narrow Diameter Implants for mandibular Denture retentionDocument Transcript
c da j o u r n a l , vo l 3 6 , n º 4
s narrow Diameter
Implants for mandibular
eugene e. labarre, dmd, ms; robert h. ahlstrom, dds, ms;
and warden h. noble, dds, ms
a bstract Narrow diameter implants are a lower cost alternative
to conventional implants and are used to retain mandibular dentures.
The experiences at a dental school predoctoral clinic are reviewed.
The cumulative success rate for 626 fixtures placed in a six-year
period is 92.6 percent with high patient satisfaction. Narrow diameter
implants are a useful adjunct in the long-term management of
eugene e. labarre, dmd, warden h. noble, dds, ms, n 2002, an international symposium solutions to the inaffordability di-
ms, is associate professor is clinical professor and at McGill University concluded that a lemma. They are endosseous implants
and chairman, Department director, Complex Care Clinic, conventional denture was no longer made of titanium alloy and less than 3
of Removable Prostho- Department of Restorative
dontics, University of the
the most appropriate option for mm in diameter. They were introduced
Dentistry, University of the
Pacific Arthur A. Dugoni Pacific Arthur A. Dugoni restoring the edentulous mandible commercially to the dental profes-
School of Dentistry, San School of Dentistry, San and that the two-implant retained over- sion in the 1990s and were first used
Francisco. Francisco. denture should become the first choice for transitional prosthesis support.3,4
prosthodontic treatment.1 While the Recently, manufacturers have mar-
robert h. ahlstrom, dds,
ms, is associate professor
McGill consensus summarized numerous keted them widely to the profession and
and director, Implant randomized controlled trials and longi- patients as lower cost, less invasive, and
Clinic, University of the tudinal clinical studies as overwhelming technically easier alternatives to conven-
Pacific Arthur A. Dugoni evidence for preferring implant-retained tional implants. They are now used in a
School of Dentistry, San dentures, the issues of affordability and variety of applications, including orth-
access to this level of care were unre- odontic anchorage, single and multiple
solved. In the United States, coverage of tooth fixed replacement, bridge repair,
dental implants by third parties is in its and removable prosthesis retention.5-10
infancy and is nonexistent in the Med- The small diameter of each fixture (1.8
icaid system. Edentulism in this country mm to 2.4 mm), as well as the reduced
is strongly associated with low income, surgical and prosthetic armamentarium,
and most edentulous patients cannot result in lower overhead and fees com-
afford the high cost of implant dentistry.2 pared with conventional implants. A
The use of narrow diameter or patient can receive a mandibular over-
mini-implants is potentially one of the denture retained by four narrow diam-
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f ig ur e 1a. Four sites were marked on ridge f igure 1 b . Four Atlas implants have been placed f i g u r e 1 c. Postoperative panoramic radiograph
crest tissue of anterior mandible and pilot osteoto- in the anterior mandible. Note the lack of tissue of 14 mm length Atlas implants.
mies will be created through the tissue. The drill trauma.
(Atlas Implant, Dentatus USA, New York, N.Y.) is
used at slow rotational speed with copious sterile
irrigant, to half the length of the proposed implant
length if the bone is soft or to the full length of the
implant length if the bone is resistant.
f ig ur e 2a. Preoperative view of periodon- f igure 2 b . The mandibular canines have f i g u r e 2 c. The patient’s original transi-
tally compromised mandibular canines. been extracted and four 15 mm- length MDI tional partial denture was converted to an
collared implants (IMTEC Corp., Ardmore, Okla.) immediate complete denture and this was
have been placed through the soft tissue at retrofitted over the implants at the conclu-
sites No. 21, 23, 26, and 28. sion of the surgery. The patient left the clinic
with function and esthetics fully restored.
eter implants (figure 1 ) for less than A multiclinic study of 1,029 mini-implants A. Dugoni School of Dentistry has an
half the cost of the standard treatment used for mandibular denture reten- edentulous patient base typical of urban
with two conventional implants. tion, with service range of five months areas in the United States. Many of
Additional benefits of narrow im- to eight years, had an overall success these patients struggle with unstable
plants are the ability to place them in rate of 91.2 percent, and 89 percent for mandibular dentures but are unable to
horizontally narrow sites (4 mm of fixtures in place for at least five years.14 afford the undergraduate clinic’s basic
bone required), minimally invasive Another study reported the long-term two-implant overdenture protocol that
surgical technique, and the ability to results for 2,514 mini implants placed in has been in place since 1982 and reliably
load the implants immediately. a single office over a five-year period and improves oral function and patient self-
A contentious issue with narrow di- subjected to a spectrum of prosthetic confidence. Narrow diameter implants
ameter implants is the lack of evidence for anchorage in both jaws: single crowns, are part of the curriculum at Pacific and
clinical suitability and success, particularly fixed partial dentures, removable par- have been offered as an alternative and
the absence of objective long-term and tial dentures and complete dentures; less costly treatment for our patients
prospective comparative studies. It has the overall success rate was 94.2 per- with edentulous mandibles since 2001.
been shown that narrow diameter im- cent.15 The encouraging results of both In the last six years, more than 150
plants osseointegrate to the same extent these long-term studies are restrained operators, most of them senior dental
as conventional implants, and success by the disclosure statements that the students with close faculty supervi-
rates reported for limited patient cohorts lead authors had commercial interests sion, have placed 626 narrow diameter
over brief service periods have been favor- in the products cited in the papers. implants, and 37 percent of these were
able (93 percent to 98 percent).11-13 The University of the Pacific Arthur inserted at the time of extraction and
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f igure 3 b. Panoramic radiograph showed lack of
bone around implant at site No. 20, with dangerous prox-
resulting in extravagant bone loss and
imity to the mental foramen (fortunately, the patient had delayed healing. There have been no
figure 3a. This patient complained that both
remaining implants were painful and loose. Four MDI
no paresthesia). The implant at site No. 24 demonstrated paresthesias, as would be expected,
significant funneling in the bone. Both implants were
collared implants had been placed at a private office
because no implants have been placed
12 months previously, and two had been lost already. in the posterior mandible, and all im-
Both implants have total exposure of the collar (nor-
mally collars are completely embedded in soft tissue). plants were placed at least 5 mm medial
to the radiographic mental foramina.
immediate denture placement (figure 2 ). surgical/prosthetic treatment. Exclusion The Implant Clinic at Pacific has had
Forty-six implants have been lost, due to criteria for patients were conservative: experiences other than treating its own
loosening, chronic pain, or infection, for severe or recent cardiac pathology, severe patients. Multiple patients with narrow
an overall success rate of 92.6 percent. hypertension, uncontrolled diabetes, or diameter implant problems and failures
The protocol of placing four fixtures bleeding disorder, AIDS, any condition who were referred to Pacific from local
intraforaminally provided 1 to 3 pounds that seriously compromised bone heal- communities have been evaluated and
of resistance to vertical displacement of ing potential or autoimmune response, treated. Common issues included atypi-
the denture, and substantially reduced intravenous bisphosphonates, heavy cal implant location, extreme divergence
the tendency of the denture to wander smoking, personality disorder or psycho- of implant axes, infection, implant
laterally during function. The o-ring sis, substance abuse, and physician veto. rejection, and poor prosthesis fit.
retainer (MDI system, IMTEC Corpora- In addition, patients with Class IV Also, the authors have received reports
tion, Ardmore, Okla.) or soft liner (Atlas edentulous mandibles (American College from other parts of the United States
system, Dentatus USA, Ltd., New York, of Prosthodontists classification, indicating regarding inappropriate treatment with
N.Y.) permitted the denture to be entirely less than 11 mm of vertical bone height or these implants (figure 2 ). Egregious fail-
supported by soft tissue. If the implants absent clinical ridge) were excluded. Pre- ures have been published.16 Dentists who
were placed without raising a soft tissue surgical planning was accomplished with a are accustomed to a disciplined approach
flap, patients noted the lack of surgical study model and a panoramic radiograph. to achieve success with conventional im-
drama and generally, the healing interval If available, the existing denture plants are dismayed by these instances of
was mild. When a conventional denture was used as a general guide for artificial poor planning, execution, and follow-up.
was retrofitted to the implants, patient tooth position, location of the bulk of To make matters worse in this field,
appreciation of the improvement in den- the denture base and for occlusal plane aggressive marketing strategies feature
ture comfort and function was universal. orientation. As a cost control measure, CT patient-targeted infomercials and Web-
The word-of-mouth referral of new scans and laboratory fabricated surgical based advertising; dentists are enticed
patients by satisfied implant overdenture stents were not used on a routine basis. with promises of enhanced profitabil-
patients has been a notable aftereffect of Procedures to retrofit and reline ity; and small diameter implants have
this program at Pacific. Another sig- existing dentures were more stringent become the organizational axis for
nificant outcome of the narrow diameter than normally encountered in denture profit-dominant denture franchises.
overdenture program for students at prosthetics, due to the unforgiving nature This business-first energy obscures the
Pacific was the learning and practice of of implant attachments. Post-treatment message that narrow diameter implants
distributive justice, which is specifically, swelling, surgical pain, and denture sore can be a useful adjunct to dentistry and
in this case, the allocation of implant spots were encountered routinely. Three a benefit to many denture patients.
resources and effective procedures among patients had severe local postsurgical The usual high standards of dedica-
a diverse edentulous population. swelling that did not respond to anti- tion to scientific inquiry and excellence
The experiences at Pacific with narrow biotics, and all fixtures were removed in clinical practice are required of the
diameter implants reflected the learning within one month. The worst surgical professional and manufacturing commu-
curve associated with the development of complication was a chronic osteomyelitis nities before narrow diameter implants
a predictable protocol for a new elective around one narrow diameter implant, will be wholly accepted in dentistry.
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Conclusions tional implants for partially edentulous patients: a case study. diameter implants with overdentures in severely atrophic
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