Fig.1
Initial situation. The patient presented with a fractured tooth 26, which had been restored one month earlier with an overlay. The patient reported cold sensitivity, but no other symptoms.

Fig.2
Clinical examination revealed insufficient material thickness in the central region of the overlay and inadequate caries removal. The decision was made to remove the restoration, restore the tooth with composite, and fabricate a new indirect overlay with uniform material thickness.

Fig.3
The initial situation was scanned using the Trios 3 (3Shape). A digital impression of the opposing arch (Lower), the unprepared maxillary arch (Upper Pre-Prep), and the occlusal records were taken. It is essential to follow the manufacturer’s scanning protocol and consider ambient lighting conditions. The dental chair light should be turned off during scanning, as excessive light may negatively affect accuracy, mesh quality, and scanning time.

Fig.4
The restoration shade was selected using the 3Shape color tool prior to tooth dehydration to avoid errors in color matching.

Fig.5
Local anesthesia was administered, and complete isolation achieved with a rubber dam (Nic Tone, Manufacturera Dental Continental, Mexico City, Mexico). The isolation should include at least one tooth distal and two teeth mesial to the tooth being restored to ensure adequate field exposure.

Fig.6
As a first step, the previous restoration was removed.

Fig.7
Residual caries was detected and removed using a caries-detecting dye (Caries Detector, Kuraray). The tooth was then prepared for an overlay, including coverage of the buccal cusps due to insufficient remaining thickness (<3 mm).

Fig.8
Cusp reduction was performed: 1.5 mm on cusps and 1 mm at the central groove.

Fig.9
A selective-etch technique was applied, with enamel etched for 15 seconds.

Fig.10
Immediate dentin sealing (IDS) was performed using a two-step self-etch adhesive (Clearfil SE Bond, Kuraray), light-cured for 20 seconds.

Fig.11
A flowable composite layer was applied over the adhesive and cured for 20 seconds. This step is known as “Resin Coating” technique, improves polymerization by increasing monomer conversion and protects the IDS layer during provisionalization and cleaning.

Fig.12
To prevent bonding of the provisional, the oxygen-inhibited layer was removed with an alcohol-moistened cotton pellet. Enamel margins were refreshed using a red-coded football bur.

Fig.13
Before scanning the preparation, the digital model was modified using the Trios cutting tool. Any artifacts or unrelated areas interfering with the margin zone were trimmed. All unnecessary data that could interfere with the rescan area must be removed.

Fig.14
The preparation was then scanned. To facilitate scanning, the tip was initially positioned on the mesial adjacent teeth, and the rubber dam was stretched to clearly expose the cervical area. Once the software recognized the geometry, scanning proceeded occlusally and distally. The intraoral scan was verified by zooming, rotating, and adjusting the visualization of the virtual model.

Fig.15
One of the main challenges when using intraoral scanners—regardless of the isolation technique—is the accurate capture of preparation margins located close to the gingiva.
It is well established that, irrespective of the scanner type, preparation morphology (e.g., inlay, onlay, overlay, or full crown) and access to critical areas significantly influence scanning precision. These limitations directly impact the marginal fit of CAD/CAM restorations. As a result, digital scans that involve proximal areas tend to be less accurate than those of more conservative preparations, such as inlays or onlays. To ensure accurate margin registration, especially in interproximal areas, at least 0.3–0.5 mm of interdental space and 0.5 mm of tissue clearance are required to distinguish the margin from surrounding tissues.

Fig.16
Scanning under rubber dam isolation ensures a clean and dry environment, allowing rapid and efficient capture of the preparation without cords or hemostatic agents. The dam itself is the most effective retraction tool. In contrast, scanning after dam removal is often hindered by saliva or blood contamination, which may interrupt or delay the procedure.
One limitation is scanner handling: large scanner heads may have difficulty accessing distal areas. Additionally, exported STL files may present issues for CAM fabrication if the mesh is incomplete. Nonetheless, advances in CAD/CAM and skilled technicians often render physical models unnecessary for monolithic restorations.

Fig.17
The selected restorative material was a hybrid ceramic from Aidite, featuring a dual cross-linked resin matrix with three types of modified inorganic fillers. Its wear behavior is similar to enamel, minimizing abrasion on opposing dentition.

Fig.18
Thanks to its high strength, toughness, and dentin-like modulus of elasticity, this hybrid ceramic provides excellent load resistance. Its low water and chemical solubility contribute to sustained polish and color stability.

Fig.19
No sintering is required, allowing faster milling and finishing. The material’s natural color gradient and surface polish replicate the appearance of natural teeth. Aesthetic characterization was performed using Optiglaze (GC).

Fig.20
Immediate result of the restoration, designed in Exocad and fabricated by Rafa Jaén, TPD. The natural color gradient and the absence of a sintering phase allow hybrid ceramics to closely mimic natural teeth through simple polishing and post-milling characterization. The double cross-linked structure enhances long-term esthetic stability by reducing susceptibility to staining from dietary pigments.

Fig.21
At the second appointment, the provisional was removed and the overlay tried in. Color, interproximal and occlusal contacts were verified. After anesthetizing the gingiva, complete isolation was placed.

Fig.22
A second try-in under rubber dam isolation ensured marginal adaptation. If seating issues occurred without clamp or dam interference, wooden wedges were used to counteract tension-related displacement. The restoration exhibited continuous and smooth margins, reducing microleakage and the risk of secondary caries.

Fig.23
Adjacent teeth were protected using preformed matrices secured with wedges. Air abrasion with 27 µm aluminum oxide for 10 seconds was performed to clean the abutment and activate composite monomers.

Fig.24
The tooth was cleaned with 37% phosphoric acid for 60 seconds and enamel etched for 30 seconds. After rinsing and drying, silane (Monobond Plus) was applied and left for 5 minutes. A non-filled adhesive was applied and left uncured to avoid potential misfit of the restoration.

Fig.25
The hybrid-ceramic restoration was previously cleaned with alcohol before adhesive protocol. Air-abraded with 27 µm aluminum oxide, etched with 37% phosphoric acid for 60 seconds, rinsed, dried, silanized, and coated with a layer of non-filled adhesive left uncured to prevent misfit.

Fig.26
A preheated composite (Empress Direct, Enamel A1) was used as luting material. After placement, excess was removed and the restoration was tack-cured for 5 seconds. Floss was used to remove the interproximal excess.

Fig.27
Final curing for 60 seconds per surface completed the bonding procedure.

Fig.28
To eliminate the oxygen-inhibited layer and prevent staining, a hydroalcoholic gel was applied to cover the restoration, preventing oxygen contact during polymerization.

Fig.29
The bonding interface was mechanically cleaned with a microbrush for 20 seconds. The cloudy appearance within the gel corresponded to unpolymerized monomers from the oxygen-inhibited layer. The area was then rinsed, suctioned, and dried.

Fig.30
Margins were finished using a coarse rubber disc (EVE Diacomp Twist system).

Fig.31
Final polishing was done with a fine rubber disc (EVE Diacomp Twist system).

Fig.32
Final result after finishing and polishing

Fig.33
Final occlusal adjustment was performed using the PIC system during functional movements. Adjustment areas were repolished to complete the case.

Fig.34

Conclusions

Accurate digital capture of preparation margins is essential for the long-term success of indirect restorations. Multiple factors influence this accuracy, including scanner optical technology, finish line design and depth, soft tissue management, and intraoral conditions during scanning.
Scientific evidence indicates that intraoral scanners require a minimum gingival displacement of 0.3–0.5 mm to reliably capture subgingival or interproximal margins. While this value may vary slightly among systems, it remains clinically significant. Even high-performance scanners benefit from optimal isolation and margin exposure, as direct visibility remains a key limiting factor regardless of resolution.
The protocol presented demonstrates how intraoral scanning under rubber dam isolation enhances clinical efficiency within a digital workflow. This approach provides a clean, dry working field and acts as an effective retraction method. Unlike conventional techniques, which are highly sensitive to contamination, rubber dam isolation enables uninterrupted scanning—even in deep or narrow areas—without the need for retraction cords or hemostatic agents.
The combination of proper margin design (e.g., rounded shoulder), strict adherence to scanning protocols, and absolute isolation results in significantly improved marginal accuracy and workflow efficiency. This digital protocol not only enhances the quality and fit of CAD/CAM restorations but also reduces treatment time and minimizes biological complications.

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