites with development of gingivitis.

The purpose of this investigation was to determine whether the presence of selected disease-associated bacteria in health-associated plaque correlated with future gingivitis. Sites of periodontal health were identified in 65 adults. Six months later (recall 1) plaque was collected from sites that remained in periodontal health, and 5 species of specific bacteria and pathogen-related oral spirochetes were detected using monoclonal antibodies in a microscopic assay. Members of the spirochete morphogroup were also identified by phase contrast microscopy. The relationship between site-specific detection of bacteria at recall 1 and development of gingivitis at recall 2 or 3 was evaluated by means of logistic regression using generalized estimating equations, from which odds ratios (OR) were estimated. Significance was conservatively defined as OR > 2.0 and P < 0.05. We found that 488 of 1,424 healthy sites developed gingivitis over the 12-month interval between recall 1 and 3. Only the spirochete morphogroup (OR =2.04; P=0.002) was significantly associated with the transition from health to gingivitis. The association of Treponema socranskii with future gingivitis was higher than expected (OR=2.27), but the relationship was not statistically significant (P=0.163). Campylobacter rectus, Eikenella corrodens, Porphyromonas gingivalis, and pathogen-related oral spirochetes did not correlate well with gingivitis (OR < 2.0). Health-associated plaque from 5 sites contained Treponema denticola, and all 5 sites progressed to gingivitis. An OR could not be calculated because T. denticola was not detected in health-associated plaque from stable healthy sites. These findings indicated that the presence of T. denticola and unidentified spirochetes in health-associated plaque was associated with increased susceptibility to gingival inflammation. Future studies assessing a larger panel of dental plaque microorganisms, with shorter intervals between baseline and follow-up assessment, are necessary to more fully evaluate the association between detection of specific organisms at healthy sites and risk for gingivitis.

Comparison of a bioabsorbable GTR barrier to a non-absorbable barrier in treating human class II furcation defects. A multi-center parallel design randomized single-blind trial.

This multi-center single-blind study compared clinical outcomes following guided tissue regeneration (GTR) treating human Class II furcation defects with a new polylactic-acid-based bioabsorbable barrier (test treatment) or a non-absorbable ePTFE barrier (control treatment). Clinical parameters evaluated were change in vertical attachment level (VAL), horizontal attachment level (HAL), probing depth (PD), and gingival margin location (REC). Surgical treatment resulted in clinically and statistically equivalent changes when comparisons were made between test and control treatments. VAL gain was 2.0 mm for test and 1.6 mm for control groups; HAL gain was 2.1 mm for both test and control groups. PD reduction was 2.3 mm for the test group and 2.1 mm for the control group. Test sites experienced an additional 0.3 mm of recession beyond baseline; control sites, 0.5 mm. Within-group comparisons showed that the amount of recession was not significantly different from baseline in the test group. Recession in the control group was significantly different from baseline. All other parameters in both the test and control groups were significantly different from baseline. Evaluation of safety data indicated no significant differences between test and control treatments, although there was a strong trend for the control group to have more postoperative abscess or suppuration than test sites (control = 11; test = 4; P = 0.06).

Evaluating the validity of probing attachment loss as a surrogate for tooth mortality in a clinical trial on the elderly.

Most periodontal trials are based on the assumption that the superior treatment, as judged by short-term intangible changes in probing attachment levels (the surrogate), is also the treatment most likely to affect tooth mortality. This assumption is valid if: (1) the surrogate is informative about tooth mortality, and (2) the surrogate captures a substantial proportion of the treatment effect on tooth mortality (e.g., > 50% or 75%). The goal of this study was to evaluate whether both conditions were satisfied in a randomized controlled trial (RCT) of elders at high risk for dental diseases. The results suggested that the first condition for a valid surrogate was satisfied: Both one- and two-year changes in probing attachment level were informative about tooth mortality risk. A 1-mm loss measured over a one-year period was associated with a 56% increased tooth mortality risk (relative risk = 1.56; 95% confidence interval, 1.08 to 2.26; p = 0.017); a 1-mm loss measured over a two-year period was associated with a 102% increased risk for tooth mortality (relative risk = 2.02; 95% confidence interval, 1.26 to 3.25; p = 0.004). The second condition necessary for a valid surrogate could not be confirmed in the present trial. With 95% confidence, it was concluded that one-year changes in probing attachment level measurements did not capture a significant proportion of the treatment effect (point estimate, 6%; 95% confidence interval;-38% to 53%). No useful statements could be made regarding the proportion of treatment effect captured by two-year changes, due to the width of the confidence interval (point estimate, 18%; 95% confidence interval;-151% to 140%). It is concluded that (1) the evidence surrounding the one-year change in probing attachment level indicates that it can be ruled out as being anything more than a weak surrogate marker for tooth mortality, and (2) further research is required to study the validity of two-year change in probing attachment level as a surrogate marker. Due to characteristics of the population and the treatments investigated, the generalizability of these findings to other RCTs is questionable.

Association of oral spirochetes from sites of periodontal health with development of periodontitis.

The purpose of this investigation was to determine whether the presence of disease-associated bacteria in health-associated plaque correlated with susceptibility to periodontitis over time. Sites of periodontal health were identified in 65 adults. Six months later (recall 1), plaque was collected from sites that remained in periodontal health, and specific bacteria were detected using monoclonal antibodies in a microscopic assay. The spirochete morphogroup was identified by phase contrast microscopy. The relationship between detection at recall 1 and development of periodontitis over two successive 6-month intervals (recalls 2 and 3) was evaluated by means of logistic regression using generalized estimating equations (GEE), from which odds ratios (OR) were estimated and tested for significance. Significant relationships were defined as those having ORs with P < 0.05. Ninety-three of 1,032 sites developed signs of early periodontitis over the 12-month interval between recall 1 and recall 3. The spirochete morphogroup (OR = 3.13, P < 0.001) and pathogen-related oral spirochetes (PROS) (OR = 3.68, P < 0.001) were significantly associated with healthy sites that developed periodontitis. The association of Treponema socranskii was not significant (OR = 3.62, P = 0.0918). Odds ratios for Campylobacter rectus, Eikenella corrodens, and Porphyromonas gingivalis were less than 2.0 and not significant. Treponema denticola was not detected in health-associated plaque from stable health sites and was detected in only three sites that progressed to periodontitis. These findings indicate that the presence of PROS and some unidentified spirochetes in health-associated plaque is associated with increased susceptibility to periodontitis.