Clinical performance of implant crowns with customized zirconia abutments: A prospective cohort study with a 4.5- to 8.8-year follow-up

Evaluation of microgaps and microleakage at the implant-abutment interface of individualized abutments in the maxillary anterior region under functional loading: A pragmatic clinical trial

PURPOSE

This study aimed to evaluate the effect of functional loading on microgaps and microleakage at implant-abutment interfaces (IAIs) in the aesthetic zone when using different abutments and to provide a clinical reference for abutment selection.

METHODS

This study included 30 patients with 36 implants divided into three groups: zirconia (Zr)-one-piece custom abutment, titanium (Ti)-custom abutment, and Ti-original abutment. Scanning electron microscopy was used to examine alterations in the microgaps at the IAIs under functional loading. Changes in the bacterial endotoxin levels within the inner cavities of the implant were evaluated using a quantitative chromogenic Tachypleus amebocyte lysate test. These findings were subjected to statistical analysis using SPSS 18.0.

RESULTS

Before functional loading, there were no significant differences in the microgaps between groups (P > 0.05). In the Zr one-piece custom abutment group, the lingual microgaps significantly increased after 24 months of functional loading (P < 0.05). The bacterial endotoxin content significantly increased after 24 months of functional loading compared to the pre-loading levels (P < 0.05); however, no statistically significant difference was observed among the groups (P > 0.05).

CONCLUSIONS

Considering the limitations of this study, individualized one-piece Zr abutments exhibited a significant increase in lingual microgaps and comparable changes in microleakage to Ti abutments after 24 months of functional loading. Patients should be alert to the potential risks associated with the use of these abutments when they have heightened aesthetic expectations during functional loading.

The Bio-Restorative Concept for Implant-Supported Restorations

OBJECTIVE

This study aims to present the bio-restorative approach in implant dentistry, which combines biological and restorative concepts through digital planning. This concept combines periodontal, surgical, and prosthetic variables, aiming to reduce patient morbidity while achieving satisfactory esthetic and functional outcomes in implant-supported restorations in the long term.

OVERVIEW

Implant dentistry evolved from a primarily surgical to a recent prosthetically driven approach. This evolution was partly due to advancements in bone reconstructive techniques and an increased demand for esthetic outcomes. Recently, digital planning has introduced a new paradigm that allows for the full integration of both approaches. The bio-restorative concept considers functional, esthetic, and biological variables in a virtual planning environment. This is achieved through the simultaneous digital assessment of (A) anatomical site characteristics and (B) implant restorative variables. These variables include digital tooth arrangement, soft-hard tissue conditions, implant variables, supra-platform components, and a surgical plan that respects or modifies peri-implant phenotype.

CONCLUSIONS

The bio-restorative concept is intended to improve contemporary implant dentistry by integrating updated biological and prosthetic notions through digital planning. Adopting this paradigm has the potential to redefine the standards in implant dentistry, fostering a holistic and patient-centered approach.

CLINICAL CONSIDERATIONS

It enhances patient and clinician satisfaction through more efficient and less invasive procedures. Significantly, it improves predictability, leading to successful implant-supported restorations in the long term.

Material and abutment selection for CAD/CAM implant-supported fixed dental prostheses in partially edentulous patients - A narrative review

Restorative material selection has become increasingly challenging due to the speed of new developments in the field of dental material science. The present narrative review gives an overview of the current indications for implant abutments and restoration materials for provisional and definitive implant-supported fixed dental prostheses in partially edentulous patients. For single implant restorations, titanium base abutments for crowns are suggested as an alternative to the conventional stock- and customized abutments made out of metal or zirconia. They combine the mechanical stability of a metallic connection with the esthetic potential of ceramics. For multiple-unit restorations, conical titanium bases especially designed for bridges are recommended, to compensate for deviating implant insertion axes and angulations. Even though titanium base abutments with different geometries and heights are available, certain clinical scenarios still benefit from customized titanium abutments. Indications for the definitive material in fixed implant restorations depend on the region of tooth replacement. In the posterior (not esthetically critical) zone, ceramics such as zirconia (3-5-Ymol%) and lithium-disilicate are recommended to be used in a monolithic fashion. In the anterior sector, ceramic restorations may be buccally micro-veneered for an optimal esthetic appearance. Lithium-disilicate is only recommended for single-crowns, while zirconia (3-5-Ymol%) is also recommended for multiple-unit and cantilever restorations. Attention must be given to the specific mechanical properties of different types of zirconia, as some feature reduced mechanical strengths and are therefore not indicated for all regions and restoration span lengths. Metal-ceramics remain an option, especially for cantilever restorations.

Clinical and radiographic performance of late placed and early loaded dental implants with a conditioned hydrophilic surface in posterior mandible sites: A prospective case series with an 8.5- to 9.5-year follow-up

OBJECTIVE

To assess the clinical outcomes by means of implant and prosthetic survival of late placed and early loaded implants with a hydrophilic, moderately rough surface for partially edentulous patients after a follow-up of 8.5 to 9.5 years.

MATERIALS AND METHODS

A prospective case series study involving 15 patients with single, late placed and early loaded implants in the posterior mandible was performed. Clinical and radiographical parameters, including biological and technical complications and patient satisfaction, were assessed.

RESULTS

From an initial sample of 15 patients, 12 were included. A total of 16 implants were observed. After a mean follow-up of 9 years and 7 months (SD ± 3.8 months), implant success and survival rate were 100%. The prosthetic survival rate was 100%, and the prosthetic success rate was 93.8% since a major chipping was observed. No biological complications were observed, and the mean modified plaque index was 0.03 (SD ± 0.09) with a mean probing pocket depth of 2.95 mm (SD ± 0.09). A mean marginal bone level (MBL) of 0.04 mm (SD ± 0.88) and a mean VAS of 9.42 (SD ± 0.90) for patient satisfaction were recorded.

CONCLUSION

Late placed and early loaded implants with a moderately rough endosseal surface are a reliable option for rehabilitating partially edentulous patients. An implant survival rate of 100% and a prosthodontic success rate of 93.8% were observed. Patient satisfaction scores were high and peri-implant hard and soft tissues remained healthy. The study findings should be carefully interpreted because of the small sample.

CAD/CAM Abutments in the Esthetic Zone: A Systematic Review and Meta-Analysis of Soft Tissue Stability

Computer-aided design and computer-aided manufacturing customized abutments are increasingly used in everyday clinical practice. Nevertheless, solid scientific evidence is currently lacking regarding their potential advantages in terms of soft tissue stability. The main aim of this systematic review and meta-analysis was to compare the soft tissue outcomes of prefabricated versus customized (CAD/CAM) abutments. The present review was registered with PROSPERO (CRD42020161875) and the protocol was developed according to the PRISMA statement. An electronic search was performed on three databases (PubMed, Embase and Cochrane Central) up to May 2023. Data extraction was followed by qualitative and quantitative analysis of the included studies. Three randomized controlled clinical trials and three controlled clinical trials (number of patients = 230; number of dental implants = 230) with a follow-up of between 12 and 36 months were included. No significant differences were observed between prefabricated versus customized (CAD/CAM) abutments regarding midfacial mucosal recession, interproximal papillae and pink aesthetic score (PES) after 12 months. Conclusion: The potential benefits of CAD/CAM abutments on soft tissues should be better clarified in future investigations. The usage of customized CAD/CAM abutments in everyday clinical practice should be based on a careful case-by-case evaluation (CRD42020161875).

CAD/CAM Abutments versus Stock Abutments: An Update Review

With the evolution of CAD/CAM technology, custom titanium and/or zirconia abutments are increasingly being used, leading to several comparisons in the literature, both mechanical and aesthetic, to evaluate performance differences between these two types of abutments. Therefore, the aim of this comprehensive review is to present the most recent data on the latest comparisons between CAD/CAM and stock abutment applications. The PICO model was used to perform this review, through a literature search of the PubMed (MEDLINE) and Scopus electronic databases. CAD/CAM abutments allow individualization of abutment parameters with respect to soft tissue, allow increased fracture toughness, predict the failure mode, show no change in the fracture toughness over time, reduce the prosthetic steps, and reduce the functional implant prosthesis score and pain perceived by patients in the early stages. The advantages associated with the use of stock abutments mainly concern the risk of corrosion, time spent, cost, and fit, evaluated in vitro, in the implant–abutment connection. Equal conditions are present regarding the mechanical characteristics during dynamic cycles, screw loss, radiographic fit, and degree of micromotion. Further randomized controlled clinical trials should be conducted to evaluate the advantages reported to date, following in vitro studies about titanium and/or zirconia stock abutments.

Microleakage assessment of CAD-CAM Cobalt-Chrome and Zirconia abutments on a conical connection dental implant: A comparative in vitro study

Objective

To assess the marginal and bacterial microleakage in zirconia and CAD‐CAM or cast Co‐Cr implant abutments.

Methods

Sixty‐four conical connection implants with their respective abutments were divided into four groups (Co‐Cr (milled, laser‐sintered, and cast) and Zirconia (milled)). All specimens were subjected to a chewing simulation and thermocycling. After aging process, specimens were submerged in a 0.2% methylene blue solution with Porphyromonas gingivalis (P.g) for 48 h. The marginal microleakage was measured using a 40× optical microscopy at the internal part of the implant, and when positive microleakage was observed, a DNA isolation with a polymerase chain reaction (PCR) test was used. The microbiological assessment was based on colony forming units (CFUs).

Results

Thirty (47%) implant‐abutments presented microleakage and the PCR was performed on those specimens (1 Zirconia, 1 Co‐Cr milled, 14 Co‐Cr laser‐sintered and 14 cast). Seven specimens (1 Co‐Cr laser‐sintered and six cast) presented values below the PCR detection limit (< 100 CFUs). The lowest CFUs count occurred in the Co‐Cr milled group (5.17E+02 CFUs/ml) followed by zirconia (7.70E+03 CFUs/ml). The Co‐Cr cast (9.39E+03 CFUs/ml) and laser‐sintered (2.4E+05 CFUs/ml) groups had higher bacterial count. The CFU count comparison performed between Co‐Cr cast and laser‐sintered resulted in a statistically significant differences in favor of Co‐CrCL (p < .05).

Conclusions

The abutment material and fabrication technique affected the implant‐abutment microleakage. Although the CAD‐CAM abutments presented favorable results, all tested groups presented microleakage.

Survival Rate and Deformation of External Hexagon Implants with One-Piece Zirconia Crowns

This study aimed to evaluate the survival rates of several external hexagon implants directly connected to zirconia crowns after thermomechanical fatigue. The deformation of the hexagons and the integrity of zirconia crowns were also evaluated. A monolithic zirconia crown (Y-TZP) and four different external hexagon dental implants (n = 10, N = 40) were mounted together and embedded in polyurethane. The specimens were subjected to thermomechanical cycling for 2.5 × 106 cycles, at 3.0 Hz frequency, at 200 N loading. The interface of the implant/zirconia crown system, zirconia crowns integrity before and after cycling, and the implant hexagon surface were evaluated under stereomicroscopy and SEM. A nanohardness analysis was performed to verify the hardness of zirconia and implants. Statistical analysis was performed using the Kaplan-Meier test, Multi-Sample Survival Tests, Logrank Test, (p = 0.05). The data did not show significant differences in the survival rates of different implant groups. However, some crowns presented fractures (16.67%) and the external hexagon region of the implants presented plastic deformations (100%). During chewing simulation, the interface between titanium implant and zirconia abutment can promote plastic deformation in the metal and surface defects in the ceramic. In addition, the types of interface defects can be affected by the external hexagon design.