Prosthodontics Sheet #11 PDF

11 Asma’a Abu-Qtaish Abdullah Alrawashdeh Rasha Alomoush 0|Page  Wax up of complete denture Today’s lecture will be about wax up of complete denture, we will talk about: o The importance of denture wax up o Wax up procedure So far, we...

11 Asma’a Abu-Qtaish Abdullah Alrawashdeh Rasha Alomoush 0|Page  Wax up of complete denture Today’s lecture will be about wax up of complete denture, we will talk about: o The importance of denture wax up o Wax up procedure So far, we learnt about some clinical steps starting with primary impression then secondary impression, jaw relation, try in and denture insertion, along with these clinical steps there are some laboratory steps starting with special tray construction and ending with flasking, packing & curing and processing to the final denture. So, after we have finished the teeth setting, we should do a wax-up procedure for complete denture. → What do we mean by wax-up? Waxing: is contouring of wax pattern or the wax base of trial denture into desired form. Festooning: is the process of carving the denture base to stimulate the contour of the natural tissue surrounding the artificial teeth. In this picture we see different surfaces of the denture (principal surfaces are involved in the functional stability of dentures): 1. Impression surface (basal): which we recorded it already in primary & secondary impression. 2. Polished surface: which is the outer surface of complete denture that come in contact with the oral tissue. 3. Occlusal surface: which has been recorded by bite registrations and accordingly we do the tooth setting. ❖ The surfaces that we apply wax-up in We actually apply waxing to polished surface that represent outer surface which will be in contact with oral tissue (surface contact the lip, cheek & tongue), to have smooth surface & reflect the natural details of oral tissue. 1|Page → Why do we do that? Because the form of the polished surface of a denture will influence: o Denture retention o Stability. o Aesthetic (simulate natural anatomy of the patient’s mouth which includes size, shape & contour of missing oral tissue). o Ensure optimal phonetics & avoid lip and cheek biting. ❖ The proper form to wax-up the polished surface The polished surface should have a favorable angle (proper form) with the cheek, lip & tongue, and this is achieved by: o Accurate impression of the tissue (denture border) that limits the extent of denture. o Accurate buccolingual position of teeth (in relation to the ridges); it is important because lateral forces also are exerted on the dentition during function, Teeth positioned too buccally or too lingually allow the musculature of the cheek or tongue to create unfavorable forces on the inclined plane of the surface of the teeth and the polished denture. o The fullness of wax and its curvatures buccally and lingually. There are 2 important borders in the denture that we should shaped in way to keep the original width of impression: 1. The wax surfaces around the teeth are known as the art portion of the polished surface For esthetic reasons this portion should imitate the form of the tissues around the natural teeth so attend to carving cervical exposure of teeth (slight projection around the teeth that mimicking the root, but no fancy or excessive carving). 2. The other border is called anatomical portion and is shaped in a way not to lose the original width of the impression. 2|Page ❖ The criteria that we should follow in upper & lower denture during shaping The denture bases between the teeth and the border should be shaped in such a manner as to aid retention by the mechanical directional forces of the muscles and tissues, generally the contours are full on the buccal aspect of the denture but are quite concave “curved inward“ on the palatal and lingual surfaces to conform the space requirements of the tongue. **This criteria in general to both upper & lower denture** ▪ If we specified the mandibular denture: 1. lingual & buccal border are concave - Why? o To conform to the tongue and cheek so the muscles will grip and tend to seat the denture o If made convex the inclined plane forces resulting from pressures of the tongue and cheeks will tend to unseat the denture. o The borders should be concave to allow the tissues to function around the denture while the denture sits in its place. o Allow sufficient space for the tongue o Allow seating of the denture. 2. The buccal surface of mandibular dentures in the first premolar region should be vertical to concave in shape - Why? o To prevent interference with the action of the modiolus because if the polished surface inclines toward the cheek or if the dental arch in the premolar region is too wide this connecting point (modiolus) of muscles can displace the mandibular denture ✓ Remember: modiolus connects the facial muscles with the orbicularis oris muscle. 3|Page 3. The lingual flange of the mandibular denture should have the least possible amount of bulk, except at the border, which must be quite thick. (lingual flange should be concave while you should keep the thickness of borders) - Why? o To allow the seal all around the denture peripheries. o Because this thickness is under the narrower portion of the tongue, and it greatly enhances the seal by contacting the mucolingual fold. ▪ If we specified maxillary denture: 1. should be a gentle concave contour of the denture base extending from the palatal surface of canine and first premolar to the horizontal shelf of the palate. - Why? o Because Airflow for speech sounds is greatly affected by the contact or approximation of the lateral tongue in these areas o If this contour has deep concavity or a near right angle, the lateral border of the tongue will not control air during speech. Particularly, the “s” sound will be distorted, sounding more like a “sh.” Fricative sounds of “f” and “v” also may be distorted 2. The rest of palatal surface of the maxillary denture should be waxed to a uniform thickness of 2.5 mm, so the palatal area will be as thin as possible as this had minimal resorption. - Why? o If made thick it will affect speech. Before the addition of wax to finalize the wax-up, it is important to evaluate the prosthetic occlusion, and after the proper occlusion is established and finalized, additional baseplate wax is added on the buccal and labial surfaces of the mandibular and maxillary trial dentures and along the cervical collars of the teeth. During this stage of wax-up procedure there are some general considerations for both dentures to take into account: - Excess wax is removed first so the land area of the master cast is exposed. (fig A&B) 4|Page - then the small end of wax knife is held at 45◦ to the tooth surface to form the gingival margin (fig C) - Gingival outline form and contours must be reproduced. This is particularly useful in patients with a high smile line who display significant amounts of gingiva. (fig D) - Maxillary and mandibular canine eminences are reproduced to support the lips and the corners of the mouth (this will give aesthetics appearance and avoidance of lip biting). (fig E) - From interproximal area we draw triangles for the roots, then carve the wax between these triangles, so that roots are more prominent, then round the triangles to make them less prominent. - The interdental papilla must be flat or slightly concave to provide a more natural appearance and avoid food impaction. - Expose all clinical crowns of the anterior teeth to achieve better aesthetics because most adult natural dentition reveals the teeth to the cementoenamel junction (CEJ). - Avoid forming undercuts, especially lingual of mandibular, because this will accumulate food. The lingual surface of the mandibular denture may be made slightly concave without extending the depth of the concavity under the lingual surface of the teeth. A projection of the tooth beyond the polished surface acts as an undercut into which the patient’s tongue will slip, thereby causing the denture to be unseated and also allowing food to accumulate (Fig. 12- 5). 5|Page - The denture base must be uniform in outer thickness, because Lumps and bumps are very uncomfortable, draw attraction to their presence, and provide a site for debris accumulation. - The waxed denture is exactly duplicated in the final denture, care must be taken to wax the denture exactly as you wish the final denture to appear. - The posterior palatal seal must be cut/refined into the cast before the denture is sealed down and processed. - In the maxillary denture, palatal festooning restores part of the palatal surface of the tooth that is not supplied in artificial teeth. (Fig. 12-6). - After wax-up and festooning are completed, seal the periphery of the denture flange to the inner edge of the land of the cast. (Fig. 12-7) Until here we end the wax-up importance & consideration, so you should know why we do the wax- up, the specifications for each area of the denture, and why we care about polished surface and what it will affect. Now we will talk about wax-up procedure step by step (what we will do in lab): 1. Adding sheet of wax labially then we will contour the wax-up carefully you should avoid a bulky wax-up because it contributes to porosity and dimensional processing error, Place strips of base plate wax along the facial surface of the trail denture so that they extend from the gingival third of the teeth to the edge of the cast. (fig 7&8) 2. With a hot spatula lute the strips to the underlying wax at 1⁄4 inch intervals and melt the wax into contact with the necks of the teeth. 3. After the wax has cooled, carve the interdental papillae & gingival margins by holding the lacron carver at 45o angle to the neck of the teeth or by using ash #5 6|Page 4. Remove palatal wax (8 mm palatal to the teeth), then Place the wax in the palate and adapt it. 5. Preformed palate with rugae area (rugae wax patterns) 6. Seal and smooth the wax with a spatula and/or torch. Extend the sheet of base plate wax beyond the posterior border of the posterior palatal seal. 7. Carve the palatal surface. Use the knife end of a Roach carver to carve wax on the palatal side of the posterior teeth 8. Remove all wax from the palatal of the teeth above the collar or finish line. 9. Wax the lingual flange of the mandible denture thickly enough to full all depressions and to slope down from the necks of the teeth and inward toward the tongue. The slope of the flange should be free from the undercuts and very slightly concave at or near the lower border. Once you’ve done the wax-up all around the teeth & palate you may add some Stippling of the wax using a soft brush or a small burnishing bur. → Why do we do this stippling? To give an orange-peal effect of gingival contouring that will give more aesthetic appearance as it will reflect the natural tissue appearance. Avoid doing it too much because it is a rough surface, and it will be liable to food impaction & contamination. → How do we do that? By Tapping the surface of the wax with a bristle of a toothbrush after first warming the surface soften the wax or by running over the surface of the wax with a small burnishing bur rotating in a hand piece. Now after the wax has been contoured, how should the wax appear? o Smooth it by flaming and then polish it with cotton to give it shiny appearance as the adjacent picture. 7|Page ❖ Establishing the posterior palatal seal Remember, we say previously that the posterior palatal seal must be cut/refined into the cast before the denture is sealed down and processed. → Why we reestablishing the posterior palatal seal region ? Because it has a significant advantage: 1) Determine the posterior border of maxillary denture 2) Compensate for the shrinkage of the acrylic resin in this area during processing. 3) Provide a good seal in the posterior area of the maxillary arch which increase retention. 4) Prevents food to enter under the maxillary denture 5) Reduces the tendency for gag reflexes. → How do we do that? The location must be marked by pencil near left & right hamular notches and this is toward the posterior portion of the post-dam area and we can use a fovea palatine to guide us the vibrating line position. o Posterior border of the denture is determined in the mouth and its location is transferred onto the cast. o The locations of right and left hamular notches are marked with an indelible pencil. o The location of fovea palatinae near the median palate suture is marked o The vibrating line of the soft palate normally used as a guide to the ideal posterior border of the denture ❖ Procedure for carving of posterior palatal seal area: o A V-shaped groove (1-1.5) mm deep is carved into the cast at the location of the bead. o A large sharp scraper is used to carve it passing through the hamular notches and cross the palate of the cast. o The groove will form a bead (B) on the denture that provides the posterior palatal seal area (1-1.5mm high and 1.5 wide at its base). 8|Page ❖ Advantages of posterior palatal seal o Determine the posterior border of maxillary denture o Compensate for the shrinkage of acrylic resin in this area during processing, because as we know it’s a thicker area so shrinkage might affect it more. o Provide a good seal in the posterior area of the maxillary arch which increases retention. o Prevents food from entering under the maxillary denture. o Reduces the tendency for gag reflexes. THE END OF SHEET #11 ُ ،‫اجعلن ِممن َج ربت قلبه‬ ‫ي‬ ‫اللهم‬ ُ ُ ُ ُ ‫ ورضيت عنه وأرضيته‬،‫ وآتيته ُسؤله‬.. 9|Page