Clinical Corner: Information on Dental Procedures

Articles

What's Hot: Dr. Glazer on Jazz
Combating Hidden Decay with Early Detection
Atraumatic Removal of Defective Crowns
Balancing: The Art, Science and Business of Dentistry
Intra-Oral Preparation of Titanium Abutments in Order to Obtain Ideal Angulations and Contours
SS White Express Line High Speed Laboratory Metal Finishing Burs
Direct Preparation Of Preexisting Implant Abutments For Case Rehabilitation
Flextime Xtreme: The 80/20 Rule
Fast and Smooth - Efficient Crown Preparation With Carbide Instruments
When Advancing the Bur, One Can Feel the Presence of Dentinal Caries
Precision Trimming and Finishing of Current Dental Restorations Using the Safe End Bur System
Indirect Restorative Tooth Preparation: Extreme Efficiency and Accuracy
Creating Maximum Efficiency and Accuracy In Indirect Restorative Tooth Preparation
Preparation Protocol To Ensure Predictable Aesthetic Restorations
Tooth Preparation Mastering Quality and Efficiency
Fissurotomy: Proactive Treatment for Incipient Decay
Anatomically Adapted Carbide Finishing Burs - Creating Super-Smooth Composite Surfaces in Two Steps
Directions for Use: Dr. David Clark Kit
Placing Traditional Sealants with Enhanced Magnification: Methodology to Increase Both Short-term and Long-term Success - David Clark, DDS
How to Quickly and Conservatively Restore a Natural Shine after Orthodontic Bracket Removal
SS White Surgical Length Oral Surgery Burs: Atraumatic Removal of Teeth for Maximum Bone Preservation

"Creating Maximum Efficiency and Accuracy In Indirect Restorative Tooth Preparation”

Dr. Ian Shuman 

There are infinite options to prepare teeth for indirect restorative care. 1,2,3,4 The ultimate goal of full coverage tooth preparation should be the complete removal of enamel, existing restorative materials and caries. This preparation must be accomplished in a fast, clean and easy manner. One school of thought is to accomplish this using diamond burs. While this method is safe and unlikely to cause enamel fracturing, it is slow to cut enamel and even slower at cutting metal based restorations like amalgam or the sectioning of existing cast metal copings and crowns.5,6,7,8 These problems occur because diamond surfaces fill with debris and clog, wear smooth and can cause burnishing and overheating of the tooth surface. In response to this problem, carbide burs have been used to easily accomplish all of these tasks.

The techniques that employ carbide burs for these tasks have been studied in depth and have shown a favorable outcome versus diamond burs. In a study conducted at Ohio State University by Ayad, etal.9 One hundred and five standardized tooth preparations for complete crowns were performed using a modified milling machine on extracted human teeth with diamond, tungsten carbide, and tungsten carbide finishing burs of similar shape. The prepared dentin was analyzed with a surface profilometer and a scanning electron microscope (SEM). Teeth completed with the tungsten carbide burs appeared to result in a smoother surface (1.2 mum).

Figure 1 The Great White Ultra Crown and Bridge Preparation Kit

Today, the use of carbide burs is a highly accepted method for fast, clean bulk reduction of enamel, existing restorations and caries. 10,11,12,13 There was however one problem with the “traditional” full coverage preparation using 557 or similar shaped carbide burs; following the stripping of bulk enamel, a large shoulder type step would remain in the preparation requiring significant after-finishing with a diamond to achieve an acceptable beveled margin, be it chamfer or other margin designs of choice. That issue has now been solved with a unique series of highly designed carbide burs, the Great White Ultra Crown and Bridge Preparation Kit, (SS White, Lakewood, NJ) (Fig 1) which accomplish bulk reduction while simultaneously creating an ideal chamfer or shoulder margin. (Fig 2)The new Great White Ultra carbide preparation burs combine a fast and smooth uniquely dentate carbide design while providing superb cutting action. The smooth tip helps ensure marginal integrity creating a smooth margin and finish line. These burs cut fast with minimal clogging or vibration. Geometric specifications have been designed into the Great White Ultra to produce a sharp, clean cutting tip that will produce an impression ready margin finish line. In addition, these burs are manufactured in a process known as concentric engineering. This has proven superior qualities in bur design.

Figure 2 The Great White 856 Series bur is designed to create a rounded axial-gingival line angle for full and partial coverage restorations

In a study conducted at the At the Department of Conservative Dentistry, United Medical School of Guy's Hospital, Guy's Dental School, London, United Kingdom, Watson and Cook conducted a study aimed to determine the degree of eccentricity between different tungsten carbide bur manufacturing techniques and to study the effect of bur inaccuracy on dental enamel.13 High-speed cutting interactions with dental enamel between carbide burs were studied by means of a video-rate confocal microscope. Videotape showing the interactions of high-speed rotary cutting instruments (at 120,000 rpm) was taken under simulated normal wet-cutting environments, and the consequent damage to the tooth tissue was observed as it occurred. Concentrically engineered bur types produced a superior quality cut surface at the entry, exit, and advancing front aspects of a cavity, as well as less subsurface cracking. This study has shown that there is reduced substrate damage with high-concentricity carbide burs.

Included in the kit are the 856 series of chamfer preparation burs designed to create a rounded axial-gingival line angle for metal to ceramic restorations, the 847 series shoulder preparation burs designed to develop a 90° axial-gingival line angle suitable for anterior all ceramic and PFM restorations and the 379 football shaped bur designed for occlusal and lingual reduction.

The following two case reports demonstrate the usefulness of the Great White Series Ultra Carbide Burs:

Case 1:

The patient presented for a consultation regarding his fractured tooth. The lower right first molar, tooth #30
(Fig 3) presented as missing the mesio-facial-occlusal portion of the coronal structure due to caries. In addition, the presence of a failing amalgam restoration contributed to the ongoing decay of the carious lesion necessitating full coverage treatment. Once the patient was locally anesthetized, the tooth was mocked up with Systemp (Ivoclar, Amherst, NY) (Fig 4) and light cured followed by making a triple tray impression using a medium body polyvinyl siloxane (Flexi Velvet, J Morita USA, Irvine, CA). The tooth was then prepared using the 856- 016 Great White Ultra bur that has a tip diameter of 1.20mm and a cutting head length of 8mm. An initial 1.5mm depth cut was made along the occlusal and the entire occlusal table was reduced. (Fig 5).

Figure 3 Laufer BZ, Pilo R, Cardash HS. Surface roughness of tooth shoulder preparations created by rotary instrumentation, hand planing, and ultrasonic oscillation. J Prosthet Dent. 1996 Jan;75(1):4-8

Figure 4 Dalvit DL, Parker MH, Cameron SM, Hawkins MC, Agar JR, Brousseau JS. Evaluation of margin angles of collarless metal ceramic restorations. Gen Dent. 2004 Mar-Apr;52(2):148-50

Figure 5 Schuchard A, Watkins EC. Cutting effectiveness of tungsten carbide burs and diamond points at ultra-high rotational speeds. J Prosthet Dent. 1967 Jul;18(1):58-65

A depth cut was made on the facial of the molar using this same bur and this action was continued circumferentially, removing amalgam, enamel and caries while simultaneously creating a margin. (Fig 6) A core buildup was then fabricated using Photocore (Kuraray North America, New York, NY), the margin refined, (Fig 7) and the occlusion reduced using the Great White 379- 023. (Fig 8) This football or egg shaped bur has a cutting head length of 4.5mm. The final full coverage preparation can be seen with subgingival facial margins, preserving the gingiva and creating crisp subgingival margins. (Fig 9) Upon the patients return for case delivery, the porcelain-fused to metal crown (Aesthetic Porcelain Studios, Universal City, CA) was luted to the tooth preparation using a resin reinforced glass ionomer cement (Fuji II, GC America, Alsip, Il). (Fig 10).

Figure 6 The 856- 016 easily removes all remaining amalgam, enamel and caries while simultaneously creating a margin	Figure 7 Following the core buildup, the margin is refined	Figure 8 The occlusion is properly reduced using the Great White 379- 023 occlusal/lingual reduction Bur
Figure 9 The final crown preparation, ready for impressioning	Figure 10 The lab fabricated porcelain-to metal crown immediately following cementation

Case 2:

Figure 11 The lower left first molar with an open distal contact and subgingival carious lesion

The patient presented with an open contact between the lower first and second left molars FIG 11 with a defective amalgam restoration in the lower left first molar and a carious lesion was detected at the distal margin of this tooth by explorer examination. Radiographic examination confirmed that there was a significant radioluscent area associated with the distomarginal aspect of the amalgam. It was decided that in order to preserve the maximum amount of tooth structure while maintaining high restorative strength, a ceramic polymer onlay preparation would be created.

The facial amalgam was removed using a Fissurotomy bur (SS White) FIG 12 and replaced with a flowable composite. FIG 13 This was followed by the removal of the existing amalgam restoration using the Great White 845- 016 onlay preparation bur. FIG 14 This bur has a cutting diameter of 1.10mm and length of 4mm allowing for complete, rapid removal of the amalgam restoration while simultaneously creating divergent axial walls. FIG 15 This was followed by removal of the distal portion of the existing amalgam restoration along with any associated caries using the Great White 847- 018 flat end taper bur. FIG 16 With a cutting tip diameter 1.50mm and a cutting length of 8mm, this bur allows easy access into narrow, long areas such as the distal box preparation areas of lower molars. Because the isthmus of missing tooth structure in the bucco-lingual was greater that 1/3 the width of the entire bucco-lingual width of the tooth, the cusps required coverage. Rapid cuspal reduction was accomplished using the Great White 379- 023 occlusal reduction bur. FIG 17,18 At the delivery appointment several weeks later, the onlay was luted to place using a dual cure, resin cement (UltraBond Plus, DenMat, Santa Maria, CA). FIG 19.

Figure 12 The facial amalgam is easily removed using a Fissurotomy bur	Figure 13 The preparation is restored using a flowable composite resin	Figure 14 Amalgam removal is initiated using the and the onlay prepared simultaneously using the Great White Bur
Figure 15 This is followed by the continued removal of the remaining occlusal core and completion of the truing of the axial walls using the Great White Bur	Figure 16 This same bur is used to remove the most distal portion of the remaining defective amalgam and decay while continuing to create an inlay box preparation	Figure 17 The occlusion is reduced using the 379- 023 Great White Bur
Figure 18 The nearly completed onlay preparation prior to removal of any remaining unsupported enamel	Figure 19 The lab fabricated ceramic polymer onlay (Aesthetic Porcelain Studios) immediately following resin bonding

Bibliography

1. Bass EV, Kafalias MC. Systematized procedure of crown preparation. J Prosthet Dent. 1989 Oct;62(4):400-5.
2. Zena RB, Khan Z, von Fraunhofer JA. Shoulder preparations for collarless metal ceramic crowns: hand-planning as opposed to rotary instrumentation. J Prosthet Dent. 1989 Sep;62(3):273-7.
   
3. Laufer BZ, Pilo R, Cardash HS. Surface roughness of tooth shoulder preparations created by rotary instrumentation, hand planing, and ultrasonic oscillation. J Prosthet Dent. 1996 Jan;75(1):4-8.
   
4. Dalvit DL, Parker MH, Cameron SM, Hawkins MC, Agar JR, Brousseau JS. Evaluation of margin angles of collarless metal ceramic restorations. Gen Dent. 2004 Mar-Apr;52(2):148-50.
   
5. Schuchard A, Watkins EC. Cutting effectiveness of tungsten carbide burs and diamond points at ultra-high rotational speeds. J Prosthet Dent. 1967 Jul;18(1):58-65.
   
6. Elias K, Amis AA, Setchell DJ. The magnitude of cutting forces at high speed. J Prosthet Dent. 2003 Mar;89(3):286-91.
   
7. Matson E, Kikuchi HK. Appraisal of the cutting efficiency of rotary instruments of tungsten carbide at high speed. Rev Assoc Paul Cir Dent. 1981 Mar-Apr;35(2):150-5.
   
8. Atkinson AS. The significance of blade geometry in the cutting efficiency of tungsten carbide dental burs at ultrahigh speeds. Br Dent J. 1983 Sep 24;155(6):187-93.
   
9. Ayad MF, Rosenstiel SF, Hassan MM. Surface roughness of dentin after tooth preparation with different rotary instrumentation. J Prosthet Dent. 1996 Feb;75(2):122-8.
   
10. Price RB, Sutow EJ. Micrographic and profilometric evaluation of the finish produced by diamond and tungsten carbide finishing burs on enamel and dentin. J Prosthet Dent. 1988 Sep;60(3):311-6.
    
11. Eames WB, Nale JL. A comparison of cutting efficiency of air-driven fissure burs. J Am Dent Assoc. 1973 Feb;86(2):412-5.
    
12. Galindo DF, Ercoli C, Funkenbusch PD, Greene TD, Moss ME, Lee HJ, Ben-Hanan U, Graser GN, Barzilay I. Tooth preparation: a study on the effect of different variables and a comparison between conventional and channeled diamond burs. J Prosthodont. 2004 Mar;13(1):3-16.
    
13. Watson TF, Cook RJ. The influence of bur blade concentricity on high-speed tooth-cutting interactions: a video-rate confocal microscopic study. J Dent Res. 1995 Nov;74(11):1749-55.
    
    

At the Department of Conservative Dentistry, United Medical School of Guy's Hospital, Guy's Dental School, London, United Kingdom Watson and Cook conducted a study aimed to determine the degree of eccentricity between different tungsten carbide bur manufacturing techniques and to study the effect of bur inaccuracy on dental enamel. High-speed cutting interactions with dental enamel between carbide burs were studied by means of a video-rate confocal microscope. Videotape showing the interactions of high-speed rotary cutting instruments (at 120,000 rpm) was taken under simulated normal wet-cutting environments, and the consequent damage to the tooth tissue was observed as it occurred. Concentrically engineered bur types produced a superior quality cut surface at the entry, exit, and advancing front aspects of a cavity, as well as less subsurface cracking. This study has shown that there is reduced substrate damage with high-concentricity carbide burs.