Clinical efficacy of veneered zirconium dioxide-based posterior partial fixed dental prostheses: five-year results.

STATEMENT OF PROBLEM: In recent years, zirconium dioxide-based partial fixed dental prostheses (FDP) have been suggested as an alternative treatment to traditional metal ceramic FDPs. However, clinical studies evaluating their longevity and related complications are limited. PURPOSE: The purpose of this cohort clinical study was to assess the efficacy of zirconium dioxide-based posterior 3-unit FDPs. MATERIAL AND METHODS: Twenty 3-unit posterior FDPs (Lava) were placed in 16 participants missing a second premolar or a first molar. All participants met specific inclusion and exclusion criteria and provided informed consent. All teeth were prepared in a standardized manner: occlusal reduction of 1.5 to 2 mm; axial reduction of 1 to 1.5 mm; a 1.0 mm 360-degree rounded shoulder placed 0.5 mm subgingivally on the facial aspect and supragingivally on the lingual aspect on sound tooth structure; and rounded internal line angles. Definitive impressions were made with vinyl polysiloxane impression material. Frameworks were fabricated by using computer-aided design and computer-aided manufacturing (CAD/CAM) technology with a uniform retainer thickness of 0.6 mm and a minimal connector surface area of 9 mm(2). Restorations were luted with resin-modified glass ionomer cement (Rely-X Luting). Participants were recalled at 2 weeks, 6 months, and 12 months, and thereafter, annually for up to 60 months. Clinical fracture measurements, marginal discoloration, marginal adaptation, radiographic proximal recurrent caries, and periapical pathoses were assessed over time by using modified Ryge criteria. The probability distributions of these variables were calculated for the baseline data and for the recall data. An analysis of survival was made by using the Kaplan-Meier method. RESULTS: Eighteen FDPs were clinically evaluated at 5 years and 1 at 48 months. Fifteen were rated Alpha for fracture measurements, and 2 were rated Bravo (minor chipping of veneering porcelain and not requiring restoration replacement). Two were rated Charlie (major chipping of veneering porcelain and requiring restoration replacement). Eighteen FDPs were rated Alpha for marginal integrity, and 1 rated Bravo. All restorations were rated Alpha for marginal discoloration. One participant experienced root fracture after 60 months, while another was treated surgically for a periapical pathosis on an endodontically treated abutment. CONCLUSIONS: Zirconium dioxide-based posterior 3-unit FDPs performed well after 5 years of service.

Bond strength of different veneering ceramics to zirconia and their susceptibility to thermocycling.

PURPOSE: To evaluate the bond strength of recently developed feldspathic veneering ceramics to zirconium-oxide ceramic core material (Y-TZP). In addition, the effect of thermocycling on the bond strength was investigated. METHODS: 90 square Lava framework Y-TZP specimens were randomly assigned to three groups (n = 30) and veneered with one of the three zirconia veneering ceramics Cerabien ZR (CZR), GC Initial (GCI), or Lava Ceram (LC). 30 additional metal-ceramic specimens served as the control (VO). 15 specimens per group were stored in a saline solution for 3 days. To test the durability of the bond, 15 specimens per group were thermocycled for 10,000 cycles between 5 degrees to 60 degrees C with a 15-second dwell time. Shear strength was tested with an Instron universal testing system. A two-way ANOVA model and Tukey's HSD were applied for statistical analyses (alpha = 0.05). RESULTS: The different material combinations revealed significantly different shear bond strength values (CZR > GCI > LC > VO). All veneering ceramic/zirconia combinations showed significantly higher bond strength than the metal-ceramic control VO. Bond strength values were not affected by thermocycling, except for CZR, which had significantly higher bond strength after thermocycling. Microscopic evaluation of failure modes revealed 100% cohesive failures in the veneering ceramic for all specimens.

Comparison of marginal fit between all-porcelain margin versus alumina-supported margin on Procera Alumina crowns.

PURPOSE: Procera Alumina crowns are widely used; however, the effect of crown margin design on marginal fit is unknown. This study measured and compared the precision of fit of Procera Alumina crowns with two crown margin designs: all-porcelain versus alumina-supported margins. MATERIALS AND METHODS: Sixteen noncarious extracted human premolars were prepared for Procera((R)) Alumina crowns with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with type IV dental stone. The specimens were randomly divided into two groups. Procera Alumina crowns were fabricated: eight crowns with circumferential porcelain-butt (all-porcelain) margins and eight crowns with coping (alumina-supported) margins (control). Precision of fit was measured at six points on each crown with a profilometer (profile projector). The data were statistically analyzed with an independent-samples t-test (alpha < 0.05). RESULTS: The mean marginal gap size (microm) of coping margins was 68.07 +/- 16.08 and of porcelain-butt margins was 101.29 +/- 43.71. There was no statistically significant difference (p= 0.065) of the marginal gap size between coping margins and porcelain-butt margins. CONCLUSION: The results of this study demonstrate that there was no statistically significant difference in the marginal fit of coping and porcelain-butt margins. Both margin designs are within clinically acceptable ranges. Therefore, clinicians may choose to use a coping margin, as it is less labor intensive and requires less time for fabrication, unless there is a specific high esthetic need for a porcelain-butt margin.

Novel Approach to Managing Malsequenced and Malpositioned Immediately Placed Implants in the Esthetic Zone.

Esthetic implant therapy can be challenging in the anterior maxilla, and meticulous treatment is often required to deliver optimal esthetics. Close collaboration between surgical and prosthetic team members using the novel approach of prosthetic crown lengthening helped camouflage a shallow implant platform location, providing the proper gingival frame for esthetic restorations. This case report presents an interdisciplinary approach that included ridge augmentation, second-stage crown lengthening, and prosthetic soft tissue manipulation to address an implant placed too shallow in the alveolus of an extraction socket.

Efficacy of a computerized shade selection system in matching the shade of anterior metal-ceramic crowns--a pilot study.

OBJECTIVE: The purpose of this study was to determine whether anterior crowns fabricated using a computerized shade selection system (ShadeScan, Cynovad) (experimental procedure) match adjacent teeth better than anterior crowns fabricated using conventional shade prescription and clinical slides (control). METHOD AND MATERIALS: Five subjects who required a crown to restore a maxillary central incisor were selected. Two metal-ceramic crowns were fabricated for each incisor, 1 using the experimental procedure and 1 using the control method. The shade selection method to be used for the first and second crowns was randomly assigned. The duration of each procedure was recorded. Each restoration was tried-in in a double-blind manner and evaluated for its level of match to adjacent teeth using modified Ryge criteria. Data were analyzed within each subject using descriptive statistics and paired t test (alpha = .05). RESULTS: In 40% of the cases, both procedures did equally well. In the remaining 60% of the cases the control procedure (two-thirds of the cases) performed better than the experimental procedure (one-third of the cases). Duration of the control procedure was 14.4 +/- 5 minutes, and the experimental procedure was 5.2 +/- 3.3 minutes. A paired t test showed the difference was significant (P = .0045). CONCLUSION: The level of matching of crowns fabricated with the ShadeScan system was not different from crowns fabricated using the control. However, it took significantly less time to record the shade with the ShadeScan system.

Precision of fit of two margin designs for metal-ceramic crowns.

STATEMENT OF PROBLEM: Although metal-ceramic restorations are widely used, there is a lack of information about how the fit is affected by margin designs. PURPOSE: This study measured and compared the precision of fit of metal-ceramic crowns with two margin designs. MATERIAL AND METHODS: Thirty-two extracted human premolar teeth were prepared for complete-coverage restorations with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with improved stone type V. MC crowns were fabricated with a porcelain-butt margin on the buccal aspect (n = 32) and a feather-edge metal margin on the lingual aspect (n = 32), which served as a control group. Precision of fit was measured three times at the mid-buccal and mid-lingual margins of each crown with a profilometer. The data were statistically analyzed with the paired t-test (alpha < .05). RESULTS: Mean marginal gap size of porcelain-butt margins was 27.93 microm (+/-15.84) and of feather-edge metal margins 42.43 microm (+/-24.12). The marginal gap size of feather-edge metal margins was statistically significantly greater than that of porcelain-butt margins (p = 0.0045). CONCLUSION: The marginal fit of porcelain-butt margins was significantly better than that of feather-edge metal margins. CLINICAL IMPLICATIONS: Porcelain-butt margins in this study had a better marginal fit than feather-edge metal margins, and thus have given clinicians evidence to prefer the use of porcelain-butt margins.

The efficacy of posterior three-unit zirconium-oxide-based ceramic fixed partial dental prostheses: a prospective clinical pilot study.

STATEMENT OF PROBLEM: Although zirconium-oxide-based restorations for fixed partial denture prostheses (FPDPs) are available for use, clinical studies evaluating their longevity and related complications have not been published. PURPOSE: The aim of this pilot clinical study was to assess the efficacy of zirconia-based posterior 3-unit FPDPs. MATERIAL AND METHODS: Twenty 3-unit posterior FPDPs (Lava) were placed in 16 subjects who were missing a second premolar or a first molar, met specific inclusion and exclusion criteria, and provided informed consent. All teeth were prepared in a standardized manner: occlusal reduction of 1.5 to 2 mm; axial reduction of 1 to 1.5 mm; a 1.0-mm, 360-degree rounded shoulder placed 0.5 mm subgingivally on the facial aspect and supragingivally on the lingual aspect on sound tooth structure; and rounded internal line angles. Impressions were made with vinyl polysiloxane (Express) impression material. Frameworks were fabricated using a computer-aided design/computer-assisted manufacturing technique with a retainer thickness of 0.6 mm, and a minimal connector surface area of 9 mm(2). Restorations were luted with resin-modified glass-ionomer cement (Rely X luting). Recall appointments were made after 2 weeks and 6, 12, 18, 24, and 36 months. Clinical fracture resistance, marginal discoloration, marginal adaptation, radiographic proximal recurrent decay, and periapical pathoses were assessed over time using modified Ryge criteria. The probability distributions of these variables were calculated for the baseline data as well as for recall data. RESULTS: Mean follow-up was 31.2 months. Fifteen restorations were rated Alpha in all measured parameters. Minor chipping of veneering porcelain was detected in 5 restorations rated Bravo for clinical fracture resistance and Alpha for all other assessed parameters. One restoration was rated Bravo in terms of marginal integrity at 36 months. CONCLUSIONS: Zirconia-based posterior 3-unit FPDPs performed well after short-term service.