Time benefits of 3D planning in orthognathic surgery: a systematic review.

This systematic review aimed to evaluate the possible time benefits when using 3-dimensional (3D) planning prior to orthognathic surgery compared with a conventional method alone. The databases utilised were PubMed, Medline, Web of Science, and the Cochrane Library. Studies were selected based on eligibility criteria and reviewed independently by two authors. A total of eight studies were included. The review concludes that there are a limited number of studies with the appropriate experimental protocols in place. Therefore, although there is low-grade evidence to suggest that 3D planning in orthognathic surgery is more time-efficient, the field would benefit from the publication of more rigorous studies.

Admicellar polymerization of methyl methacrylate on aluminum pigments.

Micrometer-sized aluminum particles used as pigments in silver inks and coatings are reactive in water-based formulations. This leads to hydrogen gas evolution in the paint containers and loss of the silvery appearance of the coating. The protection of aluminum pigments from water is called inhibition and it was shown in earlier work that anionic surfactants of the phosphate ester type are effective as inhibitors, forming a protective bilayer on the aluminum pigment surface. In this work, the protection of aluminum pigments has been extended by means of an encapsulating polymer layer. A poly(methyl methacrylate) (PMMA) coating was applied on aluminum pigment particles by admicellar polymerization of methyl methacrylate. A surfactant is first adsorbed on the aluminum pigment surface and a hydrophobic monomer and initiator is subsequently solubilized inside the hydrophobic domain of the surfactant aggregates that cover the pigment. Diffuse Reflective Infrared Fourier Transform (DRIFT) spectrometry showed that PMMA was formed on the pigment particles and the amount of organic material was up to 24% of the particle weight, as measured by Thermo Gravimetric Analysis (TGA). A hydrophobic initiator, such as benzoyl peroxide, gave good results but the hydrophilic sodium persulfate resulted in poor yield of encapsulating polymer. Sodium dodecyl sulfate, which by itself is not an efficient inhibitor, was used as surfactant. Good results were obtained in terms of protection from an alkaline solution, indicating that the polymer coating per se is an efficient inhibitor. The highest amount of polymer formed on the pigment surface was obtained when the surfactant concentration was around the CMC.

Effectiveness of composite cure associated with different light-curing regimes.

This study investigated the use of various light-curing regimens with standardized light energy density on the effectiveness of cure of a visible light activated resin composite (Z100, 3M-ESPE). A light-cure unit (Variable Intensity Polymerizer (VIP), BISCO Inc) which permitted individual control over time and intensity, was used. The five light-curing modes investigated include Pulse Delay (PD), Pulse Cure (PC), Soft-start (SS), Turbo (T) and Control (C). Effectiveness of cure was established by measuring the top and bottom Knoop hardness of 2-mm thick composite specimens using a digital microhardness tester (n=5, load=500g; dwell time=15 seconds) immediately and at one-day post-polymerization. Data obtained was analyzed using one-way ANOVA/Scheffe's post hoc test and Independent Samples t-tests (p<0.05). Top KHN observed immediately after polymerization with C was significantly lower than PD. At one day post-polymerization, the top KHN obtained with C was significantly lower than PD, SS and T. No significant difference in bottom KHN was observed among the different curing modes immediately after curing. At one day post-polymerization, the bottom KHN obtained with C was significantly lower than SS and T. Regardless of curing regimens, top and bottom values at one day were significantly higher than those observed immediately after light polymerization. No significant difference in mean hardness ratio was observed among the different curing regimens immediately and one day later. Effectiveness of the cure at the bottom surfaces of composites may be increased by soft-start and turbo polymerization regimens.