ABSTRACT:
This article describes a technique in which second molar replacement therapy is simplified using the Viazis straightwire bracket system, in place of a sagittal appliance, to distal drive the first molars.

INTRODUCTION:
Second molar replacement therapy has many advantages for the orthodontic clinician. The extraction of second molars has predictably good results in a high percentage of cases if extraction guidelines are followed and treatment biomechanics are properly designed. The author recommends the removal of second molars in place

of premolar extractions to limit the unwanted changes to a patient’s facial profile caused by anterior retraction mechanics. (fig.1)

THE VIAZIS BRACKET:

The Viazis system offers the clinician the speed of the smallest single slot bracket available and the control and stability of the largest twin slot bracket on the market. (fig.2) The various ligations that are available with the Viazis bracket allow unsurpassed control of individual tooth movement. (fig.3) When used in combination with bio-efficient archwires the Viazis system has fewer instances of root resorption than conventional systems. (fig.4)

LEVELLING AND ALIGNING WITH THE VIAZIS BRACKET:

The super elastic 0.020” x 0.020” wires allow initial full bracket engagement for correction of rotations, alignment, initial leveling, and space closure. In contemporary orthodontics a clinician may approach the first three stages of orthodontic therapy (alignment, leveling, and space closure) as part I of treatment and finishing as part II. The reduced time required to complete stage I with the Viazis bracket means more time is available to detail the occlusion. This immediately preconditions the clinician to spend an equal amount of time finishing a case as leveling and aligning the crowded teeth. (fig.5 and 6)

In cases where canines are excluded from the arch the author recommends that a 0.020” x 0.020” thermal nickel titanium archwire is placed, but not engaged into the canine brackets. The clinician is able to align the incisors and premolar teeth very rapidly by using an inverted V ligation and allowing the archwire to undergo austenitic transformation. (fig.7)

In the past, sagittal appliances would have been utilised, prior to fixed appliance therapy, to distal drive the first molars into the second molar extraction site. (fig.8) With the new Viazis system it is possible to distal drive the first molars on a rectangular 0.019” x 0.025” stainless steel archwire. Open nickel titanium coil spring is placed between the second premolar and the first molar and a Guerin lock is utilised to activate the coil spring. (fig.9)

ANCHORAGE CONSIDERATIONS:

To prevent the anterior teeth from being pushed labially in response to the distal movement of the first molars the author recommends that all teeth mesial to the first molars, on either side of the arch, are “under tied” using 0.012” ligature wire. (fig.10) Furthermore, all teeth mesial to the first molars should be anchored using an inverted V ligature tie. Those brackets with elbow extensions should have the elastomeric ligature tied beneath the elbow extension to further boost the individual tooth anchorage. The nickel titanium coil spring is compressed to half its original length and reactivated every six or eight weeks. Enough archwire should be left distal to the first molar tube to allow the first molar to slide along the rectangular stainless steel archwire. A ball of composite resin is bonded to the end of this archwire to prevent soft tissue trauma.

The reduction friction in the Viazis system allows a first molar to be pushed back into the second molar extraction site in three to four months. The first molar is anchored in its new position using a palatal or lingual arch. (fig.11) The clinician may then move the premolars distally using power chain or a nickel titanium closing coil spring.

ALIGNMENT OF THE ECTOPICALLY POSITIONED CANINES:

Once the premolars have been retracted distally, and are contacting the first molar, an under tie ligature is used to created a posterior anchor unit which ligates the first premolar, second premolar and the first molar. The clinician then removes the 0.019” x 0.025” stainless steel archwire and replaces the original 0.020” x 0.020” thermal nickel titanium archwire. After under tying the central and lateral incisors as one unit the doctor can engage the canines with a bio-efficient wire to rapidly bring these teeth into the line of the arch. (fig.12)

The new super elastic nickel titanium wires are significantly different from earlier work hardened nickel titanium wires or stainless steel. Their super-elastic properties assure light, constant forces regardless of the amount of activation. (fig.13) There is a significant difference in the flexibility of rectangular super-elastic wires in vertical and horizontal activation. For example, it is much easier to engage a bio-efficient wire in a high cuspid with a vertical activation of 5 – 7 mm than to fully engage the wire in the bracket slot of a tooth that needs to be rotated 2 – 3 mm. (fig.14)

It is recommended that a lingual or palatal arch is placed between the first molars until the third molars have fully erupted. (fig.15) This permits the clinician the flexibility of using the palatal or lingual arch as an anchor unit to upright any third molar that may erupt at an unfavorable angle. (fig.16) This uprighting is completed with sectional mechanics. The uprighting procedure will be described, in detail, in a subsequent article on the Viazis bracket.

CONCLUSION:

Second molar replacement therapy, in combination with the new Viazis system, allows the clinician to achieve predictable results in a minimum period of time. Second molar replacement therapy maintains a pleasing facial profile, creates a functional occlusion, and ensures that the patient has healthy tempro-mandibular joints. Historically, this technique has been very time consuming because a sagittal appliance was required for a period of six months after the removal of second molars.

With the Viazis system a doctor is able to level and align the crowded anterior teeth very quickly and utilise the reduced frictional properties of the Viazis bracket to distal drive the molars on a rectangular stainless steel archwire. Final alignment is commenced once the premolars have been retracted to create space for the canines. Severely crowded cases may now be completed within 12 – 18 months. (fig.17 – 24)