Marginal adaptation of different types of all-ceramic partial coverage restorations after exposure to an artificial mouth.

OBJECTIVES: To determine the influence of the preparation design and the dimensions of all-ceramic partial coverage restorations (PCR) on the marginal accuracy before and after masticatory simulation. METHODS: In this in vitro study 80 extracted human maxillary molars were restored with MOD inlay restorations and four different modified PCR restorations using a new press ceramic IPS e.max Press (IPS e.max Press VP 1989). The teeth were divided into five groups of 16 specimens each and prepared as follows: Group A received an MOD inlay preparation and Group B, C, D and E received modified PCR. The restorations were adhesively luted and exposed to a mastication simulator. The discrepancies of the marginal fit were examined on epoxy replicas before and after luting as well as after masticatory simulation at 200x magnification. RESULTS: The mean (geometrical) [95% confidence limits] marginal gap decreased from Group A to E before cementation (A-83[77-90]microm, B-68[65-70]microm, C-59[55-64]microm, D-56[52-61]microm, E-50[45-55]microm). Group A had significantly higher marginal gap values than group B (p = 0.017) and the other groups (p<0.0001). After cementation the marginal accuracy was recorded as following: A-103[93-114]microm, B-101[94-108]microm, C-93[89-98]microm, D-102[98-105]microm and E-99[96-102]microm. Cementation increased the marginal gap in groups B-E significantly (p<0.00001), not significantly in group A (p = 0.059). Artificial ageing (A-116[106-127]microm, B-114[109-120]microm, C-106[103-110]microm, D-109[100-118]microm and E-109[105-112]microm) led to further significant decrease of marginal accuracy in Group B (p = 0.029) and C (p = 0.026) only. After cementation and masticatory simulation of the ceramic restorations, the marginal gap values of Groups A, B, C, D and E did not significantly differ from each other (p = 1.00). CONCLUSIONS: The result of this in vitro study showed that IPS e.max Press can be used to fabricate all-ceramic inlays and PCR which meet the requirements in terms of a clinically acceptable marginal gap, irrespective of the preparation design used. However, the preparation design and dimensions of the restorations appeared to affect the initial marginal fit and flowing off of luting material during the cementation process. The factors responsible for these findings require further substantiation.

Marginal adaptation of three-unit fixed partial dentures constructed from pressed ceramic systems.

PURPOSE: This study compares the marginal accuracy of posterior metal ceramic (MC), all-ceramic IPS Empress 2 and experimental pressed ceramic (EPC-VP 1989/4) three-unit fixed partial dentures (FPD), before and after luting and after thermo-mechanical fatigue in a dual-axis chewing simulator. MATERIALS AND METHODS: Caries-free human teeth (n=160) were used as abutments for the fabrication of eighty posterior three-unit FPD, divided into two test-groups, IPS Empress 2 and EPC, of 32 samples each and one control group of 16 samples metal ceramic FPD. All FPD were cemented with Variolink II dual-curing resin cement. Half of the samples in each group were exposed to a dual-axis chewing simulator. RESULTS: The geometric mean marginal gap values (microm, before cementation, after cementation and after thermo-mechanical fatigue) amounted to 53, 63 and 62 for the ceramic metal FPD, 57, 71 and 68 for the Empress 2 FPD and 55, 67 and 68 for the EPC FPD. In all groups a statistically significant increase in marginal gap width was observed after cementation. The effect of functional loading in the chewing simulator on marginal gap was not significant. Marginal gap was lowest in the control group but differences with all-ceramic materials were small in all evaluation stages. CONCLUSION: Within the limits of this investigation, it can be concluded that marginal gap values of these all-ceramic materials and conventional MC techniques are on a similar level. In particular, almost all marginal gap values observed in this study were within the limits of clinical acceptance.

Partial coverage restoration systems on molars--comparison of failure load after exposure to a mastication simulator.

This in vitro study evaluated the failure load of partial coverage restorations (PCR) made of various materials cemented on natural molars after exposure to the mastication simulator. Sixty-four maxillary molars were divided into four groups of 16 test specimens each. The specimens in one group remained unprepared (group NP); the teeth in the other groups were prepared equally according to standardized guidelines and restored with the following PCR: Group GO (Gold-Pontor-MPF; Metaux Precieux SA, Metalor, Neuchatel, Switzerland), group TA (Targis; Ivoclar Vivadent AG, Schaan, Liechtenstein) and group EM (IPS-Empress; Ivoclar Vivadent AG). The restorations in group GO were cemented conventionally, while those in groups TA and EM were luted adhesively. Groups NP and GO served as control groups. All test specimens were subjected to 1.2 million cycles (F = 49 N) in a mastication simulator. Subsequently, all test specimens were loaded occlusally until fracture occurred using an universal testing machine. All specimens withstood the masticating simulation. The median (IQR = x(0.25)-x(0.75)) failure loads were as follows: group NP: 1960.3(1480.5-2227.5) N, group TA: 1478.6(1293.4-1856.7) N and group EM: 1400.1(1043.1-1721.6) N. All test specimens of group GO achieved fracture strength values which exceeded a fracture load of 5500 N. The values of group GO were statistically significantly higher than those of groups NP, TA and EM (P < 0.00001). Furthermore, the results of group NP were significantly higher (P = 0.0226) than those of group EM. The results of groups NP and TA (P = 0.2022) as well as of groups TA and EM (P = 0.5340) did not differ significantly. The median values of all PCR systems obtained were within the limits of clinical acceptance. Long-term clinical investigations which take additional parameters into consideration are required before the composite-based Targis(R) (Ivoclar Vivadent AG) material can be recommended for indirect PCR.

Survival rate and fracture strength of maxillary incisors, restored with different kinds of full veneers.

This in vitro study evaluated the survival rate and fracture strength of different kinds of ceramic full veneers, fabricated with a new experimental press ceramic (EPC VP2117/TC2, Ivoclar-Vivadent AG, Schaan, Liechtenstein). Eighty, caries-free human maxillary central incisors were used as abutments and were randomly divided into one control group and four test-groups of 16 samples each. In group A, unprepared teeth served as control. In the test groups, four different types of full veneer preparations were performed. In test groups B/C, the preparation was maintained in enamel and the contact point was on the tooth/on the veneer, respectively. In test groups D/E, the preparation was extended into dentin and the contact point was on the tooth/on the veneer, respectively. All veneers were adhesively luted using Variolink II (Ivoclar-Vivadent AG). Then, the samples were exposed to the artificial mouth for 1.2 million chewing cycles (49 N). After exposure in the artificial mouth, a survival rate of the abutment teeth of 81-100% was reported among the different groups, but was not significantly different between the groups. However, no failures of the ceramic materials could be recognized. The median fracture strength of group A was 713.3 N, of group B 647.1 N, of group C 594.8 N, of group D 483.8 N and of group E 502.6 N. Among the different groups no significant difference was found. All mean values obtained were within the limits of clinical acceptance, indicating further clinical investigations on full veneers made out of the EPC.