Secondary Dentin Formation Mechanism: The Effect of Attrition

Abstract

Human dentin consists of a primary layer produced during tooth formation in early childhood and a second layer which first forms upon tooth eruption and continues throughout life, termed secondary dentin (SD). The effect of attrition on SD formation was considered to be confined to the area subjacent to attrition facets. However, due to a lack of three-dimensional methodologies to demonstrate the structure of the SD, this association could not be determined. Therefore, in the current study, we aimed to explore the thickening pattern of the SD in relation to the amount of occlusal and interproximal attrition. A total of 30 premolars (50–60 years of age) with varying attrition rates were evaluated using micro-computerized tomography. The results revealed thickening of the SD below the cementoenamel junction (CEJ), mostly in the mesial and distal aspects of the root (p < 0.05). The pattern of thickening under the tooth cervix, rather than in proximity to attrition facets, was consistent regardless of the attrition level. The amount of SD thickening mildly correlated with occlusal attrition (r = 0.577, p < 0.05) and not with interproximal attrition. The thickening of the SD below the CEJ coincided with previous finite element models, suggesting that this area is mostly subjected to stress due to occlusal loadings. Therefore, we suggest that the SD formation might serve as a compensatory mechanism aimed to strengthen tooth structure against deflection caused by mechanical loading. Our study suggests that occlusal forces may play a significant role in SD formation.

The Influence of New Bioactive Materials on Pulp–Dentin Complex Regeneration in the Assessment of Cone Bone Computed Tomography (CBCT) and Computed Micro-Tomography (Micro-CT) from a Present and Future Perspective—A Systematic Review

“…Apart from the fact that these teeth should be free from caries, they should not be exposed to occlusive stress, should not be abraded, and should not be taken from old people. These factors irritate the pulp and induce its return mechanisms in the form of reactive dentin deposition [ 7 , 8 ]. This dentin is also a form of tertiary dentine, however; in contact with bioactive material, it has a chance to form only in the indirect pulp-capping procedure [ 4 ].…”

“…Additionally, the age of the individual, rather than the attrition level, may affect SD accumulation in pulp chamber. [ 7 ]. In response to external stimuli, particularly due to caries, the pulp induces the formation of tertiary dentin.…”

“…Reactionary dentin is a defence mechanism against physiological factors, forming sclerotic tissue that reduces dentin permeability. It is a mechanism that protects the pulp against harmful irritation [ 7 , 8 ]. Nowadays, in asymptomatic teeth or those with reversible pulpitis, the tissues affected by caries (deep caries) are selectively removed to avoid injury or pulp exposure [ 2 ].…”

“…Recently, terms such as dentin-like, bone-like and reparative dentin bridge have been used to describe the newly formed hard tissue [ 14 ]. From the regenerative–biological perspective, this process is to be treated as pulp wound repair aimed at healing the pulp–dentin complex, however, without restoring the original tissue microanatomy [ 7 , 15 ]. In such a case, there is a formation of a new tissue (tertiary dentin) which, despite the fact that it is not an exact copy of the original, is physiologically sufficiently functional [ 4 ].…”

“…Both pure regeneration as well as repair constitute the finalisation of the healing process; however, the repair results in a formation of a replacement tissue (cicatrisation) which, to varying degrees, can contain regenerative components [ 17 ]. However, when the microbiological load is excessive and the pulpitis is uncontrolled and destructive in nature, the tissue is at risk of necrosis and is unable to form tertiary dentin [ 7 ]. In such a case, vital pulp therapy involves the partial or complete amputation of the pulp [ 18 , 19 , 20 ].…”