The Schwarz appliance was designed by Dr. Artur Martin Schwarz from Vienna Austria. Dr. Schwarz served as a military surgeon in World War I. In 1928 his interest turned to orthodontics. He is credited with developing the Schwarz double plates in 1956. This appliance served as the basis for the development of the Twin-Block appliance. (See fig.#1)

Dr. Artue Martin Schwarz

Fig.#1

The Schwarz appliance can be used in the upper and lower archs for the dvelopment of dermal bone. The appliances contain expansion screws that when activated place a light pressure on the dermal bone. This causes the bone to model changing its size and its shape. (See fig.#2)

Fig.#2

The entire maxilla is dermal bone so these changes are seen in the width of the maxilla, the height of the maxillary vault, the nasal airway, the ethmoid sinuses, and the upper mid face including the skeletal orbits. In the case of the lower arch only the dental alveolar process is dermal bone so the modeling occurs only in the width of the arch.(See fig.#3)

Fig.#3

If permanent teeth are present the orthodontic remodeling (osteoblastic- osteoclastic tooth movement) also occurs. (See fig.#4)

Fig. #4

The Schwarz appliance usually has a Hawley labial bow. The bow is used to retract and to rotate anterior teeth. Clasping of the appliance varies depending upon its use in the primary, mixed, or permanent dentition. Springs can be incorporated in the appliances for moving permanent teeth. The expansion screws are placed to create force for the desired movement. (See Fig.#5)

3-D 3-Screw Fan

Fig.# 5

Occlusal coverage of Acrylic

The rational for using occlusal coverage of acrylic on a Schwarz appliance is to eleminate the normal function between the upper and lower arches. The occlusal coverage is usually placed on the upper appliance and is flat plane.(See fig.#6)

Fig.#6

Occlusal coverage of acrylic is needed when the patient has an open bite with the associated anterior tongue thrust. Minimum thickness for the acrylic to prevent breakage is 1.5mm to 2mm between the most posterior teeth in occlusion. The appliance is modified with tongue wires and a tongue spinner to assist with the myofunctional swallowing therapy. The patient must eat in the appliance. (See fig.#7)

Fig.#7

If the patient has an anterior cross-bite the occlusal coverage needs to be sufficeently increased in thichness to clear the incisal edges of the teeth that are in cross-bite. The patient must eat in the appliance until the anterior cross-bite has been corrected. The occlusal coverage is then removed and the patient no longer needs to eat in the appliance. (See fig.#8)

Fig.#8

Occlusal coverage of acrylic is used on the upper Schwarz appliance when treating a skeletal Class III patient in conjunction with the R.P.H.G. The occlusal coverage enhances the effectivness of the R.P.G.H to move the maxilla forward. The R.P.H.G hooks are placed at the front of the appliance to prevent the Kline effect on the maxilla. Hooks are placed at the posterior of the appliance for the intra oral Class IIIelastics.The patient does not eat in the appliance unless they also have an anterior cross-bite or an open bite andanterior tongue thrust. (See Fig.#9)

Fig.#9

The reverse posterior skeletal cross-bite, sometimes called a sissor bite, requires occlusal coverage of acrylic to disengage the reverse cross-bite. The occlusal coverage of acrylic is ectended further into the palate to provide a table in which the lower posterior teeth can occlude. The appliance is constructed with constriction screws to reduce the width of the maxillary alveolar proces. The patient must eat in the appliance until the reverse skeletal cross-bite has been corrected. (See fig.#10)

Fig.#10

Cross-Over Wire

Many patients in the mixed dentition have underdeveloped arches. As the permanent incisors erupt into the inderdeveloped arch they prematurely ectopically recorb the roots of the adjacent decidious incisors. This results in a significant dental mid line shift. (See fig.11)

 

Fig. #11

Using the Schwarz appliance to develop the arch creates the space for a blocked out incisor. The cross-over wire which is secured in the acrylic opposite the midline cut corrects the dental midline shift. (See fig.#10)

Fig.#10

The Hawley Labial Bow

The Hawley labial bow on the Schwarz appliance is used to retract a dental protrusion and/or to rotate the incisors. The bow has two large superior loops and two smaller inferior loops. (See fig.#11)

Fig.#11

The wire gague of the bow varies depending upon its intended use. If the bow is to be used to retract the incisors the gague is .030 and it is placed in the gingival one third of the incisors. This promotes a bodly movement of the incisors.

The adjustment are made with the 3-Jaw pliers on the superior follower by the inferior loops on th Hawlwy labial bow. The adjustment must be made symetrically to prevent strain from building in the bow which will cause the bow to fracture.(See fig.#11)

Fig.#11

If the Hawley labial bow is to be used to rotate teeth the gague of the wire is increased to .040. This heaver gague wire prevents the bow from retracting the incisors durring the initial adjustment of the midline expansion screw. The bow is placed in the incisal one third of the tooth and in light contact with the tooth. This creates a center of pivitol resistance which rotates the tooth without retracting the tooth. Every four weeks the bow is adjusted back into light contact to prevent retraction until the rotation has been corrected. (See fig.#12)

Fig.#12

Expansion Screws

The Schwarz appliance was initially designed to develop the transverse width of the maxillary and mandibular arches. The maxillary appliance has one screw in the primary and mixed dentition and two screws in the permanent dentition due to the longer arch. The objective of the treatment is to place a gentel pressure on the dermal bone causing the dermal bone to model.

A complete revolution of the gear in most screws results in a 1mm change in its length. Therefore a single adjustment of the screw is 1/4mm change. (See fig.#13)

Fig. #13

The screws are adjusted twice a week in the primary and mixed dentition and once a week in the premanent dentition following the correct sequence of arch development. If the patient has an open bite and the associated anterior tongue thrust the activation is reduced by 50%. It requires twice as much time to develop the open bite case.

The Schwarz appliance is frequently uses as a reainer after the arches are fuly developed. If the appliances are to be used as the retainer the screw should be stabalized. The options are to tie the screw with brass wire, or to fill the entite cut in the appliance with acrylic. (See fig.#14)

Fig.#14

The Schwarz appliance can be modified with screws to recover lost arch length. The two most common times to make this modification is for lost E-Space in the mixed dentition and for termanal arch extraction cases in the permanrnt dentition.

In the mixed dentition the screw is turned twice a week at the beginning of the treatment to fully recover the lost E-Space. If the E-space loss is bilateral in the maxilla the arch length loss can be recovered bilaterally simotaniousuly. If the E-Space loss is bilateral in the mandibular arch the lower arch length it must be recovered uniterally to maintain anchorage within th appliance. (See fig.#15)

Fig.#15

The objective of termanl arch extraction therapy is to remove the second molar, distal drive the buccal segmnet as a unit with a sagittal appliance, and allow the third molar to replace the extracted second molar. This trchnique is a rapid way to recover lost arch length in any of the four quadrants and to compensate for generalized macrodontia

The sahittal screws in the appliances are turned twice a week. The concept of anchorage is the same in the terminal extraction treatment as with the E-Space regaining appliance. Bilateral activation of the lower Sagittal appliance is always unilateral. (See fig.#16)

Fig.#16

Adjusting Sptings In The Schwarz Appliance

Springs to the incisors can be incorporated into both the upper and the lower Schwarz appliance. There springs are either lap springs that when activated apply force to the contralateral incisors. Or recurve springs which apply force to individual teeth. The springs are activayed with either a flat on flat plier or with a Jaraback pliers. The activation of sptings should be below the systolic blood preassure. This allows the remodeling (osteoclastic & osteoblastic) of teeth through the dermal bone. (See fig.#17)

Fig. #17