Safety of increasing vertical dimension of occlusion: a systematic review.

To review all the literature investigating the implications of increasing the vertical dimension of occlusion (VDO). A comprehensive electronic search was conducted through PubMed with the aid of Boolean operators to combine the following key words: "occlusal vertical dimension," "increasing vertical dimension," "bite raising," "occlusal space," "resting vertical dimension," "rest position," "altered vertical dimension," "mandibular posture," "temporomandibular joint," and "masticatory muscles." The search was limited to peer-reviewed articles written in English and published through August 2011. Further, the literature search was endorsed by manual searching through peer-reviewed journals and reference lists of the selected articles. A total of 902 studies were initially retrieved, but only 9 met the specified inclusion criteria for the review. From the selected studies, four variables were identified to be relevant to the topic of VDO increase: magnitude of VDO increase, method of increasing VDO, occlusion scheme, and the adaptation period. Considering the limitations of this review, it could be concluded that whenever indicated, permanent increase of the VDO is a safe and predictable procedure. Intervention with a fixed restoration is more predictable and results in a higher adaptation level. Negative signs and symptoms were identified, but they were self-limiting. Due to the lack of a well-designed study, further controlled and randomized studies are needed to confirm the outcome of this review.