A new, accurate and fast digital method to predict unerupted tooth size

The sum of the lower incisor tooth width has been proposed as the best predictor for calculating unerupted canine and premolar mesiodistal tooth sizes. The aims of this study were to develop a new, fast, and accurate computerized method to predict unerupted mesiodistal tooth sizes and to determine which reference tooth or combination of reference teeth was the best predictor for canines and premolars in a Spanish sample. The dental casts of 100 Spanish adolescents with permanent dentition were measured to the nearest 0.05 mm with a two-dimensional computerized system. The goal was to predict unerupted canine and premolar mesiodistal tooth sizes using the sizes of the upper central incisor, upper and lower first molar, or a combination of these as a reference and using a specific mesiodistal tooth-size table. The results showed that the Digital Method proposed was very accurate in predicting unerupted canine and premolar tooth size. The combination of the sums of the permanent upper central incisor and the lower first molar was the best predictor for canines and premolars in this sample. Upper arch teeth were better predicted than lower arch teeth. The upper lateral incisor provided the worst predictions.     

Dental crowding in primary dentition and its relationship to arch and crown dimensions among preschool children of Davangere

The purpose of the present study was to evaluate dental crowding in the deciduous dentition and its relationship to the crown and the arch dimensions among preschool children of Davangere. Stratified randomized selection of one hundred, 3-4 year old healthy children with all primary teeth erupted was done and divided into two groups. One group had children with anterior crowding in both the arches while the other had spacing. Alginate impressions of the upper and lower arches were made and the study casts were obtained. The tooth and arch dimensions were determined. Mesiodistal dimensions of all the teeth were significantly larger in the crowded arch group. However, the buccolingual dimensions of the maxillary right central incisor, mandibular lateral incisors and the maxillary molars and the crown shape ratio of maxillary lateral incisors, mandibular canines and mandibular right second molar was statistically different. No significant correlation was found between the arch width and the presence of crowding of deciduous dentition. The arch depth of the spaced dentition was greater when compared to the crowded ones. The arch perimeter of the crowded arches was significantly less than the spaced arches.     

应用Time自锁托槽与传统托槽矫治牙列拥挤的临床比较研究

目的　比较使用Time自锁托槽与传统直丝托槽矫治上颌轻中度拥挤前后的牙弓宽度和上前牙凸度变化的差异。方法　选择46例轻中度拥挤的骨性Ⅰ类患者（女26例,男20例,13～16岁）,治疗组23例,采用Time自锁托槽矫治技术,对照组23例,采用传统直丝托槽结扎矫治技术。分别测量矫治前后牙弓宽度和上前牙唇倾度,比较2种方法所致的牙弓宽度和上前牙凸度的变化,并进行统计学分析。结果　2组患者的前磨牙宽度和上前牙凸度在矫治后均增大,其改变量比较,差异有统计学意义(P＜0.05);2组患者的尖牙宽度和磨牙宽度在矫治后也增大,但其改变量比较,差异无统计学意义(P＞0.05)。结论　自锁托槽在矫治牙列拥挤过程中较传统结扎托槽有更好的后牙弓扩展作用,但也会导致前牙的唇倾,故临床上可选择面型良好的轻中度拥挤患者进行非拔牙矫治。     

The prevalence and pattern of hypodontia of the permanent teeth and crown size and shape deformity affecting upper lateral incisors in a sample of Jordanian dental patients

OBJECTIVE: The aim of this study was to determine the prevalence and pattern of hypodontia and the extent of congenital malformation in the permanent teeth of a sample of Jordanian adults. MATERIAL AND METHODS: Clinical examinations were carried out on 1045 dental patients aged 16 to 45 years to record any congenital absence of teeth except 3rd molars and to note any crown shape or size deformities affecting the upper lateral incisor. The congenital absence of permanent teeth was confirmed by taking complete dental history and orthopantomograms. Impacted teeth and teeth lost as a consequence of extraction or trauma were recorded as present. RESULTS: The prevalence of hypodontia was found to be 5.5% of the sample and the lower second premolar was the most frequently missing tooth. The number of missing upper lateral incisors was significantly higher than that of lower lateral incisors, (p < 0.05). Peg-shaped and reduced size upper lateral incisors were observed in 2.3% and 2.9% of the sample respectively. There were no significant differences according to gender, location of tooth according to arch or side of the jaw and hypodontic pattern. CONCLUSION: The prevalence of hypodontia was 5.5%, that of peg-shaped lateral incisor was 2.3% and that of reduced crown size was 2.9%.     

Maxillary canine transpositions in two brothers and one sister: associated dental anomalies and genetic basis

Transposition is an uncommon dental anomaly involving positional interchange of two teeth. The maxillary canine is the tooth more frequently transposed in man. Maxillary canine-first premolar appears to be the most common type of tooth transposition, followed by maxillary canine-lateral incisor transposition. Maxillary canine transpositions are frequently associated with other dental abnormalities such as agenesis and pegshaped incisors. This report describes the presence of transposed canines in one sister and two brothers. The female showed bilateral maxillary canine-first premolar transposition with the left canine fully mesial to its neighboring first premolar, and the right canine blocked-out facially between the first and second premolar. One of the brothers showed full maxillary left canine-lateral incisor transposition. The other brother showed maxillary canine-first premolar transposition and agenesis of maxillary lateral incisors, with the left canine blocked-out facially between the first and second premolar. Findings from this case report and other previously published cases provide strong evidence that maxillary canine transpositions are a disturbance of tooth order and eruptive position resulting from genetic influences within a multifactorial inheritance model.     

Maxillary tooth transpositions: characteristic features and accompanying dental anomalies.

Transposition is a dental anomaly manifested by a positional interchange of 2 permanent teeth. The maxillary permanent canine usually transposes with the first premolar and occasionally with the lateral incisor. The records of 65 orthodontically treated individuals with maxillary tooth transpositions (40 females and 25 males) with an age range of 9 to 25 years (mean age, 13.4 years) were studied to determine the distribution of transposition and to evaluate the accompanying dental anomalies. Thirty-six individuals (55%) had a transposition of the maxillary canines and first premolars, 27 (42%) of the canines and lateral incisors, and 2 (3%) of the central and lateral incisors. Females had 60% more transpositions than did males. Substantially more transpositions were unilateral (88%), with a moderate left side dominance (58%). All dental anomalies associated with transposition--including missing lateral incisors and second premolars, undersized lateral incisors, retained deciduous canines, impaction of permanent canines and central incisors, and severely rotated adjacent teeth--were observed on the side of the transposition. This dominance of the affected side suggested that unknown local factors may play a major role in these dental anomalies.     

Intra-arch occlusal indicators of crowding in the permanent dentition.

INTRODUCTION: The objective of this study was to identify the intra-arch occlusal characteristics that best discriminated 3 groups with different grades of dental arch discrepancies. This cross-sectional analysis was conducted in Lima, Peru, in 2003. METHODS: Intra-arch measurements were made on 150 sets of dental casts of high school students (aged 12-16; 75 boys, 75 girls). Stepwise multiple discriminant analysis (SMDA) was used to obtain a better understanding of the morphological relationships between tooth and dental-arch variables and their relationship with crowding. RESULTS: Mesiodistal tooth sizes and crown proportions of some teeth differed among significantly crowded, mild-to-moderately crowded, and spaced dental arches. Buccolingual tooth sizes were similar in the 3 groups. Of the arch dimensions evaluated, only intermolar arch width and arch length differed between the groups. An SMDA was developed to classify dental-arch discrepancies in the permanent dentition based on several intra-arch occlusal characteristics. The variable with the highest discriminatory capability between groups was arch length. When arch length was taken out of the SMDA, the explanatory capability from the variability on the dental arch discrepancies diminished from 51% to 14%. When the remaining arch dimension variable (intermolar width) was taken out, the explanatory capability diminished more (from 14% to 8%). CONCLUSIONS: Although other tooth-size and arch dimensions are indicators of crowding, arch length is the most important factor.     

Midline correction by asymmetric reciprocal torque: a pilot study

Objective

Can we correct dental midline discrepancies by systematic torque bends on all canines and premolars without extraction and mesiodistal tooth movement?

Patients and methods

Eight orthodontic patients (4?males, 4?females, mean age 31?years) presented a dental midline discrepancy of 2–4?mm, moderate deviation of the chin, no skeletal asymmetry, and a horizontal orientation of the occlusal plane in the frontal aspect. On the side where the mandible was shifted medially, asymmetric torque bends moved the antagonist canine and both premolar crowns buccally, while palatal crown torque was used on the maxillary canine and premolars on the other side. Lingual crown torque corrected the medially shifted canine and premolars in the mandibular dental arch, and buccal crown torque the laterally shifted lower canine and premolars.

Results

On average, torque effects altered the canine guidance by 6.5?±?4.7°, the first premolar guidance by 7?±?4.1°, and the second premolar guidance by 6.3?±?3.7°. Correction of the dental midline shift averaged 1.6?±?0.8?mm after the torque, and eliminated the midline discrepancy completely (n?=?2) or partly (n?=?6).

Conclusion

In this pilot study, asymmetric reciprocal torque represented a treatment option for midline corrections of approximately 2–4?mm and improvement in the chin position without mesiodistal tooth movement or extraction.     

Occlusal stability in shortened dental arches

Shortened dental arches consisting of anterior and premolar teeth have been shown to meet oral functional demands. However, the occlusal stability may be at risk as a result of tooth migration. The aim of this nine-year study was to investigate occlusal stability in shortened dental arches as a function over time. Occlusal stability indicators were: 'interdental spacing', 'occlusal contacts of anterior teeth in Intercuspal Position', 'overbite', 'occlusal tooth wear', and 'alveolar bone support'. Subjects with shortened dental arches (n = 74) were compared with subjects with complete dental arches (controls, n = 72). Repeated-measurement regression analyses were applied to assess age-dependent variables in the controls and to relate the occlusal changes to the period of time since the treatment that led to the shortened dental arches. Compared with complete dental arches, shortened dental arches had similar overbite and occlusal tooth wear. They showed more interdental spacing in the premolar regions, more anterior teeth in occlusal contact, and lower alveolar bone scores. Since the differences remained constant over time, we conclude that shortened dental arches can provide long-term occlusal stability. Occlusal changes were self-limiting, indicating a new occlusal equilibrium.     

Tooth diameters and arch perimeters in a black and a white population

This study was undertaken to test the hypothesis that a sample of black patients will have larger mesiodistal tooth diameters and larger dental arch perimeters than a corresponding sample of white patients. In this study, the black sample's mean canine, first and second premolar, and first molar mesiodistal diameters were significantly larger than those of the white sample. The dental arches of the black patients were significantly wider and deeper but did not show significantly more crowding. Gender and race differences did exist, but gender differences were controlled by sampling procedures. The black sample also had a larger mean MP-SN angle but this was not accompanied by the increased crowding and the narrower dental arches that had been reported associated with high-angle white samples.     

Tooth size variability and relevance of numerical variation in the Japanese serow

We analysed the variability of the lower cheek teeth of the Japanese serow, Capricornis crispus, from Aichi Prefecture, Japan, based on the coefficient of variation (CV), and examined tooth size variability. The mesiodistal (MD) and buccolingual (BL) crown diameters of permanent cheek teeth were measured, and an index of the crown surface (MDxBL) was calculated. As a result, the CV for MD measurements ranged from 3.6 to 6.3, and that for BL measurements ranged from 3.6 to 6.5. In males and females, the first molar (M(1)) was the least variable (3.6-4.1) and the second premolar (P(2)) was the most variable (5.0-6.5), except for the case of BL in females. The crown surface index showed a morphological gradient that increased from mesial to distal, and the values of P(2) in both sexes were extremely small. Overall, cheek tooth variability was not influenced by developmental factors, but appeared to be inversely related to functional factors. The highest coefficient of variation was observed for P(2), which was characterised by a simple shape with a single cusp, and an extremely small size compared to other teeth. Only P(2) showed congenital absence or impaction in the lower dentition. We also confirmed the relationship between tooth size variability and numerical variation.     

Objective assessment of occlusal and coronal characteristics of untreated normals: a measurement study.

To determine whether tooth shape and position are constant within tooth types, dental casts of 68 Indians (age range, 10-32 years; mean, 18.72 years) were analyzed. The casts were selected from a larger sample and met the following criteria: Class I molar and canine relationships; overjet and overbite within normal limits; well-related vertical, transverse, and anteroposterior relationships with pleasing profiles and well-aligned arches; and no supernumerary teeth or large restorations. None of the subjects had received orthodontic treatment, and all were in good health and exhibited normal growth. Crown angulation, inclination, offset of maxillary molar, curve of Spee, crown facial prominence, horizontal crown contour, and vertical crown contour were assessed. Means, standard deviations, and standard errors were calculated. The measurements were compared with Andrews's data on 120 nonorthodontic normal occlusion casts. The Student t test was used to determine the significance of differences between the 2 sets of data. It was found that teeth of the same tooth type have similar values of horizontal and vertical crown contours. Values for inclination, angulation, and relative prominence were also similar. Hence, we concluded that tooth shape and position are constant for each tooth type. The data from this study were comparable with Andrews's findings. However, from this study, it would be safe to presume that all teeth except the maxillary second molars require alterations in the bracket base inclination value, and that the maxillary lateral incisor, canine, second premolar, and second molar, and the mandibular canine, require alterations in angulation values.     

Management of an Extremely Displaced Maxillary Canine

AbstractCase Report Aligning a displaced maxillary canine into the dental arch is one of the most complicated problems in orthodontics. In cases of extremely high displacement, the tooth is frequently removed surgically. Because of the upper canines’ significance to dental esthetics and functional occlusion, such a decision is a very serious one. This case report illustrates the treatment of an extremely high displaced maxillary canine.Clinical Findings: The main diagnosis was the displacement and the retention of tooth 13 (in nearly horizontal position, apical to the neighboring teeth); further diagnoses were: transversal maxillary deficiency with frontal crowding and a distal bite of one premolar in width, a deep bite of 6 mm with contact in the palatal mucosa, mandibular midline deviation of 2.5 mm to the right, lingual eruption of teeth 32 and 42, retroinclination of the maxillary incisors, and retarded eruption of the permanent teeth.Therapy: Initial treatment with active and functional appliances to correct the distal bite, midline deviation and deep bite. Surgical exposure of the high displaced canine at the age of 14. Onset of cuspid elongation with removable appliances and elastics, further movement with a transpalatinal bar and welded arm, and full alignment of the upper and lower arches with fixed appliances in both jaws. Stabilization of the orthodontic treatment results with retention devices. Duration of treatment: 5 years and 8 months. For the alignment of tooth 13, 2 years and 10 months were required; 1 year and 4 months were necessary with complete fixed appliance.Conclusions: The aim of this case report was to demonstrate the potential of aligning an extremely displaced canine. Because of the esthetic and functional importance of the upper canines, therapeutic alignment should be initiated, provided there are no indications to the contrary.     

The chronological distribution of enamel hypoplasia in human permanent incisor and canine teeth

The frequencies and chronology, based on a standard tooth development chart, of enamel hypoplasia derived from permanent upper central incisors and mandibular canines were compared for 42 prehistoric Amerindians. Between 0.5 and 4.5 years, when the crowns of both these teeth are developing, hypoplasias were 1.36 times more common on the incisors (54 hypoplasias/incisor; 40 hypoplasias/canine). Hypoplasias on incisors occurred earlier (mean = 2.50; median at 2.0-2.5 years) compared to the canine (mean = 3.51; median at 3.5-4.0 years). Differences in published frequencies and chronologies of hypoplasias may be explained, in part, by an indefinable variation in the teeth studied. The highest density of hypoplasias on both tooth crowns was just cervical to the midpoint, suggesting that developmental rates and crown geometry may influence the ability of the crown to record stressful events.     

Interrelation of tooth crown diameters

The purpose of this study was to clarify the interrelation of the tooth crown diameters using statistical methods. The material consisted of 414 dental casts from orthodontic patients in the Japanese female. The mesiodistal diameters of all permanent teeth on the left side were measured, excluding the third molars. These values were examined by correlation coefficient matrix and multivariate analyses such as multiple regression, principal component and canonical correlation, etc. The results were as follows: 1) The tooth crown diameters showed a strong intercorrelation within each jaw and between both jaws. 2) When the incisors and the canine were large in size, the premolars and the molars tended to be small. 3) When the incisors and the molars were large in size, the canine and the premolars tended to be small. 4) When the incisors and the premolars were large in size, the canine and the molars tended to be small. 5) All of the teeth except the upper lateral incisor were classified according to size into the four groups of incisors, canines, premolars and molars. 6) The dentition with small teeth tended to show a spaced arch.     

Simultaneous presence of a congenitally missing premolar and supernumerary incisor in the same jaw: report of case

Supernumerary teeth and hypodontia can be regarded as opposite developmental phenomena. An eight-year-old girl presented a concomitant occurrence of a supernumerary tooth and two congenitally missing teeth. The supernumerary tooth was found in the left maxillary incisor region, while the left second premolar in the maxilla and the left lateral incisor in the mandible were congenitally missing. The supernumerary tooth showed a similar color and morphology to those of the maxilla lateral incisor, and the lateral incisor on the mesial side was diagnosed as a supernumerary tooth from dental age, eruption time, and mesiodistal crown dimension. The supernumerary incisor was guided labially to cure an anterior cross-bite, and the lateral incisor, canine, and first premolar were guided distally to compensate for the space left by the congenitally missing left second premolar.     

两种正畸粘接剂托槽生存率的比较研究

目的：比较自酸蚀粘接剂和全酸蚀粘接剂粘接托槽的临床效果。方法：选择42名固定正畸患者,采用自身对照研究,分别使用一步法自酸蚀粘接剂和两步法全酸蚀粘接剂粘接726个托槽,计算12个月内托槽的脱落率,卡方检验比较4种因素（粘接剂、牙弓、牙位和性别）对托槽脱落率的影响;Kaplan-Meier法绘制托槽生存率曲线,log-rank检验分析上述4种因素对托槽生存率的影响,同时评价牙釉质表面的剩余粘接剂指数。结果：两种粘接剂的托槽脱落率无统计学差异;生存分析表明粘接剂类型和牙弓位置对托槽生存率的影响无统计学差异,但前磨牙托槽的生存率比切牙和尖牙低,女性患者的托槽生存率高于男性;自酸蚀粘接剂的剩余粘接剂指数与全酸蚀粘接剂无统计学差异。结论：自酸蚀粘接剂与两步法全酸蚀粘接剂都具有较高的托槽生存率,均能满足正畸临床粘接的要求。     

The lower incisors as a predictor for the size of unerupted canine and premolars in the Iranian ethnicity

The purpose of this study was to find the correlation coefficients between the mesiodistal widths of the permanent mandibular incisors and the permanent canine and premolars for each quadrant and establish a regression equation for prediction of the sum of canine and premolars based on the dimension of the lower incisors. 90 patients 12–20 years old (45 females and 45 males) were selected. The mesiodistal crown diameters of the permanent teeth were measured. The correlation coefficients between the permanent mandibular incisors and the permanent canine and premolars sizes varied from 0.63 to 0.8. An Iranian mixed dentition analysis based on the Tanaka and Johnston method was constructed with linear regression equations; for maxillary arch y = 6.3 + 0.65x (SEE = 0.8 mm) and for mandibular arch y = 5.1 + 0.67x (SEE = 0.8 mm). No significant sexual dimorphism was found in tooth sizes. This study revealed that Iranian population has smaller teeth than white North American. We found that prediction equations of Tanaka and Johnston or Moyers charts cannot accurately predict the size of buccal segment in Iranian population.