Mineral Acquisition Rates in Developing Enamel on Maxillary and Mandibular Incisors of Rats and Mice: Implications to Extracellular Acid Loading as Apatite Crystals Mature
Bibliographic record
Abstract
UNLABELLED: The formation rates of mineral in developing enamel were determined by microweighing of incisors of mice and rats. Computations indicated that a large excess of hydrogen ions would result from creating apatite at the calculated rates. Enamel organ cells (ameloblasts), therefore, likely excrete bicarbonate ions to prevent pH in fluid bathing enamel from becoming too acidic. INTRODUCTION: Protons (H+) are generated whenever calcium and phosphate ions combine directly from aqueous solutions to form hydroxyapatite. Enamel is susceptible to potential acid loading during development because the amount of fluid bathing this tissue is small and its buffering capacity is low. The epithelial cells covering this tissue are also believed to form permeability barriers at times during the maturation stage when crystals grow at their fastest rates. The goal of this study was to measure the bulk weight of mineral present in rodent enamel at specific times in development and estimate the amount of acid potentially formed as the apatite crystals mature. MATERIALS AND METHODS: Upper and lower jaws of mice and rats were freeze-dried, and the enamel layers on the incisors were partitioned into a series of 0.5 mm (mouse) or 1.0 mm (rat) strips along the length of each tooth. The strips were weighed on a microbalance, ashed at 575 degrees C for 18-24 h to remove organic material, and reweighed to determine the actual mineral weight for each strip. RESULTS AND CONCLUSIONS: The data indicated that, despite differences in gross sizes and shapes of maxillary and mandibular incisors in rats and mice, the overall pattern and rates of mineral acquisition were remarkably similar. This included sharply increasing rates of mineral acquisition between the secretory and maturation stages, with peak levels approaching 40 microg/mm tooth length. Computer modeling indicated that quantities of H+ ions potentially generated as apatite crystals grew during the maturation stage greatly exceeded local buffering capacity of enamel fluid and matrix proteins. In other systems, bicarbonate ions are excreted to neutralize highly acidic materials generated extracellularly. Data from this study indicate that ameloblasts, and perhaps cells in other apatite-based hard tissues, use similar bicarbonate release mechanisms to control excess acid arising from mineral formation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".