Relapse and Retention

Definition: Retention, which is the last phase of orthodontic treatment, is a most important one, where teeth are held in an esthetic and functional position.

Definition: Relapse is the change in tooth position toward the former location following active orthodontic treatment.

First part: Review 1.Occlusion Kinsley Occlusal relationship is the most essential factor on the stable position of the posterior teeth after treatment.

Review 2. Root apicalis bascal bone Axel Lundstrom ：Root apicalis bascal bone is one of the most important factors to correct the malocclusion and maintain the normal occlusal relationship. Mc cauley proposed that if the intercuspid width and the molar width can maitain ,the mini retention is needed.

Review 3.The mandibular incisor Grieve and Tweed: the mandibular incisors should be positioned on the bascal bone of mandibular vertically. Rogers introduced that it’s necesseary to establish the functional balance between the muscles.

Second Part: The principle of Retention Stability 1.The tendency that the teeth move to the oringinal position muscles, root apicalis bascal bone, fibers and the bone morphology. 2. Remove the pathogeny of malocclusion could prevent relapse Tongue gesture is the most covert oral habits that affect the retention.

3.Over correction is a protective issue. 4.Good occlusal relationship is advantage for the stability of the teeth. 5.To rebuild the bone and the tissue surrounding takes time. 6.The mandibular incisor placed vertically is propitious to retention.

7.The treatment in the develop phases reduces the possibility of retention. 8.The farer teeth moved,the lower pollibility of retention there is. 9.The configuration of mandibular is hard to be remained permanencely.

Third part: Factors affecting stability 1.The maladjustment of the tooth size 2.Inclination 3.The horizontally maladhustment 4.The third molars 5.The growth development and gender difference.

Third part: Factors affecting stability 6.Relapse (1)Alveolar bone (2)Treatment speed (3)Retetion time

Third part: Factors affecting stability (4)Muscle system On retention,besides to control the tongue gusture and abnormal swallow hapits, there’s no standard research discussing the relationship between the normal muscle activity and the stability of teeth position.

Third part: Factors affecting stability (5)Occlusal balance Adjust the specific teeth is advantage to the function system.

Third part: Factors affecting stability 7. Special consideration on mandibular tooth arche (1)．Intercuspid width The width between mandibular canines are apt to return to the origin before the treatment in all the cases. So the original width could be regarded as a standard to guide the diagnosis and treatment.

Third part: Factors affecting stability (2)．The stability of mandibular anterior teeth (3)．Extraction of incisors

1.Natural retention (1)Post treatment of crossbite ①The overbite is deep enough after the correction of crossbite ②The appropriate inclination can be maintained in posterior teeth.Sometimes the over correction should be involved.

(2)Usually retention is not necesseary if there’s no following treatment in serial extraction. ①Extraction of gingival erupted canine ②The cases in which extraction of a canine or more teeth is necesseary.

(3) The cases in which the maxillary development has stopped,retention is not necesseary (4)Low positioned or embedded tooth that involved in the dental arche by enlarging it.

2.Limited retention Many cases are this type. Most of them needs adjustment of muscle and peridontal tissue.Some of them have to keep retention until the period of growth is over.

（1） Vertical Rretention is needed in the deep overbite cases. ①Anterior teeth guide plate could be applied when the correction was obtained by anterior intrusion.

②The correction of overbite with fixed appliences is accompanied with the extusion,so the retention must be kept until the vertical height was caught up.

③The correction obtainted by inclining the occlusal plate should be involed in retention for longer period.

(2)Correctino of the rotated tooth in early period ①Retention should be applied until the tooth root forms completely. ②Correction of the rotated mandibular incisors. In these cases the labial arch should be applied .

③After the rotation of the canine,pre-molar and the molar,transverse fiber operation should be applied to enhance stability.

3.Permanent and hemi-permanent retention (1)The correction of mandibular arche needs permanent and hemi-peramanent retention to maintain the occlusal attachment of posterior teeth.

(2)Permanent retention is necesseary for the cases with spaces in anterior teeth originally. (3)Permanent retention should be applied when there’r badly rotated or ligulaly dislocated teeth in adult cases. (4)The space between the upper incisors has been closed when other teeth are nomally placed.

Hawley’s retainer

Hawley ‘s retainer

positioner

Fixed labial and lingual arch retainer

Special retention of different type of malocclusion

First Skeletal Ⅱ Relapse 1. Upper arche moves forwardly,lower arche moves backwardly at the same time 2.Growth causes 3. overcorrection Control 1.Removable+Headgear 2.Activator retaining appliance 1-2years in worse cases

Second Skeletal Ⅲ Relapse Growth of mandibular Control mildly activator retainer Positioner Worse Operation

Third Retention of deep overbite cases Biteplate Avoid deep overbite Fourth、Retention of openbite 1.Control the eruption of upper molars 2.Removable retainer+ high pull Headgear Bite block with posterior teeth

Retaining period The retention period depend on the type of the retainer above，combining with diagnosis ,treatment design,the original malocclusion,and the growth situation .

According to the standard period of half a year , retainer is worn fulltime in the first 3 months,and step down the time. This standard is more appropriate for most of the patients who are treated with removable appliance.

More people would agree to spend another 1 year or more on retention after the treatment through fixed appliances and some people believe it should be worn as long as the appliances. Usually full time a day is necesseary during the first 3 mounths，and only night in the following half year,and in the last 3 years tertianly to 1-2days a week .One year or a half is necesseary if fixed appliances are applied.

Othodontics Fundaments Etiology Growing development Biologic mechanism Diagnosis Taxology Cephalometrics Treatment design Treatment Orthodontic appliances and techniques Treatment for different type of malocclusion Relapse and retention