The arrangement of teeth must be Physiologically And esthetically acceptable. Physiologically , They must be in a position compatible with the lips , Tongue, and cheeks whether the mandible is in a Relaxed position or in motion.
The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior-superior position against the shapes of the articular eminencies.
3. A nonanatomic tooth is essentially flat and has no cusp heights to interdigitate with an opposing tooth and has sulci to enhance its comminuting effect on food. They articulate in only two dimensions.
History of the evolution of the posterior tooth form
- These teeth constructed with curved grooves & curved cusps forming segments of an arc, concentrically arranged from a radial centre corresponding to the right & left rotation centers in the head of condyle in the glenoid fossae
The posterior plane of occlusion is an extension of this anterior plane level with the junction between the middle and upper third of the retromolar pads bilaterally.
These references will place the overall plane at a level that is familiar to the tongue (2-3 mm below the dorsum of the tongue). If the plane located higher or lower, will interfere with normal tongue action.
Maxillary posterior teeth are arranged in their correct Buccolingual position, a straightedge is placed over the crest of the mandibular ridge and a line is scratched in the wax , the lingual cusps of the maxillary teeth are placed over this line.
The mandibular teeth then assume their buccolingual and mesiodistal position by intercupating with maxillary teeth.
The posterior teeth are positioned in such a way that they are properly related to the bone that supports them and to the soft tissues that contact their facial and lingual surfaces. The posterior form of the arch will be determined largely by the “neutral zone” between the cheeks and tongue.
The angle formed by the intersection of the plane of occlusion and a line within the sagittal plane determined by the incisal edges of the maxillary and mandibular central incisors when the teeth are in maximum intercuspation (GPT-8)
The anteroposterior curving (in the medial plane) and the mediolateral curving (in the frontal plane) within the alignment of the occluding surfaces and incisal edges of the artificial teeth that is used to develop the balanced occlusion(GPT-8)
The anatomic curve established by the occlusal alignment of the teeth, as projected onto the median plane, beginning with the cusp tip of the mandibular canine and following the buccal cusp tips of the premolar and molar teeth, continuing through the anterior border of mandibular ramus, ending with the anterior most portion of the mandibular condyle.(GPT8)
In the theory the occlusion should be spherical, the curvature of the cusps as projected on the frontal plane expressed in both arches; the curve in the lower arch being concave & one in the upper arch being convex. The curvature in the lower arch is affected by an equal lingua inclination of the right & left molars so that the tips point of the corresponding cross-aligned cusps can be placed into the circumference of the circle. The transverse cuspal curvature of the upper teeth is affected by the equal buccal inclinations of their long axes (GPT-8)
For a proposed ideal curve of occlusion in which each cusp & incisal edge touches or conforms to a segment of a surface of a sphere 8 inches in diameter with its centre in the region of the glabella. (GPT-8)
Sphere of Monson : Two curves of Spee and Wilson are studies in 3D the cusps tips of posterior teeth resting on a sphere.
CUSPS ON TEETH OR THE INCLINATION OF CUSPLESS TEETH
These modify the effect of the plane of occlusion and the compensating curve.
It was shown that the mesiodistal cusp heights that interdigitate lock the occlusion so that reposition of the teeth due to setting of the base cannot take place.
To prevent this all mesiodistal cusp heights be eliminated in anatomic type teeth and only buccolingual inclines need be considered as determinants of balanced occlusion.
The primary objective was to prevent the destruction of tissue and preserve the integrity of the residual ridge.
Many dentists believe that use of monoplane occlusion , which is flat mesiodistally and buccolingually and is oriented as close as possible parallel to the upper and lower mean foundation planes, will create more stable dentures
With this concept of occlusion, there is no attempt to eliminate deflective occlusal contacts in lateral or protrusive excursions.
When the nonanatomical teeth are arranged to satisfy the monoplane occlusal concept, the condylar inclinations on the articular are set at 0 degrees. When the positioning of the maxillary posterior teeth completed, the occlusal surfaces of them should be flat against the mandibular wax occlusal rim.
Many factors enter into the arrangement of the Artificial teeth in a denture. They act as a unit; And attached to a movable base resting on movable and displaceable living tissue, which are subject to damage; therefore, they must be Arranged to function as a unit.
However, Leverages, forces, vector of forces, discrepancies in residual ridges, maxillomandibular Relationships, residual ridge relationships, Functional and parafunctional mandibular Movements, and preferences of patients vary. The arrangement of teeth must be Physiologically And esthetically acceptable. Physiologically , They must be in a position compatible with the lips Tongue , and cheeks whether the mandible is in a Relaxed position or in motion