Chapter 7. Tooth Eruption Disturbances

The eruption of deciduous and permanent teeth, as a rule, proceeds without complications; however, due to various conditions including disturbance of phylogenesis and ontogenesis, the eruption of the lower wisdom teeth, less often of the upper wisdom teeth, canines, and premolars of both jaws can be accompanied by inflammation.

Endogenous and exogenous factors form the basis for anomalies of eruption and position of teeth.

• Endogenous (genetic) anomalies in the size of the jaws and the position of teeth in them, which arise under the influence of dysfunction of the endocrine system, lead to the change in the ratio of the sizes of the jaws to the teeth. The lack of space in the alveolar part or the alveolar process of the jaws causes retention of the teeth.
• Exogenous factors including infant formula feeding and the intake of soft food by the child lead to anomalies of the dentition.

The prevalence of caries and its complications, as well as early extraction of primary teeth, can cause displacement and lack of space for the eruption of permanent teeth.

Early trauma to the maxilla or the mandible during the period of bone growth in children adversely affects the development of the jaws and the teeth as it can contribute to the formation of secondary deformities of the jaws, loss of primordia of permanent teeth, impaired occlusion, deformation of the dentition and the development of inflammatory diseases.

Tooth eruption disturbances that are encountered in the practice of oral surgery include an anomaly of the tooth position and an anomaly of its eruption, particularly, impaction, primary retention, and primary failure of eruption.

According to the ICD-10 classification (Version: 2019), anomalies of eruption and position of the teeth are included in the following class: Diseases of the digestive system (K00-K93).

K00-K14 Diseases of the oral cavity, salivary glands, and jaws.

• K00 Disorders of tooth development and eruption. Excluded entities are: embedded and impacted teeth (K01).
  • K00.0 Anodontia.
    • Hypodontia.
    • Oligodontia.
  • K00.1 Supernumerary teeth.
    • Distomolar.
    • Fourth molar.
    • Mesiodens.
    • Paramolar.
    • Supplementary teeth.
  • K00.7 Teething syndrome.
• K01 Embedded and impacted teeth. Excluded entities are: embedded and impacted teeth with abnormal position of such teeth or adjacent teeth (K07.3).
  • K01.0 Embedded teeth. An embedded tooth is a tooth that has failed to erupt without obstruction by another tooth.
  • K01.1 Impacted teeth. An impacted tooth is a tooth that has failed to erupt because of obstruction by another tooth.
  • K07.3 Anomalies of tooth position:
    • crowding;
    • diastema;
    • displacement;
    • rotation;
    • spacing, abnormal;
    • transposition

of tooth or teeth. Impacted or embedded teeth with abnormal position of such teeth or adjacent teeth.

Excluded entities are: embedded and impacted teeth without abnormal position (K01).

Inflammatory complications are most frequently associated with anomalies of the eruption of the third molars of the lower jaw. Thus, the occurrence of periostitis, abscesses, and phlegmons of the maxillofacial region sometimes accompanies the disturbance of tooth eruption and accounts for 11.6% of cases of their total amount.

The wisdom teeth of the lower jaw erupt mainly at the age of 18-25 years or later. The third molar often has two roots and a well-defined crown, sometimes the number of the roots can be different, the shape is curved.

The difficulty of the eruption of these teeth may be due to the following factors:

• the absence of a precursor, namely, of the primary tooth, as a result of which the bone in this area is compacted;
• the presence of a powerful buttress in this area in the form of the external oblique line, which includes a thick and dense cortical plate;
• lack of space in the dental arch, as a result of which the tooth is located in the branch of the lower jaw or abuts against it;
• thickening of the mucous membrane containing the fibers of the buccal muscle and the superior constrictor of the pharynx, which creates an additional dense barrier for the tooth eruption.

An important reason for the complicated eruption is the lack of space in the jaw, in particular in the retromolar space, which leads to the delayed eruption of the wisdom tooth, sometimes for months and years. This occurs due to the reduction of the lower jaw during phylogenesis when the distal alveolar part is shortened. The third molar is the last to erupt, and there is not enough space in the dentition. It was found that for the normal eruption of a wisdom tooth, the distance from the distal surface of the second molar to the branch of the lower jaw should be 29 mm, in other cases conditions for pathology arise (Fig. 7.1).

Fig. 7.1. Variants of the inclination of the tooth axis in relation to the distal alveolar part of the lower jaw and its branches

Complicated eruption of the lower wisdom tooth with sufficient space between the second molar and the ramus of the mandible may be associated with the thick keratinized mucous membrane covering the retromolar fossa and its relationship with the erupting tooth.

The eruption of the wisdom teeth is also affected by:

• inflammation of the root of the adjacent tooth;
• early loss of deciduous teeth;
• convergence of the crowns of two permanent teeth;
• the curvature of the root of the wisdom tooth;
• the anomaly of the anatomical structure of the tooth;
• hypercementosis;
• the cementoma of the root.

The growth period of the lower jaw, including its longitudinal changes, is of great importance since it determines whether a wisdom tooth will erupt or not. Statistically, 9.5 to 39% of th lower wisdom teeth fail to erupt in the oral cavity. Incorrect location of the germ of the wisdom tooth in the jaw, pathology of growth and development of the jaw leads to its mesioangular impaction (the tilt to the direction of the second molar), less often distal-angular, vertical, horizontal, inverted impaction. The anomaly in the growth and development of the jaw and the germ of the wisdom tooth, which is associated with the zone of appositional bone growth, also becomes the cause of the complicated eruption.