Nak Heon Kang

Current Methods for the Treatment of Alveolar Cleft

Alveolar cleft is a tornado-shaped bone defect in the maxillary arch. The treatment goals for alveolar cleft are stabilization and provision of bone continuity to the maxillary arch, permitting support for tooth eruption, eliminating oronasal fistulas, providing an improved esthetic result, and improving speech. Treatment protocols vary in terms of the operative time, surgical techniques, and graft materials. Early approaches including boneless bone grafting (gingivoperiosteoplasty) and primary bone graft fell into disfavor because they impaired facial growth, and they remain controversial. Secondary bone graft (SBG) is not the most perfect method, but long-term follow-up has shown that the graft is absorbed to a lesser extent, does not impede facial growth, and supports other teeth. Accordingly, SBG in the mixed dentition phase (6–11 years) has become the preferred method of treatment. The most commonly used graft material is cancellous bone from the iliac crest. Recently, many researchers have investigated the use of allogeneic bone, artificial bone, and recombinant human bone morphogenetic protein, along with growth factors because of their ability to decrease donor-site morbidity. Further investigations of bone substitutes and additives will continue to be needed to increase their effectiveness and to reduce complications.

Effects of Growth Factors From Platelet-Rich Fibrin on the Bone Regeneration

Abstract Platelet-rich fibrin (PRF) has simple manufacturing process without risk of immunologic rejection or infection by additional materials. This study was designed to investigate the effects of platelet-derived growth factors and transforming growth factors-&bgr; in PRF on the proliferation and differentiation of osteoblasts. The authors analyzed platelet-derived growth factors and transforming growth factors-&bgr; in normal human serum (NHS) and PRF by enzyme-linked immunosorbent assay quantitatively and those in PRF group were significantly increased when compared with NHS. After harvesting osteoblasts from iliac bone, the authors added 10% fetal bovine serum, 10% NHS, and 3% PRF to osteoblasts, respectively and incubated for 24, 48, 72 hours. For analysis of osteoblast proliferation and differentiation, the authors measured DNA synthesis by [3H]-thymidine isotope activity, protein synthesis by sulforhoamine B assay and those were increased according to elapsed time in all groups, but they were significantly increased in 3% PRF. The authors measured alkaline phosphatase activity of osteoblasts, it was increased according to elapsed to time in all groups, but significantly increased in 72 hours. In conclusion, application of PRF to bone defect sites may have an enhanced effect of bone regeneration with low risk of complications, and relatively simple manufacturing process.

Hydroxyapatite synthesis using EDTA.

AbstractBone comprises structure of the body and consisted of inorganic substances. It exists in an organic structure in the body. Even though it is firm and has self-healing mechanism, it can be damaged by trauma, cancer, or bone diseases. Allograft can be an alternative solution for autologous bone graft. Hydroxyapatite (Ca10(PO4)6(OH)2), an excellent candidate for allograft, can be applied to bone defect area. There are several methods to produce hydroxyapatite; however, economical cost and being time consuming make the production difficult. In this study, we synthesized hydroxyapatite with EDTA. Freeze-dried bone allograft (Hans Biomed) was used as the control group. Synthesized hydroxyapatite was a rod-shaped, white powdery substance with 2- to 5-&mgr;m length and 0.5- to 1-&mgr;m width. X-ray diffraction showed the highest sharp peak at 32°C and high peaks at 25.8°C, 39.8°C, 46.8°C, 49.5°C, and 64.0°C, indicating a similar substance to the freeze-dried bone allograft. After 3 days, the cell growth of synthesized hydroxyapatite showed 1.5-fold more than did the bone allograft. Cellular and media alkaline phosphate activity increased similar to the bone allograft. In this study, we came up with a new method to produce the hydroxyapatite. It is a convenient method that can be held in room temperature and low pressure. Also, the product can be manufactured in large quantity. It can be also transformed into scaffold structure, which will perform a stronger configuration. The manufacturing method will help the bony defect patients and make future medical products.

Properties of Sterilized Human Skin Allografts by Gamma-Irradiation

The most commonly used sterilization method of human skin allografts is ethylene oxide (EO). EO gas, however, can change the biomechanical properties of the grafts and produce toxic residues which are harmful to the recipient. The heating method cannot be applied for sterilization of soft tissues because of damage due to heat. The purpose of this study was to determine whether it is possible to apply gamma-irradiation for sterilization of soft tissues as well as for hard tissues.

Enhancement of the Strength and Stability of Ultraviolet-Irradiated Acellular Dermal Matrix by Adding Glucose

In theory, Ultraviolet (UV)-generated free radicals can expedite Acellular dermal matrix (ADM) crosslinking with glucose via the formation of reactive, linear glucose molecules. The aim of this study is to maintain strength and stability of UV-irradiated ADM without the introduction of cytotoxic chemical crosslinkers. The strength and stability changes of ADM by UV-irradiated with glucose (GLUC) were investigated under various conditions. ADM strength and stability were determined by tensile testing, differential scanning calorimetry (DSC), and swelling ratio. After exposure to UV-irradiation, ADM containing glucose revealed different mechanical properties compare to ADM without glucose, greater resistance to enzymatic degradation, and higher heatdenatured breaking loads. DSC explained that glucose-incorporated ADM sterilized by UVirradiation decreased peak width (Tpeak-Ts) compared to one another. On the other hand, Area (J/g) and Ts increased glucose-incorporated ADM. The exposure of ADM to UV caused significant increase in hydration, but a significant decrease in the swelling ratio compared with the nonirradiated ADM. These data strongly suggests that free radical-dependent, glucose-derived crosslinks provide enhanced strength and enzyme resistance in glucose-incorporated, UV-exposed ADM.

Hydroxyl Groups in Demineralized Bone Matrix

Human demineralized bone matrix (DBM) containing bone morphogenetic proteins (BMPs) is naturally biocompatible and can be remodeled by patients’ own bone. The major shortcoming of many of the currently used DBM gel formulations is that they have a tendency to flow, particularly if there is continuous bleeding at the application site. In this study, the physicochemical properties of human DBM were examined to improve the efficiency of DBM formulations. DBM remarkably showed higher water absorption than nondemineralized bone powder after 150 min. Hydroxyl groups in DBM appeared in fourier transform infrared analysis, although hydroxyl band in nondemineralized bone powder was not observed. The results suggested that hydrogels such as CMC, hyaluronic acid, or poloxamer as carriers can be applied for injectable DBM products, such as gel or putty types.

Contracted Nose after Silicone Implantation: A New Classification System and Treatment Algorithm

Background Silicone implants are frequently used in augmentation rhinoplasty in Asians. A common complication of silicone augmentation rhinoplasty is capsular contracture. This is similar to the capsular contracture after augmentation mammoplasty, but a classification for secondary contracture after augmentation rhinoplasty with silicone implants has not yet been established, and treatment algorithms by grade or severity have yet to be developed. Methods Photographs of 695 patients who underwent augmentation rhinoplasty with a silicone implant from May 2001 to May 2015 were analyzed. The mean observation period was 11.4 months. Of the patients, 81 were male and 614 were female, with a mean age of 35.9 years. Grades were assigned according to postoperative appearance. Grade I was a natural appearance, as if an implant had not been inserted. Grade II was an unnatural lateral margin of the implant. Clearly identifiable implant deviation was classified as grade III, and short nose deformation was grade IV. Results Grade I outcomes were found in 498 patients (71.7%), grade II outcomes in 101 (14.5%), grade III outcomes in 75 (10.8%), and grade IV outcomes in 21 patients (3.0%). Revision surgery was indicated for the 13.8% of all patients who had grade III or IV outcomes. Conclusions It is important to clinically classify the deformations due to secondary contracture after surgery and to establish treatment algorithms to improve scientific communication among rhinoplasty surgeons. In this study, we suggest guidelines for the clinical classification of secondary capsular contracture after augmentation rhinoplasty, and also propose a treatment algorithm.

Proper Choice of Vessels for Supermicrosurgery Training: An Experimental Animal study

Background Reconstruction using supermicrosurgery, a technique of microneurovascular anastomosis for smaller vessels (< 0.8 mm), has become popular. Experimental animal studies for supermicrosurgery training have been reported; however, there have been few studies performed according to vessel diameter and pedicle length. In this study, the external diameters of four vessels (femoral, superficial epigastric, axillary, and common thoracic) and pedicle length of two flaps (superficial epigastric and common thoracic‐long thoracic) were measured. Methods The inguinal and pectoral regions of Sprague‐Dawley rats (n = 19) were dissected anatomically, and the external diameters of the four vessels were measured (right and left, artery and vein measured separately). After elevating the superficial epigastric and common thoracic‐long thoracic flaps, the pedicle length of the flaps was also measured. Results Among the 16 vessels examined, the external diameters of 11 and 5 vessels were above and below 0.8 mm, respectively. The external diameters of the superficial epigastric vessel and common thoracic vessel (both arteries and veins) were below 0.8 mm. The external diameters of the femoral and axillary vessels (veins) were above 0.8 mm. The length of the common thoracic‐long thoracic pedicle was approximately10 mm longer than that of the superficial epigastric pedicle. Conclusions The external diameters of the superficial epigastric vessel and common thoracic vessel are small enough for supermicrosurgery training. The pedicle lengths of both the superficial epigastric and common thoracic‐long thoracic flaps are sufficient to perform free flap experiments. Supermicrosurgical free flaps using these two vessels and a study of the physiology and pharmacology of the flaps will likely be possible in the future.

Delayed Orbital Hemorrhage around Alloplastic Implants after Blowout Fracture Reduction

Alloplastic implants have been used to repair orbital wall fractures in most cases. Orbital hemorrhage is a rare complication of these implants and has been reported rarely in Korea. The purpose of this article is to report a late complication case focusing on their etiology and management. A 20-year-old male patient underwent open reduction with Medpor (porous polyethylene) insertion for bilateral orbital floor fractures. The initial symptom occurred with proptosis in the right side as well as vertical dystopia, which had started 4 days earlier, 8 months after surgery. Any trauma history after the surgery was not present. We performed an exploration and removal of hematoma with Medpor titanium meshed alloplastic implant. A case of delayed orbital hematoma following alloplastic implant insertion was identified. It occurred within the pseudocapsule of the implant. One week after surgery, overall symptoms improved successfully, and no complications were reported during the 11-month follow-up period. Although rare, orbital hemorrhage is a potential complication of alloplastic orbital floor implants, which may present many years after surgery. As in the case presented, delayed hematoma should be included in the differential diagnosis of late proptosis or orbital dystopia.