An In Vitro Evaluation of Fracture Resistance of Endodontically Treated Teeth Restored With New Contemporary Core Build-up Materials
Condition: Fracture Resistance
MeSH terms: Tooth, Nonvital; Fractures, Bone
Study type: Interventional

Summary: 
      Endodontic treatment is performed frequently which often results in weakening of tooth
      structure. Coronal restoration is done to restore these endodontically treated teeth. Posts
      have been used to retain the coronal restoration and reinforce these teeth but unfortunately
      posts placement results in further weakening of tooth structure. Newer contemporary core
      buildup materials will be used to restore coronal part of tooth without using endodontic
      posts and then the fracture resistance of these teeth will be evaluated.

      This study will be performed to evaluate the fracture resistance of endodontically treated
      teeth restored with newer contemporary core buildup materials.

      80 recently extracted single rooted caries-free and unrestored premolars will be taken and
      mounted in acrylic resin blocks. Roots of teeth will be covered with light bodies of
      condensation silicone impression material to simulate periodontal ligaments. Class 1 and
      class 2 cavities will be prepared and endodontic treatment will be performed in these teeth
      specimens. Coronal restoration will be done with three core buildup materials (Cention-N,
      Zirconomer and Aristaloy Amalgam). Teeth specimens are then divided into group 1 and group 2
      (class 1 cavity preparation and class 2 cavity preparation respectively) and each group is
      further divided into four subgroups: Subgroup A: Control group Subgroup B: Cavities restored
      with Zirconomer (Shofu) Subgroup C: Cavities restored with Cention-N (Ivoclar vivodent)
      Subgroup D: Cavities restored with Aristaloy Amalgam (Cookson) Fracture resistance of
      endodontically treated teeth restored with different core buildup materials will be tested by
      the Universal testing machine.
    

Detailed description: 
      Total 80 recently extracted single rooted lower second premolars, extracted for orthodontic
      treatment, will be selected for this study. Because lower second premolars are commonly
      extracted for orthodontic purposes and during mastication, the anatomic shape ofpremolars
      create tendency for separation of cusps. Indenter contacts the tooth and acts as a wedge
      between buccal and lingual cusps and decrease mean fracture resistance values. So the
      application of force vertically on cusp inclines found to be appropriate to simulate
      intraoral clinical conditions.

      Teeth will be washed under running water and any soft tissue attached to root surfaces will
      be scraped off with hand scaler. Teeth disinfected with 0.1% thymol solution and will be
      stored in 10% formalin solution for four days atleast, until they are used, teeth will be
      stored in 0.9% saline solution at room temperature.

      With the help of computer generated software, Teeth will be randomly divided into two groups.
      Each group contains 40 teeth. Class 1 cavity preparation will be done in teeth of group 1
      with straight fissure diamond bur (HiCare ISO. 109/010) in high speed handpiece (Nsk, Japan)
      along with water coolant and cavity will be prepared on occlusal fissures.

      Intercuspal distance and mesio-distal dimension of teeth will be measured with digital
      caliper. The buccolingual width of class 1 cavity will be one-third of the distance between
      buccal and lingual cusps and mesiodistal width would be one-third of mesio-distal distance.
      Buccal and lingual walls will be parallel to one other and cavo-surface angle of
      approximately 90 degree will be prepared. Class 2 cavity will be prepared in teeth of group
      2, in the same way as class 1 except that proximal box will also be prepared in class 2. The
      width of occlusal isthmus will be the one-third of intercuspal distance and the buccolingual
      dimension of approximal preparation will be the one-third of buccolingual dimension of
      overall crown. Gingival extent of this approximal preparation will be 1mm coronal to
      cemento-enamel junction and the gingival width would be of 2 +/- 0.2mm. Buccal and lingual
      walls of occlusal preparation will be parallel to each other.

      Class 1 and class 2 cavities are prepared because occlusal and proximal surfaces of teeth are
      the main surfaces which are subjected to higher forces during mastication and these two
      surfaces are more susceptible to caries attack and standard method for access opening is from
      occlusal and proximal surface (if carious lesion involve proximal surface too).

      Access cavity for endodontics will be prepared with diamond round bur (HiCare ISO.

      001/010). The working length will be taken by introducing the #10 K-file (Mani) in the canal
      until it becomes visible from apical foramen, The working length will be determined by
      subtracting 1mm from this estimated length. Endodontic procedure will be carried out in all
      teeth specimens by using rotary Protaper files (Densply). Sequence of S1, S2 and then F1 and
      F2 will be followed to prepare the canals at the working length. Canals will be irrigated
      thoroughly after every file with 2.5% NaOCl solution. After cleaning and shaping, canals will
      be dried with paper points and obturation will be done with sealer (Sealapex,
      SybronEndo-Kerr, Glendora, CA, USA) and F2 gutta percha cone (Densply).

      Modeling wax will be melted and root of tooth will be dipped in it below cement-enamel
      junction, this will produce a layer of 0.2 to 0.3 mm of wax on root surfaces. This thickness
      of wax on root surfaces will be representative to the thickness of periodontal ligament.
      Teeth will be placed in acrylic resin block of 3cmx 2.5cm such that 1.0 mm of root below
      cement-enamel junction will be out of the block to simulate the biologic width. Wax will be
      used as spacer between root and acrylic resin block and will be removed. Light body of
      condensation silicone impression material will be mixed and poured into resin block. Teeth
      will be reinserted into acrylic resin blocks with the silicone impression material, which
      will simulate periodontal ligament. Since the PDL acts as an effective support during the
      masticatory function and absorb and transmit forces between teeth and alveolar bone. So, to
      produce the clinical situation and to provide a more accurate assessment of fracture
      resistance of teeth, teeth are embedded in light body of condensation silicone impression
      material.

      Now, Each group will be randomly divided into four sub-groups. In each sub-group, there will
      be 10 teeth specimens. To make identification of specimens, each group and sub-group will be
      color coded. There will be one positive control group and one negative control group among
      the four subgroups and rest 2 sub-groups will be restored with new contemporary core buildup
      materials.

      GROUP 1 (Yellow color coded) Class 1 cavity preparation

      Sub-groups

      A (Blue color coded) negative control group: Normal teeth with no cavity preparation and no
      endodontic procedure.

      B (Pink color coded): teeth specimens in which endodontic procedure was performed and coronal
      restoration was done with Zirconomer (Shofu) C (Green color coded) : teeth specimens in which
      endodontic procedure was performed and coronal restoration was done with Cention-N (Ivovclar
      vivodent) D (Black color coded) : teeth specimens in which endodontic procedure was performed
      and coronal restoration was done with Aristaloy Amalgam (cookson)

      GROUP 2 (Purple color coded) Class 2 cavity preparation

      Sub-groups

      A (Blue color coded) negative control group: Normal teeth with no cavity preparation and no
      endodontic procedure B (Pink color coded): teeth specimens in which endodontic procedure was
      performed and coronal restoration was done with Zirconomer (Shofu) by using tofflemire
      retainer and matrix band.

      C (Green color coded) : teeth specimens in which endodontic procedure was performed and
      coronal restoration was done with Cention-N (Ivovclar vivodent) by using tofflemire retainer
      and matrix band.

      D (Black color coded) : teeth specimens in which endodontic procedure was performed and
      coronal restoration was done with Aristaloy Amalgam (cookson) by using tofflemire retainer
      and matrix band.

      Each tooth specimen will be individually tested in the Universal testing machine (UTM,
      INSTRON - 4301 Sr. # H1853, PCSIR Karachi). Tooth specimen will be placed in the holding slot
      that will be attached to the lower part of testing machine. Rounded stainless steel probe of
      diameter 6mm will be attached to the upper part of machine. Since, We are evaluating the
      fracture resistance of tooth that whether the new contemporary material enhances the fracture
      resisting ability of tooth, the probe will contact the inclined planes of facial and lingual
      cusps of tooth beyond the margins of restoration. The force will start from 'zero' Newton and
      then indenter will apply the increasing compressive loads to the inclined planes of buccal
      and lingual cusps until the tooth fractures and final force (Newtons) will be noted. The
      applied load would be parallel to the long axis of teeth. Load will be applied at crosshead
      speed of 1mm/min and will be increased gradually until fracture occurs. Maximum force
      required to fracture the tooth will be recorded in Newtons.

      All sample preparation will be done by the principle investigator and sample testing and
      scoring will be done by a blinded examiner.
    

Intervention name(s): class 1 and class 2 cavity preparation and restored with contemporary materials
Intervention type(s): Other
Intervention description(s): class 1 and class 2 cavities prepared in extracted teeth after endodontic procedure and then these cavities were filled with new contemporary core buildup materials.
Allocation: Randomized
Intervention model: Factorial Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment