Biomedical subjects

Dan Nathanson

Publications and source records attributed to Dan Nathanson.

4 recordsLinked to original sources

PubMed2003

In vitro assessment of retention of four esthetic dowels to resin core foundation and teeth.

STATEMENT OF PROBLEM: Several new esthetic dowel systems are currently available for the restoration of endodontically treated teeth. These dowel systems enhance the esthetic quality of all-ceramic restorations better than metallic dowel systems. PURPOSE: The purpose of this study was to evaluate the retentive strength of composite and ceramic endodontic dowel systems to the tooth and to the core foundation. MATERIAL AND METHODS: The following dowel systems were tested: resin dowels (Fibrekor [FR]; Luscent [LU]; Twin Luscent Anchor [TLU]); ceramic dowels (Cerapost [CR]; Cosmopost [CO]); and a titanium dowel (ParaPost XH [Ti]). In Part I of the study, core retention was tested by forming Bis-Core resin (n=12) cores around dowels followed by separation using a universal testing machine. In Part II, 60 (n=12) extracted human canines were endodontically treated, and dowel spaces were prepared using the corresponding drill for each dowel system. Nine-millimeter resin and ceramic dowels were cemented with C & B resin luting agent. Additionally, 2 groups (n=12) of Ti dowels cemented with C & B resin luting agent and zinc phosphate luting agent served as control groups. Retention was tested using a universal testing machine to separate the dowels from teeth. One-way analysis of variance and Student Newman-Keuls tests were conducted for statistical analysis (alpha=.05). Surface texture of all dowel systems tested was examined using SEM at original magnification x25 and x250. RESULTS: Core retention of Ti was higher than all esthetic dowels tested (alpha<.05), but FR had higher core retention than the other esthetic dowels tested. Resin dowels had better retention to teeth than ceramic dowels (alpha<.05). CONCLUSION: The esthetic dowel systems were less retentive for the resin core material than the titanium control. Resin dowel systems were more retentive in the root than the ceramic dowels but were similar to the titanium control.

Analysis of Variance↗

PubMed2002

Microbial profile on metallic and ceramic bracket materials.

The placement of orthodontic appliances creates a favorable environment for the accumulation of a microbiota and food residues, which, in time, may cause caries or exacerbate any pre-existing periodontal disease. The purpose of the present study was to compare the total bacterial counts present on metallic and ceramic orthodontic brackets in order to clarify which bracket type has a higher plaque retaining capacity and to determine the levels of Streptococcus mutans and Lactobacillus spp on both types of brackets. Thirty-two metallic brackets and 24 ceramic brackets were collected from orthodontic patients at the day of debonding. Two brackets were collected from each patient; one from a maxillary central incisor and another from a maxillary second premolar. Sixteen patients who used metallic brackets and 12 patients who used ceramic brackets were sampled. Bacterial populations were studied using "checkerboard" DNA-DNA hybridization, which uses DNA probes to identify species in complex microbial samples. The significance of differences between groups was determined using the Mann-Whitney U-test. Results showed no significant differences between metallic and ceramic brackets with respect to the caries-inducing S mutans and L acidophilus spp counts. Mean counts of 8 of 35 additional species differed significantly between metallic and ceramic brackets with no obvious pattern favoring one bracket type over the other. This study showed higher mean counts of Treponema denticola, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum ss vincentii, Streptococcus anginosus, and Eubacterium nodatum on metallic brackets while higher counts of Eikenella corrodens, Campylobacter showae, and Selenomonas noxia were found on ceramic brackets.

Aggregatibacter actinomycetemcomitans↗

PubMed2002

Are adhesive technologies needed to support ceramics? An assessment of the current evidence.

Despite large variations in the reported fracture strengths of dispersion strengthened, glass infiltrated, castable, pressable and machinable ceramics utilised for the construction of all-ceramic crowns, the annual clinical failure rate reported for these materials in the dental literature is remarkably consistent at ca 3%. These results emphasise that there may be little correlation between the average fracture strength and resultant clinical performance. Consequently, if ceramics are to be used for dental applications, then clearly more detailed information on the statistical variations in strength combined with the influence of cementation media are required. The effect of adhesive technology has been examined in laboratory and clinical studies. The laboratory studies focused on the effect of cement lute on crown performance, whilst surface degradation and strengthening effects with different systems were examined utilising conventional materials science techniques. Clinical studies focused on the failure rates of conventionally luted and adhesively luted crowns and inlays. There would appear to be evidence from clinical studies that crowns luted with a resin cement and with the placement procedure incorporating a dentine bonding stage have enhanced rates of survival. It is therefore concluded that the available research strongly suggests that the use of resin as a luting material for ceramic restorations is indicated, given the research from three differing sources - laboratory fracture studies comparing restorations luted with resin vs other materials, clinical studies, and laboratory studies examining the surface sealing/strengthening effect of resin on ceramic. Laboratory studies also confirm the enhanced resistance to fracture of crowns cemented with an adhesive procedure.

Adhesives↗

PubMed2002

Color stability of resin cements--an in vitro study.

The long-term success of an aesthetic restoration is predicated on numerous factors that include its color stability. As clinicians incorporate conservative tooth preparation into their restorative designs, the color stability of the underlying cement material increases in importance. This in vitro study evaluated the color stability of several commercially available resin cements under accelerated conditions. The investigation demonstrated that, under the experimental conditions, resin cements tended to change color between 1 week and 14 weeks, and their color change values increased with accelerated aging times.

Bisphenol A-Glycidyl Methacrylate↗