Influence of jaw opening on occlusal vertical dimension between incisors and molars.

STATEMENT OF PROBLEM: Modification of the occlusal vertical dimension (OVD) is a significant procedure in prosthodontics. Improper estimation of the space available between opposing teeth may lead to an improper framework design. PURPOSE: The purpose of this clinical study was to evaluate the average opening ratio in the molar area in relation to the extent of opening in the incisor area. MATERIAL AND METHODS: A total 34 adults with a complete dentition and stable occlusion participated in the study. The change in vertical distance was evaluated in 3 areas: between the maxillary and mandibular central incisors, between the maxillary and mandibular canines, and between the maxillary and mandibular first molars. Digital photographs were made at the intercuspal position (ICP) and at a 2-mm and 8-mm OVD increase. The OVD opening was standardized with the aid of a Woelfel sliding guide device. The measurements were made by recording the distance between the maxillary and mandibular teeth at different openings. For calibration and quantitative evaluation of the photographs, image-processing analysis was used. RESULTS: The collected data showed that the average ratio of the opening between the first molars and the opening between the central incisors was 0.73. The average ratio of the opening between the canines and the opening between the central incisors was 0.95. The values were plotted, and a mathematical model was derived. CONCLUSIONS: A vertical dimension opening of 1 mm between the central incisors resulted in 0.73 mm of occlusal clearance in the first molar region and 0.95 mm in the canines.

Determining the interchangeability of KaVo PROTAR semi-adjustable articulators.

OBJECTIVE: Interchangeable articulators are crucial for a precise clinical outcome. Lack of interchangeability will affect the accuracy of the occlusion of prosthetic restorations. The objective of this study was to evaluate the interchangeability of KaVo PROTARevo articulators. METHOD AND MATERIALS: KaVo PROTARevo semi-adjustable articulators in routine use were employed. Identical casts were transferred among the articulators and the distance between casts was measured using digital photos of sagittal and frontal aspects of each articulator by two independent examiners. Interchangeability was assessed and analyzed by designated software. RESULTS: Inter-examiner reliability was found to be high. Of 231 possible pairs of articulators only 27 pairs were found to be interchangeable (less than 166 µm in all measured dimensions), and of the other 204 pairs of articulators at least one of the dimensions measured was larger than 166 µm. CONCLUSION: The majority of articulators tested did not pass the 166-µm criterion to establish them as interchangeable. Therefore, in order to maintain accuracy while producing restorations, it is advisable to use the same articulator throughout the entire process, both at the clinic and in the dental laboratory.

Existing concepts and a search for evidence: a review on implant occlusion.

The prevalence of dental implant treatment raises the question: What factors may challenge osseointegration? The dental literature presents two main approaches, which are well-documented: loss of bone around the implant due to infection and a presumed association between implant load and bone loss. This article discusses the effect of load or overload on the bone loss around dental implants. The dental literature is reviewed to assess the scientific evidence related to the effect of occlusal load on osseointegration. Recommendations found in the literature for occlusal schemes for implant-supported prostheses are examined and discussed, and statements regarding implant occlusion are assessed for their validity today, after more than four decades of implants service in prosthetic dentistry.