Untitled Flashcards Set

Here are the answers to your questions:

1. Is alginate reversible or irreversible hydrocolloid?

- Alginate is an irreversible hydrocolloid. Once it sets, it cannot return to its original state.

2. What is the water temperature for water when taking alginate impressions?

- The water temperature for mixing alginate is typically between 60°F (16°C) and 70°F (21°C) for standard setting. Warmer water speeds up the setting time, while cooler water slows it down.

3. Is an impression a positive or negative reproduction?

- An impression is a negative reproduction of the oral structures.

4. Mixing time, setting time of alginate:

- Mixing time: 45 seconds to 1 minute.

- Setting time: Typically 2 to 3 minutes for normal-set alginate, and about 1 to 2 minutes for fast-set alginate.

5. Placement of tray in the mouth:

- The tray should be placed in the mouth with a gentle, firm motion, starting from the back of the arch and moving forward.

6. Method of tray removal:

- To remove the tray, use a quick, snapping motion to break the suction and gently lift it from the mouth.

7. How to prevent gagging:

- To prevent gagging, use smaller amounts of material, avoid overfilling the tray, have the patient breathe through their nose, and keep the impression tray as far back as necessary without causing discomfort.

8. What goes in the bowl first, powder or liquid?

- Powder should go into the bowl first, followed by the liquid.

9. What is gypsum mainly used for?

- Gypsum is mainly used to make dental casts or models (both positive and negative replicas of the oral structures).

10. Endothermic vs Exothermic:

- Endothermic processes absorb heat, while exothermic processes release heat. For example, the setting of gypsum is exothermic, as it releases heat during the reaction.

11. Adding extra water to the gypsum mix can cause the cast to be:

- Adding extra water can cause the gypsum cast to be weaker and more porous.

12. Uses of alginate in dentistry - (why):

- Alginate is used for making impressions for study models, diagnostic casts, dentures, and other appliances because it's easy to mix, sets quickly, and provides an accurate negative impression.

13. What must we do to impressions before sending them to the lab?

- Impressions should be disinfected and wrapped in a damp paper towel to prevent them from drying out before sending them to the lab.

14. What is working time? Setting time? Spatulating? Gelation?

- Working time is the time you have to manipulate the material before it begins to set.

- Setting time is the time it takes for the material to harden completely.

- Spatulating refers to mixing the material with a spatula.

- Gelation is the process by which the material transitions from a fluid to a gel-like state during setting.

15. Position of patient in dental chair while taking an impression?

- The patient should be positioned with their head slightly tilted back, with their mouth in a natural bite position to facilitate a proper impression.

16. How and why do we need to avoid air bubbles in plaster?

- Air bubbles should be avoided because they can create defects or inaccuracies in the final cast. To minimize bubbles, mix slowly, use proper spatulating techniques, and tap the container to release trapped air.

17. Why do we sometimes use wax on the impression tray?

- Wax can be used to modify the tray for better fit, comfort, or retention, or to add a border for better control of the material during impression-taking.

18. Trimming differences between maxillary and mandibular casts:

- Maxillary casts are typically trimmed to form a U-shape, while mandibular casts are trimmed to form a V-shape to reflect the natural shape of the arches.

19. What is a wax bite registration?

- A wax bite registration is a technique where a patient bites into a softened wax material to capture the occlusion or bite relationship between the upper and lower arches.

20. What can be used to polish a cast?

- A dental polishing stone, a soft brush, or a buffing wheel can be used to polish a cast.

21. Dental study models are a negative or positive reproduction?

- Dental study models are positive reproductions of the original impression.

22. Study models are three-dimensional views of the arches. (T/F)

- True, study models are three-dimensional representations of the upper and lower arches.

23. What are stock trays, tray adhesives, custom trays?

- Stock trays are pre-manufactured trays that come in various sizes.

- Tray adhesives are used to help alginate or other materials adhere to the tray.

- Custom trays are made to fit an individual patient’s mouth for more accurate impressions.

24. What is agar, hydro-, syneresis, hysteresis?

- Agar is a reversible hydrocolloid material used for impressions.

- Hydrocolloid is a material that forms a gel when hydrated.

- Syneresis refers to the process where water is expelled from the gel, causing it to shrink.

- Hysteresis refers to the difference in temperature at which agar changes from gel to sol and vice versa.

25. Inverted pour method:

- The inverted pour method is used in making gypsum models, where the impression is first poured with a thicker mix of gypsum, and then a second pour is made with a thinner mix to form the base of the cast