Tasks for independent work during preparation to practical classes.
4.1. Recommendations for students’ independent work and album for independent work of students.
4.2 Theoretical questions to the lesson:
1. The definition of "Record Base".
2. Technique of maxillary record base and occlusion rims.
3. Technique of mandibular record base and occlusion rims.
4. Materials for record base and occlusion rims.
4. Stages of determining of the central occlusion.
4.3. Practical work (task) that are fulfilled in class:
With the help of diagnostic models and micro stands students demonstrativly consider: 1. On phantom micro stand to demonstrate stages of manufacturing of removable partial laminar dentures.
2. Using the diagnostic models and clinical cases to learn how to identify defects of dentition, depending on the complexity by A.I. Betellmann.
3. Learn to compare plaster models in the position of the central occlusion by I complexity group of defects in dentition by A.I. Betellmann by various clinical conditions.
4. Learn to identify the central occlusion by II defects group in dentition by A.I. Betellmann by various clinical conditions.
Content of the theme:
Record Base (trial base) - A temporary device representing the base of a
denture and used for making jaw relation records and for arranging teeth, but is
NOT part of the final denture. Record bases emulate as nearly as possible the
contours and dimensions of the finished dentures. Record bases should
preserve the shape and detail of the master casts and not abrade or damage the
Record bases may be made with wax, light curing resin (Triad) or autopolymerizing resin (Orthodontic resin). Occlusion rim - An occluding surface usually made of wax placed on a record base for the purpose of making jaw relation records and arranging artificial teeth.
1. The rim should approximate the position of the natural teeth. Remember the facial surfaces of the central incisors are 5-9 mm anterior to the center of the incisive papilla. The wax rim must be anterior to the crest of the maxillary ridge.
2. Occlusal plane is flat .
3. The width of the occlusion rim in the molar area is 8-10 mm, 5-7 mm in the premolar region, and 3-5 mm in the anterior.
4. The facial surface of the wax rim is approximately 5-9 mm anterior to the center of the depression of the incisive papilla.
5. Posteriorly, the wax rim should be inclined 2 to 5° towards the lingual direction. The buccal surfaces of the rim are contoured to simulate the buccal surfaces of the natural teeth. The posterior vertical height measuring from the basal seat surface of the tuberosity to the occlusal plane is 8 to 10 mm.
6. Anteriorly, the rim is positioned slightly labial to the residual ridge. While the rim is still soft, mold the canine areas to develop a slight eminence.
7. The rim will measure 22 mm from the anterior labial border to the incisal edge.
8. The rim must be clean, neat and of proper dimension and contour.
The procedure for making the mandibular rim is very similar to that for the maxillary rim. The height of the rim about 15 to 18 mm from the anterior
border to the incisal edge. The shape, position and dimensions of the rim should
represent those of the natural teeth. The rim will follow the ridge crest with a slight labial inclination anteriorly. The buccal edge of the wax rim represents the position of the buccal cusps of the natural posterior teeth.
NOTE: The labial surface of the mandibular wax rim rises from the depth of the
sulcus. The lingual border of the occlusal surface is directly above the ridge crest.
Posteriorly the occlusal surface gradually widens in width from 3 - 5 mm in the
anterior region to 8 - 10 mm in the molar region.
Note that a line drawn through the ridge crest bisects the occlusion rim.
Posteriorly the wax rim parallels the base of the cast (and residual ridge) on a plane
intersecting the retromolar pad at 2/3 of the pad's height. Note that the rim's occlusal surface ends at the distal of the first molar and is beveled posteriorly and inferiorly from this point. The rim is 15-18 mm in height. The rim ends 8 mm
short of the posterior border of the record base.
1. Occlusal width incisal area 3-5 mm
2. Occlusal width pre-molar area 5-7 mm
3. Occlusal width molar area 8-10 mm
Second clinical visit is devoted to recording the jaw relationship of the patient prior to mounting casts on the articulator (occludator) and developing a design.
Neuromuscular dentistry considers the entire system that controls the positioning and function of the jaw. The resting tonus of the elevators and depressor muscles depends on motor neuron activity related to the simple stretch reflex. The sources of impulses are the mesocephalic nucleus and the proprioceptors and exteroceptors in the mucous membrane, the periodontal ligament, all the facial muscles, ligaments, and the capsule of the temporomandibular joint. The goal is to establish a three-dimensional (3D) lower jaw position that is based on the harmonious relationship of the three main factors affecting occlusion: the teeth, muscles, and jaw joints.
Centric relation – a maxillo-mandibular relationship in which the condyles articulate with the thinnest a vascular portion of their respective disks with the complex in the anterior-superior position against the slopes of the articular eminences. This position is independent of tooth contact and is repeatable position.
Centric Occlusion – the occlusion of opposing teeth when the mandible is in centric relation. In natural dentition this may or may not coincide with maximal intercuspal position (MIP). In complete denture CR=CO=MIP.
Plane of occlusion - An imaginary surface that is related anatomically to the
incisors and tips of the occluding surfaces of the posterior teeth. In complete denture, this plane is parallel to Camper's line, a line running from the inferior border of the ala of the nose to the superior border of the tragus of the ear.
Physiologic rest position - The habitual postural position of the mandible when the patient is resting in an upright position and the condyles are in a neutral, unstrained position in the glenoid fossae, and the involved muscles, particulary the elevator and depressor groups, are in equilibrium in tonic contraction.
Vertical Dimension of Rest (VDR) - The length of the face when the mandible is the rest position. The wax rims should not touch.
Vertical dimension of occlusion (VDO) – is the distance between two points when occluding members are in contact.
Freeway space (interocclusal rest space) is the diference between VDR & VDO.