Teeth that have been moved into or through bone by orthodontic appliances often tend to return to their former positions. Relapse trends follow the severity of initial malocclusion.

Arch form, particularly in the mandibular arch, cannot be permanently altered by appliance therapy. Therefore, all efforts should be made to preserve the arch form presented by the original malocclusion.

There is often concern about the maintenance of inter-canine and inter-molar width of the mandibular arch. ^, Much of the relapse of lower anterior crowding is linked to the collapse of the expanded lower arch. A balance of muscular forces is inherent to the individual and dictates the limits of the buccolingual position of teeth. The buccinator mechanism is defined as a balance between the orbicularis oris of the lip and the buccinator of the cheek outside, being opposed by a muscular tongue from within the mouth. In some instances, the inter-canine width of more than 3 mm or more can be stable, where pre-treatment mandibular canines had been considerably constricted or blocked lingually to the general outline of the arch form.

The maxillary expansion can only be stable when carried out in a narrow maxilla with an increase in the width of the skeletal base before the closure of the mid-palatal sutures.

According to Kaplan, teeth can be moved with success within the area of tolerance where they will not be in conflict with the forces of the closed stomatognathic system. When teeth are moved outside the area of tolerance, relapse follows.

Elimination of the cause of malocclusion will prevent recurrence.

The orthodontic diagnosis and planning must entail the aetiology of the malocclusion. If the extraneous neuromuscular influences are in the form of deleterious habits or mouth breathing, they must be eliminated for the results to be stable. The influencing factors that bring the teeth back could arise from the musculature surrounding the teeth, the apical base in which the teeth are housed or supracrestal and transseptal periodontal fibres, attaching one tooth to the other.

Malocclusion should be overcorrected. A malocclusion is overcorrected to make a provision for some degree of relapse, which is unavoidable. Overcorrection is especially required for rotations and deep overbite.

Rotational relapse has been linked to many factors: the stretching of the supragingival fibres, discrepancies of tooth dimensions, altered Peck and Peck ratio, late mandibular growth and third molars. There is a general tendency for relapse of the deep bite. ^, The different malocclusion and traits of malocclusion have a variable tendency for relapse. For example, the lower anterior segment alignment and overbite are the most unstable occlusal features and tend to worsen during retention.

Good occlusion is a major contributor to retention. Therefore, an orthodontist should attempt to achieve the best possible occlusion. In other words, proper inter-digitation is the key to holding the teeth in their correct positions.

The occlusion achieved following orthodontic treatment should pertain to the principles of static and functional occlusion. The traditional Angle’s concept of stability involved a full complement of teeth in class I relationships. The extraction approach was later proved to give stable results in the cases with tooth size jaw size discrepancy. Charles H. Tweed suggested that upright mandibular incisors are a prerequisite for the stability of occlusion and aesthetics. Later, a concept of functional occlusion and harmony with the neuromuscular apparatus of the individual was included in the definition of normal occlusion.

Class II malocclusion can be treated to attain normal overjet and overbite while maintaining a class II relation if the lower arch permits it. Such an occlusion may be stable and harmonise with the neuromuscular apparatus.

A therapeutic class III occlusion may be a goal in cases where extraction of the premolars is performed in the lower arch only. Andrews concept of normal occlusion entails inter-arch relations and each tooth should occupy its correct labiolingual and mesiodistal angulations in its respective position ( Fig. 106.2 ).

Excellent finish of occlusion is a prelude to minimising relapse.

Coordination of arch forms, normalisation of overjet and overbite, tight proximal contacts and good inter-digitations are prerequisite for finished occlusion. These are, in turn, contributed by proper mesiodistal crown angulations and labiolingual inclinations of teeth. (A) Improperly inclined maxillary anterior crowns with insufficient torque result in all upper contact points being mesial, leading to improper occlusion. (B) Overlay shows how institution of lingual root torque allowed anterior crowns to be properly inclined in labiolingual inclination, the contact points moved distally, allowing normal occlusion and thus minimising relapse. (C) Insufficiently distally tipped teeth are the cause of residual spacing. (D) When buccal segment finished to proper mesiodistal angulations, occlusion is settled without spacing.

The current views on occlusion have broadened from merely static anatomical intercuspation to the functional aspects of occlusion.

A smooth functional forward guidance should be created so that the lower anterior teeth smoothly glide to the protrusive position from a centric occlusion position; when posterior teeth are in intercuspation, the anterior teeth are separated by 0.005 in., thereby protecting the anterior teeth from excessive forces. Similarly, during anterior guidance, typically, the posteriors should not interfere for a smooth disocclusion. Such a functional occlusion is a mutually protected occlusion.

The lateral excursions are guided by the cuspid inclines without any interference from posterior teeth or buccal (canine protected occlusion) cusps both on working and balancing sides.

Bone and adjacent tissues must be allowed time to reorganise around new tooth positions.

Orthodontic tooth movements happen in the bone with the disruption of the periodontal ligament and the gingival fibre-network complex. The period required for the reorganisation of these fibres after the removal of the appliances is the retention phase.

A variety of periodontal and gingival ligaments hold the teeth to the bone, gingiva and each other. The classic group of periodontal fibres are oblique, horizontal, alveolar crest, apical and inter-radicular fibres, which attach the tooth to the bone and are responsible for the restriction of movement of teeth in the lateral, apical or occlusal direction. The gingival ligament fibres are circular, alveolar dental, dentogingival, dentoperiosteal and transseptal fibres ( Fig. 106.3 ).

Periodontal fibres involved in relapse.

(A–D) The gingival fibre bundles remain displaced and stretched for 232 days while principal fibres readjust rapidly. Oxytalan fibres of an elastic-like nature proliferate and get accumulated in the gingiva and particularly in transseptal fibres during mechanical stress and orthodontic tooth movement. It has been hypothesised that the elastic properties of oxytalan fibres might induce relapse. (E) Stretched supra-alveolar fibres as observed during rotation. Experimental trans-section of these fibres, as indicated by stippled lines, did not cause any marked difference in the degree of relapse, but there is little relapse tendency following removal of the supra-alveolar structures. Over-correction followed by retention will also result in stabilisation of the rotated tooth.

The periodontal ligament fibres are made of collagen types I and III. The elastic system fibres consist of three different types: oxytalan, elaunin and elastic fibres.

The oxytalan fibres are distributed in the periodontal ligament and in the gingiva, while elaunin and elastic fibres are present only in the gingiva. The remodelling of collagen fibres takes around 4–6 months, according to histological evidence, while the elastic fibres take about 1 year to remodel. Some evidence suggests that elastic fibres may take up to 6 years to remodel. It is believed that the slow remodelling of the supra-alveolar fibres of the gingival complex contributes to the relapse of teeth after the orthodontic treatment, especially in the rotated teeth.

The supracrestal fibres, in general, and transseptal fibres, in particular, have a lower rate of remodelling because these fibres insert on both ends on the cementum of adjacent teeth, which is avascular and fibre-ends in cementum are also mineralised. This contrasts with bone, which is highly vascular, and the fibre ends in the bone are non-mineralised.

Apart from maintaining the teeth with full-time retention until the fibres remodel, the orthodontist can opt for a simple surgical procedure of supracrestal fiberotomy or pericision. This minor yet definitive procedure involves the severing of fibres present in the supracrestal region by an incision deep down to the alveolar bone encircling the tooth crown in the gingival sulcus ^, ( Fig. 106.3 E).

Upright lower incisors are the key to stability. Charles H. Tweed ^, considered the aesthetics and stability of occlusion from the perspective of axial inclination of the lower incisors and their relationship with the mandibular plane. He suggested that upright mandibular incisors are prerequisites for the optimum aesthetics and stability of occlusion. The incisor inclination compensates for a variable mandibular plane angle. In the horizontal growers, lower incisors are proclined to provide an eccentric relation to the upper incisors (relation between the long axis of upper and lower incisors). On the contrary, in vertical growers, a more stable relation would be one with upright incisors so that the interincisal angle would be obtuse ( Chapter 23 ).

Orthodontic malpositions corrected in growing children are less likely to relapse. Growing individuals show greater adaptations to the newly acquired skeletal jaw positions. Early treatment is also preferred as sutures are immature and are amenable to alterations. Therefore, skeletal maxillary expansion is stable when carried out before the fusion of palatal suture around 8 years of age. The teeth and the periodontium show faster adaptations, and so does the neuromuscular system following the orthodontic treatment. The occlusion outcome achieved should also consider the remaining growth of the craniofacial skeleton, particularly mandibular growth, which continues until late adulthood.

The farther the teeth have been moved, the less the likelihood of relapse. Real evidence supporting this belief is not available. Logically, teeth that move far away from their original environment have less of a tendency for relapse compared to teeth that move close to their former environment.

The years of experience and review of treated cases have shown that multiple factors and variables influence the stability of occlusion. Many treated cases require permanent retaining devices. These include median diastema, severe rotations and severe crowding of lower incisors. Half of the total relapse takes place in the first 2 years after retention. All occlusal traits relapse gradually over time but remain stable 5 years post-retention except lower anterior contact point displacement.

In addition, the final detailing and finishing of occlusion should conform to functional needs for orthodontic results to be sustained.

Charles H. Tweed has recognised three types of growth trends in the craniofacial region that are relevant to occlusion development and influence orthodontic treatment decisions and prognosis.

• Type A , both mandible and maxilla grow downward and forward but at the same pace.

• Type B , both grow downward and forward, but the maxilla grows at a greater pace than the mandible.

• Type C , the mandible grows at a greater pace than the maxilla.

Active orthodontic treatment is likely to conclude during the age group of 14–15 years, while anteroposterior and vertical growth does not cease till 17–18 years, particularly in males. Sagittal growth declines to adult level at 14–15 years in females and 16–17 years in males, and vertical growth declines to adult levels at 17–18 years in females and early 20s in males. Transverse growth is completed first before the adolescent growth spurts at 11–12 years in females and 13–14 years in males.

In children having short face syndrome, that is, those with a low mandibular plane angle, management of deep bite is difficult due to the presence of a strong chain of elevator muscles, which tend to keep the mandible in an anti-clockwise rotation, thus worsening the bite. Such children require longer retention with an anterior bite plane touching the lower incisors and no separation of posteriors. Such an appliance must be worn until the maxillomandibular growth is complete, that is, around 16 years in females and 18–20 years in males.

In our experience and practice contrast, in children with a dominant vertical growth pattern, an over eruption of buccal segment teeth is expected, and the vertical position of molars retained with high pull headgear or posterior bite blocks is required to prevent the opening of the bite.

Growth modulations achieved with functional appliances must be maintained until the skeletal growth is complete. Retention using a bionator appliance is practical and effective in maintaining the sagittal forward position of the mandible.

A reverse twin block positioner can be given in mild class III cases if the correction required is less than 3 mm. Chin cup for retention can only be given in average facial growth patterns and should be avoided in vertical growers since the chin cup tends to rotate the mandible downward and backwards.

The lower incisor position depends on the patient’s skeletal pattern for stability. For patients with hyperdivergent skeletal patterns, mandibular incisors must have an overly upright position over the basal bone to have a balanced face at the end of treatment. For a hypodivergent skeletal pattern, mandibular incisors can be left in their pre-treatment position or proclined position.

The late mandibular growth continues, especially in horizontal growers (Type C) after adulthood and is thought to be responsible for lower incisor crowding. As the mandible continues to grow downward and forward, the bite deepens, and lower incisors confined by the upper incisors are bound to tip lingually in a crowded state. The untreated lower incisors in adults show increased crowding with age, while inter-canine widths and arch lengths continue decreasing ( Fig. 106.4 ).

Physiological mesial migration is a life-long process and thought to be a contributory factor for relapse.

The integrity of the arch through tight proximal contacts is maintained by the periodontium exerting a continuous force on the mandibular dentition. This force is increased manifold during occlusal loading which is considered a major contributor to long-term appearance of crowding of the mandibular anterior teeth.

Orthodontic treatment should compensate for any significant variation in the ratio of the mesiodistal width of maxillary and mandibular teeth. The key factor is to maintain tight proximal contacts without any rotation or crowding and adequate overjet and overbite to ensure the stability of occlusion. Deviation in the Bolton’s discrepancy would not allow a good finish of occlusion, that is, overjet and overbite with good functional contacts. Most often, the discrepancy is in the form of mandibular tooth excess, which can be balanced by judicious reduction of the proximal tooth surfaces of the lower anterior teeth. The amount of interproximal reduction on lower incisors can be calculated by Peck and Peck analysis, which essentially reconfirms the large mesiodistal width of incisors in proportion to their labiolingual thickness.

In other situations, maxillary tooth material may be deficient; small lateral incisors are not uncommon. Such cases would require proximal composites or veneers on the teeth to restore them to normal mesiodistal dimensions.

The stable occlusion is the outcome of a balanced ratio of tooth material of maxillary teeth to mandibular teeth. Any deviation would result in inappropriate intercuspation and, therefore, the tendency for relapse. Removal of teeth from the arch is a known method to achieve the reduction of tooth material, which creates space for the resolution of the crowding and reduction of the protrusion. The actual space requirements may be smaller (say 3/4 or 1/2 the tooth dimensions); however, the orthodontist cannot make partial tooth sacrifices, resulting in some compromises with tooth size and jaw size discrepancy.

Dr. Williams said that inter-proximal reduction of lower anterior teeth provides better inter-proximal contacts and, therefore, a stable position.

The role of erupting third molars in the causation of the relapse has long been debated. Many clinicians recommended therapeutic removal of the third molars following the completion of the orthodontic treatment. Recent research has questioned the role of third molars in the causation of anterior crowding. The therapeutic removal of third molars for the prevention of relapse of lower anterior crowding is not justified. Between the ages of 18 and 21 years, the lower arch is stable in terms of tooth alignment and mesial drift, regardless of third molar status or continuing mandibular growth.

Three systematic reviews on the role of third molars have appeared in literature with somewhat different conclusions.

The 2014 review conducted by Zawawi and Melis, which analysed 12 controlled studies, concluded that no definitive inferences regarding the involvement of third molars in the development of anterior tooth crowding could be made. Most of the studies did not support a causal relationship, thus negating the justification for the extraction of third molars to prevent anterior tooth crowding or post-orthodontic relapse. Another systematic review in 2023 also concluded, ‘…we assert that there is no proven connection between mandibular wisdom teeth and lower anterior crowding relapse after orthodontic treatment’.

In a systematic review conducted in 2024, encompassing 13 studies, it was deduced that lower third molars may contribute to mandibular crowding within the constraints of the present systematic review. The review emphasised that patients with third molars exhibited elevated degrees of anterior dental crowding. Furthermore, post-orthodontic patients possessing third molars displayed a notably lower mean arch length in comparison to those devoid of third molars.

The controversy surrounding the impact of third molars on post-orthodontic relapse in the lower arch persists, making it difficult to justify the extraction of third molars solely for relapse prevention.

The integrity of the dentition is maintained by the healthy teeth that are held in tight contact with a healthy periodontium. A healthy periodontium is a prerequisite for well-functioning occlusion. The presence of periodontal disease causes the forces of occlusion to act adversely and, therefore, induce migration of the teeth. Occlusal trauma was considered a significant contributor to periodontal migration. However, research has proven that occlusal trauma alone would be incapable of causing migration in the absence of disease of the periodontium. In patients with previously treated severe periodontal disease, permanent retention is advised. A routine retention protocol can be used for those with minimal to moderate disease.

It is a well-known fact that females are early maturer than males. The mandibular growth in females may be completed by 13 years, while males continue to grow beyond 16 years. Hence, age and sex are essential considerations not only in terms of the prognosis of orthodontic treatment but also for relapse. Skeletal adaptations occur better at younger ages, hence the stability of the outcome. Skeletal changes with functional appliances and rapid maxillary expansion are two good examples. When the periodontal supporting tissues are normal, and no further occlusal settling is required, there is no evidence to support any changes in retention protocol for adult patients compared with adolescent patients, but for growth considerations.

Some malocclusion types have racial predilections. For example, class III is more common in Mongoloids, and bimaxillary protrusion with a large tongue and thick lips is more common in Africans and some races in South India and Islanders. Accordingly, the bimaxillary patients treated with extractions of all first premolars encroach upon the tongue space and, therefore, have greater possibilities of relapse.

Systemic diseases that may affect bone turnover would cause an adverse relapse. The common diseases that affect bone turnover are hyperparathyroidism and disorders of the pituitary gland, like acromegaly. While in hyperparathyroidism, the lamina dura may not be directly affected; the jaw bones show the area of bone formation and resorption where the bone is replaced with multinucleated giant cells contained in ‘brown tumour’. In acromegaly, the mandibular condyle would show excessive growth and lengthening of the mandible, therefore causing a relapse of the treatment outcome. These diseases require the attention of medical specialists.

Ricketts recommended that for optimum position for lower incisor stability, the incisal edge of the lower incisor should be placed on the A-Po line or 1 mm in front of it.

For better stability, the lower incisor apices should be positioned distally to the crowns more than is generally considered appropriate, and the apices of the lower lateral incisors must be more than those of the central incisors. All four lower incisor apices must be in the same labiolingual plane. Similar to the incisors, the apex of the lower cuspid should be positioned distal to the crown, but the lower cuspid root apex must also be positioned slightly buccal to the crown apex.

The factors influencing the stability of post-orthodontic occlusion are numerous, and some of these are associated with ageing, maintenance of sound dental health and good oral hygiene. The goals of maintaining post-orthopaedic optimum occlusion are a lifelong effort and require the active participation of the subject, general dentist and specialist. With the best of efforts, some changes are unavoidable with age.

These are vacuum-formed plastic retainers (VFR), which can be issued to the patient immediately after debonding. The appliance is prepared from a rigid transparent thermoplastic sheet of 1-1.5 mm thickness. The appliance is nearly invisible, and allowance can be made for minor corrections of derotation or space closure to be incorporated by making necessary changes to the dental plaster model. This appliance serves as a transitionary appliance until a laboratory fabricated retainer is issued. The life of VFR is much less comparable to that of acrylic and wire Hawley’s retainer. If the patient is unwilling to go for a Hawley’s appliance, another interim VFR can be provided. The lower arch is often supported with a lower lingual fixed retention appliance.

The appliance can be cleaned with soap and water. The main drawback is the possibility of plaque and decalcification under the appliance if food habits are not restricted and strict oral hygiene is not practised.

This appliance does not allow for vertical settling of occlusion ( Fig. 106.5 ).

Essix retainer or Tru tain.

A vacuum-formed plastic retainer, a good immediate post-debond appliance. However, does not allow for vertical settling. Should be substituted with proper retainer.

Source: Lyros I, Tsolakis IA, Maroulakos MP, Fora E, Lykogeorgos T, Dalampira M, Tsolakis AI. Orthodontic retainers-a critical review. Children (Basel). 2023 Jan 28;10(2):230. doi: 10.3390/children10020230. PMID: 36832359; PMCID: PMC9954726.

A study found that patients receiving VFRs seem to be significantly more likely to be ‘very satisfied’ currently (50%) compared to those with Hawley (35%) or permanently bonded (36%) retainers.

The study compared full-time wear of VFR in the lower arch for 6 months full-time and 6 months part-time, and clear plastic retainers provided similar stability to Hawley’s retainers. However, the evidence was not based on a robust study.

Tooth positioners are trans-maxillary appliances prepared from the upper and lower study models. The process of making a positioner is more exacting. The study models are mounted on an articulator; teeth are cut into individual units in a process similar to Kesling’s setup. The teeth are moved to ideal occlusion by correcting minor intra-arch and inter-arch discrepancies left untreated by orthodontic treatment on the mounted and plaster models. The teeth are reset in an ideal position on study models with 0.25 mm of tooth movement possible. If more tooth movement is required, teeth must be set at 0.25 mm increments with a new appliance. Clear aligners are now being increasingly used for short durations to achieve the perfect finish of alignment or treat minor relapses that occur after the completion of the treatment.

A clear positioner is prepared in a thermoplastic soft silicon material. The positioner helps the child patient achieve minor tooth movements and final settling of the occlusion that has been earlier set on the study models.

The appliance is bulky and inconvenient in use; however, it is effective in settling the occlusion and acts like a trainer to close lips, thereby improving lip incompetence and tone of the circumoral musculature.

Tooth positioners are potentially active retainers as they cause finer tooth movement to the pre-destined position ( Fig. 106.6 ).

Tooth positioner.

Source: Lyros I, Tsolakis IA, Maroulakos MP, Fora E, Lykogeorgos T, Dalampira M, Tsolakis AI. Orthodontic retainers-a critical review. Children (Basel). 2023 Jan 28;10(2):230. doi: 10.3390/children10020230. PMID: 36832359; PMCID: PMC9954726.

Standard Hawley’s retainer typically utilises a cuspid-to-cuspid labial bow with clasps and/or rests on molars, and acrylic body covers the palate or lingual contours of the mandible ( Fig. 106.7 ).

Hawley’s retention appliance.

(A) The distal margin of acrylic plate usually terminates distal to first molars. The appliance should be thick enough to retain wire components, yet not bulky, and well fitting into embrasures. Slight anterior bite platform is needed for the cases who have tendency for the deep bite relapse, such as those with low FMA, and class II division 2 malocclusion. The distal palatal border of acrylic is thinned to gently merge with palatal mucosa. The labial bow is kept passive yet in gentle contacts with labial surfaces of teeth. The retaining end wires of Adams clasps and pin head clasps should very closely adapt on occlusal marginal ridges from buccal to palate, not to interfere with opposite tooth cusps. (B) The U loop of labial bow should be checked for any pressure or injury to gingiva clinically. (C) Intraoral photo of Hawley’s appliance in occlusal view (D) Intraoral photo of Hawley’s appliance in frontal view.

Source for C and D: Lyros I, Tsolakis IA, Maroulakos MP, Fora E, Lykogeorgos T, Dalampira M, Tsolakis AI. Orthodontic retainers-a critical review. Children (Basel). 2023 Jan 28;10(2):230. doi: 10.3390/children10020230. PMID: 36832359; PMCID: PMC9954726 .

Occlusal interferences present after treatment may require slight wire placement and clasp design modifications. A Hawley’s retainer with an anterior bite plane facilitates maintenance of the deep bite correction and allows settling of the buccal occlusion during the first few months of retention.

Demerits of Hawley-type retainers include occlusal interferences resulting from wires of retentive devices such as the Adams’ clasp crossing over the embrasure and inter-dental areas, which does not allow occlusion contacts with the opposite arch. Circumferential clasp or C clasp may partly resolve the issue where contacts are tight and interferences are significant.

Also, in the first premolar extraction cases, the extraction space may reopen from the wedging effect of the labial bow between the canine and premolar. A wrap-around labial bow wire retainer extending up to the first molars can assist in maintaining the proximal contact, especially in the extraction cases.

Dr. P.R. Begg used a circumferential retainer made up of a single wrap-around labial bow extending from the distal of the right terminal (except 3rd molar) molar to the left molar. Retention can be achieved through a pinhead clasp between the second premolar and first molars. The wrap-around wire distal to the second molars eliminates potential occlusal interferences inherent to Adams’ clasps, allowing vertical settling of the occlusion. It also offers the advantage of maintaining canine-second premolar in tight contact at extraction cases ( Fig. 106.8 ).

Mandibular wrap-around retainer or Begg’s retainer. The appliance has an advantage in maintaining the integrity of the arch and tight contacts, particularly in extraction cases.

(A and B) Upper and lower wrap-around or Begg’s retainer in all first premolar extraction cases. (C) Wrap-around retainer fabricated upto terminal molar.

Source: Lyros I, Tsolakis IA, Maroulakos MP, Fora E, Lykogeorgos T, Dalampira M, Tsolakis AI. Orthodontic retainers-a critical review. Children (Basel). 2023 Jan 28;10(2):230. doi: 10.3390/children10020230. PMID: 36832359; PMCID: PMC9954726 .

Anterior bite plane can be incorporated into removable upper retainers to intrude lower incisors and control overbite relapse ( Fig. 106.9 ).

(A) Maxillary Begg’s wrap-around retention appliance with bite platform in a non-extraction case. Slight anterior bite platform is needed for cases with a tendency for deep bite relapse. The bite platform can be given a reverse incline should there be a class II tendency or a remaining overjet. Note: first order bends on labial bow. (B) Wrap-around retainer in the mandibular arch.

Posterior bite plane or acrylic extends onto the occlusal surfaces of the buccal teeth. These may be used to intrude molars and control open bite relapse.

An anterior locking plate during daytime and nighttime wear of the bionator is recommended for retaining class II correction.

In children with a tendency for excessive vertical growth of the maxilla, a high pull headgear with Kloehn’s facebow can be used.

Frankel III or reverse twin blocks are used for the maintenance of class III treatment. Night time wear of chin cup appliance is usually continued till completion of growth.

Active retainers: They are used for the realignment of irregular incisors or as functional appliances to manage class II or class III relapse tendencies.

• 1.

  Lingual retainers are invisible and permit effective retention with the simultaneous individual movement of the teeth, which is essential for the biological integrity and survival of teeth.

• 2.

  This type of retainer keeps extraction spaces closed in adults and maintains diastema closure and pontic or implant space.

• 3.

  Fixed retention is favourable in preventing relapse at 5 and 10 years post-retention.

• 1.

  Calculus and plaque deposition around the retainer.

• 2.

  Maintenance of oral hygiene would need extra attention.

• 3.

  Unwanted tooth movement: X and twist effect.

The bonded fixed retainers may extend from the canine on one side to the other or premolar to premolar or even segmental on two or more teeth. A smaller diameter multistrand wire, usually 0.0175 or 0.0215 in., bonded to each tooth in the buccal segment, can be used in adults with periodontal problems.

Indications Lee considered the following indications for placement of a bonded canine-to-canine retainer :

• •

  Planned alteration in the lower inter-canine width.

• •

  After the advancement of the lower incisors during active treatment.

• •

  After non-extraction treatment in mildly crowded cases.

• •

  After correction of deep overbite.

The flexible wire retainer has different indications for clinical use.

Zachrisson listed the following indications :

• 1.

  Closed median diastemas

• 2.

  Spaced anterior teeth

• 3.

  Adult cases with potential post-orthodontic tooth migration

• 4.

  Accidental loss of maxillary incisors, requiring closure and retention of large anterior spaces

• 5.

  Space reopening after mandibular incisor extractions

• 6.

  Severely rotated maxillary incisors

• 7.

  Palatally impacted canines

The main indications for the canine-to-canine retainer are related to the alteration of the anteroposterior or lateral position of the lower labial segment during treatment. Relapse manifests as the lingual tipping of the central and lateral incisors due to the differential growth of the mandible. In these cases, the retainer of choice is a fixed retainer extending from canine to canine.

Bonded fixed retainers are now commonly used for long-term aesthetic retention and are widely accepted and used by most clinicians around the globe. The lingual bonded retainers show bond failures and breakages. The failure rate is approximately twice as great in the maxilla as in the mandible, and this is most likely because of occlusal factors.

When placing maxillary retainers, it is essential to ensure that the retainer is free from occlusal trauma to minimise the risk of failure. The most common point of failure occurs at the wire–composite interface. Insufficient adhesive material and loss due to abrasion contribute to the detachment of the wire from the composite, leading to failure. Using a greater amount of composite or selecting materials with abrasion-resistant properties may enhance the longevity of the retainer.

Bonded fixed retainers may be fabricated in waved shape to follow gingival contours or plain fixed retainers in the form of contoured wire. A meta-analysis was done to determine the differences in gingival health and plaque index between wave-fixed retainers and plain-fixed retainers. The results revealed no differences in plaque index and calculus index between wave fixed retainer (FR) and plain FR.

Any of the wire types can be used for FSW retainers. These are ( Figs 106.11 and 106.12 ):

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