Effect of Different Cementation Techniques on Retained Excess Cement and Uniaxial Retention of the Implant-Supported Prosthesis: An In Vitro Study Zubeda Begum, MDS1/Radhika Sonika, BDS2/Chheda Pratik, BDS2 Purpose: The aim of this study was to identify the different techniques of cementation (half filling, practice abutment, and venting) that will reduce the amount of retained cement and the effect of these techniques on retention of implant-supported prostheses. Materials and Methods: Thirty implant-abutment assemblies were prepared and were subdivided further into three groups: half filling, practice abutment, and venting techniques. Crowns were prepared for each sample and cemented according to the respective techniques. The retention values were then determined using a universal testing machine, and the net weight of the retained cement was determined using a digital scale. Results: Analysis of variance (ANOVA) tests revealed that there was not a significant difference in the retention values of the three cementation techniques, but a significant difference was observed in the amount of retained excess cement. Tukey honestly significant difference tests further showed that there was a significant difference in retained excess cement between the half-filling technique vs the venting and practice abutment techniques. Conclusion: The venting and practice abutment techniques are suitable methods for reducing retained excess cement with optimal retention values. Int J Oral Maxillofac Implants 2014;29:1333–1337. doi: 10.11607/jomi.3724 Key words: dental implant, cementation, venting, practice abutment, retention, residual cement

S

uccessful osseointegration of implant materials and soft tissue management techniques have allowed implants to become a viable treatment option to replace missing teeth.1 Implant restorations may be cemented or screw-retained; each method has inherent advantages and disadvantages.2 Implant restorations often receive cyclic loading because of the nature of chewing, and consequently, screw-retained restorations experience screw loosening and fatigue fracture of their prosthetic screws.3 Screw-retained crowns have exhibited evidence of screw loosening in 50% of restorations during the first year in function.4 This phenomenon has also been observed in 43% of

1Professor

and Postgraduate Guide, Department of Prosthodontics and Implantology, M R Ambedkar Dental College and Hospital, Bangalore, Karnataka, India. 2Postgraduate Student, Department of Prosthodontics, M R Ambedkar Dental College and Hospital, Karnataka, India. Correspondence to: Dr Radhika Sonika, Postgraduate Student, Department of Prosthodontics, M R Ambedkar Dental College and Hospital, 1/36, Cline Road, Cooke Town, Bangalore 560005, India. Email: [email protected] ©2014 by Quintessence Publishing Co Inc.

single-tooth implant crowns; moreover, they are usually less esthetic and more expensive to fabricate because of the extra components and laboratory costs.5 Implants placed during the development era had high failure rates, and, consequently, easy and frequent removal of the prostheses was of paramount importance. Screw retention in implant-supported prostheses was developed in response to the need for retrievability even though occlusion and esthetics were sacrificed. As knowledge increased and techniques advanced, implant survival rates moved rapidly from the 50% to the 90% range.3 With this dramatic increase in survival rates, cemented crowns were introduced for esthetic reasons and to compensate for screw-loosening problems encountered with the screw-retained restorations. Cemented restorations have the advantage of simplicity, hermetic sealing, passive fit, and more favorable esthetics and crown contours.2 Crestal bone loss around dental implants has been a subject of discussion in implant dentistry since its inception. While there are a variety of causes for crestal bone loss around dental implants, one iatrogenic cause is retained dental cement.6 Wilson reported that excess dental cement was associated with signs of periimplant disease in the majority (81%) of the cases.7 The following are usually observed: peri-implant inflammation associated with swelling, soreness, increased The International Journal of Oral & Maxillofacial Implants 1333

© 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

Begum et al

probing depths, bleeding and/or exudation on probing, and radiographic loss of peri-implant bone. The removal of residual excess cement can be difficult and can only be confirmed and evaluated with exploratory flap surgery or with a dental endoscope.7 Cleaning excess cement using dental instruments after cementation may damage the implant surfaces. Roughened implant surfaces may lead to increased plaque accumulation, impaired plaque removal, and compromised soft tissue compatibility.8 Various cementation techniques such as venting, escape channels, etching, die spacing, half filling of the crowns, coating the axial walls only, etc, have been documented to reduce the amount of retained excess cement, but such techniques have also been believed to reduce the retention of the prosthesis as the amount of cement used is decreased. However, there are no conclusive recommendations for standardized cementation techniques. Therefore, the purpose of this study was to compare three different techniques of cementation that will reduce the retained excess cement and also to determine their effect on retention of the implant-supported prosthesis.

MATERIALS AND METHODS Specimen Preparation

Thirty 3.5 × 11 mm EZ Hi-Tec dental implants (Hi-Tec) were used for this study. Each was embedded in an acrylic block. Solid machined abutments, 5.5 mm long with margins at a height of 3 mm, were tightened to 35 Ncm of torque to each implant. Gingiva, 1.5 mm at the facial and lingual aspects and 3.0 mm at the interproximal aspect, was simulated using light body polysiloxane material (Aquasil, Dentsply) for each sample. Wax patterns were fabricated for each sample. All wax patterns were sprued, invested in a phosphate-bonded investment material (Bellasun, Bego), and cast in a metal-ceramic alloy (Bellabond Plus, Bego) according to the manufacturer’s laboratory protocol. After divesting and ultrasonic cleaning, the internal aspect of the castings was inspected under a magnifying glass, and surface irregularities were removed using a small round tungsten carbide bur. Residual investment materials were removed using an ultrasonic cleaner with mild detergent and airborne-particle abraded using 50-μm aluminum oxide particles. The specimens were divided into three groups of 10 samples according to the cementation techniques: • Group 1: Half filling of the crown • Group 2: Practice abutment technique • Group 3: Venting technique

The implant and the abutment assemblies were preweighed on a digital scale, and the weight was noted for each sample. Glass-ionomer cement type 1 (Fuji 1, GC) mixed according to the manufacturer’s instructions and a standardized quantity of 0.01 mL, measured using an insulin syringe, was used for cementation for all three groups.

Cementation

For Group 1, the crowns were cemented by filling the occlusal half of the intaglio surface of the crown with the glass-ionomer cement and then placing the crowns on the abutments, followed by removal of excess cement, if any. A controlled load of 10 kg was applied for 10 minutes. For Group 2, the crowns were cemented by the practice abutment technique. The intaglio surfaces of the crowns were coated with glass-ionomer cement. Each casting was seated on a practice abutment with finger pressure. The practice abutment consisted of one 3.5 × 11-mm dental implant (EZ Hi-Tec) with an abutment 5.5 mm long with margins at a height of 3 mm, tightened to 35 Ncm of torque. Excess cement was removed with cotton gauze. The castings were immediately removed along the same path of withdrawal from the practice abutment and seated on the implant embedded in the acrylic block. A controlled axial load of 10 kg was applied for 10 minutes. For Group 3, the crowns were cemented by a venting technique in which a vent hole was prepared on the occlusal aspect so that the excess cement could flow out. Access could be gained in case of abutment screw loosening through this escape hole as well. The vent hole was made using a 1.0-mm round bur. The intaglio surfaces of the crowns were coated with glassionomer cement, and these crowns were placed on the abutment-implant assemblies. The excess cement that flowed out was removed using a gloved finger or a cotton tip applicator. A controlled axial load of 10 kg was applied for 10 minutes.

Removal Torque Testing

All specimens were stored in 100% humidity at 37°C for 24 hours prior to tensile testing. Each specimen was placed in a universal testing machine (Instron) using a jig fabricated specifically to ensure the application of vertical forces only. Using a 50-kg load cell at a crosshead speed of 0.5 mm/min, each casting was pulled from the abutment, and the force at which retentive failure occurred was recorded.

Excess Cement Measurement

After removal of the crowns, the abutment-implant assembly was reweighed using a digital scale. The cement retained in the crown was minimal and was not

1334 Volume 29, Number 6, 2014 © 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

Begum et al

evaluated, as this excess cement would not have a significant effect on the bone and the tissues surrounding the implant. The difference between the preweighed assembly and the post-cementation weight was calculated. This provided the net weight of the retained excess cement.

Statistical Analysis

The data collected were analyzed using the analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests to determine the technique that leads to the minimum residual cement with maximum retention. The separation forces between the three groups were compared using the ANOVA statistical test at P ≤ .05. The weight of the implant-casting assembly was also compared using the same statistical test. The Tukey HSD test (α = .05) was performed to determine the significance of differences in cement weight for all three groups.

RESULTS The results of the tensile strength test are shown in Tables 1 to 3 for each cementing technique. The mean and standard deviations of tensile strength and residual excess cement are listed in Table 4 and depicted in Figs 1 and 2. Statistically insignificant difference (P = .932) shows that retention is not affected by the cementation technique when glass-ionomer cement is used. The differences in the retained excess cement are also shown in Tables 1 to 3. The difference was determined by subtracting the assembly weight prior to cementation from that recorded after cementation and removal of the casting. The residual cement weight of the practice abutment technique was the least (0.013 g), followed by venting technique (0.015 g). The half-filling technique showed the greatest amount of residual cement (0.029 g). Statistically significant difference was found in the amount of residual excess cement for the half-filling technique compared to the practice abutment and venting techniques. However, the two latter techniques showed statistically homogenous values.

DISCUSSION When implant restorative margins are placed subgingivally, the likelihood that residual excess cement is present in the surrounding peri-implant tissue increases.9 Agar et al reported that the use of metallic instrumentation such as curettes and scalers to remove residual cement on titanium implant components may increase implant surface roughness, which may cause

Table 1   Retention and Residual Excess Cement Values for Group 1, Half-Filling Technique Sample No.

Retention (N)

Residual excess cement (g)

1

135.19

0.06

2

124.80

0.03

3

188.72

0.03

4

111.30

0.01

5

171.60

0.02

6

178.21

0.02

7

121.70

0.04

8

128.60

0.03

9

140.30

0.02

10

155.10

0.03

Table 2   Retention and Residual Excess Cement Values for Group 2, Practice Abutment Technique Sample No.

Retention (N)

Residual excess cement (g)

1

147.78

0.02

2

173.12

0.01

3

145.68

0.01

4

101.30

0.01

5

103.60

0.02

6

120.70

0.02

7

158.40

0.01

8

158.40

0.02

9

162.30

0.01

10

148.90

0

Table 3   Retention and Residual Excess Cement Values for Group 3, Venting Technique Sample No.

Retention (N)

Residual excess cement (g)

1

167.90

0.02

2

135.10

0.01

3

107.60

0.01

4

103.50

0.01

5

121.60

0.01

6

130.50

0.01

7

170.00

0.02

8

151.14

0.02

9

160.11

0.02

10

168.25

0.02

The International Journal of Oral & Maxillofacial Implants 1335 © 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

200  180  160  140  120  100  80  60  40  20  0 

Retained excess cement (g)

Retention (N)

Begum et al

Group 1

Group 2

Group 3

Fig 1  Mean retention values for the three cementation techniques.

0.05  0.045  0.04  0.035  0.03  0.025  0.02  0.015  0.01  0.005  0 

Group 1

Group 2

Group 3

Fig 2  Mean retained excess cement values for the three cementation techniques.

Table 4   Retained Excess Cement and Retention Mean and Standard Deviation Values Group 1 Half-filling Retained excess cement (g)

Mean SD

Tensile strength (N)

Mean SD

0.029 0.015492 145.552 26.4465

Group 2 Practice abutment 0.013** 0.006749 142.018 24.9394

Group 3 Venting 0.015** 0.00527 141.57 25.4191

P value .005* .932

*P < .01; statistically significant difference. **P > .05; statistically not significant.

microbial adherence.8 Incomplete removal of excess cements may result in peri-implant inflammation, soft tissue swelling, bleeding or exudation, and, in the worst case, implant failure.10 The choice of cement for an implant-retained restoration should be based on the need for retrievability of the prostheses and ease of excess cement removal. There is little evidence regarding which cements are most suitable for retrievability of implant-supported prostheses. Many clinicians prefer to use provisional cement or the least retentive cement for final cementation to ensure retrievability of implant-supported prostheses.11 However, such cements often have low tensile strength and are soluble. These cements may wash out into the oral cavity, leaving a gap at the margin of the restoration and thereby risking peri-implant health; such restorations may require frequent recementation. Singer and Serfaty12 observed a 9.8% rate of cement washout on 92 cement-retained fixed partial dentures supported by 225 implants in a 6-month to 3-year survey. The result was attributed to the use of short abutments and provisional cements such as TempBond (Kerr). Resin cements have the highest retentive strength in cementation of prostheses on natural teeth and implants. However, Agar and coworkers showed that resin cements were the most difficult cements to remove in subgingival implant restorations.8

Akça and coworkers13 compared the uniaxial resistance forces of 10 different luting cements on four different Straumann abutments. They found that provisional cements had significantly lower uniaxial resistance forces when compared with permanent cements. The investigators compared the resistance force of zinc oxide–eugenol (Kerr) (mean tensile strength 40.6 ± 4.00 N) with that of glass-ionomer cement (Vitremer, 3M ESPE) (236.5 ± 38 N). Agar et al also showed in his study that it is much easier to remove the glass-ionomer cement from the metal surfaces as compared to the resin cements or resin-modified glass-ionomer cement.8 Therefore, in this study the authors used glass-ionomer cement, which has retention values less than resin cements but greater than provisional cements and is much easier to remove than others. Some authors have showed that reducing the amount of permanent cement applied to the restoration does not reduce retention. The use of a cementation technique such as half-coating of the restorations with cements did not result in reduced retention values compared to the complete-coating technique.14 These studies showed that using less cement results in a better marginal fit of cemented implant restorations. However, the amount of residual excess cement was not recorded. Clark et al15 has advocated the use of vents to reduce the excess cement pressure in the

1336 Volume 29, Number 6, 2014 © 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

Begum et al

ceramic crown. This technique has been used with implants as well. Yeung et al showed that use of the venting technique significantly reduced the excess residual cement and also improved the marginal fit of CeraOne implant abutments.2 Schwedhelm et al also demonstrated the use of a cement escape or vent for cementation of implant-supported crowns.16 Santosa et al showed that this same practice abutment technique significantly reduced the amount of excess cement weight prior to final cementation without much effect on retention values.10 Chee et al also showed that the least amount of excess cement was present when a cementation device was used to displace excess cement before seating the castings on an abutment.17 Similarly, Wadhwani et al has advocated the use of practice cement to minimize the detrimental effect of excess cement.18 However, to the authors’ knowledge no study has compared the three techniques of half-filling, practice abutment, and venting regarding the weight of retained excess cement and retention. Therefore, this study was conducted to evaluate the retention of the prosthesis using the different cementing techniques and also to determine an effective technique to reduce the amount of residual cement with optimal retention values. Within the limitation of this study, it was found that the residual cement was minimum with the practice abutment technique, and there was no significant difference between practice abutment and venting techniques. Hence, the authors recommend using the practice abutment or venting techniques for cementation of implant-supported prostheses using glassionomer cement. Abutment screw loosening has been a common problem since implants have been used. It has been recommended by some authors to tighten these screws every 3 months. Therefore, the same occlusal vent can be used to access the screw for tightening. Hence, additional damage to the crown in gaining access to screws can be avoided. These vents are closed by composite restorations; hence, accurate occlusal anatomy can also be achieved. This additional benefit of the venting technique makes it a viable option for cementing implant-supported prostheses.

CONCLUSIONS Within the limitation of this study, it can be concluded that the practice abutment and the venting techniques can be used to minimize the amount of retained excess cement without affecting the retention of the implantsupported prostheses. Additionally, an occlusal vent can be used to access the abutment screw in case of any screw loosening.

ACKNOWLEDGMENTS The authors reported no conflicts of interest related to this study.

REFERENCES 1. Covey DA, Kent DK, St Germain HA Jr, Koka S. Effects of abutment size and luting cement type on the uniaxial retention force of implant-supported crowns. J Prosthet Dent 2000;83:344–348. 2. Yeung TC, Lai YL, Hsieh YL, Lee SY. The effect of cement and venting design on the retentive strength and marginal adaptation of CeraOne implant prostheses. Chin Dent J 2005;24(2)95–100. 3. Hebel KS, Gajjar RC. Cement-retained versus screw-retained implant restorations: Achieving optimal occlusion and esthetics in implant dentistry. J Prosthet Dent 1997;77:28–35. 4. Ekfeldt A, Carlsson GE, Börjesson G. Clinical evaluation of singletooth restorations supported by osseointegrated implants: A retrospective study.  Int J Oral Maxillofac Implants 1994;9:179–183. 5. Jemt T, Lekholm Y, Gröndahl K. A 3-year follow-up study of early single implant restorations ad modum Brånemark. Int J Periodontics Restorative Dent 1990;10:341–349 6. Shapoff CA, Lahey BJ. Crestal bone loss and the consequences of retained excess cement around dental implants. Compend Contin Educ Dent 2012;33:94–96, 98–101. 7. Wilson TG. The positive relationship between excess cement and peri-implant disease: A prospective clinical endoscopic study. J Periodontol 2009;80:1388–1392. 8. Agar JG, Cameron SM, Hughbanks JC, Parker H. Cement removal from restorations luted to titanium abutments with simulated subgingival margins. J Prosthet Dent 1997;78:43–47. 9. Keith SE, Miller BH, Woody RD, Higginbottom FL. Marginal discrepancy of screw-retained and cemented metal ceramic crowns on implant abutments. Int J Oral Maxillofac Implants 1999;14:369–378. 10. Santosa RE, Martin W, Morton D. Effects of a cementing technique in addition to luting agent on the uniaxial retention force of a single-tooth implant-supported restoration: An in vitro study. Int J Oral Maxillofac Implants 2009;25:1145–1152. 11. Dumbrigue HB, Abanomi AA, Cheng, LL. Techniques to minimize excess luting agent in cement-retained implant restorations. J Prosthet Dent 2002;87:112–114. 12. Singer A, Serfaty V. Cement-retained implant-supported fixed partial dentures: A 6-month to 3-year follow-up. Int J Oral Maxillofac Implants 1996;11:645–649. 13. Akça, K, Iplikçioğlu H, Çehreli MC. Comparison of uniaxial resistance forces of cements used with implant-supported crowns. Int J Oral Maxillofac Implants 2002;17:536–542. 14. Wolfart M, Wolfart S, Kern M. Retention forces and seating discrepancies of implant-retained castings after cementation. Int J Oral Maxillofac Implants 2006;21:519–525. 15. Clark MT, Richards MW, Meiers JC. Seating accuracy and fracture strength of vented and nonvented ceramic crowns luted with three cements. J Prosthet Dent 1995;74:18–24. 16. Schwedhelm ER, Lepe X, Aw TC. A crown venting technique for the cementation of implant-supported crowns. J Prosthet Dent 2003;89:89–90. 17. Chee WW, Duncan J, Afshar M, Moshaverinia A. Evaluation of the amount of excess cement around the margins of cement-retained dental implant restorations: The effect of the cement application method. J Prosthet Dent 2013;109:216–221. 18. Wadhwani C, Pineyro A. Technique for controlling the cement for an implant crown. J Prosthet Dent 2009;102:57–58.

The International Journal of Oral & Maxillofacial Implants 1337 © 2014 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

Effect of different cementation techniques on retained excess cement and uniaxial retention of the implant-supported prosthesis: an in vitro study.

The aim of this study was to identify the different techniques of cementation (half filling, practice abutment, and venting) that will reduce the amou...
118KB Sizes 3 Downloads 4 Views