May C. M. Wong

Preservation of quality of life after intensity‐modulated radiotherapy for early‐stage nasopharyngeal carcinoma: Results of a prospective longitudinal study

Xerostomia is a ubiquitous complication after conventional radiotherapy for nasopharyngeal carcinoma (NPC) that seriously impairs patient quality of life (QOL). The effect on QOL of parotid‐sparing intensity‐modulated radiotherapy (IMRT) for early‐stage NPC was assessed prospectively.

Effects of smoking on healing response to non-surgical periodontal therapy: A multilevel modelling analysis

AIM To investigate the factors predicting non-surgical periodontal treatment responses using multilevel multiple regression. MATERIAL AND METHODS Forty men (mean 45.6 years) were recruited; 20 were smokers. A 12-month reduction in probing pocket depth (PPD) and gain in probing attachment level (PAL) of 5814 sites were analysed, with 594 being initially diseased sites (initial PPD> or =5 mm). RESULTS Variance Component models showed that site-level variations contributed about 70-90% of the total variance. About a 10% reduction of the total variations of PPD reduction in initially diseased sites was achieved with the inclusion of the 10 predictors in the multilevel multiple regression. Multilevel multiple regression showed that three predictors, subject level: non-smokers; tooth-level: anterior teeth; and site level: sites without plaque at baseline, were significantly associated with a greater reduction in PPD in initially diseased sites over the 12-month study period (p<0.05). No consistent predictor was found for PAL gain. CONCLUSION Multilevel analysis was applied on periodontal treatment response data. Smokers showed less favourable PPD reduction at deep sites after non-surgical periodontal therapy.

Salivary gland function and xerostomia in southern Chinese following radiotherapy for nasopharyngeal carcinoma.

Nasopharyngeal carcinoma (NPC) is rare among Caucasians but very common among southern Chinese. No information is presently available on the relationship between salivary gland function and xerostomia in irradiated southern Chinese. Salivary gland function and xerostomia were measured in irradiated NPC patients, recently diagnosed NPC patients, and a matched control group. Stimulated whole saliva was collected from each participant and flow rate, pH and buffer capacity measured. All participants completed a multi-item dry mouth questionnaire. Comparisons were made using Chi-square and Mann-Whitney tests and correlations assessed using Spearmans rank correlation coefficients. The mean saliva flow rate and pH were significantly lower and the buffer capacity impaired in irradiated NPC patients compared with the other groups (P<0.01). Significantly more irradiated NPC patients had negative impacts associated with dry mouth generally, sticky saliva, and hoarse voice (P<0.01). Subjective dry mouth symptoms and associated reduced saliva flow were also relatively common in non-irradiated participants. Salivary gland hypofunction and xerostomia were major complications in irradiated NPC patients. In irradiated and non-irradiated southern Chinese, subjective dry mouth symptoms appeared to be correlated with actual salivary gland function.

Key factors associated with oral health-related quality of life (OHRQOL) in Hong Kong Chinese adults with orofacial pain

OBJECTIVES To investigate key factors associated with oral health-related quality of life (OHRQOL) of Hong Kong Chinese adults with orofacial pain (OFP) symptoms. METHODS A cross-sectional study was conducted amongst a random sample of registered patients at a primary medical care teaching clinic in Hong Kong. Patients who were aged 35-70 years and had experienced OFP symptoms in the past 1 month were included. The OHRQOL was assessed by the Chinese version of the Oral Health Impact Profile (OHIP-14). A structured questionnaire on OFP symptoms and characteristics in the past 1 month, the depression and non-specific physical symptoms (NPS) scale in the research diagnostic criteria for temporomandibular disorders (RDC/TMD) questionnaire, and questions about professional treatment and dental attendance were administered before a standard clinical assessment. Negative binomial regression with forward stepwise selection was used to investigate key factors associated with the OHIP-14 additive score. RESULTS The mean OHIP-14 additive score of the 200 participants was 10.1 (SD 9.4). Regression analysis revealed that five independent factors were significantly associated with higher OHIP-14 additive scores (indicating a poorer OHRQOL): a higher pain scale rating in the past 1 month (p=0.001), OFP clinical classification as musculoligamentous/soft tissue (MST) or dentoalveolar (DA) instead of neurological/vascular (NV) (p<0.001), more frequent dental attendance (p=0.008), moderate/severe RDC/TMD depression (p=0.005) and moderate/severe RDC/TMD NPS with pain (p=0.003). CONCLUSION Various factors were associated with OHRQOL and could have implications for the improvement of OHRQOL in people in the community who have OFP symptoms.

Confirmatory factor analysis on the health domains of the Child Perceptions Questionnaire.

BACKGROUND The Child Perceptions Questionnaire for children aged 11-14 years (CPQ(11-14)) with 37 items (full questionnaire) and short forms with 16 and 8 items were developed in Toronto as measures of the oral-health-related quality of life (OHRQoL) for children. OBJECTIVES To confirm the four hypothesized health domains (oral symptoms, functional limitations, emotional well-being and social well-being) of CPQ(11-14) in measuring OHRQoL for children in Hong Kong. METHODS The instrument was administered to 542 children aged 12 years. Confirmatory factor analysis (CFA) was used to confirm the health domains of the full and short forms of CPQ(11-14). RESULTS The usual goodness-of-fit measurements indicated that the model using all 37 items fitted the data below the acceptable level, while the models with 16 items and 8 items fitted the data well. CONCLUSION The hypothesized factor structure with the four health domains of the short forms of CPQ(11-14) has been confirmed by CFA. The results in the current study indicated that the items used in the short forms contain sufficient information in measuring OHRQoL for children in Hong Kong.

The consequences of orofacial pain symptoms: a population-based study in Hong Kong

OBJECTIVES To investigate the impacts associated with orofacial pain symptoms among adult Chinese people in Hong Kong. Associations between impacts, pain characteristics and professional treatment seeking behaviour were explored. METHODS A cross-sectional, population-based study was conducted using a telephone survey method. A sample of Cantonese-speaking Chinese people aged 18 years and over living in Hong Kong was interviewed. The questionnaire incorporated questions on recent orofacial pain experience and characteristics. Respondents with orofacial pain symptoms were asked about the consequences of the pain on various aspects of daily life and whether they had sought treatment for the pain. RESULTS Of the 1222 survey respondents, 41.6% reported some form of orofacial pain. 79.3% of those who reported orofacial pain and about one-third of the total sample had experienced at least one impact. The most common impact was worried about oral and dental health (59.8%) followed by avoided certain food (50.4%). Respondents with toothache were found to be more likely to have experienced all the impacts investigated (OR range: 2.048-3.309). People who had stayed in bed more than usual (OR = 2.342), experienced sleep disturbance (OR = 2.149), and worried about their oral and dental health (OR = 2.851) were more likely to seek professional treatment. CONCLUSIONS The adverse impact of orofacial pain on the well-being of the adult population of Hong Kong was substantial. Despite this, treatment seeking was low with a high level of untreated orofacial pain symptoms.

Analysis of multilevel grouped survival data with time‐varying regression coefficients

Correlated or multilevel grouped survival data are common in medical and dental research. Two common approaches to analyze such data are the marginal and the random-effects approaches. Models and methods in the literature generally assume that the treatment effect is constant over time. A researcher may be interested in studying whether the treatment effects in a clinical trial vary over time, say fade out gradually. This is of particular clinical value when studying the long-term effect of a treatment. This paper proposed to extend the random effects grouped proportional hazards models by incorporating the possibly time-varying covariate effects into the model in terms of a state-space formulation. The proposed model is very flexible and the estimation can be performed using the MCMC approach with non-informative priors in the Bayesian framework. The method is applied to a data set from a prospective clinical trial investigating the effectiveness of silver diamine fluoride (SDF) and sodium fluoride (NaF) varnish in arresting active dentin caries in the Chinese preschool children. It is shown that the treatment groups with caries removal prior to the topical fluoride applications are most effective in shortening the arrest times in the first 6-month interval, but their effects fade out rapidly since then. The effects of treatment groups without caries removal prior to topical fluoride application drop at a very slow rate and can be considered as more or less constant over time. The applications of SDF solution is found to be more effective than the applications of NaF vanish.

Assessing consistency in oral health-related quality of life (OHRQoL) across gender and stability of OHRQoL over time for adolescents using Structural Equation Modeling.

BACKGROUND The Child Perceptions Questionnaire for children aged 11-14 years (CPQ(11-14) ) was developed in Toronto as a measure of the oral health-related quality of life (OHRQoL) for children/adolescents. The short form with eight items (RSF:8) was also derived. OBJECTIVES (i) To investigate the consistency of RSF:8 in measuring the OHRQoL between boys and girls, (ii) to investigate the measurement invariance and stability of RSF:8 in measuring OHRQoL for Hong Kong adolescents over time, and (iii) to determine the latent mean differences across gender and over time. METHODS The instrument was administered to 542 adolescents aged 12 years and re-administered to the same group of adolescents 3 years later. Structural Equation Modeling (SEM) was used to test the measurement invariance at different levels. A series of hierarchically nested models (configural structure, factor loadings, error variances, factor variances and covariance, intercept invariance) were tested by the chi-square difference tests, and the more restricted model would be accepted if the chi-square difference test was insignificant (P > 0.05). The latent means would be estimated if intercept invariance was not accepted. The stability of OHRQoL over time was investigated by computing the stability coefficients. RESULTS For multiple group analysis, the model with the level of invariance up to factor variances and covariance was accepted (P > 0.05). The latent mean of girls was significantly lower (indicating better OHRQoL) than boys in social well-being (SWB). For panel data analysis, the model with the level of invariance up to factor variances and covariance was accepted (P > 0.05). The latent mean of the four domains decreased significantly (indicating improved OHRQoL) for adolescents aged 12-15 years. The stability coefficients ranged from 0.14 to 0.73 which demonstrated moderate stability except functional limitation (FL) with a relatively low stability. CONCLUSION This study indicated that RSF:8 measured OHRQoL for adolescents in Hong Kong consistently across gender. The OHRQoL in SWB for girls was better than boys. Also, the OHRQoL for adolescents was in the same factor structure with moderate stability and improved significantly over time.