OBJECTIVETo investigate the effect of different premolar extraction models on postextraction Bolton overall ratio among different classes of malocclusion.

METHODS180 patients with equivalent skeletal and dental classifications were chosen(Group I, II and III, with 60 per group). According to dental casts, the Bolton overall ratios of each group were measured and compared before and after hypothetical premolar extraction (the four premolar extraction models were all first premolars, all second premolars, upper first and lower second premolars, and upper second and lower first premolars). Chi-square Test analysis was taken within each group in order to compare the abnormal rates of postextraction Bolton overall ratios.

RESULTSThe differences of pretreatment Bolton overall ratios among three types of malocclusions were found statistically significant (P=0.000). For Class I and Class II group, the four extraction models made no statistically significant differences in the abnormal rates of postextraction Bolton overall ratio (P>0.05). For Class III group, the four extraction models made statistically different results that was the upper second and lower first premolar extraction model creating lower abnormal rates than the upper first and lower second premolar extraction model (P=0.002).

CONCLUSIONAs far as the postextraction Bolton overall ratios are concerned, Class I and II malocclusions can choose any of four premolar extraction models, while to Class III malocclusions, the upper second and lower first premolar extraction model fits better than the upper first and lower second premolar extraction model.

Bicuspid ; Female ; Humans ; Male ; Malocclusion ; Malocclusion, Angle Class III ; Odontometry

OBJECTIVE: To analyze the relationship between the width of the maxillary anterior teeth and the anterior arch perimeter, to analyze the change rule of the width of the anterior teeth and the anterior arch perimeter, when altered the convexity of the anterior arch, with the width of the maxillary anterior arch keeping constant, and to provide a reliable basis for later digitized and personalized aesthetic analysis of front teeth. METHODS: In the study, 61 front teeth complete and well-arranged models had been selected from the working models after the prostheses in Department of Prosthodontics, Peking University School and Hospital of Stomatology, including 22 male models and 39 female models. A photograph was taken from the occlusal surface of each model using the fixed magnification with a single lens reflex camera. The width of anterior teeth, the width of anterior arch and the convexity of anterior arch had been measured using the Photoshop software. The ratio of the width of the anterior teeth to the width of the anterior arch was calculated. Keeping the width of anterior arch unchanged, the layer free transformation function used to add or decrease the curvature of the anterior arch from 1-5 mm, each circumference of the anterior arch was measured. According to the proportion of their anterior teeth in the anterior arch perimeter, the width of each anterior teeth crown under different convexities of anterior arch was calculated. SPSS 23.0 was used to analyze the ratio of the width anterior teeth to the anterior arch perimeter and correlation between the convexity of the anterior arch and the width of the anterior teeth. RESULTS: The percentages of the median length of the anterior arch in the central incisor, lateral incisor and canine were 36.2%±1.3%, 30.2%±1.5%, and 33.6%±1.4%, respectively. The proportions were normal distributions and not related to the perimeter of the anterior arch. When the width of the anterior arch was constant, there was a positive correlation between the convexity of anterior arch in the range of 5 mm and the width of anterior teeth or the front arch circumference. With each increase or decrease of 1 mm of the convexity of anterior arch, the width of the middle incisor increased or decreased by about 0.18 mm, the half circumference of the anterior arch increased or decreased by about 0.50 mm. CONCLUSION The width of the anterior teeth in the middle-distal direction remained stable in the anterior arch circumference. Within a certain range, when the width of the maxillary anterior arch remains unchanged, the width of the anterior teeth and the perimeter of the anterior teeth are positively correlated to the convexity of the anterior arch.
Cuspid ; Dental Arch ; Female ; Humans ; Incisor ; Male ; Maxilla ; Odontometry ; Software

OBJECTIVETo find the dentoskeletal characteristics of pseudo Class III malocclusion in mixed dentition.

METHODSThirty-six patients (15 females, 21 males with mean age: 10.7 +/- 2.0 years) were included in the pseudo Class III malocclusion group. Forty patients (21 females, 19 males with mean age: 9.7 +/- 2.2 years) with Class III incisor relationship and Class III molar relationship were included in the skeletal Class III malocclusion group. All the subjects were followed up after growth spurt and were diagnosed either as pseudo Class III malocclusion or skeletal Class III malocclusion. Thirty-one patients with Class I malocclusion were included in the Class I malocclusion group. Selection criteria included: 1. skeletal Class I malocclusion with normal overjet and overbite. 2. mild to moderate crowding with Class I molar relationship. 3. straight facial profile. Cephalograms were taken in the mixed dentition for pseudo Class III malocclusion, skeletal Class III malocclusion and Class I malocclusion groups to compare the dentoskeletal characteristics.

RESULTSFemales in the pseudo Class III malocclusion group showed more retrusion of "A" point with an average value of -1.63 mm compared with 0.52 mm in the Class I malocclusion group (P < 0.05). The upper incisors in the pseudo Class III malocclusion group were upright.

CONCLUSIONSPseudo Class III malocclusion is characterized by decreased midface length, mandibular displacement, retroclined upper incisors and normal vertical development.

Adolescent ; Child ; Dentition, Mixed ; Diagnosis, Differential ; Female ; Humans ; Male ; Malocclusion, Angle Class III ; pathology ; Odontometry ; methods

OBJECTIVETo evaluate accuracy of Propex, Raypex 5, Root ZX electronic apex locator in positions of the perforation with different irrigations in the root canal.

METHODSPerforation lengths were measured with Propex, Raypex 5, Root ZX electronic apex locators in 19 extracted human teeth embedded in model after simulate perforation preparation by ultrasonic ET40 and compared with the actual canal length measurements taken before embedding the teeth in model. Measurements were taken with the different canal contents. RESULTS; Propex, Raypex 5, and Root ZX could locate the positions of the perforation with different irrigations in the root canal. The differences between actual root canal perforation length and measured root canal perforation length of same electronic apex locators in different irrigations were no statistically significant (P > 0.05). Meanwhile, the differences between actual root canal perforation length and measured root canal perforation length of three kinds of electronic apex locators in same irrigations were not statistically significant (P > 0.05).

CONCLUSIONPropex, Raypex 5, and Root ZX electronic apex locators can detect perforation accurately.

Dental Pulp Cavity ; Humans ; In Vitro Techniques ; Molar ; Odontometry ; Root Canal Therapy ; Tooth Apex ; Tooth Root

OBJECTIVEThis study was undertaken to evaluate the influence of labial surface contours and collum angles of the maxillary anterior teeth on torque.

METHODS206 extracted maxillary teeth were selected, including 77 central incisors, 68 lateral incisors and 61 canines. All specimens were scanned by cone beam dental computed tomography (CT). Three-dimensional reconstructed images were made by using the CT software. The median sagittal planes of all teeth were selected and then analyzed by the Auto CAD software. For each tooth, the angles between tangent lines to the labial surface at four different heights along the surface and the longitudinal axis of the crown were measured. The collum angle was also measured.

RESULTSBetween 3.5 mm and 5.0 mm level of bracket heights, for the variation of 0.5 mm, the torque differed by 1.5 degrees for the maxillary central incisors and 2 degrees for the maxillary lateral incisors and canines. The mean collum angle values for the maxillary central incisors, lateral incisors and canines were 0.88 degree, 3.87 degrees and -3.30 degrees.

CONCLUSIONThe biological variation in tooth morphology would influence the torque after orthodontic treatment in different ways.

Cone-Beam Computed Tomography ; Cuspid ; Humans ; Incisor ; Maxilla ; Odontometry ; Tooth Crown ; Torque

OBJECTIVEThe study was designed to investigate the relationship between the accuracy of Root ZX and the size of apical foramen, when the apical constrictions were intact or not. Methods Lengths were taken when the needle reached the '0.5' mark and 'APEX' mark on the Root ZX. The electronic apex locator (EAL)-measured canal working length (L2) and EAL-measured canal length (L1) were then compared with the actual canal working length (L') and actual canal length (L). Besides, the areas of apical foramens CS) were measured when the apical constriction were intact or not. Then the measurement deviations and the areas of apical foramens were analyzed by linear correlation and linear regression using the software SPSS 12.0. Statistical significance was considered at P < 0.05.

RESULTSThere were no significantly correlations between the area of apical foramen and the accuracy of Root ZX if the apical constriction was intact (P > 0.05). However, the accuracy of Root ZX and the size of apical foramen had significant negative correlation when the apical constriction was destroyed (P < 0.001). Then the linear regression was completed, and the linear regression equation was deltaL2 = -0.623 + 6.5965, so the critical area of the apical foramen was 0.135 mm2 if the tolerant error was set at 0.5 mm according to the statistic control.

CONCLUSIONThe size of apical foramen has little effect on the accuracy of Root ZX if the apical constriction is intact. However the measurements of Root ZX should be used carefully when the apical constriction was destroyed.

Dental Pulp Cavity ; Humans ; In Vitro Techniques ; Odontometry ; Root Canal Preparation ; Tooth Apex ; Tooth Root

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

OBJECTIVETo evaluate the accuracy of Root ZX root apex locator in detecting stimulated horizontal root fractures.

METHODSA total of 20 single-canal maxillary anterior teeth were collected. All roots were simulated horizontal root fracture. Root ZX root apex locator measured the canal length in 3 stages: Broken ends of horizontal fractures without separation; broken ends of horizontal fractures with separation, but no impression material; broken ends of horizontal fractures with separation and impression material. The lengths measured by Root ZX root apex locator were compared with actual canal length.

RESULTSTo horizontal root fracture without separation or without impression material, Root ZX root apex locator couldn't detect the horizontal root fracture. To horizontal root fracture with separation and impression material, Root ZX root apex locator detected the horizontal root fracture within +/- 0.5 mm in 100%.

CONCLUSIONRoot ZX root apex locator lacks of diagnostic value for horizontal root fractures without soft tissue ingrowth, but provides with preferable veracity for horizontal root fractures with soft tissue ingrowth.

Bicuspid ; Dental Instruments ; Dental Pulp Cavity ; Humans ; In Vitro Techniques ; Odontometry ; Root Canal Preparation ; Tooth Apex ; Tooth Root

Dental Pulp Cavity ; anatomy & histology ; Humans ; Male ; Maxilla ; Middle Aged ; Molar ; anatomy & histology ; Odontometry ; Tooth Root ; anatomy & histology

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*