• Journal of Technologic Dentistry
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• v.6 no.1
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• pp.27-30
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• 1984

This investigation was performed to study the relationship of the dental midline(an imaginary line between the centeal incisors) to the philtrum. 2,400 subjects with natural dentitions were examined. The group of the subjects was composed of 1,560 men and 840 women who had all of the upper and lower six anteriors and 0 to 4 missing teeth. Ages of the subjects ranged from 18 to 27 years. The obtained results were as follow: 1. The rates of the subjects whose philtrum and maxillary dental midline coincided was 64.92% and that of the subjects whose upper and lower dental midlines coincided was 29.17%and these rates are statistically significant, when compared respectively with those of the subjects whose philtrum and maxillary dental midline, and whose upper and lower dental midline's didn't coincide. 2. The difference between rates for the two sexes is not statistically significant. 3. Tooth missing significantly decreases the rates of the coincidence of the upper and lower dental midlines but its influence on the rates of coincidence of the dental midline to the philtrum is not significant.

• Journal of Technologic Dentistry
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• v.12 no.1
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• pp.95-102
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• 1990

The distances from the center line between maxillary right and left central incisors(the dental midline) to the various anatomical landmarks were measured. Fifty five students(thirth four males and twenty one females) who have at least natural teeth including maxillary and mandibular incisors and bicuspids were examined. 1. There was statistically significant difference between the dental midline and the center line of maxillary labial frenum(p<0.05). 2. There was no statistically significant difference between the dental midline and the point of incisive papilla, philtrum line, the center line between two mandibular central incisors, and the median palatine suture line(p>0.05). 3. There was no statistically significant sexual difference among data. 4. The philtrum line showed the highest value of correspondence to the center line between two maxillary central incisors followed by the center point of incisive papilla, the center line of two mandibular central incisors, median plaltine suture line and the center line of maxillary labial frenum at the decreasing rate.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.48.1-48.7
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• 2019

Background: Soft tissue asymmetry such as lip canting or deviation of the philtrum is an important influencing factor for unbalanced facial appearance. Lip canting could be improved by the correction of the occlusal canting or positional change of the mentum. Although there are many studies about changes of lip canting, however, postoperative changes of philtrum deviation have not been yet reported. In this study, we investigate the positional change of the philtrum after orthognathic surgery and influencing factors. Methods: Positional change of the philtrum was evaluated in 41 patients with facial asymmetry who underwent bimaxillary surgery, in relation to other anatomical soft tissue landmarks using a frontal clinical photo. The surgical movement of the maxillary and mandibular dental midline and canting were measured in postero-anterior cephalogram before and 1 day after surgery. The same procedure was repeated in patients with more than 1.5 mm perioperative change of the mandibular dental midline after bimaxillary surgery. Results: Maxillary dental midline shifting and canting correction did not have a significant correlation with lateral movement of the philtrum midline. However, the mandibular shift had a statistically significant correlation with a lateral movement of the philtrum (p < 0.05) as well as other linear parameters and angle values. Conclusion: The horizontal change of the philtrum is influenced by lateral mandibular movement in patients with facial asymmetry, rather than maxillary lateral movement.

• Imaging Science in Dentistry
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• v.50 no.3
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• pp.217-226
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• 2020

Purpose: The purpose of this study was to analyze the quantity and quality of the mandibular anterior alveolar bone in terms of alveolar width, density, and total alveolar height (TAH) based on dental status, gender, and age. Additionally, this study aimed to quantitatively evaluate the available alveolar height for graft harvesting (AHGH) and examine its variability based on the aforementioned factors. Materials and Methods: This retrospective cone-beam computed tomographic study included a total of 100 subjects. On the basis of gender, dental status, and age, the scans were divided into 3 primary groups and 8 subgroups. The mandibular alveolar width and density were measured 5 mm mesial to the mental foramen bilaterally and at the midline. The TAH was measured at the midline, and the AHGH was measured as the midline distance between 5 mm apical to the root of the canines and 5 mm superior to the lower border. Results: The mandibular alveolar width was statistically similar between dentulous and edentulous patients (P>0.05). A significantly greater density was observed at the midline in edentulous patients (P<0.05). The TAH was significantly greater in edentulous male patients than in edentulous female patients (P<0.05). Dentulous and male patients had significantly greater AHGH than edentulous and female patients, respectively (P<0.05). Conclusion: Based on the data evaluated in this study, it can be concluded that the mandibular symphyseal area has adequate bone quality and quantity for bone graft harvesting for dental implant therapy.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.4
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• pp.700-708
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• 2007

A midline deviation is divided into three types, such as a skeletal midline deviation, a dental midline deviation, and a combination. Among them, the midline deviation which appear in the early mixed dentition without any skeletal problem can be managed differently by the stage of dental development. The location of the permanent incisors can be improved without using artificial force in consideration of the condition of the space, the eruption timing or the eruption path of the adjacent permanent teeth in early mixed dentition, especially when the permanent incisors are erupting. Therefore, the space supervision technique, which can have the teeth align themselves utilizing physiologic events such as sequence or timing of the eruption of permanent teeth, can be an alternative to orthodontic movement. This case report describes midline deviation improvement by space supervision.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.49 no.4
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• pp.223-227
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• 2023

A midline or median cleft lip is rare, and a midline cleft associated with a unilateral cleft and a proboscis-like structure is rarer still. We present a case managed at our center in which a 5-year-old male had a median cleft of the upper lip with an associated 'proboscis' and a microform unilateral cleft lip.

• The korean journal of orthodontics
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• v.53 no.3
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• pp.163-174
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• 2023

Objective: This study evaluated the influence of various gingival displays on the esthetic perception in the presence of upper dental midline discrepancy. Methods: A smiling image of a male subject was altered digitally to produce five image series: normal smile (series A), decreased tooth show (series B), increased gingival show (series C), maxillary cant (series D), and asymmetric upper lip elevation (series E). In each image series, the midline was deviated to the right and left incrementally. A total of 210 raters (four professional groups and laypersons, n = 42 in each group) determined the midline deviation threshold and the attractiveness of midline position in each series. Results: The right and left thresholds were statistically similar for the symmetrical series (A, B, and C), while for series D, the right threshold was significantly lower. In most rater groups, the mean threshold order was: B > A > E > C > D. In all the series, the raters selected the coincident midline as the most attractive series except for series D, for which 1-2-mm deviations to the left were selected as the most attractive by almost all the groups. Conclusions: It is crucial to establish the coincident midline position in a symmetrical smile, especially when a gummy smile exists. In the asymmetrical gingival show, a coincident midline might not be the most esthetic midline position.

• The Journal of the Korean dental association
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• v.13 no.5
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• pp.457-461
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• 1975

The author observed the relationships beween the dental midline and the midsagittal plane by taking 242 cases P-A cephalo-graphy grouped by male and female 2-6 years age group, 7-15 years age group, and adult age group. The following results were obtained by the observation. 1. Generally, the median line almost coincided with dental midline ineach age group. 1. It showed som degree of deviation in each age group. 2. It showed some degree of deviation in each age group. 3. The some degree of deviation shifted in accordance with each age group. 4. In adult age group, the dental milline more coincided with median line in male than in female.

• The korean journal of orthodontics
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• v.54 no.1
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• pp.48-58
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• 2024

Objective: To quantify the effects of midline-related landmark identification on midline deviation measurements in posteroanterior (PA) cephalograms using a cascaded convolutional neural network (CNN). Methods: A total of 2,903 PA cephalogram images obtained from 9 university hospitals were divided into training, internal validation, and test sets (n = 2,150, 376, and 377). As the gold standard, 2 orthodontic professors marked the bilateral landmarks, including the frontozygomatic suture point and latero-orbitale (LO), and the midline landmarks, including the crista galli, anterior nasal spine (ANS), upper dental midpoint (UDM), lower dental midpoint (LDM), and menton (Me). For the test, Examiner-1 and Examiner-2 (3-year and 1-year orthodontic residents) and the Cascaded-CNN models marked the landmarks. After point-to-point errors of landmark identification, the successful detection rate (SDR) and distance and direction of the midline landmark deviation from the midsagittal line (ANS-mid, UDM-mid, LDM-mid, and Me-mid) were measured, and statistical analysis was performed. Results: The cascaded-CNN algorithm showed a clinically acceptable level of point-to-point error (1.26 mm vs. 1.57 mm in Examiner-1 and 1.75 mm in Examiner-2). The average SDR within the 2 mm range was 83.2%, with high accuracy at the LO (right, 96.9%; left, 97.1%), and UDM (96.9%). The absolute measurement errors were less than 1 mm for ANS-mid, UDM-mid, and LDM-mid compared with the gold standard. Conclusions: The cascaded-CNN model may be considered an effective tool for the auto-identification of midline landmarks and quantification of midline deviation in PA cephalograms of adult patients, regardless of variations in the image acquisition method.

• Journal of Oral Medicine and Pain
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• v.26 no.1
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• pp.75-85
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• 2001

This study was performed to investigate the effect of mandibular midline shift and difference of mandibular height between both sides on the electromyo- graphic(EMG) activity of the masticatory muscles on clenching or gum chewing movement. For this study, 105 patients with temporomandibular disorders(TMD) were selected and panoramic radiograph were taken. Amount and side of the midline shift and height of the mandible from antegonial notch to the top of the condylar head were measured on panoramic view. $BioEMG^{(R)}$ (Bioresearch Inc., Milwaukee, USA) was used for recording of EMG activity(${\mu}V$) of the anterior temporalis and the superficial masseter on clenching or gum chewing movement. EMG activity on clenching during 533msec period were measured for activity of the starting point and the one second-after activity as the early EMG and the maximum EMG, respectively. EMG activity on gum chewing movement were measured for activity of the first and the second chewing stroke. The data collected were analysed by SPSS windows program, and the results of this study were as follows : 1. Height of the mandible was 8.06cm on right side and 8.03cm on left side, and showed no difference by age, but significantly differed by sex with higher in male subjects. 2. Mean value of the midline shift was 0.1mm with range of 0~5mm on both sides. The amount and side of the midline shift did not related with height difference of the mandible and/or the EMG activity of the masticatory muscles on clenching. 3. Prevalence of higher right side and higher left side of the mandible were almost same, and the EMG activity of higher side was not higher than that of the other side. 4. In the subjects with height difference of more than 5mm between both sides of the mandible, the early EMG activity on clenching were differed for the anterior temporalis, but the maximum activity were differed for the superficial masseter. 5. In the subjects with height difference of more than 5mm between both sides of the mandible, EMG activity of the anterior temporalis of the gum chewing side was not higher than that of the other side when chewing on the side of lower height, but in the subjects with height difference of less than 5mm, the EMG activity was higher than that of the other side.