Orofacial Complex: Form and Function

Orofacial Form And Function

Size Of Crown And The Root Of A Tooth

It is important that the crown and root of a tooth be proportional to each other. The function of the tooth depends on the size and shape of the root.

• The long root of the canine at the corners of the mouth and the trifurcated roots of the molar are meant to bear the shear forces and provide anchorage.
• Roots with developmental depressions on the lateral surface provide anchorage in the alveolar bone.

Read And Learn More: Oral Anatomy Notes

Tooth Form And Jaw Movements

• The jaw moments are directly influenced by the incisal and occlusal forms of the teeth.
• Prominent canines and limited lateral movements are found in primates and carnivores.
• When human jaw moments are compared with those of animals, humans have An increased range of movements due to the specialized temporomandibular Joint and complex occlusal anatomy of the teeth.

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Interproximal Spaces And Protection Of Interdental Gingiva

When teeth are viewed from the facial and lingual aspects, triangular spaces are seen between the approximating teeth just cervical to the contact area. These spaces protect and accommodate the gingival tissues and are referred to as interproximal spaces. The gingival tissues that fill these spaces are called the gingival papilla/interdental papilla.

The alveolar processes of the jaw bones are covered by attached gingiva, and the gingiva around the cervical area of the teeth are termed as marginal gingiva. The junction between the alveolar mucosa and the attached gingiva is marked by the mucogingival line.

Col is a part of the interdental gingiva which lies beneath the contact area and extends labiolingually. It is nonkeratinized and could be subject to trauma due to mastication and bacterial invasion.

The col and interproximal gingival tissues are protected by tight contacts and interproximal spaces.

Sufficient alveolar spaces between the tapered roots securely anchor the teeth to the jaws and provide space for adequate nerve and blood supply.

Proximal Contact Areas

When the tooth erupts, it comes in contact with the tooth mesial and distal to it. These contacts between the erupted teeth are termed as contact areas. Every tooth other than the last molar has a mesial and distal contact area.

• Proper and tight contacts are important for the following reasons:
  • shunts the food towards the lingual and buccal surfaces, thereby Protecting the interproximal gingiva.
  • prevents food impaction, which can cause decay and periodontal Problems.
  • occlusal stability is provided for by the combined anchorage.
  • Masticatory forces are well distributed due to the dental arch functioning as a single unit with tight contacts.

Facial view of contact areas:

Clinical significance of contact areas:

• When loss of contact occurs between adjacent teeth due to caries or loss of tooth structure, food accumulation between the teeth leads to pathologic changes in the nature of the tissue. Inflammation of the gingiva occurs leading to gingivitis and further causes periodontitis if left unresolved. It is important to establish proper contacts during the treatment of malocclusion, restorations and crown prosthesis to prevent failures.

Occlusal view of contact areas:

Embrasures (Spillways)

• Curvatures adjacent to the contact areas form ‘v’-shaped spaces when two Adjacent teeth come into contact. These spaces are termed as Embrasures/spillways.
• The narrowest space of the v shape is at the contact area and it widens facially to form labial/buccal embrasure, lingually to form the lingual embrasure.
• The triangular space cervical to the contact areas filled by the interdental papilla is termed as the interproximal space.
• Occlusal/incisal embrasures are observed when viewed from the facial aspect and the facial and lingual embrasures are observed from the incisal/occlusal aspect. The characteristics of an ideal embrasure are given in flowchart 21.2 and the functions of an ideal embrasure are given in flowchart.

Facial And Lingual Physiologic Contours Of Teeth

Curvatures of the cervical line:

The cervical line marks the junction between the enamel and cementum.

• The curvature of the cervical line on the mesial and distal aspects of adjacent teeth is almost at the same level.
• The curvature is more on the mesial side than the distal by about 1 mm.
• The level of the contact area is dictated by the extent of the cervical line.
• The contact areas are located more cervically as the length of the crown Decreases from the anterior to the posterior teeth.

Facial and lingual physiologic contours of teeth:

Imaginary occlusal plane and curves:

The curves discussed here are:

1. Curve of spee (anteroposterior curve)
2. Curve of wilson (side to side curve)
   1. The curve ofspee is defined as an imaginary curve that begins from the
      Tip of the canine and runs through the buccal cusps of the premolars
      And molars and along the ramus of the mandible to the condyle of the
      Mandible. This is a concave curve and the maxillary counterpart will
      Be convex to attain centric occlusion.
   2. The curve ofwilson is an imaginary curve that starts from the buccal
      Cusp of the mandibular posteriors to the buccal cusp of the
      Mandibular molars on the contralateral side. The glabella is the centre
      Of the arc of the sphere. The curve is concave in the mandible and
      Convex in the maxilla when viewed from the frontal aspect.

Crown outlines:

Crown outlines of anterior and posterior teeth:

Orofacial Form And Function Synopsis

• Size of crown and root: The function of the teeth depends on the size and shape of the root.
• Tooth form and jaw movements: The jaw movements are directly influenced by the incisal and occlusal forms of the teeth.
• Interproximal spaces and protection of interdental gingiva: The triangular spaces between the approximating teeth just cervical to the contact area protect and accommodate the gingival tissues and are referred to as interproximal spaces.
• Col is a part of the interdental gingiva which lies beneath the contact area and extends labiolingually. It is nonkeratinized and could be subject to trauma due to mastication and bacterial invasion. The col and interproximal gingival tissues are protected by tight contacts and interproximal spaces.
• Proximal contact areas: When the tooth erupts, it comes in contact with the teeth mesial and distal to it. These contacts between the erupted teeth are termed as contact areas. Every tooth other than the last molar has a mesial and distal contact.

Proper and tight contacts protect the interproximal gingiva, prevent food impaction and distribute masticatory forces as the dental arch functions as a single unit.

• Embrasures are curvatures adjacent to the contact areas and form ‘v’-shaped spaces when two adjacent teeth come into contact.
• The cervical line marks the junction between the enamel and cementum.
• Imaginary occlusal plane and curves: The curves discussed here are the curve of spee (anteroposterior curve) and curve of wilson (side to side curve).
  • The curve of spee is defined as an imaginary curve that begins from the tip of the canine and runs through the buccal cusps of premolars and molars and along the ramus of the mandible to the condyle of the mandible. This is a concave curve and the maxillary counterpart will be convex to attain centric occlusion.
  • The curve of wilson is an imaginary curve that starts from the buccal cusp of mandibular posteriors to the buccal cusp of the mandibular molars on the contralateral side. The glabella is the centre of the arc of the sphere. The curve is concave in the mandible and convex in the maxilla when viewed from the frontal aspect.