Distraction Osteogenesis - Jc - George

Distraction osteogenesis

it is a process of growing new bone by mechanical stretching of the preexistingbone tissue. The most common technique indistraction osteogenesis is mechanical stretching of the reparative bone tissue by a distraction device through an osteotomy or corticotomy site. With this technique, new bone is generated in the gap of osteotomy or corticotomy at the approximate rate of 1 mm per day.

Periodontal ligament distraction (dental distraction)ERIC JW LIOU AJO 1998

Gradual distraction of PDL (rapid canine distraction) is done by premolar extraction , followed by undermining of the interseptal bone distal to the canine to reduce on the compression side.Next the PDL is stretched gradually via distraction of the tooth bearing segment , and new bone is created mesial to the distally moving teeth.

Clinical Procedures A fixed orthodontic appliance was placed before the first premolar extraction. The tooth to be distracted was a canine, and the first molar and second premolar were the anchor units.

A 0.051 inchwire oriented vertically was soldered on the buccalside of the canine band and a lingual cleat was weldedon the lingual side. A buccal vertical sheath and a lingualcleat were soldered on the molar band . Noarch wire or active appliance was placed on the secondpremolar or first molar before the first premolarextraction

Right after the first premolar extraction, the interseptalbone distal to the canine was undermined with abone bur, grooving vertically inside the extractionsocket, along the buccal and lingual sides, and extendingobliquely toward the base of the interseptal bone toweaken its resistance. The interseptal bone was not cutthrough mesiodistally toward the canine . Thedepth of the undermining grooves was dependent onthe thickness of the interseptal bone, as revealed on theperiapical films.

A custom-made intraoral distraction device was delivered for canine distraction right after the first premolar extraction. It was activated 0.5 to 1 mm/day right after the extraction until the canine was distracted into the desired position and amount. Power chains were placed on the lingual side between the canine and the first molar to prevent rotation of the canine during distraction

Rapid Osteogenesis in the Distracted Periodontal LigamentThe radiographic changes of the periodontal ligamentson the mesial side of the canines could be classifiedinto five stages, from the initiation of the distractionto the complete remodeling of the new alveolarbone.

Stage 1. Stretching and widening of the periodontalligament. This was in the first week after initiatingthe distraction. Bone formation was not evident inthis stage

Stage 2. Active growing of striated bone (new bonespicules) in the distracted periodontal ligament. Thisoccurred during the second week

Stage 3. Recovery of the distracted periodontal ligament.This occurred in the first to fourth week aftercompleting the distraction. The striated bonebecame denser, gradually extending from the distallamina dura (native lamina dura) of the interseptalbone, distal to the lateral incisor, toward the canine.

Stage 4. Remodeling of the striated bone occurredfrom the fourth week to the third month after completingthe distraction. The radiodensity of the remodelingstriated bone was similar to the cancellousalveolar bone. The native lamina dura disappearedgradually.

Stage 5. Maturation of the striated bone was 3months after completing the distraction. The nativelamina dura disappeared and the new lamina durawas of normal thickness. On the radiographs, theinterseptal bone between the lateral incisor and thecanine was indistinguishable from the other interseptalbones.

Advantages of PDL distraction

The mesial movement of the first molar is minimal.The root resorption is minimalThe canine CAN be distracted so fast while the first molar was still in the lag period.After distraction, the anterior tooth retraction can be rapid as well, while the new bone tissues distal to the lateral incisors are still fibrous.

Why the mesial movement of the first molar is minimal?

After the initial tooth movement by a light orheavy orthodontic force, a lag period of minimal toothmovement persists for approximately 2 to 3 weeksbefore tooth movement again proceeds. The canine distraction was completed while thefirst molar was still in its lag period or just initiatingits mesial movement.

Why the root resorption is minimal?

Externalroot resorption is initiated 2 to 3 weeks after the orthodonticforce is applied and may continue for the durationof force application. The duration ofthe applied force is an aggravating factor for the rootresorption, and it is regarded as a more critical factorthan the magnitude of the force, especially in connection with long treatment periods.

Why can the canine be distracted so fast while the first molar was still in the lag period? The orthodontic tooth movement is faster and root surface resorption is less in an alveolar bone with loose bone trabeculae and less bone resistance.

After tooth extraction, regenerative bone tissue willrefill the extraction socket in 3 weeks and becomeresistant and solid in 3 months. If the canine is notretracted across the first premolar extraction socket inthe first 3 weeks, the rate of tooth movement will slowdown, root surface resorption will increase, and theanchor unit will start to move forward.