To study the application of prosthetic labelling in implant-supported fixed prostheses, acrylic models were prepared and implant analogues were generated at Erciyes University, Turkey. For labelling, the phantom jaw model (Frasaco Phantom, Tettnang, Germany) was used.
Sample generation
A total of 60 implants and analogues were used in our in vitro study. Implant analogues were fixed using a specifically prepared metal mould (Fig. 1). An auto-polymerising acrylic resin was poured into the metal mould, and the specimens were numbered. Prepared samples were subsequently transferred to the laboratory where metal-supported porcelain restorations were made for use as a master model. Subsequently, occlusion spray (Occlusion-Spray; Bausch, Cologne, Germany) was applied to the abutment surfaces to improve the quality of scanned images, and the models were scanned using a scanner (Activity 885; Smart Optics, Bochum, Germany). A virtual model of the right lower first molar tooth was created with a 4-mm metal band on the lingual side. Obtained data were transferred to a computer-aided design and computer-aided manufacturing (CAD/CAM) device (Quadro MILL Comfort; Quadro, Ontario, Canada) to generate a hard wax model. The wax model was evaluated, and necessary adjustments were made. Subsequently, metal coping was fabricated using a laser-sintering machine (SLM 125; SLM Solutions, Lübeck, Germany), and the sintering process was completed using a metal sintering machine (PLF 120/5; Protherm Furnaces, Istanbul, Turkey). Next, dental porcelain (Ceramco-Dentsply, Burlington, NJ, USA) was made in the form of the right lower first molar and was glaze-phase finished. Finally, the lingual metal band (4 mm wide) was polished, and the samples were prepared for laser barcoding.
Preparation of quick response (QR) code labelling
QR code labelling was performed on the lingual metal band restorations using a laser (TruMark Series 3000; OTES Electronic, Istanbul, Turkey). The data to be stored in the QR code were generated using the CAD program and Tru Tops Mark (TTM) software of Trumpf. The ‘barcode’ option was preferred in the CAD program. Under the barcode type option, the QR code (data matrix) preference was selected. The QR code content included the 11-digit patient citizenship number, and the QR code size information (3–3 mm) was set (Fig. 2). In the program, we selected metal as the material type, and laser parameters such as power, speed, and frequency were adjusted accordingly.
Following generation of the QR, samples were read using the barcode reader terminal (HCR 6200 DPM—Mobile 2D-Code Reader; Leuze Electronic, Owen, Germany) to determine whether the recorded data could be accessed.
Preparation of microchip labelling
Microchips (2 × 3 × 0.75 mm) with a data capacity of 16 kb (16,320 characters) were placed in the prepared samples (n = 30) (Fig. 3). Prior to insertion of the microchips in the implant abutment, an imaginary patient’s identification, dental records, and medical history were recorded on the microchip. To transfer this data, ‘Labelling Program of Fixed Implants Software’ and ‘USB (Universal Serial Bus) Chip Programmer’ hardware were used.
USB chip programmer
The electronic circuit was designed using the Altium Designer program. The prepared prototype was transferred to an FR4 plate, and fixation was completed at the soldering station (ERSA, Istanbul, Turkey). The prepared circuit was placed in a plastic housing box, HH055. In the USB Chip Scheduler hardware, a control card with a USB 2.0 type B Jack output was used. Computer connection was achieved using a USB type B cable.
Computer software preparation and virtual library creation
USB Chip Programmer software was developed for Windows X32 and Windows X64 platforms using the Delphi XE7 code development program. After the USB Chip Programmer hardware had been connected to the computer, a microchip was inserted. Information regarding the imaginary patient was entered on both the microchip and the computer.
Cementation of restorations
Microchips were covered with a Teflon band. Restorations were cemented using polycarboxylate cement (Adhesor Carbofine; Spofa Dental, Prague, Czechia), in accordance with the manufacturer’s protocols. Cement residue was removed following the completion of cement polymerisation.
Evaluation of methods
A questionnaire was prepared using a visual analogue scale (VAS) to evaluate the effect of both techniques on aesthetic appearance and to compare the applicability of the two techniques. In total, 51 dentists completed this questionnaire.
Samples prepared by labelling with the QR code were subjected to heat exchange at temperatures between − 80 °C and 910 °C, and we explored whether the recorded data could be retrieved. Samples labelled with the microchip were stored at − 40 °C for 24 h and then labelled with the QR code for 24 h at − 80 °C (Ultra-low − 86 °C Dual Cooling Freezers, MDF-U500VX; Panasonic, Kocintok Laboratory Materials Trade Corporation, Istanbul, Turkey). They were then subjected to high-temperature treatment at 120 °C, and samples labelled using the QR code were subjected to 910 °C.
Thermal cycle test
Restorations from both groups were subjected to a thermal cycle test. The restoration samples were prepared after the cement residue had been cleaned. Subsequently, they were subjected to the thermal cycle test. This assay was conducted as described previously. The water bath temperature was set between 5 °C and 55 °C, and samples underwent 2500 hot-cold thermal cycles.
Evaluation of labelling techniques in terms of aesthetics and applicability
A questionnaire was prepared using a VAS to compare the aesthetics and applicability of the two techniques. In total, 51 dentists completed the questionnaire. Applicability of the techniques, application steps, the effects on aesthetic appearance, and localisation on the restoration were evaluated in the questionnaire.
Statistical evaluation
The Statistical Package for Social Science (SPSS) program (version 16.0, SPSS Inc., Chicago, IL, USA) was used for statistical analysis in this study. A p value < 0.05 was considered statistically significant. Mann-Whitney U tests were used to compare the aesthetic and applicability evaluation results.