[In vitro study of a new lasso device for intra-canal broken instrument removal].

PURPOSE: To collect facial stereo images of different lip protrusion by using three dimensional surface imaging device, and investigate facial aesthetic evaluation and differences between orthodontists, general dentists and laypeople. METHODS: In this study, one college student was recruited to take a three-dimensional image of the natural head and face. The software was simulated with a gradient of 2 mm to make the soft tissue lips move back and forth along the sagittal axis from the VSL line.The movement limit was 6 mm in front of and behind the VSL line. The observers included orthodontists, general dentists and laypeople. The data were analyzed with SAS 9.4 software package,visual analog scoring (VAS) was used for evaluation, and fixed-effect model was used for statistical analysis. RESULTS: The results showed that when the lip was on the VSL line, it got the highest scores amount all three groups and had no significant difference.When the lip became protrusive or retractive, it had negative impact on facial esthetics. There were significant differences in the scores of three groups in every 2mm of lip protrusion and lip retraction(P＜0.05). VAS 5 points or less were used as the unacceptable facial aesthetic score. The results showed that lip protrusion was 4 mm before the VSL line in the orthodontist group and less than 5 in the laypeople group . When the lip protruded 6mm before the VSL line and retracted 4 mm behind the VSL line, the scores of the three groups were lower than 5 points. The results also showed that male evaluation of lip protrusion 2 mm before the VSL line had a lower score than female; On the other hand, female evaluation of lip retraction behind the VSL line above 4mm had a lower score than male. CONCLUSIONS: Lip position has significant effect on facial aesthetics. Different observers had significant differences in the evaluation of lip position on facial aesthetics. It is suggested that orthodontists need more communication with patients in determining the target position of orthodontic treatment to improve treatment satisfaction.

[Assessing the influence of chin prominence on perceived facial aesthetics among three groups of observers].

PURPOSE: To assess the influence of chin prominence on facial aesthetics with 3D images, to investigate the cognitive boundaries of chin prominence among orthodontists, general dentists and laypeople and compare the variance of their cognitive data, in order to provide quantitative reference for selection of clinical treatment. METHODS: A 3D facial image was obtained by 3dMD. The soft tissue pogonion point was altered in 2 mm increments from -10 to 10 mm with Geomagic Wrap 2015, in order to represent retrusion and protrusion of the chin. These images were rated by orthodontists, general dentists and laypeople with VAS scores. Multivariate mixed linear regression was used to analyze the influence of gender, age and chin prominence on VAS scores, and whether there were differences among different groups with SAS 9.4 software package. ANOVA was also applied for comparison of each prominence. RESULTS: This study was composed of 243 subjects, including 90 orthodontists, 101 general dentists and 52 laypeople. Chin prominence had significant effect on VAS scores. VAS scores decreased by 0.8910 for each unit increase in chin retrusion and decreased by 1.0958 for each unit increase in chin protrusion（P<0.01）. Desire for treatment started when chin retrusion exceeded 6 mm in orthodontist group and layperson group, 4 mm in general dentist group, and chin protrusion reached 6 mm in all groups（VAS scores <5）. There was no significant difference in the scores among orthodontists, general dentists and laypeople with the variance of chin prominence, and there was no significant difference in gender and age. CONCLUSIONS: Chin prominence had significant effect on facial aesthetics. Soft tissue pogonion point located on the zero meridian was considered as the most attractive. Treatment needs increased significantly when chin protrusion reached 6 mm or chin retrusion exceeded 6 mm. There was no significant difference in the assessment among orthodontists, general dentists and laypeople.

Management of an impacted maxillary central incisor with dilacerated root.

Dilaceration is a comparatively uncommon dental deformity generally characterized by an angulation between crown and root, and consequently causing non-eruption of the tooth. Dilaceration generally occurs following trauma to the apices of deciduous dentition, which lies close to the permanent tooth buds. As a result, surgical extraction used to be the first choice when making the treatment plan for a case with severely dilacerated teeth. This case report presents the orthodontic alignment of a permanent maxillary right central incisor in an 8-year-old boy who had an impacted inverted maxillary central incisor, with distoangular root dilaceration through the crown. Following surgical exposure with the closed-eruption technique and appropriate orthodontic traction, the tooth was successfully aligned into the dental arch and the root was radiologically shown to be straightened and relatively well developed. The impacted dilacerated incisor diagnosed in the early mixed dentition should be treated with the aid of orthodontic traction.

Validity assessment and determination of the cutoff value for the Index of Complexity, Outcome and Need among 12-13 year-olds in Southern Chinese.

To validate the use of the Index of Complexity, Outcome and Need (ICON) in assessing orthodontic treatment need among 12-13 year-olds in southern China, we determined the threshold value of ICON based on Chinese orthodontists' judgments. The samples consisted of 335 students in grade 7 from 16 randomly selected middle schools in Chengdu, China. Three associate professors provided ICON scores for each participant and the results were compared with the gold standard judgments from 25 experts on treatment needs. Based on the gold standard, 195 casts belonged to the treatment category, while the rest 140 belonged to the no-treatment category. With the international cutoff point of 43, the sensitivity and specificity of the ICON score were 0.29 and 0.98.The best compromise between sensitivity and specificity in Chengdu, compared with the gold standard, was found at a cutoff point of 29, and the sensitivity and specificity were 0.88 and 0.83. When used to evaluate the treatment need of 12-13 year-olds in southern China, the international ICON cutoff value did not correspond well with Chinese orthodontists' judgments; a lower cutoff value of 29 offered a greater sensitivity and specificity with respect to expert orthodontists' perception of treatment need.