Comparison of Crestal Bone Loss and Implant Stability Among the Implants Placed With Conventional Procedure and Using Osteotome Technique: A Clinical Study

The replacement of missing teeth is carried out frequently with the help of implants in most surgically indicated cases. Dental rehabilitation of partially or totally edentulous patients with dental implants has become common practice in recent decades and has reliable long-term results.1–6 After loss of tooth, the remaining alveolar and basal bone provides anchorage to the endosteal implants for retaining and supporting prosthesis. Current trends and demands have revealed the need for faster restoration of dental function using implants, which led to the introduction of early and immediate loading protocols.

The success rate obtained with dental implants in various clinical situations depends to a great extent on the volume and quality of the surrounding bone.7–10 Successful osseointegration of an endosseous titanium implant requires adequate stability at the time of placement.8,11–13 Achieving stability depends on the bone density, the surgical technique, and the microscopic and macroscopic morphology of the implant used. In bone that is not very dense, it is often difficult to obtain implant anchorage.14 Sufficient density and appropriate volume of the bone are therefore crucial for successful implant treatment.15,16 

To achieve better primary stability and expand the range of indications with inferior bone quality, a procedure known as the osteotome technique for bone condensing was developed by Summer in 1994.17–20 The objective of this procedure is to retain the bone that would otherwise be removed by compressing it laterally and axially to create a precisely formed implant site. Biomechanical research on peri-implant bone loading has shown that a maxillary implant surrounded with firm bone is more desirable than reliance on bicortical anchorage with inferior bone quality.21,22 The osteotome technique is used primarily for type III and type IV bone that is typically found in maxilla. This technique can be used if ridge expansion and condensation of spongious bone of reduced density is required to improve the primary stability of the implant.23 

It has been claimed that using Summer's technique of bone expansion and simultaneous implant placement results in less chance of heat generation and increases initial stability because of lateral condensation of bone. It is also claimed that this approach gives better primary stability, results in less chance of crestal bone loss around the implant, and so leads to less fear and anxiety related to implant failure.17–20 

Because there are no clinical studies to date comparing the conventional approach of implant placement with the osteotome technique in the same patient, the aim of this in vivo study was to evaluate the crestal bone loss exhibited by the bone around early nonfunctionally loaded implants placed with conventional approach and with the osteotome technique and to examine the effect of osteotome technique on the stability of the implants. Conventional implant site preparation with drills served as a control group. Stability was measured using a resonance frequency analysis (RFA) device.

The total number of patients was 5 (2 women with a mean age of 29 years and 3 men with a mean age of 23 years), and they had a minimum of 2 teeth missing in the maxillary anterior region (Figure 1). Patients were excluded if they had a history of immune disease, uncontrolled diabetes, ongoing chemotherapy, radiation treatment to the head and neck, alcohol or drug abuse, or psychological instability. Patients were given oral and written information regarding the risks of surgery, and their written informed consent was obtained. All surgical work was performed at the Department of Prosthodontics and Implantology, Sri Ramachandra University, Chennai, India.

In this study we used 10 Uniti (Equinox Medical Technologies, Zeist, The Netherlands) screw-type self-tapping threads implants with a length of 13 mm and a diameter of 3.7 mm.

Preoperative antibiotics were prescribed to the patients before surgery. All surgeries were performed under aseptic conditions. Local anesthesia was achieved by infiltrating lignocaine 2% containing 1∶100 000 adrenaline. A crestal incision was made, and a full-thickness mucoperiosteal flap was raised (Figure 2). Thereafter, the implants were placed in the first quadrant using the conventional technique (group A) and in the second quadrant using the osteotome technique (group B). For group A, the implant sites were sequentially enlarged to 3.7 mm in diameter with pilot and spiral drills according to the standard protocol of the manufacturer (Equinox Medical Technologies; Figure 3). When the osteotome technique was performed, the implant sites were prepared initially by a 2-mm diameter pilot drill. This was followed by condensing the bone using osteotomes of increasing diameter (MIS bone compression kit, MIS Implants Technologies Ltd, Shlomi, Israel) using a hand ratchet (Figure 4). Extreme care was taken to proceed as slowly as possible, and continuous external saline irrigation was used to minimize bone damage caused by overheating (Figure 4). After each half turn, there was a pause of 20–30 seconds before turning the ratchet another half turn. This is important because at each half turn, as the osteotome sinks further, the bone needs time to accommodate to the expansion. It should be kept in mind that rapid expansion would obviously result in fracture of the labial bone plate and should be avoided.

After each osteotome had reached a depth of 13 mm (this can be checked against the black marks on the osteotome) it was allowed to remain in the implant site for a minimum of 1 minute before the next diameter osteotome was used. Once both osteotomy sites were prepared, implants were inserted (Figure 5). As we planned for early nonfunctional loading, impressions were made using elastomeric impression material after placing posts and sutures (Figure 6). Patients were sent home with gingival formers in place and recalled after 5–7 days for suture removal and prosthesis cementation (Figures 7 through 9). Temporary luting agent (RelyX Temp NE, 3M ESPE, Seefeld, Germany) was used to ensure that the restoration could be removed to facilitate monitoring and maintenance.

Resonance frequency measurements (RFMs) were made on each implant on the day of fixture placement and on 180th day after fixture placement by attaching a standard transducer (Osstell, Integration Diagnostics, Goteborg, Sweden) to each implant. The frequency response of the system was measured by attaching the smartpeg type 21 to the implant (Figure 11).24–26 The excitation sign was given over a range of frequencies (typically 5–15 KHz with a peak amplitude of 1V), and the first flexural resonance was measured.24–26 

Radiographic examination was carried out using Radio Visio Graphy taken with RINN X-ray holders (Rinn Corp Com, Dentsply, Elgin, Ill) using a paralleling long-cone technique (Figure 10). These examinations occurred on the day of fixture placement and 6 months after completion of the restoration. The radiopaque implant length was used as a measuring reference. The implant shoulder and the alveolar crest were used as reference points. Measurements of the distance between 2 reference points were performed at mesial and distal aspects digitally, 3 times per implant, using SOPRO digital imaging software (SOPIX, La Ciotat, France; Figure 12). Mean values were calculated and recorded for each implant. Crestal bone loss was analyzed by calculating the difference between measured bone levels in radiographs on the day of surgery and 180 days after surgery.

Descriptive statistics, including mean value and standard deviation, were used to compare the implant stability and crestal bone loss over time for the conventional procedure and the osteotome technique. Comparisons between both techniques were performed using paired t tests. Difference was considered significant when P < .05. Calculations were performed using SPSS for Windows (SPSS Inc, Chicago, Ill).

A total of 10 implants were placed in 5 patients. At the end of 6 months all 10 implants showed good primary stability of the osseointegration at the clinical level. No problems with soft-tissue healing were observed.

The RFA measurements (Table 1) showed an implant stability quotient (ISQ) of 64.77 as a mean value, indicating the high primary stability for conventional procedure of implant placement (group A) than osteotome technique (group B), which showed ISQ of 59.60 as a mean value on the day of surgery. So, RFA demonstrated a statistically significant higher primary stability for implants in group A than that of group B (P  =  .026; n  =  5). However, RFA demonstrated no statistically significant difference between both groups 6 months after the surgery (P  =  .076; n  =  5). A decrease in RFM values were found after 6 months with group A, that is, 55.40. In contrast, in group B there was a slight increase in RFM values after 6 months, that is, 61.50. But this difference in RFM values between the 2 groups failed to reach a level of significance.

A statistically significant difference was found in the level of the crestal bone loss after 6 months of surgery between both groups (P  =  0; n  =  5) with less crestal bone loss in group A (Table 2). The mean crestal bone loss for group A and group B was 0.99 mm and 1.19 mm, respectively.

Compression of trabecular bone to improve density has been successfully used in reconstructive surgery and cleft palate surgery for a long time.27–32 With modifications, this method has been introduced to dental implantology.17–20 The use of the osteotome technique has been investigated in clinical studies with emphasis given on the survival rate of the implants.33–37 However, there is a lack of clinical studies that compare the osteotome technique with the conventional technique of implant placement in the same patient. Therefore, the aim of this clinical study was to evaluate the crestal bone loss and biomechanical outcome of implant placement in condensed bone. Conventional implant placement was used as a control.

Various methods have been introduced to measure implant stability, including primitive methods, such as percussion and mobility testing by applying lateral forces with mirror handles, and more recent methods, such as measuring cutting torque resistance, insertion torque values, reverse torque tests, periotest, dental fine tester, and histomorphometric and histologic analysis of the bone-implant interface. All of these have some disadvantages, including questionable accuracy and reliability, lack of repeatability, and an invasive or destructive nature, so they are not practical in a clinical setting.38 The need for a user-friendly, noninvasive, reliable, and clinically applicable technique to measure implant stability led to the development of RFA by Meredith and coworkers in 1996.24 A commercially available electronic device, based on RFA, with the trade name Osstell, is widely used for experimental and clinical purposes. This device measures implant stability and quantifies it in ISQ values.25 

Radiographic evaluation of the peri-implant bone, in addition to assessment of several clinical parameters, has become one of prerequisite for estimating implant success.1,39 Grondahl and Lekholm40 showed a high predictive value of radiographs for the identification of implant stability using the Branemark system. Bone-level determination based on evaluation of radiographs lacked sufficient precision because of the methodologic difficulties in obtaining standardized and reproducible radiographs, excentric beam guiding, and inaccessibility of the labial and lingual or palatal aspects. These methodologic limitations may result in false diagnosis and measurement errors.41 The method of computer-assisted measurement of digitalized radiographs was associated with similar problems. The amount of distortion of the measuring scale could be determined taking into account the known length and diameter of the radio-opaque implant, thus serving as a measuring reference. Several options for optimizing the images in contrast and brightness made it easier to evaluate and measure the radiograph. Use of the Rinn device also helps standardize radiographs.

Endosseous implant placement using a bone condensing and expansion technique is not new, and several studies have shown excellent bone response and implant survival using osteotomes for placement of dental implants in the maxilla. The key to proper expansion is a slow, gradual technique with controlled force application that leads to gradual expansion and minimal site trauma.42 There are no reports available on heat generation during the preparation of the implant site by the osteotome technique.43 

Although alveolar ridge expansion can be achieved by the osteotome technique, this kind of preparation seemed to put pressure on the crestal cortical bone layer, causing a significant peri-implant marginal bone loss.44 The results of our investigation showed a significant mean crestal bone loss of 1.19 mm measured after 6 months of fixture placement using the osteotome technique. This decrease in marginal bone height of maxillary implants is comparable with results published by De Wijs and Cune in 1997 on implants inserted with the bone-splitting technique, which revealed a peri-implant ridge height reduction ranging from 0.8 to 1.3 mm.45 

In our study we found less RFMs for implants placed with osteotome technique than for implants placed using a conventional approach. This is in accordance with the removal torque values and histologic findings of Buchter et al46 in 2005, who demonstrated significantly impaired implant stability in terms of a reduced removal torque values when the osteotome technique was used. Buchter and colleagues also demonstrated that trabecular fractures accompany the osteotome technique. Trabecular fractures were observed on day 7 in all specimens of condensed bone, whereas conventionally inserted implants failed to damage bone trabeculae. At later stages of osseointegration (28 days) peri-implant histology resembled the histologic findings of control implants.46 This could explain why there was no significant difference between RFMs of both the groups after 6 months.

No controlled clinical longitudinal studies are available on the prognosis of the implants inserted using the osteotome technique. Although the power of the results of the present investigation is limited because of the short investigation period and the small sample size, our data suggest that the use of osteotome technique should be restricted to its indications. Further investigations including a large number of patients and considering long-term evaluation of peri-implant alveolar bone loss are necessary to enhance the power of the conclusions concerning use and predictability of osteotome technique.

The use of the osteotome technique for implant placement in normal ridge cases revealed an average crestal bone loss of 1.19 mm compared to 0.99 mm bone loss with conventional procedure. The osteotome technique also showed lower RFM than the conventional approach on the day of surgery. Within the limitations of this study we concluded that the indications for the use of osteotome technique should be limited to those for which it was introduced, that is, knife-edge ridges and for bone with less density. It should not be considered a substitute or replacement for the conventional procedure of implant placement. Local anatomy and density of the implant site should be considered in the indication for and planning of implant-bed preparation by osteotome technique.

ISQ

implant stability quotient

RFA

resonance frequency analysis

RFM

resonance frequency measurement