The tilted posterior tooth. Part II: Biomechanical therapy

Adrian Becker, B.D.S., L.D.S., D.D.O.,* Maya Zalkind, D.M.D.,** and Noah Stern, D.M.D., M.S.D.*** Hebrew University-Hadassah Faculty of Dental Medicine, Jerusalem, Israel

w hen a tilted tooth borders on an edentulous space, it is generally possible to provide a mechanical solution to replacing the missing unit.’ As long as the abutment remains tilted, however, the restoration will generally be a compromise. The dentist should consider the possibility of adjunctive orthodontic therapy to return the malposed tooth to its former position.‘. ,’ The teeth of adults with normal invest- ing tissues respond to orthodontic forces in much the same way as do those of children, although the response may be slower in adults.

The advantages of such preprosthetic groundwork include (1) simplification of abutment preparation, (2) transmission of occlusal forces through the long axes of the teeth, (3) improved occlusal contour and intercuspation. (4) alteration of the pontic area may be achieved, (5) prevention of infrabony pockets associated with tilting, and (6) elimination of extrac- tion spaces in some instances.

ORTHODONTIC DEVICES

Both removable and fixed orthodontic devices are suitable for the movement of teeth in the adult, and each has its place in treating the many problems that arise.

Removable devices are easier to construct, since a designed cast, sent to the laboratory technician with appropriate instructions, requires only minimal chairside time. Such devices may be used to tip individual teeth mesially, distally, buccally, and palatally with great efficiency; however, they cannot

Supported in part by a grant from the Joint Research Fund of the Hebrew University-Hadassah Faculty of Dental Medicine.

*Clinical Senior Lecturer, Department of Orthodontics.

**Lecturer, Department of Oral Rehabilitation. ***Associate Professor, Department of Oral Rehabilitation.

Of~22-3913/R2/OX0149 + 07$00.70/O IV’ 1982 The C. V Mosby Co.

move teeth bodily, nor can they produce root move- ment. They can be used to temporarily increase the occlusal vertical dimension, clearing the teeth to be moved from occlusal interference. These removable devices are often a problem to the patient because of their size, their disturbance of normal function, and perhaps because the patient can too easily remove them (Fig. 1).

While the fixed devices are of more modest dimen- sions, they generally require a greater degree of technical skill in their construction and activation. They may be designed to effect all forms of move- ment of the teeth in all directions. They cannot be used to separate the two dental arches when oc- clusal interference occurs during tooth movement and, therefore. they may require the addition of a Hawley-type removable device to enhance their efficiency.

When a mesially tilted tooth is tipped distally, it meets with resistance from the occlusion of the opposing teeth since distal tipping is accompanied by elongation of the affected tooth. As uprighting progresses, using a fixed device, the upper and lower dental arches become further separated because a premature occlusion develops between the tipped tooth and its antagonist. This increase in the vertical dimension of occlusion may result in transitory or permanent injury caused by the abnormal occlusal contact. In general, occlusal grinding of the affected teeth is periodically necessary during the orthodontic procedure. The insertion of a Hawley-type device with a bite platform has the effect of separating the teeth. This simplifies the desired movement of the teeth by eliminating occlusal resisting forces. At the same time, occlusal grinding may be delayed until the end of treatment when the tooth is in its correct axial relation. Often, however, a full reassessment of the vertical dimension of occlusion is made when

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Fig. 1. Right second maxillary molar has tilted mesially to partially obliterate first molar extraction space. Adams’ clasps are placed on second premolar and canine on each side of arch since molars of opposite side are missing. A, Simple finger spring is held in place by palatal acrylic resin base. 8, Orthodontic device seated. C, Activation of spring may be seen in this view in which orthodontic device is not fully seated.

Fig. 2. A, Diagrammatic representation of elements of simple fixed device with tube which carries facility for inserting fine wire vertically between tube and pad. Wire is fashioned into configuration suitable to its attachment to horizontal bar which has been bonded to both premolars and canine of same side. B, Device in mouth. Third molar was extracted at time of insertion. C, Initial placement radiograph. D, Posttreatment radiograph.

uprighting has been achieved; prosthetic occlusal on the side opposite the extraction site and dasps on rehabilitation of the dentition, as a whole, will then both first premolars, while a simple finger spring include the readjustment of the height of the clinical exerts light pressure (30 to 50 gm) on the potential crown. abutment tooth in a distal direction (Fig. 1). The

DISTAL MOLAR TIPPING addition of an acrylic resin platform anteriorly, acts as a bite plane for the lower incisors, clears the posterior teeth from occlusion, and facilitates the desired movement.

With a removable device, adequate clasping may be provided using Adams’ clasps on the first molar

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Fig. 3. A, Orthodontic device similar to that shown in Fig. 1, with Adams’ clasps on first premolar and molar on unaffected side. B, Second molar of affected side has tilted and rotated meslally, but some space of extracted first molar has been lost to distally drifted premolars. Adams’ clasp is placed on canine on this side, and acrylic resin is judiciously cleared to allow for mesial movement of premolars to be achieved with similar spring at same time as that being used in opposite direction on molar. C, Activated springs with device partially seated. D, Activated springs with device fully seated

Some years ago, orthodontic attachments welded to orthodontic bands were used for all fixed devices. Today, however, bands have largely been super- ceded by directly attaching orthodontic brackets and tubes to the enamel.‘. i

By using the acid-etch technique for bonding composite resin directly to enamel, a round buccal tube of 1 mm in diameter (0.040 inch) may be welded to a small pad of stainless steel mesh. The mesh acts as a mechanical retention for the tube, which, through the medium of a composite resin may be directly bonded to the buccal surface of the tilted molar. The tube should be parallel to the occlusal plane of the tilted tooth. A length of 0.5 mm spring steel wire is inserted in the tube, with its mesial end lying passively in the buccal vestibule opposite the premolar teeth. This spring is raised to hook over a simple wire bar which has been similarly bonded to the premolar and canine teeth (Fig. 2).

Using either of the methods described, the move- ment should be achieved rapidly and with no ill effects on other teeth. provided there is no tooth

(erupted or unerupted) distal to the molar. The space for the pontic will be increased as uprighting proceeds.

DISTAL MOLAR AND MESIAL PREMOLAR TIPPING

Distal drifting of premolars will often accompany mesial tilting of the second molar when time has lapsed since the extraction of the first molar. This may be expeditiously treated with a removable device similar to that described (Fig. Y,.

A second finger spring is used to move both premolars mesially, applying force in the opposite direction to the spring which tips the molar distally. To accomplish this, good retention of the device is necessary, which demands the use of Adams’ clasps on two teeth of the opposite side. Since teeth that are to be moved cannot be clasped, the canine on the affected side becomes the most distal tooth to carry a clasp; should this tooth fail to have a sufficiently bulbous contour, it may become necessary to add a clasp anteriorly. The addition of an anrerior biting

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Fig. 4. Flexed sectional rectangular archwire is tied into edgewise attachments on both distally tilted second premolar and mesially tilted second molar. A, Diagrammatic represent- ation of mechanism, with archwire shown above in its passive state and undistorted length (Lj. Its new length (L’) is dictated by distance between attachments, into which it is tied to produce reciprocal mesial pressure on premolar and distal pressure on molar. B, Radiograph with device in place at start of treatment. C, Radiograph with device in place at end of treatment. Note change in shape of archwire. D, Position, deep in vestibule, of mesial end of archwire when only distal end is engaged. E, Clinical view of device at start of treatment. F, Clinical view of device at end of treatment.

platform, to free the posterior teeth from occlusion, is ments is smaller than the distance between the also often advised, particularly where the tipping of corresponding bends of the archwire. Full engage- the molar has been severe. ment of the wire dictates that it be sprung into the

Probably the simplest method of tipping a molar brackets, thereby exerting a force in both directions distally and a premolar mesially is the use of an to move both teeth by a simple tilting movement and edgewise bracket or tube placed on the molar (either increasing the pontic space. welded to a band or directly bonded) and an edgewise bracket on the premolar (Fig. 4). A section- al rectangular archwire is fashioned so that when placed in only one of the attachments, its other end lies passively in the vestibule sulcus below the other attachment. The distance between the two attach-

UPRIGHTING ABUTMENTS WITH CONTROLLED LENGTH OF PONTIC SPACE

Movement of the roots of the teeth is required. independent of any alteration in the distance between their crowns. This is not possible with thr

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Fig. 5. A, Note similarity to mechanism used in Fig. 4. Important difference is unaltered length of archwire between passivity and flexion. It is altered angulation of engaged ends of wire which flexes wire and produces root movement only. B, Severe tilting of premolar and molar. Corrective tipping alone would open pontic area equal to almost two premolar teeth. C, Bands were placed on first and second molars, first premolar, and canine on the affected side. Opposite side had bands placed on canine and first molar. Vertical slotted Begg brackets were used on bands. Carrying uprighting auxiliary springs which were hooked over 0.018 Inch round archwire. Elastic ligature was used to limit degree of tipping of intended abutments tu limit space for pontic. D, Treated result.

removable devices but may be expeditiously per- formed as described, using edgewise attachments and the same type of sectional archwire. Here, however, it is essential that the interattachment distance be the same or slightly greater than the distance between the corresponding bends on the archwire (Fig. 5, A). This prevents the crowns from further separation. Since each attachment is at right angles to the long axis of each of the two teeth, the engagement of the archwire (the two ends of which are extensions of the same straight line) will bring pressure to bear on the roots of the two teeth. This pressure will only be relieved when the teeth become parallel.

An alternative mechanism is presented to show a different technique for achieving root movement, using the Begg bracket and round cross-section archwires (Fig. 5, B to D). Teeth must be banded on both sides of the arch. Uprighting is achieved with the use of auxiliary springs. The degree of alteration

of the pontic length is then controlled by the ligation of the two teeth with a steel or elastic ligature.

FULL CLOSURE OF EXTRACTION SPACE

The greatest advantages of full space closure are that fixed restorations may be rendered entirely unnecessary and that third molars may erupt and become useful members of the masticatory appara- tus. This approach is particularly pret&rable when both lower, both upper, or all four lirst molars require extraction (or have recently been extracted) and where adequate alveolar bone is present in the extraction spaces. Undoubtedly, the rnesial move- ment of teeth is achieved only with its surrounding alveolar bone; however, when thr first molar has been missing for several years. the residual bone ma) be thin. In this circumstance, ir SWIIIS likely that mesial movement into such an area ma)’ result in some loss of the buccal plate of boric 1 ovcrine the

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bucc :a1 surfac e of the roots. Fenestration of the buccal surfa ces of th te roots may thus occur.

In suitable instances, however, there is no reason

why this trea tment should not be used to advantage to e liminate an excessive horizontal overlap or crow rding in the treatment of malocclusion. Full mult i banded devices and a high degree of technical

Fig. 6. A, Lateral jaw radiographs of young adult showing missing left mandibular f$st molar and remaining three first molars with questionable prognosis. B, Preorthodontic/orthodontic conditions of left side. C, Postorthodontic condition of left side showing fully erupted and well placed third molars in occlusion. D. View of latter stages of orthodontic treatment, showing complex device used. E, Right and left views taken from panoramic radiograph made 2 years after treatment was completed.

skill are essential, but the results are ml ing (Fig. 6).

DISCUSSION

It is neither necessary nor desirable 1 tilted abutment teeth prior to prostheti tion. Where minimal advantage is to I

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adopting this procedure, it should be avoided. How- ever, where periodontal problems exist, and the solution may partially depend on improvement of tooth position, or where the number of missing teeth to be replaced may be reduced, orthodontic inter- vention should be considered. Consideration should be given to all factors which might benefit from such treatment. Only then should the decision to alter the position of the abutment teeth be made. If there is value to be gained by this treatment, it will become obvious almost solely in enhancing the long-term prognosis of the results.

X word on the matter of prevention, as was mentioned in an earlier communication,” is in order. It is not often that a posterior tooth is extracted in circumstances other than the result of long-term neglect. The most common occurrence is an episode of acute dental pain. Either the seriousness of the tooth’s condition or disinterest on the part of the patient as to extended conservative treatment gener- ally dictates extraction as the most likely form of treatment. These patients are usually far from recep- tive to the construction of devices aimed at prevent- ing tipping movements of the adjacent teeth at this point, as evidenced by their refusal of more conser- vative initial measures which would not have allowed their dental health to have deteriorated to this level. However, many patients may be led to greater awareness of the benefits that sound treat- ment can provide if a little time and effort is spent educating them in the nature of their potential problem. Temporary space maintainers may be simply constructed and successfully used for months until repair has occurred or until the patient is ready to accept construction of a fixed permanent restoration.

SUMMARY

There are several reasons that may justify the use of adjunctive orthodontic intervention prior to, or instead of, the prosthetic replacement rlf missin,g dental units. These have been outlined. Methods arr described where the space for the pontic may be altered in length while the abutment teetlr are made parallel. Techniques which attempt to p~oduw root movement or techniques in which full space closure

is planned are best performed by ;j i:ornpetent orthodontist.

REFERENCES

1. Revah, A., Rehany, A., and Zalkind, M.: ‘I‘hr tilted posterior tooth. Part III. An abutment for a fixed pan~ai denture. (To be published.)

2. Marks, M. H.: ‘I’oofh movement in prriodonial therapy. In Goldman. H., and Cohen, I.). W.. editors. Periodontal Therapy, ed 5. St. Louis, 1973, ‘I% <:. 1’ Vlosby Co.. pp 491-546.

3. Brown, S.: The effect of orthodontic therapy 011 terrain tvprs of periodontal defects. I. Clinical iindinss ,i Pwioc-lonr 44~742. 1973.

4. Becker, A.: The median diastema. I)enr <al~rr North Am 22:685, 1978.

5. Way, D. C.: Direct bonding and its ~pplicx:ron to minor rooth movements. Dent Clin North .Am 22:‘i’)i. 19713.

6. Stern, N.. Revah. A., and Becker, :\: ‘l‘hv !iltrd posterior tooth. Part I: Etiology, syndrome, and p~ev<‘~~t‘~x~. ,] I’KOS- 1HFl DlW 46:404. 1981.

Kqmt reyue.t1., to: DR. ADRIAN BECKER HEBREW U~~IVERSIT~-H.~DASSA~~ FACLI.TY OF DENTAI. MEDKXNE P.O.B. 1172 JERUSALEM IsR.411

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