Study Protocol, Sample Characteristics, and Loss to Follow-Up: The OPPERA Prospective Cohort Study

When studying incidence of pain conditions such as temporomandibular disorders (TMDs), repeated monitoring is needed in prospective cohort studies. However, monitoring methods usually have limitations and, over a period of years, some loss to follow-up is inevitable. The OPPERA prospective cohort study of first-onset TMD screened for symptoms using quarterly questionnaires and examined symptomatic participants to definitively ascertain TMD incidence. During the median 2.8-year observation period, 16% of the 3,263 enrollees completed no follow-up questionnaires, others provided incomplete follow-up, and examinations were not conducted for one third of symptomatic episodes. Although screening methods and examinations were found to have excellent reliability and validity, they were not perfect. Loss to follow-up varied according to some putative TMD risk factors, although multiple imputation to correct the problem suggested that bias was minimal. A second method of multiple imputation that evaluated bias associated with omitted and dubious examinations revealed a slight underestimate of incidence and some small biases in hazard ratios used to quantify effects of risk factors. Although “bottom line” statistical conclusions were not affected, multiply-imputed estimates should be considered when evaluating the large number of risk factors under investigation in the OPPERA study

Salivary cortisol level and uncooperative behavior in pediatric dental practice

investigate the relation between uncooperative behavior and salivary cortisol level in children who underwent preventive dental care. Methods: The sample was composed by 10 children of both sexes aged 40 to 52 months, presenting uncooperative behavior during dental preventive treatments. The saliva collection was performed using a cotton wheel and an Eppendorf tube (Sarstedt Salivete®) in 3 different moments: a) at home, on a day without dental treatment and at the same time on the day of the sessions treatment; b) 30 min after the end of the session, when there was manifestation of uncooperative behavior; c) 30 min after the end of the session, when there was a cooperative behavior of the child. A sample of saliva was centrifuged for 5 minutes at 2400 rpm, 1 of mL of saliva was pipetted in an Eppendorf tube and stored in a freezer at -20 ° C. For the determination of the levels of salivary cortisol was used an Active® kit for cortisol enzyme immunoassay (EIA) DSL-10- 67100, composed of specific rabbit antibody anti-cortisol. Data were analyzed statistically for the uncooperative behavior issued in the beginning and at the end of sessions, using the paired t test (p<0.05). Results: During expression of uncooperative behavior in preventive dental care sessions the salivary cortisol level was significantly higher (0.65 ± 0.25 µg/dL) compared with expression of collaborative behavior (0.24 ± 0.10 µg/dL). Conclusions: It is possible to conclude that, even under preventive intervention, the stress must be controlled in order to reduce dental anxiety and fear

Study Protocol, Sample Characteristics, and Loss to Follow-Up: The OPPERA Prospective Cohort Study

When studying incidence of pain conditions such as temporomandibular disorders (TMDs), repeated monitoring is needed in prospective cohort studies. However, monitoring methods usually have limitations and, over a period of years, some loss to follow-up is inevitable. The OPPERA prospective cohort study of first-onset TMD screened for symptoms using quarterly questionnaires and examined symptomatic participants to definitively ascertain TMD incidence. During the median 2.8-year observation period, 16% of the 3,263 enrollees completed no follow-up questionnaires, others provided incomplete follow-up, and examinations were not conducted for one third of symptomatic episodes. Although screening methods and examinations were found to have excellent reliability and validity, they were not perfect. Loss to follow-up varied according to some putative TMD risk factors, although multiple imputation to correct the problem suggested that bias was minimal. A second method of multiple imputation that evaluated bias associated with omitted and dubious examinations revealed a slight underestimate of incidence and some small biases in hazard ratios used to quantify effects of risk factors. Although “bottom line” statistical conclusions were not affected, multiply-imputed estimates should be considered when evaluating the large number of risk factors under investigation in the OPPERA study. PERSPECTIVE: These findings support the validity of the OPPERA prospective cohort study for the purpose of investigating the etiology of first-onset TMD, providing the foundation for other papers investigating risk factors hypothesized in the OPPERA project

Genome-wide association reveals contribution of MRAS to painful temporomandibular disorder in males

Abstract Painful temporomandibular disorders (TMDs) are the leading cause of chronic orofacial pain, but its underlying molecular mechanisms remain obscure. Although many environmental factors have been associated with higher risk of developing painful TMD, family and twin studies support a heritable genetic component as well. We performed a genome-wide association study assuming an additive genetic model of TMD in a discovery cohort of 999 cases and 2031 TMD-free controls from the Orofacial Pain: Prospective Evaluation and Risk Assessment (OPPERA) study. Using logistic models adjusted for sex, age, enrollment site, and race, we identified 3 distinct loci that were significant in combined or sex-segregated analyses. A single-nucleotide polymorphism on chromosome 3 (rs13078961) was significantly associated with TMD in males only (odds ratio = 2.9, 95% confidence interval: 2.02–4.27, P = 2.2 × 10⁻⁸). This association was nominally replicated in a meta-analysis of 7 independent orofacial pain cohorts including 160,194 participants (odds ratio = 1.16, 95% confidence interval: 1.0–1.35, P = 2.3 × 10⁻²). Functional analysis in human dorsal root ganglia and blood indicated this variant is an expression quantitative trait locus, with the minor allele associated with decreased expression of the nearby muscle RAS oncogene homolog (MRAS) gene (beta = −0.51, P = 2.43 × 10⁻⁵). Male mice, but not female mice, with a null mutation of Mras displayed persistent mechanical allodynia in a model of inflammatory pain. Genetic and behavioral evidence support a novel mechanism by which genetically determined MRAS expression moderates the resiliency to chronic pain. This effect is male-specific and may contribute to the lower rates of painful TMD in men