The effect of Fränkel's function regulator type III on the apical base.

Dento-alveolar and skeletal effects of orthopaedic treatment have always been the subject of controversial scientific discussions. The objective of this retrospective study was to demonstrate the changes in the dental arch and the apical base of both jaws following therapy with Fränkel's function regulator type III (FR III). For this purpose, 42 Class III patients (28 females, 14 males, mean age 7.5 years) were selected according to strict criteria. The control group consisted of 16 patients (eight females, eight males, mean age 8.3 years) with minor malocclusion symptoms. Study models of all patients at the beginning and end of treatment were evaluated using a sophisticated measuring system. Apart from common parameters of model analysis, cusp inclination of the first molars, and apical bases of the maxilla and mandible were recorded to facilitate a comprehensive evaluation of treatment effects (including growth). The FR III stimulated the development of the maxilla, thus resulting in a more physiological growth pattern. Mandibular prognathism, however, was still discernible after therapy in the Class III patients, even though mandibular growth did not differ significantly between the two groups.

No correlation between primary mandibular anterior crowding and vertical craniofacial configuration or lower incisor inclination.

The aim of the present study was to evaluate the correlation between primary mandibular anterior crowding and vertical craniofacial configuration or sagittal lower incisor inclination. The collective comprised 100 consecutive patients (50 males, 50 females) subject to 4 selection criteria: mandibular anterior crowding > or = 1.0 mm, no previous orthodontic therapy, completely preserved deciduous canines and molars, and lateral cephalograms of good diagnostic quality before initiation of orthodontic treatment. Study casts of all patients were used to measure the mesiodistal width of the incisors and deciduous canines as well as the anterior arch circumference. The difference between the 2 represented the amount of crowding. On all cephalograms 16 parameters of vertical craniofacial configuration and 9 parameters of lower incisor inclination were measured. For error evaluation all measurements were repeated independently on 10 randomly selected study casts and cephalograms. This error amounted for the combined tooth width to 0.51% +/- 0.81, for arch circumference to 0.03% +/- 0.68, and for all cephalometric parameters to 0.38% +/- 4.81. For all parameters, arithmetic means, standard deviations and ranges were calculated. Further, correlation coefficients were calculated between anterior crowding and all 25 cephalometric parameters. The arithmetic mean of crowding was m = 2.0 +/- 1.3 mm with a range of 1.0 to 6.6 mm. The values of all cephalometric parameters were close to well accepted norms in the literature. The correlation coefficients between crowding and all cephalometric parameters varied from r = 0.0 to 0.3. According to this study there is no correlation between primary mandibular anterior crowding and vertical craniofacial configuration or sagittal lower incisor inclination.

Ultrasonographic measurement of tongue movement during swallowing.

Previous ultrasonographic studies on tongue functions were limited by the possibility of artifacts caused by movement of the submental area during function. Consequently, tongue movements were misinterpreted. A dynamic tongue imaging technique, the cushion-scanning technique, was used to overcome this problem. Later, swallowing was investigated and divided into five phases using cushion-scanning technique-aided M-mode ultrasonograms. In this study, cushion-scanning technique in combination with the B-mode and M-mode ultrasonography was applied to investigate and measure the tongue movement during swallowing in 55 normal persons. The average duration, range of motion and speed of swallowing were found to be 2.43 s, 24.06 mm, and 10.34 mm/s, respectively. The computer-aided B-mode plus M-mode ultrasonography in combination with the cushion-scanning technique is a valuable tool for study of tongue functions.

Random errors in localization of landmarks in postero-anterior cephalograms.

The aim of the present study was to evaluate the random error in localization of the most common landmarks in postero-anterior cephalograms (PAC). The study took place at the Department of Orthodontics of Aarhus University during the period 1993-1995. The material consisted of 30 standardized PAC taken in natural head position. Five examiners had to identify 34 landmarks on each cephalogram. Subsequently, all examiners had to identify again the same 34 landmarks on one randomly selected cephalogram five times with a time interval of at least 24 hours. All landmarks were digitized, related to an X-Y co-ordinate system, and an arithmetical mean was calculated. The accuracy of digitizing was evaluated by digitizing one randomly selected cephalogram 10 times. The main findings of this study are: (1) The digitizing error is negligible compared to the errors introduced by landmark identification. (2) Each landmark has its own characteristic pattern of variance, which is very similar on both sides. (3) Significant differences in accuracy exist between the various postero-anterior landmarks. The six most accurate landmarks are mastoid left (l) and right (r), latero-orbitale (l) and (r), and antegonion (l) and (r). The six least accurate landmarks are coronoid (l) and (r), condylar (l) and (r), and mandibular foramen (l) and (r). (4) A significant difference in the accuracy of landmark identification between the five examiners was only seen for seven of the 34 landmarks. (5) No evidence was found that one examiner was consistently better/worse than the others. (6) No improvement in the accuracy was found after repeated identification, thus there seems to be no short-term 'learning process'. Refereed Paper

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.

Shear bond strengths of ceramic brackets bonded with different light-cured glass ionomer cements: an in vitro study.

The purpose of this study was to evaluate the shear bond strengths of four light-cured glass ionomer cements used for direct bonding of ceramic brackets, and to compare the results with a two-paste chemically-cured composite resin. Two commercially available polycrystalline ceramic brackets, with either chemically or mechanically retentive bracket bases, were evaluated. The brackets were bonded to 100 freshly extracted bovine incisors, and, after storage in tap water at room temperature for 24 hours, they were subsequently tested in a shear mode using a universal testing machine. The maximum bond strength and the site of bond failure were recorded. With the mechanically retentive base, Fuji Ortho LC produced the highest bond strength (18.50 MPa), which was not significantly different from the values achieved with Concise (14.88 MPa) (P > 0.1) and Photac Bond (13.86 Mpa) (P = 0.1). The lowest bond strength was provided by locomp A20 (5.23 MPa). With the chemically retentive base, the highest bond strength was measured with Concise (29.27 MPa), which was significantly (P < 0.01) higher than the values for Photac Bond (16.27 MPa) and Fuji Ortho LC (13.48 MPa). Again locomp A20 produced the lowest bond strength (3.21 MPa). Three cements (Dyract Ortho, locomp A20 and Fuji Ortho LC) provided higher shear bond strengths with the mechanical retention system, whereas Concise and Photac Bond gave higher strengths with the silane-treated bracket bases. However, the strengths were statistically significantly different only for locomp A20 (P = 0.001) and Concise (P = 0.001). With the mechanically retentive base, Dyract Ortho and locomp A20 failed at the enamel-adhesive interface, whereas Photac Bond and Concise debonded at the bracket-adhesive interface. Fuji Ortho LC failed at both, the bracket-adhesive (40 per cent) and the adhesive-enamel (60 per cent) interface. With the chemically retentive base, all the adhesives failed at the enamel-adhesive interface. Only one bracket fracture occurred in this study, and no enamel damage was detected.

An experimental evaluation of effects and side effects of asymmetric face-bows in the light of in vivo measurements of initial tooth movements.

By using a magnetic sensing system, the translational and rotational molar movements under the application of various asymmetric face-bows were measured two-dimensionally in human subjects to evaluate their primary effects and side effects. The asymmetric face-bow designs tested were three types of power arm face-bows, swivel offset face-bow, and internal hinge face-bow. Although all face-bow designs were considered to be effective in achieving asymmetric distalizations of the molars, they generated lateral displacements that may lead to an undesirable crossbite. The swivel offset face-bow may produce unexpected results and its fabrication is complicated. The internal hinge face-bow is remarkably effective for asymmetric molar distalizations. Unfortunately, it causes a strong crossbite tendency on the molar to be more distalized. Therefore the use of the power arm face-bow is thought to be relatively recommendable because it showed an acceptable asymmetric effect and is easily fabricated from a commercially available face-bow. It is concluded that all asymmetric face-bows generate lateral forces as side effects as long as the force delivery system with a combination of an asymmetric face-bow and a neck strap or head cap is applied. The current study suggests a method whereby the side effect of asymmetric face-bows can be eliminated.

Effects of saliva and water contamination on the enamel shear bond strength of a light-cured glass ionomer cement.

The purpose of this study was to evaluate the shear bond strengths of Fuji Ortho LC (GC Corp., Tokyo, Japan), a light-cured resin-reinforced glass ionomer, used for direct bonding of stainless steel and ceramic brackets under four different enamel surface conditions: (A) nonconditioned and dry, (B) conditioned with polyacrylic acid and moistened with saliva, (C) conditioned with polyacrylic acid and moistened with water, (D) nonconditioned and wet. Stainless steel lingual buttons and two types of polycrystalline ceramic brackets, with either mechanically or chemically retentive bracket bases, were evaluated. The brackets were bonded to 120 freshly extracted bovine incisors; after storage in tap water at room temperature for 24 hours, they were subsequently tested in a shear mode with a universal testing machine. The maximum bond strength and the site of bond failure were recorded. With stainless steel brackets, subgroup B produced the highest bond strength (23.8 MPa), which was significantly (p < 0.05) higher than all the other enamel conditions tested. With ceramic brackets, the highest bond strengths (20.9 MPa and 25.4 MPa, respectively) were measured with subgroup C. Bond failure analysis revealed that each bracket type failed predominantly at the enamel-adhesive interface, except for Transcend 6000. The results indicate that the shear bond strength of Fuji Ortho LC is significantly enhanced by contaminating the enamel surface with either saliva or water after conditioning, depending on bracket type used. Even water contamination of nonconditioned enamel surfaces does not seem to preclude clinically acceptable bond strengths of both stainless steel and ceramic brackets, allowing, at the same time, a safe debonding without enamel damage.

Third order tooth movements with straight wire appliances. Influence of vestibular tooth crown morphology in the vertical plane.

1. The labial surface in the vertical plane was investigated in 3 sections: center, mesial, and distal edge of an ideally positioned bracket. The material consisted of 28 casts taken from 14 female and male individuals with a mean age of 26.8 years. 2. After trimming each cast, the resulting surface was photocopied, enlarged 8 times, then digitized under a 2.0 mm grid (corresponding to 0.25 mm of the original size). 3. Using a statistical computer program, mean curves including standard deviations and non-linear regression curves were calculated from the individual data. In accordance with their anatomy 3 groups of teeth were formed in each jaw: front teeth, premolars, and molars. The curves, including the comparison of the squared regression curves, provide an accurate mathematical description of the labial tooth crown in the above-stated sections. 4. The angle differentials between a reference tangent and 20 other tangents were calculated. From a practical standpoint, information is obtained on the extent to which the torque of a tooth would be changed if a bracket was to be positioned vertically (in 0.5 mm increments) from its ideal position. These changes of torque fluctuate on average between 1.3 degrees (mandibular front teeth) and 3.3 degrees (mandibular molars) for every 0.5 mm of vertical deviation. 5. The calculated comparisons of the curves permitted the construction of bracket bases filling-at least in the vertical dimension-the tooth surface most accurately in the "optimal" position.

The cushion scanning technique: a method of dynamic tongue sonography and its comparison with the transducer-skin coupling scanning technique during swallowing.

RATIONALE AND OBJECTIVES: We describe the cushion scanning technique (CST), which solves common difficulties encountered during ultrasound investigations of swallowing. These problems arise when the transducer is held in direct contact with the submental area. Some of these problems include movements of the ultrasound transducer during swallowing and compression of the submental region, which causes abnormal swallowing patterns. METHODS: To compare ultrasound images produced with the conventional hand-held transducer-skin coupling scanning technique with the CST, we studied five participants with no clinical signs of tongue dysfunction. All tongue movements were recorded by real-time B+M-mode sonography. RESULTS: Images produced with the hand-held transducer were found to be unstable because the transducer moved during swallowing, thereby changing the scanning section. By contrast, the transducer and the participant's head remained in a constant position throughout the CST trial. There was no obvious compression of the submental muscles. CONCLUSION: The CST allows for a better intraindividual reproducibility of the swallowing pattern and for a more standardized and objective ultrasound examination than the hand-held transducer-skin coupling scanning technique.

[A damping method makes possible a more exact sonographic study of tongue movements]. / Eine Dämpfungsmethode ermöglicht eine exaktere sonographische Untersuchung von Zungenbewegungen.

If the home-made cushioning appliance presented here is placed during ultrasonic examinations between the submental region and the probe head, then the problems caused by probe head movement and pressure on the submental region, as have been encountered in the past, can be solved. The use of such a cushioning appliance makes possible a more accurate B-mode ultrasonic evaluation of tongue function. The prevailing method and the cushioning method presented here were studied on 50 test patients. Comparison of the 2 methods revealed that in fact the use of the cushioning method prevented movement in the ultrasonic probe and also its use hardly impaired the patient's ability to swallow. We therefore recommend that this cushioning method be routinely applied during ultrasonic examinations of tongue function.