Sagittal discrepancies

• It is important to study the relationship between increased overjet, commonly found in Class II division 1 malocclusion, and lip function (Fig 3.2). If the lower lip is trapped between maxillary and mandibular incisors, its posture and function in the same area along with hyperactive mentalis muscle function leads to progressive deforming activity on dentition.

• To differentiate between functionally true Class II and forced bite Class II malocclusions, it is essential to assess the relationship between rest position and occlusion.

• Tongue posture and function should be carefully assessed to find out its role in the development of malocclusion.

Horizontal types: There are many variations in horizontal types of Class II malocclusions ranging from those having normal skeletal features but Class II dental characteristics to distinctly different skeletal types (Fig 3.4).

Biologic variables: The basic strategy in the management of dentoalveolar Class II malocclusion is to achieve normal molar and incisal relationships, maintaining the existing normal skeletal relationship and the vertical dimension. Efficient tooth movement is ultimately the result of optimal biologic response to the orthodontic force system. The physiologic activity of alveolar bone resorption and deposition to produce tooth movement is induced by the mechanical stimulus through the delivery of orthodontic force systems. It is important that the force levels produced by orthodontic appliances are optimal, which will promote the most efficient treatment response without any damage to the teeth and the supporting structures (Table 3.1). The clinician should avoid excessive orthodontic force levels to prevent periodontal ligament necrosis and associated pain and bring about efficient tooth movement. It is essential to update on the knowledge of the force levels delivered to teeth through the medium of the appliance to understand optimal forces.^26–28 These optimal force values depend on the type of the tooth and the size of the tooth.

Dentoalveolar problems: Early treatment: The sagittal dental discrepancies in the primary dentition, seen in children having sucking habits, are expressed in the form of anterior displacement of upper incisors and posterior displacement of lower incisors. At this stage of development, if the sucking habit stops before the eruption of permanent teeth, it is usually self-correcting and therefore does not require any orthodontic intervention.

The mixed dentition phase is a very critical developmental stage. During this phase, children should be carefully examined and assessed for existing and potential or developing discrepancies. There are many treatment options available, depending upon the severity of the problem. The discrepancies in their severe form are best treated with two phases of treatment: phase 1 in the mixed dentition and phase 2 during the early permanent dentition period. It has been universally recognized that prevention is better than cure. The development of a space discrepancy when primary first or second molars are missing is best prevented by space maintenance protocol. This is indicated when there is adequate available space, and the premolar eruption will take more than 6 months. If the patient presents with bilateral problem, it is better to use lingual arch rather than two isolated appliances in the posterior segments. However, if the available space is not adequate for the permanent tooth or if there is significant amount of space loss due to the drifting of adjacent teeth, the lost space should be regained by repositioning the drifted dental units.

One of the basic tenets of any mixed dentition treatment protocol is to monitor the transition from the mixed to the permanent dentition. The simple procedure of maintaining the available arch length during the mixed dentition period helps to resolve minor to moderate tooth-size and arch-size discrepancies²⁹ along with the other methods of space gaining.

In the mandibular arch, the combined average width of the deciduous cuspid, the first deciduous molar and the second deciduous molar is approximately 1.7 mm greater than the combined width of the canine, the first premolar and the second premolar teeth (Fig 3.10A). In the maxillary arch, this combined width difference is approximately 0.9 mm.³⁰ The practitioner should assess each patient radiographically to determine the size differential between the second deciduous molars and their successors, as the tooth size varies significantly among individuals³¹ (Fig 3.10B).

Patients with thumb sucking habit present with flared maxillary incisors and loss of vertical contact with the mandibular incisors and are frequently associated with variable degree of narrowing of the maxillary arch. Prolonged thumb sucking habit increases the severity of symptoms, leading to the development of anterior open bite. In an effort to improve swallowing and speech, the child often positions the tongue anteriorly between the maxillary and mandibular incisors to seal off the anterior open bite with the consequent development of ‘tongue thrust’. In patients with such problems in mixed dentition stage, the treatment goal should be to establish proper lip seal by retraction of maxillary incisors. It is interesting to note that the tongue thrust habit usually disappears following the retraction of maxillary incisors, since it is considered to be due to ‘physiologic adaption’.

Maxillary molar distalization: Contemporary orthodontic treatment ideologies focus on soft tissue assessment and management. There is a general shift from hard tissue goals, where the face is the determinant of orthodontic treatment. Advances in mechanotherapy and changes in treatment concepts and philosophies now minimize the need for extractions, even in severe discrepancies. One nonextraction treatment approach is the distal movement of maxillary molars to establish Class I molar relationship.

Precise distalization of maxillary molars is of significant value for nonextraction treatment of dentoalveolar Class II malocclusion with a normal mandible. Over the past few years, the focus of the maxillary molar distalization treatment modality has been on the introduction of fixed intra-arch appliances to eliminate the need for patient compliance, following the findings of rapid Class II corrections with nonremovable appliances.^32,33

Essentially, this approach is very useful in cases with midline discrepancies, to regain the space lost due to mesial drifting of first molars following premature loss of deciduous teeth, and in cases with Class II molar relationship due to ectopic eruption of first or second bicuspids and impacted or high labially placed cuspids. Based on the author's extensive experience in this field, spanning over last many years, there are basically three elements that determine the efficiency and effectiveness of distal driving of maxillary molars. They are:

Several appliances have been introduced to accomplish distal molar movement with or without the need for patient cooperation.^34–42 Most produce tipping, rotation and extrusion of the molars during distalization therapy; some produce a significant amount of incisor flaring due to anchorage loss, which is seen clinically as increased overjet.³⁹ After distalization of the molars, the distalizing modules and existing palatal anchorage appliances are removed and a Nance palatal button is delivered to maintain the first molars in their new positions.

Case selection criteria The degree of space discrepancy and the facial profile characteristics of the patient are the two main important factors that should be considered in case selection criteria. Patients with mild to moderate space discrepancy are good candidates for maxillary molar distalization therapy. A maximum of 8 mm space has been achieved by certain appliances.⁴³ Even upto 10.5 mm of space gain has been achieved by some clinicians.⁴⁴

Ideally, the patient should have orthognathic profile; and it is not the modality of choice when there is significant dental protrusion and/or convexity of profile as intraoral distalizing appliances do not cause significant soft tissue changes.⁴⁵ On the contrary, certain appliances may cause mild increase in profile convexity.⁴⁶ Therefore, the maxillary molar distalization therapy should be employed when the maxilla and mandible are skeletally normal with mild to moderate maxillary dental proclination or crowding. The patient should exhibit normal lower facial height as most distalizing appliances have an extrusive effect on the molars when they are distalized, leading to an increase in lower facial height.

Also, the patient should not have posterior arch crowding. According to Ricketts,⁴⁷ the distance between the pterygoid vertical (PTV) plane and the distal aspect of the maxillary first molar should be ‘age + 3 mm’ (Fig 3.11). In normal skeletal and dental relationship, the facial axis passes through the mesiobuccal cusp of the first molar. If the distance M1-PTV is shorter than the normal, the possibility for molar distalization is less and extractions may be required depending upon the growth potential and the presence of third molars.⁴⁷

In distalization therapy, the position of the second molar determines the type of the first molar movement.⁴⁸ If second molar is developing, one should expect more tipping of first molar as compared to fully erupted second molar, as the developing second molar tooth bud acts as a fulcrum for the distal movement of first molar. In the absence of third molars, if second molars are fully erupted, molars will be distalized bodily, requiring greater force levels that result in more anchorage loss.

Appliance selection An ideal distalizing appliance should be rigid and compliance free. It should distalize molars bodily with minimal anchorage loss. Also, it should allow passive free floating of teeth immediately anterior to the distalized teeth. The design of the appliance should be such that it should readily be convertible into a holding appliance after the distalization.

Anchorage The anchorage for intraoral distalizing appliances should ideally be derived from nondental sources like palatal vault and midpalatal screws. However, in most appliances, it is partially obtained from bicuspids. In planning the anchorage system, it is important to consider that rigidity is essential for good anchorage, and the reactive anterior forces generated by the active components are distributed over a large area of the palate. A large acrylic button is made in the region of the vertical portion of the palatal vault.

It extends to approximately 5 mm from the teeth, relieving the incisive papilla anteriorly. The precise fabrication of the palatal button is the key to anchorage preservation, as any space between the palatal tissues and the inner surface of the button would lead to anchorage loss. There is little anchorage value to mobilized teeth. Simultaneous levelling and aligning the rest of the dentition taxes the anchorage, resulting in lesser amount of net distal molar movement. Therefore, it is advisable to distalize maxillary molars without full arch fixed appliance.⁴⁹

Expansion Some maxillary expansion is often a prerequisite for Class II molar correction. It should either precede or be concomitant with the distalization, which can be made possible by incorporating an expansion device in the distalizing appliance.⁴⁰

Force levels For efficient and effective distal molar movement, force levels in the range of 100–120 g are considered to be ideal. Continuous forces are preferred than intermittent or interrupted forces. The direction of force should be along the line of arch and should be as close to the centre of resistance of the molar as possible. A good control over the direction and the magnitude of distalizing forces is essential to avoid tipping, rotations and intrusion or extrusion of molars. It is advisable to distal drive maxillary first molars into super Class I relationship to compensate for some anchorage loss during the postdistalization phase of orthodontic treatment.

Stabilization of molars There are various options available to stabilize molars in their new positions, postdistalization. These include utility arch, continuous archwire with molar stops, headgears, Nance holding arch, etc. A secure molar stabilization system should be stable and rigid enough to hold molars and should serve as good anchorage units during the subsequent phase of treatment mechanics.

Postdistalization mechanics Postdistalization stabilization of molars is difficult and highly critical. It should be immediate and as rigid and precise as possible. A lag phase of 3–6 months is desirable before commencing further mechanics to allow passive free floating of bicuspids. It is highly recommended to monitor new molar position and use minimal force levels in postdistalization treatment mechanics.

The Karad's Integrated Distalizing System (KIDS) was developed to address the disadvantages of other distalizing appliances (Figs 3.12–3.16).⁴² This appliance system is designed on the following principles:

Nonextraction headgear treatment: The use of headgears in contemporary management of Class II malocclusions is mainly aimed at controlling the anchorage and the cant of the occlusal plane, tooth movement and orthopaedic correction (Figs 3.17–3.22).

With the introduction of fixed intraoral appliances to distalize maxillary molars or other tooth movements in noncompliant patient, the use of headgear has been considerably reduced. However, there are certain clinical situations that require headgear forces to be used in association with contemporary mechanotherapy to prevent adverse effects of intraoral forces from the archwire in order to achieve high quality and stable correction of Class II malocclusions.

For successful use of headgears in clinical Practise, sound knowledge of force systems produced by various designs of headgears is essential. In tipping orthodontic tooth movement, even if the forces are light, the stress levels at the periodontal-tooth and bone interfaces are beyond acceptable physiologic limits.⁵⁰ Therefore, the practitioner should avoid distal tipping headgear forces to prevent any untoward tissue reactions due to high localized stress levels at the marginal ridge and at the root apices. However, the bodily movement of teeth produced by headgears takes considerable amount of time. In patients with Class II dentoalveolar malocclusion, the use of headgear for 14 h each night, consistently with a force direction passing through the centre of resistance of the maxillary first molar, will move the teeth distally by 2 mm in 2–4 months without tipping.⁵¹ In a treatment approach that uses a combination of removable appliance and headgear to gain maxillary arch length, the removable appliance tips the maxillary first molar crown distally and the molar-inserted headgear moves the root distally, resulting in a net bodily distal movement of the tooth.³⁵

The combined removable appliance and headgear essentially consists of three components.

The active components of the removable appliance are distalizing springs made from 0.028 inch stainless steel wires, which are activated by 1 mm–1.5 mm exerting a force of approximately 30 g per side. This appliance is worn by the patient for 24 h a day except for meals and hygiene. The headgear, either cervical pull or combination pull, is worn by the patient for 12–14 h per day, exerting a force of approximately 150 g per side. Postdistalization, molars are held in their new positions during the subsequent phase of space consolidation.

For any orthodontic application, the following sequential steps may guide a clinician to design the headgear force system.^51,52

Extraction treatment approach: Over the last few years, it is certainly true that the advances in orthodontic treatment mechanics, philosophies and material science have curtailed the need for extractions in severe discrepancies. However, on many occasions, it has always been a difficult task for the clinician to make the extraction or nonextraction treatment decision to resolve a specific malocclusion. There are several factors that influence this decision. The severity of malocclusion like the amount of intra-arch crowding requires extraction of some dental units; however, its impact on the soft tissue profile of the face should be considered in the treatment planning process.

Management of extraction space One of the most important factors in extraction treatment approach is effective utilization of extraction space to resolve the existing discrepancy (Fig 3.23). There are several techniques that maybe employed for orthodontic space closure; however, the clinician should select the technique that efficiently brings about the desired tooth movement. Also, the orthodontic space closure planning should be individualized and should address the individual patient problems and the patient's chief complaint. One can use either a two-step space closure mechanics in which individual retraction of cuspids is followed by incisor retraction, or an en masse retraction of all six anterior teeth in a single stage (Fig 3.23E and F). However, it is the author's experience that the two-step space closure method, which is believed to be less detrimental to the anchorage, temporarily impairs the anterior aesthetics due to shifting of the extraction space from the distal of canine to the mesial of canine and prolongs the treatment duration. However, independent cuspid retraction can be the method of choice in certain cases, which requires space for decrowding of anterior teeth.

The following factors influence extraction space closure.⁵³

Management of vertical dentoalveolar problems: As mentioned earlier, the sagittal discrepancies are not a single entity and are often associated with vertical problems. Class II malocclusions are also associated with vertical discrepancies like deep overbite or open bite. For the successful and stable correction of Class II malocclusion, the treatment plan must include the identification and the correction of these vertical components. The management of these problems is explained in detail in Chapter 4.

Functional criteria as the determinant of treatment method: In functional retrusion cases, it is essential to perform a functional analysis as a part of the clinical examination before selecting a specific appliance therapy. The practitioner should determine the path of closure of the mandible and analyze the relationship between the postural rest and habitual occlusal position. The mandible moves upward and backward from rest position into a forced retrusive habitual occlusion. There is a rotary action of the condyle in the glenoid fossa from postural rest to initial contact of teeth. From the initial contact to habitual occlusion, the action of the condyle is rotary and translatory – upward and backward. This is also called a distally forced bite or posterior shift. This type of condylar movement is commonly seen in patients with excessive overbite. The Class II malocclusion with functional disturbances appears more severe than it actually is sagittally.

Usually the base of the mandible is of normal size with no growth deficiency. The SNB angle is smaller in habitual occlusion, but it improves in the postural resting position. The Class II relationship is mainly of dental nature caused by improper intercuspation. The treatment goal is to eliminate the functional disturbance and not to alter the postural resting position of the mandible. The early treatment of such problems involves interceptive functional therapy – screening type of appliances or activators and twin-blocks with or without the occlusal equilibration in the later stages of therapy.

Maxillary prognathism: It is characterized by a large maxillary base or a normal maxilla, which is positioned anteriorly with respect to the cranial base associated with a normal mandible (Fig 3.27). In the management of patients with skeletal problems, the growth direction plays an important role in the selection of a treatment strategy. In a Class II relationship, with a fault in the maxilla during mixed dentition, the treatment goal is to inhibit growth in the midface region and allow the normal growth of the mandible. This produces orthopaedic midface changes to alter the maxillary position in relation to the mandible and the anterior cranial base.

Extraoral heavy forces, with the help of a headgear assembly, applied to the maxillary first molars are used for growth inhibition in the midface region. This treatment approach used in growing patients produces a desired maxillary skeletal change.⁵⁴ A headgear used for this purpose should be designed to deliver an optimal extraoral orthopaedic force to compress the maxillary sutures, modifying the pattern of bone apposition at these sites. To be effective for this purpose, the extraoral force should be of much greater magnitude, in the range of 400–600 g per side, worn at least 12–14 h per day to produce a skeletal change and to minimize dental effects.⁵²

Apart from the force magnitude and duration, the direction of the extraoral force should be determined based on the vertical relationships observed in the patient or the growth pattern. The extraoral attachment can be cervical or occipital to establish a low or a high angle of force vector. To achieve the maximum skeletal improvement by affecting the maxillary sutures, a superior and posterior force vector through the centre of resistance of the maxilla appears to be the most appropriate direction. The extraoral force vector also depends on the height and length of outer bow. Raising or shortening the outer bow moves the force vector superiorly, and lowering or lengthening the outer bow moves the force vector inferiorly. Often, the mandibular arch is normal and the occlusal plane is flat; however, if the maxillary incisors are flared and tipped labially, they should be retracted first. If the maxillary arch is constricted, an extraoral traction should be preceded by an initial phase of maxillary expansion.

The goal of orthopaedic treatment with the headgear is to restrict normal downward and forward maxillary growth by compressing the maxillary sutures and altering the growth and apposition of bone at these sutures, while allowing the mandible to grow normally.

Mandibular retrusion: The Class II malocclusion, characterized by mandibular deficiency and orthognathic maxilla, is often associated with some degree of dental compensations. The treatment strategies in such cases are directed to establish orthognathic profile and lip seal and to improve facial muscle function by promoting optimal mandibular growth in the first phase of treatment, followed by detailing of dentition using the contemporary fixed appliances in the second phase (Figs 3.28-3.30). This desired sagittal change can be achieved by posturing the mandible forward using one of the functional jaw orthopaedic appliances.

This sagittal change is dependant on growth guidance and adaptive processes for the desired skeletal modification. One of the treatment methods in patients with deficient mandible is to hold the normally positioned maxilla and allow the mandible to express its normal growth. The literature shows that the patients wearing headgear that is attached to the maxilla exhibit more mandibular growth than untreated Class II patients.⁵⁵ It remains to be seen whether this statistically significant extra mandibular growth is clinically significant. The author's treatment of choice in patients with mandibular deficiency is to enhance the mandibular growth using a variety of functional appliances. It is believed that mere unloading of the condyle by forward mandible posturing contributes to a significant condylar growth.^56,57 It should be recognized that it is not only the apparent condylar position in glenoid fossa but the more retruded fossa itself to be used as a criterion in Class II malocclusion.^58,59 More condylar growth increments and a change in the direction of growth to a more upward and backward vector are associated with the use of functional appliances.^60,61 The research has also shown significant change in the position of the glenoid fossa with respect to the anterior cranial base.⁶² Unloading of the condyle associated with downward and forward posturing of the mandible also enhances metabolic action in the temporomandibular joint (Fig 3.31).⁶³ It is not just a mere forward posturing of the mandible but an increased anabolic and catabolic exchange that may contribute to enhanced growth of the condyle and posterior wall proliferation.^64,65

Dentoalveolar movements to camouflage skeletal Class III discrepancy: For patients with Class III malocclusions diagnosed during the permanent dentition period, treatment options are very limited. Such problems that are not resolved during mixed dentition by orthopaedic treatment usually require comprehensive fixed appliance therapy or surgical intervention. For some reasons, if surgical correction is not considered in the final treatment plan to resolve the underlying skeletal discrepancy, camouflage by dentoalveolar movements is the only treatment option (Figs 3.35-3.37). In mild discrepancy cases, camouflage involves the use of mid Class III elastics with or without extraction of teeth to produce acceptance facial profile change.

Though this approach improves interincisal relationship and overall occlusion, retraction of mandibular incisors makes the chin more prominent and often magnifies the facial aesthetic problems. Therefore, camouflage treatment in Class III malocclusions is generally considered less successful than in Class II problems.

Maxillary skeletal retrusion: The skeletal Class III malocclusion due to maxillary skeletal retrusion is characterized by small and retrognathic maxillary base with small SNA and normal SNB angles. Early treatment of such patients involves growth guidance during the eruption of the maxillary incisors.

The orthopaedic facial mask The orthopaedic facial mask is the appliance of choice in the management of patients with mild to moderate Class III malocclusions having a retruded maxilla and a hyperdivergent growth pattern in the early mixed or late deciduous dentition (Figs 3.39–3.41). For patients exhibiting vertical or hyperdivergent growth pattern, the use of bonded acrylic maxillary expansion appliance controls the vertical eruption of molars. The orthopaedic facial mask is a very versatile appliance and produces the most dramatic improvements in the shortest period of time. It affects almost all areas contributing to the development of Class III malocclusion like maxillary basal retrusion, retrusion of maxillary dentoalveolar region, prognathic mandible and decreased lower facial height.

The orthopaedic facial mask system has various components: an acrylic bonded maxillary splint that provides a rigid maxillary anchorage, the facial mask and elastics (Fig 3.40C and D).

The optimal time to resolve skeletal Class III malocclusion with maxillary basal retrusion and orthopaedic facial mask is at the time of initial eruption of the maxillary central incisors. The primary and early mixed dentition developmental periods are considered to promote better skeletal and dental response.⁷¹ However, recent evidence shows that the protraction of maxilla is effective through puberty with less skeletal response as the sutures mature.^72,73

To elicit a maximum skeletal change, the patient should wear the appliance for at least 12–14 h a day, with orthopaedic force levels of 300–400 g per side in the primary and mixed dentitions. Most patients with maxillary retrusion are also vertically deficient. Therefore, the elastic pull can be directed little downward to lower the maxilla, which increases the face height and rotates the mandible downward and backward, contributing to the sagittal and vertical skeletal correction. It is the author's experience that, on an average, approximately 6–8 months of prescribed use of orthopaedic facial mask produces desired skeletal changes.

Several circummaxillary sutures – frontomaxillary, nasomaxillary, zygomaticomaxillary, zygomaticotemporal, pterygopalatine, intermaxillary, lacrimomaxillary and ethmomaxillary sutures – contribute to the development of the nasomaxillary complex. To bring about rapid and significant maxillary protraction, it is essential to disarticulate the maxilla and initiate cellular response in the circummaxillary sutures. It has been found that the forward displacement of the maxilla is significantly greater when face mask is used in association with rapid maxillary expansion when compared with the protraction without rapid maxillary expansion.⁷⁴ The timing of the protraction pull on the retruded maxilla is critical. The protraction of the maxilla appears to be greater when it is carried out during maxillary expansion when compared with protraction after expansion.⁷⁴

In pseudo-Class III patients, it is common to observe a rapid shift in the occlusal relationship and a correction of a CO-CR discrepancy. Along with skeletal improvements, the face mask produces forward movement of maxillary dentition and lingual tipping of mandibular incisors.

In patients who do not require increase in transverse dimension, it is still advisable to activate the expansion appliance for a week to disrupt the maxillary sutural system to generate more positive reaction to protraction forces.⁷⁵

The key to prevent posttreatment relapse is to maintain a positive overjet and overbite during the retention period. As some degree of regression of the overjet is expected during the early posttreatment period, it is important to achieve a positive overjet of approximately 4 mm before the facial mask therapy is discontinued.

Mandibular skeletal protrusion: Skeletal Class III malocclusion with a mandibular prognathism and normal maxilla is characterized by larger SNB angle and normal SNA angle, producing a negative ANB difference. The mandible is longer with frequent findings of large gonial angle and small articular angle. Quite often, it is also anteriorly positioned. Patients with this malocclusion exhibit dentoalveolar compensation – maxillary incisors are tipped labially and the mandibular incisors are lingually inclined. A wider part of the mandible occludes with a narrower part of the maxilla, leading to a posterior crossbite. These malocclusions are extremely difficult to correct, and in severe problems, surgery is the only treatment option.

The early treatment of mandibular skeletal protrusion involves the use of functional appliances and orthopaedic chin cups. Functional appliances have very limited role in the management of mandibular prognathism and usually work by rotating the mandible downward and backward, allowing the maxillary posterior teeth to erupt downward and forward while inhibiting the eruption of mandibular teeth and promoting proper occlusal relationships. This treatment approach is indicated in patients with normal or decreased lower anterior facial height and mild mandibular skeletal problem.

Another approach to deal with mandibular prognathism is the use of orthopaedic chin cups of two different types; the occipital-pull chin cup that is indicated in case of mandibular prognathism and vertical-pull chin cup that is advocated in patients with increased lower facial height and steep mandibular plane angle. The treatment with chin cup to influence mandibular skeletal protrusion is effective in patients during the primary or early mixed dentition period⁷⁶ (Fig 3.42A and B).

There are two ways in which the direction of the chin cup pull is applied. If the orthopaedic force is directed below the condyle, the downward and backward rotation of the mandible is expected. This is helpful in patients with short lower anterior facial height; however, in patients in whom the vertical dimension needs to be maintained, the force should be applied through the condyle to help restrict mandibular growth (Fig 3.42C).

It is recommended that the patient should use the chin cup for 12–14 h per day with orthopaedic force levels of 300–400 g per side. It has been shown that the early correction of an anterior crossbite with a chin cup appliance prevents impaired sagittal growth of the maxilla.⁷⁶ There has been some concern among clinicians about chin cups creating pressure on the TMJ, since several patients were reported of having temporary soreness of TMJ.⁷⁷ It is recommended that patients undergoing chin cup therapy should be monitored for TMD signs and if noted, the treatment should be discontinued immediately.