Review: treatment strategies for ankylosed primary molars.
Abstract: AIM: The purpose of this article is to focus on aetiology and appropriate treatment techniques concerning anklyosis of primary molars. LITERATURE: The dental literature is reviewed in detail concerning aetiology, frequency of occurrence, diagnosis and longevity of ankylosed primary molars without successors. Treatment concepts are discussed. Long term implications of treatment decisions made in the mixed dentition are emphasised. Areas of treatment that are unsupported by evidence are identified as potential research topics. CONCLUSION: When the underlying premolar is present and the infra-occlusion is not progressive, then observation is appropriate. Only when there is severe disruption to the occlusion and/or the underlying premolar, extraction and space management may be appropriate. When the ankylosed primary molar has no underlying premolar, orthodontic input is needed to determine if extraction and space closure, extraction and transplantation or extraction and prosthetic replacement is the best plan. Key words: ankylosis, primary molars, infra-eruption, treatment
Article Type: Report
Subject: Tooth diseases (Care and treatment)
Molars (Diseases)
Implant dentures (Usage)
Implant dentures (Health aspects)
Author: Kennedy, D.B.
Pub Date: 12/01/2009
Publication: Name: European Archives of Paediatric Dentistry Publisher: European Academy of Paediatric Dentistry Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 European Academy of Paediatric Dentistry ISSN: 1818-6300
Issue: Date: Dec, 2009 Source Volume: 10 Source Issue: 4
Accession Number: 227281651
Full Text: Introduction

The ankylosed infra-erupted primary tooth has stopped its vertical movement relative to others along the occlusal plane such that marginal ridges are not at the same height as adjacent teeth [Noble et al., 2007]. Frequently such infra-erupted teeth are identified as ankylosed and clinically appear submerged [Kurol, 1984]. This implies that the tooth was at the correct level and has subsequently submerged. In reality, the adjacent teeth are erupting while the affected ankylosed tooth is maintaining its position because of root cementum fusion to the alveolar bone. This infra-occlusion has the potential to cause significant occlusal problems. Since Kurol's thesis on infra-erupted teeth [1984] there has been little new research. The purpose of this article is to focus on appropriate treatment techniques after briefly reviewing the aetiology, frequency and diagnosis; readers are referred to Teague et al., [1999a, 1999b] and Sabri [2008] for further review. Long term implications of treatment decisions made in the mixed dentition will be emphasised. Areas of treatment that are unsupported by evidence will be identified as potential research topics.


The true aetiology of ankylosed primary molar teeth remains unknown although trauma and genetics may be significant factors [Kurol, 1984]. The high frequency of ankylosis in reimplanted avulsed incisors together with traumatically induced ankylosis in experimental animals suggests that trauma to the periodontal membrane may be an aetiological factor. This traumatic disruption to the periodontal membrane may result in fusion of the root cementum to the adjacent alveolar bone. The higher frequency of infra-erupted teeth in siblings supports a genetic aetiology [Kurol, 1981]. Also, children with one infra-erupted tooth frequently show other teeth that subsequently present with infra-eruption [Brearley and McKibben, 1973]; this, in conjunction with the correlation of ankylosed primary molars and other dental anomalies [Baccetti 1998, Bjerklin et al., 1992 Garib et al., 2009], also supports a genetic aetiology.


The reported frequency of ankylosed infra-erupted teeth ranges from 1.3 to 38.5% and varies according to age [Kurol, 1981; Steigman et al., 1973]. In the primary dentition, the mandibular first primary molar is the most commonly affected tooth [Steigman et al., 1973]. The most common presentation is in the middle mixed dentition stage of development with second primary molars being more affected than the first primary molars [Biederman, 1962]; the mandible demonstrates a higher prevalence of ankylosed primary molars compared with the maxilla [Biederman, 1962].

There appears to be two kinds of ankylosed teeth. One demonstrates absence of progressive infraocclusion and self-resolution with slight delay in eruption [Kurol and Thilander, 1984a]. In the other type, infraocclusion deteriorates with increasing age which can create greater consequence in young children because there will be increased vertical compensatory eruption of adjacent teeth during continued growth to magnify the submergence. Therefore the potential impact is much less on a skeletally mature 12-year-old girl with an ankylosed retained primary molar than on a preadolescent 9-year-old male with a similar tooth who has yet to undergo his adolescent growth spurt.


The diagnosis is made from clinical signs and radiographic findings. Clinically there is a disturbance in the occlusal plane such that the marginal ridges of the ankylosed infra-erupted tooth or teeth are apical to the occlusal plane. This is quantifiable both radiographically and on study models. [Kurol, 1984; Kurol and Thilander, 1984; Kurol and Koch, 1985]. Clinically, such teeth may demonstrate a 'cracked teacup sound' or a dull sound on percussion compared to the adjacent teeth that are not infra-erupted [Biederman, 1962]. This subjective percussion testing has not withstood scientific documentation and therefore should not be given much credence. When the infra-eruption is severe, there is a break in the contact area with tipping of adjacent teeth within the same arch and supra-eruption of the teeth in the opposing arch. [Kurol 1981; Kurol 1984; Kurol and Koch, 1985; Kurol and Thilander, 1984a; Messer and Cline, 1980].


Radiographically, a step in the occlusal plane is observed and there may be an angular defect of the alveolar bone angled towards the ankylosed tooth [Brearley and McKibben, 1973; Kokich and Kokich, 2006]. This angular bone defect indicates at least temporary disturbance of eruption. By contrast, when the infra-erupted tooth has flat adjacent alveolar bone, then the tooth is not becoming progressively submerged. Successive radiographic evaluation can show self-correction and/or resolution of the angular defect with normal premolar eruption (Figure 1) [Brearley and McKibben, 1973; Kurol and Thilander, 1984a; Kurol and Koch, 1985; Messer and Cline, 1980]. The break in the periodontal membrane space is not likely to be observed radiographically because the ankylosis is not likely to present in the plane of the radiograph [Messer and Cline, 1980].

Ankylosis and submergence has been classified as slight, moderate and severe, based upon the amount of infra-occlusion [Messer and Cline, 1980]. Slight ankylosis involves less than 2 mm of submergence (Figure 1) while moderate submergence shows infra-occlusion to the contact area (Figure 5, 6). Severe ankylosis results in clinical submergence well below the adjacent contact area (Figure 2).


Other Associated Findings

Infra-erupted primary molars are associated with higher frequencies of infra-eruption in siblings and other family members [Kurol 1981; Bjerklin et al., 1992]. Also, there is a higher frequency of other associated dental anomalies such as supernumerary teeth, ectopic canines, ectopic first permanent molars and congenitally absent teeth [Baccetti 1998; Bjerklin et al., 1992; Garib et al., 2009]. One study has associated enamel hypocalcification of permanent first molars with ankylosed primary molars [Rule et al., 1972].

The association between ankylosed retained second primary molars and missing permanent successors has been reported [Ruprecht and Wright, 1967; Kurol and Thilander, 1984g; Rune and Sarnas, 1984; Baccetti, 1998; Hansen and Kjaer, 2000; Bjerklin and Bennett, 2000; Garib et al., 2009]. More mandibular second primary molars showed infra-occlusion (31%) than maxillary second primary molars (0%) when underlying premolars were absent [Rune and Sarnas, 1984]. The frequency of ankylosis of retained second primary molars without successors was 45% over a 10-year follow-up period [Bjerklin and Bennett, 2000]. With underlying aplasia 18 of 20 primary molars (90%) showed progressive infraocclusion; also the degree of infra-occlusion was greater in the primary molar which had a missing successor [Kurol and Thilander, 1984]. Using cross-sectional data, 25% of second primary molars without successors show ankylosis [Garib et al., 2009].

Longevity of Second Primary Molars Without Successors

Longevity studies on retained second primary molars that have no permanent successors are mainly available from Scandinavia [Kurol and Thilander, 1984a; Rune and Sarnas, 1984; Hansen and Kjaer, 2000; Bjerklin and Bennett, 2000; Sletten et al., 2003]. These involved longitudinal evaluation of second primary molars that orthodontists made the decision to retain. As such, the samples were biased towards those teeth that the orthodontist felt might have a good prognosis. The longevity of 123 retained primary second molars without successors was studied over 5 years with 26% of maxillary primary second molars lost to resorption and none to infra-occlusion [Rune and Sarnas, 1984]. Approximately half of the retained mandibular primary molars showed progressive root resorption over the 5-year mean observation period [Rune and Sarnas, 1984]. By contrast, in a similar study, the degree of root resorption was unchanged in 23 of 26 second primary molars with a 15-year observation period [Hansen and Kjaer, 2000]. As a result, the primary second molar lasted up to 15 years beyond normal anticipated exfoliation, which is the mean survival time of a bridge [Scurrin et al., 1998].

Kurol and Thilander [1984] reported that root resorption occurred in 21 of 36 mandibular second primary molar roots when there was underlying aplasia. The root resorption slowed as patient age increased [Kurol and Thilander, 1984]. In another longitudinal study from ages 10 to 20 years, Bjerklin and Bennett, [2000] showed that all 59 retained second primary molars exhibited mild progressive root resorption over the 10 year follow up. In adults from ages 36 to 48 years who had retained second primary molars with absent underlying second premolars, Sletten et al., [2004] reported negligible root resorption. Their sample had a less than expected incidence of retained maxillary primary second molars compared with mandibular teeth, implying that mandibular primary molars may be more durable than their maxillary counterparts [Rune and Sarnas, 1984; Sletten et al., 2003]. These studies likely reflect those retained second primary molars that had a good prognosis and were the 'survivors', as the decision had been made to retain these teeth. They give clinicians the reassurance that, if the retained second primary molars reach adulthood without significant root resorption or infra-occlusion, then they can be expected to last decades [Bjerklin and Bennett, 2000].

General Concepts of Treatment:

Potential consequences of leaving ankylosed teeth. Infraocclusion may become magnified coincident with skeletal growth due to compensatory eruption of adjacent teeth. Therefore, the earlier that ankylosis and infra-occlusion occurs, the greater potential there is for the problems reported by Becker et al., [1992 a,b,c]. Space loss occurred from tipping of the teeth adjacent to the infra-occluded primary molar with the space loss being greater than that normally lost by the leeway space [Becker et al., 1992a] (Figure 2). The teeth adjacent to infra-occluded primary molars tipped significantly and showed reduced vertical eruption [Becker et al., 1992b] (Figure 2). In unilateral cases, the midline was deflected towards the side of the ankylosis of the infra-occluded primary molar [Becker et al., 1992c]. The problem is greater when there is severe ankylosis in the late primary or early mixed dentition of second primary molars adjacent to the first permanent molar (Figure 2) [Messer and Cline, 1980]. Ankylosed second primary molars may be a potential periodontal threat to the adjacent first permanent molar [Kurol and Olson, 1991].

The further that an ankylosed primary molar is allowed to become infra-occluded, the more challenging is its surgical removal. This can lead to alveolar problems in the underlying premolar [Messer and Cline, 1980]. Furthermore there is increased likelihood of space loss and severe tipping of adjacent teeth (Figure 2). Also, this compromises the alveolar bone level both vertically and bucco-lingually for future prosthetic replacement where space is to be left open for restoration of an underlying missing premolar (Figure 2, 3). As many children exhibit low decay rates, the preferred long term restorative option for replacing missing premolar teeth is an implant-supported crown; the alveolus needed to support an implant must therefore be preserved.


Children with permanent successors below the ankylosed primary molars. In instances of ankylosed primary molars, the eruption of the underlying premolar teeth needs to be closely monitored radiographically. Kurol and Thilander [1984a] have demonstrated that, without intervention, in 92.5% of cases the ankylosed primary molar exfoliates with normal eruption of the permanent successor albeit with temporary delay of 6 months and therefore requires no intervention. Kurol and Thilander [1984a] reported that only 5 of 149 infra-occluded teeth (3.35%) did not exfoliate naturally and required extraction; there was minimal disruption to the adjacent teeth and to the occlusal table. Radiographic assessment is essential for the practitioner managing the child patient so that eruption deviations can be handled with extraction of the infra-erupted primary molar and space management procedures, such as a lingual holding arch in the mandibular arch and a Nance space maintainer in the maxillary arch. However, we are lacking studies that show this intervention actually works in terms of holding space and facilitating eruption. Indeed early extraction of infa-occluded primary molars may delay eruption and result in space loss [Kurol and Koch, 1985]. Early removal of an ankylosed primary molar will require longer space management through the transitional dentition; by contrast, late removal can accelerate premolar eruption and reduce space management.

The clinician would be wise to monitor the eruption of permanent successors beneath ankylosed primary teeth to ensure that there is no ectopia or tilting of adjacent teeth as described by Becker et al., [1992a, b, c]. Usually slight and moderate ankylosis will self-resolve; intervention is needed for the severe ankylosis cases. Intervention before space loss has occurred is preferable to management after negative sequelae have occurred.

Children without a permanent successor beneath ankylosed primary molars. The status of the primary molar crown, roots, restorative status, and alveolar support in conjunction with its level to the occlusal plane all need consideration [Rune and Sarnas, 1984]. Decisions made in the mixed dentition can significantly impact the overall management of the occlusion. It is therefore prudent for an orthodontist to be consulted relative to situations where there are missing teeth especially as missing teeth are associated with other eruption problems [Bjerklin et al., 192; Baccetti, 1998; Garib et al., 2009]. The long-term decision that has to be made is whether the ankylosed primary molar will be maintained in the arch or whether extraction is indicated followed by either space closure, or space retention followed by restorative replacement, or a transplant treatment plan. The clinician needs to answer the following questions to help establish the best treatment plan:

* What would you do if the absent tooth were present?

* Can this malocclusion be satisfactorily treated with an extraction and a space closure approach?

* What is the expected longevity of the primary molar?

There are several goals that need to be addressed when managing patients with retained second primary molars that show no permanent successors. A major goal is to establish the proper space in the arch for the missing tooth. The leeway space is mainly due to the difference in widths of the mandibular second primary molar versus the narrower underlying permanent second premolar. Failure to reduce the mesial distal width of the retained primary second molar results in a cusp to cusp, end on or half cusp Class II molar relationship despite a Class I canine occlusion (Figure 3). Interproximal reduction of the approximately 10 mm retained mandibular second primary molar in conjunction with restoration as described by Kokich and Kokich [2006] approximates the mesio-distal width closer to the average 7.5 mm width of the absent second premolar, thereby facilitating Class I molar and canine occlusion (Figure 4). This strategy is limited by the size of the pulp, the curvature of the primary second molar roots and their proximity to the adjacent first permanent molar and premolar [Sabri, 2008]. When this interproximal reduction is done on the second primary molar, the clinician should not challenge the pulp horns by excessive reduction, as this may cause pulpal inflammation and could stimulate premature root resorption. Whilst this supposition makes physiologic sense, there is no research to support this statement.


Another factor limiting the amount of interproximal reduction that can be done on a retained second primary molar is the curvature of the roots [Sabri, 2008]. With too much interproximal reduction, the adjacent first permanent molar drifts mesially and the first premolar distally resulting in root proximity of the retained second primary molar and the adjacent permanent teeth. It is supposed that this would accelerate root resorption but again, whilst this supposition makes physiologic sense, there is no research to document whether this indeed occurs. The literature is lacking long-term studies on retained second primary molars that have been reduced.

Another goal is to maintain the integrity of the occlusal table if the retained primary tooth is ankylosed. This can be done by building up the primary tooth with composite or a preformed metal crown (PMC) to prevent tipping of adjacent teeth and to restore the occlusion to the correct height, thereby preventing opposing arch supra-eruption. One potential disadvantage of a PMC is the risk of over-sizing the retained primary molar and compromising the leeway space. Another goal is to ensure that the alveolar ridge is preserved in instances where the long-term treatment plan involves prosthetic replacement of the missing tooth after extraction of the ankylosed primary molar.

When the infra-eruption is severe in a young patient, it is imprudent and even impossible to build the occlusal table up with either composite resin or a PMC, as progressive vertical growth will take the tooth out of occlusion. In such instances extraction is appropriate. When the primary molar is extracted in the absence of underlying permanent successors, there will be alveolar bone loss. This alveolar bone is usually necessary for future prosthetic replacement with an implant-supported crown. Ostler and Kokich [1994] have demonstrated that 25% of buccal lingual width will be lost in the first 3 years post extraction of a mandibular second primary molar; after this time, there is only 4% loss with most loss occuring on the buccal surface.

When adjacent teeth continue to erupt, consistent with passive eruption associated with normal growth, there is seldom loss of vertical bone since the compensatory passive eruption of the adjacent teeth carires the bone occlusally. In instances where extraction of primary infra-erupted molars occurs when permanent successors are absent, the buccal lingual reduction of the alveolar ridge usually does not compromise future placement of implants [Ostler and Kokich, 1994], though it may dictate the buccal lingual orientation of the implant. To minimize alveolar width loss, coral granules can be placed in the primary molar extraction site [Sandor et al., 2003]. In the posterior maxilla and mandible, this technique was 93.5% successful in preserving the alveolar process such that osseo-integrated implants were placed without the need for a bone graft [Sandor et al., 2003].

Malmgren et al., [1984] have recommended an alternative plan to extraction of ankylosed incisor teeth in pre-adolescent children. Their approach involves removal of the crown and leaving the root in place to preserve alveolar bone height and width. This intervention has mainly been used for ankylosed permanent incisors that previously have been traumatically luxated and whose extraction would result in deterioration in the bone height and width. This decoronation procedure has been recommended prior to the major growth spurt to preserve alveolar width and height and reduce or eliminate the need for alveolar ridge augmentation prior to future implant placement. Although this decoronation procedure is recommended for ankylosed permanent incisors, the same principle may be appropriate for managing primary second molars that have no successors, whilst they are awaiting completion of growth and future implant placement [Smalley 2008]. However, scientific study of its effectiveness is lacking.

Another goal is to ensure that the lower incisor position is maintained in the most favourable position such that, when the patient has a normal overjet, there is no detriment to the facial profile by excessive retraction of the lower incisors. Patients with minimal crowding, deep overbites, retrusive incisors, decreased anterior lower facial height and flat mandibular plane angles are usually best treated with a non-extraction approach. Therefore, in patients with these characteristics, second primary molars should be retained for as long as possible, provided there is good root structure and absence of infra-occlusion and they are interproximally reduced. Alternatively if the ankylosis is progressive, extraction and transplantation, or extraction and space retention for future prosthetic replacement is appropriate.

In patients with significant crowding who demonstrate infra-occluded primary molars with absent permanent successors, a modified serial extraction program may be appropriate under the direction of an orthodontist. The crowding, the infra-occluded primary molar and the congenitally absent tooth are simultaneously managed with the long-term objective of eliminating the infra-occluded primary tooth and closing the space where the permanent tooth is absent.

Clinical Examples

Various clinical examples have been selected to demonstrate the treatment options that are available for managing young growing patients with ankylosed primary molars.

Retain Primary Molar: Disk and build-up as needed. When a non-extraction treatment plan is undertaken, primary molars should be retained with interproximal reduction when necessary to make the tooth width similar to that of the absent second premolar (Figure 4). When there is minimal infraocclusion secondary to ankylosis and the child has limited anticipated future growth, restorative build-up of the occlusal surface maintains proximal contact integrity and prevents both supra-eruption of the opposing dentition and tilting of the adjacent teeth and short-term build up can be done with composite resin (Figure 4). More durable restorative build up with onlays or crowns (Figure 5) should be deferred until the long-term prognosis of the retained primary molar has been established. Once infra-occlusion results in the occlusal surface of the primary molar dropping below the maximum convexity of the adjacent permanent teeth, restorative build up is impossible and extractions must be considered (Figure 3). An alternative strategy is to leave space in the maxilla arch and not reduce the lower primary molar, which maintains both a Class I molar and canine (Figure 5).


Extract Ankylosed Primary Molar and use a Space Maintainer. Moderately ankylosed mandibular primary molars are observed with mild incisor crowding and radiographic evidence of ectopic eruption of second premolars and available leeway space (Figure 6a). A lingual arch space maintainer was used and then mandibular second primary molars were extracted. Follow up photographs show improvement in incisor alignment and eruption of the previously ectopic mandibular second premolars (Figure 6b).


Extract Retained Primary Molar, Maintain the Space and Restore the Missing Second Premolar Prosthetically. When a non-extraction approach is indicated, but there is potential for progressive ankylosis, and/or loss of root structure of the primary molar, the primary molar(s) should be extracted and the space proportioned for future prosthetic replacement as shown in Figure 7. Leaving the progressively ankylosed primary molars in place invites compromise in the alveolus of the future restorative site. Pre-treatment records (Figure 7a) demonstrated minimal crowding and infra-occlusion of the retained mandibular second primary molars that had no underlying second premolars, deep overbite and retrusive incisor position. A long-term non-extraction treatment plan was selected. The infra-occluded primary molars were extracted at age 10 before infra-occlusion became too extensive, and a lingual arch space maintainer was placed. Kokich and Kokich [2006] have suggested that most often space maintainers are not needed as the adjacent molar and first premolar then erupt towards each other. A longer orthodontic treatment plan pushes these teeth apart creating a robust implant site with the technique named implant site development [Kokich and Kokich, 2006]. Then a non-extraction approach was used in the permanent dentition followed by implant-supported crowns (Figure 7b, 7c). Despite extraction of the mandibular primary second molars, the alveolar ridge was not compromised for the implant.

In the non-growing individual, the best restorative option in a patient with a low decay rate is an implant-supported crown as shown in Figure 7c. Prior to debanding, radiographs were taken to ensure that there was adequate space and satisfactory root angulation to accommodate implant placement. Also there was collaboration between the orthodontist and the restorative dentist to confirm satisfactory pontic widths and co-ordination of de-banding, retention and restorative care. Cessation of facial growth was confirmed by serial lateral cephalometric radiograph superimposition before implant placement. In a growing individual, a temporary intermediate restoration could be a Maryland bridge, a removable partial denture, or a bonded wire retainer.

The introduction of temporary anchorage devices allows protraction of posterior teeth without any lower incisor retraction. This recent advance in technology provides treatment options that were unavailable decades ago. Failure to use these during a space closure treatment plan would result in excessive incisor retraction, which would compromise facial aesthetics. Mandibular arch molar protraction treats to a Class III molar and Class I canine, which leaves the maxillary second molar with no antagonist inviting supra-eruption.

Extract Primary Molars in the Mixed Dentition and Close the Spaces with Modified Serial Extraction. Patients who exhibit crowding and missing teeth can be treated with a modified serial extraction plan involving primary tooth extraction in the quadrant with missing teeth. Figure 8a shows a Class I mixed dentition crowded malocclusion with congenital absence of the maxillary right second premolar. The overlying maxillary right second primary molar was significantly infra-occluded from ankylosis. Also there was a deep overbite and maxillary constriction. Stage 1 treatment goals involved relief of crowding through serial extraction and control of the maxillary right molar position and the maxillary dental midline. The maxillary right primary molars were extracted and a Nance space maintainer placed for control of both the maxillary dental midline prevention of mesial drift of the maxillary right first permanent molar. In the other 3 quadrants, first premolars were extracted followed by a period of spontaneous dental drifting. During this time, the crowded maxillary right canine and first premolar drifted distally into the primary molar extraction spaces and the maxillary midline and right molar were held, as shown in Figure 8b. Full fixed appliances with maxillary expansion were used to complete treatment (Figure 8c).



Transplant. There are selected instances where transplantation should be considered, such as an uneven distribution of missing premolar teeth [Zachrisson et al., 1994]. One example is a case that exhibits crowding in one arch or quadrant in conjunction with missing teeth in other areas (Figure 9). To manage crowding, premolar teeth may have to be extracted in one arch. If there are congenitally absent teeth in the opposing arch, consideration can be given to an autogenous tooth transplant [Jonsson and Sigurdson, 2004]. Figure 9a shows mandibular crowding with absent maxillary lateral incisors, an absent maxillary right second premolar and root resorption on the retained maxillary right second primary molar. Mandibular first premolars were extracted and the mandibular left first premolar was transplanted to the maxillary right second premolar space at two-thirds root development (Figure 9b) Subsequently fixed appliances were used to complete treatment. After transplantation, there was some pulp canal calcification but continued apical development (Figure 9c). Autogenously premolar transplants are 92.5% successful over a 10 year period but carry with them risks of pulp calcification and ankylosis [Jonsson and Sigurdson, 2004].

A second transplant option is when children have a Class II malocclusion with good facial balance and missing mandibular second premolars [Zachrisson et al., 1994; Jonsson and Sigurdson, 2004]. Treatment involves removal of maxillary premolar(s) and transplanting the extracted maxillary premolar(s) to the mandibular arch where premolars are absent. Figure 10a shows that the canines are Class II with an absent maxillary and mandibular second premolar and mandibular infra-occluded second primary molars. The mandibular left second primary molar was extracted and the maxillary left second premolar was transplanted to its socket (Figure 10c, 10d). Future orthodontics is done to close maxillary spaces treating to a Class I canine and Class II molar relationship.


This article describes treatment alternatives for patients who exhibit ankylosed primary molars. When the underlying premolar is present and the infra-occlusion is not progressive, then observation is appropriate. Only when there is severe disruption to the occlusion and/or the underlying premolar, extraction and space management may be appropriate. When the ankylosed primary molar has no underlying premolar, orthodontic input is needed to determine if extraction and space closure, extraction and transplantation or extraction and prosthetic replacement is the best plan.




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D.B. Kennedy

Specialist in Paediatric Dentistry and Orthodontics, Vancouver, British Columbia, Canada.

Postal address: Dr D.B. Kennedy. 200, South Tower, Vancouver, British Columbia, Canada, V5Z 2M9

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