James C. Kessler - Fundamentals of Fixed Prosthodontics

Fig 2-19 (a) A pronounced vertical overlap of the anterior teeth permits posterior teeth to have longer cusps. (b) A minimum anterior vertical overlap requires shorter cusps.

Fig 2-20 (a) A pronounced horizontal overlap of the anterior teeth requires short cusps on the posterior teeth. (b) A minimum anterior horizontal overlap permits the posterior cusps to be longer

The palatal surface of a maxillary anterior tooth has both a concave aspect and a convexity, or cingulum. The mandibular incisal edges should contact the maxillary palatal surfaces at the transition from the concavity to the convexity in the centric relation position. The concavity represents a uniform shape in all subjects. 59

Anterior guidance, which is linked to the combination of vertical and horizontal overlap of the anterior teeth, can affect occlusal surface morphology of the posterior teeth. The greater the vertical overlap of the anterior teeth, the longer the posterior cusp height may be. When the vertical overlap is less, the posterior cusp height must be shorter ( Fig 2-19). The greater the horizontal overlap of the anterior teeth, the shorter the cusp height must be. With a decreased horizontal overlap, the posterior cusp height may be longer ( Fig 2-20).

Fig 2-21While a shallow protrusive path would require short cusps in the presence of minimal anterior guidance (a) , the posterior cusps can be lengthened if the anterior guidance is increased (b) .

Fig 2-22 (a) A pronounced immediate lateral translation would dictate short cusps where there is little anterior guidance. (b) However, the cusps can be lengthened if the anterior guidance is increased.

By increasing anterior guidance to compensate for inadequate condylar guidance, it is possible to increase the cusp height. If the protrusive condylar inclination is shallow, requiring short posterior cusps, the cusps may be lengthened by making the anterior guidance steeper ( Fig 2-21). In like manner, increasing anterior guidance will permit the lengthening of cusps that would otherwise have to be shorter in the presence of a pronounced immediate lateral translation ( Fig 2-22).

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