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Prosthodontics & Occlusion · patient case with 3 questions

Occlusal analysis with articulating paper

Patient: Female, 41 years old

Chief Complaint: Referred for occlusal assessment before restorative treatment.

Background: Full dentate arches. No history of orthodontic treatment.

Current Findings: Articulating paper has been used to mark the maxillary arch through a range of mandibular movements. A single isolated blue mark is present on the LINGUAL cusp of tooth #4 (maxillary right first premolar), shown below.

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Question 1

Which mandibular movement most likely produced this contact?

  1. Right lateral excursion
  2. Retrusion
  3. Left lateral excursion
  4. Protrusion
Show answer and explanation

Correct answer: C. Left lateral excursion

  • A. In right lateral excursion the right side is the WORKING side. Working contacts are normally distributed across buccal-cusp inclines and involve several teeth, not one isolated lingual cusp tip.
  • B. Retrusive contacts occur near centric relation on distal inclines of mandibular cusps and mesial inclines of maxillary cusps, not as a solitary lingual cusp mark.
  • C. Tooth #4 is on the patient's RIGHT. During a LEFT lateral excursion the right side becomes the NON-WORKING (balancing, mediotrusive) side. The classic non-working contact is between the maxillary LINGUAL cusp and the mandibular BUCCAL cusp — precisely the surface marked here. An isolated mark on a maxillary lingual cusp is the textbook signature of a mediotrusive interference.
  • D. In protrusion the anterior teeth should disclude the posteriors entirely. A posterior protrusive contact would be a separate finding, and it would mark on mesial inclines rather than a lingual cusp tip.

Note: ⚑ This item is genuinely two-sided and the group should talk it through. Maxillary lingual cusps DO also contact on the working side, so a right lateral excursion is defensible. What tips it toward the balancing side is that the mark is ISOLATED and sits on the lingual cusp — the hallmark description of a non-working interference. Rule of thumb: maxillary lingual cusp meeting mandibular buccal cusp on the opposite excursion = mediotrusive interference.

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Question 2

In a fully dentate patient such as this one, which guidance should disclude the posterior teeth during protrusion?

  1. Condylar guidance
  2. A balanced occlusal scheme
  3. Incisal (anterior) guidance
  4. Group function on both sides
Show answer and explanation

Correct answer: C. Incisal (anterior) guidance

  • A. Condylar guidance is set by the anatomy of the articular eminence. It is a determinant of mandibular movement, but it is not adjustable and is not what discludes the posteriors.
  • B. A balanced (bilaterally balanced) scheme deliberately maintains simultaneous contacts in excursions and is used for COMPLETE DENTURES, where it aids stability. In a dentate patient it produces destructive interferences.
  • C. CORRECT. In a dentate patient the anterior teeth carry the protrusive load and immediately disclude the posterior teeth. Incisal guidance is the one determinant of occlusion the clinician can actually alter — condylar guidance is fixed by anatomy.
  • D. Group function distributes WORKING-side lateral contacts across several posterior teeth. It is an alternative to canine guidance for lateral movements, not the protrusive mechanism.

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Question 3

Where is the proximal contact located on the distal surfaces of teeth #8 and #9?

  1. In the middle of the middle third
  2. At the junction of the incisal and middle thirds
  3. At the junction of the middle and cervical thirds
  4. At the incisal edge
Show answer and explanation

Correct answer: B. At the junction of the incisal and middle thirds

  • A. The centre of the middle third is the typical contact location for POSTERIOR teeth, not maxillary centrals.
  • B. CORRECT. On maxillary central incisors the distal contact sits at the junction of the INCISAL and MIDDLE thirds. The mesial contact of a central incisor is more incisal still — essentially at the incisal third.
  • C. The junction of the middle and cervical thirds is far too apical for an anterior proximal contact and would leave a large open embrasure incisally.
  • D. Contacts are never at the incisal edge itself; they sit slightly cervical to it.

Note: The general rule: proximal contacts move APICALLY (from incisal third toward middle third) as you move POSTERIORLY through the arch. Anterior teeth contact incisally, premolars and molars contact around the junction of the occlusal and middle thirds.

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