Paolo Vigolo

Internal vs. external connections for abutments/reconstructions: a systematic review.

OBJECTIVES The objectives of the review were (1) to evaluate the accuracy of implant-level impressions in cases with internal and external connection abutments/reconstructions, and (2) to evaluate the incidence of technical complications of internal and external connection metal- or zirconia-based abutments and single-implant reconstructions. MATERIALS AND METHODS A MEDLINE electronic search was conducted to identify English language publications in dental journals related to each of the two topics by inserting the appropriate keywords. These electronic searches were complemented by a hand search of the January 2009 to January 2012 issues of the following journals: Clinical Oral Implants Research, The Journal of Prosthetic Dentistry, The International Journal of Prosthodontics, The International Journal of Periodontics and Restorative Dentistry, The International Journal of Oral Maxillofacial Implants, Clinical Implant Dentistry and Related Research. RESULTS Seven in vitro studies were included in the review to evaluate the accuracy of implant-level accuracy. No clinical study was found. There was no study that directly compared the influence of internal and external implant connections for abutments/reconstructions on the accuracy of implant-level impressions. All in vitro studies reported separately on the two connection designs and they did not use same protocol and, therefore, the data could not be compared. Fourteen clinical studies on metal-based abutments/reconstructions and five clinical studies on zirconia-based abutments/reconstructions satisfied the inclusion criteria and, therefore, were included in the review to evaluate the incidence of technical complications. The most frequent mechanical complication found in both implant connection design when employing metal abutments/reconstructions was screw loosening. CONCLUSIONS Implant-level impression accuracy may be influenced by a number of variables (implant connection type, connection design, disparallelism between multiple implants, impression material and technique employed). Implant divergence appears to affect negatively impression accuracy when using internal connection implants. Based on the sparse literature evaluating the incidence of technical complications of metal or zirconia abutments/reconstructions, it was concluded that: The incidence of fracture of metal-based and zirconia-based abutments and that of abutment screws does not seem to be influenced by the type of connection. Loosening of abutment screws was the most frequently occurring technical complication. The type of connection seems to have an influence on the incidence of the screw loosening: more loose screws were reported for externally connected implant systems for both types of materials. However, proper preload may decrease the incidence of such a complication.

An In Vitro Evaluation of Fit of Zirconium-Oxide-Based Ceramic Four-Unit Fixed Partial Dentures, Generated with Three Different CAD/CAM Systems, before and after Porcelain Firing Cycles and after Glaze Cycles

PURPOSE The purpose of this study was to assess in vitro the marginal fit of four-unit fixed partial dentures (FPDs) produced using three different computer aided design/computer aided manufacturing (CAD/CAM) all-ceramic systems before and after porcelain firing cycles and after glaze cycles. MATERIALS AND METHODS An acrylic resin model of a maxillary arch was fabricated. Teeth #6 and 9 were prepared; teeth #7 and 8 were absent. Forty-five four-unit zirconium-oxide-based ceramic FPDs were made following conventional impression and master cast techniques: 15 were made with the Everest system, 15 with the Procera system, and 15 with the Lava system. Marginal gaps along vertical planes were measured for each bridge before (Time 0) and after (Time 1) porcelain firing cycles and after glaze cycles (Time 2) using a total of 8 landmarks (4 for tooth #6 and 4 for tooth #9) by means of a microscope at a magnification of x50. MANOVA was performed to determine whether the 8 landmarks, jointly considered, differed between CAD/CAM systems and time phases. Two-way ANOVA was performed to investigate in detail, for each landmark, how gap measurements were related to CAD/CAM systems and time phases. Differences were considered to be significant at p < 0.05. RESULTS The mean values of the Everest system (microm) were: 63.37 (Time 0), 65.34 (Time 1), and 65.49 (Time 2); the mean values of the Lava system (microm) were: 46.30 (Time 0), 46.79 (Time 1), and 47.28 (Time 2); the mean values of the Procera system (microm) were: 61.08 (Time 0), 62.46 (Time 1), and 63.46 (Time 2). MANOVA revealed quantitative differences of the 8 landmarks, jointly considered, between the three CAD/CAM systems (p < 0.0001), but it did not reveal any quantitative differences among the three time phases (p > 0.4). Two-way ANOVA revealed that the Lava system produced gap measurements statistically smaller than the Everest and Procera systems (p < 0.0001 for each landmark). CONCLUSIONS Within the limitations of this study, it was concluded that the three zirconium-oxide-based ceramic CAD/CAM systems demonstrated a comparable and acceptable marginal fit; however, the Lava system produced gap measurements statistically smaller than the Everest and Procera systems. The porcelain firing cycles and the glaze cycles did not affect the marginal fit of the zirconium-oxide-based ceramic CAD/CAM systems.

In vitro comparison of master cast accuracy for single-tooth implant replacement.

STATEMENT OF PROBLEM The inaccuracy in transferring the position of the hexagonal head of a single implant to the working cast can result in a final single tooth crown, which clinically may present occlusal and/or interproximal contacts that are different from those contacts on the master cast obtained by the technician. PURPOSE This in vitro study evaluated the accuracy of the master casts obtained using square pick-up impression copings for single-tooth replacement. Copings used were (1) copings as sold by the manufacturer, and (2) copings modified by sandblasting and coating with impression adhesive their roughened surfaces before final impression procedures. MATERIAL AND METHODS A polymeric resin model with a standard single implant was used to simulate a clinical situation. A group of 20 impressions were made using nonmodified impression copings; a second group of 20 impressions were fabricated with modified copings. Master casts fabricated for both groups were analyzed to detect rotational position change of the hexagon on the implant replicas in the master casts in reference to the resin model. RESULTS The rotational position changes of the hexagon on implant replicas were significantly less variable in the master casts obtained with the modified impression copings than in the master casts achieved with the nonprepared copings. CONCLUSION Improved precision of the impression was achieved when the adhesive-coated copings were used.

Evaluation of Zirconium-Oxide-Based Ceramic Single-Unit Posterior Fixed Dental Prostheses (FDPs) Generated with Two CAD/CAM Systems Compared to Porcelain-Fused-to-Metal Single-Unit Posterior FDPs: A 5-Year Clinical Prospective Study

PURPOSE The purpose of this prospective clinical study was to determine the success rate of single-unit posterior fixed dental prostheses (FDPs) with zirconia copings generated with two CAD/CAM systems, compared to porcelain-fused-to-metal (PFM) single-unit posterior FDPs after 5 years of function. MATERIALS AND METHODS From 2005 to 2006, 60 patients who needed a single-unit FDP on a first molar in the mandibular jaw (left or right) in a private office setting were included in this study. The 60 first mandibular molars were randomly divided into three groups (n = 20): in the control group (group C), 20 PFM FDPs were included. In the other two groups CAD/CAM technology was used for the fabrication of the zirconium-oxide copings: 20 single-unit posterior FDPs with zirconia copings were generated with the Procera system (group P, Nobel Biocare); 20 single-unit posterior FDPs with zirconia copings were generated with the Lava system (group L, 3M ESPE). For the ANOVA follow-up data, the clinical life table method was applied. The statistical analysis was performed using two nonparametric tests, the log-rank test for k-groups and the Fisher exact test. RESULTS No statistically significant difference in the clinical outcome of zirconia-ceramic FDPs of both groups (P and L) evaluated together and metal-ceramic posterior single FDPs was found at 5 years of function; however, clinical data showed that technical problems, such as extended fracture of the veneering ceramic, tended to occur more frequently in the zirconia-ceramic FDP groups. The difference in the frequency of failure was statistically significant only in the comparison of groups C and P. CONCLUSIONS Even if no statistically significant difference in the clinical outcome of zirconia-ceramic FDPs of both groups (P and L) considered together and metal-ceramic posterior single FDPs was found at 5 years of function, clinical data showed that the two zirconia-ceramic FDP groups tended to have more frequent clinical problems: for this reason all the clinical and technical variables related to the use of zirconia-ceramic FDPs generated with CAD/CAM systems should be carefully considered prior to all treatment procedures.

An in vivo evaluation of fit of zirconium-oxide based ceramic single crowns, generated with two CAD/CAM systems, in comparison to metal ceramic single crowns.

PURPOSE The purpose of this study was to assess in vivo the marginal fit of single crowns produced using two CAD/CAM all-ceramic systems, in comparison to more traditional metal ceramic crowns. MATERIALS AND METHODS Thirty vital, caries-free, and previously untreated teeth were chosen in five patients who needed extraction for implant placement and therefore were included in this study. In the control group (C), 10 regular metal ceramic crowns with porcelain occlusal surfaces were fabricated. In the other two groups (Z and E), CAD/CAM technology was used for the fabrication of 20 zirconium-oxide-based ceramic single crowns with two systems. All zirconia crowns were cemented with glass-ionomer cement, always following the manufacturers instructions. The same dentist carried out all clinical phases. The teeth were extracted 1 month later. Marginal gaps along vertical planes were measured for each crown, using a total of four landmarks for each tooth by means of a microscope at a magnification of 50×. On completion of microscopic evaluation, representative specimens from each group were prepared for ESEM evaluation. Mean and standard deviations of the four landmarks (mesial, distal, buccal, palatal) at each single crown were calculated for each group. Multivariate analysis of variance (MANOVA) was performed to determine whether the four landmarks, taken into consideration together, differed between groups. Two-way ANOVA was performed to study in detail, for each landmark, how the three systems used to produce the FPDs affected the gap measurements. Differences were considered to be significant at p < 0.05. RESULTS MANOVA revealed no quantitative differences of the four landmarks, when taken into consideration together, between the three groups (p < 0.0001). Two-way ANOVA, performed at each landmark, revealed no quantitative differences between the three groups (p < 0.0001 for each landmark). CONCLUSIONS Within the limitations of this study, it was concluded that the two zirconium-oxide-based ceramic CAD/CAM systems demonstrated a similar and acceptable marginal fit when compared to more traditional metal ceramic crowns.

Dimensional accuracy of an epoxy die material using different polymerization methods.

PURPOSE Shrinkage of resinous die materials during setting reaction limits their acceptance, even though these materials show several advantages compared to stone die materials with respect to strength, abrasion resistance, and detail reproduction. The purpose of this study was to determine if retarding the setting reaction during polymerization and altering the base-to-catalyst ratio, as suggested by previous studies, can be recommended for resinous die materials to reduce the inaccuracy in transferring the spatial position of teeth or implants from the oral cavity to the master cast. MATERIALS AND METHODS A Blue Star Type E epoxy resin die material was tested. A reference triangular metal master die was fabricated. Forty medium-consistency polyether impressions of this model were made. Four groups (S, M, N, P) were compared, and ten dies were fabricated for each group. In the S group, the epoxy resin die material was manipulated according to the manufacturers instructions; in the other three groups, the epoxy resin die material was manipulated by retarding the setting reaction and by modifying the epoxy resin base/activator ratio. RESULTS One-way ANOVA revealed significant differences between the four groups of the epoxy resin die material (p < 0.0001). Tukeys multiple comparisons test (p < 0.05) revealed that none of the resin groups was similar to the metal master die for each of the tested dimensions (A, B, and C). For the specific dimension C, however, the P group was statistically closer to the metal master die than the S group. CONCLUSION The epoxy resin die material tested in this research did not improve its dimensional accuracy following retarding polymerization or modifying the epoxy resin base/activator ratio. The epoxy resin material exhibited higher contraction variability across all tested groups. This shrinkage can significantly affect the dimension of the master cast.

Shear Bond Strength between Feldspathic CAD/CAM Ceramic and Human Dentine for Two Adhesive Cements

PURPOSE The purpose of this study was to evaluate the shear bond strength values between dentin substrate and a feldspathic ceramic material, based on computer-assisted design and manufacture (CAD/CAM) technology, bonded together with two adhesive systems coupled with two dual-polymerized luting agents. In addition, the effect of a silane coupling agent on bond strength was evaluated. MATERIAL AND METHODS Forty cylinders (6 mm in diameter, 5 mm thick) obtained from feldspathic ceramic blocks were cemented to the dentin of 40 recently extracted human teeth stored in saline solution at room temperature until testing. The specimens were randomly divided into four groups of ten teeth each. All specimens were airborne-particle abraded and etched with hydrofluoric acid. In the first two groups (A1, A2) 20 ceramic cylinders were cemented using Excite DSC and Variolink II; in the A2 group the bonding surfaces were also treated with a silane coupling agent. In Groups B1 and B2, 20 ceramic cylinders were cemented using Scotchbond MPP and RelyX ARC; in the B2 group the bonding surfaces were also treated with a silane coupling agent as in Group A2. All cemented specimens were submitted to a shear bond strength test to check the strength of adhesion between the two substrates, dentin and ceramic. The data were analyzed with two-way analysis of variance (p < 0.05). RESULTS The mean values of the shear bond strength were (in MPa): 22 +/- 7 for Excite DSC/Variolink II without silanization (Group A1); 29 +/- 3 for Excite DSC/Variolink II with silanization (Group A2); 22 +/- 4 for Scotchbond MPP/RelyX ARC without silanization (Group B1); and 26 +/- 5 for Scotchbond MPP/RelyX ARC with silanization (Group B2). Two-way ANOVA revealed a significant effect of silanization (p < 0.01) and did not reveal any significant effect for either the bonding agents (p > 0.1) or the interaction between silanization and bonding agent (p > 0.05). Multinomial logit model did not show any statistical effects on the failure mode by the shear bond strength (p > 0.1). The hypotheses of independence between failure mode (cohesive vs. adhesive) and both the adhesive system (p < 0.05) and silanization (p < 0.05) were rejected by Pearsons chi-square test. CONCLUSION Within the assumptions and limitations of this study (including the small number of specimens) both bonding systems used achieved good shear bond strength values. The application of a silane coupling agent on the ceramic surface after etching with hydrofluoric acid increased the adhesion strength with both adhesive materials used.

Clinical evaluation of marginal bone level change around multiple adjacent implants restored with splinted and nonsplinted restorations: a 10-year randomized controlled trial.

PURPOSE The management of occlusal forces on implant restorations may influence their long-term prosthetic success. The purpose of this randomized controlled trial was to compare marginal bone level changes around adjacent splinted and nonsplinted implants, functionally loaded with cemented restorations, up to 10 years in maxillae. MATERIALS AND METHODS During 2002 and 2003, all patients who received three adjacent implants in a private office and a university setting were included in this study. All implants featured an external-hexagon design and were placed in the posterior maxilla. Implants in the left maxilla were randomly selected to be restored with splinted cemented restorations; maxillary right implants were restored with nonsplinted cemented restorations. Marginal bone resorption was measured with intraoral radiographs yearly over a period of at least 10 years after placement of abutments and restorations. The amount of bone loss in each group was analyzed with the two-sample Wilcoxon rank-sum (Mann-Whitney) test because variable bone loss was normally distributed at the fifth year only. RESULTS One hundred thirty-two implants were placed in 44 patients. Three implants failed at stage-two surgery. Five years after initial loading, two patients moved away and were lost to follow-up (6 implants in total); three additional patients did not complete the study (9 implants in total). Of the remaining 114 implants, 60 left implants were restored with splinted cemented restorations and 54 right implants were restored with nonsplinted cemented restorations. At 10 years, the splinted group showed a mean of 1.2 mm (interquartile range: 0.2 mm) of bone loss; the nonsplinted group showed 1.3 mm (interquartile range: 0.2 mm). CONCLUSION A significant difference in bone loss was seen between the two groups. However, the difference of 0.1 mm was not considered clinically meaningful.

An in vitro evaluation of zirconia surface roughness caused by different scaling methods

STATEMENT OF PROBLEM Plaque control is essential for the prevention of inflammatory periodontal disease. Ultrasonic scaling and hand scaling have been shown to be effective for the removal of plaque. However, routine periodontal prophylactic procedures may alter the surface profile of restorative materials. PURPOSE The purpose of this study was to assess in vitro the changes in roughness of zirconia surfaces treated by various scaling procedures. MATERIAL AND METHODS One hundred forty identical disks (10 mm in diameter, 2 mm thick) were made. The specimens were divided into 7 groups of 20 each; the surfaces of the specimens were exposed to different types of scaling methods simulating standard clinical conditions. In the control group (C), no scaling procedures were performed; in the other groups, a steel curette (SC), a plastic curette (PC), a titanium curette (TC), a piezoelectric ultrasonic scaler (PUS), an ultrasonic scaler (US), and a magnetostrictive ultrasonic scaler (MUS) were used. The surface texture was analyzed quantitatively and qualitatively with a profilometer and a scanning electron microscope (SEM). A 1-way ANOVA was performed to assess whether roughness profile (Ra) differed among groups, while pairwise comparisons between groups were evaluated by the Tukey HSD test (alpha=.05). RESULTS The 1-way ANOVA revealed significant differences among groups (P<.001); the Tukey HSD test demonstrated that all methods achieved different results. Analysis of zirconia surfaces treated by different ultrasonic scaling systems demonstrated some deeper scratches, whereas zirconia instrumented with various types of periodontal curettes exhibited smaller scratches. Scaling with a steel curette produced the least alteration of zirconia surfaces. CONCLUSIONS All instrument types evaluated altered the smoothness of zirconia surfaces. Follow-up in vivo studies are indicated to assess potential clinical problems associated with increased roughness at the margin of zirconia restorations following routine dental prophylaxis.

Evaluation of rotational freedom of In-Ceram ceramic blank abutments before and after infiltration.

Purpose:Laboratory processing of implant-supported prostheses may alter the surface of the abutment in contact with the corresponding surface and thus the interface fit. This study assessed changes in the rotational freedom (R) at the interface of 1 implant ceramic abutments before and after preparation and glass infiltration processes. Materials and Methods:The abutment R was assessed for 20 as-received In-Ceram Ceramic Blanks over synOcta abutments and after both preparation and infiltration procedures. Results:Compared with the as-received blanks, there was a statistically significant (P < 0.009) increase of 0.8 minutes in the R after preparation and glass infiltration processes. Conclusion:The results of this investigation suggest that, if all laboratory steps are observed carefully, changes at the abutment interface of Ceramic Blanks do not occur.