Tongue Retraining Appliance: Clear Tongue Crib and Clear Tongue Cage Appliance

ABSTRACT

Aims and background

This article introduces a novel tongue training appliance “clear tongue cage or clear tongue crib appliance” designed to address and correct tongue thrusting and improper tongue positioning, which are common contributors to malocclusion, speech difficulties, and other orthodontic issues. The innovative design incorporates materials and features that enhance comfort and effectiveness. The appliance functions by gently guiding the tongue to an optimal position, promoting proper swallowing and resting posture. Additionally, it aids in the effectiveness of orthodontic treatments by preventing the tongue from interfering with dental alignment processes.

Results

Clinical trials demonstrate significant improvements in tongue positioning, speech clarity, and overall oral health among users.

Conclusion

The findings suggest that consistent use of the appliance, under professional supervision, can lead to lasting benefits in tongue positioning and thereby prevent malocclusion.

Clinical significance

This appliance represents a significant advancement in myofunctional therapy, offering a noninvasive, user-friendly solution for patients of all ages.

How to cite this article

Peter J, Kumar KR, Methippara JJ, et al. Tongue Retraining Appliance: Clear Tongue Crib and Clear Tongue Cage Appliance. Int J Clin Pediatr Dent 2025;18(7):902–906.

INTRODUCTION

The human tongue is a complex muscular organ comprising eight muscles—four intrinsic and four extrinsic—that coordinate to enable its diverse range of movements and functions.¹ Unlike most organs with a rigid, bony framework, the tongue achieves its remarkable versatility through a unique design—the muscular hydrostat.

The tongue plays a crucial role in several stages of deglutition. The tongue helps in forming the chewed food into a bolus (a soft mass). Once the bolus reaches the pharynx, involuntary muscle contractions take over, directing the food bolus down the esophagus and away from the airway (trachea). During swallowing, the lower esophageal sphincter briefly relaxes to allow the bolus to pass through into the stomach. Under physiological conditions, the tongue contacts the palate just posterior to the incisive papilla during deglutition, with the tip pressing against this area. Myofunctional therapists often refer to this region as the “spot,” which is believed to function as a neural relay between palatal sensory receptors and the cerebral cortex.²

Our tongue exerts an average pressure of 0.8 gm/cm at rest,³ while an average tongue pressure of 112 gm/cm was observed during swallowing⁴ much higher than resting pressure. While swallowing pressure might be stronger than resting pressure, the constant nature of low-level force exerted by an abnormal resting tongue posture can play a significant role in teeth malocclusion.

An abnormal tongue posture during swallowing can disrupt this process and lead to several potential problems such as dysphagia, speech difficulties, temporomandibular joint (TMJ) dysfunction, etc. Abnormal tongue posture includes conditions such as low tongue positioning, tongue thrusting, and related dysfunctional patterns. When the resting posture of the tongue is low, the tongue rests on the floor of the mouth instead of the palate during a swallow, and it cannot effectively create the necessary seal to prevent food or liquid from entering the nasal cavity (nasopharyngeal reflux). When the tongue habitually rests in a low or forward position, the surrounding muscles adapt to this position. Swallowing then becomes a more forceful “push” with the tongue to clear food from the mouth, resulting in a thrusting motion. This leads to a tongue-thrusting habit where the tongue pushes forward against or between the teeth during swallowing, leading to various malocclusions. Therefore, an objective assessment and correction of tongue posture, position, and movement are clinically essential in the management of malocclusion.

Studies have reported that, compared to children with normal dentition, those with conditions such as frontal open bite, lateral crossbite, and increased overjet are more likely to exhibit static functional disturbances—such as open mouth posture and compensatory tongue positioning. Postural anomalies and related habits appear to have a significant influence on the development of dental occlusion across all three spatial dimensions.⁵

The persistence of an infantile swallow pattern during childhood and adolescence, known as tongue thrust, is an oral habit that often leads to an open bite and protrusion of the anterior tooth segment.⁶ Tongue thrusting can be defined as the forward movement of the tongue tip between the teeth to meet the lower lip during deglutition and in sounds of speech so that the tongue becomes interdental.⁷

Research indicates tongue thrusting as one of the most common oral habits in Indian children. Studies report prevalence rates ranging from 1.8 to 28.8%.^8,9

Tongue thrust in children has been associated with increased upper lip thickness and maxillary incisor proclination. This habit appears to influence various softtissue and dental characteristics, leading to lip incompetence, mouth breathing, lisping, open bite, proclination of the maxillary incisors, and hyperactivity of the mentalis muscle. Since orthodontic treatment outcomes are often unstable in the presence of muscle dysfunction, it is essential for clinicians to address orofacial dysfunctions at the earliest.¹⁰

Orofacial myofunctional therapy has demonstrated a significant positive impact on the management of tongue thrust. It promotes neuromuscular reeducation of orofacial muscles, thereby improving functional activities such as swallowing, tongue movement, oral respiration, and the resting posture of the lips, tongue, and cheeks. When used as an adjunct to orthodontic treatment, it contributes to the stabilization and integration of orofacial functions, supporting long-term treatment outcomes.¹¹

Orofacial myofunctional therapy consists of a structured set of exercises designed to reeducate orofacial muscles involved in swallowing, speech, and resting posture.¹² Sessions typically focus on strengthening the tongue and lip musculature, modifying the swallowing mechanism, and coordinating the overall swallowing movement. Patients are guided in developing both conscious and unconscious habit formation, particularly concerning the resting posture of the tongue.¹³

Functional habits can be addressed by preventing the tongue from resting against the anterior teeth. This is commonly achieved using lingual or palatal cribs and spurs. Cribs are typically fixed to the palatal surface of the maxillary arch, serving as a barrier to discourage anterior tongue positioning. However, these structures are smooth and purposefully enable the tongue to rest on them so that in several cases it may block the functional restoration of the tongue. Hence, the tongue then returns to its original position, resulting in relapse of anterior open bite (AOB).¹⁴ The altered tongue position influences sensory input to the brain, thereby generating a new motor response that can become permanently encoded. This mechanism explains the long-term change in tongue posture induced by the use of spurs, contributing to the stability of AOB treatment outcomes.¹⁵

A variety of appliances have been employed to manage the tongue-thrusting habit, including the conventional tongue crib, tongue bead, and temporary anchorage device (TAD)-supported tongue crib. Among these, the conventional tongue crib is most commonly used, which, however, presents several limitations, such as patient discomfort, indentation on the tongue, appliance breakage—particularly at soldered joints—and excessive bulk, which may hinder patient compliance.

This article describes two custom-made habit-breaking appliances—clear tongue cage and clear tongue crib appliance—which can be used effectively to retrain and correct tongue posture.

APPLIANCE DESIGN

Clear tongue crib appliance is a newly designed appliance in which a metallic crib has been incorporated into an Essix retainer that restricts the tongue and reminds it to be in a more backward position. A palatal crib fabricated from 0.9 mm stainless steel wire was positioned obliquely across the palatal surface of the patient's cast, extending from one canine to the contralateral canine (Fig. 1). The tip of the crib was aligned approximately with the incisal edge of the maxillary central incisors or extended 2 mm beyond, not to interfere with the lower incisors during occlusion.

Fig. 1:

The palatal crib positioned over the palatal surface of the patient cast, obliquely from one canine to the other canine

A high-performance Essix Plus plastic, 0.040 thickness, is placed over the cast with the acrylic block. The Essix Plus plastic, is then heated to soften and then vacuum-suctioned in the pressure thermoforming machine onto the cast of the patient's teeth. After removing the molded appliance from the machine (Fig. 2), the excess material is trimmed using a heat knife, lab knife, or trimming wheel 1–3 mm above the gingival margin from both the lingual and labial surfaces. Then the appliance is gently removed from the cast, and the edges are smoothed using polishing brushes to make the fit more comfortable(Fig. 3).

Fig. 2:

The Essix Plus plastic is vacuum-suctioned in the pressure thermoforming machine to the cast of the patient's teeth

Fig. 3:

Clear tongue crib appliance after final trimming and polishing

Clear tongue cage appliance is made with an acrylic block incorporated into an Essix retainer that cages the tongue and reminds it to be in a more backward position. An acrylic block was first made in the upper cast of the patient, extending from canine to canine. The height of the acrylic block was made almost in line with the incisal edge of the maxillary central incisor or 2 mm longer, not to interfere with the lower incisors when in occlusion. The Essix Plus plastic is similarly vacuum-suctioned onto the cast of the patient's teeth followed by trimming the excess from both the lingual and labial surfaces followed by polishing (Fig. 4).

Fig. 4:

Clear tongue cage appliance after trimming and polishing the edges

Patients were asked to swallow while pressing on the acrylic block or the metallic crib to imbibe the normal swallowing pattern. Patients were advised full-time wear of the appliance (Fig. 5).

Fig. 5:

Intraoral image of clear tongue cage appliance

DISCUSSION

Centrally positioned within the oral cavity, the tongue is a powerful muscular organ capable of influencing the position of the teeth and adjacent structures. Although primarily attached to the mandible and hyoid bone,¹² the tongue's role in guiding the development and positioning of the dentoalveolar complex has long been recognized. Any abnormality in its function or posture can contribute to alterations in the surrounding dentoalveolar structures, potentially resulting in malocclusion.¹⁶

The influence of tongue thrust on dentofacial development is multifactorial, depending on factors such as the frequency of swallowing (i.e., how often the tongue applies pressure to the teeth), the magnitude of the force exerted, the counterbalancing action of perioral muscles like the lips, the resistance of dentoalveolar structures to displacement, and the tongue's resting posture during periods of inactivity.¹⁷

The duration of swallowing has been examined in several previous studies. In an electromyographic investigation conducted by Findlay and Kilpatrick, the average swallowing time was reported to be approximately 2 seconds.¹⁸ Similarly, Sonies et al. observed that the duration of saliva swallowing ranged between 1.7 and 3.4 seconds.¹⁹ Tongue tip protrusion is frequently linked to a low, forward tongue posture, which may contribute to altered dentofacial development. Even when the exerted force is minimal, its prolonged duration can influence tooth position both horizontally and vertically. Studies have demonstrated that a persistently low tongue posture during the growth period may contribute to excessive molar eruption, leading to clockwise mandibular rotation, increased lower anterior facial height, retrognathia, and AOB. In addition, a low tongue position can impede lateral expansion and anterior development of the maxilla.²⁰

Tongue posture and functional habits have been implicated in both the etiology of malocclusions and the stability of posttreatment outcomes. “Atypical tongue function” has been particularly associated with relapse following various orthodontic interventions.¹⁷

According to Proffit²¹, the duration of light, continuous pressure from a forward resting tongue posture can have a greater impact on tooth positioning than the brief forces generated during tongue-thrust swallowing. Therefore, achieving and maintaining a correct resting tongue posture is critical for both effective treatment and long-term stability.

A study by Winders reported that the tongue exerts greater pressure on the dentition than the buccal musculature.²² These findings were later supported by Kydd and Neff, as well as Kydd et al., who concluded that the magnitude of muscular forces generated by the tongue—both at rest and during function—exceeds those produced by the lips and cheeks.²³

A limited number of methods are available for analysis of tongue position on radiographs. Accurate analysis requires high-quality radiographic images that clearly depict the tongue outline and appropriate selection of reference lines. According to Guay,²⁴ the use of a radiopaque material is recommended to enhance the visibility of soft tissue contours, thereby facilitating more precise analysis. So, in this study, we have used radiopaque barium sulphate oral suspension for the tongue coating to make the tongue outline clear. It possesses mild adhesiveness and maintains its integrity for approximately two swallowing cycles. Its narrow dimensions and minimal bulk ensure that it does not interfere with tongue movements.

Lin et al. proposed that the posttreatment stability of AOB following crib therapy may be attributed to alterations in tongue posture. It has been proposed that the functional and/or mechanical “unlocking” of transverse maxillary deficits—aimed at establishing proper tongue posture and managing tongue habits—is a critical factor in maintaining long-term treatment stability.²⁵ Also, the functional matrix theory suggests that the width of the maxillary palatal complex is influenced by the spatial position of the tongue.²⁶

Orofacial myofunctional therapy serves as an important adjunct to both speech therapy and orthodontic management in the correction of tongue-thrust habits.

Treatment approaches aimed at correcting low tongue posture and tongue-thrusting behavior typically include elimination of the underlying etiology, implementation of orofacial retraining exercises, and the use of mechanical restraining appliances. Tongue-thrust appliances are designed to fit behind the anterior teeth, against the palate, to prevent the tongue from exerting forward pressure against or between the teeth. These appliances may be either removable or fixed. A commonly used fixed option is the palatal crib, which consists of a metal grate that obstructs anterior tongue movement. However, they can cause discomfort and irritation, particularly in pediatric patients.

In this study, myofunctional exercises and myofunctional appliances have been used for correcting the tongue posture and position. Tongue cage or tongue crib appliances have proven to be highly effective in breaking the tongue-thrusting habit. They are used for a duration of 3 months, during which patients are encouraged to spot and swallow by pressing the barrier. Cephalometric findings show significant improvements in tongue posture, with the tongue adopting a higher and more posterior position as a result of appliance use.

This study suggests that these myofunctional appliances act as the best reminder therapy in children that redirects and reinforces the tongue to a high palatal position. The modified tongue crib offers a dual advantage over the conventional design by combining mechanical restraint with functional reeducation of the tongue. It incorporates a metallic crib and an acrylic block within an Essix retainer, which not only restricts anterior tongue movement but also promotes a more posterior and elevated tongue posture through positive reinforcement and neuromuscular retraining. Moreover, these appliances are cost-effective compared to the fixed tongue guard appliances that are usually chosen for the treatment. They are easy to make chair-side appliances if there is availability of a vacuum former and a clear sheet.

Some limitations of the appliance include cracking or breaking if not handled with care, and it requires diligent hygiene as they can accumulate plaque, and they initially might cause slight speech difficulties.

So the key roles of a clear tongue cage appliance in dentistry include encouraging the tongue to adopt a more appropriate position in the mouth, which is crucial for proper dental alignment and overall oral health. Additionally, the appliance can enhance the effectiveness of orthodontic treatments by ensuring that the tongue does not interfere with the movement of teeth into their correct positions. This appliance can also aid in improving speech by guiding the tongue to a better position for articulation, which is particularly beneficial for correcting issues like lisping. Moreover, tongue cage appliances can discourage habits such as thumb sucking, which can contribute to dental misalignment. In myofunctional therapy, which involves exercises to improve the function of the oral and facial muscles, a clear tongue cage appliance can help train the tongue to move correctly.

CONCLUSION

The clear tongue crib or the clear tongue cage appliance can be effectively used to correct tongue thrusting and retrain the associated musculature. It acts as a mechanical restrainer and a reminder to discontinue the habit. The use of this appliance should be monitored by a dental professional to ensure its effectiveness and to make any necessary adjustments, and it is important for patients to follow their dentist's instructions carefully to achieve the best results.

ORCID

Krishna Kumar R https://orcid.org/0000-0003-3275-5494

Chaithanya NV https://orcid.org/0009-0003-5622-9824