# Habit Breaking in Orthodontics > Habit breaking in BDS Orthodontics: thumb sucking effects, Dunlop's hypothesis, cribs, bluegrass, tongue thrust and oral screen use with exam favourites. - Canonical URL: https://prepelephant.com/topics/bds/orthodontics/habit-breaking-ortho-bds - Exam / course: BDS · Subject: Orthodontics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Habit Breaking in Orthodontics", PrepElephant, https://prepelephant.com/topics/bds/orthodontics/habit-breaking-ortho-bds ## Direct answer An oral habit becomes an orthodontic problem when it persists beyond the preschool years with enough frequency and intensity to deform the arches: a digit habit held past about four years of age typically produces proclined upper incisors, retroclined lower incisors, anterior open bite, posterior crossbite from cheek pressure on a maxilla left without tongue counter-pressure, and increased overjet with a lip trap. Management runs a ladder from the least to the most invasive — counselling and reminder therapy, bitter nail preparations or adhesive bandaging, then reminder and mechanical appliances (palatal crib, bluegrass roller, tongue crib, oral screen) — with psychological handling throughout, because punishment entrenches habits. Dunlop's beta hypothesis frames the classic behavioural trick: forcing the child to perform the habit deliberately and consciously abolishes the pleasure and with it the habit. ## What you must remember - **Normal versus abnormal:** thumb and finger sucking is a normal settling behaviour until about three to four years of age; persistence beyond that, particularly at school age, is pathological. - **Graber's classification:** pressure habits (thumb sucking, tongue thrusting, mouth breathing) versus biting habits (nail biting, pencil and lip biting), each with a distinct dental signature. - **Digit-sucking signature:** proclined maxillary incisors with increased overjet, retroclined or suppressed lower incisors, anterior open bite, posterior crossbite (compressed maxilla from cheek pressure without tongue counter-pressure), and a high-vaulted palate. - **Tongue thrust:** a forward tongue posture and thrust on swallowing that maintains or re-opens an anterior open bite; differentiate a retained infantile swallow from an adaptive thrust secondary to the existing open bite. - **Mouth breathing:** long-face tendency, gingivitis of the exposed anterior gingiva, narrow arches; demand an ENT evaluation for adenoids, tonsils and allergy before any appliance — the habit may be pure airway need. - **Appliance menu:** palatal crib and bluegrass (roller) appliance for digit habits; tongue crib and orofacial regulator for thrust; oral screen (vestibular screen) for mouth breathing and lip exercise; lip bumper to restore lip competence and gain arch length. - **Dunlop's beta hypothesis:** consciously repeated performance of the habit, on prescription, strips its gratification — the behavioural principle behind reminder therapy. - **Sequencing rule:** correct the airway and the counselling first; an appliance on a mouth breather with untreated adenoids fails and is then blamed. ## Breaking one habit properly A six-year-old with a 3 mm anterior open bite, increased overjet and a thumb habit active at sleep-time only illustrates the ladder. Begin with two weeks of counselling and a calendar reward chart — most sleep-only habits in motivated six-year-olds yield here, and the open bite closes as the incisors erupt unopposed. If the habit survives, add reminder therapy with an adhesive bandage on the thumb at night, and a bluegrass appliance two months later if it is still active. If it survives that, fabricate a bluegrass appliance: bands on the first deciduous or permanent molars carrying a palatal crib with a rolling six-sided bead, turning the thumb's resting spot into an uninteresting obstacle — worn about three to six months, including through the relapse-prone first weeks of success. The tongue comes next in the audit: if a thrust persists after the open bite closes, it is usually adaptive and fades as the incisor relation normalises; a crib for the tongue is reserved for a persistent infantile swallow. Throughout, the parents' role is to reward the absence and ignore the relapse — the case is lost the day the habit becomes a battle, which is the practical reading of Dunlop. ## Where the viva probes habits Examiners ask for the dental effects of thumb sucking and the age at which it turns abnormal (beyond about four years), then jump to appliances: the crib for the digit, the bluegrass variant, the oral screen for the mouth breather — and the trap of placing any appliance before the ENT clears the airway. The tongue-thrust question tests the adaptive-versus-primary distinction: thrust accompanying an open bite usually disappears once the bite closes; the retained infantile swallow with teeth-apart posture does not. Graber's classification of habits is the expected opening of any theory answer, and Dunlop's beta hypothesis is the named-concept mark in behavioural management. Indian short cases frequently present exactly the thumb-sucking child with an open bite, and the first scoring sentence is the age cutoff plus the plan ladder, in that order. ## Frequently asked questions ### Until what age is thumb sucking considered normal? Roughly until three to four years of age; persistence into the mixed dentition is considered a deforming habit. ### List the dental effects of a persistent digit habit. Proclined upper incisors with increased overjet, retroclined lower incisors, anterior open bite, posterior crossbite from maxillary constriction, and a deeper palatal vault. ### What is Dunlop's beta hypothesis? Forcing the child to practise the habit consciously and deliberately removes its unconscious gratification, so the habit extinguishes itself. ### Which appliance manages tongue thrusting? A tongue crib or an orofacial regulator that blocks forward tongue posture; myofunctional therapy retrains the swallow once the mechanical block is in place. ### Why must mouth breathing be evaluated by an ENT surgeon first? Because adenoid hypertrophy, tonsillar enlargement or allergy may make the habit obligatory — no appliance succeeds while the nasal airway remains blocked.