Sequestration of alveolar wall
The most common complication following oral extraction is sequestration of segments of alveolar bone with or without concurrent alveolar infection. Kennedy et al. (2020) found alveolar sequestration to be the most common post-extraction problem and was identified in 38/428 cheek teeth extractions (including 343 oral extractions). Clinical signs of alveolar disease were present in 17 of these cases (4% of 428 cases) but in 15 cases (3.5%) the (usually smaller) sequestrae that were detected on routine post-extraction alveolar examinations did not cause a detectable clinical problem (Kennedy et al. 2020). Giegert and Bienert (2021) found a 6.6% (20/302 cases) prevalence of clinical post-extraction complication with mandibular cheek teeth oral extractions, with 18 of 20 complications being alveolar sequestration and infection, including sequestration of the complete alveolar wall.
Due to the great length (up to 9cm long) of equine cheek teeth reserve crowns, high and prolonged mechanical forces are required to break down their periodontal membranes. High forces are also required to deform the layer of dense bone (i.e., bundle bone or cribriform plate – radiologically termed the lamina dura [denta] ) that lines the alveolus and compress it into the underlying spongy bone to enlarge the periodontal space and so allow dental movement and later extraction (Fig 4 ). This necessary alveolar bone deformation can cause it to fracture deeply and/or may disrupt its local blood supply. The partial coronectomy technique (Rice and Henry, 2018) may less traumatically create additional intra-alveolar space to facilitate extraction.
Fragments of fractured alveolar bone may be detected immediately following exodontia if the fractured bone segment is displaced by exodontia forces. More commonly, alveolar fragments are recognised a week or more later (Fig 5 ), especially if caused by extraction-induced loss of blood supply to a local area of fractured alveolar bone. The presence of alveolar sequestrae prevents alveolar healing and can acts as a nidus of infection, often leading to alveolar infection and even osteomyelitis of the supporting bones (Fig 6 ). Such infected alveoli are usually malodorous and on digital palpation have areas of exposed bone and contain loose sequestrae. Alveolar sequestration occurs more commonly in mandibular as compared to maxillary cheek teeth, as is also the case in human dentistry (Chiapascoet al . (1993), possibly related to differences in the thickness and rigidity of these bones and their blood supply. The effects of gravity in retaining alveolar bone sequestrae and infected exudate in mandibular as compared to maxillary alveoli may also be significant.