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At least 379 records · Page 21Linked to original sources
PubMed2006

Extreme variations in the shape of mandibular premolars.

INTRODUCTION: Human mandibular premolars (MnP) are highly variable in shape. An extreme variation, called here MnP tooth-shape deviation (MnP-TSD), is characterized by a squeezed faciolingual (FL) dimension and an enlarged mesiodistal (MD) dimension, reversing the typical premolar proportions. This is the first in-depth study of the MnP-TSD anomaly. METHODS: Eighteen subjects with 29 MnP-TSD teeth were selected for odontometric analysis by using dental casts. For each affected MnP, an MD/FL proportional index and a representation of crown area (MD x FL) were calculated from maximum MD and FL crown diameters. Data were compared with reference values for MnP. RESULTS: MnP-TSD was observed over 8 times more frequently in second premolars than in first premolars. Male expression was slightly greater (ratio, 1.4:1), and bilateral occurrence was observed in 59% of the subjects. Occurrence was noted among all ethno-racial groupings in the sample (16 whites, 1 black, 1 Asian). The MD/FL index of premolars with the MnP-TSD anomaly always exceeded 100 (103 to 148); this is significantly higher than normal values. In contrast, the crown areas of the affected teeth were remarkably similar to normal reference values. In addition to the squeezed tooth shape, subjects with pronounced MnP-TSD also had mesiolingual/distofacial twisting in MnP occlusal features. CONCLUSIONS: Extremely abnormal MD/FL proportions coupled with normal crown-area values provide reliable factors for differential diagnosis of the MnP-TSD anomaly. This uncommon MnP dysmorphology can be a challenge to orthodontic movement and achievement of ideal occlusal intercuspation.

Bicuspid↗
PubMed2006

Peer assessment of dental attractiveness.

INTRODUCTION: The objectives of the study were to determine the relative importance of various dental features that contribute to overall dental attractiveness and to test the validity of the concepts of golden proportion and golden percentage as applied to the human dentition. METHODS: Sixty 30-year-old subjects (29 men, 31 women) were selected from the 20-year longitudinal Cardiff Survey. Color photographs of the subjects' dentitions were taken with the lips retracted so that their teeth and gums were clearly exposed. Twelve nondentists, aged 32 to 33 years, equally divided according to sex, rated the subjects' dental appearances on a 5-point Likert attractiveness scale. The maxillary anterior teeth were measured, and relevant ratios were calculated and compared with the golden proportion. Factor analyses and linear regression were used to investigate the hierarchy of dental features, and variance components analysis was used to estimate interrater agreement. RESULTS AND CONCLUSIONS: Overall dental attractiveness did not depend on any particular feature of the dentition. A hierarchy of various features was established, with crown shape ranked highest, and tooth and gum color ranked lowest. The golden proportion and the golden percentage were not decisive factors in determining dental attractiveness.

Adult↗
PubMed2006

Do Bolton's ratios apply to a Spanish population?

INTRODUCTION: Previous studies have shown that populations differ with respect to interarch tooth-size relationships, and differences in tooth sizes are not systematic. The aims of this study were to determine the Bolton ratios in Spanish subjects. METHODS: We used a digital method and measured the casts to the nearest 0.05 mm. The sample consisted of 100 pairs of dental casts of Spanish subjects. The Kolmogorov-Smirnov test, t test, and 95% confidence intervals were used. RESULTS: Anterior tooth-width ratios were 78.31% +/- 2.59% for women and 78.34% +/- 2.16% for men (P = .955). Total tooth-width ratios were 91.91% +/- 2.04% for women and 92.10% +/- 1.73% for men (P = .668). No significant differences were found in tooth-width ratios according to sex, so the sexes were pooled and new ratios calculated: 78.32% +/- 2.45%, CI 95% (77.83%-78.81%), for the anterior tooth-width ratio and 91.97% +/- 1.95%, CI 95% (91.58%-92.35%), for the total tooth-width ratio. CONCLUSIONS: Twenty-one percent of the subjects had a significant anterior discrepancy (greater than 2 SD from Bolton's), and 5% had a total discrepancy. Differences between Spanish values and Bolton's were significant, and specific standards for Spanish people might be needed.

Adolescent↗
PubMed2006

Correlation between mandibular incisor crown morphologic index and postretention stability.

INTRODUCTION: Considering postretention stability as a result of successful orthodontic treatment, we aimed to verify the influence of mandibular-incisor-crown morphology in the relapse of mandibular anterior crowding. METHODS: The sample comprised 56 white subjects of both sexes with Class I and Class II malocclusions at pretreatment, treated with extraction of 4 first premolars and edgewise mechanics. No patient underwent interproximal stripping during or after treatment. Mean pretreatment age was 13.23 years. Mean treatment time was 2.11 years, and mean posttreatment evaluation time was 5.12 years. Mandibular anterior crowding was measured with the Little irregularity index, and the mesiodistal and buccolingual proportion of the mandibular incisor crowns was measured with the Peck and Peck index. The measurements were obtained from dental casts at the pretreatment, posttreatment, and postretention stages. The Pearson correlation coefficient was calculated to determine the correlation between mandibular-incisor-crown morphology and the amount of postretention-crowding relapse. RESULTS: The mandibular-incisor-crown morphologic index was not significantly correlated with the amount of mandibular-anterior-crowding relapse. CONCLUSIONS: Mandibular-incisor-crown morphology is not correlated with the amount of mandibular-anterior-crowding relapse.

Adolescent↗
PubMed2006

Quantitative evaluation of cortical bone thickness with computed tomographic scanning for orthodontic implants.

INTRODUCTION: The purpose of this study was to quantitatively evaluate cortical bone thickness in various locations in the maxilla and the mandible. In addition, the distances from intercortical bone surface to root surface, and distances between the roots of premolars and molars were also measured to determine the acceptable length and diameter of the miniscrew for anchorage during orthodontic treatment. METHODS: Three-dimensional computed tomographic images were reconstructed for 10 patients. Cortical bone thicknesses were measured in the buccal and lingual regions mesial and distal to the first molar, distal to the second molar, and in the premaxillary region at 2 different levels. Differences in cortical bone thickness at 3 angles (30 degrees, 45 degrees, and 90 degrees) were also assessed. Distances of the intercortical bone surface to the root surface and the root proximity were also measured at the above areas. RESULTS: Significantly less cortical bone thickness was observed at the buccal region distal to the second molar compared with other areas in the maxilla. Significantly more cortical bone was observed on the lingual side of the second molar compared with the buccal side. In the mandible, mesial and distal to the second molar, significantly more cortical bone was observed compared with the maxilla. Furthermore, significantly more cortical bone was observed at the anterior nasal spine level than at Point A in the premaxillary region. Cortical bone thickness resulted in approximately 1.5 times as much at 30 degrees compared with 90 degrees Significantly more distance from the intercortical bone surface to the root surface was observed at the lingual region than at the buccal region mesial to the first molar. At the distal of the first mandibular molar, significantly more distance was observed compared to that in the mesial, and also compared with both distal and mesial in the maxillary first molar. There was significantly more distance in root proximity in the mesial area than in distal area at the first molar, and significantly more distance was observed at the occlusal level than at the apical level. CONCLUSIONS: These data show that the safest location for placing miniscrews might be mesial or distal to the first molar, and an acceptable size of the miniscrew is less than approximately 1.5 mm in diameter and approximately 6 to 8 mm in length.

Adult↗
PubMed2006

Prediction of mandibular third-molar impaction in adolescent orthodontic patients.

INTRODUCTION: The purpose of this study was to identify risk factors for mandibular third-molar impaction in adolescent orthodontic patients. METHODS: Radiographs made before (T1) and after (T2) treatment and at least 10 years postretention (T3) of 134 patients that allowed accurate diagnosis of impaction vs eruption of at least 1 mandibular third molar were evaluated. RESULTS: Univariate logistic regression analyses at T1 showed that the decision to extract premolars (P <.05), an increase of 1 mm in mesial molar movement (P <.05), and an increase of 1 mm in eruption space measured from second molar to Xi point (centroid of the ramus) (P <.01) reduced the risk of impaction by 63%, 22%, and 30%, respectively. An increase of 1 degrees in mandibular third-molar angulation relative to the occlusal plane increased the risk of impaction by 11% (P <.01). Multivariate logistic regression analyses at T1 showed that reduced eruption space (P <.01), signs of forward mandibular growth rotation (P <.01), and female sex (P <.05) increased the risk of impaction. However, association tests documented increased frequencies of extractions and more mesial molar movement in female patients with erupted third molars. Univariate logistic regression analyses at T2 showed that every millimeter of increase in eruption space measured from the second molar to the anterior border of the ramus and to Xi point reduced the risk of impaction by 29% and 22%, respectively (P <.01), whereas every degree of increase in the angle between the occlusal surface and the occlusal plane increased the risk of impaction by 11% (P <.01). Multivariate logistic regression analyses at T2 showed that increased eruption space reduced the risk of impaction (P <.05), whereas increased mesial angulation of the third-molar bud (P <.01) and signs of forward growth rotation (P <.05) increased the risk of impaction.

Adolescent↗
PubMed2006

Perceptions of dental professionals and laypersons to altered dental esthetics: asymmetric and symmetric situations.

INTRODUCTION: Previous studies evaluated the perception of laypersons to symmetric alteration of anterior dental esthetics. However, no studies have evaluated the perception of asymmetric esthetic alterations. This investigation will determine whether asymmetric and symmetric anterior dental discrepancies are detectable by dental professionals and laypersons. METHODS: Seven images of women's smiles were intentionally altered with a software-imaging program. The alterations involved crown length, crown width, midline diastema, papilla height, and gingiva-to-lip relationship of the maxillary anterior teeth. These altered images were rated by groups of general dentists, orthodontists, and laypersons using a visual analog scale. Statistical analysis of the responses resulted in the establishment of threshold levels of attractiveness for each group. RESULTS: Orthodontists were more critical than dentists and laypeople when evaluating asymmetric crown length discrepancies. All 3 groups could identify a unilateral crown width discrepancy of 2.0 mm. A small midline diastema was not rated as unattractive by any group. Unilateral reduction of papillary height was generally rated less attractive than bilateral alteration. Orthodontists and laypeople rated a 3-mm distance from gingiva to lip as unattractive. CONCLUSIONS: Asymmetric alterations make teeth more unattractive to not only dental professionals but also the lay public.

Adult↗
PubMed2006

Flaws in root resorption assessment algorithms: role of tooth shape.

INTRODUCTION: The purposes of this study were to analyze and critique the mathematical algorithms used in the clinical assessment of root resorption. METHODS: Geometric constructions and derived mathematical expressions were used to investigate the influence of tooth shape on the relationships between tooth, root, and crown lengths and their respective sizes as measured on before and after radiographs. results: The ambiguities of root-loss assessment protocols are demonstrated. CONCLUSIONS: Root resorption assessment algorithms are unsuited for their intended applications.

Algorithms↗
PubMed2004

The mesiodistal crown diameters of primary dentition in Indonesian Javanese children.

Dentition analysis of primary teeth is necessary for recognising and correcting occlusal problems in every stage of dental development to enable normal adult occlusion. To do this, normative data of mesiodistal tooth crown diameters from the same ethnic population are needed. The aims of this study were to gather normative data of mesiodistal crown diameters of primary dentition in Indonesian Javanese children and to compare this normative data with published data of other ethnic populations. Dental casts of 160 males and 137 females with acceptable occlusion, aged 3.25-6.58 years, were taken in Yogyakarta, Indonesia. Mesiodistal diameter was measured as the distance between the anatomic contact points using calipers with accuracy to within 0.05 mm. Each measurement was taken twice on different occasions. The results indicated that the magnitude of asymmetry between right and left teeth was larger in distal teeth within a tooth field, larger in males than females, and larger in mandibular than maxillary teeth. The stability of mesiodistal tooth crown diameters was less in males than in females, and was most prominent in the mandibular central incisor. Sexual dimorphisms were found in, the lateral incisor and first molar in the maxilla, and the canine, first and second molars in the mandible. Compared with other ethnic populations, Indonesian Javanese falls between Hong Kong Chinese and Australian Aboriginal.

Child↗
PubMed2005

Fluctuating dental asymmetry of multiple crown variables measured by an image analysis system.

OBJECTIVE: Fluctuating dental asymmetry as an indication of the effect of environmental insults during tooth development requires further investigation. The aim of this study was to assess asymmetry in tooth crown dimension for the increased range of parameters possible with image analysis compared to previous manual measurements. METHODS: Study models of 25 male and 25 female white Caucasian subjects were measured from buccal and occlusal views to determine mesio-distal, bucco-lingual, occluso-gingival and tooth surface area dimensions using image analysis. Method errors were assessed by the repeatability coefficient RC and asymmetry assessed calculating intra-class correlation coefficients between pairs of antimere teeth. RESULTS: The method errors calculated using RC were small. There was a high degree of symmetry with correlation coefficients with a range of 0.67-0.96 for linear measurements and 0.80-0.97 for tooth surface areas. No significant differences were found between the genders or between the upper and lower jaws. Asymmetry tended to follow a pattern in morphogenic tooth fields with the mesial tooth showing greater symmetry than the more distal. There were differences in the degree of symmetry among the variables measured with the mesio-distal dimension showing the greatest symmetry. CONCLUSIONS: This new technique was reliable and readily applicable, providing also a greater range of measurements. While the asymmetry generally followed a similar pattern to earlier manual studies, there were variations in the degree of symmetry between different parameters.

Adolescent↗
PubMed2004

Tooth size in patients with supernumerary teeth and a control group measured by image analysis system.

OBJECTIVE: The aim of this study was to compare tooth size measurements between patients with supernumerary teeth and a control group. METHOD: The supernumerary group consisted of 56 subjects (21 females and 35 males) and the control group of 40 subjects (20 females and 20 males). All available permanent teeth on the dental casts were imaged and measured from both buccal and occlusal views using an image analysis system. Mesio-distal, bucco-lingual or occluso-gingival dimensions, area and perimeter were measured from each view. RESULTS: Supernumerary tooth patients tended to have larger tooth size measurements for almost all variables than controls. Significant differences (p<0.05) were found for the mesio-distal dimension of the upper and lower incisors and the bucco-lingual dimensions of the lower first premolars. CONCLUSIONS: The results are compatible with supernumerary teeth being a complex dental anomaly with a multifactorial aetiology in which both genetic and environmental factors are important. There is some evidence of a local effect with greater differences in tooth dimension adjacent to the site of the supernumeraries.

Adolescent↗
PubMed2005

Histological description of tooth formation in adult Eretmodus cf. cyanostictus (Teleostei, Cichlidae).

The Eretmodini, a tribe of closely related cichlids (Teleostei, Cichlidae) originating from Lake Tanganyika, possess oral tooth shapes ranging from conical (in Tanganicodus) over cylindrical (in Spathodus) to spatulate (in Eretmodus). Prior to a study aiming to understand how these distinctly different tooth shapes can be acquired in such closely related taxa, a detailed histological study was required of tooth formation in a representative of the eretmodines. Here, we present a histological description of replacement tooth development in Eretmodus cf. cyanostictus. Using light-microscopic observations on semithin as well as on ground sections, microradiographs and stereo-microscopic observations of both alizarine red S stained and unstained jaws we can conclude that tooth formation in adult E. cf. cyanostictus roughly corresponds with what is known for teleost tooth development in general. Remarkable features include the localization and shape of the epithelial downgrowth, the transient presence of a layer intermediate between inner dental epithelium (IDE) and outer dental epithelium (ODE), the asymmetric shape of the enamel organ, the fact that the pulp cavity recedes in front of the forming enameloid during enameloid formation, and finally, the pattern of matrix mineralisation and maturation, and the presence of pigment in the enameloid. The observation that the enamel organ in adult E. cf. cyanostictus develops asymmetrically is significant for understanding tooth shape variation in the Eretmodini.

Animals↗
PubMed2006

A new technique for symmetry determination in tooth morphology using image analysis: application in the diagnosis of solitary maxillary median central incisor.

OBJECTIVE: To develop a new technique for determining symmetry in tooth morphology and to evaluate this in the investigation of a patient with a solitary maxillary median central incisor (SMMCI) and a control group. DESIGN: A 9-year-old Caucasian female presented with SMMCI. Clinically the tooth appeared symmetrical. Morphology measurements of the maxillary central incisor were made using an image analysis system. Symmetry was determined by outlining the tooth from labial and axial views. These images were block filled, duplicated, flipped horizontally and then superimposed on the original image. The coincident area and perimeter of the two images from both views were measured. The method was repeated for the maxillary central incisors of 20 sets of control study models for young adult patients from which reference intervals for comparison with the SMMCI case were prepared. RESULTS: From the labial view, the area and perimeter of the two images of the SMMCI tooth were 98.85% and 98.97% coincident, respectively. From the axial view the area of the two images was 96.17% coincident, while the perimeter was 99.03% coincident. In all but one comparison for coincidence the SMMCI was above the upper limit of the reference range from the control group. CONCLUSIONS: This new technique is a valid method of assessing symmetry and is a useful clinical tool in cases of SMMCI.

Adult↗
PubMed2006

Modern human molar enamel thickness and enamel-dentine junction shape.

This study examines cross-sections of molar crowns in a diverse modern human sample to quantify variation in enamel thickness and enamel-dentine junction (EDJ) shape. Histological sections were generated from molars sectioned buccolingually across mesial cusps. Enamel cap area, dentine area, EDJ length, and bi-cervical diameter were measured on micrographs using a digitizing tablet. Nine landmarks along the EDJ were defined, and X and Y coordinates were digitized in order to quantify EDJ shape. Upper molars show greater values for the components of enamel thickness, leading to significantly greater average enamel thickness than in lower molars. Average enamel thickness increased significantly from M1 to M3 in both molar rows, due to significantly increasing enamel cap area in upper molars, and decreasing dentine area in lower molars. Differences in EDJ shape were found among maxillary molars in combined and individual populations. Sex differences were also found; males showed significantly greater dentine area, EDJ length, and bi-cervical diameters in certain tooth types, which resulted in females having significantly thicker average enamel. Differences in enamel thickness and EDJ shape within molars were also found among populations, although few consistent trends were evident. This study demonstrates that enamel thickness and EDJ shape vary among molars, between sexes, and among populations; these factors must be considered in the categorization and comparison of ape and human molars, particularly when isolated teeth or fossil taxa are included. Human relative enamel thickness encompasses most values reported for fossil apes and humans, suggesting limited taxonomic value when considered alone.

Animals↗