Analysis of Enamel Wear Against Ceramic Restorations
Condition: Tooth Wear
MeSH terms: Tooth Wear
Study type: Observational

Summary: 
      1. To characterize the microstructure (fracture toughness, particle size of ceramic, and
           inter-particle spacing) of three ceramic materials

        2. To test the hypothesis that lower fracture toughness of glass and/or crystal phase in
           ceramics reduce wear damage of enamel.

        3. To test the hypothesis that smaller sized crystals reduce wear damage of enamel.

        4. To test the hypothesis that larger inter-particle spacing reduces wear damage of enamel.

        5. To test the hypothesis that equivalent wear patterns exist in all directions between
           enamel versus enamel and ceramic versus enamel.

        6. To test the hypothesis that bite force does not correlate with wear rates.

        7. To test the hypothesis that salivary flow does not correlate with wear rates.

        8. To test the hypothesis that a greater amount of wear is not associated with a loss in
           vertical dimension of occlusion.

        9. To test the hypothesis that a greater amount of wear does not correlate with secondary
           cementum deposition as part of the passive eruption process.

       10. To test the hypothesis that maximum wear occurs early and wear rates level off within
           the first two years.

       11. To test the hypothesis that in vitro wear analysis does not correlate with in vivo wear
           measurements
    

Detailed description: 
      A total of 36 teeth (1 crown per patient) needing crowns will be selected with the following
      acceptance criteria:

        1. Subjects must be over 18 years of age with good overall health. No contraindications to
           dental treatment must be present.

        2. Subjects must have overall good dental health with no active tooth decay (caries)
           present and no periodontal disease. Pocket depth on all remaining teeth must not be more
           than 4 mm.

        3. Subjects must have no existing temporomandibular disorder, (e.g. clicking, popping, pain
           on opening) or parafunctional habits (e.g. bruxism, clenching)

        4. Subjects must need a crown on either a second premolar, first molar or second molar on
           any arch. Abutment teeth must be restorable and have a crown root ratio of at least 1:1.
           Abutment teeth must have a complement of opposing non-restored or minimally restored
           natural teeth. Minimally restored means nothing beyond a Class II amalgam restoration.
           Opposing arch cannot be a full coverage restoration or a partial denture. Contralateral
           tooth must be preferably present.

        5. Subjects must exhibit good oral hygiene and compliance.

        6. Subjects must not have any existing condition that could limit the flow of saliva; e.g.
           saliva flow must be of normal quantity.

      Baseline data will be collected and will consist of:

        1. General medical history and physical examination

        2. Primary casts taken with polyvinylsiloxane impression material

        3. Bite force measurement in Newtons using a gnathodynamometer

        4. Pocket depths of abutment teeth must be recorded

        5. Periapical radiographs of abutment teeth. Radiographs will be taken at the exact
           position with the use of the longitudinal radiographic analysis (LRA) technique.

        6. Vertical dimension measured from the nasion to the lowest point on the chin

        7. A saliva sample will be collected to ascertain quality (viscosity) and quantity. The
           parameters for analysis will be salivary pH, buffer capacity, secretion (ml/min),
           protein (mg/ml), phosphate (mmol/l), Ca (mval/l), Na (mval/l), K (mval/l).

      A total of 36 teeth will be randomly assigned to receive either a metal-ceramic (D'Sign) or
      an all-ceramic crown (IPS Empress2, Eris EXC). Randomization will be done through a random
      number table. Teeth will be prepared by two operators: Dr. Josephine Esquivel-Upshaw and Dr.
      William Rose both from the General Dentistry department. Provisional restorations will be
      made from Integrity (Dentsply, USA) and final impressions will be made with a
      polyvinylsiloxane material using the two-stage technique. Master casts will be mounted in
      centric relation.

      A single unit crown will be made from either two types of an all-ceramic material or a
      metal-ceramic material and cemented with a dual cure resin cement. Adjustments will be made
      with a high-speed handpiece and a fine diamond bur. Prior to cementation, all adjusted
      surfaces must be polished or glazed. Occlusal surface thickness of the crowns will be
      measured at baseline.

      Baseline examination will be performed one week after cementation to ensure that the patient
      is comfortable with the crown and no further adjustments are needed. A polyvinylsiloxane
      impression will be made of the maxillary and mandibular arches to record the cemented crown
      and its antagonist arch.

      The post-cementation casts will be poured with a Type IV gypsum product to enable proper
      scanning. A 3D Laserscanner will be used to scan in the x, y and z planes of tooth/teeth
      casts made from natural teeth. The vertical dimension will be recorded as well as periapical
      radiographs taken of the abutment teeth.

      The subjects will be asked to return after six months of cementation. Polyvinylsiloxane
      impressions will once again be made of maxillary and mandibular arches and poured with Type
      IV stone. The antagonist teeth and the crown will be scanned using the 3D Laserscanner.
      Superimposition of baseline image and the six-month image will be performed and the amount of
      wear in three dimensions calculated mathematically. Vertical dimension of occlusion will also
      be determined by measurement of nasion to the lowest point on the chin and periapical
      radiographs taken of the restored teeth using the LRA technique. This procedure will be
      repeated every year for the next four years.

      The amount of wear in microns will be determined for the x, y and z axes. Data will be
      subjected to a one-way ANOVA (α = 0.05 ) to determine any significant difference in wear of
      natural antagonist teeth and the ceramic crowns between baseline and yearly 3D images and
      also differences in wear between the yearly 3D images. Occlusal thickness of restorations
      will be determined based on the amount of wear calculated. Any presence of cracks or
      fractures will be recorded. Correlation of the amount of wear and any changes in vertical
      dimension and root cementum length will also be determined by comparison of nasion-chin
      height at different intervals.
    

Intervention name(s): crown placement
Intervention type(s): Device
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients needing a crown on a tooth that was opposed by a natural tooth. Patients seeking
        care in the UTHSCSA dental clinic.
      
Keywords: enamel wear against ceramic crowns