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In Vitro and in Vivo Follow-Up of Titanium Transmucosal Implants with a Zirconia Collar

September 2004
Journal of Applied Biomaterials and Biomechanics 2(3):143-50

DOI:10.1177/228080000400200303

Source
PubMed

Authors:

Andrea Edoardo Bianchi

Istituto Stomatologico Italiano, Italy, Milano

Michela Bosetti

University of Piemonte Orientale Amedeo Avogadro

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The advantages of transmucosal healing implants with a bioactive zirconia collar as a support for partially fixed prosthodontic restorations are optimal peri-implant marginal tissue sealing, reduction in plaque accumulation and satisfactory aesthetic results. The zirconia used in this study evidenced not only optimal clinical performances, but also good biocompatibility. The results from this study demonstrated that zirconia coating enhances fibroblasts and osteoblast-like cell adhesion, spreading and proliferation, favoring microscopic tissue/cell in-growth and clinical implant fixation improvement. From clinical analysis, it emerged that the treatment group obtained better scores in every peri-implant parameter. This evidence attests faster stabilization of soft and hard tissues around both the transmucosal zirconia collar and at the crestal level of the implant. A reduced plaque accumulation around the implant with zirconia collar could provide a better peri-implant microbiological en-vironment by allowing the soft tissues expression of optimal sealing and good bone adaptation to loading. From these clinical and radiographic comparative analyzes, it emerged that in the treatment group the mean values were always similarly low. A rapid stabilization of both hard and soft peri-implant tissues was documented in the 1st yr. In the treatment group, there was the formation of stable tissue sealing the zirconia collar, which could preserve mucosal and bone levels. In conclusion, 2-yr clin-ical results demonstrated that implants supporting fixed restorations using transmucosal healing implants with a zirconia collar appeared a valid method, reporting 100% implant survival rates. Moreover, in vivo results obtained using strict parame-ters to assess the peri-implant status affirmed that a zirconia collar offers excellent biological acceptance. Our preliminary in vitro results statistically evidenced increased fibroblast and osteoblast adhesion and proliferation to zirconia compared to tita-nium, and an index of enhanced material integration with bone and soft tissue cells. (Journal of Applied Biomaterials & Biomechanics 2004; 2: 143-50).

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INTRODUCTION

The improved understanding in material-cell inter-

actions results in a high degree of predictability in

the clinical success of biomaterials used for dental

implants (1, 2). Titanium has been established as

the first choice material for endosseous implants

because of its chemical-physical properties and its

biocompatibility (3, 4).

Restorations in the anterior esthetic zone present

significant challenges in both the surgical and pros-

thetic phases of implant dentistry and many types

of implants require transmucosal abutments to re-

tain implant restorations. In these cases, the gray

color of the titanium is transmitted through the

peri-implant tissues causing patient discomfort.

The use of ceramic abutments in methods with sub-

merged implants allows the minimization of the

gray color associated with metal components. Sub-

merged implants, on the other hand, evidenced

limits connected to the operative phases: a second

surgical step, longer clinical times, and the irre-

versibility of the prosthetic structure. Therefore,

some previous studies compared non-submerged

healing implants, also defined as one-stage im-

plants or transmucosal healing implants, with sub-

merged healing implants, also defined as two-stage

implants. These studies, found no differences in

Journal of Applied Biomaterials &Biomechanics 2004; 2: 143-150

In vitro and in vivo follow-up of titanium

transmucosal implants with a zirconia collar

A.E. BIANCHI1, M. BOSETTI2, G. DOLCI Jr1, M.T. SBERNA1, F. SANFILIPPO1, M. CANNAS2

1 Cattedra di Clinica Odontoiatrica, Ateneo Vita e Salute, San Raffaele Hospital, Milano - Italy

2 Department of Medical Sciences, University of Eastern Piedmont, Novara - Italy

ABSTRACT:The advantages of transmucosal healing implants with a bioactive zirconia collar as a support for partially fixed

prosthodontic restorations are optimal peri-implant marginal tissue sealing, reduction in plaque accumulation and satisfacto-

ry esthetic results. The zirconia used in this study evidenced not only optimal clinical performances, but also good biocompati-

bility. The results from this study demonstrated that zirconia coating enhances fibroblasts and osteoblast-like cell adhesion,

spreading and proliferation, favoring microscopic tissue/cell in-growth and clinical implant fixation improvement. From clin-

ical analysis, it emerged that the treatment group obtained better scores in every peri-implant parameter. This evidence attests

faster stabilization of soft and hard tissues around both the transmucosal zirconia collar and at the crestal level of the implant.

A reduced plaque accumulation around the implant with zirconia collar could provide a better peri-implant microbiological en-

vironment by allowing the soft tissues expression of optimal sealing and good bone adaptation to loading. From these clinical

and radiographic comparative analyzes, it emerged that in the treatment group the mean values were always similarly low. A

rapid stabilization of both hard and soft peri-implant tissues was documented in the 1st yr. In the treatment group, there was

the formation of stable tissue sealing the zirconia collar, which could preserve mucosal and bone levels. In conclusion, 2-yr clin-

ical results demonstrated that implants supporting fixed restorations using transmucosal healing implants with a zirconia col-

lar appeared a valid method, reporting 100% implant survival rates. Moreover, in vivo results obtained using strict parame-

ters to assess the peri-implant status affirmed that a zirconia collar offers excellent biological acceptance. Our preliminary in

vitro results statistically evidenced increased fibroblast and osteoblast adhesion and proliferation to zirconia compared to tita-

nium, and an index of enhanced material integration with bone and soft tissue cells. (Journal of Applied Biomaterials &Bio-

mechanics 2004; 2: 143-50)

KEY WORDS: Osteoblast like cells, Osteointegration, Zirconia

Received 04/01/04; Revised 25/01/04; Accepted 04/11/04

1722-6899/143-08$15.00/0

the long-term prognosis of endosseous dental im-

plants (5, 6), promising important clinical advan-

tages for the one-stage surgery technique.

The use of a new implant with a white transmucos-

al ceramic collar allowed the combination of the

advantages offered by transmucosal implant meth-

ods with a one-stage technique with natural trans-

parency and increased biocompatibility at the trans-

mucosal portion.

Zirconia is an advanced ceramic used in the bone

medical field (7) due to its important mechanical

properties and tissue biocompatibility. In addition,

zirconia has been shown to reduce bacterial adhe-

sion (8) and plaque accumulation (9).

In this study, we evaluated in vitro the biocompati-

bility of titanium compared to zirconia coated tita-

nium by studying fibroblasts and human osteoblast-

like cell adhesion and proliferation. In addition, we

performed preliminary clinical evaluations of trans-

mucosal healing implants with and without a zirco-

nia collar.

MATERIALS AND METHODS

Materials

Two types of solid screw transmucosal healing im-

plants with rough endosseous surfaces (Z1 im-

plants, T.B.R.®ide@, Sudimplant, Toulouse,

France) were used. For both types, the endosseous

surface was titanium, while the transmucosal collar

was titanium or titanium covered by a zirconia ring.

The ceramic ring was a yttria stabilized medical

grade zirconium dioxide.

The implants used for the clinical studies, in rela-

tion to bone height disposal, had an intraosseous

length ranging from 10.5 to 15.5 mm, and concern-

ing the bone width disposal, had an intraosseous di-

ameter from 3.5 to 5 mm. For in vitro tests, titanium

and zirconia disks of 0.4 cm diameter were used. Pri-

or to use, the coated and uncoated materials were

sterilized for 2 hr in dry heat at 160 °C.

In vitro evaluations

Cell behavior on the materials tested was studied us-

ing human fibroblasts (MRC5, ATCC cell-line) and

human primary osteoblast-like cells obtained by en-

zymatic isolation from trabecular fragments of

adult human bone removed during surgery, and

treated as described previously (10). Briefly, parti-

cles of 3-5 mm, after treatment with bacterial colla-

genase, were plated in 90 mm tissue culture dishes

and cultured at 37 °C in 95% air/5%CO2in 10 ml

ISCOVE’s supplemented with 20% FBS, 50 U/ml

penicillin, 15 µg/ml streptomycin and 2 mM gluta-

mine. Cell outgrowths from the bone fragments ap-

peared within 1 week and formed a confluent

monolayer at 3-4 weeks. The isolated bone cells

were characterized including osteoblastic morphol-

ogy, alkaline phosphatase expression and hormone

responsiveness (parathyroid hormone, 1,25(OH)2D3).

Fibroblasts and osteoblasts were used at a cell den-

sity of 1 x 104cells/cm2.

Cell adhesion and proliferation results were com-

pared to that obtained on a polymeric substrate

used as a control (Thermanox®slides, Nunc, Mi-

lano, Italy) known to induce cell adhesion (11).

As the materials tested were unsuitable for normal

transmitted light microscopy, we observed cell mor-

phology and distribution with fluorescence mi-

croscopy. After 6 hr (cell adhesion study) and 4

days (cell proliferation study), fibroblasts and os-

teoblast-like cells on the materials tested were

rinsed in phosphate buffered saline, fixed for 20

min at 60 °C and stained for 5 min in a 0.025% acri-

dine orange solution, a nucleic acid staining (12).

Cell morphology and the number on each material

were evaluated using a fluorescent microscope

Aristoplan (Leitz Leica, Milano, Italy). Cell number

was evaluated on a surface of 0.1715 mm2using 25x

microscope magnification and results are reported

as mean ± standard deviation of 30 fields obtained

from three different experiments.

Clinical evaluation

A 2-yr randomized study was performed from 2000-

2002. Twenty patients were admitted to the trial,

and 44 implants were placed; 29 implants had zir-

conia collars (Z1 implants, T.B.R. ide@, Sudim-

plant, Toulouse, France) and 15 implants had stan-

dard titanium collars. Thirteen patients received

only the implants with a zirconia collar, while five

patients received implants with the same shape but

with a titanium collar. The remaining two patients

were implanted with both implants. Data from pa-

tients who received implants with a zirconia collar

were processed as the treatment group, while data

collected from patients who received implants with

titanium collar were analyzed as the control group.

The number of implants placed in the maxilla was

24, and 20 implants were placed in the mandible.

The implants were used to support partially fixed

prosthesis and underwent loading at 3-4 months af-

ter their placement.

The cumulative survival rate was calculated accord-

ing to the method described by Cutler and Ederer

(13). The establishment of successful outcomes re-

144

In vitro and in vivo follow-up of titanium transmucosal implants with a zirconia collar

quired the periodical evaluation of specific para-

meters, such as the stability of peri-implant crestal

bone levels and the health and stability of peri-im-

plant soft tissue. According to Brägger et al (14),

crestal bone levels were evaluated calculating the

linear distance implant-shoulder to the bone

(DIB), measured with periapical radiographs on

mesial and distal sites (Fig. 1). When the DIB value

is <3.5 mm, peri-implant bone is considered stable;

>3.5 mm bone crest resorption has occurred.

The soft tissue status was evaluated clinically by the

method proposed by Mombelli et al (15) for trans-

mucosal healing implants and the following mea-

sures were recorded (Fig. 1).

Plaque index (PLI): This index is used to measure

the level of patient oral hygiene performance; it

confirms the quantity of bacterial deposits around

the implant emerging from soft tissues. Value 0 =

no plaque deposit, value 1 = small plaque deposit,

value 2 = large plaque deposits.

Bleeding on probing (BOP): This index is used to

measure the inflammation level of the mucosal tis-

sues in response to peri-implant sulcus probing.

Value 0 = no bleeding occurred during the prob-

ing, value 1 = small mucosal bleeding occurred, val-

ue 2 = significant bleeding occurred and value 3 =

spontaneous bleeding, even if the mucosal sulcus

has not been probed.

Probing depth (PD): This index measures (in mm)

the mucosal sulcus depth around the implant. A

small thin calibrated linear probe is inserted in the

peri-implant sulcus with a pressure of only 25 g. As

a starting point for the measurement, the free mar-

gin of the peri-implant mucosa is used, and an end-

point is reached when the resistance of the soft tis-

sue does not allow further probing. When the PD

value is <3 mm, peri-implant tissues are considered

healthy; >3 mm mucosal pathology has occurred.

Probing attachment level (PAL) is related to the im-

plant shoulder. An analogous procedure of PD

measurement, but as a starting point the platform

of the implants is used. When the PAL value is <2.5

mm, peri-implant tissues are considered healthy;

>2.5 mm mucosal pathology and bone resorption

have occurred.

Regular follow-ups from 4-6 months were established

based on individual oral hygiene performance, but

clinical data considered in this study were only those

recorded annually.

Statistical analysis

Statistical analysis of the data was carried out using

SPSS for Windows software. The Student’s t-test for

independent data was performed to compare ad-

hesion and proliferation results. A p value was ob-

tained from the ANOVA table; the conventional

0.05 level was considered statistically significant.

RESULTS

In vitro results

As shown in Figure 2, fibroblasts and osteoblast-like

cells evidenced statistically higher cell adhesion

when cultured on zirconia compared to the con-

trols (Thermanox®slides) and compared to the un-

coated titanium material.

145

Bianchi et al

Fig. 1 - Illustration depicting reference point and distances of clin-

ical and radiographic measurements: PD (probing depth), PAL

(probing attachment level, related to implant shoulder), DIB

(distance implant shoulder/first implant bone contact).

Fig. 2 - Fibroblasts and osteoblast-like cells quantification at 6 hr

cell incubation (adhesion test) on titanium (Ti), zirconia coated

titanium (Ti-Z1) and on control Thermanox®slide (CTR). Cell

number was the mean of 20 measurements in three experiments

(n=60) and was referred to a surface area of 0.1715 mm2.

* p<0.05 with respect to controls; ° p<0.05 with respect to Ti.

*°

Figure 3 shows the results of fibroblasts and os-

teoblast-like cells at 4 days proliferation on the ma-

terials tested. Results evidenced increased cell num-

bers on the titanium and zirconia coated titanium

with respect to the adhesion experiments, compa-

rable to that obtained at 6 hr.

Human fibroblasts (Fig. 4a) and osteoblast-like cells

(Fig. 4b) cultured on the surfaces of the two mate-

rials and observed at 6 hr incubation showed good

fibroblast and osteoblast-like cell spreading on zir-

conia coated titanium, comparable to the control

Thermanox®wells.

Clinical results

During the 2-yr observation, no implant was lost ei-

ther in the treatment group or in the control

group. In the follow-up period, all implants showed

no mobility denoting clinical signs of stable os-

seointegration; therefore, an implant survival rate

146

In vitro and in vivo follow-up of titanium transmucosal implants with a zirconia collar

Fig. 3 - Fibroblasts and osteoblast-like cells quantification at 4 days

cell incubation (adhesion test) on titanium (Ti), zirconia coated ti-

tanium (Ti-Z1) and on control Thermanox®slide (CTR). Cell num-

ber was the mean of 20 measurements in three experiments (n=60)

and was referred to a surface area of 0.1715 mm2. * p<0.05 with

respect to controls; ° p<0.05 with respect to Ti.

Fig. 4 - Morphology of fibroblasts (a) and osteoblast-like cells (b) adhesion on cell culture dish, titanium and zirconia coated titanium.

Materials were incubated for 6 hr with fibroblasts and human osteoblast-like cells. Samples were examined by fluorescence microscopy

at 250



magnification.

Fibroblast adhesion

Osteoblast adhesion

CTR

*°

of 100% was confirmed. Table I depicts the longevi-

ty of the implants, showing interval and cumulative

survival rates both for the treatment and control

groups.

Many patients exhibited good oral hygiene perfor-

mance, and in most patients, crowns or partially

fixed dentures were free from plaque or calculus

deposits. Recorded peri-implant parameters

demonstrated a PLI of 0 at 64.5% of all sites, and 1

at 29.5% and 2 at 6% of the other sites, respective-

ly. During the observation period, analogous mean

results were recorded in both groups, with a small

percentage increase in the scores for the treatment

group (Tab. II). Table II reports the differences in

the mean values of BOP at the final evaluation. The

BOP scores in the treatment group appeared lower

as compared to the control group.

In both procedures, a slight increase in PD mean

values, from 2.5 mm to approximately 3.5 mm, was

encountered during the 1st yr of load application

(Tab. III). Taking into consideration that the

healthy conditions of the soft tissue does not admit

a PD up to 3 mm, an analysis of PD for mean scores

>3 mm was required. The data revealed better

mean values of PD scores in the treatment group

during the 2-yr interval suggesting a faster stabiliza-

147

Bianchi et al

TABLE I - LIFE TABLE ANALYSIS FOR 44 IMPLANTS SURVIVAL

Interval N° of implants Drop-outs Implants Failure Survival Cumulative

months at start during under risk during rate within survival

of interval interval interval period (%) rate (%)

Total Treat* Cont** Total Treat Cont Total Treat Cont Total Treat Cont Total Treat Cont Total Treat Cont

12 44 29 15 2 2 0 42 27 15 0 0 0 100 100 100 100 100 100

24 9 5 4 0 0 0 9 5 4 0 0 0 100 100 100 100 100 100

* Treatment group ** Control group

TABLE II - PLI AND BOP INDEXES, PERCENTAGE OF MEAN VALUES AT LAST CONTROL

Collar Value 0 Value 1 Value 2

PLI Zirconia 72 24 4

Titanium 50 40 10

BOP Zirconia 88.9 8.3 2.8

Titanium 53.3 36.7 10

Mean values of PLI and BOP were significantly lower in treatment group

TABLE III - PERI-IMPLANT MEASURES RELATED TO OBSERVATION PERIOD, MEAN VALUES IN MILLIMETERS

Groups Time period Time period Time period Time period

0 months 6 months 12 months 24 months

PD Treatment 2.3 2.8 3 2.5

Control 2.8 3.2 3.4 3.3

PAL Treatment 1.8 2 2.1 0.5

Control 2.2 2.2 2.3 2.6

DIB Treatment 3 3 3.2 3

Control 3 3.2 3.6 3.4

Mean peri-implant values were lower in treatment group during interval

tion of peri-implant tissues (Tab. IV).

The trend in PAL scores was similar to PD scores

(Tab. III). For PAL scores it was also necessary to

confirm the percentage of healthy sites. Therefore,

the percentage of sites probed was calculated for

each single interval group with values up to 2.5 mm

(Tab. IV). The trend in this parameter appeared

analogous to PD for scores up to 3 mm.

Biologically, the distance between DIB crest should

be approximately 3.5 mm for the implants used in

this study. A linear measure of DIB ≤3.5 mm was as-

sumed as optimal. DIB scores >3.5 mm were then

collected and processed for comparative analysis.

The data collected in Table IV demonstrated the

different trend in the values among the treatment

group and the control group during the 1st yr. The

percentages of DIB scores >3.5 mm were integrated

with the percentage of PAL mean scores >2.5 mm

and with PD scores >3 mm.

DISCUSSION AND CONCLUSIONS

In the past 25 yrs, numerous in vivo studies have

demonstrated that non-submerged titanium im-

plants achieve osseointegration as predictable as

that of submerged titanium implants (4). This ob-

servation was confirmed in prospective clinical

studies. The studies demonstrated success rates well

above 90%. In summary, the non-submerged ap-

proach is a true alternative to the original healing

modality with submerged titanium implants. The

non-submerged approach offers several clinical ad-

vantages: 1) the avoidance of a second surgical pro-

cedure and less chair time per patient, resulting in

overall reduced treatment cost; 2) the lack of mi-

crogap at the bone crest level, leading to less crestal

bone during healing and resulting in a more favor-

able crown-to-implant length ratio; and 3) a simpli-

fied prosthetic procedure, presenting an ideal basis

148

In vitro and in vivo follow-up of titanium transmucosal implants with a zirconia collar

TABLE IV - COMPARATIVE ANALYSIS OF PERCENTAGE OF PERI-IMPLANT MEAN SCORES RECORDED WITH PD

> 3 mm, PAL > 2.5 mm AND DIB > 3.5 mm

Groups Time period Time period Time period Time period

0 months 6 months 12 months 24 months

PD > 3 mm 0 5.2 10.3 0

Treatment PAL > 2.5 mm 0 5.2 11.1 0

DIB > 3.5 mm 0 1.7 5.6 0

PD > 3 mm 0 60 53.3 50

Control PAL > 2.5 mm 0 30 56.7 50

DIB > 3.5 mm 0 6.7 20 0

More stable peri-implant status was attested in treatment group

Fig. 5 - Comparative analysis depicting the trend of peri-implant tissues in the treatment group (a) and the control group (b). Mean

values were calculated with PAL >2.5 mm, PD >3 mm and DIB >3.5 mm. Mean scores attested more stable peri-implant status in treat-

ment group, during 2 yrs of analysis.

for cemented implant restorations. Due to these

significant clinical advantages, the non-submerged

approach will become more important in implant

dentistry in the near future, particularly in implant

sites without esthetic priority. The creation of a new

implant with a white transmucosal ceramic collar al-

lowed the combination of the advantages offered

by a transmucosal implant method with natural

transparency at the transmucosal level widening ap-

plications in restorations in the anterior esthetic

zone.

The advantages of transmucosal healing implants

with a bioactive zirconia collar as a support of par-

tially fixed prosthodontic restorations are optimal

peri-implant marginal tissue sealing, reduction in

plaque accumulation and satisfactory esthetic re-

sults. Zirconia is a widely studied material that has

evidenced good mechanical performances (7) with

reduced bacterial colonization (8) and reduced

plaque accumulation (9). In addition, the zirconia

used in this study evidenced not only optimal clini-

cal performances but also good biocompatibility. In

vitro tests demonstrated that zirconia coated titani-

um, compared to titanium, has a better compatibil-

ity related to the aspect considered. Results from

this study show that zirconia coating enhances fi-

broblasts and, particularly, osteoblast-like cell adhe-

sion, spreading and proliferation, favoring micro-

scopic tissue/cell in growth and clinical implant fix-

ation improvement.

From clinical analysis, it emerged that the treat-

ment group obtained better scores in every peri-im-

plant parameter. This evidence attests faster stabi-

lization of soft and hard tissues around both the

transmucosal zirconia collar and at the crestal level

of the implant (Fig. 5a). The same parameters eval-

uated for implants with titanium collars demon-

strated, instead, a major sensitivity of the peri-im-

plant tissues to the modifications of the biological

and biomechanical environment once the implant

supporting rehabilitation started working (Fig. 5b).

The association of factors such as plaque accumula-

tion and load can perhaps play an important role in

determining this tissue response. Reduced plaque

accumulation around the implant with a zirconia

collar could provide a better peri-implant microbi-

ological environment by allowing the soft tissue ex-

pression of optimal sealing and good bone adapta-

tion to loading. From these clinical and radi-

ographic comparative analyzes, it emerged that in

the treatment group the mean values were always

similarly low. A rapid stabilization of both hard and

soft peri-implant tissues was documented in the 1st

yr. In the treatment group, there was the formation

of stable tissue sealing the zirconia collar, which

could preserve mucosal and bone levels.

In conclusion, 2-yr clinical results demonstrated

that implants supporting fixed restorations using

transmucosal healing implants with zirconia collars

appeared as a valid method, reporting 100% im-

plant survival rates. In addition, in vivo results ob-

tained using strict parameters to assess the peri-im-

plant status confirmed that a zirconia collar offers

excellent biological acceptance according to our

preliminary in vitro results, which evidenced statisti-

cally increased fibroblast and osteoblast adhesion

and proliferation on zirconia coated titanium com-

pared to the uncoated form, and an index of en-

hanced material integration with bone and soft tis-

sue cells.

Address for correspondence:

Dr. Andrea E. Bianchi

Servizio di Odontoiatria,

Ateneo Vita e Salute,

Ospedale San Raffaele

Via Olgettina, 60

20132 Milano - Italy

bifasa@fastwebnet.it

149

Bianchi et al

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Screw-retained monolithic zirconia vs. cemented porcelain-fused-to-metal implant crowns: a prospective randomized clinical trial in split-mouth design

Article

Full-text available

Mar 2019
CLIN ORAL INVEST

Objectives: The objective of the present study was to compare the clinical performance of screw-retained, monolithic, zirconia, and cemented porcelain-fused-to-metal (PFM) implant crowns. Materials and methods: In a prospective, randomized, clinical, split-mouth trial, 22 patients' bilateral premolar or molar single-gap were restored with either screw-retained (test group) or cemented supraconstruction (control group). Clinical parameters, soft-tissue health, crestal bone-level changes, technical complications, and patient's subjective feelings were recorded during a follow-up period of 12 months. Results: No implant was lost during the follow-up period. Of the crowns, 4.5% (test) and 9.1% (control) showed bleeding on probing (P = 1.000), and plaque was visible in 13.6% (test) and 27.3% (control) of the crowns (P = 0.240). Changes in bone crest level seemed to have no correlation with the restoration method (P = 0.77/0.79). Technical failures were observed in three restorations of the test and four of the control group. Evaluation of patients' satisfaction revealed high acceptance regarding fit, esthetics, and chewing effectiveness in both groups. Conclusion: Over a 12-month follow-up, screw-retained and cemented crowns could show comparable clinical and radiological results regarding soft tissue health, marginal bone level, and patient satisfaction. Duration of treatment alone was significantly shorter in screw-retained crowns. Clinical relevance: Prosthetic retention methods are related with the occurrence of complications, such as peri-implantitis. However, scientific valuable data that proof superiority of a specific retention technique are rare. In single-gap implants, screw retention and cementation seemed to achieved comparable results.

Synthèse par pulvérisation cathodique magnétron et caractérisation de revêtement d'oxydes biocompatibles pour application aux implants dentaires en alliage de titane

Thesis

Dec 2012

André Marlot

Les procédés de dépôt en phase vapeur sont particulièrement performants pour la synthèse de revêtements à propriétés contrôlées. Plus spécifiquement, ce travail de recherche porte sur l'élaboration de revêtements biocompatibles, sur alliage titane TiAl6V4, obtenus par pulvérisation magnétron en conditions réactives. Dans un premier temps, nous avons décrit les procédés de mise en forme des implants commerciaux pour pouvoir les reproduire au niveau du laboratoire. Dans un second, nous avons focalisé notre étude sur l'effet de la structure cristallographique de films de zircone sur leur caractère biocompatible à partir de cultures cellulaires de fibroblastes. Les résultats ainsi obtenus démontrent très nettement des différences de comportement entre des films de zircone monoclinique, quadratique ou cubique. Dans l'objectif d'apporter des éléments d'information permettant de discuter de ces effets, d'autres séries de revêtements céramiques ont été élaborées comme par exemple des oxydes de titane ou de zirconium amorphes, de l'oxyde d'yttrium, de l'oxyde d'aluminium ou encore du carbone amorphe. Les cultures cellulaires pratiquées sur ces échantillons ont permis de démontrer le caractère biocompatible de l'oxyde d'yttrium excluant ainsi tout effet nocif de cet élément dans les zircones dopées

Reduction of Bacterial Proliferation by Zirconium Collar in Dental Implants

Article

Jan 2018

The peri-implant bacterial colonization is one of the current major problems facing dental implants with no actual protocols for prevention. The use of zirconium for bacterial eradication has already been reported and discussed in the dental literature. In this study we evaluated for the first time the ability of a “hybrid” dental implant model – where the implant collar is made out of titanium and zirconium - to reduce the peri-implant bacterial colonization, using traditional implants from the same manufacturer as controls. The results of microbiological analysis and the evaluation of the classic parameters of an implant success confirmed that, in all the 30 patients in this study, the zirconium collar had a vital role in reducing peri-implant bacterial colonization, and that the “hybrid” implants show lower plaque index values, less bleeding and less marginal bone loss than the traditional implants. Our data therefore suggest that a zirconium collar can effectively reduce the bacterial colonization around a titanium implant favoring a better long-term prognosis.

Zirconia Heads in Perspective: A Survey of Zirconia Outcomes in Total Hip Replacement

Article

Jul 2007

Zirconia ball heads have been implanted successfully from the late 1980s, but reports of wear and fractures have raised concerns about this ceramic biomaterial. This paper reviews the literature on clinical wear of zirconia-polyethylene bearings, zirconia head degradation and fractures, analysing the different factors that have led to clinical failure, such as material source, manufacturing process and type of polyethylene. The results underline the need for more homogeneous clinical series. Careful follow-up of patients with zirconia-polyethylene bearings is recommended.

Characterization of Transitional Stress Concentrations In Molar and Premolar Implants modelled as Hemispherical Shells under Uniaxial Pressure using Seth's Transition Theory

Article

Full-text available

May 2023

Shivdev Shahi

In this paper, elastic-plastic transition stresses have been analytically characterized in titanium and zirconia based crowns of dental implants. The crown of the implant is modelled in the form of a hemispherical shell which possesses transversely isotropic material behaviour. Seth’s transition theory has been implemented to model the elasticplastic stress state. The hemispherical shell so modelled is subjected to external pressure to analyse the state of compression. The results for titanium and zirconia based implant are compared with hydroxyapatite (HAP), Ca10(PO4)6(OH)2, mineral present in the enamel and dentine of molars and premolars. Elastic stiffness constants for these are taken from the available literature, and obtained using ultrasonic resonance spectroscopy, a non-destructive technique of obtaining stiffness constants. Radial and circumferential stresses are obtained for radii ratios which can handle any type of dataset for crown thicknesses.

Mechanical Stability of Restorations Supported by Titanium Base, Zirconia, and Polyetherketoneketone Abutments on One- and Two-Piece Zirconia Implants

Article

Apr 2021

Purpose: To evaluate survival, complication rates, and bending moments of one- and two-piece zirconia implants restored with different abutment materials and lithium disilicate crowns after aging, compared to titanium implants restored with titanium base-supported lithium disilicate crowns. Materials and methods: Sixty anterior crowns were either screwretained on two-piece titanium implants (C) and two-piece zirconia implants (T1, T2, T3) or cemented on one-piece zirconia implants (T4), resulting in 5 groups with 12 specimens each. For the screw-retained crowns, different abutment materials and implant connections were tested: titanium base with internal conical connection and horizontal joint component (C and T2), zirconia with internal hexagonal connection and horizontal joint component (T1), and polyetherketoneketone with internal hexagonal connection and horizontal joint component (T3). After artificial aging with thermocycling (5°C to 50°C) and chewing simulation (1,200,000 cycles, 49 N, 1.67 Hz), the surviving specimens were loaded until fracture, and the bending moments were calculated. Survival rates and respective differences during aging were analyzed with the Kaplan-Meier log-rank test, while complication rates were compared with chi-square tests. Bending moment data were evaluated using the Kruskal-Wallis test (α = .05). Results: Survival rates after artificial aging ranged from 75% (T1) to 100% (C and T4) without significant differences between the groups (P > .05). Only 41.5% of the surviving specimens were free of complications, while the remaining presented screw-loosening, loss of retention of crowns, or cracks on the crown or implant level. The complication rates varied significantly among the groups (P < .05). The mean bending moments were 173.7 × 20.1 (C), 114.5 × 20.1 (T1), 171.1 × 46.1 (T2), 258.1 × 147.4 (T3), and 194.7 × 30.9 Ncm (T4), and group T1 exhibited significantly lower median bending moment values than the other groups (P < .001). Conclusion: The zirconia one- and two-piece implants presented high survival rates after aging, yet the number of technical complications was high. New prosthetic solutions, such as titanium bases or polyetherketoneketone abutments, may offer a comparable treatment option to restore two-piece zirconia implants.

10 manikant

Article

Full-text available

Mar 2011

Ahila S,c

Zirconia compared to titanium dental implants in preclinical studies—A systematic review and meta‐analysis

Article

Mar 2019

Objectives: To evaluate whether zirconia implants demonstrate differences in hard and soft tissue integration compared to titanium implants in preclinical studies. Material and methods: In March 2017, electronic (MEDLINE, EMBASE) and hand search was performed to identify preclinical studies comparing zirconia and titanium implants. Primary outcomes were bone-to-implant contact (BIC) and removal torque out (RTQ), respectively, push-in (PI) measurements. Secondary outcomes included biologic width (BW) dimensions. Results: A total of 37 studies were included for data extraction after screening of 91 from 1,231 selected titles. Thirty-seven experimental studies using six different species were identified. The follow-up periods ranged between 0.4 and 56 weeks. For titanium, mean values of 59.1% (95% CI: 53.3 - 64.8), 102.6 Ncm (95% CI: 81.5 - 123.6), and 25.1 N (95% CI: 20.2 - 30.0) for BIC, RTQ, and PI were estimated, respectively. The mean values for zirconia were 55.9% (95% CI: 51.6 - 60.1), 71.5 Ncm (95% CI: 51.1 - 91.9), and 22.0 N (95% CI: 13.2 - 30.7) for corresponding parameters. Confounding factors such as animal species, implant material, loading protocol, and study or loading duration significantly influenced the outcomes. Similar qualitative soft tissue integration was reported for zirconia and titanium implants. However, faster maturation processes of epithelial and connective tissues around zirconia implants were assumed. Quantitatively, similar BW dimensions were evaluated for titanium (3.5 mm; 95% CI: 2.9 - 4.2) and zirconia (3.2 mm; 95% CI: 2.7 - 3.7), whereas the loading protocol significantly influenced the outcomes. Conclusions: Zirconia and titanium implants demonstrate a similar soft and hard tissue integration capacity. However, titanium tended to show a faster initial osseointegration process compared to zirconia. Importantly, not only material characteristics but predominantly animal species and study protocols can significantly influence the outcomes.

A review of biocompatibility of zirconia and bioactivity as a zirconia implant: In vivo experiment

Article

Full-text available

Jan 2019

In vitro performance of two-piece zirconia implant systems for anterior application

Article

Apr 2016

Objectives: To investigate the influence of the implant-abutment connection on the long-term in vitro performance and fracture resistance of two-piece zirconia implant systems for anterior application. Methods: Six groups of two-piece zirconia implant systems (n=10/group) with screw-retained (5×) or bonded (1×) connections were restored with full-contour zirconia crowns. A two-piece screw-retained titanium system served as reference. For simulating anterior loading the specimens (n=8/group) were mounted at an angle of 135° in the chewing simulator, and subjected to thermal cycling (TC: 2×9000×5°/55°C) and mechanical loading (ML: 3.6×10(6)×100N). Failed restorations were examined (scanning electron microscopy). Fracture resistance and maximum bending stress of surviving restorations were determined. 2 specimens per group were loaded to fracture after 24h water storage without TCML. Data were statistically analyzed (ANOVA; Bonferroni; Kaplan-Meier-Log-Rank; α=0.05). Results: The bonded zirconia system and the titanium reference survived TCML without any failures. Screw-retained zirconia systems showed fractures of abutments and/or implants, partly combined with screw fracture/loosening. Failure frequency (F) varied between the groups (F=8×: 3 groups, F=3×: 1 group, F=1×: 1 group). The Log-Rank-test showed significant (p=0.000) differences. Fracture forces and maximum bending stresses (mean±standard deviation) differed significantly (ANOVA: p=0.000) between 233.4±31.4N/317.1±42.6N/mm(2) and 404.3±15.1N/549.2±20.5N/mm(2). Fracture forces after TCML were similar to 24h fracture forces. Significance: Screw-retained two-piece zirconia implant systems showed higher failure rates and lower fracture resistance than a screw-retained titanium system, and may be appropriate for clinical anterior requirements with limitations. Failures involved the abutment/implant region around the screw, indicating that the connecting design is crucial for clinical success.

Use of fluorochromes for direct enumeration of total bacteria in environmental samples: Past and present

Article

Full-text available

Jan 1995
Microbiol Rev

Understanding the role of bacteria in microbial food webs is intimately connected to the methods applied in the direct enumeration of bacteria. We have examined over 220 papers describing studies in which fluorochrome staining followed by epifluorescent microscopic direct counts was used to estimate total bacterial abundances. In this review, we summarize patterns in the use of 3,6-bis[dimethylamino]acridinium chloride (acridine orange) and 4',6-diamidino-2-phenylindole (DAPI), the two stains most frequently used in bacterial enumeration. The staining of samples with these fluorochromes, followed by filtration and direct counting of bacterial cells on filter surfaces, has become routine over the past 10 years. We examine trends in features of the standard direct count methods, such as sample preservation and preparation techniques, membrane filter types used, applied stain concentrations, duration of staining, and counting strategies, in relation to the types of samples being examined. The high variability in bacterial counts observed within similar sample types may be partially accounted for by differences in methods. Synthesizing review findings, we include a recommended method for the direct enumeration of bacteria in environmental samples.

Clinical Experience with One-Stage, Non-Submerged Dental Implants

Article

Full-text available

Jul 1999

This review article describes the scientific documentation of one-stage, non-submerged dental implants. In the past 25 years, numerous in vivo studies have demonstrated that non-submerged titanium implants achieve osseointegration as predictable as that of submerged titanium implants. This observation was confirmed in prospective clinical studies, mostly done with the ITI Dental Implant System. ITI implants have been widely documented for up to 10 years of prospective follow-up at various centers. All studies showed success rates well above 90%. In summary, the non-submerged approach is a true alternative to the original healing modality with submerged titanium implants. The non-submerged approach offers several clinical advantages: (i) the avoidance of a second surgical procedure and less chair time per patient, resulting in overall reduced treatment cost; (ii) the lack of microgap at the bone crest level, leading to less crestal bone during healing and resulting in a more favorable crown-to-implant length ratio; and (iii) a simplified prosthetic procedure, presenting an ideal basis for cemented implant restorations. Due to these significant clinical advantages, the non-submerged approach will become more important in implant dentistry in the near future, particularly in implant sites without esthetic priority.

Maximum Utilization of the Life Table Method in Analyzing Survival

Article

Jan 1958
J Chron Dis

Measurement of patient survival is necessary for the evaluation of treatment of usually fatal chronic diseases. This is particularly true for cancer. The American College of Surgeons, recognizing this, requires the maintenance of a cancer case registration and follow-up program for approval of a hospital cancer program [1], Acceptance of survival as a criterion for measuring the effectiveness of cancer therapy is also attested to by the very large number of papers published every year reporting on the survival experience of cancer patients.

The microbiota associated with successful or failing osseointegrated titanium implants

Article

Dec 1987
ORAL MICROBIOL IMMUN

Abstract In this study the microbiota associated with oral endosteal titanium hollow cylinder implants (ITI) was studied using microscopic, immunochemical and cultural methods. Samples from 5 edentulous patients with successfully incorporated implants serving as abutments for overdentures for more than one year were compared with samples from 7 patients with clinically failing implants. Unsuccessful sites were characterized by pocket probing depths of 6 mm or more, suppuration and visible loss of alveolar bone around the implant as visualized on radiographs. These sites harbored a complex microbiota with a large proportion of Gram-negative anaerobic rods. Black-pigmented Bacteroides and Fusobacterium spp. were regularly found. Spirochetes, fusiform bacteria as well as motile and curved rods were a common feature in the darkfield microscopic specimens of these sites. Control sites in the same patients harbored small amounts of bacteria. The predominant morphotype was coccoid cells. Spirochetes were not present, fusiform bacteria, motile and curved rods were found infrequently and in low numbers. The microbiota in control sites in unsuccessful patients and in site in successful patients were very similar. On the basis of these results, it is suggested that “periimplantitis” be regarded as a site specific infection which yields many features in common with chronic adult periodontitis.

Maximum Utilization Of The Life Table Method Of Analyzing Survival

Article

Dec 1959
J Chron Dis

We have illustrated the life table method for computing survival rates with 5-year survival data for cancer patients, emphasizing the advantage gained by including survival information on cases which entered the series too late to have had the opportunity to survive a full 5 years. The advantage is measured in terms of reduction in standard error of the survival rate. For the five series of patients in this paper, the reduction in standard error ranged from one-third to two-thirds.

Evaluation of postsurgical crestal bone level adjacent to non-submerged dental implants

Article

Sep 1998

In most of the studies on long-term radiographic evaluations of crestal bone levels adjacent to dental implants, no baseline radiographs taken immediately postsurgically had been obtained. The aim of this study was to test the reproducibility of a simple radiographic method for linear measurements of changes in bone levels and to evaluate changes in crestal bone levels adjacent to non-submerged ITI implants 1 year following the surgical procedure. From 128 patients enrolled in a clinical and radiographic longitudinal study 40 patients also had radiographs taken immediately postsurgically. They were, however, not obtained as "identical" images. The radiographs were mounted onto slides and projected on a screen. Mesially and distally from 57 implants triplicate linear measurements of the distance implant shoulder to bone crest were taken, using known dimensions of the implants as internal reference distances. The median difference of 213 (out of 228 possible) duplicate measurements was 0.00 mm (ranging from -1.72 mm to +1.47 mm when comparing the second to the third reading). Some 81% of the double measurements were within +/- 0.5 mm and the precision was 0.30 mm. In the immediate postoperative radiographs the median mesial bone level was located at 2.07 mm (distally 2.19 mm) from the implant shoulder. A statistically significant amount of bone loss in the first year was observed mesially (median = -0.78 mm) and distally (-0.85 mm) (Wilcoxon matched pairs signed rank test P < or = 0.001). No statistically significant influence of the implant location, the implant length, type of the implant (screw; cylinder) was observed (Kruskal-Wallis P > 0.05). The age of the patients was not correlated significantly to the amount of bone loss observed. In conclusion, methodological limitations existed when evaluating linear bone changes in non-identical radiographs using reference dimensions of the implants. The amount of postsurgical bone loss estimated in other studies was confirmed when using an immediate postoperative radiograph as a baseline.

A Radiographic Evaluation of Bone Healing Around Submerged and Non-Submerged Dental Implants in Beagle Dogs

Article

Mar 1999

The rehabilitation of the oral cavity with dental implants has become a predictable treatment modality. However, there have been only a few direct comparisons evaluating the submerged and nonsubmerged placement techniques. The purpose of this study was to characterize radiographic peri-implant bone changes following the insertion of submerged and nonsubmerged implants in the beagle dog. At the end of the extraction healing phase, 19 submerged and 19 nonsubmerged implants were randomly placed in a split-mouth study design and observed over an 18-week period. For submerged implants, a second stage surgery and transmucosal abutment attachment was performed at week 12. Standardized dental radiographs taken at baseline, week 12, and week 18 were used to measure peri-implant bone changes. The radiographs were analyzed with a simple computer assisted method. A total of 43 standardized radiographs were exposed to evaluate the 38 implants. During the study period, all submerged and nonsubmerged implants demonstrated peri-implant bone loss. At baseline, both submerged and nonsubmerged implants had similar bone levels (P > or = 0.05). When the mean peri-implant bone levels for submerged and nonsubmerged implants were compared from baseline to week 12, nonsubmerged implants had a significantly greater amount and rate of bone resorption than submerged implants (P < or = 0.05). Following week 12, the initially submerged implant had a significantly higher rate and amount of peri-implant bone loss than the nonsubmerged implants (P < or = 0.05). However, by the end of the study period, week 18, both submerged and nonsubmerged implants had comparable bone levels (P > or = 0.05). The study indicates that, although the temporal patterns of peri-implant bone resorption differed, there were no differences between submerged and nonsubmerged implants in the overall amount and rate of peri-implant bone loss.

Effect of hyaluronic acid on morphology and proliferation of human chondrocytes in primary cell culture

Article

Feb 2001
ANN ANAT

Hyaline articular cartilage is a specialised connective tissue with weight bearing and adsorbing functions. Injury or loss of which often leads to impaired joint function and severe pain. Since the self-renewing abilities of hyaline articular cartilage are limited, there is major interest in the development of bioengineered cartilaginous implants. A cell-matrix-biocomposite composed of a collagen I/III scaffold seeded with autologous chondrocytes is currently being used in clinical trials; however, in order to optimise culture conditions, we cultured human condrocytes and seeded them on type I/III collagen membranes and on Thermanox plastic coverslips with media containing 0 to 500 microg/ml Hyaluronic Acid. After 4 days, the cells were either fixed or BrdU incorporation procedures begun. HE staining clearly demonstrated that cells grown in HA form three dimensional clusters and produce secretory vesicles as opposed to the monolayer control cells with noticeably fewer secretory vesicles. BrdU incorporation revealed a noticeable increase in cell proliferation in cells grown in 100 microg/ml; however, no comparable increase in 500 micorg/ml but rather a slight depression in proliferation. Immunohistochemistry for collagen II and aggrecan revealed an obvious increase in deposition of these two substances with increased HA administration as compared to the control; however, again, the higher concentration of HA, 500 microg/ml, did not result in a further increase in production. These results suggest that HA at 100 microg/ml not only influences chondrocytes to differentiate and produce more Collagen II and aggrecan, but also increases proliferation. We, therefore, propose that the addition of HA at low to middle dosages in condrocyte culturing might help improve condrocyte redifferentation and thus, the bioengineered cartilage.

Physical and Biological Characteristics of Implant Materials

Article

Jul 1999

John C. Keller

In vitro Characterization of Zirconia Coated by Bioactive Glass

Article

Jun 2001
BIOMATERIALS

An in vitro evaluation of a biomedical device, which combines the mechanical properties of zirconia substrates with the bioactivity of two different glass layers (AP40 and RKKP), was performed. In this work, data on different kinds of analysis were reported both on as-sintered zirconia samples and on RKKP- and AP40-coated zirconia substrates. Structure, composition and morphology of the apatite layer growth on the coated samples after 30 days of soaking in an acellular simulated body fluid, serum protein adsorption, fibroblasts and human osteoblast-like cells adhesion, growth, morphology and biochemical aspects were studied. Results of soaking test in SBF, revealed the growth of an apatite layer on the surface of the glass-coated samples. Proteins adsorbed to the materials were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and results evidenced that the two glass-coated materials bound a higher amount of total protein than did the zirconia substrate. Fibroblasts and osteoblast-like cells cultured on RKKP- and AP40-coated zirconia showed a higher proliferation rate, leading to confluent cultures with higher cell density and a generally better expression of osteoblast alkaline phosphatase activity in comparison with zirconia substrate. In conclusion, our results indicate that the surface chemical characteristics of the two glass coatings AP40 and RKKP, with no great differences between them, substantially enhance zirconia integration with bone cells at least in vitro. This effect may be of significance in the stability of glass-coated zirconia orthopaedic and dental implants.