Treatment
Reference
Number of quotation (PubMed in 3.12.2014)
Calcium
Sodium p-glycerophosphate and calcium acetate
Ishizawa et al. [7]
221
Calcium glycerophosphate
Suh et al. [8]
62
Calcium acetate and calcium glycerophosphate
Li et al. [9]
73
Calcium acetate and calcium glycerophosphate
Laurindo et al. [10]
−
Sulfuric acid
Sulfuric acid
Veleten et al. [11]
127
Sulfuric acid
Zhao et al. [12]
94
Sulfuric acid
Peterson et al. [13]
−
Sulfuric acid
El-wassefy et al. [14]
−
Phosphoric acid
Phosphoric acid, hydrogen fluoride, and sulfuric acid
Phosphoric acid and sodium fluoride
Hieda et al. [15]
−
Hydrogen fluoride
Hydrogen fluoride
Puckett et al. [16]
108
Hydrogen fluoride
−
Hydrogen fluoride
−
Sodium hydroxide
Sodium hydroxide, calcium hydroxide, phosphoric acid, and acetic acid
Sul et al. [4]
255
Sodium hydroxide
−
).
On behalf of anodized surfaces, the TiUnite surface was introduced in 2000 by Nobel Biocare. The TiUnite surface is an anodized surface, which presents with good osseointegration [17]. The TiUnite surface features a moderately rough, thickened titanium oxide crystalline layer with phosphorus content. During anodizing, the gas included in the titanium oxide layer of the implant is discharged, pores are formed, and it is believed that the surface area is increased.
The ceramic-like properties and micropores of TiUnite ensure high osteoconductivity and fast anchorage of newly formed bone compared with the turned surface [18]. The negatively charged TiUnite surface attracts blood proteins and inactive platelets immediately after implant insertion. Simultaneously, fibrils from the fibrin meshwork become visible. The platelets begin to swell and form pseudopodia. By releasing adenosine diphosphate (ADP), they become sticky and clump together to close the injured blood vessels at the wound edges and stop the bleeding. The newly formed fibrin matrix allows the blood to clot. Activated platelets become embedded in the matrix and release granules full of enzymes as well as growth factors needed for wound healing and bone formation. Blood cells, activated platelets, and fibrin form a blood clot that adheres to the moderately rough TiUnite surface. It is crucial for contact osteogenesis that the blood clot remains attached to the surface [19]. Neutrophils and, later, macrophages remove the blood clot during the first 2 days of wound healing, enabling a provisional matrix to occupy the wound area. Osteogenic cells stream to the TiUnite surface and migrate – using their pseudopodia and the open pores as attachment points – to the bone-formation front, where they transform into osteoblasts. Newly formed bone spreads over the osteoconductive TiUnite surface and forms a thin band of woven bone deposited directly on and along the surface. This thin bone layer will grow by further bone apposition and become lamellar bone. Bone-forming osteoblasts attach to the TiUnite surface with their pseudopodia and cover the orifices of the open pores [20]. They start to secrete the collagen matrix of woven bone directly into the pores and move away from the surface, forming the collagenous bone matrix that will eventually mineralize.
Numerous in vitro examinations have been carried out, and various properties such as the surface energy, variation in surface texture at the nanolevel, increase in infiltration, and chemical stability have been reported [21, 22]. Despite these in vitro studies, no definite clarification has been made regarding the biological basis for the acceleration of osseointegration which is recognized in vivo.
TiUnite Surface After Implant Insertion
When the implant is placed in the jaw bone, the inserted portion of the TiUnite surface is polished by the bone. This results in a several-micron-thick smear layer composed of bone debris and blood, which has osteoinductive potential because of the presence of growth factors needed for bone formation [23]. However, since this smear layer covers the implant surface, it may be argued that the properties of the TiUnite surface itself do not have any remarkable influence on either the initial wound healing or the subsequent bone formation. The macro design of the implant, the degree of surface roughness, and the drilling protocol are considered to influence the existence and amount of the smear layer. When the diameter in a cervical section in the extraction socket is greater than the implant diameter, no smear layer occurs over the implant surface. However, the TiUnite surface implant still accelerates the bone-healing process, compared to nontreated titanium surfaces, even in the absence of a smear layer; this implies that the surface properties of the implant itself also improve healing [23].
TiUnite Surface and Integration to Surrounding Tissue
The observations described in the section above clarified the biological basis for osseointegration and in particular explain the high predictability of osseointegration of implants with TiUnite surfaces. The TiUnite surface is well studied and also has a very long clinical history in the field of implant dentistry.
Direct adhesion between titanium implant surface and surrounding soft tissue is said to be promoted when the epithelium in the periphery of the implant attaches to the surface through the hemidesmosome. Cellular soft tissue adhesion behaves similarly to soft tissue around a natural tooth [24]. Research into the implant surface originally focused on promotion of osseointegration, and TiUnite surface processing was only applied to the part of the implant intended to be embedded inside the bone. However, in recent years, sealing of the peripheral edge via direct adhesion to implant surfaces by fibrous and epithelial cells is desired [25], and use of implants with TiUnite surface treatment on the top section of the implant has also begun.
Reports About TiUnite
Changes Between Turned and TiUnite Surfaces
Many in vivo and in vitro studies involving the surface properties of oxidized implants have overlooked the fact that the electrochemical-microarc oxidation (MAO) process used for oxidized implants not only alters surface roughness but also changes the surface chemistry, pore configuration (pore size, density, morphology), and crystal structure of TiO2 [25, 26]. These studies found that when the initial implant stability values were very high, the degree of osseointegration increased only slightly or sometimes even decreased at early healing times, while when the implant stability at placement was lower, the subsequent stability increased rapidly over time [25]. From a biological perspective, this discrepancy could be explained in part by the fact that dissimilarities in bone properties (density, volume, thickness, architecture, and associated modeling/remodeling) between experimental animals (rabbit, dog, goat, pig, and sheep) and between different bones in humans (mandible, maxilla, anterior, and posterior area) have a strong impact on the various measurements.
In the first clinical studies reporting the success of osseointegrated implants, the survival rates of Brånemark implants (Nobel Biocare, Gothenburg, Sweden) were 86 % in the mandible and 78 % in the maxilla after 15 years of function in completely edentulous arches [27]. The survival rates of this implant system have improved in recent years, after the surface of the Brånemark implant system was changed from a turned surface to the TiUnite surface. As discussed above, this surface is characterized by many open pores in the low micrometer range [28], which are thought to improve the bone-to-titanium surface contact. The survival rate for the TiUnite surface implants was shown to be higher (98.6 %) than that for Brånemark implants with turned surfaces (92.1 %) [29]. The overall survival rate of the TiUnite implants in this study compares favorably with previous reports.
Why do turned and TiUnite implants produce such different results in clinical studies? In the clinical field, each dentist might have subjective thoughts on the relationship between the risk of implantitis and the type of implant surface. Charalampakis et al. [30] showed that, following ligature placement (to induce plaque formation) and subsequent ligature removal 10 weeks after placement, the total bacterial load increased over time for each of the groups in their study (tooth, implant with turned surface, and TiUnite implant) [30]. The TiUnite implants with enhanced surface characteristics (micropores obtained via electrochemical oxidation) were introduced by Nobel Biocare to accelerate the osseointegration process. Several studies have indeed clearly confirmed this accelerated healing and bone-to-implant contact [28, 31, 32]. Therefore, TiUnite implants showed a clear decrease in early failure, especially in areas with poor bone density such as the maxilla [33, 34]. Nobel Biocare’s new treatment concept, All-on-4™, has been studied by many groups (Table 10.2). This concept uses two axial implants in the anterior region and two tilted posterior implants as has been published by Malo et al. with cumulative survival rates well above 92.2 %. This concept based on only four implants per arch is able to provide an edentulous arch with an immediate function fixed aesthetic provisional prosthesis [41–43]. However, it has been suggested that the higher incidence of retrograde peri-implantitis for TiUnite implants can also be explained by faster osseointegration [44]. When the turned implants come into contact with a granuloma or endodontic pathology, they will soon be completely surrounded by granulation tissue; however, the TiUnite surface implants will not have the same fate, because of the accelerated bone apposition. As such, the coronal part of the TiUnite implant still integrates before the fibrous encapsulation can reach this area. Although this hypothesis still needs to be proven by further research, it is consistent with some experimental observations.
Short-Term Clinical Findings
Preclinical studies show that the speed of osseointegration is enhanced for TiUnite-coated implants compared with the turned surfaces implants. This effect was measured as an increase in bone-to-implant contact at a given time point. In fact, the surface properties of TiUnite stimulate bone growth directly on its surface. Compared with turned surfaces, clinical findings demonstrate that the drop in initial stability during the healing phase was significantly reduced with implants featuring TiUnite [45]. The benefit of this observation is that the risk over the first 6 months is significantly reduced. Bone formation follows the contours of the threads of the implant even during the early phase of healing.
This yields higher maintained initial stability than that offered by implants with a machined surface. During its first 5 years on the market, more than 84 scientific publications documenting in vitro investigations as well as preclinical and clinical studies have been generated. These support the clinical success of TiUnite implants in two-stage procedures as well as for immediate loading protocols, and for all types of bone qualities.
Long-Term Clinical Findings
Of the 84 publications, five recently published studies demonstrate the long-term stability of TiUnite [46, 47]. In these, more than 550 TiUnite implants of different designs demonstrated a cumulative survival rate of 94–100 %. Follow-up periods were at least 2 years, and implants were inserted in both immediate function and two-stage protocols. The report by Glauser et al. is a 5-year follow-up of immediately loaded TiUnite implants in regions of soft bone finalized in 2007, which confirms the long-term stability of TiUnite implants [47]. What is more, TiUnite stability had cleared by clinical reports over a period of 10 year by Ostman et al. and Degidi et al. [48, 49].
In these publications, which demonstrated an implant survival of more 97 %, it was shown that TiUnite implants are clinically stable over the 10-year period. In other words, no drop in the clinical stability, as measured by resonance frequency analysis (RFA), was observed. Furthermore, these reports show that bone levels around TiUnite implants remain stable for long term. Albrektsson et al. concluded on their paper that TiUnite implants do result in somewhat greater first year crestal bone loss than the other modern implants, but as observed in a recent paper, TiUnite develops a steady-state situation with respect to further bone loss with good clinical long-term results with maintained bone levels [50].
Representative Dental Implants Used in Clinical Research
Is the success rate of TiUnite implants different from those of other dental implants? Polizzi et al. [51] reported that the treatment outcome for implants with TiUnite surfaces was entirely different from that observed for other implant types [51]. Two TiUnite implants were lost after surgical treatment of peri-implantitis, and radiographic and histological analyses of remaining sites revealed that continuous bone loss occurred and that large inflammatory lesions persisted in the peri-implant soft tissues. However, the longer-term findings from Polizzi’s study confirm the favorable results that were previously mentioned and those subsequently published by other authors [44, 52]. In 2004, Cornelini and colleagues reported on the immediate restoration of 30 unsplinted transmucosal International Team Implantology (ITI) solid implants with a sandblasted, acid-etched surface (Straumann Institute, Waldenburg, Switzerland) in mandibular molar sites [53]. In that study, only one implant was lost during the 1-year follow-up period, resulting in a 96.7 % survival rate after 12 months. They concluded that, in the molar mandibular area with good implant primary stability, this protocol of immediate restoration can be safe and successful.
In 2007, Rao and Benzi published a report on single, mandibular first-molar implants (Replace Select Tapered TiUnite) placed with flapless guided surgery and immediately loaded with premanufactured individualized abutments and crowns [54]. All 51 tapered implants placed were stable and functioning after 1 year, providing a 100 % survival rate.
More recently, Schincaglia and colleagues published the findings from a randomized controlled study comparing immediate versus delayed loading of wide-body implants (TiUnite Wide Platform MK III) supporting single-unit restorations in the molar area [55
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