Frederick C. Finzen

Incidence of various classes of removable partial dentures

The purpose of a classification for removable partial dentures (RPDs) is to simplify identification and enhance its teaching. A classification also allows a longitudinal comparison of various classes of RPDs to determine whether the teaching of RPD design is consistent with the relative frequencies of RPD use. This study surveyed the types of removable partial dentures being fabricated in a regional dental laboratory and compared these findings with data from previous studies. Results indicate that mandibular RPDs are more common than maxillary RPDs and the class I mandibular RPD is the most common type of RPD for either dental arch. A palatal strap was the most frequently used maxillary major connector and a lingual bar was used three times more often than a lingual plate in the mandibular arch. Cast circumferential clasps were used twice as often as RPI clasp designs. The percentage of Kennedy class I RPDs was 40%, class II 33%, class III 18%, and class IV 9%. Comparisons with a previous study indicate the percentage of Kennedy class II has increased, whereas class I, class III and class IV RPDs have not changed significantly. Findings of the study indicate that the frequency of use of the various types of RPDs have changed in the past 30 years.

Failure load of acrylic resin denture teeth bonded to high impact acrylic resins

STATEMENT OF PROBLEM Techniques for bonding denture teeth to an acrylic resin denture base remain empirical, with little consensus from the literature, among clinicians, or among dental laboratories. PURPOSE This study evaluated the failure load of acrylic resin teeth bonded to 2 high impact acrylic resins. METHODS AND MATERIAL The ridge lap portion on 120 identical denture teeth were modified with 3 variables: (1) placing a diatoric, (2) using monomer to prewet the denture tooth, and (3) breaking the glaze. Variables were combined to form 6 groups of 10 teeth each, and processed with Lucitone 199 (Lucitone) or SR-Ivocap (Ivocap) acrylic resin. Data analysis included the use of a heterogeneous variance linear regression model. RESULTS Mean (+/- SD) failure load ranged between 10.25 +/- 1.48 Kg to 28.43 +/- 11.05 Kg for the 6 Ivocap groups and 16.63 +/- 5.87 Kg to 28.05 +/- 5.35 Kg for the Lucitone groups. For Lucitone 199 acrylic resin, the highest failure loads resulted when the ridge lap was left with an intact glaze and did not have a diatoric, with no significant influence from the use of monomer. For Ivocap resin, the highest failure loads resulted when the ridge lap had a diatoric but did not have monomer placed, with no significant influence from glaze. CONCLUSION Failure load of bonding highly cross-linked denture teeth to SR-Ivocap or Lucitone 199 acrylic resin was significantly influenced by modifications to the ridge lap before processing.

The effect of clinical remount procedures on the comfort and success of complete dentures

Fifteen patients were treated with complete dentures in a routine manner that included a clinical remount. A second group of 15 was treated in the identical manner except that the clinical remount was not performed. The occlusal patterns of all dentures were recorded in the patients mouths at delivery and again 1 week later by using a photoelastic membrane to provide a permanent record. The presence or absence of soreness was also noted for each patient during the week after delivery. Results indicate that clinical remounts significantly reduced the incidence of soreness, preserved the occlusal force, and reduced the changes in occlusal patterns of the dentures. Although both cusped and flat teeth were used in both treatment groups, no significant differences were noted in relation to either form on the basis of the indices studied.

Er:YAG laser debonding of porcelain veneers.

The removal of porcelain veneers using Er:YAG lasers has not been previously described in the scientific literature. This study was designed to systematically investigate the efficacy of an Er:YAG laser on veneer debonding, possibly without damage to the underlying tooth, and preservation of the veneer integrity.

The effect of E-glass fibers and acrylic resin thickness on fracture load in a simulated implant-supported overdenture prosthesis

STATEMENT OF PROBLEM Implant overdenture prostheses are prone to acrylic resin fracture because of space limitations around the implant overdenture components. PURPOSE The purpose of this study was to evaluate the influence of E-glass fibers and acrylic resin thickness in resisting acrylic resin fracture around a simulated overdenture abutment. MATERIAL AND METHODS A model was developed to simulate the clinical situation of an implant overdenture abutment with varying acrylic resin thickness (1.5 or 3.0 mm) with or without E-glass fiber reinforcement. Forty-eight specimens with an underlying simulated abutment were divided into 4 groups (n=12): 1.5 mm acrylic resin without E-glass fibers identified as thin with no E-glass fiber mesh (TN-N); 1.5 mm acrylic resin with E-glass fibers identified as thin with E-glass fiber mesh (TN-F); 3.0 mm acrylic resin without E-glass fibers identified as thick without E-glass fiber mesh (TK-N); and 3.0 mm acrylic resin with E-glass fibers identified as thick with E-glass fiber mesh (TK-F). All specimens were submitted to a 3-point bending test and fracture loads (N) were analyzed with a 2-way ANOVA and Tukeys post hoc test (α=.05). RESULTS The results revealed significant differences in fracture load among the 4 groups, with significant effects from both thickness (P<.001) and inclusion of the mesh (P<.001). Results demonstrated no interaction between mesh and thickness (P=.690). The TN-N: 39 ±5 N; TN-F: 50 ±6.9 N; TK-N: 162 ±13 N; and TK-F: 193 ±21 N groups were all statistically different (P<.001). CONCLUSIONS The fracture load of a processed, acrylic resin implant-supported overdenture can be significantly increased by the addition of E-glass fibers even when using thin acrylic resin sections. On a relative basis, the increase in fracture load was similar when adding E-glass fibers or increasing acrylic resin thickness.

A radiograph positioning technique to evaluate prosthetic misfit and bone loss around implants

A radiograph positioning device was developed to fit with commercially available film holders and implant systems. The device is indexed to the dental implant body and the adjacent dentition by using an implant placement driver and polyvinyl siloxane occlusal registration material. By fitting the device to a conventional film holder, accurate orthogonal radiographs can monitor changes in bone architecture and prosthetic misfit.

Laser all‐ceramic crown removal—a laboratory proof‐of‐principle study—Phase 2 crown debonding time

The removal of all‐ceramic crowns is a time consuming procedure in the dental office. Little research has been done in alternative removal techniques for all‐ceramic crowns. The objective of the second phase of this proof‐of‐principle laboratory pilot study was to evaluate whether Ivoclar Vivadent all‐ceramic crowns can be efficiently removed from natural teeth without damage to the underlying tooth structure using an Erbium laser.

Laser all-ceramic crown removal-a laboratory proof-of-principle study-phase 1 material characteristics.

The removal of all‐ceramic crowns is a time consuming and destructive procedure in the dental office. The removal of all‐ceramic crowns using Er:YAG lasers has not been previously described in the scientific literature. The objective of this laboratory proof‐of‐principle study was to evaluate whether with regards to absorption and transmission characteristics of bonding cements and ceramics all‐ceramic crowns can be removed from natural teeth using an Erbium laser.

Assessing fit at the implant-abutment junction with a radiographic device that does not require access to the implant body.

STATEMENT OF PROBLEM Radiograph paralleling devices provide an excellent means of obtaining orthogonal radiographs for the evaluation of the fit of implant restorations. Unfortunately, the clinical applicability of such devices is a significant issue because access to the implant body must be obtained at each radiographic appointment. PURPOSE The purpose of the study was to investigate whether the fit or microgap at the implant-abutment junction could be more accurately and confidently assessed with a novel radiograph paralleling device that did not require access to the implant body once a proper registration index was made. MATERIAL AND METHODS Microgaps of 0, 50, and 100 μm were introduced at the implant-abutment junction of a provisional implant crown in a manikin-typodont assembly. Dental assistants made 54 radiographs (18 per microgap) of the crown with and without a radiograph paralleling device; 9 clinicians then evaluated the standardized radiographs for the presence of misfit. The Cochran-Mantel-Haenszel test and the corresponding odds ratios were used to evaluate the effectiveness of the paralleling device in helping clinicians better assess misfit from the radiographs made. RESULTS The use of the device led to a higher percentage of accuracy under all conditions (79.0% vs 70.4% at the 0-μm gap, 77.8% vs 16.1% at the 50-μm gap, and 100% vs 92.6% at the 100-μm gap); the improvement was statistically significant at the 50-μm gap (P<.001) and 100-μm gap (P=.049) but not at the 0-μm gap (P=.364). The odds ratio (95% confidence interval) of obtaining correct versus wrong answers with the device compared with without the device was 18.64 (7.94-43.77) at the 50-μm gap and 5.40 (0.25-114.25) at the 100-μm gap. CONCLUSIONS The study indicated that the paralleling device helped the clinician more accurately assess the implant-abutment junction with the 50- and 100-μm gaps.

The effects of an airborne-particle abrasion and silica-coating on the bond strength between grooved titanium alloy temporary cylinders and provisional veneering materials.

STATEMENT OF PROBLEM Even though mechanical retentive features, such as grooves, are incorporated into the surface of titanium alloy temporary cylinders, a reliable bond to veneering provisional materials is not always achievable for screw-retained provisional implant restorations. There is insufficient information about the effect of tribochemical silica coating on the bond strength between provisional materials and grooved titanium alloy temporary cylinders. PURPOSE The purpose of this study was to evaluate, in vitro, the effect of an airborne-particle abrasion and silica-coating technique on the bond strength between grooved titanium alloy temporary cylinders and provisional veneering bisphenol-A glycidyl methacrylate and polymethyl methacrylate materials. MATERIAL AND METHODS Forty grooved titanium alloy (Ti-6Al-4V) internal connection implant temporary cylinders were used. A disc of veneering material (7.1 × 3.4 mm) was created around the midsection of each cylinder. Forty specimens were divided into 4 groups (n=10): group NoTxPMMA, no surface treatment and polymethyl methacrylate veneering material; group NoTxBisGMA, no surface treatment and BisGMA veneering material; group AbPMMA, airborne-particle abrasion, silica-coating surface treatment (Rocatec), and polymethyl methacrylate; and group AbBisGMA, airborne-particle abrasion, silica-coating surface treatment (Rocatec), and BisGMA. Each specimen was subjected to ultimate shear load testing at the interface of the veneering material and the temporary cylinder in a universal testing machine at a constant crosshead speed of 5 mm/min. Data were analyzed with a 1-way ANOVA (α=.05) followed by post hoc Student-Newman-Keuls test. Each specimen underwent surface observation with a light microscope at ×40 magnification to compare fracture patterns. RESULTS Airborne-particle abrasion and silica-coating surface treatment significantly lowered the shear bond strength (P<.05). The type of provisional material did not significantly affect the shear bond strength, with or without surface treatment. Group AbBisGMA demonstrated the lowest mean value (3.49 MPa) compared to the other groups. CONCLUSIONS Airborne-particle abrasion and silica-coating treatment did not improve the bond between grooved titanium alloy temporary cylinders and provisional veneering materials. It weakened the provided mechanical retention, especially when it was used with BisGMA veneering material. Material choice, whether it was polymethyl methacrylate or BisGMA, did not make a statistically significant difference.