The Royal College of Surgeons of England defines delayed eruption of the maxillary incisors when these teeth do not emerge one year after the mandibular incisors have erupted, especially if the normal eruption sequence in the same arch is disturbed. For example, the lateral incisor may have erupted before the central incisor. Some clinicians consider a tooth as impaction surpassing the typical eruption age by over 2 years.

In clinical practice, a comprehensive clinical examination and thorough radiological investigation are typically undertaken when a tooth fails to erupt within a year of the anticipated eruption age. This approach aims to facilitate the identification of suitable interceptive measures based on the aetiology. In cases where a discernible soft tissue barrier is present along with a palpable tooth, the overlying fibrous tissue is excised surgically or with a laser to facilitate natural tooth eruption.

Surgical orthodontic guidance with gentle traction procedures may involve the removal of physical barriers, such as supernumerary teeth, and guiding the tooth to erupt at its anatomical site. These procedures are performed with meticulous care following a comprehensive diagnosis of the three-dimensional (3D) anatomical location of the affected tooth or teeth, evaluation of proximal anatomical tissues and forming teeth and a judgement of prognosis. Challenging impactions associated with multiple teeth or significant root dilaceration with a poor prognosis may necessitate surgical removal or transplantation. Royal College of Surgeons of England has issued comprehensive guidelines on managing unerupted maxillary central incisors. This chapter delineates common clinical diagnostic and therapeutic modalities for managing potential impactions or true-impacted anterior teeth, excluding canines, which were dealt with in Chapter 74 . A separate chapter on maxillary incisor impaction is necessary because the clinical presentation, aetiology and treatment options differ significantly from those of maxillary canine impactions.

Many patients with impacted maxillary central incisors are referred to orthodontists by general practitioners or paediatric dentists due to parental concerns about the potential for incisor impaction in early mixed dentition, even though such occurrences are infrequent.

A comprehensive clinical examination involves carefully observing the space available for the eruption of tooth or teeth. It includes checking for retained and non-vital deciduous teeth and assessing their mobility. Additionally, look for fibrous gingiva, a visible crown when stretching the mucosa, erupting rudimentary teeth around the unerupted tooth, and any bulging upon palpation of the labial alveolus ( Fig. 75.2 A and B).

Case HG, a 10-year-old girl with erupted maxillary lateral incisors.

The central incisors are unerupted. (A and B) Missing upper central incisors, constricted maxillary arch with a bilateral cross-bite. (C) Panoramic radiograph shows an unerupted upper incisors in a vertical impaction and a supernumerary tooth. (D and E) CBCT multiplanar reconstruction (MPR) view shows the palatal position of the left upper central incisor, and the eruption is impeded by the presence of supernumerary teeth.

Lack of a bulge at the usual site of tooth eruption, a bulge far away from the usual site of eruption or a bulge in the palate should make the clinician suspicious of the abnormal path of tooth eruption. The lack of a bulge, knife-edge or a thin edentulous ridge at the summit in both mesiodistal and vestibulopalatal dimensions indicates that the tooth is embedded deep in the bone. Occasionally, impacted incisors and supernumerary teeth can lead to the formation of dentigerous cysts and may cause root resorption in adjacent teeth.

Although commonly prescribed X-rays include an orthopantomogram (OPG) of the maxilla and mandible, the author prefers to supplement OPG after carefully evaluating intraoral periapical radiograph (IOPA) and occlusal films. A lateral cephalogram assists in the labiolingual and vertical location of the impacted teeth.

Intraoral X-rays are usually the first to be requested and are the simplest and the most informative films. They are most useful for assessing the impacted tooth’s vertical and mesiodistal position in the alveolus. The IOPA reveals significant information like the extent of root completion, the presence and the size of the dental follicle, any crown or root resorption, the root pattern and integrity, the presence of any hard tissue obstruction and its description and the presence of cysts/pathologies in the affected region. They also offer superior image clarity and excellent detail. For greater radiographic detail of the maxillary arch and mandibular anterior segment, the X-ray beam should be angulated 20–55 degrees to the occlusal plane. Here, one must be careful not to try to measure the length of the tooth from the film because the beam is so angulated as to give the maximum details about the impacted tooth and causes the distortion of the length of the tooth. The beam should be kept parallel to the occlusal plane for the mandibular posterior region.

Considering as low as reasonably achievable (ALARA) principles, should a clinician suspect complex aetiology, unusual impaction location or multiple impactions, a cone bean computed tomography (CBCT) with field of view (FOV) limited to the maxilla may be prescribed, eliminating the need for various radiographs ( Fig. 75.2 C–E).

Volumetric images and multiplanar reconstruction (MPR) in sagittal, coronal and axial views provide a precise anatomical perspective of the impaction and any dysmorphology of the root and assist in determining the prognosis of efforts to orthodontic guidance.

Clinically, all impactions can be grouped as follows:

• A.

  Extraosseous impaction: (impacted teeth) when the tooth has erupted in the oral cavity close to its site but held under a mucosal barrier. A bulge can be palpated at the eruption site.

• B.

  Intraosseous impactions lie deep within the alveolus without compromising its integrity, and sometimes they are deep in the palate, maxilla or sinus.

When reviewed with multiplanar imaging in axial, coronal and sagittal views, these impacted teeth may have different types of locations in the XYZ plane ( Figs 75.3 and 75.4 ). A series of 94 cases of unilateral maxillary incisor impaction using CBCT found some interesting features. These are summarised in Table 75.2 .

Impacted maxillary incisors in different orientations in CBCT.

(A) Labial position and extraosseous impaction with dilacerated root, (B) vertical position and intraosseous position with upright root and (C) palatal position and extraosseous position with upright root. a, b, c, Impacted maxillary incisors.

Reproduced with permission from Hui J, Niu Y, Jin R, Yang X, Wang J, Pan H, Zhang J. An analysis of clinical and imaging features of unilateral impacted maxillary central incisors: A cross-sectional study. Am J Orthod Dentofacial Orthop. 2022 Feb;161(2):e96–e104. doi:10.1016/j.ajodo.2021.03.014 . PMID: 34373151 .

Three-dimensional models of impacted maxillary incisors and dentitions in different orientations.

(A) Labial inversely impacted maxillary central incisors in a central position in the coronal plane, (B) vertically inclined impacted maxillary central incisors in a mesial position in the coronal plane and (C) palatally inclined impacted maxillary central incisors in a distal position in the coronal plane. a, b, c, Impacted maxillary incisors.

Reproduced with permission from Hui J, Niu Y, Jin R, Yang X, Wang J, Pan H, Zhang J. An analysis of clinical and imaging features of unilateral impacted maxillary central incisors: A cross-sectional study. Am J Orthod Dentofacial Orthop. 2022 Feb;161(2):e96–e104 . doi:10.1016/j.ajodo.2021.03.014 . PMID: 34373151 .