From Volume 4, Issue 2, April 2011 | Pages 38-41
This paper aims to highlight the benefits of the use of double tubes on molar bands. The specific techniques that can be utilized during fixed appliance treatment are described. These techniques have the advantage of allowing a greater number of treatment mechanics to be used during treatment and therefore increasing treatment efficiency.
In the 1960s the introduction of double tubes on molar bands popularized highly effective mechanics developed by Burstone and Ricketts.1,2,3 The modern day pre-adjusted straight-wire operator generally favours single straight-wire molar tubes, unless an additional tube is required to accept a headgear facebow. The single straight-wire tube is less bulky than its double or triple counterpart but this advantage can be overshadowed when an additional tube is required to execute certain mechanics. This article presents rationale to stock upper and lower molar bands or bonds incorporating multiple tubes.
The stabilization arch is constructed in 0.016″ or 0.018″ round stainless steel wire. Posteriorly it passes through the accessory tubes and anteriorly it overlies the incisor brackets and is secured in place by the base archwire. The stabilization arch has multiple uses. As nickel titanium archwires can easily be distorted with the use of intermaxillary elastics, a popular use of the stabilization arch is to allow for the early use of Class II elastics whilst still in nickel titanium archwires (Figure 1). The anchorage bends mesial to the molar tubes and facilitates overbite reduction as well as assisting in reinforcing posterior anchorage. This technique enables the overbite and overjet to be addressed earlier in treatment thus decreasing the overall treatment time. Stabilization arches may also be used to maintain bite opening mechanics until a rigid base archwire may be used. Case 1 demonstrates the use of the stabilizer arch in the treatment of a Class II division II case with a deep overbite.
These bypass the premolar and canine teeth. They are based on the principle of uprighting and distal tipping of the molars, pitted against intrusion of the incisors. The use of double tubes allows these intrusion arches to be used at the same time as aligning wires. Figure 2 shows a Burstone arch, which is used to intrude the lower incisors. The posterior and anterior teeth are held together separately by sectional archwires following initial alignment. An intrusive force is then delivered by an 0.018″ × 0.025″ steel accessory arch which is attached posteriorly to an anchor molar via an accessory tube and anteriorly to the anterior teeth by ligatures. The segmented arch was designed to increase wire length so that relatively light constant forces could be delivered in an apical direction. Figure 3 shows a Rickett's utility arch, which is a 0.016″x 0.016″ round blue Elgiloy segmented arch that delivers light forces to reduce overbite by a combination of incisor intrusion and molar extrusion. A modified Rickett's utility arch can be constructed from 0.016″ × 0.016″ round Australian special wire, which is more resilient than the Elgiloy wire and therefore less susceptible to deformation when in use.
An E-arch is constructed from 0.9 mm–1.135 mm round wire bent into the shape of an expanded archform and inserted into the extra-oral traction tubes on the first molars.4 The arch can be used at any stage during treatment. It may be used to achieve active transverse expansion in the upper arch, to eliminate a buccal crossbite, or in the lower arch to correct a scissorbite. Occlusal interference, which may prevent correction of the transverse discrepancy, can be overcome with the use of dental cement on the occlusal surfaces of the posterior teeth. Additionally, the E-arch can be used to maintain expansion produced by other means (eg maintaining crossbite correction post rapid maxillary expansion (RME), whilst applying buccal root torque with a working archwire, may reduce relapse). An E-arch can also be contracted to contract the arch. The E-arch can be fabricated to rest in the buccal sulcus (Figure 4). This approach offers better aesthetics but may result in soft tissue trauma and can be removed by the patient. Alternatively, it may be simpler just to bend molar insets into the E-arch so that it overlies the base archwire. The E-arch can then be prevented from removal by securing it with a stainless steel ligature (Figure 5). Case 2 demonstrates the use of the E-arch to maintain maxillary expansion following RME during the application of buccal root torque to the upper buccal segments.
A step down bend may be placed in the working archwire mesial to the molar tube so that the archwire passes through the accessory tube. Using the larger accessory tube rather than the straight-wire tube means that the friction is significantly reduced (Figure 6). This approach may slightly intrude the molar which may be useful in avoiding cuspal contacts during space closure. The archwire should be slightly expanded as the lower molars can roll lingually, but these can be uprighted once the more difficult task of space closure has been achieved. Case 3 demonstrates the enhanced space closure achieved with this technique.
The additional molar tube can be used in conventional piggy-back mechanics for aligning displaced teeth. A stainless steel base archwire occupies the straight-wire molar tube, whilst the flexible (usually 0.012″ or 0.014″ round NiTi) wire applying traction to the displaced tooth extends posteriorly through the accessory tube. A piggy-back approach can also be used to align second molars once space closure has been completed. The stainless steel working archwire is bent to pass through the accessory tube to maintain a rigid arch whilst a 0.014″ round NiTi archwire passes through the molar tube on the first molar to pick up the second molar (Figure 7). Case 4 demonstrates the advantage of this technique, which allows the simultaneous alignment of the second molars and the continued use of the rigid working archwires.
The Begg and Tip-Edge techniques5 also use the accessory tube in stage I as a means of overbite reduction and molar anchorage and this maximizes the effect of the reduced friction in the larger diameter gingival tube. Gingival accessory tubes are preferable to prevent the anchor bends from being bitten out by occlusal forces. In stage III of the Tip-Edge Plus technique, the NiTi auxiliary wire is inserted into the gingival tube to permit mesial root uprighting of the second premolar in first premolar extraction cases.
Lip bumpers are removable arches inserted into the accessory tubes of the lower first molars (Figure 8). They are used predominantly in the mixed dentition to increase or maintain lower arch length. The action of the lip bumper uses the force of the lower lip to tip back the molars. Anteriorly, the wire lies 2–3 mm in front of the incisor teeth. In order to increase the distal tipping force on the molars, the wire should be positioned more incisally. If the anterior section lies at the middle of the incisor crown, increased labial movement of the incisors will occur. Incisor position can be stabilized by placing the lip bumper at gingival level to enable the lower lip to rest over the lip bumper and contact the incisal edges. In more crowded cases, the anterior section of the arch may have an acrylic shield. The buccal section of the arch should be 4–5 mm from the premolars for non-extraction treatment where expansion is desirable. U-loops mesial to the accessory tubes function as stops and permit sagittal and vertical adjustment. The arch may be constructed either in the laboratory or at the chairside from 0.9–1.45 mm hard stainless steel wire. However, if a buccal shield is required then laboratory input is necessary. In Class II cases, lip bumpers should be used in conjunction with headgear in the maxillary arch as distal tipping of the lower first molars will worsen the Class II relationship. In compliant patients, the lip bumper can be removed by the patient to assist with oral hygiene.
Multiple molar tubes offer the orthodontist a greater range of treatment mechanics to treat challenging cases. Foresight is more beneficial than hindsight and it is preferable to fit multiple molar tubes from the onset than regret the decision later on in treatment.
