What occlusal scheme should be used for tooth-supported fixed partial dentures?

Purpose: The purpose of this review of occlusion for fixed partial dentures (FPD) placed on natural teeth was to determine the level of scientific evidence available regarding the occlusal scheme during eccentric mandibular movements and the scheme for occlusal contact in the maximal intercuspal position (MIP).

Materials and methods: A PubMed search of "natural teeth, dental occlusion, fixed partial dentures, bridges" using the filters: Case Reports, Clinical Trial, Randomized Controlled Trial, Systematic Review resulted in 7 citations, none of which were relevant. Two were on complete dentures, 2 on implants, and 1 on removable partial dentures. As a result of the literature search and review, it was determined there is a lack of compelling evidence to support a specific eccentric occlusal relationship, tooth form, or how opposing teeth interdigitate, necessitating a look back at First Principles.

Results: Three natural dentition eccentric occlusal relationships have been described in the dental literature: canine protected articulation (CPA), group function (GF), and balanced occlusion. There are no clinical trials focused on the differences between occlusal schemes for occlusal rehabilitation of natural teeth using FPDs. Most clinical studies of natural dentitions determined that GF occurs more commonly than CPA but there is a lack of data supporting the superiority of either of these two eccentric occlusal relationships. There were no clinical studies on occlusal contact schemes with FPDs. Two basic intercuspal schemes have been advocated, cusp-to-fossa and cusp-to-marginal ridge. There is no evidence for how many occlusal contacts are necessary for a stable occlusion with some authors having recommended buccalized or lingualized occlusion.

Conclusions: With FPD occlusion involving natural teeth, there is no clinical evidence supporting the superiority of one eccentric occlusal relationship over another. During protrusive movements, guidance by only the incisors without posterior tooth contact is the most common type of relationship and it is more common in Angle's Class Type I occlusions than in Angle Class II and III occlusions. Posterior tooth contact can occur during protrusion, and it is most common in Angle Class III occlusions and least common in Angle Class II occlusions. The canines can make occlusal contact during protrusive movements. Clinicians have used both GF and CPA in the restoration of teeth with FPDs. When restoring one arch the prostheses should harmonize with the patient's existing occlusal scheme if no other pathology exists. Nonworking side (mediotrusive) contacts should not be present on posterior teeth during lateral mandibular movements. In MIP, occlusal forces should be directed along the long axis of teeth. Some clinicians prefer that occlusal forces not be present on inclined surfaces in MIP and have cuspal contact on opposing flat fossae whereas others use multiple contacts on inclined surfaces around cusps, a process known as tripodizing. There is no clinical evidence that tripodizing or cuspal contact on flat surfaces enhances positional stability of the teeth or improves masticatory function. There is a need for extensive research of excursive and MIP schemes involving fixed partial dentures attached to natural dentition.