Wow, time flies when you are having fun! It has been a year since I printed the last newsletter edition. In 2002, Mary and I did a lot of international travel, both for our seminars and to obtain current information for those seminars. The international demand for "bondodontics" lectures has been quite astonishing. So here is the next newsletter issue, a bit later than I intended. Hopefully it will serve as an update as well as an indicator of your currency in the concepts I am teaching.

I do not seem to be slowing down any in my schedule, contrary to previous plans. We are very proud to continue bringing you guest lecturers who are among the best in the world, the ones I personally want to hear. The next one will be at Yosemite, featuring Dr. David Winkler from London, one of Europe's best. Sadly this will be our last Yosemite seminar; the new Yosemite Concession Company is not group friendly and has become unreasonable in their reservation policies.

We have also announced our third Alaska cruise, this one departing Vancouver (a great destination in itself) on June 1 and arriving at Seward, just south of Anchorage, a week later. (Marie Cameron, our travel agent for many years, has secured some very good cruise rates. She can be reached for cruise information at (510) 276-1190.) Besides many excellent stops, we cruise Hubbard Glacier, the ship captain's favorite. This cruise features guest speakers Tom Orent (the Gems Guy) and Tom Hughes (famous for those smile books). The seminar will be a blend of esthetic dentistry and marketing of that dentistry.

Our schedule this year will be a one day format. This one day format on Contemporary Bondodontics is my favorite and is getting excellent reviews. Note the very civilized venues, like Santa Fe and Darwin. Also to be noted is the guest program at Tahoe with John Kanca and yours truly, a sort of "battle of the bonds". That is on June 21 and should be a great one.

Have a great year.

Sincerely,

Ray

H&H impressions

I am grateful to Jeff Hoos of Connecticut for telling me about this technique. Jeff is a "must hear" for his daylong program, which includes a remarkable story on how he discovered the H&H technique. H&H stands for hydraulic and hydrophobic. You use hydraulics to push a hydrophobic impression material. The hydrophobic material is a polyvinyl siloxaine (VPS) capable of displacing blood and saliva. When done properly, there is no need for retraction string (nor for some overpriced and under performing syringable clay). H&H seems to be very atraumatic to the gingival tissues. Jeff helped develop J Morita's PerfectimTM VPS materials for this technique; likewise I helped dial-in Danville's materials for the technique. What I wanted was a blazing fast set, a very hard "moose-like VPS", a thixotropic character to the wash (non-runny but very easily movable, sort of like whipped cream), and a very dark color for easy margin reading. So what we have are two very capable but different systems; it might be a good idea to try both. (Tin Man sells both, (800) 554-6394. They even have the appropriate Danville materials assembled into a custom H&H "trial kit" and they can also supply suitable and inexpensive trays.) The tray "moose" needs to be quite hard; Danville's StarTM VPS Stiff Bite is the hardest I have seen. Actually the hardness is more properly described by the Shore A Durometer measurement. The Shore A Durometer instrument consists of a blunt-pointed indenter attached by a lever to a scale that is graduated from 0 to 100 units. A reading of 0 indicates the indenter has completely penetrated the sample; a reading of 100 units indicates no penetration has occurred. Danville's Stiff Bite has a value about 91, quite impressive by industry comparison. Likewise the wash should have a low durometer reading in addition to the above-mentioned handling properties. If you want to use other than Danville or J Morita materials, check that the durometer reading is above about 88 for the moose, below 40 for the wash. The more the difference, at least in theory, the better. In my estimation, all VPS materials are sufficiently hydrophobic to repel the fluids, even those labeled "super hydrophilic".

Here is the technique but don't even think of using it without informing your lab. The lab must use die spacing as is described below, otherwise you will have crowns that are too tight to seat and you will be among the 20% of naysayers. They should also be informed about the best method to record the occlusion provided by the closed bite impression (see below).

Stiff Bite VPS is injected onto a plastic rimless tray (Fig 1). ). Blood is displaced so there is no need to wash it off. The patient closes into the Stiff Bite VPS, which forms a "peripherally sealed custom tray" around the prep area. (I use the rimless plastic trays like Dentamerica's to deliver the impression material to the mouth.) After the Stiff Bite sets, the patient opens while your fingers retain the impression on the opposing arch (Fig 2). It is important that the tray remain in the mouth, not yet removed. Removal and re-seating is prone to re-seating errors. The impression surface is spray washed and dried while in the mouth. Using an auto mix tip, First Quarter Light VPS is syringed onto the Stiff Bite VPS in the prep areas and adjacent areas (Fig 3). There is no need to syringe Light VPS directly onto the teeth; that procedure tends to trap bubbles. The patient closes fully and forcefully, thereby exerting hydraulic force on the Light impression material. The Light flows and follows the path of least resistance, first flowing subgingivally since the periphery is sealed by the Stiff Bite. Typically the Light flows even past the margins (Fig 4). The excess then flows out the periphery. Again, blood is displaced form the teeth so there is no need to wash it off! It is ideal to hold your hand on the patient's chin and masseter muscle while the Light polymerizes to avoid patient movement. After the initial forceful closure, the closure need not be forceful but it must be steady. If you are using First Quarter Light, the patient can open in 1 min, 30 sec. You have the impression.

Fig 1	Fig 2	Fig 3	Fig 4

Now a word of warning: There is a small percentage of dentists who simply can't get the H&H technique to work. There is a large percentage who say that it is the best and most accurate technique ever (I am in that group). Proper die spacing is the critical difference; you need about 40 microns in the area backed by the Stiff Bite, that is the supragingival areas. I presume that the Light wash elastically displaces the Stiff Bite and when the impression is removed from the mouth, an elastic rebound occurs to create an undersized die. In the subgingival margin areas, there seems to be no need for die spacing since presumably there is no significant elastic distortion in that area. Therefore the 40 microns of die spacer is used on the die in the areas corresponding to the Stiff Bite backing and away from the margins. J Morita's PerfectimTM removable die spacer seems ideal for this application. It can be removed from the die after the crown is completed and the margins of the restoration checked on the die.

Since I don't want die spacers applied to margin areas, I reserve H&H for subgingival margin impressions. (For supragingival margins, simultaneous use of First Quarter Monophase on the tray and First Quarter Light on the tooth, the Light dispensed thru Danville's exclusive needle on an automix tip, will give you the same blazing speed and accuracy.)

Some problems that lead to bad results are worth mentioning: not forming enough Stiff Bite around the prep (Stiff Bite must have rigidity to resist the elastic distortion of the Light wash); use of VPS putty (its durometer reading is too low) rather than Stiff Bite; and undetected patient movement during the closed bite. However, the most common problem is improper die spacing.

Now this may seem obvious but apparently not to at least one: never use Stiff Bite in a rigid metal tray; such a hard and stiff VPS can lock into undercuts! Also note that H&H is strictly a closed bite technique. Severe undercuts (such as a bridge) should be blocked out; I often use Surgident Periphery wax to accomplish the blockout.

Laboratory procedures for closed-bite impressions

Unfortunately dental labs often have problems dealing with closed bite impressions, whether or not they are taken with the H&H technique. A recent Quintessence paper reads: "Technician not keen on combined arch system", "required time consuming adjustments" , and "time-consuming technique" (Quintessence Inter 2001; 32:805-810). These comments signal a resistance to using an unfamiliar laboratory procedure. For this reason, I have posted complete lab instructions in the previous newsletter edition. See Newsletter, Issue 23, New Year 2002, below.

First composite increment: flowable composite

Use of flowable composite as a first increment has become an almost standard procedure. Hannu Laamanen and yours truly published the technique in 1999 (Quintessence Int 1999; 30:419-422). We found that flowable composite adapts to the preparation far better than condensable composites, a "sure-fail" proposition. I prefer to use a low viscosity, "runny", flowable composite such as Starflow or Tetric Flow for the first increment of composite. (Starflow is stronger, Tetric Flow is more radiopaque.) Low viscosity helps assure a well-adapted first increment. It is known that all composites "shrink toward the best bonded surface". If the only bonded surface is the gingival margin, it's obvious what the composite shrinks toward (Fig 5). Many lecturers have expressed concern that flowable composites shrink too much compared to conventional composites. This is only half of the pertinent story. The other half is elastic modulus, usually ignored. Basically what should concern us is the stress placed on the composite to tooth interface as a result of polymerization shrinkage. Stress is determined by the shrinkage multiplied by the elastic modulus, known as Hooke's Law. Fortunately with flowable composite the elastic modulus goes down as the shrinkage percentage goes up, about equalizing the bond stresses for conventional and flowable composites. In other words, increased polymerization shrinkage is irrelevant to interface integrity! Now let's consider a real problem encountered in use of low viscosity flowables, bubbles.

Fig 5

Bubbles in a flowable composite primarily result from air originating in the needle tip. Air in the needle can "float" on the composite if the syringe is placed horizontally. Think of what happens when a bottle of wine turned on its side. The solution is to push out the air (Fig 6) before allowing it to float in the syringe. Storing the syringes vertically is a further safeguard to prevent the air from entering the syringe (Fig 7). (Thanks to Tom Hughes, our guest speaker on the Cruise, for that idea. )

Fig 6	Fig 7

Post/ Core - bonded throughout

While there are many methods and materials that can be used for bonded post and core, here is my most frequently used procedure. This is a popular topic in the seminars these days.

It is my belief that the post should have a tapered cross section to gradually dissipate stress. Additionally a taper prevents the hydraulic forces that can result from blunt-end posts inserted into viscous resin, causing root blowouts. I want the radiopacity to be as high as possible (Fig 8). I want the elastic bending to mimic that of dentin but the lengthwise stiffness to be greater than dentin. In other words, I want it to bend but not stretch. There should be no stress raising notches or slots. These properties best describe Carbotech's Snowpost, a pre-silanated, zirconia-silica fiber post (Fig 9). It is marketed by Danville in the USA and Canada. In Fig 8, Snowpost is shown in the center along with two competition posts. Note the blunt end on the post to the left and low radiopacity in the tapered post to the right.

The dedicated Snowpost reamers are slightly oversized so the reamer, marked with a silicone endo ring for length, can be the "try-in post", preventing contamination of the actual Snowpost's silanated surface. Here is the procedure based on using Snowpost.

Fig 8	Fig 9

Loose fitting post

1. Etch the canal with liquid phosphoric etchant (gel is too difficult to wash out).
2. Wash with water, preferably using a blunt needle endo syringe.
3. Dry with air and perhaps paper points. (Need not be bone dry if you use Photo Bond in the next step.)
4. Place Clearfil Photo Bond in the canal, a small or mini Microbrush is a handy delivery tool. There is no need to light cure the Photo Bond since it is dual cure and cures fine in the dark in about 5 minutes. Air thin the Photo Bond or remove excess with a paper point.
5. Mix and place Starfill 2B (a runny, dual cure composite) into the canal with a Centrix needle tip.
6. Coat the Snowpost with Photo Bond and insert it into the canal. You should have at least 1 minute working time to insert the post.
7. Wait for the Starfill 2B to self cure for optimal shrinkage, around 2 minutes (this is not critical), and then light cure the post area after the 2B jels.
8. Clearfil Photo Core makes a very nice buildup; just sculpt it against the 2B and the post, and then light cure. Photo Core will cure at least 7 mm deep with a good light in 30 seconds time. If you choose to use DenMat's Core Paste or Clearfil self-cure Core rather than Photo Core, they are compatible with all the previously placed materials. For speed, I prefer the Photo Core.
9. Prep after the core material has cured.
10. 
    

Tight fitting post

1. Etch the canal with liquid phosphoric etchant (gel is too difficult to wash out).
2. Wash with water, preferably using a blunt needle endo syringe.
3. Dry with air and perhaps paper points. (Need not be bone dry if you use Photo Bond in the next step.)
4. Place Clearfil Photo Bond in the canal, a small or mini Microbrush is a handy delivery tool. There is no need to light cure the Photo Bond since it is dual cure and cures fine in the dark in about 5 minutes. Air thin the Photo Bond or remove excess with a paper point. Use of Photo Bond rather than ED Primer will allow a far greater working time for the next step, Panavia F.
5. Mix and place Panavia F (a thin, dual curing composite adhesive) into the canal with a Centrix needle tip.
6. Coat the Snowpost with Photo Bond and insert it into the Panavia F filled canal. You should have at least 1 minute working time. Some Panavia F should extrude, insuring complete fill.
7. Wait for the Panavia F to cure some for optimal shrinkage (this is not critical), and then light cure the post area.
8. 
   

Now proceed to build the core as in step 8 above.

Tempting as it seems for its tremendous bond strength, use extreme caution in selecting SE Bond for use in canals since it is a light cure only and you can not light cure it well in the canal. Even if you can light cure it, it is NOT compatible with self-cure core pastes (contrary to what CRA says, in my opinion.) SE is compatible with light curing Photo Core, so you may use SE Bond if you are positive that light will fully penetrate the Photo Core to reach all of the SE Bond. It is NOT sufficient to cure the SE Bond before you place the Photo Core, light must penetrate all the way to the SE Bond through the Photo Core. (The explanation, too long to print here, is in the current seminars.) There is some interesting research in Italy that shows Photo Core in a canal can be cured by light curing down a light transmitting post. If you want to try that technique, Danville's SnowLIGHT post would be a logical choice. SnowLIGHT has an epoxy bonder rather than Snowposts' composite. Otherwise the posts are similar.

Bonded matrix bands?

One problem with Clearfil bonds, my favorites, is that they all adhere to metal matrix bands, making their removal difficult. Don't even think about burnishing the band or worse, sandblasting the band surface. If you do you will have created a new class of stainless steel reinforced composite! Thankfully there is a new tool to greatly facilitate matrix removal: the MegaGrip forcep (Fig 10). It sure makes the competitive products look and feel wimpy! MegaGrip can be ordered from any Danville dealer such as Tin Man (800) 554-6394.

Fig 10

Think Adhesion!

The following case nicely illustrates what adhesion can do to conserve tooth structure. I calculate that retention from 1 mm2 of bonded surface is equivalent to about 3-4 mm of cemented crown ferrule. Recognizing the potential of adhesion, this case was restored with zero invasion, I utilized pure adhesion to restore vertical dimension. The lab marking of the margins on the casts are shown below (fig 11).

Fig 11	Fig 12	Fig 13

The vertical dimension was first tested with a hard splint (Fig 12). Gold was bonded to the 2nd molars, the rest were restored with feldspathic porcelain on the anteriors and IPS Empress on the posteriors (Figs 13, 14 and 15). Excellent esthetics in the anterior region was achieved with minimally invasive preps (Fig 16 and 17).

Fig 14	Fig 15	Fig 16	Fig 17

We have learned that incompletely seated restorations are the sole cause of bite pressure sensitivity. I will quote Gary Unterbrink (our last guest speaker): "If the prep has retention form, it is probably wrong!" What Gary is talking about is the potential space created under a restoration when it does not fully seat. It is clear that creating a prep without retention form would help preclude incomplete seating. The composite bonding agent shrinks during polymerization, bringing the restoration closer to the tooth, rather than creating an internal gap.

Special thanks to Dennis Mihalka for this tip. Apparently certain green prophy pastes such as Nupro can cause a DIAGNOdent reading. I will quote Dennis: " One can smear the finest film (not seen with human eye) on a paper tray cover and it will still read very high. If by chance Nupro mint is used, I do not even bother to use the DIAGNOdent. It will cause you to believe cavities exist and will waste an appointment or worse, waste a virgin tooth."

Suspecting problems related to products with green color, I looked at Caries Finder G (green) and to learn exactly what a trace of the green does to the DIAGNOdent readings. Even when it was washed off both healthy enamel and dentin, I got false positive DIAGNOdent readings. This needs some further investigation so for now, be cautious in using DIAGNOdent and any green colored dental product.

Last year, 2001, was a year most of us would prefer to erase, at least in part. On Sept 11 Mary and I were in Perth, Western Australia, about to begin a seminar. When I reached outside our hotel room door to get the morning paper, I was greeted with headlines "America at War". Somehow we managed to do the seminar but I can tell you positively that the Aussies were as shocked as we were and all of us were quite distracted that day. A week later it was quite heartwarming to see flowers lining the steps of the American Consulate offices in Sydney, Australia.

We had actually planned a sabbatical time last fall, perhaps a fortuitous move. Our seminars were well attended and well received last year. We noted remarkable numbers of new attendees joining our "regulars". It sure is nice to be able to tell the newbies that they can seek reassurance from one of the regulars that the concepts taught do in fact work as stated. Several of our regulars mentioned, after missing a couple of years, how far behind they felt. Those comments gave me the idea to print here some of the seminar handout pages so that you can determine if you are current. I selected the day 1 series on posterior composite and from day 2, a new series on lab use of closed bite impressions. The wet field, even blood wet, stringless, H & H impression technique was a big hit this year. This is a concept taught to me by Jeff Hoos of Connecticut. The lab procedure given optimizes this technique. You can get the details of H&H at www.dentalexplorations.com, Jeff's web site.

Mary and I are increasingly booking seminar venues that are in very "civilized" locations. For example, New Zealand in May. New Zealand is one of our favorite places and quite a bargain these days due to the favorable exchange rate. (Mary, can we afford to go home?) Even the airfares to New Zealand are quite reasonable. There are two Hawaii venues in July, one in Princeville on Kauai and one in an almost secret bit of paradise, Ko Olina, near Honolulu. Both are world-class properties. The room rate we negotiated at Ko Olina is the best deal I have seen in a long time.

Also at Yosemite, one of our most popular venues, on November 7-9 we are very proud to present Dr. Gary Unterbrink of Austria. Gary is back by popular demand. He will be covering indirect restorations following his superb presentation on direct resins two years ago. If there ever was a guy who can think outside the box and back it up with science, this in the guy. Absolutely tops. Don't miss it. These Yosemite seminars attract many of the best dentists we know. It's a great place to relax and meet some of your finest colleagues, mostly top Bondodontists. Yosemite is great in all seasons (except perhaps in summer when it is too busy). We have a very civilized schedule, Thursday and Friday afternoons and Saturday morning. I suppose that is why we sometimes sell out as far as 6 months in advance!

Let's all look forward to a super 2002.

Sincerely,
Raymond L. Bertolotti DDS, PhD

Here is the current procedure for posterior composites, using the "bite-formed" technique. This is in the Day 1 seminar. At the end, there is a quiz to test your knowledge.

"Bite-formed" posterior composites

1. Cut conservative prep, using Caries Finder or Caries Detector to guide prep and caries removal. (fig. 1)
2. An optional but desirable step is to use air abrasion to clean and roughen the prep after caries removal. (fig.2)
3. Apply SE Prime to dry or damp enamel and dentin for 20 seconds. This is a minimum time, longer is OK, agitation improves it. (fig. 3) Take care to be sure that the occlusal margin remains wet with SE Prime.



Figure 1

Figure 2

Figure 3

4. Air dry only (no wash). (fig. 4)
5. Apply SE Bond (fig. 5), "wicking" off excess with a dry Microbrush to avoid radiolucency (fig.6).

Figure 4

Figure 5

Figure 6

6. Light cure . (fig. 7)
7. Place Danville long or short Contact matrix. Wedge if margin needs to be closed. It usually is best to invert the wedges, "apex down". When placed upward, the apex tends to distort the contour of the matrix. Check that centric occlusion is possible and adjust matrix height if necessary. If using a rubber dam, be sure matrix does not extend above marginal ridge to allow for CO closure (fig.8). Add the Danville Contact ring. The converging tines (fig. 9) of the Danville ring allow placement above the wedge with good retention.

Figure 7

Figure 8

Figure 9

8. Apply a thin coat of light cure flowable composite (Starflow or Tetric Flow recommended) with needle tip to cervical margin. (fig. 10) Light cure. (fig. 11) Then add flowable composite to all dentin, and on the matrix up to near the contact. Light cure again.
9. The ring may be removed now or later, after the final composite increment is placed. The matrix has been stabilized by the flowable composite. Place light cure posterior composite (such as Heliomolar, Charisma, AP-X, Herculite, etc.) slightly overfilling, taking care to insure all margins are covered. (fig. 12) (One increment will suffice after the cured flowable, except in very large or deep preps. Clearfil Photo Core is a nice intermediate material for big increments.) Do not cure yet.

Figure 10

Figure 11

Figure 12

10. Apply Danville Liquid Lens to the occlusal surface of the composite (an air block and separator). (fig. 13)
11. Remove Contact ring (and rubber dam if one is used) if it was not already done.
12. Have patient bite into CO (fig. 14), then open. While in CO, it is sometimes possible to trans-enamel cure from the buccal. (fig 15) The bite will establish the occlusion, leaving only composite flash.

Figure 13

Figure 14

Figure 15

13. 13. Light cure from occlusal. A "soft start" with the curing light tip about 1 inch away decreases stress in the composite.
14. 14. Remove the matrix band. It is often helpful to bend the matrix away from the composite before attempting to remove it. Normally a hemostat will be required to sufficiently grip the matrix. (fig. 16)
15. 15. Finish and polish. Very useful diamonds to define grooves are "Top Spin" diamonds that resembles an acorn amalgam burnisher (fig. 17). For final polish, I prefer Astropol (Vivadent) cups and points.
16. 16. Option: Etch occlusal with liquid (not gel) phosphoric acid, wash, dry, Fortify (Bisco), cure.
17. 17. The restoration is now complete. (fig 18)

Figure 16

Figure 17

Figure 18

Test your understanding of the above:

While the above procedure works beautifully if you follow it cookbook style, here are a few questions (Q) to test your true knowledge. These answers (A) would be part of a typical program. (Answers follow questions, at end).

A1. Air thinning tends to over-thin the SE Bond on the occlusal while not removing puddles deep in the prep. The overthinning reduces bond strength and the pooling leads to radiolucency.

A2. Starfill 2B works fine so long as you thoroughly cure through it to get light to the SE Bond. If you anticipate not being able to get light through the 2B, my recommendation is to abandon SE Bond and switch to the dual-curing version, known as Liner Bond 2V. Another possibility is to switch to total etch followed by MicroPrime and then dual-curing Photo Bond prior to the 2B.

A3. Sometimes not at all. If the matrix is closed at the gingival and you plan to use a low viscosity flowable composite, there is no need to wedge since Danville (as well as Palodent, but not the 3M/Garrison and Hawe-Neos) rings provide more than sufficient tooth separating forces.

A4. The apex is down so as to avoid disturbing the contour of the Contact Matrix. Remember that the Contact Ring separates the tooth, the wedge only serves to close the gingival margin. A large gutta-percha point will often close an open matrix without disturbing a contact.

Laboratory procedures for dual-arch impressions

The dual-arch impression technique is documented to work well. A recent paper reviews previous literature as well as validates a new impression material.1

In my estimation, the real problem with utilization of the dual-arch technique is the laboratory treatment of the impression. Indeed the referenced paper prints comments received from technicians such as "Technician not keen on combined arch system" and " Time-consuming technique". These comments obviously signal a paradigm shift to an unknown technique. I offer the following method based on over 20 years experience with dual-arch impressions, thousands of them. It is faster and more accurate than any separate arch impression technique that I have ever utilized.

The most important point is that the opposing models be poured but not be separated from the closed bite impression (fig 1) before being mounted in an articulator. The objective is to utilize the bite registration as well as the impressions recorded on both sides of the tray.

Figure 19

Figure 20

Figure 21

Sometimes I pour the impression myself so I can check the casts and sometimes I leave it all to the lab. I prefer to pour the prep side first (fig 2), dropping a "twin pin" into the stone, in alignment with the prep. I drop in two more twin pins in adjacent areas of the impression, parallel to the first pin, just in case I need to separate those parts of the model. (In the illustration, only one additional pin is shown since the prep tooth is the most distal tooth.) After the first pour sets, I pour the opposing side and mount the poured impression in the articulator with the same mix of stone (fig 3). Finally, after the second mix sets, I close the articulator over the initial stone pour and pins (that initial stone surface having been lubed with hand soap as a separator) and make the final stone pour (the yellow stone in the illustration) (fig 4). Note that the two casts have not yet been removed from the impression - this is the key to accuracy in bite registration (fig 5). Now that the case is mounted in the articulator, I use a die saw to cut the pinned cast and lift out the pin die (fig 6).

Figure 22

Figure 23

Figure 24

If the lab separately pours each side and then attempts to re-use the impression to articulate the casts, articulation errors occur frequently. The usual result is "high" occlusion since the casts have not been fully reseated. (If your lab work arrives with remnants of sticky wax or if the impression is cut into a "bite registration", the chances are your lab does not understand the concept of closed bite articulation.)

Some labs are further concerned that the impression in a rimless tray is too flexible and will distort upon pouring with stone. If this is a concern, just support the impression on a wadded up paper towel for support during the initial pour. Years of experience have shown that this supposed distortion is not a problem.

Disposable metal closed bite trays (such as Temrex and Clinician's Choice) should be avoided since the metal, unlike plastic, often permanently distorts during removal of the first pour casts and thereby distorts the impression which precludes accurate second pours.

I suggest these lab supplies: Twin pins with Sleeve (cat #177-5889) and chrome spring articulator (cat# 356-8982), Zahn Dental. Zahn Dental is the laboratory branch of Sullivan-Schein, USA.

Reference

1. Burke FJT and Crisp RJ. A practice-based assessment of the handling of a fast-setting polyvinyl siloxaine impression material used with the dual arch tray technique. Quintessence Int 2001;32:805-810.

Proper use of die spacer prevents sensitivity!

Now that we have captured the information in the impression, let's look at another lab problem. That is the use of block out materials on the occlusal floor of the die. I learned about this one from Dr. Gary Unterbrink, the speaker scheduled for Yosemite this November. (Don't miss Gary, this will be one of our very best seminars.)

Let's recall that all composites shrink during polymerization. Shrinkage occurs toward the best (strongest) bonded surface; in most cases this surface is the restoration rather than the tooth. The more the composite thickness, the more the stress placed on the bonds by the shrinking composite. It follows that the use of block out on the occlusal floor could result in a sealed-in space adjacent to the pulpal floor, the area where the bond is most easily broken. We already know that a similar sealed-in space is the source of post-op sensitivity to bite pressure for direct posterior composites. We must avoid this sealed-in space since bite pressure would hydraulically move fluid in dentinal tubules intersecting this space. The remedy is to have indirect restorations "bottom out" on the pulpal floor.

Gary Unterbrink correctly places highest priority on the gingival margin since that is a frequent source of clinical failure. No spacer is used in the gingival area. Note that several layers of spacer are placed on the vertical walls up to and over the occlusal margin.

Again, as with closed bite impression technique, we need to work closely with the labs. It will take a bit of convincing to get the lab to assure bottoming out of the inlay/onlay even if quality of the occlusal margin is compromised.