Early and Immediate Loading of Implants
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Immediate Implants and Immediate Loading in Periodontally Compromised Patients—A 3-Year Prospective Clinical Study-Int J Periodontics Restorative Dent 2010;30:447–455
A total of 23 periodontally compromised patients (11 women, 12 men; 4 smokers, 4 controlled diabetics) were included in this study. Pretreatment casts weretaken and vertical dimension of occlusion was determined. In most patients, 6 Straumann implants were distributed along the arch according to the surgical guide or bone availability, with the most distal ones in the maxilla slightly tilted so they could emerge more distally. A total of 168 implants (146 Straumann, 10 Nobel Biocare, 8 Biomet 3i, and 4 Lifecore) were placed (83 in the maxilla, 85 in the mandible). Of those in the maxilla, 74 were loaded imme- diately (implant stability quotient mentor [ISQm] > 70) and 9 placed with delayed loading (ISQm = 70). Of the 85 implants placed in the mandible, all were loaded immediately (ISQm > 70). If an FPD had not been fabricated already, impressions were taken during surgery to do so. The prosthesis was then adapted (cemented or screwed) to the 6 implants within the first 48 hours postsurgery. After 2 months, definitive impressions were taken, and a definitive porcelain-fused-to-metal implant-supported 12-element FPD was fabricated and cemented or screwed to all 6 implants. Of the 168 implants, 108 were immediate implants and 159 immediately loaded. Only 2 implants (1 in the mandible, 1 in the maxilla) did not osseointegrate. This yields a 3-year cumulative survival rate of 98.74% (98.65% in the maxilla, 98.82% in the mandible). From a total of 26 immediately loaded prostheses (12 in the maxilla, 14 in the mandible), 6 were cemented and 20 screw-retained. The 3-year cumulative survival rate was 100%.
Immediate loading in mandibular and maxillary periodontally compromised patients presents itself as a predictable technique with a 100% cumulative survival rate for provisional and definitive prosthetic rehabilitations
Immediate Implant Loading: Current Status From Available Literature.
Clinical Science and Techniques
Implant Dentistry. 16(3):235-245, September 2007.
Avila, Gustavo DDS, PhD *; Galindo, Pablo DDS, PhD +; Rios, Hector DDS, PhD *; Wang, Hom-Lay DDS, MSD ++
Abstract:
The introduction of osseointegrated implants in dentistry represents a turning point in dental clinical practice.
Thanks to their multiple therapeutic possibilities and the high predictability of success, implant therapy is now
regarded as an extremely reliable approach to replace missing teeth. The concept of immediate implant loading has
recently become popular due to less trauma, reduced overall treatment time, decreased patient's anxiety and
discomfort, high patient acceptance and better function and esthetics. Nonetheless, research and understanding
in this area are confuse and sometimes contradictory. Hence, it is the purpose of this review to provide rational
for immediate implant loading, summarize current available literature, and analyze factors that influencing this
newly introduced treatment method. Results from this review indicated that immediate implant loading achieved
similar high success rate as that noted in the conventional approach (delayed protocols). However, a careful
case selection, proper treatment plan, meticulous surgery and proper design of prosthesis are essential for
optimal outcomes when this approach is adopted.
1. Listgarten, M.A., Clinical trials
of endosseous implants: issues in analysis and interpretation. Ann Periodontol,
1997. 2(1): p. 299-313.
The majority of contemporary endosseous dental implant systems are based on
designs and materials that, over the last three decades, have proved to be
predictably reliable. With proper surgical and prosthetic protocols, rates of
implant loss have been held to 15% or less over a 5-year period. This
information was obtained largely through longitudinal descriptive studies,
primarily aimed at obtaining implant survival rates under ideal clinical
conditions, with strict inclusion and exclusion criteria for admitting patients
into the studies.
It is important to emphasize that under conditions of routine
clinical practice, where patient selection may be more relaxed than in clinical
trials and clinicians attempt to stretch the limits of current technology, the
survival rates may not necessarily match those reported in the literature. Since
"surviving" implants may exhibit characteristics likely to lead to
eventual loss of the implant, for example severe osseous defects, such implants
may not necessarily be considered successful.
Successful implants should fulfill
a list of other criteria considered essential for long-term survival.
Differences in implant design preclude some of these criteria from being
uniformly applied to all systems. There is a need to identify criteria for
success that can be applied to the majority of implant systems. Implants that
fail to meet these criteria should be considered failures. Since failure rates
may include "failed" as well as "failing"
("ailing") implants, the two categories should be listed separately.
From a practical standpoint, implant failures can be grouped into
"early" failures, primarily the result of surgical and/or
postoperative complications, and "late" failures that arise during and
following the restorative phase.
The ability of individual systems to achieve
excellent success rates, despite some major differences in their design from
other systems, suggests that some requirements, initially considered essential
for success, may not be as critical as originally believed. Examples include the
need for submerging implants during initial wound healing or the need for stress
breaking devices. On the other hand, a basic requirement for implant success,
such as primary stability at the time of insertion and following loading of the
implant, may be the unifying principle behind the need for adequate bone volume
and density, longer or wider implants, and the 3 to 6-month delay recommended
before implants are placed in function. With relatively low failure rates, a
large number of patients may have to be included in long-term clinical trials
before a statistically significant association can be established between
failure rates and potential contributing factors. For the same reasons, and to
avoid type 2 errors, large populations may be needed to show that two systems
have comparable success rates.
Proving the superiority of one system over
another may require fewer subjects. Given the overall low failure rate and the
tendency of failures to cluster in individual subjects, failure rates could be
markedly affected by the attrition of a few critical subjects. Additional
research is needed to validate methods in current use for the clinical
determination of osseointegration, and the diagnosis and treatment of occlusal
trauma and microbial infections around implants. Also, more reliable methods are
needed for the identification of the primary cause(s) of implant morbidity;
i.e., infection or occlusal factors.
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2. Holt, R., et al., Effect of early
exposure on the integration of dental implants: Part 2--Clinical findings at 6
months postloading. Int J Periodontics Restorative Dent, 2001. 21(4): p. 407-14.
Implant exposure during initial healing after placement has been considered
important in both implant integration and postloading effects. This study
evaluated the effect of early implant exposure on the clinical findings
prerestoration and 6 months postrestoration. Forty-eight implants (24 CPTi and
24 Ti-13-13) were placed in maxillary and mandibular posterior sites in six
baboons. Implant exposure was evaluated for 24 of the submerged implants at
placement and at each weekly visit for 3 weeks after implant placement. The
crestal bone level at maxillary posterior sites was measured at 6-month
uncovering, and mandibular sites were measured at 3-month uncovering.
All sites were again measured 6 months after restoration placement. Periotest readings
were recorded at implant uncovering and again 6 months postloading. Arbitrary
groupings of the Periotest values were assigned as good = -7 to -1; guarded = 0
to +2; and poor = +3 to +27. At 6 months postloading, there were no statistical
differences between CPTi and Ti-13-13 for change in crestal bone height in
either arch. The mean change in maxillary crestal bone height varied from a
0.59- to 1.35-mm loss. The differences between the mean exposed and nonexposed
changes were not statistically significant The mean change in mandibular crestal
bone height varied from a 0.25- to 0.88-mm loss. Changes in crestal bone height
for nonexposed sites from 3-month implant uncovering to 6 months postloading
were statistically significant at the mesial, buccal, and lingual aspects. The
mean change for the nonexposed distal aspect approached significance. The
differences between the mean exposed and nonexposed changes were not
statistically significant. The overall percentage of maxillary implants in the
good category for nonexposed sites decreased by 41% from uncovering to 6 months
after loading, while no change occurred for exposed sites; the percentage of
implants in the good category was comparable for early exposed and nonexposed
sites (57% and 59%, respectively). At 6 months after loading, the percentage of
implants in the good category was more favorable for early exposed (88%) than
nonexposed sites (50%). A one-stage implant approach should provide similar
postloading clinical results as the two-stage surgical approach.
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3. Payne, A.G., et al., One-year
prospective evaluation of the early loading of unsplinted conical Branemark
fixtures with mandibular overdentures immediately following surgery. Clin
Implant Dent Relat Res, 2001. 3(1): p. 9-19.
BACKGROUND: Prospective evaluation of the early loading of unsplinted Branemark
implants with mandibular overdentures opposing conventional dentures is not
evident in the implant-related literature. PURPOSE: To clinically evaluate
progressive and early loading of 20 unsplinted conical Branemark implants in
edentulous mandibles with overdentures.
MATERIALS AND METHODS: Ten edentulous
patients all had two conical Branemark implants placed in the anterior mandible
with mandatory primary stability with bicortical anchorage. Ball abutment
connection was performed simultaneously. Previously constructed conventional
mandibular dentures were temporarily relined with tissue conditioner
postoperatively and worn with moderation for the first 2 weeks to allow
progressive loading. Early loading of the implants followed after 2 weeks, with
inclusion of the respective matrices in the mandibular dentures, using a
definitive reline procedure. RESULTS: All patients successfully functioned with
their mandibular implant overdentures from 2 to 52 weeks postoperatively. Mean
marginal bone loss was within established criteria for success: 0.22 mm (SD =
0.48 mm) mesially and 0.30 mm (SD = 0.39 mm) distally on the conical implants.
Mobility tests using the Periotest instrument became more negative, although not
at statistically significant levels. Difficulties in the management of the peri-implant
mucosa between surgery and loading at 2 weeks were observed in 40% of the
patients. CONCLUSIONS: These preliminary 1-year results show that successful
early loading of unsplinted conical Branemark implants with mandibular
overdentures is possible.
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4. Naert, I., et al., Biologic outcome
of single-implant restorations as tooth replacements: a long-term follow-up
study. Clin Implant Dent Relat Res, 2000. 2(4): p. 209-18.
BACKGROUND: The replacement of a single tooth or several teeth by means
of single-implant restorations is an increasingly used method that needs
long-term validation. PURPOSE: The goal of this study was to evaluate the
outcome of single-implant restorations by means of fixed restorations and to
define the prognosis through marginal bone level estimations. MATERIALS AND METHODS: From November 1986 to June 1998, 270 Branemark implants (215 in the
upper jaw) were installed in 219 patients (106 males). Both anterior and
posterior sites were involved. Of the 263 single restorations, 28 were placed in
private dental offices. The patients were followed until June 1999. RESULTS:
Twelve implants failed before or at abutment connection or within 6 months
afterward. Only four implants failed later. The cumulative success rates were
93% for the implants and 96.5% for the restorations over a period of 11 years.
The marginal bone loss during the first 6 months after abutment connection
reached 0.71 mm and then dropped to 0.036 mm annually over a period of 10 years.
CONCLUSIONS: Single-implant restorations (Branemark System) are a reliable
treatment with a good long-term prognosis. Failures were concentrated during the
healing period and early loading phase.
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5. Ericsson, I., et al., Early
functional loading of Branemark dental implants: 5-year clinical follow-up
study. Clin Implant Dent Relat Res, 2000. 2(2): p. 70-7.
BACKGROUND: Short-term clinical studies have indicated the possibility of
one-stage surgery and early loading of machined titanium implants. However,
long-term data comparing the outcome to the conventional two-stage technique are
missing. PURPOSE: A clinical and radiographic study was performed to compare the
outcome of oral rehabilitation of the edentulous mandible by fixed
suprastructures connected to implants installed according to either (1) a
one-stage surgical procedure and early loading (experimental group--EG) or (2)
the original two-stage concept (reference group--RG). The EG and RG comprised 16
and 11 subjects, respectively. MATERIALS AND METHODS: The following specific
inclusion criterion were adopted: (1) all patients had to consider themselves to
be in good general health, (2) the amount of bone had to enable the installation
of five to six, at least 10-mm long fixtures (Mk II fixtures; Nobel Biocare AB,
Goteborg, Sweden) between the mental foramina, and (3) the patients had to be
available for the follow-up and maintenance program. A total of 88 implants were
placed in the EG compared to 30 in the RG. In the EG, fixed appliances were
connected to the implants within 20 days following implant installation while
the fixed appliances in the RG were connected about 4 months following fixture
installation. At delivery of the suprastructures, all patients were
radiographically examined, an examination that was repeated at the 18- and
60-month follow-ups. RESULTS: The analysis of the radiographs from the EG
disclosed that during the observation period, between 18 and 60 months, the mean
loss of bone support amounted to 0.2 mm (SD = 0.4). The corresponding value
observed in the RG was 0.0 mm (SD = 0.5). During the 60-month observation
period, no fixture was lost in any of the two groups examined. The implants
under study as well as those in the reference material were at all observation
intervals found to be clinically stable. CONCLUSIONS: This clinical study
demonstrated that it is, at least based on a 5-year observation period, possible
to successfully load via a permanent fixed rigid cross-arch suprastructure
titanium dental implants soon after installation. However, such a treatment
approach has to be strictly limited to the interforamina area of the edentulous
mandible. Furthermore, the bone resorption was found to be within the same range
around such implants as around implants installed and loaded according to the
original two-stage protocol.
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6. Kronstrom, M., et al., Early implant
failures in patients treated with Branemark System titanium dental implants: a
retrospective study. Int J Oral Maxillofac Implants, 2001. 16(2): p. 201-7.
Implant failure has been associated with factors such as poor bone
quality, insufficient bone volume, implant instability, unfavorable implant
loading, and smoking habits. Infections and host responses may also be important
factors in dental implant failure. The objectives of the present study were to
identify various explanatory factors associated with titanium implant failure.
Forty subjects with stage 1 non-osseointegrated titanium dental implants (NOTI)
ad modum Branemark and 40 age- and gender-matched control subjects with
successfully osseointegrated titanium implants (SOTI) were studied.
Clinical data and gamma G immunoglobulin (IgG) antibody titers were studied. An
independent t test revealed that significantly longer implants were placed in
subjects with SOTI (P < .05). Statistically significant differences in bone
shape and resorption (BSR) scores were found between SOTI and NOTI (P < .05).
Logistic regression analysis identified 3 significant explanatory outcome
variables: serum antibody avidity scores for Bacteroides forsythus (P <
.0001), serum antibody titers to Staphylococcus aureus (P < .001), and the
BSR scores (P < .05). Antibody avidity to B forsythus and antibody titer to S
aureus were therefore the 2 most important factors associated with early implant
failures and with a significant predictive ability. This indicates that
immunologic factors are involved in osseointegration.
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7. Testori, T., et al., A prospective
multicenter clinical study of the Osseotite implant: four-year interim report. Int J Oral Maxillofac Implants, 2001. 16(2): p. 193-200.
This article reports the 4-year interim results of a multicenter study
evaluating the clinical performance of the Osseotite dental implant. At 4 study
centers, 485 Osseotite implants were consecutively placed in 181 patients (219
were placed in the mandible and 266 in the maxilla). A total of 355 implants
were placed in posterior regions. Short implants (10 mm or less) represented
31.5% (n = 153) of all implants placed in this study.
Patients were restored
with 210 restorations, distributed as 123 short-span prostheses, 58 single-tooth
replacements, 28 long-span prostheses, and 1 maxillary overdenture. At this
4-year interim evaluation, the mean time from implant placement to the most
recent evaluation was 52.6 +/- 3.0 months, with a mean loading time of 43.3 +/-
3.8 months. Of the 485 implants placed, there have been 6 failures.
All implant
failures occurred prior to loading and were categorized as early implant
failures. Five of the 6 failures occurred in the maxilla. Only one of the 153
short implants failed to integrate. Baseline radiographs were obtained at
prosthesis connection. Radiographic analysis 1 year post-restoration showed a
mean bone loss of 0.09 +/- 0.7 mm. From baseline to the end of the second year
of function, an overall mean bone loss of 0.13 +/- 0.8 mm was recorded,
indicating no additional bone was lost after the first year of implant function.
At 4 years, the cumulative implant success rate for all implants placed in this
study was 98.7%, with a 99.4% success rate in the posterior mandible and 98.4%
success rate in the posterior maxilla. Results of this 4-year interim analysis
indicate that this implant achieved a high success rate in posterior regions and
that all failures with this implant in this patient population occurred prior to
implant loading. When the clinical success of implants 10 mm or shorter was
compared to that of implants greater than 10 mm in length, the shorter implants
in this study performed similarly to longer implants.
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8. Widmark, G., et al., Rehabilitation
of patients with severely resorbed maxillae by means of implants with or without
bone grafts: a 3- to 5-year follow-up clinical report. Int J Oral Maxillofac
Implants, 2001. 16(1): p. 73-9.
Forty three patients with severely resorbed maxillae who had been
referred for implant treatment were assigned to 1 of 3 treatment options: bone
grafting and implant placement (graft group), modified implant placement with no
bone grafting (trial group), or optimized complete dentures (no-implant group).
Sixteen, 20, and 7 patients, respectively, were assigned to the 3 groups. The
patients have been examined annually, and at the time of this report they had
been followed for 3 to 5 years after treatment. At the 1-year follow-up, 10% (22
of 221) of the implants had been lost, and at the 2-year follow-up, 18% of the
implants had been lost (40 of 221; 25% in the graft and 13% in the trial group);
after that time, no further losses occurred. Life table analysis showed
cumulative success rates of 82% in the graft group and 96% in the trial group
after 1 year, and 74% and 87%, respectively, at the final examination after 3 to
5 years. The failure rate was higher in smokers than in non-smokers. A
substantial reduction of the grafted bone, especially of onlay grafts, occurred
early after grafting surgery in many patients. Mean marginal peri-implant bone
loss was 0.6 mm during the period from prosthesis connection to the 1-year
follow-up, and from the 1-year to the 3-year follow-up, average peri-implant
bone loss was 0.3 mm in the graft group and 0.5 mm in the trial group. The
results corroborated previous findings that patients with severely resorbed
maxillae have an increased risk of implant failure in comparison to patients
with good bone quantity and quality. However, in this investigation, practically
all implant losses occurred during the first 2 years, whereupon a steady state
seemed to follow for up to 5 years after loading.
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9. Davarpanah, M., et al., The
self-tapping and ICE 3i implants: a prospective 3-year multicenter evaluation.
Int J Oral Maxillofac Implants, 2001. 16(1): p. 52-60.
This multicenter prospective clinical evaluation was undertaken to
determine the therapeutic success and marginal bone level stability of 3i's
self-tapping and ICE implants after 3 years of prosthetic loading. Between July
1995 and June 1996, 189 completely or partially edentulous patients were treated
with 614 machined-surface screw-type commercially pure titanium implants
(self-tapping or ICE). Two hundred seventy-seven self-tapping implants were
placed in 85 patients (average age of 56 years), and 337 ICE implants were
placed in 104 patients (average age of 61 years). A total of 360 implants
(58.6%) were placed in posterior segments. Easier placement was reported with
the ICE implant in normal or dense bone. For the self-tapping implants, survival
rates of 92.9% and 91.6% were noted after 1 and 3 years of prosthetic loading,
respectively. Survival rates of 95.4% and 93.8% were obtained with the ICE
implant for the same periods. Late failures (after loading) were more common
than early failures (before loading) for both types of implants. The marginal
bone level of 238 self-tapping implants (85.9%) and of 307 ICE implants (91%)
was radiographically evaluated at 3 years. Marginal bone level was at the first
thread for 95.1% of implants. A loss of marginal bone level of 2 to 4 threads
was noted for 4.9% of the evaluated implants. No implant showed bone loss
greater than the fourth thread. Overall survival rates of 94.3% and 92.9% were
obtained after 1 and 3 years of prosthetic loading, respectively, for 596 and
588 implants.
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10. Brunski, J.B., In vivo bone response
to biomechanical loading at the bone/dental-implant interface. Adv Dent Res,
1999. 13: p. 99-119.
Since dental implants must withstand relatively large forces and moments
in function, a better understanding of in vivo bone response to loading would
aid implant design. The following topics are essential in this problem.
(1)
Theoretical models and experimental data are available for understanding implant
loading as an aid to case planning.
(2) At least for several months after surgery, bone healing in gaps between implant and bone as well as in
pre-existing damaged bone will determine interface structure and properties. The
ongoing healing creates a complicated environment.
(3) Recent studies reveal that an interfacial cement line exists between the implant surface and bone for
titanium and hydroxyapatite (HA). Since cement lines in normal bone have been
identified as weak interfaces, a cement line at a bone-biomaterial interface may
also be a weak point. Indeed, data on interfacial shear and tensile
"bond" strengths are consistent with this idea.
(4) Excessive interfacial micromotion early after implantation interferes with local bone
healing and predisposes to a fibrous tissue interface instead of
osseointegration.
(5) Large strains can damage bone. For implants that have healed in situ for several months before being loaded, data support the
hypothesis that interfacial overload occurs if the strains are excessive in
interfacial bone.
While bone "adaptation" to loading is a
long-standing concept in bone physiology, researchers may sometimes be too
willing to accept this paradigm as an exclusive explanation of in vivo tissue
responses during experiments, while overlooking confounding variables,
alternative (non-mechanical) explanations, and the possibility that different
types of bone (e.g., woven bone, Haversian bone, plexiform bone) may have
different sensitivities to loading under healing vs. quiescent conditions.
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11. Caudill, R., et al., Effect of
unintentional exposure of 2-stage implants upon subsequent osseointegration:
histologic findings 6 months postloading. Int J Periodontics Restorative Dent,
2000. 20(3): p. 307-14.
The purpose of this study was to evaluate the effect of early spontaneous
exposure of 2-stage implants upon subsequent histologic bone contact following
occlusal loading. As part of a study comparing 2 types of metallic threaded
implants, 48 implants (24 CPTi and 24 Ti-13Nb-13Zr) were placed in maxillary and
mandibular posterior sites in 6 baboons. Implant exposure was evaluated at time
of placement and at each weekly visit for the first 3 weeks, then at 1, 2, and 3
months, and also at 6 months for the maxilla. Block sections were removed 6
months after the implant restoration was placed into function. One third (33%)
of the maxillary implants became exposed, while 66.5% of the mandibular implants
became exposed, mostly at 1 to 3 weeks. For all maxillary implants, fibrous
tissue contact in the unintentionally exposed group (20.0%) was significantly
greater than in the group that remained submerged (7.7%). Maxillary implants
remaining submerged exhibited more sinus contact. For all mandibular implants,
bone contact in the exposed group (38.9%) was significantly greater than in the
submerged group (24.3%). Similarly, exposed implants exhibited less fibrous
tissue contact. All other parameters in both maxillary and mandibular arches
were statistically similar when comparing unintentionally exposed implants to
those that remained submerged. This study suggests that accidental exposure of
2-stage implants should result in overall similarities in postloading bone
contact to 2-stage implants that remain submerged during the early postoperative
healing period.
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12. van Winkelhoff, A.J., et al., Early
colonization of dental implants by putative periodontal pathogens in partially
edentulous patients. Clin Oral Implants Res, 2000. 11(6): p. 511-20.
There is limited scientific information available on the early
colonization of the peri-implant pockets in partially edentulous individuals.
Knowledge about this process is one step in better understanding the etiology
and pathogenesis of peri-implantitis. In this study, the early colonization of
the peri-implant pockets by putative periodontal pathogens was studied in 20
partially edentulous individuals using anaerobic culture techniques. At
baseline, the presence and levels of putative periodontal pathogens in the
microflora of periodontal pockets and saliva were established. Immediately after
loading of the titanium implants and after 6 and 12 months the presence and
levels of selected putative periodontal pathogens were determined in periodontal
and peri-implant pockets. A second aim was to detect bacterial contamination of
the implant site and the inside of the implant. At baseline, the most frequently
isolated species from the periodontal pockets were Fusobacterium nucleatum,
Prevotella intermedia and Peptostreptococcus micros. Bacteroides forsythus,
Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were isolated
from 9, 2 and 3 patients respectively. Six months after placing of the bridges,
the majority of the implant sites had detectable levels of most periodontal
bacterial species with the exception of A. actinomycetemcomitans which could not
be isolated from any of the peri-implant samples during the experimental period,
although 2 patients had this organism at baseline. In 2 patients with detectable
subgingival P. gingivalis at baseline this species was found after 12 months in
the peri-implant sites. One of these patients lost 2 implants which was
associated with a high proportion of P. gingivalis in the peri-implant pockets.
A second patient developed 2 fistulas around 2 implants at 8 months and this
event was also associated with the presence of P. gingivalis. It is concluded
that proper periodontal infection control before installment of dental implants
in partially edentulous patients may prevent early bacterial complications.
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13. Kovacs, A.F., Clinical analysis of
implant losses in oral tumor and defect patients. Clin Oral Implants Res, 2000.
11(5): p. 494-504.
In the period between 1990 and 1996, 279 endosteal dental Bone-Lock
implants were placed in 79 patients. Of them 63 have been treated with ablative
tumor and reconstructive surgery in the oral cavity, the rest presented with
maxillo-mandibular defects of different origin. The circumstances of implant
loss were noted down for descriptive analysis concerning age, sex, topography,
implant dimensions, loading, time in place and type of superstructure. Failure
analysis was done concerning the implants and the patients. Five causes for
implant loss could be detected: lacking primary osseointegration, acute
inflammation, bone loss, biomechanical overloading and tumor recurrence. No
predictive factors for implant loss and no age influence on implant loss could
be detected, no specific local implant site and no specific superstructure had
an identifiable higher risk. Survival rate of all placed implants in oral tumor
and defect patients was 83.5% after 6 years observation. Male tumor patients
were found to have a higher risk to lose implants than females. Free iliac bone
grafts impaired osseointegration of implants. The mandible offered a better
prognosis for the implants than the maxilla. Shorter and thinner implants had a
higher risk of being lost. A quarter of all patients (26.3%) had to face implant
loss. Clustering of implant loss in several patients was caused by free iliac
bone grafting and by prosthetic faults. Chemotherapy had no negative influence
on implant survival. Most implants were lost early (76%) before fabrication of
the prosthesis. After restoration there was a nearly 100% probability of
function. It is concluded that implant treatment can be equally effective for
tumor and defect patients as it is known for healthy subjects.
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14. Zubery, Y., et al., Immediate
loading of modular transitional implants: a histologic and histomorphometric
study in dogs. Int J Periodontics Restorative Dent, 1999. 19(4): p. 343-53.
Modular Transitional Implants (MTI) are made from pure titanium and are
used to support fixed provisional restorations during the osseointegration of
definitive implants. This study histologically examined the jaw response to
loaded MTIs in the dog mandible. Three implants were inserted transmucosally
into each side of the mandible in 3 dogs. Stability was examined using a
Periotest. Anterior and posterior implants were splinted using a cemented
acrylic resin fixed partial denture to allow immediate loading. The middle
implant remained unloaded and was used as a control. Dogs were sacrificed 11 to
12 weeks after implantation, and tissue blocks containing the implants were
removed. Histologic examination showed that 10 of the 18 implants had good
bone-to-implant contact, with the percentage of bone contacting the threaded
portion of the implant varying from 30% to 65%. There was no statistical
difference (p > 0.1) in percentage of bone-to-metal contact between loaded
and unloaded implants. Six implants were entirely surrounded by connective
tissue with or without inflammation; two implants were lost during the study.
The success rate did not differ between loaded and unloaded implants. In the
successful implants trabecular bone made good contact with the implant, forming
supporting struts. There was bone remodeling in some bone-to-metal contact
areas. It is believed that success was mainly influenced by the initial bone
density at the implant site and by the uncontrolled load that the animals
applied to the implants during the early healing stage.
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15. Misch, C.E., Implant design
considerations for the posterior regions of the mouth. Implant Dent, 1999. 8(4):
p. 376-86.
The posterior regions of the mouth sustain greater forces, yet often
present poorer bone density. A biomechanical approach, often presented to
decrease risk factors in such regions, is to increase implant surface area. Most
manufacturers provide implants in various lengths. The longest implants are
typically inserted into the anterior regions of the mouth, where forces of less
magnitude and superior bone quality are present. A finite element analysis
supports the hypothesis that implant length is a secondary parameter for stress
distribution. A common approach is to enhance implant surface area in the
posterior regions primarily by focusing on diameter. However, this increases
surface area by only 30% for conventional thread designs despite the fact that
forces increase by > 300% in the posterior regions. A change in implant
diameter and thread design may increase surface area by > 300%. Such
increases in surface area may decrease stresses to the crestal bone regions and
reduce both crestal bone loss and early loading implant failure.
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16. O'Mahony, A. and P. Spencer,
Osseointegrated implant failures. J Ir Dent Assoc, 1999. 45(2): p. 44-51.
This article discusses the criteria used for implant success and failure,
the classification of implant failures, the causative factors, and diagnosis of
the failing and failed implant. In spite of the impressive success rates of
osseointegrated dental implants, failures occur and in some studies the
incidence of failure is high. Many studies do not use objective criteria to
define success and confuse survival with success. The criteria used affect
reported success rates. Implant failures may occur early (primary) after implant
placement or after the implant is loaded (secondary). There is no single
aetiological factor and failures have been attributed to poor surgical
technique, host factors that impair healing, poor bone quality, peri-implant
infections, poor prosthesis design and traumatic loading conditions. Early
diagnosis of problems is critical and every effort should be made to treat the
problem while the damage can still be managed or even reversed.
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17. Emmer, T.J., Jr., et al.,
Measurement of submucosal forces transmitted to dental implants. J Oral
Implantol, 1999. 25(3): p. 155-60.
Early loading of dental implants after placement is believed to be a
major cause for premature implant failure. If a transitional denture or partial
denture is used during the healing period, occlusal forces may be transmitted to
the submerged implant, leading to poorly differentiated growth of bone cells
and/or potential inhibition of osseointegration at the bone-implant interface.
The objective of this study was to develop an experimental model to measure the
force transmission and to characterize the effect of selected loading conditions
and relief methods on the forces transmitted to the implant. The loading
conditions studied included unilateral and bilateral loading of the prosthesis.
Forces were measured at two different relief conditions (relief with and without
soft liner) and were compared against a control with no relief. The results show
that fabrication of the prosthesis with a proper relief at the implant-denture
junction can eliminate the submucosal force transmission to the implant on
loading the denture both under unilateral and bilateral loading conditions. When
a soft liner is used at the relief site, the transmitted force is small, but a
finite value is reproducibly recorded. With no relief, the submucosal force
transmission is high and may adversely affect the healing process or
osseointegration. The experimental model is valuable in measuring and
understanding the submucosal forces that are transmitted to the implant by
loading the transitional prosthesis, and such measurement may assist in the
proper design of the prosthesis for improved clinical durability and for other
uses.
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18. Misch, C.E., et al., A bone
quality-based implant system: first year of prosthetic loading. J Oral Implantol,
1999. 25(3): p. 185-97.
This interim report presents the data from a prospective study of
BioHorizons, a bone quality-based implant system, with four implant designs. The
surgical survival of 975 implants was 99.4%, with the survival 100% for D4 bone.
Three critical phases of crestal bone loss have been identified: bone remodeling
from stage I to stage II surgery; stage II uncovery to prosthesis delivery
(transition period); and prosthesis delivery up to the first year of loading
(early loading bone loss). The stage I to stage II uncovery crestal bone
remodeling resulted in a mean vertical bone loss of 0.21 mm to 0.36 mm (SD =
0.90 mm), dependent on whether the implant became exposed in the oral cavity
during osseous healing. No statistically significant difference was found among
the four implant designs, diameter, bone density, or location. The stage II to
prosthesis delivery mean vertical bone loss ranged from 0.12 mm to 0.20 mm. One
hundred three consecutive patients (partially and totally edentulous) were
restored, with 360 implants and 105 prostheses in function for a period of 12 to
26 months. No early loading implant failure occurred, and all patients with
implants are in satisfactory to optimum health according to the Misch Implant
Quality Scale. The mean early loading bone loss was 0.29 mm (SD = 0.99 mm). Past
clinical reports in the literature indicate most failures or crestal bone loss
occur by the first year of loading. This study suggests the bone quality based
dental implant design minimizes overall implant failure and crestal bone loss,
regardless of bone density.
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19. Majzoub, Z., et al., Bone response
to orthodontic loading of endosseous implants in the rabbit calvaria: early
continuous distalizing forces. Eur J Orthod, 1999. 21(3): p. 223-30.
The purpose of this experimental study was to evaluate the effect of
early orthodontic loading on the stability and bone-implant interface of
titanium implants in a rabbit model. Twenty-four short threaded titanium
fixtures were inserted in the calvarial mid-sagittal suture of 10 rabbits. Two
weeks following insertion, 20 implants (test group) were subjected to continuous
distalization forces of 150 g for a period of 8 weeks. The remaining four
implants (control group) were left unloaded for the same follow-up interval.
Clinically, all implants except for one test fixture were stable, and exhibited
no mobility or displacement throughout the experimental loading period.
Histologically, all stable implants were well-integrated into bone. No
differences could be found between the pressure and tension surfaces of the test
implants relative to bone quality and density within a range of 1000 microns
from the fixture surface. Similarly, qualitative differences were not observed
between the apical and coronal portions of test fixtures. Morphometrically, a
mean percentage bone-to-implant contact of 76.00 +/- 18.73 per cent was found at
the test pressure sides, 75.00 +/- 11.54 per cent at the test tension sides, and
68.00 +/- 15.55 per cent at the control unloaded surfaces. No statistically
significant differences in the percentage of bone-to-metal contact length
fraction were found between test pressure surfaces, test tension surfaces, and
unloaded control surfaces. Marginal bone resorption around the implant collar or
immediately beneath it was found in roughly the same percentage of analysed
sites in the test and control fixtures. In contrast, slight bone apposition was
demonstrated at the implant collar of the test pressure surfaces, while no
apposition or resorption were observed in the test tension zones. This study
suggests that short endosseous implants can be used as anchoring units for
orthodontic tooth movement early in the post-insertion healing period.
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20. Preiskel, H.W. and P. Tsolka,
Treatment outcomes in implant therapy: the influence of surgical and
prosthodontic experience. Int J Prosthodont, 1995. 8(3): p. 273-9.
In this retrospective study reviewing 30 months of treatment, 53
partially or completely edentulous patients were provided with implant-supported
restorations. The restorative aspects of the therapy were undertaken by an
experienced prosthodontist who had just begun involvement with implant
rehabilitation techniques. Patients were treated in two centres, 21 in a major
teaching institution (Group A) and 32 in a private practice (Group B). In Group
A, the implants were placed by experienced oral and maxillofacial surgeons just
beginning involvement in implant techniques. The implants of the Group B
patients were placed by surgeons with a minimum of 2 years implant experience.
It appeared that the surgeon's experience had a major impact on the failure
probability of unloaded implants. Loading conditions and the design of the
prosthesis may be the decisive determinants for the probability of success with
loaded implants. The hazards of extensive cantilevered extensions were
demonstrated. The results suggest that those entering implant prosthodontics
should not expect their early work to match the results obtained from
established centres.
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21. Lazzara, R.J., et al., A prospective
multicenter study evaluating loading of osseotite implants two months after
placement: one-year results. J Esthet Dent, 1998. 10(6): p. 280-9.
Historically, the recommended time between placement and functional
loading of machined-surface dental implants has been 3 months for the mandible
and 6 months for the maxilla. However, such recommendations are a result of
evaluating randomly chosen healing times during the initial phase of implant
development and are based on the subsequent clinical outcome of either implant
integration or mobility. In recent years, histologic and experimental studies
have shown that specifically designed micro-topographic implant surfaces can
result in increased bone-to-implant contact at earlier healing times than
obtained with machined-surface implants. Histologic and clinical studies
investigating early and immediate implant loading support the premise that
implants can be placed into function earlier than previously recommended. With
the development of specifically designed implant surfaces and the utilization of
time-saving surgical (one-stage surgical protocol) and prosthetic (implant
position indexing) techniques, patients are now being restored and returning to
function sooner than previously thought possible. The purpose of this
multicenter clinical investigation is to evaluate the efficacy of loading
Osseotite dental implants (3i-Implant Innovations Inc., Palm Beach Gardens,
Florida) at 2 months and to determine the effect of early loading on implant
performance and survival. A total of 429 Osseotite implants were placed in 155
patients (87 females and 68 males; mean age 54.0 +/- 13.7 yr), at 10 study
centers, and subsequently loaded 2.1 +/- 0.7 months following placement. A
single-stage surgical protocol was followed, with implants indexed immediately
or impressed 4 to 6 weeks following placement. Patient restorative treatments
included placement of 83 single-implant provisional restorations and 129
splinted, two-, three-, and four-implant supported maxillary and mandibular
provisional restorations. The mean time from prosthetic loading to the most
recent follow-up evaluation was 10 +/- 1.3 months. Seven of the 429 implants did
not integrate; of these, six were identified prior to loading and one was
identified 1 month after loading. The cumulative implant survival rate was 98.5%
at 12.6 months. The cumulative post-loading implant survival rate was 99.8% at
10.5 months. The preliminary results of this clinical investigation suggest that
successful functional loading of the Osseotite dental implant is possible at 2
months following noncomplicated implant placement.
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22. Pilliar, R.M., Overview of surface
variability of metallic endosseous dental implants: textured and porous
surface-structured designs. Implant Dent, 1998. 7(4): p. 305-14.
A variety of successful endosseous dental implants with different surface
forms are currently available for clinical use. These all achieve
implant-to-bone fixation primarily (if not totally) through mechanical interlock
of bone with implant surface features introduced by design or chance during
implant fabrication. Equally important to establishment of rigid fixation is the
rate at which it is achieved, because faster rates allow earlier implant loading
and less chance of inadvertent early loading that might prevent implant "osseointegration."
Investigations of surface modification to favorably affect osteoconductivity and
bone bonding represent an active area of research in the field of dental implant
development. This article presents a review of available surface designs and
future research directions for improved devices.
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23. Esposito, M., et al., Biological
factors contributing to failures of osseointegrated oral implants. (II).
Etiopathogenesis. Eur J Oral Sci, 1998. 106(3): p. 721-64.
The aim of the present review is to evaluate the English language
literature regarding factors associated with the loss of oral implants. An
evidence-based format in conjunction, when possible, with a meta-analytic
approach is used. The review identifies the following factors to be associated
with biological failures of oral implants: medical status of the patient,
smoking, bone quality, bone grafting, irradiation therapy, parafunctions,
operator experience, degree of surgical trauma, bacterial contamination, lack of
preoperative antibiotics, immediate loading, nonsubmerged procedure, number of
implants supporting a prosthesis, implant surface characteristics and design.
Excessive surgical trauma together with an impaired healing ability, premature
loading and infection are likely to be the most common causes of early implant
losses. Whereas progressive chronic marginal infection (peri-implantitis) and
overload in conjunction with the host characteristics are the major etiological
agents causing late failures. Furthermore, it appears that implant surface
properties (roughness and type of coating) may influence the failure pattern.
Various surface properties may therefore be indicated for different anatomical
and host conditions. Finally, the histopathology of implant losses is described
and discussed in relation to the clinical findings.
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24. Collaert, B. and H. De Bruyn,
Comparison of Branemark fixture integration and short-term survival using
one-stage or two-stage surgery in completely and partially edentulous mandibles.
Clin Oral Implants Res, 1998. 9(2): p. 131-5.
The aim of this prospective study was to compare the clinical integration
and survival of Branemark fixtures when using the conventional 2-stage surgical
procedure to 1-stage surgical approach in completely and partially edentulous
mandibles. A total of 85 patients were consecutively treated for partial (n =
35) or complete (n = 50) mandibular edentulousness. Fixtures removed because of
mobility, pain or infection were counted as failures. The first 10 patients of
each group were selected for radiographical analysis of crestal bone changes 1
year after prosthesis insertion. In 33 patients with edentulous mandibles, 170
fixtures were placed in a 1-stage approach. In this group, 4 fixtures (2.4%)
were lost prior to prosthetic restoration. Seventeen edentulous patients
received a total of 70 fixtures in a 2-stage procedure. Out of these, 5 fixtures
(7.1%) were lost at abutment connection. In 17 partially edentulous patients, 41
fixtures were inserted in a 1-stage approach. Two fixtures (5%) were lost in
this group. Finally, 18 partially edentulous patients received a total of 49
fixtures in a 2-stage procedure. Out of these, 6 fixtures (12%) were lost at
abutment connection. In total 313 of the 330 installed mandibular implants were
loaded between 6 and 12 months (94.8% success). No further losses occurred in
the implants functioning at least 1 year (267 implants) or at least 2 years (59
implants). Statistical analysis (Chi square test) revealed no difference in
fixture survival between the treatment modalities. Radiographical analysis after
1 year of functional loading showed the typical bone resorption changes up to
the most coronal implant thread in both modalities. Although this study pertains
to relatively early loading of 2 years, the results seem to indicate that in the
mandible a 1-stage surgical approach with Branemark fixtures may be as
predictable as the conventional 2-stage procedure.
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25. Bergendal, T. and B. Engquist,
Implant-supported overdentures: a longitudinal prospective study. Int J Oral
Maxillofac Implants, 1998. 13(2): p. 253-62.
The aim of this study was to evaluate the clinical function and long-term
prognosis of overdentures retained by a small number of implants in the maxilla
and mandible using one of two different attachment systems. Included in the
study were all patients referred to specialty clinics in Jonkoping and Linkoping,
Sweden, during the treatment period who needed an overdenture and could be
provided with a minimum number of two bilaterally-placed implants. Excluded were
patients with bone-grafted jaws, irradiated cancer patients, heavy bruxers, and
patients who had lost a fixed prosthesis because of implant losses. The patients
were randomly assigned to receive one retentive system, either a round
2-mm-diameter bar with clips or ball attachments (Nobel Biocare). Eighteen
overdentures were placed in maxillae and 32 in mandibles, supported by a total
of 115 Branemark implants. Of the implants placed, 86.1% were continuously
osseointegrated. The cumulative implant survival rates after 7 years of loading
were 75.4% in the maxillae and 100% in the mandibles. There was no difference in
implant survival rate between the attachment systems. Patients with implant
losses were characterized by severely resorbed maxillary ridges and inferior
bone quality, together with unfavorable loading circumstances such as short
implants combined with long leverages. Complications and prosthetic adjustments
were mostly resolved early and easily.
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26. Piattelli, A., et al., Bone reactions to early occlusal loading of two-stage
titanium plasma-sprayed implants: a pilot study in monkeys. Int J Periodontics
Restorative Dent, 1997. 17(2): p. 162-9.
This pilot study analyzed the bone reactions to early loaded titanium
plasma-sprayed implants. A total of 24 titanium plasma-sprayed implants (12 in
the maxilla and 12 in the mandible) (Primary Healing Implant, Legnano) were
inserted into four Macaca fascicularis monkeys with instruments specially
designed to obtain a precise fit of the implant in the bone socket. A metal
superstructure was cemented into 10 mandibular and 10 maxillary implants 15 days
after implant insertion. The four remaining implants were used as controls.
Eight months after implant placement, a block section was carried out, the
defect was filled with nonresorbable hydroxyapatite, and all 24 implants were
retrieved. The implants were treated to obtain thin ground sections that were
examined under normal and polarized light. Histologic analysis showed that bone
was observed around the implant surface in all implants. Morphometric analysis
demonstrated that bone lined 67.2% (SD = 3.1%) of the maxillary implant surface,
and 80.71% (SD = 4.6%) of the mandibular implant surface. No differences were
found in the percentage of bone-implant contact in the control implants. In the
loaded implants, however, the bone around the implants had a more compact
appearance. The study demonstrated that it is possible to obtain a high
percentage of bone-implant contact in early loaded titanium plasma-sprayed
implants.
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