Help! Explain me this text please!

[vietanh91]

I read this paragraph in a endodontic book. But i dont understand it. Can anyone explain it for me?
Cementum contacts dentin inside the canal coronal to the cementum surface. This is the cementodentinal junction (CDJ). The CDJ level varies not only from tooth to tooth but also within a single root canal. One study estimated the junction to be located 0.5 to 0.75 mm coronal to the apical opening. Theoretically, that is the point where the pulp terminates and the PDL begins.

I dont understand what "inside the canal coronal to the cementum surface" means. Does"CDJ level" mean CDJ thickness? And i dont understand "the junction is located 0.5 to 0.75 mm coronal to the apical opening". In apical opening, isn't there CDJ junction?

Please help me explain these text and give me some illustaion (if available). Thanks so much!

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[lemoncurry]

It means if you are to start at the apex of the root and go up (coronally), the first thing you see is cementum, which is the outermost covering of the tooth root. According to the text, about 0.5 mm "up" from the apical opening is the junction where cementum stops and dentin begins. I guess they wanted to stress that the inner surface of the root canals is not completely made of dentin but has a small cementum cap at the apex.

 

[vietanh91]

Thanks so much! I understand it!
I have two other questions:
1)Odontoblast participate in dentin formation in three ways: (1) by syn-thesizing and secreting inorganic matrix, (2) by initially transporting inorganic components to newly formed matrix, and (3) by creating an environment that permits mineralization of matrix
I think the first way should be ..... organic matrix. Is it right?
2)Dentin and pulp are really a single-tissue complex whose histologic appearance varies with age and exposure to external stimuli.
I dont understand what "single-tissue complex" and "exposure to external stimuli" mean!
Please help me! Thanks so much!

 

[vietanh91]

http://en.wikipedia.org/wiki/Dentinogenesis
According to this article, "They begin secreting an organic matrix..." I think, the above text have a orthographic mistake. The true sentence, i think, is "synthethizing and secreting organic matrix 😀.

Please help me with the second problem. I dont understand that sentence's meaning 🙁. Thanks so much!

 

[lemoncurry]

As with epithelium and other tissues, there are layers of specialized cells. In the pulp, the outermost layer of cells is the odontoblasts, which produce the dentin layer. These cells continue to make dentin throughout a person's life, so that the size of the pulp chamber narrows over time and in some cases completely obliterates due to calicification. Dentin may also be produced by odontoblasts as a result of an external stimulus, such as caries progression or traumatic injury. That is why a dentist will place calcium hydroxide (e.g. DyCal) on the bottom of a deep cavity prep; it is to stimulate the production of reparative dentin.

As far as other external stimuli, the pulp can become infected by bacteria from caries or periodontal disease and eventually necrose. All of this will cause changes in the histologic appearance of this tissue. But the main point of it being a "single tissue complex" is the idea that you should consider the dentin as an extension of the pulp tissue, and not a separate tissue unto itself.

Question for you: is this not something you would be able to get clarification from a professor since your status says you are a dental student? I would trust them more than what we say on this forum.

 

[vietanh91]

Hi! I'm on summer holiday and i want to read some dental books before learning dentistry at my university. Now i dont know any lecturer so i cant ask them 🙁.
Thanks so much!

 

[lemoncurry]

If you're getting ready to start your first year, I recommend you just relax and enjoy your free time while you still can. Once dental school starts, you will be eating, sleeping and crapping dentistry.

 

[jinhomc]

Please relax. Those questions will be answered in your first semester. You will study the embryology of it step by step.
I was like you before, thinking if I should study a little, getting ahead of everything a bit. But when you know what you will be willing to study right now in these few months would not get you too far but one or two quizes worth of content, you know you'd better enjoy your summer.
As for your question, dentin and pulp both are originated from dental papilla - the "single tissue complex".

 

[vietanh91]

I have learnt 3 years of basic medicine. Next year I'll learn dentistry. Thanks so much!