Patterns and forces of occlusal contacts during lateral excursions recorded by the T-Scan II system in young Chinese adults with normal occlusions.

The objective was to characterise the patterns and forces of occlusal contacts during lateral mandibular excursions in a young Chinese adult population. Angle Class I normal occlusions in 85 dental students aged 20-29 were evaluated using the T-Scan II occlusal imaging and analysis system. The frequency of occlusal contacts was recorded for right and left lateral excursions at the position of lateral disclusion, at the canine-to-canine position and at the lateral maximal position. At the canine-to-canine position, the occlusal contact patterns were classified, and the relative forces were compared by multiple regression analysis, with α = 0·05. At the position of lateral disclusion, a high percentage of canine contacts (58·5%) and individual posterior tooth contacts on the working side was observed. At the canine-to-canine position, the canines on the working side contacted most frequently (68·9%), and the occlusal contact patterns could be classified into six groups. At the lateral maximal position, incisors (39·0%) and canines (32·3%) contacted most frequently. At the canine-to-canine position, subjects with occlusal contacts only on canines or on first premolars on the working side had the lowest relative occlusal forces (P < 0·001). Canine protection and group function do not identify all descriptors for lateral occlusal contact patterns in the natural dentition. Six occlusal contact patterns were found at the lateral canine-to-canine position.

Effect of fluoride iontophoresis on the microtensile bond strength between dentin and two adhesive systems.

AIM: To evaluate the effect of fluoride iontophoresis on the microtensile bond strength (MTBS) between coronal dentin and two resin-based adhesive systems, and to measure quantitatively dentinal tubule occlusion. METHODS: Twelve freshly extracted intact human mandibular third molars were divided randomly into four groups. The superficial occlusal dentin of each tooth was exposed and treated. Group A1: One-Step Plus total-etch adhesive system; group A2: One-Step Plus total-etch adhesive system after fluoride iontophoresis; group B1: ACE BOND SE self-etching adhesive system; group B2: ACE BOND SE self-etching adhesive system after fluoride iontophoresis. A resin composite buildup was made for each tooth, which was then sectioned along its long axis to produce 10 beams (1.0 mm x 1.0 mm) for the microtensile bond strength (MTBS) test. Five dentin disks were cut in half and their occlusal surfaces etched with 6% citric acid. The test halves were treated with fluoride iontophoresis. Four SEM photomicrographs were taken from corresponding sites on each test and each non-treated control half-disk. Image-Pro Plus 4 software quantified the percentage of tubule occlusion. Data were analyzed using one-way ANOVA, chi(2)- and t-tests, with the probability level set at alpha=0.05. RESULTS: The mean MTBS (MPa) for each group was, A1: 30.86 (S.D. 6.84); A2: 25.04 (8.49); B1: 19.22 (6.88); B2: 19.40 (6.92). There were significant differences among all groups (P < or = 0.02), except between groups B1 and B2 (P=0.92). Fluoride iontophoresis resulted in significantly increased dentinal tubule occlusion (P<0.001). CONCLUSIONS: Fluoride iontophoresis treatment reduced significantly the dentin bond strength of One-Step Plus total-etch adhesive, but not that of ACE BOND SE self-etching adhesive. However, the bond strength of the former remained significantly higher than that of the latter adhesive system.

Restoration of teeth with more-viscous glass ionomer cements following radiation-induced caries.

OBJECTIVE: To assess the suitability of more-viscous conventional restorative glass ionomer cements (GICs) in a high-caries risk group of patients. METHODS: Fifteen adult patients with radiation-induced caries were treated at a dental hospital by one dentist. Two encapsulated aesthetic GICs were used in each patient to restore 146 carious lesions in the exposed dentine and cementum of 93 teeth. The restorations were assessed directly over two years for their retention, secondary caries, anatomic form, marginal integrity, marginal discolouration, and surface texture. RESULTS: Both GICs were placed in similar sized cavities (P = 0.63). After two years, although 30.0% of Ketac-Molar Aplicap and 12.5% of Fuji IX GP restorations had been lost (P = 0.01), there were no instances of secondary caries. The remaining GICs showed ongoing marginal deterioration, but there were very few instances where this required the repair or replacement of the restorations. No restorations failed from surface erosion. CONCLUSIONS: In these high-caries risk patients the placement of more-viscous GICs appeared to prevent secondary caries, even when the restorations were subsequently lost.