INTRODUCTION

Canines are important in establishing and maintaining the dentition's form, function, and aesthetics. The maxillary canine is one of the most frequently impacted teeth with an incidence of about 2%.12 Previous studies have found palatal impaction in 85% of ectopically positioned maxillary canines.3–5 In a more recent study, 50% of impacted maxillary canines were palatally impacted.6

Impacted teeth may cause neighboring teeth to migrate or become excessively mobile due to root resorption, loss of arch length, dentigerous cyst formation, local infections and referred pain, ankylosis, or resorption of the impacted tooth.7–10 On the other hand, surgical-orthodontic treatment may damage impacted canines, adjacent teeth, and supporting structures and eventually cause detrimental changes in the periodontal status.11–15 The anatomical structure of the soft tissue that covers impacted maxillary canines and the treatment technique are considered major factors that influence posttreatment periodontal health of the canines and their adjacent teeth.1617

The initial vertical and horizontal position of the maxillary impacted canine may also affect posttreatment periodontal status, but data on this issue are scarce. The mesiodistal and vertical position of the cusp of the impacted canine was mainly used to predict canine eruption and impaction probability.1819 Orthodontic correction of impacted canines requires movement in all three directions—vertical, palatal, and buccal—which rarely occurs in orthodontic treatment of other types of malocclusion and may affect the final periodontal status of the impacted tooth.12 The distance and direction of movement of palatally impacted canines during treatment is determined by the canines' initial vertical and horizontal position. The effect the initial vertical and horizontal position of an impacted canine has on the canine's periodontal status after surgery with the closed-eruption eruption technique is unknown.

This retrospective study evaluates the impact of surgical treatment with the closed-flap eruption technique combined with orthodontics and the initial vertical and mesiodistal position of palatally impacted maxillary canines on the periodontal health of the impacted canines and adjacent teeth.

MATERIALS AND METHODS

This retrospective study included 32 patients (22 female and 10 male) previously treated for unilateral palatally impacted maxillary canines. Mean treatment time was 17.1 ± 6.7 months (range: 6–30 months). Average patient age at the periodontal examination 3 months after removal of the fixed appliances was 18.2 ± 5.1 years (range: 12–42 years).

The initial position of the impacted canine was assessed on a panoramic image using a modified version of the criteria proposed by Ericson and Kurol18 (Figure 1). The vertical and horizontal position of the impacted canine was evaluated in relation to the adjacent lateral incisor. A horizontal line was drawn through the midpoint of the lateral incisor root to determine the vertical position of the impacted canine. The impacted permanent canine could have one of two vertical positions: the canine's cusp could be above (V1) or below (V2) the horizontal reference line. The horizontal position of the impacted canines was determined according to the long axis of the adjacent lateral incisor. The impacted permanent canine could have one of two horizontal positions: the canine's cusp could be distal (H1) or mesial (H2) to the vertical axis of the lateral incisor (Figure 1).

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The material consisted of all patients who were treated by one of the authors (DS) during a period of 4 years and underwent surgery with the closed-eruption technique according to Kokich and Mathews20 (Figure 2). An orthodontic eyelet connected to a ligation chain was bonded to the surface of the impacted canine after surgical exposure, and the flap was repositioned with the ligation chain extending through the flap. The canine was brought into position with a light force. The palatal arch was used for anchorage at the start of treatment and a fixed appliance was used later for the final positioning of the canine into the dental arch. The patients' oral hygiene was assessed monthly after instruction at the start of treatment.

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The posttreatment periodontal examination was carried out by one periodontologist 3 months after the fixed appliances were taken off and a removable retainer was fitted. The periodontal status of the first premolar, canine, and lateral incisor was evaluated by assessing periodontal pocket depth and gingival recession. Pocket depth was measured from the base of the pocket to the gingival margin with an accuracy of 1 mm.21 A Williams probe was inserted parallel to the vertical axis of the tooth and “walked” circumferentially around each surface of the tooth to detect the areas of deepest penetration. Six tooth surfaces were probed (Figure 3): mesiolabial (ML), labial (L), distolabial (DL), distopalatal (DP), palatal (P), and mesiopalatal (MP). The technique used to evaluate pocket depth was also used to evaluate gingival recession, but the distance from the cementoenamel junction to the gingival margin was measured.21 Four tooth surfaces were used for measurement of gingival recession: mesial (M), palatal (P), distal (D), and labial (L). A split-mouth method was used to compare the affected side with the unaffected side in the same patient. Significance was determined with the Mann-Whitney U-test.

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The Simplified Oral Health Index (OHI-S) by Greene and Vermillion22 was used to assess oral hygiene at the posttreatment examination and avoid bias of the latter factor on pocket depth. Measurement errors were analyzed using a method suggested by Bland and Altman.23 Pocket depth and gingival recession were measured twice for 10 patients. The estimated error between measurements was calculated with this formula:

where ±2 SD are the limits within which 95% of the differences between repeated measurements are expected to lie, d₁ = first measurement, d₂ = second measurement, and N = number of patients. Error in pocket depth is reported as ±2 SD of the differences between repeated measurements and does not exceed ±0.4 mm. The limits of mean gingival recession were ±0.1. The effects of these errors on the reliability of the pocket depth and gingival recession measurements were deemed nonsignificant.

RESULTS

Mean pocket depth at the mesiopalatal point (MPP) on the canine that had undergone surgery combined with orthodontics was 3.1 mm (±1.0 mm). This was greater than mean pocket depth at the same point on the contralateral canines (2.4 ± 0.6 mm; P < .01) (Table 1).

Table 1.  Periodontal Pocket Depth of Impacted Canines and Adjacent Teeth After Surgical-Orthodontic Treatment^a

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Pocket depth varied in some sectors: at the distopalatal point (DPP) on the lateral incisor, pocket depth was greater in the group of impacted canines with initial vertical position V2 (2.93 ± 0.92 mm) than in the group with a vertical position V1 (2.33 ± 1.14 mm; P < .05). At other points on the teeth, differences in pocket depth in groups V1 and V2 were nonsignificant (Table 2).

Table 2.  Influence of the Initial Vertical Position of the Impacted Canine on Periodontal Pocket Depth (mm) After Surgical-Orthodon tic Treatment ^a

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Table 3 presents pocket depth dependence on the initial mesiodistal position of the impacted canine. Pocket depth at the adjacent premolar labial point (LP) was greater (2.7 ± 0.5 mm; P < .01) in the group of impacted canines with initial horizontal position H2 than in the group with horizontal position H1 (2.04 ± 0.68 mm). Increases in pocket depth at the premolar distal labial point (DLP, P < .05) and mesiolabial point (MLP, P < .05) were similar. Deeper pocket depths occurred at the lateral incisor MLP (P < .05) and the canine LP (P < .01) in group H2.

Table 3.  Influence of the Initial Mesiodistal Localization of the Im pacted Canine on Periodontal Pocket Depth (mm) After Surgical-Orthodontic Treatment ^a

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The opposite was observed at the canine MPP. Pocket depth was smaller (2.4 ± 0.8 mm) when the initial mesiodistal position of the canine cusp was in sector H2 than in sector H1 (3.2 ± 1.0 mm; P < .01).

Six of 32 (18.75%) canines had gingival recession. Differences in gingival recession between the test and control groups were nonsignificant (Table 4). No gingival recessions were found at the first premolars. The mean OHI-S score was 0.6 ± 0.7, and there was no difference in oral hygiene comparing test and control sides.

Table 4.  Effect on Gingival Recession (mm) in Patients Treated for Impacted Maxillary Canines^a

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DISCUSSION

Most patients in our study were 20 years old or younger. Only two were older than 25 years. The periodontal status of the older subjects after surgical-orthodontic treatment showed no pathologic changes and did not influence our results. The patients were selected from all patients treated during the year 2000–2004 and were not randomly selected. The closed eruption technique is the most often used technique in our University because of advantages presented, for example, by Woloshyn and Artur15 and Kokich and Mathews.20

We found that surgical-orthodontic treatment affected pocket depth at the MPP on the impacted canine, which was greater (3.1 ± 1.0 mm) than on the control canines (2.4 ± 0.6 mm; P < .01). These findings support those of other research studies. D'Amico et al24 found that pocket depths were greater (by 5%) at the distobuccal surface of the impacted canines and at the mesiolingual, distolingual, and mesiolabial surfaces of the adjacent lateral incisors. Other authors found greater pocket depths on adjacent lateral incisors distolingually and on first premolars mesiolingually.25 In contrast to our study, Quirynen et al26 found no differences between test and control sides.

Analyzing the initial vertical and mesiodistal localization of the impacted canine and its influence on pocket depth, we found that pocket depth at the incisor DPP was greater (2.93 ± 0.91 mm) in the group of impacted canines with initial vertical position V2 than in the group with initial vertical position V1 (2.33 ± 1.13 mm; P < .05). This suggests that the periodontal tissue of the adjacent teeth undergoes increased stress during canine extrusion. The horizontal position of the impacted canine was also found to affect pocket depth when the groups of canines located in sectors H1 and H2 were compared. Pocket depths in group H2 were greater at the incisor MLP and premolar MLP, the LP, and the DLP than in group H1.

We found pocket depth differences between teeth adjacent to the impacted canine. Other authors have made similar observations.24–25 This suggests that surgical-orthodontic treatment mainly influences adjacent teeth, which are exposed to larger intrusive forces and root torque during extrusion, distal movement, and alignment of the impacted canine. Differences in pocket depth at the canine MPP may be explained by lack of root torque on the canine during correction of its position from the palatal position.

It could be said that the initial vertical and mesiodistal position of an impacted maxillary canine influences the periodontal condition of adjacent teeth following orthodontic-surgical treatment. However, pocket depth differences between control canines and adjacent teeth and between previously impacted canines and adjacent teeth were less than 4 mm and therefore clinically not significant.27 Therefore, our results indicate that a combined surgical-orthodontic approach in the treatment of impacted maxillary canines produces clinically acceptable periodontal conditions in the majority of patients treated.

CONCLUSIONS

• A combined surgical-orthodontic approach in the treatment of impacted maxillary canines produces clinically acceptable periodontal conditions.

• No significant differences in gingival recession were found between the test and the controls.

• Periodontal conditions of the impacted canine and adjacent teeth after surgical-orthodontic treatment depend on the initial vertical and horizontal position of the impacted canine.