Periodontal Review Q&A (eBook)

Anatomy

Q: Identify the anatomical structures of the periodontium shown below.

Fig 2-1a Illustration of the periodontium. (Reprinted from Fan and Berry1 with permission.)

The answers are shown in Fig 2-1b.

Fig 2-1b Labeled anatomy of the periodontium. (Reprinted from Fan and Berry1 with permission.)

Q: Where does the vascular supply of the periodontium originate?

The external carotid artery and its main branches, which include the lingual, facial, and maxillary arteries, are the vascular supply for the periodontium. Locally, the blood supply comes from the supraperiosteal vessels and vessels from the periodontal ligament (PDL) and bone.2

Q: What is the main innervation for the periodontium?

The trigeminal nerve and its branches provide the main innervation for the periodontium.

Definitions

Q: What is attached gingiva?

The attached gingiva is the area from the base of the sulcus to the mucogingival junction. It prevents the free gingiva from being separated from the tooth. Its height is determined by subtracting the sulcus probing depth from the total width of the keratinized tissue. It consists of thick lamina propria and deep rete pegs. Goaslind et al3 reported that the attached gingival thickness is 1.25 ± 0.42 mm.

Q: What is keratinized attached gingiva?

The keratinized attached gingiva is that found from the gingival margin to the mucogingival junction.

Q: What is alveolar mucosa?

Alveolar mucosa is the covering of the alveolar process that is nonkeratinized, unstippled, and movable. It extends from the mucogingival junction to the floor of the mouth and vestibular epithelium.

Q: What is clinical attachment loss (CAL)?

If the marginal gingiva is below the cementoenamel junction (CEJ):

CAL = pocket depth + [CEJ to marginal gingiva]

If the marginal gingiva is above the CEJ:

CAL = [marginal gingiva to CEJ] – [marginal gingiva to bottom of pocket]

Q: What is Ante’s law?

Ante’s law states that the root surface area of the abutment teeth must be equal to or greater than that of teeth being replaced with pontics. This helps determine the number of abutments needed for a fixed partial denture.

Gingival Epithelium

Q: What are the characteristics of healthy gingiva?

Healthy gingiva is coral pink, firm, follows the CEJ of the teeth, and may be stippled. The color of the gingiva is associated with the pigmentation of the patient. In dark-haired individuals, the gingiva can be darker than that in blond patients.

Q: What are the five types of gingival fibers?

There are five types of gingival fibers:

1. Dentogingival group: There are three types of fibers within this group.

▪ Fibers extending coronally toward the gingival crest

▪ Fibers extending laterally to the facial gingival surface

▪ Fibers extending horizontally beyond the alveolar crest height and then apically along the alveolar bone cortex

2. Alveologingival group: Fibers in this group run coronally into the lamina propria from the periosteum at the alveolar crest.

3. Dentoperiosteal fibers: These fibers insert into the periosteum of the alveolar crest and fan out to the adjacent cementum.

4. Circular group: These are the only fibers that are confined to the gingiva and do not attach to the teeth.

5. Transseptal group: These fibers bridge the interproximal tissue between adjacent teeth and insert into the cementum.

Q: What is the composition of the oral mucosa (the tissue lining the oral cavity)?

The oral mucosa is composed of masticatory, lining, and specialized tissues (Fig 2-2).

Fig 2-2 Composition of the oral mucosa. (Based on Avery.4)

Q: What is the composition of the gingival epithelium?

The gingival epithelium consists of oral (masticatory), oral sulcular, and junctional epithelia (average width < 1 mm) (Fig 2-3).

Fig 2-3 Composition of the gingival epithelium. (Based on Clerehugh et al.5)

Q: What are the four layers of cells that comprise the masticatory epithelium?

There are four layers of cells that comprise the masticatory epithelium2:

1. Stratum basale: Cuboidal cells found at the basement membrane; epithelial cell replication takes place in this location. This layer contains melanocytes and Merkel cells.

2. Stratum spinosum: The “spines” are desmosomes allowing intracellular contacts. It is the thickest layer and contains Langerhans cells, which are derived from bone marrow and take part in immune surveillance.

3. Stratum granulosum: Cells in this layer appear flat. Keratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer. These cells contain keratohyalin granules, protein structures that promote hydration and cross-linking of keratin.

4. Stratum corneum: Outermost layer containing dead cells and consisting of ortho- and parakeratinization. It is composed of compactly packed tonofilaments.

Q: Where are the widest and narrowest zones of gingiva?

The average thickness of the gingiva is 1.25 mm.3 The widest zone of gingiva is in the maxillary anterior region; the narrowest zone is at the facial aspect of the mandibular first premolar.2

Connective Tissue

Q: What is the composition of connective tissue?

Connective tissue (average width slightly greater than 1 mm) is fibrous, consisting of mostly type I collagen, ground substances, and mucopolysaccharides. It also contains white blood cells, blood vessels, lymphatics, and nerves.2

Q: What determines whether epithelium is keratinized or nonkeratinized?

The underlying connective tissue determines whether the epithelium is keratinized.6

Q: What is periosteum? What is its function?

The periosteum is a highly vascular connective tissue sheath covering the external surface of all bones except areas of articulation and muscle attachment. It consists of an inner cambium layer (contains osteoblasts and osteoprogenitor cells) and an outer fibrous layer.7

The periosteum is involved in bone healing and bone regeneration.8 It also serves as protection as well as a channel for the blood supply and nutrients for bone tissue.

Periodontal Ligament (PDL)

Q: Where is the average width of the PDL greatest and where is it narrowest?

The width of the PDL is greatest at the apex and narrowest in the middle. Older individuals have thicker fiber bundles in the PDL than younger individuals. The average width of the PDL is 0.2 mm.

Q: What provides the blood supply to the PDL?

Superior and inferior alveolar arteries provide the blood supply to the PDL, which is a vascular tissue.

Q: What are the functions of the PDL?

▪ Protect vessels and nerves

▪ Transmit occlusal forces

▪ Attach the tooth to bone

▪ Perform formative and remodeling functions

Q: What are the fibers of the PDL?

The fibers of the PDL include the alveolar crest, horizontal, oblique (most numerous), interradicular, and apical fibers.

Q: Describe and define ankylosis.

Ankylosis is the fusion of the cementum and alveolar bone with obliteration of the PDL. It develops after chronic periapical inflammation, tooth reimplantation, and occlusal trauma.

Alveolar Bone

Q: What is the composition of alveolar bone?

Alveolar bone consists of2:

▪ Cortical bone

▪ Cancellous trabeculae (more prevalent in the maxilla)

▪ Alveolar bone proper (lines the tooth socket)

Q: What are the functions of the alveolar bone?

The alveolar bone has three functions2:

1. Protection

2. Support

3. Calcium metabolism

Cementum

Q: Where are acellular cementum and cellular cementum located?

▪ Acellular cementum is located on the enamel at the CEJ. It does not contain cementocytes and forms slowly.

▪ Cellular cementum is located at the apical third of the root. It is more irregular and forms rapidly. With age, there is an increase in width of the cellular cementum.

Q: What percentage of the cementum and enamel overlap?

▪ 60% of the cementum and enamel overlap.

▪ 30% of the cementum and enamel form a butt joint.

▪ 10% of the cementum and enamel are separated by a gap.

Q: What is the difference between extrinsic and intrinsic cementum?

Extrinsic fibers are made of Sharpey fibers from the PDL, whereas intrinsic fibers are cementum fibers produced by cementoblasts (Fig 2-4).

Fig 2-4 Characteristics of extrinsic and intrinsic...