On the relationship between crown form and clinical features of the gingiva in adolescents

Abstract The purpose of the present study was to examine the relationship between the form of the crowns in the maxillary front tooth segment and (1) a group of morphological characteristics and (2) the thickness of the gingiva. 108 subjects devoid of symptoms of destructive periodontal disease were examined regarding, e.g., probing depth, thickness of the free gingiva, width of the keratinized gingiva and the contour of the marginal gingiva. From clinical photographs of the maxillary front tooth region, the width (at the apical third – CW) and the length (CL) of the crowns of the 6 front teeth were determined. A CW/ CL-ratio was calculated for each tooth and averaged for each tooth region. The individual mean CW/CL-ratio values for the central incisors were ranked. After correction for incisal attrition, the 10 subjects ranked highest and the 10 ranked lowest were selected as having either a long-narrow (group N) or a short-wide (group W) form of the crown of the tooth. The data for each of the examined parameters were averaged for each tooth region in each subject and mean values for subjects in groups W and N were compared using the Student t-test. Stepwise multiple regression analysis, including data from the whole sample, was performed for each tooth region with the thickness of the free gingiva as the dependent variable. The results from the analyses demonstrated that individuals with a long-narrow form of the central incisors displayed, compared to individuals with a short-wide crown, form (i) a narrow zone of keratinized gingiva, (ii) shallow probing depth, and (hi) a pronounced “scalloped” contour of the gingival margin. There was no significant difference between groups N and W with respect to the thickness of the free gingiva. The CW/CL-ratio data revealed that a certain form of the crowns in the central incisors was accompanied by a similar form in the lateral incisor and canine tooth region. The regression analyses demonstrated that the thickness of the free gingiva in central incisors was significantly related to (i) the width of the keratinized gingiva, (ii) the buccolingual width of the crown and (iii) the presence of an interproximal gingival groove. In lateral incisors, the thickness of the free gingiva was associated with the probing depth at the buccal surface. No single variable was significantly related to the thickness of the gingiva in canines.     

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.     

Gingival phenotypes in young male adults

Abstract In a previous study on 42 young adult, periodontally healthy subjects without any attrition, abrasion or crown restoration, gingival thickness (GTH) was determined at facial aspects of premolars, canines and incisors by a novel ultrasonic device. GTH strongly depended on periodontal probing depth, width of gingiva (WG), and tooth type. Whereas the ratio of crown width to its length (CW/CL) was not identified as an explanatory variable, a significant influence of the subject was ascertained. The aim of the present study was to extend these analyses in order to identify subjects with different morphological characteristics of gingiva, i.e., gingival phenotypes. When employing cluster analysis on standardized parameters mean GTH, WG and CW/CL of upper canines, lateral and central incisors, 3 clusters were identified. Cluster A comprised 2/3 of subjects, displaying “normal” GTH, WG and CW/CL. Cluster B (n=9, 21%) had a significantly thicker and wider gingiva, and a more quadratic form of upper front teeth. A 3rd cluster (cluster C, n=5, 12%) was identified showing “normal” GTH, high CW/CL, but a narrow zone of keratinized tissue. Some characteristics of gingival phenotype of the upper front tooth region were also found at upper premolars (WG, CW/CL) but in general not at mandibular teeth. Present results clearly indicate evidence for the existence of different gingival phenotypes. Clinical relevance of these observations has to be tested in longitudinal studies.     

Does the canine dental follicle cause resorption of permanent incisor roots? A computed tomographic study of erupting maxillary canines

We performed computed tomography (CT) on 107 children and adolescents aged 9-15 years with 176 unerupted maxillary canines (152 erupting ectopically and 24 erupting normally) to determine whether there is an association between widened dental follicles of the maxillary canines and resorption of the adjacent incisors during eruption. Contiguous axial (transverse) CT scans were obtained through the maxilla in the region of the canines. The width and shape of the dental follicles were recorded, as were any contacts between the follicles and the crowns of the maxillary canines and neighboring incisors. Fifty-eight lateral incisors (38%) and 14 central incisors (9%) had some type of root resorption. The position of the maxillary canine in relation to the root of the lateral incisor varied greatly, as did the width and shape of the canine dental follicle. Follicle width ranged from 0.5 mm to 7.0 mm. The mean +/- SD width of dental follicles was, on average, larger for the ectopically positioned canines (2.9 +/- 0.8 mm) than for the normally erupting canines (2.5 +/- 0.8 mm) (P < or = .01). We found that during eruption, the follicle of the erupting maxillary canine frequently resorbed the periodontal contours of adjacent permanent teeth but not the hard tissues of the roots. We concluded that the dental follicle did not cause root resorption of permanent teeth. Resorption of neighboring permanent teeth during maxillary canine eruption was most probably an effect of the physical contacts between the erupting canine and the adjacent tooth, active pressure during eruption, and cellular activities in the tissues at the contact points, all of which are part of the eruptive mechanism. The findings also confirm an association between root resorption of deciduous canines and the dental follicles of erupting permanent canines.     

Influence of incisal length of ceramic and loading orientation on stress distribution in ceramic crowns

For ceramic crowns, the recommended depth of tooth reduction from the incisal edge of anterior teeth is 1.5 mm to 2.0 mm. Although some prosthodontists have suggested that incisal heights of ceramic which exceed 2 mm are associated with dangerously high intra-oral stresses, this theory has not been verified. The objective of this study was to test the hypothesis that the stress distribution in ceramic crowns designed for a prepared maxillary central incisor which are subjected to applied loading is relatively insensitive to the incisal length of ceramic. Finite element stress analyses were performed on three crown designs loaded with a horizontal or vertical force of 200 N along the lingual surface near the incisal edge. Ceramic crowns for maxillary central incisors were modeled with incisal lengths of 1.0 mm (Case I), 1.9 mm (Case II), and 4.0 mm (Case III). Zinc phosphate cement with a film thickness of 30 micron was included for each case. Plane-stress finite element analyses indicated that tensile and compressive stresses which were induced in cement and ceramic due to a vertically applied load of 200 N were comparable in magnitude for all three cases within the gingival third of the crowns. For Cases I, II, and III, tensile stresses at the facial region were 6.7, 5.4, and 6.5 MPa, respectively, in cement and 46.2, 48.6, and 49.2 MPa, respectively, in the ceramic. The results of this study tend to support the hypothesis that the amount of tooth reduction (1 to 4 mm) in an incisogingival direction does not significantly influence the stress distribution in the crown or cement layer.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical crown length and reduction in overjet, overbite, and dental height with orthodontic treatment

To evaluate the clinical crown length relative to fixed-appliance orthodontic treatment of excessive overjet and deep overbite and to correlate such changes to the vertical dental height, the following measurements were undertaken for 12 females and 8 males, between the ages of 16 and 20 years, on three separate occasions--2 days before banding, 2 days after debanding, and 12 months after debanding: (1) overjet, overbite and dental height measured from right lateral cephalometric x-ray films; (2) clinical crown length, measured from study models, of 400 teeth divided into four groups--maxillary incisors and canines (120 teeth), maxillary second premolars and first molars (80 teeth), mandibular incisors and canines (120 teeth) and mandibular second premolars and first molars (80 teeth); and (3) gingival condition by means of the gingival index of L?e and Silness. Fixed edgewise orthodontic appliances were used and the four first premolars were extracted. From the results of the investigation, the following conclusions were evident: after a 12-month follow-up observation period, the achieved reduction in overjet, overbite, and dental height showed relapses of 9%, 11%, and 29%, successively; only 7% of the 400 teeth examined showed reductions in clinical crown length. This change was probably the result of gingival hyperplasia. The gingival condition greatly improved by approximately 64% after 12 months of debanding, accompanied by 25% to 50% relapse in the amount of change in clinical crown length (noted 2 days after debanding); and the intrusive tooth movement during orthodontic correction of deep overbite was the result of vertical movement of the tooth, with its investing tissues and soft-tissue attachment, into the jaws.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mesiodistal crown dimensions of the permanent dentition in North Indian children

This investigation was conducted on 110 individuals, (40 males and 70 females) in the age range of 12-18 years. The results revealed the mesiodistal crown dimensions of teeth of males to be more than that of the females. Further the ratio of the mesiodistal crown dimension of the maxillary lateral incisors to the maxillary central incisors was 80% in females and 78% in males. The total arch length in males was 117.77 mm in maxilla and 111.60 mm in mandible, while in females, the figures were 113.98 mm in maxilla and 107.10 mm in the mandible.     

Dens invaginatus on a geminated tooth: a case report

AIM: To present a case of a concomitant occurrence of dens invaginatus (DI) and gemination in a mandibular left lateral incisor. BACKGROUND: DI is a developmental anomaly resulting from the invagination of a portion of a crown in the enamel organ stage of odontogenesis. It is commonly found in the maxillary lateral incisors but also occurs in the central incisors, premolars, canines, and molars in descending order of frequency. The occurrence of DI in the mandible is extremely rare. Gemination results from one tooth bud attempting to split into two. Geminated teeth present with a single root structure and rarely occur in mandibular teeth. REPORT: A 13-year-old girl presented with a chief complaint of spontaneous nocturnal pain in the mandibular left lateral incisor tooth. Intraoral examination revealed the tooth was enlarged with a notch on the incisal edge extending to the coronal 1/3 of the crown. The radiological examination revealed a Type 2 DI in a Type I geminated mandibular left lateral incisor. SUMMARY: DI is clinically significant due to the possibility of the pulpal involvement; pulpitis, necrotic pulps, and chronic periapical lesions are often associated with this anomaly without clinical symptoms. Clinicians should be mindful of the possibility of DI when a tooth presents pulpitis without history of trauma or caries and examine the suspicious tooth and the periodontium radiographically.     

Normal torque of the buccal surface of mandibular teeth and its relationship with bracket positioning: a study in normal occlusion

This study evaluated the degree of buccolingual inclination of mandibular tooth crowns relative to torque. For such purpose, mandibular and maxillary stone casts from 31 Caucasian Brazilian adults with normal occlusion, pleasant facial aspect and no history of previous orthodontic treatment were examined. A custom device was developed for measuring the degree of inclination (torque) of bracket slots of orthodontic appliances relative to the occlusion plane, at three bonding height: standard (center of clinical crown), occlusal (0.5 mm occlusally from standard) and cervical (0.5 mm cervically from standard). Except for the mandibular incisors, which presented a small difference in torque from one another (lingual root torque for central incisors and buccal root torque for lateral incisors), the remaining average values are close to those found in the literature. Due to the convexity of the buccal surface, the 1-mm vertical shift of the brackets from occlusal to cervical affected the values corresponding to the normal torque, in approximately 2 degrees in central and lateral incisors, 3 degrees in canines and 8 degrees in premolars and molars.     

牙科锥形束CT评价上颌前牙唇面形态对转矩的影响

目的研究上颌前牙的唇面形态及牙冠牙根成角关系对转矩的影响,为临床治疗中调整牙齿的转矩提供参考。方法选择206颗离体上颌前牙为研究对象,其中中切牙77颗、侧切牙68颗、尖牙61颗。利用牙科锥形束CT将全部牙齿进行扫描,在CT工具软件下进行影像的三维重建并提取全部牙的正中矢状切面图像,利用Auto CAD软件测量图像,分别测量牙冠唇面4个不同高度的切线与牙冠长轴所成的角度,以及牙冠长轴与牙根长轴所成的角度（冠根角）。结果当托槽高度为3.5～5.0 mm时,其高度每变化0.5 mm,上颌中切牙转矩变化约为1.5°,上颌侧切牙和尖牙的转矩变化约为2°。上颌中切牙、侧切牙、尖牙冠根角的均数分别为0.88°、3.87°、-3.30°。结论牙体形态的生物学变化从多方面影响矫治后牙齿的转矩角。     

恒尖牙双尖牙近远中径预测方程

目的：为口腔正畸临床混合牙列间隙分析提供简捷,便利的诊断依据。方法：在模型上测量牙冠近远中径,对测量值进行直线回归与相关分析。结果：下切牙与尖牙,双尖牙近远中径存在直线相关关系。结论：建立了汉族人群上,下颌尖牙双尖牙近远中径观测方程。     

The variability of the curvature of the labial surface of the upper anterior teeth along the facial axis of the clinical crown

OBJECTIVE: To mathematically assess the curvature of upper anterior teeth along the facial axis of the clinical crown (FACC) line to provide information valuable for assessment of enamel growth. METHODS: Forty upper study models were chosen from the Orthodontic clinic at the Charles Clifford Dental Hospital, Sheffield, UK. The study model incisors and canines were sectioned longitudinally down the FACC line, using a Microslice II cutting machine. Images were captured that showed the proximal view of the tooth curvature from incisal edge/cusp tip to the gingival margin. The images were converted into silhouettes and saved as bitmap files. These were vectorised and converted to an outline of xy data points. The forty xy files were mathematically adjusted so the distance between incisal edge and gingival margin were of equal length. Non Rotational Principal Component Analysis (PCA) was then applied at 20 equal intervals along the curve of each xy file to describe the shape of the teeth. RESULTS: Intra class correlation coefficient for intra-operator repeatability ranged from 0.821-0.998 showing good or excellent levels of reliability. PCA showed variation between tooth types. CONCLUSIONS: The method proved reliable. All tooth types showed that the mid-point region had the greatest rise variable, indicating that the most-prominent point was central or incisal for central and lateral incisors. All were skewed towards the incisal end and had kurtosis at both ends. Central incisors showed least variability. Greater variability was seen within the incisal third than within the gingival third for all tooth types.     

Bone augmentation and autogenous transplantation of premolar to the site of the fissure in a cleft palate patient

This article presents a case report of autogenous tooth transplantation to the site of the fissure, in addition to bone augmentation with graft of autogenous bone harvested from the iliac crest, performed in a cleft palate patient, who had insufficient bone volume. A non‐syndromic 10‐year‐old girl, with a unilateral cleft lip and palate, incisal transforamen fissures, agenesis of the maxillary left central incisor and both maxillary lateral incisors, was treated with autogenous bone graft in the cleft area. The orthodontic treatment plan was to replace the missing lateral incisors with the maxillary canines and to extract the mandibular first premolars. One of the mandibular premolars was extracted from its site with 2/3 of its root formation completed and transplanted to the maxillary left central incisor area. After orthodontic treatment, the anatomic crowns were characterized with composite resin. Autogenous tooth transplantation can be performed in the area of the fissure in young cleft palate patients, by performing bone graft augmentation before transplantation of the tooth, to gain sufficient recipient alveolar bone volume. A multidisciplinary approach is mandatory for the success of this clinical procedure, especially in cleft palate patients.     

Modeling and characterization of the CEJ for optimization of esthetic implant design

This study evaluated the dimensions and characteristics of the cementoenamel junction (CEJ) of maxillary anterior teeth; the natural CEJ was compared to current implant design and used for design optimization. Standardized digital images of 137 extracted human teeth (45 central incisors, 46 lateral incisors, and 46 canines) were used to measure cervical dimensions, CEJ curvature, and distance from zenith of CEJ to interdental contact on proximal views. The x- and y-coordinates of the CEJ contour were digitized before mathematic processing to allow the representation of a single average curve for buccal, palatal, mesial, and distal surfaces for each tooth type. These measurements were combined to existing data related to dentogingival and "implantomucosal" junction to extrapolate specific biologic landmarks around teeth and implants. Mean cervical dimensions, distance from zenith of CEJ to interdental contact, and CEJ curvature were compared. Cervical dimensions significantly differed, with a more symmetric cervical cross-section for central incisors, slightly more rectangular shape for lateral incisors, and distinctly rectangular shape for canines. CEJ curvature was statistically different between all tooth groups (centrals > laterals > canines); within groups, curvature value was always superior at the mesial aspect compared to distally (3.46 mm vs 3.13 mm for centrals, 2.97 mm vs 2.38 mm for laterals, and 2.55 mm vs 1.60 mm for canines). Tooth-implant biologic width discrepancies ranged from 4.10 to 5.96 mm and were different between all groups of teeth (centrals > laterals > canines); within groups, the discrepancy was always superior at the mesial aspect compared to distally. Current implant design featuring a flat, rotation-symmetric shoulder should be reconsidered in view of natural CEJ contour to improve biologic considerations and related esthetics.     

Dental morphology and crowding. A multivariate approach

The objective of this study was to compare, combined and individually, the mesiodistal (MD) and buccolingual (BL) tooth sizes as well as their respective crown proportions in the permanent dentition in dental arches with moderate, mild, and no crowding. Dental casts from two-hundred 12 to 16-year-old school children from a typical high school from Lima, Peru, were used. The MD and BL tooth sizes of all permanent teeth except second and third molars were measured, and their crown proportion (MD/BL ratio) was estimated. Each dental arch was classified as presenting moderate (-5.1 mm or more of discrepancy), mild (-0.1 and -5 mm of discrepancy), and no crowding (zero or a positive discrepancy). Combined and tooth-specific comparisons among the crowding groups for the tooth sizes as well as crown proportions were performed with a multivariate analysis of variance (MANOVA, using Wilks lambda). Combined MD tooth sizes and crown proportions differed among crowding groups. Subsequent individual comparisons indicated differences for MD tooth size of all upper teeth and for lower premolars and central incisors. Differences were also detected for crown proportions of the upper second premolar, canine, and both incisors; as well as for the lower first premolar, canine, and central incisor. No differences were found for the BL tooth sizes among crowding groups. MD tooth sizes and crown proportions from specific teeth are significantly different between dental arches with moderate, mild, and noncrowded arches. This study helps to understand the odontometric component of the dental crowding multifactorial origin.     

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.     

Anterior tooth morphology and its effect on torque

This study was undertaken to determine the variation in crown-root angle (CRA) of the upper incisors and canines as well as the variation in their labial contour. In addition, the influence of the variability of the labial contour and of different bracket heights on torque was evaluated. Proximal radiographs were taken of 160 extracted maxillary teeth (81 incisors and 79 canines). They were digitized and analysed with Jasc Paint Shop Pro 7TM and Mathcad 2001 Professional. The incisal edge, the centre of the cemento-enamel junction (CEJ), and the root apex were digitized to define the crown and root long axis. For all teeth the CRA was measured. At several heights of the labial surface a tangent was determined, enabling measurement of the inclination of the labial surface.The CRA had great variability, ranging from 167 to 195 degrees for the canines (mean value 183 degrees) and from 171 to 195 degrees for the incisors (average 184 degrees). The mean inclinations of the labial surfaces for the incisors varied greatly. Between 4 and 4.5 mm from the incisal edge the standard deviations (SD) were the smallest and between 2 and 4.5 mm from the incisal edge the labial surface angle differed by approximately 10 degrees. For the canines the mean inclinations of the buccal surface also varied. This angle differed by around 10 degrees between 2 and 4.5 mm from the incisal edge, but the SD were much larger than for the incisors.It can be concluded that placement of a bracket on a tooth at varying heights, still within a clinically acceptable range, results in important differences in the amount of root torque.     

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.     

A case of oculo-facio-cardio-dental syndrome with integrated orthodontic-prosthodontic treatment.

OBJECTIVE: Oculo-facio-cardio-dental (OFCD) syndrome is a very rare condition that requires comprehensive dental management because of associated multiple dental anomalies such as canine radiculomegaly, delayed dentition, oligodontia, persistent primary teeth, microdontia, and macrodontia. This report presents a case of OFCD in a Japanese girl (13 years 1 month old). We analyzed cephalograms, panoramic roentgenograms, and dental casts and discuss our integrated orthodontic-prosthodontic treatment. DESIGN: The sizes of the tooth crown and root as well as lateral cephalograms were compared with those from a Japanese control group. The outcome of orthodontic treatment was evaluated by comparing cephalograms taken before and after treatment. RESULTS: Radiculomegaly was found not only in the upper and lower canines but also the upper central incisors and lower first premolars. Macrodontia was found in the upper central incisors, upper canines, lower canines, and lower first premolars. Microdontia was found in the upper lateral incisor. Lateral cephalometric analysis showed a remarkable hypoplastic midface in both the sagittal and vertical dimensions, coupled with a significantly decreased cranial base length and an increased gonial angle. Serial lateral cephalograms during orthodontic treatment from 13 to 23 years of age demonstrated only slight maxillary growth and significant downward mandibular growth with clockwise rotation in addition to pronounced labial tipping of the upper central incisors. CONCLUSIONS: Characteristic dental anomalies together with a unique craniofacial dysmorphology were clarified. Successful oral rehabilitation was achieved by integrated orthodontic-prosthodontic treatment.