Journal of Dental Medicine

Background and Aims: The vertical growth pattern of the face depends on several factors. One of these factors can be the muscle strength of the jaw. Maximum occlusal force (MOF) can be considered as an index to measure the function of the muscles of the masticatory system. Despite the various studies, the relationship between the facial pattern and muscle function is still controversial. According to soft tissue paradigm theory, muscle can affect the shape and form of bones of the jaw, face and head. The aim of this study was to determine the relationship between the maximum occlusal force and head and face growth pattern in dental students of Shahed University in Tehran.
Materials and Methods81 dental students (40 males and 41 females) were participated. MOF was measured with a loadcell designed for this purpose, and the anthropometric points of the face and head were measured with digital caliper. Two-way ANOVA and Tukey HSD tests were used to determine the effect of facial and head patterns on the maximum occlusal force. Statistical analysis was performed by SPSS23.
Results: The mean MOF in males was 480 N and in females 320 N. Head forms in our sample research were 54.32% Brachycephale, 32.09% Mesocephale, and 13.58% Dolicocephale. The form of the face was 23.45% euprosopic, 39.5% mesoprosopic, and 37.03% leptoprosopic. According to the statistical analysis, the relationship between the maximum occlusal force and leptoprosopic form of face was statistically significant (P=0.02). However, there was not significant relationship between the maximal occlusal force and none of the three type of head forms (P=0.813).
Conclusion: MOF was related to the leptoprosopic pattern of face, and these individuals had less bite power. No relationship between the maximum occlusal force and head forms and neither between the head pattern and facial pattern was found in this study. The maximum occlusal force in men was higher in all three facial patterns than that of women, although this relationship was not significant.

Background and Aims: Information collection about the malocclusion and oral health in blind children is essential to plan for their education in schools. Therefore, this study aimed to evaluate the status of malocclusion and oral health among blind children and teenagers in Mazandaran, Iran.
Materials and Methods: The population of this included 150 blind children and teenagers aged from 10 to 18 years who were referred to the public and private centers cities including Sari, Babol, Freydoonkenar, and Babolsar in Mazandaran, Iran in 2019. Information on maxillary occlusion status, oral hygiene index, and DMFT index was extracted through clinical examination. Data were analyzed using SPSS23 software by ANOVA and Chi-square tests in addition to the descriptive statistics.
Results: The mean DMFT was 10.25 (SD 4.67). Oral hygiene status was good in 16% of participants, moderate in 82%, and poor in 2%. There was no significant difference between girls and boys in terms of oral hygiene status (P=0.5). In all cases, 35.8% had class I malocclusion, 29.8% had class II malocclusion, and 14.6% had class III malocclusion. Class II malocclusion was more common in girls and class I in boys (P=0.01).
Conclusion: Dental caries and occlusal abnormalities were common among blind children and adolescents living in Mazandaran province. Addressing the oral and dental needs of the blind should be a priority for health policymakers in this province in Iran.

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: One side effect of orthodontic treatment is microcrack formation during debonding process. Since the type of ligation may affect the applied debonding force, this study was conducted to investigate the effect of ligation method on the enamel microcrack formation following debonding of orthodontic brackets.
Materials and Methods: The present study was an experimental in vitro study. 69 extracted human premolar teeth were divided into 3 groups with 23 teeth by a simple random method. A bracket was bonded on the buccal surface of the teeth, then the desired tooth was placed in a typodont where the rest of the teeth were mounted. Then, the arch wire was passively placed in the bracket slot. The samples were ligated by one of these three methods based on the study group: 1. Oring ligation 2. Tight ligation with a wire ligature for each tooth separately 3. Ligation of all arch teeth together, using a wire ligature. The buccal surfaces of the teeth were observed under a stereomicroscope and the length, location, and the number of microcracks were recorded before and after debonding process. In order to analyze the data, generalized estimating equation analysis was used.
Results: In all three groups, a significant increase was observed in the average total length and number of enamel microcracks following the debonding process. (P<0.001 in all three groups), with no statistically significant difference between the three study groups. However, it was greater in group 2 than that of groups 3 and 1 respectively. In general, the number of new cracks was more in mid-buccal area followed by cervical and occlusal areas.
Conclusion: The debonding process caused an increase in the average total length as well as the number of enamel microcracks. Type of ligation might affect the enamel microcrack formation so that in tight ligation group we had the greatest increase in the enamel damage especially in mid-buccal area of the tooth. Tight ligation method can cause more enamel cracks than O-ring ligation and full arch ligation methods.

Background and Aims: Ensuring the long-term stability of orthodontic treatments and preventing tooth relapse remains a significant challenge in orthodontics, often addressed through the extended use of retainers. Given the pivotal role of retainers' physical and mechanical properties in this regard, this study aimed to investigate the tensile strength, flexural strength, and deflection of three distinct types of fixed orthodontic retainers.
Materials and Methods: In this laboratory study, each group comprised 12 samples of twisted, flat, and coaxial retainer wires, each measuring 8 mm in length. These samples were affixed onto the polyethylene blocks using cyanoacrylate adhesive and subsequently subjected to compressive loads using a universal testing machine. The maximum bending strength and deflection rate were recorded from stress-strain diagrams. To evaluate the tensile strength, the identical samples underwent tensile loading. Statistical analysis was performed utilizing SPSS software, employing analysis of variance tests to compare data between groups.
Results: Significant differences were observed in the bending strength (P=0.004), deflection (P<0.001), and tensile strength (P<0.001) among the investigated retainer wires. The flat retainer wire exhibited the highest bending strength, averaging 822.876±136.07 MPa, while the coaxial retainer wire showed the lowest, with an average of 673.65±73.35 MPa. Regarding deflection, the flat retainer wire displayed the highest average at 4.04±0.6 mm, surpassing the other two types of retainers. However, the tensile strength of the twisted retainer wires, averaging 699.7±83.46 MPa, exceeded that of both the flat and coaxial retainer wires.
Conclusion: The flat retainer wires demonstrated the highest bending and deflection strength, while the twisted retainer wires exhibited the highest tensile strength. Overall, the bending strength, deflection, and tensile strength of the 3-strand twisted and flat retainer wires outperformed those of the 5-strand coaxial retainer wires, increased flexural and tensile strengths imply a higher resistance of the wires to the forces induced by harder and more viscous foodstuffs.

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: Artificial intelligence (AI) has emerged as a transformative force in various fields, including orthodontics. AI has demonstrated encouraging results in enhancing diagnostic precision, treatment decision, and outcome prediction. With the accessibility of different AI software, its utilization in orthodontics has grown significantly. In this review study, we examined various applications of artificial intelligence within the field of orthodontics.
Materials and Methods: A comprehensive search was conducted in the PubMed database using the keywords; “Orthodontics” and “Artificial intelligence” between 2020 and 2025. 643 articles were found in the initial search. After eliminating articles based on the inclusion and exclusion criteria, 293 articles remained for full-text review, and finally 38 articles were included in our review to obtain a comprehensive review of the applications of artificial intelligence in orthodontics.
Results: Today, artificial intelligence has been used in different stages of orthodontic treatment, including diagnosis, decision making, outcome prediction and education. It has shown high accuracy in many areas, including cephalometric analysis and treatment planning. However, enhancements are necessary in certain aspects, particularly in space analysis and the prediction of treatment outcomes.
Conclusion: Conducting systematic reviews focusing on each of these applications can provide a better perspective for clinicians to use this technology in their everyday practice.

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: Over the past two decades, the use of mini-screws in orthodontics has become increasingly common. Various factors such as design, length, diameter, and insertion angle of the miniscrew, as well as the quality and thickness of the patient's bone, would influence the success and stability of miniscrews. This study aimed to investigate the effects of miniscrew shape, cortical and cancellous bone thickness, and insertion/removal torque on the stress distribution in the mandibular bone surrounding the miniscrew.
Materials and Methods: This study was conducted using finite element analysis (FEA). Bone thickness parameters were extracted from the literature, and the mandibular bone along with cylindrical and tapered miniscrew models were simulated using ABAQUS software. By altering the relevant variables, the resulting stress were evaluated.
Results: An increase in both insertion and removal torque led to a corresponding rise in the stress around the miniscrew. Stress variations were more pronounced in tapared miniscrews in response to the changes in bone thickness and torque. The influence of cancellous bone thickness on stress distribution was found to be minimal.
Conclusion: Although, the tapered miniscrews offer greater retention and stability compared to the cylindrical types, their heightened sensitivity to variations in parameters such as bone thickness and torque necessitates cautious application.

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.

Background and Aims: Despite the functional and aesthetic benefits, orthodontic treatment is often associated with pain and discomfort that can adversely affect patients’ quality of life. Given the growing emphasis on the patient-reported outcomes in clinical care, this study aimed to investigate the association between the pain intensity caused by orthodontic treatment and orthodontic-related quality of life in patients undergoing fixed orthodontic therapy.
Materials and Methods: This descriptive-analytical cross-sectional study was conducted in 2022 on patients receiving fixed orthodontic treatment with a metallic MBT system (slot 0.022 inch) at a private clinic in Babol, Iran. A total of 85 patients aged 15–25 years were selected using convenience sampling. Pain intensity was assessed using a visual analog scale (VAS) ranging from 0 to 10. Quality of life was evaluated using the persian version of the Orthodontic Quality of Life questionnaire, with a scoring range of 22 to 88. Data were analyzed using independent samples t-test and Pearson’s correlation coefficient in SPSS, with a significance level set at P<0.05.
Results: Among the participants, 72.9% were female, 68.2% were under the age of 20, and 31.8% were aged between 20 and 25 years. The mean pain score was 4.75 ± 1.91, and the mean  Oral Health Related Quality of Life (OHRQoL) score was 37.95 ± 9.51. A significant negative correlation was found between the pain intensity and overall OHRQoL, as well as all of its subdomains (oral function, social impact, dentofacial aesthetics, and self-awareness of appearance) (P≤0.001). No statistically significant differences in pain or OHRQoL scores were observed based on gender or age group (P>0.05).
Conclusion: Orthodontic pain has a significant negative impact on patients’ quality of life. Early pain management strategies and supportive interventions during the initial phases of orthodontic treatment can enhance patients’ overall treatment experience and improve compliance.