The influence of mild versus severe hypodontia on facial soft tissues? A three-dimensional optical laser scanning-based cohort study.

OBJECTIVE: To determine whether there are differences in the facial soft tissue morphology between participants with mild (up to two) or severe (six or more) hypodontia. DESIGN AND SETTING: A prospective hospital-based cohort study. PARTICIPANTS AND METHODS: Ninety-two participants, aged 11-16 years, with confirmed hypodontia were recruited. Participants were sub-grouped based on the severity (mild, two or less and severe, six or more) and distribution of the missing teeth and age. They underwent a three-dimensional (3D) optical surface scan of the facial soft tissues. Facial surface scans were compared quantitatively, applying landmark measurements and surface-based analysis. RESULTS: In total, 92 participants, with an equal distribution between the mild (n=46) and severe (n=46) categories, were recruited. Patients with severe hypodontia displayed a reduced alar base, lower facial height, nasolabial angle (P = 0.02) and transgonial width (P < 0.001) compared to those with milder hypodontia. Furthermore, significant differences were observed between mild-male and severe-female groups regarding alar base, lower anterior face height and transgonial width and between mild-male and mild-female groups regarding nasolabial angle and transgonial width. CONCLUSION: Significant reductions were seen in the 3D soft tissue morphology of participants with severe hypodontia, in terms of the nasolabial angle, lower facial height, alar base and transgonial widths, emphasising the importance of using facial scanning as a relatively simple non-invasive method of assessment.

A three-dimensional soft tissue analysis of Class III malocclusion: a case-controlled cross-sectional study.

OBJECTIVE: The present study used the optical surface laser scanning technique to compare the facial features of patients aged 8-18 years presenting with Class I and Class III incisor relationship in a case-control design. MATERIALS AND METHODS: Subjects with a Class III incisor relationship, aged 8-18 years, were age and gender matched with Class I control and underwent a 3-dimensional (3-D) optical surface scan of the facial soft tissues. RESULTS: Landmark analysis revealed Class III subjects displayed greater mean dimensions compared to the control group most notably between the ages of 8-10 and 17-18 years in both males and females, in respect of antero-posterior (P = 0.01) and vertical (P = 0.006) facial dimensions. Surface-based analysis, revealed the greatest difference in the lower facial region, followed by the mid-face, whilst the upper face remained fairly consistent. CONCLUSION: Significant detectable differences were found in the surface facial features of developing Class III subjects.

The reliability of thermoform retainers: a laboratory-based comparative study.

AIM: Despite a very significant increase in the use of thermoform retainers, within orthodontics, to date, there is no evidence regarding the quality of fit between the dental cast and retainer. The current study aims to compare the fit of different thermoform retainer materials, under laboratory standardized conditions. MATERIALS AND METHODS: A prospective, laboratory-based study design was adopted to compare the fit of four different commercially available thermoform retainer materials. A master dental cast was fabricated in dental stone, to which three and five specific reference points were located on the central incisors and upper first molars, respectively. The master cast was then duplicated to produce a total of 40 such dental casts. The performance of the following four test materials was investigated: ACE, C+ (Raintree Essix Glenroe), True Tain (True Tain Inc.), and Iconic Clear (DB Orthodontics). For each material, 10 thermoform retainers were fabricated within the dental laboratory. Subsequent scanning and analysing of the casts and thermoform retainers was performed in a dedicated area, using the co-ordinate measuring machine, in order to calculate their respective fit at the incisor and first molar regions. RESULTS: At all eight recorded landmark points, the mean values for the following thermoform materials: ACE, True Tain, and Iconic Clear, a similar trend was observed. At all eight points, there was a significant difference between the performance of the four different materials (P < 0.001), with the greatest difference observed in the mean values in relation to material C+. CONCLUSION: Statistically significant differences were observed in the fit behaviour of all four thermoform materials being tested.

Abrasive wear of enamel by bioactive glass-based toothpastes.

PURPOSE: To determine the abrasivity of a 45S5 bioactive glass based toothpaste on enamel as a function of the particle size and shape of the glass. METHODS: 45S5 glass was synthesized ground and sieved to give various particle sized fractions < 38, 38-63 and 63-110 microns. Two different grinding routes were used: percussion milling and ball milling. The glass powders were formulated into toothpastes and their tooth brush abrasivity measured according to BS EN ISO11609 methodology. RESULTS: Enamel loss increased with increasing particle size. The percussion milled powder exhibited particles that had sharp edges and the pastes were significantly more abrasive than the pastes made with round ball milled powders. One interesting observation made during the present study was that there was preferential wear of the enamel at the dentin-enamel junction (DEJ), particularly with the coarse particle sized pastes.