A Prospective Randomized Study on the Immediate Loading of Mandibular Overdentures Supported by Parallel Sided or Tapered Dental Titanium Implants
Phase: NA
Conditions: Dental Implants
Sponsor: University of Washington

Study Title: A Prospective Randomized Study on the Immediate Loading of 
Mandibular Overdentures Supported by a Parallel Sided or Tapered Dental 
Titanium Implant 
NCT#: 03272828 
 
Principal Investigator: Mats Kronstrom, DDS, PhD 
 
Document Name: Study Protocol 
 
Approval Date: May 18, 2012 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Brief Title: Mandibular Overdenture Clinical Trial Comparing Parallel Sided and 
Tapered Dental Implants 
Study Protocol 
Recruitment process 
Subjects will be recruited using flyers/posters on the University of Washington Campus. Brief 
information about the study including criteria for inclusion and contact information will be provided. 
Subject will be informed to contact the research coordinator to schedule a screening appointment. 
 
Pre-screening procedure 
The research coordinator will be providing oral information about the study including criteria for 
inclusion. If a subject is interested to participate, he/she will be scheduled for a screening appointment.  
 
Screening Procedure 
Part I 
The screenings will be performed at the Regional Research Clinic, School of Dentistry at the University of 
Washington. Dr. Kronstrom and Dr. Shor will do all the screenings. These investigators will inform the 
patient about the screening procedures and collect information about the patient’s medical and dental 
history. To be considered for inclusion the subject must:  
Inclusion criteria 
• 
Be between 20 and 75 years of age  
• 
Be edentulous and have both upper and lower complete dentures  
• 
Present with ASA I or ASA II and no medical contraindications to implant treatment 
• 
Have adequate bone volume for placement of one (1) 4.0 mm diameter titanium dental implant 
with a minimum length of 10 mm in the symphyseal area (=midline) of the anterior mandible  
• 
Show absence of pathology such as cysts, infections in the gum tissue or bone and remaining 
roots. 
• 
Be able to understand the procedures and have a jaw opening range of 30 mm or more 
 
Exclusion criteria 
• 
Ongoing chemotherapy 
• 
Previous radiation to head/neck 
• 
Ongoing corticosteroid medication 
• 
Ongoing blood thinner medication 
• 
Ongoing medication with psychopharmacological drugs 
• 
History of alcohol/drug abuse 
• 
Remaining teeth/root tips 

• 
Poor quality /fractured/severely worn dentures that cannot be modified to fit the implant 
• 
Jaw opening range less than 30 mm 
 
If a subject is found not to qualify after reviewing the dental and medical history, he/she will be 
informed about the reasons and all information collected up to that point will be immediately 
destroyed.  
Subjects enrolled in the study will sign a consent which includes information about the costs for the 
treatment. The cost for the CBCT is $ 150 which will be charged to the subject at the time of the 
radiographic examination. There will be no charge to the subjects of the surgical implant placement 
procedure and denture modification. Further, the titanium dental implant and the attachment 
components will be provided free of charge to the subjects. Follow-ups will be done at no charge to 
the patient.  
 
 
Part II 
• 
Those who are eligible to participate in the study will have opportunity to ask the investigators 
and the research coordinator any question he/she might have about the study before signing 
the consent form. Once the subject has consented to participate, he/she will be scheduled for a 
clinical examination, including evaluation of the dentures and a panoramic radiograph (large size 
radiograph of the upper and lower jaw extending from the left to the right glenoid fossa) taken 
to evaluate bone height and to ensure absence of infections, cysts and root tips.  
• 
Subjects who qualify for inclusion in the study will then be scheduled for the pre-surgical 
procedure. Subjects who have dentures with poor fit will be offered a reline (adding acrylic resin 
to the denture base) for improved denture fit/stability prior to implant surgery. 
• 
The subject will be excluded if the clinical and radiographic examination reveals that bone 
grafting (adding bone to the site before implant surgery) or surgical removal of cyst/residual 
roots prior to implant surgery are necessary.  
• 
Subjects who are excluded from the study due to poor denture quality or oral 
disease/cysts/remaining root tips/infections will be informed and recommended seeking 
treatment either with their regular dentist or referred to specialist. All information collected for 
study purposes up to that point will be destroyed. 
 
 
Pre-surgical Procedure 
• 
The pre-surgical procedures include having a Cone Beam Computed Tomography (CBCT) 
examination to evaluate the bone volume/width in the mandibular midline where the implant is 
being placed. This examination is considered standard of care and is used regularly when 
planning for surgical implant placement. The patient’s denture will be duplicated and the 
denture replica will serve as a guide when placing the implant. A 2 mm diameter hole will be 
drilled in the denture replica acrylic in the ideal implant position and used during the surgical 
implant placement.  
 

Surgical Implant Placement 
• 
The surgical implant placement will be done at the Regional Research Clinic, School of Dentistry, 
at the University of Washington. Each subject will have a titanium dental implant placed in the 
midline of the lower jaw (mandible).  The type of implant (parallel sided or tapered) will be 
determined using a computer random sampling program (Research Randomizer, JavaScript, and 
the patient will be informed what implant he/she will have the day of surgery. Each implant will 
have an attachment (metal coping to provide denture retention) connected immediately 
following placement. The subject will receive 2 g Amoxicillin as prophylactic antibiotics 1 hour 
before the surgical procedure to minimize the risk of infection. Those reporting allergy to 
Penicillin will have 600 mg Clindamycin orally 1 hour before the procedure. Local anesthetics 
(3.6 cc, 2% Lidocaine 1:100000 epi) will be used to numb the subject. The subject will receive 
post-op information and prescription of Chlorhexidine mouth rinse. 
Prosthodontic Procedures 
• 
Immediately following the surgical implant placement, the subject’s lower denture will be 
modified to fit over the implant attachment. A metal housing (with a snap-on plastic insert) 
placed on the implant attachment will be secured to the denture base using fast setting acrylic. 
A non-latex rubber dam will be used to protect the gum tissue against resin monomer during 
the attachment pick-up procedure. The denture will be polished and inserted to assure correct 
fit. The subject will be instructed to keep the denture in the mouth for 24 hours to avoid post-
operative swelling and scheduled for a follow-up visit the next day. 
 
Follow-ups 
• 
Subjects are scheduled for follow-up 6- and 12-months after implant placement and annually 
thereafter for 4 years. A periapical radiograph will be taken to evaluate peri-implant bone 
support. Implant stability will be assessed and soft tissue condition, denture fit, wear and 
occlusion (bite) will also be evaluated. Subjects will be asked to fill out the OHIP questionnaire at 
all follow-up appointments to evaluate oral comfort, chewing ability and oral health related 
quality of life.