The selection and application of experimental animals in the study of stomatology
A common experimental animal oral anatomy and physiological characteristics
The stomatology and other sciences of medicine as is the rapid development. New therapeutic methods, drugs, orthopedic materials, etc. are constantly discovered, some of which can be directly used in the clinic, and some of which must be verified by animal validation before they can be applied to the clinic. As a result, the status of experimental animals in stomatology research has become more and more important. Laboratory animals can be selected for the study of congenital malformations, defects, acquired trauma, inflammation and tumors of oral organs. Such as caries or non-caries dental disease, endodontics, periapical disease, periodontal disease, oral mucosal diseases, tumors, as well as salivary glands, joints, jaw disorders and malformations, etc., the etiology, pathology, course, diagnosis, prevention and treatment (including inlay, filler technology) method of research. In the selection of experimental animals for various studies in stomatology, first of all, must be familiar with these experimental animals oral anatomy, physiological characteristics.
(A) the number of teeth and growth characteristics of commonly used experimental animals
1. tooth type and number (to the permanent teeth as the standard)
Monkey 2 (2123/2123)=32 dog 2 (3142/3143)=42;
Cat 2 (3131/3121)=30 rabbit 2 (2033/1033)=28;
Guinea pig 2 (1013/1013) = 20Gopher 2 (1003/1003) = 16;
Rat 2 (1003/1003) = 16; mouse 2 (1003/1003) = 16.
The number of teeth in commonly used laboratory animals is shown in Table 10-34.
Table 10-34 Permanent Teeth in Humans and Commonly Used Laboratory Animals Number
Human and animal incisors (cut) teeth cusps (canines) premolars molars Number of permanent teeth
Human 8 4 8 12 32
Monkey 8 4 8 12 32
Dog 12 4 16 10 42
Cat 12 4 10 4 30
Rabbit 6 0 10 12 28
Guinea pig 4 0 4 12 20
Gopher 4 0 0 12 16
Rat 4 0 0 12 16
Mouse 4 0 0 12 16
2. Dental growth characteristicsThe monkey's teeth grow and fall off in a certain pattern. Newborn monkeys are generally edentulous and occasionally have two incisors. 20 milk teeth come out within 6 months, and growth stops in the middle of the period until 14 to 16 months. Then they start to grow and replace their milk teeth at a constant age. The order of growth of rhesus monkey teeth is as follows, milk teeth: lower middle gate → upper middle gate → lower side gate → upper side gate → upper canine → lower canine → upper premolar 2 → lower premolar 2 → lower premolar 3 → upper premolar 3; permanent teeth; lower molar 1 → upper molar 1 → upper middle gate or upper side gate (change) → lower middle gate (change) → upper side gate (change) → lower side gate (change) → upper molar 2 → lower molar 2 → premolar 1 (change) → former molar 2 (change) → canine change → molar 3.
The age and dental growth of rhesus monkeys are shown in Table 10-35
Table 10-35 Dental growth of rhesus monkeys
Age (months) Dental growth
Births Newborns are generally edentulous, with a few occasional two-column incisors
1.0 Four central incisors grow simultaneously in both the upper and lower jaws
1.5 Fast-growing 36 days. 8 incisors in 36 days
2.0 Maxillary canines just emerging
3.0 Maxillary canines and first premolars emerging at the same time
4.0 Upper and lower mandibular first premolars emerging
4.5 Mandibular second premolars emerging or all first premolars emerging
5-6 All milk teeth complete
14-16 Right side of the lower jaw. First molars come in first, followed by 1st molars on the left side of the lower jaw
17～18 First molars grow in different conditions
19～31 Maxillary and mandibular first molars come in full length
32～40 Middle incisors and lateral incisors are replaced, with a great deal of variation in the order. The canine teeth are replaced and the second molars emerge
42～43 The mandibular lateral incisors and middle incisors are replaced. The second molars come out, and the first premolars are replaced
44-56 The second premolars are replaced, and the canines are replaced
65-78 The mandibular third molars come out
72-82 The maxillary third molars come out, and then all the permanent teeth are complete
There are 42 permanent teeth in the dog, and the incisors are gradually enlarged from the 1st to the 3rd, with the lower incisors being smaller than the upper incisors. The canine teeth are well developed, large and sharp curved. The number of molars also varies according to breed, the general type of teeth for 6/7, but in the short-head type of dog's molar often 5/7 molar size is also a big difference, of which the upper molar of the 4th tooth and the lower molar of the 1st tooth is the largest, before and after the teeth are gradually becoming smaller. Ten days after the birth of the puppy that is born milk teeth, two months after the beginning of the incisors, canines, molars gradually replaced by permanent teeth, 8 to 10 months for all teeth, but the canine teeth need to be 1.5 years old after the growth of solid. Age and tooth growth, replacement, and wear in dogs are shown in Table 10-36.
Table 10-36 Age and Teeth in Dogs
Age Teeth
Below 2 months Milk teeth only (white, fine, and sharp)
2 to 4 months Replacement of incisors
4 to 6 months Replacement of canines (white, with rounded cusps)
6 to 10 months Replacement of molars
1 year old Full set of teeth, white and shiny, incisors cuspidate
2 years old Lower incisors cuspidate partially smoothed out
3 years old Upper and lower incisors cuspidate partially smoothed out
4 to 5 years old Upper and lower incisors begin to wear down to a slight bevel and yellowed
6 to 8 years old Incisors worn down to the roots, canines yellowed and worn down to the lips, whiskers whitish
10 years old and older Incisors worn down to the root, canine yellow and worn down to the lip
Over 10 years of age The incisors are worn down to the roots, the canines are yellowed and worn down to the lips, and the whiskers on the lips are whitened
(2) Some anatomical and physiological features in the oral cavity of commonly used experimental animals
Dogs, cats, and other carnivorous animals have particularly well-developed canine teeth. The filiform papillae on the cat's tongue are covered with a thick cuticle, which is barb-shaped, making it easy to lick and scrape the flesh from the bone. Rabbits are herbivores, the incisors are developed to cut the grass, no canines, in the roof of the mouth, the surface of the hard palate has a smooth mucous membrane, there are many transverse folds in the mucous membrane. The upper lip of sheep and goats is sensitive and flexible.
Dogs have well-developed salivary glands, including four pairs of parotid, submandibular, sublingual and orbital glands. It is believed that the dog's saliva does not contain amylase, but contains lysozyme, can kill bacteria, so it is common for dogs to lick wounds with the tongue, there is a cleaning and disinfecting effect. Because the dog lacks sweat glands, when it is hot, it can secrete a lot of saliva to dissipate heat.
Cats have five pairs of salivary glands, i.e., the subauricular, submandibular, sublingual, molar and infraorbital glands, which all open in the oral cavity and make up a mixed secretion-saliva.
The salivary glands of the rabbit are well developed, and in addition to the three pairs of salivary glands (parotid, submandibular, and sublingual glands) that are found in mammals in general, there is also a pair of infraorbital glands, in addition to a number of small scattered glands. Rabbit saliva contains amylase, but the ability to break down starch is weak.
The guinea pig has five pairs of salivary glands, parotid, submandibular, zygomatic, sublingual and sublingual glands. In addition, there are lacrimal glands near the corners of the lips and buccal glands in the cheeks of the lateral walls of the mouth.
There are three pairs of salivary glands in rats and mice, namely, the subauricular, submandibular and sublingual glands.
The surface of the rabbit tongue has many papillae, which are taste receptors, and are most densely distributed on the tip and sides of the tongue. The dog's tongue is wide and thin at the front and thicker at the back, with a longitudinal groove in the center of the back of the tongue, and a dense layer of filiform papillae covering the surface. There are myxomatous papillae distributed on the two lateral edges of the tongue, and on the posterior part of the dorsal surface of the tongue, in addition to filiform papillae, there are conical papillae, all of which are taste receptors. The rat has 1 pair of small salivary gland papillae on the back of the incisors near the midline. Near the base of the tongue there are contour papillae, and on the dorsum of the tongue there are cone papillae and filiform papillae.
The shape and size of the dog's oral cavity are closely related to its skull formation. Long-headed dogs have a long, narrow mouth, while short-headed ones have a short, wide mouth. The dog's mouth cleft is very large, and the corner of the mouth is about opposite the 3rd or 4th molars. The lips are thin and flexible, with long tactile hairs on the surface, a small cell in the center of the upper lip without tactile hairs but with a central groove (manubrium), and a jagged protuberance on the lateral edge of the lower lip.
II. Selection and application of animals
(I) Rhesus monkeys and marmosets
Rhesus monkeys are the animals of choice for experimental research in dentistry. In particular, it is more commonly used in orthopedics and endodontics, such as for observation of the effect of re-implantation of teeth; histopathological changes; study of histopathological changes in dry socket; and exploration of the effects of various treatments and therapeutic materials on tissue healing, etc., in order to seek optimal clinical treatment results.
The number of teeth of rhesus monkeys is the same as that of human beings, the arrangement of teeth is similar to that of human beings, and many microorganisms present in the oral cavity are also the same as those present in the human oral cavity, such as giving rhesus monkeys food to increase the content of sugar after feeding the animals. Caries can be induced in milk teeth and permanent teeth, and the caries changes that occur are similar to those in humans, so rhesus monkeys can be selected for research on caries etiology, pathogenesis and treatment.
The periodontal tissues of marmosets are extremely sensitive to general metabolic changes. The periodontal membrane changes in aged marmosets are extremely similar to those in the elderly. In addition, the process of periodontitis and the histopathologic changes in marmosets are similar to those in humans, making marmosets extremely desirable animals for the study of periodontal disease.
The rhesus monkey is also used for the study of the way and degree of tooth fracture, as well as the treatment time, treatment method and histopathological changes, in order to explore the therapeutic effect; it is also commonly used in the study of the toxicity and carcinogenicity of filling materials and veneering materials on the pulp and periodontal tissues as well as on the bone tissues.
(B) Rabbit
The distribution of blood vessels in the cervical and maxillofacial regions of rabbits is similar to that of humans. Surgery of the human cervical and facial regions often requires ligation of the external carotid artery. For a series of problems arising after ligation, such as impaired circulation and recovery time of blood flow, adult rabbits can be used to ligate the external carotid artery unilaterally, and the changes of vascular image in its distribution area can be observed to explore the recovery of vascular image and the development of collateral circulation pathways.
Cleft lip is commonly known as hare's lip, and the domestic rabbit is an excellent animal to study the relationship between the etiology of cleft lip and cleft palate (e.g., genetics, drugs, environment, etc.) and other congenital defects (e.g., hydrocephalus, spina bifida, cretinism, and chondrodysplasia, etc.).
Mandibular protrusion has been reported in rabbits, and the causes of protrusion are similar to those in humans. It can be used to study the causes of mandibular protrusion (e.g., heredity, malocclusion, acromegaly) and to explore measures of mandibular protrusion to guide clinical practice.
The rabbit is a sensitive animal for observing the Arthus inflammatory reaction of the dental pulp.The Arthus reaction is an inflammatory reaction characterized by local edema, erythema, hardness and necrosis within a few hours after intradermal injection of the same antigen into an animal that has already been exposed to the antigen.The reaction mechanism belongs to the type III metamorphosis and is commonly used clinically to detect the presence or absence of circulating specific antibodies in the body. The experiment used male 2.5kg, with O hemolysin sensitization rabbits, until the antibody potency rises, after the emergence of Arthus skin reaction, and then the same antigen in the incision of the pulp for local attack, and thereafter at different times to take out the pulp, with histological methods and immune-fluorescence technology for observation, light microscopy confirmed that there is acute inflammation in the pulp, immune-fluorescence confirms that there is an immune complex in the pulp tissues, and the specific fluorescence Immunofluorescence confirmed the presence of immune complexes in the pulp tissue and specific fluorescence, mainly in the vessel wall, confirming the presence of Arthus inflammatory reaction in the pulp, with the help of which it is shown that if the organism is re-exposed to the same antigen through the pulp, inflammation occurs in the bone marrow tissues, and that this inflammation is a result of the local reaction of the antigen-antibody.
Rabbits are model animals for establishing oral mucosal ulcer disease. Oral mucosal ulcers are extremely common and are generally thought to be due to autoimmunity or impaired immune function. Antigen selection of normal birth of dead babies (death time is not more than 2 ~ 3 hours), in aseptic conditions to collect oral mucosa, saline rinse clean into the 0.1MpH7.4 phosphate buffer, the mucosa will be sheared and ground into a tissue hook slurry, add an equal amount of Fuchs' complete adjuvant or incomplete adjuvant, mixing is emulsified, rabbits spinal column, two side of the intradermal injection of the liquid, the injection of 8 to 10 points, every 1 week injection 1 time,***4 times,0.5ml for the first time,1~3ml for the 2nd~4th times.The oral mucosal ulcers started to appear on the 3rd day after the 4th injection,and then repeated until the 4th month when the ulcers still appeared.
The rabbits were injected intradermally on the second side of the spine with 8~10 spots,every 1 week.
Rabbits are suitable for experimental studies of cancellous bone marrow transplantation. Particulate Cancellous Bone and Marrow (PCBM) grafting is the repair of maxillofacial bone defects with grafts of cancellous bone excavated from the iliac crest, endosteum and bone marrow. Healthy rabbits are often used to anesthetize the right iliac crest to cut a 1.5×0.5 cm2 iliac bone block and excavate an appropriate amount of PCBM, and then carry out the restoration surgery.
Rabbits are also suitable for toxicity experiments of oral plastic materials. Polytetrafluoroethylene composite is a more ideal and widely used artificial bone material in maxillofacial surgery and plastic surgery, which can replace both bone and cartilage and soft tissue. Large white-eared rabbits are often selected for toxicity experiments.
Rabbits are also used for oral mucosal disease, periodontal disease etiology, pathological changes in the study, such as damage to the rabbit trigeminal nerve of the maxillary branch or mandibular branch, can cause experimental trophic ulcers on the lips of rabbits. It can also be used for experimental studies in orthopedics, such as pad experiments, to explore the mechanism of dental function adjustment.
(C) dog
Dog in stomatology research is widely used, such as dog 2, 3, 4 premolar extraction, such as removing the inter-root bone septum, quite similar to the human extraction of tooth trauma, for dry leukemia animal model research. When extracting the dog's teeth, the periodontal ligament is tough, and the pulp cavity is large, and often the teeth are fractured or the alveolar bone is fractured, and the periodontal ligament is still not easy to be broken off, and when extracting the teeth, the teeth should be firstly increased by the thin and narrow moth-eye chisel along the periodontal repeatedly, and the periodontal ligament should be chiseled off as far as possible, and then the teeth will be loosened with the narrow teeth, and then the teeth will be clenched by the dental pliers, and then the teeth will be flushed out by the hammer percussion of the pliers along the direction of the teeth's long-axis, which will often cause the root to break off if it is pulled by the dental pliers. Bleeding more, should carefully scrape the extraction nest, to stop the bleeding with gauze, before the later experiments.
The histology of the periodontal membrane, the histopathology of periodontitis, and the epidemiologic etiology of periodontal disease in dogs are similar to those in humans, so the dog as an animal model of periodontal disease is extremely ideal for research.
Dogs are commonly used in research problems of autologous dental transplantation and radiation therapy. Some congenital disorders in dogs, such as cleft lip, cleft palate, and mandibular protrusion, have a genetic component. The way of mandibular protrusion in dogs is similar to human mandibular iliac protrusion, so dogs can also be used as an animal model for the study of maxillofacial deformities.
(D) Golden gopher
Golden gopher cheek capsule coated with carcinogen dimethylbenzanthracene (DMBA), 6 weeks after all the animals induced the generation of epithelial anomalous hyperplastic leukoplakia, and clinical patients with leukoplakia of the oral mucosa when the pathological changes are similar to, so the golden gopher is the study of the epithelial anomalous hyperplastic leukoplakia is more suitable for the animal, general selection of the body weight of 60 g golden gopher is easy to succeed.
Chronic mechanical injury, tobacco and alcohol stimulation of the back of the hard palate of the golden gopher or rat soft palate anterior, can be successfully induced with the same human oral mucosal leukoplakia, the formation of mucosal leukoplakia in animals and human oral mucosal leukoplakia are basically similar to the clinical and pathological, the constant period of a longer, the lesions did not malignant in the experimental period, after stopping the stimulation, in the short term, also does not subside.
The golden gopher was also used in the study of tongue cancer, and in 1973 Fujita et al. produced tongue cancer in 100% of the animals after 13 to 25 weeks of scratching the tongue with a root canal extraction needle and then applying an acetone solution containing DMBA.
(E) Rats and mice
The rapidly proliferating epithelial and mesenchymal dentinoblasts at the base of incisors in rats are the most sensitive to cyclophosphamide, and their leaning glaucomatous epithelium tolerates the cytotoxic effect of 40 mg/kg of cyclophosphamide, which can be used to explore the effect of cyclophosphamide cytotoxicity on incisal growth.
The rat palatal mucosa contains a large number of palatal glands with ducts opening on the surface of the mucosa, and this structure can serve as an excellent gateway for the invasion of carcinogens. By surgically implanting carcinogens into the mandible of rats, osteosarcoma of the mandible can be successfully induced and studied as an animal model of osteosarcoma.
The latent short-term of white class formation induced by foaming DMBA on the tongue of rats, with a high percentage, 100% of animals can generate white spots, but it is difficult to induce the generation of epithelial abnormally proliferative white spots, and after the formation of the lesion, it gradually fades away, which may be related to the strong resistance of rats to the disease, the salivary secretion in the oral cavity, and the tongue movement has a cleansing effect to the applied drugs. The results of the experiments were different for different parts of the body. However, the cleaning effect of the applied drugs on the rats can be reduced and the carcinogenicity rate can be increased by artificial methods, such as designing an artificial brood pouch lined with the mucosal epithelium of the lower lip, and then applying the carcinogenic agent to prolong the duration of the action of the carcinogen on the mucosa, which can successfully induce oral mucosal carcinoma in rats.
Rats are suitable animals for candidal leukoplakia changes. Candida infection has been implicated in the production of certain types of white spots, particularly granular white spots. Often choose 6 months old rats, tongue dorsal inoculation of Candida albicans, tongue normal papilla structure disappeared, Candida albicans filaments invade the stratum corneum of normal keratinized epithelium, and cause hyperplasia and inflammatory changes, the epithelium gradually become or incomplete keratinized epithelium, the final external similar to human Candida albicans white spot changes, but the end of the lip mucosa appeared incomplete keratinized layer.
Cleft lip and cleft palate in mice are similar to those in humans. A similar genetic profile has been reported, making the mouse a very suitable animal model for cleft lip and cleft palate.
The enamel thickness of rodent teeth is thinner than that of human teeth, and rodents do not have the function of caries production, so once caries occurs, it develops faster and the damage is severe, so it is necessary to inject this characteristic in the experimental analysis. In addition, the incisors of rats are constantly growing, therefore, their incisors are not suitable for caries research.
Rats of different species, strains, and ages have different susceptibility to dental caries. For example, the susceptibility of juvenile NIH rats is significantly lower than that of Sprague-Dawley rats; Streptococcus anomalius causes a much less extensive range of caries variability in mice than in gophers and rats, while Streptococcus anomalius induces more extensive smooth surface caries in gophers than in rats. With age, rodents become insensitive to caries, probably due to enamel maturation. Therefore, most caries experiments need to be initiated when the animals are 17 to 24 days old.
Different strains of mice have different sensitivities to periodontal disease. For example, STR/N mice are susceptible to periodontal disease, whereas DBA/2A mice are resistant to periodontal disease.
Mice and rats have more developed salivary glands and can be used to replicate animal models of salivary gland disease.
Croton oil has a promoting effect on herpes simplex virus-induced lip cancer in mice, and is often used in experiments with 2-month-old mice.
Sprague-Dawley rats, Charles River COBC rats, Fisher rats, Osborn-Mendel rats, Wistar rats and golden gophers, rhesus monkeys, pigs and other animals have fossa on the surface of the molar teeth, the anatomical morphology is similar to that of human molar teeth, and if you give the pathogenic clusters of bacteria and cariogenic food can produce the meatus and the tissue. If given cariogenic bacteria and cariogenic food, they can produce carious lesions that are visually and histologically identical to those of human teeth, and these animals can be used to establish animal models for the study of dental caries.
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