Which one of the following options is the tooth tissue that has collagen fibres from the periodontal ligament inserted into its outer structure?

Cementum is the specialized calcified tissue that forms the outer layer of the tooth root, and it plays a crucial role in anchoring the teeth within the jawbone. The unique feature of cementum is that it contains collagen fibers from the periodontal ligament embedded within its structure. These fibers help establish a strong link between the tooth and the surrounding bone, contributing to the overall stability of the tooth during functional activities like chewing.

Dentine, while being a major component of the tooth structure beneath the enamel and above the pulp, does not feature the insertion of periodontal ligament fibers. Enamel is the outermost layer of the tooth, primarily composed of hydroxyapatite and does not contain collagen or fibers. The pulp is the innermost part of the tooth that contains nerves and blood vessels but is not involved with cementum or the support of the tooth within the jaw. Hence, the correct answer identifies cementum as the tissue that features the characteristic insertion of periodontal ligament fibers.