Editor’s note: Original article, published 2018, updated September 2020 for information on new surfaces.

Titanium has been long established as the standard bearer for dental implant material. However, when considering the factors that can affect dental implant success both long and short term, one of the most crucial is undoubtedly the implant’s surface.

In this article, we explain the importance of surfaces, compare different types of dental implant surfaces, and explore recent developments in anodized surfaces – for implants and abutments – that have been introduced with the Xeal™ and TiUltra™ surfaces.*

Why dental implant surface matters

At first glance, titanium might seem a strange choice for dental implant material. Though it has high strength, great biocompatibility, low level of toxicity potential and high resistance to corrosion, titanium in its pure state is highly reactive.1 When it interacts with oxygen, however, a surface layer of titanium oxide (TiO2) is formed, stabilizing the surface and allowing osseointegration to occur.2

Surface has an important role in healing time for osseointegration and, ultimately, the success of implant treatment.3 It is the only part of the implant exposed to the surrounding oral environs, and its chemical, physical, mechanical, and topographic surface characteristics are all crucial to maximizing the likelihood of successful osseointegration.3

TiUnite dental implant

Figure 1 Scanning electron microscopy image showing a dense blood coagulation at the surface of the anodized TiUnite™ implant. Blood coagulation is the first step of the peri-implant bone healing; a strong initial reaction indicates the osteoconductivity of this anodized surface.

Developments in implant surface modification

Today, there is a wide range of titanium dental implant surfaces. P-I Brånemark’s initial implants over 50 years ago had a smooth, turned surface, and as he described, they require three to six months of healing before successful implant loading can take place.4

Since then, the design of dental implants and their surfaces have frequently changed and evolved over time to allow for improved osseointegration and better long-term implant survival rates. There are three distinct groups of methods through which implant surfaces can be modified at manufacture.

  • Mechanical treatments: These include grinding, blasting and machining to create rougher or smoother surfaces.
  • Chemical treatments: Conducted with acids, alkali, sol gel or through anodization, among other methods, chemical treatments alter the implant surface’s roughness and composition and enhance surface energy.5
  • Physical treatments: These treatments include plasma spraying and ion deposition.

Some of the more common titanium implant surface treatments used in recent years include anodization, and blasting and acid etching. Anodization, which works by increasing the thickness of the implant’s TiO2 layer, moderately roughening it, and improving osteoconductivity, has been shown to enhance osseointegration.6,7,8 Sandblasting and acid etching, on the other hand, removes parts of the implant material, creating small irregularities and a roughened surface that can encourage rapid osseointegration.9

Sandblasted acid-etched dental implant surface compared to anodized.

Figure 2 Low (top) and high (bottom) magnified scanning electron images of dental implants produced with different methods: anodization (left) and sandblasting-acid etching (right). While methods result in a microrough topography favorable for osseointegration, they vary in morphology and composition.

Confocal microscopy image from TiUnite

Figure 3 Confocal microscopy image of blood components adhered and reacted to an anodized implant surface (TiUnite). Blood cells and proteins immediately attach to the surface and initiate the coagulation process leading to the formation of fibers mainly composed of a blood plasma protein – fibrin – and platelets. These fibers grow into a dense network which is the provisional tissue that will support bone healing around the implant.

Though these treatment methods vary, their intended outcome remains the same: To provide a strong biological and mechanical connection to the alveolar bone in a short time period and, ultimately, reduce the likelihood of implant failure.10 Despite the range of implant surfaces being developed over many years, their relative rates of long-term success have only recently been significantly compared.

Confocal microscopy, 3D reconstruction of the early blood-to-implant surface interface

Figure 4 Confocal microscopy, 3D reconstruction of the early blood-implant surface interface. The blood components adhere immediately and over the whole implant surface. Fibrin fibers, early sign of the formation of a blood coagulum span between threads of the implant.

Study comparing types of dental implant surfaces

A 2018 study, led by Professor Ann Wennerberg, sought to correct this gap in the literature through a systematic review of the long-term clinical outcomes of implant treatment with different surfaces. The study showed that implants with the anodized surface showed the best survival rate (98.5%) with at least 10 years’ follow-up.10

Comparing the performance of implants with anodized, blasted, turned, titanium plasma-sprayed, and sandblasted and acid-etched surfaces, Wennerberg found that there was a mean marginal bone loss for all implant surface types in the study of less than 2 mm, even for implants with older designs and surfaces, and well within what is considered to be an acceptable level.11

Largest ever meta-analysis of a single implant brand

In their 2017 study, Profs. Mattias Karl and Tomas Albrektsson analyzed outcomes from 4,694 clinically evaluated patients treated with 12,803 anodized TiUnite implants reported in 106 studies.12

Their results confirm that implants with the anodized TiUnite surface have a remarkably low early failure rate and very good long-term survival; at implant level, the projected survival rate was over 99% after one year, and 95.1% after 10 years.** As one of the most clinically researched implant surfaces on the market,13 TiUnite has been proven to enhance osseointegration8 and maintain implant stability during the critical healing phase.14 As a result, it is able to play a vital role in assisting clinicians to meet patient demands for shorter time-to-teeth.

Entering the Mucointegration™ era: Developments in anodized surfaces, with Xeal and TiUltra

Building on the substantial evidence showing the success of anodized implants, research has explored ways to further utilize this technology. This culminated in the recent introduction of the Xeal and TiUltra surfaces, which apply anodization to the full implant–abutment system.

The development of these surfaces looked beyond just microroughness for osseointegration. It investigated ways in which chemistry, nanostructure and porosity/morphology could be tailored to enhance cell attachment, and, to do so at every level – from cortical and cancellous bone osseointegration with the implant, to a soft tissue Mucointegration™ process with the abutment.

Dental implant surface and abutment surface

Figure 5 Xeal abutment surface: Smooth surface (Sa ~ 0.2 µm) and non-porous, with enhanced surface chemistry, and a nanostructured oxide layer that results in a golden hue.
TiUltra implant collar: Minimally rough (Sa ~ 0.5 μm) and ultra-hydrophilic, with a nanostructured oxide layer.
TiUltra implant body/apex: Moderately rough and ultra-hydrophilic, with gradual change in topography (from Sa ~ 0.9 to 1.4 μm), and a low-to-high pore density.

Smooth abutment surface for the Mucointegration™ process

Xeal is a smooth, non-porous, nanostructured abutment surface. Dense soft-tissue contact with an abutment can act as a barrier to protect the underlying bone and is the basis for long-term tissue health and stability. With this in mind, Xeal’s surface chemistry and topography were designed to promote soft tissue attachment.15 In clinical and non-clinical studies comparing Xeal-surface abutments with a machined surface, a significantly faster proliferation of human gingival epithelial cells has been observed on the Xeal surface,16and in a randomized, controlled prospective clinical trial, it demonstrated:

  • Significantly higher keratinized mucosa – (2.37mm vs 1.79mm for control (p= 0.024)) 17
  • Significantly lower soft tissue bleeding upon abutment removal (P = 0.006)17
  • 4× less bacteria – (primary endpoint, not significant)17
  • Stable bone levels17

 

More than roughness – The multi-zone TiUltra™ implant surface

TiUltra is an ultra-hydrophilic, multi-zone surface with a gradual change in topography from collar to apex.15 At collar level it is minimally rough (Sa ~ 0.5 μm) and non-porous, with a nanostructured oxide layer. It then transitions to the apex in terms of roughness (from Sa ~ 0.9 to 1.4 μm), and a low-to-high pore density.15

Studies have shown that human mesenchymal stem cells adhere to and proliferate on each area equally15 (in vitro) and all implant zones osseointegrate with high bone-to-implant contact (in vivo).19

Human mesenchymal stem cells on TiUltra dental implant surface

Figure 7 Human mesenchymal stem cells adhere to and proliferate on all TiUltra implant areas equally. All implant zones osseointegrate with high bone-to-implant contact.(15,19)

LEARN MORE ABOUT NEW SURFACES


The Xeal abutment surface is now available for the On1™ Base and Multi-unit Abutments, and the TiUltra surface on NobelActive®, NobelReplace CC®, and NobelParallel CC™. These surfaces are also a feature of the new Nobel Biocare N1™ implant system, available in select markets in Europe.

* Some products may not be regulatory cleared/released for sale in all markets. Xeal and TiUltra not available in the US.
**Results of regression analysis. Details can be found in full publication.

References

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Posted by Chris Kendall