CLEAR, THIN, & STRONG making bite splints successful through effective design Elizabeth D. Caughey, DDS Pankey Institute Visiting Faculty from Atlanta, GA Summer 2015
START WITH THE GOAL visualize a smooth, dense, anatomically correct splint
SET YOUR STAGE clear your schedule, your desk, and your head and plan to make it correctly the first time
ARM YOURSELF mounted study models wax for blocking out rotated and spaced teeth tin foil as barrier lubricant for upper model pressure pot large enough to house articulator, filled with 1/2 distilled water, heated, and ready to be pressurized Biocyrl Ice monomer + polymer - ratio 1:2 liquid:powder Spatula for initial mixing and Bard-Parker scalpel for removing excess flexible large dappen dish for mixing
STUDY YOUR CASTS study each arch separately first; notice areas of rotated and malposed teeth that need consideration for material thickness and where you will compromise in order to achieve desired occlusal harmony evaluate clinical crown height - longer teeth need less embrasure retention; shorter teeth may require more lingual flange evaluate depth of lower lingual vestibule and shape of palatal vault - plan how the acrylic will position and support tongue posture Look for mandibular tori - if flange needs to be shorter to go around tori, does it then need to extend deeper into posterior mylohyoid space? observe gumline recession - lower lingual anterior frequently suggest tongue tie or low tongue resting posture; generalized lingual and buccal recession needs to be blocked out during splint fabrication and delivery
SET UP THE ARTICULATOR! Set models using facebow taken at Frankfurt horizontal plane; lower model set using wax bite at same thickness as future splint using a protrusive wax record, dial in the correct horizontal condylar settings confirm accuracy by taking mounted models through excursive movements and reference contact pattern with photographs of patient take note of close proximity in lateral guidance to either molars or incisors and adjust height of pin to achieve ideal material thickness accordingly (ideally 2mm in all dimensions)
PREPARE THE MODELS FOR FABRICATION use hot white rope wax on curved #7 wax spatula to block out embrasures, rotations, and gingival margin contours lubricate upper model lightly
PREPARE THE MODELS FOR FABRICATION! apply tin foil (not aluminum - it is too rough) to lower model, deeply creasing into embrasures and gingival margins this provides a barrier and makes removal of splint possible without damaging model
MIX YOUR ACRYLIC liquid:ratio is 1:2 - first add one increment of liquid monomer to large flexible dappen dish then over low vibration, sprinkle in 2 increments of powder after all powder is wetted, gently fold wet acrylic once or twice with spatula - do not stir repeatedly (avoid bubbles) after it is all wet leave it alone for 3 minutes. No stirring or other manipulation.
WORK YOUR ACRYLIC after shine is just lost from top surface of liquid acrylic, begin manipulating it by bending the sides of the rubber bowl in on the material continue until the material no longer sticks to the side of the bowl remove material with lubricated fingers and begin to shape into a thick rope do not overwork the material.
ADAPT ACRYLIC TO MODEL apply thick rope of nearly dry acrylic in arch shape adapt first to depth of lingual flange with side of finger adapt to lingual of lower incisors with thumb very gentle pressure is used to avoid fenestration or other weak thin areas when in doubt about the material s readiness to set, discard material and start again with mixing process. do not attempt to remove and reposition the same rope of acrylic or bubbles will result.
INDEX OCCLUSAL SURFACES place lower cast with acrylic back into articulator - be sure horizontal elements are locked slowly close upper over acrylic until it just touches; smooth out indentations with gentle finger pressure from lingual toward buccal once pin touches with horizontal elements in locked position, unlock one at a time and LIFT upper cast away from acrylic, shift across lateral excursion, and gently index cross-over into soft acrylic repeat other side, and lock both sides NOTE: do not allow the acrylic material to become opaque before putting in pressure pot - that will result in bubbly weak splint.
CURE ACRYLIC USING HEAT + PRESSURE seat articulator into pressure pot with pre-heated water at 160 F. close and lock lid, pressurize to 20 PSI for 10 minutes. Remove articulator from pressure pot and allow to fully cool bench top for 10 minutes - this allows the for slight shrinkage to occur on the model
OUTLINE LANDMARKS BEFORE TRIMMING UPPER PHOTO: use pencil to lay a straight line for incisal overlap, a curvy outline of upper buccal cusp tips, and a vertical line for distal of canine (very helpful not to remove this acrylic as it is needed for guidance) LOWER PHOTO: identify depth of lingual flange and lingual extent of occlusal table; preview again flange design to optimize tongue positioning before going to the lathe
TRIM DOWN INTO SPLINT UPPER PHOTO: thoughtful use of lathe-trimming can result in a mostly finished splint. when in doubt, use E-cutters to handtrim the lingual flange to protect tongue positioning. See that deepest indentation from upper model stamping has not been removed by lathe (arrow) LOWER PHOTO: finished, smooth, polished lower splint ready for final check.
PRE-DELIVERY CHECK using articulating paper, confirm all posterior teeth simultaneously touch a flat occlusal receiving area loosen horizontal condylar guidance elements and confirm smooth excursions that are no steeper than patient s own guidance look at anterior coupling from an incisal view to ensure close approximation without heavy occlusion (zoomed next slide)
FINAL SPLINT CHECK: clear - without bubbles thin - 2mm across all dimensions
PREPARE FOR DELIVERY reline every splint! use cold-cure acrylic for this stage
RECLINE + SUPPORT PATIENT Position the patient to take strain off as many joints as possible, using bolsters Very posturally sensitive patients relax better with support under wrists and shoulders as well position head within cradle so that SCM tone is visually as relaxed as possible. Confirm patient can feel headrest support at base of skull/occiptal ridge use hand towel under curvature of neck; check lordosis and rotation encourage relaxation breathing while giving gentle cervical distraction with towel under base of skull
CHECK SPLINT IN THE MOUTH Remember how splint fit models; then hold splint loosely against inside of upper teeth; confirm that it meets just under anterior teeth Gently try splint over lower teeth, noticing whether it is passive or binds as it goes on; relieve any too-tight areas Once seated, alternately lift from right and from left, to determine which side should develop the path of insertion Evaluate proximity of upper anteriors to splint; if splint was made using a neutral bite record, do what is necessary to seat to a neutral cranial relationship (patients who have already received PRI instruction may know an exercise for this; dentists preparing a patient for PRI referral may use whatever technique they used to get the bite record made)
PREPARE FOR RELINING Lubricate patient s lips and teeth. Mix Cold-Pac cold curing acrylic in 1:1 ratio - add liquid to dapper dish then sprinkle powder. Allow weight of powder to wet the powder until it is all incorporated. Run a thin stream of liquid through intaglio surface of splint, allow excess to drain away. Once acrylic has lost its gloss, load into the splint evenly. Quickly seat with firm pressure on the teeth. Remove excess. Lift on the side of the designated path of insertion to create correct degree of retention, as the material sets (approximately 8 minutes).
ADJUST OCCLUSION Ask patient to bite on Kleenex blotters to dry upper teeth and splint. Use a double thickness of red articulating paper to mark excursions, and a single thickness of blue or green to mark the arc of closure contacts. Use fine E-cutter to rough in the bite, then a trued up polishing point Working out anterior guidance first allows patient engagement early in the process - as the patient moves over too-steep or too-bumpy inclines, help patient relate teeth to muscles Use caution when removing any heavy canine contact marks made in arc of closure - this is a necessary starting point for lateral excursion and should touch definitively on a clench, but not on a light tap-tap. Hold the polisher at an angle that allows a vertical relief of a heavy canine contact, to prevent wiping away the lateral portion needed for starting the excursion (upper picture) In adjusting excursive contacts, always adjust splints with the grain - the polisher moves across the splint in the direction that the the tooth would (bottom picture)
FINALIZE OCCLUSION Send patient for a walk, and for patients with PRI exercises, to do those. Use cotton rolls to prevent errant occlusal contacts from limiting the benefit of the exercise. Check splint again. Ideally balanced posterior contacts and well distributed occlusal transitions during excursions.
Left lateral excursion: start with close canine approximation; slide smoothly and shallowly across; crossover smoothly onto incisors
Right lateral excursion: start with close canine approximation; slide smoothly and shallowly across; crossover smoothly onto incisors