Periodontics. Fernando Suarez

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СКАЧАТЬ with neighboring control sites.¹²²

      CLASSIFICATION FOR ROOT PROXIMITY

      Vermylen et al proposed a classification system for root proximity to indicate location (apical, middle, and coronal third) and severity based on modification of the ruler used by Schei et al¹²³ and findings from Heins and Wieder¹²⁰ as depicted in Table 5-9.¹¹³

TABLE 5-9 Classification for root proximity by Vermylen et al¹¹³

Location	A	Apical third of the root
	B	Intervening (middle) third of the root
	C	Coronal third of the root
Severity	1	> 0.5 and ≤ 0.8 mm. A small amount of cancellous bone is present between the adjacent roots.
	2	> 0.3 and ≤ 0.5 mm. Only cortical and connective tissue attachment is present between the adjacent roots.
	3	≤ 0.3 mm. Only connective tissue attachment is present between the adjacent roots.

      Root Surface Anomalies

      INTERMEDIATE BIFURCATIONAL RIDGE

      Intermediate bifurcational ridge (IBR) is defined as a distinct ridge running across the bifurcation in a mesiodistal direction.¹⁰ It originates from the mesial surface of the distal root at about 2 mm from the height of the furcation area and ends high up on the distal surface of the mesial root by merging within the root concavity.¹⁰ Histologic evaluation of IBRs has shown that these developmental anomalies are formed mostly by dentin but also contained cementum.¹⁰

      Everett et al reported that among 328 extracted mandibular first molars, the prevalence of IBRs was 73%.¹⁰ This finding was confirmed by two other studies that revealed a presence of IBRs in 70% and 76.8% of extracted first molars.^68,124 Moreover, Hou and Tsai found that IBRs are highly associated with CEPs (63.2%) and Class III furcations (25.3%).⁵⁵

      Grading system

      Hou and Tsai introduced a grading system for IBRs using an electronic digital caliper to calculate dimensions as less than 1 × 1 mm, between 1 × 1 mm and 2 × 2 mm, and 2 × 2 mm or greater as Grades I, II, and III, respectively.⁵⁵ It is important to bear in mind that when IBRs are present in furcation defects, these may predispose to further attachment loss by hindering the patient’s plaque control and the clinician’s ability for proper mechanical instrumentation during active and/or supportive therapy.

      PALATORADICULAR GROOVES

      The palatal groove is a developmental, anomalous groove usually found on the palatal aspect of maxillary central and lateral incisors. It is also known as palatogingival groove or palatoradicular groove.¹ These structures are considered a funnel-like anomaly predisposing to the accumulation of biofilm and calculus formation.^125–132 The prevalence of this condition ranges from 1.9% to 18%, affecting primarily maxillary lateral incisors and central incisors with a possible predilection for individuals of Asian descent (Table 5-10).^{70,127,128,131,133–135}

TABLE 5-10 Prevalence of palatoradicular grooves

Authors	Population	Affected teeth	Prevalence
Everett and Kramer133	American	Lateral incisors	1.9%
Gher and Vernino70	American	Lateral incisors	3%
Withers131	American	Lateral and central incisors	Overall: 2.33%Bilateral: 0.75%Lateral incisors: 4.4%Central incisors: 0.28%
Kogon127	Canadian	Lateral and central incisors	4.6%
Bačić et al128	Croatian	Lateral and central incisors	1.01%
Hou and Tsai134	Taiwanese	Lateral and central incisors	18.06%
Albaricci et al135	Brazilian	Lateral and central incisors	Overall: 9.3%Lateral incisors: 11.1%Central incisors: 7%

      Embryologically, these anomalies arise as a mild form of invagination from the folding of the enamel epithelium and are closely related to dens in dente.¹³³ As a result, a clinically detectable hollow groove can be observed proceeding apically for a variable distance along the length of the root. Hou and Tsai noted an increased predilection of these grooves for midpalatal areas (42.5%) when compared with mesial (27.4%) and distal (30.1%) surfaces.¹³⁴ Moreover, it has been reported that 58% of the grooves extended more than 5 mm from the CEJ,¹²⁷ whereas 8.6% can reach the root apex.¹³⁵ Radiographically, these might be detected as radiolucent, parapulpal lines representing a radicular extension of the palatal groove.^126,130

      Localized forms of periodontitis have also been associated with the presence of palatoradicular grooves.^{128,130–132} Teeth with palatoradicular grooves revealed worse periodontal health as evidenced by higher gingival index, plaque index, and periodontal disease index scores when compared to teeth without grooves.¹³¹ Similarly, Bačić et al reported significantly greater probing depths (mean: 8.8 mm) at sites with palatoradicular grooves among periodontal patients.¹²⁸ Hou and Tsai also noted deeper pocket depths when palatoradicular grooves were present.¹³⁴

      ACCESSORY CANALS

      Accessory root canals are considered a lateral branch of the main root canal most often found in the apical half of the roots and in furcation areas.¹ The formation of these accessory root canals has been labeled as lines of weakness and attributed to a defect in the HERS during the development of the root at the site of a larger vessel.^136,137 The size of the foramina of these canals might range between 4 and 250 μm, and the canals are more numerous and larger in diameter among maxillary molars than mandibular molars.¹³⁸ Early studies reported the presence of an accessory apical artery entering the tooth via the periodontal ligament.¹³⁹ Kramer demonstrated large blood vessels within the furcation region running through the radicular dentin to supply one root canal vascular system.¹⁴⁰ At times, these vessels appeared to contribute more to the root canal vascular supply than those entering the apical foramen.¹⁴⁰

      The terminology used to describe root canal ramifications is diverse. De Deus identified different types of root canals based on their location (eg, apex, body, and coronal third) as accessory, secondary, and lateral canals.¹⁴¹ Some authors have referred to them as furcation canals when they are exclusively located at the furcation region.^142,143

      Vertucci and Williams reported a 46% prevalence of accessory canals in a study of 100 mandibular molars.¹⁴³ The authors also established an association between their occurrence and the site of origin (pulp chamber or root surface) and the possibility to have multiple accessory canals. Conversely, Kirkham found that 23% of the teeth had accessory canals and reported an association with periodontal defects in 2% of the cases.¹⁴⁴ In a similar manner, Gutmann reported a prevalence of 28.4% of accessory canals at furcation regions from maxillary and mandibular molars.¹⁴² Finally, De Deus used a sample of 1,140 teeth and reported an overall (27.4%) and a site-specific prevalence (apex: 17%; body: 8.8%; and base: 1.6% of the root)¹⁴¹ (Fig 5-4).

      Fig 5-4 Prevalence СКАЧАТЬ