Removable prosthetics workflow 4/7 – Tooth set up

Removable prosthetics workflow 4/7 – Tooth set up

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The dental technician receives two functional impressions, which are secured in the correct occlusal
height and centric position by means of the intraoral registration of the Gnathometer M. Measure the patient‐specific intervestibular distance in the anterior region and note it down. After that, carefully separate the functional impressions and carefully remove the support pin registration plate. The following reference points must be observed for the correct model orientation: The incisive papilla and palatine raphe provide the anatomical midline. Mark the highest elevation of the tuberosities on both sides. This allows you to determine the dorsal centre. Extend the midline to the edge of the model. Mark the lowest point of the vestibulum. It is situated approx. 5 mm away from the labial frenum. Expose the vestibulum. In the lower jaw, mark the retromolar pad and the path of the alveolar ridge. Mark the occlusal plane in the area approx. 5 mm below the dorsal end of the retromolar pad. Transfer it to the model edge. The horizontal guide supports the average‐value model orientation of fully and partially edentate or edentulous models within the Bonwill triangle of the articulator. Set the symphysis fork of the horizontal guide to half the intervestibular distance. Make sure that the side wings are aligned bilateral to the half of the retromolar pad. The fork sits on the lowest point of the mucolabial fold, oriented according to the midline. Mount the horizontal guide in the articulator with the help of the instrument carrier. Mount the base plate in the articulator and secure the mandibular model using dental plaster. Wait until the plaster has set. Then cautiously remove the horizontal guide and clean the mandibular model. Cut back the functional impression of the lower jaw on the vestibular side. Check whether it closely fits the model. Position the mandibular model with the support pin in centric position on the upper bite
registration. Combine the models until the mandibular model contacts the silicone key. Transfer the esthetic midline marked by the clinician to the mandibular model. If the models fit into the registration without any problem, secure them in this position. Mount the maxillary model in this position using the magnetic base block. Articulation is done in the conventional manner with or without a split cast system. Precise and stable resin plates made of tray material facilitate the try‐in and prevent deformation. Ideally, use a hard wax with a high softening point for setting‐up the teeth. Determine the inter‐vestibular distance and note down the value measured on the edge of the
maxillary model and half the value on the edge of the mandibular model. In this way you determine the position of the occlusal plane in the anterior region. Half the inter‐vestibular distance plus 2 mm overjet results in the length of the maxillary incisors in a
normal bite situation. Half the papilla incisiva plus 7 to 9 mm indicates the labio‐palatal alignment of the central incisors, the so‐called lip support. Align the two central incisors mesially towards the midline. The central incisors are set‐up perpendicular, the lateral incisors are set‐up slightly inclined towards
the mesial aspect. Usually, the maxillary incisors point toward the lower mucolabial fold in a bow direction. Their labial curvature harmoniously blends in with the vertical anterior tooth arch. The position of the canines is of decisive importance for the function and esthetic appearance of the
set‐up. The symmetric positioning of the canines, the most distinctive teeth in the maxillary anterior region, facilitates the set‐up. The canines are again set‐up perpendicular along the longitudinal axis. Ideally, the distal ridge runs parallel to the sagittal course of the alveolar ridge. After the set‐up of the maxillary anterior teeth, they can be checked using the setting‐up template. The symmetrical line system of the template enables the verification of the harmonious position of
the teeth. This “lively” set‐up supports the natural effect of the dental reconstruction. The extension of the longitudinal axis of the mandibular canine points between the maxillary lateral
incisor and the canine. Basically, bilateral symmetry to the setting‐up template has to be kept in mind during the set‐up, in other words the average‐value orientation. It is important to set‐up the canine out of contact, which ensures reliable group guidance in the posterior region. Position the first premolar in such a way that a smooth transition to the canine is achieved. This means that the distal slope of the incisal edge is flush with the mesial rise of the first premolar. Adjust the template for the posterior tooth set‐up, for which the bottom side of the anterior part is aligned according to the cusp tip of the mandibular canines. In the posterior area, the underside of the template ends in the area of the distal thirds of the
retromolar pads. With the setting‐up template, the curves of Wilson and Spee are automatically taken into consideration. This results in a bilateral standardized Monsen compensating curve with the posterior teeth. Now the mandibular “Typ” posterior teeth can be symmetrically aligned with the template on both sides. Pound’s line and the centre of the alveolar ridge are reference points for the orientation of the functional corridor for the posterior tooth set‐up. In this way, the lingual and buccal limit and the tatics are taken into consideration. The posterior teeth have contacts with the template as follows: The first premolar with buccal cusps The second premolar with buccal and mesio‐lingual cusps The first and second molar with mesio‐ and disto‐buccal as well as mesio‐lingual cusps Check whether the teeth are correctly positioned within the functional corridor. The line system of the template facilitates the symmetrical set‐up of the posterior teeth. Nevertheless, there is a certain range of variation. The “Typ” teeth from Ivoclar Vivadent implement the concept by Dr Strack. It is based on the simultaneous group contact both on the working and balancing sides. Remove the setting‐up template and mount the maxillary model. Set‐up the posterior teeth of the upper jaw in accordance with a normal bite situation in a onetooth to two‐teeth relation to the lower jaw. When the teeth are set‐up correctly, the primary contacts in the centric position are located in the central fossae as well as on the marginal ridges. In the mandible, the “Typ” teeth are supported by a secondary contact area on the buccal cusps. If there is not enough space or for reasons of statics, the maxillary second molar can be omitted. If space conditions permit it, set‐up the second molar in the mandible to support the cheeks. As far as the mandibular anterior teeth are concerned, in most cases only the incisal edges can be seen in the top view. In order to achieve an esthetic appearance, interlock the anterior teeth and
grind in wear facets. The overjet should be in the range of 0.5 to 1.0 mm. Make sure that the maxillary anterior teeth are placed on the alveolar ridge cervically and that the incisal area shows a slight inclination towards the labial in a normal bite situation so that the orbicularis oris muscle can adapt. To facilitate the final contouring, secure the teeth with hard wax. For the remainder of the denture body, use a more contouring‐friendly, slightly softer wax. The following important points have to be considered in this context: Basically, contour the gingiva in such a way that it is easy to clean and has a lifelike appearance. Too prominent contours such as balconies must be avoided. In the maxillary anterior region, the gingival margin tends to run the highest in the distal third. In contrast, the lowest point in the mandible tends to be in the centre area. Slightly outline the course of the root in a true‐to‐nature manner. Create the corresponding freeway space for the labial and cheek frenulum. Avoid small concave areas, as they can be difficult to clean by the patient. Embrace tubera and trigona, as they assume important support and holding functions. Give the vestibular parts of the lower denture a concave design to accommodate muscle dynamics. In this way, the cheeks and muscles can optimally adapt to the denture body. The vestibular parts of the upper denture should be given a convex design – particularly in the
molar region. This then supports the masseter muscle and minimizes the possibility of “cheek
biting”. The gingival design should correspond with the completed work as closely as possible. Our tip: Use a synthetic hair brush to remove wax residue from the teeth. Polish the wax to a high gloss using a foam polishing pad. A polished surface is pleasant for the patient and simplifies the completion of the denture later on. As soon as the dentures have been completed in wax, check their occlusal function. Open the centric lock, and the Immediate Side Shift movement in the articulator. The protrusion angle should remain secured at 30 degrees, according to average values. Check the occlusal functions, starting from the centric position. Check whether the bucco‐mesial surfaces of the upper premolars slide over the bucco‐distal edges of the lower premolars on both sides. The mesio‐palatal cusps of the upper molars slide on the disto‐buccal cusps of the lower molars. The disto‐buccal facets of the upper premolars slide over the mesio‐buccal facets of the second premolar and the first molar. Set‐up or grind in the anterior teeth in such a way that they come into group contact with the posterior teeth. Premature contacts must be avoided! Prevent a mere anterior/canine guidance in any case!

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