Record bases occlusion rims Record bases Definition l

Record bases & occlusion rims

Record bases Definition : l. A record base or base plate is a temporary form representing the base of a denture. It is used in recording maxillomandibular relations and in the arrangement of the teeth. Requirements : lshould be rigid. lshould be accurate. lshould be stable. lthe borders should be round & smooth as the borders of finished dentures. lshould be thin at the crest , labial & buccal slopes to provide space for tooth arrangement.

Objectives: l To retain the recording medium or device used for recording maxillomandibular relations. l To aid in transfer of accurate jaw relation ships to an articulator. l To enable the setting of artificial teeth for the trial denture.

Materials & methods : l It is generally agreed that maxillomandibular relations are difficult to record accurately on poorly fitting bases fabricated from bulky material and from material that is subject to distortion and dimensional change. record bases are made of several different materials.

Types Temporary record bases: They are discarded and replaced by denture base material, once their role in establishing jaw relation, teeth arrangement and try in is complete. Types of temporary record bases: l. Shellac base plate l. Reinforced shellac base plate l. Cold cure acrylic resin l. Visible light cure acrylic resin l. Vacuum formed vinyl and polystyrene l. Base plate wax

Permanent record bases: They are not discarded and become part of the actual base of the finished complete denture. Types of permanent record bases: l. Heat cure acrylic resin l. Gold l. Chromium-cobalt alloy l. Chromium-nickel alloy

Shellac base plate Advantages: l l l They will adapt to intimate contact with the master cast. Require short time for construction. Inexpensive. Can be corrected easily by reheating and readapting to the master cast. Uniform thickness.

Disadvantages : Although shellac record bases are easily and quickly adapted, they are not considered satisfactory. l They warp, do not fit accurately, distort easily, lack rigidity, become brittle and break, and will not permit polishing of the borders

Shellac l l Any undercuts are relieved, and separating medium is applied to the cast. The shellac record base forms are manufactured in the shapes of the maxillary and mandibular arches.

l l l The forms are softened with an open flame and molded to the cast with an instrument or the fingers. While the material is in a softened state, the excess is removed with scissors. After hardening, the borders are smoothed but as a rule will not take a polish.

Reinforced shellac • Any undercuts are relieved, and separating medium is applied to the cast. • the manufactured form of shellac is softened with an open flame. • A flattened wire is contoured and adapted across the posterior palatal seal area of the maxillary record base and adapted to the lingual flange of the mandibular record base and incorporated in the base. l l A thin layer of zinc oxide eugenol impression paste is spread over the tissue side of the base and seated on the cast in the manner of making impression. The excess flash is removed and the borders are smoothed.

l Disadvantages : Although this procedure results in abase that is more rigid and stable than shellac but its still subject to distortion and breakage. It is bulky, the odor and taste of the paste are objectionable to some patients, and it is unsuitable for arrangement of teeth in cases of limited inter arch space.

Cold cure acrylic resin Advantages: l Good strength no need for reinforcement l Good dimensional stability l Does not wrap during manipulation l Closely fit to the master cast

Disadvantages: l Require more time in fabrication l Difficult to control the thickness l Residual monomer can cause irritation to oral tissues

Methods Sprinkle on method l Finger adapted dough method l Flasking method l Stone mold method l Wax-confined method l

Sprinkle on method l l l Any undercuts are relieved, and separating medium is applied to the cast. Using an eye dropper apply the monomer to the cast, carefully add the polymer (salt and pepper technique) until a sufficient thickness is gained over the entire surface of the cast. The processed base is removed from the cast, smoothed, and polished at the borders.

Finger adapted dough method l l l Any undercuts are relieved, and separating medium is applied to the cast. The self curing resin is mixed according to manufacturer instructions When it reach the dough stage, it is molded to the cast with instrument or fingers. It is allowed to polymerized completely. The processed base is removed from the cast, smoothed, and polished at the borders.

Flasking method l l l a wax pattern is constructed over the cast with a thickness and contour desired for complete denture. The cast and pattern are flasked, the wax is eliminated, acrylic resin is packed and allowed to set under the pressure of clamps or press. The processed base is removed from the cast, smoothed, and polished at the borders.

Visible Light cured acrylic resin Any undercuts are relieved, and separating medium is applied to the cast. l Adapt a sheet of pink base plate material to the cast by fingers and prevent trapping of air. l

l l l Extend the material to the depth of vestibule. Cure the record base for 4 minutes in the light cure unit. Carefully removed from the cast, invert and cure the tissue surface for 4 minutes. The processed base is removed from the cast, smoothed, and polished at the borders

Vacuum formed vinyl and polystyrene l l l Any undercuts are relieved, and separating medium is applied to the cast. A sheet of base plate material placed over the cast and inserted in the vaccum chamber. Electric heater switched to heat the sheet. Turn on the vacuum. The sheet will adapt closely to the cast. Switch of the heater and allow the record base to cool. Remove the record base and cut the excess material.

Advantages l l Easy to fabricate Uniform thickness Accurate adaptation to the master cast Good rigidity Disadvantages l l Expensive Difficult to form smooth rounded borders

Base plate wax l l l Wet the cast Soften the base plate wax over the flame and adapt it to master cast Remove the excess wax and make the borders round and smooth.

Advantages l l Easy and method Inexpensive available Disadvantages rapid l l and It lacks rigidity It lacks dimensional stability

Heat processed acrylic resin l l l a wax pattern is constructed over the cast with a thickness and contour desired for complete denture. The cast and pattern are flasked, the wax is eliminated, acrylic resin is packed and heat processed. The processed base is removed from the cast, smoothed, and polished at the borders.

Advantages : they are rigid, accurate, stable, not subject to distortion, and suitable for arrangement of teeth. l Disadvantages : require considerable time, more expensive. l

Occlusion rims l l l l Definition : occlusion rims are occluding surfaces constructed on record bases or permanent denture bases to be used in recording jaw relations and for arranging teeth. Requirements : the position should be in the anticipated position of the artificial teeth. it must be securely attached to the base. the occlusal surface must be smooth and flat. it should be contoured to support the lip and cheeks accurately. all the surfaces should be smooth.

Uses : The occlusion rims are used : l to establish the level of the occlusal plane. l to establish the arch form. l to record the maxillary mandibular relations. l for arrangement of the teeth.

Wax Rim l l l Wax rims are smooth and have a flat occlusal surface. They are about as wide buccolingually as denture teeth – wider in the posterior, narrower in the anterior The occlusal rim must be centered buccallingually over and parallel to the residual ridge crest. The anterior portion of the maxillary occlusal rim is labially oriented

Maxillary arch l l l The anterior wax rim height is 20 -22 mm The posterior wax rim height is 16 -18 mm. The width of the anterior rim is approximately 3 - 5 mm. The width of the occlusal rim in the posterior region is approximately 8 - 10 mm. The occlusal rim is properly sealed to the baseplate without any voids. The posteriors of the occlusion rims are cut at a 30º angle to the occlusal plane

Mandibular arch l l l The anterior wax rim height is 16 -17 mm The posterior wax rim height covers 2/3 of the retromolar pad. The width of the anterior rim is approximately 3 - 5 mm. The width of the occlusal rim in the posterior region is approximately 8 - 10 mm. The occlusal rim is properly sealed to the baseplate without any voids.

Materials & methods wax

ready made occlusion rim l l l its supplied as a horse shoe shaped rim, adapt it in the proper position on the record base. Softened it slightly, sealed it with the record base by the aid of a wax knife. Smooth all the surfaces

Hand made occlusion rim l l l Half a sheet of paraffin wax is softened and folded upon itself to produce a rectangular rim, approximately the length of the alveolar ridge. Softened it slightly, sealed it with the record base by the aid of a wax knife. Smooth all the surfaces