2. Occlusal forces and the Periodontium

what are the physical functions of PDL?

• Attachment of tooth to bone

• Shock absorption

• Space for blood vessels and nerves

• Transmission of forces to bone

what are adaptive functions of PDL?

• Adaptation and remodeling in response to occlusal forces

• Remodeling in response to orthodontic forces

what is considered normal occlusal load in terms of force?

70-150 N

what is considered normal occlusal load in terms of angle?

axial with limited lateral component

what is considered normal occlusal load in terms of duration?

normal chewing is episodic (vs clenching which is continuous)

t/f: there is no/minimal direct contact between antagonist teeth during normal chewing

true

what is considered excessive occlusal load?

force:

angle:

duration:

• force: 300-500 N

• angle: 30 degrees

• duration: 5 million cycles (or continuous)

(as illustrated by implant testing protocols but applies to normal dentition as well)

what dental structures may be damaged under excessive occlusal load?

1. fracture of tooth and restorations (most common)

2. fracture of root

3. damage to periodontium and alveolar bone

what craniofacial structures may be damaged under excessive occlusal load?

5. masticatory muscles

6. TMJ

can occlusal trauma damage periodontal soft tissues?

• can widen PDL space

BUT does not cause:

• increased BOP

• increased probing depth

• attachment loss

can occlusal trauma damage alveolar bone?

• can cause tooth mobility

BUT can not cause:

• horizontal/vertical bone loss

• tooth loss

what is Irving Glickman’s concept of occlusal trauma? (debated)

• occlusal trauma jiggles the tooth and “pumps” the infection apically along PDL

  • vertical bone loss is due to occlusal trauma + inflammation

  • horizontal bone loss is result of inflammation without occlusal trauma

• trauma from occlusion was suggested to be co-destructive factor of bone loss

what do opposing views to Irving Glickman’s concept of occlusal trauma like Waerhaug’s concept suggest?

• extent of inflammation alone determines extent of bone loss

• thickness of bone determines bone loss type:

  • thin bone + inflammation = horizontal bone loss

  • thick bone + inflammation = vertical bone loss

• OVERALL: occlusal trauma is NOT a contributing factor to vertical bone loss

what conclusion was reached during the Lindhe & Svanberg (1974) experiment?

while occlusal trauma alone does not cause periodontal attachment loss or bone loss, it may accerlerate existing periodontal disease (effect show in animal experiments)

Acute occlusal trauma results form acute injury (e.g. biting on an olive pit). Acute occlusal trauma results in …?

toothache, percussion sensitivity and tooth mobility

Chronic occlusal trauma occurs in response to chronic overload (e.g. bruxism, faulty restorations or insufficient number of teeth). Chronic occlusal trauma results in..? 

often asymptomatic; only tooth mobility is detected clinically

what is the difference between primary and secondary occlusal trauma?

• primary → results from excessive occlusal forces

• secondary → results from normal occlusal forces on a weakened (reduced periodontium)

what histologic findings were discovered in animal studies researching occlusal trauma via repeated off-axis jiggling (back-and-forth) forces?

1. resorption of collagen, bone, cementum

2. widened PDL

3. increased mobility 

4. no attachment loss

Q1. Occlusal trauma may be due to:

A. Accidentally biting on a hard object

B. Clenching while asleep

C. Chewing with just a few teeth left

D. All of the above

D

Occlusal trauma can cause:

A. attachment loss

B. increased mobility

C. vertical bone loss

D. tooth loss

B

what are the 3 stages of tissue response to acute occlusal trauma (primary)?

1. injury

2. repair

3. adaptation

what occurs during stage 1 of tissue response to acute occlusal trauma (primary)?

• PDL inflammation (microscopic vascular changes)

• bone resorption (microscopic)

• widened PDL
  increased tooth mobility

what occurs during stage 2 of tissue response to acute occlusal trauma (primary)?

• no more inflammation

• formation of new PDL, bone, cementum

what occurs during stage 3 of tissue response to acute occlusal trauma (primary)?

• widened PDL + tooth mobility remains

  • these compensate for persistent occlusal trauma (aka it’s not going to keep getting worse and worse, the periodontium adapts to the “new normal” but this doesn’t mean treatment like an molar implant is not indicated)

• no pocketing, no attachment loss

normal occlusal forces on a reduced periodontium may cause which type of occlusal trauma? this can be caused by…?

secondary

• existing attachment/bone loss

• too few remaining teeth (no molars)

what are the consequences of secondary occlusal trauma?

same as primary

• widened PDL

• increased mobility

• but NO progression in attachment loss

what are clinical signs of pathologic tooth migration (a form of secondary occlusal trauma)?

• periodontitis

• increased mobility

• new interproximal gaps

• tooth extrusion

pathologic tooth migration is generally a sign of mild/moderate/severe advanced disease

severe

in this experiment/clinical trial, what was the result/conclusion?

occlusal adjustment resulted in minimal but measureable (0.5 mm) increase in attachment gain

occlusal trauma can cause…? (2)

but occlusal trauma by itself does NOT cause…? (2)

Occlusal trauma can:

••• Increase tooth mobility

••• Cause widened PDL

But occlusal trauma by itself does not cause:

••• Periodontal attachment loss

••• Bone loss

There is a physiological tooth mobility due to the orientation and elasticity of periodontal ligament fibers.

Under normal forces this physiological mobility is up to…?

100 microns (0.1mm)

How does physiological mobility vary from tooth to tooth?

larger on single-rooted anterior teeth and less on multi-rooted molars

what factors determine tooth mobility?

1. Height of the alveolar bone in relation to the length of the root

   1. more bone loss means more mobility

2. Width of the periodontal ligament space

   1. wide PDL means more mobility

3. Shape and number of roots

   1. more roots and thicker roots means less mobility

how is tooth mobility assessed?

by moving the crown in a bucco-lingual direction with two instruments or with one instrument and a finger

what classificaiton system do we use to grade tooth mobility?

Miller classification

• No mobility: <0.1 mm

• Grade I: 0.1-1mm

• Grade II: more than 1mm

• Grade III: vertical or twist mobility

what are causes of tooth mobility?

• occlusal trauma

• periodontal abscess

• periodontitis

• root fracture

treatment of tooth mobility depends on the ______.

cause

how is tooth mobility caused by occlusal trauma treated?

occlusal adjustment, distributing occlusal forces (molar support)

how is tooth mobility caused by periodontal abscess treated?

elimination of cause (SRP, root canal treatment)

how is tooth mobility caused by periodontitis treated?

SRP, splinting for patient comfort

how is tooth mobility caused by root fracture treated?

extraction, implant placement

splinting of teeth

what are some indications for splinting teeth?

• For patient comfort on mobile teeth

• Pathologic tooth migration

• Guided tissue regeneration on mobile teeth

• Prosthetics where multiple abutments needed

what is a prerequisite to splinting?

control of periodontal inflammation

t/f: splinting itself induces periodontal regeneration

false. Splinting only mechanically stabilizes teeth, it does NOT by itself induce periodontal regeneration

what consequences may occur when there is no occluding antagonist to a teeth?

• Thin PDL

• Reduction in bone density

• Supra-eruption of tooth

• Apparent attachment loss

• Furcation exposure

what principle applies to the periodontium as demonstrated by the consequences of lack of occlusion?

use it or lose it

Posterior bite collapse as a result of 1st molar extraction demonstrates multiple occlusal issues that may result in periodontal problems such as

• Super-eruption, resulting in root and furcation exposure

• Molar tipping, creating a pseudopocket (5)

• Open contact, a risk factor for food impaction and gingival inflammation (4)

what are wedge-shaped defects in the buccal cervical region of the tooth?

non-carious cervical lesions (NCCLs)

what are 2 chief mechanisms of non-carious cervical lesions?

• Abrasion (toothbrush and toothpaste)

• Abfraction (micro-cracks due to occlusal trauma)

t/f: non-carious cervical lesions show signs of periodontitis.

false

Increased frequency of NCCLs are found in subjects with…?

• Improper brushing technique (horizontal scrubbing) causes 2-3x more wear than vertical brushing

• Excessive manual force

• Hard bristle toothbrush

• Frequent brushing (twice a day vs once a day)

what is the loss of hard tissue in the cervical region of the tooth by non-axial forces exerted on the occlusal surface, which cause microfractures of dental tissues in areas of stress concentration?

Abfraction

The chief supporting evidence for abfraction comes from …?

computer modeling of stress development in teeth after lateral loads

what is the current accepted concept of the cause of NCCLs?

toothbrush abrasion AND chemical erosion due to acidic foods/drinks

Tooth is suspended in socket by PDL fibers

Low PDL fiber strain leads to…?

High PDL fiber strain leads to…?

bone resorption

bone formation

can there be tooth movement without PDL?

no

moving tooth through cortical bone can lead to…? (1)

creates bony defects (dehiscence)

extrusion can lead to…? (2)

bone and gingiva will follow (benefiticial for implant planning)

intrusion can lead to…? (3)

• unlikely to create new attachment

• may create deeper pockets

molar uprighting may lead to…? (4)

• eliminating mesial pocketing

• may expose furcation

can orthodontic treatment be done in a perio pt?

• yes as long as periodontium is inflammation-free

• Active periodontitis on the other hand may be aggravated by orthodontic treatment

t/f: Orthodontic treatment may improve the chances of saving periodontally compromised tooth

true

t/f: Tooth movement causes attachment loss in the absence of inflammation

false. Tooth movement does not cause attachment loss in the absence of inflammation

Q3. Tooth #24 can be moved bucco-lingually more than 1mm but not in any other direction. What is the grade of mobility?

0

I

II

III

II

Q4: Which of the following root exposures is caused PRIMARILY by inflammation?

A.Non-carious cervical lesion

B.Periodontitis

C.Orthodontic extrusion

D.Tooth super-eruption

B