Osteo-odonto-keratoprosthesis (OOKP) and the testing of three different adhesives for bonding bovine teeth with optical poly-(methyl methacrylate) (PMMA) cylinder

Corneal Repair and Regeneration: Current Concepts and Future Directions

The cornea is a unique tissue and the most powerful focusing element of the eye, known as a window to the eye. Infectious or non-infectious diseases might cause severe visual impairments that need medical intervention to restore patients' vision. The most prominent characteristics of the cornea are its mechanical strength and transparency, which are indeed the most important criteria considerations when reconstructing the injured cornea. Corneal strength comes from about 200 collagen lamellae which criss-cross the cornea in different directions and comprise nearly 90% of the thickness of the cornea. Regarding corneal transparency, the specific characteristics of the cornea include its immune and angiogenic privilege besides its limbus zone. On the other hand, angiogenic privilege involves several active cascades in which anti-angiogenic factors are produced to compensate for the enhanced production of proangiogenic factors after wound healing. Limbus of the cornea forms a border between the corneal and conjunctival epithelium, and its limbal stem cells (LSCs) are essential in maintenance and repair of the adult cornea through its support of corneal epithelial tissue repair and regeneration. As a result, the main factors which threaten the corneal clarity are inflammatory reactions, neovascularization, and limbal deficiency. In fact, the influx of inflammatory cells causes scar formation and destruction of the limbus zone. Current studies about wound healing treatment focus on corneal characteristics such as the immune response, angiogenesis, and cell signaling. In this review, studied topics related to wound healing and new approaches in cornea regeneration, which are mostly related to the criteria mentioned above, will be discussed.

Comparison of an Er: YAG laser osteotome versus a conventional drill for the use in osteo- odonto-keratoprosthesis (OOKP)

OBJECTIVES

The osteo-odonto-kerato-prosthesis (OOKP) procedure is a complex, multi-stage, multidisciplinary surgical intervention for the treatment of severe corneal blindness. One step of the OOKP consists of creating a precise hole into a tooth in which an optic cylinder is subsequently inserted; its shape must ensure a perfect watertight fit. The Er: YAG laser (L) used in this study is part of CARLO®, the first laser osteotome that enables surgical planning based on computed tomography data, robot guidance, and a precise execution of laser cuts in teeth and bone tissue, using laser photoablation rather than conventional mechanical methods. The purpose of this study was to assess whether the Er: YAG laser is non-inferior compared to a conventional drill.

METHODS

Thirty-two bovine incisors were grounded to a thickness of 1.5 mm. In 16 teeth, a 3.5 mm hole was drilled progressively into each tooth, using dental burs (B) of increasing diameter that were attached to a fixed drill machine. In the other 16 teeth, a hole was created using an Er: YAG laser at a wavelength of 2.94 µm (Part of CARLO®). In seven teeth of each group, the cylinder was inserted and fixated with polymethylmethacrylate (PMMA) bone cement. In the remaining seven teeth of each group, the cylinder was inserted without fixation material (press-fit). After bonding and drying, all specimens were stored in water until force measurements were recorded using a uniaxial traction machine. The force required to move the optical cylinder out of the hole in the tooth was measured using an Instron 3344 testing system. Scanning electron microscope (SEM) and light microscope (LM) visualization of the holes created with the laser and the drill were performed in two teeth (SEM)/four teeth (LM) per method.

RESULTS

Significant differences (P < 0.001) were found for the following parameters: B PMMA versus B press-fit; B PMMA versus L press-fit; L PMMA versus B press-fit; L PMMA-L press-fit. This shows that PMMA bone cement fixation is superior to press-fit. No significant differences were found between B PMMA-L PMMA (P = 0.93) and B press-fit-L press-fit (P = 0.83). The SEM pictures showed a smoother surface using L.

CONCLUSIONS

The laser cut holes were as strong as bur-drilled holes, although SEM pictures showed a smoother surface of the laser cut holes. Hence, laser osteotomes open the possibility to custom fit the hole exactly to the width of the cylinder, which represents a potential advantage of the laser over the conventional bur. Lasers Surg. Med. 51:531-537, 2019. © 2019 Wiley Periodicals, Inc.

Keratoprosthesis: A Review of Recent Advances in the Field

Since its discovery in the years of the French Revolution, the field of keratoprostheses has evolved significantly. However, the path towards its present state has not always been an easy one. Initially discarded for its devastating complications, the introduction of new materials and the discovery of antibiotics in the last century gave new life to the field. Since then, the use of keratoprostheses for severe ocular surface disorders and corneal opacities has increased significantly, to the point that it has become a standard procedure for corneal specialists worldwide. Although the rate of complications has significantly been reduced, these can impede the long-term success, since some of them can be visually devastating. In an attempt to overcome these complications, researchers in the field have been recently working on improving the design of the currently available devices, by introducing the use of new materials that are more biocompatible with the eye. Here we present an update on the most recent research in the field.