Orthodontic Treatment of Impacted Teeth. Adrian Becker

Fig. 2.3 As the impacted tooth is about to erupt, the high‐profile Siamese edgewise bracket has fenestrated the swollen gingival tissue.

      As the displaced tooth moves towards its place in the arch, exuberant gingival tissue bunches up in front of it, leading to a confrontation with a conventional orthodontic bracket. The existence of the exuberant gingival tissue in advance of the tooth can often cause ‘pinching’ between this tissue and the teeth in the arch immediately adjacent to it. This is less likely to occur if a deliberately generous space has been previously provided in the arch for the tooth. Such a precaution may avoid unnecessary periodontal damage.

      A simple eyelet or button

An eyelet, welded to orthodontic bond material with a mesh backing (Figure 2.4), is soft and easy to contour, enabling its adaptation to the bonding surface to be more intimate and retentive. Its relatively small size and low profile make the mid‐buccal position of several of the more awkwardly placed teeth considerably more accessible as compared with the placing of a conventional bracket. Its modest dimensions are also less of an irritant to the surrounding tissues, particularly during the critical phase as it breaks through gingival tissues in the final stages of its eruption into the oral cavity [15].

Fig. 2.4 Eyelets welded to a pliable band material base, backed by steel mesh.

      The need to properly adapt the base of the attachment to the shape of the recipient surface of the crown of the tooth cannot be over‐emphasized. Thus, the use of standard brackets with ‘anatomic’ bases, as supplied by the manufacturer, has been shown [14] to fare considerably better in the mid‐buccal position of the impacted tooth (80.6%) than on any other surface, particularly the palatal surface. The chances of the survival on a palatal site were shown to be 58.3% – i.e. a failure rate of almost 1 in 2. By comparison, a small attachment (such as an eyelet) on a pliable base, properly and individually adapted to the form of the recipient site, which demonstrated a 96.7% level of reliability against detachment, will allow the orthodontist to work with the greatest degree of confidence.

      A button is useful for engaging elastic chains and is usually placed on the lingual side of a tooth in circumstances where rotation of the tooth is required. However, it is also suitable in the present context.

      For these reasons, small eyelets and buttons are recommended as the initial attachment, which is placed at the time of surgery and removed only when the tooth has progressed to the point where it is in close proximity to the archwire. At that point in time, they should be replaced by the same type of sophisticated bracket that is being used on the other teeth, thereby initiating the more intricate root manipulations of the tooth (rotating, uprighting and torqueing). Also at this point, the impaction will have been treated and there will be no ectopically displaced teeth. All the teeth will be located close to the line of the arches, forming what would otherwise constitute a typical pre‐orthodontic scenario. Elsewhere in this book I have called this environment the ‘orthodontic ballpark’, because the case will have now become a routine orthodontic case.

Intermediaries/connectors

We shall see in Chapter 4 and again in Chapters 6 and 7 that there are important periodontal advantages to be gained by full closure of the surgical flap at the end of the visit at which the surgical exposure is performed [15]. The impacted tooth will have been re‐covered by the surgical flap and will be lost from sight, unless the impacted tooth is fairly superficially placed. The only manner in which contact may be maintained with it is through some form of physical connection, such as a ligature wire, gold chain or elastic thread, which was attached to the eyelet before or immediately after it was bonded to the tooth. These may be termed intermediaries or connectors.

      Since elastic thread can only be tied once, it is not recommended to be used as an intermediary. Gold chain has found a surprising degree of acclaim and acceptance worldwide because it is undoubtedly suitable and sufficiently strong to serve as an intermediary. However, it is unnecessarily sophisticated, expensive and not widely available. There is also one practical drawback to its use, which relates to its physical properties. If a closed surgical approach is used after bonding of its attachment base to a tooth, the end of the chain will need to be held in locking tweezers or artery forceps until it is ligated to its active traction element, be it a spring or elastic thread. If the gold chain is not thus held, then the fine‐linked chain may collapse down and slip between the recently sutured edges of the flaps and be lost from sight. This may also happen when an open surgical approach is performed, where the collapsed chain may fall between the wound edges and into the cervical area of the newly exposed tooth. Indeed, this entire unfortunate series of events may also occur during later visits for re‐ligation of the still only partially erupted tooth. In all the above cases, the subsequent search for the lost chain is very uncomfortable for the patient and may even require reopening of the healing soft tissue cover.

      The use of a stainless steel ligature is far easier from every point of view. It is cheap, abundant and readily at hand in every orthodontic and surgical operatory. The ligature is passed through the eyelet and twisted into a long braid with an artery forceps before bonding is undertaken. The braided wire, or pigtail, hangs loosely in the eyelet until bonding and suturing have been completed. It should be of sufficient substance for it to be rolled up into a loop, which will not easily be unravelled by extrusive forces. On the other hand, it must not be so thick that the effort needed to twist the braid or bend into a hook will seriously test the bond strength of the newly placed attachment. In practice, the use of a soft stainless steel ligature wire of 0.012 in. or 0.014 in. gauge is generally the most suitable.

A popular and simple modification of the stainless steel ligature recommends that the pigtail be braided in such a way that each two or three turns of the braid is followed by a small loop, then two or three more turns, another loop and so on. In this way, the braid comprises a convenient chain of loops, which may be shortened as necessary by cutting off the excess, while exploiting the loop closest to the gingival tissue [16]. However, as the tooth progresses, ‘rolling up’ the terminal loop of a merely twisted stainless steel ligature (Figure 2.5) is simple and eminently ‘user‐friendly’.

Fig. 2.5 A direct tie using a very short length of elastic thread.

Elastic ties and modules versus auxiliary springs

      At first glance, elastic ties of one sort or another present the orthodontist with the most convenient means of applying light forces to a tooth, with a good range of action. However, their use is more disappointing than might initially be thought.

      The manufacturer’s spool of elastic thread usually comes in the form of fine hollow tubing, which is easier to tie than a solid elastic thread. Most orthodontists tie the thread with a simple knot that, when used to tie ordinary string, will not unravel. The stretch factor is set by trial and error, as there can be no accurate control on the amount of force applied. Unlike ordinary string, however, when tying elastomeric thread the knot tends to loosen and much of the original force