Residents’ journal review

Statistical modeling of lip movement

Popat H, Zhurov AI, Toma AM, Richmond S, Marshall D, Rosin PL. Statistical modelling of lip movement in the clinical context. Orthod Craniofac Res 2012;15:92-102

The relationship of the lips to the central incisors in both repose and smile should be evaluated during treatment planning to achieve the most esthetic relationship possible. Lip movement during speaking might be as important as static lip position. The authors presented a statistical method of characterizing lip movements to distinguish various lip movements and to establish 3-dimensional normative data on lip movements. Lip movement analysis of the smile has been conducted in the treatment of patients with cleft lip and facial nerve impairments. This cross-sectional observational study was based on 115 healthy white patients (average age, 33.4 years) who were orientated in natural head position and asked to say 4 words— puppy , rope , baby , and bob —while being scanned with the 3dMDFace Dynamic Systems. Six landmarks defined by anthropometric studies were manually placed on the subjects by the examiners. The landmarks were labrale superior, labrale inferior, crista philtri (left and right), and cheilion (left and right). Landmark reproducibility was greatest with labrale superior and labrale inferior. The least reproducibility was noted with cheilion. With this system, lip movement was illustrated, and normative reference data were constructed. Lip movement was generally symmetrical with differences between male and female subjects. Women displayed more protrusive articulation with narrower and shorter resting lip shapes than did the men.

Reviewed by Mohammad S. Mainayar

Force decay of latex and nonlatex orthodontic elastics

Lopez N, Vicente A, Bravo LA, Calvo JL, Canteras M. In vitro study of force decay of latex and non-latex orthodontic elastics. Eur J Orthod 2012:34:202-7

In orthodontics, nonlatex elastics have been available since the early 1990s. The purpose of this in-vitro study was to evaluate force degradation of latex and nonlatex elastics from 2 sources (GAC and Lancer) at time intervals of 5 seconds, 8 hours, and 24 hours after constant stretching. The elastics were stretched to 3 times their initial internal diameter of 0.25 both in dry and wet environments. Both brands showed significantly greater initial forces than those specified by their manufacturers. Both brands also showed greater force values in dry conditions than in wet conditions at all 3 time periods. No significant differences were found between the 2 brands of nonlatex elastics in dry conditions. In wet conditions, however, Lancer latex and nonlatex elastics showed significantly greater forces than the values generated by their GAC equivalents at the 8-hour mark, whereas no significant differences were seen at 24 hours. The average maximum force decay in a wet environment after 24 hours was less than 20% of the initial force. Further investigation of the clinical significance of this decrease in force is necessary, since the reported initial force was greater than the manufacturers’ specifications for both brands. This study showed that nonlatex elastic force degradation levels are comparable with those of latex elastics. Since up to 6% of the general population is hypersensitive to latex, the use of nonlatex elastics can be considered an effective alternative in orthodontic treatment.

Reviewed by Jesse Ko

Force decay of latex and nonlatex orthodontic elastics

Lopez N, Vicente A, Bravo LA, Calvo JL, Canteras M. In vitro study of force decay of latex and non-latex orthodontic elastics. Eur J Orthod 2012:34:202-7

In orthodontics, nonlatex elastics have been available since the early 1990s. The purpose of this in-vitro study was to evaluate force degradation of latex and nonlatex elastics from 2 sources (GAC and Lancer) at time intervals of 5 seconds, 8 hours, and 24 hours after constant stretching. The elastics were stretched to 3 times their initial internal diameter of 0.25 both in dry and wet environments. Both brands showed significantly greater initial forces than those specified by their manufacturers. Both brands also showed greater force values in dry conditions than in wet conditions at all 3 time periods. No significant differences were found between the 2 brands of nonlatex elastics in dry conditions. In wet conditions, however, Lancer latex and nonlatex elastics showed significantly greater forces than the values generated by their GAC equivalents at the 8-hour mark, whereas no significant differences were seen at 24 hours. The average maximum force decay in a wet environment after 24 hours was less than 20% of the initial force. Further investigation of the clinical significance of this decrease in force is necessary, since the reported initial force was greater than the manufacturers’ specifications for both brands. This study showed that nonlatex elastic force degradation levels are comparable with those of latex elastics. Since up to 6% of the general population is hypersensitive to latex, the use of nonlatex elastics can be considered an effective alternative in orthodontic treatment.

Reviewed by Jesse Ko

Self-perception of smile appearance and occlusion

Moura C, Cavalcanti AL, Gusmão ES, de Souza Coelho Soares R, Cavalcante Moura FT, Hordonho Santillo PM. Negative self-perception of smile associated with malocclusions among Brazilian adolescents. Eur J Orthod 2012 Apr 24 [Epub ahead of print]

These authors investigated the association between the severity of occlusal abnormalities and smile dissatisfaction among Brazilian students 12 to 16 years of age. They randomly selected 1290 boys and girls, who received a standardized questionnaire asking “Are you satisfied with your appearance when you smile?” Those who answered negatively were further questioned to determine whether the negative self-perception of their smile was associated with occlusal abnormalities; 41.8% of the participants were dissatisfied with their smile. Of those, 69.2% self-assigned their dissatisfaction to occlusal problems, and 30.8% cited other reasons. The students were examined and assessed with a standardized index that included missing teeth, crowding, spacing, midline diastemata, overjet, anterior open bite, and molar relationship. The most common reason for dissatisfaction was incisal crowding (63.0%). No statistically significant differences associated with sex were found in this study. The results showed that dissatisfaction with the smile was directly associated (in order of decreasing strength) with maxillary anterior irregularity of 2 mm or more, incisal spacing, vertical open bite of 2 mm or more, missing maxillary teeth, and incisal diastemata. Transverse crossbite was not included in the index assessment and might need to be added in future studies. The authors concluded that a negative self-perception of the smile was associated with an objective assessment of occlusal abnormalities, and self-perception should be included in the decision-making process during orthodontic treatment planning.

Reviewed by Elliot Jolley

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Apr 8, 2017 | Posted by in Orthodontics | Comments Off on Residents’ journal review
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