Anterior Crossbite in primary and mixeddentition• Dentoalveolar anterior crossbite represents a linguoversion of one or more maxillary anterior teeth with resultant “locking” behind the opposing mandibular teeth in full closure.• Is usually an acquired malocclusion resulting from local etiological factors that interfere with the normal eruptive positioning of the maxillary anterior teeth.•
• May result from premature contacts, pseudo-class III.• In most cases anterior crossbites should be treated as soon as it is discovered.• Delayed treatment can lead to serious complications: • Loss of arch dimensions • Asymmetric midlines • Traumatic occlusion with stripping of gingival tissue on the labial aspect of the lower tooth, wear facets on involved incisors • Untoward growth patterns if a functional shift is involved.
Important considerations for diagnosis Dental Crossbite Skeletal CrossbiteNumber of teeth Involved One or two Suspicious arise with the number of teeth involvedInclinations of maxillary Max: lingual inclination Max:normal to proclinedand mandibular incisors. Mand:normal to slight Mand: retroclined labial inclinationMandibular closure Displacement of the Close in a smoothpattern and facial profile mandible as a shift pattern without from neutroclusion to anteroposterior class III disruption. Facial profile and Mesiocclusion of molar buccal occlusion positioning and should present a prognathism of the neutroclusion at rest. profile should persist at all times.Familial appearance No YesCephalometric analysis No Yes
Decision factors for treatment in dental crossbites1. Incisor positioning and space available. Tipping movements of involved maxillary incisors if the root of the lingual tooth is in the same relative position as it would occupy in normal occlusion.2. Stage of eruption. • Active eruption: leveraging techniques to redirect the tooth forward into acceptable position. • Fully erupted: Directed forces to effect labial repositioning of the involved maxillary anterior teeth will be required.3. Degree of overbite. • Occlusal bite planes are often proposed to remove overbite interferences during labial movement. • the 3- to 4-mm freeway space at rest position and use of directed lingual applied forces from fixed appliances negates the need for bite- opening.
1. Two treatment approaches 1. Passive incisal guides that during mandibular closure redirect or “leverage” maxillary anterior inclinations in a labial orientation 2. Active appliances that use directed orthodontic forces to achieve labial repositioning of the maxillary anterior teeth.
TONGUE BLADE/POPSICLE STICK THERAPY• Cooperative children,dependent in frecuency,duration and accuracy.• Use of the wedging effect of a tongue blade or popsicle stick.• Teeth in initial eruption with a minimal degree of locking can often be repositioned within 24 to 72 hours.• The child is instructed to place the stick behind the locked tooth and, using the chin as a fulcrum, exerts pressure on the tooth toward the labial.• The procedure is done in 15 to 30 minute increments at a time for at least several hours of engagement.• The advantage is “self-correction” in avoiding the expense and time involved with appliance therapy.• Very unlikely if the tooth is erupted into full crossbite.
LOWER INCLINED PLANE• An acrylic extension from the lower anterior teeth designed to engage the incisal edge of lingual displaced maxillary teeth during closure applies pressure upon patient closure that will direct the engaged tooth labial into normal bite position.• Prerequisites: • Adequate space in the maxillary arch • A normal or excessive overbite • Sufficient mandibular teeth for retention of the acrylic.• Constructed using self-curing resin on a working model to enclose the lower canine to canine anterior segment.• The acrylic should engage only the upper tooth or teeth in crossbite and incorporate approximately a 45-degree incline to the long axis of the lower incisors.• The incline portion should extend about ¼ inch posteriorly such that the patient cannot readily bite behind the inclined plane.
• The posterior “bite opening” should be slightly beyond rest position (not more than 2 to 3 mm) to avoid excessive muscle fatigue.• This bite opening limits the time the appliance can be worn as eruption of posterior teeth may occur within 2 weeks and a tendency to an anterior open-bite may result.• Physical activities restricted• Follow up in1 week with adequate bite jumping usually achieved within this time.• If not “jumped” may be continued to use for 1 more week.
• Advantages: • Ease of fabrication • Simplicity of action • Rapid correction time • Possible use when there is insufficient eruption to engage active appliances.• Disadvantages: • Discomfort associated with forced bite opening • Poor esthetics • Limitations on diet • Potential for gingival irritation • Possibility of creating an open-bite • Risk of traumatic injury if the child hits their chin while the inclined plane is positioned in the mouth • The inclined plane may be dislodged by occlusal stress and require recementation.
PALATAL-SPRING APPLIANCES• Best option for dental anterior crossbites if tongue-blade guidance is not possible.• Properly oriented springs exert targeted labial directed pressures against the teeth from the palatal side and are not impacted by the reverse overjet.• The major disadvantages are technical in nature and can be overcome with proper fabrication and management of the appliance.• A removable Hawley-type retainer modified with auxiliary springs can reduce lingual displacement of maxillary incisors with correction usually achieved in 6 to 12 weeks.
FIXED TRANSPALATAL WIRES WITH SPRINGS• Very effective method to labialize maxillary incisors involved in anterior crossbite.• A transpalatal connector wire of 0.036 or 0.040 stainless steel soldered to banded molars that incorporates a helical-loop spring of 0.020 stainless steel.• The fixed approach results in significantly less tooth tipping in offering a more bodily applied tooth movement and provides continuous force application that is not dependent on the childs cooperation.• Average treatment times of 1 to 3 weeks.• Abutment support may be from either second primary molars or first permanent molars.
Labial Edgewise Archwires• Edgewise brackets and labial archwire mechanics are used when multiple incisors are in crossbite, palatal displacement and rotations are severe, and adjacent tooth movements are needed to adjust anterior spacing• Disadvantages • Increased chair time in placement,djustment, and removal Need for special equipment and supplies • Increased soft tissue irritation, decalcification of teeth, risk of injury to developing teeth with excessive biomechanical movements • Expectations and expenses associated with “braces.”
POSTERIOR CROSSBITE IN THE PRIMARY ANDMIXED DENTITIONS• Differential diagnosis between dental or skeletal determine treatment of posterior crossbites• Dental posterior crossbites involve atypical eruption and alignment with localized displacement of individual teeth into crossbite configurations.• Within an interceptive context, isolated first permanent molar crossbites can be corrected by use of cross-arch elastics• Usually can be corrected with cross-arch elastics in 4 to 8 weeks.• If either of the opposing molars are in correct alignment before treatment, an anchorage appliance (lower lingual arch or upper Nance/Trans Palatal Bar) may help prevent movement of that tooth.
• Skeletal posterior crossbites present as gross discrepancies in basal relationships of the maxilla and mandible, usually presenting a full bilateral crossbite with severe constriction of the maxilla.• Midlines are generally coincident to the facial midline in occlusion with no functional deviations observed on closure.• Functional posterior crossbites involve a lateral shift of the mandible during closure in response to transverse occlusal interferences between the maxillary and mandibular archwidths.• Unilateral crossbite in centric and cusp to cusp transverse contacts bilaterally at initial contact.• Factors contributing to constriction in maxillary width include upright primary canine interferences, thumb and finger habits, and mouth-breathing/airway problems.
• Incidence rate of 5% to 8% of children.• Less than 10% of posterior crossbites present in the primary dentition self-correct into the mixed dentition.• In conjunction with functional posterior crossbites, asymmetric condylar positioning has been demonstrated on tomograms and transcranial radiographs.• Hesse andcolleagues documented condylar positioning using temporomandibular joint tomograms in 22 functional posterior crossbite patients corrected with maxillary expansion at a mean age of 8.5 years. • The condyle on the noncrossbite side was positioned more anterior before treatment and moved posteriorly and superiorly after treatment. • The condylar position was similar at pretreatment and post treatment stages on the crossbite side. • Correction of the crossbite with maxillary expansion established symmetry of condylar relationships in all planes of space.• Other studies confirm displacement of the mandible in growing children produces asymmetric mandibular length with the crossbite side shorter than the noncrossbite side.
• Early correction of posterior crossbites has been shown to enhance developmental patterns.• Early treatment also allows simplified approaches that are less complex, less time consuming, and more physiologically tolerable to structural tissues than treatment demands in older patients.
Selective Equilibration• Offer some potential for functional crossbite correction without appliances.• The equilibration involves selective reduction of the lingual aspects of the upper primary canines and labial reduction of the lower primary canines.• Is successful according to Lindner when the maxillary intercanine width difference is larger than the mandibular intercanine width by a positive 2 to 3 mm.• In most full primary or mixed dentition cases, equilibration procedures alone are insufficient to eliminate a functional discrepancy associated with a constricted maxillary dentoalveolar width.
MAXILLARY EXPANSION• Appliances: • Fixed palatal wire designs: W-arch, quad-helix • Fixed jackscrew expanders:Hyrax, Haas • Removable split-acrylic plate appliances: Schwarz Plate.• Greater than 90% success rate and for removable appliances at 70% success.• Early expansion techniques in children require an average final overall increase of about 3 to 4 mm in intramolar width and 2 to 3 mm of intracanine width change for successful correction.• Overexpansion of about 2 to 3 mm beyond these final desired increments during the active phase to accommodate settling adjustments after treatment.• Transverse expansion of the maxillary arch is directed at a combination of dentoalveolar expansion and orthopedic separation of the midpalatal suture. It is considered desirable to optimize opening of the midpalatal suture to provide more stable basal arch expansion than orthodontic oriented lateral expansion.• The nature of orthodontic and orthopedic movements is closely related to the rate of expansion, the magnitude of force application, and the patients developmental stage in considering the appliance options.• Fixed palatal jackscrew appliances, such as the RPE of Haas (see Fig. 27-40) and the Hyrax (Fig. 27-43), are applied bilaterally to maxillary posterior teeth with the midline screw generally expanded at a rate of one to two turns per day (one turn equals 0.25 mm of screw widening) during an active treatment time of 1 to 4 weeks.• Retention periods using fixed appliances of 3 to 6 months.
• Fixed palatal wire appliances accomplish maxillary expansion following “low-force” and “slow-expansion” procedures compared with the jackscrew appliances.• The conceptual model of fixed palatal wire appliances in the primary and mixed dentitions is that favorable orthopedic and orthodontic ratios of expansion are realized with less disruption than rapidly expanded sutures.• Advantages: • Increased molar rotational ability • Relative comfort • Minimal effect on speech and deglutition • Reduced soft tissue irritation • Removal of adjustment responsibility from the patient/parent
• In primary dentition are usually treated at ages 4 to 5 years with banding of the deciduous second molars and n the mixed dentition with bands in the first permanent molars.• During the active eruption stage of the first permanent molars, from about 6 months before emergence until opposing occlusion is established, maxillary expansion procedures should usually be delayed.• The laterally tipped dental elements will upright after retention.
W- Arch• Very stable in situations that require 4 to 5 mm of maxillary buccal expansion such as typically required in functional posterior crossbites.• Some palatal expansion may occur with the W-arch.• The wire is expanded to the bilateral width of the central fossae of the banded molars before cementation such that the appliance must be compressed 2 to 3 mm bilaterally to place it on the banded teeth.• Reactivated by being removed for additional adjustment every 3 or 4 weeks if necessary until the crossbite has been corrected.• The appliance may be used as a retainer for 3 to 6 months after active treatment.
Q-helix• The quad-helix appliance, by incorporating four helical loops into the W-arch design, provides refined adjustment capability in providing a longer range of force application• All loops should be as horizontal as possible with the anterior loops circling toward the palate at the level of the primary canines and the posterior loops away from the palate.• The posterior loops should extend approximately 2 to 3 mm distal to the molar bands for enhanced molar rotation and expansion.
• Follow up appointments 2- to 3-week .• Adjustments are made only when progress between successive appointments is static and the amount of increased arch width is inadequate.• The appliance should be removed for activations to ensure appropriate expansion increments both in amount and location.• Opening with finger “accordion” type action or incorporating strategic bends along the wire-lengths to increase lateral expansion.• Expansion is considered adequate when the occlusal aspect of the maxillary lingual cusps contact the occlusal slope of the mandibular buccal cusps in representing approximately 2 to 3 mm of overexpansion to compensate for later uprighting of laterally tipped teeth once appliances are removed.• Successful expansion with slight overcorrection is usually achieved in 4 to 6 weeks.• The appliance is left in the expanded position to serve as a retainer with a recommended minimum retention period of at least 3 months.
Hyrax• Hyrax jackscrews are preferred for bilateral posterior crossbites with pronounced maxillary constriction that require 6 to 8 mm of expansion to correct the transverse discrepancy and in older patients where sutural integrity requires greater force magnitudes to achieve basal arch changes.• Expansion effects are related to the rigidity of the appliance, positioning of the jackscrew relative to the palatal archform, and resistance of the maxillary complex.
• If employed in the mixed dentition, the first permanent molars and second primary molars provide excellent anchorage for the appliance and first permanent molars and either first or second premolars for the permanent dentition.• An activation rate of one turn per day is advised to achieve expansion on the order of 6 to 8 mm (24 to 32 turns) during an active treatment time approximating 1 month.• After sufficient expansion is obtained, the appliance is left in place for 6 months to allow reorganization of the expanded suture and enhanced stability of achieved arch width.