Journal of Dental Medicine

Background and Aims: Considering the extensive connections of anatomical components in the head and neck region, it is expected that a change in one of the components of this functional unit will have effects on other parts. The aim of this study was to investigate the effect of correction of class III skeletal relationship with orthognathic surgery on the angles between cervical vertebrae.
Materials and Methods: This descriptive-analytical retrospective study was conducted in 1403 at the orthodontic department of Babol Dental School. 30 patients with class III skeletal malformations in the age group of 18 to 48 years who underwent orthognathic surgery (single jaw or double jaw) and had a good quality lateral cephalometric radiography were randomly selected and available based on entry and exit criteria. Dependent variables including 13 parameters in the cranial (angles of SNA, SNB, ANB and Wits App), cervical (the angle between the OPT and CVT lines with each other and with the true perpendicular line) and craniocervical area (the angle of the OPT and CVT lines with the horizontal planes of the head, including the mandibular and palatal plane) of the head and neck were used to evaluate the angles between the cervical vertebrae. The data were analyzed using SPSS22 software and independent t-test, and in case of non-normality, Will-Coxon test was used.
Results: In this study, a total of 30 samples were examined. None of the measured parameters of the cervical area before and after surgery showed a statistically significant change (P<0.05). By comparing the angles between the cervical vertebrae, the PP/CVT angle in the craniocervical region showed statistically significant changes (P=0.024). The values of PP/OPT, MP/OPT, SN/CVT, and MP/CVT angles increased slightly after surgery, but they were not statistically significant (P≥0.05), which showed a relative increase in the tension of the head on the upper part of the cervical spine.
Conclusion: Changing the position of the jaw following orthognathic surgery could cause head extension, but it had no effect on the position of the first 4 cervical vertebrae.

Background and Aims: The display of an individual's teeth varies in different facial expressions, which significantly affects the beauty of the lower face and overall appearance. The ideal display of incisors is influenced by lip morphology and is an essential aspect of treatment planning. This study aimed to evaluate the ideal display of incisors at rest in women with different lip forms, as assessed by dentists and laypeople.
Materials and Methods: This was a cross-sectional study that was conducted in 2024 at Babol University of Medical Sciences. 46 dentists and 92 laypeople were selected and included in the study in an easy and accessible way. The distance between the uppermost area from the lower edge of the vermilion of the upper lip to the imaginary line between the two commissures was used to classify the lip shape, which was divided into three categories: straight (0-3 mm), medium (3-6 mm) and long (more than 6 mm). Smile images of three women in the age range of 15-30 years were collected and manipulated, resulting in six new images from each original image with varying degrees of incisor display using Photoshop (a total of 18 images). The designed images were randomly placed in a booklet and given to participants, who scored each image on a scale of zero to 100. The data were analyzed by SPSS software version 22 and using the Mann-Whitney test at a significance level of 0.05.
Results: A total of 138 participants took part in the study, including 46 dentists (33.3%), comprising 17 males (37%) and 29 females (63%), and 92 laypeople (66.7%), including 46 males (50.0%) and 46 females (50.0%). Laypeople gave higher scores to images of straight and moderate lip forms than dentists. However, this difference was not statistically significant (P>0.05). In addition, dentists gave significantly higher scores to all images related to the  long lip form than laypeople (P<0/05). In addition, among laypeople, men gave a higher score than women to images related to straight and moderate lip form, which was statistically significant (P<0.05).
Conclusion: The findings of this study indicated that a 2.5 mm incisal display at rest was suitable for patients with a straight lip form. In general, it can be concluded that by changing the shape of the lip from straight to long, there is a preference for increasing the amount of incisal display in the resting state.

Background and Aims: Dentists’(specialists and general practitioners) perceptions of smile esthetics, which are often shaped academically based on standard criteria and hard and soft tissue relationships, may differ from those of the general public and patients, potentially failing to meet patients’ expectations of treatment. This study aimed to assess and compare the views of dental specialists, general dentists, and members of the general public regarding the influence of different labio-palatal inclinations of maxillary incisors on smile esthetics.
Materials and Methods: This descriptive cross-sectional study was conducted in 2024 on general dentists, dental specialists, and laypersons. General dentists and specialists practicing in Mazandaran Province were recruited, while laypersons were selected through convenience sampling from patients attending the Faculty of Dentistry in Babol-Iran. One male and one female subject were chosen based on the clinical and lateral cephalometric criteria, and two photographs (neutral facial expression and smiling) were taken of each. After image editing, five final photographs of each subject were prepared and presented in a questionnaire to evaluate participants’ perceptions of smile esthetics according to different labio-palatal inclinations of maxillary incisors, rated on a five-point Likert scale. Data were analyzed using SPSS software with independent t-tests and ANOVA.
Results: A total of 92 laypersons, 47 general dentists, and 141 specialists (47 orthodontists, 47 restorative dentists, and 47 oral and maxillofacial surgeons) participated in this study. Across all three groups, the most attractive male smile was associated with the -5° inclination (medium negative), whereas, the most attractive female smile was rated at 0°. Conversely, the least attractive smile in all groups was the −10° inclination (severe negative) in female images. Photographs with −10° inclination received the lowest scores for both male and female subjects. Specialists assigned lower mean scores to the 0° inclination images compared to general dentists and laypersons.
Conclusion: The divergence between dentists’ and laypersons’ perceptions of the impact of different labio-palatal inclinations of maxillary incisors on smile esthetics highlights the need for greater attention to patients’ expectations and treatment goals.

Background and Aims: Bimaxillary dentoalveolar protrusion (BDP) is a common orthodontic anomaly characterized by protrusive dental arches and lip prominence. Extraction of the first premolars is a frequently employed treatment approach in these patients. However, the effect of this intervention on Bolton ratios-particularly the overall and anterior ratios-remains unclear. This study aimed to evaluate the impact of first premolar extractions on Bolton ratios in patients with BDP.
Materials and Methods: This experimental study was conducted on archived physical models of 34 Class I patients with BDP and functional lip incompetency (>4 mm) accompanied by lip protrusion, available at the Orthodontics Department of School of Dentistry, Babol, in 2024. All patients had a full complement of teeth from the first incisor to the first molar in each quadrant. After digitizing the models, mesiodistal tooth widths and the overall and anterior Bolton ratios were calculated. Digital simulation of first premolar extraction was performed, followed by reassessment of Bolton ratios. Pre- and post-treatment values were statistically compared using paired t-tests in SPSS (significance level set at 0.05).
Results: Among 34 studied casts, 67.6 % belonged to females. The mean overall Bolton ratio decreased significantly from 90.33 ± 2.23% to 87.72 ± 2.39%, and the anterior ratio declined from 78.19 ± 2.96% to 77.85 ± 3.03% (P<0.001). Additionally, 15 patients exhibited residual space post-treatment, primarily in the mandibular arch.
Conclusion: Based on the results of the present study, first premolar extraction significantly reduced both the overall and anterior Bolton ratios in patients with bimaxillary dentoalveolar protrusion. However, the likelihood of residual space—particularly in the lower arch-should be carefully considered during orthodontic treatment planning to ensure long-term stability and success.