Dental model surveying using a surveyor.pptx

Before starting a removable partial denture restoration it is important to first survey the model to identify retentive undercuts, guide lines and the unwanted undercuts

1. DENTAL MODEL SURVEYING It’s the determination of the relative parallism of two or more surfaces of the teeth or other parts of the cast of the dental arch. Or It is the analysis and comparison of the prominence of intraoral contours associated with the fabrication of the removable partial denture (RPD).

2. PROCEDURES OF MODEL SURVEYING This may be divided into the following distinct phases: Preliminary visual assessment of the study cast. Initial survey. Analysis. Final survey.

3. Cont’n Preliminary visual assessment of the study cast It can also be known as eyeballing the cast and is a useful preliminary, to the surveying procedure proper. The cast is kept in the hand and examined from above. The general form and arrangement of the teeth and ridge can be seen, any apparent problems noted and an idea taken as to whether or not a tilted survey should be applied.

4. Cont’n Initial survey The cast is positioned with the occlusal plane horizontal. The teeth and ridges are then surveyed to identify undercut areas that might be utilized to provide retention in relation to the most likely path of displacement. The position of the survey lines and the variations in the horizontal extent of undercut associated with them should be noted. The amount of undercut can be judged approximately from the size of the triangle of light between the marker and the cervical part of the tooth, or measured more precisely by using an undercut gauge. An assessment can then be made as to whether the horizontal extent of undercut is sufficient for retention purposes.

5. Cont’n Analysis The Removable Partial can be created on a cast which has been surveyed with the occlusal plane horizontal (i.e. so that the path of placement equals the path of displacement). Still, there are times when tilting of the cast is indicated so that the paths of insertion and displacement vary. Before deciding if the cast should be turned for the final survey the graphite marker in the dental surveyor is changed for an analyzing rod so that various positions of the cast can be examined without marking the teeth. Following aspects, in last survey with the cast tilted, are considered : Appearance. Interference. Retention.

6. Cont’n Final Survey If it is decided that the cast should be tilted, the analyzing rod is exchanged for a marker different in color from that used in the first survey, and the final survey is carried out. It will then usually be found that the teeth to be clasped have two separate survey lines which cross each other. The former can be achieved by the use of guide surfaces or clasps while the latter is provided by clasps alone. Alternatively, the analyzing rod is placed against one side of the base of the cast and a line drawn on the cast parallel to the rod. This is repeated on the other side and at the back of the cast so that there are three widely spaced lines parallel to the path of insertion

7. OBJECTIVES OF DENTAL MODEL SURVEYING To determine the most desirable path of placement that will eliminate or minimize interference to placement and removal. To identify proximal tooth surfaces that are, or need to be, made parallel so that they act as guiding planes during placement and removal. To locate and measure areas of the teeth that may be used for retention. To determine whether tooth and bony areas of interference will need to be eliminated surgically or by selecting a different path of placement. To determine the most suitable path of placement that will permit locating retainers and artificial teeth to the best esthetic advantage. To permit an accurate charting of the mouth preparation to be made. To delineate the height of contour (survey line) on abutment teeth and to locate areas of undesirable tooth undercut those are to be avoided, eliminated, or blocked out. To record the cast position in relation to the selected path of placement for future reference. This may be done by locating three dots(tripods)or parallel lines on the cast; three dotes or lines, one anterior and two posterior to permit its reorientation.