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Executive | Lab Tech Talk

Upper Two Way Sagittal (with up to four clasps)

Category:

Appliance Purpose / Function:

Two-way Sagittal appliances are intended to create space in a crowded dentition, but they do so by lengthening the patient’s arch. Screws imbedded in the acrylic plate are positioned so that they open in an anterior/posterior direction. When they are activated, the posterior teeth are gradually pushed back and the anterior teeth are gradually pushed forward.
Appliance Components:

  • Adams Clasp on the 1st molars
  • Ball Clasp between the 1st and 2nd bi-cuspids
  • Distalizing Screw on each side of arch
  • Acrylic Plate
  • Posterior Bite Plate

Suggested Materials:
Wire: Chromium Cobalt or Stainless-Steel
Screws: 6mm acrylic borne vector screws

Options:

Appliance Fabrication Standards:
Clasps must be properly adapted to give maximum retention
Acrylic must fully encase the screws and be thick enough to resist breakage
The wires on the tissue side are formed about 1mm off tissue to provide clearance for the acrylic

WIRE STANDARDS:

  • The standard design has Adams clasps on the first molars and ball clasps between the first and second bicuspids. The clasping scheme may be changed according to Client preference or the teeth present in the arch.
  • Special attention must be paid to the placement of the acrylic retention portion of the clasps to avoid interfering with the cuts that must be made for the sagittal screws
  • Acrylic borne 6mm vector screws must be placed in the middle third of the sagittal walls with the long axis of the screw lined up approximately with the gingival margins of the posterior teeth on that side of the arch. The split of the screw must be positioned approximately in-line with middle of the second bicuspid or second primary molar

ACRYLIC STANDARDS:

  • Uniform overall thickness of approximately 2mm except in area of screws where there should be enough acrylic to cover the acrylic borne screws
  • All wires completely encased in acrylic on lingual portion
  • Posterior border tapered towards the tissue with a rounded edge (thin, sharp knife-like edges not acceptable)
  • The posterior bite plate must be built to the Client’s specifications or approximately 2-3mm thick
  • The bite plate must be the approximate width of the posterior teeth which it is covering without excess bulk and the surface must be smooth and as flat as possible while still allowing for contacts with the opposing arch
  • The splits must begin at the embrasure between the cuspids and first bicuspids and proceed towards the midline until they are level with the superior portion of the tabs on the screws. From there the splits must be directed towards the superior portion of the tabs of the screws. The splits are then continued on the same line on the opposite side of the screw thru the posterior border of the plate. These cuts must be very clean and straight to avoid binding when the screw is activated.
  • The tissue side of the plate is generally left alone unless otherwise requested by the Client, but it must be inspected for pits/voids or sharp areas. Pits/voids must be patched with acrylic, and sharp areas must be carefully ground smooth without removing too much acrylic. Additionally, the tissue side of the two splits must be inspected and any sharp edges carefully removed without removing too much acrylic