Healing of gingevectomy wounds, extraction wound, Fracture and bone healing, Factors

affecting healing

Wound healing, or wound repair, is an intricate process in which the mucosa, skin or dermis repairs itself after injury

In normal skin, the epidermis and dermis (inner or deeper layer) exists in a steady-stated equilibrium, forming a protective barrier against the external environment

Once the protective barrier is broken, the normal (physiologic) process of wound healing is immediately set in motion.

Generally considered to be a phase of inflammatory reaction since there is angiogenesis and granulation tissue formation

Hence healing is a response of the body to injury in an attempt to restore normal structure and function

Two phases involved:◦ Regeneration

◦ Repair

1. Age

2. Type of tissue

3. Location of wound

4. Mobility of wound

5. Trauma

6. Local temperature

7. Radiation

8. Circulatory factors

9. Infections

10. Hormonal effects

Extraction

Bleeding

clotting

Edema

neutrophils

Fibroblast

epithelization

Debris removal

by

macrophages

Clot

organization

Epithelium

covers the

socket

Fibrosis

Osteoid at

periphery

Osteoid fills

up socket

Granulation

tissue

replaced

3 weeks to 6

months

Osteoid

replaced

Mature

bone

Wound

healed

Bone healing, or fracture healing, is a proliferative physiological process in which the body facilitates the repair of a bone fracture

The length of the process depends on the extent of the injury

Two to three weeks are given for the reparation of most upper bodily fractures

FACTORS AFFECTING BONE HEALING

◦ Angle of dislocation or fracture

◦ Location of wound

◦ Mobility of wound

◦ Age

◦ Infections

Phases of fracture healing

There are three major phases of fracture healing;

1. Reactive Phase◦ i. Fracture and inflammatory phase

◦ ii. Granulation tissue formation

2. Reparative Phase◦ iii. Callus formation

◦ iv. Lamellar bone deposition

3. Remodeling Phase◦ v. Remodeling to original bone contour

REACTIVE◦ After fracture, the first change seen by light and

electron microscopy is the presence of blood cells within the tissues which are adjacent to the injury site. Soon after fracture, the blood vessels constrict, stopping any further bleeding.Within a few hours after fracture, the extravascular blood cells, known as a "hematoma", form a blood clot

◦ Cells within the blood clot degenerate and die

◦ Fibroblasts survive and replicate

◦ Granulation tissue is formed

REPARATIVE◦ Days after fracture, the cells of the periosteum

replicate and transform

◦ Periosteal cells proximal to the fracture gap develop into chondroblasts

◦ Hyaline cartilage formed

◦ Periosteal cells distal to the fracture gap develop into osteoblasts and form woven bone

◦ Fibroblasts within the granulation tissue also develop into chondroblasts and form hyaline cartilage

◦ These two new tissues grow in size until they unite with their counterparts from other pieces of the fracture

◦ This process forms the fracture callus

◦ Eventually, the fracture gap is bridged by the hyaline cartilage and woven bone, restoring some of its original strength

◦ Next phase is the replacement of the hyaline cartilage and woven bone with lamellar bone

◦ Replacement process is known as as endochondral ossification

◦ Substitution of the woven bone with lamellar bone precedes the substitution of the hyaline cartilage with lamellar bone

◦ Lamellar bone begins forming soon after the collagen matrix of either tissue becomes mineralized

◦ At this point, "vascular channels" with many accompanying osteoblasts penetrate the mineralized matrix

◦ Osteoblasts form new lamellar bone upon the recently exposed surface of the mineralized matrix

◦ This new lamellar bone is in the form of trabecular bone

◦ Eventually, all of the woven bone and cartilage of the original fracture callus is replaced by trabecular bone, restoring most of the bones original strength

REMODELING◦ The remodeling process substitutes the trabecular

bone with compact bone

◦ Trabecular bone is first resorbed by osteoclasts, creating a shallow resorption pit known as a "Howship's lacuna”

◦ Then osteoblasts deposit compact bone in the pit

◦ Eventually, the fracture callus is remodelled into a new shape which closely duplicates the bone's original shape and strength

Collagen fibers of woven bone Osteoblasts forming compact bone,

containing 2 osteocytes within the

resorption pit in trabacular bone