Bjørn Einar Dahl

• Sagen, Mina Aker & Dahl, Bjørn Einar (2022). Resin-baserte sementer – egenskaper som påvirker klinisk suksess av indirekte restaureringer. Den norske tannlegeforenings tidende. ISSN 0029-2303. 132(9), p. 716–722. doi: 10.56373/2022-9-4.
• Dahl, Bjørn Einar; Dahl, Jon Einar & Rønold, Hans Jacob (2018). Digital evaluation of marginal and internal fit of single-crown fixed dental prostheses. European Journal of Oral Sciences. ISSN 0909-8836. p. 1–6. doi: 10.1111/eos.12576. Show summary

  The present study used a new, digitized version of the impression replica technique, namely the dual‐scan technique, to evaluate the adaptation of single‐crown fixed dental prostheses (FDPs). Scans of the bare master model and of the master model with a silicone layer representing the cement layer were superimposed and analyzed using designated software. Single crowns produced using the lost‐wax metal casting technique were included. The cement space of the band width, 0.5–1.0 mm from the preparation margin (marginal fit), was smallest for crowns made from laser‐sintered cobalt‐chromium. The internal fit in both mesial‐distal and buccal‐palatal directions was statistically significantly better for crowns made using the conventional lost‐wax metal casting technique than for crowns produced using computer‐aided design/computer‐aided manufacturing (CAD/CAM). Fixed dental prostheses produced by milled cobalt‐chromium had the loosest internal fit. The results agree with those of our previous study of the same test specimens, in which the triple‐scan method was used, and imply that the dual‐scan method is well suited for adaptation studies.

• Dahl, Bjørn Einar; Dahl, Jon Einar & Rønold, Hans Jacob (2018). Internal fit of three-unit fixed dental prostheses produced by computer-aided design/computer-aided manufacturing and the lost-wax metal casting technique assessed using the triple-scan protocol. European Journal of Oral Sciences. ISSN 0909-8836. 126(1), p. 66–73. doi: 10.1111/eos.12394. Show summary

  Suboptimal adaptation of fixed dental prostheses (FDPs) can lead to technical and biological complications. It is unclear if the computer-aided design/computer-aided manufacturing (CAD/CAM) technique improves adaptation of FDPs compared with FDPs made using the lost-wax and metal casting technique. Three-unit FDPs were manufactured by CAD/CAM based on digital impression of a typodont model. The FDPs were made from one of five materials: pre-sintered zirconium dioxide; hot isostatic pressed zirconium dioxide; lithium disilicate glass-ceramic; milled cobalt-chromium; and laser-sintered cobalt-chromium. The FDPs made using the lost-wax and metal casting technique were used as reference. The fit of the FDPs was analysed using the triple-scan method. The fit was evaluated for both single abutments and three-unit FDPs. The average cement space varied between 50 μm and 300 μm. Insignificant differences in internal fit were observed between the CAD/CAM-manufactured FDPs, and none of the FPDs had cement spaces that were statistically significantly different from those of the reference FDP. For all FDPs, the cement space at a marginal band 0.5–1.0 mm from the preparation margin was less than 100 μm. The milled cobalt-chromium FDP had the closest fit. The cement space of FDPs produced using the CAD/CAM technique was similar to that of FDPs produced using the conventional lost-wax and metal casting technique.

• Dahl, Bjørn Einar; Rønold, Hans Jacob & Dahl, Jon Einar (2017). Internal fit of single crowns produced by CAD/CAM and lost-wax metal casting technique assessed by the triple-scan protocol. The Journal of prosthetic dentistry (Print). ISSN 0022-3913. 117(3), p. 400–404. doi: 10.1016/j.prosdent.2016.06.017. Show summary

  Objectives: To digitally study the internal fit of single crown fixed dental prostheses produced by CAD/CAM and by lost-wax and metal casting techniques. Methods: On an upper jaw simulator with KaVo typodont teeth, the left insisor was prepared for single crown. Impression and scans were taken and three copings were manufactured from each group: milled pre-sintered zirconia, milled hot isostatic pressed zirconia, milled lithium disilicate, milled cobalt-chromium, and laser-sintered cobalt- chromium using CAD/CAM technique and cobalt-chromium by the conventional lost-wax and metal casting technique. The internal fit of crowns produced by CAD/CAM technique was compared to crowns produced by metal casting technique. The internal fit was evaluated in buccal-palatinal and in mesio-distal directions using the triple-scan protocol and GOM Inspect software. Results: The internal gaps in mesio-distal and buccal-palatinal directions were statistically smaller for crowns made by conventional lost-wax and metal casting technique compared to crowns produced by CAD/CAM technique (Table 1). Conclusions: The triple-scan method revealed that single crowns made by lost-wax and metal casting technique had better internal fit than crowns produced by CAD/CAM technique.

• Tibballs, John Earl & Dahl, Bjørn Einar (2015). Computer-controlled production of prosthetic constructions in the dental office – what are the quality requirements? In Holmstrup, Palle (Eds.), Aktuel Nordisk Odontologi 2015. Munksgaard Forlag. ISSN 9788762814363. p. 141–153. Show summary

  With equipment for computer-aided design and manufacturing (CAD/CAM) in the dental office, the dentist again becomes his own dental technician. While the equipment itself is not subject to health-related regulation, the European Medical Devices Directive imposes requirements on the prosthodontic devices it produces. As a manufacturer of custom-made, medical devices, the dental office is required to document its ability to ensure that the produced prostheses function satisfactorily, and that any failure to meet the defined quality criteria is followed up systematically. The capability to analyse the cause of failure is essential to the systematic improvement of quality. In the face of market forces favouring interoperable components rather than a vertically integrated CAD/CAM system, this requirement places an increased responsibility on the dental office to use the comprehensive data generated by the CAD system to understand the reasons for a cli- nical failure or the need for rework of a prosthetic device, and to prevent recurrence of the problem. Frequently, knowledge of the behaviour of materials both during production and in the finished prosthesis is needed in order to attain the necessary understanding of sub-optimal, clinical performance.

• Dahl, Bjørn Einar & Rønold, Hans Jacob (2014). Digitale avtrykk. Den norske tannlegeforenings tidende. ISSN 0029-2303. 124(2), p. 108–114.

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• Dahl, Bjørn Einar; Rønold, Hans Jacob & Dahl, Jon Einar (2017). Internal Fit of Fixed Dental Prostheses Made From Zirconia.
• Dahl, Bjørn Einar (2017). Internal fit of FDPs made from different types of zirconia
. Show summary

  Objectives: To compare the internal fit of 3-unit fixed dental prostheses (FDP) made from two types of zirconia using the digital triple-scan protocol. Methods: On an upper jaw simulator with KaVo typodont teeth the right first molar and first premolar was prepared for 3-unit FDP. Digital impression was taken and three copings were manufactured from each group; milled hot isostatic pressed zirconia and milled pre-sintered zirconia using CAD/CAM technique. The internal fit of the FDPs of the two groups was evaluated in buccal-palatal and distal-mesial directions using the triple-scan protocol described by Holst et al. and GOM Inspect software. The statistical analysis was performed with a spreadsheet (Excel 2011 for Mac v14.6.2; Microsoft Corp) using the Student t test (α=.05). Results: The internal gaps in buccal-palatal and distal-mesial directions were larger than the manufacturer´s settings for the production of the copings. No statistically significant differences were observed between the different materials and between first molar and first premolar copings. Conclusions: The triple-scan method revealed that the internal fit of FDPs made by milled hot isostatic pressed zirconia and milled pre-sintered zirconia were not statistically significant different.

• Dahl, Bjørn Einar (2016). Internal fit of single crowns produced by CAD/CAM 
and lost-wax metal casting technique assessed 
by the triple-scan protocol
. Show summary

  Objectives: To digitally study the internal fit of single crown fixed dental prostheses produced by CAD/CAM and by lost-wax and metal casting techniques. Methods: On an upper jaw simulator with KaVo typodont teeth, the left insisor was prepared for single crown. Impression and scans were taken and three copings were manufactured from each group: milled pre-sintered zirconia, milled hot isostatic pressed zirconia, milled lithium disilicate, milled cobalt-chromium, and laser-sintered cobalt-chromium using CAD/CAM technique and cobalt-chromium by the conventional lost-wax and metal casting technique. The internal fit of crowns produced by CAD/CAM technique was compared to crowns produced by metal casting technique. The internal fit was evaluated in buccal-palatinal and in mesio-distal directions using the triple-scan protocol and GOM Inspect software. Results: The internal gaps in mesio-distal and buccal-palatinal directions were statistically smaller for crowns made by conventional lost-wax and metal casting technique compared to crowns produced by CAD/CAM technique. Conclusions: The triple-scan method revealed that single crowns made by lost-wax and metal casting technique had better internal fit than crowns produced by CAD/CAM technique.

• Dahl, Bjørn Einar (2020). Mind the gap - internal fit of fixed dental prostheses. Universitetet i Oslo. ISSN 978-82-8327-043-3.

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