A Comparative Evaluation of Fracture Strength of Natural Tooth Pontic Reinforced with Polyethylene-fiber Post vs Glass-fiber Post: An In Vitro Study
1-5Department of Conservative Dentistry and Endodontics, People’s College of Dental Sciences and Research Centre, Bhopal, Madhya Pradesh, India
Corresponding Author: Vatsal Chauhan, Department of Conservative Dentistry and Endodontics, People’s College of Dental Sciences and Research Centre, Bhopal, Madhya Pradesh, India, Phone: +91 9926738267, e-mail: firstname.lastname@example.org
Aim and objective: The purpose of this study was to evaluate and compare the fracture strength of natural tooth pontic reinforced with polyethylene-fiber post vs glass-fiber post.
One of the most conservative solutions for the replacement of missing anterior tooth can be using patient’s own tooth as a pontic. As no laboratory procedures are required, it is well suited for patients who need an immediate replacement of tooth in esthetic zone.
Materials and methods: Twenty polymethyl methacrylate (PMMA) resin blocks were prepared. Two abutment teeth were embedded in each PMMA resin block. Twenty central incisors were sectioned at the level of cementoenamel junction using a diamond-cutting disk with water coolant and used as pontics. The samples were divided into two groups at random; group A—polyethylene (Ribbond) fiber post (n = 10) used to strengthen pontics and group B—glass (Interlig) reinforcement fiber post (n = 10) used to strengthen the pontics. The fracture strength of the samples was tested in universal testing machine. Student’s t -test was done for statistical analysis to find the difference between two groups.
Results: The mean fracture strength of polyethylene (Ribbond) fiber post was 56.7 ± 13.0 MPa and glass (Interlig) reinforcement fiber post was 38.56 ± 8.68 MPa. A significant difference was observed between mean fracture strength of polyethylene (Ribbond) fiber post and glass (Interlig) reinforcement fiber post (p -value = 0.002).
Conclusion: Both the fiber reinforced splint materials are effective in stabilizing the natural tooth pontic. Ribbond fiber, a polyethylene fiber post, had better fracture strength than Interlig glass fiber post and can be used effectively for stabilization of the natural tooth pontic.
How to cite this article: Chauhan V, Sharma A, Mishra P, et al. A Comparative Evaluation of Fracture Strength of Natural Tooth Pontic Reinforced with Polyethylene-fiber Post vs Glass-fiber Post: An In Vitro Study. Int J Prosthodont Restor Dent 2021;11(4):178-182.
Source of support: Nil
Conflict of interest: None
Keywords: Interlig reinforcement fiber, Natural tooth pontic, Ribbond fiber, Splint material
The rehabilitation of a single missing or failing tooth presents one of the greatest challenges in dentistry.1 The most substantiated option for single tooth replacement nowadays is implant supported crown, but a restorative option has to be kept in mind due to number of factors like expectations, desires, clinical conditions, and financial conditions of the patient.2
Among all the conventional treatment options available, the resin bonded fixed partial dentures (FPDs) have minimum operating time, lower cost, and extensive surgical procedures are also not needed. It has a conservative approach as it requires no/minimum preparation of the natural abutment teeth present.3 Fiber reinforced composite (FRC) materials are designed by reinforcing dental resins with Kevlar, carbon, glass, silane-treated glass, and ultra-high molecular weight polyethylene.4-6 Glass fiber reinforced composite material are known to have good esthetics, good fatigue life, and good chemical resistance to acids and solvents.7
The instant bonding of a natural tooth to adjoining elements presents a low-cost substitute for direct tooth replacement.8,9 The actual tooth anatomy is replicated by this technique, providing excellent function and esthetics (size, shape, and color) at the same time.
One of the conservative solutions can be using patient’s own tooth as pontic. As it requires no laboratory procedure, it is suited for immediate replacement of irreparable tooth in esthetic region. It also provides promising results by means of a combined application of fiber-reinforced materials and adhesive technologies.10,11
Researchers12-14 had done studies to find the fracture strength of glass fiber reinforced composite materials and polyethylene fiber but not much is known about the fracture strength of natural tooth pontic reinforced with polyethylene-fiber post and glass-fiber post. This in-vitro study aimed to evaluate and compare the fracture strength of natural tooth pontic reinforced with polyethylene-fiber post (Ribbond) vs glass-fiber post (Interlig).
MATERIALS AND METHODS
This in-vitro study was conducted in the Department of Conservative and Endodontics and ethical clearance was obtained from the institutional ethics committee. This study consists of two groups with ten samples in each (1) polyethylene (Ribbond) fiber post group and (2) glass (Interlig) reinforcement fiber post group (Fig. 1).
PREPARATION OF SAMPLES
Sixty freshly extracted maxillary incisors (40 central incisors and 20 lateral incisors) were collected from the Department of Oral and Maxillofacial Surgery. Twenty polymethyl methacrylate (PMMA) resin blocks were prepared. Two incisors (one central and one lateral incisor) were embedded in each PMMA resin block at a distance of 8.5 mm to simulate the abutment teeth (Fig. 2). The remaining 20 central incisors were sectioned at the level of cementoenamel junction using a diamond-cutting disk with copious irrigation with water (Fig. 3). These sectioned teeth were placed in each PMMA block in between the previously mounted central and lateral incisors to simulate as pontic. Residual pulp tissue was completely removed from the pulp chamber of the pontic tooth.
The lingual surface of both the abutments and pontic was etched using 37% phosphoric acid, washed, and dried after 15 seconds (Fig. 4). Bonding was done using tetric N-bond universal bonding agent (Ivoclar Vivadent) (Fig. 5) and cured with a light curing gun for 40 seconds.
The samples were randomly divided into two groups (n = 10 blocks per group). In both groups, each block consisted of two intact teeth (lateral and central incisor) embedded in PMMA block and a natural tooth pontic (sectioned central incisor). In polyethylene (Ribbond) fiber post group, the pontic was strengthened by placing ribbond fiber post (Ribbond Inc., Seattle, WA, USA) and secured by nanohybrid composite (tetric N-ceram, Ivoclar Vivadent) (Fig. 6) and cured with a light curing gun for 40 seconds. In glass (Interlig) fiber post group, the pontic was strengthened by placing Interlig reinforcement fiber post (Angelus, Brazil) and secured by nanohybrid composite (Fig. 7), and cured with a light curing gun for 40 seconds (Fig. 8).
FRACTURE STRENGTH TESTING
The samples were tested by Instron universal testing machine (Fig. 9), using a round steel ball of diameter 0.5 mm, at an angle of 45° to the long axis of the pontic with cross head speed of 1 mm/minute until fracture.
The data obtained was subjected to statistical analysis using Statistical Package for the Social Sciences (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.). The statistical analysis was done using Student’s t -test to find the difference between two groups. A p -value < 0.05 was considered statistically significant. The confidence interval was set at 95%.
The mean fracture strength of polyethylene (Ribbond) fiber post was 56.7 ± 13.0 MPa and it was higher when compared to glass (Interlig) reinforcement fiber post (38.56 ± 8.68 MPa) (Fig. 10). A significant difference was observed between mean fracture strength of polyethylene (Ribbond) fiber post and glass (Interlig) reinforcement fiber post (p -value = 0.002) (Table 1). The minimum fracture strength in polyethylene (Ribbond) fiber post group was 41.33 MPa and maximum fracture strength was 87.39 MPa. The minimum fracture strength in glass (Interlig) reinforcement fiber post group was 30.07 MPa and maximum fracture strength was 57.86 MPa.
|Group||Number of samples (n)||Mean±SD||95% Confidence interval mean||F-value||P-value|
|Lower limit||Upper limit|
|Polyethylene (Ribbond) fiber post||10||56.7±13.0||47.34||66.02||13.428||0.002*|
|Glass (Interlig) reinforcement fiber post||10||38.56±8.68||32.35||44.78|
The maxillary central incisors are the most common ones to sustain traumatic injuries, while the mandibular incisors and maxillary lateral incisors are less intermittently involved. A large fraction of population undergoes such trauma once in their lifetime. Up to 92% of all traumatic injuries are reported to be crown fractures of permanent dentition, while prevalence of avulsion is estimated to be around 17.5%. Many times, teeth having hopeless prognosis are also extracted due to periodontal reasons. In anterior region it is even more challenging as esthetics is a major concern too. Various techniques and designs have been proposed for the replacement of missing anterior tooth like implant supported crown, FPDs, and so on. But these are expensive and time consuming as well.2,15-17 Hence using patient’s own tooth as pontic gives us an immediate as well as conservative solution with no laboratory procedure.18
The null hypothesis, which supposed that different fibers will not affect the fracture strength of stabilized natural tooth pontic was rejected. The different post systems significantly influenced their ultimate fracture strength (p ≤ 0.002).
The major drawback of conventional method where metal wire splints were used with composite resin was brittleness and rigidity. This limitation has been overcome with the replacement of metal wire by FRC. This conservative splinting can be done using various commercially available FRC splints.19,20
Electrical glass, high-strength glass, or quartz fibers are different types of glasses that are used to fabricate glass fiber posts. While fibers used are silica-based (50-70% SiO2), in addition to other oxides. Polyethylene fiber-reinforced posts (PFR) are made of ultrahigh molecular weight polyethylene-woven fiber ribbon (Ribbond, Ribbond Inc., Seattle, WA). This material has a leno weave or triaxial braid composition that gives it a three-dimensional structure. Due to this unique structure mechanical interlocking is provided with composite resin at different planes. In addition, microcracking is minimized during polymerization of the resin. They are not posts of conventional type as this post is coated with a dentin bonding agent, which is then packed into the canal, and light cured in position.21,22
While Interlig (Angelus, Brazil) are adaptable glass fibers, pre-wetted with light-cured composite resin, manageable and easy to cut (special scissors are not required). These reinforcement fibers are packed in sachets that protects fibers from light and heat.21
Brauchli et al.23 stated that the most important merit of using fiber reinforced composite resin splints is their high transparency. These retainers are almost invisible which makes them esthetically more pleasing. The research by Vallittu24 concluded that there was slight increase in transverse strength after reinforcement of polymers with ribbon layer. According to Singla and Grover,25 the chemical, adhesive, and esthetic characteristics of composite resin was combined with the strength of thin high elastic modulus reinforcing ribbon via fiber reinforced splints. Tayab et al.26 claimed that both glass and polyethylene fiber has immense potential as reinforcement, but having an understanding of their distinct attributes will facilitate clinician to make relevant choices for framework construction. Similar result was obtained when pontic was reinforced with the polyethylene (Ribbond) and glass (Interlig) reinforcement fiber.
In a study done by Bechir et al.,21 62 patients were appraised for the clinical success of FRCs splints on mobile anterior teeth (grade I and II). Two types of FRC splints were used, glass FRC (Interlig) and polyethylene FRC (Ribbond) where both of them had commendable effects in decreasing the mobility. It also had remarkable esthetic desirability. Nonetheless, better results appeared in polyethylene FRC group (96.04%), compared to glass FRC group (95.80%). Similar result was obtained with good fracture resistance with the polyethylene (Ribbond) and glass (Interlig) reinforcement fiber groups.
Finally, it can be concluded that the use of glass fiber and polyethylene fiber post can be a validated solution for the replacement of anterior teeth by stabilizing natural tooth pontic. Limitations of this study may include the objectification of a single load in the fracture test. Dynamic loading, temperature effects, and oral environment effects were excluded but may also be considered as limitations. Further studies should be conducted with thermocycling and dynamic fatigue loading. Further investigations on other teeth in the dental arch (molars or premolar teeth) are recommended to complement the present study results.
Within the limitations of this study, it can be concluded that both the fiber reinforced post materials are effective in stabilizing the natural tooth pontic. Ribbond fiber (polyethylene fiber) had better fracture strength than Interlig glass fiber. Although the technique is technically demanding, it has major advantages like — excellent esthetic results, preservation of natural crown structure with no laboratory work being involved. Although, long-term clinical studies are needed to assess its effects on prolonged use.
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