Does anchorage loss differ with 0.018-inch and 0.022-inch slot bracket systems?

OBJECTIVES

To compare maxillary first molar anchorage loss between 0.018-inch and 0.022-inch slot fixed appliance systems.

MATERIALS AND METHODS

Patients requiring bilateral maxillary premolar extractions (n = 74) within a randomized clinical trial comparing the effectiveness of 0.018-inch and 0.022-inch slot MBT bracket systems (3M-Unitek, Monrovia, Calif) were included. Three-dimensional pre- and posttreatment digital models were landmarked and measured (R700 scanner and OrthoAnalyzer software, 3Shape, Copenhagen, Denmark). Anteroposterior position of the first molars was measured using the third medial rugae point as a reference. Anchorage loss (AL) represented the subtraction of the posttreatment distance from the pretreatment distance for both anchorage loss right (ALR) and left (ALL) sides. The values were then compared using a two-way analysis of variance.

RESULTS

There were 41 and 33 cases for the 0.018-inch and 0.022-inch bracket slot systems, respectively. The baseline characteristics were similar between groups, except for the presence or absence of anchorage devices (P = .050). For the total sample: 0.018-inch ALR = 3.86 mm, ALL = 3.30 mm and 0.022-inch ALR = 3.73 mm, ALL = 3.47 mm (P = .970). There was also no significant difference between the 0.018-inch and 0.022-inch groups when subjects with anchorage devices were excluded (P = .383).

CONCLUSIONS

Bracket slot size does not influence maxillary molar anchorage loss during orthodontic treatment.

Asymmetric molars' mesial rotation and mesialization in unilateral functional posterior crossbite and implications for interceptive treatment in the mixed dentition

Introduction

Symmetric transverse expansion is the main outcome of the early treatment in subjects with unilateral functional posterior crossbite. The aim of this study was to analyse mesial rotation and mesialization of upper first molars as sagittal parameters to be corrected in the treatment of these patients during the mixed dentition.

Methods

Digital dental cast measurements (rotation and mesialization) were performed in a sample of 48 subjects with unilateral posterior crossbite (UPXB; 19 males and 29 females, mean age 10.2 ± 1.2 years) and in a control group of 35 subjects with normal Class I occlusion (17 males and 18 females, mean age 9.9 ± 1.3 years). An independent sample t-test, the Mann-Whitney test, Fisher's exact test, and Pearson correlation were used for statistical comparison.

Results

The amount of upper molar rotation was significantly greater in the experimental group when compared with the control group. A clinically significant 'upper molar rotation' (UMR) was present in 66.7 per cent of the subjects with UPXB versus 5.7 per cent of the control group. The UMR group presented also a significant mesialization of upper first molars when compared with the control group. In the experimental group, there was a significant difference between rotation and mesialization in the right and left side and a correlation has been found between these two variables and the amount of Class II molar relationship at the crossbite side.

Limitations

This is an epidemiological case-control study and the discussed effects of an early correction of the asymmetric upper molars' migration are only speculations based on an association relationship.

Conclusions

The findings of this study show an asymmetric upper first molars' migration (rotation and mesialization) in unilateral functional posterior crossbite versus a control group. An early evaluation and correction of the molars' migration during the mixed dentition should be considered in order to obtain a correct inter-occlusal sagittal molar relationship, space for an adequate eruption of permanent teeth, and perhaps reduce the need of a following fixed appliance treatment in the permanent dentition.

Measuring molar movement: A reliable technique

A technique of accurately assessing left and right maxillary molar movement is described, using superimposition of digital study models. This method has distinct advantages over the traditional method of measuring tooth movement using cephalometric radiographs.

Registration of serial maxillary models via the weighted rugae superimposition method

OBJECTIVES

We introduce a weighted method for superimposition of serial digital maxillary models based on the variable stability of rugae points.

SETTING AND SAMPLE POPULATION

Plaster maxillary models of 24 randomly selected 12-year-olds as well as their models at the age of 14 were obtained and scanned using a benchtop structured-light 3D scanner.

METHODS

The models were registered twice, once via the unweighted and again via the proposed weighted rugae superimposition method based on 12 rugae landmarks. For each superimposition, distances between the corresponding rugae points were measured and compared with reported displacements of rugae points in literature.

RESULTS

The unweighted superimposition produced no meaningful differences in terms of total displacements of registration landmarks, whereas the weighted method recognized the medial points of the third ruga as the most stable landmarks. Results of the weighted method also demonstrated statistically significant smaller changes for medial rugae points in almost every dimension compared to the lateral rugae points. These results comply with the growth patterns of maxilla and rugae point displacements reported in similar studies.

CONCLUSION

Considering the variable stability of rugae points during growth, the weighted rugae superimposition method results in more promising registrations on serial models. This method prioritizes registration landmarks based on clinical criteria of choice and is suitable for analysis of other structures such as tooth movements.

A method for mandibular dental arch superimposition using 3D cone beam CT and orthodontic 3D digital model

OBJECTIVE

The purpose of this study was to develop superimposition method on the lower arch using 3-dimensional (3D) cone beam computed tomography (CBCT) images and orthodontic 3D digital modeling.

METHODS

Integrated 3D CBCT images were acquired by substituting the dental portion of 3D CBCT images with precise dental images of an orthodontic 3D digital model. Images were acquired before and after treatment. For the superimposition, 2 superimposition methods were designed. Surface superimposition was based on the basal bone structure of the mandible by surface-to-surface matching (best-fit method). Plane superimposition was based on anatomical structures (mental and lingual foramen). For the evaluation, 10 landmarks including teeth and anatomic structures were assigned, and 30 times of superimpositions and measurements were performed to determine the more reproducible and reliable method.

RESULTS

All landmarks demonstrated that the surface superimposition method produced relatively more consistent coordinate values. The mean distances of measured landmarks values from the means were statistically significantly lower with the surface superimpositions method.

CONCLUSIONS

Between the 2 superimposition methods designed for the evaluation of 3D changes in the lower arch, surface superimposition was the simpler, more reproducible, reliable method.

Accuracy and reliability of palatal superimposition of three-dimensional digital models

OBJECTIVE

To evaluate the accuracy of the superimposition of three-dimensional (3D) digital models using the palatal surface as a reference for measuring tooth movements.

MATERIALS AND METHODS

Maxillary plaster models were selected from 20 patients. The right and left canines, premolars, and molars were individually cut underneath the gingival margins and set up in wax (plaster model 1 = PM1). The PM1s were scanned to create 3D digital models (digital model 1 = DM1). Teeth on the PM1s were randomly moved (plaster model 2 = PM2) and subsequently scanned to produce another set of 3D digital models (digital model 2 = DM2). DM1s and DM2s were superimposed using the palatal area as reference via surface-to-surface matching software, and the changes in tooth movement were calculated. In the plaster models, the tooth movements were directly measured using the Reference Measurement Instrument. A paired t-test and a correlation analysis were performed to determine whether the two measurement methods differed significantly.

RESULTS

The means of the anteroposterior (x-axis), transverse (y-axis), and vertical (z-axis) tooth movements of the plaster models and the digital models did not differ significantly, and very high correlations were found between the plaster models and the digital models.

CONCLUSION

From a technical point of view, the superimposition of 3D digital models using the palatal surface provides accurate and reliable measurements, but it remains to be investigated how stable the palatal surface is longitudinally after growth and/or orthopedic treatment take place.

A Novel Method for the Assessment of Three-Dimensional Tooth Movement during Orthodontic Treatment

Objective: To (1) evaluate the stability of palatal rugae as landmarks for superimposition of dental casts and (2) establish a three-dimensional superimposition method of maxillary dental casts for analyzing orthodontic tooth movement.

Materials and Methods: The sample consisted of dental casts obtained from 10 patients treated with extraction of bilateral maxillary first premolars and placement of three palatal miniscrews as anchorage for retraction of the anterior teeth. Dental casts were measured by means of laser surface scanning system, and three-dimensional images were reconstructed. Serial dental casts were superimposed on the three miniscrews as registration landmarks (miniscrew-superimposition method), and the displacement of each palatal ruga point during the closure of extraction spaces was measured. Displacement of the central incisors was measured by the miniscrew-superimposition method and the proposed superimposition technique (ruga-palate-superimposition method). Correlation analysis and paired t-tests were performed to determine whether a significant difference existed between the measurements of the two superimposition methods.

Results: The medial points of the third palatal rugae and the shape of the palatal vault were stable throughout the treatment. The displacement of the central incisors measured using the ruga-palate-superimposition method showed no significant difference with that measured using the miniscrew-superimposition method.

Conclusion: The maxillary dental casts can be reliably superimposed on the medial points of the third palatal rugae and the palatal vault as reference landmarks.

Dental arch widths of Southern Chinese

OBJECTIVE

To investigate the dental arch width of the Southern Chinese across buccal cusps, central fossae, or lingual cusps and compare these values with study findings in different populations and using different definitions.

MATERIALS AND METHODS

The dental arch dimensions of study casts of an unselected sample from a 12-year-old Hong Kong Oral Health Survey of 12-year-old children (n = 358; 210 boys and 148 girls) were measured.

RESULTS

When compared with Caucasians, the Southern Chinese were characterized by a wider dental arch width. However, variations were great. All maxillary and mandibular male arch widths were significantly larger than female arch widths, except at the incisor regions.

CONCLUSION

This study yielded a database about dental arch widths by which different studies on these widths can be compared.

Palatine rugae and their significance in clinical dentistry: a review of the literature

BACKGROUND

The palatine rugae have interested dentists not only because of their typical pattern of orientation but also because of their usefulness as a reference landmark in various dental treatment modalities. The pattern of orientation is formed by the 12th to 14th week of prenatal life and remains stable until the oral mucosa degenerates after death. The palatine rugae possess unique characteristics that could be used in circumstances in which it is difficult to identify a dead person according to fingerprints or dental records.

TYPES OF STUDIES REVIEWED

The authors reviewed the literature by using key words regarding the anatomy, development, classification, clinical significance and forensic aspects of palatine rugae.

CONCLUSION AND CLINICAL IMPLICATIONS

Palatine rugae are permanent and unique to each person, and clinicians and scientists can use them to establish identity through discrimination. If particular rugae patterns could be established for different ethnic groups, they would assist the forensic odontologist in the identification of a person. Because they are a stable landmark, the palatine rugae also can play a significant role in clinical dentistry.

Three-dimensional computer-assisted study model analysis of long-term oral-appliance wear. Part 1: Methodology

INTRODUCTION

The aim of this study was to test a 3-dimensional (3D) computer-assisted dental model analysis system that uses selected landmarks to describe tooth movement during treatment with an oral appliance.

METHODS

Dental casts of 70 patients diagnosed with obstructive sleep apnea and treated with oral appliances for a mean time of 7 years 4 months were evaluated with a 3D digitizer (MicroScribe-3DX, Immersion, San Jose, Calif) compatible with the Rhinoceros modeling program (version 3.0 SR3c, Robert McNeel & Associates, Seattle, Wash). A total of 86 landmarks on each model were digitized, and 156 variables were calculated as either the linear distance between points or the distance from points to reference planes. Four study models for each patient (maxillary baseline, mandibular baseline, maxillary follow-up, and mandibular follow-up) were superimposed on 2 sets of reference points: 3 points on the palatal rugae for maxillary model superimposition, and 3 occlusal contact points for the same set of maxillary and mandibular model superimpositions. The patients were divided into 3 evaluation groups by 5 orthodontists based on the changes between baseline and follow-up study models.

RESULTS

Digital dental measurements could be analyzed, including arch width, arch length, curve of Spee, overbite, overjet, and the anteroposterior relationship between the maxillary and mandibular arches. A method error within 0.23 mm in 14 selected variables was found for the 3D system. The statistical differences in the 3 evaluation groups verified the division criteria determined by the orthodontists.

CONCLUSIONS

The system provides a method to record 3D measurements of study models that permits computer visualization of tooth position and movement from various perspectives.

Morphologic changes of the palate after rapid maxillary expansion: a 3-dimensional computed tomography evaluation

INTRODUCTION

The purpose of this retrospective study was to estimate the area change of the palate after rapid maxillary expansion (RME) in the early mixed dentition stage by using a 3-dimensional (3D) helical computed tomography (CT) scanning technique. In addition, linear changes in the maxillary arch were evaluated.

METHODS

The treated sample consisted of 43 children (mean age, 9 years 1 month) treated with a bonded RME appliance. The untreated control group consisted of 7 children (mean age, 9 years 3 months). Pretreatment and posttreatment dental casts were evaluated by using 3D helical CT scanning procedures. The Student t test was used to compare the linear, area, and angular differences between the treatment times.

RESULTS

RME produced clinically significant increases in interdental widths across the canines, the deciduous first molars, and the permanent first molars in the maxillary arch. Significant increases in cross-sectional area were observed across the permanent first molars (15.3 mm(2)). There was marked variability in the buccal tipping of the permanent first molars.

CONCLUSIONS

Three-dimensional helical CT scanning is an accurate and cost-effective method of assessing dental cast morphologic changes. It can also provide fast and accurate data acquisition and subsequent analysis.

Stability of upper incisor inclination changes in Class II division 2 patients

The aim of this study was to evaluate the changes in incisor inclination following orthodontic treatment in Class II division 2 patients, and to assess the long-term stability after retention. Dental casts and cephalograms of 61 Class II division 2 patients (31 males and 30 females, mean age 13.4 years) with a closed lip seal were available before (T1), at the end of treatment (T2), and 3.5 years (mean) post-treatment (T3). A method of measuring upper incisor inclination on dental casts was developed for the purpose of the investigation. This involved placing markers on the study casts and then taking radiographs which were measured to establish the upper incisor inclination. Statistical analysis of the data included the calculation of mean values, standard deviation, standard errors, and ranges for each variable. Spearman ranked correlation coefficients were computed for selected model variables and scattergrams plotted. To investigate the influence of the chosen retention therapy, a Mann-Whitney U-test was used. The mean change in incisor inclination during orthodontic treatment was 15.2 degrees. There was a mean relapse of 2.2 degrees between T2 and T3, but this was not considered clinically relevant. The amount of relapse was independent of the type of the retention appliance (Hawley type retainer or lingual retainer). The relationship between long-term stability of the incisor inclination and between the lip line relative to the upper incisors was also investigated, based on cephalometric data. A mean decrease in lip line height of 0.6 mm was seen at T2 and, although the observed change was statistically significant, it would not be clinically relevant.

Palatal development of preterm and low birthweight infants compared to term infants - What do we know? Part 1: The palate of the term newborn

Background

The evidence on prematurity as 'a priori' a risk for palatal disturbances that increase the need for orthodontic or orthognathic treatment is still weak. Further well-designed clinical studies are needed. The objective of this review is to provide a fundamental analysis of methodologies, confounding factors, and outcomes of studies on palatal development. One focus of this review is the analysis of studies on the palate of the term newborn, since knowing what is 'normal' is a precondition of being able to assess abnormalities.

Methods

A search profile based on Cochrane search strategies applied to 10 medical databases was used to identify existing studies. Articles, mainly those published before 1960, were identified from hand searches in textbooks, encyclopedias, reference lists and bibliographies. Sources in English, German, and French of more than a century were included. Data for term infants were recalculated if particular information about weight, length, or maturity was given. The extracted values, especially those from non-English paper sources, were provided unfiltered for comparison.

Results

The search strategy yielded 182 articles, of which 155 articles remained for final analysis. Morphology of the term newborn's palate was of great interest in the first half of the last century. Two general methodologies were used to assess palatal morphology: visual and metrical descriptions. Most of the studies on term infants suffer from lack of reliability tests. The groove system was recognized as the distinctive feature of the infant palate. The shape of the palate of the term infant may vary considerably, both visually and metrically. Gender, race, mode of delivery, and nasal deformities were identified as causes contributing to altered palatal morphology. Until today, anatomical features of the newborn's palate are subject to a non-uniform nomenclature.

Conclusion

Today's knowledge of a newborn's 'normal' palatal morphology is based on non-standardized and limited methodologies for measuring a three-dimensional shape. This shortcoming increases bias and is the reason for contradictory research results, especially if pathologic conditions like syndromes or prematurity are involved. Adequate measurement techniques are needed and the 'normal palatal morphology' should be defined prior to new clinical studies on palatal development.

Development of the palatal size in Pan troglodytes, hominids and Homo sapiens

As the hard palate plays an important role in speech production it was the aim of this study whether similarities or dissimilarities in palatal size may allow conclusions about the ability to produce speech in the extant investigated species. The palatal size of Pan troglodytes, Homo sapiens, Australopithecus afarensis, Australopithecus africanus, Australopithecus robustus, Australopithecus boisei, Homo erectus, Homo neanderthalensis and Cro-Magnon has been investigated using euclidian distance matrix analysis (EDMA) and thin-plate-spline analysis. The results show that the palatal size of all australopithecine specimens and H. erectus is very similar to that of P toglodytes, whereas the palatal size of H. neanderthalensis more closely resembles that of H. sapiens. Postnatal development of palatal size in P troglodytes is different from that of H. sapiens. In P troglodytes not only the size of the palate changes but also the form. In H. sapiens there is little change in form, but a continuos uniform growth from infantile to adult specimens. From the results we conclude that in all australopithecine samples which have been investigated, the palatal size is similar to that of P troglodytes. Therefore, it is unlikely that austraopithecine individuals were capable of producing vowels and consonants. The palatal size of H. neandethalensis and Cro-Magnon is similar to that of H. sapiens which may indicate the possibility that they were capable of speech production.

Does the transition temperature of Cu-NiTi archwires affect the amount of tooth movement during alignment?

OBJECTIVES

To examine whether the transition temperature of Cu-NiTi archwires has an effect on the tooth movement during the alignment phase of orthodontic treatment.

DESIGN

'Split mouth' design in randomly selected patients.

SETTING AND SAMPLE POPULATION

The Department of Orthodontics, School of Dentistry, University of Aarhus. Fifteen randomly selected patients with identical level of irregularity in the alignment phase of their treatment. Experiment Variable - Specially manufactured Cu-NiTi archwires for the upper arch were inserted. These consisted of two separate halves, each with its own transition temperature, respectively 27 degrees and 40 degrees C, and clamped together in the middle.

OUTCOME MEASURE

The tooth movement, expressed as two translations and a rotation, in the occlusal plane was measured from the patients' intraoral photographs taken upon insertion of the archwires and again after 1 month.

RESULTS

Tooth movements tended to be larger on the 40 degrees C-side, however only in case of the total translation of the premolars was this difference significant. In general, patients had not noticed any difference between the two sides of the archwire, although one patient stated the 27 degrees C-side to be more comfortable as the 40 degrees C-side had bothered her when drinking hot beverages.

CONCLUSION

The transition temperature of Cu-NiTi archwires has indeed an effect on the amount of tooth movement during alignment. However, the differences are so small though that it is the question whether they can be noticed clinically. The study corroborates the trend towards the use of lower forces within orthodontics.

A 3-dimensional analysis of molar movement during headgear treatment

Superimposition of serial cephalograms provides a limited description of tooth movement that could be complemented by data obtained from serial dental casts. The aim of this study was to develop a mathematical method for superimposing 3-dimensional data obtained from selected landmarks on longitudinally collected dental casts to describe maxillary first molar movement during headgear treatment. The material consisted of dental casts taken bimonthly from 36 children whose Class II Division 1 malocclusion was treated with straight-pull headgear during a 24-month period. Control data were collected from initial and final models of 38 subjects with a similar malocclusion who were not treated during a 24-month observation period. Spatial data from each subject's initial model were oriented similarly in an anatomically derived coordinate system, and a best-fit superimposition of palatal rugae landmarks from subsequent models allowed the measurement of molar movement. On average, headgear treatment resulted in distal movement of the molars, and the fitted net difference between treated and control subjects was 3.00 mm (SE, 0.37 mm; P < .001). Also, the headgear caused significantly more molar extrusion (0.56 mm; SE, 0.20 mm; P < .006) and buccal expansion (0.58 mm; SE, 0.17 mm; P < .001) on average than in the control group. Poor reliability of the method for measuring molar rotations indicated that they could not be determined accurately. Longitudinal description of molar movement for each subject revealed great individual variability in the amount and pattern of tooth movement. Several reasons could account for the wide range of individual variation and warrant exploration.

The use of palatal rugae for the assessment of anteroposterior tooth movements

Currently, cephalometric superimpositions are the accepted means for the assessment of orthodontic tooth movement. The present investigation evaluated the use of palatal rugae as reference points for the measurement of tooth movement, in a manner comparable with cephalometric superimpositions. The sample consisted of pretreatment and posttreatment maxillary study models and lateral cephalometric radiographs from 33 patients who had received orthodontic treatment that involved the extraction of the maxillary first permanent premolars. The mean age at the start of treatment was 13 years 11 months, and the average time between records was 35 months. The anteroposterior movement of the maxillary first molars and central incisors was evaluated with the use of 2 cephalometric variables and 12 study model variables that were reduced to 6 by the combining of the left and right sides. No statistical differences were found between the mean molar movement that was measured cephalometrically and the mean molar movement that was relative to the medial and lateral ends of the first and second palatal rugae or relative to the medial end of the third palatal ruga. Also, no statistical differences were found between the mean incisor movement that was measured cephalometrically and the mean incisor movement that was relative to the medial and lateral end of the third palatal ruga. These findings suggest that ruga landmarks can be used as reliably as cephalometric superimpositions to assess anteroposterior molar movements.

Palatal asymmetry in cleft palate subjects

In subjects with different types of cleft palate, palatal shape and symmetry were evaluated utilizing the moiré contourography technique. The sample consisted of 95 subjects with cleft palate and 68 controls. The differences between cleft and control subjects in the transverse and anteroposterior location of the highest point of the palate, palatal axis angle, and the palatal index were assessed by analysis of variance. Effects of cleft type, gender, developmental stage of the dentition, missing teeth, and eight skeletal and pharyngeal cephalometric variables on palatal shape and symmetry were assessed using multiple-regression analyses. In comparison with the noncleft individuals, the cleft palate subjects showed parallel but clearly more remarkable asymmetry in palatal shape and position of the first maxillary molars. The anteroposterior location of the deepest point in the palate was more posterior, and the palate was relatively shallower. The severity of the cleft type affected both the anteroposterior and transverse position of the highest point in palatal morphology.

Changes concurrent with orthodontic treatment when maxillary expansion is a primary goal

A retrospective study of dental and maxillary skeletal changes occurring during a period of orthodontic treatment was made from pretreatment and posttreatment dental casts. Sixty maxillary expansion cases were examined. Thirty cases had maxillary expansion accomplished with a fixed rapid palatal expander and 30 were expanded with a quadhelix appliance. All cases were finished with full fixed edgewise appliances. Multiple linear regression analyses were completed for both groups with upper molar width change as the criterion and age, tipping of the upper molars, palatal width change and maxillary tipping as the predictors. All predictors were included in the analysis for the quadhelix group with a significant R2 value of 0.55. For the rapid expansion group, a significant R2 value of 0.33 was achieved with the inclusion of palatal width change and age only. The other variables did not meet the level of significance for entry into the model. Although both groups demonstrated similar amounts of maxillary dental expansion, the rapid expansion group demonstrated greater average skeletal expansion. In addition, there was a significant relationship between skeletal and dental expansion for the rapid expansion group, but not the quadhelix group. Palatal depth increased more on average in the rapid expansion group suggesting that there was greater dental eruption in that group. Expansion across the mandibular molars was greater on average in the quadhelix group. There was no difference in the degree of upper molar rotation or final upper and lower arch forms between the two groups.

A comparative study of palatal height in a Saudi and Egyptian population

The present study constitutes an attempt to compare normal traits for palatal height and width at different stages of dentition development of two ethnic groups of the Middle East. The observations were obtained from 346 randomly selected normal subjects, 188 Saudis and 158 Egyptians. The stone models were divided into three categories in both groups--primary, mixed and permanent dentitions. Palatal index values were calculated at two levels. Vernier calipers were used to measure the palatal width. Palatal depth was measured by profile Gauge by Vitrex. The results of this study demonstrate no significant difference between ethnic groups at levels 1 and 2 in relation to the palatal height, width and index. For both groups, palatal index increased significantly from the primary to mixed and permanent dentition at level 1. At level 2, palatal index and height showed decreases in measurement in the mixed dentition compared with the primary and the permanent dentitions. Subjective assessment of the palatal height correlated with palatal index. The casts were then labelled so that the shallow group had the smallest palatal index followed by the normal and the deep group had the largest palatal index. The results contribute to the information available on the development of palatal shape within two Middle Eastern populations. Knowledge of the normal range in shape can act as a baseline for studies of certain oral developmental abnormalities.

The development of a new method of cephalometric and study cast mensuration with a computer controlled, video image capture system. Part II: Study cast mensuration

A computerized system for mensuration of dental casts, developed at the Royal Berkshire Hospital in Reading was tested against a conventional manual method and a computer controlled reflex microscope. Systematic errors, calibration, and handling aspects are discussed. Results showed that the computerized system provided data which while statistically different, were clinically comparable with the same measurements carried out using conventional manual or digitizing techniques. The results indicated that future research is required with respect to object illumination for all indirect techniques.

Palatal measurements of prematurely born, very low birth weight infants: comparison of three methods

To enable investigation of palatal changes in infants who are prematurely born, it is necessary to first establish a reliable method of measurement of these tiny edentulous palates. This study compared the Olivetti-Inspector machine, Vernier calipers, and stereophotogrammetry for this purpose. Measurements were taken of 12 palatal casts of four infants at prescribed time intervals during the neonatal period. In each of the three methods, measurements were recorded as variables generated in the X and Z axes of the Cartesian scale in relation to three specified points along the Y axis. The results revealed that all methods were comparable, but the Vernier calipers differed significantly from the other two methods in height measurements, (p < 0.001). It was also found that both the Olivetti-Inspector machine and the Vernier calipers consistently underestimated the width, compared with Olivetti-Inspector machine, (p < 0.05). Stereophotogrammetry was found to be the most consistent method of measuring the configuration of preterm infant palates.

The holodent system, a new technique for measurement and storage of dental casts

A system for producing holograms and for three-dimensional measuring on holograms is described. The precision of the system was evaluated when three-dimensional measurements were made on (1) a holographic image superimposed on the corresponding object and (2) two superimposed holographic images of the same object. When a metal test object with sharp well-defined contours, easy to reorientate was used, the precision was 0.02 to 0.11 mm for x, y, and z coordinates (transverse, longitudinal, and vertical planes). When dental casts that have less distinct contours were used, precision was reduced to 0.03 to 0.43 mm. Precision was high for the x and y coordinates and satisfactory for the z coordinate. The system has a precision that is equal to that of previously reported methods and may be well-suited for studies of dental positional changes in longitudinal materials of study models. Holograms of dental casts may solve storage problems by replacing space consuming plaster models.

Retrospective analysis of 135 secondary alveolar cleft grafts using iliac or calvarial bone

This retrospective study summarizes experience with 135 secondary alveolar cleft bone graft procedures over 8 years. The overall success rate was 83.7%. The group of patients (n = 108) that had particulate cancellous bone and marrow obtained from the iliac crest as donor bone had an 89.8% success rate. The group (n = 27) that had calvarial bone as the donor material had a success rate of only 63%. It is felt that inferior results with calvarial bone are probably related to the procurement technique. In both the iliac crest and calvarial groups, there was a trend toward declining success rates with advancing age of the patient. Morbidity associated with these procedures, consistent with other reported series, was low.

[3-Dimensional model analysis of normal and dysgnathic bites using a coordinate measurement technic]

In this article results of three-dimensional measurements are compared for normal occlusions, protrusion cases and class III patients. The results were divided into dental measurements values, values related to the jaws and values of the intermaxillary comparison. They were obtained with the help of a three-coordinate measurement device and a computer. The author takes especially the values of intermaxillary comparison into consideration as a new basis for orthodontic diagnosis from cast measurements.

A longitudinal study of anteroposterior growth changes in the palatine rugae

Palatine rugae have been used as internal dental cast reference points for quantification of tooth migration. Some, but not all, investigators have reported the medial rugal region to be stable or to show predictable change. The purpose of this study was to use the longitudinal data base of the Child Research Council of Denver to examine the anteroposterior stability of the medial rugal region. Dental casts of 20 females and 21 males with untreated normal Angle Class I occlusions were selected. Time intervals measured were: T1--primary teeth erupted, T2--earliest cast with permanent first molars erupted, T3--earliest cast with canines and pre-molars erupted, and T4--ages 16 to 22. Distinctive left and right anterior and posterior rugae which appeared on all four casts were identified, the medial ends marked, and the anteroposterior distances measured. The data were evaluated with the paired t test, repeated-measures ANOVA, and Tukey's multiple comparison procedure. From T1--T4, the medial rugal region increased 1.4 +/- 0.6 mm in females and 2.3 +/- 0.8 mm in males. Only two cases showed a trend toward stability. There were no significant differences by side. Significant increases in size occurred between T2 and T3 for females and males and between T3 and T4 for males. Analysis of these data indicates that the medial rugal region increases significantly in anteroposterior length, but not uniformly between the sexes across observation times. Such changes are characteristic of general craniofacial growth and suggest that the rugal region is responding to the differential growth of the underlying bone. Therefore, medial rugal landmarks appear not to be stable reference points for tooth migration research.

The reconstruction of anterior residual bone defects in patients with cleft lip, alveolus and palate. A review

A re-evaluation is presented more than a decade after the 1973 review by Koberg of bone grafting in cleft palate. The various indications for, and aims of the procedure, are enumerated. The optimal age for grafting is discussed as well as operative procedures. Results of a few more detailed studies are included in the review. In the conclusion the present shifts of emphasis are mentioned: An in depth analytical study of numerical comparisons between the many studies covering this subject is hardly appropriate. Initially, primary and early secondary osteoplasties became very popular, thereafter late secondary or tertiary osteoplasty found general favour. At present a clear trend exists to operate at a younger age again: secondary osteoplasty being performed at 6-12 years of age. However, in a number of cleft centres primary osteoplasty remains in favour. The overall results of the different procedures appears to continue to improve, though the ideal solutions are still not exactly known, nor generally agreed upon. For the time being, a good overall result should be obtained in more than 80% of cases, complete failures should not be seen in more than 5% of a series. Autogenous bone appears to be by far the best graft material. Disagreement exists on the viability of autogenous bone from different donor sites. Periodontal criteria and parameters are used more frequently in a number of recent publications for assessment of the results of the different procedures. Osteoplasty has a relatively high chance of success, especially in the younger age groups. In most institutions, however, too early an age at operation is considered to cause disturbance in growth and development of the middle third of the face. Nevertheless, in this respect operative technique and/or orthodontic treatment seem to play an important role.

Early results of secondary bone grafts in 106 alveolar clefts

Eighty-three patients with cleft lip and cleft palate were treated by secondary bone grafts to the 106 alveolar clefts. In 98% of the alveolar clefts, the graft was successful and the oronasal fistula was closed. There were only occasional other complications, all but one of which were minor and did not affect the final result. Morbidity was low. Compared with older patients, the pre-teen group of patients not only had no complications of consequence but experienced less morbidity. The 100% success rate and the lower morbidity in the pre-teen group of patients thus favor operating on patients at the younger age.

Some variables of the craniofacial complex in a Venezuelan population of Negroid ancestry

A total of 226 individuals (101 males and 125 females), from La Sabana, a Venezuelan Negroid isolate, with ages between 8 and 60 years, were studied in order to characterize the population for its craniofacial variables and to study the behavior of these variables in relation to age and sex. The variables studied were grouped in three categories: direct cephalometric variables, which included 6 measurements taken directly on the individuals; indirect cephalometric variables, which included 18 measurements (9 angular and 9 linear), taken on lateral head films; and dental variables, which included 9 measurements taken from dental models. In general the direct variables showed the lowest coefficients of variation (CV), suggesting homogeneity within this sample. They were followed by the dental and the indirect variables, which had the highest CV values. In order to detect age and sex effects on the variables, sex and age group comparisons were performed with Student t tests. A greater proportion of significant differences were found among the direct variables, indicating that age and sex have more influence on this group of variables than upon the other two. Comparisons of our sample from La Sabana, with samples from African Negroid, Caucasoid, and Amerindian population show that La Sabana individuals have a craniofacial pattern basically Negroid, as we expected, although some contribution from Caucasoides and especially Amerindians is also suggested in our data.

Tooth position measurements on dental casts using holographic images

A new accurate method for comparing tooth positions on dental casts at different stages is described. Holograms of casts were prepared with a helium-neon gas laser. For evaluation of tooth movements, a cast and hologram representing different time points were superimposed by means of an adjustable x-y stage. Occlusal surface detail was used as a reference for the superimposition. Positional changes of the upper incisors were detected as discrepancies between the cast and the hologram image.

Assessment of palatal height in children

In this study a palatal index (P.I.) was established for 121 randomly selected normal Australian children. Mean P.I. indices were compared in the primary, mixed and permanent dentitions. A subjective assessment of relative palatal height was also carried out by two independent examiners and an attempt was made to examine the reliability of the subjective assessment, and its validity compared with the P.I. Measurements were recorded on stone casts at Level 1 (distal to the primary second molars/second premolars) and Level 2 (between primary first and second molar/first and second premolars). At Level 1 the mean P.I. increased significantly from the primary to the mixed and permanent dentitions. At level 2 the P.I. remained stable. Findings indicate that subjective assessment of relative palatal height was fairly reliable: there was approximately 80% interexaminer and intraexaminer agreements. Subjective assessment of palatal height correlated reasonably well with the P.I.

Frames of reference for the measurement of occlusal change and the integration of data from orthodontic models and cephalometric radiographs

The problems of establishing a suitable basis for the measurement of tooth movements from models is discussed, together with the ways in which such measurements of the occlusion can be related to data from cephalometric radiographs.

D E space--a realistic measure of changes in arch morphology: space loss due to unattended caries

By using only a portion of the dental arch, rather than some geometric construction that conforms to the dental arch, more pertinent information can be gathered regarding the sequelae of some event or insult to the arch. The measurement, D E Space, has been explained and utilized to describe the effectss of unattended dental caries on arch form. Only caries which become severe have a significant effect on the dental arch--a reduction in D E Space, which can be interpreted as relative arch length (depth) and is significant only for the year after its exfoliation. This occurs one year early and is also significant.

An analysis of the relationship between posterior dental cross-bite and vertical palatal asymmetry

The relationship between unilateral posterior cross-bite and vertical proportions of the palatal vault observed in the frontal plane was studied in twenty cross-bite cases wtih asymmetric palates and twenty control cases. The contour of the palate was registered from study models at three different anteroposterior levels with an adjustable template. The tracings of the contours obtained from roentgenograms of the instrument were used to measure the asymmetry of the palate.

Significance of the Frankfort-mandibular plane angle to prosthodontics

Cephalometric information, specifically, vertical facial types and the Frankfort-mandibular plane angle, pertinent to prosthodontics has been discussed. The Frankfort-mandibular plane angle (FMA) is formed by the intersection of the Frankfort horizontal plane and the mandibular plane. This angle can be traced and measured by means of a diagnostic overlay. An FMA of 25 +/- 5 degrees is within normal range. A high-angle patient has an FMA of 30 degrees or more, and a low-angle patient has an FMA of 20 degrees or less. A high FMA is characterized by open-bite skeletal patterns, and a low FMA by closed-bite skeletal patterns. The clinical manifestations pertinent to prosthodontics in high- and low-angle (FMA) patients are shown in Table I. However, not all clinical characteristics are present in a given patient. The classification in Table I is a beginning. The authors consider the prosthodontic study of cephalometrics an unexploited research tool. Hopefully, in the future, it will help to bridge the gap of the biological-technical interplay that is such an integral part of prosthodontics.