Bite Point

Telechron Clocks and the Selfish Pursuit of Batteries

Here is a splendid Telechron clock from 1928 or so, "The Tudor" in beautiful Bakelite:

And "The Oxford," from the same era:

This is my newly acquired 1950s-era Telechron wall clock, "The Replica":

It's sixty years old and all you have to do is plug it in and it keeps perfect time. There are apparently thousands and thousands of Telechrons from the 1920s and 1930s that are in prime working order as well.

Telechron clocks, manufactured from 1912 to 1992, had their heyday from the 1920s to the 1950s. Telechrons were robust, reliable and also beautiful: most embodied Art Deco principles of design.

Telechrons employed an ingenious method to keep accurate time. Electric power in the U.S., once standardized in the Twenties, provides alternating current at 60 cycles per second: 60 Hz. In a Telechron, a synchronous motor spins at the same rate as the cycle of the alternating current that's driving it. This method ensures that the clock always keeps the correct time.

The inventor of the Telechron clock technology, Henry Warren, anticipated one significant flaw in this arrangement: if the electric power grid is used as a system for the "distribution of time," as he phrased it, then, in the case of a power failure, the clocks stop and lose their connection with the "master clock" as provided by the 60 Hz AC current from the power company. If there is a temporary power outage, after the power comes back on, the time will be incorrect. To address this issue, Warren designed his clocks with an "indicating device." This is a red dot that appears on the dial whenever the power is interrupted:

 

This red dot informs the clock's owner to reset the time. Even years ago, the correct time could be checked via telephone or the radio. Resetting the clock changes the indicating device back to white again.

Here's a beautiful working "The Acorn" from 1930s vintage:

Much of the appeal of Telechron clocks derived from the fact that early batteries were unreliable and didn't last long. Once battery technology improved in the 1950s and 1960s, people began buying battery-powered clocks in preference to plug-in models, especially in wall and mantle clock applications.

We all chose batteries in large part because we didn't want clock cords to show on our walls and mantles.

And what have we done....

We've littered the landscape and our groundwater with countless millions, perhaps billions, of used batteries that contain acids and toxic heavy metals. Heeaven only knows what this has done to crops, fish and wildlife, and even rates of cancer in humans.

Rechargeable batteries, like the one in this laptop I'm writing on, can and should be recycled. Though I wonder how "clean" a process that really is. And newer technologies are coming that will allow us to store energy at high density without employing heavy metals at all. But we've already thrown away so many disposable batteries, and caused so much damage to our world.

And part of the reason we did all that is because we don't like seeing cords on our walls. We are a self-involved species indeed.

 

A Warning to Patients About Corporate Dentistry

Yes--

Corporate dentistry's fees for a given procedure are often
less than in private practice.

But--

In corporate dentistry,
you will be seriously
over-diagnosed and over-treated.

So--

You will end up paying far more in the end.

In money.

And in your oral health.

There is No "Get," Part II.

I AM SO SICK AND TIRED OF EVERY IDIOT
WHO FANCIES THEMSELF A DENTAL MARKETER YELLING 
"GET MORE NEW PATIENTS"
AT US!!!!!

THERE IS NO "GET"!

WHAT THERE IS IS,

MEET NEW FELLOW HUMAN BEINGS
FOR WHOM WE CAN SOLVE PROBLEMS.

IN THE REALM OF THEIR ORAL HEALTH.

NOT "GET."

"SOLVE."

GET IT?!?!?!

Placing the Finest Composite Resin Restorations

Adhesive composite resin restorations in posterior teeth are superb and long-lasting at this point in their technological development--if we use the latest technology correctly. In this post I will share what I've learned about placing them with excellence. Dr. Ray Bertollotti's list of literature references will follow.

In this post I am talking about posterior teeth, Class Is, Class IIs and Class Vs, and all other clinical situations where lots of dentin is involved.

Ready?

Step One:
Use Self Etch Primers. Do not use Total Etch.

Why?
Essentially, because we get high enough enamel bonds (around 28-30 MPa) with Self Etch and the dentin bonds are exceptional--on the order of 35 MPa. And they're stable over time. They also don't vary according to how much we dry or don't dry the dentin. With Total Etch, the bond strengths vary all over the map. Mostly they're low. And with Self Etch, transudation is low to nonexistent, providing we use Prelude SE, SE Bond, or Bond Force. These are the best three Self Etch Primers on the market in 2018.

Here is a great overview reference on this topic by the renowned David Pashley:
http://www.dentistrytoday.com/materials/1483
or
http://freece.vivalearning.com/contrib/PDF/DT_freece_pashley_kuraray.20103292119456965.pdf

Also, as of 2018, do not use one-bottle Self Etch systems. Those bottles contain a lot of chemistry. Due to differential evaporation, they are not the same chemicals after two weeks as they were when you first opened the bottle. And they allow terrible amounts of transudation, which wrecks the dentin bond in minutes after it is formed. Plus, in an absurd marketing twist, the one-bottle systems take five to ten times longer to use than the two-bottle systems. What's more important--the number of bottles in your setup, or clinical chairtime?

Note: Total Etch remains preferred for all clinical situations where enamel bond strength is the main consideration, like Class IIIs and Class IVs in anterior teeth.

Step Two
Work in a Surgical Operating Microscope

Microscope dentistry is defect-free dentistry. Cost considerations may dictate loupes, but make that a temporary situation. As soon as you can, obtain a Microscope.

Step Three
Use Ozone
Ozone gas kills bacteria by fracturing their cell walls. They burst open, lyse and die. This is thorough and instantaneous. What may matter most is that ozone, being a gas penetrates farther into the dentin tubules than anything else we have at hand. For instance, while Self Etch Primers do kill bacteria their effects on dentin run 10 microns deep. Chlorhexidine presumably kills a percentage of bacteria on the dentin surface only.
Ozone likely kills a high percentage of bacteria several millimeters into the dentin.

Step Four
Use flowable composite in the first layers of your fill.
Build up the flowable in thin layers.
Build up the flowable in flat layers, not banked.
Cover the dentin in flowable first, without letting it touch the enamel. Then layer it on up to the enamel walls.

In these images from the remarkable DDS GP app, I've added the flowable composite in beige. The white represents the packable posterior composite.

In our office our flowble is StarFlow from Danville Engineering. StarFlow is a submicron particle size low viscosity flowable composite Our packable is currently Filtek. Note how the increments are small. Working in the Microscope, I place several thin layers of flowable in large Class IIs.

Composite resin compressive strength is related mainly to particle size, not fill ratio. Flowable composite with small particle size has the same compressive strength as standard posterior composite.

When cured, composite resin shrinks towards the best bonded surface. That's why we want to bond to flat surfaces. Flat surfaces bond best. Every bump creates the potential for gaps between the resin and the hybrid layer.

 

Layering of composite resin can be done in flat increments or banked. Which creates the least polymerization stress? The answer might be, "it depends."

Keeping in mind that composite resin shrinks towards the best bonded surface not towards the light--

On the one hand a banked resin increment has a "corner." If the resin pulls away from that corner upon polymerization, a void will occur. On the other hand, a flat resin increment in a Class I prep has no less than thirteen sides, if it's in a plus-sign shape typical of molar occlusal restorations.  That's a lot of force vectors, as the material polymerizes.

On balance, banked resin increments are probably generally best.

Make Heavy Occlusal Adjustments With Water Spray

Heat at the tip of the bur is reduced, and debris is carried away faster. Once you get it close, go dry.

Polish Well, But Don't Polish Aggressively

Once again, it's a matter of heat. Be gentle, yet get those surfaces smooth.

Some final notes:

Post-operative sensitivity is less with Self Etch Primers than with Total Etch. In fact, in my experience, barring frank irreversible pulpitis, sensitivity does not exist with Self Etch Primers. This is because we do not remove the smear layer on the dentinal surfaces, we just modify it. We create a chemical bonding with the partially demineralized dentin surfaces through Hydroxyapatite. Further, the hybrid zone penetrates precisely as far as the etching effects, and the dentinal tubules remain plugged.

Also the shelf-life of Self Etch Primers (two-bottle!) is longer than that of Total Etch products.

Strong acids will ruin the effects of Self Etch Primers! Self Etch Primers employ weak acids to create their hybrid layers. The 37% phosphoric acid that we use in Total Etch will etch the dentin too deeply and thoroughly to allow the Self Etch Primers to work properly. The smear layer will have even been rinsed away, and that's an integral part of the Self Etch bond. On the other hand, pre-etching enamel does increase the bond strength of Self Etch Primers. Even this can be dangerous: there is evidence that even if a gel is used with careful enamel-only placement, it etches the dentin as it is rinsed away. What to do? If enamel etching is desired it can simply be done before the prep starts at all. While waiting for anesthesia to take effect, perhaps.

Hemodent and other vasoconstrictors designed for use in subgingival cords are also highly acidic. In fact, they have a lower pH than phosphoric acid etchants. This will interfere with the bonding from Self Etch Primers. Use Visine instead--it stops bleeding, but has a neutral pH.

Handpiece oil interferes with Self Etch Primers. Run your handpieces first, which is a good idea in terms of obtaining a clean water spray anyway. If oil contamination occurs, alcohol on the prep will eliminate it, as will a light sandblasting.

*****

Here are references from Dr. Ray Bertollotti's current lectures. If we don't know the literature, we can't solve problems for our patients properly.

His website, by the way, is www.adhesion.com

 

Selected references
1. Pulp reactions to different preparation techniques on teeth exhibiting periodontal disease. Zollner A and Gaengler P, J Oral Rebibil. 2000 Feb;27(2):93-102. The severity of endodontal reactions depends more on remaining dentin thickness than on the type of preparation.

 

2. Biocompatibilty of Clearfil Liner Bond 2 and Clearfil AP-X system on nonexposed and exposed primate teeth. Akimoto et al, Quint Inter 1998; 177-188. There was no difference in pulpal inflammation between Clearfil Liner Bond 2 / AP-X and calcium hydroxide controls in either class V or class I cavities at various time periods.

 

3. Contraction stress of flowable composite materials and their efficacy as stress relieving layers. Braca RR, JADA 2003:134:721-728. There was no significant difference in stress on the bond between flowable and non-flowable composites. Microfills produced lower strain than conventional fills (both flowable and non-flowable.)

4. Bite-formed posterior resin composite restorations, placed with a self-etching primer and a novel matrix. Bertolotti RL and Laamanen H, Quint Inter 1999; 30:419-422. This procedural paper focuses on tight and anatomically correct contacts, post-operative sensitivity, occlusion, and clinical efficiency.

 

5. Factors and prevention of pulp irritation by adhesive composite restorations. Fusayama T, Quint Inter 1987:18:633-641. A classic paper which explains why insufficiently adhesive bases lead to post operative bite-pressure sensitivity.

 

6. Glass-ionomer cement restorations and secondary caries: a preliminary report. Mjor IA, Quint Inter 1996:27:171-174. The clinical diagnosis of secondary caries is the most common reason for failure of glass ionomer restorations in a survey from general dentists. Glass-ionomer did not survive as long as composite and amalgam restorations.

 

7. An in vivo evaluation of hemorrhage control using sodium hypochlorite and direct capping. Hafez AA et al, Quint Inter 2002;33:261-272.
Normal soft tissue reorganization and dentinal bridge formation were observed in 86% of pulps treated with sodium hypochlorite and All Bond 2 /composite or One Step / compomer. Good review of Dycal research.

 

8. Adhesive monomers for porcelain repair. Bertolotti RL et al, Int J Porosthodont 1989; 2:483-489. Adhesion strengths to many surfaces are reported and protocols are given for intraoral porcelain repairs.

 

9. Adhesion monomers utilized for fixed partial denture (porcelain/metal) repair. Bertolotti RL and Paganetti, Quint Inter 1990;21:579-582.
A fractured “solder joint” in a 10 unit bridges is repaired intraorally. Surface preparation techniques and adhesive materials are discussed.

 

10. Intraoral metal adhesion utilized for occlusal rehabilitation. Bertolotti RL et al, Quint Inter 1994;25:525-529. An occlusal rehabilitation is completed with adhesion and minimal to zero invasion. Illustrated is gold to gold adhesion and the necessary intraoral procedurtes.

 

11. Fatigue span of porcelain repair systems. Llobell A et al, Int J Pros 1992;5:205-213. Only All Bond and Clearfil Porcelain Bond did not fail before reaching the 2,000,000 cycle test limit. “Clearfil Porcelain Bond (uses no HF) undoubtedly appears to be the simplest system to use”.

 

12. Two unit cantilevered resin-bonded fixed partial dentures. Botelho et al.;Inter J Pros 2000;13:25-28. Found good results with cantilevered adhesion bridges, bonded with Panavia and using Yamashita prep design.

 

13. Fracture load and mode of failure of ceramic veneers with different preparations. Castelnuevo et al, J Pros Dent 2000;83:171-180. Found strongest veneer to have 2 mm of unsupported incisal porcelain and butt joint on lingual (lingual chamfer did not add strength). This paper is reprinted in the Calif Dental Journal, Feb 2004.

 

14. Bonding of glass infiltrated alumina ceramic: Adhesive methods and their durability. Kern M and Thompson VP, J Pros Dent 1995;73:240-249.
Neither HF etching nor adding silane resulted in adequate bond to Inceram. Two methods worked: Panavia and Rocatec (presumably also CoJet would work).

 

15. The effect of a “Resin Coating” on the interfacial adaptation of composite inlays. Jayasooriya PR et al., Operative Dentistry 2003; 1 28-35.
Looks at "immediate dentin sealing" and the resulting effects on gaps between restoration and tooth.

16. Longevity and reasons for failure of sandwich and total-etch posterior composite resin restorations. Opdam NJM et al., J Adhes Dent 2007; 9:469-475. Class II composites placed with resin modified glass ionomer lining showed more frequent fractures than fillings place with total-etch technique (SA Primer and Photo Bond). Survival rates at 9 years: 88.1% for total etch, 70.5 for RMGIC lining.

 

17. Factors contributing to the incompatibility between simplified step adhesives and self-cured or dual-cured composites. Part II. Tay F et al; J Adhes Dent 2003;5:91-105. Shows pulpal fluid permeability through adhesives and how it affects composite/adhesive compatibility.

 

18. Nightguard vital bleaching of tetracycline stained teeth: 90 months post-treatment. Leonard RH et al, J Esthetic Restorative Dent 2003;15: 142-153. Some very good results for extended (6 months) bleaching times. Good list of references on bleaching.

 

19. Effect of three adhesive adhesive primers for a noble metal on the shear bond strengths of three resin cements. Yoshida et al, J Oral Rehab 2001;28:14-19. Tested Panavia F and Bistite with Alloy Primer or Metaltite primer. Generally Metaltite performed better, both with Bistite and with Panavia F.

 

20. A clinical evaluation of adhesively luted ceramic inlays. Högland C, van Dijken J, Olofsson AL. Swed Dent J 1992;16:169-171
Adhesive much lower fracture rate than GIC.

 

21. Immediate dentin sealing supports delayed restoration placement. Magne P et al., Journal of Prosthetic Dentistry 2007:98(3):166-174. Control (C) specimens were prepared using an immediate bonding technique and direct composite Z100 restoration. Immediate dentin sealed (IDS) teeth had provisional restorations (Tempfil inlay) placed for 2 weeks (IDS-2W), 7 weeks (IDS-7W), or 12 weeks (IDS-12W) before restoration placement. (Final bonding procedure used sandblast and more bonding agent.) Delayed dentin sealing (DDS) used an indirect approach without dentin prebonding. Both C and IDS-2W groups demonstrated interfacial failure that was typically mixed with both areas of failed adhesive resin and areas of cohesively failed dentin while IDS-7W and IDS-12W failed consistently between the existing resin coating (used during IDS) and the overlaying composite resin. Failures in DDS group were all interfacial and purely adhesive. C and all IDS groups were not significantly different and exceeded 45 MPa. DDS groups exhibited lower tensile bond strength than all others.

 

22. Cumulative effects of successive restorative procedures on anterior crown flexure: intact vs. veneered incisors. Magne P and Douglas W. Quint Inter 2000;31:5-18. Showed that tooth is far more flexible (about 2X) when all the enamel is removed than when only some or no enamel is removed.

 

23. Papathanasiou A, et al. Clinical evaluation of a 35% hydrogen peroxide in-office whitening system. Compendium 2002; 23(4):335-346. A nice summary of bleaching efficacy. (Although not peer-reviewed, you will find similar conclusions in detail in CRA Newsletter issues: April 2000, and March 2003.)

 

24. Bond strength to bovine dentin over 6 years, Burrow MF et al, First International congress on adhesive dentistry, Tokyo 2002, paper S-17.
The bond strength of Amalgambond Plus (total etch) decreases over 72 months while the bond strength of (self-etching) Liner Bond 2 showed no change.

 

25. Effect of eugenol-containing endodontic sealer on retention of prefabricated posts luted with adhesive composite resin cement Tyan AH and Nemetz H. Quintessence Inter. 1992 Dec;23(12):839-44. Findings of this study demonstrated a substantial decrease in retention of posts luted with Panavia composite resin cement in the presence of eugenol. Irrigation with ethyl alcohol (ethanol) or etching with 37% phosphoric acid gel was found to be effective in restoring the resistance to dislodgment of the posts, but alcohol produced the most consistent and reliable results.

26. Clinical evaluation of a composite resin system with a dentin bonding agent for restoration of permanent posterior teeth - a 3 year study, Roberts MW, Folio J, Moffa JP, Guekes AD, J. Pros. Dent 1992;67:301-306.
Showed that composite resin restorations outperformed amalgam restorations over the period studied. Note date of publication 1992; restorations placed in 1988 with “old-fashioned“ bonding, etc.

 

27. A two year clinical study of light cured composite and amalgam restorations in primary molars. Barr-Agholme M, Oden A, Dahllif G, Modeer T, Dent. Mater 1991;(7)230-233. Showed that the success rate of class II composite restorations were significantly higher than for class II amalgam fillings in primary molars.

 

28. Resistance to cusp fracture in Class II prepared and restored premolars. Gelb MN, Barouch E., Simonsen RJ. J Pros Dent 1986;(55)184-185. While both amalgam and composite restorations may restore some strength, only etched and bonded composite restorations return the tooth to a fracture strength as high or higher than that of sound, unprotected teeth.

 

29. The effect of restorative materials on cuspal flexure. Medige J, Deng Y, Yu X, Davis EL, Joynt RB. Quintessence International 1995;(26) 571-576. Show that a amalgam is totally incapable of restoring the physical integrity of a tooth weakened by a cavity preparation, while a properly placed composite totally restores the internal strength of tooth equal to or better than that of an intact tooth.

 

30. Micro-leakage of All-ceramic Crowns Using Self-etching Resin Luting Agents. Trajtenberg CP, Caram J, Kiat-amnuay S. Operative Dentistry 2008: (33-4)392-399. Showed Panavia F to have far less leakage than Unicem and Multilink after thermal cycling. Showed results with and without spacing.

 

31. Use of a Pressure Chamber to Compare Microleakage of Three Luting Agents. Lyons KM, Rodda JC, Hood JAA. Int J Prosthodont 1997; 10: 426-433. Zinc phosphate showed highest leakage and it developed quickest, glass ionomer about 50% of this, but no microleakage with resin (Panavia 21).

 

32. Flowable resin composites as filled adhesives: Literature review and clinical recommendations. Unterbrink GL and Liebdenberg. Quint Inter 1999; 30: 249-257. Flowable resin composites were used as an adhesive over thinned single component bonds.

 

33. Do Low-shrink Composites Reduce Polymerization Shrinkage Effects? Tantbirojn et al. J Dental Research 2011:(90) 596-601. Two low-shrink composites, despite having the lowest and highest total shrinkage values, did not cause significant differences in cuspal deflection. Deflection seemed most related to the combination of post-gel shrinkage and elastic modulus. Therefore, even for significantly lower total shrinkage values, shrinkage stress is not necessarily reduced.

 

34. Cell and tissue reactions to mineral trioxide aggregate (MTA) and Portland cement. Saidon J et al. OS OM OP OR Endod 2003;95:483-489.
MTA and PC show comparative biocompatibility when evaluated in vitro and in vivo. The Portland cement was sterilized by ethylene oxide.

 

35. Direct Pulp Capping With Mineral Trioxide Aggregate- An Observational Study. Bogen, G et al. JADA 2008;;39(3)305-315. Over an observation period of nine years, the authors followed 49 of 53 teeth and found that 97.96 percent had favorable outcomes on the basis of radiographic appearance, subjective symptoms and cold testing.

 

36. The “Bottom Line” on Bleaching 2008, Haywood VB, Inside dentistry 2008: 4(2)2-6. This is an excellent summary of all bleaching techniques and their outcomes.

 

37. Porcelain laminate veneers. A retrospective evaluation after 1 to 10 years of service. Part 2- Clinical results. Dumfahrt H and Schaffer H. Inter J Pros 2000;13:9-18 Survival rate of over 90% at 10 years.

 

38. A 15 year review of porcelain laminate veneer failure – A Clinician’s observations. Friedman MJ, Compendium 1998;19:625-636. A 7% failure rate was reported at 15 years and classified as to type.

 

39. Durability of the resin bond strength to zirconia ceramic after using different surface conditioning methods. Wolfart M et al., Dental Materials 2006;23:45-50. Showed sandblasting followed by Panavia F to bond well to zirconia, far better adhesion than with Variolink II.

 

40. Influence of contamination on zirconia ceramic bonding. Yang B et al.
J Dent Res 2007, 86;749-753. Contamination that existed after try-in simulation was best removed by air abrasion with aluminum oxide. Confirmed zirconia bond with Panavia.

 

41. Influence of c-factor and layering technique on micro-tensile bond strength to dentin. Nikolaenko SA et al. Dental Materials 2004, 20, 579-585. Horizontal layers resulted in significantly higher bond strengths than did vertical or oblique layers.

 

42. Clinical reversal of root caries using ozone: 6-month results. Baysan A and Lynch E, Am J Dent 2007:20(4):203-8. Shows HealOzone to be effective on root caries.

43. Effect of ozone on non-cavitated fissure lesions in permanent molars. A controlled perspective clinical study. Huth KC et al, Am J Dent 2005: 18(4)223-228. This study presents some very important information on the risk factors for the patient, where ozone works and where it does not, in agreement with our clinical observations.

44. Assessment of the ozone-mediated killing of bacteria in infected dentine associated with non-cavitated occlusal carious lesions. Baysan A and Breighton D, Caries Res2007;41(5):337-41. This study shows that ozone is not effective when there is too much tooth structure and/or debris in the way (HealOzone used in a manner contrary to manufacturers instructions).

 

45. Clinical reversal of root caries using ozone: 6-month results. Baysan A and Lynch E, Am J Dent 2007:20(4):203-8. The results show HealOzone efficacy on root caries where there is minimal tooth structure and/or debris in the way.

 

46. The inability of Streptococcus mutans and Lactobacillus acidophilus to form a biofilm in vitro on dentine pretreated with ozone. Knight GM et al, Australian Dental Journal 2008:(4):349-353. This study showed that the infusion of ozone into non-carious dentine prevented biofilm formation in vitro from S. mutans and L. acidophilus over a four-week period.

47. Inability to form a biofilm of Streptococcus mutans on silver fluoride- and potassium iodide-treated demineralized dentin. Knight GM et al, Quintessence Int 2009:(2):155-161. Demineralized dentin disks treated with AgF and AgF/KI prevented the formation of an S. mutans biofilm and were significantly more resistant to further demineralization than the control and KI-treated disks over the experimental period.

 

EndoVac Hack to Keep its Lines Clear

(This post is mainly for the dentists in the audience, as it's about a specific technology. But anyone can read it!)

We use the remarkable EndoVac in our endodontic treatments.

The EndoVac is a combined suction and syringe that does a much better job than blunt needles at flushing the canals with NaOCl. There is a small suction tip that you actually put in the canals. This draws the NaOCl down by negative pressure, getting much more irrigant to the apex and agitating it there. And then there’s a tiny metal canula that you put all the way to working length.

Looking in the Microscope, I cannot believe the amount of debris that comes out of the canals when I use the EndoVac.

I also notice that the rotary files are working with half the effort when I use the EndoVac. Which means faster treatment and less chance of file breakage.

Studies have even shown that patients have less post-operative pain when the EndoVac is used for root canal irrigation. I find this too. Patients just don't have much pain after treatment anymore.

The EndoVac is thus a remarkable innovation, but it's also a bit of a hangar queen! What I mean is, it clogs frequently. We obturate with Resilon in our office. I found that the Smear Clear (which is necessary after NaOCl when using Resilon) crystallizes and blocks the tubing, especially at the junction with the main hub; see arrow:

I have found a hack for preventing clogs in the EndoVac. It has two parts.

(1) The Blue line comes with opaque, soft tubing, and the White line comes with clear, more firm tubing. Switch the opaque tubing out for another clear one on the Blue line. The opaque tubing is more prone to clogs, especially with Smear Clear.

(2) After each case, flush both lines with HOT water. And flush the metal irrigation canula as well. But especially flush the suction lines.

Every now and then you may need to clean that junction with a small brush as well.

The EndoVac is a remarkable device with all kinds of benefits. It takes a little maintenance to keep 'er flying though!

Gemination of Teeth

Sometimes, a tooth will geminate--branch into two as it develops in the jaw. What results is one tooth, but with a cleft in it, giving an appearance that suggests two teeth. There is a large single root and a single root canal.

In cases of gemination, the number of teeth in the arch is normal. There are no extras or missing teeth.

Geminated teeth bring out the importance of symmetry and proportion in teeth. If a tooth is wider than its neighbors, even just a little, the smile looks "off." And human teeth have specific ratios of height to width; when this ideal ratio is altered, teeth don't look right either.

Another phenomenon is fusion, where two tooth buds unite during development. There may be two entirely distinct root canals, or even separate roots. And in cases of fusion, there is one less tooth in the arch.

Geminated and fused teeth present challenges for restorative dentists and orthodontists, as it is difficult to create a symmetrical smile. Re-contouring or crowing such teeth in conjunction with orthodontics can usually resolve the issues, but sometimes extraction and implant replacement must be considered. Such treatment is aggressive, but has the advantage that an implant crown can be made to the desired size and shape.

Abutment Gone

There are no words...

Employment Advice for Recent Grads and Associate Dentists

Recent grads and young dentists, here is the framework for you to use in evaluating an employer and a practice.

What you do is ask: Which of the following two questions is the practice owner asking of their business--

"How can I grow my practice?"

or

"How can I grow my practice sustainably, and with respect for my patients?"

You will know the answer when you see it, with each and every practice at which you interview. When a dentist asks the question the first way, they may meet many new patients, but will still primarily focus on themselves and their own needs. As a result, a significant percentage of new patients will not stay in the practice long-term. (Modern consumers are smart, well-informed and generally have a powerful tendency to act in their own self-interest. And they act fast.)

When a dentist asks the question the second way, patients almost never leave, unless they move away.
How could they leave? They are being listened to.

That's how you decide with whom to associate.

Enamel Microabrasion

Recently, we started using a new technique for Enamel Microabrasion. The results are spectacular. Here is one notable case:

Enamel Microabrasion is a technique for reducing or removing internal enamel stains from teeth. Such stains can range from bright white to dark brown. This technique is not entirely predictable. The benefit however is that it reduces the need for composite resin bondings and even veneers.

Enamel Microabrasion has been an accepted technique since the 1980s. It uses an abrasive, and the same 37% phosphoric acid that we use to etch tooth enamel in the Total Etch technique. Don't worry when we say the word "acid." This stuff is less acidic than the contents of your stomach. But it creates microscopic roughness on the enamel surface. We then create a chemical and micromechanical bond to this roughened surface, and that's how we bond resin and porcelain restorations to the tooth.

That's really magnified etched enamel. Beautiful, isn't it?

Our recent tweak to Enamel Microabrasion was suggested by Dr. Ray Bertollotti. Instead of commercial products, we use our own etch that we made ourselves, combined with the 50-micron aluminum oxide powder that we use in our microetchers. OK, sandblasters. Don't worry about them either, they're small.

We do a deep polish of the teeth, just as in other forms of the technique. Gums protected by the rubber dam; eyes protected by goggles; and ears protected by making sure no one has the operatory monitor tuned to C-SPAN.

Folks always wonder "How much tooth is being taken away?" Well, studies show that, on average, Enamel Microabrasion removes 12 microns of enamel. That's twelve thousandths of a millimeter. Front tooth enamel ranges from 0.5 to 2.5 millimeters thick. Compare removing 0.012 mm with Enamel Microabrasion to a veneer, where roughly half the enamel (0.5 to 1.0 mm) is removed, and you get a sense of how conservative Enamel Microabrasion is.

Oh, and Enamel Microabrasion does an odd thing. The stain-affected teeth look better a week after Enamel Microabrasion is done than they do immediately. This has to do with how the process dries out the enamel; when it re-wets with saliva for a week or so, the stains fade even further. And Enamel Microabrasion can be combined with whitening techniques to achieve a bright and stain-free smile in the majority of cases.

Will My Dental Anesthetic Injection Hurt?

That's actually a very difficult question to answer, because there is such variation in our perception of these sorts of things. For instance, many in my family wear contact lenses, but I never will because "I can't bear the thought of sticking something in my eye." And as much as I love my opthamologist's office, having my eyes checked stresses me out a bit, whereas many folks look at an eye exam as the day-at-the-beach of medical visits.

Here's the thing. I perform local anesthetic injections the very same way each and every time. And yet there is a spectrum of patient reactions. At one end is, "I hardly even felt that!" At the other end of the spectrum, there are some patients who experience pain along with anxiety, with muscles tensing up and vocalizations too.

And yet I always do exactly the same thing in my technique.

Knowing something about that technique may help you through the process of getting numb. What we do first is apply powerful modern topical anesthetic (a gel meant for the surface) to the gums in the area the anesthesia is planned for. This provides surprisingly numb gums.

Plus, "numb gums" is fun to say out loud.

Now, before going on, let's just deal with that infamous word and get it out of the way: "needle." It's just a word, folks. Like "nutmeg" or "necktie." So, yes, we use a needle, which can be scary for some, but needles are just a way to deliver certain types of drugs to where they have to go. Until something better gets invented, it's the only thing we've got. But it doesn't have to be so bad.

What I do is to give the first drops of anesthetic very slowly. In this manner, it numbs the tissues as it's going in. The very purpose of anesthetic, numbing, works for us as it protects our patient from feeling pain from the temporary pressure increase. As we go along, I gradually increase the speed of administration so that the total time it takes to give the injection is reasonable.

Pre-numbing with topical anesthetic, and taking our time so that the anesthetic can numb as it is administered, are ways to make "the shot" as comfortable as possible. And for most patients, being numb, as stressful and annoying as it can be, is preferable to feeling the full effects of a tooth being treated.