Maxillary and Mandibular Casts
Guidelines for Properly Marking the Maxillary and Mandibular Casts
- Outline the incisal papilla on the maxillary cast.
- Identify the distal aspect of the incisal papilla. Viewing the cast from the superior aspect, hold a transparent millimeter ruler over that point, being sure it is also perpendicular to a line visualized down the center of the palate (the mid-palatal suture). Extend lines onto the left and right land areas from distal aspect of the incisal papilla.
- Visualize a line directly over the mid-palatal suture and through the center of the incisal papilla. Extend this line onto the anterior portion of the land area using the transparent ruler. This line will represent the midline of the denture teeth set-up. In clinical situations, the midline will be determined by bisecting the patients face. Determining the denture set-up midline by using the mid-palatal suture is a clinically unreliable method.
- Outline the left and right retromolar pads.
- Place dots which bisect each retromolar and pad anterior-posteriorly.
- While viewing the cast from the facial perspective (not from a superior view), extend lines laterally onto the land area of the mandibular cast at the level of the dots.
- We must now transfer the posterior mandibular ridge crest to the land area of the cast. Identify the anterior pad. The crest will extend anteriorly from this point. Visualize the left and right mandibular ridge crests. All ridges will exhibit some degree of curvature, therefore always use the longest straight portion of the ridge, or the best average that you can judge, on a totally curved ridge. Identify the crest of the mandibular left and right ridges by holding a transparent ruler over each and transferring these locations to the land areas posteriorly and anteriorly.
- On the left and right sides of the mandibular cast, draw a vertical line at the area where the ascending ramus begins.
- Draw a horizontal line of the left and right sides of the mandibular cast parallel to the mandibular mean foundation plane. Remember this plane is established by connecting the most superior point of the anterior mandibular ridge to the points on the left and the right where the respective ascending rami begin.
- Hold the transparent ruler over the crest of the anterior mandibular ridge and perpendicular to the midline of the cast. Draw lines on the left and right land areas at this point.