A Randomised Controlled Clinical Trial comparing the results of the Immediate Loading (within 48 hours) of Mandibular Overdentures supported by either 2 standard Straumann dental implants or 4 Mini Dental Implants (MDIs).

Implant-retained overdentures are an established treatment option to improve
oral health-related quality of life in edentulous patients. (1-5). The most
common protocol used is the implant-retained overdenture treatment which
includes placement of 2 implants in the anterior region of the mandible. There
is now overwhelming evidence that 2 implants splinted with a rigid
interconnected bar that incorporates an attachment mechanism for the retention
of the overdenture is a viable option for rehabilitation of the edentulous
mandible (6-12). Immediate loading with mandibular overdentures is a protocol
in which implants are connected to the prosthesis within 1 week after implant
placement (4th ITI Consensus Conference).The immediate loading of implants with
overdentures was first reported by Ledermann (13,14), where 4 implants
supported an overdenture.
The initial treatment protocols were based on several prospective studies that
have been published on immediate loading of implants supporting overdentures in
the edentulous mandible, most of them related to four or more implants
(15-20). The proposed advantages for such loading protocols with shorter
healing times prior to implant loading are a reduction in the number of
surgical and prosthodontic procedures, associated clinical time, healing
periods, treatment costs and an improvement of the patients quality of life.
Immediate or early loading of 2 implants in the edentulous mandible to support
an overdenture has also been investigated in the literature (21-26). Stoker and
Wismeijer (27) describe in a recent article an immediate loading protocol where
the overdenture is inserted within 48 hours after implant surgery. The implant
survival rate in these studies is more than 95%. An alternative to standard or
narrow diameter implants in the edentulous mandible is the use of Mini Dental
Implants (MDIs). The MDI is a one-piece implant that does not require a
separate abutment. This simplifies the restorative phase resulting in reduced
costs for the patient. Although initially MDIs were used for temporary
prosthetic stabilization during the healing phase of standard implants (28-30)
their reproducible success has expanded their use. Recently they have been used
for long term fixed and removable prosthetics (31). Griffitts et al. 2005 (32)
placed 116 MDIs in the anterior zone of the mandible. The reported success rate
for the implants was 97.4% whereas a great improvement was mentioned by the
patients with regard to retention of the prosthesis, chewing ability, comfort
in a comparison of questionnaires completed pre-operatively and at five months
post-operative. In a cost benefit analysis the authors concluded that the cost
of four (4) MDIs was equivalent to one conventional implant. Shatkin et al.
(33) have placed 2514 MDIs over a period of 5 years with an overall survival of
94.2%. The literature review shows that the *Mini Dental Implant* has the
potential of substituting the current standard care for the edentulous mandible
(2 implant overdenture) and can be a viable alternative to the current
treatment. In case of narrow ridges the alternative to mini implants is an
augmentation of the ridge in order to provide adequate bone width for placement
of conventional implants (34). Compared to an augmentation procedure, the use
of MDIs is a significantly less invasive procedure resulting in reduced
bleeding, decreased postoperative discomfort and shortened healing time. If the
research outcome shows that this treatment is viable then it might be a
solution particularly suited for medically compromised patient. That means
patients who would otherwise be excluded as a result of health problems that
preclude extensive surgical procedures can benefit from implant treatment
resulting in an improvement in the quality of their lives. Naturally further
research will be necessary to prove this. Clinical and radiographic outcomes of
immediately loaded MDIs used for long term stabilization of overdentures as an
alternative to standard sized implant overdentures have been already published
in the literature (35,36).

The cumulative survival and success rates of MDIs were 96.4% and 92.9%
respectively. Although the mini dental implant has a reduced surface area
compared with a conventional dental implant histology has shown that the
percentage bone to implant contact for MDI is comparable to conventional
implants. The narrow diameter of the MDI allows a simplified insertion
technique involving placement without raising a flap (43). To summarize, the
benefits of providing an implant overdenture on mini implants include the fact
that the treatment is cheaper ( of course the cost is not relevant with regards
to The Nederlands because the insurance will cover the cost, but in other
countries this can be a significant advantage) and it is simpler (the
prosthetic part requires less appointment and of shorter time). If we prove
that their clinical performance is as good as the clinical performance of the
standard treatment, then the MDIs can be a viable alternative because of the
aforementioned extra advantages. However, a Randomised Controlled Clinical
Trial to compare the clinical performance of MDIs with an already well
documented treatment modality has not yet reported in the literature.

In this randomized controlled clinical trial we aim to apply the-already
investigated-concept of immediate loading protocol and examine the performance
of implant-retained overdentures using 2 SLAactive Straumann implants connected
by bar ( Contol Group), versus 4 MDIs with ball attachments (Test Group) in
comparable situations. To be able to randomize both treatment modalities, a
minimum width of 5.5mm of residual ridge is required with regard to surgical
requirements to accommodate the wider diameter Straumann implants (3.3mm) in
both the control and the test group.

Following comprehensive discussion about the aims and objectives of the study,
risks-cost/benefits, advantages and disadvantages of each treatment option an
informed consent will be signed and each patient will undergo a complete dental
examination.
Patients who are deemed eligible for the study after this initial screening
will be asked to undergo a more detail examination by the investigator. An
overview of the 6 phases of the study procedures is shown in the flow chart of
study procedures.

1.EXAMINATION OF THE PATIENT
A summary of these procedures is shown in the flow chart of the examination of
the patient.
a.Comprehensive History A thorough and systematic history and examination of
the patient will ensure that all relevant information is recorded. History will
include:
*History of the present complaint
*Dental History
*When the natural teeth were extracted
a.The reasons for the extractions
b.The occurrence of any surgical complications
c.The number of dentures that have been worn subsequently
d.The degree of success or failure of the dentures
e.The degree of adaptation of the patient
*Medical History
*Social History
The patients will be presented with self administered questionnaires of the VAS
type on denture functioning, satisfaction, speech, aesthetics, retention,
mastication and social functioning. They will also be presented with
questionnaires on somatisation and depression, parafunction activities, and
overall quality of life before and after treatment. These questionnaires will
be presented again 3 months after the dentures have been placed and again after
1, 2 and 4 years.

b.Clinical examination

Extraoral Examination
*TMJ pain or discomfort
*Skeletal relationship
*Occlusal Vertical Dimension (OVD)
*Dental appearance (during speaking, smiling)
*Extra-oral lesions (inflammation, angular stomatitis)
*Intolerance or other difficulties with the dentures

Intraoral examination:
The broad objectives of this part of the examination are to determine:
*Any pathology such as mucosal inflammation, ulceration, hyperplasia,
herostomia
*The shape and size of ridges and hard palate
*The depth and width of the sulci, including the presence of prominent frena
*The degree of compressibility of the denture-bearing mucosa determined by
palpation

c. Examination of the dentures
Each denture will be examined in the mouth separately for:
*Retention
*Stability
*Border extension
The dentures are then examined together to assess the:
*Occlusion
*Occlusal vertical dimension
*Appearance

d.Radiographic examination Preliminary radiographic examination (OPT) which
will provide some general information for evaluating residual lesions and the
amount of bone available.

2.FABRICATION OF NEW DENTURES
Before proceeding with the fabrication of the new dentures any inflammation of
the denture-bearing mucosa will be treated.
Stages:
1.Preliminary impressions will be taken with alginate using metal trays
2.Master impression will be taken using customized trays (light cured acrylic
resin will be used) for the particular patient after border moulding. The
impression material will be an addition-cured silicone material
3.Jaw relations recording. We will make sure that:
*The rims are stable
*There is adequate freeway space
*An consistent retruded jaw relationship is established
*There is even occlusal contacts
*There is a pleasing appearance with the rims in the mouth and the lips brought
together
4.Choice of teeth (colour, shape and size of the artificial teeth)
5.Try-in stage to ensure that the patient is happy with appearance, phonetics,
function. The type of occlusion provided will be lingualised occlusion
6.Provision of final dentures. In the prosthesis an radiological marker will be
incorporated for future radiographic reference.
7.Review appointment.
8.Dental Hygiene Instructions
The need for meticulous cleaning will be explained to the patient and the
methods for carrying it out will discussed, demonstrated and subsequently
monitored both at this and consequent stages.

A period of at least 3 weeks will be allowed prior to surgery for overall
evaluation of the prostheses by both the patient and the clinician and also to
let patients adapt to their new prosthesis.

3.PRESURGICAL PROCEDURES
Under local anesthesia the thickness of the mucosa will be measured, using a
modified UTC 15 modified probe. Due to the limitation of OPTs in accurate
treatment planning (e.g. distortion) we intend to make a CBCT for each patient
prior to implant placement which will facilitate a precise radiographic
diagnosis.
The new mandibular denture will be copied and a diagnostic template using
radiopaque teeth will made which the patient will wear during the CBCT. In this
way the exact amount of bone and shape of the ridge in the planned implant
position will be calculated. This is in accordance with the EAO guidelines
(Cone Beam CT for dental and maxillofacial radiology, Evidenced Based
Guidelines 2011). Although the relative risk of exposure to radiation during
the period of the study is extremely low, in order to reduce even further the
exposure of the patient to radiation, we intend to narrow the field of view in
the intraforaminal region, since this localized part of the lower jaw is our
region or interest. The patient will be then allocated randomly in Control and
Test treatment groups.

4.SURGICAL PROTOCOL
A summary of these procedures is shown in the flow chart of the surgical
protocol.

Control Group .(3.3mm Straumann Implants)
A crestal incision in the mandible will be made. The mucoperiosteum will be
elevated and the bone gently drilled to prepare osteotomy sites for the
implants. Where appropriate, the crestal jawbone will be trimmed to provide an
adequate site for implant placement. Two SLActive straumann implants of 3.3 mm
diameter will be placed tightened with a torque of at least 35 Ncm. The
distance between the 2 implants will be approximately 20 mm to allow
fabrication of a bar superstructure.
ISQ measurements will be made at the levels of the implant and the abutment
using an Osstell Mentor device and a Smartpeg (type 4; ref. 100350) (Osstell
AB, Göteborg, Sweden). The ISQ measurements will be made parallel and
perpendicular to the bone crest in the buccolingual direction, and parallel to
the bone crest in mesial*distal direction, as advised by Osstell.
Themucoperiosteal flaps will be sutured in place with non resorbable sutures.

Test group (MDIs)
All surgeries will be carried out under Local Anesthesia.
*4 implants with diameter 2.1 mm (3M ESPE Mini Dental Implant) will be placed
interforaminal.
*Immediate loading with metal housing only if primary stability is above 35
Ncm.
*The selection of the implant would depend on the thickness of the mucosa.
If > 2mm the collared type implant will be used
If <2mm the non collared type implant will be used
*In the test group where the ridge has sufficient width a flapless,
transgingival technique for the pilot drill will be used. In case of mobile
mucosa the 1.5 mm tissue punch is going to be used prior to using the pilot
drill. The MDI implants will be placed into the bone by a self tapping
compression technique.
*Small modifications on the surgical preparation of the MDI implant bed will be
made dependent on the density of the bone at the surgical site, according to
the manufacturer recommendations.

All implants will be inserted in the symphysial area under local anesthesia.
The new dentures will act as a drilling template.

5.RESTORATIVE PROTOCOL
Immediately after surgery the existing mandibular dentures will be hollowed
out. Following confirmation of impression copings seating, a pick up impression
will be made with the denture serving as a customised tray. This will be sent
to the laboratory and the impression will be poured in dental stone.
The patient will be administered paracetamol as an analgesic and sent home to
return later in the day or the day after for the insertion of the bar and the
overdenture.
An egg shaped Dolder bar (CMST53012P20, Cendres et Métaux SA, Biel,
Switzerland) will be fabricated and returned to the clinic at the same day. The
SynOcta gold copings (048.204, Straumann AG) will be soldered and the retention
clip mounted in the lower denture.
After passive fit of the bar is confirmed in the patient*s mouth, the
overdenture will be inserted. In the test group the new denture will be fitted
with the O-ring attachments following the prescribed protocol within 48 hours
after implant placement. The overdenture will be adjusted following a relining
procedure in the laboratory.

Postoperative Instructions
During the first night, the patient will be instructed to wear the overdenture,
which acts as a pressure bandage for optimal wound healing. For the following 3
weeks, the patient will be instructed not to wear the overdenture at night. The
patient will be permitted to eat with the overdenture in place, but will be
advised to avoid biting hard food. No further restrictions will be imposed. On
the first postoperative day, a control visit will be planned to check for
possible denture problems and wound healing. The patient will be instructed how
to remove the overdenture and how to disinfect the mouth, the wound, and the
superstructure with 0.12% chlorhexidine (4 times a day for 5 days). The patient
will be advised to begin brushing the bar twice daily after 3 days. One week
after surgery, the sutures will be removed.

6.FOLLOW UP
*Standardised per apical X-rays will be taken at implant insertion, after 12,
24 and 36 months. Standardized periapical radiographs will be obtained with the
long-cone technique and a standardized jig locator at a 10cm film to cone
distance.
Test group: for standardisation of radiographic film position in relation to
the beam during subsequent film exposures, an acrylic resin bite registration
record with compound rim will be constructed over the resultant cast on which
the denture will be rebased to capture the matrices. The maxillary denture
teeth indentations on the compound rim will be used for future orientations of
the film holder. The film holder will be attached to the record base with
self-cure acrylic resin to obtain standardised intraoral radiographs.
Control group: radiographs will also be obtained with appropriate aiming
devices for standardised images for marginal bone level follow-up in the
transversal plane.
All radiographs will be exposed using the same X-ray unit with an exposure
factor of 70 kvp, 8 mA, and 0.25 exposure time. All films will be processed
using an automatic machine.
For the radiographic analysis we will use the subtraction technique.

*Periodontal parameters will be documented in a standardized method evaluating
the scenario of the treatment at three months, six months, one year and at
yearly intervals thereafter. These parameters are:
oPlaque and bleeding index according to Mombellli et al.
oMarginal bone height
oProbing depth. These are all measured at the buccal, distal, lingual and
mesial postion around the implant.
Using the Ostell mentor Resonance Frequency Analysis device the ISQ value of
the implants will be tracked over time (1, 6 weeks after surgery and then at 3,
6, 12, 24, 36 months). In all groups the measurements will be done at abutment
level. The measurements that will be made at weeks 1 & 6 will be performed only
at the abutment level to avoid the risk of rotating the implant when dislodging
the abutment. A percussion-sounding or implant-sounding test will be used as a
subjective control. Twelve weeks after surgery, the ISQ measurements will be
made at both the implant and the abutment level. The SynOcta abutment will be
retightened at 35 Ncm.
An independent colleague will evaluate the patients (will perform the
periodontal measurements, record the ISQ values and register the results of the
questionnaires into the computer).

Immediate loading (within 48 hours) of two interconnected implants with an
overdenture (Control group) Immediate loading (within 48 hours) of 4 mini
implants and an overdenture in patients with adequate bone width (test group).

As any other type of oral rehabilitation the provision of implant-retained
overdentures requires a regular and ongoing maintenance program to ensure long
term clinical success. This requires patient*s understanding, compliance and
commitment during the whole study period. The surgical risks involved in the
aforementioned treatment modalities provided will not exceed those of other
conventional surgical procedures in the same region of the oral cavity. Some
minor postoperative pain and discomfort will be expected in both the control
and the test group. The most severe complication during surgery is the
perforation of the lingual plate and subsequent damage of the lingual artery.
The literature shows that this complication is extemely rare(*0,1%), , and the
possibility of this occurring will be even lower due to the comprehensive
clinical and radiographic examination. Altered sensations of the mental nerve
caused by the surgery is also another complication that might occur. These
complications are also rare. The meticulous and thorough clinical and
radiographic planning will reduced further the chance of this happening. Early
complications after surgery include lack of osseointegration and loss of the
implant. The literature has shown that the 5 year success rate of the implants
in the edentulous mandible is well above 95%. Later complications can be either
biological (e.g. peri-implant diseases) or technical complications. Every care
will be taken to minimize these complications to occur. The patients however
will be informed of the fact that a strict maintenance protocol is important to
detect potential complications at an early stage.
A vast improvement in terms of function, mastication, retention and overall
quality of life is expected for the treated patients. For the patients
allocated to the test group, the procedure is potentially less invasive and the
pain and discomfort may be reduced. The patients will be placed in a
maintenance program for several years, in an academic environment in which a
high level of care is provided. *