Physiology of Endosseous Implant Healing & Retention

Question 1

Bone modeling

Answer 1

Any change in the form, size, or shape of bone; it can be anabolic (apposition of bone on the surface) or catabolic ( resorption of the surface)

Question 2

When does bone modeling occur?

Answer 2

• During growth as part of wound healing (ex. during stabilization of an endosseous implant) &
• in response to bone loading

Question 3

Why is modeling considered an uncoupled process

Answer 3

Formation does not have to be preceded by resorption

Question 4

Bone remodeling

Answer 4

= replacement of existing bone
It involves removal of mineralized bone by osteoclasts followed by formation of bone matrix thru osteoblasts that subseq become mineralized

Question 5

3 consecutive phases of bone remodeling

Answer 5

(i) resorption - osteoclasts digest old bone
(ii) reversal - mononuclear cells appear on the bone surface; and
(iii) formation - osteoblasts lay down new bone until the resorbed bone is completely replaced

Question 6

Significances of bone modeling and remodeling

Answer 6

• fundamental physiological mechs of adaptation

- req for osseous repair and implant healing

Question 7

Why is bne modeling considered a site-specific phenomenon?

Answer 7

because the 2 processes (anabolic and catabolic) can occur separately on different surfaces

Question 8

Xstics of bone remodeling (4)

Answer 8

• internal turnover of existing bone
• coupled process (activation -> resorpt -> formation)
• cortical bone turnover (2-10% per yr)
• trabecular bone ( 20-30% per yr)
  hence source of Ca

Question 9

How long is the bone remodeling cycle in humans

Answer 9

~ 4 months

  - activation ~ 1 wk
  - resorption ~ 2 wks
  - formation ~ 13 wks

Question 10

Internal turnover of existing bone involves (4)

Answer 10

• growth and maturation
• wound healing
• repair of fatigue damage
• continuous source of Ca

Question 11

Bone healing sequence

Answer 11

Primary events
  - woven bone callus formation
  - lamellar compaction
Secondary events (inside bone)
  - remodeling of devitalized bone (RAP)
  - maturation of remodeled bone
       (~1 yr to full mineralization)
  - gradual return of basal remodeling
      (seen in reg bone healing NOT w/implants)

Question 12

Main property of woven bone

Answer 12

its ability to form quickly thus plays a principle role during healing
- considered phase I bone

Question 13

Why does woven bone have a low biomechanical strength

Answer 13

it is formed rapidly thus develops in a disorganized fashion without lamellar architecture or haversian systems therefore it is soft

Question 14

Lamellar compaction

Answer 14

resorption and replacement of phase I (woven) bone w/more mature phase II (lamellar) bone

Question 15

Composite bone

Answer 15

term used to describe the transitional state btwn woven bone and lamellar bone; it is a woven bone lattice that’s filled with lamellar bone

Question 16

Lamellar bone

Answer 16

the principle, mature, load-bearing bone in the body & is extremely strong

Question 17

Xstics of lamellar bone (3)

Answer 17

• forms very slowly
• well organized in its collagen & mineralized structures
• consists of multiple oriented layers

Question 18

Callus formation

Answer 18

the osteogenic cells that form the callus reside in the periosteum and endosteum

Question 19

What is the difference seen in fracture site stabilization between long bones and orofacial bones

Answer 19

Callus formation is req’d in stabilizing fracture sites; therefore there’s an increased risk of implant failure in the long bones if periosteum is stripped during implant placement; unlike orofacial bones, long bones do not have the same degree of blood supply. The endosteum remains undisturbed except at the trauma site (so callus formation is interrupted there)