PROGRAMACIÓN POR UNIDADES DE APRENDIZAJE (SYLABUS

The purpose of this study was to use Micro-CT to compare two cement cleanup

procedures which were conducted with a resin modified glass ionomer and a self-adhesive resin cement, making volumetric measurements of voids at the margins of full coverage restorations. Our results show that there was no statistically significant difference in the volume per void between the two cleanup methods, irrespective of cement type. Therefore, we must accept our Null Hypothesis.

However, during the course of our research we analyzed other outcomes, such as number of voids and width per void. It is interesting to note that no statistically significant difference existed for all outcomes (number of voids, volume per void, and width per void) when comparing the two cement cleanup methods. Another interesting finding, although not the

original focus of this study, is that a statistically significant difference in the number of voids, the volume per void and the width per void were found between the two cements, irrespective of the cleanup method used, the RMGI having the higher value for all outcomes.

The results of this study constitute a contribution to the advancement in research methodology, considering that, to date only one study has measured the volume of voids at the margin using micro computed tomography. Dauti, et al. fabricated polymer infiltrated ceramic

network full-coverage restorations, using digital scans and CAD/CAM technology, and cemented with RelyX Unicem. They found an average volume of marginal porosity between 0.363mm3 and 0.517mm3_.12 _{In their study, though, the entire margin was scanned and the excess cement} was wiped from the margins with a foam pellet before it was set instead of following the manufacturer’s recommended method of cement cleanup, making our studies difficult to

compare. However, if our data were extrapolated to estimate the total void for the entire margin, we find an average void of 0.051 mm3 _{which is an order of magnitude lower in average}

volume/sample. The use of Micro-CT to evaluate voids at the margin allowed the quantification of several parameters in three dimensions in a non-destructive manner. With a resolution of 8µm/voxel and sufficient differences in x-ray attenuations of the crown, die, and cement layer, we were able to clearly identify and measure the number, volume, and width of each void present along the entire margin. This study focused on the buccal margin due to its ease of access within our cementation rig and to the fact that the cleanup method employed experimentally does not translate to the clinical method of cleaning cement interproximally. Nevertheless, we may come to some conclusions. It is important to remember the clinically relevant fact that open voids in the marginal areas can support the penetration of fluids and bacteria in the cement space leading to cement dissolution, secondary caries, periodontal inflammations up to loss of restoration or tooth.54 _{If we consider the clinical implications of our findings, they suggest that the type of} cement has a greater influence on the outcome of void formation at the margin than does the cement cleanup method. Our results would suggest that the clinician may choose either method of cement cleanup investigated in this study and would potentially choose the adhesive resin cement over the resin modified glass ionomer. Also, the successful implementation of a novel use of Micro-CT in dental research has led us to conclude that Micro-CT is a promising method

of researching hitherto uninvestigated aspects of dental practices and materials.

The experiments in this study, and those that plan to use Micro-CT, must be limited to the in vitro design. Standardized laboratory conditions were employed to minimize bias as much as possible. Factors such as blood, saliva, gingiva, and adjacent teeth in the clinical setting are certainly a limitation of the study and would certainly impact the cementation process in vivo. It is recognized that the sample sizes in this study are inadequate to lend substantial statistical power to the results.

The first suggestion of ways to expand on this experiment would be to increase the sample size and variety of dental cements investigated. This would greatly improve the power of the results obtained. Also, while milled lithium disilicate was adequate for this study, it may be worthwhile to attempt to replicate this study using polymer infiltrated ceramic network crowns because their x-ray attenuation levels were shown to be superior when differentiating the resin die, the cement layer, and the crown from each other.12 _{Lastly, it may be beneficial to incorporate} an additional experimental method of cement cleanup which is widely performed clinically. This method involves placing the crown and immediately wiping the unset cement away from the margin before it has begun to set. It would be interesting to compare accepted manufacturer’s recommended methods to this clinician accepted method of cement cleanup.

REFERENCES

1. Manhart J, Chen H, Hamm G, Hickel R. Buonocore Memorial Lecture. Review of the clinical

survival of direct and indirect restorations in posterior teeth of the permanent dentition. Oper Dent. 2004 Oct;29(5):481–508.

2. Contrepois M, Soenen A, Bartala M, Laviole O. Marginal adaptation of ceramic crowns: a

systematic review. J Prosthet Dent. 2013 Dec;110(6):447–454.e10.

3. Pelekanos S, Koumanou M, Koutayas S-O, Zinelis S, Eliades G. Micro-CT evaluation of the

marginal fit of different In-Ceram alumina copings. Eur J Esthet Dent. 2009;4(3):278–92.

4. Scanco Micro-CT general information [Internet]. Scanco.ch. [cited 2020 Apr 15]. Available from:

http://www.scanco.ch/en/support/faq-general.html

5. Amano M, Agematsu H, Abe S, Usami A, Matsunaga S, Suto K, et al. Three-dimensional analysis

of pulp chambers in maxillary second deciduous molars. J Dent. 2006 Aug;34(7):503–8.

6. Fanuscu MI, Chang T-L. Three-dimensional morphometric analysis of human cadaver bone:

microstructural data from maxilla and mandible. Clin Oral Implants Res. 2004 Apr;15(2):213–8.

7. Nevins ML, Camelo M, Rebaudi A, Lynch SE, Nevins M. Three-dimensional micro-computed

tomographic evaluation of periodontal regeneration: a human report of intrabony defects treated with Bio-Oss collagen. Int J Periodontics Restorative Dent. 2005 Aug;25(4):365–73.

8. Lee B-S, Lee C-C, Wang Y-P, Chen H-J, Lai C-H, Hsieh W-L, et al. Controlled-release of

tetracycline and lovastatin by poly(D,L-lactide-co-glycolide acid)-chitosan nanoparticles enhances periodontal regeneration in dogs. Int J Nanomedicine. 2016 Jan 18;11:285–97.

9. Bissinger O, Probst FA, Wolff K-D, Jeschke A, Weitz J, Deppe H, et al. Comparative 3D micro-CT

and 2D histomorphometry analysis of dental implant osseointegration in the maxilla of minipigs. J Clin Periodontol. 2017 Apr;44(4):418–27.

10. Neves FD, Prado CJ, Prudente MS, Carneiro TAPN, Zancopé K, Davi LR, et al. Micro-computed tomography evaluation of marginal fit of lithium disilicate crowns fabricated by using chairside CAD/CAM systems or the heat-pressing technique. J Prosthet Dent. 2014 Nov;112(5):1134–40. 11. Duqum IS, Brenes C, Mendonca G, Carneiro TAPN, Cooper LF. Marginal Fit Evaluation of

CAD/CAM All Ceramic Crowns Obtained by Two Digital Workflows: An In Vitro Study Using Micro-CT Technology. J Prosthodont. 2019 Dec;28(9):1037–43.

12. Dauti R, Cvikl B, Lilaj B, Heimel P, Moritz A, Schedle A. Micro-CT evaluation of marginal and internal fit of cemented polymer infiltrated ceramic network material crowns manufactured after conventional and digital impressions. J Prosthodont Res. 2019 Jan;63(1):40–6.

13. Kim J-H, Jeong J-H, Lee J-H, Cho H-W. Fit of lithium disilicate crowns fabricated from conventional and digital impressions assessed with micro-CT. J Prosthet Dent. 2016 Oct;116(4):551–7.

14. Malkoç MA, Sevimay M, Tatar İ, Çelik HH. Micro-CT Detection and Characterization of Porosity in Luting Cements. J Prosthodont. 2015 Oct;24(7):553–61.

15. Nomoto R, Komoriyama M, McCabe JF, Hirano S. Effect of mixing method on the porosity of encapsulated glass ionomer cement. Dent Mater. 2004 Dec;20(10):972–8.

16. Stock SR. Microcomputed tomography: methodology and applications. CRC Press; 2018. 17. Mesu FP. Degradation of luting cements measured in vitro. J Dent Res. 1982 May;61(5):665–72. 18. Rosenstiel SF, Land MF, Crispin BJ. Dental luting agents: A review of the current literature. J

Prosthet Dent. 1998 Sep;80(3):280–301.

19. Kydd WL, Nicholls JI, Harrington G, Freeman M. Marginal leakage of cast gold crowns luted with zinc phosphate cement: an in vivo study. J Prosthet Dent. 1996 Jan;75(1):9–13.

20. Ibarra G, Johnson GH, Geurtsen W, Vargas MA. Microleakage of porcelain veneer restorations bonded to enamel and dentin with a new self-adhesive resin-based dental cement. Dent Mater. 2007 Feb;23(2):218–25.

21. Alani AH, Toh CG. Detection of microleakage around dental restorations: a review. Oper Dent. 1997 Aug;22(4):173–85.

22. Felton DA, Kanoy BE, Bayne SC, Wirthman GP. Effect of in vivo crown margin discrepancies on periodontal health. J Prosthet Dent. 1991 Mar;65(3):357–64.

23. Pierce CN. Filling materials of oxide of zinc and glacial phosphoric acid. Dent Cosmos. 1897;21:696.

24. Rosner D. Function, placement, and reproduction of bevels for gold castings. J Prosthet Dent. 1963 Nov;13(6):1160–6.

25. Fleck H. The chemistry of oxyphosphates. Dent Items Interest. 1902;906–35. 26. Lane JG. Crowns. Dent Dig. 1910 Feb;16(2):71–82.

27. ISO. ISO 9917-1: dentistry-water-based cements—part 1: powder/liquid acid–base cements. International Organization for Standardization, Geneva, Switzerland. 2007;

28. ISO. ISO 9917-2: dentistry-water-based cements—part 2: resin-modified cements. International Organization for Standardization, Geneva, Switzerland. 2010;

29. Anusavice KJ. Phillips’ science of dental materials. 12th ed. Elsevier/saunders; 2012.

30. Donovan TE, Cho GC. Contemporary evaluation of dental cements. Compend Contin Educ Dent. 1999 Mar;20(3):197–9, 202.

31. Ramaraju DV S, Krishna Alla R, Ramaraju Alluri V, Makv R. A review of conventional and contemporary luting agents used in dentistry. AJMSE. 2014 Aug 12;2(3):28–35.

2012 Oct;28(10):e187-98.

33. RelyX Unicem 2 Technical Data Sheet [Internet]. [cited 2020 Apr 14]. Available from:

https://multimedia.3m.com/mws/media/669183O/3m-relyx-unicem-2-automix-self-adhesive-resin- cement-technical-data-sheet.pdf

34. Behr M. Marginal adaptation in dentin of a self-adhesive universal resin cement compared with well-tried systems. Dental Materials. 2004 Feb 1;20(2):191–7.

35. Revised american national standards institute/american dental association specification no. 8 for zinc phosphate cement. The Journal of the American Dental Association. 1978 Jan;96(1):121–3. 36. Sulaiman TA, Abdulmajeed AA, Altitinchi A, Ahmed SN, Donovan TE. Physical Properties, Film

Thickness, and Bond Strengths of Resin-Modified Glass Ionomer Cements According to Their Delivery Method. J Prosthodont. 2019 Jan;28(1):85–90.

37. RelyX Luting Plus Technical Product Profile [Internet]. [cited 2020 Apr 14]. Available from: https://multimedia.3m.com/mws/media/250363O/3m-relyx-luting-cement-technical-product- profile.pdf

38. Kelly JR, Benetti P. Ceramic materials in dentistry: historical evolution and current practice. Aust Dent J. 2011 Jun;56 Suppl 1:84–96.

39. Rosenblum MA, Schulman A. A review of all-ceramic restorations. J Am Dent Assoc. 1997 Mar;128(3):297–307.

40. Weinstein M, Katz S, Weinstein AB. Permanent Manufacturing Corporation, assignee. Fused Porcelain-to-Metal Teeth. US Patent No 3,052,982. 1962 Sep 11;

41. Willard A, Gabriel Chu T-M. The science and application of IPS e.Max dental ceramic. Kaohsiung J Med Sci. 2018 Apr;34(4):238–42.

42. Ivoclar e.max CAD solutions chairside [Internet]. IvoclarVivadent. [cited 2020 Apr 14]. Available from: https://www.ivoclarvivadent.us/mam/celum/celum_assets/9514750640158_IPS_e-

max_CAD_Monolithic_Solutions_Chairside_pdf_4774.pdf?2

43. Holmes JR, Bayne SC, Holland GA, Sulik WD. Considerations in measurement of marginal fit. J Prosthet Dent. 1989 Oct;62(4):405–8.

44. McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J. 1971 Aug 3;131(3):107–11.

45. Taylor MJ, Lynch E. Microleakage. J Dent. 1992 Feb;20(1):3–10. 46. Kidd EAM. Microleakage : a review. J Dent. 1976 Sep;4(5):199–206.

47. Boeddinghaus R, Whyte A. Current concepts in maxillofacial imaging. Eur J Radiol. 2008 Jun;66(3):396–418.

49. Brüllmann D, Schulze RKW. Spatial resolution in CBCT machines for dental/maxillofacial applications-what do we know today? Dentomaxillofac Radiol. 2015;44(1):20140204. 50. Factsheet 3Shape D800/810. [cited 2020 Apr 14]; Available from: http://s3-eu-west-

1.amazonaws.com/core3d-website/content/pdfs/core3dcentres-3shape-d800_810-product-sheet.pdf 51. Goracci C, Cury AH, Cantoro A, Papacchini F, Tay FR, Ferrari M. Microtensile bond strength and interfacial properties of self-etching and self-adhesive resin cements used to lute composite onlays under different seating forces. J Adhes Dent. 2006 Oct;8(5):327–35.

52. RelyX Unicem 2 Automix Technique Guide [Internet]. [cited 2020 Apr 15]. Available from: https://multimedia.3m.com/mws/media/684611O/3m-relyx-unicem-2-automix-self-adhesive-resin- cement-technique-guide.pdf

53. RelyX Luting Plus Technique Guide [Internet]. [cited 2020 Apr 15]. Available from:

https://multimedia.3m.com/mws/media/735193O/3m-relyx-luting-plus-automix-resin-modified- glass-ionomer-cement-technique-guide.pdf

54. Milutinović-Nikolić AD, Medić VB, Vuković ZM. Porosity of different dental luting cements. Dent Mater. 2007 Jun;23(6):674–8.