General Classification of Hard Tissue Pathologies
All diseases of the dentition are divided into developmental defects and acquired pathologies. While dental caries (caries) is a process of demineralization and destruction of the inorganic matrix beginning strictly after eruption, many non-carious lesions originate much earlier.
Such maxillofacial dysmorphias can have various etiologies:
- Hereditary (caused by gene or chromosomal mutations);
- Multifactorial;
- Prenatally acquired (a striking example is fetal alcohol spectrum disorder, resulting from systematic maternal alcohol consumption during pregnancy).
Developmental defects can be isolated, combined (a combination of several defects), or syndromic (when they are part of multiple malformations in Down, Wolf-Hirschhorn, Edwards, or Patau syndromes).
Tooth Formation Disorders: Quantity, Shape, and Timing
Non-carious lesions include a wide range of dental arch anomalies. Pathological anatomy classifies them by several key features:
- Anomalies of number: this group includes adentia (complete absence), hypodontia and oligodontia (insufficient number of tooth germs), as well as hyperdontia (presence of supernumerary elements).
- Anomalies of position: formation of impacted and retained teeth that cannot occupy the correct position in the dental arch.
- Size and morphological defects: development of abnormally large (macrodontia) or small (microdontia) crowns, pathological changes in root length, atypical number of cusps, and fusion of adjacent tooth germs.
- Deviations in eruption timing: both premature appearance (so-called natal teeth present in newborns) and marked delay are possible. The latter often accompanies congenital hypothyroidism and gingival fibromatosis.
In addition, there is the problem of premature tooth loss, which is a characteristic diagnostic sign of conditions such as hereditary neutropenias and hypophosphatasia.
Enamel and Dentin Developmental Defects
Qualitative defects of hard tissues also belong to non-carious lesions. They can be divided into structural disorders and pathological pigmentations.
Structural disorders include:
- Enamel hypoplasia — partial or complete underdevelopment of the enamel layer;
- Amelogenesis imperfecta — a genetically determined disorder of enamel formation;
- Dentinogenesis imperfecta — a pathology of dentin layer formation.
Pigmentations (exogenous and endogenous) manifest as persistent changes in tooth color. This condition accompanies a number of severe systemic diseases: erythroblastosis fetalis, congenital porphyria, and various congenital liver pathologies. Of particular note are so-called "tetracycline teeth" — specific, persistent staining of enamel and dentin triggered by the use of tetracycline antibiotics during the period of tooth tissue formation and mineralization.
Combined Anomalies and Concomitant Factors
Non-carious tooth malformations rarely exist in complete isolation. Very often, they are associated with other anomalies of the orofacial region. For example, in Robin sequence (a combined defect including cleft palate, micrognathia, microglossia, and glossoptosis), the absence or retention of the maxillary lateral incisor is frequently detected.
Salivary gland developmental defects (aplasia, duct atresia, polycystic disease, or ectopy) also have a colossal impact on the state of hard tissues. These anomalies often lead to xerostomia ("dry mouth syndrome"). A lack of saliva severely impairs the natural cleansing of teeth, making them vulnerable to periodontitis and rapidly progressing caries.