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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 14  |  Issue : 4  |  Page : 178-184

Comparative evaluation of the effect of degree of convergence and surface area on the retentive force of titanium crowns cemented with various adhesive luting agents on extracted human teeth – A laboratory study


1 Department of Prosthodontics and Crown and Bridge, School of Dental Sciences, Sharda University, Greater Noida, Uttar Pradesh, India
2 Department of Endodontics and Conservative Dentistry, School of Dental Sciences, Sharda University, Greater Noida, Uttar Pradesh, India

Date of Submission06-Oct-2021
Date of Acceptance23-Jan-2022
Date of Web Publication15-Nov-2022

Correspondence Address:
Ashish Choudhary
Department of Prosthodontics and Crown and Bridge, School of Dental Sciences, Sharda University, Greater Noida - 201 310, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijds.ijds_132_21

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  Abstract 


Introduction: The retention of base metal crowns and noble metal crowns cemented with various luting agents is well documented. However, little emphasis was given to the degree of convergence and surface area of tooth preparation. Aim and Objective: A study was planned to analyze the effect of the degree of convergence and surface area of the tooth preparation on the retention of titanium crowns with various adhesive luting agents. Materials and Methods: Forty-five caries-free extracted human premolars were obtained. They were divided into three groups according to the degree of convergence and further subdivided based on the type of luting agents used. The teeth were prepared with an angle of convergence of 5°, 10°, and 15° with a flat occlusal surface using K9 crown finishing installation, complete. Light body copper band impressions were made to determine the surface area. Titanium crowns thus obtained were sandblasted, ultrasonically cleaned, and cemented using Panavia F, Calibra, and Glass Ionomer Cement. Results: Results showed that Panavia F was the best luting agent exhibiting maximum retentive force to dislodge the crown in a vertical direction using the universal tensile testing machine at a cross-head speed of 1 mm/min. Conclusion: The force required to dislodge the titanium crown from the prepared tooth was maximum for Panavia F on 5°, 10°, and 15° angle of convergence at 65.23 kgf, 48.52 kgf, and 40.14 kgf. Retentive force values drastically reduced as the degree of convergence increased. There was a reduction in the surface area due to an increase in the taper.

Keywords: Adhesive luting agents, degree of convergence, retentive force, surface area, titanium


How to cite this article:
Choudhary A, Choudhary E, Duggal S. Comparative evaluation of the effect of degree of convergence and surface area on the retentive force of titanium crowns cemented with various adhesive luting agents on extracted human teeth – A laboratory study. Indian J Dent Sci 2022;14:178-84

How to cite this URL:
Choudhary A, Choudhary E, Duggal S. Comparative evaluation of the effect of degree of convergence and surface area on the retentive force of titanium crowns cemented with various adhesive luting agents on extracted human teeth – A laboratory study. Indian J Dent Sci [serial online] 2022 [cited 2022 Dec 9];14:178-84. Available from: http://www.ijds.in/text.asp?2022/14/4/178/361195




  Introduction Top


The dilemma involved with displaced crowns/cast restorations is quite common. Cemented crowns may be dislodged because the preparation underneath does not oppose forces directed against the restoration. As a result, the design of tooth preparation must be a relevant consideration in the retention of artificial crowns. Restricting the number of directions along which the restoration can be withdrawn from a tooth preparation enhances the retention. A single direction provides utmost retention. Since the introduction of cast restorations, numerous studies have been conducted, but no significance is given to the surface area and design specifications affecting retention. In the era of adhesive types of cement bonding to a tooth as well as metal or materials of artificial crowns such as titanium, several factors that influence retention are as follows:

  1. Film thickness beneath the prosthesis
  2. High strength value of the cement
  3. Minimal dimensional changes during setting
  4. Cement with a potential of chemically bonding to the tooth and prosthesis.[1]


The degree of convergence, the surface area of the prepared tooth, and the type of adhesive luting agents used are among the most common factors that would affect the retention. The purpose of this study is one such effort to evaluate these factors, and the findings would be useful for the selection of better luting agents, resulting in maximum retention of titanium crowns on the prepared teeth having a different degree of convergence and surface area.


  Materials and Methods Top


Forty-five caries-free extracted human premolars of comparable crown size and length were selected. They were cleaned with hydrogen peroxide and stored in saline, following which a hole was drilled mesiodistally through each tooth [Figure 1] and an 18-8 stainless steel wire passed through it. They were then inserted in a block of self-cure autopolymerizing acrylic resin (self-cure acrylic, Dental Products of India, Mumbai, Maharashtra, India), and the block was mounted on the crown twin table. The occlusal surface of all the specimens was flattened so that they become parallel to the base of the twin table. Heights of all the specimens were maintained. Tooth preparation was done (K9-crown finishing installation complete) and fixed in place [Figure 2], thus achieving an axial orientation at 5°, 10°, and 15° [Figure 3].
Figure 1: Extracted premolars with a hole drilled in middle one-third of the root

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Figure 2: K9-crown finishing installation, complete with mounted specimen and high turbine hand piece

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Figure 3: Specimens prepared with 5°, 10°, and 15° angle of convergence to the long axis of tooth

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All the teeth were divided into three groups according to the taper provided, i.e., 15 per group. The location of the gingival finish line was marked on all the specimens using a permanent black thin marker. From this marking, a height of 4 mm was marked toward the occlusal surface for standardizing the height of preparation. The occlusal surface was made flat at this height.

The second part consisted of determining the fitting surface area. It was estimated by using a copper band impression made in polyvinyl siloxane medium body material (Dentsply Reprosil impression material) [Figure 4]. The band was removed, impressions were cut exactly at the margins, and an imprint of the fitting surface was made on the graph paper [Figure 5]a, [Figure 5]b, [Figure 5]c. The number of squares of each imprint on the graph paper was added and then counted, which gave the approximate surface area.
Figure 4: Copper band impression made in medium body and cut exactly at the margins

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Figure 5: (a-c) Imprints of fitting surfaces of cut impressions on graph paper

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Fabrication of wax pattern and casting in titanium

The wax patterns were fabricated and casting was done in titanium. On purpose, the die spacer was eradicated to prevent differences in thickness. A loop created in the form of an upside-down “U” was secured on the occlusal surface of the patterns, and that served as the main Sprue. This loop would later serve as an attachment for the “S”-shaped hook cast in nickel chrome for testing the retentive force of the crowns with different adhesive luting agents.

The wax patterns were then invested in “Titec” investment material. Wax elimination was done after 90 min followed by titanium casting in a single-chamber argon pressure semi-automatic casting machine.

Cementation of the casting using three different adhesive luting agents

Each group of 15 samples was divided and named as follows:

5P, 5C, 5G, 10P, 10C, 10G, 15P, 15C, 15G.

In each subgroup, the samples were suffixed by numerical from 1 to 5. The first digit denotes the angle of convergence which is 5°, 10°, and 15°. The second alphabet denotes the type of luting agent used such as P – for Panavia, C – for Calibra, and G – for Glass Ionomer Cement [Figure 6]. The third digit denotes the sample number in each subgroup for example, 5P1, 10P1, 15P1, 5G1, 10G1, 15G1, 5C1, 10C1, 15C1. All the samples mounted in an acrylic block were marked for groups and subgroups.
Figure 6: Three different adhesive luting agents

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Each test coping was cemented one at a time using cement of the respective group that was mixed according to the manufacturer's specifications. The excess cement was wiped out with a cotton pellet around the periphery of the test coping [Figure 7]. Following cementation and storage in distilled water for a period of 24 h, each specimen was mounted on a custom fixture on the universal tensile testing machine with the S-shaped hook attached on the upper fixture and the inverted U-shaped loop of the specimen on the lower fixture [Figure 8]. The bonded specimens were then pulled in the opposite direction to deliver a tensile force at 1 mm/min cross-head speed. The values obtained were calculated and recorded in Kilo-Newton, which formed the basic data of the study.
Figure 7: Titanium copings cemented with the three luting agents

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{Figure8}


  Results Top


Student's t-test was conducted on the observed values [Table 1], [Table 2], [Table 3] to equate the retentive force with samples cemented to 5°, 10°, and 15° angle of convergence with Panavia F, Calibra, and Glass Ionomer Cement, respectively.
Table 1: Statistical comparison by (Students “t” test, Paired) for retentive force (Kg/cm2) with samples cemented to 50, 100 and 150 angle of convergence with Panavia F

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Table 2: Statistical comparison by (Students “t” test, Paired) for retentive force (Kg/cm2) with samples cemented to 50, 100, 150 angle of convergence with Calibra

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Table 3: Statistical comparison by (Students “t” test, Paired) for retentive force (Kg/cm2) with samples cemented to 50, 100 and 150 angle of convergence with Glass Ionomer Cement

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The results demonstrated a significant outcome between 5° and 15° of convergence for Panavia F. Considerable results were obtained between 5° and 15° of convergence for Calibra as well as between 10° and 15° of convergence for glass ionomer cement. The mean and standard deviation of force counted upon to dislodge the titanium crowns combined with three different luting agents for all three angles of convergence were calculated [Table 4]. One-way ANOVA test was carried out to calculate the retentive force for all the three angles of convergence for all the cement [Table 5] and was found to be significant. One-way ANOVA was performed for the retentive force for each angle of convergence for all the cement [Table 6] and was found to be highly significant.
Table 4: Mean and standard deviation of force required to dislodged the titanium crowns cemented with three different luting agents on teeth prepared with 50, 100 and 150 angle of convergence

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Table 5: Statistical Analysis (One Way ANOVA) of retentive force of specimens cemented with various cements on to the teeth prepared with 50, 100, 150 angle of convergence

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Table 6: Statistical Analysis (One Way ANOVA) of retentive force of specimens cemented with various angles of convergence cemented with Panavia-F, Calibra, GIC

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  Discussion Top


The favorable outcome of a fixed prosthesis as far as patient satisfaction is concerned relies on the retention of the prosthesis. Retention is attained by tensofrictional resistance and the quality of the luting agent used. The development of resin cement that can chemically bond to the tooth structure, as well as dental alloys, has streamlined the regular path for obtaining retention in fixed partial dentures. The luting cement bonds with the tooth structure and metal surface, thus enhancing the retention of the prosthesis.

The bonding of resin-based adhesive luting agent to dental alloy has been markedly refined over a decade, and different bonding means and systems for base metal alloys have been developed. Findings indicate better retention forces for metallic crowns united with resin-based cement in comparison with nonpolymeric cement such as Glass Ionomer Cement.[2],[3],[4],[5] Studies also show that crowns cemented with zinc phosphate demonstrated higher retentive properties without fracture of the crown.[6] Glass Ionomer Cement in combination with a shoulder finish line showed better retention than zinc phosphate and chamfer when used for seating silver-palladium crowns.[7],[8]

Despite the collective advantages of resin cement over traditional cement, additional determinants, such as preparation taper, surface area, and height, can influence the retention of metallic crowns. Several studies[9],[10],[11],[12],[13],[14],[15] have included these parameters for base metal alloys such as nickel-chromium, cobalt-chromium, and noble metal alloys, but this study evaluates the retentive force of titanium crowns bonded with various luting agents enhancing the retention of the prosthesis to the prepared teeth with different degree of convergence. However, these cement are primarily meant to prevent microleakage. Nearly all the evaluation of metal cement bonding has been based on in vitro bond strength evaluation. The fitting surface area in this study was considered as: (i) in the axial direction, it was a shear force which produces shear stress, and (ii) in the occlusal direction, it was the tensile force that produces the tensile stress which when combined would give “the retentive force per unit area” required to dislodge the titanium crown. In the present study, 45 caries-free extracted premolars were selected and prepared at 5°, 10°, and 15° convergence to the long axis of the tooth. The occlusal/cuspal inclinations of the preparation were made flat to determine the surface area to find out the retentive force/unit area that could be standardized. The preparations were then divided according to taper into three groups. Three luting types of cement were selected based on evolution as gradually developed cement from ionomer to resin ionomer and the dual-cure resin-based adhesive luting agent. Each group was split into three subgroups according to the titanium crowns. These subgroups were named accordingly as 5P, 5C, 5G; 10P, 10C, 10G; and 15P, 15C, 15G. Five samples of each subgroup were cemented with respective luting agents using firm digital pressure. These specimens were then subjected to a universal tensile testing machine till the dislodgement of the titanium crowns.

The study revealed that 90% of the dislodged crowns left no cement on the tooth, indicating higher bond strength between cement and titanium than cement and prepared tooth. This also indicates that it was a cohesive-adhesive type of failure. Failure was also noticed in preparations cemented with Panavia F on a 5° angle of convergence due to dislodgement of a tooth from the acrylic block because of fracture of the root. A decrease in the surface area was also noticed as the taper increased from 5° to 15°. The average mean surface area calculated for 5°, 10°, and 15° angle of convergence was 1.266 cm2, 1.089 cm2, and 0.980 cm2, respectively. This study indicates that preparations with the mentioned angle of convergence showed sudden decrease in the retentive force values when cemented with three different types of cement. From these values, it is apparent that retention in crowns on 15° tapered preparations cemented with Panavia F was even greater than crown cemented with Calibra and Glass Ionomer Cement on 5° tapered preparations. However, with an increase in taper, Panavia F showed the highest retentive force to dislodge the titanium crown vertically. This can be attributed to the greater or lesser attraction of adhesive monomer 10-methacryloyloxydecyldihydrogen phosphate to tooth structure and dental metal alloy (titanium),[2] which has a stronger bond to titanium than the adhesive forces of Calibra and Glass Ionomer Cement. On statistical comparison of equity of means between 5°, 10°, and 15° angle of convergence showed that the means calculated were not equal [as shown in [Table 4]] and F = 8.88, P = 0.0051 was found to be statistically significant at 1% level. A similar study showed that a 5°–10° taper greatly improved retention in addition to proving that adhesive resin exhibits better retention than zinc polycarboxylate.[16]

Similarly, the retentive force/unit area for specimens cemented with Calibra and Glass Ionomer Cement on 5°, 10°, and 15° prepared teeth was found to be significant (F = 52.17, P = 0.0000 for Calibra, F = 30.75, P = 0.0001 for Glass Ionomer Cement). On statistical comparison by one-way ANOVA, a highly significant difference was observed at 5°, 10°, and 15° angle of convergence cemented with three different luting agents with P = 0.0000 in all the cases and F = 182.6, 194.32, and 327.92 for Panavia F, Calibra, and Glass Ionomer Cement, respectively. Cementation of teeth prepared with 5°, 10°, and 15° angle of convergence with Panavia F on statistical analysis revealed nonsignificant retentive force/unit area values [t = 2.72, P = 0.0297 for 5°, 10° and t = 1.43, P = 0.1915 for 10°, 15° as shown in [Table 6]] similarly prepared with 5°, 10°, 15° angle of convergence with ionomer cement. Comparing the mean retentive force values of 5P, 15P, significant difference in retentive force/unit area was observed (t = 4.11, P = 0.0045); similar trend in results was obtained for Calibra and Glass Ionomer Cement where a significant difference was observed while comparing groups: 5C and 10C; 5C and 10C and 15C. On comparing the groups, 5G and 15G and 10G and 15G, significant difference was achieved (t = 7.72, P = 0.0001; t = 7.63, P = 0.0006). The samples prepared at 5°, 10°, 15° angle of convergence and cemented with Panavia F showed better retentive force/unit area followed by Calibra and then Glass Ionomer Cement. This also may be attributed to the adhesive monomer contained in Panavia F paste which absorbs chemically to the metal atoms of the base metal alloy, providing high bond strength.[17] The outcome of the study is similar to the previous studies as described.[2],[4],[5],[18],[19] As reported by Tylman,[19] for optimal preparation, the angle of convergence should be 2° and 5°. Still, it appears that clinically, this kind of taper is scarcely accomplished. In one study, the mean convergence angle of crown preparation made by general dental practitioners and by specialists was noted to be 20°, and a convergence angle of 24° was chosen to approximate a clinical situation. Several authors[20] have proposed a semi-imperious model to explain the relationship between cement, taper, retention, and resistance. The relationship between abutment taper and dynamic loading is approximately linear.[21] One study reported significantly improved crown seating when a dynamic technique was compared with a static loading procedure frequently used for in vitro studies of cementation.[22]


  Conclusion Top


From this study, it can be concluded that the bond between the adhesive cement and titanium as well as the taper plays an important role in the retention of crowns on abutments. There is a reduction in surface area due to an increase in the taper. Further, retentive force values indicate that as the degree of convergence increased, the retention of crowns drastically reduced. The force required to dislodge the cemented titanium crown from the prepared tooth was maximum for Panavia F on 5°, 10°, and 15° angle of convergence, respectively (65.23, 48.52, and 40.14 kgf).

Panavia F is a cement of choice for preparations with an apparent taper of more than 10° angle of convergence to the long-axis tooth than any other cement. The optimum bond strength values for clinical success need to be ascertained for different alloys as well as different adhesive luting agents, particularly for tapered preparations.

These conclusions are based on the comparative results obtained following the materials and methods used in this study as well as testing and may change in magnitude with variation in materials and methods being employed.

Ethical clearance

Since the study was an laboratory study no ethical clearance was required.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Anusavice KJ. Philips Science of Dental Materials. 10th ed. Philadelphia: W.B. Saunders Co.; 1996.  Back to cited text no. 1
    
2.
Kashiwada T. In vivo, bond strength of a new dental adhesive to dentin. IADR General Session and Exhibition. Chicago, IL 1993;10-4.  Back to cited text no. 2
    
3.
Kobayashi K, Kodama T, Uchiyama Y. Effect of a new dental adhesive on dentin bonding. IADR 1993:0261.  Back to cited text no. 3
    
4.
Triolo PT, Kelsey WP, Barkmeier WW. Bond strength of an adhesive resin system with various dental substrates. J Prosthet Dent 1995;74:463-8.  Back to cited text no. 4
    
5.
Tjan AH, Li T. Seating and retention of complete crowns with a new adhesive resin cement. J Prosthet Dent 1992;67:478-83.  Back to cited text no. 5
    
6.
Parisay I, Khazaei Y. Evaluation of retentive strength of four luting cements with stainless steel crowns in primary molars: An in vitro study. 2018;15:201-7.  Back to cited text no. 6
    
7.
Piemjai M. Effect of Seating Force, Margin Design, and Cement on Marginal Seal and Retention of Complete Metal Crowns. Int J Prosthodont 2001;14:412-6.  Back to cited text no. 7
    
8.
Hammood ED, Ibraheem AF. Evaluate and Compare the Effect of Different Marginal Cement Space Parameter Setting in the CAD Software on the Marginal and Internal Fitness of Monolithic Zirconia Crowns with Different Types of Luting Agents (A comparative in vitro study). J Res Med Dent Sci 2020;8:74-80.  Back to cited text no. 8
    
9.
El-Sherif MH, El-Messery A, Halhoul MN. The effect of alloy surface treatments and resins on the retention of resin-bonded retainers. J Prosthet Dent 1991;65:782-6.  Back to cited text no. 9
    
10.
EI-Mowafy OM, et al. Retention of metal-ceramic crowns cemented with resin cements: Effects of preparation taper and height. J Prosthet Dent 1996;76:524-9.  Back to cited text no. 10
    
11.
Felton DA, Kanoy BE, White JT. The effect of surface roughness of crown preparation on retention of cemented castings. J Prosthet Dent 1987;58:292-6.  Back to cited text no. 11
    
12.
Nordlander J, et al. The taper of clinical preparations for fixed prosthodontics. J Prosthet Dent 1988;60:148-51.  Back to cited text no. 12
    
13.
Murakami I, Barrack GM. Relationship of surface area and design to the bond strength of etched cast restorations: An in vitro study. J Prosthet Dent 1986;56:539-45.  Back to cited text no. 13
    
14.
Pegoraro LF, Barrack G. A comparison of bond strengths of adhesive cast restorations using different designs, bonding agents and luting resins. J Prosthet Dent 1987;57:133-8.  Back to cited text no. 14
    
15.
Rubo JH, Pegoraro LF, Ferreira PM. A comparison of tensile bond strengths of resin-retained prosthesis made using five alloys. Int J Prosthodontics 1996;9:277-81.  Back to cited text no. 15
    
16.
Alsharif BS, Elsayed S. Retention of All-Ceramic Crown Preparation with Two Different Tapers Luted by Two Different Cements. J Clin Exp Dent 2018;10:e1192–7.  Back to cited text no. 16
    
17.
Noritake. Adhesive Resin Cement System Panavia V5, Technical Information, Kuraray Co. Ltd., Japan. V 2005.  Back to cited text no. 17
    
18.
Galum EA, Saleh N, Lewinstein I. Diametral tensile strength and bonding to dentin of type I glass ionomer cement. J Prosthet Dent 1994;72:424-9.  Back to cited text no. 18
    
19.
Tylman's theory and practice of fixed prosthodontics, 8th ed. Tokyo, St. Louis: Ishiyaku Euro America, Inc. Publishers; 2002.  Back to cited text no. 19
    
20.
Nicholls JI. Crown retention. Part II. The effect of convergence angle variation on the computed stresses in the luting agent. J Prosthet Dent 1974;31:651-7.  Back to cited text no. 20
    
21.
Wiskott HW, Nicholls JI, Belser UC. The relationship between abutment taper and resistance of cemented crowns to dynamic loading. Int J Prosthodont 1996;9:117-30.  Back to cited text no. 21
    
22.
Tjan AH, Dent, Sarkissian R. Effect of preparation finish on retention and fit of complete crowns. J Prosthet Dent 1986;56:283-8.  Back to cited text no. 22
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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