20- Jaw relation registration. Part 1: Checking occlusal rims - Orientation of occlusal plane

• The trial denture base may be made from self-cure acrylic or light-cure acrylic resin.
• Shellac base plates are not recommended because of its dimensional inaccuracy.
• Occlusal wax rims should be made from high quality base plate wax it must be dimensionally stable inside and outside the patient mouth.
• The dimensional stability is must to maintain the vertical and centric relations during and after registration.
• Checking of the occlusal rims outside the patient mouth away from the cast & on the cast.
• Examination away from the cast. Sharp and irregular borders must be avoided. Fitting surface must be clean from dental stone, wax & sharp areas.
• Examination on cast. It must be well adapted to the cast & fill the vestibule in length and width. Review the standard height of wax rims.
• Instruments & materials:
• wax knife, wide blade wax spatula, flame source, rubber bowl with cold water, Fox ruler, base plate wax, inter-occlusal record material (light rubber base, ZnO, wax) Vaseline, adhesive tape, Fox ruler used for proper orientation of anterior & posterior occlusal plane, Face bow & semi adjustable articulator should be ready for transfer of jaw relation record.
• Checking the occlusal rims inside the patient mouth.
• Checking extension, retention & stability of occlusal rims.
• Checking extension of labial and buccal flanges by manipulating lips and cheeks with gentle pressure to hold the occlusal rim in place by the other hand.
• Checking extension of lingual flanges by instructing the patient to move his tongue in movements similar to that of border molding.
• Checking retention & stability of lower occlusal rim.
• Suction sound ensures that a good retention exist :)
• Checking retention & stability of upper occlusal rim.
• Wet the trial denture base before insertion into the patient mouth to enhance the physical means of retention.
• Checking extension of labial and buccal flanges by manipulating lips and cheeks with gentle pressure to hold the occlusal rim in place by the other hand.
• Check stability to occlusal stresses. Occlusal wax rims must be centralized over the alveolar ridge.
• Examination of retention for upper occlusal rim. It should resist the vertical displacement away from the tissues.
• The high suction sound ensures that excellent retention exist.
• Orientation of the occlusal plane:
• Contouring of wax rims (Labial & buccal) surface to obtain better lip support before orientation of the occlusal plane.
• Over-contouring to mask facial wrinkles makes the lip line higher, affect phonetics& biomechanically not favorable (more denture displacement).
• Review proper lip contouring from facial and profile views.
• Detection of the height of occlusal plane: Upper (maxillary) & lower (mandibular) - Anterior & Posterior.
• Maxillary occlusal plane:
• Maxillary anterior occlusal plane:
• Esthetics: 2 mm below relaxed normal lip line.
• Phonetics: instruct the patient to say F or V sound. The occlusal surface of upper occlusal rim touches the superior surface of lower lip.
• Anatomical: Anterior occlusal plane must be parallel to Inter-pupillary line.
• Maxillary posterior occlusal plane:
• Parallel to Ala-Tragus line - At Linea Alba - Just 3/4 inch below Stenson's duct.
• Fox ruler is a very efficient tool to ensure parallelism of occlusal planes to the anatomical lines.
• If the occlusal plane is not parallel modify the wax occlusal surface inclination until you achieve the required parallelism.
• Mandibular anterior occlusal plane
• Flushed with superior surface of lower lip and ended by angle of the mouth.
• Parallel to inter-pupillary line & maxillary anterior occlusal plane.
• Mandibular posterior occlusal plane
• Functional & Biomechanical: height not more than 3/4 retromolar pad area.
• Functional & Biomechanical: Just below the maximal convexity of the tongue.
• Neutral zone impression: Located at the Buccinator groove.
• Anatomical: It should be parallel to the mean of both ridges.
• The Guide Lines: Midline - Canine Line - relaxed lip line - active lip line - orientation lines.
• The canine line is highly significant to detect the width of missing anterior teeth.
• The orientation of relaxed and active smile lines used to detect the proper length of missing anterior teeth (Making an ideal smile).