Simplified Technique for Parallel Placement of Mini-Implants

Mini-dental implants (MDIs) (also referred to as small-diameter implants) have been used successfully to treat patients previously unable to receive standard diameter implants. Applications/indications include: single tooth replacement, temporary anchorage devices for orthodontic therapy, and maxillofacial prosthetics. Perhaps the most widely used application of MDIs is for the stabilization of loose dentures, which has been shown to have long-term clinical success.^1-3
There have been several techniques employed for the parallel placement of a MDI in preparation for an implant-retained overdenture. Parallelism is important to allow an even draw of the prosthesis without undue force on an individual implant or prematurely distorting the nylon male insert of o-ball retention systems.^4,5
The use of 4 MDIs within the parasymphyseal region of the mandible for complete overdenture retention has proven to be a successful clinical protocol.^6,7 Additionally, by placing the implants within this area, they will be situated out of the way of the mental nerve, including any existing anterior loop.^8,9
The following case report demonstrates the use of a novel paralleling technique for the placement of MDIs.

CASE REPORT
Diagnosis and Treatment Planning
A 63-year-old edentulous male with no contributory medical history presented with a chief complaint of looseness of his mandibular complete denture (Figures 1 and 2). His existing dentures had been fabricated 2 years earlier. The patient was sent for a computed tomography scan. From the scan, it was determined that four 1.8 x 13 mm MDIs (3M ESPE) could be placed 15 mm on either side of the midline (Figure 3). Mini-implants were selected due to a less invasive protocol, and for budget and time considerations.

Figure 3. Computed tomography scan: 3-dimensional picture of the mandible.	Figure 4. Points of Boley Gauge (Hu-Friedy), after sharpening the tines.
Figure 5. Marking of initial insertion points with Boley Gauge.	Figure 6. Marking of 10-mm implant intervals with Boley Gauge.

Figure 7. Four insertion points demarcated.

Clinical Protocol
The patient was anesthetized via bilateral mental blocks. The tines on a standard Boley Gauge (Hu-Friedy) were honed to 2 sharp points using carborundum rotary disks (Henry Schein) (Figure 4). The gauge was set at 30 mm, which equated to 15 mm from the mandibular midline in either direction. The modified Boley Gauge was then used to puncture the keratinized gingival tissue directly on the ridge, creating a bleeding point that would be used as a marker (Figure 5). Additional markers were placed at 10-mm intervals using the previous marker as a new starting point (Figure 6). Markers were placed for 4 mini-implants, each 10 mm apart (Figure 7).
A flapless approach with a No. 4 high-speed round bur was used to cut through the gingiva and cortical plate using copious irrigation (Figure 8). The 1.1-mm Surgical (Pilot) Drill (3M ESPE) was then inserted, taking care to ensure a proper angle and drilled approximately 6 mm (the length of the cutting surface of the drill) (Figure 9). Next, a customized stainless steel paralleling pin, which has identical dimension as the surgical drill (1.1 mm x 30 mm) was then placed into the 6-mm pilot hole. Using the paralleling pin as a guide, subsequent pilot holes and paralleling pins were placed until all implant sites have been prepared (Figure 10).
The MDI was then initially placed using an insertion tool (Figure 11), followed by the Finger Driver (3M ESPE) to screw down the implant until resistance was met (Figure 12). A Winged Thumb Wrench (3M ESPE) was then used for increased torque to penetrate the bone and continue to the cortical plate (Figure 13). This process was repeated until all the implants were seated (Figures 14 to 16). A Ratchet Wrench (3M ESPE) can be used for further torque as needed to complete the implant insertion (Figure 17). Primary stability was noted for all implants.

Figure 8. Four-mm high-speed round drill was used to cut through gingiva and cortical plate.	Figure 9. Pilot drill in slow speed handpiece to create initial osteotomy.
Figure 10. Pilot drill for third implant showing alignment with paralleling pins of first 2 implants.	Figure 11. Placement of mini-dental implant (MDI [3M ESPE]) using insertion tool.
Figure 12. Finger Driver (3M ESPE) was used to screw in implant until resistance was met.	Figure 13. Winged Torque Wrench (3M ESPE) was used for increased torque.

Figure 17. Ratchet Wrench was used for additional torque when necessary.	Figure 18. Heads of implants marked with indelible pencil.
Figure 19. Positional marking of implant location transferred to intaglio of denture.	Figure 20. Intaglio of denture was relieved to allow for no pressure on implants during healing.

An indelible pencil was used to mark the o-ball in order to transfer the positional information to the intaglio of the existing denture (Figure 18). The positions of the implants were transferred to the denture (Figure 19). These areas were relieved using an acrylic bur to allow a passive seating of the denture, allowing for healing for a period of 4 to 6 weeks, as per the protocol of Balshi et al10 (Figure 20). The patient was then given instructions on the use and care of the denture during the healing period.

Figure 23. View of intaglio of denture after pickup of retentive metal housings using cold-cure acrylic.	Figure 24. Final frontal view of mandibular denture.

Figure 25. Final radiograph demonstrating parallel placement of MDIs.

After a 6-week healing period, the integration of the implants was noted. The female metal housing (3M ESPE) was then placed over each implant (Figures 21 and 22). A shim was used to block out any undercut areas between the metal housing and the tissue. A hard cold-cure acrylic (SECURE [3M ESPE]) was placed into the relieved areas of the denture. Then the denture was seated and the patient was instructed to close and hold in centric occlusion for approximately 5 minutes while the material set. Any excess acrylic was removed and the denture was polished (Figure 23). Figure 24 demonstrates the final occlusal position of the implant-retained denture. The final radiograph demonstrates parallel placement of the MDIs (Figure 25).

CLOSING COMMENTS
The technique presented here provides a simple and effective method for the parallel placement of MDIs. It allows for direct vision by looking down on the parallel pin, in relation to the surgical drill. Direct eyeballing ensures precise positioning of the drill on the alveolar ridge, which is often irregular in shape or knife-edged. It also allows for placement within the confines of the keratinized attached gingiva, which is critical for periodontal health.^11,12
The use of a paralleling pin with equal dimensions (as the pilot drill) allows for better visualization and orientation than other paralleling systems, which often have shorter pins or may block the surgical area. It also gives a better indication of off-angles, which can be easily corrected in the pilot stage.

References

1. Shatkin TE, Shatkin S, Oppenheimer BD, Oppenheimer AJ. Mini dental implants for long-term fixed and removable prosthetics: a retrospective analysis of 2514 implants placed over a five-year period. Compend Contin Educ Dent. 2007;28:92-99.
2. Arisan V, Bölükbaşi N, Ersanli S, Ozdemir T. Evaluation of 316 narrow diameter implants followed for 5-10 years: a clinical and radiographic retrospective study. Clin Oral Implants Res. 2010;21:296-307.
3. Degidi M, Piattelli A, Carinci F. Clinical outcome of narrow diameter implants: a retrospective study of 510 implants. J Periodontol. 2008;79:49-54.
4. Ortegón SM, Thompson GA, Agar JR, Taylor TD, Perdikis D. Retention forces of spherical attachments as a function of implant and matrix angulation in mandibular overdentures: an in vitro study. J Prosthet Dent. 2009;101:231-238.
5. Alsabeeha NH, Swain MV, Payne AG. Clinical performance and material properties of single-implant overdenture attachment systems. Int J Prosthodont. 2011;24:247-254.
6. Bulard RA, Vance JB. Multi-clinic evaluation using mini-dental implants for long-term denture stabilization: a preliminary biometric evaluation. Compend Contin Educ Dent. 2005;26:892-897.
7. English CE, Bohle GC. Diagnosic, procedural, and clinical issues with the Sendax mini dental implant. Compendium. 2003;24(suppl 1):1-23.
8. Apostolakis D, Brown JE. The anterior loop of the inferior alveolar nerve: prevalence, measurement of its length and a recommendation for interforaminal implant installation based on cone beam CT imaging. Clin Oral Implants Res. 2012;23:1022-1030.
9. Greenstein G, Tarnow D. The mental foramen and nerve: clinical and anatomical factors related to dental implant placement: a literature review. J Periodontol. 2006;77:1933-1943.
10. Balshi SF, Allen FD, Wolfinger GJ, Balshi TJ. A resonance frequency analysis assessment of maxillary and mandibular immediately loaded implants. Int J Oral Maxillofac Implants. 2005;20:584-594.
11. Greenstein G, Cavallaro J. The clinical significance of keratinized gingiva around dental implants. Compend Contin Educ Dent. 2011;32:24-31.
12. Boynueğri D, Nemli SK, Kasko YA. Significance of keratinized mucosa around dental implants: a prospective comparative study. Clin Oral Implants Res. 2012 Apr 30. [Epub ahead of print]

Dr. Wank is a clinical professor of peridontics and implantology, and former postgraduate director at the New York University College of Dentistry. He is a past consultant at the New York Verterans’ Hospital, as well as a consultant in perio-ortho-prosthodontics at Coler-Goldwater Specialty Hospital and Nursing Facility in Roosevelt Island, NY. Dr. Wank is an international lecturer and has published in many peer-reviewed journals. He is a dental advisory board member for Dentistry Today. Additionally, he has received Fellowships in the American College of Dentists, International College of Dentists, American Academy of Oral Medicine, New York Academy of Dentistry, American Public Health Association, and AGD. He can be reached at gwank@aol.com.

Disclosure: Dr. Wank reports no disclosures.

Dr. Volker graduated from the Columbia University School of Dental and Oral Surgery. He received a Fellowship from the AGD and is the chairman of the New Dentist Committee and a member of the Continuing Education Committee for the New York State AGD. Additionally, he is a clinical attending at the Coler-Goldwater Specialty Hospital and Nursing Facility in Roosevelt Island, NY, and is in private practice in Queens, NY. He can be reached at volkerdds@gmail.com.

Disclosure: Dr. Volker reports no disclosures.