Stanley G. Jacobs, BDSc(Melb), FDSRCS(Eng), DOrthRCS(Eng)*

Transcription

1 Australian Dental Journal 1998;43:(1):20-7 Reducing the incidence of unerupted palatally displaced canines by extraction of deciduous canines. The history and application of this procedure with some case repor t s Stanley G. Jacobs, BDSc(Melb), FDSRCS(Eng), DOrthRCS(Eng)* Abstract The procedure of extracting the deciduous canine to reduce the incidence of the unerupted palatally displaced canine was first described in 1951, and an article solely devoted to the technique appeared in The procedure then virtually vanished until A prospective study published in 1988 created the first widespread interest in the method which now appears in major texts. Why the procedure succeeds is uncertain. In the 1950s nonresorption of the deciduous canine was thought to cause palatal deflection of its successor and therefore it appeared appropriate to extract the obstructing deciduous tooth. It has been estimated that the technique should be successful in approximately one in three of all cases in the population aged 10 to 13 years. The earlier the detection the better the prognosis, because the unerupted canine frequently moves more mesially with time. Before the procedure is attempted it is important to discuss possible outcomes with the patient. Three successfully treated cases are illustrated. The first conformed with the guidelines of having an uncrowded maxillary arch and being aged between 10 and 13 years. The second was aged 15 years 2 months at commencement. An unsuccessful surgical exposure of the permanent canines followed by extraction of the deciduous canines was carried out in the third case. Key words: Malocclusion, mixed dentition, interceptive orthodontics, impacted tooth, unerupted tooth, case reports. (Received for publication August Revised December Accepted March 1997.) Introduction The aims of this article are: 1) To review the l i t e r ature about the procedure of reducing the incidence of the palatally displaced canine (PDC) by extraction of the deciduous canine. The history, application and precautions to be observed will be *Specialist Orthodontist, Dental Health Services, Victoria; Senior Associate, The University of Melbourne. examined. 2) To illustrate the procedure with some case reports. Discussion about the procedure of reducing the incidence of PDC by extraction of the deciduous canine first appeared in the 1950s and then virtually disappeared for some decades before being reintroduced in the 1980s. Lappin 1 in 1951 reported that Broadbent in a communication to him (1950) demonstrated that, by taking a series of anteroposterior and lateral headplates of children starting at the age of six years and then at three to six-monthly intervals, it was possible to accurately monitor the eruption path of the permanent canine. By noting deviations from n o rmal Broadbent could predict when the perm a n e n t maxillary canine was being deflected palatally long before its normal eruption time. As soon as this condition was detected he removed the offending tooth, the deciduous canine, so that the permanent canine would not be deflected palatally. In 1956, Hitchin 2 in the United Kingdom noted L a p p i n s 1 r e p o rt. Kettle 3 (1958) wrote that emphasis must be placed on the early diagnosis and treat m e n t of impacted canines. He said the extraction of a deciduous maxillary canine often allowed a misplaced p e rmanent canine to erupt into a good position. His list of references contained Lappin s art i c l e. 1 In 1959 Newcomb 4 published the first art i c l e totally devoted to the subject. He declared that the bulk of the literature on PDCs incorrectly implied that they cannot be prevented. Newcomb 4 s t ated that he wished to interest orthodontists in the routine seri a l use of both lateral and posteroanterior head films, p rior to placement of appliances, to help recognize potential PDCs and intercept them. He detailed s e veral cases where, by the extraction of deciduous canines, PDCs erupted in the line of the arch. He s h owed that the lateral head film provided no guide to potential impactions (in contradiction to his hope s t ated above). He illustrated a case to indicate that the procedure did not always prevent impaction. After 20 Australian Dental Journal 1998;43:1.

2 N e w c o m b s article the technique seems to have been ignored for two decades. In 1963, Miller 5 wrote an article on the influence of congenitally missing teeth on the eruption of the upper canine. He also recommended extraction of the deciduous canine when the permanent tooth was becoming displaced but made no reference to the work of Broadbent, Lappin 1 or Newcomb. 4 Howard 6 (1978) in an article on impacted teeth with unexpected improvements presented two cases (out of six) involving PDCs. After extraction of the deciduous canine the PDC erupted. Howard 6 said the cases presented in his paper were curious. Again, no reference was made to the work of Broadbent, Lappin 1 or Newcomb. 4 Established texts of the time by Moyers, 7 Tulley and Campbell, 8 and Graber 9 whilst dealing with many aspects of PDC did not mention the possibility of intercepting/preventing the impaction. In 1981, Williams 10 published a paper reviewing the use of radiographs in diagnosing and preventing PDC; he demonstrated clinical results (three cases) in the treatment of potential impaction by the extraction of the deciduous canine. Williams 10 confined his observations to Class I malocclusions without stating the reason for this limitation. He a c k n owledged the work of Broadbent and Newcomb. 4 However even later, in 1986, the popular text by Proffit 11 did not mention the procedure. The spur for renewed interest came from the 1988 work of Ericson and Kurol. 12 They carried out a prospective study to analyse the effect of extraction of the deciduous canine on PDC in young individuals. They also investigated how much time elapsed until correction occurred. Forty-six consecutive PDCs were studied in children aged between 10 and 13 ye a rs. The PDCs were followed clinically and radiologically at six-monthly intervals. All cases were uncrowded. In 36 of the 46 canines the initially palatal eruption changed to normal and the canines finished in a clinically correct position. Six months after the extractions 23 canines (50 per cent of the ori ginal) already showed radiogr a p h i c a l l y i m p r oved positions. After 12 months the position of the other 13 teeth had improved. All the canines which improved showed clinically good positions at the 18 months follow-up visit. No new cases of i m p r ovement occurred between the 12 months and 18 months observation. Ninety-two per cent of the canines which overlapped the roots of the adjacent l ateral incisor by less than half in the panoramic r a d i o graph normalized. Sixty-four per cent of the canines which initially overlapped the lateral incisor by more than half of the root normalized. For ethical reasons Ericson and Ku r o l 12 did not design a study with an untreated control. This lack of a control has been criticized by Collett and D Adamo. 13 Lindauer et al. 14 also noted this lack of a control group and stated that it is difficult to evaluate the efficacy of the procedure without a reliable way to predict which canines will become impacted. In an attempt to find a way to predict PDC, they carried out a retrospective study examining the location of the cusp tip of the unerupted canine relative to the lateral incisor root in panoramic radiographs of patients in the late mixed dentition. There were two groups studied at two stages of dental development. One group had PDC (28 patients with 41 PDCs), the other group was a control (28 patients with all 56 canines normally erupted). The two stages of dental development were: a) the late mixed dentition; and b) the permanent dentition when impaction had been confirmed for the first group and normal eruption had occurred in the control group. Reviewing the panoramic radiographs of the late mixed dentition they noted: 1) Seventy-eight per cent of PDCs had cusp tips which overlapped or were mesial to the lateral incisor root; 2) In the control group only 4 per cent of non-impacted canine cusp tips overlapped the lateral incisor root and none of these was mesial to the mid-line of the lateral incisor. They did not indicate whether the 4 per cent of non-impacted canine cusp tips which overlapped the lateral incisors were investigated to ascertain whether the canine was palatal or labial at that mixed-dentition stage. Lindauer et al. 14 also expressed their findings in other terms: 1) The sensitivity (the proportion of people who test positive to a condition who really do have a condition) of this criterion of predicting PDC from mixed dentition panoramic radiographs was 0.78; 2) The specificity (the proportion of people who test negative to a condition who really do not have a condition) was These findings support Ericson and Ku r o l s 12 s t at e- ment that it is hardly likely that, as reported above, the 22 out of 24 canines (92 per cent) in positions distal to the midline of the lateral incisor root and 14 out of 22 (64 per cent) in positions medial to the midline of the lateral incisor root would have corr e c t e d s p o n t a n e o u s l y. Another prospective study was carried out by Power and Short 16 in 1993 to confirm whether the procedure was successful and to assess fa c t o rs possibly influencing the outcome. Again, there was no u n t r e ated control gr o u p. Among the differences from E ricson and Ku r o l s 12 work were that 1) c r ow d e d cases and 2) cases with adjacent lateral incisors missing were also included. Power and Short 16 f o u n d t h at : 1 ) Twenty-nine (62 per cent) of 47 PDCs a c h i e ved a normal eru p t i ve position and nine (19 per cent) showed some improvement. 2) The degree of h o rizontal overlap of the adjacent incisor was the most i m p o rtant single factor determining whether success was achieved or not. 3) Eighty-six per cent of successful cases had adequate space within the arch, whilst over half of those in which only an improvement or outright failure occurred had crow d i n g. Australian Dental Journal 1998;43:1. 21

3 Ericson and Kurol s 12 work stimulated Jacobs 17 to publish some case histories employing the procedure. An abbreviated ve rsion of this article was subsequently published in the Year Book of Dentistry so increasing awareness of the procedure even more. As a result of Ericson and Kurol s 12 work the procedure now appears in current editions of major texts which omitted mention of it in the past. Why the procedure succeeds a) Aetiology of PDC and deciduous canines In the past, non-resorption of the deciduous canine was considered to be an important aetiologic factor in PDC. Lappin 1 wrote, as stated earlier, that as soon as this condition was detected Broadbent removed the offending tooth, the deciduous canine. N e w c o m b 4 also supported this view. Howe ve r, Moss 19 in 1972 said that in some cases failure of resorption of the deciduous tooth may be due to the canine being displaced, resulting in an abnormal path of eruption. Current opinion does not ascribe a ny importance to the non-resorption of the deciduous canine as an aetiologic factor in PDC. 20 The findings of Schmuth et al. 21 refute the influence of apparently unresorbed deciduous canines. In a computerized tomography (CT) study of 13 aberrant canines they found cases where the CT image revealed root resorption of the deciduous canines which was not apparent on conventional X-ray images of the same area. Currently there are two main schools of thought about the aetiology of PDC. They are the lack of guidance from the lateral incisor root theory, and the anomaly of genetic origin theory. A spirited debate has recently been published by the main proponents of each theory. 22,23 Becker 22 even stated that there m ay be several different types of canine displacement: some genetically controlled, some not. It is not readily apparent, if the genetic theory is valid, why the comparatively minor intervention procedure of extraction of the deciduous canine is so successful. b) Öhman and Öhman s work Jacobs 24 drew on Öhman and Öhman s25 work for an explanation. Öhman and Öhman25 studied factors associated with eruption as well as the eruption route of impacted and unerupted teeth following surgical exposure and packing of the socket. Their findings support the hypothesis that forces within the surrounding tissues act upon the exposed crown in such a way as to direct it towards the area where the tissues were removed. They drew an analogy between the way a cyst cavity fills after marsupialization and the forces acting upon a tooth crown after surgical exposure. However, this work does not seem to explain why a PDC which is distant from the extraction site and completely surrounded by bone, erupts in the line of the arch. Application of the technique a) Success rate If Ericson and Kurol s 12 figure of 78 per cent PDC changed to normal eruption is combined with the low prevalence of crowding in cases with PDC (approximately 50 per cent) then this procedure of extraction of the deciduous canine should be successful in approximately one in three of all cases in the population aged between 10 and 13 years. 24 Because impacted canines frequently move more mesially with time, early detection before the canine cusp tip overlaps the adjacent incisor by more than half is important for this would increase the success rate. Manipulation of the space conditions by distal movement of upper buccal segments or by localized permanent tooth extractions 3,24 may also increase the success rate. b) To relieve resorption present In Ericson and Kurol s cases of PDC there were four cases with resorption of the root of the lateral incisor diagnosed at the start. The position of the PDC normalized in two cases, was unchanged in one, and deteriorated in the other. c) To prevent incisor resorption If instituted early, the procedure may help to reduce the incidence of root resorption of adjacent incisors. Ericson and Kurol 26 carried out a detailed radiographic study of 46 cases of maxillary incisor resorption related to unerupted canines. There were 40 lateral incisors and 6 central incisors. In the resorbed lateral incisor cases 68 per cent of the canines were positioned palatal or disto-palatal. The age of the children when resorptions were radiographically verified ranged from 10.1 to 14.9 years (mean 12.2±1.2 years SD). Six lateral incisors were diagnosed as resorbed between years. Early diagnosis of impaction is necessary if extraction of the deciduous canine is to be most effective in allowing PDC to correct and this early correction may reduce the incidence of incisor root resorption. Precautions a) Discussion with patients Before a deciduous canine is extracted in an attempt to prevent/intercept PDC, the clinician must discuss possible outcomes with the patient (and parent). If the canine does not erupt there will be a g a p, which the patient usually dislikes, therefore treatment will be required. This may be by ort h o d o n t i c s f o l l owing surgical uncove ring of the canine, or by r e s t o r at i ve means. If a fixed or removable restorat i ve solution is chosen the patient will have to wear one or more prostheses for the rest of his/her life. Some patients may not wish to consider any form of treatment if he/she is satisfied with the dental appearance. This will often be the case where the 22 Australian Dental Journal 1998;43:1.

4 deciduous canine is retained, has not suffered extensive attrition or carious attack, and where there are no other significant features of a malocclusion. 27 It is not possible to estimate how long a deciduous canine will be retained, even if it has a non-resorbed root at the time of the initial examination. If it has been decided to leave the permanent canine in place radiological monitoring is desirable in case complications, such as resorption of an adjacent incisor root, occur. b) Permanent tooth extraction Space maintenance, a form of appliance therapy, may be indicated if a permanent tooth is extracted. Therefore, if the PDC does not erupt subsequently the patient must wear appliances longer than if u n c ove ri n g, followed by the placement of appliances, was carried out immediately the impaction was discovered. The patient should be warned of this prior to commencement of treatment. An uncommon complication of unerupted teeth is a n k y l o s i s. Sometimes orthodontic and surgi c a l measures fail to move an ankylosed tooth which must then be extracted. The operator should be aware of this potential complication when considering the extraction of a permanent tooth to make space for a P D C. Case repor t s Case 1 Male, date of birth 8/6/77 The patient was first seen at the Royal Dental Hospital of Melbourne on 30/3/89. Figure 1a, the panoramic radiograph, shows that the patient was in the mixed dentition and that all permanent teeth were developing. He was referred to the orthodontic department on 7/8/90 with his major concern being prominent maxillary incisors. The vertical image shift of 13, 23 between the radiographs taken that day, the panoramic radiograph of Fig. 1b and the anterior maxillary occlusal of Fig. 1c, shows that 13, 23 were palatally displaced. On the same day 53, 63 were extracted. Figure 1d, the panoramic radiogr a p h of 14/2/91, shows that the position of 13, 23 had improved. By 2/8/91 1 mm of 13 and 3 mm of 23 had erupted in the line of the arch. Figure 1e, an intra-oral photograph taken 7 months later, shows 13, 23 fully erupted. Comments In Fig. 1b, 13, 23 overlap the adjacent incisors by less than half of the root so the prognosis for corr e c t i o n, based on Ericson and Kurol s 12 findings, was 92 per cent. The canines improved their position after extraction of the deciduous canines within six months (as did 50 per cent in Ericson and Kurol s 12 study) and were in a clinically good position within 12 months. The 13, 23 moved mesially in the 16 months between the radiographs in Fig. 1a and 1b, that is, between the ages of 11 years 9 months and 13 years 2 months. The panoramic radiograph of Fig. 1a did not give rise to any suspicion that 13, 23 were displaced. However, the overlap of the lateral incisors by the canines 16 months later gave rise to suspicion. The 13, 23 were also palpable in the palate at that time. Case 2 Male, date of birth 29/12/78 Figure 2a, the panoramic radiograph of 11/2/86, shows 12, 22 are missing, that the cusp tips of 13, 23 are superimposed on the apices of 53, 63 and a large median diastema is present between 11, 21. Figure 2b, the panoramic radiograph of 27/8/91, shows 23 superimposed on the distal half of the root of 21. Figure 2c is a periapical radiograph taken on 24/3/93 because the patient sustained some trauma to his front teeth. Figure 2d is a panoramic radiograph taken on 21/7/93. He was seen in the orthodontic department on 5/1/94. At that time 23 was palpable in the palate. In addition, the vertical image shift of 23 between the periapical radiograph of Fig. 2c and the panoramic radiograph of Fig. 2d confirmed that 23 was palatal. On 4/2/94 53, 63 were extracted. Figure 2e, the panoramic radiograph of 12/9/94, shows the position of 23 has improved. Figure 2f, the intra-oral photograph of 18/5/95, shows the tip of 23 emerging in the line of the arch. Comments The 23 overlapped the adjacent incisor (which is not the lateral incisor) by less than half of the root of that incisor. If Ericson and Kurol s 12 work can be extrapolated to cases with missing adjacent lateral incisors then the prognosis for correction was 92 per cent. However, the patient was 15 years 2 months when 63 was extracted, much older than the oldest in Ericson and Ku r o l s 12 s t u d y. Therefore, the clinician was uncertain of the prognosis and the patient was advised of this. Fortunately, 23 did improve within seven months (Fig. 2e) and was erupting in the line of the arch within 15 months of the extraction. Although Ericson and Kurol 12 concluded that with l ater diagnosis altern at i ve modes of treat m e n t should be considered, this case and another published by Jacobs 24 show that the procedure can sometimes be successful after 13 years of age. In addition, this case with another described by Jacobs 24 and the study of Power and Short 16 show that the procedure can be successful when adjacent lateral incisors are missing. The 23 did not move more mesially in twenty-three months (Fig. 2b-Fig. 2d). Why PDCs move more mesially in some cases and not in others has not been determined. As awareness of the significance of the appearance on a panoramic radiograph of an unerupted canine superimposed on the root of an adjacent incisor Australian Dental Journal 1998;43:1. 23

5 a b c d Fig. 1. Case 1. a, Cropped panoramic radiogr a p h in the mixed dentition 30/3/89. b, Cropped panoramic radiograph with 13, 23 overlapping 12, 22 7/8/90. c, Anterior maxillary occlusal 7/8/90. d, Cropped panoramic radiograph after extraction of 53, 63. The position of 13, 23 has improved 14/2/91. e, 13, 23 fully erupted 27/3/92. e 24 Australian Dental Journal 1998;43:1.

6 a b c d e f Fig. 2. Case 2. a, Cropped panoramic radiograph with 12, 22 missing and cusp tips of 13, 23 superimposed on apices of 53, 63 11/2/86. b, Cropped panoramic radiograph with 23 superimposed on distal of 21 root 27/8/91. c, Periapical radiograph of 23 region 24/3/93. d, Cropped panoramic radiograph 21/7/93. e, Cropped panoramic radiograph seven months after extraction of 53, 63. The position of 23 has improved 12/9/94. f, Tip of 23 emerging in line of the arch 18/5/95. Australian Dental Journal 1998;43:1. 25

7 b a c d Fig. 3. Case 3. a, Cropped panoramic radiogr a p h with 12 missing but a supernumerary present, 22 peg-shaped, 13, 23 ectopic and 75 ankylosed 16/11/93. b, Right maxillary occlusal 31/5/94. c, Left maxillary occlusal 31/5/94. d, Cropped panoramic radiograph supern u m e r a ry extracted, 13, 23 position unchanged, 35 erupting 2/6/95. e, Cropped panoramic radiograph 13 and 35 erupted, 23 close to eruption 9/12/96. e 26 Australian Dental Journal 1998;43:1.

8 becomes more widespread delays in referral or treatment, as occurred in this case, will become less frequent. Case 3 Female, date of birth 17/6/82 Figure 3a, the panoramic radiograph of 16/11/93, shows that the patient was in the mixed dentition, 12 was absent but there was a small unerupted supernumerary in the area, 22 was peg-shaped, 13, 23 were ectopic, and 75 was ankylosed. The patient was first seen in the Orthodontic Department on 31/5/94 when two lateral maxillary occlusals were taken (Fig. 3b, 3c). The horizontal tube shift between the two occlusals (Fig. 3b, 3c) and the vertical tube shift between the radiograph of Fig. 3a and the two occlusals (Fig. 3b, 3c) show that 13, 23 were palatally placed. On 20/10/94 the supern u m e r a ry and the ankylosed 75 were extracted; 13, 23 were surgically uncovered and their sockets packed. Twenty days post-surgery the crowns of 13, 23 had been re-covered. Figure 3d, the panoramic radiograph of 2/6/95, shows that the position of 13, 23 had not changed but 35 was erupting. On 17/7/95 53, 63 were extracted. The panoramic radiograph of 9/12/96 (Fig. 3e) shows that 13, 35 had erupted and that 23 was in a favourable position to erupt (the tip of its cusp was blanching the mucosa). Comments Usually, if extraction of the deciduous canine is unsuccessful, uncovering of the impacted tooth is part of the definitive solution. In this case it was the other way round. Once again the impacted canines were in a clinically good position within eighteen months, in agreement with Ericson and Kurol s 12 findings. The ankylosed 75 was the reason 35 did not erupt. When 75 was extracted 35 erupted. Conclusion This review has shown how a useful technique can be introduced, taken up for a time, and then ignored for some decades. Revival was brought about by the publication of the results of a prospective study. This type of study has more standing in the scientific literature than articles illustrated with a few case reports. The procedure has been confirmed by another prospective study and now features in major orthodontic texts. However, neither study included an untreated control. References 1. Lappin MM. Practical management of the impacted maxillary cuspid. Am J Orthod 1951;37: Hitchin AD. The impacted maxillary canine. Br Dent J 1956;100: Kettle MA. Treatment of the unerupted maxillary canine. Dent Practit 1958;8: Newcomb MR. Recognition and interception of aberrant canine eruption. Angle Orthod 1959;29: Miller BH. The influence of congenitally missing teeth on the eruption of the upper canine. Dent Practit 1963;13: H oward RD. Impacted tooth position: unexpected improve m e n t s. Br J Orthod 1978;5: Moyers RE. Handbook of orthodontics. 2nd edn. Chicago: Year Book Publishers, Tulley WJ, Campbell AC. A manual of practical orthodontics. 3rd edn. Bristol; John Wright and Sons, Graber TM. Orthodontics principles and practice. 3rd edn. Philadelphia: Saunders, Williams BH. Diagnosis and prevention of maxillary cuspid impaction. Angle Orthod 1981;51: Proffit WR. Contemporary ort h o d o n t i c s. St Louis: M o s b y, E ricson S, Kurol J. Early treatment of palatally erupting maxillary canines by extraction of the primary canines. Eur J Orthod 1988;10: Collett A, D Adamo S. Letter to the editor. Am J Orthod Dentofacial Orthop 1991;100:25A. 14. Lindauer SJ, Rubenstein LK, Hang WM, Andersen WC, Isaacson RJ. Canine impaction identified early with panoramic radiographs. J Am Dent Assoc 1992;123: Polgar S, Thomas SA. Introduction to research in the health sciences. 3rd edn. Melbourne: Churchill Livingstone, 1995: Power SM, Short MBE. An investigation into the response of palatally displaced canines to the removal of deciduous canines and an assessment of factors contributing to favourable eruption. Br J Orthod 1993;20: Jacobs SG. Reducing the incidence of palatally impacted maxillary canines by extraction of deciduous canines: a useful preventive/ interceptive orthodontic procedure. Case reports. Aust Dent J 1992;37: Jacobs SG. Reducing the incidence of palatally impacted maxillary canines by extraction of deciduous canines: a useful preventive /interceptive orthodontic procedure. Case reports. In: Meskin LH, ed. The year book of dentistry. St Louis: Mosby, 1993: Moss JP. The unerupted canine. Dent Practit 1972;22: Peck S, Peck L, Kataja M. The palatally displaced canine as a dental anomaly of genetic origin. Angle Orthod 1994;64: Schmuth GPF, Freisfeld M, Köster O, Schüller H. The application of computerized tomography (CT) in cases of impacted maxillary canines. Eur J Orthod 1992;14: Becker A. Palatal canine displacement: guidance theory or an anomaly of genetic origin? In defense of the guidance theory of palatal canine displacement. Angle Orthod 1995;65: Peck S, Peck L, Kataja M. Palatal canine displacement: guidance theory or an anomaly of genetic origin? Sense and nonsense regarding palatal canines. Angle Orthod 1995;65: Jacobs SG. Palatally impacted canines: aetiology of impaction and the scope for interception. Report of cases outside the guidelines for interception. Aust Dent J 1994;39: Öhman I, Öhman A. The eruption tendency and changes of direction of impacted teeth following surgical exposure. Oral Surg Oral Med Oral Pathol 1980;49: Ericson S, Kurol J. Incisor resorption caused by maxillary cuspids. A radiographic study. Angle Orthod 1987;57: Ferguson JW. Management of the unerupted maxillary canine. Br Dent J 1990;169:11-7. Address for correspondence/reprints: Dental Health Services, Victoria, 711 Elizabeth Street, Melbourne, Victoria Australian Dental Journal 1998;43:1. 27