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PubMed1988

Changes in the molar relationship between the deciduous and permanent dentitions: a longitudinal study.

The purpose of this study was to describe the changes in the molar relationship from the deciduous dentition to the permanent dentition in 121 subjects from the Iowa Longitudinal Growth Study. In addition, an attempt was made to determine the association between the various dentofacial variables and the changes in the molar relationship in 55 persons (33 male and 22 female subjects) with normal occlusion. All subjects were evaluated at three stages of dental development: stage I, completion of the deciduous dentition (means age = 4.94 years); stage II, when permanent first molars initially erupt into occlusion (means age = 6.91 years); and stage III, at the completion of eruption of the permanent dentition excluding third molars (means age = 13.01 years). The following sets of variables were evaluated: molar relationship, mesiodistal crown diameters of single and groups of deciduous and permanent teeth, dental arch widths, arch lengths, and various cephalometric dentofacial variables. Correlation coefficients and regression analyses were used to assess the relationships between these measurements and the changes in the molar relationship from the deciduous to the permanent dentition. The findings indicate that of the 242 sides evaluated in the deciduous dentition, 61.6% developed into a Class I molar relationship, 34.3% into Class II, and 4.1% into Class III. Those sides that started with a distal step in the deciduous dentition proceeded to develop into a Class II molar relationship in the permanent dentition. Of the sides with a flush terminal plane relationship in the deciduous dentition, 56% progressed to a Class I molar relationship and 44% to Class II in the permanent dentition. The presence of a mesial step in the deciduous dentition indicates a greater probability for a Class I molar relationship and a lesser probability for a Class II molar relationship. In the 55 subjects who achieved normal occlusion, the magnitude of change in the molar relationship was 1.91 mm in male subjects and 1.64 mm in female subjects. On the average, these cases had a mesial step in the deciduous dentition of 0.8 mm in male subjects and 1.0 mm in female subjects. There was a favorable difference between the maxillary and mandibular leeway spaces of 1.3 mm in male subjects and 1.1 mm in female subjects. There was also a favorable decrease in the Wits appraisal of 1.2 mm in male subjects and 0.6 mm in female subjects.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1988

Dental crowding and its relationship to mesiodistal crown diameters and arch dimensions.

An investigation was carried out to determine the correlation among cumulative mesiodistal crown widths, arch dimensions, and the degree of primary dental arch crowding. Two different ethnic groups were studied--namely, indigenous British and Pakistani immigrant groups--to determine whether similar correlations existed as part of a larger study of ethnic comparisons. Correlation matrix computation and multiple regression analysis were among the tests used. The results showed that in both ethnic groups there were very significant correlations between certain arch dimensions and the degree of crowding. There was no significant correlation between cumulative mesiodistal crown widths and dental crowding when considered in isolation. In combination with the other parameters, however, cumulative mesiodistal crown widths contributed significantly to the overall regression equation. This suggested a complex interrelationship among cumulative mesiodistal crown widths, the various arch dimensions, and primary dental crowding.

Adolescent↗
PubMed1988

Tooth size, spacing, and crowding in relation to eruption or impaction of third molars.

A study was conducted for the purpose of comparing mesiodistal tooth diameters, sum of tooth widths, and the degree of spacing or crowding in the dentitions of two groups of young adults. The subjects in the first group had complete dentitions including third molars (M3s). In the second group, all M3s had been extracted for failure to erupt. Tooth size and consequently the sum of mesiodistal tooth widths were found to be greater in the extraction group than in the group with complete dentitions. The relationship between tooth size and M3 impaction was most pronounced in female subjects. The sum of mesiodistal tooth widths is apparently one factor of importance in the cause of M3 impaction in women. The results suggest that tooth size in girls could be used at preadolescent age as one predictive variable for third molar eruption. The sexual dimorphism demonstrated regarding the relationship between tooth size and M3 impaction implies that studies in the field of M3 development and eruption should be performed on male and female subjects separately. The dental arches in the extraction group tended to be more crowded than in the group with complete dentitions. However, the differences were small and significant only as they related to the upper arches in males.

Adult↗
PubMed1989

Comparisons of mesiodistal and buccolingual crown dimensions of the permanent teeth in three populations from Egypt, Mexico, and the United States.

The purpose of this study is to examine the mesiodistal and buccolingual crown dimensions in three populations--57 subjects (35 boys and 22 girls) from Iowa City, Iowa; 54 subjects (30 boys and 24 girls) from Alexandria, Egypt; and 60 subjects (26 boys and 34 girls) from Chihuahua, Mexico. All subjects had normal Class I occlusion, with no history of orthodontic treatment. Comparisons of single teeth as well as sums of groups of teeth were performed between boys and girls within and between the two populations. The analysis of variance general linear models procedure was used for statistical comparisons. The findings from this investigation indicated that (1) differences between antimeres are of small magnitude and of no statistical significance; (2) all populations have significant differences in tooth dimensions between the sexes with boys having larger canines and first molars; (3) there is greater variation in the buccolingual than in the mesiodistal dimensions among the three populations; (4) there is a greater similarity in tooth dimensions among the boys from the three populations than among the girls, but the magnitude of these differences is considered to be of little clinical significance; and (5) standards for the buccolingual diameters were developed for the three populations. As a result, it was concluded that prediction equations used for space analysis in the mixed dentition to determine tooth size-arch length discrepancies in the Iowa population can also be used for persons from Egypt and from the northern part of the Mexican Republic, with some suggested modifications.

Adolescent↗
PubMed1989

Three biologic variables modifying faciolingual tooth angulation by straight-wire appliances.

The facial surface contours of 600 maxillary and mandibular teeth, including 50 of each type of tooth from central incisors to first molars, were measured. Facial contours present at the same location, facial contours from occlusal/incisal to gingival surfaces and the angle formed by the coronal and radicular long axes varied among teeth of the same type. The magnitude of the variation found was so great as to suggest that differences between patients or differences in height of bracket placement are greater than the differences between the standard torque prescriptions now used in orthodontics. No single point, including the coronal midpoint (LA point), was found to be constant among teeth of the same type. Variation in facial surface contour tended to be greater in the posterior teeth than in the anterior teeth. Future custom construction of brackets, adjusted to individual facial contour differences, will also require information regarding optimal tooth position in the head, including compensations necessary for variations in facial skeletal pattern.

Humans↗
PubMed1989

The occurrence of tooth size discrepancies among different malocclusion groups.

This study consisted of 109 patients with varying malocclusions (Class I; Class II, Division 1; Division 2; and Class II surgery) who were treated orthodontically. Tooth size analyses were performed on the pretreatment models of these patients and mesial-distal tooth size ratios were measured as described by Bolton. The incidence of mesial-distal tooth size discrepancies in the malocclusion groups was analyzed and compared with Bolton's means and standard deviations. The results showed no difference in the incidence of tooth size discrepancies from one malocclusion group to another. When the sample was taken as a whole, there was no significant difference in the mean of the mesial-distal tooth size ratios as computed in the present study and compared to Bolton's mean. There were, however, higher standard deviations seen in the present study compared with Bolton's study. Even though there was no significant difference in the incidence of tooth size discrepancies among malocclusion groups, there was a large number of tooth size discrepancies in each group. Therefore it is suggested that Bolton's tooth size analysis be performed before initiation of orthodontic treatment.

Humans↗
PubMed1990

Effects of phosphoric acid concentration and etch duration on enamel depth of etch: an in vitro study.

In a previous study we reported no significant differences among the shear bond strengths resulting from the application of an orthodontic bonding resin to enamel surfaces etched with three phosphoric acid (H3PO4) concentrations, each for three etch durations. The objective of the current study was to determine the depths of etch on ground enamel surfaces exposed to the nine etching procedures. The facial surfaces of 45 extracted human maxillary permanent central incisors were ground wet on 600-grit silicon carbide paper. Annular adhesive disks of 6 mm outer diameter and 3 mm inner diameter were positioned on the ground enamel surfaces and etched with 10 mm3 of 37%, 15%, and 5% H3PO4 for 60, 30, and 15 seconds, respectively. The calcium concentrations of the etching solutions were determined and the depths of etch calculated. The depths of etch were then measured with a surface profilometer. A stepwise decrease in the calculated depths of etch with decreasing acid concentration and duration of etching was obtained. The calculated etch depths ranged from 27.1 microns by etching with 37% H3PO4 for 60 seconds to 3.5 microns by etching with 5% H3PO4 for 15 seconds. The measured depths of etch followed a similar pattern. A highly significant correlation between calculated and measured depths of etch was obtained.

Acid Etching, Dental↗
PubMed1990

Eruption of mandibular third molars after second-molar extractions: a radiographic study.

The purpose of the present study was to analyze the posteruptive contact relationship and inclination of mandibular third molars after extraction of second molars and to determine whether predictors could be formulated for the dental relationships observed. In all, 140 mandibular quadrants were evaluated from 95 sets of panoramic radiographs taken at the time of second molar extraction (T1) and at the time of final evaluation (T2). For analysis of a consecutive sample of patients, a subsample of 25 sets of radiographs from all the patients who had received such treatment during one calendar year was also quantified. Subjective evaluation indicated that 46% of the sites examined had satisfactory tooth contact relationship between the first and third molars at T2. Third-molar impaction was found in 4% of the sites in the subsample of 25 consecutively treated patients. Measurements of crown axis inclination revealed that the third molar invariably erupted into a mesially tilted position. The first molar showed only minor distal tipping between T1 and T2. Inclination of the third molar bud at the time of second molar extraction was not found to be a useful predictor for posteruptive third molar position. The clinical significance of these results and the need for studies regarding a rationale for mandibular second molar extraction are discussed.

Adolescent↗
PubMed1990

A long-term study of the relationship of third molars to changes in the mandibular dental arch.

The purpose of this study is to determine the relationship of third molars to changes in the mandibular dental arch. The sample for this study consisted of four groups and subgroups. The groups consisted of premolar extraction treated, nonextraction treated with initial generalized spacing, nonextraction treated, and serial extraction untreated subjects. The subgroups were divided into persons who had mandibular third molars that were either impacted, erupted into function, congenitally absent, or extracted at least 10 years before postretention records. The mean postretention time interval was 13 years, with a range of 10 to 28 years. The mean postretention age was 28 years 6 months, with a range of 18 years 6 months to 39 years 4 months. Two-way analysis of variance with repeated measures was used to compare the changes over time (before treatment, at end of active treatment, and after retention) of groups and third molar subgroups. With time, mandibular incisor irregularity increased while arch length and intercanine width decreased. The eruption patterns of mandibular incisors and first molars were similarly dispersed in all groups studied. The findings between the subgroups in which mandibular third molars were impacted, erupted into function, congenitally absent, or extracted 10 years before postretention records revealed no significant differences between any of the subgroups for the parameters studied. No significant differences in mandibular growth were found between the third molar subgroups; this suggests that persons with third molars erupted into satisfactory function do not have a significantly different mandibular growth pattern than those whose third molars are impacted or congenitally missing. In the majority of cases some degree of mandibular incisor crowding took place after retention, but this change was not significantly different between third molar subgroups. This finding suggests that the recommendation for mandibular third molar removal with the objective of alleviating or preventing mandibular incisor irregularity may not be justified.

Adult↗
PubMed1990

Australian aboriginal tooth succession, interproximal attrition, and Begg's theory.

In 1954, P.R. Begg analyzed interproximal attrition as a prehistorically universal mechanism to reduce tooth size. With modern processed diets and the virtual disappearance of constant interproximal attrition, Begg asserted, teeth remain too large for the arches and become crowded. Later investigators have questioned Begg's estimate of attritional tooth-size reduction, as well as aspects of his theory relating the succession sequence of permanent teeth to different malocclusions. The present paper examines the theory using longitudinal casts and records of modern Australian aborigines who are among the first generation lacking notable interproximal attrition thanks to a "modernized" diet. Deciduous and permanent tooth size, arch size, and occlusal relational variables were analyzed with respect to the expected occlusal outcomes in the absence of attritional tooth reduction. Permanent incisor overjet correlated with crowding status, as predicted by Begg. On the other hand, longer teeth did not relate to crowding in general nor to crowding in relevant local areas or during developmental stages. Unfavorable leeway space did not relate clearly to crowding or other malocclusions. Lowered correlations among structures and narrowness of the maxilla related more significantly to malocclusion. These results are in keeping with recent thinking that small jaws rather than large teeth underlie tooth/arch discrepancy.

Australia↗
PubMed1990

Changes in the morphology of the buccal alveolar bone of protruded mandibular permanent incisors secondary to orthodontic alignment.

The cephalometric radiographs of 17 children and adolescents whose orthodontic treatment involved lingual positioning of procumbent mandibular central permanent incisors were examined to determine the morphologic changes in the buccal alveolar bone that resulted from orthodontic treatment. Comparison of tracings fom radiographs taken before and after treatment indicated that the alveolar height increased in 58.8% of the cases. In these cases a significant increase in the distance from the incisal edge to the "D" point was evident (t = 2.5, p less than or equal to 0.03), whereas this dimension decreased significantly in the rest of the cases (t = 3.0, p less than or equal to 0.02). In addition, a significant positive correlation (r = 0.95) was found between the changes in the distances from the "D" point to the incisal edge and the alveolar bone height. These findings indicate that during orthodontic treatment that involves lingual positioning of procumbent teeth but no intrusion, an increase in the amount of buccal alveolar bone may take place.

Adolescent↗
PubMed1991

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.

Black People↗
PubMed1992

Patterns of incisor root resorption before and after orthodontic correction in cases with anterior open bites.

External root resorption is a frequent iatrogenic consequence of orthodontic treatment, particularly in the maxillary anterior teeth. Since resorption also occurs is a normal function of aging and since altered behaviors such as bruxism and chronic nailbiting accelerate resorption even in the absence of treatment, it was hypothesized that the long-term orthopedic forces of tongue thrusting leading to anterior open bites would also enhance the rates of clastic activity. In a series of 32 adolescents with open bites, the roots of permanent maxillary central incisors were significantly shorter and exhibited higher modal grades of periapical resorption than a matched series with deep bites before treatment. The open bite group also had less facial bony support for these teeth. Both series experienced discernible resorption during full-banded treatment but to comparable extents so that, after active treatment, the open bite series continued to possess significantly greater degrees of resorption. Consequently, the oral forces leading to apertognathia are themselves destructive of root integrity and merit early recognition and interception.

Adolescent↗
PubMed1993

Resorbed lateral incisors adjacent to impacted canines have normal crown size.

The importance of detecting maxillary canine impaction is that it may compromise dental health, particularly since a small but significant proportion of impacted canines is associated with the resorption of the roots of neighboring teeth. It has been shown that the existence of small and peg-shaped lateral incisors is highly correlated with maxillary canine palatal impaction. To date, however, it has not been established whether the root resorption that occurs has a similar correlation or a predilection for one or other types of lateral incisor crown structure. Accordingly, a group of patients with buccally or palatally impacted canines, in which root resorption of the lateral incisor could be diagnosed roentgenographically, was examined and compared with a group of cases with palatally impacted canines, none of which showed root resorption, which served as controls. The mesiodistal crown dimension of the lateral incisor in the experimental group was found to be normal in all patients except three (13%), which was significantly different from the distribution of lateral incisor size in the control group (p < 0.001). In the majority of the cases, aggressive root resorption of the lateral incisor root had occurred. We would speculate that in these cases, the normal-sized and early developing lateral incisor root obstructs the deviated eruption path of the canine and consequently stands a considerably greater chance of being damaged by resorption.

Adolescent↗
PubMed1993

The effect of facial growth, attrition, and age on the distance from the cementoenamel junction to the alveolar bone crest in the deciduous dentition.

The aim of this study was to describe the distances from the cementoenamel junction to the alveolar bone crest (CEJ-ABC) in the deciduous dentition and to relate them to age, facial, and tooth structure in 72 dry human skulls. Age correlated significantly with anterior face height (AntFH), the distance from condyle to gnathion (Co-Gn), lateral face height (LatFH), molar anatomic crown (MAC), and molar space (MS). The CEJ-ABC per skull and for the molars correlated with age, LatFH, AntFH, Co-Gn, MS, and MAC. The CEJ-ABC for the canines and the incisors correlated with age, LatFH, AntFH, and Co-GN. Multiple regression analysis on the effect of age, AntFH, LatFH, Co-Gn, and MAC on the CEJ-ABC distances indicated that they account for 36.3% of the CEJ-ABC distance per skull, 68.8% for the molars, 34.3% for the canines, and 44.2% for the incisors. The effect of each variable while controlling for the others indicated that age, LatFH, and MAC had a significant effect on the CEJ-ABC of the molars, whereas only age had a significant effect on the CEJ-ABC of the canines and incisors. These results indicate that there is a site-specific effect of facial growth and attrition on the CEJ-ABC distances in the deciduous dentition.

Age Factors↗
PubMed1993

The use of twins in dentofacial genetic research.

A literature review is given on the different results obtained with twin and family studies in relationship to the development and structure of the dentofacial complex. Recent advances in twin and family studies are mentioned. Attention is focused on functional components considered to be of primary importance in craniofacial growth.

Cleft Palate↗
PubMed2004

Tooth-width ratio discrepancies in a sample of Peruvian adolescents.

Previous studies have demonstrated different tooth-width ratio discrepancies in different populations. The objective of this study was to determine maxillary to mandibular tooth-size ratios in a Peruvian sample; 200 children were selected who had complete permanent dentition, without clinically visible dental caries or proximal restorations, and no previous or active orthodontic treatment. Their dental casts were measured to the nearest 0.1 mm with a sliding caliper and a Vernier scale. The Kolmogorov-Smirnov test, t test, and Pearson correlation test were used. No significant differences were found in anterior (P =.713) and total (P =.174) tooth-size sums according to sex. The anterior tooth-width ratios were 77.78% +/- 2.44% for females and 78.39% +/- 2.81% for males (P =.103). The total ratios were 90.79% +/- 1.71% for females and 91.33% +/- 2.07% for males (P =.048). For this reason, the combined male and female anterior total ratio was calculated (78.09 +/- 2.64%). There were clinically significant tooth-size discrepancies in almost one third of the sample. The 2-standard deviation range from the Bolton standard did not predict clinically significant anterior and total tooth-width ratio discrepancies.

Adolescent↗
PubMed2004

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.

Adolescent↗