In current times, dentists must be able to create clinically sound treatment plans that take into consideration their patients’ needs. This includes patient expectations to have timely dental treatment and “teeth” when leaving the office. While immediately loaded prostheses may be preferred by patients, as clinicians, it is essential that there is stability and long-term predictability in the delivered work.
In order to deliver an immediate prosthesis that is functional, it is extremely important that primary stability of the implants has been achieved. Clinically, this translates to the absence of movement of the implant immediately after it has been placed.1 Implant design and surface morphology, bone quality and density, and surgical technique are all significant predictors of implant stability and implant success rates.2 Implants placed in type I, II, and III bone show better implant stability, whereas those placed in type IV bone have higher failure rates.3 Additionally, implant survival in the mandible is better than that of the maxilla due to the characteristics of the bone in these sites.3 Surgical techniques in which bone is removed during drilling compromise the stability of implants. Over time, other techniques in which bone tissue is preserved have been introduced (such as undersizing preparations and bone compaction using osteotomes). Recently, a new osseous densification procedure has been introduced that uses a series of specially designed Densah Burs (Versah) to increase the density of the bone during the expansion of the osteotomy.4
When implants are being loaded immediately, primary stability is a critical factor. It has been suggested that single implants should have an insertion torque of at least 30 Ncm and multiple splinted implants should have an insertion torque of at least 20 Ncm.3 There are several ways in which primary stability can be evaluated.5
1. Cutting torque resistance analysis
In this method, the energy required to cut bone using an electric motor is measured. The amount of energy used to cut bone is related to the density of the bone. A torque gauge within the handpiece measures the insertion torque.
This method uses a handpiece with a metallic tapping rod. An electric-driven and electronically monitored head taps the implant a total of 16 times. The tapping produces signals that are converted to values corresponding to the stability of the implant.
3. Resonance Frequency Analysis (RFA)
RFA evaluates the stability and stiffness at the implant-bone interface as measured by an Osstell monitor that records an implant stability quotient (ISQ). In this method, a sensor (SmartPeg [Osstell]) is screwed to the implant. The SmartPeg is then brought to vibration by gently moving it with magnetic pulses. The measurement of the frequency with which it vibrates corresponds to an ISQ scale, which correlates to the micro-mobility or primary stability of the implant.
|Figure 1. Clinical and radiographic information was merged digitally.||Figure 2. The anterior view of a prepared maxillary digital wax-up.|
|Figure 3. The occlusal view of a maxillary digital wax-up.||Figure 4. The occlusal view of a mandibular digital wax-up.|
Site Preparation Techniques
Osseodensification is the time-dependent plastic deformation of trabecular bone. This technique allows the clinician to create ideal-sized osteotomies with compaction autografting during the osteotomy preparation to create a precise size for the chosen implant through the spring-back effect.4 This process is delivered through specially designed burs. Densah Burs are designed to rotate in non-cutting direction at 800 to 1500 rpm with irrigation to create osseodensification as they drill into the bone. Unlike traditional drill bits, bone is not removed from the implant bed; rather, it is compacted and, thus, becomes denser. Additionally, the tapered design of the Densah burs allows the clinician to modulate the needed force to advance the bur and allow irrigation with a pumping motion to create bone plasticity.
This article discusses the treatment of a fully edentulous patient, utilizing different bone preparation modalities and measure implant primary stability of upper and lower fixed immediate prostheses with the NDX nSequence Guided Surgery/Guided Prosthetics protocol. This innovative technique uses integrated digital technology to achieve a predictable prosthetic result.6 The author uses 3 different modalities of site preparation to determine if higher stability can be achieved:
1. Using Densah Burs in Osseodensification mode (ccw rotation) with irrigation
2. Using BioHorizons surgical drills
3. Undersizing the osteotomy
|Figure 5. The check-bite step, done on the day of surgery using a hard, acrylic bite, fabricated from the records sent to the dental laboratory team.||Figure 6. The patient biting into the monostrut to verify the midline and occlusion.|
|Figure 7. Bone reduction was achieved using a round carbide bur.||Figure 8. A Versah C-Guide is shown in place.|
Diagnosis and Treatment Planning
A fully edentulous, healthy, and young-at-heart 74-year-old male patient presented to the office with a well-fitting upper acrylic complete denture and an ill-fitting lower complete denture. His lower denture had been converted from a partial denture to a complete denture. The patient was unhappy with the function and quality of life afforded to him by his current removable prostheses. Given his active lifestyle, he requested a more comfortable fixed option. His medical and dental history revealed no significant findings.
As a starting point, given the patient’s dissatisfaction with his existing lower denture, a new removable complete lower denture wax-up was fabricated to fit with his current upper denture. This helped in creating better phonetics and aesthetics and also in idealizing the vertical dimension of occlusion (VDO).
Full clinical records of the patient were taken at his new VDO. This included intraoral and extraoral photographs of the patient as well as digital models (CS 3600 [Carestream Dental]) and a face-bow registration (Kois Dento-facial Analyzer [Panadent]). A vinyl polysiloxane bite registration (Blu-Mousse [Parkell]) was also obtained at the idealized VDO.
Subsequently, a CBCT scan (CS 9300 Select [Carestream Dental]) of the patient was taken with his dentures and bite registration in place. In addition, a CBCT image of each denture was also taken separately. It is important to note that radiographic fiduciary markers were added to the patient’s dentures prior to imaging to help the software recognize and accurately align the position of the dentures on the CBCT scanner during the treatment planning phase.
The clinical information was sent to NDX nSequence to create the digital treatment plan and digital wax-up. Because of the patient’s advanced age and the length of time he had worn dentures, the quality and density of the bone was suboptimal for achieving primary stability, which may compromise immediate loading of the implants. As such, it was determined that it would be beneficial to improve the bone density, and thus the primary stability of the implants, through osseodensification.
|Figure 9. A Densah Bur (Versah) with Telestop is shown in place.||Figure 10. Preparing the osteotomy using the Densah Bur.|
|Figure 11. Preparing the osteotomy using the BioHorizons drills.||Figure 12. A BioHorizons drill is shown in place, down to the stopper.|
|Figure 13. Placing the dental implant through the BioHorizons implant placement guide.||Figure 14. A SmartPeg, with handle in place.|
|Figure 15. Obtaining the Osstell reading on the buccal aspect of the implant.||Figure 16. Obtaining the Osstell reading on the palatal aspect of the implant.|
Digital Planning Phase
Once the necessary records were received, NDX nSequence merged the clinical and radiographic information to prepare the digital wax-up (Figures 1 to 4). The facially driven treatment plan was reviewed and discussed through a virtual meeting. The use of the radiographic markers in the dentures facilitated the reproduction of the VDO and tooth positions in the patient’s arch.
In addition, the digital representation enabled visualization of the quantity of bone, including sites where bone reduction and/or augmentation may be required. In this particular case, only bone reduction was required. The CBCT scan provided an estimate of the bone quality, which was determined to be poor for this specific patient. The information was also used in combination with the photographs to idealize the final aesthetics of the prostheses.
The decision was made to place BioHorizons implants. As such, the corresponding implant sizes and components (implant analogs, multi-unit abutments, and temporary titanium cylinders) were determined. The information was then communicated to BioHorizons to have the appropriate parts delivered to the dental laboratory team at NDX nSequence. In addition, the laboratory team was informed that, due to the poor bone density, an osseodensification protocol using Densah Burs and a Versah C-Guide system would be done. It is critical that the laboratory team is aware of the implant system and surgical technique being employed to ensure that the appropriate rings and sleeves are used in the fabrication of the surgical and prosthetic guides. All necessary materials and guides were ordered or fabricated, respectively, and delivered directly to the dental office.
|Figure 17. Osstell readings were recorded for both the maxillary and mandibular implants.|
The most important step on the day of surgery is to perform a check bite. This is accomplished by using a hard, acrylic bite fabricated by the lab team from the records sent to the dental laboratory (Figure 5). The check-bite step is used to verify the accuracy of the merged data. Every step of the procedure is based on this initial bite relationship and is, therefore, crucial to the final success of the surgical and prosthetic treatments.
The surgery began by raising a full-thickness flap in the maxilla. A midcrestal incision was made, leaving at least 3.0 mm of keratinized tissue on the facial. Vertical releasing incisions were made laterally to the tuberosity on each side. The flap was then reflected facially in the anterior, up to the floor of the nose; posteriorly, up to the zygomatic arch; and palatally, up the lateral walls to the palate and premaxilla. A foundation guide was then seated over the alveolus, and 3 fixation pins were placed. The foundation guide was fabricated with a monostrut containing indentations so that the positioning of the guide could be verified by having the patient bite into the monostrut (Figure 6). In addition, this monostrut incorporates the shapes of the teeth as they are on the provisional, which verifies the midline and occlusion. Once the position was verified, the monostrut was removed and bone reduction was performed (Figure 7) according to the guide to ensure the junction of the prosthesis was hidden. Next, the implant placement guide was indexed to fit the foundation guide. It was predetermined that 7 implants would be placed in the maxilla at sites 3, 5, 6, 8, 10, 12, and 14.
The following instrumentation modalities were used:
1. Versah’s osseodensification system, using the Densah Burs (implants at sites 3 and 6 were placed using this system)
2. BioHorizons drills (implants at sites 5 and 8 were placed using this technique)
3. Undersizing the osteotomy (implants at sites 10, 12, and 14 were placed using this technique)
The NDX nSequence protocol allowed for the use of Densah Burs to prepare the osteotomy for sites 3 and 6 using a specially fabricated C-Guide (Figures 8 to 10). Once the 2 osteotomies were created to the equal corresponding size of the implant using the C-Guide, it was removed, and the implants were placed into the 2 sites using the BioHorizons implant placement guide. This same BioHorizons implant placement guide was then used to prepare the other 6 osteotomies and place the dental implants (Figures 11 to 13). For sites 5 and 8, BioHorizons drills were used sequentially for the appropriate implant size. For sites 10, 12, and 14, the BioHorizons drills were used sequentially; however, the last drill for that implant size was not used so as to undersize the osteotomy. After the dental implants were placed through the guide, the implant placement guide was removed.
|Figure 18. Titanium cylinders, with
block-out tubes in place.
|Figure 19. Verifying the bite using the provisional maxillary prosthesis, mandibular denture, and silicone bite registration.|
|Figure 20. The retracted view of the
immediate upper and lower fixed
prostheses in maximum intercuspation.
|Figure 21. The immediate load upper and lower fixed provisionals in place.|
SmartPegs were then placed on the implants (Figure 14), and Osstell values were obtained and recorded in the patient’s chart (Figures 15 to 17). Subsequently, using the abutment placement guide, multi-unit abutments were placed and torqued to 30 Ncm.
Next, temporary titanium cylinders were hand-tightened to the multi-unit abutments. The cylinders have block-out tubes, are pre-notched, and help to engage the acrylic pick-up material (Figure 18). Then a flexible silicone gasket was placed over the temporary titanium cylinders to block out undercuts, guide the provisional apically and laterally, and account for the thickness of the underlying soft tissue. The provisional prosthesis was then fitted into the gasket, and the bite was once again verified using the mandibular denture wax-up and silicone bite registration provided by NDX nSequence (Figure 19). When the patient bit into the registration, the prosthesis was stabilized at the correct VDO.
The provisional prosthesis was then picked up using a material utilizing visible light cure technology (Triad [Dentsply Sirona]) and finished while the maxilla was sutured. After finishing the provisional, it was torqued in place.
|Figure 22. A happy patient, with his wife, following surgery. Also present in this photo are Dr. Natalie Wong (far right) and Rudy Ghoubrial (far left), her trusted dental laboratory technician from ADL Dental Laboratory.|
|Figure 23. A panoramic radiograph was taken after surgery with the upper and lower fixed provisionals in place.|
Once the upper provisional was secured, a midcrestal incision that bisected the keratinized tissue was made in the mandibular arch. Vertical releasing incisions were made lateral to the retromolar pad, and the full-thickness flap was reflected facially. The mental foramina were identified and noted. Lingually, the flap was reflected to the level of the mylohyoid ridge.
Similar to the upper arch, the foundation guide was placed with the fixation pins and seated with the monostrut in place. The guide’s position was verified by having the patient bite into the monostrut with the maxillary fixed provisional. Once the midline and occlusion were checked, the monostrut was removed and the surgical procedure continued as outlined above.
In the mandibular arch, 5 BioHorizons implants were placed using the NDX nSequence guided surgery protocol at sites 19, 21, 23, 26, and 29. The implants were then torqued into place, and the insertion torques and Osstell readings were recorded in the chart. Once primary stability was achieved, the lower fixed provisional was delivered according to the steps outlined above for the upper arch. The immediate lower fixed provisional was checked for fit and occlusion against the upper provisional with the acrylic bite registration that was provided by the dental laboratory team, then finished.
At the end of the surgical procedures, the patient left with immediately loaded upper and lower fixed long-term provisionals (Figures 20 to 23) constructed from a monolithic polymethylmethacrylate. His occlusion was noted to be stable, with simultaneous, bilateral posterior contacts.
The success of osseointegration depends on several factors, including the biocompatibility of the implant material, the site of implant placement (ie, its health and quality of bone), the surgical technique during implant placement, the healing phase, the prosthetic design, and the long-term loading of the implant.7,8 The predictability of an immediate restoration relies heavily on adequate primary stability.
This article demonstrates the use of 3 site preparation techniques available today to improve the primary stability of dental implants in poor-density bone of the maxilla. It is interesting to note that the Osstell readings recorded on all the implants in the maxillary arch appeared to be similar, regardless of the technique utilized. In fact, the highest readings were on implants at sites 10 and 12, where undersizing of the osteotomy protocol was followed. Additionally, all of the implants achieved 30 Ncm or more initial torque. This allowed us to confidently load all of the implants.
We evaluate new techniques and technology in hopes of improving the outcome for our patients. This preliminary case report has demonstrated that the various site preparation techniques led us to the similar ISQ readings at the day of implant placement. And so, in terms of primary stability alone measured by ISQ readings, the author is not convinced that any of these techniques show superiority to the others. Certainly, further evaluation with more cases over a long-term basis is required. In addition, an evaluation of how these modalities affect the other indicators of implant success also needs to be done.F
Dr. Wong would like to thank Rudy Ghoubrial, RDT, from ADL Dental Laboratories, Inc, in Toronto for his assistance with this case report.
- Molly L. Bone density and primary stability in implant therapy. Clin Oral Implants Res. 2006;17(suppl 2):124-135.
- Elias CN, Rocha FA, Nascimento AL, et al. Influence of implant shape, surface morphology, surgical technique and bone quality on the primary stability of dental implants. J Mech Behav Biomed Mater. 2012;16:169-180.
- Farré-Pagés N, Augé-Castro M, Alaejos-Algarra F, et al. Relation between bone density and primary implant stability. Med Oral Patol Oral Cir Bucal. 2011;16:e62-e67.
- Huwais S, Meyer EG. A novel osseous densification approach in implant osteotomy preparation to increase biomechanical primary stability, bone mineral density, and bone-to-implant contact. Int J Oral Maxillofac Implants. 2017;32:27-36.
- Javed F, Romanos GE. The role of primary stability for successful immediate loading of dental implants. A literature review. J Dent. 2010;38:612-620.
- Pikos MA, Magyar CW, Llop DR. Guided full-arch immediate-function treatment modality for the edentulous and terminal dentition patient. Compend Contin Educ Dent. 2015;36:116-128.
- Vootla NR, Reddy KV. Osseointegration: key factors affecting its success—an overview. IOSR Journal of Dental and Medical Sciences. 2017;16:62-68.
- Albrektsson T, Zarb G, Worthington P. The long-term efficacy of currently used dental implants: a review and proposed criteria of success. Int J Oral Maxillofac Implants. 1986;1:11-25.
Dr. Wong received her DDS degree from the University of Toronto in 1996 and her certificate in prosthodontics from the University of Michigan in 2007. She is the only dentist who has attained a combination of the US board certification in implant dentistry (she is a Diplomate of the American Board of Oral Implantology [ABOI]), US board certification in prosthodontics (she is a Diplomate of the American Board of Prosthodontics), and the Canadian board certification in prosthodontics (she is a Fellow of the Royal College of Dentists of Canada). She is also a Diplomate of the International Congress of Oral Implantologists and holds fellowships with the AGD; the American Academy of Implant Dentistry (AAID); and the Misch International Implant Institute Canada, for which she is also a faculty member. She is a past president of the ABOI and is currently the president-elect for the AAID and past president of the Association of Prosthodontists of Ontario. Dr. Wong is also founder and director of the Toronto Implant Institute, Inc. She lectures internationally on implant dentistry and continues to practice both the surgical and prosthetic phases of implantology in Toronto. She can be reached at (647) 748-3550 or by visiting drnataliewong.com.
Disclosure: Dr. Wong is a consultant for BioHorizons, NDX nSequence, and Carestream Dental.