Distraccion Alveolar Rev

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Alveolar distraction osteogenesis vs.vertical guided bone regeneration for thecorrection of vertically deficient

edentulous ridges: A 13-yearprospective study on humans

Matteo ChiapascoEugenio RomeoPaolo Casentini

Lia Rimondini

Authors affiliations:Matteo Chiapasco, Paolo Casentini,

Unit of Oral SurgeryEugenio Romeo, Unit of ProsthodonticsLia Rimondini, Unit of Oral Medicine, Departmentof Medicine, Surgery, and Dentistry, San PaoloHospital, University of Milan, Italy

Correspondence to:Dr Matteo ChiapascoDental BuildingVia Beldiletto 1/320142 MilanoItalyTel.: 39 02 50319000Fax: 39 02 50319040e-mail: [email protected]

Key words:alveolar distraction osteogenesis, Dental implants, e-PTFE membranes, guided

bone regeneration

Abstract:The purpose of this prospective study was to compare vertical guided bone

regeneration (GBR) and vertical distraction osteogenesis (DO) for their ability in correcting

vertically deficient alveolar ridges and their ability in maintaining over time the vertical

bone gain obtained before and after implant placement. Eleven patients (group 1) were

treated by means of vertical GBR with autogenous bone and e-PTFE membranes, while 10

patients (group 2) were treated by meansof DO.In group 1, six patients received implants at

the time of GBR (subgroup 1A), while five patients had implants placed at the time of

membrane removal (subgroup 1B). In group 2, implants were placed at the time of

distraction device removal. A total of 25 implants were placed in group 1 and 34 implants

were placed in group 2 patients. Three to 5 months after implant placement, patients were

rehabilitated with implant-borne dental prostheses. The following parameters were

evaluated: (a) bone resorption of the regenerated ridges before and after implant

placement; (b) peri-implant clinical parameters 1, 2, and 3 years after prosthetic loading of

implants; (c) survival and success rates of implants. Bone resorption values before and after

implant placement were significantly higher in group 1. The results suggested that both

techniques may improve the deficit of vertically resorbed edentulous ridges, although

distraction osteogenesis seems to be more predictable as far as the long-term prognosis of

vertical bone gain is concerned. Implant survival rates as well as peri-implant clinical

parameters do not differ significantly between the two groups, whereas the success rate of

implants placed in group 2 patients was higher than that obtained in group 1 patients.

Dental rehabilitation of partially or totally

edentulous patients with dental implants

has become common practice in the last

decades with reliable long-term results

(Albrektsson et al. 1986; Albrektsson

et al. 1988; Adell et al. 1990; Laney et al.

1991; Lekholm et al. 1994; Lindquist

et al. 1996; Buser et al. 1997; Arvidson

etal. 1998; Weberetal. 2000; Leonhardtet al.

2002). However, local conditions of the

edentulous alveolar ridges may be unfavor-

able for implant placement. In particular, a

relevant vertical defect of the alveolar ridge

may render the use of dental implants

difficult or impossible due to an insuffi-

cient bone volume to harbor implants of

adequate dimensions. To correct this situa-

tion, a variety of surgical procedures have

been proposed, such as onlay bone grafts,

vertical guided bone regeneration (GBR),

and alveolar distraction osteogenesis (DO).

The reconstruction of vertically atro-

phied ridges with onlay bone grafts was

the first procedure to be used and today

there is ample documentation in terms of

number of cases treated and follow-up of

implants placed in the reconstructed areas

(Breine & Branemark 1980; Keller et al.Copyrightr Blackwell Munksgaard 2004

Date:

Accepted 25 March 2003

To cite this article:

Chiapasco M, Romeo E, Casentini P, Rimondini L.Alveolardistractionosteogenesis vs. verticalguided boneregeneration for the correction of vertically deficientedentulous ridges: a 13-year prospective study onhumans.Clin. Oral Impl. Res.15, 2004; 8295

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1987; Listrom & Symington 1988; Kahn-

berg et al. 1989; Nystrom et al. 1993;

Donovan et al. 1994; Keller 1995; William-

son 1996; Brusati et al. 1997; Lundgren

et al. 1997; Chiapasco et al. 1998). How-

ever, results reported are non-homoge-

neous, due to the unpredictable bone

resorption that may occur before and after

implant placement. Moreover, the reported

data are difficult to compare due to the

different donor sites of autogenous bone

(intraoral sites, calvaria, tibia, iliac crest)

and due to the different systems used for

the evaluation of implant survival and

success rates (Weingart & Petrin 1999).

Vermeeren et al. (1996) reported very

unfavorable results of mandibular onlay

grafts, attributable to the severe bone

resorption that occurred after bone grafting

and the relevant peri-implant bone resorp-

tion after implant placement and prostheticloading. Another disadvantage may include

the need for bone harvesting from intraoral

or extraoral sites, with increased morbidity,

operating times, and duration of hospitali-

zation. Therefore, clinical research has

been oriented towards other alternatives,

such as vertical GBR with semipermeable

barriers (Simion et al. 1994; Jovanovic et al.

1995; Simion et al. 1998; Cornelini et al.

2000; Simion et al. 2001). The rationale of

this technique is based on long-term results

obtained from implants inserted in hori-zontally augmented bone ridges, demon-

strating that semipermeable barriers

allowed an undisturbed healing of the bone

transplant in a secluded space, thus redu-

cing significantly the risk of bone resorp-

tion (Dahlin et al. 1991, 1995; Nevins &

Mellonig 1992; Lang et al. 1994; Buser

et al. 1990, 1996).

The clinical experience on vertical GBR

is limited if compared to that concerning

horizontal augmentation, but promising

results have been presented (Simion et al.

1994; Jovanovic et al. 1995; Tinti et al.

1996; Simion et al. 1998,2001). In a recent

retrospective multicenter study by Simion

et al. (2001), 49 partially edentulous pa-

tients presenting 53 vertically deficient

sites were treated with vertical bone

augmentation by means of e-PTFE

membranes. Forty-nine patients received

implants at the time of the augmentation

procedure, whereas the remaining four pa-

tients were treated with a staged approach.

A total of 123 implants were inserted.

Complications such as abscesses and mem-

brane exposures occurred in nine out of 49

patients (18.4%), while the cumulative

survival rate of implants was 97.5%. The

authors concluded that this technique is

reliable and the vertically augmented bone

with GBR techniques responded similar to

native, non-regenerated bone. It must be

stressed, however, that Rasmusson et al.

(1999) demonstrated extensive bone resorp-

tion of the regenerated bone after mem-

brane removal. The study concluded that a

barrier may help preserve bone grafts as

long as the barrier is in place, whereas the

entity of bone resorption after its removal

was similar to that occurring in the case of

bone grafting without membranes.

Alveolar DO is another method used to

correct vertically atrophied alveolar ridges.

Originally applied in the orthopedic field

(Ilizarov 1975; Codivilla 1905), it has beenextended more recently to correct maxillo-

facial deformities such as Franceschetti

syndrome, hemifacial microsomia, etc.,

(McCarthy et al. 1992; Molina & Ortiz-

Monasterio 1995; Carls & Sailer 1998) and,

since 1996, it has been suggested to correct

vertical defects of the alveolar ridges (Block

et al. 1996, 1998; Chin and Toth 1996;

Hidding et al. 1998; Chiapasco et al 2000,

2001, 2002; Nocini et al. 2000; Urbani

2001; Raghoebar et al. 2000; Consolo et al.

2000; Robiony et al. 2002; Jensen et al.2002). Preliminary results seem to be very

promising: however, the reported data are

difficult to compare, due to the different

systems used for the evaluation of implant

survival and success rates.

Thus, despite a relevant number of

publications concerning these different

techniques, much controversy still exists

as far as the choice of the more reliable

technique is concerned, and, to the authors

knowledge, no comparative studies among

these techniques have been published yet.

The aim of this prospective study was to

compare vertical GBR and vertical DO for

their ability in correcting vertically defi-

cient alveolar ridges and their ability in

maintaining over time the vertical bone

gain obtained around implants.

Material and methods

In a 3-year period (19982000), 21 systemi-

cally healthy individuals, nine males and

12 females, aged between 18 and 59 years

(mean: 39.8 years), who presented with

vertical alveolar ridge defects were selected

for surgical correction of the deficit to

improve implant support, the crown-to-

implant ratio, and the final esthetics of

implant-borne prostheses constructed in

the edentulous areas.

Patients exclusion criteria were: (a)

vertical defects of the edentulous ridge

associated to a severe knife-edge ridge; (b)

bone defects following tumor resection; (c)

tobacco abuse (more than 15 cigarettes per

day); (d) severe renal and liver disease; (e)

history of radiotherapy in thehead andneck

region; f) chemotherapy for treatment of

malignant tumors at the time of the

surgical procedure; (g) non-compensated

diabetes; (h) active periodontal disease

involving theresidual dentition; (i) mucosal

disease, such as lichen planus in the areasto be treated; (j) poor oral hygiene; (k) non-

compliant patients.

Routine radiographic documentation of

the treated patients was obtained with: (a)

panoramic and intraoral radiographs taken

preoperatively, immediately after the re-

generative procedure or application of the

distractor, at the end of the distraction

procedure, at the time of the implant

placement, at the time of prosthetic reha-

bilitation, and annually thereafter.

The 21 patients were randomly assignedto two different groups. Group 1 patients

(11 patients) were treated by means of

vertical GBR with e-PTFE titanium rein-

forced barriers (Gore-Texs

, W.L. Gore and

Associates, Inc., Flagstaff, AZ, USA) and

particulated autogenous bone taken from

intraoral sites (chin and/or ramus of the

mandible). Group 2 patients (10 patients)

were treated by means of alveolar DO with

an intraoral extraosseous distraction device

(Gebruder Martin GmbH & Co., KG,

Tuttlingen, Germany). Randomization

was concealed to the surgeon until the

surgical procedure.

Surgical procedure for group 1 patients

Vertical GBR was performed under local

anesthesia in six patients, under local

anesthesia with intravenous sedation (dia-

zepam 0.2 mg pro/kilo) in three patients,

and under general anesthesia with nasotra-

cheal intubation in two patients. The type

of anesthesia was chosen according to

Chiapasco et al . Alveolar DO vs. vertical GBR

83 | Clin. Oral Impl. Res.15, 2004 / 8295


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extension and site of the defect, accessi-

bility, predetermined duration of the pro-

cedure, and patient compliance.

The procedure started with a midcrestal

incision on the edentulous ridge with

mesial and distal releasing incisions accord-

ing to surgical needs. In case of residual

dentition on the mesial or distal aspect of

the surgical field, the horizontal incison

was continued in the gingival sulcus,

involving one or two adjacent teeth. A

full-thickness mucoperiosteal flap was

then elevated, the bone defect exposed,

and connective tissue remnants were re-

moved. Cortico-cancellous autogenous

bone blocks were then harvested from

intraoral sites. The mandibular ramus was

the site of first choice for bone harvesting.

Only in two cases, where larger amounts of

bone were needed, bone harvesting was

performedfrom both thesymphysis andtheramus. The bone blocks were then particu-

lated with a bone mill, to facilitate graft

adaptation to the defect. The cortical bone

of the recipient bed was then perforated

with a 1-mm diameter round bur to

increase blood supply from endosseous

vessels to the transplanted bone. In six

out of the 11 patients treated (subgroup

1A), 13 Branemark system implants were

inserted immediately, with the guidance of

preformed surgical templates. The implant

shoulder was placed in an ideal position

from theprosthetic viewpoints, leaving part

ofthe implant to protrude 27 mm from the

bone level. In these cases, endosseous

implants acted as supporting and tenting

devices forthe membrane. In theremaining

five patients (subgroup 1B), one or two

titanium microscrews, 1.5 mm in diameter

and 713 mm long, were left to protrude 4

7 mm from the bone level and used to

support/tent the membrane. In this sub-

group, implants were inserted at the time of

membrane removal. A staged procedure

was used whenever a risk of insufficient

primary stability of implants was subjec-

tively expected.

Defects that remained around implants

or screws were packed with autogenous

bone chips and covered with a titanium

reinforced e-PTFE stabilized with titanium

fixating pins (Frioss

by Friadent, GmbH,

Mannheim, Germany) and/or microscrews(Gebruder Martin GmbH & Co., KG,

Tuttlingen, Germany). Flaps, after perios-

teally releasing incisions to obtain a ten-

sion-free closure, were accurately sutured

with e-PTFE 4-0 sutures.

All patients received 3 g of ampicillin per

day, starting approximately 1 h before

surgery and continuing for 6 days after

surgery) and non-steroidal analgesics post-

operatively. Postoperative instructions in-

cluded a soft diet for 2 weeks and

appropriate oral hygiene with 0.2% chlor-

hexidine mouthrinse. In case of intrave-

nous sedation or general anesthesia, anti-

biotics were administered intravenously at

the time of induction and then continued

orally for 6 days.

Sutures were removed 710 days post-

operatively. Removable prostheses were

not allowed in the reconstructed areas until

membrane removal. In case of pre-existing

bridges or adhesive provisional prostheses

(Maryland bridges), provisional prostheses

anchored to adjacent teeth were fabricated

to reduce patient discomfort, but special

care was dedicated to avoid any contact

between the prosthesis and the soft tissues

overlying the reconstructed areas.

In subgroup 1A, membranes and retain-

ing minipins or microscrews were removed

67 months after surgery, implant abut-

ments connected and the prosthetic reha-

bilitation was initiated.In subgroup 1B, membranes and retain-

ing minipins or microscrews as well as the

screws used for supporting membranes

were removed 67 months after surgery,

and 12 Branemark system implants were

inserted according to surgical templates.

Three to 5 months after implant place-

ment, implants were uncovered and the

same procedure described for subgroup 1A

was followed. Anagraphic data and clinical

features of patients, number and type of

implants are reported in Tables 1 and 2.

Table1. Anagraphic data and clinical features of subgroup 1A Vertical GBR with immediate placement of implants

Pt.

number

Age

(years)

Date of

stage-1

surgery

Date of

abutment

connection

Number and

type of implants

Implant

length (mm)

Implant

site

Site of bone

harvest

Mean bone

gain at stage-1

surgery (mm)

Complications

#1 51 Jan-98 Jun-98 1 Branemark 13 45 Ramus 4.0 No

1 Branemark 13 46 3.0

#2 47 Feb-98 Jul-98 1 Branemark 13 36 Ramus 7.0 Membrane exposure infection1 Branemark 13 37 7.0

#3 49 Jun-98 Oct-98 1 Branemark 11.5 44 Ramus 5.0 No

1 Branemark 11.5 45 5.0

1 Branemark 11.5 46 4.0

#4 57 Jan-99 Jun-99 1 Branemark 15 43 Ramus 5.0 Membrane exposure

1 Branemark 15 41 3.01 Branemark 15 32 2.5

#5 44 Apr-99 Oct-99 1 Branemark 13 44 Ramus 4.0 No


#6 31 Apr-99 Nov-99 1 Branemark 15 11 Ramus 4.0 No


84 | Clin. Oral Impl. Res. 15, 2004 / 8295


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Surgical procedure for group 2 patients

The DO procedure was performed under

local anesthesia in three patients, under

local anesthesia with intravenous sedation

(diazepam 0.2 mg pro/kilo) in five patients,

and under general anesthesia with naso-

tracheal intubation in the remaining two

patients. The procedure started with an

intraoral incision in the buccal vestibule,

without lateral releasing incisions. Carefulsubperiosteal dissection was performed to

obtain adequate visibility of the underlying

bone, but no mucoperiosteal dissection was

performed toward the alveolar crest and on

the lingual/palatal side to preserve adequate

blood supply to the bone segment to be

osteotomized. A preplating and modelling

of the intraoral distractor (Gebruder Martin

GmbH & Co., KG, Tuttlingen, Germany)

was performed before the osteotomy. With

an oscillating saw and/or a fissure bur, the

bone segment to be vertically distracted

was completely separated from the basal

bone. Once the osteotomy was completed,

the intraoral distractor was fixated to both

the basal bone and the osteotomized seg-

ment with 1.5-mm large titanium micro-

screws (Gebruder Martin GmbH & Co.,

KG, Tuttlingen, Germany). The osteoto-

mized segment to be distracted was im-

mediately moved by activating the

distractor to check the direction of distrac-

tion and freedom in movements. Finally,

the osteotomized segment was repositioned

at its initial position and the surgical access

was sutured with 4-0 sutures.

Antibiotics, non-steroidal analgesics,

diet, and oral hygiene regimens followed

the same protocol used in group 1 patients.

After a waiting period of 7 days for

closure of the surgical wound, sutures were

removed and the activation of the distrac-

tion device was started. A distraction of

1 mm per day (subdivided into two activa-

tions of 0.5 mm every 12 h) was performeduntil the desired amount of distraction was

obtained (range: 49 mm). The distractor

was then maintained in position for 23

months to obtain maturation of the

neocallus formed between the basal bone

and the distracted segment. After this

waiting period, the distractor was removed

and endosseous implants were placed

following the prefabricated surgical

templates.

A total of 34 titanium screw-shaped

endosseous implants were placed in the

distracted segments (eight patients received

28 Branemark system implants and two

patients received six screw-type ITI im-

plants). After to 36 months, abutments

were connected to the implants and the

prosthetic treatment was initiated.

Only one surgeon (MC) performed all the

reconstructive and implant placement

procedures for both groups. Anagraphic

data and clinical features of patients,

number and type of implants are reported

in Table 3.

Parameters evaluated andfollow-up for groups 1 and 2patients

The following parameters were evaluated

by a calibrated examiner: (a) radiographic

assessment of bone resorption between the

GBR procedure and the time of implant

placement (subgroup 1B) and between the

end of DO and the time of implant

placement; (b) radiographic assessment ofperi-implant bone resorption before and

after implant loading; (c) radiographic as-

sessment of peri-implant clinical para-

meters 1, 2, and 3 years after prosthetic

loading; (d) implant survival and success

rates.

Radiographic assessment of bone resorp-tion between GBR (subgroup 1B) and thetime of implant placement and DO pro-cedures and the time of implant placement

In subgroup 1B, this parameter was eval-

uated by comparing periapical radiographs

taken immediately after the GBR procedure

and immediately before implant place-

ment. The bone level obtained at the end

of the GBR procedure was considered the

baseline for the following measurements.

Measurements were taken on each micro-

screw with a transparent millimeter ruler,

measuring the distance between the top

of the screw head and the most coronal

level of direct bone-to-screw contact. The

Table2. Anagraphic data and clinical features of subgroup 1B vertical GBR with delayed placement of implants

Pt.

number

Age

(years)

Date of

stage-1

surgery

Date of

stage-2

surgery

Date of

abutment

connection

Number and

type of

implants

Implant

length

(mm)

Implant

site

Site of

bone

harvest

Mean bone

gain at stage-1

surgery (mm)

Complications

#1 28 Jan-98 July-98 Nov-98 1 Branemark 15 13 Ramus 4.0 No

#2 39 Feb-98 Sept-98 Feb-99 1 Branemark 13 23 Ramus chin 6.0 Paresthesia of

chin area1 Branemark 13 24 5.0


#3 30 Jun-99 Dec-99 Apr-00 1 Branemark 15 23 Ramus 5.0 No


#4 59 Sept-99 Apr-00 Sept-00 1 Branemark 13 12 Ramus 5.0 No1 Branemark 15 13 4.5


#5 45 Feb-00 Sept-00 Jan-01 1 Branemark 11.5 44 Ramus chin 7.0 Paresthesia of chinarea and Membrane

exposure






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measurements were taken to the nearest

0.5 mm.

In group 2, this parameter was evaluated

by comparing periapical radiographs taken

at the end of distraction and at the time of

implant placement and the distance fromthe upper margin of the osteotomized

segment and the upper margin of the

distractor plate. The measurements were

taken to the nearest 0.5 mm.

Radiographic assessment of peri-implantbone resorption after implant placement

Peri-implant bone resorption was recorded

by comparing periapical radiographs taken

immediately after implant placement, at

the time of prosthetic loading, and then

annually. Measurements were made mesial

and distal to each implant by means of a

transparent millimeterruler, measuring the

distance between the top of implant head

shoulder and the most coronal level of

direct bone-to-implant contact. The bone

level measured on periapical radiographs

takenimmediately afterimplant placement

was considered the baseline for further

measurements. The measurements were

recorded to the nearest 0.5 mm.

Peri-implant clinical parameters

Modified plaque index (MPI) and modified

bleeding index (MBI) were recorded at four

sites of each implant (mesial, distal, buccal,

lingual/palatal) (Mombelli et al. 1987).

Probing depth (PD) measurements were

performed at four sites of each implant

(mesial, distal, buccal, lingual/palatal) to

the nearest millimeter using a calibrated

plastic probe (TPS Probes

by Vivadent - FL

9494 Schaan, Liechtenstein). Measure-

ments were recorded every 12 months after

the initial prosthetic loading.

Implant success and survival rates

Successful implants can be characterized by

the following criteria: (a) absence of persis-

tent pain or dysesthesia; (b) absence of peri-

implant infection with suppuration; (c)

absence of mobility; (d) absence of contin-

uous peri-implant radiolucency; and (e)

peri-implant bone resorption less than

1.5 mm in the first year of function and

less than 0.2 mm in the following years

(Albrektsson et al. 1986).

Criteria for implant survival may include

absence of persistent pain or dysesthesia,

absence of peri-implant infection with

suppuration, absence of mobility, absence

of continuous peri-implant radiolucency,

but with peri-implant bone resorption

greater than the values proposed by Al-

brektsson et al. (1.5 mm in the first year of

function and less than 0.2 mm annually inthe following years).

Statistical analysis

Homogeneity of variance were tested with

the Levene test. Because Levene test was

significant, the Kruskal-Wallis ANOVA

exact test with the Monte Carlo method

to compute probability was applied to

multiple comparisons.

Because of lack ofpost hoctest for non-

parametric ANOVA, the MannWhitney

U-exact test was used for two sample

comparisons (group 1A vs. group 1B; group

1A vs. group 2; group 1B vs. group 2). the

Monte Carlo method was used to compute

probability.

ResultsGroup 1 patients

Recovery of donor sites in group 1 was

uneventful in all cases of bone harvesting

Table3. Anagraphic data and clinical features of group 2 patients distraction osteogenesis

Pt.

number

Age

(years)

Date of

stage-1

surgery

Date of

stage-2

surgery

Date of

abutment

connection

Number and

type of

implants

Implant

length

(mm)

Implant site Mean bone

gain at stage-1

surgery (mm)

Complications

#1 27 Jan-98 Apr-98 Oct-98 1 Branemark 11.5 45 8.0 No


#2 20 Mar-98 Jun-98 Nov-98 5 Branemark 15 4443413334 7.0 No

#3 37 May-98 Oct-98 Feb-99 4 ITI 12 41323335 7.0 No

#4 33 Feb-99 May-99 Nov-99 4 Branemark 13 13141516 7.0 No

#5 42 Apr-99 Jun-99 Nov-99 2 ITI 12 4546 4.0 No

#6 18 Nov-99 Feb-00 May-00 3 Branemark 13 424344 6.0 No

2 Branemark 10 4536 6.0

#7 19 Feb-00 May-00 Oct-00 2 Branemark 15 4231 6.0 Lingual inclination

bone fragment

#8 55 Mar-00 Jun-00 Nov-00 4 Branemark 15 44423234 9.0 No

#9 46 Jun-00 Sep-00 Feb-01 3 Branemark 10 343536 6.0 No

#10 39 Jul-00 Oct-00 Jan-01 3 Branemark 13 444546 5.0 Lingual inclination

bone fragment




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from the mandibular ramus. A transient

paresthesia of the lower lip occurred in two

patients who underwent bone harvesting

from the chin, lasting 1 and 4 weeks,

respectively. A paresthesia to the frontal

mandibular teeth was also present in bothcases, but in one of these (patient

#5subgroup 1B), this symptom, although

reduced, is still present 2 years after

surgery.

Recovery of the reconstructed sites was

uneventful in eight patients. Early exposure

of the membrane occurred in three patients.

For patient #5 of subgroup 1B membrane

became exposed 3 weeks after suture

removal. Despite oral antibiotic therapy

and local antispetic control (0.2% chlor-

hexidine mouthrinse 3 times/day plus

topical chlorhexidine gel, persistent sup-

puration remained that resulted in early

removal of the membrane at 4 weeks

postoperatively. Although bone regenera-

tion in this patient was partially compro-

mised (3-mm bone resorption after a gain of

6.5 mm), implants placed in these compro-

mised conditions still achieved osseointe-

gration after 4 months of healing. These

implants remained in function even after

18 months. For patient # 2 of subgroup 1A,

membrane exposure and suppuration oc-

curred 10 weeks after the GBR procedure.

Although the membrane was immediately

removed, a significant amount of granula-

tion tissues were found beneath the mem-

brane. Despite infection, implants were

clinically stable and were left in place. Atthe time of abutment connection, intraoral

radiographs demonstrated a perimplant

bone loss ranging from 3 to 3.5 mm (initial

bone gain7 mm). Three years after the

start of implant loading, despite a bone loss

ranging from 4 to 4.5mm and threads

exposed, implants and the suprastructure

are still clinically stable. For patient #4 of

subgroup 1A, early exposure of the mem-

brane occurred 8 weeks after suture re-

moval, with no clinically evident sign of

infection. Therefore, the patient was trea-

ted only with application of topical

chlorhexidine gel for 5 months, until

membrane removal and abutment connec-

tion. No exposure of implant threads was

found.

The mean follow-up from the start of

prosthetic loading of group 1A and 1B

implants was 41 months (range: 3048

months) and 29 months (range: 1848

months), respectively. All patients in this

group had acceptable function of the im-

plant-borne prostheses, with no pathologic

signs or symptoms such as paresthesia,

dysesthesia, pain, etc.

The mean peri-implant bone resorption

between implant placement and abutment

connection, between abutment connection

and 13 years after the start of prostheticloading in group 1A were 1.27mm

(SD0.8), 1.83 mm (SD1.0), 1.88 mm

(SD0.9), and 2.06 mm (SD0.9), respec-

tively. Medians and quartile ranges are

reported in Table 4.

The mean bone resorption beforeimplant

placement in subgroup 1B was 1.35 mm

(SD0.9). The mean peri-implant bone

resorption between implant placement and

abutment connection, between abutment

connection and 13 years after the start of

prosthetic loading in group 1B were

0.69 mm (SD0.3), 1.29 mm (SD0.4),

1.52 mm (SD0.3), and 1.69 mm (SD

0.3), respectively. The total bone resorption

at the end of the observation period (the

sum of measurements before and after

implant placement) was 2.96mm

(SD1.1). Medians and quartile ranges

are reported in table 4.

In group 1A, the mean MPI values at 1,

2, and 3 years after the start of prosthetic

loading were 0.31 (SD0.6), 0.40 (SD

0.6), and 0.35 (SD0.5), respectively.

Table4. Comparison of bone resorption in group 1A, 1B, and 2 before and after implant placement

Time

interval

Patient

group

Mean

(mm)

SD Median First

quartile

Third

quartile

Min

range

Max

range

Kruskal

Wallis ANOVA

P-values

MannWhitney

U-test P-values

BRIP GBR (1B) 1.35 0.9 1.0 1.0 2.0 0.5 3.0 < 0.01 1A vs. 1B P


7/14

The mean MBI values at 1, 2, and 3 years

were 0.22 (SD0.5), 0.20 (SD0.4), and

0.26 (SD0.4), respectively. The mean PD

values at 1, 2, and 3 years were 2.16mm

(SD0.7), 2.49mm (SD0.9), and

2.68mm (SD0.8), respectively.

In group 1B, the mean MPI valuesat 1, 2,

and 3 years after the start of prosthetic

loading were 0.34 (SD0.6), 0.38

(SD

0.4), and 0.30 (SD

0.6), respec-tively. The mean MBI values at 1, 2, and

3 years were 0.24 (SD 0.4), 0.22

(SD0.4), and 0.29 (SD0.5), respec-

tively. The mean PD values at 1, 2, and 3

years were 2.73mm (SD0.9), 2.75 mm

(SD0.8), and 2.67 mm (SD0.8), respec-

tively.

None of the patients in groups 1A and 1B

dropped out of the follow-up and no

implants were lost in both subgroups, but

five out of 13 implants in group 1A and

three out of 12 implants in group 1B

presented peri-implant bone resorption

values higher than those for implant

success proposed by Albrektsson et al.

(1986). Thus, cumulative survival and

success rates of implants placed in group

1A patients at the end of the follow-up

period were 100% and 61.5%, respec-

tively (Table 5). In group 1B these

values were 100% and 75%, respectively

(Table 6).

A case treated with the vertical GBR

principle is presented in Figs 17.

Table5. Group 1A (GBR and immediate implants) life table analysis showing cumulative survival and success rates of implants

Interval Implants

at start of

interval

Withdrawn

implants

Failing

implants

Implants

under risk

at the end

of interval

Cumulative

survival rate (%)

Cumulative

success rate (%)

Placement to loading 13 0 2 13 100 84.6

Loading to 1 year 13 0 2 13 100 84.6

12 years 13 0 3 13 100 76.9

23 years 13 3 5 10 100 61.5

Failing implants implants with bone resorption > 1.5 mm after the first year of loading and > 0.2 mm in the following years but fulfilling the other criteria

of Albrektsson et al.

Table6. Group 1B (GBR and delayed implants) life table analysis showing cumulative survival and success rates of implants

Interval Implants at

start of

interval

Withdrawn

implants

Failing

implants

Implants under

risk at the

end of interval

Cumulative

survival rate

(%)

Cumulative success

rate (%)

Placement to loading 12 0 0 12 100 100

Loading to 1 year 12 0 2 12 100 83.3

12 years 12 0 2 12 100 83.3

23 years 12 8 3 4 100 75

Fig.1. Preoperative situation showing loss of 43424131 and vertical defect of the alveolar ridge.

Fig.2. Preoperative panoramic radiograph showing relevant bone loss in the area corresponding to 434241.




8/14

Group 2 patients

Recovery of the surgical sites was unevent-

ful in all cases. In two patients (patients #7

and #10), a progressive lingual inclination

of the distracted segment occurred during

distraction, probably due to the traction on

the osteotomized segment by muscle forces

on the floor of the mouth. To avoid a

consolidation of the distracted segment in

an unfavorable position, an orthodontic

traction was applied to the distracted

segment. The orthodontic appliance was

maintained until consolidation of the neo-

callus in the desired position was reached.

No other adverse effects were encountered.

The mean follow-up from the start of

prosthetic loading was 31 months (range:

1854 months). All patients in this group

referred acceptable function of the implant-

borne prostheses with no pathologic signs

or symptoms such as paresthesia, dysesthe-

sia, pain, etc.

The mean bone resorption between the

end of DO and the time of implant

placement was 0.37 mm (SD0.4). The

mean peri-implant bone resorption be-

tween implant placement and abutment

connection, between abutment connection

and 13 years after the start of prosthetic

loading were 0.50 mm (SD0.4), 1.13 mm(SD0.3), 1.24mm (SD0.3), and

1.41mm (SD0.3), respectively. The total

bone resorption at the end of the observa-

tion period (the sum of measurements

before and after implant placement) was

1.93mm (SD0.7). Medians and quartile

ranges are reported in Table 4.

The mean MPI values at 1, 2, and 3 years

after the start of prosthetic loading were

0.42 (SD0.5), 0.41 (SD0.6), and 0.35

(SD0.6), respectively. The mean MBI

values at 1, 2, and 3 years were 0.33(SD0.5), 0.29 (SD0.4), and 0.30

(SD0.4), respectively. The mean PD

values at 1, 2, and 3 years were 2.23mm

(SD0.7), 2.37mm (SD0.5), and

2.41mm (SD0.5), respectively.

None of the patients in group 2 dropped

out of the follow-up and no implants were

lost during the follow-up. Only two im-

plants presented peri-implant bone resorp-

tion values higher than the criteria

proposed by Albrektsson et al. Thus,

cumulative survival and success rates of

implants placed in group 2 at the end of the

follow-up period were 100% and 94.1%,

respectively (Table 7).

A case treated with the DO principle is

presented in Figs 814.

The comparison of results between the

two groups can be summarized as follows:

The difference in bone resorption before

implant placement between groups 1B and

2 was statistically significant (P < 0.01).

The difference at the time of abutment

connection, and 13 years after prosthetic

Fig.3 . Placement of three implants at an ideal prosthetic position with supracrestal exposure of implant

threads.

Fig.4 . The surgical field after bone grafting with autogenous bone chips and fixation of a titanium-reinforcede-PTFE membrane.

Fig. 5. At the time of abutment connection, implants appear completely embedded by new bone.




9/14

loading between groups 1B and 2 was

statistically significant (P-values < 0.05,

< 0.05, < 0.01, < 0.05, respectively).

The difference in bone resorption be-

tween groups 1A and 1B between implant

placement and abutment connection and

1 year after prosthetic loading were statis-

tically significant (P-values0.01 and

0.05, respectively). No statistically signifi-

cant differences were found between groups

1A and 1B at 2 and 3 years after prostheticloading.

The difference in bone resorption be-

tween groups 1A and 2 at the time of

abutment connection and 13 years after

prosthetic loading was statistically signifi-

cant (P < 0.01 at all intervals).

The difference concerning the total bone

resorption at the end of the observation

period (the sum of measurements before

and after implant placement) between

group 1B and group 2 was statistically

significant (P < 0.01).No statistically significant differences

were found between the groups as far as

clinical parameters are concerned.

A significant difference was found be-

tween the groups as far as the success rates

of implants is concerned, whereas no

differences were found as far as survival

rates are concerned.

Discussion

Results from this study demonstrated that

vertically deficient edentulous ridges may

be corrected either by GBR or DO techni-

ques. Nevertheless, some considerations

have to be made.

The first issue refers to the complication

rate related to the two techniques. As far as

vertical GBR is concerned, membrane

exposure, which partially compromised

the final outcome of the bone regeneration,

occurred in three out of 11 patients

(27.3%). Instead, in the case of DO, two

cases only of lingual inclination of the

distracted segment occurred, but they were

easily corrected with an orthodontic appli-

ance without negative effects on the final

outcome of the prosthetic rehabilitation.

The second issue relates to the ability of

vertical GBR and DO in maintaining the

vertical bone gain over time. Two observa-

tion periods were considered: (a) before

implant placement (groups 1B and 2); and

(b) after implant placement (groups 1A, 1Band 2).

Groups 1B and 2 showed a significant

difference (P0.01) in bone resorption

before implant placement (1.35 mm, SD

0.9, range 0.53 mm and 0.37 mm, SD 0.4,

range 01.5 mm, respectively). Because of

the higher rate of initial bone loss in group

1B, it was necessary to place implants in a

more apical position, with suboptimal

prosthetic result from an esthetic and

functional point of view.

In group 1A, the mean peri-implant boneresorption values 13 years after prosthetic

loading were higher than those proposed by

Albrektsson et al. (1986). The mean bone

resorption during the follow-up period was

2.06mm (SD 0.9). Although 100% im-

plant survival rate was observed, the

success rate was significantly lower

(61.5%). In fact, five out of 13 presented

did not fulfill Albrektsson criteria. A bone

resorption of such magnitude (range: 1.5

4 mm) may be less than ideal, particularly

in case of implants placed in esthetic sites,

where the implant shoulder and threads

may become visible.

Fig.6 . Final prosthetic result.

Fig.7 . Radiographic control 1 year after the start of

prosthetic loading.

Table7. Group 2 (distraction osteogenesis) life table analysis showing cumulative survival and success rates of implants

Interval Implants at

start of

interval

Withdrawn

implants

Failing

implants

Implants under

risk at the end

of interval

Cumulative survival

rate (%)

Cumulative success

rate (%)

Placement to loading 34 0 0 34 100 100Loading to 1 year 34 0 0 34 100 100

12 years 34 6 0 28 100 100

23 years 28 17 2 11 100 94.1




10/14

In group 1B patients, the mean peri-

implant bone resorption values 13 years

after prosthetic loading were apparently

within the limits proposed by Albrektsson

et al. (1986), but these values may be

misleading. Because implants were placed

in a staged approach, bone resorption of the

reconstructed area already occurred before

implant placement. Therefore, if we con-

sider the bone level obtained at the time of

the vertical GBR procedure as the baseline

of our measurements, the amount of bone

resorption at the end of the observation

period was the sum of bone resorption

before and after implant placement:

2.96mm (SD1.1). This value is signifi-

cantly higher than that obtained in the DO

group 1.93 (SD0.7).

This study demonstrated that higher

values of peri-implant bone resorption after

the removal of the membrane may occur as

compared to implants placed in native,

non-regenerated bone. This study also

demonstrated that success rates of implants

placed in areas treated with vertical GBR

are significantly lower than those obtained

in the case of implants placed in native,

non-reconstructed bone (Adell et al. 1990;

Chaytor et al 1991; Quirynen et al. 1992;

Lekholm et al. 1994; Bragger et al. 1996;

Lindquist et al. 1996; Buser et al. 1997;Arvidson et al. 1998; Behneke et al. 2000;

Weber et al. 2000; Leonhardt et al. 2002). In

these publications, bone resorption values

within the limits proposed by Albrektsson

et al. were reported, with cumulative

success ranging from 89% to 98.9% after

follow-up periods ranging from 3 to 15

years.

In group 2, the mean peri-implant bone

resorption values 13 years after the start of

prosthetic loading were within the limits

proposed by Albrektsson et al. (1986) andwere consistent with the results obtained in

case of implants placed in native bone

(Adell et al. 1990; Chaytor et al 1991;

Quirynen et al. 1992; Lekholm et al. 1994;

Bragger et al. 1996; Lindquist et al. 1996;

Buser et al. 1997; Arvidson et al. 1998;

Weber et al. 2000; Behneke et al. 2000;

Leonhardt et al. 2002). Only two implants

in one patient did not fulfill this parameter,

as reported in Table 6. It is worth noting

that in case of DO, the total bone resorption

at the end of the observation period (the

sum of bone resorption occurred before

implant placement and that occurred at

the end of the observation period was equal

to 1.93mm (SD0.7). This value is

significantly lower than that obtained after

GBR with staged implants (group 1B). This

seems to demonstrate that DO has a better

ability than GBR in maintaining the bone

gain obtained.

A survival rate of 100% and a success

rate of 94.1% seem to confirm that

implants placed in the neogenerated tissue

Fig.8 . Post-traumatic defect with loss of 314142 and vertical defect of the alveolar ridge.

Fig9. Panoramic radiograph showing the bony defect.

Fig.10. The surgical field after the osteotomy of the bony segment to be distracted and fixation of the

distraction device.




11/14

by distraction osteogenesis can successfully

withstand the biomechanic demands of

implant loading, comparable to the results

obtained in case of implant placement

in native, residual alveolar bone (Albre-

ktsson et al. 1986; Adell et al. 1990; Laney

et al. 1991; Lekholm et al. 1994; Lindquist

et al. 1996; Buser et al. 1997; Arvidson

et al. 1998; Weber et al. 2000; Leonhardt

et al. 2002).

As far as clinical parameters are con-

cerned, no statistically significant differ-

ences were found in this study between the

two groups, and these values were consis-

tent with those reported in the literature(Mericske-Stern et al. 1994; Nishimura

et al. 1997; Levy et al. 1996; Behneke

et al. 2000; Leonhardt et al. 2002).

Conclusion

The following conclusions can be drawn

from the data of the present study and from

the analysis of the literature.

Vertical GBR appears to be a relatively

reliable reconstructive technique, but itneeds autogenous bone harvesting, which

increases operating times and postoperative

morbidity. In addition, early membrane

exposure may cause infection that may

compromise the final outcome of the

rehabilitation. This technique has been

mainly applied to limited defects with ver-

tical bone gains ranging from 2 to 7 mm, on

average (Simion et al. 1994; Jovanovic et al.

1995; Simion et al. 1998, 2001).

DO has proven to be a reliable technique,

as demonstrated by this study and other

publications (Hidding et al. 1998; Chiapas-

co et al. 2000, 2001; Consolo et al. 2000;

Robiony et al. 2002; Jensen et al. 2002;

Zaffe et al. 2002). The vertical bone gain

may reach more than 15 mm, it is obtained

in a more physiologic way, with no need of

bone transplantation, thus reducing morbid-

ity. Another advantage may include a

progressive elongation of the surrounding

soft tissues (neohistogenesis) with very

limited risk of wound dehiscence and bone

exposure. In this study as well as in previous

Fig.11. Radiographic control 2 days after the start of distraction.

Fig. 12. Control at the end of distraction: the correction of the vertical defect is clearly visible.

Fig. 13. Final prosthetic result.

Fig.14. Radiographic control 2 years after the start

of prosthetic loading.




12/14

publications (Chiapasco et al. 2000, 2001),

the incidence of infection was 0%.

The results from this study seem to

indicate that DO, as compared to GBR,

may offer a better long-term prognosisas far

as bone gain maintenance and peri-implant

bone resorption after prosthetic loading are

concerned.

Survival rates of implants do not differ

between DO and GBR groups, whereas

success rates of implants differ significantly

(61.5% in group 1A; 75% in group 1B;

94.1% in group 2).

It must be stressed, however, that the

distraction device used in this study al-

lowed the correction of the vertical defect

only, whereas GBR permitted to correct

simultaneously a vertical and horizontal

defect. GBR techniques may be more

indicated for small defects and in case of a

combination of vertical and horizontaldefects. DO with intraoral extraosseousdis-

tractors of a single-tooth space may be in

fact more difficult to perform, due to the

limited space available for osteotomies and

to the dimensions of the distraction device.

Instead, in case of severe vertical defects

with the presence of a broad bony base, DO

may be more indicated because more

vertical gain may be achieved by DO than

GBR.

Resume

Le but de cette etude prospective a etede comparer

la regeneration osseuse guidee verticale (GBR) et

losteogenese de distraction verticale (DO) pour leur

potentiel a corriger les insuffisances verticales du

rebord alveolaire et leurs possibilites a maintenir

dans le temps ce gain osseux vertical obtenu avant et

apres le placement de limplant. Onze patients

(groupe 1) ont etetraites avec la GBR verticale avec

de los autogene et des membranes en teflon, tandis

que dix patients (Groupe 2) etaient traites avec la

DO. Dans le groupe 1, six patients ont recu des

implants au moment de la GBR (sous-groupe 1A)

tandis que cinq patients avaient des implants places

au moment de lenlevement de la membrane (sous-

groupe 1B). Dans le groupe 2, les implants ont ete

places au moment de lenlevement du systeme de

distraction. Au total, 25 implants etaient places dans

le groupe A et 34 dans le 2. Trois acinq mois apres le

placement des implants les patients ont ete traites

par des protheses dentaires portees sur implants. Les

parametres suivant ont eteevalues : a) la resorption

osseuse des rebords regeneres avant et apres le

placement de limplant, b) les parametres cliniques

paromplantaires un, deux, trois annees apres lamise

en charge, c) les taux de survie et de succes des

implants. Les valeurs de la resorption osseuse avant

et apres le placement des implants etaient significa-

tivement plus importantes dans le groupe 1. Les

resultats suggerent que les deux techniques peuvent

ameliorerle deficit durebordedenteresorbebienque

losteogenese de distraction semble etre plus pre-

visible along terme. Les taux de survie implantaire

ainsi que les parametres cliniques paromplantaires

ne differaient pas significativement entre les deux

groupes tandis que le taux de succes des implants

places dans le groupe 2 etait plus important que chez

les patients du groupe 1.

Zusammenfassung

Alveolare Distraktionsosteogenese gegenuber verti-

kaler gesteuerter Knochenregeneration fur die Kor-

rektur von vertikalen Defekten am zahnlosen

Kieferkamm: eine prospektive Studie an Menschen

uber 1 bis 3 Jahre

Das Ziel dieser prospektiven Studie war der Vergle-

ich zwischen der vertikalen gesteuerten Knochenre-

generation (GBR) und der vertikalen Distrak-

tionsosteogenese (DO) bei der Korrektur von

vertikalen Defekten an zahnlosen Kieferkammen.Zusatzlich wurde die Stabilitat des gewonnenen

Knochens uber die Zeit vor und nach Implantatplat-

zierung untersucht. Elf Patienten (Gruppe 1) wurden

mit vertikaler GBR mit autologem Knochen und e-

PTFE Membranen behandelt, wahrend bei 10

Patienten (Gruppe 2) die DO angewendet wurde.

In Gruppe 1 erhielten 6 Patienten zum Zeitpunkt

der GBR auch die Implantate (Untergruppe 1A),

wahrend bei 5 Patienten die Implantate nach der

Membranentfernung gesetzt wurden (Untergruppe

1B). In Gruppe 2 wurden die Implantate nach

Entfernung des Distraktionsapparats eingesetzt. In-

sgesamt wurden in Gruppe 1 25 Implantate und in

Gruppe 2 34 Implantate eingesetzt. Drei bis 5

Monate nach Implantation wurden die Patientenmit implantatgetragenen Prothesen rekonstruiert.

Die folgenden Parameter wurden ausgewertet: a)

Knochenresorption der regenerierten Kieferkamme

vor und nach Eingliederung der Implantate; b)

periimplantare klinische Parameter 1,2 und 3 Jahre

nach Beginn der prothetischen Belastung der Im-

plantate; c) Ueberlebens- und Erfolgsraten der Im-

plantate. Die Werte der Knochenresorption vor und

nach Implantatplatzierung waren in Gruppe 1

signifikant hoher.

Die Resultate lassen vermuten, dass beide Techni-

ken die Situation bei vertikal resorbierten zahnlosen

Kieferkammen verbessern konnen. Die Distraktion-

sosteogenese scheint bezuglich Langzeitprognosedes

vertikalen Knochengewinns besser abzuschneiden.

Die Ueberlebensraten der Implantate und die peri-

implantaren klinischen Parameter unterschieden

sich nicht signifikant zwischen den beiden

Gruppen. Aber die Erfolgsrate der Implantate war

bei Patienten der Gruppe 2 hoher als bei Patienten

der Gruppe 1.

Resumen

El proposito de este estudio prospectivo fue comparar

la regeneracion osea guiada vertical (GBR) y osteo-

genesis de distraccion vertical (DO) por su habilidad

en corregir crestas alveolares deficientes verticales y

su capacidad en mantener a lo largo del tiempo la

ganancia de hueso vertical obtenida antes y despues

de la colocacion del implante. Se trataron once

pacientes (grupo 1) por medio de GBR vertical con

hueso autogeno y membranas de e-PTFE, mientras

que 10 pacientes (grupo 2) se trataron por medio de

DO. En el grupo 1, seis pacientes recibieron

implantes en el momento de GBR (subgrupo 1A),

mientras que cinco pacientes recibieron los im-plantes en el momento de retirada de la membrana

(subgrupo 1B). En el grupo 2 los implantes se

colocaron en el momento de la retirada del disposi-

tivo de distraccion. Se colocaron un total de 25

implantes en el grupo 1, y 34 en los pacientes del

grupo 2. Tras 3 a 5 meses de la colocacion de los

implantes, los pacientes se rehabilitaron con protesis

dentales implantosoportadas. Se evaluaron los si-

guientes parametros: a) reabsorcion osea de las

crestas regeneradas antes y despues de la colocacion

de los implantes; b) parametros periodontales cln-

icos 1, 2, y 3 anos tras la carga protesica de los

implantes; c0 supervivencia e ndices de exito de los

implantes. Los valores de reabsorcion osea antes y

despues de la colocacion de los implantes fuesignificativamente mas alta en el grupo 1.

Los resultados sugieren que ambas tecnicas pueden

mejorar el deficit de la cresta edentulas vertical-

mente reabsorbidas, aunque la Osteogenesis de

distraccion parece ser mas predecible en cuanto al

pronostico a largo plazo de la ganancia de hueso se

refiere. Los ndices de supervivencia de implantes al

igual que los parametros clnicos no difirieron

significativamente entre los dos grupos, mientras

que el ndice de exito de los implantes colocados en

el grupo 2 fue mayor que aquel obtenido en los

pacientes del grupo 1.




13/14

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