An introduction to latent growth curve modelling for longitudinal continuous data in dental research

Do psychological factors predict changes in oral health-related quality of life and clinical status after periodontal treatment?

AIMS

To determine psychological factors predicting changes in OHRQoL and clinical status after periodontal treatment.

METHODS

Cohort of 140 patients with chronic periodontitis receiving non-surgical treatment consisting of scaling, root surface debridement and instruction in plaque control. Participants self-completed questionnaires enquiring about sense of coherence, locus of control, self-esteem and task-specific self-efficacy before treatment, and the Oral Health Impact Profile-14 before treatment, at oral hygiene review and end of study. Relationships among OHRQoL, clinical changes, individual factors (demographic and psychological) and environmental characteristics were analysed using latent growth curve modelling guided by the Wilson and Cleary model.

RESULTS

OHRQoL and periodontal status improved after treatment. Being male and having a greater sense of coherence predicted better OHRQoL before treatment. Stronger internal dimension of locus of control predicted a greater rate of improvement in OHRQoL, whereas greater external dimensions predicted a slower rate of improvement. Greater task-specific self-efficacy predicted less gains in probing attachment and reductions in probing depth.

CONCLUSIONS

Knowledge of psychological factors may be helpful in explaining individual differences in OHRQoL and clinical responses to periodontal treatment, and in identifying where health-promoting interventions may strengthen relevant factors to improve these outcomes.

Metabolic syndrome and masticatory hypofunction: a cross-sectional study

The objective of this paper is to clarify the rate of abdominal obesity (AO), waist-to-height ratio (WHtR), metabolic syndrome (MetS) and determine the relationship with the masticatory capacity (MC) in terms of total functional tooth units (t-FTU) in a representative sample of older Spanish adults. This cross-sectional study included 544 adult subjects aged 50 or over, who were prospectively selected and who had participated in a survey conducted in a primary dental care service in a Public Oral Health Service in Spain. Anthropometric, clinical variables and t-FTUs were obtained through a calibrated and well-established protocol. Univariate and multivariate binary and multinomial logistic regression analyses were developed. With regards to the t-FTU or MC, it was poor in 60.3%, good in 17.6%, and complete in 22.1% of the sample. The univariate odss ratio (OR) for MetS and AO increased as the MC decreased and as the age group increased. With regards to gender, women presented with an OR of 5.56 (CI 95% 3.70-8.38). With regards to the WHtR-a3 (WHtR grouped into three categories), the univariate ORs were all significant for morbid obesity compared to the healthy group, with a risk of 6.86 (CI 95% 3.23-14.58) for patients with poor MC compared to those with complete MC. Masticatory hypofunctionality could be associated with the presence of MetS. Clinical relevance: The number of t-FTUs is directly related to AO.

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.

Differential effects of the changes of LDL cholesterol and systolic blood pressure on the risk of carotid artery atherosclerosis

BACKGROUND

The effects of baseline and changes in blood pressure and low density lipoprotein (LDL) cholesterol on the carotid intima media thickness (IMT) have not been well documented.

METHODS

A total of 2572 adults (mean age 53.8 years, 54.6% women) in a Taiwanese community undertook three blood pressure and LDL cholesterol examinations over 6 years. Latent growth curve modeling was used to investigate the effects of baseline and change in blood pressure and LDL cholesterol on IMT.

RESULTS

Greater baseline LDL and blood pressure were associated with an increase in IMT (0.005 ± 0.002 mm per 1 mg/dL [p = 0.006] and 0.041 ± 0.004 mm mm Hg [p <0.0001], respectively. Change in blood pressure was associated with a significant increase in IMT (0.047 ± 0.016, P = 0.004), whilst the association between change in LDL and change in IMT was not statistically significant (0.008 ± 0.006, P = 0.20).

CONCLUSIONS

Carotid IMT was associated with baseline blood pressure and LDL cholesterol, yet only changes of blood pressure, not LDL cholesterol, were related to carotid IMT during the 6-year observation.

Non-surgical periodontal therapy with and without subgingival minocycline administration in patients with poorly controlled type II diabetes: a randomized controlled clinical trial

The aim of this study was to evaluate changes in clinical parameters and levels of inflammatory biomarkers in plasma in periodontal patients with poorly controlled type 2 diabetes mellitus (T2DM) after non-surgical periodontal therapy. Twenty-eight poorly controlled T2DM patients were randomly assigned to treatment with scaling and root planning (SRP) and SRP + subgingival minocycline administration. Clinical parameters, including the probing depth (PD), bleeding on probing (BOP), plaque score (PS), clinical attachment level (CAL), and plasma interleukin (IL)-6, soluble receptor of advanced glycation end products (sRAGE), chronic reactive protein (CRP), and hemoglobin A1c (HbA1c) were measured before and after a 6-month treatment period. Significant changes in PD, BOP, PS, and CAL were found in both groups. The latent growth curve model showed an overall reduction in the log HbA1c level in the SRP group (-0.082, p = 0.033). Small changes in the log sRAGE level and log CRP level in plasma were found in both groups. IL-6 in the plasma increased in the SRP group, but slightly decreased in the SRP+minocycline group (0.469 pg/ml, p = 0.172). Non-surgical periodontal therapy with or without subgingival minocycline application may achieve significant periodontal improvement and moderate improvement in HbA1c, but had no significant effect on plasma levels of IL-6, CRP, or sRAGE in patients with poorly controlled T2DM. For patients with both periodontal diseases and diabetes, non-surgical periodontal treatments may be helpful in their diabetic control.