The impact of bone grafting with/without barrier membrane placement on the outcome of apical surgery: A systematic review and meta-analysis.

BACKGROUND: Regenerative techniques are increasingly being advocated in endodontic apical surgery (AS) to enhance the healing of periapical lesions. Various grafting and membrane materials are employed as adjuncts to modern AS. OBJECTIVES: This systematic review aimed to answer the following PICO question: In patients with apical periodontitis (P) what is the impact of bone grafting with/without barrier membrane materials (I) compared with surgery without grafting materials (C) on the outcome of AS evaluated clinically and radiographically (O). METHODS: A systematic search was conducted in four databases (Embase, Web of Science, PubMed and Cochrane Central Register of Controlled Trials) until 1 August 2023. Google Scholar was also manually searched. Studies with a prospective randomized design were included. Cochrane risk-of-bias (RoB) tool 2.0 assessed bias. Two independent reviewers performed the study selection, data extraction and appraisal of studies. Meta-analysis was performed using R3.5.1 software. RESULTS: From the identified 2582 studies, eight randomized clinical trials were included for meta-analysis. Two studies had low RoB, while six had some concerns. Analysis revealed significantly better outcomes when surgery involved bone regeneration techniques than conventional surgery (OR = 2.18, 95% CI: 1.32-4.31, p = .004). Subgroup analyses on individual grafts (OR = 0.22, 95% CI: -0.99 to 1.44, p = .720) (OR = -0.09, 95% CI: -1.42 to 1.23, p = .885) and membranes (OR = -1.09, 95% CI: -2.94 to 0.76, p = .247) and their combinations (OR = 0.03, 95% CI: -1.50 to 1.55, p = .970) did not yield any significant results. The type of membrane used did not significantly impact the outcome (OR = -1.09, 95% CI: -2.94 to 0.76, p = .247) nor did altering the combination of graft/membrane. DISCUSSION: This systematic review examined the effects of bone grafting with/without membrane placement on the outcome of AS. It highlights the potential advantages of regenerative techniques and the need for further research in this area. CONCLUSIONS: Based on current evidence, bone grafting with/without barrier membrane placement significantly improves healing after AS. Subgroup analysis of resorbable membranes or grafting did not significantly influence the outcome. The combination of membrane and graft was also not significant. Future well-designed, randomized controlled trials in this area are essential before these materials can be recommended for routine use to enhance healing outcomes in AS. REGISTRATION: PROSPERO (CRD42021255171).

Dispersion design in gradient index elements using ternary blends.

We show that a gradient-index element designed from a blend of three materials allows a designer to specify independently the element's refractive index and its change in refractive index with respect to wavelength. We show further the effectiveness of this approach by comparing modeled chromatic performance of deflectors consisting of a single material, a binary blend of materials, and a ternary blend.

Chromatic analysis and design of a first-order radial GRIN lens.

From the expression for optical power of a radial first-order graded-index (GRIN) lens with curved surfaces, we derive an expression for chromatic aberration. Our expressions for optical power and chromatic aberration are valid under the paraxial approximation. By applying a series of further simplifying assumptions, namely a thin lens and thin GRIN, we derive a set of equations with which one can design an achromatic GRIN lens. We also derive expressions for the dispersive property of a GRIN element. Our analysis enables us to derive the relationship between material pairs that indicate their suitability as a material pair for a GRIN achromat. We use this relationship to search a standard glass catalog for attractive GRIN material pairs for a particular achromat design. We compare the optical performance of our GRIN design to that of a conventional homogeneous doublet and demonstrate that our approach is capable of identifying material pairs that perform well for achromatic GRIN lenses which would not generally be considered for conventional achromatic design. We also demonstrate our approach is capable of designing GRIN achromats with superior performance.

Refractive index measurements of poly(methyl methacrylate) (PMMA) from 0.4-1.6 µm.

Using a transmission-spectrum-based method, the refractive index of a 50 µm thick sample of poly(methyl methacrylate) (PMMA) was measured as a function of wavelength. To mitigate the effects of nonplane-parallel surfaces, the sample was measured at 16 different locations. The technique resulted in the measurement of index at several thousand independent wavelengths from 0.42 to 1.62 µm, with a relative RMS accuracy <0.5×10(-4) and absolute accuracy <2×10(-4).

Thin sample refractive index by transmission spectroscopy.

Transmission spectroscopy and a small number of refractometer index measurements are combined to provide refractive index measurements of transparent samples ~50 um thick at hundreds of wavelengths with absolute accuracies <1 x 10(-4). Key to the technique is the use of independent index measurements to circumvent the need for an independent thickness measurement of the sample. The method was demonstrated on glass samples where fits to Cauchy curves had RMS accuracies <3 x 10(-5) from 415 to 1610 nm. Issues that must be addressed to reach this level of accuracy are discussed.

Achromatic GRIN singlet lens design.

Gradient refractive index (GRIN) materials are attractive candidates for improved optical design, especially in compact systems. For GRIN lenses cut from spherically symmetric GRIN material, we derive an analogue of the "lens maker's" equation. Using this equation, we predict and demonstrate via ray tracing that an achromatic singlet lens can be designed, where the chromatic properties of the GRIN counterbalance those of the lens shape. Modeling the lens with realistic materials and realistic fabrication geometries, we predict we can make an achromatic singlet with a 19 mm focal length using a matrix of known polymers.

A bio-inspired polymeric gradient refractive index (GRIN) human eye lens.

A synthetic polymeric lens was designed and fabricated based on a bio-inspired, "Age=5" human eye lens design by utilizing a nanolayered polymer film-based technique. The internal refractive index distribution of an anterior and posterior GRIN lens were characterized and confirmed against design by µATR-FTIR. 3D surface topography of the fabricated aspheric anterior and posterior lenses was measured by placido-cone topography and exhibited confirmation of the desired aspheric surface shape. Furthermore, the wavefronts of aspheric posterior GRIN and PMMA lenses were measured and simulated by interferometry and Zemax software, respectively. Their results show that the gradient index distribution reduces the overall wavefront error as compared a homogenous PMMA lens of an identical geometry. Finally, the anterior and posterior GRIN lenses were assembled into a bio-inspired GRIN human eye lens through which a clear imaging was possible.

Counter-propagating optical trapping system for size and refractive index measurement of microparticles.

We propose and demonstrate a novel approach to measure the size and refractive index of microparticles based on two beam optical trapping, where forward scattered light is detected to give information about the particle. The counter-propagating optical trap measurement (COTM) system exploits the capability of optical traps to measure pico-Newton forces for microparticles' refractive index and size characterization. Different from the current best technique for microparticles' refractive index measurement, refractometry, a bulk technique requiring changing the fluid composition of the sample, our optical trap technique works with any transparent fluid and enables single particle analysis without the use of biological markers. A ray-optics model is used to explore the physical operation of the COTM system, predict system performance and aid system design. Experiments demonstrate the accuracy of refractive index measurement of Deltan=0.013 and size measurement of 3% of diameter with 2% standard deviation. Present performance is instrumentation limited, and a potential improvement by more than two orders of magnitude can be expected in the future. With further development in parallelism and miniaturization, the system offers advantages for cell manipulation and bioanalysis compatible with lab-on-a-chip systems.

Two-beam optical traps: refractive index and size measurements of microscale objects.

A counter-propagating optical trap measurement (COTM) system is proposed and analyzed based on the ray-optics model. In this system, refractive index and size of trapped objects can be estimated by using forward scattered light from the two-beam laser trap with resolution Delta n = 0.013 for the refractive index measurements and 3.3% for the size measurements, which is comparable with current bulk techniques, such as refractometry, and flow cytometry. The unique advantage of the COTM system over conventional approaches lies in its capability of marker-free single-particle characterization in whatever transparent buffer required by living cell, eliminating the necessity of changing the fluid composition of the sample in refractometry, and of tagging target with toxic fluorescence dyes in flow cytometry. Noise analysis predicts a potential improvement in the system resolution by more than two orders of magnitude. This non-invasive and sterile tool complements lab-on-a-chips with single cell manipulation and analysis in living friendly ambient.