Light-curing of orthodontic bracket adhesive by transillumination through dentine and enamel

Bonding properties of light-curing adhesive cured by transillumination through the tooth were compared to those achieved by the conventional technique. The study analyzed the degree of cure (DC%), debonding force (DF) and adhesive remnant index (ARI) when light was transmitted through dental hard tissues. Slices of dentin and enamel of 1 mm in thickness were combined with total thicknesses of 3 or 4 mm to simulate tooth structure without the pulp tissue. DC% with curing time of 20 s, 40 s and 60 s and irradiance power was measured for each group (n ¼ 5). Brackets were bonded using transillumination on extracted incisors (n ¼ 6) and premolars (n ¼ 10), and DF was measured and ARI was scored. No statistical difference was found in light transmission between the simulated samples and incisors (p > .05). Increasing the curing time from 40 s to 60 s enhanced the DC% only in premolars (p < .05). An adequate DF was achieved through transillumination both in incisors and premolars, but in premolars, the DC% remained low compared to conventionally cured brackets. Most of the bracket failures resulted from weak bracket-adhesive bond.</p

Temporomandibular joint and Giant Panda's (Ailuropoda melanoleuca) adaptation to bamboo diet

Here, we present new evidence that evolutionary adaptation of the Ailuripodinae lineage to bamboo diet has taken place by morphological adaptations in the masticatory system. The giant panda in the wild and in captivity removes without an exception the outer skin of all bamboo shoots, rich in abrasive and toxic compounds, by the highly adapted premolars P3 and P4. The temporomandibular joint (TMJ) allows sidewise movement of the jaw and the premolars can, in a cusp-to-cusp position, remove the poorly digestible outer skin of the bamboo before crushing the bamboo with molars. Based on the evidence presented here, we suggest that adaptation of TMJ to lateral movement for enabling cusp-to-cusp contact of premolars is the crucial evolutionary factor as which we consider the key to understand the Ailuropodinae lineage adaptive pathway to utilize the bamboo resource