Prediction of the mesiodistal width of unerupted permanent canines and premolars: a statistical approach.

INTRODUCTION: Prediction of the mesiodistal width of unerupted permanent canines and premolars is of major interest for orthodontic diagnosis and treatment planning. METHODS: To improve the accuracy of the prediction, we looked for the best combination of independent variables with multiple linear regression. RESULTS: The most accurate prediction was obtained for the combination of the mandibular right first molar and lateral incisor, and the maxillary left central incisor. Adding to the regression equation 1 erupted canine or premolar improved the accuracy of the prediction considerably. Because of the variable character of the eruption sequence during the second transitional period, a separate regression model for every canine or premolar was necessary. The precision of our new method and other methods from the literature was tested in a separate study group. CONCLUSIONS: The results of this study show that our prediction method of the mesiodistal crown diameters of unerupted canines and premolars during the dental transition is accurate. A computer program was developed for user-friendly clinical application.

The development of the cervical vertebrae as an indicator of skeletal maturity: comparison with the classic method of hand-wrist radiograph.

OBJECTIVE: The objective of this study was to compare three methods with which to determine the skeletal maturity of children. MATERIALS AND METHODS: The methods were Greulich & Pyle's atlas method based on hand-wrist radiographs (1959), and the cervical vertebrae methods based on lateral cephalograms of Lamparski (1972) and San Roman et al. (2002). We evaluated hand-wrist radiographs and the lateral cephalograms of 392 children (195 girls and 197 boys age 7-18). The morphology of the second (C2), third (C3) and fourth (C4) cervical vertebrae was assessed and the stage of skeletal maturity determined along with chronological age. RESULTS: Our results revealed a significant correlation (p

Sagittal space relations in the maxilla during molar eruption.

OBJECTIVE: The aim of this study was to measure the space relations in the maxilla during upper molar eruption, and to interpret associations. MATERIAL AND METHODS: 154 skulls ranging from infant to adult were measured on the basis of defined distances. The age of the skulls was determined by tooth development. The data were compared and qualitatively interpreted. RESULTS: We observed that, immediately after eruption of the primary dentition, there was nearly enough space in the upper jaw for the first permanent molar. Yet eruption does not occur until the age of 5 to 6 years, at the beginning of the first transition phase. As opposed to the first permanent molar, the second erupted as soon as there is enough space in the upper jaw. This tends to happen at the end of the second transition phase at ca. 12-13 years of age. We noted that there was almost enough space in the maxilla until the age of 17 to accommodate all the teeth in the upper jaw. According to our measurements, growth at the posterior edge of the maxilla also took place after eruption of the third molar. CONCLUSIONS: This leads us to consider that we can postpone the extraction of the upper third molars until after the 18th year, and to consider the possibility that the upper third molar may erupt correctly while the maxilla is still growing. It is precisely this trend that is significant in clinical practice, since maxillary wisdom teeth are often extracted prematurely due to an apparent lack of space.

The angle between the Frankfort horizontal and the sella-nasion line. Changes in porion and orbitale position during growth.

AIM: The starting point of this study was the statement made in the literature that the angle between the two reference planes Frankfort horizontal (FH) and sella-nasion line (SN) changes relatively little during growth. The growth-induced relocation of the orbitale (Or; anterior reference point of the FH) in relation to SN is known from implant studies, whereas the relocation of the porion (Po; posterior reference point of the FH) has been the subject of only little research. The present study was aimed at analyzing the factors contributing to the almost constant angle between FH and SN. MATERIAL AND METHOD: The study material consisted of two groups of macerated skulls and the relevant lateral cephalograms. The first group comprised 32 skulls of individuals aged 2.5 to 5 years, and the second group ten skulls of individuals aged 18 to 20 years. A diagram showing the growth-dependent changes was prepared with reference to the mean values for the two groups. The cephalograms were superimposed on the anterior cranial base line at sella point (S). RESULTS: A 3.1 degrees increase in the angle between FH and SN during growth was recorded in our investigations. The distance between Or and SN increased by 3.9 mm while Po remained vertically almost constant with respect to SN. In sagittal direction the distance between Or and S also increased, while Po was displaced to almost the same extent in the opposite direction. The increasing vertical distance between the anterior and posterior reference points of FH and SN was largely compensated by the sagittal developments of the reference points Po and Or, so that the angle between these two planes changed very little. The relatively stable angle between FH and SN thus showed by no means a constant relationship of the four reference points to one another.

Comparison of linear measurements in cephalometric studies.

Five longitudinal cephalometric studies were evaluated with regard to discrepancies in their methodology. The roentgenographic enlargement was determined for each study separately. One linear cephalometric distance was then depicted graphically with and without correction for enlargement. This revealed that, besides other inaccuracies in the method, it was primarily the neglecting of radiographic enlargement that created considerable distortion of linear dimensions. Growth velocity curves were computed for three selected dimensions and graphically depicted. The determination of a growth spurt according to accepted definitions was impossible in these growth velocity curves. Problems arising in the determination of a growth spurt are discussed.

Comparison of linear cephalometric dimensions in Americans of European descent (Ann Arbor, Cleveland, Philadelphia) and Americans of African descent (Nashville).

Eleven dimensions, extracted from four commercially available cephalometric atlases were compared. Three populations were American of European descent and one was American of African descent. The source data were carefully corrected for linear enlargement. The confounding effect of linear radiographic enlargement is exemplified by depicting the often-used distance, sella-nasion, before and after correction. Total face height was smallest in the Cleveland population and largest in the Nashville population. The difference was fully accounted for by differences in lower face height and that was the most variable of all dimensions studied. Upper face height was almost identical in all four populations. Posterior face height was largest in the Nashville population. The mandible in the Nashville population had an average ramus height, but a longer corpus. Mandibular dimensions were equal in the three other populations. The maxilla was clearly shortest in the Cleveland population and almost of equal length in the three others.

Effect of magnification on lateral cephalometric studies.

The effect of radiographic magnification on the horizontal distance sella-nasion, the vertical distance nasion-menton, and the oblique distance sella-gnathion was explored. Five different longitudinal cephalometric studies provided the data for this survey. Two series of graphs were created: 1 from the raw data as they originally were published, the other in natural size after meticulous compensation for radiographic magnification. The importance of correction for magnification at once became obvious when these graphs were reviewed. The following conclusions were made: the distances listed in commonly used cephalometric atlases differ greatly because of different magnification and cannot be compared directly. The distances from the Ann Arbor, Michigan, study must be multiplied by 0.886, and those from the Bolton Standards and the Philadelphia studies must be multiplied by 0.943 to obtain natural dimensions. Correction to natural size is essential when comparing cephalometric distances from different sources; publication of data corrected to an arbitrary "standardized enlargement" creates confusion. Although differences between the corrected distances were small, regional variation seems to exist.