FINISHING LINES

FINISHING LINES
The finishing line junction with the major connector should take the form of an angle not greater than 90°, therefore being somewhat undercut.
FUNCTIONS
1- A finish line creates a definite limit to the plastic of the denture base, in this way the plastic ends in a bulk of material. Thin areas of plastic are weak and subjected to fracture.
2- Undercut finishing line provides mechanical retention for the plastic denture base.
3- Finish line provides a smooth transition from the plastic base to the removable partial denture metal framework.

Of course the medial extent of the minor connector depends on the lateral extent of the major palatal connector.
• If the finishing line is located too far medially, the natural contour of the palate will be altered by the thickness of the junction and the acrylic resin supporting the artificial teeth, when the palatal contours are restored, enhancing speech and contributing to a natural feeling for the patient.
• If, on the other hand, the finishing line is located too far buccally, it will be most difficult to create a natural contour of the acrylic resin on the lingual surface of the artificial teeth.

Junction of major connector and minor connector at palatal finishing lines should be located 2 mm medial from an imaginary line that would contact lingual surfaces of missing posterior teeth. Finish line on right is too far toward midline of palate.

Extension of finishing line to area of pterygomaxillary notch provides butt-type joint for attachment of border portion of resin base through pterygomaxillary notch (arrows).

TYPES OF FINISHING LINE
1- Vertical finishing line
It is the finishing line at the junction of ladder area and major connector in free end extension cases (class I and class II) in mandibular arch, and class IV mandibular arch with labial bar major connector. It represents the area where the acrylic resin that supporting artificial teeth ending.

2- Horizontal finishing line
It is the junction of major connector and ladder area and it extends horizontally forming an undercut area that support acrylic resin that carrying artificial teeth, this type of finishing line is detected in all maxillary partial denture cases and in class III mandibular cases.