Objective: To explore the relationship between the width ratios of maxillary anterior teeth, the width/height ratios of maxillary central incisor and the esthetic proportions among individual normal occlusion, and to provide reference for the esthetic design of anterior teeth. Methods: A total of 300 Shanxi Medical University students who were residents from Shanxi province with normal occlusion (110 males, 190 females, aged 18-30 years) were recruited in this study from October 2020 to March 2021. Standardized digital photographs of the maxillary anterior tooth in natural head position were obtained, the perceived width of the maxillary anterior teeth (maxillary central incisors, lateral incisors and canines) on the left and right sides and height of maxillary central incisor were measured on the standardized digital photographs, then the width ratios of adjacent maxillary anterior teeth including the lateral incisor/central incisor width ratio (LI∶CI), the canine/lateral incisor width ratio (C∶LI), and the width/height ratios (W/H ratio) of the maxillary central incisor were calculated. The independent sample t test was used to compare the sex differences of each measurement project, Single sample t test was used to compare the difference of adjacent maxillary anterior teeth width ratios with golden proportion (0.618 and 0.618), Preston proportion (0.66 and 0.84), the recurring esthetic dental (RED) proportion (0.70 and 0.70). The percentage of anterior tooth width/intercanine width was calculated, the number and proportion of teeth conforming to golden percentage (25%, 15%, 10%)±1% or modified golden percentage (22.5%, 15.0%, 12.5%)±1% were calculated. The number and proportion of width/height ratio of maxillary central incisor ranged from 0.75 to 0.85 was counted. Results: The widths of maxillary central incisor, lateral incisor and canine were (8.50±0.52), (6.23±0.53) and (5.18±0.55) mm, respectively, the corresponding tooth of male [(8.74±0.49), (6.37±0.52), (5.41±0.47) mm] was significantly higher than that of female [(8.37±0.50), (6.15±0.52), (5.04±0.54) mm] (t=6.40, 3.55, 6.23,P<0.05). The width ratio of maxillary lateral incisor/central incisor was 0.73±0.05, and there was no significant difference between genders (t=-1.06, P>0.05). The width ratio of canine/lateral incisor was 0.84±0.10, and it was significantly higher in male (0.85±0.10) than in female (0.82±0.10) (t=2.42, P<0.05). Two width ratios of maxillary anterior teeth were significantly different from golden proportion and the RED proportion (t=38.50, 35.74, 11.48, 22.20, P<0.05). The lateral incisor/central incisor was significantly different from that of Preston proportion (t=24.66, P<0.05), while the canine/lateral incisor was not significantly different from that of Preston proportion (t=-0.92, P>0.05). In this study, a total of 0% (0/600) of central incisors, 63.0% (378/600) of lateral incisors and 5.8% (35/600) of canines met the golden percentage±1%. There were 42.8% (257/600) of central incisors, 63.0% (378/600) of lateral incisors and 56.7% (340/600) of canines met the modified golden percentage±1%. The width/height ratio of maxillary central incisors was 0.86±0.08, and there was no significant difference between genders (t=-0.88, P>0.05). Only 36.3% (218/600) of the subjects in this study ranged from 0.75 to 0.85. Conclusions: Gender differences should be considered in the esthetic design of anterior teeth; for the width ratios of maxillary anterior teeth, the golden proportion, the RED proportion and golden percentage do not accord with the natural tooth morphological characteristics of Shanxi nationality college students in normal occlusion. Preston proportion and modified golden percentage are of more reference value. The width/height ratio of maxillary central incisors is different from 0.75-0.85.
Cuspid/anatomy & histology* ; Esthetics, Dental ; Female ; Humans ; Male ; Maxilla/anatomy & histology* ; Odontometry ; Students

OBJECTIVE: To analyze the esthetic proportions of maxillary anterior teeth in term of the apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown in 120 Chinese adults. METHODS: Maxillary gypsum casts were obtained from the dental laboratories of stomatological hospitals in North China, Southeast China, and Southwest China, according to the inclusion criteria and exclusion criteria. Standardized digital photographs of each cast were recorded. The apparent widths and actual widths and heights of the central incisors, lateral incisors and canines were determined by ImageJ software for the calculation of apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown. The ideal apparent widths proportion (Golden proportion and Preston proportion) and width/height ratio (0.80) were tested. The gender, arch side, and regional differences were investigated. RESULTS: The apparent widths proportion of the lateral/central incisor was 0.724±0.047, of the canine/lateral incisor was 0.814±0.092. The width/height ratio of the central incisor was 0.848±0.072, of the lateral incisor was 0.834±0.094, of the canine was 0.883±0.098. The esthetic proportions were different from the predicted ideal ratio (P < 0.001). The apparent widths proportion of lateral/central incisor was significantly larger in the right side than that in the left side (0.730± 0.044 vs. 0.718±0.050), and was significantly smaller in North China than that in Southwest China (0.711±0.051 vs. 0.731±0.044). The width/height ratio of the central incisor was significantly larger in the female than that in the male (0.855±0.074 vs. 0.835±0.068), and in the right side than that in the left side (0.855±0.073 vs. 0.842±0.072). The width/height ratio of the lateral incisor was significantly larger in the female than that in the male (0.843±0.097 vs. 0.817±0.084). CONCLUSION The apparent widths proportion of adjacent teeth and the width/height ratio of the clinical crown in Chinese adults are different from the foreigner's. The esthetic proportion parameters have significant population specificity, and the measurements cannot be generalized as well as it should be applied with caution.
Adult ; Asians ; China ; Cuspid ; Esthetics ; Esthetics, Dental ; Female ; Humans ; Male ; Maxilla/anatomy & histology* ; Odontometry ; Tooth Crown/anatomy & histology*

During smile evaluation and anterior esthetic construction, the anatomic and racial variations should be considered in order to achieve better matching results. The aims of this study were to validate an objective method for recording spontaneous smile process and to categorize the smile and upper lip curvature of Chinese Han-nationality youth. One hundred and eighty-eight Chinese Han-nationality youths (88 males and 100 females) ranged from 20 to 35 years of age were selected. Spontaneous smiles were elicited by watching comical movies and the dynamics of the spontaneous smile were captured continuously with a digital video camera. All subjects' smiles were categorized into three types: commissure, cuspid and gummy smile based on video editing software and final images. Subjects' upper lip curvatures were also measured and divided into three groups: upward, straight and downward. Reliability analysis was conducted to obtain intra-rater reliabilities on twice measurements. The Pearson Chi-square test was used to compare differences for each parameters (α=0.05). In smile classification, 60.6% commissure smile, 33.5% cuspid smile and 5.9% gummy smile were obtained. In upper lip measurement, 26.1% upward, 39.9% straight and 34.0% downward upper lip curvature were determined. The commissure smile group showed statistically significant higher percentage of straight (46.5%) and upward (40.4%) in upper lip curvatures (P<0.05), while cuspid smile group (65.1%) and gummy smile group (72.7%) showed statistically significant higher frequency in downward upper lip curvature (P<0.05). It is evident that differences in upper lip curvature and smile classification exist based on race, when comparing Chinese subjects with those of Caucasian descent, and gender.
Adult ; Cephalometry ; methods ; China ; ethnology ; Cuspid ; anatomy & histology ; Ethnic Groups ; Female ; Gingiva ; anatomy & histology ; Humans ; Image Processing, Computer-Assisted ; methods ; Lip ; anatomy & histology ; Male ; Smiling ; Video Recording ; methods ; Young Adult

Typodont models of bilateral canines gingival displaced vertically for 3 mm and bilateral lateral incisors palatal displaced horizontally for 3 mm are made and every kind of the two kind models was divided into four groups: MDD, MBT, self-ligating and Tip-Edge. Each group of the two kinds of models had 5 models, so a total of 40 models for the two kinds of models were set up. The experimental models were aligned with a 0.30 mm of nickel titanium round wire in a water-bath with constant temperature 45 degrees C for 30 minutes. The three-dimensional digital images of the experimental models before and after the water bath were obtained by scanning with the three dimensional optical scanner ATOS. Geomagic software was used to overlap the digital images taken before and after the water bath treatment. The vertical changes of sign points of canines, the movements of sign points of lateral incisors in the sagittal plane and the horizontal plane were quantified by using the Color map. The data was then processed by a two-factor analysis of variance by using SAS 9.2 software package. Analysis of the results shows that the vertical changes of sign points of canines , the movements of sign points of lateral incisors in the sagittal plane and the horizontal plane of MDD group are all less than those in the other three groups, a statistically significant difference (P < 0.0001). And the size of the teeth displacement is directly related to the size of orthodontic force on the typodont models. Thus the preliminary results suggest that MDD appliance might have advantages of light force in the alignment stage, and that the possible relevant factors are the improvement of its sub-slot and the single ligation wing design.
Cuspid ; Dental Models ; Humans ; Imaging, Three-Dimensional ; methods ; Incisor ; anatomy & histology ; Malocclusion ; therapy ; Orthodontic Appliance Design ; Tooth Movement Techniques ; instrumentation ; methods

OBJECTIVETo evaluate the alveolar bone thickness and root length changes of anterior teeth with cone-beam computed tomography (CBCT).

METHODSCBCT scans were taken for 12 skeletal Class III patients who accepted the improved corticotomy (IC) procedures during pre-surgical orthodontics. The CBCT data in T1 (the maxillary dental arch was aligned and leveled) and T2 (extraction space closure) were superimposed and the alveolar bone thickness at root apex level and root length measurements were done.

RESULTSFrom T1 to T2, the buccal alveolar bone thickness for the upper lateral incisors increased from (1.89±0.83) to (2.47±1.02) mm (P<0.05), and for central incisors and for canines from (2.32±0.71) to (2.68±1.48) mm and from (2.28±1.08) to (2.41±1.40) mm, respectively. According to Sharpe Grading System, the root resorption grade for 69 teeth of 72 was located in Grade 1, two teeth in Grade 2, one tooth in Grade 3.

CONCLUSIONSThe improved corticotomy had the potential to increase the buccal alveolar bone thickness and the root resorption in most teeth was in Grade 1 according to Sharpe grading system.

Alveolar Process ; anatomy & histology ; diagnostic imaging ; surgery ; Cone-Beam Computed Tomography ; Cuspid ; Humans ; Incisor ; Malocclusion, Angle Class III ; diagnostic imaging ; surgery ; Root Resorption ; pathology ; Tooth Root ; Zygoma

OBJECTIVETo classify the relationship of the sagittal root positions of the maxillary anterior teeth to their respective osseous housings, and to measure the thickness of facial and palatal alveolar bone by cone-beam computed tomography (CBCT).

METHODSTwenty-three subjects [9 male, 14 female, mean age: (24.5 ± 1.6) years] who fulfilled the inclusion criteria were involved in this study. The CBCT images were evaluated and the relationship of the sagittal root position of the maxillary anterior teeth to its associated osseous housing was recorded as Kan's Class 1, 2, 3, 4. The facial and palatal alveolar bone thickness at three locations:2 mm apical to crest level, mid-root level and apical level, was measured respectively.

RESULTSNinety seven point one percent(134/138)of the anterior maxillary teeth were classified as Class 1. Only 2.9% (4/138) were Class 4.Occurrences of > 2 mm thickness of maxillary facial alveolar bone were found 2.2% (6/276 sites) at 2 mm apical to crest level and mid-root level in the sample of maxillary anterior teeth.

CONCLUSIONSThe majority of the anterior maxillary teeth roots were positioned close to the labial cortical plate. Most tooth sites in the anterior maxilla had a thin facial bone wall.

Adult ; Alveolar Process ; anatomy & histology ; diagnostic imaging ; Asian Continental Ancestry Group ; Cephalometry ; Cone-Beam Computed Tomography ; Cuspid ; anatomy & histology ; diagnostic imaging ; Female ; Humans ; Incisor ; anatomy & histology ; diagnostic imaging ; Male ; Maxilla ; anatomy & histology ; diagnostic imaging ; Tooth Root ; anatomy & histology ; diagnostic imaging ; Young Adult

Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament (PDL) as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g (100 g=0.98 N) were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 kPa (capillary pressure) and 12.8 kPa (80% of human systolic blood pressure) was considered to be optimal, whereas an absolute strain exceeding 0.24% (80% of peak strain during canine maximal moving velocity) was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces (40-44 g for distal-direction and 28-32 g for labial-direction) were smaller than the translation forces (130-137 g for distal-direction and 110-124 g for labial-direction). In addition, the optimal forces for labial-direction motion (110-124 g for translation and 28-32 g for tipping) were smaller than those for distal-direction motion (130-137 g for translation and 40-44 g for tipping). Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.
Biomechanical Phenomena ; Computer Simulation ; Cuspid ; anatomy & histology ; physiology ; Dental Models ; Finite Element Analysis ; Humans ; Imaging, Three-Dimensional ; Maxilla ; Orthodontic Friction ; physiology ; Periodontal Ligament ; physiology ; Rotation ; Stress, Mechanical ; Tooth Movement Techniques ; statistics & numerical data