Octacalcium phosphate

Key takeaways

Octacalcium phosphate belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Octacalcium phosphate to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Octacalcium phosphate from memory before moving on to harder problems.

Reference excerpt

Octacalcium phosphate (OCP) is a form of calcium phosphate with formula Ca8H2(PO4)6·5H2O. OCP may be a precursor to tooth enamel, dentine, and bones. OCP is a precursor of hydroxyapatite (HA), an inorganic biomineral that is important in bone growth. OCP has garnered lots of attention due to its inherent biocompatibility. While OCP exhibits good properties in terms of bone growth, very stringent synthesis requirements make it difficult for mass productions, but nevertheless has shown promise not only in-vitro, but also in in-vivo clinical case studies.

Background Johan Gottlieb discovered calcium phosphate in 1769, and since its discovery calcium phosphate has been widely researched and been found to be one of the most important inorganic structures in hard tissue of vertebrates. Calcium phosphate has been used to treat various illnesses such as rickets, scrofula, diarrhea, ulcer, and inflammation, but its uses in orthopedics and dentistry have been the main area of focus for many years. Before the use of calcium phosphates in orthopedics, bioceramics were widely utilized due to their bio inertness and advantageous mechanical properties, but despite the success of bioceramics, this material simply substituted broken bones, and did not provide a means of bone regrowth within the damaged tissue. By the 1900s scientists had started using calcium phosphate during surgeries as a means of applying simple bone grafts, and by 1950 the genesis of self-setting calcium phosphate in combination with bioceramics had been discovered. Between 1976 and 1981 calcium phosphates started to be used more prominently as coatings for orthopedic and dental implants in order to stimulate stronger osseointegration, and by the 1990s calcium phosphate had started to become utilized as an effective mode for drug transportation and had started to branch into other fields such as tissue engineering. Octacalcium phosphate (OCP) was discovered in the 1950s, when scientists discovered that by varying the calcium phosphate ratio, various forms of calcium phosphates could be created. OCP has widely been seen as an inorganic precursor for hydroxyapatite which is similar to calcium phosphate in that it is an inorganic mineral found in bones and teeth that plays a major role in the overall structure, strength, and regeneration capabilities of bone. Along with this, compared to other forms of calcium phosphate OCP has been found to have greater levels of biocompatibility and increased rates of osteointegration. The advantageous properties of OCP have made it a primary candidate for many orthopedic uses, and although mass production has been utilized, extremely strict chemical constraints make it difficult to mass-produce and fast paces.

Type of ceramic–tissue interaction Ceramics can be categorized into four categories based on their interaction with tissues. Type #1 (dense, nonporous, and inert) ceramics are strong, stiff, and attach to bone/tissue resulting in a cementing of the device into the tissue. Type #2 (porous and inert) ceramics exhibit a lower overall strength but are useful as coatings and result in biological fixation. Type #3 (dense and nonporous) ceramics exhibit biological fixation by chemically attaching directly to bone. Finally, type #4 (dense, nonporous, and resorbable) ceramics are slowly replaced with bone. The nature of octacalcium phosphate resembles that of type #4 ceramics. Type #4 ceramics differ based on the ratio of calcium to phosphate (Ca:P); the most stable/ideal ratio (Ca:P=10:6=1.67) results in hydroxyapatite (HA) which is often used in orthopedic settings due to the inherent biocompatibility and similarity to natural bone tissue. While HA has been widely used and established as an excellent candidate for orthopedic usage, OCP (Ca:P=1.33), while harder to synthesize and more difficult to sinter and mold, has been proven to not only be more resorbable than HA, but also proven to result in greater overall bone formation than HA.

Material properties The table below displays various octacalcium phosphate material properties and descriptions of said properties.

The three crystal types (spherule, ribbon like, and plate) all exhibit flexural behavior; some have brittle characteristics, others have ductile characteristics. Spherule- and ribbon-like crystals are brittle, similar to ceramics; deforming elastically up to a maximum stress, then immediately fracturing (irreversible deformation). Plate crystals, however, displayed more ductile characteristics. Unlike spherule and ribbon like crystals, plate crystals deformed elastically up to the maximum stress, but did not fracture, instead transitioning into plastic deformation similar to metals and some polymers.

Synthesis Due to the multitude of implications of octacalcium phosphate (OCP), many synthesis methods have been developed as well as strides to upscale the overall production rate of octacalcium phosphate. Methods include precipitation reactions, hydrolysis reactions, aging, and ion substitution. Previously stated methods have all been able to produce high-purity OCP; but, to upscale the production of OCP, it is imperative to control the reaction conditions as slight deviations in molarity, pH, or temperature can easily lead to different calcium phosphate variations such as dicalcium phosphate or hydroxyapatite.

Precipitation Precipitation involves mixing Ca(CH3COO)2 (calcium acetate) with a sodium phosphate solution usually consisting of a mixture of Na2HPO4 (disodium phosphate) and NaH2PO4 (sodium hydrogen phosphate). The reaction constraints for precipitation reactions consisted of a calcium acetate molarity of 0.04 M, and sodium phosphate solution molarity of 0.04 M. pH ranged from 5.0 to 6.5; temperatures ranged from 37 – 90 °C.

Hydrolysis OCP is typically synthesized via hydrolysis of α-tricalcium phosphate (ɑ-TCP). To create OCP, ɑ-TCP along with calcium carbonate and brushite (CaHPO4·2H2O) are formed into a solid state in preparation for the hydrolysis. The hydrolysis reaction can then be performed by combining the previously prepared ɑ-TCP and 0.0016 M phosphoric acid at 25°C and a pH of 6. During hydrolysis, in order to prevent deviation from octacalcium phosphate, it is imperative to maintain a calcium phosphate (Ca/P) ratio of 1.33.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Octacalcium phosphate

Start with the simplest possible case. Write down what Octacalcium phosphate claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Octacalcium phosphate before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Octacalcium phosphate ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Octacalcium phosphate

In research: Octacalcium phosphate appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Octacalcium phosphate in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Octacalcium phosphate is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bones, Calcium compounds, Dental enamel, so understanding it makes those chapters shorter.
In everyday life: Look for Octacalcium phosphate outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Octacalcium phosphate in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Octacalcium phosphate means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Octacalcium phosphate out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Octacalcium phosphate in simple terms?

Octacalcium phosphate (OCP) is a form of calcium phosphate with formula Ca8H2(PO4)6·5H2O. OCP may be a precursor to tooth enamel, dentine, and bones.

Why does Octacalcium phosphate matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Octacalcium phosphate?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Octacalcium phosphate.