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ORIGINAL ARTICLE
Year : 2019  |  Volume : 37  |  Issue : 1  |  Page : 55-59
 

A comparative evaluation of fractural strength and marginal discrepancy of direct composite veneers using four different tooth preparation techniques: An in vitro study


1 Department of Pediatric and Preventive Dentistry, Pacific Dental College and Hospital, Udaipur, Rajasthan, India
2 Department of Pediatric and Preventive Dentistry, Surendra Dental College and Research Institute, Sri Ganganagar, Rajasthan, India
3 Department of Pediatric and Preventive Dentistry, Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab, India
4 Department of Pediatric and Preventive Dentistry, JCD Dental College, Sirsa, Haryana, India

Date of Web Publication25-Feb-2019

Correspondence Address:
Dr. Kanika Gupta Verma
Professor, Department of Pediatric and Preventive Dentistry, Surendra Dental College and Research Institute, H. H. Gardens, Power House Road, Sri Ganganagar - 335 001, Rajasthan
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/JISPPD.JISPPD_279_18

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   Abstract 


Background: The direct composite veneers follow the concept of no preparation or minimal preparation that has developed an appropriate enamel bonding procedure. The composite veneers can be easily repaired and thus they are economically favorable. The long-term clinical performance of direct composite veneers depends on a number of factors, with fracture resistance and marginal adaptation being one of the significance. Aim and Objective: The aim of the present study was to evaluate the fractural strength and marginal discrepancy of direct composite veneers using four different tooth preparation techniques (window preparation, feather preparation, bevel preparation, and incisal overlap preparation). Settings and Design: The present study is an in vitro study with the sample size of 75 participants. A total of 75 human extracted maxillary central incisors were collected and then divided into four experimental groups and one control group (n = 15 each). Materials and Methods: A total of 75 human extracted maxillary central incisors were collected and then divided into four experimental groups and one control group (n = 15 each). Four tooth preparation techniques were performed followed by direct composite veneering. All the study samples were then splitted into two equal halves. One half of all the samples was subjected to a cell load from 0 N to 100 KN at a crosshead speed of 1 mm at 90° angulation using universal testing machine to evaluate the fractural strength. The other halves were sectioned longitudinally, and the samples were then subjected under the travelling microscope at ×200 magnification to measure the marginal discrepancy at cervical, middle, and incisal locations. Statistical Analysis: The data obtained were subjected to statistical analysis using SPSS Version 20.0. Results: The fractural strength showed the maximum strength in Group V: Control group (273.33 ± 81.01), Group III: Bevel preparation (193.80 ± 66.59), Group IV: Incisal overlap preparation (188.93 ± 76.14), Group II: Feather preparation (160.33 ± 53.59), and least in Group I: Window preparation (147.74 ± 48.95). The marginal discrepancy showed maximum discrepancy in Group IV: Incisal overlap preparation (49.11 ± 6.33), Group II: Feather preparation (48.44 ± 6.01), Group III: Bevel preparation (46.67 ± 7.07), and least in Group I: Window preparation (45.33 ± 6.31). Conclusion: The fractural strength was maximum in Group V, followed by Group III, Group IV, Group II, and the least mean value score was found for the Group I, and the marginal discrepancy was maximum in Group IV, followed by Group II, Group III, and the least mean value score was found for the Group I.


Keywords: Direct composite veneers, fractural strength, marginal discrepancy, tooth preparation techniques


How to cite this article:
Narula H, Goyal V, Verma KG, Jasuja P, Sukhija SJ, Kakkar A. A comparative evaluation of fractural strength and marginal discrepancy of direct composite veneers using four different tooth preparation techniques: An in vitro study. J Indian Soc Pedod Prev Dent 2019;37:55-9

How to cite this URL:
Narula H, Goyal V, Verma KG, Jasuja P, Sukhija SJ, Kakkar A. A comparative evaluation of fractural strength and marginal discrepancy of direct composite veneers using four different tooth preparation techniques: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2019 [cited 2019 May 26];37:55-9. Available from: http://www.jisppd.com/text.asp?2019/37/1/55/252858





   Introduction Top


Esthetic dentistry has become one of the main areas of dental practice and the main reason for applying restorative dental materials is not only to restore dental tissues loss but also to correct the form and color of teeth for social acceptance.[1]

“A thin sheet of material usually used as a finish or superficial or attractive display in multiple layers is termed as veneers.”[2] Two main types of materials are used to fabricate a veneer: composite and dental porcelain. A dental porcelain is fabricated in a dental laboratory and later bonded to the tooth, typically using a resin cement is known as indirect veneers, whereas a composite veneer can be used directly or indirectly and is termed as direct and indirect composite veneers.[3] The direct composite veneers are composite resin restorations that are placed onto the labial surface of teeth.[4]

The direct composite veneers follow the concept of no preparation or minimal preparation that has developed an appropriate enamel bonding procedure. The color and integrity of dental tissue substrates to which veneers will be bonded are important for clinical success, using additional veneers' thickness between 0.3 and 0.5 mm; 95%–100% of enamel volume remains after preparation and no dentin is exposed.[5] The four basic direct composite incisal preparations designs are – (a) Window preparation, (b) Feather preparation, (c) Bevel preparation, and (d) Incisal overlap preparation. In Window preparation technique, the veneer is taken close to but not up to the incisal edge. In Feather preparation technique, the veneer is taken up to the height of the incisal edge of the tooth, but the edge is not reduced. In bevel preparation technique, a buccopalatal bevel is prepared across the full width of the preparation, and there is some reduction of the incisal length of the tooth. In incisal overlap preparation technique, the incisal edge is reduced and then the veneer preparation extended onto the palatal aspect of the preparation [Figure 1].[6]
Figure 1: Diagrammatic representation of four experimental tooth preparation groups. (a) Window preparation; (b) Feather preparation; (c) Beveled preparation; (d) Incisal overlap preparation

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The composite veneers can be easily repaired and thus they are economically favorable.[5] The long-term clinical performance of direct composite veneers depends on a number of factors, with fracture resistance and marginal adaptation being one of the significance.[1] The majority of failures were observed in the form of fracture or marginal defects of the restoration.[7] According to the literature, the most frequent failure modes associated with laminate veneers are fracture and debonding. Thus, the aim of the present study was to evaluate the fractural strength and marginal discrepancy of direct composite veneers using four different tooth preparation techniques.


   Materials and Methods Top


The present study was done in the Department of Pediatric and Preventive Dentistry, Surendera Dental College and Research Institute, Sri Ganganagar, Rajasthan, India, from August 2015 to October 2017. A total of 75 human maxillary central incisors teeth were taken to evaluate the fractural strength and marginal discrepancy of direct composite veneers using four different tooth preparation techniques (window preparation, feather preparation, bevel preparation, and incisal overlap preparation). Maxillary central incisors teeth extracted because of periodontal problem were collected and used in the present study. The teeth were selected on the basis of inclusion criteria, i.e., teeth should be free of cracks and fracture.

The external surfaces of each tooth were cleaned with ultrasonic scaler, to remove the debris and periodontal soft tissue, and were stored in 20.2% thymol solution till they were used further for the study. The study samples were divided into four experimental and one control group (n = 15). The samples were subjected to impressions using vinyl polysiloxane impression material. The labial surfaces of all the study samples were prepared uniformly with air rotor and diamond burs (tapered flat ended, tapered round, and tapered ellipse) to make veneers of uniform thickness of 0.5–0.75 mm extending till the enamel borderlines. The vestibule-gingival reduction was 0.5–0.75 mm and vestibule-incisal depth will be 1–1.2 mm, respectively. The preparation design for direct composite veneers most often finishes with chamfer-edge gingival and interproximal finish line. The incisal edge of all the study samples was reduced to 1 mm, and the preparation was finished lingually with enamel bevel according to their respective groups as follows: Group I: Window preparation, Group II: Feather preparation, Group III: Bevel preparation, Group IV: Incisal overlap preparation, and Group V: Control group.

Each specimen was etched with 37% phosphoric acid for 15 s and then washed thoroughly for 30 s with water. The bonding agent was applied and cured with light-emitting diode curing light. Ceram X-Mono, the nanohybrid composite, was used as direct composite veneer material. After 24 h, finishing and polishing were done. The restorations were glazed with a bonding agent and final curing was done.

For evaluation of fracture strength, half sections of all the study samples were mounted vertically in small standardized plastic containers using self-cure polymerizing powder and liquid resin, 2 mm below the cementoenamel junction to examine tensile fractural strength of direct composite veneers. The specimens were subjected for fractural load cell from 0 N to 100 kN on the incisal edge of the tooth, with the help of a universal testing machine at an angle of 90° to the long axis of the tooth at a crosshead speed of 1 mm/min with the help of endodontic plugger until bond failure was noticed. The value of load required for fracture of direct composite veneer was recorded for each study sample.

The rest of half sections of all the study samples was sectioned into thin longitudinal sections to examine the marginal discrepancy at cervical, incisal, and middle locations of the tooth, using travelling microscope at ×200 [Figure 2]. The results obtained were subjected to statistical analysis using Statistical Package for the Social Sciences (SPSS) version 20.0, (IBM corporation, Chicago, Illinois, United States of America).
Figure 2: (a) Study sample subjected to load application at 90° with the help of an endodontic plugger; (b) Study sample under the travelling microscope at ×200 magnification

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   Results Top


The mean fractural strength was maximum in Group V (Control Group), followed by Group III (Bevel preparation), Group IV (Incisal overlap preparation), Group II (Feather preparation), and the least mean value score was found for the Group I (Window preparation). The level of significance calculated was highly statistically significant (P ≤ 0.01) [Table 1].
Table 1: ANOVA statistical analysis to compare mean fractural strength among all the study groups

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The mean marginal discrepancy was maximum in Group IV (Incisal overlap preparation), followed by Group II (Feather preparation), Group III (Bevel preparation), and the least mean value score was found for Group I (Window preparation). The level of significance obtained was significant (P < 0.05) [Table 2].
Table 2: The mean marginal discrepancy in all the experimental groups at cervical-, middle-, and incisal-thirds and ANOVA statistical analysis to compare mean marginal discrepancies among all the experimental groups

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   Discussion Top


The long-term clinical performance of laminate veneers depends on a number of factors, with marginal adaptation and fractural strength being one of the significances. It is critical to establish an acceptable, marginal adaptation in laminate veneers because of the inherent limitations of composite resins, such as relatively high polymerization shrinkage, low resistance to clinical wear, and a high coefficient of thermal expansion.[8]

In the present study, the direct composite veneers were placed using nanohybrid composite, Ceram “X Mono.” They are used for simple restorations using an anatomic layering procedure, which aids the clinician in correctly defining the color and shape of the tooth, using the residual dental structure as a reference. Ceram “X Mono” is more likely to absorb stress than silica-based ceramic materials.[1] Finishing and polishing and glazing were done so as to contribute smooth and harmonious transition from the tooth to veneer.[1]

The result of the present study was similar with the study conducted by Khaliq and Al-Rawi in 2014,[1] who evaluated the fracture strength of the laminate veneers and reported that control group showed higher mean fracture strength with a highly significant difference in comparison to other experimental groups.

After control group, the maximum fractural strength was obtained by Bevel preparation group, which was similar with the study conducted by Jankar et al. in 2014,[9] in which three different incisal preparations (window preparation, bevel preparation, and incisal overlap preparation) were used to evaluate the fracture resistance. They concluded that the tooth preparation with Bevel preparation design had the highest fracture resistance due to an increase in the buccolingual width. Similarly, Shetty et al. in 2011[10] reported that laminate veneers produced using the incisal overlap cutting technique have lower fracture resistance when compared to the natural teeth due to high interfacial stresses.

After bevel preparation, incisal overlap preparation showed better fractural strength, as observed in the study conducted by Duzyol et al. in 2016,[11] who evaluated the fracture resistance of most commonly used three preparation techniques applied for laminate veneers restoration. According to the results, incisal overlap preparation and direct technique had higher fracture resistance values than other groups, which were not in favor with the present study because incisal overlap cuts are three times more resistant to axial forces than feather-type cuts.

Lower fracture resistance was seen in Feather preparation as compared to incisal overlap preparation. The results of the present study were contradictory with the study conducted by Prasanth et al. in 2013,[12] who measured the fracture load of ceramic veneers made in teeth with three different designs of preparation. They concluded that the Feather preparation design offered better fracture resistance followed by incisal butt joint and palatal chamfer preparation due to less tooth reduction and ease in handling for cementation, whereas the results of the present study were in accordance with the same study in relation to the least fracture strength obtained from Window preparation when compared with feather preparation and incisal overlap preparation.

The least fracture resistance was observed in Window preparation design which was similar to the study conducted by Zlatanovska et al. in 2016,[13] who evaluated the fracture load of composite veneers using three different preparation designs as follows: (1) Feather preparation, (2) Bevel preparation, and (3) Incisal overlap palatal chamfer. They concluded that teeth with window preparation design do not provide a definite path of placement of the veneers and hence lead to thin incisal edges.

A very few in vitro studies were done with relation to the marginal discrepancy of veneers. The advantage of evaluating marginal discrepancy was to view the marginal opening for plaque accumulation. According to the study conducted by Celik and Gemalmaz in 2002,[8] maximum width of resin was observed at incisal edge in incisal overlap preparation design because of the high probability of chipping of the resin from the incisal edge.

During carving of final placement of veneer, it may vary the replacement of the original form which results in higher marginal discrepancy, which was similar to the present study.

A factor that contributes to the variation in marginal discrepancy is the regular morphology of the surface of the veneer, which was found with the minimum discrepancy in Window preparation in our study. This factor was similar to Baratieri et al. in 1992,[14] who examined the influence of the fabrication technique on the marginal fit of veneers. The marginal openings were with less mean values in window preparation group due to no or less involvement of the incisal edge.

However, some variations and other factors also affect the fractural strength and marginal discrepancy width which exist irrespective of the veneer technique and preparation design. Thus, there is a need to conduct a more elaborated study, considering all relevant limitations.


   Conclusion Top


The present study concluded that the fractural strength was maximum in Group V (Control Group), followed by Group III (Bevel preparation), Group IV (Incisal overlap preparation), Group II (Feather preparation), and the least mean value score was found for the Group I (Window preparation). Moreover, the marginal discrepancy was maximum in Group IV (Incisal overlap preparation), followed by Group II (Feather preparation), Group III (Bevel preparation), and the least mean value score was found for the Group I (window preparation).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Khaliq AG, Al-Rawi II. Fracture strength of laminate veneers using different restorative materials and techniques: A comparative in vitro study. J Bagh Coll Dent 2014;26:1-8.  Back to cited text no. 1
    
2.
Denry I. All ceramic restorations. In Rosenstiel SF, editor. Contempory Fixed Prosthodontics. New Delhi: Elsevier Publishing; 2008. p. 774-804.  Back to cited text no. 2
    
3.
Layliev E, Evans J. Direct veneers. In: Freedman G, editor. Contempory Esthetic Dentistry. USA: Elsevier Publishing; 2012. p. 405-10.  Back to cited text no. 3
    
4.
Dieter M. Direct veneers in anterior smile design. Int Dent Afr 2015;5:16-22.  Back to cited text no. 4
    
5.
Re D, Augusti G, Amato M, Riva G, Augusti D. Esthetic rehabilitation of anterior teeth with laminates composite veneers. Case Rep Dent 2014;2014:849273.  Back to cited text no. 5
    
6.
Walls AW, Steele JG, Wassell RW. Crowns and other extra-coronal restorations: Porcelain laminate veneers. Br Dent J 2002;193:73-6, 79-82.  Back to cited text no. 6
    
7.
Ghag HS. Designing a Process to Reliably Split Extracted Teeth to Access the Dental Root Canal. Las Vegas: University of Nevada; 2014.  Back to cited text no. 7
    
8.
Celik C, Gemalmaz D. Comparison of marginal integrity of ceramic and composite veneer restorations luted with two different resin agents: An in vitro study. Int J Prosthodont 2002;15:59-64.  Back to cited text no. 8
    
9.
Jankar AS, Kale Y, Kangane S, Ambekar A, Sinha M, Chaware S. Comparative evaluation of fracture resistance of ceramic veneer with three different incisal design preparations – An in vitro study. J Int Oral Health 2014;6:48-54.  Back to cited text no. 9
    
10.
Shetty A, Kaiwar A, Shubhashini N, Ashwini P, Naveen D, Adarsha M, et al. Survival rates of porcelain laminate restoration based on different incisal preparation designs: An analysis. J Conserv Dent 2011;14:10-5.  Back to cited text no. 10
[PUBMED]  [Full text]  
11.
Duzyol M, Duzyol E, Seven N. Fracture resistance of laminate veneers made with different cutting and preparation techniques. Int J Dent Sci Res 2016;4:42-8.  Back to cited text no. 11
    
12.
Prasanth V, Harshakumar K, Lylajam S, Chandrasekharan Nair K, Sreelala T. Relation between fracture load and tooth preparation of ceramic veneers. Health Sci 2013;2:1-11.  Back to cited text no. 12
    
13.
Zlatanovska K, Guguvcevski L, Popovski R, Dimova C, Minovska A, Mijoska A. Fracture resiatance of composite veneers with different preparation designs. Balk J Dent Med 2016;20:99-103.  Back to cited text no. 13
    
14.
Baratieri LN, Monteiro Júnior J, de Andrada MA, Aracari GM. Composite resin veneers: A new technique. Quintessence Int 1992;23:237-43.  Back to cited text no. 14
    


    Figures

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    Tables

  [Table 1], [Table 2]



 

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