What is the Difference Between Cellular and Acellular Cementum

The key difference between cellular and acellular cementum is that cellular cementum is relatively thick and covers the apical half of the root, while acellular cementum is relatively thin and covers the cervical half of the root.

Cementum is a bone-like mineralized tissue that lines the dentin of the root while protecting the root. It is a thin layer of hard dental tissue formed by cells called cementoblasts. It develops from undifferentiated mesenchymal cells in the connective tissues of dental follicles. Cementum contains collagen fibrils. The cells of cementum entrap cementocytes, and each cementocyte lies in a lacuna. Lacuna also consists of canals, but unlike bones, they lack nerves. These canals orient towards the periodontal ligament and contain cementocytic processes to diffuse nutrients from the vascularized ligament. Sharpey’s fibres are a part of the principal collagen fibres of the periodontal ligament embedded in the cementum and alveolar bone to attach the tooth to the alveolus. Cementum is divided into acellular and cellular cementum based on the presence and absence of cementocytes in the matrix of cementum.

1. Overview and Key Difference
2. What is Cellular Cementum
3. What is Acellular Cementum
4. Similarities – Cellular and Acellular Cementum
5. Cellular vs Acellular Cementum in Tabular Form
6. Summary – Cellular vs Acellular Cementum

What is Cellular Cementum?

Cellular cementum is the medium of attachment for collagen fibres to the alveolar bone, and it contains cells. It is responsible for minor repairs of any resorption followed by deposition to maintain the attachment apparatus intact. Generally, the cellular cementum is thick and covers the apical root. Cellular intrinsic fibre cementum (CIFC) corresponds with cellular cementum. It is composed of intrinsic fibres that run parallel to the root surface. It has no sharp fibre formation. Cellular cementum is less cellular than bone and contains a cemented seam on the outer surface. CIFC usually contains both extrinsic and intrinsic fibres. It contains an unmineralized central core surrounded by a highly mineralized cortical portion.

Cellular vs Acellular Cementum in Tabular Form

Figure 01: Human Tooth

What is Acellular Cementum?

Acellular cementum does not contain cells and mainly has an adaptive function. Acellular cementum is thin and covers the cervical root. Acellular extrinsic fibre cementum (AEFC) corresponds with acellular cementum found in the cervical two-thirds. The fibres derived are Sharpey’s fibres. They form slowly, and the root surface of this cementum is smooth. AEFC covers the cervical root surfaces in both permanent and deciduous teeth. It contains collagen fibres and non-collagenous proteins as organic matrices; however, they are fully mineralized. These are also densely packed and are arranged perpendicularly to the root surface.

What are the Similarities Between Cellular and Acellular Cementum?

Cellular and acellular cementum are two parts found in the teeth.
Both are calcified.
Moreover, they contain Sharpey’s fibers.
Extrinsic collagen fibers are present in both cellular and acellular cementum.

What is the Difference Between Cellular and Acellular Cementum?

Cellular cementum is relatively thick and covers the apical half of the root, while acellular cementum is relatively thin and covers the cervical half of the root. Thus, this is the key difference between cellular and acellular cementum. The majority of the cellular cementum forms after the tooth reaches the occlusal surface, while the majority of acellular cementum forms before the tooth reaches the occlusal plane. Moreover, cellular cementum consists of cementocytes, while acellular cementum does not consist of cementocytes.

The below infographic presents the differences between cellular and acellular cementum in tabular form for side by side comparison.

Summary – Cellular vs Acellular Cementum

Cementum is a bone-like mineralized tissue that lines the dentin of the root while protecting the root. Cellular cementum is relatively thick and covers the apical half of the root, while acellular cementum is relatively thin and covers the cervical half of the root. Moreover, cellular cementum is the medium of attachment for collagen fibres to the alveolar bone, and it contains cells. Acellular cementum, on the other hand, does not contain cells and mainly has an adaptive function. Acellular cementum is formed initially, and cellular cementum is formed after. The majority of the cellular cementum forms after the tooth reaches the occlusal surface, while the majority of acellular cementum forms before the tooth reaches the occlusal plane. The developmental rate of cellular cementum is faster than acellular cementum. So, this is the summary of the difference between cellular and acellular cementum.

Reference:

1. “Cementum.” An Overview | ScienceDirect Topics.
2. Yamamoto, Hitoshi, et al. “Diversity of Acellular and Cellular Cementum Distribution in Human Permanent Teeth.” Journal of Hard Tissue Biology, vol. 18, no. 1, 2009, pp. 40–44., https://doi.org/10.2485/jhtb.18.40.