Py Owman-Moll

Continuous versus interrupted continuous orthodontic force related to early tooth movement and root resorption

The aim of the present clinical investigation was to assess the effects of continuous and interrupted continuous forces of the same magnitude (50 cN = 50 g) on orthodontic tooth movement and related adverse tissue reactions, i.e., root resorption. Thirty-two maxillary first premolars in 16 patients, 8 boys and 8 girls (mean age 13.9 years), were moved buccally by means of a fixed orthodontic appliance with a sectional arch. The patients were divided into two groups of 8, for experimental periods of 4 and 7 weeks. The continuous force was checked and reactivated weekly to 50 cN. The interrupted continuous force applied to the contralateral premolars was left uncontrolled for 3 weeks, after which the arch was made passive for 1 week for tissue rest and recovery. Tooth movements were studied on dental casts using a coordinate measuring machine (Validator 100, TESA SA, Renens, Switzerland). Horizontal tooth movement with continuous force was more effective than with interrupted continuous force after 7 weeks. Histological sections of the experimental teeth, however, showed no difference in the amount or severity of root resorption between the two forces. Individual variations in both the magnitude of tooth movement and the amount and severity of root resorption for both of the two force systems were great.

Time-related root resorption after application of acontrolled continuous orthodontic force*

The aim of this investigation was to study root resorption after application of a weekly controlled, continuous orthodontic force of 50 cN (approximately 50 gm). Fifty-six maxillary premolars in 18 boys and 38 girls (mean age 13.8 years) were moved buccally with a fixed orthodontic appliance. The contralateral premolar served as a control. The experimental periods varied from 1 to 7 weeks with eight children in each group. Root resorption was registered after 1 week and occurred in all test teeth but four. The surface extension as well as the depth of the resorption showed a marked increase after 2 weeks. Starting from the third week, eight test teeth exhibited apical root resorption that had reached half way to the pulp, or more. After 7 weeks, the test teeth showed on average more than 20 times larger mean resorbed root contour than the control teeth. Individual variations were considerable regarding both extension and depth of root resorption within each test group and were not correlated to the magnitude of tooth movement achieved. The radiographs failed to reveal any adverse tissue reactions. The great individual variations in root resorption without association to the amount of tooth displacement indicate that so far unknown individual factors are influential in these adverse tissue reactions.

Effects of a doubled orthodontic force magnitude on tooth movement and root resorptions. An inter-individual study in adolescents

The aim of this clinical and histological study was to compare the effects of two controlled, continuous forces of 50 cN (approximately 50 g) and 100 cN (approximately 100 g) on tooth movement and root resorptions. The patients, consisting of 32 individuals, 14 boys and 18 girls (mean age 13.1 years), were divided into four groups of eight individuals. The experimental periods were 4 and 7 weeks. In this investigation, designed as an inter-individual study, only the maxillary first premolar on the right side was utilized. The test tooth was buccally moved by means of a fixed orthodontic appliance. A continuous, weekly controlled force of 50 cN was applied to 16 premolars and a force of 100 cN to the remaining 16 test teeth. The force declined on average 22 per cent during the first week when 50 cN was applied and 27 per cent when 100 cN was applied. Tooth movements were studied on dental casts using a coordinate measuring machine. After 4 and 7 weeks, the tooth movements ranged between 0.5 and 3.4 mm (4 weeks) and 2.7 and 7.1 mm (7 weeks) for 50 cN and between 1.0 and 2.9 mm (4 weeks) and 2.2 and 8.3 mm (7 weeks) for 100 cN, with no significant difference when the force magnitude was doubled. Root resorptions were registered in histological sections in all experimental teeth, more frequently after application of 50 cN compared with 100 cN after 7 weeks. However, the severity of root resorption (extension and depth of resorbed root contour and size of root area on histological sections) did not differ significantly when the applied force was doubled to 100 cN. Great individual variations were noted regarding both the magnitude of tooth movement and amount of root resorption.

Repair of orthodontically induced root resorption in adolescents.

The aim of this investigation was to study the reparative potential of orthodontically induced root resorption. Sixty-four maxillary right and left first premolars in 32 patients (15 boys and 17 girls, mean age 13.7 years) were moved buccally with fixed orthodontic appliances and a continuous force of 50 cN (approximately 50 g), activated weekly for 6 weeks. The patients were divided into 4 groups of 8. Retention periods varied from 1 week to 8 weeks. Histological preparations showed that root resorption affected all the test teeth. The percentage of resorptive areas that had begun to repair ranged from 28% after 1 week of retention to 75% after 8 weeks. The healing cementum was almost exclusively of the cellular type. Partial repair, with the resorption cavity walls only partially covered with cementum, was the most frequent type of repair during the first 4 weeks of retention (17% to 31%). Functional repair, with the total surface of the resorption cavity walls covered with varying thicknesses of cementum, dominated after 5, 6, 7 and 8 weeks of retention (33% to 40%). There were no large differences in the healing potential in the cervical, middle, and apical thirds of the root. After 8 weeks, three out of four resorptive areas showed some degree of repair. Individual variations in healing potential were large.

Hyalinization and root resorption during early orthodontic tooth movement in adolescents.

The aim of this investigation was to study the hyalinization of the periodontal ligament with time and its relationship to root surface resorption after the application of an orthodontic force, reactivated weekly, of 50 cN (approximately 50 g). Fifty-six patients (18 boys and 38 girls, mean age 13.8 years) were divided into 7 groups of 8. In each patient, one premolar was moved buccally 161 with a fixed orthodontic appliance. The contralateral premolar served as a control. The experimental periods ranged from 1 to 7 weeks. Local areas of overcompression in the periodontal ligament were recorded in 33 test teeth (59%) and 2 controls (4%). Hyalinization was seen in all experimental groups, more often after the first 4 weeks of force application. Hyalinized areas were recorded opposite an intact root surface (54%) or close to and just apical or coronal to an area of root resorption (45%), and were usually located buccocervically and linguoapically, corresponding to expected pressure zones of the periodonal ligament.

Development of the residual cleft in the hard palate after velar repair in a 2-stage palatal repair regimen

Delayed closure of the hard palate is believed to improve maxillary growth and facial appearance in cleft lip and palate patients. However, the cleft opening in the hard palate after velar closure might impair speech development. The aim of this investigation was to study the development of the residual cleft in the hard palate after 2-stage palatal repair (TSPR) in children born with complete cleft lip and palate (bilateral [BCLP]; n=7 or unilateral [UCLP]; n=22) or isolated cleft palate (CP; n=9). Moreover, we aimed to investigate whether any morphologic factors before surgery might predict development of the residual cleft. Dental casts obtained prior to velar repair (mean age 7 months) and postoperatively at 1 1/2, 3, 4, 5 and 7 years were analyzed with a Reflex Microscope regarding the width, length and area of the cleft in the hard palate.The palatal cleft varied in size both pre- and postoperatively in all 3 types of cleft patients. The width of the cleft in the UCLP subgroup showed a marked reduction immediately after velar repair, but then, on average, remained stable until final surgical closure of the hard palate. In the BCLP subgroup the initially rather narrow width of the clefts remained unchanged postoperatively. Clefts in the CP subgroup, especially in those with a complete cleft, remained large after veloplasty. In 4 of the UCLP and 2 of the BCLP patients, the cleft width increased gradually. In some other subjects, both in the UCLP and BCLP subgroups, the residual cleft closed functionally with time, but this development could not be foreseen.ZusammenfassungEs gibt Hinweise darauf, daß ein relativ später Verschluß des harten Gaumens das Oberkieferwachstum und die Harmonie des Gesichtsprofils bei Patienten mit Lippen-Kiefer-Gaumen-Spalten verbessert. Jedoch könnte die Spaltöffnung im harten Gaumen nach dem Verschluß des Gaumensegels die Sprachentwicklung behindern. Das Ziel dieser Studie war, die Entwicklung der Restspalte im Hartgaumen nach einem zweizeitigen Gaumenspaltverschluß bei Kindern mit totaler Lippen-Kiefer-Gaumen-Spalte (bilateral [BCLP]; n=7 oder unilateral [UCLP]; n=22) bzw. mit isolierter Gaumenspalte (CP; n=9) zu untersuchen. Darüber hinaus sollte eruiert werden, inwieweit bestimmte morphologische Faktoren bereits vor der chirurgischen Intervention eine Prognose der Entwicklung der Restspalte zulassen.Mit Hilfe eines Reflexmikroskops wurden Breite, Länge und Fläche des Spaltbereichs am Hartgaumen an Gipsmodellen erfaßt, die vor der Velumplastik (durchschnittlich im Alter von sieben Monaten) und postoperativ im Alter von anderthalb, drei, vier, fünf und sieben Jahren hergestellt worden waren. Die Größe der Restspalte variierte bei allen drei Spalttypen, sowohl prä- als auch postoperativ. Die Breite der Spalte in der UCLP-Untergruppe zeigte sofort nach dem Verschluß des Weichgaumens eine markante Reduktion, blieb aber dann im Durchschnitt stabil bis zum endgültigen chirurgischen Verschluß des Hartgaumens. In der BCLP-Untergruppe erschien die anfangs relativ schmale Spalte postoperativ unverändert. Die Restspalte nach der Velumplastik in der CP-Untergruppe blieb groß, speziell bei denjenigen Patienten mit einer durchgehenden Gaumenspalte. Bei vier der UCLP- und zwei der BCLP-Patienten vergrößerte sich die Restspalte allmählich. Bei einigen anderen Patienten aus der UCLP- und der BCLP-Untergruppe verschloß sich die Restspalte funktionell mit der Zeit; diese Entwicklung war aber nicht vorhersehbar.

Sagittal split advancement osteotomy: Comparison of the tendency to relapse after two different methods of rigid fixation

Mandibular advancement was studied in 32 patients with mandibular retrognathia in whom the only intervention was in the mandible. Fifteen patients were treated with fixation by lag screws and 17 with monocortical miniplates. Lateral radiographs were taken preoperatively, postoperatively, 2 months postoperatively, and 1.5 years postoperatively, and mandibular movement analysed. All patients healed uneventfully. Cephalometric analysis of lateral radiographs showed no significant differences between the two groups in skeletal relapse during any of the control periods up to 18 months. Mandibular advancement for treatment of mandibular retrognathia using rigid fixation with either lag screws or miniplates was reproducable with only minor skeletal relapse.

Accuracy of Orthodontic Force and Tooth Movement Measurements

This study was designed to test the accuracy of measurement methods for assessment of force and tooth movement in orthodontic procedures. Daily in vivo measurements of the force produced by activated archwires showed that the initial force declined substantially (by 20 per cent of mean value) within 3 days. Both the ‘trueness’ (validity) and precision of the force measurements, obtained with a strain gauge, were found to be high (SD values were 1·0 cN and 0·4 cN, respectively). Horizontal tooth movements were measured with three different instruments: a slide calliper, a co-ordinate measuring machine, and laser measuring equipment based on holograms. There was a good level of agreement between these methods. This was also confirmed by calibration data. The precision of the methods was (SD values) 0·06, 0·07, and 0·13 mm, respectively. The benefits of the use of the co-ordinate measuring machine are obvious, since it can measure tooth movements in relation to reference planes in all directions.

EVALUATION OF A SURGICAL TECHNIQUE FOR TRIGONOCEPHALY

Clinically diagnosed trigonocephaly have been treated by a standard surgical technique developed at Göteborg University Craniofacial Unit. To evaluate the technique we designed a study to include both subjective and objective assessments. Of 30 patients operated on between 1988-1997, 15 patients with at least three years postoperative follow-up have been included. An evaluation of the surgical outcome of the bitemporal width, the forehead contour, and the intercanthal distance was made both subjectively using a visual analogue scale (VAS) and objectively with analyses of cephalograms taken preoperatively and postoperatively at 3 and 5 years of age. For the subjective evaluation a control group of 10 randomly selected children from a Child Welfare Centre were selected. For the objective evaluation the control group consisted of cephalograms from children born with cleft lip and palate who were matched regarding sex and age. Both cephalometric analysis and subjective studies of the outcome indicated improvement. When the forehead contour was investigated the number of patients who had been improved or corrected completely was higher when evaluated subjectively. When interorbital distance on cephalograms and intercanthal distance scores on VAS were evaluated, again the subjective study indicated improvement in more subjects.Clinically diagnosed trigonocephaly have been treated by a standard surgical technique developed at Göteborg University Craniofacial Unit. To evaluate the technique we designed a study to include both subjective and objective assessments. Of 30 patients operated on between 1988-1997, 15 patients with at least three years postoperative follow-up have been included. An evaluation of the surgical outcome of the bitemporal width, the forehead contour, and the intercanthal distance was made both subjectively using a visual analogue scale (VAS) and objectively with analyses of cephalograms taken preoperatively and postoperatively at 3 and 5 years of age. For the subjective evaluation a control group of 10 randomly selected children from a Child Welfare Centre were selected. For the objective evaluation the control group consisted of cephalograms from children born with cleft lip and palate who were matched regarding sex and age. Both cephalometric analysis and subjective studies of the outcome indicated improvement. When the forehead contour was investigated the number of patients who had been improved or corrected completely was higher when evaluated subjectively. When interorbital distance on cephalograms and intercanthal distance scores on VAS were evaluated, again the subjective study indicated improvement in more subjects.

Maxillary dental arch and occlusion in repaired clefts of the secondary palate : Influence of surgical closure with minimal denudation of bone

A change in the method of surgical repair of cleft palate initiated this study of 64 patients with various degree of clefts of the secondary palate. Study casts were obtained at different ages. Certain measurements were taken and compared with those made in a previous investigation of similar patients operated on by the so-called ?push-back? technique. Growth in the width of the maxillary dental arch and occlusion had improved, but there were significant differences only for the patients with velar clefts.