Orthodontic problems of dental aetiology
Eruption disturbances and ectopic eruption
One of the most frequent disturbances in the normal sequence of eruption of teeth is related to asymmetric dental development. It expresses itself with a deviation greater than 6 months in the time of eruption between the right and left side of analogous teeth. This means that while from the one side of the mouth a tooth has erupted normally and at the expected age, its counterpart on the other side has not appeared yet in the mouth. This can be due to the presence of obstacles in its path of eruption, abnormal root formation, previous infection, or trauma of the primary tooth. Based on the aetiology of the condition, treatment can vary from careful monitoring every few weeks or months to direct initiation of orthodontic treatment.
Another reason for an eruption disturbance is an over-retained primary (baby) tooth that stays in the mouth more than normal. A primary tooth normally exfoliates when the 2/3s of the permanent tooth root have developed; however, in certain situations such as primary tooth ankylosis or missingness of its successor, the presence of a primary tooth is prolonged and can be accompanied by tipping of the neighboring teeth, space problems and underdevelopment of the underlying bone.
With the term ectopic eruption, we describe any condition that a permanent tooth does not follow its normal path and appears in the mouth at a position other than its normal. Often this tooth can be blocked out either to the buccal or to the palatal/lingual side. This situation can happen in any tooth and can be corrected with orthodontic treatment.
Transposition of teeth is a type of severe ectopic eruption and it includes the positional interchange of 2 adjacent or non-adjacent teeth. This means that 2 teeth can either swap positions or a tooth can “travel” within the jaw and erupt far away from its normal position. Depending on the position of the roots of the transposed tooth and these of the neighboring teeth, with orthodontic treatment we can either decide to align teeth in the transposed position or fully correct the transposition.
Supernumerary teeth
A supernumerary is called any ‘tooth’ or ‘tooth-like’ structure that develops in addition to the normal number of 32 teeth.
Their localization in 80-90% of the cases is in the anterior maxillary area. They are usually accidentally discovered on radiographs. If they are not discovered early, they are diagnosed by the subsequent problems they create with the most common being the failure in the eruption of one or more permanent teeth. This is because supernumerary teeth act as obstacles and block the path of eruption of other teeth.
The mesiodens is the most frequent supernumerary tooth and it is found in the middle of the anterior maxilla. Its pathologic presence can often be expressed by the absence of a maxillary central incisor while the other central incisor or even the lateral incisors are in the mouth. Other side-effects due to a mesiodens can be the over-retention of primary teeth, spacing of maxillary anterior teeth, deviations of the midline and loss of space for the eruption of permanent teeth.
A supernumerary tooth can either erupt normally or stay impacted. In all cases, its extraction is indicated while orthodontic treatment ensures proper alignment of all permanent teeth.
In some cases, supernumerary teeth are part of syndromes or other developmental congenital anomalies.
Congenitally missing teeth
One or more teeth might be absent, meaning that are never going to develop and erupt.
Teeth that are most often congenitally missing and lead patients to seek orthodontic treatment are either the maxillary lateral incisors or the 2nd mandibular premolars. In the case of missing maxillary lateral incisors, permanent canines usually migrate mesially and erupt in the lateral incisors’ positions. As aetiology is genetic, with various genes being involved, this problem can also be detected in the parents or siblings.
Depending on the number of missing teeth, the skeletal pattern of the patient, the profile of the soft tissues (cheeks and lips), the accompanying crowding or spacing within the jaws and patients’ preferences, orthodontic treatment may involve complete closure of all spaces with redistribution of remaining teeth within the arch or opening of spaces and restoration of the missing tooth/teeth either with conventional prosthodontics or dental implants.
In some cases, congenitally missing teeth are part of syndromes or other developmental congenital anomalies.
Impacted teeth
Any tooth can stay impacted, meaning it will not manage to emerge in the mouth at the normal age in case certain conditions and obstacles (pathology such as cystic formation, odontomes, supernumerary teeth) impede its normal eruption.
The most prevalent impacted teeth are the maxillary upper canines. The aetiology can be multifactorial with most of the cases attributed to genetic factors, small or missing lateral incisors and the presence of other dental anomalies. In case of very abnormal position, the impacted tooth can cause root resorption of the neighboring teeth.
Abnormal inclination and tendencies for future impactions can be diagnosed with clinical examination and conventional radiography while further imaging might be required for proper localization of the impacted tooth prior to its surgical exposure and orthodontic traction. In this way, the ideal direction of orthodontic forces can be outlined for protecting and preserving the integrity of the neighboring teeth and anatomic structures as we bring the impacted tooth to its normal position.
In very severe cases and when iatrogenic intervention will harm other tissues, it might be indicated either to extract the impacted tooth or leave it untreated.
Space problems (crowding & spacing)
The origin of space problems in orthodontic patients is the inconsistencies between the size of teeth and the size of jaws. More specifically, crowding can be due to either big teeth, small jaws, or a combination of both. On the contrary, spacing can be due to small or missing teeth, big jaws, or a combination of them.
The available space and space requirements can be quantified as part of the orthodontic diagnosis process by space analysis using methods available both for the primary and the permanent dentition. The orthodontic treatment planning and decisions depend on the amount of the discrepancy, in other words the severity of the space problem, the patient’s skeletal pattern and face aesthetics.
Crowded teeth can be difficult to clean, and this can lead to caries (cavities) and gum disease (gingivitis or periodontitis) because of plaque accumulation.
In crowding situations, we can gain space with various methods. In some cases, when the amount of crowding is severe and excessive, orthodontic treatment cannot be performed without the extraction of permanent teeth because otherwise harm will be caused to the gums, the supporting bones and face esthetics. In such cases, the extraction of permanent teeth is indicated while the spaces are used for aligning the rest of the teeth and are fully closed at the end of orthodontic treatment.
Similar problems to the gums and teeth can arise by tooth spacing. Orthodontic approaches to spacing problems vary similarly to crowding situations.
Depending on the number of affected teeth (one or more small or missing teeth), the extra available space within the jaw, face esthetics and the size of the jaws, orthodontic treatment can include either space closure, space opening for extra teeth or redistribution of spaces for building up and reshaping the existing teeth.
