In vivo experimentation on rat incisor enamel organs through a surgical window

Abstract

Experimental agents administered systemically are costly and often toxic to animals. An in vivo technique has been developed whereby a surgical window in the alveolar bone allows selected areas of the rat incisor enamel organ and underlying enamel to be exposed to various drugs, radiolabeled molecules, and molecular weight markers. Sherman rats weighing 100 gm were anesthetized and the inferior surface of each hemimandible was surgically exposed. A slow‐speed dental hand drill was used to drill a small hole through the alveolar bone overlying the secretion or maturation zones of the enamel organ. The wound was closed and during recovery the mechanical trauma to the underlying tissue moved away from the hole due to the continuous eruption of the tooth. Two to 5 days later the hole was reexposed and microinjections of 3H‐proline, 125I‐salmon calcitonin, vinblastine sulphate, and normal saline (as control) were administered through the hole with a micro‐manipulator and a microliter syringe. Radioautographic detection of 3H‐proline incorporation in secretory ameloblasts and enamel at 10 minutes, 30 minutes, 1 hour, 4 hours, 1 day, and 2 days after microinjection was identical to that obtained previously by systemic injection. Two hours after microinjection of vinblastine sulphate the cellular response was again identical to that following systemic injection; 125I‐salmon calcitonin (M.W. ∼ 3,600D) was used as a molecular weight marker and was seen to diffuse into the enamel of the maturation zone at 10 minutes after microinjection. This study has demonstrated the feasibility of this new technique for experimentation on rat incisor enamel organs.

In Vivo Model for the Experimental Manipulation of Calcified Tissues: A Surgical Approach for Accessing the Odontogenic Organ and Associated Tissues of the Rat Incisor

“…Vinblastine sulfate was infused over a 3-day period to obtain local tissue alterations without any systemic effects. The changes obtained in the enamel organ are consistent with previously published data using local or systemic injection of vinblastine (Moe and Mikkelsen 1977;Miake et al 1982;McKee and Warshawsky 1984;Nanci and Warshawsky 1984;Nanci et al 1987). In addition, alterations induced in the pulp, dentin, cementum, and periodontal tissue indicate that the drug diffuses locally and demonstrate the efficacy of our approach in targeting all the tissues of the tooth organ.…”

“…Some experiments have involved removal of blocks of bone and apical portions of the incisor to study cell activity during bone remodeling and tooth eruption (Redondo et al 1995;Berkovitz and Thomas 1969;Berkovitz 1971a,b). Others have used the surgical creation of a hole through the alveolar bone at the labial surface of the tooth to obtain direct access to the underlying tissues (McKee and Warshawsky 1984;Eisenmann et al 1989;McKee 1993;McKee and Nanci 1996a). These approaches were designed to target both secretory and maturation stage ameloblasts as well as the adjacent enamel.…”

An In Vivo Model for Short-Term Evaluation of the Implantation Effects of Biomolecules or Stem Cells in the Dental Pulp

“…Afterwards, endogenous aging processes, and odontoblast and pulp degeneration [16, 21], may interfere with the biological reaction under investigation. Previous studies have used a similar surgical approach by drilling a cavity through the basal bone to gain access to the enamel organ of the rat incisor [22, 23]. Another surgical attempt to selectively target the odontogenic organ was described, using an osmotic minipump connected to a bony window overlying the apical end of the rat incisor [24].…”

Comparison of Rates of Enamel Synthesis in Impeded and Unimpeded Rat Incisors

“…Reported eruption rates of rat mandibular incisors range from 443 ± 5 Rm per day (Steigman et al, 1974) to 750 imper day (McKee and Warshawsky, 1984). Notwithstanding the variability, a two-fold acceleration in the eruption rate in unimpeded mandibular incisors is generally expected (Berkovitz, 1974;Robinson et al, 1988;Steigman et al, 1974).…”

“…These differences maybe related to the difficulty in obtaining accurate reference points and/or lack of uniformity in variables such as age, gender, and strain of rats used. In spite of this, it is clear that unimpeded rat incisors erupt faster than impeded controls (Bryer, 1957;Michaeli and Weinreb, 1968;Berkovitz, 1974;Steigmanet al, 1974;McKee and Warshawsky, 1984;Robinson et al, 1988). Furthermore, in occluding rat incisors, the rate of incisal migration ofsecretory-stage ameloblasts was measured by 3H-thymidine and found to be faster than the eruption rate (Smith and Warshawsky, 1975).…”