Management of Maxillary Cluster Implant Failures with Extra-Maxillary Implants: A Clinical Report

Late cluster implant failures can be one of the most devasting outcomes of implant therapy for patients. It can have anatomic, functional, psychological and financial consequences for patients, and sometimes the loss of residual bone can preclude subsequent implant placement. Fortunately, management of cluster implant failures in the maxilla can be mitigated by using implant anchorage from remote sites like zygomatic and pterygoid regions. Few reports exist in the literature that have described the management of cluster implant failure using extra-maxillary implants such as zygomatic and pterygoid implants. This case report describes the management of a female patient with bruxism who experienced late cluster implant failure in the maxilla after 9 years of function with an overdenture. Due to the loss of residual bone, subsequent implant therapy involved the use of bilateral zygomatic, pterygoid and anterior maxillary implants, which were immediately loaded and thereafter used to support a complete arch fixed implant-supported zirconia prosthesis.

Precision fMRI and cluster-failure in the individual brain

Advances in neuroimaging acquisition protocols and denoising techniques, along with increasing magnetic field strengths, have dramatically improved the temporal signal-to-noise ratio (tSNR) in functional magnetic resonance imaging (fMRI). This permits spatial resolution with submillimeter voxel sizes and ultrahigh temporal resolution and opens a route toward performing precision fMRI in the brains of individuals. Yet ultrahigh spatial and temporal resolution comes at a cost: it reduces tSNR and, therefore, the sensitivity to the blood oxygen level-dependent (BOLD) effect and other functional contrasts across the brain. Here we investigate the potential of various smoothing filters to improve BOLD sensitivity while preserving the spatial accuracy of activated clusters in single-subject analysis. We introduce adaptive-weight smoothing with optimized metrics (AWSOM), which addresses this challenge extremely well. AWSOM employs a local inference approach that is as sensitive as cluster-corrected inference of data smoothed with large Gaussian kernels, but it preserves spatial details across multiple tSNR levels. This is essential for examining whole-brain fMRI data because tSNR varies across the entire brain, depending on the distance of a brain region from the receiver coil, the type of setup, acquisition protocol, preprocessing, and resolution. We found that cluster correction in single subjects results in inflated family-wise error and false positive rates. AWSOM effectively suppresses false positives while remaining sensitive even to small clusters of activated voxels. Furthermore, it preserves signal integrity, that is, the relative activation strength of significant voxels, making it a valuable asset for a wide range of fMRI applications. Here we demonstrate these features and make AWSOM freely available to the research community for download.

Cluster behavior in dental implant failure - A scoping review

PURPOSE

To provide an overview of cluster behavior in dental implant failure including the reported prevalence in modern roughened surface implants as well as the risk factors associated with cluster failures.

MATERIAL AND METHODS

An electronic search for articles in the English language literature published from January 1, 2000, to March 8, 2023, was performed using PubMed, Embase, Dentistry and Oral Sciences, ProQuest, and Central search engines. Using a standardized systematic search process and predetermined inclusion and exclusion criteria in three stages, the final list of selected articles reporting on cluster behavior in dental implant failure was obtained. Cluster behavior was defined as the failure of two or more implants in the same patient within a 2-year period irrespective of the site. Data from the selected articles were reviewed, critically analyzed, interpreted, and reported.

RESULTS

The initial electronic search resulted in 948 titles. After applying inclusion and exclusion criteria, the systematic search process resulted in five clinical studies reporting data on cluster behavior of dental implant failure with modern roughened surfaces. These five studies reported on a total of 9986 implants with 858 reported failures (early and late) over varying periods. Out of the 858 implant failures, 217 implants (25.2%) exhibited cluster behavior. The overall prevalence of cluster behavior of modern roughened surface implant failure was 2.1%.  The most common location risk factors reported were posterior maxilla, history of previous implant failures, poor bone quality, and occlusal overload.

CONCLUSIONS

Cluster behavior occurs in 25% of modern roughened surface implant failures which is significantly less than machined surface cluster implant failures. Nevertheless, the overall prevalence of cluster pattern of implant failure of modern roughened surface implants is reasonably low at 2%.