Fiber-reinforced Composite Core Filling in the Restoration of Endodontically Treated Molars - a Clinical Study.
Condition: Dental Materials; Tooth, Nonvital
MeSH terms: Tooth, Nonvital
Study type: Interventional

Summary: 
      A short fiber reinforced composite base filling material has been shown to improve the
      strength of a direct composite filling significantly. It prevents fracture propagation and
      reduces shrinkage strain. These features are needed especially in endodontically treated
      molars, as root-canal treated teeth are structurally compromised and their restoration is
      associated with technical failures such as debonding and vertical root fractures.

      Application on this core fiber-reinforced composite (FRC) material is simplified when
      compared to post and core techniques commonly used to restore endodontically treated teeth.
      Clinically, the use of core FRC offers a cost-effective way to restore endodontically treated
      molars without root canal involvement.

      The purpose of this study is to compare the clinical performance of endodontically treated
      molars restored with either direct composite restorations with a FRC substructure, or with
      indirect full-ceramic onlay restorations, i.e. endo-crowns.
    

Detailed description: 
      INTRODUCTION

      Composite resins are routinely used for restoring vital and non-vital posterior teeth by most
      practitioners in Finland. Various clinical studies have found that the three main reasons for
      failure of direct composite fillings are secondary caries, wear and fracture of composite
      resin especially at molar region (1, 2, 3). Non-vital (endodontically treated) teeth are
      structurally compromised and their restoration is associated with technical failures such as
      debonding and vertical root fractures (4). Techniques, like root canal post insertion, that
      are used to overcome these problems, are time consuming and may even further increase the
      risk for root fractures.

      This study is a continuum on material development conducted at the the Department of
      Prosthetic Dentistry, Biomaterials Science and Turku Clinical Biomaterials Centre - TCBC,
      University of Turku, in collaboration with TEKES (Technology Development Center of Finland)
      and StickTech (Turku, Finland). The data obtained has shown that, the use of a bilayered
      structure consisting of a fiber-reinforced composite substructure (core FRC) combined with an
      upper layer of conventional restorative composite, increases the fracture load of a
      restoration significantly (5,6 and 7). This newly developed material has increased mechanical
      properties when compared to conventional materials, while maintaining its clinical
      applicability. Moreover, volumetric polymerization shrinkage of the core FRC is found to be
      lower than commercially available composites (<1.8% for the new FRC-material; 2.0% for a
      commercial composite Z250) (8). This may be expected to result in less marginal leakage and
      secondary caries in long term. With this backround a multidirectional short-fiber composite
      (everX, StickTech) has been introduced as a base material (FRC substructure) for large
      cavities in vital or non-vital teeth.

      The investigators in vitro experiments have shown that the FRC substructure retains and
      significantly reinforces composite crowns in endodontically treated molars. Moreover, in case
      of failure, the presence of the FRC substructure seems to orient the fracture propagation and
      result in more easily restorable fractures. Application on the core FRC material is
      simplified when compared to post and core techniques commonly used to restore endodontically
      treated teeth. Clinically, the use of core FRC offers a cost-effective way to restore
      endodontically treated molars without root canal involvement. In a recently published
      clinical pilot study the investigators have reported successful 1 year results of this
      technique (9).

      Ceramic onlay-restorations, so called "endo-crowns", are currently used to restore
      endodontically treated molars with similar indications (without root canal involvement). Case
      studies have reported good clinical results with this type of method (10). The use of an
      indirect technique (multiple patient visits), material and technical fabrication costs make
      this treatment modality, however, more costly and not in the reach of every patient.

      .

      AIM OF STUDY

      The purpose of this study is to compare the clinical performance of endodontically treated
      molars restored with either direct composite restorations with a FRC subtructure, or with
      indirect full-ceramic onlay restorations, i.e. endo-crowns.

      Specific study hypotheses are:

        1. The five year survival of direct FRC restorations is equal to that of ceramic
           endo-crowns

        2. Direct FRC restorations and ceramic endo-crowns perform equally with regard to

             1. marginal integrity

             2. fracture resistance

             3. occlusal wear

             4. secondary caries

        3. Less bleeding on probing is present around ceramic restorations when compared to
           composite restorations

        4. Less chair-side time is needed to restore a tooth with a direct FRC restoration than
           with a ceramic endo-crown

      MATERIALS AND METHODS

      The study will be carried out at the Institute of Dentistry of Turku University at Dentalia
      building (Lemminkäisenkatu 2, Turku). Subjects are enrolled among the patients of the
      undergraduate dental students (Dental teaching clinic, Turku city health care). Operators are
      experienced dental practitioners. Ethical committee approval was obtained (20.6.2006) form
      the Joint Commission on Ethics of the Turku University and The Turku University Hospital. A
      written informed concent will be obtained from all participants prior to their enrolment in
      the study.

      Exclusion/inclusion is based on anamnestic data, clinical and radiographic examination.
      Exlusion criteria at patient level are known nocturnal bruxism, active periodontal disease
      and poor oral hygiene. Exclusion criteria at tooth level are: periapical pathosis, root canal
      filling >3 mm short from apex, vertical fracture observed in cavum dentin, more than 50% of
      cavity margin situated subgingivally, less than 2mm of coronal tooth tissue present and lack
      of occluding antagonist.

      Alltogether 30 restorations, 15 direct composite restorations and 15 ceramic restorations,
      are made in endodontically treated posterior teeth (molars and premolars). Study teeth are
      randomly divided into two groups, the other receiving direct composite fillings and the other
      indirect ceramic fillings. In the composite group root canal orifices and the pulpal chamber
      is filled with the FRC substructure material forming a core restoration (everX, StickTech)
      and covered with an upperlayer of commercial restorative composite (Filtek Supreme 3M ESPE).
      In the ceramic group teeth are prepared for endo-crowns and optical impressions are made.
      CAD/CAM ceramic fillings are fabricated (CEREC, Dentsply Sirona) and subsequently cemented
      with resin cement at place. Special attention is payed to finishing and occlusal adjustment
      of the studied restorations.

      Chair-side time consumed in the making of the studied restorations is recorded in order to
      determine the cost-effectiveness of the methods.

      In addition to clinical examination, two to three visits per patient are required to
      fabricate the studied restorations. Impressions of the preparations are taken of all teeth to
      study the effect of remaining coronal tissue on the clinical survival.

      Patients are recalled and restorations examined at yearly follow-up visits up to five years.
      The clinical appearance, marginal integrity, fracture resistance, occlusal wear and color
      stability as well as the condition of marginal periodontal tissues close to the studied
      materials are assessed.

      X-rays at baseline, 2 and 5 year follow-up visits, are taken to determine the periapical
      status of the teeth and the intergrity of the restorations. Accordingly, impressions are
      taken and gypsum models casted to study the occlusal wear rate of the restorations.

      STUDY TIMETABLE

      Patient enrolling and examination, fall 2012 Clinical procedures, fabrication of
      restorations, 2012 - 2013 Follow-up examinations, 2013 - 2018 Analysing and reporting of the
      results, , 2018-2019
    

Intervention name(s): local anesthesia; Tooth restored using SFRC filling; Tooth restored using Ceramic indirect endocrown
Intervention type(s): Procedure; Procedure; Procedure
Intervention description(s): administering local anesthesia in the region of the planned restorative procedure; Restoration of an endodontivally treated molar using a shor-fiber base filling and veneering composite; Restoration of an endodontically treated molar using a ceramic indirect restoration
Intervention MeSH terms: Anesthetics
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: fiber-reinforced composite