Dental implant Hybrid abutment is also known as the H abutment
Hybrid abutment is an abutment with a titanium section that is against the dental implant and a ceramic section over it to hide the metal. The H abutment is often specifically a lithium disilicate sleeve that the lab lutes to the titanium base.
Hybrid abutment IDT 2012 Vol 3 Issue 6 – a Ti-Zi or Ti-emax hybrid. 3M and several other companies manufacture different versions, but I feel the custom hybrid abutments that the labs make are the best.
Ideal custom abutment…
- The same shape as the natural tooth at the original gumline. That is rectangular for anteriors, oval for canines and premolars and rectangular for molars.
- The emergence profile is trumpet shaped.
- Margin is at or slightly below gingiva on facial
- Margin slightly above gingiva IP and on lingual
- The height of the abutment is more than 2mm. Chen JPD 2019
There is a balancing act when it comes to how smooth the abutment should be. Extremely smooth abutments appear to reduce bacterial colonization they also reduce adherence of fibroblasts. Titanium is better at least at the interface. The height should be as tall as possible and preferably more than 2mm. Internal conical (Morse taper0 and internal hex have the least microleakage. The abutment needs to create an environment where the resulting crown does not convex uncleansable surfaces. Mahn 2019 Compendium
The H abutment is an abutment consisting of emax sleeve that we lute to a Ti abutment IDT 2013 Feb
- Ti base and chimney (4mm and emax part no more than 2x chimney height) sandblast 50 um
- Universal primer like Monobond Plus
- Custom stained Emax abutment – HF etch and Monobond Plus
- Opaque shade of LC cement extra oral
- Clean, HF, phosphoric etch, silane, bond, emax abutment and emax crown
Why do you not use pure zirconia abutments?
Pure zirconia for a dental implant abutment is not a good idea for two main reasons. First of all the abutment is more likely to fracture. The second is that the two materials will wear against each other and will damage the internal aspect of the dental implant.
Zirconia abutment damages the internal aspect of the dental implant more than titanium abutment. Gehrke JPD 2016
Material Research IJOMI=The highest fracture resistance was obtained with titanium abutments restored with emax crowns. This study is also in JADA
Hybrid abutment with porcelain stacked on titanium
Design of a custom abutment
For anterior teeth where esthetics are critical, the abutment design will influence the gingival height. It has been shown that overcontouring will generally cause apical positioning of the gingival margin, while undercontouring will cause a coronal position. For posterior teeth where esthetics are less critical, everyone has their favorite design. We like the chart below to show how you want the custom abutment to look, although most companies have very similar things for dentists to use. Some of this will be influenced by how your custom healing abutment looks.
Critical contour vs subcritical contour.
Critical area is the area area of the implant abutment and crown located 1mm apical to the gingival margin. This may be on the crown, on the abutment, or both depending on the location of
the finish line. The subcritical contour is everything apical to the critical contour. For the most part we just need to ensure we provide “running room”, which is the distance from the implant neck to the ginigval margin. This area allows for the establishment of the proper cervical contour. As this area moves facially, the gingival margin will migrate apically. On the other hand, when the critical contour is moved lingually, coronal migration of the gingival margin should be anticipated.
Alteration of the sub-critical contour within a certain physiologic range will not alter the gingival margin level significantly. However, one can over-contouring the facial subcritical contour beyond the range of physiologic tolerance. This will result in gingival edema and possible sinus tract formation. Ultimately, gingival recession may occur.
Increasing the convexity of the critical and subcritical contour may squeeze the interdental papillae, causing an increase in height of 0.5 to 1.0 mm, provided there is sufficient inter-dental space. When the interproximal critical contour is altered, the shape of the implant crown will become square. Modifying only the subcritical contour may achieve a similar outcome while preserving ideal crown form. Care must be taken to avoid impinging the adjacent alveolar bone while altering the interproximal subcritical contour. Su has a great article on the topic. Critical-Contour-Su