Tooth Ankylosis: Etiology, Diagnosis and Treatment Review and Case Series

Tooth ankylosis is a type of tooth eruption disorder, which results in the fusion of cementum and alveolar bone, whereas the periodontal ligament is gradually replaced by alveolar bone. Tooth ankylosis can occur in both erupted and impacted teeth. The most common ankylosed impacted teeth in the adult population are the maxillary canines creating functional and esthetic issues. This review analyzes the etiology, diagnosis and treatment of ankylosed impacted teeth. Four clinical cases are also presented, displaying different treatment options for ankylosis of impacted teeth.

Introduction

Dental eruption refers to the vertical displacement of a tooth from its initial non-functional towards its functional position. Tooth eruption disorders can manifest in several clinical conditions. One of them is tooth ankylosis, a type of tooth resorption resulting in loss of periodontal ligament. Specifically, in tooth ankylosis, dentin is fused to the cementum and alveolar bone, whereas the periodontal ligament is gradually replaced by alveolar bone.

Studies have reported that the incidence of tooth impaction varies from 5.6% to 18.8% of the population. Among permanent teeth with the exception of third molars, maxillary canines are the most frequently impacted teeth [1].

Since little is known about impacted ankylosed teeth in the adult population, the goal of the present study is to give insight into the causes, diagnosis and treatment of ankylosis of impacted teeth.

Materials and Methods

We carried out a literature search of the MEDLINE databases and the Cochrane Registry of Tooth Ankylosis. We used the medical subject heading terms: ankylosed tooth, tooth impaction and treatment of ankylosed teeth.

Results

Etiology

Ankylosis of impacted teeth can be caused by several reasons. The most common of them is trauma or excessive masticatory pressure associated with injury to the periodontal ligament (PDL) [2], [3]. Moreover, tooth ankylosis can occur when teeth remain unerupted and, as a result, unfunctional, leading to PDL thinning [4]. Furthermore, the reason might be a genetic predisposition which causes discontinuation in the periodontal ligament [1], [2], [5]. In addition, iatrogenic ankylosis can be a result of vigorous orthodontic treatment when improper tooth movement or excessive force is applied [1]. Finally, in some cases, tooth ankylosis cannot be attributed to a certain reason. This situation is defined as idiopathic ankylosis and happens spontaneously [5].

Dental ankylosis might be a result of disturbed local metabolism. Specifically, if traces of periodontal ligament of a deciduous tooth are not recognized by a permanent tooth, there is a risk for the permanent tooth to stay unerupted and, as a result, ankylosed [1]. Additional factors are inflammation or systemic diseases, mainly hormonal imbalances associated with the pituitary gland [6]. Specifically, a case report of multiple pituitary hormone deficiency due to an ectopic position of the posterior lobe was associated with ankylosed teeth [6].

Diagnosis

Diagnosis of ankylosed teeth might be a challenging procedure requiring several steps. Taking a dental history, including questions concerning dental trauma, might be helpful, but accurate diagnosis can only be done radiographically and clinically [2]. Radiographs are primarily used to identify ankylosed impacted teeth by showing fusion with the surrounding bone [4]. Normally, lamina dura is depicted as a radiopaque, hyperdense, well-defined line corresponding to the alveolar cortical bone [3]. PDL, which is located between the tooth and lamina dura, is observed as a well-defined hypodense line. In sites of ankylosis where PDL is absent, ankylosis can be diagnosed radiographically by impaired discrimination between the lamina dura and root dentin. There is scientific evidence suggesting that reduced vertical height of alveolar bone, the relative proximity of root apices to the lower border of the mandible, and hooked roots might be radiographical clues for tooth ankylosis since buccal or lingual plates cannot be differentiated in the two-dimensional radiographic technique [2]. Evidence from studies suggests that two-dimensional radiographs, such as Panoramic views (PVs) and periapical X-rays (PA), are not adequate because the ankylotic area is not precisely perpendicular to the X-ray beam. As a result, the affected area may not be clearly visible [2]. Recently, Cone beam computerized tomography (CBCT) has become a promising tool, since it provides a three-dimensional high-resolution inspection field, in as thin sections as possible. Lack of distinction between the lamina dura and the root surface and moreover totally weakened PDL space should be areas suspected of dental ankylosis.

Diagnosis can also be confirmed clinically. The lack of movement of the tooth, following the application of orthodontic force for 7–10 days, is considered a definitive diagnostic test [2].

Histologically dental ankylosis can be followed by replacement resorption in which the root surface loses its continuity, with bridges, lines or radiolucent spaces, and it also loses its radiopaque homogeneity or root hyperdensity. The regularity of the line of the lamina dura is interrupted and seen as areas of bone alternating with lamina dura [4].

Treatment

Ankylosed teeth resist to natural eruption process and conventional orthodontics. Several treatment options can be applied depending on the case. The gap that occurs from the impaction of the ankylosed tooth and the loss of the deciduous one can be restored by a fixed partial denture, orthodontic space closure, surgical extraction of an impacted ankylosed tooth and dental implant placement in the edentulous area [2].

Case Series

Case 1

A 67-year-old non-smoker male presented for gingival hyperplasia at a private periodontal dental office. His medical history included a kidney transplant ten years ago, and he is currently on a-blockers, mycophenolate mofetil, prednisolone, felodipine and cyclosporin. As known, both Ca channel blockers and cyclosporin can cause gingival hyperplasia [7], [8]. It has also been supported that the severity of hyperplasia depends on the concentration of the drugs and the combination of more than one drug that causes hyperplasia, in that case, cyclosporin and Ca channel blocker (Fig. 1a).

Fig. 1. (a) Baseline picture, (b) Surgical treatment of gingival hyperplasia combined with extraction of part of the impacted tooth. The arrows indicate the bone needed to be removed in order to extract part of the impacted #13, (c) CBCT reveals that the impacted tooth #13 has no periodontal ligament suggesting that the tooth is ankylosed, and (d) Reevaluation, clinical presentation of surgical treatment and placement of provisional restoration in the maxilla.

The patient was scheduled for steps 1, 2 and 3 of periodontal treatment. Step 4 was periodontal surgery, including gingivectomy and open flap debridement. At the same time, part of the ankylosed impacted tooth #13 was extracted. The apical part of the root was not extracted since the extraction would have created a severe osseous defect. During the surgery, an odontogenic cyst that was mesial to the impacted tooth was also removed, and guided bone regeneration was attempted with allograft, xenograft and collagen membrane (Fig 1b). The CBCT revealed an odontogenic cyst and an impacted canine #13. (Fig 1c). The patient tolerated treatment well and was scheduled for dental implant placement in 6 months. Unfortunately, the patient discontinued treatment due to medical reasons.

Case 2

A 54-year-old non-smoker female patient, with a clear medical history, was also referred to the same practice for periodontal treatment and full mouth rehabilitation. A radiographic exam revealed an ankylosed impacted canine (#23) which was located too coronally and to the full width of a buccolingual alveolar crest (Figs. 2a and 2b). The extraction of the impacted tooth would have created a significant bone defect. As a result, deciduous tooth #62 was extracted and the patient was scheduled for a fixed partial denture.

Fig. 2. (a) and (b) Patient presented with the major complaint of tooth mobility on #62. Radiographic evaluation revealed root resorption of #62 and the impaction of #23, (b) The impacted tooth was too coronally. The patient decided to have #62 removed and have a fixed partial denture to replace the impacted canine.

Case 3

Another 55-year-old smoker male patient with an impacted canine and need for dental implant rehabilitation was also referred to the practice. The patient’s medical history was clear and he was scheduled for dental implant placement. It was also decided not to remove the ankylosed tooth, since placement of the dental implants could not be carried without damage to impacted teeth (Figs. 3a,3b). The patient refused the construction of a fixed partial denture, because he preferred a conservative treatment without his tooth being prepared, taking his consistency with periodontal supportive treatment into consideration.

Fig. 3. A 55-year-old male patient presented for total mouth rehabilitation: (a) Radiographic evaluation revealed tooth impaction of #13, (b) Additional cbct shows the location of #13, (d) Dental implant placement in proximity with the root of the impacted tooth, (e) and (f) final dental implant restoration of #13, 14.

One of the dental implants- #13- was placed in contact with the PDL and cementum of the impacted tooth assuming that no damage to the pulp tissue would be created based on the current literature and since the osseointegrated surface of the dental implant could not be reduced significantly (Figs. 3c–3e) [9]–[12].

Case 4

A 55-year-old non-smoker female patient was presented to the practice for tooth replacement #52. (Fig. 4) The deciduous tooth was extracted due to root resorption and increasing mobility. Tooth #12 was impacted as revealed by a CBCT (Figs. 4b and 4c). The presence of the PDL was radiographically evident suggesting that the impacted tooth could be moved orthodontically. Moreover, the position of the impacted canine was apical enough for a dental implant to be placed without extracting the impacted tooth. The patient was informed about the various treatment options for the edentulous space of #12 (orthodontical movement of the impacted tooth, dental implant placement, or fixed partial denture). The patient decided to have a dental implant placed in the edentulous space which was done without extracting tooth #13. Since the buccolingual width of the alveolar ridge was not adequate for a dental implant placement, guided bone regeneration was decided to be done before implant placement by the use of a resorbable collagen membrane, allograft and xenograft (Figs. 4d–4f). 5 months after bone augmentation CBCT revealed bone formation (Fig. 4h). The dental implant was placed 5 months after the ridge augmentation procedure and the final restoration was done 3 months after implant placement (Figs. 4h–4j).

Fig. 4. Patient presents for extraction of #53 and its replacement with a dental implant: (a) and (b) CBCT at the area (c)–(f) Patient is scheduled for guided bone regeneration, with xenograft, allograft and collagen membrane, (h) CBCT 4 months after bone regeneration reveals bone formation at the previous buccal deficiency, and (i) and (j) a dental implant was placed and restored 3 months after placement.

Conclusions

Impaction of angulated permanent teeth has a high prevalence. Recently, before the radiographic evaluation of each patient’s mouth, permanent teeth remained ankylosed and the edentulous area was restored with fixed or removable partial dentures. Advances in orthodontics, implant dentistry and 3d radiographic evaluation resulted in early diagnosis and treatment of impacted ankylosed teeth with various treatment options.