1/2- bone bio + occlusal forces

definition of bone

specialized connective tissue hardened by mineralization w/ calcium phosphate in the form of hydroxyapatite

5 functions of bone

1. support

2. protection

3. movement

4. mineral storage: calcium + phosphates

5. hematopoiesis: major site of blood cell formation in adults, within marrow spaces

2 components of bone

1. extracellular matrix

2. cellular component

2 components of the extracellular matrix of bone

1. inorganic matrix (67%): mainly hydroxyapatite crystals

2. organic matrix (33%): collagen type I

4 cell types that are in the cellular component of bone

1. osteocytes: maintains bone tissue

2. osteoblasts

3. osteogenic cell: stem cell

4. osteoclast

2 components of mineralized bone structure

1. compact (cortical)

2. trabecular (spongy)

3 components of non-mineralized bone structure

1. marrow

2. cells

3. connective tissue

what’s the alveolar process

forms + supports the tooth sockets (alveoli) 

alveolar process is formed by which cells

cells from dental follicle (alveolar bone proper) + cells independent of tooth development

when does the alveolar process form

when the tooth erupts to provide the osseous attachment to the forming periodontal ligament

T/F: the alveolar process remains after a tooth is extracted

false, it gradually disappears after the tooth is lost

3 components of the alveolar process

1. compact bone

2. trabecular bone

3. alveolar bone proper

what are the numbers 

1. alveolar bone 

2. spongy (trabecular) bone 

3. cortical plate 

what are the arrows pointing to

lamina dura/cribriform plate

T/F: lamina dura/cribriform plate is compact

false, it has many perforations that allow it to have neurovascular bundles link to the PDL

how is cementum connected to alveolar bone

collagen fibers from cementum reach across PDL space and insert into alveolar bone proper

what determines the morphology of alveolar processes

size, shape, location, function of teeth

what are 2 alveolar bone defects

1. fenestration: exposed root due to absence of lingual/buccal alveolar bone lamina

2. dehiscence: roots extending through marginal bone

alveolar bone defects are more common on facial or lingual

facial

common areas of fenestrations vs. dehiscence

• fenestration: maxilla

• dehiscence: mandible

alveolar bone level runs ___ to the levels of the 2 CEJs

parallel

healthy distance from CEJ → alveolar bone 

2-3 mm

what does an implant lack compared to a real tooth

implant does not have PDL + cementum + Sharpey’s fibers (true CT attachment)

what’s the biologic width (supracrestal attached tissue width) for implants

4-4.5 mm

T/F: periodontal bone will adapt to strong occlusal forces

true

what are the characteristics of the periodontal bone adapting to strong occlusal forces

• narrow + even thickness of PDL

• widened ligament space: hour glass shape of marginal + peri-apical bone

T/F: adaptation of periodontal bone to heavy occlusion is reversible 

true 

3 types of perio pockets

1. normal: apical termination of junctional epithelium is at CEJ

2. supraboney: proliferating pocket epithelium + remnant of junction epithelium persists

3. infraboney: extends beyond alveolar crest

describe what’s being circled

vertical bone loss: furcation involvement

2 functions of the PDL that relate to occlusion 

1. shock absorption 

2. transmission of forces to bone 

PDL adapts + remodels to which 2 forces

occlusal + orthodontic forces

normal vs. excessive amount of occlusal load in newtons

70-150 N vs. 300-500 N

normal vs. excessive angle of occlusal load in newtons

axial w/ limited lateral component vs. 30^o

6 structures that can be damaged under occlusal load

1. tooth + restorations

2. root

3. periodontium + alveolar bone

4. masticatory muscles

5. TMJ

2 effects of occlusal trauma on periodontium 

1. widened PDL space 

2. tooth mobility 

what’s the Irving Glickman (Tufts) concept of occlusal trauma

• occlusal trauma jiggles the tooth + “pumps” the infection apically along the PDL → vertical bone loss from occlusal trauma + inflammation and horizontal bone loss from inflammation

• suggesting occlusal trauma as a co-destructive factor of bone loss

what’s Waerhaug’s concept

occlusal trauma is not a contributing factor to vertical bone loss:

• thin bone + inflammation → horizontal bone loss

• thick bone inflammation → vertical bone loss

what’s the relationship between active periodontitis + occlusal trauma

occlusal trauma can accelerate existing periodontal disease

acute vs. chronic occlusal trauma

• acute: acute injury → toothache, percussion sensitivity, tooth mobility

• chronic: chronic overload (ex: bruxism, faulty restorations, insufficient # of teeth) → tooth mobility

primary vs. secondary occlusal trauma 

• primary: from excessive occlusal forces 

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

4 histological signs of occlusal trauma

1. resorption of collagen, bone, cementum

2. widened PDL

3. increased mobility

4. no attachment loss

what are the numbers 

1. resorption of collagen, bone, cementum

2. widened PDL

3. increased mobility

4. no attachment loss

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. All of the above

Occlusal trauma can cause:

A. Attachment loss

B. Increased mobility

C.Vertical bone loss

D. Tooth loss

B. Increased mobility

3 stages of tissue response to acute occlusal trauma

1. stage I: injury

2. stage II: repair

3. stage III: adaptation

I R A

describe what happens during stage I of tissue response to acute occlusal trauma 

• PDL inflammation (microscopic) 

• bone resorption (microscopic, not clinical) 

• widened PDL 

• increased tooth mobility 

describe what happens during stage II of tissue response to acute occlusal trauma 

• no more inflammation

• foundation of new PDL, bone, cementum

describe what happens during stage III of tissue response to acute occlusal trauma 

• widened PDL + tooth mobility remains

• no pocketing/attachment loss

what are the consequences of secondary occlusal trauma

same as primary occlusal trauma (widened PDL + increased mobility) but NO progression in attachment loss

what’s pathologic tooth migration

form of secondary occlusal trauma: normal occlusal forces acting on reduced periodontium → tooth mobility + migration

4 clinical signs of pathologic tooth migration 

1. periodontitis 

2. increased mobility 

3. new interproximal gaps 

4. tooth extrusion 

what was the conclusion of Burgett 1992 “clinical trial to assess occlusal adjustment”

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

T/F: tx of periodontitis is necessary + tx of occlusal trauma is of secondary importance

true

T/F: occlusal trauma by itself causes perio attachment loss + bone loss

false

what’s the physiological mobility of teeth under normal forces

100 microns (0.1mm)

T/F: physiological mobility varies from tooth to tooth → larger on single-rooted anterior teeth + less on multi-rooted molars

true 

3 factors that determine tooth mobility

1. height of alveolar bone in relation to length of root: more bone loss = more mobility

2. width of PDL space: wider PDL = more mobility

3. shape + # of roots: more roots + thicker roots = less mobility

what’s the Miller classification

• no mobility: <0.1 mm

• grade I: 0.1-1mm

• grade II: 1mm<

• grade III: vertical or twist mobility

T/F: tx of occlusal trauma depends on cause of mobility

true

4 causes of tooth mobility + their tx

1. occlusal trauma: occlusal adjustment or distribution occlusal forces

2. periodontal abscess: elimination of cause (SRP/RCT)

3. periodontitis: STP, splinting for pt comfort

4. root fracture: EXT

what’s splinting 

mechanical stabilization of teeth 

when is splinting indicated

1. for pt comfort on mobile teeth

2. pathologic tooth migration

3. guided tissue regeneration on mobile teeth

4. prosthetics where multiple abutments needed

5 consequences of lack of occlusion

1. thin PDL

2. reduction in bone density

3. supra-eruption

4. apparent attachment loss

5. furcation exposure

posterior bite collapse leads to what

1. super-eruption → root + furcation exposure

2. molar tipping → pseudopocket (5)

3. open contact

NCCLs are caused by a combination of which 2 things 

1. abrasion from brushing 

2. chemical erosion due to acidic foods/drinks 

how does the PDL adapt to orthodontic forces

• low PDL fiber strain → bone resorption

• high PDL fiber strain → bone formation

T/F: orthodontic tx can be done on a periodontitis pt

true, but they must have NO inflammation

what happens to the periodontium if the tooth is moved through cortical bone

creates boney defect (dehiscence)

what happens to the periodontium if the tooth is extruded

bone + gingiva will follow (beneficial for implant planning)

what happens to the periodontium if the tooth is intruded

unlikely to create new attachment; may create deeper pocket 

what happens to the periodontium if a molar is uprighted

mesial pocketing can be eliminated; may expose furcation

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

A. 0

B. I

C. II

D. III

C. II

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. Periodontitis