Sample size and power: What Is enough?

Association of sleep quality with sociodemographic factors and lifestyle in adolescents from southern Brazil

BACKGROUND

Good sleep quality is an essential component for growth, development, and physical and mental health of the individual, in addition to being a positive indicator of health and well-being. The objective of this study was to estimate the prevalence of poor sleep quality and to identify the association of poor sleep quality with sociodemographic factors, lifestyle, weight status, and associated aerobic fitness in adolescents.

METHODS

This study included 1110 students aged 14-19 years from city of São José/SC, Brazil. Sleep quality of the subjects was assessed using a questionnaire and classified as adequate and low. Independent variables were gender, age, monthly household income, maternal education, school shift, global physical activity, proper diet, screen time, sleeping hours of full week, sleeping hours of weekdays, sleeping hours of weekends, weight status, and aerobic fitness. Binary logistic regression was used to estimate odds ratios and confidence intervals of 95%.

RESULTS

Prevalence of poor sleep quality was 60.4%. More likely to have poor sleep quality were identified in female students (OR 1.68, 95% CI 1.11-2.55), whose mothers had higher levels of education (OR 1.44, 95% CI 1.20-1.73) and low aerobic fitness (OR 1.80, 95% CI 1.02-3.19).

CONCLUSION

Adolescents who were most likely to report poor sleep quality were female, those whose mothers had a higher educational level and had low aerobic fitness. Students with sedentary risk behavior were less likely of reporting poor sleep quality.

Posterior tooth angulations in patients with anterior open bite and normal occlusion

INTRODUCTION

The aim of this study was to compare the posterior tooth angulations in patients with open-bite malocclusion and normal occlusion.

METHODS

Lateral cephalometric headfilms of 45 untreated open-bite subjects were compared with the lateral headfilms of 45 subjects with normal occlusion in the permanent dentition. The groups were matched for age and sex distribution and compared with t tests.

RESULTS

The maxillary and mandibular premolars were more mesially angulated in relation to the bisected occlusal plane, and the first and second molars were significantly more distally angulated in the open-bite group in relation to the palatal and mandibular planes.

CONCLUSIONS

The maxillary and mandibular premolars were more mesially angulated in relation to the bisected occlusal plane and therefore do not compensate for the divergence of the palatal and mandibular planes as the molars do.

The diagnostic potential of static body-sway recording in orthodontics: a systematic review

Conflicting data have been reported in dentistry regarding the diagnostic potential of monitoring body sway while in a static standing bipedalic position. This systematic review reappraises previously reported effects of mandibular position, asymmetric occlusion, and temporomandibular disorders (TMDs) on body sway to determine whether there is sufficient evidence for such correlations and to define the potential diagnostic applications in orthodontics. A literature survey was performed using the Medline, LILACS, and SciELO databases, and the Cochrane Library, covering the period from January 1980 to December 2011. Twelve articles qualified for the final analysis. All of these studies investigated the effects of mandibular position, two focussed also on asymmetrical occlusion, and three on TMDs. Only two studies were judged to be of medium or medium/high quality, with all of the rest classified as low-quality design; no study included follow-up. According to the conclusions of these reports, four studies saw significant correlations between body sway and mandibular position or TMDs. After a reappraisal of the full data set, generally no clinically relevant correlations were uncovered in the comparisons. While more investigations with improved levels of scientific evidence are needed, according to current evidence, the static monitoring of body sway as a diagnostic aid in orthodontics may not be indicated.

Análise do emprego do cálculo amostral e do erro do método em pesquisas científicas publicadas na literatura ortodôntica nacional e internacional

INTRODUÇÃO: o dimensionamento adequado da amostra estudada e a análise apropriada do erro do método são passos importantes na validação dos dados obtidos em determinado estudo científico, além das questões éticas e econômicas. OBJETIVO: esta investigação tem o objetivo de avaliar, quantitativamente, com que frequência os pesquisadores da ciência ortodôntica têm empregado o cálculo amostral e a análise do erro do método em pesquisas publicadas no Brasil e nos Estados Unidos. MÉTODOS: dois importantes periódicos, de acordo com a Capes (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior), foram analisados, a Revista Dental Press de Ortodontia e Ortopedia Facial (Dental Press) e o American Journal of Orthodontics and Dentofacial Orthopedics (AJO-DO). Apenas artigos publicados entre os anos de 2005 e 2008 foram analisados. RESULTADOS: a maioria das pesquisas publicadas em ambas as revistas emprega alguma forma de análise do erro do método, quando essa metodologia pode ser aplicada. Porém, apenas um número muito pequeno dos artigos publicados nesses periódicos apresenta qualquer descrição de como foram dimensionadas as amostras estudadas. Essa proporção, já pequena (21,1%) na revista editada nos Estados Unidos (AJO-DO), é significativamente menor (p=0,008) na revista editada no Brasil (Dental Press) (3,9%). CONCLUSÃO: os pesquisadores e o corpo editorial, de ambas as revistas, deveriam dedicar uma maior atenção ao exame dos erros inerentes à ausência de tais análises na pesquisa científica, em especial aos erros inerentes a um dimensionamento inadequado das amostras.

Comparison of EMG activity between maximal manual muscle testing and cybex maximal isometric testing of the quadriceps femoris

Two methods have been used to produce a maximal voluntary isometric contraction (MVIC) of the superficial quadriceps femoris muscles for normalization of electromyographic (EMG) data. The purposes of this study were to compare the myoelectic activity of MVIC of manual muscle testing (MMT) versus Cybex maximal isometric testing. Eighteen normal subjects were recruited. MMT and Cybex testing for MVIC of the dominant leg were performed. EMG activities of the vastus medialis, vastus lateralis and rectus femoris were recorded during MMT and Cybex trials. EMG amplitude and median frequency obtained from the two methods (MMT and Cybex testing) were used for statistical analysis of these three muscles. Statistically, the difference in the mean of the EMG signal amplitude and median frequency between MMT and Cybex testing were not significant. Considering cost and time, MMT for MVIC technique appears to be reliable and highly valuable.

Mandibular changes produced by functional appliances in Class II malocclusion: A systematic review

The aim of this systematic review of the literature was to assess the scientific evidence on the efficiency of functional appliances in enhancing mandibular growth in Class II subjects. A literature survey was performed by applying the Medline database (Entrez PubMed). The survey covered the period from January 1966 to January 2005 and used the medical subject headings (MeSH). The following study types that reported data on treatment effects were included: randomized clinical trials (RCTs), and prospective and retrospective longitudinal controlled clinical trials (CCTs) with untreated Class II controls. The search strategy resulted in 704 articles. After selection according to the inclusion/exclusion criteria, 22 articles qualified for the final analysis. Four RCTs and 18 CCTs were retrieved. The quality standards of these investigations ranged from low (3 studies) to medium/high (6 studies). Two-thirds of the samples in the 22 studies reported a clinically significant supplementary elongation in total mandibular length (a change greater than 2.0 mm in the treated group compared with the untreated group) as a result of overall active treatment with functional appliances. The amount of supplementary mandibular growth appears to be significantly larger if the functional treatment is performed at the pubertal peak in skeletal maturation. None of the 4 RCTs reported a clinically significant change in mandibular length induced by functional appliances; 3 of the 4 RCTs treated subjects at a prepubertal stage of skeletal maturity. The Herbst appliance showed the highest coefficient of efficiency (0.28 mm per month) followed by the Twin-block (0.23 mm per month).