Marginal adaptation of all-ceramic crowns on implant abutments

Background: Studies focusing on the marginal accuracy of all‐ceramic crowns on implant abutments are in short supply. Purpose: This study evaluated the marginal accuracy of all‐ceramic crowns on different implant abutments. Materials and Methods: Ninety‐six standardized maxillary central incisor crowns (48 alumina and 48 zirconia) were fabricated for each of the six test groups (n = 16) (Ti1, titanium abutments–alumina crowns; Ti2, titanium abutments–zirconia crowns; Al1, alumina abutments–alumina crowns; Al2, alumina abutments–zirconia crowns; Zr1, zirconia abutments–alumina crowns; Zr2, zirconia abutments–zirconia crowns). The crowns were adhesively luted using a resin luting agent. The marginal gaps were examined on epoxy replicas before and after luting as well as after masticatory simulation at 200× magnification. Results: The geometrical mean (95% confidence limits) marginal gap values before cementation, after cementation, and after masticatory simulation were group Ti1: 39(37–42), 57(53–62), and 49(46–53); group Ti2: 43(40–47), 71(67–76), and 64(59–69); group Al1: 57(54–61), 87(85–90), and 67(65–69); group Al2: 66(63–69), 96(90–101), and 75(72–78); group Zr1: 54(51–57), 79(76–82), and 65(63–67); and group Zr2: 64(60–68), 85(80–91), and 75(70–81). The comparison between non‐cemented and cemented stages in each group demonstrated a significant increase in the marginal gap values after cementation in all groups (p < .001), while the comparison between cemented and aged stages in each group showed a significant decrease in the marginal gap values in groups Al1, Al2, and Zr1 (p < .0001). This reduction was not significant for groups Ti1, Ti2, and Zr2 (p > .05). Conclusion: The marginal accuracy of all tested restorations meets the requirements for clinical acceptance.     

Parameters affecting retentive force of electroformed double-crown systems

The aim of this study was to determine the values of retentive forces of double crowns. The effect of the abutment height, the material of the inner crown, and the taper were evaluated. Sixty inner crowns each were fabricated from zirconia and a gold alloy having three different abutment heights (5, 7, and 9 mm) and two different tapers (0° and 2°). All outer crowns were made with an electroforming system. The removal test was performed by a standardized setup using a universal testing machine at a crosshead speed of 1,000 mm min⁻¹. Ten separation cycles were performed of each specimen, and the mean was imported into a statistical program. The retention forces were in the range of 0.37 and 2.65 N. The abutment height (p < 0.001), the material of the inner crown (p = 0.035), and the taper (p < 0.001) showed statistical influence on the retention force in the two-way ANOVA. Zirconia primary crowns performed better than gold alloy in the 0° group, especially with short abutments. However, a taper of 0° and short abutments have clinical drawbacks that were not evaluated in this study. In situations with long abutment teeth and a 2° taper zirconia is an alternative to gold alloy primary crowns.     

Fracture resistance of single-tooth implant-supported all-ceramic restorations after exposure to the artificial mouth

The purpose of this in vitro study was to evaluate the fracture resistance of single-tooth implant-supported all-ceramic restorations, composed of zirconium dioxide all ceramic restorations on different implant abutments, and to identify the weakest component of the restorative system. Forty-eight standardized maxillary central incisor zirconia crowns (Procera) were fabricated for two test groups and one control group (group Al: alumina abutments; group Zr: zirconia abutments; control group Ti: titanium abutments). All abutments were placed on the implants (Replace) using titanium screws. The crowns were adhesively luted using a resin luting agent (Panavia 21) and artificially aged through dynamic loading and thermal cycling. Afterwards, all specimens were tested for fracture resistance using compressive load on the palatal surfaces of the crowns. Pair-wise Wilcoxon rank tests were performed to test for differences in fracture resistance values with a global significance level of 0.05. All test specimens survived aging in the artificial mouth. No screw loosening was recorded. The median fracture resistance was 1251, 241 and 457 N for groups Ti, Al and Zr respectively. Statistically significant differences were found for the comparisons of group Ti with groups Al and Zr (P < 0.00001), and for the comparison of group Al with Zr (P < 0.00001). Results of this study showed that all tested implant-supported restorations have the potential to withstand physiological occlusal forces applied in the anterior region. Because of the low fracture resistance values of group Al, the combination of zirconia crowns and alumina abutments should carefully be considered before clinical application.     

Influence of different combinations of CAD-CAM crown and customized abutment materials on the force absorption capacity in implant supported restorations – In vitro study

ObjectivesTo evaluate the force absorption capacity of implant supported restorations utilizing different CAD-CAM materials for the fabrication of crowns and customized abutments.Methods80 titanium inserts were scanned to design customized abutments and crowns. The specimens were divided into four groups (n = 20/material): (Z): zirconia, (P): PEEK, (V): VITA Enamic, and (E): IPS e.max. Each group was subdivided into two subgroups according to customized abutment material: (Z) zirconia, and (P) for PEEK. For the assessment of force absorption, all specimens were loaded in a universal testing machine, applied loads curves were collected from the machine’s software, and resulting loads curves were collected from forcemeter below the assembly. The slopes of all curves were analyzed using Two-way multivariate analysis of variance with pairwise comparisons using Tukey Post Hoc test (p < 0.05).ResultsThe curve progression of the applied and resulting forces varied among the investigated materials for each specimen. For zirconia abutments, ZZ showed the highest slope values of the applied and resulting force curves, followed by EZ, VZ, and PZ demonstrating statistically significant differences (P < .001). As for PEEK abutments, ZP and EP showed the least slope values, followed by PP then VP demonstrating statistically significant differences (P < .001). For Zirconia and e.max crowns, using PEEK abutments significantly increased slope loss. As for PEEK and Vita Enamic crowns changing abutment material did not significantly affect slope loss.SignificanceCombining rigid crown materials with less rigid abutments might enhance their force absorption capacity. However, with less rigid crown materials a stiff substructure might be mandatory to preserve their force absorption behavior.     

Fatigue fracture resistance of titanium and chairside CAD-CAM zirconia implant abutments supporting zirconia crowns: An in vitro comparative and finite element analysis study

Statement of problemZirconia abutments with a titanium base are promising candidates to substitute for titanium abutments based on clinical studies reporting good short-term survival rates. However, information on the long-term performance of zirconia abutments supporting ceramic crowns is scarce.PurposeThis in vitro comparative and finite element analysis study compared the fatigue life performance of ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic restorations and zirconia abutments fabricated with a chairside workflow connected to a titanium interface versus titanium abutments.Material and methodsTwenty-two internal connection implants were divided into 2 groups, one with a zirconia abutment and monolithic ceramic zirconia crown (ZZ) and the other with a titanium abutment and zirconia crown (TiZ). They were subjected to a fatigue test to determine the fatigue limit and fatigue performance of each group as per International Organization for Standardization (ISO) 14801. Microstructural analysis of the fracture surfaces was conducted by using a scanning electron microscope (SEM). Simulations of the in vitro study were also conducted by means of finite element analysis (FEA) to assess the stress distribution over the different parts of the restoration.ResultsThe fatigue limit was 250 N for the TiZ group and 325 N for the ZZ group. In both groups, the screw was the part most susceptible to fatigue and was where the failure initiated. In the zirconia abutment models, the stress on the screw was reduced.ConclusionsChairside CAD-CAM zirconia abutments with a titanium base supporting zirconia crowns had higher fatigue fracture resistance compared with that of titanium abutments.     

Influence of anodized titanium abutments on the esthetics of the peri-implant soft tissue: A clinical study

Statement of problemThe grayish appearance of a titanium abutment discolors the peri-implant soft tissue, especially if the gingiva is thin. Whether an anodized titanium abutment can prevent the discoloration is unclear.PurposeThe purpose of this clinical study was to investigate the color change of peri-implant soft tissue surrounding a titanium abutment that had been colored by anodic oxidation.Material and methodsCommercially available titanium abutments were anodized to form a gold and pink titanium abutment and formed the experimental groups. Unanodized titanium and zirconia abutment were used as the control groups. Four types of abutments were fabricated for each participant who received dental implants in the anterior maxilla. The abutments and corresponding definitive crowns were inserted, and the color of the peri-implant soft tissue and contralateral gingiva were measured with a spectrophotometer. The thickness of the peri-implant soft tissue was recorded after probing with an endodontic file.ResultsEleven participants were included in this study. The color differences caused by all tested abutments were higher than the critical threshold of ΔE=3.7. The mean color difference (ΔE), from low to high, was the zirconia, pink-anodized titanium, gold-anodized titanium, and unanodized titanium abutment; their values of (ΔE) were 6.81, 7.63, 7.90, and 8.74, respectively. The mean thickness of the peri-implant soft tissue was 2.41 ±0.52 mm.ConclusionsWithin the limitation of the small sample size in this study, the gold-anodized and pink-anodized titanium abutment achieved better esthetics for peri-implant soft tissue than the unanodized titanium abutment. Zirconia was the optimal abutment material for the esthetic region.     

Fracture strength of yttria-stabilized tetragonal zirconia polycrystals crowns with different design: an in vitro study

Objectives: The aim of this study was to evaluate the effect of different types and design of zirconia frameworks as well as the effect of different veneering ceramics on the fracture strength of crowns. The importance of different abutment materials was also evaluated. Materials and methods: Eighty cores, 40 in a fully‐sintered zirconia material and 40 in a pre‐sintered zirconia material were made. Twenty cores of each material were made with a core of even thickness shape (ES) and 20 were made with a core with anatomical shape (AS). The cores were divided into subgroups and veneered with one of two different veneering ceramics: a porcelain and a glass–ceramic material. In total eight groups of 10 crowns were made. They were all cemented onto abutments made of resin. One extra group of 10 AS, pre‐sintered zirconia cores veneered with glass–ceramic were made and cemented onto titanium abutments. All crowns underwent thermocycling and mechanical pre‐load and were finally loaded until fracture. Results: AS crowns withstood significantly higher loads than ES crowns (P‐value <0.001), and crowns with titanium abutments withstood significantly higher loads than crowns supported by abutments made of inlay pattern resin (P‐value <0.001). Three types of fracture were noted: minor and major fracture of the veneering ceramic, and complete fracture through core and veneer. ES crowns showed significantly more major fractures of the veneering ceramic than AS crowns. Conclusions: This in vitro study indicates that the design of the core, as well as the abutment support, significantly influences fracture load and fracture mode of yttria‐stabilized tetragonal zirconia polycrystals crowns. To cite this article :
Larsson C, El Madhoun S, Wennerberg A, Vult von Steyern P. Fracture strength of yttria‐stabilized tetragonal zirconia polycrystals crowns with different design: an in vitro study. Clin. Oral Impl. Res. 23 , 2012; 820–826.
doi: 10.1111/j.1600‐0501.2011.02224.x     

Influence of implant abutment angulations on the fracture resistance of overlaying CAM-milled zirconia single crowns

Background: An in vitro study was performed to assess the effect of three implant abutment angulations and three core thicknesses on the fracture resistance of overlaying computer‐aided manufacturing (CAM) milled zirconia (Cercon^® system) single crowns. Methods: Three groups, coded A to C, with different implant abutment angulations (group A/0°, group B/15° and group C/30° angulation) were used to construct 15 crowns for each angulation. Forty‐five overlay restorations were milled using the Cercon^® system with zirconium core thicknesses of 0.4, 0.6 and 0.8 mm using five crowns for each angulation. The final restorations were prepared and stored in distilled water at mouth temperature (37 °C) for 24 hours prior to testing. The restorations were cemented using Temp Bond^®. The load required to break each crown and the mode of failure were recorded. All the results obtained were statistically analysed by the ANOVA test (level of significance p < 0.05). Tested crowns were examined using a stereomicroscope at 40X and selected crowns (five randomly selected from each group were further examined by scanning electron microscopy) to reveal the zirconia–ceramic interface and to determine the fracture origin. Results: Implant abutment angulations significantly (p < 0.05) reduced the fracture resistance of overlaying CAM‐milled zirconia single crowns. The fracture loads of Cercon^® crowns cemented onto abutment preparations with a 30° angulation were the lowest of the groups tested. The core thickness (0.4 to 0.8 mm) did not significantly (p > 0.05) affect the fracture resistance of the CAM‐milled zirconia single crowns. SEM showed that the origin of the fracture appeared to be located at the occlusal surfaces of the crowns and the crack propagation tended to radiate from the occlusal surface towards the gingival margin. Conclusions: The implant angulation of 30° significantly (p < 0.05) reduced the fracture resistance of overlaying CAM‐milled zirconia single crowns. Reducing the core thickness from 0.8 mm to 0.4 mm did not affect (p > 0.05) the fracture resistance of overlaying CAM‐milled zirconia single crowns.     

The effect of preparation taper on the resistance to fracture of monolithic zirconia crowns

ObjectiveMonolithic zirconia crowns have become a viable alternative to conventional layered restorations. The aim of this study was to evaluate whether the taper, and thus wall thickness, of the abutment or pre-defined cement space affect the fracture resistance or fracture mode of monolithic zirconia crowns.MethodsA model tooth was prepared with a taper of 15° and a shallow circumferential chamfer preparation (0.5 mm). Two additional models were made based on the master model with a taper of 10° and 30° using computer-aided design software. Twenty monolithic 3rd generation translucent zirconia crowns were produced for each model with pre-defined cement space set to either 30 μm or 60 μm (n = 60). The estimated cement thickness was assessed by the replica method. The cemented crowns were loaded centrally in the occlusal fossa at 0.5 mm/min until fracture. Fractographic analyses were performed on all fractured crowns.ResultsThe load at fracture was statistically significant different between the groups (p < 0.05). The crowns with 30° taper fractured at lower loads than those with 10° and 15° taper, regardless of the cement space (p < 0.05). The fracture origin for 47/60 crowns (78%) was in the cervical area, close to the top of the curvature in the mesial or distal crown margin. The remaining fractures started at the internal surface of the occlusal area and propagated cervically.SignificanceThe fracture resistance of the monolithic zirconia crowns was lower for crowns with very large taper compared to 10 and 15° taper even though the crown walls were thicker.     

Fatigue resistance and failure mode of novel-design anterior single-tooth implant restorations: influence of material selection for type III veneers bonded to zirconia abutments

Objectives: This study assessed the fatigue resistance and failure mode of type III porcelain and composite resin veneers bonded to custom zirconia implant abutments. Material and methods: Twenty‐four standardized zirconia implant abutments were fabricated. Using the CEREC 3 machine, type III veneers of standardized shape were milled in ceramic Vita Mark II or in composite resin Paradigm MZ100. The intaglio surfaces of the restorations were hydrofluoric acid etched and silanated (Mark II) or airborne‐particle abraded and silanated (MZ100). The fitting surface of the abutments was airborne‐particle abraded, cleaned, and inserted into a bone level implant (BLI RC SLActive 10 mm). All veneers (n=24) were adhesively luted with a zirconia primer (Z‐Prime Plus), adhesive resin (Optibond FL) and a pre‐heated light‐curing composite resin (Filtek Z100). Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 40 N, followed by stages of 80, 120, 160, 200, 240, and 280 N (20,000 cycles each). Samples were loaded until fracture or to a maximum of 140,000 cycles. Groups were compared using the life table survival analysis (Logrank test at P=.05). Results: Mark II and MZ100 specimens fractured at an average load of 216 N and 229 N (survival rate of 17% and 8%), respectively, with no difference in survival probability (P=.18). Among the fractured samples, 40% of the failures were at the abutment level for Mark II and 27% were at the abutment level for MZ100. No exclusive adhesive failures were observed. Conclusions: Type III Mark II and Paradigm MZ100 veneers showed similar fatigue resistance when bonded to custom non‐retentive zirconia implant abutments. The bond was strong enough to induce abutment fractures. MZ100 presented a higher percentage of “friendly” failures, i.e. maintaining the restoration–abutment adhesive interface and the abutment itself intact. To cite this article:
Magne P, Paranhos MPG, Burnett LH Jr, Magne M, Belser UC. Fatigue resistance and failure mode of novel‐design anterior single‐tooth implant restorations: influence of material selection for type III veneers bonded to zirconia abutments.
Clin. Oral Impl. Res. 22 , 2011; 195–200.
doi: 10.1111/j.1600‐0501.2010.02012.x     

Fracture resistance of single-tooth implant-supported all-ceramic restorations: an in vitro study

STATEMENT OF PROBLEM: High-strength ceramic materials can be used to fabricate esthetic and stable implant-supported single-tooth restorations. No study was identified that compared the fracture resistance of individual components of single-tooth implant-supported all-ceramic restorative systems after artificial aging. PURPOSE: The purpose of this in vitro study was to evaluate the fracture resistance of single-tooth implant-supported all-ceramic restorations consisting of alumina all-ceramic restorations on different implant abutments and to identify the weakest component of the restorative system. MATERIAL AND METHODS: Forty-eight standardized maxillary central incisor alumina crowns (Procera) were fabricated for each of the 3 test groups (n = 16) (Control group Ti, titanium abutments; Group Al, alumina abutments; Group Zr, zirconia abutments) for the Replace implant system. The crowns were adhesively luted using a resin luting agent (Panavia 21) and artificially aged through dynamic loading and thermal cycling. Afterwards, all specimens were tested for fracture resistance using compressive load on the palatal surfaces of the crowns. Kruskal-Wallis analysis of variance and post hoc Wilcoxon rank sum tests were performed to test for differences in fracture resistance values (alpha = .05). RESULTS: All test specimens survived the artificial aging process using simulated oral conditions. No screw loosening was recorded. The median fracture resistance was 1454 N, 422.5 N, and 443.6 N for groups Ti, Al, and Zr, respectively. Significant differences were found for the fracture resistance comparisons of group Ti with groups Al and Zr (Kruskal-Wallis test, P < .001). The test results for the comparison of groups Al and Zr were not significant. CONCLUSION: All 3 implant-supported restorations have the potential to withstand physiologic occlusal forces applied in the anterior region.     

The effect of post length and core material on root fracture with respect to different post materials

Abstract

Objective. The aim of this study was to evaluate the effect of different core materials and post length on the fracture strength of different posts (CAD/CAM zirconia post (ZR post)) and an individually formed glass fiber reinforced composite post (FRC post). Materials and methods. One hundred maxillary central incisors received endodontic treatment and were divided into two groups according to the post length: (1) 10 mm in length and (2) 15 mm in length (n = 50/per group). Then the specimens were randomly assigned into five sub-groups (n = 10/per group) as follows: One-piece milled zirconia post and core (group Zr), zirconia post with resin core (Biscore, Bisco) (group Zr/R), zirconia post with resin composite core (Admira, Voco) (group Zr/RC), FRC post with resin core (group F/R) and FRC post with resin composite core (group F/RC). The posts were cemented with a self-adhesive luting agent according to the manufacturer's instructions by using endo tips and light-cured for 40 s using a halogen light curing unit. Metal crowns were made for each specimen, cemented and loaded to failure. Fracture loads (N) and modes of failure were recorded. The data were analyzed using three-way analysis of variance (ANOVA) followed by Tukey's post-hoc test (p < 0.001). Results. Fracture strength of roots was significantly affected by the type of post material (p < 0.05) and post length (p < 0.05), but not by the type of core materials used (p = 0.078). Conclusion. Longer zirconia posts with zirconia- or resin-based cores can be recommended as an alternative to FRC posts with resin-based cores. The fracture patterns observed in teeth restored with fiber posts were more favorable than teeth restored with zirconia posts. Clinical significance. A higher restoring success rate can be achieved by fiber posts rather than zirconia posts, since the failure mode for these posts would be restorable. Additionally, post length is a more critical factor in teeth restored with one-piece milled zirconia posts than in those restored with fiber posts.     

Fracture behavior of straight or angulated zirconia implant abutments supporting anterior single crowns

The aim of the study was to evaluate the influence of artificial aging on the fracture behavior of straight and angulated zirconia implant abutments (ZirDesign?; Astra Tech, Mölndal, Sweden) supporting anterior single crowns (SCs). Four different test groups (n?=?8) representing anterior SCs were prepared. Groups 1 and 2 simulated a clinical situation with an ideal implant position (left central incisor) from a prosthetic point of view, which allows for the use of a straight, prefabricated zirconia abutment. Groups 3 and 4 simulated a situation with a compromised implant position, requiring an angulated (20°) abutment. OsseoSpeed? implants (Astra Tech) 4.5 mm in diameter and 13 mm in length were used to support the abutments. The SCs (chromium cobalt alloy) were cemented with glass ionomer cement. Groups 2 and 4 were thermomechanically loaded (TCML?=?1.2?×?10⁶; 10,000?×?5°/55°) and subjected to static loading until failure. Statistical analysis of force data at the fracture site was performed using nonparametric tests. All samples tested survived TCML. Artificial aging did not lead to a significant decrease in load-bearing capacity in either the groups with straight abutments or the groups with angulated abutments. The restorations that utilized angulated abutments exhibited higher fracture loads than the restorations with straight abutments (group 1, 280.25?±?30.45 N; group 2, 268.88?±?38.00 N; group 3, 355.00?±?24.71 N; group 4, 320.71?±?78.08 N). This difference in load-bearing performance between straight and angulated abutments was statistically significant (p?=?0.000) only when no artificial aging was employed. The vast majority of the abutments fractured below the implant shoulder.     

Randomized controlled clinical trial of customized zirconia and titanium implant abutments for canine and posterior single-tooth implant reconstructions: preliminary results at 1 year of function

Objectives: The aim of this study was to test whether or not customized zirconia abutments exhibit the same survival rates in canine and posterior regions as titanium abutments, and to compare the esthetic result of the two abutment types. Material and methods: Twenty‐two patients with 40 implants in posterior regions were included and the implant sites were randomly assigned to 20 customized zirconia and 20 customized titanium abutments. All‐ceramic (AC) and metal–ceramic (MC) crowns were fabricated. In all except two cases, the crowns were cemented on the abutments using resin or glass‐ionomer cements. Two zirconia reconstructions were screw retained. At baseline, 6 and 12 months, the reconstructions were examined for technical and biological problems. Probing pocket depth (PPD), plaque (Pl) and bleeding on probing (BOP) were assessed and compared with natural control teeth. Furthermore, the difference of color (ΔE) of the peri‐implant mucosa and the gingiva of control teeth was evaluated by means of a spectrophotometer (Spectroshade). The data were analyzed with Student's unpaired t‐test, ANOVA and regression analyses. Results: Twenty patients with 19 zirconia and 12 titanium abutments were examined at a mean follow‐up of 12.6±2.7 months. The survival rate for reconstructions and abutments was 100%. No technical or biological problems were found at the test and control sites. Two chippings (16.7%) occurred at crowns supported by titanium abutments. No difference was found regarding PPD (meanPPD_ZrO2 3.4±0.7 mm, mPPD_Ti 3.3±0.6 mm), Pl (mPl_ZrO2 0.2±0.3, mPl_Ti 0.1±1.8) and BOP (mBOP_ZrO2 60±30%, mBOP_Ti 30±40%) between the two groups. Both crowns on zirconia and titanium abutments induced a similar amount of discoloration of the soft tissue compared with the gingiva at natural teeth (ΔE_ZrO2 8.1±3.9, ΔE_Ti 7.8±4.3). Conclusions: At 1 year, zirconia abutments exhibited the same survival and a similar esthetic outcome as titanium abutments.     

Influence of preparation mode and depth on the fracture strength of zirconia ceramic abutments restored with lithium disilicate crowns

Purpose: Zirconia implant abutments offer enhanced esthetics and promote biologic sealing; however, the effect of laboratory or intraoral preparation on the mechanical stability of zirconia has not been investigated. The purpose of the study was to evaluate the influence of the preparation mode and depth on the fracture strength of zirconia abutments restored with lithium disilicate crowns. Materials and Methods: To replace a maxillary central incisor (11.0 mm in height and 8.0 mm in width), 35 lithium disilicate crowns were cemented onto zirconia abutments on 4.5- ° - 15-mm titanium implants. Lithium disilicate implant crowns were divided into five study groups (n = 7) according to the abutment preparation mode (milling by the manufacturer or milling by the Celay System [Mikrona] [P]) and preparation depth (0.5 mm [A], 0.7 mm [B], or 0.9 mm [C]). All groups were subjected to quasi-static loading (S) at 135 degrees to the implant axis in a universal testing machine. Results: Mean fracture strengths were: group SA, 384 ± 84 N (control); group SB, 294 ± 95 N; group SPB, 332 ± 80 N; group SC, 332 ± 52; group SPC, 381 ± 101 N. All specimens presented a typical fracture mode within the implant/abutment internal connection. Multiple regression analysis revealed that preparation depth up to 0.7 mm statistically influenced the fracture strength (P = .034), whereas the preparation mode did not seem to play an important role (P = .175). Conclusion: Regardless of preparation mode, circumferential preparation of zirconia abutments might negatively affect the fracture strength of adhesively cemented single implant lithium disilicate crowns.     

The effect of fatigue loading on the screw joint stability of zirconium abutment

PurposeThis study evaluated the effect of fatigue loading on the screw joint stability of a zirconium abutment connected to an external hexagon implant in vitro.Materials and methodsFifteen titanium and 15 zirconia abutments of 3 different heights (5, 8, and 11 mm) were connected to external titanium implants with titanium screws. A torque gauge was used to measure the reverse torque values before and after loading. An air cylindrical loading device was used to simulate mastication at a 45-degree angle to the longitudinal axis of the implant.ResultsThere were significant differences (P < 0.05) before and after the loading of titanium (5 mm) and zirconia (5, 8, and 11 mm) abutments.ConclusionZirconia abutments for external hexagon implants had durability rates similar to those of titanium abutments after repeating load on the reverse torque of the abutment screw, indicating that the zirconia abutment could be reliably used instead of the titanium abutment.     

Fracture loads and failure modes of customized and non-customized zirconia abutments

Objective

This study aimed to evaluate the fracture load and pattern of customized and non-customized zirconia abutments with Morse-taper connection.

Abutment Rotational Freedom Evaluation of External Hexagon Single‐Implant Restorations after Mechanical Cycling

Purpose: The purpose of this study was to evaluate the rotational freedom between implant and abutment counterpart of two abutments types over external hexagon implants submitted to mechanical cycling. Materials and Methods: Ten implants with external hexagon (3.75 mm × 13 mm), five cast abutments, and five premachined abutments both with 4.1 mm plataform size were used in this study. Ten metallic crowns were fabricated using the two types of abutments and were fixed to each implant using titanium screws (Ti6Al4V). Rotational freedom measurements were made before and after the cast procedure and after the mechanical cycling. Groups were classified according to the rotational misfit register using University of California, Los Angeles abutment and implants as new (group 1 = G1); using crowns and implants after crown casting (group 2 = G2); and using crowns and implants after mechanical cycling (group 3 = G3). Oblique loading of 120N at 1.8 Hz and 5 × 10⁵ cycles was applied on specimen. Results: Statistical analysis (p < .05) showed that no significant difference was observed when cast abutment was compared with premachined abutment after casting (p = .390) and mechanical cycling (p = .439); however, significant difference was noted before the casting (p = .005) with higher values for the cast abutments. Conclusions: Within the limitations of this in vitro study, it could be concluded that the abutment type used do not influenced the rotational freedom after casting and the amount of applied cycles (500,000 cycles) was not sufficient to significantly alter the values of rotational freedom at the implant/abutment joint.     

Fracture load of different crown systems on zirconia implant abutments

Objectives

The purpose of this study was to evaluate the fracture load of single zirconia abutment restorations using different veneering techniques and materials.

Materials and methods

The abutment restorations were divided into 6 groups with 20 samples each: test abutments (control group A), lithium disilicate ceramic crowns bonded on incisor abutments (group B), leucite ceramic crowns bonded on incisor abutments (group C), premolar abutments directly veneered with a fluor apatite ceramic (group D (layered) and group E (pressed)) and premolar abutments bonded with lithium disilicate ceramic crowns (group F). The fracture load of the restorations was evaluated using a universal testing machine. Half of each group was artificially aged (chewing simulation and thermocycling) before evaluating the fracture load with the exception of the test abutments.

Results

The fracture load of the test abutments was 705 ± 43 N. Incisor abutments bonded with lithium disilicate or leucite ceramic crowns (groups B and C) showed fracture loads of about 580 N. Premolar restorations directly veneered with fluor apatite ceramic (groups D and E) showed fracture loads of about 850 N. Premolar restorations bonded with lithium disilicate ceramic crowns (group F) showed fracture loads of about 1850 N. The artificial ageing showed no significant influence on the strength of the examined restorations.

Significance

All ceramic crowns made of lithium disilicate glass-ceramic, adhesively bonded to premolar abutments showed the highest fracture loads in this study. However, all tested groups can withstand physiological bite forces.     

Early bacterial colonization and soft tissue health around zirconia and titanium abutments: an in vivo study in man

Aim: To compare the early bacterial colonization and soft tissue health of mucosa adjacent to zirconia (ZrO₂) and titanium (Ti) abutment surfaces in vivo. Materials and methods: Twenty edentulous subjects received two endosseous mandibular implants. The implants were fitted with either a ZrO₂ or a Ti abutment (non‐submerged implant placement, within‐subject comparison, left‐right randomization). Sulcular bacterial sampling and the assessment of probing pocket depth, recession and bleeding on probing were performed at 2 weeks and 3 months post‐surgery. Wilcoxon matched‐pairs, sign‐rank tests were applied to test differences in the counts of seven marker bacteria and the clinical parameters that were associated with the ZrO₂ and Ti abutments, at the two observation time points. Results: ZrO₂ and Ti abutments harboured similar counts of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Peptostreptococcus micros, Fusobacterium nucleatum and Treponema denticola at 2 weeks and 3 months. Healthy clinical conditions were seen around both ZrO₂ and Ti abutments at all times, without significant differences in most clinical parameters of peri‐implant soft tissue health. Mean probing depths around Ti abutments were slightly deeper than around ZrO₂ abutments after 3 months (2.2 SD 0.8 mm vs. 1.7 SD 0.7 mm, P=0.03). Conclusions: No difference in health of the soft tissues adjacent to ZrO₂ and Ti abutment surfaces or in early bacterial colonization could be demonstrated, although somewhat shallower probing depths were observed around ZrO₂ abutments after 3 month. To cite this article:
van Brakel R, Cune MS, van Winkelhoff AJ, de Putter C, Verhoeven JW, van der Reijden W. Early bacterial colonization and soft tissue health around zirconia and titanium abutments: an in vivo study in man
Clin. Oral Impl. Res. 22 , 2011; 571–577
doi: 10.1111/j.1600‐0501.2010.02005.x