JOBNAME: No Job Name PAGE: 1 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 994AA9D8 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ORIGINAL ARTICLE Ultrasonic Margin Preparation for Fixed Prosthodontics: A Pilot Study jerd_477 1..10 POPPY HORNE, BDS, VINCENT BENNANI, DDS, PhD, NICHOLAS CHANDLER, BDS, MSC, PhD, 1 DAVID PURTON, BDS, MDS ABSTRACT Purpose: Atraumatic, oscillating ultrasonic instruments have recently been developed for prosthodontic margin finishing. This in vitro observational pilot study aimed to compare the condition of crown preparation margins finished using new ultrasonic instruments with margins finished with conventional rotary instruments. Methods: Two extracted human canine teeth were prepared for crowns. A split-tooth model was used to refine the margins: half of the margin was finished with conventional rotary instruments, the other with ultrasonic instruments. The profiles of the margins were observed using scanning electron microscopy, and a quantitative comparison of surface roughness was obtained using surface roughness analysis software. Results: The margins finished with the ultrasonic instruments exhibited a better-defined axial wall/margin angle and a smoother marginal surface. Rotary instruments produced a sharper and more continuous external line angle. Two-dimensional surface roughness analysis showed that the margins produced with the ultrasonic instruments were approximately half as rough as the margins prepared with the conventional rotary instruments. Conclusion: The ultrasonic instruments produce margins in better condition than the current standard and appear to have some practical advantages. CLINICAL SIGNIFICANCE Preparations for fixed prosthodontics finished with these ultrasonic instruments created better-defined margins, which could result in more successful prostheses. (J Esthet Restor Dent ••:••–••, 2011) Caries has been identified as one of the most common complications of fixed partial dentures.1 Marginal discrepancies can result in leakage. This leads to secondary caries and esthetic problems, ultimately resulting in failure of the prosthesis.2 Smooth and precise preparation margins facilitate impression taking and fabrication of a precisely fitting restoration, which contribute to a durable, esthetic, and functional result. Ultrasonic instruments have an oscillating action, compared with the rotation of conventional instruments, which has led to their recent adaptation for finish line preparation in fixed prosthodontics by Sous and colleagues.3 Ultrasonic instruments are largely atraumatic to the gingival attachment, pulp, and adjacent teeth.4,5 Esthetic restorations in the anterior dentition often demand a preparation with a subgingival finish line.4 The oscillating action of ultrasonic instruments reduces trauma to the soft tissues during subgingival margin preparation, facilitating accurate impression taking.6 1 2 Department of Oral Rehabilitation, University of Otago School of Dentistry, Dunedin, New Zealand © 2011 Wiley Periodicals, Inc. DOI 10.1111/j.1708-8240.2011.00477.x Journal of Esthetic and Restorative Dentistry Vol •• • No •• • ••–•• • 2011 1 JOBNAME: No Job Name PAGE: 2 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 68C27230 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ULTRASONIC MARGIN PREPARATION Horne et al The action also allows for a greater degree of control when preparing areas with difficult access.6 This limits dentin exposure during minimally invasive procedures, which is preferred for bonded restorations.4 Furthermore, damage to the adjacent teeth can be avoided.4,7 Vanderlei and colleagues5 reported that temperature increases during cutting with an ultrasonic instrument are not sufficient to cause pulpal damage. 1 2 3 4 5 6 7 8 9 This in vitro observational pilot study aimed to compare the condition of crown preparation margins finished using new ultrasonic instruments with margins finished with conventional rotary instruments. The null hypothesis was that there would be no difference in the condition of the margins prepared with the two types of instrument. 10 11 12 13 14 15 16 17 METHODS AND MATERIALS 18 19 Ethical approval was obtained for the use of extracted human teeth. Two canine teeth were selected for this observational pilot study. Examination under a light microscope (¥10) revealed no cracks, caries, or discoloration. The teeth were cleaned with pumice and stored in distilled water. Light-body addition silicone impression material (Exahiflex, GC Corp., Tokyo, Japan) was used to create a simulated periodontal ligament on the root surfaces. This provided tooth mobility to absorb some of the ultrasonic energy and mimic the clinical use of ultrasonic instruments. The canines were mounted in acrylic (Orthocryl, Dentaurum, Ispringen, Germany) with adjacent natural teeth forming proximal contacts. The canines were then prepared for all-ceramic crowns using conventional diamond crown preparation burs in a new high-speed handpiece (646c Powertorque, Kavo, Biberach, Germany). All tooth preparation was completed by a single operator, aiming for a six-degree taper, and the margins were prepared to a rounded shoulder configuration above the cemento-enamel junction, as described by Shillingburg.8 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 The margins were finished using the split-tooth technique. One-half of the margin on each preparation was finished using an end-cutting bur (Tissue Guard 43 44 45 2 Vol •• • No •• • ••–•• • 2011 Journal of Esthetic and Restorative Dentistry End-Cutting [TGE] bur, fine grit [60 μm], Premier Two Striper, PA, USA) in the handpiece with water spray for 30 seconds, followed by a TGE very fine grit (45 μm) bur for 60 seconds. The other half of the margin on each tooth was finished using a Satelec Perfect Margin Shoulder (PMS) Kit in a factory calibrated ultrasonic generator (P5XS Newtron, Satelec, Merignac, France) with water spray. The PMS1 tip (76-μm grit) was used for 30 seconds, followed by the PMS2 tip (46-μm grit) for 60 seconds, and the PMS3 tip (no grit) for 120 seconds, each at the power settings recommended by the manufacturer. The sequence of tooth preparation is depicted in Figure 1, and the preparations were observed under the light microscope (¥10). 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 The samples were rinsed with distilled water, dried, and sputter coated with gold. The margins were then viewed using a scanning electron microscope (SEM) (Cambridge Instruments S360, Cambridge, UK) at an accelerating voltage of 10 kV. Images were captured with a frame grabber (Dindima Image Slave, Dindima Group Pty Ltd, Ringwood, Victoria, Australia). The profiles of the margins were qualitatively compared at different magnifications. Three regions were viewed; area 1: the axial wall/margin angle, area 2: the surface of the margin, area 3: the external line angle (Figure 2). Images were also taken of the profiles of each of the instruments before use. The tooth preparation and the analysis of the SEM images were carried out by the same investigator. 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 Surface roughness analysis software (Scandium, Olympus, Adelaide, Australia) was used to obtain a quantitative comparison of the margins finished with each instrument, from SEM images, using stereo pairs. The areas of the margins where the surface roughness was calculated were randomly selected by a third party. The term roughness refers to a variety of measured parameters, and two were selected: Ra, the roughness mean parameter and Rmax, the maximum roughness. The roughness of each sample was measured both in one dimension (along a line parallel to the margin, and a line perpendicular to the margin) and in two dimensions (along a surface). DOI 10.1111/j.1708-8240.2011.00477.x © 2011 Wiley Periodicals, Inc. 78 79 80 81 82 83 84 85 86 87 88 89 90 91 JOBNAME: No Job Name PAGE: 3 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 1E17025D /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 Horne et al Colour ULTRASONIC MARGIN PREPARATION 1 FIGURE 1. Tooth preparation sequence. PMS = Perfect Margin Shoulder. 2 3 4 5 6 7 8 9 10 FIGURE 2. SEM image of split-tooth model, marked for orientation of margin prepared with rotary instruments on the left and ultrasonic instruments on the right (¥25). Area 1: axial wall/marginal angle; area 2: margin surface; area 3: finishing line. © 2011 Wiley Periodicals, Inc. DOI 10.1111/j.1708-8240.2011.00477.x Journal of Esthetic and Restorative Dentistry Vol •• • No •• • ••–•• • 2011 3 JOBNAME: No Job Name PAGE: 4 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 4A956E25 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ULTRASONIC MARGIN PREPARATION Horne et al FIGURE 3. SEM image of sample prepared with rotary instruments (¥100). Area 2, the margin surface, showing concentric patterns due to the rotation of the instrument.1. 27 28 29 30 31 32 RESULTS 1 2 When examined under the light microscope, the sections of the margin prepared with the ultrasonic tips appeared to be smoother than those finished with the rotary instruments. There was some artifactual cracking visible on the root surfaces of the samples, with SEM. 3 4 5 6 7 8 9 Under SEM (100¥) the margin finished with the rotary TGE instruments appeared rougher overall. In area 1, there was some damage to the axial surface of the preparation (Figure 2). This was nonuniform, trough-like, and in the axial direction. The axial surface/marginal angle was therefore rough and irregular. There was an obvious concentric pattern on the surface of the margin (area 2, Figure 3). Despite this, the external line angle (area 3) created with the rotary instruments was sharp, continuous, and better defined than that produced with the ultrasonic instruments (Figure 4). 10 11 12 13 14 15 16 17 18 19 20 21 22 The axial wall/margin angle (area 1) produced with the ultrasonic instruments was well defined, and very smooth (Figure 2). The margin surface (area 2) appeared smoother overall, with little evidence of 23 24 25 26 4 Vol •• • No •• • ••–•• • 2011 Journal of Esthetic and Restorative Dentistry any stroke pattern (Figure 5). The margin was also wider than the margin prepared with the rotary instrument. The external line angle (area 3) was discontinuous (Figure 6). This line was very sharp and distinct in some regions, but rough and chipped in other regions. 33 34 35 36 37 38 39 SEM images (2,000¥) were used to visualize the dentinal tubules and the presence or absence of smear layer on the margins. The margins finished with the rotary instruments were covered with copious debris, within which concentric indentations were visible. The dentinal tubules were barely visible, and those that could be identified were often occluded. The margins finished with the ultrasonic instruments appeared to have less smear layer. The margin profile was slightly irregular and appeared to have small craters within the surface. However, the dentinal tubules were conspicuous. They were arranged in a regular pattern, but appeared smaller than expected, with some cracking of their apertures. 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 Surface roughness analysis was carried out to obtain quantitative results. The profile of the margin finished with the rotary instruments showed greater roughness DOI 10.1111/j.1708-8240.2011.00477.x © 2011 Wiley Periodicals, Inc. 56 57 58 JOBNAME: No Job Name PAGE: 5 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 2E897B7E /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ULTRASONIC MARGIN PREPARATION 1 2 3 4 5 Horne et al FIGURE 4. SEM image of sample prepared with rotary instruments (¥100). Note the sharp definition and continuity of area 3, the finishing line. 6 7 8 9 10 11 FIGURE 5. SEM image of sample prepared with ultrasonic instruments (¥100). Area 2, the margin surface of the sample, and absence of any stroke patterns. 12 13 14 15 16 17 18 closer to the axial wall (area 1) and external line angle (area 3) with a smoother surface between the two areas (area 2). The roughness mean parameter (Ra) of the surface finished with the rotary instruments was 2.175 μm, and the maximum roughness (Rmax) was 119 μm. The line profiles of the margins finished with © 2011 Wiley Periodicals, Inc. DOI 10.1111/j.1708-8240.2011.00477.x the ultrasonic instruments were more uniform, but there was an area of increased roughness toward the finishing line (area 3). The roughness mean parameter (Ra) of the surface finished with ultrasonic instruments was 0.58 μm, and the maximum roughness (Rmax) was 45 μm. (Table 1). Journal of Esthetic and Restorative Dentistry Vol •• • No •• • ••–•• • 2011 19 20 21 22 23 24 5 JOBNAME: No Job Name PAGE: 6 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 5BB87F32 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ULTRASONIC MARGIN PREPARATION Horne et al FIGURE 6. SEM image of sample prepared with ultrasonic instruments (¥100). Note the rough and discontinuous finishing line in area 3. 30 31 32 33 34 35 1 4 TABLE 1. Mean surface roughness (mm) Ultrasonic instruments 2 3 4 5 6 7 8 9 10 11 5 12 13 1D Ra Rmax 2D Ra Rmax 6 0.58 45.00 0.75 15.76 Rotary instruments Ra Rmax Ra Rmax 2.18 119.00 1.63 41.14 1D = one dimension; 2D = two dimensions; Ra = the arithmetic mean of the absolute departure of the roughness profile from the mean line; Rmax = the maximum peak-to-valley height in one sampling length. 14 DISCUSSION 15 16 The margins produced with the ultrasonic instrument were in a better condition than those produced with the rotary instrument. Thus, the null hypothesis was rejected. 17 18 19 20 21 A strength of this pilot study was the use of the split-tooth model. This provided a robust control and reduced factors that may have influenced interpretation of the results. Similarly, all tooth preparation was completed by a single operator, which further reduced possible variations. The use of SEM and surface roughness analysis gave both quantitative and qualitative results. 22 23 24 25 26 27 28 29 6 Vol •• • No •• • ••–•• • 2011 Journal of Esthetic and Restorative Dentistry The surface finished with the rotary instruments was over three times rougher than the surface finished with the ultrasonic instruments in one dimension. Two-dimensional analysis produced similar results, although the surface produced with the rotary instruments was over twice as rough as the surface produced with the ultrasonic instruments. 36 37 38 39 40 41 42 43 The margins produced with the ultrasonic instrument were superior to those produced with the rotary instruments in two of the three areas studied. The ultrasonic instruments produced preparation margins that were smooth, with a well-defined and rounded axial wall/margin angle (Figures 2,5,6). Furthermore, the dentin surfaces prepared with the ultrasonic instruments exhibited less debris and were cleaner with exposed dentinal tubules, a condition that is more suitable for bonding procedures.9 However, the rotary instruments produced sharper and more continuous external line angles (Figure 4). 44 45 46 47 48 49 50 51 52 53 54 55 56 The information from the surface of the margins could be correlated to the surface of the instrument, its shape, and its functional mode. 57 58 59 60 With rotary instruments, significant damage to the axial wall of the sample was noted (Figure 2). This damage is DOI 10.1111/j.1708-8240.2011.00477.x © 2011 Wiley Periodicals, Inc. 61 62 JOBNAME: No Job Name PAGE: 7 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 786A1FF6 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ULTRASONIC MARGIN PREPARATION 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 related to the shape of the instrument and is thought to have been caused by the end-cutting tip of the bur scratching the axial surface of the preparation while cutting the interproximal margin. This caused the axial wall/margin angle (area 1) to be rough and irregular, which complicates fabrication of an esthetic and well-fitting prosthesis.8 The surface of the margin (area 2) appeared slightly rougher than the margin produced with the ultrasonic instruments (Figure 3). A possible explanation is that although the finest grit size used for the rotary and ultrasonic finishing was comparable (45 μm and 46 μm), the preparation sequence with the ultrasonic instruments ended with the use of the PMS3 tip, which has no coating of grit. There was a circular pattern noticeable on the surface of the margin prepared with the rotary instruments, which was not present on the ultrasonic preparations. This is related to the shape of the bur and its rotating action, and it is probable that the small working surface of the bur created shallow indentations in the margin surface as it rotated. The external line angles on the margins prepared with the rotary instruments however were ideal (Figure 4). 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 The margin surfaces prepared with the ultrasonic instruments were smoother and wider than those prepared with the rotary instruments (Figure 5). A smooth surface is important for a well-fitting restoration, and assists in strengthening the ceramic butt margin of a restoration, by ensuring that the material remains under compression. The increased width of this margin compared with the margin produced by the rotary instrument can be explained by the presence of diamond particles on the shank of two of the ultrasonic instruments, whereas the rotary instruments had diamond particles on the tip only, preventing axial cutting. The axial wall/margin angle (area 1) on the samples prepared with ultrasonic instruments was smooth and close to 90°, forming a well-rounded shoulder (Figure 2). It is important that this angle is smooth to enhance marginal fit, castability, and esthetics.10 A well-defined, sharp external line angle without a lip of unsupported enamel is critical to the fit of a restoration. The chipped finishing lines observed by SEM on the margins prepared with the ultrasonic instruments may have been due to the oscillating action © 2011 Wiley Periodicals, Inc. DOI 10.1111/j.1708-8240.2011.00477.x Horne et al of the instrument, which caused pieces of enamel to fracture. The PMS3 tip is thought to remove shards of unsupported enamel. It is possible that the areas with chipping were not thoroughly instrumented. This requires further investigation, as a chipped and irregular finish line could compromise the adaptation of the definitive restoration. Another method of analysis of margin accuracy could have been to evaluate the fit of definitive crowns on abutments finished with the two different instruments. 47 48 49 50 51 52 53 54 55 56 57 Bonding to dentin is complicated by a high proportion of organic material, high intrinsic water content, and the smear layer.11 In order to achieve bonding to dentin, the smear layer is often removed with an acid to expose the collagen network and increase permeability of the tubules.9 However, this increase in dentinal tubule permeability can also cause tooth sensitivity after bonding.11 The results suggest that cutting dentin with an ultrasonic instrument produces less debris than cutting with rotary instruments, providing a bonding surface that has less smear layer and a greater density of exposed dentinal tubules. Etchant application to this surface could be of shorter duration.12 58 59 60 61 62 63 64 65 66 67 68 69 70 71 The two-dimensional results of surface roughness analysis are considered to be more clinically significant than the one-dimensional results, as they are taken from a surface, rather than from a line profile. As the diameter of the ultrasonic working tip is almost the same as the width of the margin, the surface is instrumented uniformly with one stroke, thus eliminating irregularities produced by translation of the instrument tip across the margin surface. The diameter of the rotary instrument used was smaller, and the corresponding roughness of the margin is thought to be related to the different levels of instrumentation of the surface. The concentric markings produced by the rotary mode of action are also thought to contribute to the roughness value of this margin, as compared with the oscillatory action of the ultrasonic instruments. 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 The line profiles for both samples were relatively consistent across the margin, but became more irregular as they approached the external line angle. Journal of Esthetic and Restorative Dentistry Vol •• • No •• • ••–•• • 2011 90 91 92 7 JOBNAME: No Job Name PAGE: 8 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 67470F55 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ULTRASONIC MARGIN PREPARATION Horne et al This may be due to the shearing of enamel as observed on the SEM images of the margin finished with the ultrasonic instruments (Figure 6). However, this was also observed on the margin finished with the rotary instruments and may be due to the instruments behaving differently when cutting enamel, as opposed to dentin. Further research is required in this area. 1 2 3 4 5 6 7 8 There was some cracking visible on the root surfaces of both samples. This is thought to be largely artifactual and the result of specimen preparation for scanning microscopy.13 Future studies might consider using epoxy replicas made from silicone impressions as a means to reduce this effect. It was difficult to determine whether there was a higher degree of cracking associated with either finishing instrument, and further research is required into subsurface damage caused by ultrasonic diamond instruments. Xu and colleagues14 reported that preparation of enamel with diamond instruments caused subsurface damage in the form of median-type cracks and micro-cracks. Furthermore, these authors stated that larger diamond grit sizes produced longer subsurface cracks in enamel. Fine diamond finishing burs were recommended by these authors for crack removal. It is unknown whether ultrasonic diamond instruments cause subsurface damage, but they may replace fine diamond finishing burs in the future. 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 The quality of the margins produced with the ultrasonic instruments is promising. With further research and development, they have the potential to overtake rotary and hand instrumentation for finishing in fixed prosthodontics. A key advantage is their lack of rotation, permitting improved control during delicate preparations.4 The frequency of oscillation can be adjusted to change the abrasive activity of the instrument, to complete a smooth subgingival finish line.6 30 31 32 33 34 35 36 37 38 39 40 The oscillating action also prevents soft tissue damage. This has two distinct advantages in situations where esthetics is of particular importance. Damage to the gingiva, especially in individuals with a thin biotype, can result in unsightly recession of the gingival margin.15 The absence of gingival lesions produced during 41 42 43 44 45 46 8 Vol •• • No •• • ••–•• • 2011 Journal of Esthetic and Restorative Dentistry finishing line repositioning facilitates the impression taking procedure and may eliminate the need for gingival retraction cord.3 47 48 49 50 A conventional high-speed handpiece used under normal loading with a water flow of 40 mL/minute prevents increases in temperature of the pulp.16 Von Fraunhofer and colleagues17 reported higher cutting efficiency with higher coolant flow rates. Unfortunately, a higher coolant flow rate also decreases visibility. The increased length of the ultrasonic tip means that the water flow originates from further up the shaft of the instrument than with traditional burs, which improves visibility while cutting. 51 52 53 54 55 56 57 58 59 60 61 CONCLUSION 62 63 Within the limitations of this observational pilot study, the advantages of ultrasonic instruments for finishing preparations in fixed prosthodontics are illustrated. The ultrasonic instruments produce margins in better condition. 64 65 66 67 68 69 This very practical advantage in margin preparation suggests an important role in the future. 70 71 72 Further research will investigate the consequence of this on clinically relevant procedures such as resin bonding. 73 74 75 DISCLOSURE AND ACKNOWLEDGEMENTS 76 77 The authors do not have any financial interest in the companies whose materials are included in this article. 78 79 80 The authors are grateful to Satelec, a division of Acteon (France), for providing the ultrasonic generator, PMS tips, and research funding; The New Zealand Government for further funding; Premier Dental, for providing the Two Striper Tissue Guard End-Cutting burs; Ms Liz Girvan, University of Otago Centre for Scanning Electron Microscopy for assistance with the SEM and surface roughness analysis; and Olympus Soft Imaging Solutions for providing the Scandium software for surface roughness analysis. DOI 10.1111/j.1708-8240.2011.00477.x © 2011 Wiley Periodicals, Inc. 22 81 82 83 84 85 86 87 88 89 90 JOBNAME: No Job Name PAGE: 9 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 28F3A6E3 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 ULTRASONIC MARGIN PREPARATION REFERENCES 1 2 1. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 3 3 Tan K, Pjetursson BE, Lang NP, Chan ES. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years: part III. Conventional FPDs. Clin Oral Implants Res 2004;15(6):654–66. 2. Karlsson S. A clinical evaluation of fixed bridges, 10 years following insertion. J Oral Rehabil 1986;13(5):423–32. 3. Sous M, Lepetitcorps Y, Lasserre J-F, Six N. Ultrasonic sulcus preparation: a new approach for full crown preparations. Int J Periodontics Restorative Dent 2009;29(3):277–87. 4. Magne P, Besler U. Bonded porcelain restorations in the anterior dentition: a biomimetic approach. •• (IL): Quintessence Publishing; 2002, pp. 248–90. 5. Vanderlei AD, Borges AL, Cavalcanti BN, Rode SM. Ultrasonic versus high-speed cavity preparation: analysis of increases in pulpal temperature and time to complete preparation. J Prosthet Dent 2008;100(2):107–9. 6. Massironi D, Pascetta R, Romeo G. Precision in dental esthetics: clinical and laboratory procedures. Milan: Quintessenza Edizioni; 2007, pp. 151–73. 7. Moopnar M, Faulkner KD. Accidental damage to teeth adjacent to crown-prepared abutment teeth. Aust Dent J 1991;36(2):136–40. 8. Shillingburg HT, Jacobi R, Brackett SE. Fundamentals of tooth preparations: for cast metal and porcelain restorations. •• (IL): Quintessence Publishing; 1987, pp. 61–79. 9. Pashley DH, Carvalho RM. Dentine permeability and dentine adhesion. J Dent 1997;25(5):355–72. 10. Cho L, Choi J, Yi YJ, Park CJ. Effect of finish line variants on marginal accuracy and fracture strength of ceramic optimized polymer/fiber-reinforced composite crowns. J Prosthet Dent 2004;91(6):554–60. © 2011 Wiley Periodicals, Inc. DOI 10.1111/j.1708-8240.2011.00477.x Horne et al 11. Van Landuyt K, De Munck J, Coutinho E, et al. Bonding to dentin: smear layer and the process of hybridization. In: Eliades G, Watts DC, Eliades T, editors. Dental hard tissues and bonding. Berlin: Springer-Verlag; 2005, pp. 89–96. 12. Kenshima S, Reis A, Uceda-Gomez N, et al. Effect of smear layer thickness and pH of self-etching adhesive systems on the bond strength and gap formation to dentin. J Adhes Dent 2005;7(2):117–26. 13. Crang RFE, Komparens KL. Artifacts in biological electron microscopy. New York: Plenum Press; 1988, pp. 107–29. 14. Xu HH, Kelly JR, Jahanmir S, et al. Enamel subsurface damage due to tooth preparation with diamonds. J Dent Res 1997;76(10):1698–706. 15. Leblebicioglu B, Rawal S, Mariotti A. A review of the functional and esthetic requirements for dental implants. J Am Dent Assoc 2007;138(3):321–9. 16. Ercoli C, Rotella M, Funkenbusch PD, et al. In vitro comparison of the cutting efficiency and temperature production of 10 different rotary cutting instruments. Part I: turbine. J Prosthet Dent 2009;101(4):319–31. 17. Von Fraunhofer JA, Seigel SC, Feldman S. Handpiece coolant flow rates and dental cutting. Oper Dent 2000;25(6):544–8. 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Reprint requests: Vincent Bennani, DDS, PhD, Department of Oral 64 Rehabilitation, School of Dentistry, University of Otago, P.O. Box 647, 65 Dunedin 9054, New Zealand; Tel.: 0064 3 479 7061; Fax: 0064 3 479 66 5079; email: vincent.bennani@stonebow.otago.ac.nz 67 This article is accompanied by commentary, Ultrasonic Margin 68 Preparation for Fixed Prosthodontics: A Pilot Study, Mamaly Reshad, BDS, 69 DDS, MSC 70 DOI 10.1111/j.1708-8240.2011.00478.x 71 Journal of Esthetic and Restorative Dentistry Vol •• • No •• • ••–•• • 2011 9 JOBNAME: No Job Name PAGE: 10 SESS: 14 OUTPUT: Thu Aug 18 17:15:20 2011 SUM: 2DEA4146 /v2503/blackwell/journals/jerd_v0_i0_newdesign/jerd_477 Journal Code: JERD Article No: 477 Page Extent: 9 Toppan Best-set Premedia Limited Proofreader: Elsie Delivery date: 18 August 2011 AUTHOR QUERY FORM Dear Author, During the preparation of your manuscript for publication, the questions listed below have arisen. Please attend to these matters and return this form with your proof. Many thanks for your assistance. Query References Query q1 AUTHOR: Please supply the job titles for all the authors. q2 AUTHOR: Please confirm if the changes made to the acknowledgements are correct. q3 AUTHOR: Please provide the city locations of publishers for References 4 and 8. q4 AUTHOR: The text citation “Table” has been relabeled as Table 1 in this article. Please confirm that this is correct. q5 AUTHOR: one dimension: Is this the correct definition for 1D? Please change if this is incorrect. q6 AUTHOR: two dimensions: Is this the correct definition for 2D? Please change if this is incorrect. Remark