EPA Consensus Project Paper: The Influence of Prosthetic Factors on the Incidence of Peri-implantitis Around Single Implants: A Systematic Review

INTRODUCTION

The purpose of this systematic review was to evaluate how prosthetic factors affect the incidence of peri-implantitis in patients treated with single implant restorations.

METHODS

Electronic and manual search of two indexed databases up to April 2023 were conducted, to identify clinical studies reporting on the effect of different prosthetic factors on the incidence of peri-implantitis around single implants and with at least 1 year follow-up. The risk of bias was assessed with the Joanna Briggs Institute critical appraisal checklist, the ROB2 and the ROBINS-I tools.

RESULTS

From the 521 screened articles, 11 studies (1 randomized controlled trial, 7 cross-sectional, 3 retrospective) met the inclusion criteria. Based on three studies, emergence angle⟩30°, convex emergence profile and external connection are associated with a higher incidence of peri-implantitis. Nine studies pertaining to the effect of retention type on the prevalence of peri-implantitis reported conflicting results. Six out of eleven included studies presented some risk of bias.

CONCLUSIONS

There is insufficient evidence regarding the influence of prosthetic factors on the incidence of peri-implantitis around single implants. Further studies are needed to draw definitive conclusions on this issue.

Accuracy of IOS in Full-Arch Dentate Patients Compared to CBCT Cast-Scanning. An In-Vivo Study

Twenty fully-dentate patients were enrolled in the study.Full-arch maxillary and mandibular PVS impressions were acquired using stock metal trays and the dual mix technique. A full-arch maxillary and mandibular intraoral scanner (IOS) was also obtained using the Trios IOS. The impressions were cast and subsequently scanned using a Planmeca Promax cone beam computed tomography (CBCT) scanner. The casts were also scanned in a Desktop Scanner for reference(7series Dental Wings). DICOM files from the CBCT device were converted into stl files. The.stl files from the CBCT and IOS devices were compared for accuracy against the reference files from the Desktop Scanner using a 3D surface measurement software. Statistical analysis was carried out using SPSS software. Trios had a smaller error (median = 39μm) than CBCT (median = 62μm),a statistically significant difference between the 2 modalities (z=-4.6, p⟨0.005).Concerning the IOS, the anterior teeth presented with a smaller error (42±16μm) as opposed to the posterior teeth (47±16μm), a significant difference (t(39)=-2.4, p=0,019). There were no significant differences in IOS mean accuracy between maxilla and mandible or between left and right quadrants. Fullarch digitization using the Trios IOS is significantly more accurate compared to CBCT scanning of the relevant plaster models. Anterior teeth Trios IOS is statistically more accurate compared to posterior teeth IOS.

Hydrogel-Based Engineering of Beige Adipose Tissue

Brown and beige adipose tissues have a significant capacity for energy expenditure that may be exploited as a treatment for obesity and metabolic disease. However, the limited volumes of these tissues in adults hinders realization of this potential. Engineering beige adipose tissue may provide an alternative source of this tissue. In this paper we describe the preparation of poly(ethylene glycol) (PEGDA) hydrogels with mechanical properties similar to native adipose tissue. Adipose derived stem cells (ASC) were cultured in hydrogels without adhesive sequences or degradable monomers. Cells were able to differentiate, independent of scaffold properties and were maintained as a viable and functioning adipose tissue mass. The cells expressed their own basement membrane proteins consistent with the composition of adipose tissue. The ASCs could be induced to express uncoupling protein-1 (UCP-1) and cIDEA, makers of beige adipocytes with expression level varying with hydrogel stiffness. This hydrogel-based culture system serves as a first step in engineering beige adipose tissue.

Evaluation of MMP substrate concentration and specificity for neovascularization of hydrogel scaffolds

Controlled vascular response in scaffolds following implantation remains a significant clinical challenge. A critical biomaterial design criterion is the synchronization of the rates of scaffold degradation and vascularized tissue formation. Matrix metalloproteinases (MMPs) are key enzymes that regulate neovascularization and extracellular matrix remodelling. Synthetic protease-sensitive hydrogels offer controllable environments for investigating the role of matrix degradation on neovascularization. In this study, PEG hydrogels containing MMP-sensitive peptides with increased catalytic activity for MMPs expressed during neovascularization were investigated. Scaffolds were functionalized with MMP-2-, MMP-14- or general collagenase-sensitive peptides and with varying peptide concentration using crosslinkers containing one (SSite) or multiple (TSite) repeats of each protease-sensitive sequence. Increasing peptide concentration enhanced the degradation kinetics of scaffolds functionalized with MMP-specific sequences while 80% of the collagenase-sensitive scaffolds remained upon exposure to MMP-2 and MMP-14. In vitro neovascularization was consistent with in vivo tissue invasion with significantly increased invasion occurring within SSite MMP-specific as compared to collagenase-sensitive hydrogels and with further invasion in TSite as compared to SSite hydrogels regardless of peptide specificity. All scaffolds supported in vivo neovascularization; however, this was not dependent on peptide specificity. These findings demonstrate that peptide concentration and specificity regulate in vivo scaffold degradation, neovascularization and matrix remodelling.

Digital data management for CAD/CAM technology. An update of current systems

Abstract - Computer-aided design/computer-aided manufacturing (CAD/CAM) technology continues to rapidly evolve in the dental community. This review article provides an overview of the operational components and methodologies used with some of the CAD/CAM systems. Future trends are also discussed. While these systems show great promise, the quality of performance varies among systems. No single system currently acquires data directly in the oral cavity and produces restorations using all materials available. Further refinements of these CAD/CAM technologies may increase their capabilities, but further special training will be required for effective use.

An Economic Evaluation of Freeze-Dried Kefir Starter Culture Production Using Whey

An economic study is presented in which industrial-scale production of freeze-dried kefir starter culture is discussed based on results on a laboratory scale. Industrial scale-up was based on a 3-step process using 3 bioreactors of 100, 3,000, and 30,000 L for 300 kg of freeze-dried culture/d of plant capacity. The major cost component of the total investment was the freeze-drying machinery, which consisted of 57% of the total investment. Production cost was reduced from 15.4 euros/kg ($18.5/kg) to 2.9 euros/kg ($3.5/kg) when the production capacity was increased from 30 to 900 kg/d. An economic analysis revealed a 3.5-fold increase in production cost compared with the corresponding production cost of the wet product, with an added value of up to 10.8 x 10(9) euros ($13.0 x 10(9)) within the European Union.

Predictions of cement microfracture under crowns using 3D-FEA

PURPOSE

The objective of this research study was to test the effects of (1) crown margin type, (2) cement type, (3) cement thickness, (4) loading direction, and (5) loading magnitude on stress levels and distributions within luting cement that might lead to cement microfracture using three-dimensional Finite Element Analysis techniques.

MATERIALS AND METHODS

Thirty-two three-dimensional computer models, as well as models for standards, were generated for a mandibular first premolar. Crown preparations exhibited shoulder or chamfer margin configurations, and zinc phosphate, zinc polycarboxylate, glass ionomer, and resin cements were used in thicknesses of 25 or 100 microm. Modeled crowns were loaded axially or obliquely at 10 and 100 MPa. Areas and levels of stress concentrations within the cement were determined.

RESULTS

Stresses in the cement were low for all situations except 100 MPa oblique stressing. Stresses at the margins of crowns with chamfer marginal configuration were higher than those with shoulder margins. Stresses under oblique stressing were 10 to 150 times higher than under axial stressing. Except for Zn phosphate cement, cement thickness minimally affected stress levels and distributions. Greater stresses were found in cements with the greater Young's modulus.

CONCLUSIONS

Although the chamfer margin design could lead to greater stresses near the margins that places the cement at risk for microfracture and possible crown failure, glass-ionomer and composite resin cements have more favorable mechanical properties for resisting microfracture.

3D-FEA of osseointegration percentages and patterns on implant-bone interfacial stresses

OBJECTIVES

The degree of osseointegration and its patterns are important for the success of implants. 3D-FEA was used to determine interfacial stresses on a single tooth implant (IMZ) for four degrees of osseointegration (100, 75, 50 and 25%), and five patterns at 50% osseointegration (locally alternating, coronal only, apical only, facial only and lingual only).

METHODS

The implant was restored with a metal-ceramic crown and subjected to 10 MPa axial or oblique applied stress. Resolved stresses were examined at four heights along the implant-bone interface.

RESULTS

The degree of osseointegration did not affect resolved stress levels or distributions. Oblique loads elevated interfacial stresses 5 to 20 times. Stresses were always higher at the bone crest.

CONCLUSIONS

Osseointegration patterns with crestal bone reduced both crestal and apical stresses. Apical only osseointegration produced much higher apical stresses. Crestal osseointegration and axial loads minimized overall stress.

Three-dimensional finite element analysis of stress-distribution around single tooth implants as a function of bony support, prosthesis type, and loading during function

The elastic limit of bone surrounding implants may be surpassed and thus produce microfractures in bone. The purpose of this study was to use computer simulations to examine clinical situations with IMZ implants in edentulous mandibles and to identify loading conditions that could lead to bone microfractures. Three-dimensional finite element analysis models were used to examine effects of: (1) types of edentulous mandibles, (2) veneering materials, (3) the absence of cortical bone, (4) different intramobile elements, (5) loading directions, and (6) loading levels. Stress distribution patterns were compared and interfacial stresses were monitored specifically at four heights along the bone-implant interface. Stresses were concentrated toward cortical bone (0.8 to 15.0 MPa). There were no differences between types of veneering materials and the absence of cortical bone increased interfacial stresses. The use of a titanium intramobile element decreased stresses. Minor stress increases were associated with smaller mandibles. Oblique loads increased stresses 15 times, and 200 N loads increased stresses 10 times. Conditions for bone microfracturing were associated with oblique loads, high occlusal stress magnitudes, and the absence of cortical bone.

Stress concentration in all-ceramic posterior fixed partial dentures

Two-dimensional finite-element analysis was used to study levels and distribution patterns of stress within three-unit fixed partial dentures (mandibular first premolar to first molar) constructed of different materials (Type III gold alloy, Dicor, and In-Ceram) and with different connector heights (3.0 mm versus 4.0 mm). In the computer models, 10 MPa of stress was applied centrally to the prosthesis. Resultant von Mises stresses were concentrated within the connectors; the greatest stress occurred at the axial location of the connector. Stresses were 40% to 50% lower for 4.0-mm connectors. Patterns of stress distribution were similar for premolar and molar connectors. Stress levels within In-Ceram models were lower than for the other two materials and represented a lower percentage of the ultimate strength of the material. Based on a two-dimensional finite-element analysis model, In-Ceram would appear to be the best choice for posterior fixed partial dentures.

Finite element analysis of ceramic abutment-restoration combinations for osseointegrated implants

All-ceramic restorations can solve many esthetic problems associated with implant-supported prostheses. This study evaluated stress concentration and distribution in implant abutments under normal masticatory forces using computer simulations. Two-dimensional finite element analysis was used to study four different abutment-restoration combinations using Brånemark implants. The models considered two positions of the fastening screw, two positions of the crown margins, cemented versus screw-retained prostheses, and clinical loads of 200 N. Models having screws on top of abutments had the lowest stresses (3.1 to 4.8 MPa) and best stress distribution. Screw-retained prostheses and short crown margins increased overall stresses (9.9 to 11.4 MPa).

Radiotherapy effects on vertebral bone marrow: easily recognizable changes in T2 relaxation times

The effect of localized radiotherapy on vertebral bone marrow was demonstrated in two patients using quantitative MRI studies with pixel-by-pixel measurement of T2 relaxation times with generation of T2 images. Conventional T1-weighted spin-echo images were obtained as well. Irradiated vertebral bone marrow was found to have longer T2 relaxation times than the neighboring nonirradiated bone marrow. These changes corresponded to the increased signal intensity on T1-weighted images and to the field of radiotherapy and were noted 2.5 to 32 mo after radiotherapy. Radiologists should be aware of the increased T2 relaxation times in irradiated bone marrow to correctly assess spinal disorders in irradiated patients. The reported T2 changes may reflect the abundance of adipose cells that proliferate in bone marrow after radiotherapy, or may indicate an additional histological change, such as bone marrow necrosis or edema. Conclusive histological proof remains to be obtained.