Direct Factors Affecting the Periodontium

Direct Factors:

1. Proximal contact relations2. Interproximal spaces (interdental papillae)3. Embrasures or spillways4. Maximum convexities (facial and lingual contours of the crown)6. Curvature of cervical line

Recall: When describing direct factors…

1. Describe the normal physiology2. Explain the significance of normal physiology in protecting the periodontium3. List the effects if it was different

1. Proximal contact relations

Normal physiology

- Newly erupted teeth have contact points which develop into contact areas with time.

- Every tooth has 2 contact areas EXCEPT for the third molars.

- Viewed from 2 views to determine which 1/3 the contact area is found and whether or not it is centralised or shifted buccally.

- Facial view determines which third the contact area is found (incisal 1/3, incisal/occlusal and middle 1/3 junction, middle 1/3).

- Occlusal/Incisal view determines whether the contact area is centralised or shifted.

- Shifted contact areas depend on: Lingual inclination, lingual convergence, size of tooth, contact between teeth of the same group.

- Possible contact areas occur in the incisal 1/3, incisal/occlusal and middle 1/3 junction, middle 1/3

- For anterior teeth, mesial contact area is usually in the incisal 1/3 while distal contact area is at the junction of incisal and middle 1/3.

- For posterior teeth, mesial contact area is usually in the occlusal and middle 1/3 while distal contact area is in the middle 1/3.

- Exceptions are C, 4, 4. Contact areas are opposite.

- Factors that affect contact relation are:

Level and breadth of crown

Level and height of the proximal maximum curvature

Malocclusion (due to crowding of teeth)

Proximal wear (due to attrition and friction with age)

Developmental abnormalities (eg. Peg shaped teeth with only 2 lobes known as supernumary teeth)

Disproportional growth between teeth and jaw (tooth is too big/small for jaw or jaw is too big)

Extraction, unerupted or developmentally missing teeth

Significance

- Prevents food impaction and therefore prevents degenerative effect on gingiva.

- Slows down food as it touches gingival and so protects it from undue frictional trauma (but stimulates the gingival at the same time).

- Distributes forces evenly and so strengthens individual teeth .

- Prevents movement of teeth when force is applied.

- Reduces the forces acting on the periodontium.

Effects from a Lack of Contact Area

- Food impaction gum inflammation gingivitis periodontitus.

- Loss of correct tooth alignment.

- Masticatory forces not distributed evenly.

- Causes occlusal trauma due to damage to the periodontium.

2. Interproximal Spaces (interdental papillae)

Normal Physiology

- A triangular space between teeth, with the base at the alveolar process and the two sides being the proximal surfaces of the teeth. Apex is at the contact area.

- Created by the trapezoidal outline of the facial surfaces short side cervically, long side occlusal/incisally.

- Filled with gingiva.

- No contact area = no interproximal spaces

Significance

- Allows for nerve and blood supply, for sensation and nutrition.

- Creates a space for the alveolar bone so that the tooth can be supported better in the bone socket. More bone = more support.

Effects of a Lack of Interproximal Space

- Less nutrition

- Less sensation

- Less support

- More force is placed on periodontium can cause bone resorption

3. Embrasures or spillways

Normal Physiology

- A open triangular space between the proximal surfaces of adjacent teeth

- Apex is at contact area and then diverge occlusally (incisally), buccally (labially) and lingually

- The size of embrasure is determined by the location of the contact area

Significance

- Makes a Spillway for the escape of food during mastication

- Decrease the occlusal table

o So it reduce the occlusal force on teeth

- Self Cleansing effect

- Slows down food to prevent undue frictional trauma to gingiba

Effects of Lack of Embrasures

- Food impaction will be more frequent gingivitisperiodontitis

- More forces on the periodontium (bigger occlusal table) bone resorption

- Self-cleansing ability is reduced tooth decay

- Gingiva is exposed to more frictional forces gingivitis periodontitis

4. Maximum Convecities (Facial and lingual contours)

Normal Physiology

- Anterior teeth

o Maximum convexity of both labial and lingual surfaces is located in the cervical third

o Measures approximately 0.5mm in upper teeth and less than 0.5mm in lower teeth

- Posterior teeth

o Maximum convexity of buccal surface is in cervical third

o Maximum convexity of lingual surface is at middle third

o Except lower second premolar: maximum convexity lingually is located in occlusal third

Significance

- Hold the gingival under definite tension

- Deflect the food away from the gingival margin to prevent food impaction and gingival recession

- Deflect the food over the gingiva which massage it

Effects of too small/too large convexity

- Too little of lack of curvature

o Food will push the gingival tissue apically leading to gingival recession

- Too large convexcity

o Provide too much protection to the gingival

o Gingiva will lost its tone

o Food will accumulate around the gingival region

o Resulting in inflammation gingivitis periodontitis

5. Curvature of Cervical line (dentogingival junction)

Normal Physiology

- Present at dentogingival junction

- Curvature of cervical line depends on

o Height of contact are

o Thickness of crown

- Curvature is greater mesially than distally

- Curvature is greater in anterior teeth than posterior teeth

- In molars, the distal surface, the curvature of the cervical line tends to be straight

Significance

- Acts as the border between cementum (a tissue that receives attachment and involve in support) and enamel (a tissue that doesn’t receive attachment and not involved in support)

- Acts as a site of attachment of the gingival to the tooth via epithelium of the dentogingival junction

Effects of lack of curvature of cervical line

- Allows penetration of bacteria or their toxins into the peridontium

- Causing damage to the tissues of the tooth