Removal of resin composite remnants after debonding of orthodontic brackets

Transcription

1 Removal of resin composite remnants after debonding of orthodontic brackets T. Osada, U. Fritz, and W.J. Finger Background After removal of orthodontic brackets consistently resin remnants are left on the enamel surface. Grinding with tungsten carbide burs (8, 16, or 32-fluted) and final polishing with differently abrasive pastes mostly eliminates such residues. Gross removal with fast and effectively cutting burs always involves the risk of damaging the underlying sound enamel surface. This holds in particular for 8-fluted instruments, whereas instruments with higher numbers of flutes and rounded cutting edges are considerably less damaging. Therefore, alternative methods that are reasonably fast, effective, and non-destructive to enamel would be highly desirable. The French Company Carbotech has recently made Zrglass fiber reinforced resin burs available, which are primarily used as gentle stain removal instruments for use on enamel and root dentin. These burs are characterized along their working surface by exposed fiber edges, which break into small fragments upon acting on solid surfaces. At the same time the surrounding epoxy resin is gradually removed, thus exposing new fiber edges for the continued abrasive action. The disposable burs are continuously self-sharpening and simultaneously degrading. Due to their proven very gentle action on dental hard tissues, it is anticipated that they might be useful tools to remove minor portions of resin composite luting material left on enamel after bracket de-bonding without compromising the enamel. Aim of this trial is to evaluate effects of the eight following finishing and polishing methods on efficiency and of resin composite removal and polishing of the exposed enamel. Procedure The facial surfaces of extracted human upper jaw incisors are cleaned with Zircate Prophy Paste (Dentsply Caulk, DE, USA), rinsed and air-dried. The self-etching primer adhesive ibond Gluma inside (Heraeus Kulzer, Germany) is applied onto the target surface with a brush in three consecutive coats and left undisturbed for 30 seconds prior to thorough airdrying. The base of a metal bracket (Ortho-CIS; Ormco Corp., CA, USA) is coated with a thin layer of the unfilled sealant (Estiseal F; Heraeus Kulzer) and with a small portion of the microfiller-type resin composite Durafill VS (B2; Heraeus Kulzer) prior to seating on the pretreated enamel with a firm pressure. Excess resin composite is gently removed with a small spatula and the resin material is light activated from coronal, mesial, apical, and distal direction for 20 seconds each with the Translux Energy (Heraeus Kulzer) unit. The bonded specimens (prepared at ambient laboratory atmosphere, 23 C, 50% RH) are immersed into 37 C water for 24 hours prior to bracket removal with a special forceps (Direct Bond Attachment Remover, Rocky Mountain Orthodontics, CO, USA). 1

2 Finishing/polishing methods 1. TC bur (Komet H379, Brasseler) alone without water-cooling. 2. Tungsten-carbide finishing bur, 12-fluted, ISO (Komet H 379, Brasseler, Germany) without water-cooling followed by polishing paste (Clean Polish, Hawe- Neos Dental, Switzerland) applied on white rubber cups (Poliernapf PD mit Lamelle, Henry Schein Dentina, Konstanz, Germany). 3. Tungsten-carbide finishing bur (12-fluted) without water-cooling followed by fiber burs (Type???). 4. Tungsten-carbide finishing bur (Komet H379) without water-cooling followed by fiber burs (Type???) and polishing paste (Clean Polish, Hawe-Neos Dental) applied on white rubber cups (Poliernapf PD mit Lamelle, Henry Schein Dentina). 5. Fiber burs (Type???) alone without water-cooling. 6. One Midi (Shofu, Japan) alone, with intermittent water spray. 7. One Mini point (Shofu) alone, with intermittent water spray. 8. Finishing bur (16-fluted; Robot Carbide CTF9 SH 135 F, Shofu), mounted in turbine (300,000 rpm) with adequate water-cooling followed by ultra-fine finishing bur (30-fluted; SH 135 UF, Shofu) with water spray. 9. Finishing bur (SH 135 F, Shofu), mounted in high-speed contra-angle handpiece (50,000 rpm) with adequate water-cooling followed by ultra-fine finishing bur (SH 135 UF, Shofu) with water spray. 10. Finishing bur (SH 135 F, Shofu), mounted in high-speed contra-angle handpiece with adequate water-cooling followed by ultra-fine finishing bur (SH 135 UF, Shofu) with water spray and Super-Snap (Super-fine; L502, Shofu) with water-cooling. 11. Finishing bur (SH 135 F, Shofu), mounted in high-speed contra-angle handpiece with adequate water-cooling followed by ultra-fine finishing bur (SH 135 UF, Shofu) with water spray and Super-Snap (Super-fine; L502, Shofu) without water-cooling. Each procedure is repeated 5 times. The following evaluation criteria are used: 1. elapsed for each procedure. Total treatment time. 2. gloss (visual scale: high medium dull). gloss score: 1, high; 0, medium; -1, dull 3. damage (20x stereo microscope and selected specimens for SEM inspection). Visual allocation to damage vs. no damage (Y/N related to TC bur defects). - = no scratching, + = mild scratching, ++ = medium scratching, +++ = severe scratching damage score: 0, minus; 1, plus scratch score: 0 through 3 i.e. through Completeness of resin removal: - = no resin left, + = small spots, ++ = small areas, +++ = large area. left score: 0 = no resin left; 1 = approx. 1 mm 2 ; 2 = >1 mm 2, <5 mm 2 ; 3 = >5 mm 2 2

3 Statistical methods to be decided when data are available. Procedure 1 (TCB: TC bur only) TC bur 1 T m Y T m Y T m Y T m Y T m Y ,0Y 1,2 0 Procedure 2 (TCP: TC bur + polishing paste) TC Bur Polishing Paste Total time 1 U h Y U h Y T h Y T h N T h N ,0 0,6Y 0,6 0,6 Procedure 3 (TCF: TC bur + fiber bur) TC Bur Fiber bur Total time 1 U h Y U h Y T m N T m N T m N ,4 0,4Y 1,2 0 Procedure 4 (TFP: TC bur + fiber bur + polishing paste) Polishin TC Bur Fiber Total g Paste bur time Left Left Left 1 U h Y U h Y T m N T m Y T m Y ,0 0,8 0,2 0,6 3

4 Procedure 5 (FIB: Fiber bur only) Fiber bur 1 T h N T h N T h N T h N T m N ,8 0 0,8 Procedure 6 (MID: One Midi only) One Midi 1 T m N T m N T d N T m N T m N ,2 1,6 1,4 Procedure 7 (MIN: One Mini point only) One Mini point 1 T (2 instr.) d N T d N T (2 instr.) m N T (2 instr.) d N T (2 instr.) m N ,6 2,0 1,8 Procedure 8 (SHI: Fine + Ultra-fine finishing bur; 300,000 rpm) SH 135 F SH 135 UF 1 T m Y* T m Y* T m Y* T m Y* T m Y* ,0Y 3,0 0 *very severe damage 4

5 Procedure 9 (SLO: Fine + Ultra-fine finishing bur; 50,000 rpm) SH 135 F SH 135 UF 1 T m Y T m Y* T m Y* T m Y* T m Y ,0 Y 2,0 0,4 Procedure 10 (SSW: Fine + Ultra-fine finishing bur + Super-Snap wet) Super- SH 135 F SH 135 UF Snap Super- Snap Scratchin g * facetting Left 1 T h Y* T h Y* T h Y* T h Y* T m Y* ,8 1,0Y 1,0 0 * deep parallel scratching Procedure 11 (SSD: Fine + Ultra-fine finishing bur + Super-Snap dry) Scratchin SH 135 SH 135 F UF g Left 1 T h Y T h Y T h Y T m Y T h Y ,8 1,0Y 1,0 0,6 Treatment times Procedure Code TC FB PP OG Midi OG Mini 135 F 135 UF SS Total 1 TCB TCP TCF TFP FIB MID MIN SHI SLO SSW SSD SD 5

6 Procedure Code / 5 spec. 1 1) by TC / 5 spec. (0 1) Scratch Score / 5 spec. (0 3) Luting left / 5 spec. (0 3) 1 TCB 0 1,0 1,2 0 2 TCP 1,0 0,6 0,6 0,6 3 TCF 0,4 0,4 1,2 0 4 TFP 1,0 0,8 0,2 0,6 5 FIB 0,8 0 0,8 6 MID -0,2 1,6 1,4 7 MIN -0,6 2,0 1,8 8 SHI 0 1,0 3,0 0 9 SLO 0 1,0 2,0 0,4 10 SSW 0,8 1,0 1, SSD 0,8 1,0 1,0 0,6 Remarks The procedures 8 and 10 described above will be disregarded and not presented in the publication text, since they are not in accordance with the manufacturer s recommendations. Conclusions (related to the Stainbuster) TCB is the fastest procedure to remove the resin remnants completely. However, enamel damaging is consistently produced. Frequently deep rattling marks are seen. The fiber bur alone (FIB) is with 115 seconds total time budget not very fast. The time for the entire procedure is significantly longer than for TCB and significantly shorten than for TFP and SSB, however not significantly different from the other alternatives. Very little resin areas left. No visible enamel scratching under the stereomicroscope (20x). Highly glossy enamel appearance. FIB degrades very much, and the bur must be discarded after treatment of one tooth. NOTE of Carbotech: two new shapes, especially made for orthodontic purpose have been made now which are not degrading so fast! The TCF procedure results in fairly high gloss of the polished enamel, 104 seconds treatment time, very mild enamel scratching (mostly resulting from the preceding TC bur cutting, and no resin remnants left. TFP (TC bur followed by fiber bur and polishing paste) is very time consuming (159 seconds), it shows excellent enamel gloss, virtually no scratching, and very small resin remnants left occasionally. The TCF procedure is the preferred to the TFP method. TCF is reasonably fast and quite effective. The fiber bur is the only instrument tested with the advantage, that removal of luting resin from enamel is visually controlled during the treatment. As soon as enamel is reached 6

7 the area becomes glossy, whereas the surrounding resin left stays dull. With all other procedures tested the target surfaces have to be cleaned and dried for visual control. The fiber bur is available in a range of different shapes that makes them universally suitable for resin removal, irrespective of the morphology of the underlying enamel. This is in particular advantageous when lingual bracket placement techniques are used. In this case small round or pear-shaped burs are necessary. Use of fiber burs, following gentle removal of gross resin portions with tungsten carbide burs, is an innovative, minimally invasive, and effective procedure for resin removal. The price of the burs might be the most important issue, since orthodontists don t get special remuneration for bracket de-bonding and enamel polishing. 7