Handbook of Oral Pathology and Oral Medicine. S. R. Prabhu

      1.11.3 Aetiology

       Lack of space for tooth eruption due to inadequate arch length

       Crowding of teeth

       Dense overlying bone

       Excessive soft tissue in the path of eruption

       Genetic abnormalities

       Long tortuous path of eruption (for canines)

      1.11.4 Clinical Features

       Frequently impacted teeth: mandibular third molars followed by the maxillary third molars, maxillary canines and mandibular premolars

       Young adults are commonly affected; often detected on routine radiography

       Impacted deciduous teeth are extremely rare

       Impacted permanent first and second molars are rare

       Often supernumerary teeth are impacted (detected on radiography)

       Impacted teeth may or may not be symptomatic

       With no history of extraction, clinically the number of teeth present in the dentition is less than normal

       Impaction can be full or partial

       Symptomatic patients with lower third molar may complain of earache or paraesthesia of the lip

       Pericoronitis may occur (pain, inability to open the mouth, swelling of the pericoronal soft tissue)

       Often, all four third molars may be impacted

       Occasionally impactions are associated with syndromes or odontogenic cysts and tumours

      1.11.5 Radiographical Features

       Types of impaction: mesioangular, distoangular, vertical or horizontal impaction for third molars (Figure 1.9 a‐d). Canine impaction may be bilateral ( Figure 9 e) or inverted

       Proximity of the impacted tooth to the inferior dental nerve for lower third molar impactions may cause paraesthesia

       Impacted teeth may be associated with cysts or odontogenic tumours

      1.11.6 Diagnosis

       History

       Clinical examination

       Radiography (panoramic view)

      1.11.7 Management

       No treatment is required for asymptomatic impactions

       Surgical removal for symptomatic impacted teeth

       Surgery for impacted teeth associated with cysts or tumoursFigure 1.9 (a) Mesioangular impaction of the mandibular third molar. (b) Distoangular impaction of the mandibular third molar (c) Vertical impaction of the mandibular third molar. (d) Horizontal impaction of the mandibular third molar. (e) Bilateral impaction of maxillary canines.

1.12 Dens Invaginatus and Dens Evaginatus

      1.12.1 Definition/Description

       Dens invaginatus refers to an exaggeration of the process of formation of lingual pit causing invagination (also called dens in dente or dilated odontome)

       Dens evaginatus refers to an enamel and dentin covered spur extending outward from the occlusal surfaces of molars or premolars and rarely lingual surfaces of lower anterior teeth. This is the opposite of dens evaginatus (also called evaginated odontome)

      1.12.2 Frequency

       Dens invaginatus: prevalence: 0.3–10%, affecting more males than females

       Dens evaginatus: more common in people of Asian descent; prevalence: 0.06–7.7%; 15% in Inuit and Native American populations

      1.12.3 Aetiology/Risk Factors

       Dens invaginatus:Deepening or invagination of the enamel organ into the dental papilla prior to calcification of the dental tissuesGenetics may play a role

       Dens evaginatus:A result of an unusual growth and folding of the inner enamel epithelium and ectomesenchymal cells of dental papilla into the stellate reticulum of the enamel organ

      1.12.4 Clinical Features

       Dens invaginatus:The permanent maxillary lateral incisors appear to be the most frequently affected tooth (90% of all cases)Maxillary posterior teeth: 6.5% of all casesMandibular teeth are very rarely affected

       May be associated with taurodontism, microdontia, gemination, supernumerary tooth and dentinogenesis imperfectaFigure 1.10 (a) Dens invaginatus; radiograph showing dens invaginatus in a peg lateral incisor(source: by kind permission of Professor Charles Dunlap, Kansas City, Kansas, USA).(b) Dens evaginatus; radiograph showing dens evaginatus. Note a tubercle extending outward from the occlusal surface of the premolar.

       Causes food debris deposits and renders tooth vulnerable to caries

       Dens evaginatus:More common in mandibular premolar teethMay be bilateral and symmetrical tubercles on the occlusal surfaces of posterior teeth or on lingual surfaces of lower anteriorSlight female sex predilectionCan cause malocclusion with opposing teethAbnormal wear and fracture of the tubercle may occur

      1.12.5 Radiographical features

       Three types of dens invaginatus occur which can be detected on radiography:Type I: invagination ends in a blind sac, limited to the tooth crown (Figure 1.10a)Type II: invagination extends to the cementoenamel junction extending in a blind sac. It may or may not extend into the root pulpType III: invagination extends to the interior of the root providing an opening to the periodontium, sometimes this presents another foramen in the apical region of toothDens evaginatus shows a tubercle on the occlusal surface (Figure 1.10b)

      1.12.6 Diagnosis

       History

       Clinical examination (tooth morphology)

       Radiography (intraoral periapical views)

      1.12.7 Management

       Dens invaginatus: placement of sealants and endodontic treatment for severe cases

       Dens evaginatus: removal of the tubercle and application of fluorides

1.13 Fluorosis (Mottled Enamel)

      1.13.1 Definition/Description

       Dental fluorosis (mottled enamel) is a qualitative defect of enamel resulting from an increase in fluoride concentration during enamel formation

      1.13.2 Frequency

       Fluorosis