2 nd Year Prosthetic Dentistry Partial Denture Design & Surveying

1. 2nd Year Prosthetic DentistryPartial Denture Design&Surveying Alan Jack manchester dental school educating, training and preparing our students for practice

2. Filling the Edentulous Space • Histories • History of presenting complaint • Medical • Dental • Social • Special Tests • Other Investigations • Vitality tests • Periodontal assessment • Radiographic assessment • Bone assessment • Tooth assessment • Ridge assessment • Monitoring • Space assessment • Photographs • Study models

3. Why fill the space? • Aesthetic factors • Function • Comfort • Speech • Prevention • Psychological factors

4. What are the treatment options? • Leave and monitor • Shortened dental arch • Bridges (various) • Partial CoCr denture • Partial acrylic denture

5. Classification of Partial Dentures Craddock. 1956 Osborne and Lammie. 1974 The above authors described Classes I – III Now-a-days we should include Class IV as implant technology is so improved and are in more common use today.

6. Partial Denture Design Process

7. Dental Surveyors • Maps out undercut areas • Soft Tissue • Tooth Tissue • Allows measurements of depth of undercut • Fundamental part of the Partial Denture Design Process

8. Surveying Tools • Analyzing rod – is used to determine the location of undercuts on teeth and tissue. • Undercut gauges – used to determine the location of the desired depth of undercut. • Surveying chisel – used to remove excess material during blocking out. • Carbon marker – pencil lead, used to mark the survey lines, which indicates the height of contour in relation to path of insertion. (You can have various colours)

9. Partial Denture Terminology • Undercuts

10. Undercuts • What is an undercut on a tooth? • The section that lies below area of maximum convexity of the tooth.

12. Partial Denture Terminology • Undercuts • Path of insertion • Path of displacement

13. Insertion & Displacement Pathways Path of Displacement This path is at right angles to the occlusal plane and is always a vertical pathway. We have 2 undercuts that we can utilise to aid in retention if we wish.

15. Surveying The Path of Displacement The study model is positioned on the surveyor to facilitate a right angle between the occlusal plane and the vertical. The surveying graphite is carefully placed on each tooth and moved round each of the vertical surfaces of the tooth. The shaded area shown is the area of tooth that is in the undercut. Once this is completed for all standing dentition the dental technician will cut grooves in the external wall of the study model so it can be replaced on the surveyor in the Path of Displacement

16. Insertion & Displacement Pathways Path of Insertion If we did not use the abutment undercuts (m & d) and had a vertical path of insertion then both pathways would be the same. We would have areas where food could pack either side of the denture.

17. Path of Insertion & Analyzing Rod Distal tilt, uses molar’s mesial undercut and will increase the retention, but makes the premolars undercut bigger and more unsightly. Path of insertion in red .

18. Path of Insertion & Analyzing Rod • An anterior tilt will improve the aesthetics and retention will be gained from the premolar’s distal undercut. • Differing paths of insertion will have differing advantages and disadvantages, care should be taken in planning and designing the denture. • Remember that soft mucosa undercuts can also aid retention.

19. Path of Insertion & Analyzing Rod • A posterior tilt as shown will reduce the unsightly black spaces that will be present if replacing missing anterior teeth.

20. Surveyor Chisel Removing excess blocking out wax to identify the clasp’s pathway and positional depth in the undercut with the last 1/3rdengaging in the undercut

21. Partial Denture Terminology • Undercuts • Path of insertion • Path of displacement • Support • Clasps • Connectors • Saddle areas } These are the components that make up a partial denture

22. Support

23. Clasps • Clasps provide anothermeans of retention in a partial denture. • Clasps can be constructed in wrought or cast metal. Wrought metal is more flexible than cast • Undercut depths • 0.75 Wrought stainless steel • 0.5 Wrought gold wire • 0.25 Cast Cobalt Chromium

24. Clasps • Retentive Component • > length = > flexibility • Last third of the clasp engages in the undercut area • Its position is determined by the use of an undercut gauge • Bracing Component • This is necessary to prevent unwanted tooth movement. • Can be provided by either a bracing clasp arm or baseplate

25. Occlusally Approaching Clasps • “C” clasps • “3 arm clasps” • Retentive arm, bracing arm and an occlusal rest. • Circumforential Clasps

26. Gingivally Approaching Clasps These are generally more aesthetic than occlusally approaching clasps • I Bar • “T” or “L”

27. Acrylic Connectors • If the dentures are to be made from acrylic only, it is important that the denture base has optimum thickness in order to provide sufficient strength. • It is also important that maximum coverage is utilised to assist in indirect retention. • Ideally there should be a minimum of 3mm clearance of the plate from any standing teeth.

28. Upper Denture Connectors This is the component that joins the saddle areas together and provides some indirect retention. Minimum coverage is appropriate in the provision of CoCr partials. • Palatal strap • Anterior and Posterior Straps • Anterior Strap

29. Lower Connectors • Lingual Plate • Lingual Bar • This denture also has a continuous clasp which is a minor connector and provides support and indirect retention.

30. Partial Denture Terminology • Undercuts • Path of insertion • Path of displacement • Support • Clasps • Connectors • Saddle areas

31. Saddle Areas • Abutment teeth at either end of the saddle areas will or may have undercuts unwanted undercuts. • These unwanted undercuts have to be blocked-out in plaster so as acrylic will not flow into these areas when the denture is being flasked, packed and finished. • Deep soft tissue undercuts may have to be blocked-out

32. Partial Denture Terminology • Undercuts • Path of insertion • Path of displacement • Support • Clasps • Connectors • Saddle areas • Wax or Metal Try-in denture

33. Trial Insertion • A wax trial partial denture will not have clasping, if going to be acrylic only the clasps will be added after the occlusion is checked in the mouth. • Wax trial insertion should be used before constructing a CoCr denture so the saddle acrylic matrix retention can be placed appropriately. • A trial of the metal work (CoCr) then a trial of teeth in wax on the CoCr is recommended before going to finish.