Jüri Kurol

Radiographic examination of ectopically erupting maxillary canines

This study analyzes the need for and possibility of obtaining further information from different radiographic procedures in 125 children with potential ectopic eruption of the maxillary canines. After clinical examination of 3,000 10 to 15-year-old children, it was found that 7% needed radiographic examinations for determination of the canine position. Eighty-four children (2.8%), with a total of 125 potential ectopically erupting maxillary canines diagnosed clinically and by means of periapical radiographs, were selected and a stepwise extended radiographic diagnostic procedure was used. Most canines in ectopic eruption were positioned palatally; the positions could be assessed with sufficient accuracy from conventional periapical films in 92% of the cases. Only in 37% of the cases, however, could the lateral incisor be projected free from the ectopic canine by the intraoral technique. The lamina dura of the lateral incisor facing the canine was often found to be interrupted. For 29% of the ectopic canines, the lateral incisors could neither be projected free nor judged free from resorptions and a supplementary polytomographic investigation was believed to be necessary. The number of resorbed teeth was doubled by polytomography and altogether 12.5% of the ectopic canines caused resorptions. A stepwise radiographic procedure including polytomography is described and recommended in cases of ectopic eruption of maxillary canines for determining the correct position and ruling out or confirming resorptions on incisors, thereby optimizing the orthodontic treatment planning.

Early treatment of palatally erupting maxillary canines by extraction of the primary canines

The effect of extraction of the primary canine on palatally erupting ectopic maxillary canines was analysed. There were 46 consecutive ectopic canines, in 35 individuals, aged 10.013.0 years (mean age 11.4 years) at the time of discovery of the ectopic eruption. All cases showed no or minor space loss. After extraction of the primary canine, the children were investigated clinically and radiographed at 6-month intervals for up to 18 months. In 36 of the 46 canines (78%) the palatal eruption changed to normal; 23 already showed improved positions after 6 months and 13 after 12 months. No new cases normalized after 12 months. We suggest that extraction of the primary canine is the treatment of choice in young individuals to correct palatally ectopically erupting maxillary canines provided that normal space conditions are present and no incisor root resorptions are found.

Resorption of incisors after ectopic eruption of maxillary canines: a CT study.

The purpose of the study was to analyze the extent and prevalence of resorption of maxillary incisors after ectopic eruption of the maxillary canines in a sample of subjects referred to an orthodontic specialist clinic for consultation. The subjects consisted of 107 children, 39 boys and 68 girls, between 9 and 15 years of age (mean 12.5 years), with 156 ectopically and 58 normally erupting maxillary canines. All children were subjected to a basic clinical and intraoral radiographic investigation. These radiographs were supplemented with computerized tomography (CT) of the upper alveolar bones in order to get more precise information on the positions and relationships between the maxillary canines and adjacent incisors and to evaluate resorptions on the roots of the incisors. The results showed that, relative to the roots of the adjacent incisors, the crowns of 21% the ectopically positioned canines were located to the buccal, 18% to the distobuccal, 27% to the lingual, 23% to the distolingual, 5% apically and 6% between the central and lateral incisors. Ninety-three percent of the ectopically positioned canines were in contact with the roots of the adjacent lateral incisor and 19% were in contact with the central incisor. The corresponding figures for the normally erupting canines were 49%. Resorptions on the roots of the incisors adjacent to the ectopically positioned canine occurred in 38% of the laterals and in 9% of the centrals. The resorptions were graded and tended to be extensive. Among the 58 resorbed lateral incisors, resorptions were slight in 31%, moderate in 9%, and severe with pulpal involvement in 60%. The corresponding figures for the 14 resorbed centrals were 36%, 21%, and 43%, respectively. About 60% of the resorptions involved the middle and apical thirds, the tip of the apex not included. On the sides with normally erupting canines, 3 lateral maxillary incisors were slightly or moderately resorbed distally. In all, 51 of the 107 subjects with ectopically erupting maxillary canines (48%) had resorbed maxillary incisors during the eruption of the maxillary canines. There were statistically significant correlations between ectopic eruption of the maxillary canine, contacts between the teeth and resorptions on the adjacent incisors. It was concluded that resorption on maxillary incisors after ectopic eruption of the maxillary canines is a more common phenomenon than previously reported and has to be considered in all cases with seriously diverging eruption of maxillary canines. It was also concluded that the resorptions of the roots of the incisors were caused by pressure during the eruption of the adjacent, aberrant canine. Finally, it was shown that CT scanning substantially increased the detection of root resorptions on incisors adjacent to ectopically erupting maxillary canines (about 50%). The sensitivity of intraoral films was low when diagnosing the resorptions, being calculated to 0.68.

Resorption of maxillary lateral incisors caused by ectopic eruption of the canines. A clinical and radiographic analysis of predisposing factors.

Factors predisposing to resorption of adjacent permanent lateral incisors caused by ectopic eruption of maxillary canines were evaluated. The subjects consisted of two groups: one with 40 lateral incisors with resorption caused by ectopic eruption and a control group of 118 ectopic eruption cases with no lateral incisor resorption. The mean age of the children in the two groups differed by only 0.7 of a year and ranged from 10.0 to 15.0 years, covering the normal eruption period of the maxillary canine. Resorption of lateral incisors was three times as common in girls as in boys. The resorption cases showed a more advanced dental development, a more medial canine position in the dental arch, and a slightly more mesial horizontal path of eruption (an average of 10 degrees) than that of the control cases. Factors such as the width of the dental follicle and proclination or distal tilting of the lateral incisor showed no correlation to the resorption. Potential resorption cases are always those in which the canine cusp in periapical and panoramic films is positioned medially to the midline of the lateral incisor. Such situations should be carefully investigated with polytomography if necessary. The risk of resorption also will increase with a more mesial horizontal path of eruption. From 10 years of age or younger, annual clinical examination by palpation of the canine eruption path is recommended. This clinical examination should be supplemented with a stepwise extended radiographic procedure in cases in which ectopic eruption of the maxillary canines is suspected.

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.

Incisor Root Resorptions Due to Ectopic Maxillary Canines Imaged by Computerized Tomography: A Comparative Study in Extracted Teeth

The purpose of the study was to analyze the ability of computerized tomography (CT) scanning to discriminate maxillary incisor root resorptions caused by ectopically erupting canines. Seventeen maxillary incisors were radiographed in vivo by CT scanning. Contiguous transverse CT scans with a slice thickness of 2 mm were exposed perpendicular to the long axis of the lateral incisors and through the crown of the adjacent, ectopically positioned maxillary canine. Each scan was analyzed and the resorptions on the roots of the laterals were graded according to the maximum depth of the cavity. After the lateral incisors were extracted they were clinically inspected, photographed in different light settings and views, and probed at the contact area between the laterals and the canines. The assessment of the extent of resorption in 4 stages on the CT images compared with the in vitro observations of the extracted roots showed a high degree of agreement for the extent of loss of root substance for all teeth. We conclude that CT scanning performed with good technique accurately reveals tooth root resorption. The presence and influence of the inherent artifacts of tooth root resorption on CT scans are discussed.

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.

Repelling magnets versus superelastic nickel-titanium coils in simultaneous distal movement of maxillary first and second molars.

Eighteen subjects, aged 12.5 to 18.3 years, with Class II malocclusion, deep overbite and moderate space deficiency in the maxilla were treated orthodontically using repelling rare earth magnets on one side and superelastic nickel-titanium coils on the contralateral side for simultaneous distalization of maxillary first and second molars. The force values of the magnets and the coils were calibrated to 225g at the start of treatment and when reactivation was performed every fourth week. Tooth movement was analyzed by measuring dental casts, lateral photographs of dental casts, and lateral skull radiographs before and after 6 months of treatment. Mean distal molar movement was 3.2 mm for the supercoils and 2.2 mm for the magnets. Mean reduction of the overbite was 3.6 mm. Complaints of discomfort were more frequent for the magnet sides. The results indicate that superelastic coils are more effective than repelling rare earth magnets in molar distalization.

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.