Chandur Wadhwani

Technique for controlling the cement for an implant crown.

The Journal of Prosthetic Dentistry Londono and Marafie Wadhwani and Pineyro Cementation of an implant prosthesis is an accepted protocol. Less demanding surgical placement of the implant, simpler laboratory techniques, passive fit, esthetics, and control of the occlusion are among some of the advantages.1 However, disadvantages include unpredictable retention and resistance and the detrimental effect of cement flow into the soft tissues that can be difficult to remove. The soft tissue attachment onto the implant surface is more delicate than that seen at the natural tooth surface due to the lack of Sharpey fiber insertion, the reduced number of collagen fibers, and the direction in which these fibers run.2 Cement extrusion into the sulcular area may result in soft tissue swelling, soreness, and bleeding or exudation on probing.3 In some instances, the excess cement has been considered to be the cause of implant failure.4 Removal of excess cement with plastic and metal scalers may result in scratches and gouges on the implant surfaces.5 Control of cement volume has been documented previously using the ITI solid abutment (Straumann USA, Andover, Mass).6 This requires an implant analog or practice abutment, as described by the authors.6 When a custom abutment is to be used under the crown, this becomes more challenging. The dental laboratory may be instructed to make a duplicate analog using an acrylic resin, but this is time consuming for the technician and involves additional laboratory costs. Technique for controlling the cement for an implant crown

A descriptive study of the radiographic density of implant restorative cements

STATEMENT OF PROBLEM Cementation of implant prostheses is a common practice. Excess cement in the gingival sulcus may harm the periodontal tissues. Identification of the excess cement may be possible with the use of radiographs if the cement has sufficient radiopacity. PURPOSE The purpose of this study was to compare the radiographic density of different cements used for implant prostheses. MATERIAL AND METHODS Eight different cements were compared: TempBond Original (TBO), TempBond NE (TBN), Flecks (FL), Dycal (DY), RelyX Unicem (RXU), RelyX Luting (RXL), Improv (IM), and Premier Implant Cement (PIC). Specimen disks, 2 mm in thickness, were radiographed. Images were made using photostimulable phosphor (PSP) plates with standardized exposure values. The average grey level of the central area of each specimen disk was selected and measured in pixels using a software analysis program, ImageTool, providing an average grey level value representative of radiodensity for each of the 8 cements. The radiodensity was determined using the grey level values of the test materials, which were recorded and compared to a standard aluminum step wedge. An equivalent thickness of aluminum in millimeters was calculated using best straight line fit estimates. To assess contrast effects by varying the exposure settings, a second experiment using 1-mm-thick cement specimens radiographed at both 60 kVp and 70 kVp was conducted. The PSP plates with specimens were measured for a grey level value comparison to the standard aluminum step wedge, using the same software program. RESULTS The highest grey level values were recorded for the zinc cements (TBO, TBN, and FL), with the 1-mm specimen detectable at both 60- and 70-kVp settings. A lower grey level was recorded for DY, indicative of a lower radiodensity compared to the zinc cements, but higher than RXL and RXU. The implant-specific cements had the lowest grey level values. IM could only be detected in 2-mm-thick sections with a lower aluminum equivalence value than the previously mentioned cements. PIC could not be detected radiographically for either the 1-mm or 2-mm thicknesses at either of the kVp settings. CONCLUSIONS Some types of cement commonly used for the cementation of implant-supported prostheses have poor radiodensity and may not be detectable following radiographic examination.

Titanium Corrosion Mechanisms in the Oral Environment: A Retrieval Study

Corrosion of titanium dental implants has been associated with implant failure and is considered one of the triggering factors for peri-implantitis. This corrosion is concerning, because a large amount of metal ions and debris are generated in this process, the accumulation of which may lead to adverse tissue reactions in vivo. The goal of this study is to investigate the mechanisms for implant degradation by evaluating the surface of five titanium dental implants retrieved due to peri-implantitis. The results demonstrated that all the implants were subjected to very acidic environments, which, in combination with normal implant loading, led to cases of severe implant discoloration, pitting attack, cracking and fretting-crevice corrosion. The results suggest that acidic environments induced by bacterial biofilms and/or inflammatory processes may trigger oxidation of the surface of titanium dental implants. The corrosive process can lead to permanent breakdown of the oxide film, which, besides releasing metal ions and debris in vivo, may also hinder re-integration of the implant surface with surrounding bone.

Radiographic detection and characteristic patterns of residual excess cement associated with cement-retained implant restorations: A clinical report

Residual excess cement (REC) is a common complication of cement-retained prostheses and has been linked to periimplant disease. Removal of the cement residue may result in resolution of the issue if addressed early in the disease process. However, this is dependent upon the ability to locate and adequately remove the foreign material. This series of patient scenarios describes the ability to detect REC by using dental radiography. Characteristics related to cements and flow patterns specific to implants are addressed.

The Interaction of Implant Luting Cements and Oral Bacteria Linked to Peri-Implant Disease: An In Vitro Analysis of Planktonic and Biofilm Growth – A Preliminary Study

BACKGROUND There is little consensus on the most appropriate cement to use when restoring a cement-retained, implant-supported restoration. One consideration should be the interaction of pathogenic oral bacteria with restorative cements. PURPOSE To determine how oral bacteria associated with peri-implant disease grow in the presence of implant cements. MATERIALS AND METHODS Five test cements with varying composition (zinc oxide-eugenol [TBO], eugenol-free zinc oxide [TBNE], zinc orthophosphate [FL], and two resin cements [PIC and ML]) were used to fabricate specimen disks. The disks were submerged in bacterial suspensions of either Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, or Porphyromonas gingivalis. Planktonic bacterial growth within the test media was measured by determining the optical density of the cultures (OD600 ). Positive controls (media and bacteria without cement disks) and negative controls (media alone) were similarly evaluated. The mean and standard deviations (SD) were calculated for planktonic growth from three separate experiments. ANOVA statistical analysis with post hoc Tukey tests was performed where differences existed (p < .05). Selected cement disks (TBO and ML) were further examined for bacterial biofilm growth. Surface bacteria were removed and grown on agar media, and colony-forming units (CFUs) were quantified. RESULTS Planktonic growth for both A. actinomycetemcomitans and P. gingivalis was significantly inhibited (p < .05) when grown in the presence of cement disks consisting of TBNE, PIC, FL, and TBO. In contrast, neither of these bacteria displayed growth inhibition in the presence of ML cement disks. F. nucleatum growth was also significantly inhibited by PIC, FL. and TBO (p < .05), but not by ML and TBNE cement disks. CFU counts for the biofilm study for TBO gave minimal and, in some instances, no bacterial adherence and growth, in contrast to ML, which supported substantially greater bacterial biofilm growth. CONCLUSION Cements display differing abilities to inhibit both planktonic and biofilm bacterial growth. Cements with the ability to reduce planktonic or biofilm growth of the test bacteria may be advantageous in reducing peri-implant disease. Understanding the microbial growth-inhibiting characteristics of different cement types should be considered important in the selection criteria.

simple device for locating the abutment screw position of a cement-retained implant restoration

aAffiliate Faculty, Department of Restorative Dentistry, University of Washington; Private practice, Bellevue, Wash. bProfessor, Department of Restorative Dentistry, University of Washington. (J Prosthet Dent 2013;109:272-274) 1 Plate and guide rod engage abutment screw head on cast, with plate lowered and oriented to buccal of adjacent teeth. Cement-retained implant restorations have been reported to have several advantages over their screwretained counterparts, especially with respect to esthetics, occlusion, cost, passive fit, and reduced chair time.1,2 However, there are occasions when the cement-retained restoration requires removal, for example, if the abutment screws loosen or if the restoration needs repair.3,4 In this instance, the crown frequently remains cemented to the abutment. The abutment screw must then be accessed through the crown. The challenge here is to locate the screw position with minimal damage to the restoration, abutment, and possibly implant. Several authors have reported techniques to achieve this, which include reviewing a radiograph of the implant position and estimating the long axis position of the screw,5 using photography to record the position of the abutment before the crown is cemented,6,7 marking the screw access site with a porcelain stain during fabrication,8 or fabricating a vacuum-formed guide or template over the definitive restoration.9,10 The problems associated with these techniques are clear. Estimating the implant position in 2 dimensions either with radiographic or photographic records is inaccurate.5-7 Marking the screw access point may be useful in nonesthetic areas but has limitations with an anterior restoration.8 This article describes the procedure for fabricating a custom-made and precision implant-locating device (PILD) to record the access position of the abutment screw. It is simple, rapid, inexpensive, and gives 3-dimensional information for guiding directional screw access.

An introduction to the implant crown with an esthetic adhesive margin (ICEAM).

UNLABELLED This article describes a novel technique with the addition of a pressed porcelain abutment margin capable of bonding to the porcelain margin of an implant crown restoration. This allows for supragingival margin placement, reduces the potential effect of excess cement-induced peri-implant disease, and provides a controlled environment for the bonding process. Another advantage is the matching esthetics of the crown and supporting abutment, which in the event gingival recession occurs, the restoration appears as a longer tooth without the risk of exposing an underlying abutment margin with different esthetic properties. CLINICAL SIGNIFICANCE The transition margin from an implant abutment to a crown is challenging to manage especially esthetically. Placing the abutment margin in a subgingival position helps hide the unesthetic transition, however, this reduces the ability to clean excess cement, increases the risk of peri-implant disease and the inability to control gingival sulcular fluids may affect the cement bond. The implant crown with an esthetic adhesive margin provides for supragingival bonded margins that can aid in complete removal of excess cement at the same time providing an esthetically pleasing result.

Characterization of Cement Particles Found in Peri-implantitis-Affected Human Biopsy Specimens.

PURPOSE Peri-implantitis is a disease characterized by soft tissue inflammation and continued loss of supporting bone, which can result in implant failure. Peri-implantitis is a multifactorial disease, and one of its triggering factors may be the presence of excess cement in the soft tissues surrounding an implant. This descriptive study evaluated the composition of foreign particles from 36 human biopsy specimens with 19 specimens selected for analysis. The biopsy specimens were obtained from soft tissues affected by peri-implantitis around cement-retained implant crowns and compared with the elemental composition of commercial luting cement. MATERIALS AND METHODS Nineteen biopsy specimens were chosen for the comparison, and five test cements (TempBond, Telio, Premier Implant Cement, Intermediate Restorative Material, and Relyx) were analyzed using scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. This enabled the identification of the chemical composition of foreign particles embedded in the tissue specimens and the composition of the five cements. Statistical analysis was conducted using classification trees to pair the particles present in each specimen with the known cements. RESULTS The particles in each biopsy specimen could be associated with one of the commercial cements with a level of probability ranging between .79 and 1. TempBond particles were found in one biopsy specimen, Telio particles in seven, Premier Implant Cement particles in four, Relyx particles in four, and Intermediate Restorative Material particles in three. CONCLUSION Particles found in human soft tissue biopsy specimens around implants affected by peri-implant disease were associated with five commercially available dental cements.

Cementing an Implant Crown: A Novel Measurement System Using Computational Fluid Dynamics Approach

BACKGROUND Cementing restorations to implants is a widely used clinical procedure. Little is known about the dynamics of this process. Using a systems approach and advanced computing software modeling this can be investigated virtually. These models require validation against real-life models. PURPOSE The study aims to consider the system effect of a crown, abutment, and cement flow under different conditions and comparing real physical models to virtual computer simulations. MATERIALS AND METHODS A physical model of implant abutments and crowns provided three groups according to abutment screw access modification (n = 9): open (OA), closed (CA), and internal vented (IVA) abutment groups. Crowns were cemented using standardized amounts and site application. Proportion of cement retained within the crown-abutment system was recorded and compared. Differences among groups were identified using analysis of variance (ANOVA) with Tukeys post hoc test (α ≤ 0.05). Three-dimensional multiphysics numerical stimulation software (STAR-CCM+, CD-adapco) with computational fluid dynamics (CFD) approach was applied to a virtual model system of a scanned abutment and crown system. Three-dimensional real-time model simulations of cement and air displacement were produced, evaluating cement application site, speed of crown seating, and abutment modifications. RESULTS Statistically significant differences in cement retained within the system (p < 0.01) were found among the IVA > OA > OCA abutment groups. The CFD virtual simulations followed this trend. Site application and speed of seating also affected cement extrusion and cement marginal infill. Fast crown seating and occlusal cement site application produced air incorporation at the margins. CONCLUSIONS The CFD approach provides a convenient way to evaluate crown-cement-implant abutment systems with respect to cement flow. Preliminary evaluation indicates that the results achieved follow those of a physical actual cement-retained crown-implant abutment study.

A radiograph positioning technique to evaluate prosthetic misfit and bone loss around implants

A radiograph positioning device was developed to fit with commercially available film holders and implant systems. The device is indexed to the dental implant body and the adjacent dentition by using an implant placement driver and polyvinyl siloxane occlusal registration material. By fitting the device to a conventional film holder, accurate orthogonal radiographs can monitor changes in bone architecture and prosthetic misfit.