Adaptation Of Spacer On Primary Cast Notes

Adaptation Of Spacer On Primary Cast Armamentarium

• Maxillary and mandibular primary casts
• Spacer wax or modeling wax
• Red and blue pencils
• Rubber bowl with hot water
• BP Blade No. 15 with handle.

Guiding Lines:

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Step 1:

Mark the midline using the frenum as the reference point. Mark the outline of the sulcus on the primary cast. The Sulcus line is marked in the deepest part of the sulcus. A red color pencil can be used for marking the sulcus line. The Sulcus line is a continuous line. In a posterior aspect of the maxillary cast, a red line is drawn 1 mm beyond the posterior vibrating line.

Step 2:

Place scale in the sulcus and mark several points 2 mm away from the sulcus line at different areas. Join these points as a bold line 2 mm away from the sulcus on the labial and buccal side of the cast. Use a blue color pencil for this line. This line (continuous blue line) is 2 mm short of the sulcus line. It indicates an extension of the custom tray border. The blue line is not marked 2 mm short in the posterior aspect of casts.

Step 3:

Draw a spacer outline. This line is drawn as a dotted line. Draw it at a level 2 mm short of the tray outline. In the posterior part of the maxillary cast, this line is limited till the anterior vibrating line of the posterior palatal seal area.

Step 4:

Outline of tissue stops: Four tissue stops are marked on the maxillary cast, two anteriorly (canine region) and two posteriorly (molar region). On the mandibular cast, two tissue stops are marked in the canine region.

Adaptation of Spacer:

Step 1:

Take half a sheet of modeling wax (or spacer wax) and soften it over the Bunsen burner. Place it over the maxillary cast and adapt it without any wrinkles.

Step 2:

Put a cut on wax at the level of the spacer line (dotted line) with a No. 15 BP blade. Take care not to scratch the cast with the blade. Remove excess wax beyond the dotted line.

Step 3:

Cut the tissue stop area according to the outline to make a window in spacer wax. The spacer is 4 mm short of the sulcus and limited to the anterior vibrating line in the posterior palatal seal area.

Note: Wax is cut and removed from the spacer according to the tissue stop outline. This will create a window in the spacer wax. This is not the tissue stop. The tissue stop is the extension of a custom tray (through this window) that is in contact with the cast.

Adaptation Of Wax Spacer On Mandibular Primary Cast

Guiding Lines:

Step 1:

Mark the outline of the sulcus on the mandibular primary cast as done for the maxillary cast.

Step 2:

Mark custom tray extension line (continuous blue line). It is 2 mm short of the sulcus line. It indicates an extension of the custom tray border.

Step 3:

Draw a spacer outline. This line is drawn as a dotted line. Draw it at a level 2 mm short of the tray outline. In the case of a mandibular cast, the buccal-shelf area is not covered with a spacer as it is the primary stress-bearing area. Mark outline for two tissue stops (2 × 2 mm) on mandibular cast at canine region.

Note: The buccal-shelf area itself acts as a tissue stop. So no separate tissue stops are made in the posterior region of the mandibular cast.

Adaptation of Spacer:

Step 1:

Take half a sheet of modeling wax roughly shape it according to arch shape, and soften it over the Bunsen burner. Place it over the mandibular cast and adapt it without any wrinkles.

Step 2:

Put a cut on wax at the level of the spacer line (dotted line) with the No. 15 BP blade. Take care not to scratch the cast with the blade. Remove excess wax beyond the dotted line. Remove spacer wax from the buccal-shelf area.

Step 3:

Cut the tissue stop area according to the outline to make a window in spacer wax. The spacer is 4 mm short of the sulcus. Make sure that there is no spacer on the buccal shelf area.