Journal of Conservative Dentistry
Home About us Editorial Board Instructions Submission Subscribe Advertise Contact e-Alerts Login 
Users Online: 299
Print this page  Email this page Bookmark this page Small font sizeDefault font sizeIncrease font size
 


 
Table of Contents   
ORIGINAL ARTICLE  
Year : 2016  |  Volume : 19  |  Issue : 3  |  Page : 264-269
Comparative evaluation of the effect of different crown ferrule designs on the fracture resistance of endodontically treated mandibular premolars restored with fiber posts, composite cores, and crowns: An ex-vivo study


1 Department of Conservative Dentistry and Endodontics, Rama Dental College Hospital and Research Center, Kanpur, Uttar Pradesh, India
2 Department of Oral Medicine and Radiology, Rama Dental College Hospital and Research Center, Kanpur, Uttar Pradesh, India

Click here for correspondence address and email

Date of Submission14-Jan-2016
Date of Decision03-Mar-2016
Date of Acceptance06-Apr-2016
Date of Web Publication9-May-2016
 

   Abstract 

Introduction: In cases of severe hard tissue loss, 2 mm circumferential ferrule is difficult to achieve which leads to incorporation of different ferrule designs.
Aim: To compare and evaluate the effect of different crown ferrule designs on the fracture resistance of mandibular premolars restored with fiber posts, composite cores, and crowns.
Materials and Methods: Fifty freshly extracted mandibular premolars were endodontically treated and divided into five groups: Group I - 2 mm circumferential ferrule above the cementoenamel junction (CEJ); Group II - 2 mm ferrule on the facial aspect above CEJ; Group III - 2 mm ferrule on the lingual aspect above CEJ; Group IV - 2 mm ferrule on the facial and lingual aspects above CEJ with interproximal concavities, and Group V - no ferrule (control group) and were later restored with fiber posts, composite cores, and crowns. Specimens were mounted on a universal testing machine, and compressive load was applied at a crosshead speed of 1 mm/min until fracture occurred.
Results: The results showed that circumferential ferrule produced the highest mean fracture resistance and the least fracture resistance was found in the control group.
Conclusion: Circumferential ferrule increases the fracture resistance of endodontically treated teeth restored with bonded post, core, and crown.

Keywords: Composites cores; ferrule designs; fiber post

How to cite this article:
Dua N, Kumar B, Arunagiri D, Iqbal M, Pushpa S, Hussain J. Comparative evaluation of the effect of different crown ferrule designs on the fracture resistance of endodontically treated mandibular premolars restored with fiber posts, composite cores, and crowns: An ex-vivo study. J Conserv Dent 2016;19:264-9

How to cite this URL:
Dua N, Kumar B, Arunagiri D, Iqbal M, Pushpa S, Hussain J. Comparative evaluation of the effect of different crown ferrule designs on the fracture resistance of endodontically treated mandibular premolars restored with fiber posts, composite cores, and crowns: An ex-vivo study. J Conserv Dent [serial online] 2016 [cited 2019 Oct 21];19:264-9. Available from: http://www.jcd.org.in/text.asp?2016/19/3/264/181945

   Introduction Top


The rehabilitation of severely damaged coronal hard tissue in an endodontically treated tooth is always a challenge in reconstructive dentistry. [1] The lack of a protective feedback mechanism after pulp removal is the main contributing factor to the failure of endodontically treated teeth. [2] However, besides the noncontrollable risk factors, [3] high occurrence of fractures may be attributed to various operative procedures such as caries excavation, [4] access cavity preparation, [5] root canal preparation, [6] irrigation, [7] obturation, [8] post space preparation, [9] and final coronal restoration. [10]

To restore endodontically treated teeth, posts are often required to provide anchorage for the core forming material and coronoradicular stabilization. [2] Cast post and core systems have been the mainstay in dentistry for many years. However, demand for simpler procedures and esthetic restorations has led to the development of prefabricated posts, initially made from metal and more recently from ceramics and fiber-reinforced composites. [11]

Fiber-reinforced posts have a modulus of elasticity (21 Gpa) similar to that of dentine (18 Gpa), which allow uniform distribution of forces in the root. They are noncorrosive and are invisible under esthetic restorations and also evert the phenomenon of "dark root show through," [12] and often recommended in flared roots because of lower risk of catastrophic failures and better stress distribution. [13] The "ferrule effect" is a longstanding, accepted concept in dentistry that is a foundation principle for the restoration of teeth that have suffered advanced structure loss. [14] A ferrule is defined as a "360° metal collar of the crown surrounding the parallel walls of the dentine extending coronal to the shoulder of the preparation. This encircled preparation on the tooth provides a protective effect against fracture of the tooth, by reducing stresses within a tooth called the "ferrule effect." [15] Several studies have been performed about ferrule effects which suggested that the ferrule effect strengthens the teeth against functional, wedging, and lateral forces. [16]

Clinicians encounter situations where it is not possible to give a full 360° of circumferential ferrule of 2 mm. Different ferrule designs have been suggested according to different clinical situations. In cases where caries frequently affects some walls (primarily the proximal ones), as well as in noncarious lesions such as erosion and abrasion, a partial ferrule of 180° either facial or lingual is beneficial rather than no ferrule. [14]

It is important to bear in mind that a ferrule effect is just one part of the restored endodontically treated tooth that represents a complex system. Several studies have been carried out about ferrule length, showing that maintenance of about 2 mm of tooth structure above the finish line or gingival margin as ferrule is effective, but a few studied the effect of different ferrule designs on fracture resistance. [7]

Aim of the study

The aim of this study was to investigate the effect of different crown ferrule designs on the fracture resistance of endodontically treated mandibular premolars incorporating fiber posts, composite cores, and crowns.


   Materials and methods Top


Preparation of the specimens

Fifty caries-free, intact human mandibular premolars, extracted for orthodontic reasons were obtained and stored in 10% formalin until use. Only those teeth whose coronal heights were 7 ± 1 mm and root lengths 14 ± 1 mm were selected. Surface soft tissues and debris were mechanically removed using ultrasonic scalers (P6 Newtron; Acteon Satelec, Merignac, France) with attention not to damage the root surface. Teeth were maintained in normal saline at room temperature.

Root canal preparation

Endodontic access cavities were prepared using a water cooler air turbine handpiece (Unicorn DenMart, India). The teeth were biomechanically prepared using the "step-back" technique to a #70 size K-file (Chlorinox, Dentsply Maillefer, USA) and irrigated with 2.6% sodium hypochlorite (Dentpro). Each canal was obturated using the lateral condensation method with Gutta-percha points (Dentsply, USA) and AH 26 sealers (Dentsply, USA). Following root canal obturation, the adequacy of endodontic fillings was confirmed by radiographs exposed from various angles. The endodontic access cavities were filled with a temporary filling material.

The specimens were stored in an incubator at 37°C for 1 week as to allow the sealer to set. All teeth were then prepared with a circumferential 1.5 mm shoulder meeting metal-ceramic crown requirements. The prepared clinical crowns were decoronated leaving 2 mm above cementoenamel junction (CEJ), providing different ferrule designs.

The samples were divided into five groups each having 10 teeth:

  1. Group I: Circumferential ferrule 2 mm above CEJ
  2. Group II: 2 mm ferrule only on the facial aspect above CEJ
  3. Group III: 2 mm ferrule only on the lingual aspect above CEJ
  4. Group IV: 2 mm ferrule on the facial and lingual aspects above CEJ with interproximal concavities
  5. Group V: No ferrule (used as control group).
Post space preparation

The post spaces of length 8 mm were prepared using 1, 2 and 3 No. Peeso reamers (Mani Inc., Japan) in sequential manner, leaving 4-5 mm of Gutta-percha inside the canal in the apical third of the root. Glassix fiber posts (Harald Nordin sa, Chailly/Montreux, Switzerland) was cemented in the dried prepared post space using Resin Luting cement RelyX Unicem (3M ESPE, St. Paul, MN, USA), and using core build-up composite material (LuxaCore, Germany), core was built to a height of 6 mm.

Metal, ceramic crowns of 7 mm in height were fabricated and were placed using resin cement, using constant finger pressure applied for 40 s then the excess cement was removed.

Block preparation and periodontal ligament simulation

For building artificial periodontal ligament just like the natural periodontium, root surfaces of all teeth were planned and were marked by a copying pencil 1-2 mm under CEJ. Then, an aluminum foil with 0.2 mm thickness was cut in root form and was adapted to the root dimensions from the marked line to the apex. Samples were merged vertically into the autopolymerized acrylic resin orienting their long axes.

After the complete polymerization, samples were taken out of the acrylic in the straight route and the foils were taken off from the root surfaces. Addition of silicon impression material (3M ESPE) in appropriate consistency was injected into the acrylic space to stimulate the natural periodontium.

Testing fracture resistance

The fracture resistance test was performed by using a Universal Testing Machine (Instron Universal Testing Machine Model 8872, Instron Co., Canton, Massachusetts, USA). A unidirectional compressive load was applied to the buccal cusp of crowns, at an angle of 1600 from the long axis of the tooth (to stimulate the functional working side buccal cusp loading), using a cylindrical Ni-Cr alloy rod in universal load testing machine at a crosshead speed of 1 mm/minute until fracture occurred. Fracture force was recorded in Newton (N). Data were analyzed by statistical software (SPSS Statistics version 20.0, SPSS Inc., Illinois, USA), keeping significance level of P < 0.001.


   Results Top


The obtained data showed that maximum amount of loading was sustained by Group I [Table 1]. Group II showed moderate amount of force sustainability [Table 2] as compared to Groups III and IV . Groups III and IV showed nearly equal results [Table 3] and [Table 4]. The least amount of loading was sustained by Group V [Table 5].
Table 1: Initial and final failure readings for circumferential ferrule (Group I)


Click here to view
Table 2: Initial and final failure readings for facial ferrule (Group II)


Click here to view
Table 3: Initial and final failure readings for lingual ferrule (Group III)


Click here to view
Table 4: Initial and final failure readings for facial and lingual ferrule with interproximal concavities (Group IV)


Click here to view
Table 5: Initial and final failure readings for no ferrule (Group V)


Click here to view


SPSS 20.0 software was used to calculate mean and standard deviation [Figure 1]. ANOVA was used for testing the significance between all the groups. There was high to moderate significant difference (critical value F 9.24 with P < 0.001) as well as there was positive correlation between the groups [Table 6] and [Table 7].
Figure 1: Mean and Standard deviation values of the groups

Click here to view
Table 6: Statistical data showing the mean and the standard deviations for Group I ,Group II, Group III, Group IV and Group V and ANOVA test


Click here to view
Table 7: ANOVA test


Click here to view



   Discussion Top


It is believed that the presence of ferrule protects the restored teeth because it reinforces the tooth/prosthesis assembly. [16] This portion of dental tissues adjacent to the core increases the fracture resistance, [17] providing a positive effect by reducing the stress concentration on the teeth. [18]

Several studies have been carried out about ferrule heights showing that maintenance of about 2 mm of the tooth structure above the finish line or gingival margin is beneficial. [19] In contrast, others found no benefits of adding a ferrule to the preparation. [20] Only a few studied the effect of different ferrule designs on the fracture resistance. [21]

A common observation, after deliberate search in endodontic literature, led to a general perception that incorporation of ferrule whether complete or partial is always beneficial in strengthening the teeth against functional, wedging and lateral forces. [14]

Juloski [22] stated that to achieve the full benefit of the ferrule effect, it should be a minimum of 1-2 mm in height, have parallel dentine walls, totally encircle the tooth, end on sound tooth structure, and avoid invasion of the attachment apparatus of the tooth. The consensus is that a properly constructed ferrule significantly reduces the incidence of fracture in nonvital teeth by reinforcing the tooth at its external surface and redistributing applied forces which concentrate at the narrowest point around the circumference of the tooth. [23] In addition, it helps to maintain the integrity of the cement seal of the crown. [18]

Considering the results obtained, different ferrule designs improve the fracture resistance or the failure pattern of the tested specimens. On the other hand, the use of fiber post with modulus of elasticity close to that of dentin changed the catastrophic failure type to almost complete favorable fracture in all the four groups except the group without ferrule. [11]

These results are in agreement with a study conducted by Dikbas [24] to assess the impact of the different types of ferrule on fracture resistance of the upper incisors. Those teeth without post which received endodontic treatment and had the crown showed the highest mean fracture resistance and the group lacking ferrule had the lowest mean among other groups.

Although it is clear that a full 360° circumferential ferrule is desirable, there are clinical circumstances where adopting a partial ferrule is still a better option than giving a no ferrule. [14]

Facial ferrule of 2 mm above CEJ showed higher fracture resistance when compared with other groups but showed less fracture resistance when compared to circumferential ferrule.

Facial and lingual ferrule of 2 mm with interproximal concavities showed almost equal results as that of lingual ferrule. Posterior teeth with deep proximal boxes are a common outcome of interproximal caries which commonly results in a compromised ferrule in these areas. [10] Tjan and Whang [25] in 1986 did a study confirming that a ferrule preparation increases the mechanical resistance by opposing displacement. Tan and Aquilino [26] did a similar study concluding that a tooth with a nonuniform ferrule is more effective at resisting fracture than a tooth with no ferrule but not as effective as a tooth with a uniform 2-mm ferrule.

Most of the specimens in the study (90%) showed a failure pattern wherein crown displacement preceded tooth fracture. The highest concentration of stress appeared at the CEJ as sharp angles cause high concentration of stresses during force application. [27] Favorable fractures were observed in all the four groups except the group with no ferrule. Fractures were in oblique direction from lingual to buccal surface involving the middle or apical third of the roots and vertically on buccal surface or below the acrylic resin. [28]

As per the results obtained, high significant difference was visible among all the groups which in turn can indicate the fact that the different locations of ferrule will have an impact on the mean fracture resistance that is different from the results which have been achieved in the above-mentioned studies. A facial loading on mandibular premolars teeth may cause stress in the form of tension in the facial margin and may also cause stress in the form of compression in the lingual margin. [27]

As these studies were in vitro, it is difficult to achieve standardization with regard to functional age of teeth, morphologic variations of the pulp, and abnormalities in dentin composition before tooth extraction. [28] Differences in dentin composition may affect the resilience of the dentin and thus, change the fracture pattern during compression. These variations were not controlled in this study which probably constitutes a limitation of the present analysis. [29] Hence, it is suggested to carry out similar researches in more simulating conditions to obtain more precise results.


   Conclusion Top


Under data obtained in the sample size and limitations of the study, we can conclude that there was a high statistically significant difference among all the groups (P < 0.001). There was maximum fracture resistance in Group I (circumferential ferrule design) and significantly moderate difference was found in Group II (facial ferrule design) when compared with Group III (lingual ferrule) and Group IV (facial and lingual ferrule with interproximal concavities).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Chang C, Kuo J, Yang L. Fracture resistance and failure modes of CEREC endo crowns and conventional post and core supported CEREC crowns. J Dent Sci 2009;4:110-7.  Back to cited text no. 1
    
2.
Zarow M, Devoto W, Saracinelli M. Reconstruction of endodontically treated posterior teeth - With or without post? Guidelines for the dental practitioner. Eur J Esthet Dent 2009;4:312-27.  Back to cited text no. 2
    
3.
Tang W, Wu Y, Smales RJ. Identifying and reducing risks for potential fractures in endodontically treated teeth. J Endod 2010;36:609-17.  Back to cited text no. 3
    
4.
Ingber JS, Rose LF, Coslet JG. The "biologic width" - A concept in periodontics and restorative dentistry. Alpha Omegan 1977;70:62-5.  Back to cited text no. 4
[PUBMED]    
5.
Zhi-Yue L, Yu-Xing Z. Effects of post-core design and ferrule on fracture resistance of endodontically treated maxillary central incisors. J Prosthet Dent 2003;89:368-73.  Back to cited text no. 5
    
6.
Wu MK, van der Sluis LW, Wesselink PR. Comparison of mandibular premolars and canines with respect to their resistance to vertical root fracture. J Dent 2004;32:265-8.  Back to cited text no. 6
    
7.
Saleh AA, Ettman WM. Effect of endodontic irrigation solutions on microhardness of root canal dentine. J Dent 1999;27:43-6.  Back to cited text no. 7
    
8.
Williams C, Loushine RJ, Weller RN, Pashley DH, Tay FR. A comparison of cohesive strength and stiffness of Resilon and Gutta-percha. J Endod 2006;32:553-5.  Back to cited text no. 8
    
9.
Al-Wahadni AM, Hamdan S, Al-Omiri M, Hammad MM, Hatamleh MM. Fracture resistance of teeth restored with different post systems: In vitro study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e77-83.  Back to cited text no. 9
    
10.
Ng CC, Dumbrigue HB, Al-Bayat MI, Griggs JA, Wakefield CW. Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth. J Prosthet Dent 2006;95:290-6.  Back to cited text no. 10
    
11.
Alan M, Padma R. Restoration of endodontically treated tooth. Caulk Clin Dent 2013:1:20-36.  Back to cited text no. 11
    
12.
Martelli P. Fourth generation Intraradicular post for the aesthetic restoration of anterior teeth. Pract Periodont Aesthetic Dent 2000:12;579-89.  Back to cited text no. 12
    
13.
Hayashi M, Takahashi Y, Imazato S, Ebisu S. Fracture resistance of pulpless teeth restored with post-cores and crowns. Dent Mater 2006;22:477-85.  Back to cited text no. 13
    
14.
Jotkowitz A, Samet N. Rethinking ferrule - A new approach to an old dilemma. Br Dent J 2010;209:25-33.  Back to cited text no. 14
    
15.
Rosen H. Operative procedure in mutilated endodontically treated teeth. J Prosthet Dent 1961;11:973-86.  Back to cited text no. 15
    
16.
Sorensen JA, Engelman MJ. Ferrule design and fracture resistance of endodontically treated teeth. J Prosthet Dent 1990;63:529-36.  Back to cited text no. 16
    
17.
Loney RW, Kotowicz WE, McDowell GC. Three-dimensional photoelastic stress analysis of the ferrule effect in cast post and cores. J Prosthet Dent 1990;63:506-12.  Back to cited text no. 17
    
18.
Libman WJ, Nicholls JI. Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont 1995;8:155-61.  Back to cited text no. 18
    
19.
Tan PL, Aquilino SA, Gratton DG, Stanford CM, Tan SC, Johnson WT, et al. In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations. J Prosthet Dent 2005;93:331-60.  Back to cited text no. 19
    
20.
Ng CC, al-Bayat MI, Dumbrigue HB, Griggs JA, Wakefield CW. Effect of no ferrule on failure of teeth restored with bonded posts and cores. Gen Dent 2004;52:143-6.  Back to cited text no. 20
    
21.
Mahdavi Izadi Z, Jalalian E, Eyvaz Ziaee A, Zamani L, Javanshir B. Evaluation of the effect of different ferrule designs on fracture resistance of maxillary incisors restored with bonded posts and cores. J Dent (Tehran) 2010;7:146-55.  Back to cited text no. 21
    
22.
Juloski J, Radovic I, Goracci C, Vulicevic ZR, Ferrari M. Ferrule effect: A literature review. J Endod 2012;38:11-9.  Back to cited text no. 22
    
23.
al-Hazaimeh N, Gutteridge DL. An in vitro study into the effect of the ferrule preparation on the fracture resistance of crowned teeth incorporating prefabricated post and composite core restorations. Int Endod J 2001;34:40-6.  Back to cited text no. 23
    
24.
Dikbas I, Tanalp J, Ozel E, Koksal T, Ersoy M. Evaluation of the effect of different ferrule designs on the fracture resistance of endodontically treated maxillary central incisors incorporating fiber posts, composite cores and crown restorations. J Contemp Dent Pract 2007;8:62-9.  Back to cited text no. 24
    
25.
Tjan AH, Whang SB. Resistance to root fracture of dowel channels with various thicknesses of buccal dentin walls. J Prosthet Dent 1985;53:496-500.  Back to cited text no. 25
[PUBMED]    
26.
Tan PL, Aquilino SA, Gratton DG, Stanford CM, Tan SC, Johnson WT, et al. In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations. J Prosthet Dent 2005;93:331-6.  Back to cited text no. 26
    
27.
Torabi K, Fattahi F. Fracture resistance of endodontically treated teeth restored by different FRC posts: An in vitro study. Indian J Dent Res 2009;20:282-7.  Back to cited text no. 27
[PUBMED]  Medknow Journal  
28.
Smales R, Chen Y, Meng L, Meng Q. Fracture resistance after simulatedcentral incisors incorporating fiber posts, composite cores and crown restorations. Am J Dent 2009:22;147-150.  Back to cited text no. 28
    
29.
McLaren JD, McLaren CI, Yaman P, Bin-Shuwaish MS, Dennison JD, McDonald NJ. The effect of post type and length on the fracture resistance of endodontically treated teeth. J Prosthet Dent 2009;101:174-82.  Back to cited text no. 29
    

Top
Correspondence Address:
Mohammad Iqbal
Flat No 203, Staff Accommodation, Rama Dental College - Hospital and Research Center, A/1-8, Lakhanpur, Kanpur - 208 024, Uttar Pradesh
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0707.181945

Rights and Permissions


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

Top
 
 
 
  Search
 
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Email Alert *
    Add to My List *
* Registration required (free)  
 


    Abstract
   Introduction
    Materials and me...
   Results
   Discussion
   Conclusion
    References
    Article Figures
    Article Tables

 Article Access Statistics
    Viewed1911    
    Printed42    
    Emailed0    
    PDF Downloaded285    
    Comments [Add]    

Recommend this journal