Dent 684 Complete Dentures

1. Dent 684 Complete Dentures Course Introduction, Laboratory Safety, Preventive Maintenance of the Articulator & Mounting the Casts

2. Purpose • To help students understand the materials used and the processes involved in treating complete denture patients. • To acquaint students with all phases of complete denture construction. • To enable students to understand the concepts involving relationship between the location of denture teeth to residual ridges and their effect on denture stability. • To enable them to effectively communicate with dental laboratory technicians. That you may develop a“healthy philosophy” toward complete denture care.

3. If these goals are to be met, it is imperative that the students show up on time for the classes and labs and stay until they complete their projects. If a student does not meet these criteria, that student will have trouble working with a complete denture patient in the clinic. Lab instructors will not step in and do all the work for you. If you are not prepared, you may fall behind the rest of your classmates.

4. When you work on the anatomic setup of teeth for the complete dentures and all procedures following that exercise that utilizes those mounted casts, you will turn in this project on the articulator at the end of each lab period by placing it in the cabinet at the front of the lab. Failure to do so can result in disciplinary action that may lead to failure of the course and summer remediation.

5. Course Rules: • Attendance is necessary. • Seating is assigned. • No more than two unexcused absences. • Write questions down.

6. Components • Lecture • Laboratory Exercises Reading Assignments • Syllabus & handouts

7. Grades Scale listed-page 7 Dent 482.01 Lecture course ( May be lowered one letter grade if student has 2 or more unexcused absences.) Midterm & Final • Based on lectures and reading assignments • 100% of total grade (50% + 50%) Lab: 482.02 • Daily Grade: 20% • Practical: 60%

8. Laboratory Safety Rules CAUTION: Improper lathe technique can cause personal injury and damage the prosthesis.

9. Observe Safety Rules in the Lab Do not wear plastic gloves when operating a lathe or polishing wheel. The machinery can grab the glove and rip it off and the chance of injury is very high.

10. Observe Safety Rules in the Lab Use the lathes and polishing wheels on low speed.

11. Observe Safety Rules in the Lab Use the central vacuum system and wear a mask when grinding gypsum products.

12. Observe Safety Rules in the Lab When using the lathe, model trimmer, or polishing wheels, brace your hands so that they cannot be pulled into the work area. Also use the safety shields when provided.

13. Observe Safety Rules in the Lab Maintain a clutter-free work area. Materials, instruments, etc. may get lost or broken or may cause injury if the work site is not kept orderly and clean.

14. Observe Safety Rules in the Lab Insert saw blades in the saw frame so that it cuts on the pull stroke rather than the push stroke. A push stroke can cause torque on the saw blade, causing it to flex so that it breaks, injuring you and/or destroying your work.

15. Observe Safety Rules in the Lab Keep long hair up or underneath a scarf or inside your lab coat.

16. Observe Safety Rules in the Lab Always wear protective wear (safety glasses, masks, lab coat, etc.). (You can be barred from the lab.)

17. These safety glasses don’t do much good where they are located. This was not a staged photo. The student was unaware that the picture was being taken.

18. Observe Safety Rules in the Lab Don’t use your red-handled knife to trim plaster or stone.

19. Observe Safety Rules in the Lab When not using sharp instruments it is better to keep tem covered. A handy sheath can be made from your excess lab putty.

20. Observe Safety Rules in the Lab Do not have flammable liquids near a flame. Make sure the wick is covered before filling the Hanau torch.

21. This is what happens when the wick is not covered before filling the Hanau torch. The student compounded things further by throwing the torch into a wastebasket. Note the burned out liner of the basket.

22. Note also the scorched clinical smock and the burned off top of the alcohol bottle. This could all have been avoided if the student had used a little common sense.

23. Observe Safety Rules in the Lab Using a pneumatic chisel to remove any remaining stone residue is a common practice by experienced lab technicians, but be careful…it is easy to break or mar the denture or injure a hand.

24. Observe Safety Rules in the Lab Removing positive bubbles with a chisel or other sharp instruments is also a common practice by experienced lab technicians. A denture should be placed against a bench top or a rubber bumper and a push stroke is used in a direction away from your hand. Improper usage can leave a very nasty wound.

25. Injuries that have occurred in dental labs • Broken glasses. • Cuts, some requiring stitches. • Broken arms and fingers. • Severe burns. • Large patches of scalp removed by a lathe. • Injuries caused by explosions. • Broken teeth. • Loss of an eye. (Note: Most of these happened to experienced laboratory technicians. What do you think your chances are?)

26. Mounting the Casts for the 30-Degree Set-Up

27. The set screw is loosened, the condylar ball is pushed back flush with the rear wall of the condylar fossa, and locked in centric position by tightening the set screw.

28. The lateral condylar guidance is arbitrarily set by loosening the knob on top of the articulator and setting the guide at 15o.

29. The lock nut at the back of the horizontal condylar guidance is loosened and the guidance angle is set at 30o.

30. The incisal guide pin is also set at zero.

31. B C A • The incisal guide table is also set at zero. • The table is set so that the guide pin hits on the horizontal line on the surface. • The lateral wings are set on zero.

32. Before the casts are mounted on the articulator, they need to be trimmed on the model trimmer to ensure that their bases are flat and the edges of their bases are a right angle. Be careful to not remove too much.

33. The casts also will require indexing so that they may be remounted after the dentures are processed. A simple way to accomplish this is to use a stone wheel mounted on a slow-speed lathe. The indexing is about 2 mm deep and does not extend all the way to the edge of the cast to ensure neatness and permit easy separation of the cast from its mounting without risk of marring the index with the knife used for the separating procedure.

34. The maxillary cast is mounted on the articulator by the use of a mounting jig attached to the mandibular member of the articulator. A mounting plate is placed on the upper member and the mounting screws are tightened with finger pressure until there is no movement in either area. A containment wall is made of masking tape that surrounds the border of the cast and allows a neat and easy mounting.

35. After the maxillary cast is mounted, the mounting plaster is smoothed and the mounting jig is removed from the mandibular member of the articulator. A mounting plate is placed on the lower member and the mounting screws is tightened with finger pressure until there is no movement. The articulator is inverted and a mounting jig is fitted on the maxillary cast. A mandibular cast with its masking tape containment wall in place is fitted to the mounting jig. The articulator is closed to ensure that there is no binding of the containment wall with the lower member of the articulator upon closing.

36. A thin mix of mounting plaster is placed in the containment area and on the mounting plate on the lower member of the articulator. Enough plaster is placed to ensure that when the articulator is closed that the plaster on the mounting plate will close into the plaster on the cast.

37. More plaster is added if necessary and is smoothed with a wet finger. After the plaster sets, the mounted cast is removed from the articulator, the masking tape containment wall is removed, and the plaster is trimmed with a sharp knife.

38. After the mounting is trimmed with a knife, any blemishes may be filled with a thin mix of plaster. The mix needs to be extra thin as the bulk of the mounting plaster has not reached its final set and is generating heat which will draw moisture from the new plaster mix and dry it out very quickly.

39. The added plaster is smoothed with a wet finger and the mounting is checked to ensure that there are no major flaws. A piece of lightly abrasive wet/dry sandpaper is cut to be used to smooth the surface of the mounting after it is dry.

40. Use the piece of wet/dry sandpaper to finish the mountings. Notice that the casts and their mountings are very neat and clean.

41. Use the piece of wet/dry sandpaper to finish the mountings. Notice that the casts and their mountings are very neat and clean.

42. The articulator is also cleaned and the mounted casts are replaced on the articulator. The instrument and the mounted casts are checked again to ensure that they are free of any excess plaster. You should always keep your casts, instruments and work area clean and neat.

43. The added plaster is smoothed with a wet finger and the mounting is checked to ensure that there are no major flaws. A piece of lightly abrasive wet/dry sandpaper is cut to be used to smooth the surface of the mounting after it is dry.

44. The depth of the vestibule is marked in its middle just anterior to the central incisors. This mark is then transferred to the land area on both sides, because when the baseplate is placed on the cast, the center mark will be covered. When the wax rim is made, it is marked to reflect the position of this line.

45. The wax rim is then trimmed to this line. The same procedure is done on the mandibular cast. These positions will show the maximum anterior placement of teeth in these arches before instability is created.

46. Next, place dots on the highest points of the ridge over the retromolar pad areas, the first premolar areas and the center of the labial frenum. Transfer the locations of these dots to the land area of the casts by using a tongue blade. Connect the two dots on the ridge on each side with a tongue blade independently and mark the points where the tongue blade crosses the land area. Place a tongue blade over a dot in the center of the labial frenum and mark the points where the tongue blade crosses the land area.

47. When the mandibular rim is flush with the maxillary rim when the articulator is closed, place a tongue blade flat on the mandibular occlusion rim and mark where the midlines of the ridges lie and where the anterior mark is located. Adjust the anterior rim to fit within this point over the frenum, as this is the most anteriorly the teeth can be placed.

48. Q. If I forget to have the pin set on zero do I need to remount the cast? • Yes, you must always ensure that the pin is set on zero so that the VDO is retained before an after the dentures are processed. • If I don’t have the condyle securely set in centric relation when I mount the casts do I still need to remount the cast? • Yes, if you don’t have the condyles locked in centric relation, then your mounting is not accurate. • Q. If the cast comes off the mounting can I use super glue to re-attach it to the mounting. • A. No. You must be able to remove the cast from the mounting before processing the denture and replace it accurately after processing. Use sticky wax around the juncture of the cast and the mounting (not between them) to hold it in place.

49. Preventive Maintenance of the Hanau Wide-Vue Arcon Articulator

50. The End