Use of dentin as a biomaterial for bone filling
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The objective of this experimental study was to evaluate the efficacy of new bone formation of particulate teeth, immediately grafted on critical defects of 6 mm compared to sites without filling at 60 days in New Zealand rabbit shells. The results of this study show that autogenous crushed tooth particles should be considered a new biomaterial suitable for filling critical bone defects.
Bone defects result from trauma, atrophy, or resection of intraosseous lesions. Bone regeneration using autologous or biomaterial bone grafts has evolved enormously in recent decades. Several graft materials, including autografts, allografts, xenografts, and alloplastic, have been used for bone augmentation. On the other hand, the synthetic bone does not imply disease risk, cannot promote osteogenesis and osteoinduction, but is an excellent scaffold for bone neoformation. The healing of significant bone defects is directly related to the size and time elapsed since the trauma; when more time elapses, the greater the recovery and, therefore, the maturation of bone tissue. Osteogenesis, osteoinduction, and osteoconduction are the three keys to osseointegration. Osteogenesis is the process by which new bone is formed from osteoprogenitor cells; osteoinduction is the stimulation and activation of the osteoprogenitor cells of the surrounding lesion tissue, and osteoconduction is the process by which it facilitates the development of blood vessels. However, autologous grafts have disadvantages, such as the amount of graft that can be obtained, the morbidity of the donor area and the duration of surgeries, and postoperative discomfort. Autograft, allograft, xenograft, and synthetic materials have long been successfully used as bone substitutes.
The human dentin matrix, created from extracted human teeth, was developed in 2008 in Korea and evaluated for its osteoinductive, osteoconductive capacity in filling bone defects. Dentin and bone are similarly formed by collagen (30%), hydroxyapatite (60%), and body fluid (10%) in weight. Dentin is an acellular matrix rich in the collagen without blood vessels, while the bone is a cellular tissue with a high vascularization capacity. The composition of the bone and tooth are similar, so much so that the enamel has 96% inorganic substances and 4% water, while dentine has 65% inorganic substances, 35% organic substances, and water. Finally, alveolar bone has 65% inorganic and 35% organic substances.
Generally, extracted teeth have been discarded as infectious materials in the world. However, right now, non-functional extracted teeth would be given a second chance as a suitable native resource to be grafted into disadvantaged areas of bone.
Therefore, several authors have demonstrated that the properties of the crushed tooth could act as a bone substitute induced by dentin and dentin pulp, studying the medical recycling of human teeth as a new graft material for bone regeneration in Japan and Korea.
The use of Smart Dentin Grinder has been created to grind and classify extracted teeth into a dentine particle of specific size ranging from 300 to 1200 microns, where bone neoformation has been 75% in experimental animals.
The objective of this study was the histological and histomorphometric evaluation of vital bone formation (VB) after the filling of the crushed tooth graft compared to unfilled areas in rabbit caps at 60 days of follow-up.
Materials and methods
The animals
The study used 21 New Zealand rabbits weighing 3.2 to 4 kg (average 3.5 kg). The study protocol was approved by the Ethics Committee of the University of Murcia, Spain (05-09-2012), which followed the guidelines established by the Directive of the Council of the European Union; on 1 February 2013 for the care and experimentation of animals.
The animals were fed a daily diet of ad libitum granules throughout the study period. In addition, the animals received an intramuscular injection of 0.5 to 1 mg/kg of acepromazine maleate. Fifteen minutes later, intravenously administered general anesthesia of 5 to 8 mg/Kg of ketamine plus chlorbutol with 0.05 mg/Kg of atropine as an adjuvant.
The rabbit's calvary was shaved and washed with seawater with hyaluronic acid. The medial sections of the skull were exposed through a skin incision and careful subperiosteal dissection. Two defects of 6 mm diameter were created. The surgical area was irrigated with sterile physiological saline to remove bone debris.
Tooth Biomaterial
The mandibular premolars and first molars (P2, P3, P4, M1) of 6 Beagle dogs were extracted bilaterally under general anesthesia one week earlier. Teeth with multiple roots were sectioned in a buccolingual direction at the bifurcation using a tungsten carbide bur so that the sources could be extracted individually without damaging the remaining bone walls.
The clean, dry teeth were crushed using the Smart Dentin Grinder, specially designed for this procedure. The tooth particles obtained were 300-600 and 1200, then sieved through a unique classification system into two compartments.
The particle teeth were immersed in a basic alcohol cleaner in a sterile container to dissolve all organic waste and bacteria for 10 minutes. The particles are then included in EDTA to partially decalcify the particles for 2 minutes and finally washed with sterile saline for 3 minutes. They are then grafted onto the randomly chosen critical defects. After 60 days, the animals were slaughtered.
A defect was filled with crushed tooth granules. The second defect was not filled using it as a control, and the defects were covered with a collagen membrane. Later. The samples were assigned to the test groups using randomization software.
Analgesia was administered by Novalgin injection (50 mg/Kg body weight), and amoxicillin (0.1 ml/Kg intramuscularly) was administered at the end of surgery.
The animals were kept in a room specially designed for experimental animals and fed a standard laboratory diet.
Statistical analysis
The values were recorded as a mean and standard deviation. A non-parametric Wilcoxon test was applied for related samples to compare the means, assuming a significance level of 95% (p <0.05). Whether the distribution of two paired variables in two associated pieces is the same. This test considers the magnitude of the differences between two paired variables. The equal means were considered null hypotheses, while the existence of significant differences between the means acted as an alternative hypothesis. As substantial differences between the existing norms, the null hypothesis was rejected. All data were expressed as mean means and standard deviation. The student's t-test was used to analyze the differences between the variables. Statistical analysis was performed using SPSS 15.0 software (SPSS, Chicago, IL, USA). Significance was established as p <0.05.
