MANAGEMENT OF DEEP BITE INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
The Term "deep bite" describes a condition of excessive overbite where the vertical measurement between the maxillary and mandibular incisal margins is excessive when the mandible is brought into habitual or centric occlusion (GRABER). The deep bite can be defined by the amount and percentage of overlap of lower incisors by the upper incisors . The overbite may be calculated as a percentage of the clinical crown height of one of the mandibular central incisors. (NANDA)
At age of 5 to 6 years this percentage varies between 36.5 and 39.2. In adults it remains almost unchanged, varying between 37.9 and 40.7%. Fleming showed that between 9 and 12 years of age the overbite usually is increasing, whereas in the period between 12 and adulthood it is decreasing. No sex differences were noted. Moorrees in 1959 determined that ramus length was one of the most important dimensions associated with the amount of overbite. He further states that the reduction in the overbite after 12 years of age may be due to growth of the ramus of the mandible
CLASSIFICATION Broadly Deep - over bite can be classified as
TRUE •HEREDITARY •ACQUIRED
Morphological features of skeletal deep over bite: ( Petrovic) Opdebeeck named Skeletal deepbite as short faced syndrome ďƒ˜ Horizontal type of growth pattern ďƒ˜ Anterior facial height is short particularly lower facial third while the posterior facial is long (UAFH:LAFH - 2.3 normal) in skeletal deep bite is 2:2.5 or 2:2.8. ďƒ˜ Horizontal cephalometric planes;- sella-nasion, palatal, occlusal and mandibular are approximately parallel to each other.
Inter occlusal clearance small. The inclination of maxillary base is significance when evaluating the treatment plan or this type of problem.
the combination of a horizontal growth pattern with a downward and forward inclination (retroclination) of the maxillary base results in a more severe deep over bite.
INTERACTION BETWEEN JAW ROTATION AND TOOTH ERUPTION (PROFFIT) â–ş During growth the eruption of the teeth and alveolar processes is in proportion to, is greater than, or is less than the condylar growth. This combination of condylar growth and the eruption of the teeth and alveolar processes determine the facial growth rotation. â–ş In forward growth rotation larger space posteriorly (the intermaxillary growth space wedges posteriorly)was seen.. So in forward growth rotations, the posterior teeth must erupt considerably more than the anterior teeth, just to maintain the original vertical dimension and the cant of the occlusal plane.
► Bjork showed posterior teeth in an archial fashion while the anterior teeth erupt straight upward and forward, almost on a straight line. ► McNamara, Williams and Melson have reported a strong correlation between the intensity and direction of condylar growth and the resulting change in the gonial angle, as well as the direction in which the mandible rotates ► When excessive rotation occurs (forward type) in the short face type of development, the incisors tend to be carried to overlapping, position even if they erupt very little, hence the tendency for deep bite malocclusion in short face individuals. ► The forward rotation also progressively uprights the incisors, displaying them lingually and causing a tendency toward crowding.
DENTO ALVEOLAR DEEP BITE: It is characterized by, a) Infra occlusion of the molars and/or supra occlusion of the incisors. b) Growth pattern average or tends towards the vertical Deep over bite that is due to infra occlusion of the molars has following features: *The molars are partially erupted, *The inter occlusal space is large. *A lateral tongue posture and thrust are present. *The distances between the maxillary and mandibular basal planes and the occlusal plane are short.
Deep over bite caused by the over eruption of the incisors has the following characteristics. The incisal margins of the incisors extend beyond the functional occlusal plane the molars are fully erupted the curve of spee is excessive. (compensating curve) the inter occlusal space is small
Dento-Alveolar deep bite is again classified into: a) True deep over bite and b) Pseudo deep over bite. ď‚§
True - Due to infra occlusion of the molars.
Pseudo-Due to supra eruption of the incisors often seen in class- II malocclusion patients where there is an increased overjet and the lower incisors have no incisalstop. These continue to erupt till they impinge upon the palatal mucosa.
ď‚§ Another classification based on etiology given by Graber, Rakosi and Petrovic: a) Developmental deep over bite, and b) Acquired deep over bite.
There are two types of developmental or genetically determined deep over bites: 1)
The skeletal deep over bite with a horizontal growth pattern
2) The dento alveolar deep bite caused by supra occlusion of the incisors. In these cases the inter occlusal clearance is usually small meaning the overbite is functionally a pseudo-deep over bite.
Acquired deep overbite may be caused by following factors: a)A lateral tongue thrust or postural position produces an infra occlusion of the posterior teeth with large freeway space, favourable for functional appliance treatment.
b)Premature loss of decidous molars or early loss of permanent posterior teeth can cause an acquired secondary deep bite, particularly if the contiguous teeth are tipped into extraction sites.
c) The wearing away of the occlusal surfaces or tooth abrasion can produce an acquired secondary deep over bite.
Factors Related to Development of Deep bite : → Incisor angulation → Incisor supra occlusion → Excessive overjet → Mesiodistal width of the anterior teeth → Molar infra occlusion → Failure of age related natural opening of the deep bite → Mandibular Ramus height → Anterior growth of the mandibular condyle, → Retrognathic mandible, Horizontal growth patterns
LETH NIELSON (Angle91) says that vertical malocclusions develop as a result of the interaction of many different etiological factors; one of the most important of these factors is mandibular growth. Variations in growth intensity, function of the soft tissues and the jaw musculature as well as the individual dent alveolar development .In Deep bite patients upward and forward growth of the mandibular condyle often have Reduced anterior face height.
Deep bite will not develop if the mandibular incisors have proper contact with the lingual surfaces of maxillary incisors.
If proper incisal contact is lacking, as a result of lip dysfunction or finger sucking habit, or Due to sagittal skeletal jaw discrepancy, the patient will develop a skeletal deep bite.
Patients with a pronounced tendency to anterior growth rotation and a deep bite should be treated early and the occlusion supported through out the growth period. Predictions of the mandibular forward growth rotation are 1. the condylar head curves forward. 2. The mandibular canal has a definite curve. 3. The mandibular lower border generally has a curved appearance. 4. The mandibular symphysis slopes backward.
Ernest H. McDowell, Baker(AJO91) analyzed the skeletal and dental changes produced by orthodontic correction of a deep bite. They compared between adolescents and adults for any differences that accounted for increased stability in a growing patients. It is widely accepted that correction of deep bite is both easier to accomplish and more stable when it is performed on growing patients than when it is attempted on those with no appreciable growth remaining. Reasons that have been cited for the Increased relapse potential in adults include encroachment on the occlusal freeway space and the fact that correction opposes the strong and mature jaw musculature that is less adaptable to elongation.
Treatment Strategies for Correction of Deep Bite Optimal correction of deep overbite requires proper diagnosis, individualized treatment planning, and efficient execution of treatment mechanics. A careful combination of treatment planning and mechanics to correct deep overbite can help to achieve a desirable esthetic result and to minimize relapse during the post retention phase.
The three fundamental orthodontic treatment strategies for deep bite correction 1. 2. 3. 4.
extrusion of posterior teeth; and intrusion of upper and/or lower incisors. Combination of 1&2 flaring of anterior teeth;
These effects are most often achieved biomechanically via bite plates, reverse cutve archwires, step bends in arch wires, and intrusion arches
Treatment Plan Considerations The method used to treat deep bite should be determined by proper treatment planning with consideration given to › soft tissue, › inter labial gap, › upper incisor display, › smile line, › lip length, › occlusal plane characteristics, › skeletal considerations.
Soft Tissue Considerations A careful clinical examination of a patient's soft tissue facial features can help in strategy selection between extrusion of molars and intrusion of upper and/or lower incisors. The face is evaluated in frontal and profile views both with relaxed lips and lips closed. Facial evaluation should include an assessment of the interlabial gap, incision-stomion distance (incisor display), and lip support with the upper and lower lips in their relaxed position. Observation of the patient during an unforced smile is also important to determine the relationship of the upper lip to the gingival line, as well as the smile line
Interlabial Gap In a relaxed lip position, an interlabial gap of 3-4 mm is considered esthetically acceptable. The interlabial gap is increased in children with a long vertical dimension and/or respiratory obstruction. Maintaining an acceptable interlabial gap should be considered when selecting a strategy for deep overbite correction. If a patient exhibits an excessive interlabial gap, the objective should be to help reduce the discrepancy, if possible, or at least to avoid worsening the problem. Class II, Division I patients with deep overbite, normal-to-Long lower facial heights, and increased anterior vertical dimension, frequently present with these associated concerns.
An important consideration in treatment planning in these cases is the effect of posterior extrusion. Extrusion of the posterior teeth increases the lower vertical dimension by rotating the mandible downward and backward thereby worsening an already excessive inter labial gap.
UPPER INCISOR DISPLAY Burstone was among the first orthodontists to emphasize the importance of describing the relationship of the upper incisors to the upper lip and the interlabial gap . Upper incisor display has been shown to decrease with maturity in the 40s and 50s as lip musculature actually loses its tonicity .The selection of alternative treatment options should take into account the patient's age
In a clinical situation where a patient's incisor display at rest (the distance of the upper incisal edge to the lower lip, or the incision-stomion distance) measures 3-4 mm with a deep overbite and a normal-to-long vertical dimenion, the treatment of choice may be intrusion of the lower incisors. In adult patients, intrusion of the upper incisors should only be planned if the incision-stomion distance is >3 mm. A vast number of these patients with deep overbite often benefit from lower incisor intrusion, as its display increases with age.
Both adolescent and adult Class II, Division 2 patients demand a very careful evaluation of the interlabial gap and incisor display. Some patients may exhibit a minimal interlabial gap, a redundant lip length, and an inverted lower lip. Careful consideration should be given when planning to increase the vertical dimension by extrusion of the posterior teeth with or without intrusion of the lower incisors. In adolescent patients, this treatment approach. often successful in part due to the overall growth and adaptation by the neuromuscular complex of the patient. In adults, this approach may be less successful without growth and the potentially reduced neuromuscular adaptive capacity
Evaluating a natural smile provides valuable information for planning deep overbite correction .The upper lip, upper incisors, gingival levels, and lower lip contour interrelate in an esthetic smile. The arc of the upper teeth should follow the curvature of the lower lip and the upper lip should be at or slightly above the upper gingival line Females frequently show more gingival on smiling than males. Planning deep overbite correction with these important esthetic considerations aids in determining appropriate individualized treatment goals.
Lip Length Upper lip length can also contribute to the overall dental esthetics of the patient at rest or smiling. A short upper lip may play a role in an excessive interlabial gap, the appearance of excessively long maxillary anterior crown lengths, or a gummy smile. Upper incisor intrusion is a valuable alternative for patients with deep overbite and a short upper lip.
The occlusal plane The occlusal plane essentially describes the dentition relative to the facial skeleton. The level and cant of the occlusal plane can be identified from a lateral cephalometric analysis The level of the occlusal plane describes its vertical position and the cant describes its angle, usually relative to the horizontal reference (i.e. Frankfort horizontal) . Additionally, there may be steps between the anterior and posterior teeth within the occlusal plane . These considerations may impact on treatment planning for deep overbite correction.
One common presentation of deep overbite malocclusions is an excessive curve of Spee. The upper and lower occlusal planes are parallel and a step or exaggerated curve exists between the canine and first premolar.
Indiscriminate leveling of these arches may result in the undesirable effect of creating upper and lower occlusal planes that converge toward the anterior without adequate overbite correction. These convergent occlusal planes may be more difficult to correct than the original problem.
Skeletal Considerations Three skeletal considerations can significantly affect the outcome of overbite correction in patients: vertical dimension; anteroposterie'r relationship of the maxilla to the mandible; and in younger patients, the amount 0f growth remaining and its direction . Extrusion of the posterior teeth can affect the skeletal vertical dimension and soft tissue appearance. The approximate average of the anterior upper facial height ratio [N-ANS] lower facial height [ANS-Me] is 45-55%. Extrusion is contraindicated in patiems with excessive lower facial heights. The increased tooth eruption tends to promote downward and backward mandibular rotation Pure intrusion of the anterior teeth allows a correction of the malocclusion without detriment. skeletofacial side effects.
In brachyfacial (short face) patients with deep overbile malocclusions, increasing the vertical dimension through posterior extrusion may be advised. It is importam to consider function in these patients as a strong musculature increases the risk of post-treatment relapse. Slow correction during growth may allow the masticatory muscles to adopt to the treatment changes
Treatment Strategies for Correction of Deep Bite Intrusion of Incisors
Intrusion of upper and/or lower incisors is a desirable method to correct deep bite in many adolescent and adult patient. Intrusion of incisors is most reliably accomplished if a pure intrusive force is applied to the incisors. Intrusion is particularly indicated in deep bite patients with a large vertical dimension, excessive incision-stomion distance, and a large interlabial gap. The four most common methods to facilitate intrusion of the upper incisors have been described by Burstone, Begg and Keeling Ricketts, and Greig. All four designs apply tipback bands at the molars to provide an intrusive force at the incisors. The wire size, material, method of attachment to the brackets, and the application of torque in these four techniques are diverse, but all recognize the need for a light and continuous force application.
Intrusion Arch Biomechanics Burstone first described intrusion arch mechanics as part of the segmented arch technique. Intrusion refers to the apical movement of the geometric center of the root (centroid) in respect to the occlusal plane or a plane based on the long axis of the tooth. Until 1980, intrusion arches were made of stainless steel wires with helical springs in front of the molars to reduce the load deflection rate. In 1980, beta-titanium alloys replaced stainless steel, eliminating the need for a helical spring due to the titanium wire's lower stiffness. Preformed nickel-titanium wires (Connecticut Intrusion Arch)were introduced in 1998. These preactivated and precalibrated wires deliver a force of 3545 g (the force depends on the distance between the molars and incisors). Each alloy remains an alternative for the fabrication of intrusion arches.
A major objective of using auxiliary springs, such as an intrusion arch, is the improved control of the applied forces, both relative to the qualitative and quantitative force systems. The design of the intrusion arch allows accurate prediction of the directions of the forces that the springs exert on the teeth. Springs of this design are statically determinant, i.e. it is possible to measure the magnitude of all the forces produced by their activation. The vertical intrusive force on the incisors is balanced by an equal but opposite extrusive force at the molar tube. These two forces produce an "interbracket" couple which is opposed by an "intrabracket" couple of equal magnitude but in an opposite direction at the molar tube.
The following biomechanic factors are important in understanding intrusive mechanics: 1. Magnitude of force 2. Force constancy/load deflection rate 3. Point of force application 4. Molar tipback moment.
Magnitude of Force
Intrusive tooth movements appear to occur most effectively with low force magnitudes. This may be due to both the nature of the stresses acting on the periodontal ligament as well as the concentration of the stresses at the apices of the teeth. Lower force magnitudes also reduce the strength of the tipback moment acting on the molar or posterior segment. If the magnitudes of force are too great, the rate of intrusion will not increase and the rate of root resorption will increase .
Generally, it is recommended that canines are intruded separately. Induding canines into a maxillary anterior segment requires an increase in the applied intrusion force. The reciprocal extrusive force on the molars and the increased tipback moment may result in undesirable side effects. Separate canine intrusion may be readily achieved with the use of cantilever springs
Force Constancy/Load Deflection Rate Compared to conventional/continuous wire activations, segmented springs exert forces in a range greater than the intended tooth movement The deflection of the spring engaging it to the incisors exceeds the amount of overbite correction. This feature both reduces the magnitude of the applied force and improves its constancy. A more continuous, low force allows increased time intervals between adjustments and may be gentler on the responding tissues.
Springs that deliver relatively constant force have low loaddeflection rates. An intrusive arch with a 30 mm. arm (perpendicular distance from the incisor to the first molar) has a load-deflection rate of 6 Gm. per millimeter . If this intrusive arch is activated 16.5 mm., 100 Gm. of force is produced in the midline, 50 Gm per side. As the incisors intrude 1 mm., there is a change of force magnitude of only 6 Gm.; hence, the delivery of force is relatively constant. By contrast, high load-deflection mechanisms, such as some of the loops that are tried for intrusion, are activated only just a few millimeters; accordingly, the drop off of force is very dramatic for every millimeter of tooth movement.
Anterior single point contacts The intrusive arch is not placed directly into the brackets of the anterior teeth. The major reason who one avoids bracket engagement of the intrusive spring is that, inadvertently, anterior torque may be present in the arch. Even if no torque is present, as the intrusive arch works out, torque can be introduced. If, purposely or inadvertently, labial root torque is placed into the incisors, the intrusive forces are increased on the anterior teeth; this added intrusive force is not needed and can produce anchorage loss of the posterior teeth.
The advantage of not tying an intrusive arch directly into the incisor brackets is that it allows the clinician to know more positively the force system delivered. By having a single point of force application on the incisors, one knows the full force system acting at both the incisor point and the buccal tubes. A system of this type is described as being statically determinant. Placing the intrusive arch into the brackets produces a statically indeterminant system which prevents the orthodontist from knowing exactly what type of force he is delivering
Point of Force Application An essential feature of an intrusion arch is that it applies force via a point in contact with the incisors. Therefore ,the expected clinical actions may be understood by assessing the applied force vector. Force magnitude, line of action, and origin are three key features of vectors. Each feature is important in understanding the clinical effects.
The point of force application and the direction of the line of action determine the tendency for the force to produce rotational movement. An applied force with a line of action passing through the center of resistance of the tooth produces pure bodily movement. the intrusive force passes through the center of resistance, the moment of the force is zero. With no moment, there would be a vertical movement without any change in the axial inclination of the tooth
The point of force application for intrusion is most often at the central incisor brackets. A pure vertical force vector passes anterior to the center of resistance of the incisors. The effect of this force vector on the incisor is both an upward movement and a crown-labial/root apex lingual rotation due to the moment of this force. Although there is no "applied torque," the expected tooth movement has a rotational component
the intrusion force would be expected to move the incisor gingivally and to simultaneously flare it. Flaring is a result of the moment of the force. The amount of flaring depends on the magnitude of the moment, which is the product of the force magnitude times the distance of the line of action to the tooth's center of resistance.
When incisors are severely flared, the large distance between the line of force and the center of resistance causes a much larger moment on the incisors, causing further undesirable flaring
the severely upright incisor the intrusive force passes lingual to the center of resistance, producing a small moment with a crownlingual/root-labial direction. Rather than flaring the incisors, the force would tend to increase their uprightness These figures illustrate the ways that the same spring produces different clinical effects depending on the specific circumstances of its use. The point of force application is determined by selecting the appropriate tie-in point
The line of action of the intrusive force is a function of the spring's activation. To vary the line of force, applying additional force(s) is necessary. In most cases, this is a distally directed force. Combining a distal component of force to the intrusion arch alters the force by producing a resultant force . Clinically, the distal force can be produced in several ways. A small distal force may be applied by cinchback of the intrusion arch in the molar tube(A). The cinchback minimizes the potential for the overjet to increase by fixing the point of rotation of the intrusion arch . Spring Without the cinchback(B), the intrusion arch is free to slide forward, with the potential for increased expression of the incisor flaring .
An additional distal force is applied to the incisors, producing a resultant force vector that follows the long axis of the tooth. This light distal force redirects the line of action and results in an intrusive effect along the long axis of the incisor. A combination of deep overbite correction and overjet reduction can be achieved at the same time.
Molar Tipback Moment(CONTROL OF THE REACTIVE UNIT)
An intrusion arch also applies forces to the molars. An extrusive force on the molar balances the intrusive incisor force. Additionally, the spring delivers a tip back moment on the molar. The magnitude of this moment is calculated by multiplying the distance between the molar tube and the point of attachment at the incisors. The span between these points varies based on the clinical situation, but frequently ranges between 25 and 40 mm. With an intrusive force of 40 g, the tipback moment acting on the molars may range from 1000 to 1600 g-mmm
The moment magnitude is sufficient to produce a significant amount of distal molar movement This tip back moment aids in the correction of Class II molar relationships. Following tip back, molar up righting and distal root movement can be achieved with the use of a highpull headgear. Another approach is to use successively stiffer arch wires for molar up righting; however, this approach may be less predictable in maintaining the Class I molar relationships
In Class I deep overbite problems, molar tipback is usually unnecessary and unwanted. Increasing the number of teeth in the posterior anchorage unit (first molar to first premolar) with passive heavy segments helps reduce the posterior effects of the intrusion arch Two methods of boosting anchorage with the use of intrusion arches are 1. highpull headgear and 2. increasing the number of teeth in the anchor unit
In Class I patients with deep bite, posterior anchorage can be maintained by using as many teeth as possible in the buccal segment. Distributing the extrusive and tipback forces over a large unit of teeth tends to lessen the amount of anchor movement and other unwanted side effects. A passive palatal arch further enhances the anchorage control.
Occipital headgear can be used in the upper arch, designed so that its force is anterior to the center of resistance . The headgear produces a moment opposite to the moment produced by the intrusive arch and thus prevents the steepening of the maxillary plane of occlusion. With an intrusive force on the incisors, there is an equal and opposite extrusive force on the molars. Since the extrusive force is operating buccally at a tube, it can be seen that a moment is created that tends to tip the crowns lingually and the roots buccally. One of the functions of the lingual arch is to prevent any undesirable change in axial inclination of the molars or change in width. Lingual arches are not only helpful during the stage of intrusion, but they also help resist side effects at almost any stage of treatment.
Canine intrusion It is usually not possible to intrude all six anterior teeth at one time without producing undesirable axial inclination change in the posterior segment. Using the suggested force values, typically 100 Gm. of force on a side is required to intrude the incisors and the canines. shows that 100 Gm. would produce a moment of 3,000 Gm.mm. to the posterior segment if the perpendicular distance from the incisors to the center of resistance of the posterior segment was 30 mm. Since moments of this magnitude are most effective, tipping of the posterior teeth will occur more rapidly than the intrusion, and since this tipping is not required, intrusion mechanics will not be successful.
If the posterior segment were backed up with an occipital headgear in the maxillary arch, it is possible to eliminate this undesirable moment as well as the eruptive force on the posterior teeth. Without excellent cooperation from the patient in the wearing of headgear, intrusion of six anterior teeth simultaneously should not be attempted.
In patients with deep overbite it is usually a mistake to level and extrude infra erupted canines. Many of these canines should be left in their original position and the incisors should be intruded to their level. A canine-intrusion spring which is activated to produce 50 to 75 Gm. of force, it is fabricated from 0.018 by 0.025 inch wire inserted into the auxiliary tube of the first molar and into the vertical tube of a canine bracket. Since the intrusive force lies lateral to the center of resistance of the canine, it is necessary to place a slight constrictive force in the spring to keep the canine from flaring labially
Three piece Intrusion Arches Three piece intrusion arches can achieve deep overbite correction and close extraction spaces simultaneously Appliance design Treatment is initiated by aligning the teeth included in the right and the left posterior segments.. transpalatal arch placed between the first maxillary molars.. The position of the center of resistance of the anterior teeth may be estimated on a lateral cephalometric x-ray film..
A heavy stainless steel segment (0.018 Â´ 0.025 or larger) with distal extensions below the center of resistance of the anterior teeth is placed passively in the anterior brackets. The distal extensions end 2 to 3 mm distal to the center of resistance of the anterior segment. The intrusive force is applied with a 0.017 Â´ 0.025 TMA tip-back spring Distal force delivered by a Class I elastic to the anterior segment is used to alter the direction of the intrusive force on the anterior segment.
An intrusive force applied through the center of resistance of the anterior teeth will intrude the incisor segment. It is possible to change the direction of the net intrusive force by applying a small distal force. The line of action of the resultant force will be lingual to the center of resistance and a combination of intrusion and tip back of the anterior teeth will occur.. To obtain a line of action of the intrusive force through the center of resistance and parallel to the long axis of the incisors, the point of force application must distal of the lateral incisor bracket as possible.
If the intrusive force is placed farther distally and an appropriate small distal force is applied intrusion and simultaneous retraction of the anterior teeth occurs because of the tip back (clockwise) moment created around the center of resistance of the anterior segment consisting of four incisors. .
When intrusion-retraction mechanics are initiated, the anterior teeth will intrude and tip back with progressive space closure the between the incisors and the canines. Distal movement of canines may occur as the anterior segment contacts the canines. It is also possible to retract the canines individually and to include them in the buccal stabilizing segment of wire before the initiation of intrusion-retraction mechanics. Redirection and movement of the intrusive force distally reduces the moment on the buccal segment of teeth, and thus reduces the tendency for its natural plane of occlusion to steepen. Headgear is not usually required for anchorage control, since a net tip back moment is applied to the posterior segment.
Rickets utility arch Principles of overbite control The use of lighter forces cuspids can be retracted with forces of 75-100 grams and clinical observations have shown that all four lower incisors can be intruded with a force of only 60-80 grams, or 20 grams per tooth. Upper incisors, being twice as large as the lower incisors in cross-section, require 160-200 grams for their intrusion. When a reverse curve of Spee to level forces almost 10 times as high as those recommended are currently being used. A force of 400 grams is measured when a .014 round wire is ligated into the lateral incisor brackets
A force of 300 grams is measured at the lower incisor bracket when a â€œreverse-curved archwireâ€? is tied in through the buccal occlusion to the cuspids.. These heavier forces physically squeeze out the blood supply to the area and limit the biological response so necessary to the physiological alteration of the bone and the efficient movement of the teeth. In order to lessen the force being delivered to a single tooth or group of teeth the concept of a long lever arm is applied by placing more wire between the teeth the applied force is lowered and the length of time of activation is increased. Thus, the concept of lighter continuous forces that support rather than limit the necessary physiology for efficient tooth movement is presented.
Torque control As the arches are segmented and the buccal occlusion is sectioned from the incisors, very light continuous forces can be directed to the incisors through the long lever arm created by the utility arch, which spans from the molars to the incisors, bypassing the bicuspids and cuspids. Segmented arches allow the molars to be stabilized and supported by the bicuspids and cuspids against the torquing movement directed to the molars by the intrusion action of the long-levered utility spanning arch. Class II elastic force is less when directed against the upper buccal segmented arch rather than a full upper arch and, therefore, produces less strain on the supporting lower arch anchorage. At the same time that the upper buccal occlusion is being aligned, the upper incisor positioning can occur through the utility arch action, where incisor intrusion, retraction or torquing may be necessary.
Problems in continuous arch wires Efficient lower incisor intrusion suggests that the roots be torqued buccally to avoid the supporting lingual cortical bone, while the roots of the cuspids around the corner of the arch also be torqued buccally to avoid the cortical bone on their lingual surface. These movements are very difficult to effect by traditional full arch round wire leveling. Round wire rolls the incisor crowns down and forward, tipping their roots lingually against the denser cortical bone, thus limiting their effective intrusion. The cuspid roots around the corner on a continuous arch are being tipped distally, which limits their intrusion and arch leveling action. The molars on round wire are often rolled mesially and upright away from their buccal cortical bone anchorage support.
Segmented arch treatment allows us to torque the lower incisor roots away from the lingual cortical bone which aids in their intrusion, and the cuspids can then be intruded separately along a route of least resistance and still maintain molar torque and rotational control for anchorage support. Full arch treatment attempts to influence the incisor movements through the cuspids around the corner, but since the cuspids are in a different vertical plane of bony support because of their corner position, it becomes difficult if not impossible to design mechanics through the corner support and still direct proper incisor movements and keep the correct cuspid control. Efficient incisor intrusion is almost impossible on a continuous arch through the cuspids.
Less friction and arch wire binding. The upper cuspids or other teeth are limited in their movement , they first must overcome the friction and binding force of the bracket in order to be moved along an archwire. Sectional arch treatment allows the cuspid to move more freely without the binding effect of sliding around a continuous archwire. A segmented arch applied to the cuspids only, reduces the friction even more on the short segment and allows for its efficient retraction.
Appliance design 1) 30째 to 45째 Tip-back Applied to the Lower Molars. tip-back applied singularly to the lower molars will upright these teeth bringing their roots mesially (the lower molar will tip around a center of resistance near the top of its mesial root) and the crown distally. Since the lower molar is supported on the buccal by a heavy cortical plate and at the distal by the lower second molars, the most usual movement of this tooth with a straight uprighting force is a distal rotation.
2) 30째 to 45째 Buccal Root Torque Applied to the Lower Molar. Since the lower molar cannot differentiate between buccal root torque and lingual crown torque when a 45째 buccal root torque is placed on the distal legs of the utility arch, the amount of movement of the root to the buccal is proportionate to the amount of movement of the crown to the lingual. The only way that buccal root torque can be expressed by buccal movement of the root and stabilization of the crown is by expansion of the arch . it is important that the distal legs of the utility arch be generously expanded prior to placement in the mouth.
3) Long Lever Arms Applied to the Lower Incisors.
When a long lever arm works off of the lower molars, the effect at the lower incisors is a change in torque. If, at placement, there is 0° torque at the lower incisors, as the arch intrudes (moves gingivally on its arc from the molar) there is a slow progressive change to place a labial crown torque (or lingual root torque) on the lower incisors In those cases where the lower incisor is proclined more labially (such as the double protrusion), straight downward pressures to intrude the lower incisors will quite often end up tipping these teeth even further labially. The most efficient intrusion of the lower incisors— or any tooth, for that matter— is when intrusive force applied is parallel to the long axis of the tooth. In most cases, a slight labial root torque (5° to 10°) will free the apex of the lower incisor teeth from the lingual planum and allow its intrusion without labial flaring. Cephalometric appraisal of the symphysis size and form as well as the inclination and support of the lower incisor is critical in the intrusive management of the lower incisor teeth . .
4) 75 Grams of Intrusive Force Applied to the Lower Incisors.
The mandibular utility arch is best fabricated from .016 by.016 Blue Elgiloy wire in order to create a lever system that will deliver a continuous force to the lower incisors in the range of 50 to 75 grams. The design of the mandibular utility arch is dictated by the requirement that this light force be delivered in a continuous manner off of a long lever arm from the molar to the incisors.
The arch is stepped down at the molar, lies in the buccal vestibule, and is stepped back up at the incisors to avoid interference from the forces of occlusion that would distort it. This buccal bridge section is flared slightly buccally to prevent tissue irritation opposite the vertical steps as the arch approaches the tissue and the incisor teeth are intruded. Although the mandibular utility arch is a continuous arch from molar to molar, it should be considered a sectional arch in its function. Each molar is treated separately as to torque, tipback, and rotation, as are the buccal segments, as well as the lower incisors .
Cuspid Intrusion In approximately 50 percent of the deep bite cases, the lower canines must also be intruded slightly to bring them to the level of the functioning buccal occlusion. This is normally accomplished by lightly tying these teeth to the stabilizing utility arch with an elastic thread ,to keep the elastic thread from sliding along the utility arch, a small vertical loop is pinched into the wire (this can be done intraorally with a large three-prong plier). This elastic thread is brought around the vertical loop and tied prior to encircling the cuspid bracket. The elastic thread should completely encircle the cuspid bracket and a knot tied behind the base of the bracket so that it does not irritate the buccal mucosa. Normal intrusion time for the lower cuspids should be no more than one month.
K-SIR APPLIANCE An appliance for simultaneous intrusion and retraction of the six anterior teeth The K-SIR (Kalra Simultaneous Intrusion and Retraction) archwire is a modification of the segmented loop mechanics of Burstone and Nanda. It is a continuous . 019” ´ .025” TMA archwire with closed 7mm ´ 2mm Uloops at the extraction sites .
To obtain bodily movement and prevent tipping of the teeth into the extraction spaces, a 90째 V-bend is placed in the archwire at the level of each U-loop . This V-bend, when centered between the first molar and canine during space closure, creates two equal and opposite moments to counter the moments caused by the activation forces of the closing loops
â€˘ A 60Â° V-bend located posterior to the center of the interbracket distance produces an increased clockwise moment on the first molar, which augments molar anchorage as well as the intrusion of the anterior teeth
To prevent the buccal segments from rolling mesiolingually due to the force produced by the loop activation, a 20째 antirotation bend is placed in the archwire just distal to each U-loop .
Activation A trial activation of the archwire is performed outside the mouth . This trial activation releases the stress built up from bending the wire and thus reduces the severity of the V-bends . After the trial activation, the neutral position of the each loop is determined with the legs extended horizontally . In neutral position, the U-loop will be about 3.5mm wide. The archwire is inserted into the auxiliary tubes of the first molars and engaged in the six anterior brackets . It is activated about 3mm, so that the mesial and distal legs of the loops are barely apart .
The second premolars are bypassed to increase the interbracket distance between the two ends of attachment. This allows the clinician to utilize the mechanics of the off-center V-bend.
When the loops are first activated, the tipping moments generated by the retraction force will be greater than the opposing moments produced by the V-bends in the archwire. This will initially cause controlled tipping of the teeth into the extraction sites. As the loops deactivate and the force decreases, the momentto-force ratio will increase to cause first bodily and then root movement of the teeth. The archwire should therefore not be reactivated at short intervals, but only every six to eight weeks until all space has been closed.
Control of Reactive Forces Off-center V-bends will generate an extrusive force on the molars, which is usually undesirable. One of the keys to preventing unwanted side effects of an appliance is to keep the reactive forces at a minimum while exerting an optimum level of force on the teeth to be moved. The K-SIR archwire exerts about 125g of intrusive force on the anterior segment and a similar amount of extrusive force distributed between the two buccal segmentsâ€”generally the first permanent molars and the second premolars, connected by segments of TMA wire . The force of 125g is effective for intrusion of the anterior teeth, while the reactive extrusive force on the buccal segments is countered by the forces of occlusion and mastication.
Another way to reduce the effects of the reactive force is to add teeth to the anchorage unit. Including the second molar, also increase anchorage in the anteroposterior direction. If even more anchorage is needed to resist both anterior movement and the extrusive force on the buccal segments, a high-pull headgear can be added to the molars. In practice
Indications The main indication for the K-SIR archwire is for the retraction of anterior teeth in a first-premolar extraction patient who has a deep overbite and excessive overjet, and who requires both intrusion of the anterior teeth and maximum molar anchorage. Due to the frictionless mechanics used for space closure in this system and the presence of the off-center V-bend, which acts like an anchor bend, molar anchorage control is excellent, even without headgear. The clinician is thus less dependent on patient cooperation for a successful result in a maximum anchorage situation.
THE CONNECTICUT INTRUSION ARCH . Appliance Design The CTA is fabricated from a nickel titanium alloy to provide the advantages of shape memory, springback, and light, continuous force distribution. It incorporates the characteristics of the utility arch as well as those of the conventional intrusion arch. The CTA is preformed with the appropriate bends necessary for easy insertion and use
Two wire sizes are available: .016” ´ .022” and .017” ´ .025”. The maxillary and mandibular versions have anterior dimensions of 34mm and 28mm, respectively The CTA’s basic mechanism for force delivery is a V-bend calibrated to deliver approximately 40-60g of force . The V-bend mesial to the molars corrects a Class II molar relationship by tipping the molars distally. In patients with upright or lingually inclined incisors, the CTA can be used to flare the incisors without any side effects on adjacent teeth
Modification of Lingual Arch For Deep bite Developed by Winston Senior Many mechanical systems have been described for intrusion of the lower incisors. reverse curve of Spee, and sectional arch inserted in double buccal molar tubes.. Both systems apply pressure to the labial surfaces of the lower incisors, creating a downward force vector that passes anterior to the incisorsâ€™ center of resistance. This causes the crowns of the lower incisors to procline labially and the roots to impinge on the planum alveolareâ€”the cortical bone on the posterior aspect of the symphysis. An illusion is created that the incisal edges are intruding when, in fact, they are merely tipping labially. To counteract this tendency,
Appliance Design An .036â€? lower lingual arch is soldered to first molar bands. Distal extensions form occlusal rests on the second molars to prevent distal tipping of the first molars as the incisors are intruded .Four elastic chains are attached to the anterior bridge of the lingual arch with a mosquito forceps If intrusion is the primary goal and the teeth are already fairly upright, the elastic chains should come off the lingual arch on the labial side . If the priority is to retrocline the lower incisors, the elastics should come off on the lingual side. This will reduce the risk of the root apices impinging on the planum alveolare. After cementation of the arch, the elastics are stretched to four lingual buttons on the lower incisors
Preadjusted Appliance Using Sliding Mechanics Principles of overbite control Deep overbite can be effectively controlled with preadjusted appliance when the following principles are observed .Avoid extraction in low-angled cases whenever possible A non extraction approach seems to be the most effective for controlling deep bite on low angled cases with a maxillomandibular angle of less than 25Ëš.overbite control is a result of leveling and aligning as a result of up righting and slight extrusion of the posterior teeth. If the teeth are extracted overbite control becomes difficult because of the strong muscle forces that impedes the ability of the posterior teeth to move forward. As the extraction sites are closed the anterior teeth tend to upright and move posteriorly and bite will further deepen.
Great care must be taken to maintain the torque control during retraction. cases where extraction are indicated such as severe proclination and crowding leveling and aligning and space closure should be done with light forces to avoid bite opening .. Use bite planes at he beginning of treatment in moderate to low angle cases . Band or bracket the second molar as early as possible. Complete leveling of the curve of spee is not possible without banding the molars
Avoid elastic retraction of the cuspid -with pre adjusted system the tip built into the cuspid and incisor brackets causes the teeth to tip anteriorly upon initial wire placement. When this tendency is counteracted with by early application of even the lightest elastic forces the cuspids are tipped distally the overbite deepens and the posterior bite opens. this roller coaster effect invariably results in extended treatment time. Inorder to prevent this lace backs are given. if the cuspids are unfavourably positioned incisors are not included in the arch until the cuspid are retracted and a leveled cuspid slot is achieved
use of .022 slot with.019 x .025 working arch wires with bite opening curves use class II elastics selectively., the premature use of class II elastics for instance in round wire leveling stage can lead to bite deepening and to excessive interference between the advancing lower incisors and the retracting upper incisors and distal displacement of the condyle
Extrusion of posterior teeth Extrusion of posterior teeth is one of the most common methods to correct deep overbite This can be an efficacious method of bite opening. One millimeter of upper or lower molar extrusion effectively reduces the incisor overlap by 1.5-2.5mm
Extrusion of posterior teeth is indicated in patients with short lower facial height, excessive curve of Spee, moderate-to-minimal incisor display.
The stability of posterior extrusion may be questionable in non growing patients. For patients with long lower facial heights, excessive incisor display, or over eruption of upper incisors, true incisor intrusion is indicated. The major disadvantages of correcting deep overbite by extrusion are an excessive incisor display, an increase in the inter labial gap, and worsening of a gingival smile
A very common method to extrude posterior teeth in patients with a deep curve of Spee is to level the arches with the sequential use of straight continuous archwires.( Droschl H AJO96) A close variation of this technique is to use mandibular reverse curve of Spee and/or maxillary exaggerated curve of Spee wires. Other common treatment options include the use of a bite plate, which allows the posterior teeth to erupt, thereby reducing the overbite. These approaches to deep overbite correction have been advocated for several decades. In 1921 Case described the conection of "closed bites" and showed the use of removable bite planes to allow eruption of posterior teeth. Later, Case used a rigid posterior fixture on crowns to eliminate the use of a removable appliance He also used a reverse curve of Spee wire to extrude bicuspids to open the bite.
Deep overbite correction by erupting the posterior teeth occurs fairly rapidly (the eruption of teeth occurs so much faster than intrusion of teeth). \ The choice of which eruptive mechanism to use depends on the choice of a CRot. The posterior teeth can usually be leveled about several centers of rotation, depending on the amount of required arch length.
1. 2. 3. 4.
Tip-back mechanism. Base arch mechanism. 0.016-inch distal extension. Parallel eruption of the buccal segment
The indications for the use of a tip-back mechanism are as follows: 1. In growing patients with a forward growth rotation. 2. For a deep curve of Spee in the lower arch. 3. For a deep overbite. 4. For slight arch length inadequacy (1 to 2 mm per side). 5. For a steepened natural plane of occlusion.
The tip-back mechanism can be used when some arch length is required (1 to 2 mm). Sometimes a CRot is needed in which, as the buccal segment becomes upright, some arch length is gained anteriorly. Such as CRot is found at the distal most aspect of the lower second molar; as the buccal segment is uprighted, one notices space appearing between the first premolar and the canine (between 1 and 2 mm). The anterior portion of the tip-back spring consists of a hook that can be placed over the anterior segment of wire. As it is activated (hooked over the anterior segment), it produces a negative moment and an eruptive force to the buccal segment (prodcucing a CRot at the distal aspect of the root of the second molar).
The tip-back mechanism consists of 1. 0.036-inch lingual arch. 2. 0.018 x 0.025 inch anterior segment, which can sometimes be left long, distal to the cuspids. 3. Buccal stabilizing segments (BSS) of 0.018 x 0.025 inch from (ideally) 7-4, or any rectangular wire used for such as , 0.018x0.025inch SBS or 0.018x0.025 R â€“Loop or0.018x0.025 inch box loop 4. 0.018x0.025 inch tip back spring
The hook of the tip-back mechanism, made so that it can slide freely in an anteroposterior direction, can be placed strategically over the 0.018 x 0.025 inch SAS anterior segment. If, for example, the anterior segment has a normal axial inclination, the hook should be placed between the canine and the lateral incisor (the approximate location of the CRes of the anterior segment) One the other hand, if the lower anterior segment is slightly flared with the canines some-what higher than the incisors, the depressive force should be placed distal to the CRes of the anterior segment .
With the correct use of this tip-back mechanism, one will notice that 1. The CRot is placed distally, somewhere around the distal root of the second molar. 2. There is eruption and rotation of the buccal segments. 3. There is increased arch length distal to the canines (1 to 2 mm). 4. The second molar is often buried. 5. With the hook placed distal to the CRes of the anterior segment, the roots of the lower anterior segment often come forward, which is good, if one is flattening the plane of occlusion. 6. There is no flaring of the anterior teeth, because the hook is made to slide freely along the anterior segment wire.
The force values used are calculated on the basis that between 3,500 and 4,000 g-mm is required to erupt and rotate the buccal segments optimally. This is a moment of a force; the force can be calculated by knowing the distance from the CRes of the lower buccal segment (mesial to the lower first molar root for a four -tooth segment ) to the point of attachment on the anterior segment: 3,500 ____ = F L where L = the distance from the CRes of the buccal segment to the point of attachment on the anterior segment. The force can be adjusted using the Dontrix tension gauge.
Base Arch Mechanism The base arch (sometimes also called an intrusive arch) can also be used for extruding teeth in a deep overbite correction. The main difference between this applicance and the previous tip-back mechanism is in the location of the center of rotations. The buccal and anterior arch wires are identical to those of the tip-back mechanisam (0.018 x 0.025 inch buccal segments and an 0.016 inch or larger anterior segment from 3-3) and, the lingual arch wire is in place. .
The base arch mechanism is made from 0.018 x 0.025 inch stainless steel with helices , can also be fabricated from 0.017 x 0.025 inch TMA with no helices, or, instead, a washer can be crimped on or a shorter piece of wire can be welded on for a stop. When flaring of the anterior teeth is not indicated, a ligature can be passed through the helices to tie the base arch back .
The force system is nearly identical to that of the tip-back spring, except for the fact that there is no anterior hook free to slide anteroposteriorly; with the base arch tied back securely as , the CRot is moved mesially to somewhere close to the mesial root of the first molar.
0.016-inch Distal Extension Sometimes, in order to level a deep curve of Spee, both anterior and posterior segments need to be erupted and rotated . This eruption can be done with an appliance called the 0.016-inch distal extension. In order to use this appliance, there should be 1. Good growth increments remaining, since the appliance is eruptive. 2. A significant second-order discrepancy between the canines and the incisors; i.e., the incisors should be higher than the canines. 3. Minimal arch length required (2 to 3 mm per side). 4. A deep curve of Spee. 5. Extraction of teeth, usually the first premolars.
The appliance itself consists of 1. 0.018 x 0.025 inch base arch, with helices, but it may be made without them, especially in the newer, more flexible wires such as TMA are used. 2. 0.016-inch distal extension. Immediately mesial to the canine bracket a vertical loop is placed and immediately distal to the canine bracket a helix is placed. The distal extension can be adjusted to lie over the tie-wings of the second premolar bracket, or can be hooked over the buccal segment wire. 3. 0.036-inch lingual arch.
If one considers the effects of both appliances (the base arch and the 0.016-inch distal extension), one can see that both alpha (anterior) and beta (posterior) moments are produced when each respective arm is activated. If both are given equal and opposite preactivation bends , both anterior and posterior segments will erupt and rotate, (mesial root movement on the buccal segment and distal root movement on the anterior segment).
Fixed Biteplanes for Treatment of Deep Bite (simonJacksionJCO 96) Bite-opening procedures are usually instituted early in treatment, both to maximize patient cooperation and to allow anteroposterior tooth movements that might otherwise be hindered by the deep bite. Removable acrylic biteplanes are often used, especially in cases where eruption of the lower posterior teeth is needed Fixed biteplanes guarantee full-time wear. Patients therefore adjust to speaking with the appliances more quickly than with part-time acrylic biteplanes. With the opposing brackets protected against occlusal forces, fixed appliance therapy can be started immediately
Treatment of Deep Bite with Bonded Biteplanes(JULICN JCO96) Bonded biteplanes can be used in Class I and class II, division 1 and 2 cases for the correction of deep bite with moderate overjet. The shape of these biteplanes was inspired by that of the lingual orthodontic brackets designed by Kurz and others.
Bonded biteplanes simultaneously accomplish • Intrusion of maxillary incisors and canines • Intrusion of mandibular incisors and canines • Extrusion of maxillary molars • Extrusion of mandibular molars
The best time to use bonded biteplanes is at the end of the mixed dentition. The mandible is then unlocked from occlusion, so that its mobility and excursive capability increase greatly, and mandibular growth is no longer inhibited. Muscular equilibrium determines the appropriate balance of incisor intrusion and molar extrusion
Bonded Acrylic lignual Biteplanes(Ronald Madsen JCO 98) Acrylic extensions are bonded to the lingual surface of the maxillary incisors, producting an intrusive effect or growth restraint on the incisors while allowing the extrusion of the posterior teeth. Lingual biteplanes made of acrylic or composite resin can open the anterior bite and allow the posterior teeth to extrude.
Apical Root Resorption and Intrusive Tooth Movements Dermaut and DeMunck studied the relation between isolated intrusion and root resorption in the upper anterior teeth. Two radiographs were taken, one before the intrusion (but after alignment) and one after the intrusion. Thus, the observed resorption was limited to the resorption that occurred during the active intrusion period. The central and lateral incisors of the same quadrant were adjusted on a single intra-oral radiographic film in order to limit the patientâ€™s exposure to radiation. In this study a precise long cone radiographic technique was used. It was found that during orthodontic intrusion resorption of the upper incisors was obvious. No difference in resorption could be found between the central and lateral incisors.
Costopoulos and Nanda in a study on the effect of intrusion on root length showed that over a 4-month period of intrusion, root resorption was 0.6mm versus 0.2mm for controls. The amount of resorption was not found to be correlated with the amount of intrusion Goerigk andWehrbein used intrusion arches on 3 I patients for a mean treatment period of 4.3 months .An average intrusion of 2-3 mm and apical root resorption of 1.0 mm was found. Dermaut and De Munck used a modified Burstone intrusionarch with Begg brackets in 20 patients for an average of 6-7 months. The initial intrusion force on the maxillary incisors was 100 g. They showed an average intrusion of 3.6 mm with a mean apical resorption of 18% of root length
These studies confirm that lower force values provide a healthy biologic response. Based on the evidence, the risk of root resorption in response to a lower intrusion force does not appear to be any greater than with other types of orthodontic movement
FACTORS AFFECTING RELAPSE OF DEEP BITE CORRECTION In a study of 26 patients, Berg found relapse of 18.8% of the achieved deep bite correction. He also found more relapse of the deep bite in Class II, Division 2 cases. Hellekant and Lagerstrom reported a relapse of the dental deep bite in 19% of the cases . Simons and Joondeph found that proclanation of the incisors during orthodontics treatment may cause relapse of the corrected deep bite in the post retention period. They also found that clockwise rotation of the occlusal plane during treatment will go back toward its original cant, thereby causing relapse of the dental deep bite. Contrary to other authors who found more deep bite relapse in extraction cases, Simons and Joondeph, as well as Berg and Hellekant and Lagerstrom, could not find any difference between extraction and nonextraction cases in this regard.
McAlpine found that relapse of the deep bite was correlated with the interincisal angle and the lower anterior facial height. In case in interincisal angle of 125 to 130o was established, the chances of stable correction of a dental deep bite were found to be highest. Brachycephalic patients showed more relapse of the dental deep bite than others. Gordon found that intrusion of lower incisors in an attempt to correct a dental deep bite was prone to relapse in 33% of the cases. Bell and Hunt concluded that relapse of the overbite is primarily due to continued lower incisor eruption, retroclination of these teeth, and forward rotation of the mandible with continued growth.
Although Bench and co-workers reported that intrusion of lower incisors was much more difficult in patients with a narrow symphysis and easier in brachycephalic patients, Otto found that neither age nor facial type was statistically related to the amount of incisor intrusion. He also concluded that more external root changes during treatment are observed for adults than for growing children. Burzin and Nanda studied the stability of incisor intrusion in 26 patients 2.32 years post-treatment. The incisors were intruded an average of 2.30 mm and relapse was only 0.15 mm. The study concluded that the overbite correction by intrusion is a stable procedure.
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Published on May 5, 2014
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