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Welcome to The Ruddle Show. I’m Lisette and this is my dad, Cliff Ruddle.

How you doing?

Pretty good, how about you?

Never better! Hey listen, are you getting over jet lag?

Yes. So about a week and a half ago, I just got back from a little family vacation with just my family of four. We went to Florence, Italy. I’ve been to Florence a few times, but my kids had never been anywhere in Italy, so it was pretty exciting for them to visit Italy. Everyone just loved the food, the architecture, and Florence is such a nice city; you can just walk around everywhere. You’ve been to Italy, and specifically Florence, a few times.

Yeah. Starting in the late ‘80s, literally multiple times, countless times almost over many decades subsequent to the late ‘80s. It has great – you already said it, the architecture, the food, the people. And I liked all my friends I was meeting; their names all ended with Mario, Fabio, Arnoldo. I guess Giuseppe was an outlier.

Well I do remember also for decades those photos that hung in your office that you took.

Oh yeah. I was so impressed with Italy and all those trips, and I just loved the architecture as I mentioned. I actually had a lady lay in my operatory and made a scaffolding. We had the Duomo climb the bell tower and I shot the Duomo with no scaffolding. It was a fabulous picture I thought – she loved it – and she was painting elements of that on the ceiling, so when I was practicing, I thought I was in Italy. I could hear the voices, smell the foods, the people, the fun.

Yeah, I remember those photos because we actually climbed the Bell Tower ourselves. I think it’s over 450 steps; a very narrow, winding staircase with no handrails. But they have these little portals where you can see out the window of the Duomo, and I remembered those pictures you had taken. Everyone of course was trying to take pictures, but they have it now blocked off with chains so you can’t maybe jump through or something. But you have to remember; that was in the day when you actually had to take the pictures, get back from your trip, go get them developed and hope they turned out.

You never knew on the trip what was happening in your camera.

Well probably one of the highlights of our trip was we rented a car, and I actually drove the car myself. We drove to Pisa, saw the Leaning Tower, and then we went on to the sea. That was really neat when we got to the coast; it was just a beach of all white rocks. And then on the way back, we stopped by San Gimignano, which is a little town in Tuscany. I think you’ve been there, right?

Yeah, that’s a fabulous part of Tuscany that I like is the rolling hills and the walled city and the towers; the towers that give tremendous views. From the top of the city, the hills, you could see the vast countryside; it was very beautiful.

Yeah. I really liked it there. And then I thought I’d never been there, but when I got there I’m like oh; I have been here.

You can’t forget it.

Yeah, it’s been a while. But in Florence, probably a highlight for us was seeing the Ponte Vecchio, because when my kids were in grade school, they had to do an architecture project and Isaac chose to build Dodgers Stadium. And Eva was kind of stumped, she didn’t know what to choose. And I recommended she do the Ponte Vecchio, because I remember when I was there at one point being so impressed by it. So she built it and this was the first time she actually got to see it in person. It was cute, because she kept saying “Oh, the bridge I built; the bridge I built”. So that was kind of cute.

Okay, so you went all through Florence and you did the museums and you saw the David, and you did all the stuff that we like to do. And then you went to San Gimignano, then you went out to the Eastern Mediterranean. Where else did you go?

Well we went to Rome for a day. We took the high-speed train there. It only takes an hour and a half. And I’ll just say the highlight of that was seeing the Coliseum. It was very crowded, of course, but it’s just so massively impressive that you’re just like wow! So that actually made the whole trip to Rome worth it. But we were pretty happy to get back to Florence that night.

Yeah, that’s a wonderful ruins, the Coliseum of course; but then there’s a whole vast area that next time you’ll have to explore more… the Forum. And Gianluca Gambarini; if you’re out there, I remember we came to your house and we just looked across the street and there’s the Forum.

Yeah, that was a dinner you had, right?

Yeah.

And you could just see the whole thing from -

It was amazing.

Well it was such an adventure. I’m really glad to be back. Coming home to Santa Barbara is really nice. I mean we live in a very nice town. And then of course, I’m happy to see you and Mom and Lori and be back to work on The Ruddle Show.

So speaking of The Ruddle Show, we have a great show today. We have a guest presentation so let’s get on with the show.

Spaghetti [nonsense] Italiano!

Okay, so today we have a guest presentation which you will see momentarily. It is by Dr. Gordon Christensen, who you might have heard of as he is a legend in dentistry. He is a prosthodontist from Provo, Utah, and also founder and CEO of Practical Clinical Courses, which is an educational company that offers courses in all disciplines of dentistry and patient education, as well as articles and videos. And you and Dr. Christensen go way back, right?

Yeah, we’re both old. When you’re old, you get to know a lot of people over time.

Yeah, you know for literally decades I’d run into him at the big meetings in the United States; Yankee, the Chicago mid-winter, the ADA, the CDA – the California Dental Association – all the big meetings; he was always there. So after a while you hang out in the Speakers’ Room and you start to shake hands with a few people, so I got to know him early. And then we were both members of the AAED – I guess I should say that’s the American Academy of Esthetic Dentistry – and they only take 100. He was in there and I was in there for a lot of years, and got to see him more and talk to him, have a few drinks. He doesn’t drink, so I’d better clarify it was water; maybe orange juice. It wasn’t coffee – oops, sorry.

Anyway, I saw him in that context, then he started the Scottsdale Center for Dentistry. That was a magnificent, $60 million facility. And when he did that he asked me – he was the Dean and he asked me to be his endo chair, so I put – he had a little faculty of endodontists. So we were there together for a few years, two years. And then I went to Provo, went out to Provo; and he does those courses you were just talking about, two-day courses. We did the endo; first day didactic and then hands-on.

So as the years went by, we became closer and closer and I have huge admiration for him.

Okay, well I mentioned Practical Clinical Courses. But he is also founder and CEO of the Clinicians Report Foundation – which is non-profit by the way – and it tests new dental products and then reports results to the professions so clinicians can make educated purchases on what they choose to buy. So maybe you can expand on that a little bit more.

I can rattle off a bunch of numbers, and I guess I will, just to be kind to Gordon because he’s so kind to us here on the set. But if you’re ever in Provo, Utah, and you’re taking a ski trip or something to Park City, you should go to Provo and go through their operation. It’s multiple buildings, multiple stories; it’s like a real center. I mean you want to see what they’re doing, but they have 450 clinicians on this team, there are 19 countries, they test 750 products.

Every year.

Every year. And they do about 20,000 evaluations. So it’s a huge international operation. And further studied by inside, they have engineers, they have scientists and they have staff people that evaluate a lot of this stuff, put it together and package it. As an example, how many of you out there use the EndoActivator because you saw it in Gordon Christensen’s Clinical Report? And so it was in the CR report at that time, and it got thumbs up as a really good product. And of course all the science and papers had to follow. But yeah.

Yeah, it’s a really great service that he provides there. We have often talked on our show about the flood of new products that come to market every year, and how does a clinician even choose what to buy; what represents an improvement on what came before? So it’s great that the CR Foundation exists.

You know, what you said they heard and it just went right over their heads. Do you realize how much information he knows about products you’re using every day and their tendencies and how things can fracture or leak? So he is an expert to go to get a good reading on the pulse of products.

Well I feel like we need to also mention Dr. Christensen’s wife, Rella Christensen; Dr. Rella Christensen. She plays a big role it the foundation as well.

She’s a co-founder of Clinical Research Foundation. Her expertise really is running TRAC, which stands for Technologies in Restorative and Caries Research. So she does a lot of the big lifting behind the scenes and the papers get published and you’re benefitting.

Okay. Well beyond Practical Clinical Courses and the Clinicians Report Foundation, Dr. Christensen has also helped initiate two new dental schools. He lectures worldwide and has delivered over 50,000 hours of CE. He has produced hundreds – and I’m not exaggerating – hundreds of multi-media dental presentations. And he has published in countless articles and textbooks. So you can see we’re talking about a very powerful legacy.

And he’s only 40-years old.

All right. Well we are very honored to have the opportunity to show you this presentation. It is called Restoring the Endodontically Treated Tooth. So let’s watch and learn.

[Christensen Presentation Begins]

It’s my great pleasure to spend a few moments with anybody that Cliff is associated with. Thank you, Cliff, for inviting me to do this. It’s kind of a touchy topic because restoring endodontically treated teeth is frustrating; often there’s not much tooth structure there.

Well a little bit about me. Some of you know me well, some of you don’t know me at all. The CR Foundation is a non-profit organization in Provo, Utah. You’re looking at our 50 fulltime employees in Utah; we have another 450 spread throughout the world in about 100 countries. Then there’s another group of people who come free of charge to help in this non-profit orientation who are from all over North America; from young to old, male, female, and it’s been quite a thing.

By the way, if anything you want that I might happen to show – I’ll leave that up for a second – get out your camera and get that QR code, and when you go in put in your email and your name, and you will be open to look at any kind of videos or whatever you like for purchase for yourself.

Fillers, build-ups and post and cores; what am I talking about? Fillers… there’s a core to each one of these; you know that, I’m sure you do. Fillers are just holes in the tooth where there was Class 5, or an MOD where the proximals were deep. They don’t really assist in increasing strength. They basically just fill it so that the digital or analog impression will not over space. Build-ups add some strength if bonded and when pins are used effectively. Posts and cores add significant strength. Let’s just look at some of these on a couple of drawings I’ve done.

There’s that old Class 5 on the left; you took it out. There’s a pot hole there. A filler is basically something I don’t even charge for. I’ll just put some material in there, which I’ll show you in a second. Same with an MOD. Those black things on the right are where the mesial and distal approximal box form. They need to be filled in if you’re to make a decent impression, either digital or analog.

And that’s the material we usually use for just a filler. It’s a composite that is hydrophilic. In other words, the fluoride that is in it, and there’s quite a bit, it oozes out, and before I do put it in their front tooth space or otherwise, will come back into the restoration.

As you look at a pretty broken-down tooth, what is a ferrule effect? The ferrule effect, there’s where this particular drawing ends, where the prep ends. A good prep is about 4mm, and if I can judge about what 4mm is, I’m going to start the cursor right there; there would be about 4mm. But there’s no tooth there. So how do we build it up? As you observe the first molar on that, the analog situation, the first molar is just a build-up where it’s a live tooth. And I placed some pins, which you’ll see in a minute, and those pins will not only help retention; they are the retention. Do not trust bonding agents. I’ll repeat that; do not trust bonding agents. They soon dissipate in strength and you have almost nothing to connect the tooth to the build-up.

Now the other tooth, the silver nitrate treated tooth that’s almost black, it had a root canal done properly. I’ve got three posts in that; are they all necessary? No. We’ll get to that in a minute. The ferrule effect is necessary. You’ll see it around this black tooth, you’ll see it around this tooth. You have to have roughly about 1½ to 2mm.

Now a post and core, there’s controversy here on an endodontically treated tooth. Some schools are teaching oh, you don’t need a post; you don’t need a post. I need those people to walk in my shoes at least one day. My texts tell me I’ve done 40,000 crowns over my short career so far, and I’m not stopping. But with 40,000 crowns I can say at least half of those endodontically treated – well they’re not all endodontically treated teeth. About 10 of those 40,000 – 10% would be post and core. And here they are.

Bruxers and clenchers need a post. They’re getting far, far more forces; up to four times. We’ve tested that in sleep appliances. Up to four times more than normal occlusion. If a canine has a canine rise, which is about 70% of your patients supposedly need it. If that tooth is taking full load, it needs help. If the tooth has no addition to support it, a post is needed. And if the tooth is supporting a fixed prosthesis, pretty obviously. If none of the above, a post is not needed.

I have a canine rise. I haven’t worn it down in all these years I’ve been living. I have a canine rise; if I go left or right, that tooth takes the load. I don’t have endo in those two teeth, but if I did, I would want a post. If not, I have endo in some molars. None of them have posts, because I can only close straight down. There’s no lateral forces on there.

Now apparently there’s been some kind of controversy, Cliff tells me, about the so-called ferrule effect. Here’s a classic example I’m going to show you right now. This woman is about 80. I have no idea who did the endo or post. There’s nothing good about it. Apparently there’s been no ferrule. So she came in and she said this tooth has moved forward on me. Well it sure has!

Some of you are fishermen. You know how a fishing rod interdigitates. As it interdigitates, it’ll go in a half inch, and there’s no way it can go in any direction; it’s stopped. If you have a 1½ to 2mm ferrule all the way around that, it can’t come off. It can in a sticky orientation where you put a caramel in and just put tensile load on it, it can come off. But in a left/right, forward/back, it can’t come off.

I’d suggest that you look at that very thoroughly. What is a good prep? Let’s go back to one of the slides I had there a second ago. I built those up to about 4mm of tooth structure. Is it tooth structure? No. But it’s retained so solidly that it cannot come off. Now if you’re stressing bonding agents, it will fail. I pretty well guarantee it. Bonding agents are almost a joke.

What kinds of posts are available to you? The majority of them are fiber reinforced; I would say about 95% today. In all of the many sermons I give out on the lecture circuit, when I ask that, it’s almost every hand that uses #1. Occasionally somebody will use prefabricated titanium alloy. Not pure titanium, #5. Pure titanium is too malleable; it moves. The bottom line is #1 is not quite as strong as metal, but it does not create a broken tooth when you get a forceful hit.

So where are we? We’re at what you’re going to see right now. We are at fiber reinforced composite posts. And it made little difference whether they are tapered, whether they’re straight on their sides, whether they’re huge in diameter and they have horizontal striations, vertical striations. They are so porous electron microscopically that the cement flows into any microscopic irregularities there and there is never a separation from the post to the cement. The separation, which is almost always the case if a post fails, is between the tooth structure and the cement; because the bonding agents don’t bond.

Here are just a couple of classic examples for you. That’s a particularly good one because it has a color code on the post as well as on the drill. When you’re using this, I would strongly suggest you look seriously at using electric handpieces. Electric handpieces provide far more torque, and you can slow them down to 700 or maybe 1000 and just pump that slowly up and down. If you take an air handpiece, it’s going so fast you can’t control anything. I would suggest looking at NSK, Bien-Air, KaVo; those three are right in the top of our studies.

Well, can you put light down through a post? And the absolute answer is yes. If it has some clarity to it, the light will go right to the bottom of that post and make that procedure much faster for you.

Here’s something extremely important coming up right now. May I suggest that you use a diamond to roughen the internal of that post hole before you cement. Basically that’s where the failures occur. Roughen it either by hand router – you’re looking at a hand router there from Brasseler – or you could go in with a diamond.

Now let’s take a look at some posts and cores, just for a second. Here I have a natural tooth in mouth, endodontically treated with a copper band; and they’re hard to get right now, so many of us have gone to other matrices that I’ll show you in a minute. The copper band is still the best. You can just pinch that as you can see along the facial. Good luck finding it though. Put your finger on the top and when the material flows out of that little crevice, you know you’ve filled the space. It’s a pretty simple thing. You end up – this is the same patient – you end up with something like that.

Now is one post enough? I only have minimal ferrule there. No, I have four pins in that. You can’t see them, 1,2,3,4. Are pins still desirable? Are you kidding? Some schools are not teaching pins; they’re in the dark ages. You just about have pins. If you want to test that yourself, behead a tooth that was just extracted, that’s still moist, and put on any kind of bonding agent you want, I don’t even care what brand. A bonding agent is basically a bonding agent; they’re not as effective as the companies would like to make you think. Then let it sit overnight in water. Obviously there’s no heat and cold, heat and cold like there would be in the mouth. But soak it in a little cup of water overnight, and guess what? Some of them will actually float off in the water. Don’t trust bonding agents.

Well then, put some pins in. I’ll show you what kind of pins in a minute. They have to be pure titanium. If I take pins such as that and bend them over, you will see no crack around there. They are pure titanium. If they’re titanium alloy, you will see cracks. If they’re stainless steel, forget it. You will see enormous cracks. I suggest that you stay with pure titanium, and I’m going to give you a couple of brand names here. The original one was that; Filpin, it comes from England by Filhol. They’ve been a little harder to get; they have 2mm drill stop and as that pin gets in 2mm, it fractures off right there. Currently the one that we’ve tested and it will compete with Filpin very well is Nordin; quite a bit less expensive, same thing. Drill stop 2mm, pure titanium. You do not want titanium alloy or stainless steel; please remember that.

Now as far as matrices, I would prefer to use a copper band. But they’re very hard to get. So what’s an alternative? This is the Greater Curve Tofflemire Band. Put it in Google and pull it up. You can see it looks like a banana. This is a short one; there’s a long one. You put that in, and rather than tightening it up and potentially squishing all the material away off the top, it opens up as you tighten it in the old Tofflemire orientation.

I’ve got a slide here that shows that. Here it is in a Class 2, and you can see that it’s actually pushing up against the contact area. And you can see in this drawing – not drawing – slide as well. So I’d suggest that to you.

Here’s an example of what I’m saying. This is a dentinogenic, it is imperfective. We have a lot of those in Utah, because frankly, it’s hereditary and I have whole families like that. Now these are pure titanium pins, and I’m going to bend them very markedly. There would be about 15°; there would be about 30°. And you see it over here; you see no cracks anywhere with pure titanium. That is a Godsend; it literally is to have these pins. You can see it’s almost flat off with the gingiva. Now when I prep that I’ll either crown lengthen it, or I will put cord in. There is pocket depth there on that particular patient so I will make the ferrule at least 1½ to 2mm.

What kind of build-up materials would you say? Oh boy, look at that mess. Those crowns have been in quite a while right now; I remember the patient very well. There’s one that is inexpensive. I’m going to give you a couple of inexpensive ones. Why is a build-up material such as Build-It from Pentron, or here we have Absolute Dentin from Parkell. Why go with those instead of your normal composite resin? Your normal composite resin is running $50, $60, $70 a cc. These are down to a fraction of that amount. The filler particle size is larger, so you have the ability to have less shrinkage. You don’t want shrinkage on a build-up do you?

So there are a couple for you that are excellent. They’re a low cost. Now here’s the original one, Core Paste. That’s been around; it was about the first one in dentistry. It’s a little more expensive, but that has a long history. And if you want a low cost, really low cost – 50% off of a typical cost for a build-up material – Mark 3 is a company that sells almost every one of their products at about 50% off. They’re an Israeli company; they’re housed in New York. It’s an excellent way to reduce overhead on some of these.

Well where are we then? What have I really said to you? I’ve said that posts and cores are essential to build a tooth up to a minimum of 4 millimeters from the gingival line to the occlusal table. But there’s something you need to know about that. We have been plagued at this particular point with changes in crowns because of scanning.

Now I’m going to show you preps as they were before scanning came along. The full-zirconia or metal, and now only about 35-45% of you are scanning. And I’ll bet you don’t know what I’m going to tell you and you darn well need to know what I’m going to tell you. Scanning is not what you think it is. It’s allegedly more accurate. Are you kidding? It’s so inaccurate, it’s pathetic. Let’s just keep looking here for a minute; you’ll learn something.

A typical full-zirconia crown needs about .6mm to have adequate strength. If the computer scans that – you’ll see it in a minute – it’ll put ¼ to ½ millimeter space in there and you’ll just cut down most of the thickness. Oh, I didn’t know that. Most dentists don’t know that. PFM is a little deeper, and of course zirconia-based or lithium disilicate, resin-nano ceramic or resin/ceramic, all of them needed 1 millimeter for strength. And guess what? If they spaced that ¼ to ½ millimeter right where I have that cursor, what have you got? You don’t have your millimeter. Are you thinking? Is your mind on? It’s changed markedly.

And now let’s look at occlusal. It’s even worse. You’d like 2mm off the occlusal. I don’t care what you’re doing. If you even go back to gold you need 2, because there’s anatomy in there that takes part of that thickness. But now they’re spacing the inside here ¼ to ½ millimeter. If that’s spaced ½ millimeter, I’m already down to 1½ millimeter, and most of the labs are making the crown ¼ to ½ millimeter too low. I know you know that. You put in a crown and the patient says oh, that feels so good. Well it doesn’t fit. It’s a bit hat on a little head.

You can’t avoid scanning. You cannot avoid scanning. If you make an addition reaction silicone or a polyether impression, the second it gets into the lab, they scan. Now you’re going to have scanning in three ways. What? Number one, you scan the tooth. That’s the most accurate of this least accurate technique. I know that sounds like a strange statement. You either scan the tooth or the lab will scan your impression, or some dentists are pouring a cast thinking they’re going to get more accuracy; which they would if it were an ancient technique. But they will scan new casts. So you cannot avoid having a big hat on a little head.

Now let’s look at that in a little more close-up orientation. Here they were, preps before scanning. They were just this thing I showed you a moment ago. Now I’m going to put some lines on there to make this a little more clear. Red is the computer spacing. Now I haven’t drawn it all around that, but red is the computer spacing and I want you to notice something very important. It also spaces the margin. So therefore, the margin looked at microscopically is 40, 50, 60 to 100 microns open; 1/10 of a millimeter. Therefore you must now use – you must use perio static cements; resin-modified glass ionomer, which is what? What’s resin-modified glass ionomer? It is – I’ll give you two brand names – Relyx Luting from 3M, or Fugi Cem from GC. Or in very curious active patients, you’d better go back to Fugi 1 from GC. Or Ketac Cem from 3M.

I guarantee you that you will have caries there in almost every patient in a few years if you’re not using perio static cement. Do not use resin cements for your zirconia crowns – that’s why they’re coming off. You have a very flexible – I’m going to use a pen to show you. I can take that plastic pen, and watch it; I can bend that ½ inch. You’re putting that under a piece of steel – zirconia – even the slightest hit and it pops off, you know that. In hundreds of courses I’ve given over the last while we see zirconia crowns coming off right and left.

Well my 25 minutes, Cliff, is about – I’m going to put that code up again. There’s the prep that almost every type of material has to have now. It has to be a very deep prep. I don’t like that, but if you don’t make that prep 1 millimeter everywhere, or 1½ millimeters, you’re going to have a very weak crown.

At six years, which is all we’ve had the weakened zirconia, the strengthened zirconia is [inaudible] interim oxide, the labs are all giving you 4,5, and 6% [inaudible], and the bottom line is the strength is now down ⅓ to ½. You have to have a deep prep today, but it will break. At six years, which is all they’ve been out, hundreds of crowns, 100 technicians were already seeing 8% failure. I hope you heard that. Don’t believe what you’re reading, what your seeing from some of the ads. These esthetic zirconias are much weakened from the standard zirconia, which has been in the industry now for 35 years. Be very careful.

Well there’s that QR code again. Click it if you didn’t before and go on in. I have videos on everything we’ve talked about, we have courses on them, we have courses where you actually do posts and cores in the cores. You do build-ups in the cores. You see some of the things I’ve mentioned to you.

In summary, where are we? Where are we with endo? Endo is not going away, and I’ll put a slide up while I’m talking to you for a minute; two websites for you. Endo is not going away. People are aging. As they age, even good endo sometimes degenerates, While it looks excellent on the radiographic orientation, New York University in a practice-based study has shown that upwards of even 20% of general practice endo has problems by five years. And as you age, your immune response goes down.

Well let’s make that endo perfect as Cliff can show you how to do. And let’s also make sure that restorative. I’m seeing restorative that sometimes really frustrates me. When a person will come in and the whole coronal part of the tooth has come off, which is not the tooth, it’s the build-up. Where they trusted the bonding agent and did not take into consideration the inadequacy of the bonding agents on dentin. On enamel they stay, but it’s not a bond. It’s an interdigitation of the roughened crown and the roughened prep. That’s why bond stays on enamel, but does not stay on dentin.

Cliff, it’s been a pleasure to spend a moment with your group. I welcome any critique or I welcome any questions you might have. You’ve got my websites there; PCC Dental is educational Clinicians Report.org actually has a Google-like search that you can go in and put in anything you want, and generally you will get an answer.

Again, thank you. I appreciate this opportunity and wish all of you well. Thanks.

Okay, so that was an excellent presentation and thought provoking. I have to say, Dr. Gordon Christensen is a very polished speaker. And I really liked his topic because it’s very timely and relevant, and I know that there’s a lot of dentists out there every day that have some stress about restoring teeth that have lost a lot of tooth structure. And I think you have mentioned to me that this is a hot topic also on the AAE Discussion Forum.

Probably I’ll re-use the word, but we could say it’s trending. I mean you see it on the AAE constantly; people around the world doing caries control, or can’t be restored. Not even endo, just about the resto part.

Okay, and I do think it’s important that we note that in his presentation, Dr. Christensen is specifically talking about a tooth that has had root canal treatment.

Absolutely.

So that makes a difference because you are able to use the pulp chamber to help keep the crown on.

Yeah. Well I’d just like to first before I go into any comments about what I saw, I’d like to just say Gordon, thanks so much. You are an incredibly busy person. Most people don’t it, but you literally eat, breathe and sleep this, and I know you’re in your 80s and I think you’re in your 60s. So I like the juice, the knowledge, and I’ve learned a lot from you Gordon, so I want to acknowledge that publicly in front of about 100,000 people.

Okay, and what did you like best about the presentation?

Well I thought it was a good review. We already said this, but on the AAE Discussion Forum there’s just constant discussions about how do you build it up, can you build it up, should it just be extracted, could you do a hemisection, how do you get a Tofflemire on, is it a copper bed? Okay, he did all that so now I won’t even mention Tofflemire, except I think the banana band – I really liked, what did he call it, the greater curved one. So when you cinch it down cervically you have a bulk of material occlusally; I liked that. I like copper bands, I used them a lot in my career.

So I thought he gave a great discussion on fillers, build-ups, post and cores, pins. And then I was stunned by the digital scanning space at the end, which we’ll talk about.

Oh yes, we’ll get to that. One thing I did notice right off in the presentation was Dr. Christensen’s repeated emphasis that you can’t trust bonding agents, and that posts are needed to add significant strength to the restoration. And he even joked; those who say posts aren’t needed, I would like to have them walk in my shoes for a day. So maybe you can comment on this; either the need for posts or what it would be like to walk in his shoes.

You know, one thing I really value because I have it in my life, and it’s called experience. So when you have somebody who’s been practicing for 60 years and they tell you that a pin or a post or whatever, they find it in the right instances to be really effective at retaining coronal build-ups and crowns to the roots of teeth, I’m going to listen to him.

And I can read all the papers I want about bonding. You guys just love bonding, you’re on your 5th, 6th, 7th, 8th generation. But a lot of the bonding stuff as you found out, just doesn’t bond. And I think you should take him up on his challenge. Remember he said decoronate a tooth, build it up, put it in water overnight so there’s an anaerobic reaction, and the next morning, you can go in there with a paring knife and chip a lot of them off. He said some of them are floating in the water the next morning in the tub you put them in. Anyway, we don’t bond to dentin. But the profession just keeps bonding; we’re bonding, we’re past pins, we’re past posts.

So he was very specific about the posts, and I’ll just say it real quick. If you’re a clencher or a grinder, a bruxer, you need a post. If you are in canine rise – we’re talking about occlusion and gnathology – if you’re in canine rise and it’s had endo, you probably want to post the tooth; a fiber post.

If you are talking about a 3-unit bridge, a 4-unit bridge, the abutment, if it’s endodontically treated, should have a post. And he said if you are having an endodontically treated tooth with a edentulous space adjacent to it – which would be like a bridge – you need a post in the tooth.

So these are common sense, so that doesn’t mean all teeth get posts where the pendulum swinging back. He’s saying yeah, we’re doing a lot less posts. I found that I could retain a lot of my build-ups using the pulp chamber. And the pulp chamber, I was doing that in the ‘70s and ‘80s, and people started doing it in endo because they realized there’s several millimeters where you can stuff materials in – first it was amalgam for me, and then bonded amalgam, and then other things. But you can really get great build-ups if we have biological width and if we have a ferrule.

Yeah. I think he just really wanted to deter those who are heavily relying on bonding agents. And apparently some misleading advertising about companies that are exaggerating what their bonding agents can do.

All you have to do is walk into a dental school and everybody’s trying to bond. Here’s a flat surface, bond something flat to it and they think that’s going to do it. They don’t have any ferrule, they don’t have retention, they don’t have grooves, they don’t have the pulp chamber. So yeah, I thought it was really timely. Keep going.

Yeah, I kind of got the impression that he was even saying that some graduate programs are even maybe misleading their residents on the abilities of bonding agents.

Make that undergraduate.

Okay, undergraduate. Okay, so you just mentioned the ferrule effect. And when Dr. Christensen mentioned the ferrule effect, he said that there was some controversy surrounding it. So do you know what he meant by that?

Yeah. There’s no controversy between Gordon and me on the ferrule. I had prompted him if he had time – and of course we didn’t give him enough time. So a ferrule is about a millimeter and a half to two-millimeter circumferential band around the tooth where the margin of the crown meets the margin of the tooth. And that’s what keeps teeth strong and from breaking vertically.

So the controversy in endodontics is – oh yes – so the controversy in endodontics is you have a tooth, and we’ve heard of the pulp chambers and the pulp horns, and it creates triangles of dentin. Triangles of dentin. I have always said get the triangles of dentin out, upright your file handle so you’re standing up straight and tall, don’t be coming in off axis, there’s way more iatrogenics, countless papers showing that, countless papers. But yet people will say leave the triangle because we’ve got to have the ferrule effect out here on the mesial. If you do cross-sections through the mesial root of a lower molar, there’s quite a furcal side concavity.

So we are always brushing away from furcal danger, so when we’re finished with endodontics, we have a centered preparation between the mesial and distal surfaces of the root. That’s a stronger root.

Now what about the ferrule? If you take out the triangle, then maybe as you prep it in about a millimeter today, about 1 millimeter to get a shoulder on your cariostatic cements or your gold crown or maybe your porcelain; the most important part of the ferrule is buccal and lingual everybody, it’s not mesial/distal. When you’re chewing and eating and grinding through your meals – oh, I love this board. Yep, I’m going to keep it, so I don’t blow out the camera. But when you’re eating and chewing the forces are lateral, buccal and lingual. So the most important part of the ferrule – Ruddle just told you again and again, I keep repeating – is not mesial to distal, it’s buccal to lingual. So if you have like a wine barrel and you have a metal strap around it, that’s why the barrel doesn’t blow up. Well a tooth won’t blow up if you have a strap around it, and if you have a little less on the mesial or the distal, please don’t lose so much sleep over that. Okay? I think I covered it.

Okay.

Did you like that part?

Oh, thanks for explaining the controversy.

The drawings were impeccable.

Okay, one other thing I learned from this presentation – and you mentioned it – was that pins are sometimes used. Now I’ve heard you talk a lot about posts in the past, but I actually never heard you mention pins. So I was wondering; did you ever use pins yourself? And most importantly, did you use pure titanium pins?

Oh, you’re trying to embarrass me in front of a large audience! That’s my daughter. I told you, I pray that I was using pure titanium pins.

Okay, stainless steel pins, titanium alloy pins, and she just said it, pure titanium. Multiple cracks. It’s been show in the literature, that’s why they fell out of grace. But the thing is dentists don’t seem to understand. You say pins and they have an immediate impression in their head because of something that happened to them. And like you said, were they using pure titanium?

So if you listened to Gordon, and then there wasn’t enough time for him to explain, but I yesterday did a lit review on pins. The stainless steel pins, lots of SCMs and cracks, or craze marks and stuff, that became later opening up and propagating. So not good. No stainless steel.

Titanium was better; it’s a little softer, but it was an alloy. Still less cracking than stainless steel, but nevertheless crazing. Put the pin in and you could see crazing like the spokes on a bicycle. Titanium – never happens. They’re soft, you go in, you can bend the top, 2mm goes in, 2mm sticks up, you can bend the top over to get different retentive areas on teeth. I was using pins on teeth where I primarily was cleaning out caries, and I wasn’t quite to the pulp. And all of a sudden, I realized as an endodontist; this tooth doesn’t need a root canal. But I need to build it up for the dentist. I was placing pins more when I couldn’t utilize the radicular space to place a post. So my pins were pretty much in vital pulp therapy, sending it back to the general dentist for a restorative. And I thought pins were fabulous.

All right. Well the last thing I wanted to ask you about – you mentioned it briefly – and that was what he said about scanners. So maybe you can tell me – tell our viewers a little more of what you thought about that.

Well I won’t re-explain his lecture; that would be a tendency of Ruddle to make sure everybody heard the lecture properly. I will just say I was stunned. You know, I don’t do that type of dentistry, and interdisciplinary dentistry involves restoring of the teeth, obviously, so lots of stuff is going out to these big labs. Gordon is not talking about your little friendly lab. Like I’m sure your dentist in town has his little lab, and I’m sure – well I don’t know, but I wouldn’t think they’re scanning the impressions. So when I heard him say these big labs are all working off of scans, that was strike one. I’m going well that’s not good. Because as much as you love digital and science and technology, as much as you love all that stuff, you have to know; it’s a field that’s maturing. It’s not the same as it’ll be in 10 or 15 years. Remember the first whatever; bonding agents?

So they already allow for ¼ to ½ millimeter gap. So if you cut a 1mm prep and you think you’re going to have material that’s 1mm thick, you could just about – if you take the upper range at ½ millimeter, your margins just got ½ millimeter and you thought they were 1. More broken restorations; especially with tooth-colored restoratives, not metal.

Well the margins are open. He said they’re routinely open. He said you’d better use a cariostatic cement. I wasn’t assuming all of the margins were open. And we know that when the cement is like microns, it’s archival. And when you get big lakes or pools down there in the margin area, there’s more washout, more leakage, more debonding.

Then he said now you’ve got to prep a little bit deeper so you get you 1mm, because you’re going to lose ¼ to ½ because of the space gap. Now you’re going to have more pulpal problems, and I’m loving that part of it because I’m going geez, more business, more endodontics, more toothaches.

So I guess my take home message was really know who you’re working with and how the laboratory is working. Because they’re scanning your impression – you heard him say that. If you send in a stone die, they’re scanning that; same error factor. And if you just send in a digital file, of course that’s the scanning.

Okay. Well I think that’s all we have to comment on. I just want to thank Dr. Christensen again for taking the time to send us this excellent presentation. We know he’s really busy. And he is going to be on our next show briefly; that’s our Legacy show and so of course we will be including him on that.

Gordon, main camera for you, sir. Thank you again for being so insightful. That was very helpful for international endodontists to hear. For you, this was back pocket stuff 40 years ago, 50 years ago. But I think I learned again; sometimes traditional, old-fashioned stuff, it has its place.

So you can put a post, a round post – he said it didn’t matter, length, width, striations or not – but if you want to prevent that anti-rotational thing, one well-placed titanium pure pin might be something that people start to think about. Thank you for helping us.

Okay, thank you.

All right, I’m closing the show; 99 is going to get shut down with complex anatomy.

You know, short story. When I first started lecturing decades ago, how I always could win over the hearts and minds of almost any dentist in any country in any region of the world was we had one thing in common. Despite our language and our cultural differences, we all loved anatomy. We’ve been getting quite a few requests to show a little bit of anatomy, so let me make a distinction.

When I say “anatomy,” there is the lateral anatomy, the deep lateral anatomy; there is all the stuff that’s going on between systems in Frank Paque’s micro-CT. And then we see an off angle – horizontally off angled axis films we see similar anatomy showing up in the anastomoses between the MB and the ML systems. And we see three portals of exit and bla-bla-bla. You can see, right; so I don’t have to say too much. What I want to say is today we’re not going to look so much at the deep lateral anatomy; we’re going to just look at do you have good access? Think about Ninja access; think about orifice directed access, and then thing about complete access.

If you want to be a master of anatomy, you need to have an access that helps you find all the orifices. Okay, let’s get started; let’s roll.

All right, so you’re looking at this pretty insignificant tooth. It’s carrying a 3-unit bridge and you begin to map it, right? You begin to map it, you being to look at it and it comes around. Oh my goodness, are you really doing this on your films? Oh yeah. Oh, look at how that palatal root cuts up through there. Yep. You can just see that palatal root, like a little dome coming right up here, boom.

So you’re starting to map the anatomy, and if you map the anatomy, you know about Hess. Walter Hess you know -- his book showed 10,000 recovered specimens and that’s what got me hooked in the ‘70s.

So if we slide this over after a little bit of chair time work, we can keep our shapes appropriate for the roots that hold those systems. And we learned how to find the MB 2 decades and decades ago; the microscope helped. And others came along excited because they wanted to get MB 2s. Then started to say oh wait a minute; there’s MB 3s. So just a simple kind of a shape; palatal root has a little bifidity, and that’s how we do anatomy.

What I’m not asking and what you’re probably wanting to know… How’d you do it? Well that’s a Q&A isn’t it? That’s what we’re going to have to exploit. Questions are the answers.

So this film is set vertically. It’s an extremely long tooth; it was about 31mm before I took the crown off to shorten the tooth so I could use 31mm vials. Well, are you looking at the length of those roots? Are you looking at the width of those roots? Bulk and form -- are you looking at the apical part carefully?

Well after a couple hours – I know a lot of you can’t imagine a 2-hour molar. My wife would probably interrupt and say about 4 hours, 6 hours, 7 hours. You know, it was fun to do it. It was like did any neurosurgeon say we’ve got to go a little faster now because we’ve got another patient? No, you did it until it was right.

So four apical portals of exit, four systems. Look at how they’re flowing through the roots that hold them. And it’s a beautiful thing when you start to think about the mechanical objectives and all the things we’ve talked about on other shows. Irrigation, down packing, back packing; we’ve talked about pre-treatment, we’ve talked about putting bands on teeth so they don’t fracture in an appointment. There’s a lot of stuff here. You’re going to watch this little show – okay, are you listening – I think most of you five times. Because it’s short. Some of you will just watch it three times.

All right, so here we have another one. Anatomy. Let’s look at a fiver. A five holer. So think about the access. Are you working through a pea hole? Can you actually see the pulpal floor in all of its entirety? Or are you trying to feel around? Do you even have CBCT? You might want to ask all these questions. All of these were done pre-CBCT.

You slide it over; boom. How about the mid-mesial? So are you finding some mid-mesials? Are you using ultrasonics, are you tromping between the MB and the ML? You get the catch in there. Are you trying to start a file? If you do, it might merge into one of the other mesial root systems, or it might have its own, distinct, apical portal of exit.

Okay, this film is a little bit hot, a little bit blown out. But you being to look at that molar and you being to think about the task that lies ahead, and a lot of you aren’t looking very thoughtfully. I won’t trace all the roots and all the canals, but you’re thinking probably three. Okay, I heard there could be four.

Well, when we get the crown off – that was another idea we talked about. So if you want to improve access to complicated anatomy, you might take a few crowns off. But you’d have to go watch another Ruddle Show wouldn’t you, to know how to use the crown remover systems and the metal lift and things we’ve talked about.

But I’m showing you specifically a DB2. Here we have a DB, the one that we typically find. And then there was a fifth one here. I don’t know, but there were two there, you can say 1,2,3,4,5; you can say 1,2,3,4,5, but they all add up in my math to five systems; five holes. So it’s fun; it’s fun.

And when you look at the post-op, you can see straight line access. You can see that the MB root is quite complicated, you can see there’s something there and there’s something there. And then you’ve got a DB2 and a DB1, and then there’s our palatal right there. So yep, you’ve got all kinds of things going on there. And you know what? That tooth is a great abutment. And if it’s properly restored – and we’ve talked about endo resto – but if it’s properly restored, that’s a long-term result in the bank.

And we keep rolling. Are there six systems? Maybe there’s seven! Well, there’s as many as there are. So when you look at this innocuous tooth, you’re saying gee; I can – let’s do one of those Ruddle deals. We’ll trace it. We see a palatal root; whoa, there’s the palatal root. Oh, I can see the DB root gracefully flowing up into here. Oh there’s the back side of it, there’s the furcation, there’s the MB, about there and boom and back up, and the palatal root keeps coming.

All right. So you look at your films thoughtfully. I keep saying that. You analyze two or three angles. If you have CBCT, of course you’re doing your slices and you know all this pretreatment; treatment plan for no surprises. But only less than 5% of all people in the world have CBCT. So maybe you have to go back and be Ruddle in the ‘70s. It can be done! If it’s been done before, it’s possible.

So we slide it over and how many do we have? Oh my goodness, this is a fun tooth. You know, when you can do things like this, doesn’t it make you happy? When you go home at night, you don’t even know you’re driving. You might be flying. In your mind, you’re flying home in the car.

And you can see a couple of palatals, you can see an MB2 and over here is the other one. Look at the anastomosing. I’ll get that line out of there; look at the anastomosing between the MB1 and 2. Oh, but there’s a DB1; it ends right there. And then look at the DB2; the DB2. Notice it’s bifid, so maybe there’s 1,2,3,4,5,6, maybe there’s 7.

All right, I’ve had some fun with you. This show’s all over; #99 closes down. It’s another remarkable show that you’re telling your friends about. But you’re going to like the next one; it’s 100! And we’re going to talk about old Ruddle’s legacy cases, we’re going to talk about lots of people around the world, and they’ll tell you a little bit about their legacy because the legacy maps out the pathway from where you are to where you’re trying to get.