Correction of periodontal abnormalities as a preliminary phase of oral rehabilitation.

The elimination of etiological factors and the correction of periodontal abnormalities are often a necessary preliminary phase of oral reconstruction. The development of optimal gingival and bony qualities using the surgical procedures outlined when indicated improves the prognosis of prospective abutment teeth and additionally may improve esthetics, retention, and maintenance of a fixed restoration.

A technique for autogenous root transplantation.

A technique of surgically creating a socket and transplanting an autogenous root to provide a stable abutment for a fixed partial prosthesis was described. Radiographic evidence and the demonstration of physiologic mobility of the transplanted root at a three and a half year follow-up of one patient give an indication of the development of a periodontal ligament. One transplant has successfully served as an abutment for seven years.

Load fatigue of teeth restored by a dentin bonding agent and a posterior composite resin.

A three-surface MOD preparation measuring one third of the isthmus cavity distance at the isthmus was prepared for five extracted, intact human maxillary premolar teeth. The teeth were restored with a posterior resin and a dentin bonding agent. Each tooth was tested under a cyclically varying load in a fatigue machine made at the University of Washington. The cyclic load rate was 75 cycles per minute. A strain gauge was applied to the buccal surface of each tooth. Under the load applied at an angle of 60 degrees to the long axis of the tooth, reinforcement of the tooth was established by the reduced deflection of the buccal surface of the restored tooth as compared with the unrestored tooth. The loss of this reinforcement due to the application of the cyclically varying load established the end point of the fatigue testing. Four different load values of 13, 16, 19, and 22 lb loads were applied separately to each tooth. The results of this testing were classic wherein the smallest load required the greatest number of load cycles before loss of adhesion was registered by the strain gauge. Failure always occurred within the adhesive joint.

Shock-absorbing behavior of five restorative materials used on implants.

The damping effect of five restorative materials used to veneer test crowns rigidly connected to a Brånemark implant and subjected to an impact force was measured. These materials included a gold alloy; a noble metal ceramic alloy; porcelain; a laboratory-processed, light-activated microfilled resin; and a heat- and pressure-polymerized poly(methyl methacrylate) resin. The two resins were found to reduce the impact force by about 50% when compared to porcelain or the alloys. The clinical significance of the results is discussed.

Three-dimensional analysis of the casting accuracy of one-piece, osseointegrated implant-retained prostheses.

The three-dimensional distortions of implant frameworks of two designs, reflecting the early "Toronto" U-shaped design and a current L-shaped design, were measured. A conventional commercial laboratory one-piece casting method, using a silver-palladium alloy, was used. Distortion was defined by five displacement variables for the centroids of each of five gold cylinders incorporated in each casting: three orthogonal translational displacements (dx, dy, and dz) and two rotational displacements (d theta x and d theta y). A computerized coordinate measuring machine was used. Overall translational displacements measured were -17.4 +/- 15 microns for dx, 6.1 +/- 7.1 microns for dy, and -0.1 +/- 1.7 microns for dz. The overall global translational displacement, dR, was 20.2 +/- 14.5 microns. Overall rotational displacements were -0.098 +/- 0.109 degrees for d theta x and -0.020 +/- 0.097 degrees for d theta y, giving an average absolute angular change, d theta R, of 0.158 +/- 0.077 degrees. No significant differences were found between U- and L-shaped castings, except for dy values for cylinders 2, 3, and 4, and d theta x values for cylinder 1. Cylinder location within the arch was associated with a specific direction and magnitude of translational and rotational displacement. Even small rotational displacements may manifest large gap appearances with the one-screw test because of the "moment arm" effect. However, other rotational displacements may be hidden, depending on the direction of tilt and the moment arm length.

Accuracy of replacing three tapered transfer impression copings in two elastomeric impression materials.

The accuracy of replacing three manufacturers' (Dental Imaging Associates, Implant Innovations Inc, and Steri-Oss) tapered transfer impression copings into impressions made with two different materials (Impregum F and Extrude) was evaluated. Five operators replaced these copings into the elastomeric impression materials. The angular deviations (replacement error) of the copings between the control (original) position and the replaced position in the impressions were evaluated. It was found that no one coping could be replaced into the impressions accurately and consistently by all five operators. However, there were significant differences in replacement accuracy between the three copings. Lower angular deviations were found for the Steri-Oss and Dental Imaging Associates copings when compared to the Implant Innovations coping. There was no significant difference in replacement accuracy between the two impression materials.

A comparison of wire- and Kevlar-reinforced provisional restorations.

Stainless steel wire 0.036 inch in diameter was compared with Kevlar 49 polyaramid fiber as a means of reinforcing a four-unit posterior provisional fixed restoration with 2 pontics. Three reinforcement patterns for wire and two for Kevlar 49 were evaluated and compared with the control, which was an unreinforced provisional restoration. A central tensile load was placed on the cemented provisional restoration and the variables were measured: (1) the initial stiffness; (2) the load at initial fracture; and (3) the unit toughness, or the energy stored in the beam at a point where the load had undergone a 1.0-mm deflection. Statistical analysis showed (1) the bent wire configuration had a significantly higher initial stiffness (P < or = .05), (2) there was no difference between designs for load at initial fracture, and (3) the bent wire had a significantly higher unit toughness value (P < or = .05).