Effect of veneering technique on the fracture resistance of zirconia fixed dental prostheses.

To compare the fracture resistance of zirconia 3-unit posterior fixed dental prostheses (FDPs) frameworks veneered with different veneering materials and techniques before and after artificial ageing. Forty-eight zirconia 3-unit FDPs, representing a missing first molar, were adhesively cemented on human teeth. The zirconia frameworks were randomly distributed according to the veneering materials and techniques into three groups, each containing 16 samples: group LV (layering technique/Vintage ZR), group LZ (layering technique/ZIROX) and group PP (CAD/CAM and press-over techniques/PressXZr). Half of each group was artificially aged through dynamic loading and thermocycling to simulate 5 years of clinical service. Afterwards, all specimens were tested for fracture resistance using compressive load. An analysis of variance (anova) was used to assess the effect of veneering ceramic and artificial ageing on fracture resistance (P < 0·05). Except for one minor cohesive chipping in group LV1, all specimens survived artificial ageing. The mean fracture resistance values (in Newton) of different non-aged (± s.d.)/aged (± s.d.) groups were as follows: LV0 2034 (± 401)/LV1 1625 (± 291); LZ0 2373 (± 718)/LZ1 1769 (± 136); and PP0 1959 (± 453)/PP1 1897 (± 329). Artificial ageing significantly reduced the fracture resistance in groups veneered with the layering technique (P < 0·05), whereas no significant effect was found in specimens veneered with the CAD/CAM and press-over techniques. All tested systems have the potential to withstand occlusal forces applied in the posterior region. The combination of the CAD/CAM and press-over techniques for the veneering process improved the overall stability after artificial ageing, relative to the layering technique.

Prosthetic outcome of cement-retained implant-supported fixed dental restorations: a systematic review.

The aim of the article is to assess the current literature in terms of the prosthetic outcome of cement-retained implant-supported fixed restorations, as well as to determine the type of cement that can be recommended for clinical application. A review of the literature published up to May 2010 was conducted to identify clinical studies about cement-retained implant-supported fixed restorations. The search strategy applied was a combination of MeSH terms and free text words, including the following keywords: implants, implant-supported fixed dental prostheses (FDPs), bridges, implant-supported single crowns (SCs), cement-retained, cement fixation, cement, cementation, cement failure, retention, and loss of retention, technical complications, mechanical complications, prosthetic complication, retrievability and maintenance. Thirty-two studies met the inclusion criteria. The studies were divided into two categories: 15 short-term clinical studies with an observation period of less than 5 years, and 17 long-term clinical studies with an observation period of 5 years and more. The most common technical complications of cement-retained implant-supported fixed restorations were loss of retention, chipping and abutment screw loosening. The results of the current review revealed no guidelines about cement or cementation procedures. It may be stated that despite the questionable retrievability of cement-retained implant-supported fixed restorations, this treatment modality is a reliable and effective option, especially for implant-supported SCs and short-span FDPs. The literature does not provide accurate information about the clinical outcome of cement-retained implant-supported fixed restorations nor about the ideal type of cement that facilitates stability and maintains retrievability. Standardised randomised clinical trials will provide valuable information to this issue.