What percentage of patients switch from Invisalign to braces? A retrospective study evaluating the conversion rate, number of refinement scans, and length of treatment.

INTRODUCTION: This retrospective clinical study aimed to determine what percentage of patients switched from Invisalign to braces to finish treatment. We also examined the number of refinement scans per treatment and the estimated vs actual length of treatment. METHODS: Records from 500 patients (average age 33.6 years) that started with Invisalign Full or Invisalign Teen were gathered from 2 orthodontic offices and evaluated. Data was collected from the doctors' consultation notes, treatment notes, and Invisalign Web site databases. There were 2 independent variables: gender (male and female) and age groups (aged <20 years, 20-30 years, and >30 years). RESULTS: One in every 6 patients (17.2%) switched from Invisalign to braces. Invisalign treatment required an average of 2.5 refinement scans, and only 6.0% of patients could complete their treatment without a single refinement scan. The average length of Invisalign treatment was 22.8 months, this was 5.1 months more than the estimated length. The average number of aligners was 64.1, but for the patients that switched to braces, the average number of aligners was 80.6 plus an additional 6.9 months of braces. There was no statistical difference between gender or age group and the conversion to braces. However, patients in the oldest age group had a significantly greater number of refinement scans. CONCLUSIONS: We are likely overestimating an office's efficiency using Invisalign. On average, an Invisalign patient will require approximately 2-3 refinement scans and 2 years of treatment, and there should be a reasonable expectation that braces may be needed.

Zinc Oxide Nanoparticles Supported Lipase Immobilization for Biotransformation in Organic Solvents: A Facile Synthesis of Geranyl Acetate, Effect of Operative Variables and Kinetic Study.

The present study describes grafting of zinc oxide (ZnO) nanoparticles with polyethyleneimine (PEI) followed by modification with glutraldehyde used as the bridge for binding the enzyme to support. The prepared nanocomposites were then characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy, utilized for synthesis of geranyl acetate in n-hexane. Among all the three prepared nanocomposites (ZnO + PEI, ZnO + PEI + SAA, ZnO + PEI + GLU), Candida rugosa lipase immobilized on ZnO-PEI-GLU was found to be best for higher ester synthesis. The operating conditions that maximized geranyl acetate resulted in the highest yield of 94 % in 6 h, molar ratio of 0.1:0.4 M (geraniol/vinyl acetate) in the presence of n-hexane as reaction medium. Various kinetic parameters such as V max, K i(G), K m(G), and K m(VA) were determined using nonlinear regression analysis for order bi-bi mechanism. The kinetic study showed that reaction followed order bi-bi mechanism with inhibition by geraniol. Activation energy (E a ) was found to be lower for immobilized lipase (12.31 kJ mol(-1)) than crude lipase (19.04 kJ mol(-1)) indicating better catalytic efficiency of immobilized lipase. Immobilized biocatalyst demonstrated 2.23-fold increased catalytic activity than crude lipase and recycled 20 times. The studies revealed in this work showed a promising perspective of using low-cost nanobiocatalysts to overcome the well-known drawbacks of the chemical-catalyzed route.