Josef W. Freudenthaler

A study of bite force, part 1: Relationship to various physical characteristics.

A new device for measuring and recording bilateral bite force in the molar/premolar region has been developed. Because this new device is elastic and conforms to the occlusal surfaces of the teeth, and because the sensing element is relatively comfortable, it is believed that experimental subjects are less reluctant to register true maximal forces than in earlier studies. Potential correlations of maximum bite force to gender, age, weight, body type, stature, previous history of orthodontic treatment, presence of TMJ symptoms (jaw motion limitation, clicking with pain, or joint pain), or missing teeth were studied in a sample of 142 dental students. The mean maximum bite force of the sample was found to be 738 N, with a standard deviation of 209 N. The mean maximum bite force as related to gender was found to be statistically significant, while the correlation coefficients for age, weight, stature, and body type were found to be low. Even so, all data scatterplots exhibited relatively positive relationships. Correlations of maximum bite force to an earlier history of orthodontic treatment or to the absence of teeth were not found. Subjects reporting TMJ symptoms did not exhibit a significantly different maximum bite force than subjects without symptoms.

A study of maximum bite force during growth and development

Bilateral bite force was measured in a sample of 457 subjects (231 males and 226 females) from 6 years through 20 years. The mean maximum bite force was found to increase from 78 Newtons at 6 to 8 years to 176 Newtons at 18 to 20 years. While earlier studies have shown adult males have a greater mean bite force than females, this difference is not evident during growth and development. Gender-related bite force difference likely develops during the postpubertal period in association with greater muscle mass development in males.

A study of bite force, part 2: Relationship to various cephalometric measurements.

Maximum bilateral bite force, determined in 129 dental students, was evaluated with regard to six skeletal and eight dental measurements acquired from conventional lateral cephalometric radiographs. Statistically significant correlations for three of the skeletal measurements were found. Maximum bite force increased with regard to decreasing mandibular plane/palatal plane angle and to decreasing mandibular plane angles. Maximum bite force increased with an increasing ratio of posterior facial height to anterior facial height. Significant statistical correlation for only one of the eight dental measurements was found: maximum bite force related directly with increasing maxillary and/or mandibular dentoalveolar heights, and unexpected finding.

The centered T-loop—A new way of preactivation

The force system of a prefabricated and preactivated T-loop used for reciprocal space closure was determined by simultaneously measuring the horizontal and vertical forces, as well as the moments using a computer controlled measuring apparatus. Interbracket distances of 21, 24, 27, and 30 mm were used to mimic typical clinical situations. At a loop activation of 7 mm, the anterior and posterior segments first underwent controlled tipping, then translation, and finally, root uprighting as the moment-to-force ratio increased with deactivation. After the loop has been deactivated to 4 mm, however, it should be exchanged to avoid root abutment.

Cytotoxicity and shear bond strength of four orthodontic adhesive systems.

The objective of this study was to compare the cytotoxicity of four orthodontic bonding systems, Light Bond, Enlight, Concise, and Transbond, and to evaluate their shear bond strength (SBS). These orthodontic bonding materials were applied to metal brackets (Mini Diamond). Glass specimens were used as controls in all experiments. Only Concise was a chemically cured system, the other systems were light cured. The specimens were added to L-929 fibroblast cultures immediately after fabrication or after pre-incubation for 7 days. The incubation time was 72 hours and the cells were counted by flow cytometry. One hundred and fifty-seven freshly extracted human third molars were used for testing the SBS in a universal testing machine. Statistical significance was determined using analysis of variance followed by post hoc comparisons for multiple-level alpha control. Pairwise comparisons showed a significant difference only between Light Bond and Concise (P = 0.0126). The highest SBS was obtained with Light Bond (23.23 +/- 1.53 MPa) followed by Transbond (20.39 +/- 1.18 MPa) and Enlight, (20.32 +/- 1.06 MPa). Concise (17.87 +/- 1.04 MPa) showed the lowest SBS. The cytotoxicity of all light-cured systems for fresh specimens was comparable, whereas the chemically cured system, Concise, was significantly more cytotoxic. After 7 days of pre-incubation, all systems were significantly less cyotoxic than fresh specimens (P < 0.001). Brackets alone were not cytotoxic. All bonding systems showed a clinically satisfactory bond strength higher than 10 MPa, with the chemically cured system showing the lowest SBS.

Effects of rapid maxillary expansion on the airways and ears — a pilot study

The aim of this prospective study was to describe the morphological and functional changes of the upper airways and the middle ears after rapid maxillary expansion (RME). Thirteen patients comprised the original study sample, of these three patients dropped out. Of the remaining 10 subjects, seven (two females, five males; average age, 8.7 years) underwent orthodontic RME with a Hyrax screw and three (one female, two males; average age, 8.3 years) served as the controls. Inclusion criteria for the study group were a uni- or bilateral crossbite with the evidence of a maxillary deficiency. Exclusion criteria were acute or chronic respiratory disease, allergies, cleft lip and palate, or absence of adenoids. An ear, nose, and throat (ENT) examination, lateral cephalometry, anterior rhinomanometry, tympanometry, and posterior rhinoscopy were carried out for each child at baseline (E1) and after 6 months (E2). Descriptive statistics were calculated for all diagnostic variables and correlations between the study and control group were evaluated. Rhinomanometry showed a correlation (r=0.57) between the size of the nasal pharyngeal area and nasal airflow, but only at 150 daPa. The size of the adenoids measured on the lateral cephalograms was correlated with the endoscopic findings. The size of the adenoids remained the same after RME. Patients with maxillary constriction had the largest adenoids and showed a negative pressure in the middle ear. However, this was reduced after RME. The results suggest a possible impact of maxillary deficiency on otorhinological structures. RME may lead to otorhinological changes. Further interdisciplinary investigations are needed to corroborate these findings.

Comparison of Japanese and European overbite depth indicator and antero-posterior dysplasia indicator values

This study evaluated cephalometric differences between 113 Japanese (43 males and 70 females, aged 14.1 ± 5 years) and 106 European subjects (36 males and 70 females, aged 13.5 ± 7.3 years) using two compound angular measurements and their single components: the overbite depth indicator (ODI) for the assessment of vertical skeletal relationships and the antero-posterior dysplasia indicator (APDI) for an evaluation of sagittal dysgnathia. Both populations were assigned to groups representing Angle Classes I, II, and III, and an anterior open bite (AOB) group. Two sample t- and Wilcoxon signed-ranks tests were performed (P < 0.05). The ODI values showed no statistically significant differences between the Japanese and European samples. The Japanese sample showed a significantly smaller APDI but only in the Class II group. In the Japanese Class II and III subjects, the malocclusion patterns were more pronounced than those in the Caucasian sample (overbite, overjet, and APDI).

Cephalometric differentiation between vertical and horizontal malocclusions in 122 Europeans using the Denture Frame Analysis and standard measurements

This study evaluated the ability of some cephalometric measurements to differentiate between horizontal and vertical malocclusions and normal occlusion. Based upon the Angle classification and the vertical incisor overbite, 122 randomly selected subjects were assigned to 3 horizontal and 3 vertical groups: neutrocclusion, distocclusion, mesiocclusion as well as open bite, normal overbite, and deep bite. Evaluation of the lateral cephalograms was based on Denture Frame Analysis and cephalometric standard measurements (SNA, SNB, ANB, Wits appraisal, Björk polygon, overbite depth indicator, incisor inclination, incisor protrusion, facial height ratio). The statistical evaluation assessed the ability of the measurements to show significant differences between the individual horizontal and vertical groups. Using Denture Frame Analysis, all vertical groups could be differentiated by the occlusomandibular angle (OP-MP) and all horizontal groups by the angle between the A-B plane and the mandibular plane as well as by the inclination of the upper incisors to the A-B plane with statistical significance (p<0.05). Among the standard measurements, the Wits appraisal was the only one to show differences between all horizontal groups with statistical significance. None of the tandard measurements could fully differentiate the vertical groups. The above measurements from the Denture Frame Analysis distinguished the types of malocclusion in anteroposterior and vertical direction including significant distinction between the neutrocclusion group and the malocclusion groups. Therefore a cephalometric classification was feasible in terms of hyper- and hypodivergence as well as of a mesial or distal dentofacial relationship.ZusammenfassungDie vorliegende Arbeit untersuchte das Diskriminierungsvermögen einiger kephalometrischer Messungen bei vertikaler und horizontaler Malokklusion bzw. Regelbiß. Es wurden 122 randomisiert ausgewählte Patienten anhand der Angle-Klassifizierung und des Schneidezahnüberbisses in je drei horizontale und drei vertikale Gruppen eingeteilt: Neutralokklusion, Distalokklusion, Mesialokklusion bzw. offener Biß, Regelüberbiß und Tiefbiß. Zur Auswertung der Fernröntgenseitenbilder wurden die Denture-Frame-Analyse und kephalometrische Standardmessungen verwendet (SNA, SNB, ANB, Wits appraisal, Björk-Summenwinkel, Overbite Depth Indicator, Inklination und Protrusion der Schneidezähne, Gesichtshöhenverhältnis). Statistisch wurde untersucht, inwieweit die genannten Messungen signifikante Unterschiede zwischen den einzelnen horizontalen bzw. vertikalen Gruppen anzeigten. Bei der Denture-Frame-Analyse konnten alle vertikalen Gruppen durch den Okklusomandibularwinkel (OP-MP) und alle horizontalen Gruppen durch den Winkel zwischen der A-B-Ebene und der Mandibularebene sowie der Inklination der oberen Schneidezähne zur A-B-Ebene statitistisch signifikant differenziert werden (p<0,05). Unter den Standardmessungen war das Wits appraisal die einzige, welche signifikant zwischen allen horizontalen Gruppen unterschied. Keine der untersuchten Standardmessungen konnte die vertikalen Gruppen vollständig differenzieren. Die genannten Messungen der Denture-Frame-Analyse ermöglichten eine Zuordnung der Malokklusionstypen in ein anteroposteriores und vertikales Schema mit signifikanter Trennung zwischen Neutralokklusionsgruppe und Malokklusionsgruppen. Dies erlaubte eine kephalometrische Zuordnung im Sinne von Hyper- und Hypodivergenz bzw. Mesial- und Distalbeziehung.

In-vitro fluoride release

I proposed a simple concept that “for the best treatment outcome, some patients need nonextraction treatment, some need extractions, and the key goal of diagnosis is gathering data on which to base this decision, not on which bracket to use.” Implicit in this “gathering data” would be new scientific research, including TADs and so on, but ignoring past scientific evidence isn’t prudent. Samuel J. Burrow, III Chapel Hill, NC Am J Orthod Dentofacial Orthop 2008;134:7 0889-5406/

Left/right asymmetries and open/closed differences of interdental forces in the mandible

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