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PubMed1996

Facial and dentoalveolar structure and the prediction of apical root shortening.

The purpose of the present study was to determine whether pretreatment measures of facial and dentoalveolar structure can be used to predict apical root shortening liability. Four hundred patients were randomly selected from the files of the Orthodontic Clinic at the Saint Louis University Health Sciences Center. Pretreatment and posttreatment periapical radiographs of maxillary central incisors and pretreatment lateral cephalometric radiographs were traced and measured. A large amount of apical root shortening was found in 2% of the sample. A relationship that was weak but highly significant statistically (r = 0.335; p < 0.01) was found between the amount of apical root shortening and the duration of active treatment. Several measures of dentoalveolar structure were also statistically significant. However, these measures did not account for enough of the observed variability to be clinically useful as a predictor. In the absence of a history of trauma or pretreatment signs of root resorption, pretreatment facial and dentoalveolar structure cannot be used to accurately identify persons who will experience a large amount of apical root shortening during the course of comprehensive orthodontic treatment with a fixed appliance.

Age Factors↗
PubMed1997

Orthodontic probability tables for black patients of African descent: mixed dentition analysis.

Mixed dentition space analyses form an essential part of orthodontic diagnostic procedures to determine the amount of space available for the accommodation of permanent teeth. The Moyers' probability tables for computing the sizes of unerupted canines and premolars were formulated at the University of Michigan from a sample consisting of northern European white subjects and are currently used worldwide. Because tooth sizes vary significantly between different population groups, it was the purpose of this study to construct relevant probability tables that would be more applicable to black subjects. Data were collected from a series of 100 randomly selected study models of black patients. The sample was equally subdivided by gender and all subjects had Angle Class I molar relationships with only minor malocclusions such as minor crowding, rotations, or diastemas. Two investigators independently measured the teeth on the study casts with a Vernier gauge that had sharpened calliper tips. Intraexaminer and interexaminer reliability was determined at 0.2 mm. All teeth to and including the first molars were measured. These data were then utilized in regression equations for both maxillary and mandibular arches, to enable the prediction of the mesiodistal widths of the canines and two premolars. The equations and predicted values were compared with those of the Moyers' probability tables, and significant differences (p <0.05) were found (except for the prediction of maxillary canines and premolars in females at the 85 and 95 percentile probability level). New probability tables for black subjects were formulated. It is envisaged that the proposed probability tables would be more accurate for black patients of African ancestry.

Adolescent↗
PubMed1997

A heritable component for external apical root resorption in patients treated orthodontically.

External apical root resorption (EARR) is a common and occasionally critical problem in orthodontic patients. Mechanical forces compress the periodontium, leading to localized resorption of cementum that exposes dentin to destruction by clastic activity. Factors controlling occurrence and extent of EARR are poorly understood, but there may be a familial (genetic) factor in susceptibility. A sample of full siblings (103 pairs) was studied, all of whom were treated with the same technique by one orthodontist. Crown and root lengths were measured on cephalograms and panoral films before and after treatment. Six roots were scored on each patient, and decrease in root length was the dependent variable. Generalized linear models were used to quantify within and among sibship variances while controlling for sex, age, and severity of malocclusion (FMA, ANB, AOBO, overjet, NAP) as covariates. Results showed significantly greater among-than within-sibship variances, meaning there is a substantive genetic factor in susceptibility to EARR. Heritability estimates were fairly high, averaging 70% for three roots, although low for the mandibular incisor, probably because of little variation. No evidence was found for a sex or age difference in susceptibility. Quantification of a transmissible component suggests it would be useful to search for the biochemical factors controlling the familial differences in susceptibility.

Adolescent↗
PubMed1997

The influence of the masticatory hypofunction on the craniofacial growth and development in rats.

In the present study, one masticatory hypofunction group and one normal function group were comprised of growing Wistar albino rats. The influence of the masticatory hypofunction on the growth and development of the craniofacial skeleton in rats was examined. The normal function group received the diet in the form of hard pellets, but the hypofunction group was fed powdered food. To avoid growth reduction because of nutritional deficiency, the animals were fed ad libitum, diet and water. At the end of the experimental period, the 90-day-old adult animals were killed and the direct anthropometric cranial, maxillary, and mandibular measurements were made on the skulls. The significant results can be summarized as follows: Total skull length, total anterior face height, lower anterior face height, ramus mandibula height, corpus mandibula height, premaxillary length, and maxillary width have been reduced but foramen incisivum width has been increased. This study showed that there is no significant effect of the masticatory hypofunction on the cranial growth and development in the growing rats, but that masticatory hypofunction affected the growth and development of the maxillofacial skeleton.

Animal Nutritional Physiological Phenomena↗
PubMed1997

The effect of premolar extractions on tooth-size discrepancy.

The purpose of this study is to investigate whether the extraction of four premolars as a requirement of orthodontic therapy is a factor in the creation of tooth size discrepancies, and to determine whether any tooth extraction combinations create more severe discrepancies. The study is carried out on the pretreatment dental casts of 50 patients with malocclusions. The dental casts were selected according to the main criteria. No tooth-size discrepancy between the mandibular and maxillary dental arches should exist before treatment. Pretreatment mesiodistal dimensions of mandibular and maxillary teeth were measured, recorded on a computer program, and subjected to Bolton's analysis. Hypothetical tooth extractions were performed on each patient by the following combinations: all first premolars, all second premolars, upper first and lower second premolars, and upper second and lower first premolars. The resultant measurements were again subjected to Bolton's analysis to see whether a tooth-size discrepancy had been created. The results were evaluated statistically by the use of paired samples t test. The difference between the pretreatment and postextraction Bolton values was found statistically significant for the first premolar extraction and insignificant for the others. The removal of the four first premolars created the most severe tooth-size discrepancy, whereas the extraction of all four second premolars created fewer discrepancies and the smallest range in the size of discrepancies. The results of this study indicate a new point of view to the question of which teeth to extract when evaluated for tooth size aspect only.

Bicuspid↗
PubMed1998

Interdental bone changes after orthodontic treatment: a 5-year longitudinal study.

Two groups of 20 adolescents, one treated and one untreated, were followed longitudinally for 5 years. The interdental alveolar bone level was estimated as the distance between the cementoenamel junction and the alveolar bone crest on bite-wing radiographs of the upper and lower premolars and molars on three occasions, the first at the start of treatment, the second after 2.8 years, and the third at the end of the 5-year study period. Between the first and second examination, the subjects in the treatment group were orthodontically treated in the upper arch with magnets and superelastic coils succeeded by straight-wire appliances in both arches. At the start of this study, no significant difference in alveolar bone level between treated and untreated groups was found. It was demonstrated that there was a small but significant decrease in interdental alveolar bone support ranging between 0.1 and 0.5 mm during the 5-year observation period both in the treated and untreated group. Neither group had any sites with clinically significant bone loss, i.e., a distance > 2 mm between the cementoenamel junction and the alveolar bone crest. The treated group exhibited a statistically significantly larger increase of cementoenamel junction and the alveolar bone crest distance at the mesial surfaces of the first and second maxillary molars than did the untreated group. This was thought to be a direct consequence of the orthodontic treatment, either as a result of band placement, tipping, or extrusive effects, or due to tooth morphology leading to plaque accumulation.

Adolescent↗
PubMed1998

Mixed dentition analysis for Asian-Americans.

One of the important aspects of diagnosis in the mixed dentition is the determination of the tooth size-arch length relationship. Such a determination is often made before eruption of the permanent canines and first and second premolars. The most commonly used prediction method of Tanaka and Johnston is based on data from a sample of children of Northern European descent. The accuracy of this method when applied to a different ethnic population is questionable. In this study, 201 dental plaster casts of Asia-Pacific-American subjects, all of whom were under the age of 21 years, were used. The actual measurements were compared with the predicted values derived from the Tanaka and Johnston equations and significant differences were found. The data illustrate the limitations of the Tanaka and Johnston method when applied to a sample population of other than European descent. From this data, two linear regression equations were developed for tooth size prediction in Asian-American children.

Adult↗
PubMed1999

Comparison of intermaxillary tooth size discrepancies among different malocclusion groups.

The purpose of this study was to determine whether there is a prevalent tendency for intermaxillary tooth size discrepancies among different malocclusion groups. This study consisted of 60 subjects who served as the normal occlusion group and 300 patients divided into 5 malocclusion groups (ie, Class I with bimaxillary protrusion, Class II Division 1, Class II Division 2, Class III, and Class III surgery). Tooth size measurements were performed on the models of normal occlusion and pretreatment models of patients by the Three Dimension Measuring Machine. Moreover, tooth size ratios, analyzed as described by Bolton and the Student t test showed no sexual dimorphism for these ratios in each of 6 groups, so the sexes were combined for each group. Then these ratios were compared among different malocclusion groups. The results showed no significant difference between subcategories of malocclusion, so these groups were combined. There were now 120 cases in each of 3 categories: Class I, Class II, and Class III. A significant difference was found for all the ratios between the groups, the ratios showing that Class III > Class I > Class II. It demonstrated that intermaxillary tooth size discrepancy may be one of the important factors in the cause of malocclusions, especially in Class II and Class III malocclusions. Thus this study proved the fact that Bolton analysis should be taken into consideration during orthodontic diagnosis and therapy.

Adolescent↗
PubMed1999

Effect of serial extraction alone on crowding: relationships between tooth width, arch length, and crowding.

In this study, we examined the effect of serial extraction alone on crowding. We also investigated the relationships between tooth width, arch length, and irregularity index. Maxillary dental casts from 32 subjects who had undergone only serial extraction were analyzed at 3 stages: before deciduous canines extraction, after first premolars extraction, and at the end of the observation period. The mean of the irregularity index decreased significantly as serial extraction proceeded and further decreased during the observation period. In cases where the width of the incisor was more than 2 standard deviations above the means for the control subjects, there was a significant correlation between tooth width of the lateral incisors and irregularity index before extraction as well as a significant correlation between the summation of tooth widths of the central and lateral incisors and irregularity index at that time. There was a significant negative correlation between arch length discrepancy and irregularity index before extraction and also a significant correlation between arch length discrepancy and correction of the irregularity index from before deciduous canines extraction to after first premolars extraction. These results suggest that tooth width and arch length discrepancy might preferentially affect the degree of anterior crowding in cases of severe crowding. There was no aggravation of the average crowding level during the observation period in the present study. The present study quantitatively suggested that serial extraction was useful for the purpose of correcting crowding in most cases.

Analysis of Variance↗
PubMed1999

Class II malocclusion correction: an American board of orthodontics case.

A Class II open bite malocclusion with a narrowed maxilla, an increased lower anterior facial height, and a tooth size discrepancy are presented. The malocclusion was treated nonextraction in 2 phases. The mixed dentition phase of treatment was maxillary molar uprighting followed by a bonded rapid palatal expander. The vertical dimension was managed with a vertical pull chincup. The full appliance phase included buildups of the maxillary lateral incisors and mechanics to control lower incisor position.

Cephalometry↗
PubMed1999

Effect of variation in tooth morphology and bracket position on first and third order correction with preadjusted appliances.

Major effort is put into the design of brackets to accomplish an optimal completion of orthodontic treatment with respect to 1st, 2nd, and 3rd order corrections. Because such brackets are standardized, the intraindividual variation of the teeth is not taken into consideration. The influence of vertical bracket displacement on 1st and 3rd order corrections was studied on the plaster models, including all teeth from central incisors to first molars, of 28 young persons. The facial contours were evaluated at the mesial, central, and the distal aspect of the bracket. The contours were calculated with the formula of a parabola, and the fit was found sufficient. Intertooth variation was extreme, the biggest curvature was found among the first mandibular molars. The variation was also marked between corresponding teeth. It can be concluded that the intraindividual variation in tooth morphology is larger than the variation between the different types of preadjusted appliances. Thus, if the straight wire approach should be followed, the bracket would have to be custom made. All the calculations were made with the precondition that full size wires were used. If this is not the case, the discussion concerning individual prescription is only of limited importance.

Adolescent↗
PubMed1999

A new accurate approach to the anterior ratio with clinical applications. Part 1: a computer program.

The arcs of the six anterior maxillary and mandibular teeth have recently been described mathematically by the hyperbolic cosine function with a maxillary correlation coefficient (r ) of 0.885 and a mandibular correlation coefficient (r ) of 0.951. Because the geometric relationships of the anterior dental arcs are known when the occlusion is Class I, a computer program has been developed for use in clinical practice. Rapid forecasting of the interrelationships between the maxillary and mandibular arc depths (related to overjet) with variations in the mesiodistal sums of the six maxillary and mandibular anterior teeth for various intercanine widths is now possible with ease and accuracy (+/- 0.1 mm). Clinical applications are illustrated.

Adult↗
PubMed1999

A new accurate approach to the anterior ratio with clinical applications. Part II: a nomographic solution.

Evaluating the anterior ratio is useful to forecast potential tooth mass discrepancies and related overjet or underjet. Because the arcs of the six anterior teeth have recently been described by the mathematical hyperbolic cosine function, it has permitted the design of a nomograph for ready use in clinical practice. A nomograph is a simple chart on which one can draw a straight line that will intersect three scales representing variables that satisfy an equation. A clinician may now evaluate and forecast the effects on overjet with purposeful alterations in the sums of the six maxillary and mandibular anterior tooth masses for various cross-arch canine widths with an accuracy of +/-0.5 mm.

Adult↗
PubMed1999

Changes in root length from early to mid-adulthood: resorption or apposition?

A significant number of adults are seeking orthodontic treatment, therefore, it is important to determine the normal changes in root length (resorption or apposition) that occur at this stage of maturation, specifically between early and mid-adulthood. The purpose of the study was to determine on a longitudinal basis the changes in root length between 25 and 45 years of age in a normative untreated population. Two sets of complete mouth surveys were available at early and mid-adulthood, on a total of 26 subjects (12 males and 14 females). Each set consisted of at least 18 periapical radiographs. On each set of radiographs, the roots of 28 teeth were measured including incisors, canines, premolars, and first and second molars, in both the maxillary and mandibular arches. Root length was measured as the perpendicular from the root apex to a line connecting the mesial and distal points of the cementoenamel junction of each tooth. A total of 1456 teeth (1664 roots) were measured; 672 teeth in males and 784 teeth in females. Allowable intraexaminer and interexaminer measurement variability was predetermined at 0.5 mm. Paired and Student t tests were used to determine: (1) whether significant changes occurred with age; (2) whether there were differences between males and females for the incisors, canines, premolars, and molars; and (3) whether there were differences between the right and left sides. Statistical significance was predetermined at P </=.05. The present findings indicated that there were no significant changes in root length for all tooth types evaluated between 25 and 45 years of age, in both males and females. These findings are important for the orthodontist to recognize because they provide some assurance that there is no systematic shortening of root length between early and mid-adulthood.

Adolescent↗
PubMed2003

The evolution of tribospheny and the antiquity of mammalian clades.

The evolution of tribosphenic molars is a key innovation in the history of Mammalia. Tribospheny allows for both shearing and grinding occlusal functions. Marsupials and placentals are advanced tribosphenic mammals (i.e., Theria) that show additional modifications of the tribosphenic dentition including loss of the distal metacristid and development of double-rank postvallum/prevallid shear. The recent discovery of Eomaia [Nature 416 (2002) 816], regarded as the oldest eutherian mammal, implies that the marsupial-placental split is at least 125 million years old. The conventional scenario for the evolution of tribosphenic and therian mammals hypothesizes that each group evolved once, in the northern hemisphere, and is based on a predominantly Laurasian fossil record. With the recent discovery of the oldest tribosphenic mammal (Ambondro) from the Mesozoic of Gondwana, Flynn et al. [Nature 401 (1999) 57] suggested that tribospheny evolved in Gondwana rather than in Laurasia. Luo et al. [Nature 409 (2001) 53; Acta Palaeontol. Pol. 47 (2002) 1] argued for independent origins of tribospheny in northern (Boreosphenida) and southern (Australosphenida) hemisphere clades, with the latter including Ambondro, ausktribosphenids, and monotremes. Here, we present cladistic evidence for a single origin of tribosphenic molars. Further, Ambondro may be a stem eutherian, making the split between marsupials and placentals at least 167 m.y. old. To test this hypothesis, we used the relaxed molecular clock approach of Thorne/Kishino with amino acid data sets for BRCA1 [J. Mammal. Evol. 8 (2001) 239] and the IGF2 receptor [Mammal. Genome 12 (2001) 513]. Point estimates for the marsupial-placental split were 182-190 million years based on BRCA1 and 185-187 million years based on the IGF2 receptor. These estimates are fully compatible with the results of our cladistic analyses.

Animals↗
PubMed2003

Endodontic measurement accuracy and perceived radiograph quality: effects of film speed and density.

OBJECTIVES: This study sought to determine the effects of direct exposure x-ray film speed and background density on observer assessment of endodontic working lengths and on perceived radiographic image quality. STUDY DESIGN: A human cadaver maxilla section with surrounding soft tissues was used for the study. The canal length to the radiographic apex was determined on 4 canals in maxillary posterior teeth by using Trophy RVG images and adjusting the position of a No. 15 file in each canal until the file tip coincided with the radiographic apex in images made at 3 different vertical angulations. The files were measured with a micrometer from the file stop to the file tip to obtain the length to the radiographic apex. Then No. 10 files were placed in the 4 canals at varying lengths short of this previously determined length, and 5 observers assessed the distance from the file tip to the radiographic apex on radiographs made with Kodak D-, E-, and F-speed and Flow D- and E-speed direct exposure x-ray films that were exposed to produce background densities of 1.5, 2.0, and 3.0. Subjective appraisal of radiographic quality was also assessed. RESULTS: Analysis of variance and Tukey honestly significantly different post-hoc analysis results concerning measurement errors made with each film type revealed significantly less error for Kodak Ektaspeed Plus (E-speed) intraoral x-ray film than for Kodak InSight (F-speed) and Flow E; however, no difference was detected among Kodak Ektaspeed Plus (E-speed), Kodak Ultra-Speed (D-speed), and Flow D. Films with a background optical density of 3.0 received 98% favorable ratings; radiographs with a background optical density of 2.0 received 77% favorable ratings; and those with background optical density of 1.5 received only 18% favorable ratings at the 95% confidence level. Flow D film received the most favorable ratings, but there was no statistically significant difference among other film types at the 95% confidence level. CONCLUSIONS: Underexposed radiographs are perceived as inferior to slightly overexposed radiographs for endodontic file length assessment regardless of the film speed used. Current Flow and Kodak E-speed and F-speed radiographs appear to be as accurate as other accepted radiographs used in determining endodontic working lengths. Image background density should be kept constant when making comparisons among x-ray films.

Absorptiometry, Photon↗
PubMed2004

Biometric and magnetic resonance imaging assessment of dentofacial abnormalities in a case of Klippel-Trénaunay-Weber syndrome.

Klippel-Trénaunay-Weber syndrome is characterized by cutaneous hemangioma, arteriovenous fistulas or varicosities (or both), and unilateral hypertrophy of hard and soft tissues with different localization. Klippel-Trénaunay-Weber syndrome represents a syndrome of interest for those in the fields of oral and maxillofacial radiology and pathology because of the high incidence of compromise of the orofacial area in affected patients. The patient reported here presents with all of the 3 characteristic signs of the syndrome. The somatic and facial hypertrophy is contralateral to angiomata. As revealed through the use of magnetic resonance imaging, the primary component of facial hypertrophy is adipic subcutaneous tissue. Statistical analysis of the dental dimensions revealed that teeth on the hypertrophic side are significantly larger than normal.

Adipose Tissue↗