Periodontics. Fernando Suarez

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      Overall, a large variation (17% to 92.5%) for the prevalence of accessory canals has been observed. This wide range can potentially be attributed to multiple factors.^{124,141–149} It is important to bear in mind that these canals are encased by dentin, and a calcification process might cause the number of canals to diminish with age.¹⁵⁰ Also, subtle differences can be associated with the tooth type,^143,145,146 the reason for extraction (eg, caries, periodontal disease, endodontic failure), deposition of cementum,¹⁴⁷ and processing methods (eg, drying, vulcanizing).¹⁵¹

      Classification

      A classification system to describe the site of origin and course of accessory canals within the furcation was proposed by Yoshida et al¹⁵² and modified by Paras et al¹⁵³ as Type A (true), Type B (blind), Type C (looping), and Type D (enclosed) canals. Zuza et al labeled Type D canals as sealed canals.¹⁴⁶

      ENDODONTIC-PERIODONTAL RELATIONSHIP

      Over the past century, the pulpal-periodontal relationship has been a topic of controversy and extensively studied. From a periodontal perspective, it has been suggested that the cumulative effect of biofilm-induced pocket formation might cause pulp inflammation via exposed accessory canals.^147,154,155 Nonetheless, a complete disintegration of the pulp may occur only when all main apical foramina are challenged by bacterial biofilm.¹⁵⁶

      Conversely, Mazur and Massler demonstrated that the pulp condition could vary from almost normal to advanced degeneration despite the presence of periodontal disease.¹⁵⁷ Their findings suggest that the periodontal status does not exert any great influence on the pulp and addressed possible systemic factors as the cause for pulp degeneration.

      On the other hand, advanced stages of pulpitis can cause periodontal breakdown.^158–161 As such, endodontic treatment often leads to healing of untreated periodontal lesions in the presence of a endodontic-periodontal defect and supports the idea that accessory canals may act as a passageway for endodontic irritants.^158,162,163

      CEMENTICLES

      Cementicles are defined as calcified spherical bodies (0.2 to 0.3 mm) composed of cementum lying free within the periodontal ligament, attached to the cementum, or embedded within it.^1,3–6 It has been suggested that their formation is influenced by epithelial rest cells of HERS and only present on a tooth surface covered with cementum.^3,5 True cementicles consists of a collagenous matrix intermixed with a noncollagenous ground substance.⁶

      Cementicles may enlarge by deposits of calcium salts from the connective tissue. These salts fuse with adjacent free cementicles and become embedded in the root surface during cementum deposition.^164,165 According to Holton et al, cementicles are often observed in canines and molars with an overall prevalence of 34%.¹⁶⁶

      The presence of cementicles has not been correlated with the pathogenesis of periodontal disease; however, root surfaces with cementicles might hinder mechanical instrumentation.

      CEMENTAL TEARS

      Cemental tears are defined as a specific type of root surface fracture and characterized by the detachment of a cemental fragment.² Cemental tears are a rare condition able to induce periodontal attachment loss^167–176 and periapical tissue destruction.^177–179 Partial or complete separations can occur along the dentin-cement junction or following cementum incremental lines from both exposed and unexposed root surfaces leading to cemental tears.^39,180,181

      The occurrence of these cemental defects remains unclear due to its rarity. Retrospective data from a multicenter study in Taiwan reported that cemental tears are more likely to occur in mandibular and maxillary incisors (76.1%), among men (77.5%), and in patients older than 60 years (73.2%).¹⁷⁷ A predisposition for these tears in a Hindu population has also been reported.^180,182

      Müller and Zander hypothesized that the occurrence of cementum defects could be associated with the quality of cementum rather than differences in rate, speed, or lack of cementum deposition.¹⁸² Conversely, Moskow noted that these defects were located mostly at the coronal third of the cementum, serving as susceptible sites for calculus formation.³⁹ Interestingly, he pointed out that cemental tears could be the result of inadvertent root gouging during mechanical instrumentation. Additionally, observations from Leknes et al noted that cemental tears can occur away from the gingival sulcus, suggesting that these fractures can elicit a rapid periodontal breakdown in noninfected environments.¹⁶⁷ Hence, cemental tears can often be associated with traumatic occlusion or traumatic events.^{2,167,181,183–188}

      Cemental tears are detectable clinically via very localized deep pocketing and radiographically (about 50% of the cases) with a localized radiolucency surrounding a “prickle-like body.”^170,177,185 Further analysis showed that teeth with cemental tears were more likely to develop an abscess and be associated with pockets greater than 6 mm, a positive vitality test, healthy opposing teeth, and moderate to severe attrition.¹⁷⁷

      If properly diagnosed, teeth with cemental tears can be satisfactorily treated. Treatment includes removal of the cemental tear, root debridement, pocket reduction, and/or regenerative procedures with or without endodontic therapy.¹⁸⁹ A recent study showed that most of the teeth with cemental tears could be treated via surgical or nonsurgical treatments; however, teeth with cemental tears in the apical third had a worse prognosis.¹⁹⁰

      Palatal Exostosis (Tubercles)

      Exostoses are defined as benign bone growth projections outward from the surface of a bone.¹ Palatal exostoses are bony protuberances that can cause surface irregularities, leading to periodontal pockets in the area of maxillary molars. Larato proposed a classification based on their anatomical appearance as Type A (small nodule), Type B (large nodule), Type C (sharp ridge), Type D (spike-like projections), and Type E (combinations of types A to D).¹⁹¹

      Several studies using human skull specimens have reported a diverse prevalence of palatal exostosis ranging between 30% and 56% (Table 5-11).^191–193 These subtle differences might be influenced by ethnic background and/or age.^192,193 Most of the palatal exostoses (62%) are commonly found in the maxillary third molar area and directly lateral to and at a mean of 11.4 mm from the greater palatine foramen.¹⁹² The removal of these bony protuberances is often indicated to ensure proper flap adaptation during resective procedures. These can also serve as a potential source of autogenous bone for regenerative procedures.¹⁹²

TABLE 5-11 Prevalence of palatal exostosis

Authors	Prevalence
Larato191	Overall: 30%Population: Mexican
Nery et al193	Overall: 40.5%Population: European, Oceanic-Asiatic, African, and Mexican-Peruvian
Sonnier et al192	Overall: 56%Population: Caucasian and African American

      Dental Materials and Tooth Position–Related Factors

      IMPACT OF DENTAL MATERIALS

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