Evaluation of osseintegration between traditional and modified hydrophilic titanium dental implants - Systematic analysis.

The aim of the study was to conduct a systematic review to access the osseointegration between traditional and modified Hydrophilic Titanium Dental Implants for period of 10 years. PUBMed articles were searched from last ten years up to 15/12/2019 from which 24 studies included in this review. This systematic review compiles the data about osseintegration in hydrophilic titanium implants in human trials. It sheds light on the mechanism of integration of hydrophilic surfaces and numeric data to support the purpose of the review. Copyright:

INTRODUCTION

Dental implants are root analogs that take the form of a root embedded in the bone tissue. The major factor that determines the success of dental implantation is osseointegration.[1] The texture and the properties of the implant surface determine the amount of bone-implant contact (BIC), in turn determining the osseointegration, implant stability, and longevity of the restoration.

A series of different techniques and materials have led to the constant evolution of implant surfaces, from smooth to micro rough, followed by nano rough to hydrophilic surfaces. Hydrophilic surfaces are the latest development in broad-spectrum implant surface characteristics. Most studies have found that hydrophilic surfaces tend to enhance the early stages of cell adhesion, proliferation, differentiation, and bone mineralization compared to hydrophobic surfaces.[23] SLAactive, Photo-functionalized, and Electro-wetted implant surfaces are the hydrophilic surfaces that are commercially available.

Literature has lacked systematic studies of hydrophilic dental implants. We have taken this opportunity to conduct a systematic review of clinical trials conducted on hydrophilic titanium dental implants.

MATERIALS AND METHODS

An electronic search was carried out on PubMed database with the following search terms-Hydrophilic Dental Implants, Modified Dental Implant Surfaces, Hydrophilic Dental Implant Surfaces, Hydrophilic Titanium Dental Implants.

The PRISMA guidelines by the Cochrane library for the formulation of the systematic review were followed.[4]

A total of 2071 articles were obtained on the PubMed database. The authors screened through the abstract and eliminated 981 duplicate articles. 1082 articles were screened from which 984 articles were eliminated. Through this method, 98 full-text articles were assessed for eligibility, of which 74 articles did not belong to the inclusion criteria of this review. A total of 24 articles were included in the study.

Inclusion criteria

Articles published in thepast 10 years up to December 15, 2019

Studies conducting human trials

Studies using dental implants

Studies using hydrophilic implant surfaces.

Exclusion criteria

Any study published before 2009

Studies using nondental implants

In vitro and animal studies.

PICOT

The studies were included in the review following the picot research criteria as follows:

Population-clinical trials conducted on adult humans of either sex

Intervention-placement of endosseous root-form hydrophilic or modified wetted surface implants in the human jaw

Control-patients without any implants or implants with surfaces other than hydrophilic surfaces

Outcome-osseointegration of the hydrophilic implants to the bone

Time-period from the insertion of implants to the osseointegration of the implants to the surrounding bone.

Studies included in this systematic review as PRISMA format

Identification

Records obtained through the PubMed database search, n = 2071

Additional records identified through other sources, n = 0

Records after duplicates were removed, n = 1082.

Screening

Records screened, n = 1082

Records excluded, n = 984.

Eligibility

Full-text articles assessed for eligibility, n = 98

Full-text articles excluded, n = 74.

Included

Studies included in qualitative synthesis, n = 24.

OBSERVATIONS AND RESULT

Twenty-four studies included in this review; thus, a total of 4498 implants were placed in 2037 patients of which 37 implants were lost.

Therefore, the cumulative survival rate was 99.18%. The studies included in the review are listed in Table 1.

Table 1

List of the studies included into the review

Authors and year	Type of study	Hydrophilic implant brand	Number of patients	Number of implants	Number of implants lost	Parameters observed	Outcomes
Donos et al., 2011[5]	Prospective	SLActive	9	18	NA	Gene expression	SLActive is pro-osteogenic and pro-angiogenic
Lang et al., 2011[6]	Propective	SLActive	28	49	NA	histomorphometry	SLActive has better osseointegration than others
Ivanovski et al., 2011[7]	Prospective	SLActive	9	9	0	Gene ontology	I-kB kinase/NF-kB cascade, early inflammatory changes, osteogenesis-related mechanisms are regulated by TGF-b/BMP
Bosshardt et al., 2011[8]	Prospective	SLActive	28	49	NA	Histomorphometry	New bone formation mediated by old bone
Roccuzzo and Wilson 2009[9]	Prospective	SLActive	35	35		Survival rate on early loading	Surface modified hydrophilic implants are suitable for loading at 3 weeks in maxillary molar areas
Iezzi et al., 2013[10]	Retrospective	FRIADENT PLUS	14	14	NA	Histomorphometry	The efficacy of dental implants is related to biological and biomechanical stability and to the integration between the bone and the implant
Hinkle et al., 2014[11]	Prospective	INICELL	21	23	0	Clinical and radiological outcome	Hydrophilic implants loading is a safe and predictable treatment
van Eekeren et al., 2015[12]	Prospective	INICELL	32	76	0	ISQ values	Bone level implants had level of ISQ quotient throughout
Dolanmaz et al., 2015[13]	Prospective	SLActive	47	47	0	BMP 2, 7 Osteoprotegrin	Cytokines in PICF during early healing of implants reflects the degree of peri-implant inflammation, rather than differences in the implant surfaces
Gac and Grunder 2015[14]	Retrospective	INICELL	1063	2918	30	Survival rate	Failure was less with hydrophilic implants
Hicklin et al., 2016[15]	Prospective	SLActive	15	20	0	ISQ values	Functional occlusal loading possible with hydrophilic implants in posterior mandible
Hirota et al., 2016[16]	Prospective	Nobel active	7	49	0	OSI/ISQ	Photo-functionalization accelerated the rate and enhanced of implant stability
Degasperi et al., 2014[17]	Retrospective	Neoss active	49	102	1	Survival rate/MBL	Novel hydrophilic implants result in favourable short term outcomes
Şener-Yamaner et al., 2017[18]	Prospective	SLActive	55	175	3	MBL	SLActive have successful clinical results
Novellino et al., 2017[19]	Prospective	Drive cm acqua, neodent	21	64	0	ISQ	Implants with hydrophilic surfaces integrate faster
Makowiecki et al., 2017[20]	Prospective	INICELL/RN SLActive	15	15	0	ISQ/MBL	Insertion of short dental implants with a hydrophilic conditioned surface significantly shows INICELL was better than straumann in osseointegration
Cabrera-Domínguez et al., 2017[21]	Prospective	SLActive Roxolid	29	29	0	MBL	Patients with glycemic control exhibit similar outcomes
Rosen et al., 2018[22]	Retrospective	PROActive, neoss	76	86	3	ISQ	Treatment with short implants with high survival rate
Siqueira et al., 2018[23]	Prospective	Titamax cm acqua, neodent	11	55	0	ISQ	Survival rate similar in both tested implant surfaces
Ghazal et al., 2019[24]	Prospective	SLActive roxolid	47	47	0	Survival rate and MBL	Noninferiority of the narrow versus standard diameter Ti-Zr implants
Puisys et al., 2019[25]	Prospective	Biohorizons	180	360	0	Removal torque	Photoactivation increases removal torque values
Tallarico et al., 2019[26]	Prospective	Hiossen ET III (NH)/(SA)	14	28	0	ISQ	NH viable alternative to SA, as they seem to avoid ISQ drop in remodeling phase
Velloso et al., 2019[27]	Prospective	TITAMAX ACQUA	20	20	0	ISQ	Implants with modified surface showed greater ISQ values in the posterior mandible
Beena Kumary et al., 2019[28]	Prospective	Adin/chemically modified	210	210	0	ISQ	Implants with chemically modified SAE surfaces showed faster osseointegration
Total			2037	4498	37

NA: Not applicable, ISQ: Implant stability quotient, MBL: Marginal bone loss, TGF-b: Transforming growth factor beta, BMP: Bone morphogenetic protein, PICF: Peri-implant crevicular fluid, NH: New hydrophilic, SAE: Sandblasted and acid-etched, SA: Sandblasted and acid-etched

From these, seven studies observed the MBL (marginal bone loss) as listed in Table 2 and 10 studies observed the ISQ (implant stability quotient) values as listed in Table 3.

Table 2

Studies to evaluate the marginal bone loss around the implants

Authors and year	Implants placed Number and trade name	Patients in the study	Results Mean MBL
Ghazal et al., 2019[24]	SLA Roxolid - 50 implants	50	No implant loss
			Narrow diameter - 0.27±0.34 mm
			Standard diameter - 0.48±0.67 mm
Cabrera-Domínguez et al., 2017[21]	Straumann roxolid SLActive - 29 implants	29	No implant lost
			DMG - 1.28±0.38 mm
			CG - 1.11±0.59 mm
Makowiecki et al., 2017[20]	Spi element INICELL RN SLActive - 30 implants	30	No implants lost
			0.51±0.37 mm
Şener-Yamaner et al., 2017[18]	SLActive - 68 implants	55	No implant lost
			0.53 mm
Hicklin et al., 2016[15]	Spi element INICELL - 20 implants	15	No implant lost
			0.97 mm median
Hinkle et al., 2014[11]	Element rc INICELL - 23 implants	21	No implants lost
			1.98 mm
Degasperi et al., 2014[17]	Neoss active - 102 implants	49	1 implant lost
			0.7±0.6 mm mean MBL

MBL: Marginal bone loss, DMG: Diabetes mellitus group, CG: Control group

Table 3

Descriptive statistics on maximum achieved implant stability quotient values over the last 10 years by hydrophilic implants

Authors and year	Number of implants	Treatment type	Maximum mean ISQ values
Beena Kumary et al., 2019[28]	210	SLA (Group A)	Group A - 86.2
		SLA active (Group B)	Group B - 89.4
Tallarico et al., 2019[26]	28	SLA (Group A)	Group A - 78.1±5.1
		SLA with bioresorbable apetite nanocoating (Group B)	Group B - 79.2±3.9
Velloso et al., 2019[27]	20	SLA (Group A)	Group A - 61±7.2
		SLA active (Group B)	Group B - 67.1±5.9
Siqueira et al., 2018[23]	55	SLA (Group 1)	Group 1 - 69.2
		Hydrophilic (Group 2)	Group 2 - 69.2
Rosen et al., 2018[22]	86	Hydrophilic electrowetted surface	73.3±4.4
Novellino et al., 2017[19]	64	SLA (Group A)	Group A - 81
		SLA active (Group B)	Group B - 82.5
Hicklin et al., 2016[15]	20	Hydrophilic surface	85±5
Hirota et al., 2016[16]	49	Untreated (Group 1)	Group 1 - 65.6±5.5
		Photo-functionalized (Group 2)	Group 2 - 69.2±7
Van Eekeren et al., 2015[12]	76	Hydrophilic surface	86
Degasperi et al., 2014[17]	102	Electrowetted hydrophilic surface	73.6±7.2

ISQ: Implant stability quotient

DISCUSSION

Osseointegration is the process by which the titanium implants fuse to the underlying bone. Many factors seem to influence the process of osseointegration, like host factors-quality and type of bone, surgical factors like the drilling procedure, and speed.[29] Mostly the quality of surface which contacts the bone determines the type and speed of osseointegration. The role of surface characteristics gained importance since the early 80s, Albrektsson et al.[30] further pioneered the concept of osseointegration by ascribing to surface properties a possible role for the biological response to an implant.[31] Many surface modifications have been done than the traditional machined surfaces of the titanium implants.

Hydrophilicity is nothing but wettability of a surface. Contact angle (CA) is the angle between the tangent line to a liquid drop's surface at the three-phase boundary and the horizontal solid's surface. In principle, the CA can range from 0° to 180°. Surfaces with water CAs lower than 90° are designated as hydrophilic, and those with CAs very close to 0° are superhydrophilic. Surfaces with water CAs above 90° are considered hydrophobic, and those with CAs above 150° are termed superhydrophobic.[32]

Lately, the most commonly used implant surfaces are the solution instead of air (SLA) surfaces, Sandblast and acid-etched surfaces, which are inherently hydrophobic. These SLA surfaces are hydrophilized by surface neutralization after acid etching is done in a contaminant-free, protective nitrogen environment, and the implants are finally stored in a neutral saline SLA active. Recent reviews highlight numerous in vitro, in vivo and clinical studies focusing on this hydrophilic surface.[243132]

Hicklin et al.[15] describes the method to convert the hydrophilic implants (INICELL; Thommen medical AG) to super-hydrophilic by chairside conditioning procedure following the manufacturer's instructions that included wetting with 0.05M NaOH solution pH 12.24 using a dedicated applicator immediately prior to implant placement. It is observed that most manufacturers claim their implants to be super-hydrophilic and recommend the implant to be wetted by a special solution to increase its wettability and osseointegration. The purpose of the wetting could be to avoid the formation of the titanium oxide layer, which forms as soon as the implant is exposed to the atmosphere.

A recent study has revealed that time since surface preparation or aging can significantly reduce the osteoconductivity of implants.[33] This phenomenon, known as “biologic aging of titanium,”[3435] results from time-dependent loss of hydrophilicity and progressive accumulation of hydrocarbon impurities on titanium surfaces. Ultraviolet light treatment of titanium immediately before use, or photo-functionalization, has been found to counteract the biologic aging of titanium by regenerating hydrophilicity and removing hydrocarbon impurities. Indeed, the BIC of photo-functionalized implants is increased from 53% to nearly 100% in animal models.[36] Photo-functionalization of dental implants is rapid and simple to perform chairside immediately before placement. Various clinical studies have indicated that photo-functionalization may accelerate and enhance the osseointegration of dental implants.[37383940]

Researchers have quantified the wettability of an implant surface by either the sessile drop method, where liquid drops are set on a surface and the CA is directly measured from the drop shape surface[31] and second, tensiometry, where CAs are measured indirectly according to the Wilhelmy balance technique,[32] where in the samples have to be fixed to an electro balance and the forces detected during continuous immersion and withdrawal of the samples into and from the wetting liquid allow the calculation of advancing and receding CAs, respectively. In general, dynamic CAs can be measured if there is a relative movement between the material and the wetting liquid. Without such a movement, static CAs can be analyzed.

The study of osseointegration in the retrieved implants in the human trials revealed that the hydrophilic implants had a better bone to implant contact and better osseointegration than hydrophobic implants. Histology and histomorphometry[6810] show that the hydrophilicity of hydrophilic implants during the early osseointegration period help the implant surface in neovascularization and thus the bone contact around the titanium implants is more when compared to other implants. Gene ontology was done in some of the studies suggest that a hydrophilic surface indeed improves early bone deposition around the implants through the expression of bone mimetic proteins such as osteoprotegrin.[513]

Many additive morphology changes also have been done to the titanium implant surfaces to be able to osseointegrate better to the bone. Hydrogels,[41] crosslinked, have been engineered to coat on the implant surface, can act as a scaffold to deliver the biomimetic drugs like bone morphogenic proteins, antibiotics like amoxicillin. The results are improved osseointegration with bone due to increased wettability caused by the hydrogels.

This systematic review compiles the data about osseointegration in hydrophilic titanium implants in human trials. It sheds light on the mechanism of integration of hydrophilic surfaces as they have a positive impact on osseointegration. Given the limited data, the authors would like to conclude that hydrophilic implants offer better osseointegration as compared to other implants. The authors feel there is a need for more randomized clinical trials to support the findings from this review.

CONCLUSION

Total 4948 implants placed in 2037 patients in the studies included, in which almost all the implants osseointegrated and 37 were lost due to implant failure. The cumulative survival rate for the implants were 99.18%. It was observed that the hydrophilic implants showed higher ISQ values during the early osseointegration period, and then the ISQ values further increased in the duration of 3–6 months showing solid osseointegration of at least 2.25 times more.[22] The marginal bone loss also was considerably less for the hydrophilic implants as compared to the hydrophobic implants.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.