Shear's Cysts of the Oral and Maxillofacial Regions. Paul M. Speight

has been referred to as a paradental or inflammatory collateral cyst (Main 1970 ; Craig 1976 ; Speight and Soluk‐Tekkeşin 2022b ). Radicular and residual cysts are considered in this chapter. The inflammatory collateral cysts are considered in Chapter 4.

Clinical Features

      Frequency

Radicular and residual cysts are by far the most common cystic lesions of the jaw bones, probably accounting for more than half of all cystic lesions and about 60% of odontogenic cysts. In an analysis of nearly 10 000 radiolucent jaw lesions, Koivisto et al. (2012 ) found that 73% were periapical granulomas or cysts. Of these, 40.4% were granulomas and 33.0% were cysts.

      In Shear's South African series, radicular and residual cysts comprised 52.2% of cystic jaw lesions (Table 1.1) and 62% of odontogenic cysts. This is similar to the frequency in a Sheffield study (Jones et al. 2006 ), where 4297 radicular and residual cysts were diagnosed over a 30‐year period, representing 60.3% of all odontogenic cysts (Table 1.2).

      Data from other countries vary (Table 1.3), with a range from 42.1% in Mexico (Mosquedo‐Taylor et al. 2002 ) to 84.5% in Sicily (Tortorici et al. 2008). The reason for the global variation in frequency is not clear, but probably relates to variations in the prevalence of dental caries and to methods of data collection. For example, in Mexico Mosquedo‐Taylor et al. (2002 ) suggest that the low frequency is due to a large proportion of their studied population being treated in the private sector where caries is less prevalent. Conversely, Tortorici et al. (2008) believed that the high frequency in Sicily was related to a high prevalence of caries in the studied population. The low frequency in Iran was ascribed to the fact that caries and periapical lesions are common and are not routinely submitted for histological diagnosis (Sharifian and Khalili 2011 ). Overall, however, these data show that radicular (including residual) cysts are consistently the most common cystic lesion of the jaws, with a frequency of about 60%.

      In presenting these data, radicular and residual cysts have been included together, but where the information is stated, almost all the studies show that residual cysts account for between 5% and 15% of odontogenic cysts and between 10% and 20% of radicular cysts (Mosquedo‐Taylor et al. 2002 ; Jones et al. 2006 ; Sharifian and Khalili; 2011 ; Soluk Tekkeşin et al. 2012b ; Lo Muzio et al. 2017 ; Tamiolakis et al. 2019 ; Kammer et al. 2020 )

Age

The age distribution of 948 patients in South Africa is shown in Figure 3.1. Very few cases are seen in the first decade, after which there is a fairly steep rise, with a peak frequency in the third decade and large numbers of cases in the fourth and fifth decades. In a Sheffield study of 1970 cases, Jones et al. (2006 ) found cysts in older age groups, with a peak in the fourth decade and a mean age of 37.3 years (Figure 3.2). Similar data were found in French (Meningaud et al. 2006 ), Australian (Johnson et al. 2013 ), Italian (Lo Muzio et al. 2017 ), and Greek (Tamiolakis et al. 2019 ) studies, with mean ages of 40.8, 50.5, 38.2, and 41.2 years, respectively. The older ages of these patients compared with the South African patients was noted in previous editions of this book and suggests that the South African patients may have been exposed to the relevant aetiological factor, mainly dental caries, at a slightly younger age than the other groups.

The wide age range of lesions, the very low frequency in the first decade, and a peak in the fourth decade have been confirmed in a number of studies (Tortorici et al. 2008; Sharifian and Khalili 2011 ; Ramachandra et al. 2011 ; Soluk Tekkeşin et al. 2012b ; Lo Muzio et al. 2017 ; Tamiolakis et al. 2019 ). These studies also indicate that although dental caries is very common in children, radicular cysts are not often associated with deciduous teeth. Soluk Tekkeşin et al. (2016 ) identified 596 odontogenic cysts in a paediatric population (age 0–17 years), of which 387 (65%) were radicular cysts (including 17 residual cysts). Of these, only 3 arose in subjects less than 6 years old, 113 were found in the mixed dentition (age 6–12 years), and 271 were associated with permanent teeth (age 13–17 years). In a similar study in Brazil, da Silva et al. (2018) reviewed 294 odontogenic cysts in subjects younger than 20 years. They identified 145 radicular cysts, but only 9 arose in subjects younger than 10 years.

Figure 3.1 Age distribution of 948 South African patients with radicular cysts.

Figure 3.2 Age distribution of 1970 patients with radicular cysts from Sheffield, England, 1990–2004 (n = 1970).

      Source: Based on Jones et al. (2006 ).

      Residual cysts are very unusual in the first, second, or third decades and peak at a slightly older age, usually in the fifth decade. Lo Muzio et al. (2017 ) found a mean age of 49.4 years (n = 218; range: 17–90) and, in their large Greek series, Tamiolakis et al. (2019 ) found a mean age of 50.5 years (n = 749; range 11–93) for residual cysts.

      Box 3.1 Radicular Cyst: Epidemiology – Key Facts

       Radicular cysts are the most common cystic lesion of the jaws

       They comprise about 60% of all odontogenic cysts

       Residual cysts account for 10–20% of radicular cysts

       Overall radicular cysts are the most common cause of bony swellings

       They are slightly more common in males (M : F = 1.4 : 1)

       Peak age is the third and fourth decades (20–40 years)

       Rare in children

       Very rare on deciduous teeth

Sex

      Almost all studies show that all odontogenic cysts are slightly more common in males than in females (Table 1.3). With regard to radicular cysts in the South African series, 555 (58.5%) were in males and 393 (41.5%) in females (M : F 1.41 : 1), a statistically significant difference (P < 0.002). In the Sheffield study, 1914 (51.5%) were in males and 1801 (48.5%) in females (M : F 1.06 : 1; Jones et al. 2006 ), but this difference was not significant.

Site

Figure 3.3 shows that radicular cysts may arise at any site in the jaws, but are more common in the maxilla (60%) than the mandible, with a particularly high frequency in the anterior maxilla, with about 40–50% of all cases occurring in this region. There are a number of possible reasons for this. First, in addition to the hazard posed by dental caries, maxillary incisors have in the past, perhaps more frequently than other teeth, had silicate restorations placed in them, with consequent high risk to their pulps. If this were the cause, then the prevalence of cysts at this site might reduce in future generations. Second, there is a high prevalence of palatal invaginations in the maxillary lateral incisors and a high frequency in which pulp death supervenes in these teeth. Third, maxillary anterior teeth are probably