Polytetrafluoroethylene Isolation of the Periodontal Sulcus for Cementation of Full Veneer Restorations Using a Biologically Oriented Preparation Technique (BOPT): An In Vitro Study

Abstract

Background: Prosthetic cementation using the biologically oriented preparation technique (BOPT) presents challenges in removing excess cement from the gingival sulcus, due to the absence of a finishing line and the impossibility of using absolute isolation with a rubber dam. This study aimed to evaluate the effectiveness of relative isolation using polytetrafluoroethylene (PTFE) tape in reducing cement retention during BOPT cementation. Methods: Fifteen 3D-printed resin models were created from an intraoral scan of a patient restored with BOPT in both upper central incisors. Each model included removable gingiva. Splinted polymethylmethacrylate (PMMA) provisional crowns were fabricated and cemented with temporary cement. One central incisor was isolated with PTFE (0.1 mm or 0.2 mm), while the contralateral tooth was left unisolated as a control. After debonding, digital scanning and volumetric analysis using root mean square (RMS) deviation were performed to quantify retained cement. Paired t-tests were applied to compare groups. Results: The mean RMS for the PTFE group was 0.1248 ± 0.0519 mm, compared to 0.1973 ± 0.0361 mm in the non-isolated group (p < 0.001). No significant difference was found between PTFE thicknesses of 0.1 mm and 0.2 mm (p = 0.388). Conclusions: PTFE tape is effective for relative isolation when rubber dam placement is not feasible in BOPT restorations. Further clinical studies are recommended to confirm these findings in vivo.

Keywords: BOPT; PTFE; cementation; isolation; vertical tooth preparation.

Figure 1

The design of the models incorporates removable gingivae and splinted provisional prostheses. Figure (a) shows the digital model with the provisional. Figure (b) shows the digital model with the tooth preparations and figure (c) shows the sagittal section of the digital model.

Figure 2

Resin model, gingiva and provisional prosthesis. (a) Digital printed model of tooth preparations without removable gingiva. (b) Digital printed model of tooth preparations with removable gingiva. (c) Digital printed model of tooth preparations with provisional restorations.

Figure 3

Scanning of the model.

Figure 4

PTFE tape of two different thicknesses: 0.1 mm and 0.2 mm.

Figure 5

PTFE tape adapted to the sulcus of tooth 1.1, while tooth 2.1 was left untouched. (a) Starting the adaptation of the PTFE tape in the preparation. (b) The PTFE was then placed inside the sulcus with the help of a composite spatula. (c) Final adaptation of the PTFE tape in the sulcus.

Figure 6

Placement of retraction cord to adapt the Teflon tape to the inner wall of the gingival sulcus. (a) Starting the insertion of the retraction cord. (b) Using a specific instrument, the cord was inserted which enabled the adaptation of the Teflon tape to the internal wall of the gingival sulcus.

Figure 7

Isolation of the mesial, buccal, lingual, and distal tooth surfaces of the upper right central incisor.

Figure 8

Syringe with Tempbond temporary cement.

Figure 9

Placement of the temporary crowns with cement on the abutments.

Figure 10

Vestibular and incisal view of the sulcus: 1.1 (with Teflon) and 2.1 (without Teflon).

Figure 11

Scanning of the initial model. The STL1 file corresponds to the model prior to cementation.

Figure 12

Scanning after cementation. The STL2 file corresponds to the model with cement that used the 0.1 mm PTFE tape and the control group.

Figure 13

Image of the area selected to run the best fit algorithm.

Figure 14

Details of the generation of the new mesh corresponding to the gingival sulcus area. The union of the external and internal curves is drawn in the software.

Figure 15

Color map with RMS values.

Figure 16

Lower cement retention in the Teflon group (RMS 0.1248 mm) compared to the control group (RMS 0.1973 mm).

Figure 17

There are no significant differences between the two PTFE thicknesses.