Implant placement in molar extraction sockets can be difficult due to complex
multi-root anatomy and the lack of predictable primary stability. The aim of
this study was to evaluate the outcome of an 8 - 9 mm diameter tapered
implant, designed to be placed in molar extraction sockets.
Material and methods
Patients treated at least 1 year before with a Max® implant (Southern
Implants, Irene, South Africa) were invited for a clinical examination.
Variables collected were surgical and prosthetic protocol, implant dimension
and smoking habits. Peri-implant bone level was determined on peri-apical
radiographs and compared to baseline, being implant insertion.
Results
98 implants had been placed in 89 patients. One implant had failed. Thirty
eight patients representing 47 implants (maxilla 26, mandible 21) were
available for clinical examination. Mean bone loss was 0.38 mm (SD 0.48;
range - 0.50 – 1.95) after a mean follow-up of 20 months (range 12 - 35).
Implant success was 97.9%. Around 30 implants, a bone substitute was used to
fill the residual space, but this did not affect the bone loss outcome. Bone
loss was only significantly different between maxilla and mandible (0.48 mm
vs. 0.27 mm) and between the 8 and 9 mm diameter implants (0.23 mm vs. 0.55
mm). A full papilla was present at 71% of the interproximal sites and
irrespective of bone loss.
Conclusions
The Max® implant demonstrated good primary stability, when placed in molar
extraction sockets, with limited bone loss over time.
The early Brånemark protocol prescribed a healing period of 6 to 8 months between
tooth extraction and implant placement [1]. It
was believed that this was necessary to avoid infection and to allow for better
primary stability at implant placement.
Continuing research lead to the introduction of immediate placement, where the
implant is installed in conjunction with tooth extraction. The advantages of
immediate placement are the reduced number of surgical interventions and the
shortened overall treatment time [2-4]. Additionally, some researchers believe that
immediate implant placement may improve the aesthetic outcome due to the reduced
risk of bone resorption and the maintenance of gingival and crestal bone
architecture [3,5]. A 50% reduction in horizontal bone width occurs during the first
year after tooth extraction. In the vertical dimension, a 2.4 to 4.5 mm decrease in
bone height may occur. This bone resorption is especially pronounced in the molar
region and when neighbouring teeth are absent [6-9]. In some cases, the reduction
in bone volume is so extensive that it might prevent the delayed placement (16
weeks) of an implant [10,11].
On the other hand, immediate placement has some disadvantages, such as the risk of
infection, unpredictable soft and hard tissue response(s), the difficulty to achieve
primary stability and the critical positioning of the implant [12,13]. Especially in
subjects with a thin biotype, immediate placement is not recommended due to the risk
of recession over time [14]. In
periodontally-susceptible patients, immediate implantation might also increase the
risk of implant failure [15]. In
contradiction to what was initially believed, does immediate placement not prevent
the resorption of the buccal bone, which is part of the natural healing process
after tooth extraction [16-18].
According to a review by Quirynen et al. [13]
immediately placed implants demonstrate a mean failure rate of 6.2%, ranging from 0%
to 40%. However, studies comparing the outcome between immediate and delayed
placement, found no significant difference in survival rate [19-22].
Most studies deal with the replacement of a monoradicular tooth. Immediate
implantation into a molar socket raises an extra challenge for the clinician,
because of the difficulty in positioning the implant, due to the residual
inter-radicular bone [23].
Placing a regular diameter implant in one of the existing root sockets will result in
a compromised emergence profile, significant off-angle loading, and the creation of
a cantilever effect [24]. A wide diameter
implant will enhance bicortical primary stability, increase the surface for
osseointegration [25,26] and will result in a more axial, prosthetically oriented
position.
Early publications on wide diameter implants reported more than 20% implant failures
[26,27], however more recent studies using surface modified implants report
lower failure rates of less than 5% [28-31]. A moderately rough surface and adapted
surgical protocol may promote the anchorage in the bone and decrease implant
failures [32,33].
To achieve primary stability in molar extraction sockets more easily, a new wide
diameter, tapered implant was introduced. The aim of this study was to evaluate
retrospectively the clinical outcome of this implant design when placed immediately
into maxillary and mandibulary molar extraction sockets.
MATERIAL AND METHODS
Implant design
The Max® implant (Southern Implants, Irene, South Africa) can be 7 to 10 mm
wide and 7, 9 or 11 mm long. It has a tapered design with a 0.8 mm thread pitch
(Figure 1). They have an external hex and
a moderately rough surface created by sandblasting and chemically conditioned with
solvents of a grade 4 c.p. titanium, with a Sa value of 1.34 [34,35]. Due to the wide
diameter, there is a platform switching of 0.25 mm in the horizontal plane and a
further 0.35 mm when the 45 degree bevel is included.
Representation of the Max® implant.
Surgical procedure
Following comprehensive clinical and radiographic examination of the patient and the
associated molar tooth, all patients were supplied with formal written treatment
plans. The indication for tooth extraction and immediate implant placement was
extensive loss of coronal tooth material, preventing conventional prosthetic
treatment. The immediate placement approach was only considered for patients with an
intact buccal socket wall and a medium or thick periodontal biotype, since it has
been shown that a thin biotype is more prone to recession and aesthetical
complications and is therefore less suited for immediate placement [36]. Assessment of the biotype was based on the
transparency of the periodontal probe as described by De Rouck et al. [37]. A signed consent was required from each
patient prior to treatment.
On the day of surgery, local anaesthetic wasadministered, but no attempt was made to
remove the tooth with conventional extraction forceps. As immediate implant
placement is critically dependant on the preservation of the perimeter bony walls of
the socket, the extractions were carried out by sectioning of the tooth to allow for
removal of the roots individually and to avoid potential fracture of any of the
associated bony elements, especially the buccal plate (Figure 2).
Clinical case representing the surgical procedure:
A = Caries and substantial loss of tooth material indicated extraction of
first molar.
B = The roots were split to allow atraumatic extraction.
C = The intact septum was used as a reference to position the first round
drill.
D = Depending on the bone quality, the site was formed using a tapered drill,
bone tap or osteotome.
E = When the implant bed was prepared, the implant was ready to be
installed.
F = If the residual space exceeded 2 mm, a bone graft was used to fill the
residual space.
G = Baseline radiograph, taken immediately after surgery.
H = A healing abutment was connected to the implant and the flap was
closed.
I = Radiograph taken 13 months after surgery showing stable bone level around
the implant neck.
J = Intraoral view of the final implant crown.
The crown of the molar was always cut off horizontally. The roots were then carefully
separated and the inter-radicular bone within the socket was used to manipulate the
roots, which were then elevated without removal of any bone. Piezo surgery was often
utilized to assist with removal of the roots and if root removal proved to be
challenging, 4.3 times magnification surgical loupes with fibre optic illumination
were used to assist with the surgery. Once all the roots were removed successfully,
the bony socket walls were inspected to confirm the presence of 4 intact outer walls
and the absence of any pathology or fenestrations.
Preparation of the inter-radicular bonewas then initiated. A round bur waspositioned
onto the inter-radicular septum. The point at which the drill was placed was always
slightly off-centre towards the lingual in the case of a mandibular molar and often
slightly towards the mesial in the case of an maxillary molar. This is to allow for
preparation of the implant placement site in a centrally located position, but away
from the buccal bone plate. Slight mesially positioned preparation in maxillary
molar sockets was only performed, if the available interdental bone between the
maxillary first molar and the maxillary second premolar was more than that available
between the first and second molar. If this slight adjustment is overlooked, the
implant could end up being placed too close to the maxillary second molar.
Preparation was then followed by a 1.2 mm, 2.00 mm, 2.85 mm and 3.07 mm diameter
twist drill. This was followed by a 4, 5 and 6 mm diameter tapered spade drills of
the correct length. Specially designed tapered wide diameter drills were then used
next, especially in the case of mandibular molars where denser bone was encountered.
In the case of a maxillary molar, further preparation of the site was often carried
out from this point onwards with dedicated surgical taps. These allow for slow and
careful preparation of the bone and enables lateral compaction of the prepared bone
as opposed to further bone removal which is commonly anticipated with drilling. This
was especially useful in the maxillary molar sockets, where bone quality is usually
Type III-IV. To clarify in more detail, three potential preparation methods were
employed after the 6 mm tapered spade drill. These were carried out using one or a
combination of the following:
1) Custom designed osteotomes whichcorrespond to the size of the available implants:
7, 8, 9 mm diameter and 7, 9, or 11 mm in length. Osteotomes wereusually used in a
very soft bone, where no drilling is required. They were often useful in second
molar sockets with little or no inter-radicular bony anatomy.
2) Custom designed 7, 8, or 9 mm diameter tapered drills with lengths of 7, 9, or 11
mm. Usually used in hard bone and when there is a very prominent inter-radicular
bony anatomy present.
3) Custom designed surgical taps, which correspond to the size of the available
implants: 7, 8, 9 mm diameter and 7, 9, or 11 mm in length. Usually used in soft
bone and when there is little need to remove more bone with further drilling. Also,
used when the greater site preparation control was needed as the taps allow for slow
and careful preparation.
Once preparation was complete, one of the custom designed osteotomes was used to
place in the osteotomy site and act as a profile gauge. A peri-apical radiograph
would then be taken to verify the position and depth of the osteotomy preparation.To
compensate for natural bone resorption after tooth extraction, the implant site must
allow the implant to be seated 2 mm below the margin of the intact buccal bony wall
and is therefore prepared 2 mm deeper, compared to delayed implantation [16].
After site preparation, the implant is installed at low speed using the implant
surgical unit. In all cases, the implant was primarily seated at 50 Ncm with the
implant surgical unit and then finally seated by hand with an implant insertion
wrench until the implant platform ended 2 mm subcrestally. The implant must also be
positioned well away from the buccal bony wall of the socket, to avoid damage and
recession [36]. Ideally, one would like to
see the remaining buccal strut of the inter-radicular bony septum still intact and
butting up against the implant.If theresidual socket space was more than 2 mm wide,
a bone graft was used, e.g. a bovine derived xenograft (Bio-Oss®, Geistlich,
Wolhusen, Switzerland; Nu-Oss®, Ace Surgical Supply, Brockton, MA, USA) or
irradiated allogenic cancellous bone (ICB®, Rocky Mountain Tissue Bank, Aurora, CO,
USA) [38,39].
A healing abutment was then connected and tightened. Soft tissue adaptation around
the healing abutment was assisted with Vicryl 4.0 sutures and a post-operative
peri-apical radiograph was taken with a parallel-aiming device. All patients
received a course of antibiotics (2 x Amoxicillin 500 mg / day for 7 days) and
analgesics (3 x Ibuprofen 800 mg / day for 3 days, 2 x paracetamol 500 mg / day for
1 day) as well as Corsodyl mouthwash (GlaxoSmithKline Consumer Healthcare,
Brentford, Middlesex, UK) after implant surgery. All the cases were followed-up with
a postoperative evaluation within 10 - 14 days after surgery.
Patient selection
All patients, consecutively treated by one experienced periodontist (AH) with one or
multiple Max® implants, were personally invited by phone to attend a clinical
research examination. Only implants placed in molar extraction sockets with at least
1 year follow-up post-surgery were included.
Patients, who chose not to attend the examination were asked if the implant was still
in function and whether they had experienced any problems with the implant or
prosthetic restoration. This method has been described before and was done to detect
possible failures or complications [40].
This study was approved by the Ethical Comité of the University Hospital Ghent,
Belgium and is in accordance with the Helsinki Declaration.
Clinical examination
Implant data were collected from patient files and clinical examination. Surgical
parameters were time of loading, 1 or 2 stage surgery, type of bone graft, implant
position and implant dimensions.
Patient related parameters were smoking and gender.
The implant prosthetics were categorized into 3 groups: single crowns, fixed partial
prosthesis and fixed full prosthesis. The type of prosthetic retention
(cement-retained or screw-retained) was also recorded.
The papilla fill was measured according to the papilla index by Jemt [41]. If the neighbouring tooth, crown or pontic
was absent, no value was recorded.
Radiographic analyses
During examination, digital peri-apical radiographs (Vista Scan, Dürr Dental AG,
Bietigheim-Bissingen, Germany) were taken using the long-cone paralleling technique
and to determine the peri-implant bone loss after comparison with a baseline
radiograph taken immediately after surgery. An X-ray holder was used to orient the
X-ray beam perpendicular with the implant axis. Radiographic analyses were done by
the one independent examiner (SVDW) not involved in the initial implant treatment
using DBSWIN software (Dürr Dental AG, Bietigheim-Bissingen, Germany) with an
accuracy of 0.1 mm. Radiographs were calibrated using the known thread pitch as a
reference. Bone level was determined from implant-abutment connection to the first
bone-to-implant contact mesial and distal. The mean of both values was taken as the
implant bone level. The actual bone loss or bone gain was calculated as the
difference between baseline and follow-up.
Each individual implant was dichotomised as either a success (value 1) or a survival
(value 0), using a mathematical formula to link bone loss and time. Implants up to
one year in function were called "implant bone loss success", when bone loss during
the first year was ≤ 1.5 mm; implants longer than one year in function were
successful, when bone loss was ≤ 1.5 + (0.2 x [Time in months - 12]/12) mm,
based on the internationally accepted criteria of Albrektsson and Isidor [42], allowing a maximum of 1.5 mm bone loss
during the first year and 0.2 mm yearly thereafter.
Statistical analysis
Statistics were performed with PASW v18 for Windows (SPSS®, Chicago, Illinois, USA).
Mann Whitney U-test and Kruskal-Wallis Test were used for bone loss analyses.
Chi-Square was used for statistical comparison of implant failure and success rate.
P < 0.05 was considered statistically significant.
RESULTS
In total, 98 implants installed in 89 patients answered to the selection criteria.
All patients could be reached by telephone and confirmed that their implant was
still present. Only 1 implant failed prior to loading, resulting in an overall
98.98% implant survival rate.
38 patients (12 male, 26 female) with 47 implants were available for clinical
examination (Table 1). The mean age was 60 years (SD 11.64, range 25 - 83). Twenty
six implants were placed in the maxilla and 21 in the mandible. A detailed overview
of implant distribution according to implant position can be seen in Figure 3. Table 2 represents an overview of
implant length according to implant diameter. In the maxilla, 69.2% of the implants
were 9 mm in diameter, while in the mandible, 76.2% of the implants were 8 mm in
diameter. This was significantly different (P = 0.002).
Table representing frequency distribution, bone loss and implant success
for the different variables
Implantsnumber
Bone loss(mm)
P-value
Implantsuccess
P-value
Time(months)
Gender
Male
15
0.41 (SD 0.56, range 0.00 – 1.95)
0.836
14/15 (93.3%)
0.140
22 (SD 6.02; range 14 – 32)
Female
32
0.38 (SD 0.45, range - 0.50 – 1.55)
32/32 (100%)
19 (SD 5.61; range 12 – 35)
Jaw
Maxilla
26
0.48 (SD 0.52; range - 0.50 – 1.95)
0.050a
25/26 (96.2%)
0.364
21 (SD 6.01; range 12 – 35)
Mandible
21
0.27 (SD 0.42; range - 0.05 – 1.35)
21/21 (100%)
20 (SD 5.66; range 12 – 32)
Implant diameter
8 mm
24
0.23 (SD 0.42; range - 0.50 – 1.35)
0.008b
24/24 (100%)
0.302
18 (SD 3.69; range 12 – 26)
9 mm
23
0.55 (SD 0.50; range 0.00 – 1.95)
22/23 (95.7%)
22 (SD 6.76; range 13 – 35)
Implant length
7 mm
5
0.79 (SD 0.63; range 0.10 – 1.55)
0.205
5/5 (100%)
0.613
21 (SD 4.44; range 13 – 24)
9 mm
18
0.28 (SD 0.36; range - 0.50 – 0.80)
18/18 (100%)
20 (SD 4.90; range 16 – 32)
11 mm
24
0.38 (SD 0.51; range 0.00 – 1.95)
23/24 (95.8%)
20 (SD 6.70; range 12 – 35)
Smoking
Yes
2
0.83 (SD 1.03, range 0.10 – 1.55)
0.426
2/2 (100%)
0.831
19 (SD 7.78; range 13 – 24)
No
45
0.37 (SD 0.46, range - 0.50 – 1.95)
44/45 (97.8%)
20 (SD 5.81; range 12 – 35)
Bone graft
No
17
0.43 (SD 0.50; range - 0.15 – 1.55)
0.480
17/17 (100%)
0.395
19 (SD 3.77; range 13 – 28)
Bio-Oss
12
0.53 (SD 0.59; range 0.00 – 1.95)
11/12 (91.7%)
25 (SD 7.75; range 14 – 35)
ICB
14
0.18 (SD 0.29; range - 0.50 – 0.60)
14/14 (100%)
19 (SD 4.48; range 12 – 26)
Nu-Oss
4
0.48 (SD 0.53; range 0.00 – 1.20)
4/4 (100%)
16 (SD 2.38; range 12 – 17)
Prostheticrestoration
Single crown
38
0.41 (SD 0.45; range 0.00 – 1.95)
0.429
37/38 (97.4%)
0.886
20 (SD 6.02; range 12 – 35)
Fixed partial prosthesis
6
0.27 (SD 0.73; range - 0.50 – 1.55)
6/6 (100%)
18 (SD 3.66; range 13 – 24)
Fixed full prosthesis
3
0.47 (SD 0.42; range 0.00 – 0.80)
3/3 (100%)
23 (SD 6.93; range 19 – 31)
Prostheticretention
Screw-retained
45
0.40 (SD 0.48; range - 0.50 – 1.95)
0.103
44/45 (97.8%)
0.880
20 (SD 5.85; range 12 – 35)
Cemented
1
- 0.15
1/1 (100%)
17
aStatistically significant difference in bone loss between
maxilla and mandible (Mann-Whitney U test, P < 0.05).
bStatistically significant difference in bone loss between 8
and 9 mm diameter implants (Mann-Whitney U test, P < 0.05).
Implant distribution according to implant diameter and length
Diameter (mm)
Total
8
9
Length (mm)
7
2
3
5
9
11
7
18
11
11
13
24
Total
24
23
47
Overview of implant distribution according to implant position.
No implant failures occurred in the examined patients. The mean peri-implant bone
loss was 0.38 mm (SD 0.48; range - 0.50 - 1.95), after a mean follow-up period of 20
months (SD 5.75; range 12 - 35) (Figure 4).
There were no significant changes in the bone loss between the different 6 months
intervals (P = 0.487) (Figure 5). The overall
individual implant success rate was 97.9% (46/47).
Peri-apical radiographs representing the bone levels around the Max® implant
over time:
A = Pre-operative radiograph. Due to its poor prognosis, the decision was
made to extract the tooth.
B = Baseline radiograph, taken on the day of surgery. The implant is placed
slightly subcrestally.
C = Radiograph taken after 3 months.
D = Radiograph taken after 2 years of loading. The bone level is stable and
situated at the implant neck.
Box-plot representing the mean bone loss and range per 6 months' time
interval.
All implants were placed following a 1 stage approach and delayed loading. Univariate
analysis showed significantly more bone loss in the maxilla (mean = 0.48 mm, SD
0.52, range - 0.50 - 1.95) compared to the mandible (mean = 0.27 mm, SD 0.42, range
- 0.05 - 1.35) (P = 0.050). Furthermore, more bone loss was seen around the 9 mm
diameter implants (mean = 0.55 mm, SD 0.50, range 0.00 - 1.95) compared to the 8 mm
diameter implants (mean = 0.23 mm, SD 0.42, range - 0.50 - 1.35) (P = 0.008) (Table
1).
At the mesial side, the papilla filled the interproximal space completely at 76.1% of
the sites, more than half at 19.6% and less than half at 4.3% of the sites. At the
distal side, the papilla filled the interproximal space completely at 62.1%, more
than half at 31% and less than half at 6.9% of the sites. There was no significant
difference in bone loss between the different scores at the mesial side (P = 0.236)
or distal side (P = 0.180), or in success rate at mesial (P = 0.852) or distal (P =
0.316) side.
DISCUSSION
The 98.98% implant survival is in accordance with other studies on immediate
placement reporting survival rates over 92% after at least 1 year follow-up [24,43-53]. Although it was partially
based on telephonic contact, Vercruyssen et al. [40] demonstrated the reliability of this technique. The survival rate
also corresponds to the outcome of an earlier multicenter study using this implant
design, reporting a 95.7% implant survival rate for the immediately placed Max®
implants [54]. However, some of the immediate
implants in that study were submerged during healing or immediately loaded, which
might explain the lower survival rate in that study and makes comparison not
completely valid.
The population in a private practice may differ from the one in clinical research
projects executed at academic centres. Although infection control measures were
taken before surgery and oral hygiene was adequate, patients were not excluded from
the study for certain risk factors as smoking or diabetes. Despite this, these data
reflect reality and the outcome is comparable to highly-controlled studies.
Although some authors report more bone loss around wide diameter implants compared to
regular diameter implant [55], the amount of
bone loss was only 0.38 mm after at least 1 year follow-up. This is in accordance
with other studies and far within the criteria for success [29-31,56,57].
Although one could argue that the clinical follow-up is too short, one has to keep
in mind that a marked stability of the bone level during the first six months after
surgery is normally an indication of a minimal risk for future implant failure or
further bone loss unless periimplantitis or traumatic overloading are involved. This
being said, it remains of course necessary that the studied implant and presented
treatment protocol are scrutinized further after a longer follow-up time for further
validation.
Today, very few studies reported on bone loss around implants immediately placed in
molar sockets. Bianchi and Sanfilippo [58]
reported a 0.75 mm bone loss after at least 72 months follow-up and Penarrocha et
al. [19] reported 0.83 mm bone loss after 1
year. Prosper et al. [59] reported a bone
level of 0.17 mm after 1 year and 1.01 after 5 years. These results indicate that
immediate placement generates limited bone loss, which is stable over time.
Bone loss was significantly lower in the mandible compared to the maxilla, which is
in accordance with earlier studies [20,60]. Jawbone quality and quantity are more
often compromised in maxillary than in mandibular sites and may therefore affect the
implant treatment outcome [61].
Wide-diameter implants have reported an increased failure rate, mainly associated
with the operators' learning curves, poor bone density, implant design and site
preparation, and its use when primary stability had not been achieved with a
standard-diameter implant [33]. Innovations
in surgical protocol and implant design made their outcome comparable with standard
diameter implants. The increased bone loss around the 9 mm diameter implants can be
explained by the fact that 78.3% of these implants were placed in the maxilla, while
66.7% of the 8 mm implants were placed in the mandible.
In 63.8% of the cases, an additional bone graft was used to fill the residual space
of the extraction socket. However, there is no consensus on the indication and the
optimal regenerative technique [62]. The
success for full bone healing depends on the stabilization of the coagulum, which
depends on the distance from the bone to the implant [63-66]. For this reason,
some studies advise the use of a bone graft if the jumping distance is more than 2
mm [38,39].
A full papilla was present at 70.66% of the interproximal sites. Papilla presence was
not correlated with bone loss, as confirmed by Degidi et al. [67]. Studies using the same index to evaluate the papilla fill
reported a full papilla at 35% to 78% of the sites [67-70]. The disadvantage of the
Papilla Index of Jemt [41] is that scores are
based on the fill of the embrasure space and not on a comparison with the
pretreatment appearance of the papilla. This makes comparison with other studies and
treatment approaches difficult. However, there is evidence that the final form of
the papilla is similar for immediate or delayed placement as well as immediate or
delayed restoration [71].
CONCLUSIONS
Immediate molar replacement, using a wide body Max® implant, offers good primary
stability and limited bone loss over time. However, careful surgery and case
selection is recommended to obtain a good result.
ACKNOWLEDGMENTS AND DISCLOSURE STATEMENTS
The authors declare that they have no conflict of interests.