Classifications Of Elastomeric Impression Materials | Part 1 | Dr. Rashmi Singh — Transcript

Full transcript

1. 0:19So, let's begin. Today's topic is
2. 0:22elastomeric impression materials. Let's
3. 0:24start with the introduction. I have
4. 0:30kept the introduction very simple as
5. 0:32always, and I have followed the same
6. 0:33format in all my impression material
7. 0:35videos, where we introduce the material
8. 0:37to our audience through all its
9. 0:39classifications. So, first, this
10. 0:45elastomeric impression material is, in
11. 0:47general, elastic in nature. It is
12. 0:51irreversible, thermoset, non-aqueous,
13. 0:53and mucostatic. Except for putty. As we
14. 0:57move forward, you will understand this
15. 0:59better. The impression material is now
16. 1:03used to make impressions of partially
17. 1:05edentulous arches. Now, what are
18. 1:10elastomers? If we look at the molecular
19. 1:12level. So, these are a group of
20. 1:16polymers with elastic or rubber-like
21. 1:18properties. So, this is how we can
22. 1:23describe elastomers. Its ADA
23. 1:27specification number is 19. You have to
24. 1:30remember that. Then, other than
25. 1:32elastomeric impression material. It is
26. 1:35also called non-aqueous impression
27. 1:37material or rubber-base impression
28. 1:38material. What are these? These are
29. 1:46large molecular weight polymers tied
30. 1:48together at certain points called
31. 1:49cross-linking to form a
32. 1:50three-dimensional network, and the
33. 1:52amount of cross-linking determines the
34. 1:54stiffness and elastic behavior of the
35. 1:55material. Alright? So, now we have seen
36. 2:01what an elastomer is. It is a group of
37. 2:03polymers that have elastic or
38. 2:05rubber-like properties. And large
39. 2:07molecular weight, how else can we
40. 2:09describe this? Large molecular weight
41. 2:12polymers tied together, which through
42. 2:14cross-linking form a three-dimensional
43. 2:16network. As seen here. And the degree
44. 2:22of cross-linking defines how stiff the
45. 2:24material is or what the elastic
46. 2:25behavior of that material is like. We
47. 2:31introduce another term in elastomeric
48. 2:33impression material, which is
49. 2:35vulcanizing or curing. What is
50. 2:37vulcanizing or curing? The process by
51. 2:42which liquid polymers are converted
52. 2:44into solid rubber at room temperature
53. 2:46is called vulcanization. The process is
54. 2:51called vulcanization, or it is also
55. 2:52known as curing. I have explained this
56. 2:57term in the introduction slide itself
57. 2:58because we are going to be using these
58. 3:00terms in the slides ahead. Let's see
59. 3:04the definition. According to the GPT
60. 3:08Glossary of Prosthodontic Terms, which
61. 3:10we look at for every impression
62. 3:11material. According to that, elastomers
63. 3:15are defined. An elastomer is a polymer
64. 3:20that has a glass transition temperature
65. 3:22that is below its service temperature.
66. 3:25Service temperature is usually room
67. 3:27temperature itself. The temperature at
68. 3:30which we can use it. These materials
69. 3:33are characterized by low stiffness and
70. 3:35extremely large elastic strains. As we
71. 3:40saw in the previous slide, it has
72. 3:42extremely rubber-like and elastic
73. 3:43properties. And if it has elastic
74. 3:47properties, its stiffness will be low.
75. 3:50So it is explained like this. And
76. 3:56elastomeric impression materials can be
77. 3:58defined as a group of flexible chemical
78. 4:00polymers that are either chemically or
79. 4:02physically cross-linked; generally,
80. 4:03they can be easily stretched and
81. 4:05rapidly recover their original
82. 4:06dimensions when the stresses are
83. 4:08released. So, as you stress it, it will
84. 4:15stretch, and as soon as the stress is
85. 4:17released, it returns to its original
86. 4:19dimension. So these are the two key
87. 4:23definitions you need to remember.
88. 4:27Let’s see some ideal requirements—
89. 4:29what properties are required in an
90. 4:31ideal elastomeric impression material.
91. 4:35First, it should have excellent
92. 4:37reproduction of surface details. Second
93. 4:42, it should be viscous enough so that
94. 4:43we can contain it in the tray and take
95. 4:45the impression. It should be able to
96. 4:50set at mouth temperature in a
97. 4:51reasonable amount of time. It shouldn't
98. 4:55take too much time, nor should it set
99. 4:56too quickly. Resistance to distortion
100. 5:00or tearing. When we are withdrawing or
101. 5:03retrieving the impression from the
102. 5:04patient's mouth, it should not distort.
103. 5:07It should be dimensionally stable. Long
104. 5:10enough to allow one or more casts to be
105. 5:12poured. So, it should be dimensionally
106. 5:15stable enough that we can make two to
107. 5:16three casts from a single impression.
108. 5:19It should be biocompatible. Of course,
109. 5:21it should be cost-effective. In terms
110. 5:24of time as well as the expense of the
111. 5:25associated processing equipment.
112. 5:28Meaning, not only should its cost be
113. 5:30low. But the cost of any equipment used
114. 5:34to process that material should also be
115. 5:35low. It can also be used as a
116. 5:40duplicating material to make refractory
117. 5:42casts, as we saw with agar. So these
118. 5:45are the very basic ideal requirements.
119. 5:48If you think about it, you won’t even
120. 5:50need to memorize them. You will easily
121. 5:54remember what the ideal requirements
122. 5:55for an elastomeric impression material
123. 5:57might be. Now let’s look at the
124. 6:00classification. Okay? Now, the
125. 6:02classification is very important. Every
126. 6:05time, or most of the time actually,
127. 6:07whenever questions about elastomeric
128. 6:09impression materials come up, it’s
129. 6:11basically asked to define elastomers or
130. 6:13elastomeric impression materials,
131. 6:15classify them, and then write about any
132. 6:17one of them. Whatever classification we
133. 6:20look at now, any part of it could be
134. 6:22asked. But then, what are the two
135. 6:24common things? One is the definition
136. 6:25and the classification. And they might
137. 6:28not ask for ideal requirements, but you
138. 6:30should write them down to get those
139. 6:31extra marks. So, first, elastomeric
140. 6:35impression materials are classified
141. 6:37based on chemistry, viscosity,
142. 6:39wettability, or the method of
143. 6:41polymerization. Let’s look at them
144. 6:44one by one. First is the chemistry, and
145. 6:47according to the chemistry, they are
146. 6:49classified as polysulfides. This
147. 6:51classification is the most important
148. 6:53one. So, you must remember polysulfides
149. 6:55, condensation and addition
150. 6:57polysilicones, and polyethers. These
151. 7:02are your basic classifications based on
152. 7:04chemistry. Next is the viscosity, which
153. 7:08is light body or syringe consistency.
154. 7:11Right? The classification is based on
155. 7:14how much viscosity it has. The second
156. 7:17is the medium or regular body. The
157. 7:19third is the heavy body, which is also
158. 7:21called tray consistency. And the last
159. 7:24one is the very heavy or putty
160. 7:26consistency. So, this is how we can
161. 7:30classify them based on viscosity. Now,
162. 7:35viscosity depends on the amount of
163. 7:37filler. What is common among all of
164. 7:40these? All the materials we saw in the
165. 7:44previous classification: polysulfides,
166. 7:47polysilicones, and polyethers. These
167. 7:50consistencies are found in all three
168. 7:52materials. So, what is the thing that
169. 7:55makes their consistency different? That
170. 7:58is the amount of filler. You might be
171. 8:00asked this in a viva. And you should
172. 8:02also know how this viscosity changes.
173. 8:05It is changing based on how much filler
174. 8:07content it has. That is what changes it
175. 8:08. For example, it is 16%in light body.
176. 8:11In regular body, this amount increases
177. 8:14to 26%. In heavy body, it becomes 36%.
178. 8:17And in putty, it is 54%. That means,
179. 8:19what do we understand from this? That
180. 8:22viscosity increases from light body to
181. 8:24putty. Again, as I have already told
182. 8:28you, polysulfides. They are available
183. 8:30in light body, regular body, and heavy
184. 8:32body. In polysilicones, apart from
185. 8:34these three, you also get putty
186. 8:36consistency. And polyether is available
187. 8:40in regular body and body modifier
188. 8:42consistency. So, this was our
189. 8:46classification based on viscosity. Next
190. 8:49is wettability. So, according to
191. 8:52wettability, they can either be
192. 8:54hydrophobic or hydrophilic. Hydrophobic
193. 8:57means hydro means water. Phobic means
194. 9:00running away from it, like a phobia.
195. 9:03Right? So, in that case, the angle
196. 9:11formed between our solid and the water
197. 9:14particles—the angle that is formed—
198. 9:16will be a contact angle from 40 ° to
199. 9:1870 °, and when this increases from 80
200. 9:21° to 115 °, it is called hydrophilic.
201. 9:30So this is our third way of classifying
202. 9:32elastomers, that is according to their
203. 9:34wettability: hydrophobic and
204. 9:36hydrophilic. Next is methods of
205. 9:39polymerization. According to the method
206. 9:42of polymerization, these can be
207. 9:44classified as addition polymerization
208. 9:46or condensation polymerization. Now,
209. 9:49what happens in addition polymerization
210. 9:51? And what happens in condensation
211. 9:53polymerization? I have made a complete
212. 9:55individual video on this in part one of
213. 9:57my denture base resin video. So you can
214. 10:00go and watch that video. In this, the
215. 10:03examples of elastomers in addition
216. 10:05polymerization are polyether and
217. 10:07addition polysilicone, and the examples
218. 10:09of condensation polymerization are...
219. 10:11...condensation polysilicone and
220. 10:13polysulfides. So these are the four
221. 10:17methods of classifying elastomers. I
222. 10:20hope it is clear to you. Now we will
223. 10:23start with the clinical application of
224. 10:25the polymers, sorry, elastomers. So, in
225. 10:29clinical application, the first is
226. 10:31impressions for fixed partial dentures,
227. 10:33complete dentures, or removable partial
228. 10:35dentures. So it is not like it is only
229. 10:37used for partial dentures or not used
230. 10:39for complete dentures. This can be used
231. 10:42in any kind of case. Okay? So, A fixed
232. 10:51partial denture, complete denture or
233. 10:53removable partial denture, cast partial
234. 10:55denture; then polyether is used for
235. 10:57border molding of edentulous custom
236. 10:59trays, also for bite registration; also
237. 11:02silicone duplicating material is used
238. 11:04for making refractory casts during cast
239. 11:06partial denture construction. So the
240. 11:12refractory cast that we studied—we
241. 11:14can make it with agar, as seen in our
242. 11:16last impression material video—
243. 11:18similarly, we can also apply this
244. 11:20clinically for duplicating the cast. In
245. 11:25today's video, we have seen the
246. 11:27introduction, the definitions of
247. 11:29elastomers and elastomeric impression
248. 11:31materials, the four classifications of
249. 11:33elastomers, and their clinical
250. 11:34applications. In the further coming
251. 11:38videos, we will be discussing each of
252. 11:40the elastomers—the polysulfides,
253. 11:42polysilicones, and polyethers—in
254. 11:44detail. I hope you have understood this
255. 11:47video properly. We will come up with
256. 11:50the next video very soon. Till then,
257. 11:53happy studying.