Oral Bacterial Acid-Base Metabolism in Caries Screening: A Proof-Of-Concept Study.

The objective of this cross-sectional study was to clinically validate an array of biochemical tests for oral acid/alkali generation as caries screening instruments. 185 adult subjects (mean 33.6±10.6 years) were examined clinically for dental caries using the ICDAS criteria. Bitewing radiographs were used to confirm interproximal surfaces of posterior teeth. For the purposes of this study, subjects were classified as "caries-active" if they had at least one untreated caries lesion with ICDAS 4 or higher. Pooled supragingival plaque and unstimulated saliva samples were collected and assayed for pH changes from sucrose and urea metabolism using colorimetric tests. The validity of each test to discriminate between "caries-inactive" and "caries-active" subjects was assessed and compared to a commercial bacteriological caries-screening test using roc regression and logistic regression models. The AUCs of the plaque-urea (PU: 0.59 (0.51, 0.67)), plaque-urea-glucose (PUG: 0.59 (0.51, 0.67)) and saliva-urea-glucose (SUG: 0.59 (0.51, 0.67)) tests did not differ significantly from the bacteriological tests (CRT-mutans: 0.62 (0.54, 0.70); CRT-lactobacillus: 0.63 (0.56, 0.71) (P>0.05), but the plaque-glucose (SG), saliva-glucose (SG), saliva-urea (SU) and saliva-plaque-glucose (SPG) tests had significantly smaller AUCs (P<0.05). The AUCs for the PU, PUG, SUG, and the CRT-mutans tests were higher in subjects who had no existing dental restorations (PU: 0.90 (0.77, 1.04); PUG: 0.90 (0.79, 1.01); SUG: 0.89 (0.69, 1.08); CRT-mutans: 0.90 (0.73, 1.08)). The incorporation of the biochemical tests into a multidimensional bacteriological/psychosocial caries screening model significantly increased its diagnostic values (Se+Sp: 160.6, AUC: 0.846). In conclusion, as a proof of concept, the results of this study indicate that measuring the ability of dental plaque and saliva to metabolize urea together with the ability to generate acid from sugars may have a promising role in caries screening either independently, or as part of a multidimensional biological test.

Time-temperature profiles of post-cure composite ovens.

Previous research indicates that there are improved physical properties resulting from post-cure heating of light-activated resin composite. Currently, a large variety of commercial devices and techniques are used for post-cure heating. This study determined differences among the time-temperature profiles of selected commercial post-cure devices. It also compared the biaxial flexure strength of resin composite which was post-cure heated in each device.

Effect of heating delay on conversion and strength of a post-cured resin composite.

Physical property enhancement in light-cured resin composites from post-cure heating is attributed to free radicals created during initial photocuring, the number of which decreases following initial light-curing. Clinically, it is important to know when the number of remaining free radicals is too low to provide for additional conversion of monomer in post-cure-heated specimens. The hypothesis tested is that the potential for additional conversion in post-cure-heated resin composite restorations is dependent upon the time after initial light-curing at which the specimen is exposed to heat treatment. This research examined the effect of delay in post-cure heating after initial photo-activation on strength and monomer conversion of a commercial resin composite material. Discs (10 x 1 mm) of Herculite XRV (Kerr/Sybron, Orange, CA) were photocured at standardized conditions. One group was left unheated, and another was subjected to post-cure heating (Brilliant DI-500, Coltène AG, Altstätten, Switzerland) at the following times after being light-cured: 5 and 30 min, and 6, 24, 48, 72, 96, and 120 hrs. After the appropriate delay time, unheated and heated specimens (n = 10) were tested for biaxial flexural strength at a constant stressing rate. Recovered, fractured strength specimens (n = 10) were analyzed for cure by means of IR spectroscopy. Post-cure heating increased strength over that of the unheated specimens only for the shortest delay times: 5 or 30 min. Thereafter, strength values were statistically equivalent (p < 0.05). Delay in heating did not significantly enhance strength of post-cure-heated specimens, but delay in time did improve strength of the unheated groups. The greatest monomer conversion was obtained when post-cure heating was applied within 6 hrs following light-curing. The difference in cure between unheated and heated specimens remained significant up to 96 hrs of delay. Flexural strength of post-cure-heated specimens remained unchanged with time delay for heating specimens. Maximal monomer conversion of post-cured specimens is obtained only within 6 hrs of light-curing. The potential for additional conversion arising from post-cure heat treatment is dependent upon the time following initial curing at which heat is applied following initial light-curing. However, delay in heat application has no influence on flexural strength.