Grooves and Contacts on Implant Crowns — Morphology for Soft Tissue Health

An implant crown is not the same as a crown on a natural tooth. The lack of cementing agent, different soft tissue biology, and different subgingival contour all influence the morphology of the restoration that the laboratory must design. Incorrect morphology leads to soft tissue inflammation, which the clinician will notice only after several months.

Why the morphology of an implant crown is more challenging than a natural tooth

A natural tooth has cementum, a fibrous connection to the gingiva and periodontium. Soft tissue "attaches" to the tooth. An implant has a hemidesmosomal connection to titanium – weaker, more susceptible to damage from incorrect subgingival contours.

Three critical areas in implant morphology:

1. Emergence profile – the shape of the crown between the abutment platform and the gingival margin
2. Proximal contour – the contact point and embrasure (space between teeth)
3. Occlusal grooves – channels draining fluids during mastication

Emergence profile – key to healthy gingiva

The emergence profile is the cross-section of the crown just above the abutment platform. Three types:

General rule: subgingivally – slightly concave or neutral profile. Supragingivally – matched to the natural aesthetic appearance of the tooth. An overly convex subgingival profile = pressure = recession = exposed abutment metal.

The laboratory shapes the emergence profile on a model with an implant analog. Therefore, a correct model with an impression transfer is mandatory.

Occlusal grooves and their role in biodynamics

Grooves are not just an element of masticatory morphology – they are hydrodynamic channels. During chewing, salivary fluids circulate through the grooves and embrasures, cleaning the proximal space. A crown without grooves = fluid stagnation = plaque accumulation.

Designing grooves on an implant crown:

• Main grooves (central and lateral) – depth and width as on a natural tooth
• Avoid flat occlusal surfaces – no grooves = no drainage
• Grooves should "open" onto proximal embrasures

In practice: a crown with well-designed grooves has significantly better self-cleaning ability than a crown with simplified morphology, which many laboratories default to for CAD simplification.

Proximal contacts at the implant – what to avoid

A proximal contact is the point of contact between a crown and an adjacent tooth. With an implant:

Too strong contact (tight contact): risk of printing during cementation/screwing; hinders flossing; lateral pressure on the interdental papilla.

Too weak contact or no contact: food impaction – food gets wedged between the crown and the adjacent tooth; inflammation of the gingival papilla.

Proper proximal contact:

• Dental floss passes with slight resistance (not freely, not with force)
• Contact point located in the incisal/occlusal one-third of the crown – not at the gingiva
• Facial and lingual embrasures open – allowing for hygiene

What the clinician must provide to the laboratory

• Model with implant analog – without a laboratory model with an analog, it is impossible to design the emergence profile
• Soft tissue photo – condition of the gingiva around the implant, sulcus depth
• Implant system information – brand, platform, abutment type
• Aesthetic goal – for anterior teeth: width and shape of natural adjacent teeth