Laser retrieval of cemented zirconia single unit implant restoration: A pilot study: Part I - Force values.

PURPOSE: To measure the retrieval force required to remove 1.5-mm-thick CAD/CAM zirconia copings cemented on zirconia (Zr) and titanium (Ti) stock implant abutments after a single application of erbium-doped yttrium scandium gallium garnet (Er:YSGG) laser. MATERIALS AND METHODS: A total of 60 monolithic Zr copings were cemented on Zr and Ti implant abutments with either a resin-modified glass-ionomer (RelyX Luting Plus Cement, 3M ESPE; Rx) or a zinc oxide eugenol cement (Temp-Bond, Kerr; Tb). These abutment-coping specimens were randomly divided into 12 groups based on laser application (vs control [C]), abutment type (Zr vs Ti), cement (Rx vs Tb), and storage condition (dry [D] vs saline water [W]). Er:YSGG laser was applied at 6 W, 30% water-60% air, and 20 Hz (300 mJ/pulse energy) postcementation following a defined pattern. The force required to remove all the cemented copings from their abutments was measured on a universal testing machine (Instron model 4204). Descriptive statistics, multi-factor analysis of variance, and post hoc Tukey honest significant difference tests (α = .05) were performed. RESULTS: The mean peak force values at removal of the Zr abutment groups were 470.3 ± 151.33 N (ZrRxC), 161.7 ± 19.29 N (ZrRxD), 316.03 ± 95.24 N (ZrRxW), 103.27 ± 24.53 N (ZrTbC), 39.33 ± 6.21 N (ZrTbD), and 20.33 ± 6.45 N (ZrTbW); and for the Ti abutment groups were 349.80 ± 106.82 N (TiRxC), 84.63 ± 14.02 N (TiRxD), 177 ± 62.57 N (TiRxW), 54.77 ± 9.10 N (TiTbC), 22.67 ± 4.32 N (TiTbD), and 11.57 ± 2.30 N (TiTbW). CONCLUSION: Within the limitations of this study, it can be concluded that Er:YSGG laser allows for easier removal of cemented Zr copings with lower removal forces, with Ti abutment groups requiring lower forces than Zr abutment specimens. No significant difference was seen between laser and control groups for Tb compared to Rx. Er:YSGG laser shows great clinical promise for predictable retrievability of cemented, monolithic Zr implant crowns, especially with stronger resin-based cement such as Rx. With further clinical evidence, this could be very useful for clinicians managing cement-retained implant crown complications.

Fabricating a screw-retained, complete arch, fixed implant prosthesis using selective metal laser sintering: A clinical report.

In contemporary prosthodontic practice, implant-supported therapy has consistently resulted in high success rates, with satisfactory and predictable outcomes for completely edentulous patients. Of the several options, complete-arch, fixed screw-retained solutions are generally considered to be the preferred treatment solution. Screw retention offers advantages such as predictable retrievability and potentially easy prosthodontic maintenance, as well as excess cement not being a concern. However, implant mispositioning and malalignment may often necessitate the use of cement-retained prostheses. This clinical report describes a method of fabricating a complete-arch, implant screw-retained, double framework metal-ceramic prosthesis, despite the unfavorable implant positioning, by using selective direct metal laser sintering technology.

Effect of coded healing abutment height and position on the trueness of digital intraoral implant scans.

STATEMENT OF PROBLEM: Information regarding the effect of the height and position of a coded healing abutment (CHA) on the trueness of intraoral digital scans is lacking. PURPOSE: The purpose of this in vitro study was to investigate the effect of the height and position of a scannable CHA on the trueness (distance and angular deviations) of intraoral digital scans. MATERIAL AND METHODS: Scannable CHAs (BellaTek Encode Impression system; Zimmer Biomet Dental) were used in 2 different height pairs (3 mm and 8 mm) on 2 implants at mandibular left second and first molar positions. Each pair was scanned 10 times by using 1 intraoral scanner (TRIOS; 3Shape) by 1 operator to generate a total of 20 intraoral scan files. Master standard tessellation language (STL) files were created for both 3-mm and 8-mm CHA pairs by using a structured blue light scanner (COMET L3D 8M 150 Precision Structured Blue Light Scanner; ZEISS). These master STL files were imported into a software program (PolyWorks Inspector) and were used as the reference for the inspection. Scans obtained by using the intraoral scanner were aligned to the reference scan by using a best-fit alignment to measure the distance and angular deviations. Two-way repeated-measures ANOVA was used to analyze the data, and the Tukey-Kramer test was used to determine significant differences among groups (α=.05). RESULTS: The CHA position had a significant effect on distance deviation (P<.001). However, no significant effect of CHA height on distance deviation was found. The interaction between CHA height and position had a significant effect on the angular deviation (P=.041). The 3-mm posterior CHA (P=.026) and 8-mm anterior CHA (P=.039) had significantly lower angular deviations than the 8-mm posterior CHA. CONCLUSIONS: The distance deviation of CHA was significantly influenced by position. CHAs in the anterior had lower distance deviations for both 3 mm and 8 mm. The effect of CHA height on distance deviation was found to be small and was affected by the location of the CHA. Height affected angular deviation depending on the position of the CHA. Both 3-mm posterior and 8-mm anterior CHAs showed lower angular deviations than the 8-mm posterior CHA.

Marginal Adaptation of Provisional CAD/CAM Restorations Fabricated Using Various Simulated Digital Cement Space Settings.

PURPOSE: The ideal digital cement space value for the fabrication of provisional computer-aided design/computer-aided manufacturing (CAD/CAM) crowns with clinically acceptable marginal adaptation is not well known. The aim of this study was to evaluate the effect of different simulated cement space settings on the marginal fit of poly(methyl methacrylate) (PMMA) provisional CAD/CAM restorations. MATERIALS AND METHODS: An extracted premolar tooth was prepared using ceramic crown preparation guidelines and represented both natural teeth and/or custom implant abutments. The prepared tooth abutment was scanned with a three-dimensional (3D) laboratory scanner (D900, 3Shape). CAD design software was used to subsequently design a premolar crown core with three different simulated cement space settings (20 to 40 µm, 20 to 50 µm, 20 to 60 µm). PMMA blocks were used to mill the specimens (n = 9, N = 27). Using a stereo zoom microscope, a total of 36 images for each of the 3 groups (9 crowns per group, 4 sites per crown) were captured to measure the mean vertical marginal discrepancy for every group. One-way analysis of variance (ANOVA) was used to analyze the data, and the post hoc Tukey multiple comparison test was performed. RESULTS: The marginal gap values of the PMMA cores fabricated using the three cement space settings were significantly different from each other (P < .001). The marginal gap was smaller with a 20- to 60-µm setting compared with 20 to 50 µm and 20 to 40 µm, and the 20- to 50-µm setting allowed for smaller marginal gaps compared with 20 to 40 µm (P < .001). CONCLUSION: Within the limitations of this study, the marginal gaps of CAD/CAM-fabricated PMMA cores were smaller when the cement space was larger. The smallest marginal gaps were achieved when a 20- to 60-µm cement space was used (P < .001).

Fabrication of a Mandibular Implant-Supported Overdenture with a New Attachment System: A Review of Current Attachment Systems.

Since their introduction, implant-retained overdentures have represented a feasible, economical, and highly successful treatment option for completely edentulous patients. Different attachment systems have been effectively used to retain these implant overdentures, and each system has advantages and disadvantages. Locator attachment (Zest Anchors) is one system that has been widely used by clinicians, particularly, for two-implant-supported situations. Recently, Zest Anchors developed a new locator-style abutment, Locator R-Tx. This clinical report describes the fabrication of a mandibular two-implant overdenture using this newly designed attachment system and reviews the different attachment systems currently in clinical use.

A Technique to Transfer the Emergence Profile Contours of a Provisional Implant Crown to the Definitive Impression.

This clinical report describes a method to create a proper emergence profile and accurately transfer it to the definitive impression, using an indirectly fabricated modified impression post. A provisional screwretained crown was indexed with a polyvinyl siloxane material. An autopolymerizing acrylic resin was used to modify an impression post on the polyvinyl siloxane index, which was then screwed onto the implant for the definitive impression after proper soft tissue healing. The indirectly fabricated modified impression post helped to transfer the contours to the definitive impression with minimal soft tissue irritation.

An alternative approach for the management of fractured implant abutment screws on a mandibular implant-retained overdenture: A clinical report.

In contemporary implant and prosthodontic practice, high levels of surgical and biologic success rates have been achieved. However, mechanical and technical complications continue to exist. Of these, one of the biggest challenges to the clinician is the conservative retrieval of fractured screw fragments from within the implants and/or abutments. While removal is desirable, the fragments cannot always be removed, and alternative solutions for the management of such clinical situations must be considered. This clinical report describes the replacement of 2 fractured, irretrievable, Locator abutment screws of a mandibular implant-retained overdenture with a cast dowel and laser welded Locator attachments. This alternative method was successful in managing broken abutment screw fragments while using the existing prosthesis and implants.