Influence of filler content and gap dimension on wear resistance of resin composite luting cements around a CAD/CAM ceramic inlay restoration.
We investigated the influence of filler content and gap dimension on the wear resistance of composite luting cement around CAD/CAM ceramic inlay restorations. Experimental hybrid dual-cured composite luting cements containing 60, 70, 72, 74 and 80 wt% of silanated barium-silica fillers were used for cementing CAD/CAM ceramic inlay into the cavity. The specimens involving inlay-cement-tooth interfaces were subjected to a three-body wear test. The relation between the interfacial gap dimension and wear loss was also investigated using 60, 70 and 80 wt% filled cements. The cements containing more than 70 wt% filler presented significantly higher wear resistance than 60 wt% filled cement. There was a positive linear relationship between gap dimension and wear loss, and the inclination of the regression line decreased with increasing filler content. These results indicated that the higher filler content of the cement increased the wear resistance and this desirable influence appeared more remarkably in the wider horizontal gap dimension. (+info)
Influence of composite inlay/onlay thickness on hardening of dual-cured resin cements.
This investigation evaluated the effect of resin composite inlay/onlay thickness on the hardness of a group of eight dual-cure resin-based cements. Fourteen disc specimens measuring 6 mm in diameter and 2.5 mm thick were prepared from each of eight dual-cure cements: Adherence, Choice, Duolink, Enforce, Lute-It, Nexus, Resinomer and Variolink. Two specimens from each material were directly light-cured while the remainder of the specimens were light-cured through resin composite spacers varying in thickness from 1 mm to 6 mm. Curing through the spacers always resulted in a decrease in the Knoop hardness number. For some cements, hardness values were reduced by 50% or more when the resin composite spacer thickness was 4 mm or greater even when measurements were made one week after dual-curing. Low hardness values indicate the presence of a weak chemical-curing mechanism that may compromise cement quality in areas of the cavity not readily accessible to the curing light. (+info)
Persistence of deciduous molars in subjects with agenesis of the second premolars.
The purpose of the present study was to investigate persistent primary second molars in a group of young people in their late twenties with agenesis of one or two second premolars. In 1982-83 it was decided, in connection with the orthodontic evaluation of 25 patients, to allow 35 primary molars (one or two in each patient) to remain in situ. All patients had mixed dentitions and agenesis of one or two premolars. The primary teeth were generally in good condition, although root resorption and infra-occlusion (compensated by occlusal composite onlays) occurred. In 1997, 18 of the 25 patients with a total of 26 retained primary molars were reexamined, comprising a clinical examination for exfoliation, extraction, loosening, and ankylosis, and a radiographic examination for root resorption, tooth morphology (crown and root), and alveolar bone contour. The examination showed that the degree of root resorption was unaltered in 20 of the 26 primary molars. In the permanent dentitions, where these primary molars persisted, there were no morphological deviations. Three of the six remaining primary molars had been extracted and three showed extensive resorption. In three of the 26 primary molars the infra-occlusion had worsened. The present study shows that persistence of primary second molars in subjects with agenesis of one or two premolars, and normal morphology of the permanent dentition can be an acceptable, semi-permanent solution for the patient. Whether this could also be an acceptable long-term solution will be shown by follow-up studies. (+info)
Management of extensive carious lesions in permanent molars of a child with nonmetallic bonded restorations--a case report.
The badly decayed molar teeth of a 12-year-old were restored using resin composite and ceramic restorations. The maxillary first left permanent molar, which had an extensive carious lesion that had destroyed most of the coronal hard tissues of the tooth, was restored to shape and function with a heat-treated resin composite onlay restoration. The restoration was followed up for two years. The mandibular right first molar had a failing large amalgam restoration with extensive recurrent caries. After a three-month period of pulp-capping, the tooth was restored with a bonded ceramic onlay restoration. A nine-month follow-up of this restoration is provided. The maxillary right first molar, which also had a failing large amalgam/resin composite restoration, was restored with a direct resin composite restoration. Under traditional treatment regimens, these extensive cavities would have been treated using more invasive procedures such as pin-retained restorations or elective root canal therapy, post placement, core build-up and crowning. Bonded non-metallic restorations avoid the trauma, time and cost that accompany such extensive procedures and offer a more conservative approach. (+info)
Casting accuracy of experimental Ti-Cu alloys.
The purpose of the present study was to investigate the casting accuracy and the dimensional change of experimental titanium-copper alloys (3.0 and 5.0 mass% Cu; hereafter, only "%" will be used) and to compare the findings with those of pure titanium. Castings were made using an argon-arc melting/pressure difference-casting unit. The fit of the metals cast in both full crown and MOD inlay dies was evaluated by measuring the distance between the shoulder margin and the cervical shoulder of the die. The changes in the inner diameter of castings were determined. In addition, surface roughness measurements inside the castings were carried out using a conventional profilometer, and thermal expansion measurements were made on cast cylindrical specimens using a differential dilatometer. There were no significant differences in dimensional change between pure titanium and the titanium-copper alloys. The fit of the titanium-copper alloys was inferior to pure titanium. The results of surface roughness measurements showed significance differences between the roughness of the pure titanium and titanium-copper alloys. (+info)
Dental transfigurements in Borneo.
Dental transfigurement, formerly termed dental mutilation, has been practised by many societies worldwide. This article gives many of the forms that have been attributed to the indigenes of the island of Borneo. The method has been performed by review of anthropological books, sparse dental references, Borneo research literature, and popular writing. (+info)
Adhesion in vitro of oral streptococci to porcelain, composite resin cement and human enamel.
We investigated the initial adhesion in vitro of oral streptococci to porcelain inlays. Four strains of streptococci, Streptococcus mitis NCTC12261, Streptococcus oralis ATCC9811, Streptococcus sanguis ATCC10556 and Streptococcus sobrinus OMZ176, were used in this study. The disc specimens were made of porcelain, composite resin cement and human enamel. These specimens, with or without a saliva-coat, were immersed in a suspension of each streptococci strain at 37 degrees C for 1 hr, and the numbers of cells adhering to specimens were counted after staining. The saliva-coat significantly decreased the numbers of adhering cells in all strains tested (t-test, p < 0.05). The adhesion to the porcelain and resin cements could be explained by a thermodynamic approach, although the adhesion to enamel could not be explained. These results indicated the possibility that the mechanism is different in initial adhered strains of streptococci between enamel and dental restorative materials. (+info)
Crowns and other extra-coronal restorations: porcelain laminate veneers.
Porcelain veneers are resin-bonded to the underlying tooth and provide a conservative method of improving appearance or modifying contour, without resorting to a full coverage crown. The porcelain laminate veneer is now a frequently prescribed restoration for anterior teeth. The sums spent by the Dental Practice Board on this type of treatment increased from quarter of a million pounds in 1988/89 to over seven million in 1994/95, representing some 113,582 treatments. Since that time the number has stabilised at over 100,000 veneers prescribed each year. The objective of this paper is to give a practical guide on providing these restorations. (+info)