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Biomedical subjects

Chung How Kau

Publications and source records attributed to Chung How Kau.

6 recordsLinked to original sources
PubMed2006

The 3-dimensional construction of the average 11-year-old child face: a clinical evaluation and application.

PURPOSE: This article describes construction of the average face and its application in the clinical environment. SUBJECTS AND METHODS: A total of 72 children, mean age 11.8 years, were selected for the study. Laser-scanned images of the subjects were obtained under a reproducible and controlled environment with 2 Minolta Vivid 900 (Minolta, Osaka, Japan) optical laser-scanning devices assembled as a stereo pair. A set of left and right scanned images was taken for each subject and each scan took an average of 2.5 seconds. These scanned images were processed and merged to form a composite 3-dimensional soft tissue reproduction of the subjects using commercially-available reverse modeling software. The differences in facial morphology were measured using shell deviation color maps. The average face was used to compare differences between male and female groups and 3 subjects with craniofacial anomalies. RESULTS: The difference between the average male and female face was 0.460 +/- 0.353 mm. The areas of greatest deviation were at the zygomatic area and lower jaw line, with the males being more prominent. The results of the surface deviation between the subjects with craniofacial anomalies were significant. CONCLUSIONS: The construction of the average face provides an interesting perspective into measuring changes in groups of patients and also acts as a useful template for the comparison of craniofacial anomalies.

Cephalometry↗
PubMed2006

Orthodontic retention regimes: will we ever have the answer?

DATA SOURCES: The Cochrane Oral Health Group Trials Register, CENTRAL, Medline and Embase were searched to May 2005. Key journals were searched by hand, together with bibliographies of all retrieved papers and review articles. No language restrictions were applied. Authors of trials were contacted to identify unpublished trials. STUDY SELECTION: Inclusion criteria specified randomised and quasi-randomised controlled trials which involved children or adults who had retainers fitted or adjunctive procedures undertaken, following orthodontic treatment with braces to prevent relapse. The outcomes were amount of relapse, survival of retainers, adverse effects on oral health and quality of life. DATA EXTRACTION AND SYNTHESIS: Screening of eligible studies, assessment of the methodological quality of the trials and data extraction were conducted independently and in duplicate. For dichotomous outcomes, the estimate of effect of an intervention was expressed as risk ratios together with 95% confidence intervals. For continuous outcomes, mean differences and 95% confidence intervals were used to summarise the data for each group. RESULTS: The search identified 27 articles, of which five met the inclusion criteria. These trials all compared different interventions. There was weak unreliable evidence, based on data from one trial, that a statistically significant increase in stability occurs in both the mandibular (P<0.001) and maxillary anterior segments (P<0.001) when the circumferential supracrestal fiberotomy is used in conjunction with a Hawley retainer, compared with a Hawley retainer alone. There was also weak, unreliable evidence that teeth settle quicker with a Hawley retainer than with a clear overlay retainer after 3 months. The quality of the trial reports was generally poor. No data were available from any study on quality of life assessment. Meta-analysis could not be undertaken as no two studies compared the same retention techniques. CONCLUSIONS: There are insufficient research data on which to base our clinical practice on retention at present. There is an urgent need for high quality randomised controlled trials in this crucial area of orthodontic practice.

Comment↗
PubMed2006

Measuring adult facial morphology in three dimensions.

OBJECTIVES: The aim of this study is to evaluate the reliability of measuring three-dimensional soft tissue morphology using a laser imaging system. DESIGN: Prospective clinical trial. MATERIALS AND METHODS: Thirty-eight adult subjects, mean age 24.5 years, were analyzed for soft tissue changes at baseline (T1) and at 1 week (T2) using two commercially available Minolta Vivid 900 (Osaka, Japan) laser scanning devices assembled as a stereopair. Left and right images were merged to form the whole face, and these images were superimposed to assess the errors between the two faces at T1 and at T2. RESULTS: The results showed that the mean shell deviations for left and right scans at T1 were 0.32 +/- 0.08 mm and 0.30 +/- 0.09 mm for males and females, respectively. The mean shell deviations for left and right scans at T2 were 0.34 +/- 0.08 mm and 0.32 +/- 0.09 mm for males and females, respectively. The mean difference of the merged composite faces superimposed at T1 and T2 was 0.37 +/- 0.07 mm and 0.35 +/- 0.09 mm for males and females, respectively. Paired t-tests revealed that the mean difference of 0.02 mm was statistically insignificant (P > .05). The reproducibility error was 0.7 and 0.8 mm for females and males, respectively, when a tolerance of 90% was imposed on the aligned faces. CONCLUSIONS: Capturing soft tissue morphology of the face, using the technique described, is clinically reproducible within 1 week of the initial records.

Adult↗
PubMed2005

Reliability of measuring facial morphology with a 3-dimensional laser scanning system.

INTRODUCTION: The purpose of this prospective clinical trial was to evaluate the reliability of a 3-dimensional facial scanning technique for the measurement of facial morphology. METHODS: A field study was conducted in 2 comprehensive schools in the South Wales region of the United Kingdom. Forty subjects, mean age 11 years 3 months, were analyzed for soft tissue changes at baseline (T1), within 3 minutes (T2), and 3 days later (T3) by using 2 commercially available Minolta Vivid 900 (Osaka, Japan) laser-scanning devices assembled as a stereo pair. Left and right images were merged to form the whole face, and these images were superimposed to assess the errors at T1 and T2, and T1 and T3. RESULTS: The results showed that premerged left and right mean shell deviations were 0.38 +/- 0.14 mm for scans at T1, 0.31 +/- 0.09 mm at T2, and 0.34 +/- 0.12 mm at T3. The mean differences of the merged composite face were 0.31 +/- 0.08 mm between T1 and T2, and 0.40 +/- 0.11 mm between T1 and T3. Paired t tests showed no significant difference between these groups (P > .05). Shell deviation facial maps of the merged scans showed that 90% of the created composite facial scans were within an error of 0.85 mm. CONCLUSIONS: Capturing the soft tissue morphology of the face with this technique is clinically reproducible within 3 minutes and 3 days of the initial records.

Cephalometry↗