ABSTRACT
The purpose of this study was to systematically review the existing literature to assess the clinical survival and success of PICN and ZLS indirect restorations as the clinical evidence for them remains lacking. PubMed, SCOPUS, Embase, Cochrane Library, Web of Science, LILACs, and SciElo databases were searched from 1 January 2000 to 1 February 2021. Clinical trials and cohort studies published in English were included while case studies, case series, and in vitro studies were excluded. Results were analyzed qualitatively and a meta-analysis using a random effects model was performed. A strength of recommendation taxonomy (SORT) analysis was conducted and risk of bias (RoB) was assessed using the Newcastle-Ottawa scale and Cochrane RoB tools. An electronic search through the databases yielded 2454 articles, of which 825 remained after duplicate removal. Five studies investigating PICN and four investigating ZLS indirect restorations remained after assessing for eligibility. The overall survival rate of PICN over 1 year was 99.6% and 99.2% over 2 years. The overall survival rate of ZLS over 1 year was 99%. The main mode of failure for both materials was catastrophic fracture. One study had a high RoB, four had a moderate RoB, and four had a low RoB. Both materials demonstrated moderate strength of recommendation at a level 2 evidence for all studies based on SORT analysis. PICN and ZLS show promising short-term clinical performance as full and partial coverage indirect restorations, but longer follow-up studies are required to confirm their long-term performance.
ABSTRACT
OBJECTIVE: Our objective was to characterize mainstream smoke constituent deliveries from SPECTRUM variable nicotine research cigarettes under 2 machine smoking regimens. SPECTRUM cigarettes are manufactured by the 22nd Century company for the National Institute on Drug Abuse, National Institutes of Health to contain varying (including reduced) levels of nicotine. METHODS: Mainstream smoke constituent deliveries of "tar," nicotine, carbon monoxide, tobacco-specific nitrosamines (N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)), benzo[a]pyrene, aromatic amines, and carbonyls were analyzed in 23 varieties of SPECTRUM cigarettes using ISO 17025 accredited methods. RESULTS: Data are presented as means and standard deviations of 5 replicates for all analytes. CONCLUSIONS: Under the ISO smoking regimen, mean levels of many smoke emissions for SPECTRUM varieties were comparable to the 3R4F research cigarette. Calculated SPECTRUM elasticity ranged from 1.6 to 4.0. Accordingly, under intense machine smoking conditions differences in emissions of SPECTRUM cigarettes were apparent. In addition, NNN increased with smoke nicotine while the same rate of change was not seen for NNK. It is important to monitor levels of chemicals of public health concern and regulatory interest as technologies emerge to reduce levels of nicotine or other targeted chemicals in tobacco products.
