Clinical Performance of 3-Unit FPDs
Condition: Partial Edentulism
Study type: Interventional
Phase: Phase 2

Summary: 
      Objectives: The purpose of this research was to determine the clinical success rate of a
      lithia-disilicate-based core ceramic (Ivoclar, Vivadent Corp.) for use in posterior fixed
      partial dentures (FPDs) as a function of bite force, cement type, connector height, and
      connector width.

      Methods: Thirty ceramic FPD core frameworks were prepared using a hot-pressing technique and
      a lithia-disilicate-based core ceramic. The maximum clenching force was measured for each
      patient prior to tooth preparation. Connector heights and widths were measured for each FPD.
      Patients were recalled yearly after cementation for two years and evaluated using eleven
      clinical criteria. All FPDs were examined by two independent clinicians and rankings for each
      criterion were made from 1 to 4 with 4 = excellent and 1 = unacceptable.

      The aims of this research were:

        1. To test the hypotheses that three-unit fixed partial dentures (FPDs) of a high-strength
           core ceramic will exhibit good-to-excellent clinical performance (based on 11 evaluative
           criteria) and that they will adequately resist fracture in posterior situations
           (excluding third molars) if fabricated with the minimal connector size (4 mm x 4 mm).

        2. To test the hypothesis that a reinforced glass ionomer cement (ProTec CEM, Ivoclar,
           Vivadent), when used to cement core ceramic crowns in posterior FPDs, will be associated
           with significantly less marginal quality, but similar fracture resistance of the ceramic
           crowns compared with the marginal quality associated with a dual cure resin cement
           (Variolink® II, Ivoclar Vivadent AG, Schaan, Liechtenstein).

        3. To test the hypothesis that there is no significant difference in tooth sensitivity
           associated with FPDs cemented with the glass ionomer cement and dual-cure resin cement.
    

Detailed description: 
      All patient recruitment and treatment were performed at the University of Florida College of
      Dentistry, Graduate Prosthodontic Clinic by Prosthodontic faculty. Patients were initially
      screened to exclude individuals with medical contraindications to dental treatment,
      parafunctional habits, and inability to ensure residence in the area for the next five years.
      Inclusion criteria were a missing posterior tooth in a quadrant (first premolars through
      second molars) that could be restored with a 3-unit FPD, periodontal pockets of less than 4
      mm for each abutment with no periodontal disease, vital abutment teeth, and a crown root
      ratio of at least 1:1. A patient can have multiple FPDs placed as long as the above-mentioned
      criteria were met. Baseline data were obtained for each selected subject to include the
      following:

        1. General medical history and physical examination

        2. Primary casts made with irreversible hydrocolloid impression material

        3. Bite force measurement in Newtons made with a gnathodynamometer

        4. Pocket depths of abutment teeth

        5. Periapical radiographs of abutment teeth. The maximum occlusal force exerted by each
           subject was measured prior to commencing treatment using a bite force gauge that has
           been reported previously by Gibbs et al.12 The purpose of these measurements was to
           analyze the influence of occlusal force on the survival of the FPDs. A total of 30 FPDs
           were fabricated for 21 patients with the core ceramic and all patients were recalled
           each year for two years. Three clinicians performed treatment and one technician using
           an in-house laboratory accomplished all labwork. Out of the 21 patients, 18 were female
           and 3 were male with ages ranging from 30 to 62 years of age. The 3-unit FPDs were
           located in the posterior area with canines serving as the most anterior abutment and
           second molars as the most posterior abutment. All FPDs were opposed by natural
           dentition. The dimensions for tooth reduction included at least 1 mm of axial reduction;
           2 mm of occlusal reduction and incorporation of a shoulder or a deep chamfer margin
           design with rounded line angles. Final impressions were made using a dual impression
           technique with high and low viscosity polyvinylsiloxane in a stock tray. Provisional
           resin FPDs were made and cemented with temporary cement. FPDs were processed by
           hot-pressing the core ceramic (Ivoclar Vivadent AG, Schaan, Liechtenstein) and applying
           stain and glaze as necessary. The heat-pressed ceramic system uses the lost wax
           technique whereby the FPD is waxed to its proper shape and contour and then invested in
           a special flask with a special type of investment material. The desired shade of a
           precerammed ceramic cylinder is plasticized at 1100oC and pressed under vacuum and
           pressure into the mold of the investment.13 The ceramic FPDs were inspected to ensure
           that the incisogingival height and curvature of the gingival embrasure of the connectors
           were adequate to resist fracture when subjected to normal biting forces. The minimal
           dimensions recommended for premolar FPDs, 4 mm x 4 mm, and for molar FPDs, 4 mm x 5 mm,
           were applied for each FPD when esthetics and gingival contour permitted. Connector
           heights and widths were measured for each FPD using a boley gauge. FPDs were cemented
           using either a resin-reinforced glass ionomer cement (Protec CEM, Vivadent) or a
           dual-cure resin cement (Variolink II, Vivadent) using a random number table. Fourteen
           (14) FPDs were cemented with the resin-reinforced glass ionomer and 13 with the dual
           cure resin. Patients were recalled after cementation annually for two years and
           evaluated for the following clinical criteria: (1) tissue health; (2) secondary caries;
           (3) occlusion; (4) proximal contact; (5) marginal integrity; (6) absence of sensitivity
           to percussion, heat, cold, and air; (7) color match; (8) surface texture; (9) absence of
           wear of opposing teeth; (10) anatomic contour; and (11) no cracks/chips or fracture.
           This evaluative system was derived from the California Dental Association quality
           assessment evaluation system.14 FPDs were examined by two independent clinicians who did
           not prepare the teeth or cement the prosthesis, and rankings of each criterion were made
           from 1 to 4 with 4 = excellent, 3 = good, 2 = unacceptable (needs repair or replacement
           in the near future), and 1 = unacceptable (needs immediate replacement). All
           clinicians/evaluators were subjected to several calibration exercises that consisted of
           table top analysis of marginal openings as well as slide evaluations of different
           clinical situations.

      Data were analyzed by logistic regression analysis of the variables with α = 0.05. The
      consistency of the examiners' scores was evaluated for consistency using a test for the
      standard deviation of inter-examination.
    

Intervention name(s): all-ceramic fixed partial denture
Intervention type(s): Device
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment