Microleakage and marginal gap of adhesive cements for noble alloy full cast crowns.

Very limited comparative information about the microleakage in noble alloy full cast crowns luted with different types of adhesive resin cements is available. The purpose of this study was to evaluate the microleakage and marginal gap of two self-adhesive resin cements with that of other types of adhesive luting cements for noble alloy full cast crowns. Fifty noncarious human premolars and molars were prepared in a standardized manner for full cast crown restorations. Crowns were made from a noble alloy using a standardized technique and randomly cemented with five cementing agents as follows: 1) GC Fuji Plus resin-modified glass ionomer cement, 2) Panavia F 2.0 resin cement, 3) Multilink Sprint self-adhesive resin cement, 4), Rely X Unicem self-adhesive resin cement with pretreatment, and 5) Rely X Unicem with no pretreatment. The specimens were stored in distilled water at 37°C for two weeks and then subjected to thermocycling. They were then placed in a silver nitrate solution, vertically cut in a mesiodistal direction and evaluated for microleakage and marginal gap using a stereomicroscope. Data were analyzed using a nonparametric Kruskal-Wallis test followed by Dunn multiple range test at a p<0.05 level of significance. The Rely X Unicem (with or with no pretreatment) exhibited the smallest degree of microleakage at both tooth-cement and cement-crown interfaces. The greatest amount of microleakage was found for Panavia F 2.0 resin cement followed by GC Fuji Plus at both interfaces. No statistically significant difference in the marginal gap values was found between the cementing agents evaluated (p>0.05). The self-adhesive resin cements provided a much better marginal seal for the noble alloy full cast crowns compared with the resin-modified glass ionomer or dual-cured resin-based cements.

An appraisal of the literature on centric relation. Part III.

The literature directly and indirectly related to centric relation (CR) has been reviewed chronologically. More than 300 papers and quoted sections of books have been divided into three sections. The first two parts are related to CR. Studies in this group mainly compared, either the position of the mandibular condyle or the mandible itself in different CR recordings. Various tools were discussed for this purpose. The third part of the paper is about CR-centric occlusion (CO) discrepancy. CR still remains one of the controversial issues in prosthodontics and orthodontics. Debates such as mounting casts on the articulator by reproducible records for orthodontic treatment planning and end results, and whether or not orthodontic treatment based on CO causes TMJ dysfunction, remain unsolved. The references are listed at the end of Part III.

An appraisal of the literature on centric relation. Part I.

The literature directly and indirectly related to centric relation (CR) has been reviewed chronologically. More than 300 papers and quoted sections of books have been divided into three sections. The first two parts are related to CR. Studies in this group mainly compared either the position of the mandibular condyle or the mandible itself in different CR recordings. Various tools were discussed for this purpose. The third part of the paper is about CR-centric occlusion (CO) discrepancy. CR still remains one of the controversial issues in prosthodontics and orthodontics. Debates such as mounting casts on the articulator by reproducible records for orthodontic treatment planning and end results, and whether or not orthodontic treatment based on CO causes temporomandibular joint dysfunction, remain unsolved. The references are listed at the end of Part III.

Intercondylar width as a guide to setting up complete denture teeth.

A clinical study was designed to investigate the relationship between intercondylar width (ICW) and inter-dental widths of the upper and lower canines and first molars to aid in denture teeth positioning. The study was divided into two parts so that the results of the first part could be verified in the second part. In the first part, 27 adult subjects were selected according to the exclusion criteria of the study. A kinematic hinge axis locator was used to locate the true point of condylar rotation. The distance between these points was considered to be the ICW. A strong correlation was found between ICW and interdental measurements, with ICW and upper first molars being the strongest (r=0.612, P= 0.004). A set of indices developed from the results was recommended for the positioning of complete denture teeth. In the second part of the study, inter-dental measurements were estimated using the indices obtained in the first part. The estimated inter-dental widths showed no significant differences compared with the real widths (P= 0.109, P=0.849, P=0.353, P=0.41). Based on the results of this study, ICW measurements can be used for setting up canines and first molars in complete dentures.

An appraisal of the literature on centric relation. Part II.

The literature directly and indirectly related to centric relation (CR) has been reviewed chronologically. More than 300 papers and quoted sections of books have been divided into three sections. The first two parts of the paper are related to CR. Studies in this group mainly compared either the position of the mandibular condyle or the mandible itself in different CR recordings. Various tools were discussed for this purpose. The third part deals with CR-centric occlusion (CO) discrepancy. CR remains one of the controversial issues in prosthodontics and orthodontics. Debates relating to mounting casts on the articulator by reproducible records for orthodontic treatment planning and end results, and whether or not orthodontic treatment based on CO causes temporomandibular joint (TMJ) dysfunction, remain unsolved. The references are listed at the end of Part III.