Prosthodontics Record Blocks Overview

Record Blocks (Occlusion Blocks)

• These are used in prosthodontics to record the maxillomandibular relationships.
• Record bases are temporary denture bases for supporting record rim material to record maxillo-mandibular records.
• Purpose of record blocks is to retain the recording medium for maxillo-mandibular relations.
• Also aid in accurate jaw relationships transfer to articulator for positioning artificial teeth in trial dentures.
• Requirements include rigidity, accuracy, and stability, with smooth, rounded, and polished borders that contact lips, cheeks, and tongue.
• They should match the finished denture border dimensions for accurate fit.
• Types include temporary and permanent.
• Temporary record bases are discarded, replaced by denture base material.
• Permanent record bases become part of the finished denture base.

Materials for Temporary Record Blocks (bases)

• Shellac base plate:
  • Reinforced: strengthened for better stability, but still prone to distortion.
  • Stabilized: more resilient than reinforced, but still less rigid than other options.
• Cold cure acrylic resin:
  • Advantages: good strength and stability; doesn't warp during manipulation; closely fits master casts.
  • Disadvantages: requires more time in fabrication and can be difficult to control thickness. Residual monomer can irritate tissues
• Visible light cured acrylic resin:
  • Advantages: quick curing process.
  • Disadvantages: need of special equipments, possible inaccuracies or defects
• Vacuum formed vinyl and polystyrene:
  • Advantages: easy fabrication, uniform thickness; accurate adaptation to the master cast; good rigidity.
  • Disadvantages: can be expensive; difficult to ensure smooth, rounded borders.

Methods of Construction (Cold Cure Acrylic Resin)

• Sprinkle on method: monomer is applied to the cast and polymer is added.
• Non compression dough (Finger adapted) method: undercuts are blocked out, separating medium applied to the cast, and resin mixed until dough-like; then molded to the cast. Steps include allowing complete polymerization, then removing from cast, smoothing, and polishing borders.

Materials for Temporary Record Blocks (requirements)

• Retromolar pad covered.
• Thick palate (1–2 mm) and well adapted.
• Thin regions labial to the ridge.
• No excess flash on land areas of master casts.
• Record bases do not rock on master casts.
• No porosities or voids on the tissue surface.
• Flanges are smooth and rounded.
• Tissue surface adequately adapted.

Occlusion Rim Definition and Objectives

• Occlusion rims are occlusal surfaces on a record base for maxillomandibular relationship recordings or for use in tooth arrangement.
• Objectives:
  • Establish jaw relation.
  • Select teeth.
    • Determine appropriate lip position (high vs. low smile lines) for proper aesthetic tooth selection based on lip position.
  • Set up teeth
  • Support facial musculature.
  • Orient occlusal plane.

Occlusion Rim Requirements

• Position matches anticipated artificial teeth placement.
• Securely attached to the base.
• Smooth, flat occlusal surface.
• Contoured for accurate lip and cheek support.

Occlusion Rim Materials

• Wax occlusion rim:
  • Bite blocks wax (readymade): pre-fabricated wax blocks.
  • Base plate wax sheets (handmade): custom-made wax sheets for easier management in teeth arrangement.
• Modeling compound occlusion rim: used for functional recording of jaw relations and mounting graphic tracers.

Occlusion Rim (Wax Rim) Dimensions (Maxillary)

• 22 mm high from the depth of the sulcus at the canine eminence.
• 16 mm high at the posterior region from sulcus.
• Anterior portion lablelly oriented and positioned.
• Posterior border to anterior maxillary tuberosity.
• 4–6 mm wide in the anterior region
• 8–12 mm wide in the posterior region

Occlusion Rim (Wax Rim) Dimensions (Mandibular)

• 8–12 mm wide in the posterior region
• 4–6 mm wide in the anterior region
• Posterior wax rim height is 2/3 of retromolar pad.
• Maxillary rim slightly positioned forward from the ridge to compensate for ridge resorption

Marking the Occlusion Rims

• High lip line
• Smile line
• Corners of lips
• Central line or midline: below the center of philtrum
• Canines lines.