The Operating Microscope and Ultrasonics; a Perfect Marriage

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Clinicians who make the leap to microscope-centered dentistry often make this statement: “I can’t believe what I am seeing!” With time, these clinicians then begin to question the effectiveness of many traditional therapies. Finally, microscope clinicians begin to reinvent diagnosis, treatments, protocols, and finally, instruments and materials.

In November 2003, the Academy of Microscope Enhanced Dentistry held its second annual meeting. The 120 clinicians from 4 countries representing endodontists, periodontists, prosthodontists, restorative dentists, and ceramists met to share their findings. In this and subsequent articles, I will highlight the findings of many of our colleagues who are committed to microscope- enhanced dentistry.

Generations of dentists have struggled to visualize and treat certain areas of the mouth. In many situations, the operating microscope and ultrasonics together have suddenly overcome this major hurdle. The goal of this article is to introduce restorative dentists to the versatility and power of ultrasonics when combined with the operating microscope (Figure 1).

 

Figure 1. Ultrasonic unit with both endo/restorative and periodontal scaling attachments paired with the author’s 9-year-old, 6-step operating microscope.

 

One of the unfortunate patterns in dentistry is that each specialty tends to stay within its group. One result is that restorative dentists are often out of touch with endodontists, ceramists, periodontists, and so forth. A prime example is the role of ultrasonics in endodontics and endo-restorative. An informal survey of the top microscope vendors suggests that only 65% of endodontists own microscopes and only half of that number use microscopes routinely. However, nearly all endodontists own and use ultrasonics in daily practice. Most general practitioners are unfamiliar with the role of ultrasonics in an endodontic specialty practice or a microrestorative practice. Restorative dentists would do well to spend a day in an endodontic practice that is microscope-centered.

This article presents 4 case reports that showcase how ultrasonics are uniquely suited to the visual precision and ultra-conservative tooth preparation that are integral to microscope enhanced dentistry.

 

CASE 1

The patient presented with a long-term (20 years) composite buildup on her left central maxillary incisor (Figures 2 and 3). A portion of the enamel had recently fractured. The patient was leery of any treatment because she understood that the last dentist severely weakened the tooth when struggling to find the root canal system. Although the composite had held up until now, it would not serve well as a post/core.1 In this case, a 3-dimensional (3-D) endo-restorative casting2 would be the optimal foundation for a porcelain crown.3 The challenge would be to gain access without perforating or further weakening the root.

 

   
Figure 2. Preoperative radiograph of case 1. There are many poor choices to restore the case that involve prefabricated posts. Option one is a post that would be large in diameter and short in length. Option two is a narrower diameter, longer post that would not engage the coronal half of the root. Option three is a large diameter, longer post that would require extensive and perilous enlargement of the apical half of the root. Any prefabricated post in this case would lack stability and require further dentin removal. Figure 3. (Case 1) The left central incisor must be addressed before proceeding with aesthetic reconstruction of the maxillary arch. While extraction and replacement with implant, crown lengthening, or orthodontic extrusion are all options, none are as predictable in maintaining gingival aesthetics as the endo-restorative casting. 

 

After a lengthy discussion and a 30-minute Microsoft PowerPoint presentation regarding the miracle of the microscope and ultrasonics, the patient agreed to proceed. A comprehensive plan for aesthetic reconstruction was explored and agreed upon. However, everything hinged on our ability to provide an exquisite result on tooth No. 9.

As I initially accessed the tooth (Figure 4), the traditional handpiece began to obstruct my view with the microscope. As I prepared deeper into the tooth, the head of the handpiece created worsening vision impairment. In Figure 4b, note that the dentin and composite are indistinguishable. When I switched to the ultrasonic, the vision improved dramatically (Figure 4c). More light was able to enter the root. An added and critical visual aid was now brought into play; the vibrating CPR-2D ultrasonic tip (Obtura/Spartan). It leaves gray streaks (Figure 4d) that clearly indicate the presence of composite, not dentin. What a relief! Before the microscope and ultrasonics, this was a thankless and stressful task that could easily end in catastrophe. It has now been transformed into a safe and stimulating procedure.

 

Figure 4a to 4d. (Case 1 continued) Deeper into the tooth, magnification is increased from 8X to 12X to 16X. Burs are problematic when compared to ultrasonics e.g., the rotation can cause the bur to spin away from the harder composite and gouge the softer dentin. Another limitation is that the head of the handpiece blocks light and micro-visualization. Also, there are no gray streaks created that guide in selective removal of composite. Note how the ultrasonic approach (4c and 4d) is superior.

 

I then alternated using surgical-length round burs in a slow-speed handpiece and the ultrasonic. The current generation of ultrasonic tips is less effective than traditional burs at end-cutting through restorative materials. Soon, the chattering action of the ultrasonic loosened the entire composite core, giving me the luxury of not gouging the paper-thin root. Gutta-percha was removed and measured to 4 mm from the radiographic terminus. An endo-restorative casting pattern with a bizarre but appropriate shape is shown in Figure 5. This modification of the old cast post and core technique relies on microscopic visualization. It will be explored in future articles. The palatal view of the seated casting (Figure 6) demonstrates the lack of axial dentin once the tooth was prepared for a porcelain crown. The value of micro-endo-restorative excellence is demonstrated.

 

   
Figure 5. (Case 1 continued) A direct pattern for the endo-restorative casting is more predictable than the indirect method, but difficult without a microscope. As the use of the microscope and ultrasonic 3-D shaping become more common, prefabricated posts will become less useful in ovoid and highly tapered systems. Figure 6. (Case 1 continued) “Warm” yellow precious metal alloy is preferable to “cold” gray non precious metal. High strength Argenco 42 is utilized. 

 

CASE 2

Post Removal

As the population ages, retention of endodontically treated teeth and re-restoration of these teeth are becoming more common. Post removal is the ultimate use of ultrasonics. The patient in this case (Figure 7) presented with a leaking, ill-fitted crown on the lower right first bicuspid. The previous endodontic attempt was very short of the radiographic terminus. Although there was no radiographic pathology, proper re-restoration of the tooth required an appropriate endo-restorative foundation. Endodontic retreatment was performed to facilitate ideal re-restoration.

 

Figure 7. (Case 2) When no radiographic pathology is present, some clinicians would favor leaving the existing crude endodontics and endo-restorative foundation when replacing the crown. These treatments appear so deficient under the microscope that re-treatment was initiated.

 

Once the tooth was isolated, I immediately removed 2 mm of occlusal porcelain (Figure 8a). Ultrasonic instrumentation (CPR-2D) was utilized to disrupt composite and cement without removing dentin or gouging the post. A microphotograph (Figure 9) demonstrates the unique characteristics of ultrasonics. Composite and cements crumble and fall away, allowing a safer and more delicate deconstruction of the old endo-restorative foundation.

Once circumferential removal of the occlusal composite and cement was complete, the CPR-1D was placed at a 90° angle to the post (Figure 8b). Light pressure allowed the appropriate frequency to disrupt the remaining cement around the post. The ultrasonic tip should “dance lightly” on the post. The mechanism of ultrasonics is very different than other instruments. For one, increasing hand pressure or higher power settings do not necessarily increase efficiency. For loosening of posts, the shape of the CPR seems too delicate to apply enough force. In reality, it is the amplitude and frequency at the tip that create the ideal forces to break up the cement. Ordinarily, most posts can be removed with ultrasonics alone.

 

Figure 8a. (Case 2 continued) The new generation of ultrasonic tips are diamond coated and cut more efficiently than the previous generation rhodium coating; 8b and 8c: ultrasonic tips are procedure specific; a common mistake for the inexperienced clinician is to use the wrong tip or incorrect angulation or pressure; and 8d: the post is safely out in two minutes, however not all cases are this straightforward.

 

The post was atraumatically removed (Figures 8c and 8d), and the root was now ready for conservative micro-endodontic retreatment and subsequent micro-endo-restorative reconstruction.

 

Figure 9. This 24X reveals how the ultrasonic disrupts the cement around the post.

 

 

CASE 3

The patient presented with very early distal caries on the lower right first bicuspid (Figure 10). The lower right second bicuspid was congenitally missing. The patient had Down’s syndrome, and the parent opted for a removable space maintainer in lieu of an implant or bridge.

Before the advent of microrestorative ultrasonic tips and the operating microscope, it was common to cut through the occlusal surface to access the distal. This convenience form is sometimes not required in the new microscope era. Microscope clinicians are carefully studying crack initiation and propagation in posterior teeth.4 It is very likely that traditional class I and class II cavity preparations, even seemingly conservative ones, are predisposing these teeth to fracture.

 

   
Figure 10. (Case 3) Preoperative radiograph of lower first bicuspid with incipient distal caries. Figure 11. (Case 3 continued) Access for conservative treatment is virtually impossible with traditional modalities.  

 

The difficulty of accessing the distal directly with a traditional handpiece is demonstrated in Figure 11. Ideal access and angulation was achieved with Spartan tip No. SL-3A (surface lesion series, Figures 12 and 13). A microphotograph (Figure 14) demonstrates an ultraconservative cavity preparation. The unique double contra-angle of these tips is the key. A 557 bur (Figure 15) is photographed as a reference to the tiny preparation. The preparation is crisp, and surface roughness is ideal for a bonded restoration.

 

   
Figure 12. (Case 3 continued) The delicate double contra-angle of the SL-3A is a splendid design. Figure 13. (Case 3 continued) Perfect angulation, access and visualization are possible with the new micro-restorative tips.  
   
Figure 14. (Case 3 continued) The 16X magnification of the ultra conservative preparation. Accessing this lesion via the occlusal would unnecessarily weaken the tooth and potentially predispose it to future fracture. Figure 15. (Case 3 continued) The 24x magnification demonstrates the crisp margins, as opposed to the helter skelter margins of some modalities. Fissure bur pictured as a reference for size.  

 

The double contra-angle of ultrasonics, acid etch, flowable composite, and explorer are highlighted in Figure 16. As we create better methods in microdentistry, creativity with old instruments and development of new instruments are required.

 

 
Figure 16. (Case 3 continued) A double contra-angle is created for phosphoric acid etch, and flowable composite. ‘Clark Explorers’ (bottom) are titanium coated to avoid traditional gray streaks common when traditional explorers touch cured composite during incremental filling. These explorers are used to tease the flowable composite into the preparation to prevent voids caused by injecting the composite directly into these micro-preparations.

 

CASE 4

Endodontic Straight Line Access

Lack of straightline access is arguably the leading cause of broken files, perforation, and the inability to negotiate files to the radiographic terminus. Microscopic visualization and ultrasonic instruments are a safe and effective combination to achieve optimal results. In addition, many endodontic cases being treated without the microscope are not fully deroofed and do not have appropriate 3-D shape.

Additionally, entire canal systems are ignored. In many microscope-centered practices, the ultrasonic has replaced Gates Glidden and other burs. A sectioned and accessed extracted molar shows the incomplete deroofing of the pulp chamber (Figure 17). Ultrasonic tip CPR-2D was used to deroof and smooth the area (Figure 18). It can then be used (only with microscopic visualization) to shape the coronal one half of this ovoid system (Figures 19a, 19b, and 19c).

 

   
Figure 17. (Case 4) This cross sectioned molar demonstrates the incomplete de-roofing that is common without the benefit of the superior optics and coaxial shadowless light of the microscope Figure 18. (Case 4 continued) De-roofing can be done well with traditional burs and microscopic visualization; however, the shape and nature of ultrasonics provide advantages in many instances.  

 

 

 
Figures 19a to 19d. (Case 4 continued) Occlusal view of the apical half of the molar in figures 17 and 18. Note the deep flutings. In Figures 19b and 19c, ovoid roots demand 3-D visualization and shaping. In such cases, microscopic visualization with ultrasonic shaping is preferred over blindly enlarging the non round systems with burs and files into round shapes.

 

Straightline access, ideal visualization, and shaping of the coronal portion of the canal system were then complete (Figure 19d). This allows supersmart file curvature (Figure 20a) to be maintained as the file moves toward a portal of exit. A radical turn is negotiated (Figure 20b).

 

Figures 20a and 20b. (Case 4 continued) Appropriate shaping and enlarging of the coronal 2/3rds of this ovoid canal system allow the exotic file curvature to be maintained as the file moves apically. Without the shaping, the natural constrictions of the canal system would flatten out the file and it would likely begin to ledge instead of following the severe dog leg turn.

 

Advantages of The Microscope and Ultrasonics

There are 5 unique advantages to the operating microscope-ultrasonic combination: (1) ultrasonic tips can be more effective to “move” the coronal shaping away from furcations, flutings, and other high-risk anatomies; (2) microscopic visualization is improved because the bulky head of a traditional handpiece is not a factor; (3) ultrasonics can be more effective and conservative at “sweeping” the access to de-roof the chamber; (4) the MB2 or calcified chambers in posterior teeth rely on a lateral, not apical, motion that begs for the micro-ultrasonic combination (Think of these orifices as mouseholes and then you will understand why files will not enter the orifices until they are transported laterally); (5) this level of 3-D shaping cannot occur safely by “feel.”

 

SUMMARY

Ultrasonic instruments for endodontic, endo-restorative, and microrestorative procedures are underutilized by restorative dentists. These ultrasonic instruments are useful with traditional visualization (unaided vision or loupes). However, their true worth can best be appreciated in conjunction with microscopic visualization. It is imperative that the reader understand that some of the utilizations described in this article are not recommended unless accompanied by the operating microscope and some level of training.

Acknowledgment

The author would like to recognize all of the pioneers of microscope-enhanced dentistry that have contributed to this article. They can be found at microscopedentistry.com.

References

1. Heydecke G, Butz F, Strub JR. Fracture strength and survival rate of endodontically treated maxillary incisors with approximal cavities after restoration with different post and core systems: an in-vitro study. J Dent. 2001;29:427-433.

2. Clark DJ, Khademi J. Micro-Endo-Restorative, the New Frontier. Second Annual Program of the Academy of Microscope Enhanced Dentistry. November 6 to 8, 2003, Scottsdale, Arizona. (“Micro-Endo-Restorative;The New Frontier” DVD by ACT Video is available at microscopedentistry.com.)

3. Lamberg-Hansen H, Asmussen E. Mechanical properties of endodontic posts. J Oral Rehabil. 1997;24 :882-887.

4. Clark DJ, Sheets CG, Paquette JM. Definitive diagnosis of early enamel and dentin cracks based on microscopic evaluation. J Esthet Restor Dent. 2003;15:391-401.

 


Dr. Clark founded the Academy of Microscope Enhanced Dentistry. The Academy is an international association formed to advance the science and practice of microendodontics, microperiodontics, microprosthodontics and microdentistry. He is a course director at the Newport Coast Oral Facial Institute and co-director of Precision Aesthetics Northwest. He has published a completely new approach to diagnosis and treatment of cracked teeth, based on 16x magnification. He provides video and still images to CRA (Clinical Research Associates) regarding the operating microscope in dentistry. Dr. Clark is a 1986 graduate of the University of Washington School of Dentistry. He maintains a microscope-centered restorative practice in Tacoma, Washington USA and can be reached at (253) 472-4292.

Disclosure: Dr. Clark is not a paid spokesman for Obtura/Spartan or any microscope manufacturer. Royalties from sales of the “Clark Explorer Series” are donated to the Academy of Microscope Enhanced Dentistry.




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John Wilson (26.11.2012 (13:25:44))
Restorative ultrasonic tips Yes No Looking for tips to bevel the gingival-cavosurface margin


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