Abstract

Recently, several experimental and clinical investigations found that immediately loaded implants obtained satisfactory levels of osseointegration with high success percentages. Only a few long-term studies of immediately loaded implants have been reported in the literature. The aim of this study was a 7-year clinical and radiographic follow-up of 93 immediately loaded dental implants in human patients. Eleven patients were consecutively enrolled in this study. A total of 7 full and 9 partial edentulous arches were rehabilitated. Patients presented a completely edentulous mandible (n = 6), a completely edentulous maxilla (n = 1), mandibular posterior edentulous areas (n = 5), or a posterior maxillary edentulous area (n = 1). Patients were rehabilitated with a bar and an overdenture (n = 4), a provisional prosthesis of 3 to 12 elements (n = 11), or a metal-ceramic bridge of 10 elements (n = 1). A total of 93 implants were inserted and loaded within a 24-hour time frame. Six implants failed in the first year after loading. No more failures were observed in the following 6 years, and all the other implants were well integrated from a clinical and radiographic point of view. The cumulative success rate at 7 years was 93.5%, and the prostheses survival rate was 98.5%. The mean marginal bone loss was 0.6 mm after the first year and 1.1 mm at the 7-year evaluation. Primary stability is one of the most important parameters in immediately loaded implants because it avoids micromotion at the bone-implant interface. Four of the 6 failures in our patients occurred in partially edentulous patients; an excessive load applied to these small bridges could be the reason for the failure. Also, the bone quality is important, for 3 of our failed implants had been inserted in D3 bone. Our clinical and radiographic results have shown that these immediately loaded implants have remained osseointegrated for a long period. Our results point to the possibility of using the immediate loading technique in selected and well-informed cases.

Introduction

A submerged healing period of about 3 to 4 months was deemed necessary for the formation of mineralized bone around dental implants, whereas a too-early loading with excessive interfacial micromotion could affect the peri-implant tissues in an untoward manner with the occurrence of a fibrous tissue at the bone-biomaterial interface.1,2 Little is known, however, on the strain distribution in bone around dental implants after loading with its triggering effects on cells and their biological activities.2 Excessive micromotion probably damages the early scaffolding from the fibrin clot, impeding its adherence to the implant surface.2 Furthermore, the initial necrotic bone at the interface between bone and implant was believed to be unable to bear the prosthetic load until it was replaced by newly formed bone.3,4 This waiting period may cause functional and psychological problems to the patients,5 with the discomfort of wearing complete dentures, and could be one of the reasons why some patients do not choose implant-supported restorations.6 The immediate loading technique, on the other hand, reduces the morbidity associated with fewer surgical interventions and facilitates the functional rehabilitation.7 Moreover, because soft and hard tissues heal concurrently, the length of treatment can be reduced.8 Recently, several investigators found that immediately loaded implants placed in different clinical conditions were able to obtain clinically satisfactory levels of osseointegration with high success percentages.7,9–20 The term immediate loading should be reserved only for the implants that are loaded in the time frame of 24 hours. Only a few long-term studies of immediately loaded implants have been reported in the literature. The aim of this study was a 7-year clinical follow-up of 93 immediately loaded dental titanium implants in human patients.

Materials and Methods

Eleven patients (7 men and 4 women; mean age 42 years, range 32–68) were consecutively enrolled in this study between April 1996 and July 1997. The Ethic Committee of the University of Chieti, Chieti, Italy, approved the protocol. All the patients gave their informed consent. Inclusion criteria were adequate amount of bone height and width, an implant site free from acute infection, a healthy appearance of the sinuses, sufficient primary stability, and an alveolar crest that would permit a prosthetically correct sagittal implant placement. Exclusion criteria were any systemic disease; metabolic bone disease; previously grafted jaws; previously irradiated jaws; a history of parafunctions; active inflammation or active infection in the oral cavity; pregnancy; and less than 1 mm of bone available at the buccal, lingual, and apical aspects of the implant. Ninety-three implants (31 IMZ and 62 Frialit-2) (Friadent, Mannheim, Germany) were inserted and immediately loaded. A total of 7 full and 9 partial edentulous arches were rehabilitated (Table 1) (Figures 1 through 8). Six patients presented a completely edentulous mandible and were rehabilitated with 43 implants. One patient presented a completely edentulous maxilla and was rehabilitated with 12 implants, and 5 patients presented mandibular posterior edentulous areas and were rehabilitated with 23 implants. One patient presented an anterior maxillary edentulous area and received 8 implants, and 3 patients presented a posterior maxillary edentulous area and received 12 implants. Patients were rehabilitated with a bar and an overdenture (n = 4), a provisional prosthesis of 3 to 12 elements (n = 11), or a metal-ceramic bridge of 10 elements (n = 1). The implants were loaded after 1 day. Periapical radiographs were taken after 1, 3, 6, 12, 24, 36, 48, 60, 72, and 84 months. At the 12-month follow-up and at each year thereafter, the prostheses were removed and a clinical evaluation of the peri-implant tissues, the implant mobility, and the bleeding index was made for each individual implant.

Table 1

Implants inserted in the different anatomical configurations

Implants inserted in the different anatomical configurations
Implants inserted in the different anatomical configurations

Figures 1–8. Figure 1. Preoperative panoramic X ray. Figure 2. Postoperative panoramic X ray. Figure 3. Postoperative periapical X ray. Figure 4. Final restoration. Maxilla, occlusal view of the abutments. Figure 5. Final restoration. Mandible, occlusal view of the abutments. Figure 6. Final restoration. Maxilla, occlusal view. Figure 7. Final restoration. Mandible, occlusal view. Figure 8. Final restoration. Frontal view

Figures 1–8. Figure 1. Preoperative panoramic X ray. Figure 2. Postoperative panoramic X ray. Figure 3. Postoperative periapical X ray. Figure 4. Final restoration. Maxilla, occlusal view of the abutments. Figure 5. Final restoration. Mandible, occlusal view of the abutments. Figure 6. Final restoration. Maxilla, occlusal view. Figure 7. Final restoration. Mandible, occlusal view. Figure 8. Final restoration. Frontal view

Success criteria were no peri-implant radiolucent areas; confirmed individual implant stability; the implant functioning as an anchorage for the functioning prosthesis; and no suppuration, pain, or ongoing pathological processes. All implants that did not fulfill the success criteria were classified as failures.

The marginal bone level was read from periapical radiographs taken at implant insertion and at each annual evaluation. A conventional radiograph Rinn holder was used (long-cone technique). The marginal bone level was measured as the distance from the implant crown border to the most coronal point where the marginal bone met the implant. A peak scale loupe with a ×7 magnifying factor and a scale graduated in 0.1 mm was used, and the same examiner (M.D.) made all measurements at the mesial and distal surfaces.

Results

After 3 months, 1 patient complained of pain in the implant region. The bridge was removed and 2 of the 3 implants were found to be mobile and were easily removed. Another patient, on removal of the fixed provisional prosthesis on a follow-up at 6 months, presented 2 maxillary implants with a vertical bone loss of more than 50% of the implant length. These implants were consequently removed. In another case, an implant was lost as the bridge came off because of cement failure, whereas another was removed because it was not integrated (Table 2). All the failures were observed in the first year of loading; no more implant failures were observed in the following 6 years (Table 3). All the other implants were well osseointegrated from a clinical and radiographic point of view. The cumulative implant success rate after a 7-year follow-up was 93.5%, and the prostheses survival rate was 98.5 % (Table 4).

Table 2

Failures associated with immediate functional loading*

Failures associated with immediate functional loading*
Failures associated with immediate functional loading*
Table 3

Life table analysis*

Life table analysis*
Life table analysis*
Table 4

Cumulative implant success

Cumulative implant success
Cumulative implant success

The mean marginal bone loss value is the difference between the rough part of the implants length that is no longer in contact with bone and the distance from the reference point. The mean marginal bone loss (first year) was 0.6 mm (SD = 0.2) and subsequently 1.1 mm at the 7-year evaluation (SD = 0.2) (Table 5) (Figures 9 through 11). All the patients showed no progressive marginal bone loss over time.

Table 5

Marginal bone loss

Marginal bone loss
Marginal bone loss

Figures 9–11. Figure 9. Peri-apical X ray 1 year after loading. Figure 10. Periapical X ray 3 years after loading. Figure 11. Periapical X ray 7 years after loading

Figures 9–11. Figure 9. Peri-apical X ray 1 year after loading. Figure 10. Periapical X ray 3 years after loading. Figure 11. Periapical X ray 7 years after loading

Discussion

Frialit-2 implants have a stepped cylinder configuration where the axial loads acting on the implants are thought to be distributed to the step plateaus and lateral forces are dissipated to enveloping surfaces.21 A very important requirement for the long-term success of endosseous implants is primary stability. Micromotion of more than 100 μm at bone-implant interface has been shown to be important for the type of tissues that will form at the interface, particularly if the implants are loaded soon after the implant insertion.22,23 

Important factors for a proper implant integration in immediately loaded implants have been reported to be bone quality, macro- and microinterlock properties of the implant, bicortical initial stabilization, number and optimal distribution of implants, and careful use of cantilevers. These are also necessary to splint the immediately loaded implants to provide a sufficient degree of stability and to protect the bone-implant interface from the negative effects of overloading.8 Good primary stability serves to decrease the distortional strains in the newly regenerating tissues and to improve the chances of neo-osteogenesis at the interface; on the contrary, a poor stability of the implants has been shown to determine an important distortional strain with fibrous tissue formation at the interface.4 The level of strain that can be safely placed on a dental implant before the occurrence of fibrous tissue at the interface must be investigated. The control of micromotion is probably the key issue in obtaining osseointegration in immediately loaded implants.19 The reduction of micromotion can be obtained through a wide anterior-posterior distribution of the immediately loaded implants and a cross-arch stabilization of the edentulous arches with a rigid prosthesis.19 Our patients experienced a steep decline in the rate of implant loss after the first year and in the following years; no more failures were observed. We confirm data already reported in the literature.11,17,24 Almost all the failures were presented in the initial stages when the bony interface was developing. Four of these 6 failures occurred in immediately loaded bridges in partially edentulous patients; an excessive load applied to these small bridges could be the reason for these failures. Also, the bone quality is important, for 3 of our 6 failed implants had been inserted in D3 bone. In this respect, Grunder25 reported that all his failed implants were the most distal implants in that particular quadrant, and that all implants had been inserted in D3 or D4 bone.

Evaluation of the radiograps followed up to 7 years leads us to conclude that peri-implant resorption in immediately loaded implants is comparable with 2-stage implant placement methods subjected to an equal loading period. Ericsson et al26 reported an initial average bone loss of 0.4 mm in early loaded implants (18 months) an additional 0.2 mm at 5 years. No differences were observed among implants in different anatomical configurations.

Ibanez and Jalbout19 found an average radiographic bone loss of 0.65 mm at the 12-month follow-up and 0.94 mm at the 24-month follow-up. Proussaefs et al.8 found a marginal bone loss of 0.90 mm after 12 months in hydroxyapatite-coated implants used in single-premolar replacement. Wolfinger et al.14 found no differences in the marginal bone level changes betwen immediately loaded implants and 2-stage implants. Rocci et al.17 found a marginal bone loss of 1.0 mm during the first year in immediately loaded implants in the maxilla. On the contrary, Lorenzoni et al.13 found that mean bone changes at prosthetic delivery was 0.9 mm resorption for loaded implants and 0.33 mm for nonloaded implants, and this difference was statistically highly significant.

Also, a careful surgical technique that minimizes trauma to the soft tissues appears to reduce initial bone loss. In our patients, the prosthetic unit/implant (PU/I) value was 1 in the maxilla and 1.1 in the mandible (Table 6). The optimal PU/I value is found in the single-tooth restoration (PU/I = 1).

Table 6

Prosthetic unit/implant (PU/I) ratio

Prosthetic unit/implant (PU/I) ratio
Prosthetic unit/implant (PU/I) ratio

A high PU/I value could produce bending and flexure of the interim restoration, leading to an implant-interface micromovement and resulting in a fibrous implant interface.

Clinical reports with PU/I greater than 2 experienced higher failure rates than did our reports.27 A low PU/I value improves the long-term prognosis of the implants and prosthetic restorations, and this applies even more so to more demanding situations like immediate functional loading/nonfunctional loading. It is important to build a prosthetic restoration that avoids transferring excessive stresses to the interface. It is then necessary to avoid long bridge spans; use rigid metallic abutments; use metallic reinforcements to the provisional prosthesis; decrease, when possible, the height of the clinical crown; avoid occlusal contacts in parafunctions or wear a night guard; and avoid cantilevers.

Our clinical and radiographic results have shown that these implants remain osseointegrated for long periods (up to 7 years). More studies are certainly necessary concerning the loading times of dental implants, for our results can point to the possibility of an immediate loading of dental implants but only in very selected and well-informed cases.

Acknowledgments

This work was partially supported by the National Research Council, Rome, Italy; by the Ministry of Education, University and Re-search, Rome, Italy; and by Research Association for Dentistry and Dermatology, Chieti, Italy.

References

References
1
Branemark
,
P. I.
,
B. O.
Hansson
, and
R.
Adell
.
et al
.
Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period.
Scand J Plast Reconstr Surg
1977
.
11
suppl 16
:
1
132
.
2
Brunski
,
J. B.
In vivo bone response to biomechanical loading at the bone/dental implant interface.
Adv Dent Res
1999
.
13
:
99
119
.
3
Brunski
,
J. B.
Forces on dental implants and interfacial stress transfer.
In: Laney WR, Tolman DE, eds. Tissue Integration in Oral, Orthopaedic and Maxillofacial Reconstruction. Chicago, Ill: Quintessence; 1992:108–124
.
4
Carter
,
D. R.
and
N. J.
Giori
.
Effect of mechanical stress on tissue differentiation in the bony implant bed.
In: Davies JE, ed. The Bone-Biomaterial Interface. Toronto, Ontario, Canada: University of Toronto Press; 1991:367–379
.
5
Chiapasco
,
M.
,
C.
Gatti
,
E.
Rossi
,
W.
Haefliger
, and
T. H.
Markwalder
.
Implant-retained mandibular overdentures with immediate loading. A retrospective multicenter study on 226 consecutive cases.
Clin Oral Implants Res
1997
.
8
:
48
57
.
6
Andersen
,
E.
,
H. R.
Haanaes
, and
B. M.
Knutsen
.
Immediate functional loading of single-tooth ITI implants in the anterior maxilla: a prospective 5-years pilot study.
Clin Oral Implants Res
2002
.
13
:
281
287
.
7
Cooper
,
L. F.
,
A.
Rahman
,
J.
Moriarty
,
M.
Chaffee
, and
D.
Sacco
.
Immediate mandibular rehabilitation with endosseous implants: simultaneous extraction, implant placement, and loading.
Int J Oral Maxillofac Implants
2002
.
17
:
517
525
.
8
Proussaefs
,
P.
,
J.
Kan
,
J.
Lozada
,
A.
Kleinman
, and
A.
Farnos
.
Effects of immediate loading with threaded hydroxyapatite-coated root-form implants on single premolar replacements: a preliminary report.
Int J Oral Maxillofac Implants
2002
.
17
:
567
572
.
9
De Bruyn
,
H.
and
B.
Collaert
.
Early loading of machined-surface Branemark implants in completely edentulous mandibles: healed bone versus fresh extraction sites.
Clin Implant Dent Relat Res
2002
.
4
:
136
142
.
10
Collaert
,
B.
and
H.
De Bruyn
.
Early loading of four or five Astra Tech fixtures with a fixed cross-arch restoration in the mandible.
Clin Implant Dent Relat Res
2002
.
4
:
133
135
.
11
De Bruyn
,
M.
,
J.
Kisch
,
B.
Collaert
,
U.
Linden
,
K.
Nilner
, and
L.
Dvarsater
.
Fixed mandibular restorations on three early-loaded regular platform Branemark implants.
Clin Implant Dent Relat Res
2001
.
3
:
176
184
.
12
Gatti
,
C.
and
M.
Chiapasco
.
Immediate loading of Branemark implants: a 24-month follow-up of a comparative prospective pilot study between mandibular overdentures supported by conical transmucosal and standard MKII implants.
Clin Implant Dent Relat Res
2002
.
4
:
190
199
.
13
Lorenzoni
,
M.
,
C.
Pertl
,
K.
Zhang
, and
W. A.
Wegscheider
.
In patient comparison of immediately loaded and non-loaded implants within 6 months.
Clin Oral Implants Res
2003
.
14
:
273
279
.
14
Wolfinger
,
G. J.
,
T. J.
Balshi
, and
B.
Rangert
.
Immediate functional loading of Branemark System implants in edentulous mandibles: clinical report of the results of developmental and simplified protocols.
Int J Oral Maxillofac Implants
2003
.
18
:
250
257
.
15
Malò
,
P.
,
B.
Rangert
, and
M.
Nober
.
“All-on-four” immediate-function concept with Branemark System implants for completely edentulous mandibles: a retrospective clinical study.
Clin Implant Dent Relat Res
2003
.
5
suppl
:
2
9
.
16
Vanden Bogaerde
,
L.
,
G.
Pedretti
,
P.
Dellacasa
,
M.
Mozzati
, and
B.
Rangert
.
Early function of splinted implants in maxillas and posterior mandibles using Branemark System machined-surface implants: an 18-month prospective clinical multicenter study.
Clin Implant Dent Relat Res
2003
.
5
suppl
:
21
28
.
17
Rocci
,
A.
,
M.
Martignoni
, and
J.
Gottlow
.
Immediate loading in the maxilla using flapless surgery, implants placed in predetermined positions, and prefabricated provisional rstorations: a retrospective 3-year clinical study.
Clin Implant Dent Relat Res
2003
.
5
suppl
:
29
36
.
18
Malò
,
P.
,
B.
Friberg
,
G.
Polizzi
,
F.
Gualini
,
T.
Vighagen
, and
B.
Rangert
.
Immediate and early function of Branemark System implants placed in the esthetic zone: a 1-year prospective clinical multicenter study.
Clin Implant Dent Relat Res
2003
.
5
suppl
:
37
46
.
19
Ibanez
,
J. C.
and
Z. N.
Jalbout
.
Immediate loading of Osseotite implants: two-year results.
Implant Dent
2002
.
11
:
128
136
.
20
Degidi
,
M.
and
A.
Piattelli
.
Immediate functional and non functional loading of dental implants: a 2 to 60 months follow-up study of 646 titanium implants.
J Periodontol
2003
.
74
:
225
241
.
21
Gomez-Roman
,
G.
,
W.
Schulte
,
B.
D'Hoedt
, and
D.
Axman-Krcmar
.
The Frialit-2 implant system: five-year clinical experience in single-tooth and immediately post-extraction applications.
Int J Oral Maxillofac Implants
1997
.
12
:
299
309
.
22
Tarnow
,
D. P.
,
S.
Emtiaz
, and
A.
Classi
.
Immediate loading of threaded implants at stage 1 surgery in edentulous arches: ten consecutive case reports with 1- to 5-year data.
Int J Oral Maxillofac Implants
1997
.
12
:
319
324
.
23
Balshi
,
T. J.
and
G. J.
Wolfinger
.
Immediate loading of Branemark implants in edentulous mandibles: a preliminary report.
Implant Dent
1997
.
6
:
83
88
.
24
Schnitman
,
P. A.
,
P. S.
Wöhrle
,
J. E.
Rubenstein
,
J. D.
DaSilva
, and
N. H.
Wang
.
Ten-year results for Branemark implants immediately loaded with fixed prostheses at implant placement.
Int J Oral Maxillofac Implants
1997
.
12
:
495
503
.
25
Grunder
,
U.
Immediate functional loading of immediate implants in edentulous arches: two-year results.
Int Periodontics Restorative Dent
2001
.
21
:
545
551
.
26
Ericsson
,
I.
,
H.
Nilson
,
T.
Lindh
,
K.
Nilner
, and
K.
Randow
.
Immediate functional loading of Branemark single tooth implants. An 18 months clinical pilot follow-up study.
Clin Oral Implants Res
2000
.
11
:
26
33
.
27
Wolfe
,
L. A.
and
J. A.
Hobkirk
.
Bone response to a matched modulus endosseous implant material.
Int J Oral Maxillofac Implants
1989
.
4
:
311
320
.

Author notes

Marco Degidi, MD, DDS, is in private practice in Bologna, Italy, and is a visiting professor, Dental School, University of Chieti, Chieti, Italy. Address correspondence to Dr Degidi at Via S. Allende 12/A, Bologna, Italy (marcodegidi@tin.it).

Adriano Piattelli, MD, DDS, is a professor of Oral Medicine and Pathology, Dental School, University of Chieti, Chieti, Italy.