Dentin Apposition Research Articles

Apposition of dentine and its possible application in calcified tissue research.

Apposition of dentine and its possible application in calcified tissue research.

Effects of desiccated thyroid, propylthiouracil, vitamin B 12 and caloric restriction on somatic growth, food intake and dentinogenesis in cortisone-treated immature albino rats

Seven groups of twenty male rats were weaned and given an intraperitoneal injection of alizarin red S at 21 days of age. For the next 20 days the rats were reared on one of the following dietary regimes: 1, CAdeit (0d2 mg cortisone/g food) ad libitum; 2, TCAdiet (0.2 mg desiccated thyroid/g CAdiet) ad libitum; 3, PTUCAdiet (0.2 mg propylthiovracil/g CAdiet) ad libitum; 4, Rdiet (control food) ad libitum; 5, Rdiet in restricted amounts; 6, B 12CAdiet (200 μg vitamin B 12/kg CAdiet ad libitum; 7, B 12CAdiet in restricted amounts. The 21–41 day increments of dentine were measured on tracings of comparable, central, undecalcified sections (95–105μthick), cut mesio-distally, parallel to the long axes of the mandibular first molars. Body weight and food intake of the 140 rats were recorded regularly. The final wet weights of the adrenal glands, submaxillary together with the major sublingual salivary glands, testes and eyes were recorded for ten rats in each of the seven groups. Results showed that CAdiet retarded dentinogenesis and increments in body weight, depressed food intake and weights of all glands and organs. Caloric restriction also affected somatic growth, but markedly less than CAdiet. Dentine apposition was not retarded by the caloric restriction. TCAdiet resulted in greater food intake and body weight than did CAdiet. The desiccated thyroid did not alter the effects of cortisone on weights of glands and organs, but apparently augmented the depressing effects on dentine formation. Propylthiouracil produced goitre. The PTUCAdiet resulted in smaller food intake, i.e. cortisone-dosage, and did not per se augment the effects of cortisone on dentinogenesis, on body weight, on weights of organs and glands, except the adrenals which were markedly smaller than those of rats raised on the CAdiet. Vitamin B 12 resulted in greater food intake, i.e. cortisone-dosage, of rats raised on the B 12CAdiet ad libitum. B 12 did not protect the rats from the effects of cortisone on body weight, but did in part counteract the retardation of dentinogenesis and of salivary gland weight. Finally, exophthalmos occured in 80 per cent of all cortisone-treated rats, it was not due to enlarged eyes per se.

Effects of cortisone on dentinogenesis in mandibular first molars of albino rats

The effects on dentinogenesis of cortisone administered in the diet (0.2 mg per g of food) was studied on comparable central undecalcified sections cut in the mesio-distal direction of mandibular first molars of 144 young albino rats. Results showed that cortisone depressed dentinogenesis, somatic growth, and to a small extent, food intake. Body weights were rapidly recovered when cortisone treatment was stopped. Dentinogenesis at the mid-occlusal surface and below the disto-occlusal groove did not recover. The apposition of dentine at the cervical level of the tooth was only slightly influenced by the dietary regime and by cortisone. Semi-starvation per se inhibited somatic growth proportionally more than it affected the magnitude of dentine apposition.

Dentine apposition in the mandibular first molars of albino rats

Dentine formation was studied in the mandibular first molars of 264 albino rats (Holtzman Co.), equally distributed as to sex. Thirty-two animals were used to establish the onset of mineralization at the sites of measurements by means of vital staining with alizarin red S. Sixteen rats were divided in two groups, killed on the twentieth and twenty-third day, to test the reliability of the weaning line (21-day weaning) as a reference zone. The remaining 216 animals were divided into two groups. Group 1 animals were injected with a 0.2% solution of NaF at the age of 31, 41 and 61 days to produce three timed calciotraumatic dentine responses. The dose of F at each injection was 20, 20 and 10 mg F per kg of body wt., respectively. The increments of dentine in these rats were studied up to the age of 91 days. Group 2 animals, divided in three sub-groups, were injected at the same age as the experimental ones with physiologic saline solution and killed when 41, 61 and 91 days of age. The injections of saline did not result in calciotraumatic lines. The deposits of dentine were measured on comparable mid-coronal ground sections. The largest increments per day were observed prior to weaning, namely 13.8, 14.6 and 10.2 μ, on the cervical mesial, distal, and on the mid-occlusal surfaces, respectively. Subsequently, between 21 and 41 days, approximately 7.3 μ of dentine (per day) was deposited on the mid-occlusal surface and 6.7 μ (per day) on the distal cervical surface. The formation of dentine in the latter area had apparently subsided in 22–33 per cent of the rats prior to the age of 61 days because no evidence of the 61 day NaF injection could be observed. However, daily increments of 3.5 μ of dentine accrued on the distal cervical surface between 41 and 61 days in those rats that did show the 61 day NaF line. All the rats continued deposition of dentine on the mid-occlusal surface beyond the ages of 41 and 61 days, but the daily increments between 41 and 61 days were only 3.8 μ in the NaF injected rats as opposed to the 5.1 μ observed in the controls. This deceleration was only temporary, and the mid-occlusal dentine deposit (21–91 days) at age 91 days did not differ significantly from that observed in the saline injected animals. The rate of dentine formation was not associated with the increments in body weight. The magnitude of the dentine deposit and the size of the tooth appeared to be unrelated and there were no statistically significant sex differences. Persistence of the 21 day weaning line and of the induced calciotraumatic responses made it possible to obtain longitudinal data on dentine deposition. Because of the large individual variations in dentine widths at weaning, and because these variations increased in magnitude with age, it is suggested that future investigations of dentine formation should be planned as longitudinal studies.

Effects of different cutting procedures on dentin apposition in rat incisors.

Effects of different cutting procedures on dentin apposition in rat incisors.

The effect of vitamin D on the beryllium rickets of the rat incisor

This report is based on the histologic and chemical study of the effect of beryllium carbonate (6 per cent) in a synthetic diet given weaned rats of the Sprague-Dawley strain for periods of fourteen to 168 days. One group of twenty animals was given the physiologic requirement of vitamin D, and another group of twenty animals was given an excess but not toxic dose. Thirty-nine littermates were pair-fed as controls. The following results were observed: 1. 1. Beryllium was found in the feces but not in any of the organs or the incisor. 2. 2. The blood level of phosphorus fell to an average of 2 mg. per cent in the beryllium-carbonate-fed rats on physiologic doses of vitamin D. The phosphorus levels gradually increased despite continued experimental feeding and averaged 5 mg. per cent in animals 192 days old. 3. 3. The blood phosphorus levels were normal in the animals on high doses of vitamin D. 4. 4. The blood calcium levels were normal in all animals. 5. 5. The epiphyseal plate of the tibia was increased in width in rats fed physiologic doses of vitamin D and was of normal width in animals fed high doses of vitamin D. 6. 6. The changes in the incisor and its supporting tissues indicate severe rickets in the animals on physiologic vitamin D and mild rickets in the animals on an excess dose of vitamin D. The severe rachitic syndrome consisted of enamel hypoplasia and aplasia, severe retardation in the formation and calcification of dentine, failure of newly formed bone tissue to calcify, and resistance of such bone tissue to resorption. These changes were progressive up to approximately the seventieth day of the experiment. Partial recovery occurred in older animals. Secondary to the resistance to resorption of uncalcified bone, there were narrowing and obliteration of the periodontal space, arrest in eruption of the incisor, folding of the odontogenic epithelium, enamel, and dentine, and pulpal obliteration due to continued dentine apposition. In the mild form of beryllium rickets, the disease was confined to animals under 3 months of age and to the following symptoms: the rate of dentine apposition was slightly retarded and calcification of lingual dentine was impaired. The alveolar bone showed only a slightly widened osteoid seam.

Effect of Magnesium Deficiency on Dentin Apposition and Eruption in Incisor of Rat

Summary and ConclusionsIn magnesium deficiency the rate of eruption of the incisor is reduced to approximately one-third the normal. The outstanding effect is on dentin apposition which is progressively decelerated, the enamel-covered dentin being affected more acutely than the cementum-covered portion. Temporary local cessations of growth may occur. The formation of alveolar bone is also decelerated to one-half or less of the normal rate and the periodontal membrane is abnormally wide. The dentin of the rat incisor acts not only as a kymograph of calcium metabolism (Fig. 2), but also as a growth kymograph (Fig. 1, D.2).

Effect of Hibernation on Rate of Eruption and Dentin Apposition in the Ground Squirrel Incisor

SummaryThe rate of eruption and dentin apposition of the incisor in the thirteen-lined ground squirrel kept at 2–5°C is markedly retarded and, further, is retarded in approximate proportion to the number of days the animal hibernates.

Effect of Vitamin A Deficiency on the Rate of Apposition of Dentin.

The rate of apposition of dentin is selectively altered in Vitamin-A deficiency, while the life span of the formative cells is not affected. The rate of apposition is accelerated in the enamel-covered portion and decelerated in the cementum-covered portion. The findings indicate the delicate response of the rate of dentin apposition to Vitamin-A deficiency and suggest the possible use of this reaction as a biologic method of measuring the Vitamin-A content of foods.

Effects of Alizarine Red S Injections on the Teeth and Bones of Macacus rhesus Monkey.

Seventeen Macacus rhesus monkeys of mixed or adult dentition, ranging in age from 1½ to 7 years, were given multiple intravenous, intraperitoneal or subcutaneousi injections of 5-10 cc. of 2% Alizarine Red S (Sodium Sulphalizarate) of color index 1034 (Coleman and Bell Company) at 5- to 30-day intervals. The time between the last injection and death ranged from 3 hours to 125 days. The dosage ranged from 40 to 60.5 mg. per kilo. For each injection a distinct red ring was observed in the dentin and the bone that were forming and calcifying at the time. This effect was immediate, as indicated in the animals sacrificed within a few hours after the last injection. In 6 animals 4 months elapsed between the first injection and death. This long survival did not alter the staining reaction. Measurement of the distances between successive rings indicated the amount of apposition during the corresponding intervals. The rate of apposition of dentin based on 1164 measurements made chiefly in the ground sections of bicuspids and molars ranged from 1.6 to 5.6 μ per 24 hours. This range may be explained on the basis of a growth gradient with its maximum at the cusp and along the outer dentinal surface and its minimum apically and toward the pulp. Alizarine lines were also found in the cementum. Definite staining effects could be recognized macroscopically in the jaws and long bones. Subcutaneous administrations were found to be complicated by a sloughing of the tissues at the site of injection. Intravenous injections gave sharper effects than intraperitoneal injections of the same dose. However, thrombosis of the veins at or near the site of injections occurred frequently. The intraperitoneal injections were as effective as the intravenous ones when the dosage was increased to 10 cc.

RATE OF APPOSITION OF ENAMEL AND DENTIN, MEASURED BY THE EFFECT OF ACUTE FLUOROSIS

Recent findings on the effect of fluorosis on the growing teeth of lower animals paved the way for this quantitative study of the rate of apposition of human enamel and dentin. REVIEW OF THE DENTAL EFFECTS OF FLUOROSIS Historical Summary .—For many years a type of hypoplasia of the enamel known as mottled enamel was a challenging problem to members of the dental profession. The condition was endemic and characterized by a destructive chalky opacity and pitting of the enamel. Black and McKay, 1 in 1916, first attempted to elucidate the underlying cause of this dental defect, and they were instrumental in initiating the large amount of research that followed. In 1931 Churchill suggested and Smith and her associates 2 established by experiments on animals that chronic fluoride intoxication was the direct cause of mottled teeth. Churchill arrived at his discovery by a direct approach, when he analyzed the water