Border Molding

| April 20, 2012 | 1 Comment

Border Molding

Border Molding means shaping borders of impression tray

  •  Functional or manual manipulation of tissues
  •  Duplicates contour & size of vestibule
  • Performed with
  1. Thermoplastic modeling compound
  2. Waxes
  3. Impression materials

Tray Wax Spacer

  • Remains in place during border molding procedures

Custom Tray

  • Comfortable
  • 2-3 mm from vestibule
  • Dry periphery of tray (Compound will not stick to tray otherwise)

Heating Compound

  • Use Bunsen Burner not Hanau Torch
  • Warm until it starts to droop
  • Do not overheat – if catches fire or boils, it will not mold properly

Compound Application

  • Apply over periphery of tray, in a thickness just slightly narrower than the compound stick

Re-soften After Application

  • Flame with a hand torch until all seams or sharp contours have disappeared
  • Do not melt wax spacer inside tray

Preventing Slumping

  • Hold the tray upside down so that compound droops toward the depth of the vestibule

Tempering Compound

  • Temper in a water bath (135-140°F) for several seconds
  1. Prevent burning
  2. Hot water bath will keep compound soft for an extended period

Wax Spacer

 

 

  • Keep out of hot water bath to prevent melting
  1. Difficult to replace tray intraorally in the same position
  2. Results in uneven border molding

Prepare Patient

  • Patient seated, head against headrest, mouth open & relaxed
  • If patient “opens wide”, commisures constrict, limiting access

Inserting the Custom Tray

  • Place intraorally by rotating into place
  1. Mold by pulling on the cheeks, lips
  2. Have patient make functional movements

After Removal

  • Chill in cold water
  • Trim excess over wax spacer or external material that is thicker than 4-5 mm

 

  • Clean debris from tray

Assessing Peripheral Role

  • Proper thickness
  • No overlap

Burnthrough

  • Difficult to see (opaque)
  • Relieve tray

After Trimming

  • If border is sharp or has seams, re-flame, temper and readapt intraorally
  • Repeat until periphery is completed

Border Molding

  • Don’t reduce border molding prior to final impression if:

–      Modern low viscosity  materials are used

–      Sufficient relief (spacer + holes)

Maxilla – Seating the Tray

  • Seat tray firmly in mid-palatal area during border molding procedures

Maxilla – Contouring

  • Mold posterior buccal by pulling cheek down & forward with slight circular movement

Functional Movements

  • Patient moves mandible side to side & opens wide

–      Molds the retrozygomal area

–      Allows for movement of coronoid process

–      Prevents impingement of pterygomandibular raphe

Maxilla – Labial Frenum

  • Pull lip outward & downward

–      Do not pull to one side

  • Labial frenum should be narrow
  • Buccal frena usually broader, “V-shaped”

Maxilla – Posterior Border

  • Add compound across the top of the tray (not at the edge)
  • Terminates at vibrating line and hamular notches
  • Mark with an indelible stick

–      Insert tray & check visually

Evaluating Border Molding

  • Relatively symmetrical

Evaluating Maxillary Border Molding

  • Retentive

Mandible

  • More difficult
  • Changing position of the floor of the mouth

Posterior Buccal Areas

  • Pull cheek upward while holding tray in place
  • Have patient suck cheeks inward while holding tray in place

Retromolar Pad  

  • Should be covered (at least partially) to provide a seal and comfort to the patient

External Oblique Ridge

  • Don’t extend past EOR
  • Palpate cheek at angle of the mandible

–      Smooth transition between mandible & border – not palpable

Buccal Extension

  • Look for fold in vestibule

Masseter Muscle

  • Distal buccal extension
  • Patient closes against force
  • Activates the masseter, which will displace the compound

Mandibular Frenal Attachments

  • Labial frenum is narrow

–      pull lip straight up,

–      not as exaggerated as maxilla

  • Buccal frena broad & “V-shaped”

Posterior Lingual Areas

  • Have patient touch their tongue to the corners of the mouth, to the palate and stick their tongue out of their mouth
  • An “S” shaped lingual flange commonly results in posterior lingual area

Retromylohyoid Space

  • Distolingual border can extend

–      Straight down from the retromolar pads

–      Anteriorly to varying degrees

–      Almost never angles posteriorly from retromolar pads

Posterior Lingual Areas

  • Lower border at or slightly below mylohyoid ridge but not deeply into the undercut below the ridge,
  • Minimizes, abrasion and discomfort
  • Denture should not lift with normal tongue movements

Anterior Lingual

  • Patient lifts tongue to palate, to corners of mouth and sticks tongue out
  • Hold tray in place – denture should not lift with normal tongue movement

 

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Category: Articles, Prosthodontics, Prosthodontics, WIKI

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