Measuring Rabbit (Oryctolagus cuniculus) Tooth Growth and Eruption by Fluorescence Markers and Bur Marks

Rabbits (Oryctolagus cuniculus) and rodents possess continuously growing teeth, and dental problems are a major health issue in these species. Knowledge of tooth growth characteristics is required to adequately treat dental problems and advise owners concerning diets. Most research was performed using bur marks and measuring eruption and wear manually. However, this method cannot be applied to teeth less rostral than the first premolar; therefore, for evaluation of molars, other methods are needed. We evaluated the use of fluorochromes xylenol orange and calcein green to measure growth rates of rabbit teeth and compared this method to results obtained by manually measuring the distance between a bur mark and the gingival margin of the same tooth (eruption) and by measuring the distance between the bur mark and the apex of the same tooth on computed tomography scans (growth). Apical fluorochrome measurements correlated well with eruption and growth rates obtained with bur marks, whereas measurements coronal to the pulp cavity did not. Growth rates were approximately 1.9 mm/wk for maxillary and 2.2 mm/wk for mandibular incisors. Growth rates of premolars were 2.14 ± 0.28 mm/wk in rabbits on a grass/rice hulls/sand pelleted diet and 0.93 ± 0.18 mm/wk in rabbits on a hay diet. Growth of molars could only be assessed using the measurement in dentin on the wall of the pulp cavity, which does not account for the real growth. However, being similar to this measurement in premolars, one could hypothesize similar growth in molars as in premolars. We conclude that the application of fluorochrome staining can be used to measure tooth growth in teeth that are not accessible for bur marks or in animals that are too small to assess tooth eruption or growth by bur marks.

Experimental changes of the mandible: a serial roentgenographic study

The growth pattern of the mandible was investigated in nine Hampshire pigs from 8 to 20 weeks of age by means of serial cephalometric roentgenographs in combination with metallic implants. Tracings of the lateral roentgenographs were superposed on the images of the metallic implants to determine sites, increments, and direction of bone growth. The longitudinal distance between the metallic implants remained stable and thus revealed no evidence of interstitial growth in the bone. Appositional growth occurred at the posterior, inferior, anterior, and alveolar borders and at the lateral surfaces of the mandible. The most prolific sites of growth were the condyle and the posterior border. At the anterior border of the ramus, there was resorption. The mandible increased 1) in total length by growth at the posterior and anterior borders, 2) in ramus height by growth at the condyle and inferior border, and 3) in body height by growth at the alveolar and inferior borders. With changes in proportion of the growing mandible, resorption of the anterior border of the ramus resulted in the creation of a new posterior portion of the body. Thus, in the growing mandible, what was ramus at one time eventually became body. In the growing mandible, the body is stable except for changes at its borders. However, the position of the alveolar bone and teeth are subject to continuous change.

Vienna-Chicago: the cultural transformation of the model system of the un-opposed molar

The discussion over the roles of genes and environment on the phenotypical specification of organisms has held a central role in science philosophy since the late 19(th) century and has re-emerged in today's debate over genetic determinism and developmental plasticity. In fin-de-siecle Vienna, this debate coincided with a philosophical debate over empiricism/materialism versus idealism/vitalism. Turn-of-the-century Vienna's highly interdisciplinary environment was also the birthplace for the model system of the un-opposed molar. The un-opposed molar system features new tissue formation at the roots of teeth and tooth drift once opposing teeth are lost. The un-opposed molar model system was revived by a group of Viennese scientists who left Vienna during the Nazi period to address Vienna's questions about evolution and heredity and about genes and environment in Chicago's post-WWII scientific exile community. Here we are using the colorful history of the un-opposed molar to investigate the role of culture and method in the scientific evolution of a model system.

Some methods of assessing postnatal craniofaciodental growth: a retrospective of personal research

OBJECTIVE

The purposes of this review and summary are to evaluate several selected significant clinical and basic science methods utilized to assess growth of bone(s), and in particular craniofaciodental growth: appositional and resorptive (bone), endochondral (bones), and sutural (bones). This personal retrospective report includes in part anthropometry, impressions and casts, vital markers, histology, radiopaque implant markers with and without serial cephalometric radiographs, and autoradiography. Knowledge obtained from the use of these various methods on rats, ground squirrels, rabbits, pigs, dogs, monkeys, and humans has contributed to a deeper and more fundamental understanding of both the processes and roles that craniofaciodental biology plays in the advancement not only of basic biology but also of craniofacial surgery. Growth and development of the skeletal system has an important role in determining body form. The dynamics of growth of bones is a complicated process. A number of different methods have been described by which growth of bones can be evaluated on both a quantitative and qualitative basis. No single method, however, should be relied on, because although it may have certain definite advantages, it also has its limitations. The use of all available methods at both the basic and the clinical science levels will give a more complete and accurate understanding of the problems associated with the growth of bone(s).

CONCLUSIONS

Many of us are concerned with the correction of malformations and deformations that can be a result of faulty growth of bones. Thus, further knowledge obtained in regard to the sites, direction, and amount of growth as well as pattern, rate, and mechanism will lead not only to a more accurate diagnosis of the bony defect but also to a better understanding of both prevention and treatment.

Growth pattern of the mandible: some reflections

The dynamics of the growth of bones is a complex process. The growth pattern of the mandible has been assessed by the application of various methods described for the study of the growth of bones. Some of these lend themselves primarily to basic experimental rather than clinical work. The use of any one of these methods will reveal certain information. With the use of two or more of them in combination, however, considerably more accurate information can be obtained. Since John Hunter's classical descriptions more than 200 years ago, advances in the understanding of the growth pattern of the mandible have been possible with the refinement of older methods and the development of newer ones. To date, serial cephalometric roentgenography in concert with radiopaque implants, which serve as fixed reliable markers, is the most accurate method to determine the growth pattern of the mandible. To this armamentarium, digital subtraction radiography, computerized tomography, and magnetic resonance imaging may be methods that will offer more detailed and accurate information.

The growth of the first cervical vertebra in the rat

With the help of in vivo marking with alizarin red S, the patterns of growth of the first cervical vertebra are demonstrated. Major parts of the developmental events which take place during growth (differential bone formation on the bone ends facing the synchondroses, closure of the dorsal synchondrosis at 14 days, closure of the ventral synchondroses at 35 to 40 days) may be explained by the influence that a capsular matrix exerts on its protecting and supporting skeletal unit. A demonstrated continued increase of the dorsoventral diameter of the bone is suggested to be an adjustive growth process related to the translative movements of foramen magnum, a topic that has been poorly understood and incompletely investigated.

Periapical tissue reactions after pulp exposure in rat molars

Apical periodontal lesions were produced in the rat molar by exposing the pulp to the oral environment. The natural history of the undisturbed lesion was studied at time intervals ranging from 2 days to 1 year postoperatively. The earliest reactions were usually inflammatory infiltration at the apex. The severity of the lesions was related to the amount of vital pulp still present in the tooth rather than to the time lapse after exposure. After 1 month most pulps has undergone necrosis and the lesions about the apices which followed showed two main types of reaction. In the case of the suppurative reaction, pus drained along a root surface, destroying the periodontal ligament and interradicular bone until it emerged at the gingival sulcus. The sinus tract could become lined with oral epithelium. In the reparative type of reaction, suppuration was absent or minimal and the apices were surrounded by fibrous connective tissue. The fiber bundles occasionally formed a collagenous scar, but they were usually replaced by cementum and bone with a new periodontal ligament. The width of the periodontium was never restored to its normal dimensions. Secondary destruction of the teeth occurred by fracture of cusps followed by caries which started in the exposed pulp chamber. Despite the predominance of destructive factors, spontaneous repair indicated good healing potential of the apical periodontal tissues.

Effects of some staining agents on dentin apposition in young rabbits

Alizarin red S, trypan blue, chlortetracycline, and 45Ca were administered to young rabbits that received multiple injections of lead acetate as marker. Inhibiting effects of these agents on dentin apposition were studied. No evidence of toxicity of chlortetracycline or 45Ca was detected. Alizarin at 100 mg/kg reduced the rate of dentin apposition, and 150 mg/kg caused severe retardation. Trypan blue at 50 to 100 mglkg showed no adverse effects, but 350 mglkg arrested dentinogenesis completely.