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Evaluation of the effect of pulsed electromagnetic fields on osseointegration of immediate dental implants: a clinical study

EI Fadly, Mahmoud A.; Selim, Heba A.; Katamish, Mohamed A.; Metwally, Salah A.

Egyptian Journal of Oral & Maxillofacial Surgery: October 2014 - Volume 5 - Issue 3 - p 84–91
doi: 10.1097/01.OMX.0000451843.25418.e1
CLINICAL STUDY
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Purpose The aim of the study was to clinically and radiographically evaluate the effect of pulsed electromagnetic fields (PEMFs) on enhancement of dental implant osseointegration in fresh extraction sockets.

Patients and methods A total of 12 immediate implant sites were included in the study. The implant sites were divided into two equal groups: group A and group B. In group A (the study group) immediate implant placement was carried out after tooth extraction, and PEMF were applied immediately postoperatively 2 h daily for 12 days; in group B (the control group) no further intervention was carried out after implant placement. Each group was evaluated clinically using the Osstell implant stability quotient to measure implant stability at 0, 3, and 6 months postoperatively and radiographically using radiovisiography to measure bone radiodensity and the amount of vertical bone loss at 0, 1, 3, 6, and 12 months postoperatively. The data collected were statistically analyzed using the paired-sample T-test, the independent-sample T-test, and the χ2-test.

Results There was a statistically significant decrease in the amount of vertical bone loss in the study group at 1, 3, and 6 months postoperatively when compared with the control group. Also there was a statistically significant increase in the radiodensity of bone around implants in the study group at all the study intervals. In contrast, there were no statistically significant differences between the control and study cases regarding changes in Osstell (implant stability quotient).

Conclusion From the present limited series of patients, we can conclude that PEMFs stimulation might have a beneficial effect on osseointegration of immediate dental implants. However, more research using a larger sample size with longer follow-up periods is recommended.

Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Ain Shams University, Cairo, Egypt

Correspondence to Heba A. Selim, BDS, MSc, PhD, Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Ain Shams University, 1156 Cairo, Egypt Tel: +01001942251; e-mail: tarek_elzayat1959@yahoo.com

Received June 9, 2014

Accepted July 16, 2014

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Introduction

Osseointegration refers to a direct bone to metal interface without interposition of nonbone tissue. This concept has been described by Branemark 1,2 as consisting of a highly differentiated tissue making ‘a direct structural and functional connection between ordered, living bone and the surface of a load-carrying implant’.

Successful osseointegration is a prerequisite for functional dental implants.

Immediate implantation after tooth extraction is a predictable treatment modality, with survival rate comparable to that of implants placed in healed ridges 3. However, the time needed to achieve successful osseointegration is longer than that required in the delayed implant placement protocol 4.

Many factors have been studied to enhance osseointegration, with an aim to reduce treatment time and achieve relevant patient satisfaction. These factors include implant-related factors, the status of host bone bed and its intrinsic healing potential, the mechanical stability and loading conditions applied on the implant, and the use of adjuvant therapies 5.

Adjuvant therapies are used to optimize implant osseointegration. They include bone grafting, the use of osteogenic coatings, and biophysical stimulation to enhance the amount of bone ingrowth 5.

The biophysical stimulation of bone union includes noninvasive and safe methods such as low-intensity pulsed ultrasound, low-level laser therapy, and pulsed electromagnetic fields (PEMFs) 6.

PEMFs were first demonstrated in 1976 as a noninvasive method to stimulate fracture healing 7. Since then, numerous animal and human studies have shown the effect of PEMFs in different clinical situations to enhance bone regeneration 8–21.

In an in-vivo study, PEMF stimulation on the osteoprogenitor cell and osteoblast resulted in the increased division and multiplication of growth factors or division factors, including extracellular trait, TGF-β1, and bone morphogenetic proteins BMP-2 and BMP-4 22.

Regarding osseointegration, several animal and human studies have been published, discussing the effect of the clinical use of PEMFs on orthopedic implants to stimulate osseointegration, with most of them proving its beneficial effect 5,23–27.

To our knowledge, the use of PEMFs to stimulate dental implant osseointegration clinically has not yet been reported. Therefore, the aim of the study was to evaluate the effectiveness of PEMFs in enhancing dental implant osseointegration, thus shortening treatment time.

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Patients and methods

Study design

The present study was a prospective randomized clinical trial of 12 implant sites selected from patients attending the Outpatient Clinic of the Oral and Maxillofacial Surgery Department (Ain Shams University Faculty of Dentistry). Patients fulfilling the following inclusion criteria were selected:

  • Male and female patients at least 18 years old.
  • Medically free from systemic diseases.
  • Patients with rational indication for tooth extraction.
  • Presence of adequate and healthy soft-tissue drape.
  • Absence of systemic or local conditions affecting bone-implant osseointegration.
  • Presence of sufficient available bone that does not require bone grafting or any other ridge augmentation procedure.
  • Presence of sufficient interarch space.
  • Absence of acute or chronic periapical infection at the implant site.
  • Absence of acute or chronic periodontal infection at the implant site.

On initial presentation at the department, the patients were clinically and radiographically evaluated. The demographic data of patients included in the study and details of implant sites and implant parameters are listed in Table 1.

Table 1

Table 1

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Treatment phase

Each patient received a capsule of amoxicillin 875 mg/clavulanic acid 125 mg (Augmentin 1 g; Glaxosmithkline, England) 1 h preoperatively. Atraumatic extraction of the offending tooth was performed under local anesthesia with preservation of surrounding soft-tissue envelope as much as possible, drilling with copious irrigation. Then, previously selected implants according to preoperative radiographs were inserted, surpassing the apex of the socket to achieve initial stability and gain adequate bone support. Finally, healing abutments were connected for all implants (Figs 1–4).

Fig. 1

Fig. 1

Fig. 2

Fig. 2

Fig. 3

Fig. 3

Fig. 4

Fig. 4

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Patients grouping

Patients were randomly allocated into two groups: group A (the study group) and group B (the control group). Group A included six extraction sockets (cases A1–A6), in which immediate implant placement was done after tooth extraction, and the implants were exposed to PEMFs; group B (the control group) included six extraction sockets (cases B1–B6), in which immediate implant placement was done after tooth extraction and allowed to heal without any bone enhancement.

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Bone enhancement procedure

Patients in group A (the study group) were exposed to PEMFs immediately postoperatively for 2 h daily for 12 days using the Biomedici device (South Lake, Tahoe, California, USA), which was purchased from Magnetic Therapy Devices Company (South Lake, Tahoe, California, USA) (Figs 5 and 6).

Fig. 5

Fig. 5

Fig. 6

Fig. 6

The device contains eight switches; switch number 8 is used to turn on the device and switches 1–7 are used to select the desired frequencies. According to the manufacturer’s instructions, switch number 2 was selected for the first hour of device usage, which makes the device emit PEMFs with a frequency of 2 Hz. Then in the second hour we turned off switch number 2 and selected switch number 4, which makes the device emit PEMFs with a frequency of 4 Hz.

All patients received capsules of amoxicillin 875 mg/clavulanic acid 125 mg (Augmentin 1 g) twice daily for 5 days as well as pain medications and antiedematous drugs. Routine postoperative instructions were given to the patients in a written form and sutures if present were removed after 7 days.

All implants were loaded 6 months after implant placement. Healing abutments were removed and the final abutments were connected. Verification of osseointegration was done using the Osstell device to measure the implant stability quotient (ISQ). Impressions were made, and bite registration and shade selection were carried out.

Finally, ceramometallic restorations were fabricated and cemented in the patients’ mouth as single tooth replacement (Fig. 7).

Fig. 7

Fig. 7

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Postoperative follow-up

All patients were given follow-up appointments for postoperative months 1, 3, 6, and 12. At each appointment, patients were evaluated and data were collected.

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Clinical evaluation

Clinical evaluation was divided into measuring the ISQ and recording the probing depth. The Osstell ISQ, which is a resonance frequency analysis (RFA) device, was used to measure the ISQ. Two measurements were taken each time for each implant (one from the buccal side and the other from the palatal side). Then the mean value was calculated and recorded.

Readings were obtained at 0, 3, and 6 months postoperatively (Fig. 8).

Fig. 8

Fig. 8

Probing depth was measured and recorded at six points for each implant (mesiobuccal, distobuccal, midbuccal, mesiopalatal, distopalatal, and midpalatal).

Standardization was achieved by making an index from a heavy body rubber base that ensured returning the periodontal probe to the same position at each reading. Readings were obtained at 6 and 12 months postoperatively (Fig. 9).

Fig. 9

Fig. 9

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Radiographic evaluation

Radiographic evaluation was performed using standardized periapical digital radiographs at 0, 1, 3, 6, and 12 months postoperatively. The utilized radiographic machine was Xgenus DC X-ray machine (De Götzen S.r.l., Italy), whereas the radiovisiography (RVG) system (Krystal-X Easy, France) was Owandy digital RVG system. Standardization of the technique was achieved by utilization of an RVG Rinn (XCP) extension cone paralleling technique. To allow for exact repositioning of the RVG sensor, a heavy body rubber base occlusal registration was obtained for each patient (Fig. 10).

Fig. 10

Fig. 10

Manipulation of the obtained digital radiographs was performed using Digora software (Soredex, Finland), which can be used to measure the area mean and pixel value density and measure the amount of vertical bone loss. On each image, an analysis of the changes in the mean gray value was performed using the line measurement facility of the software used. The unit of measurement for bone density is pixels (mean gray value). A line was drawn on both the mesial and distal sides of the implant, extending from the crest module of the implant up to its apex. The densitometry values were obtained for each line expressed in gray levels from 0 to 255. Each of these values corresponded to the average density of the area. The amount of vertical bone loss on mesial and distal aspects of each implant was measured from the top of the implant to the highest point of the alveolar crest (Figs 11 and 12).

Fig. 11

Fig. 11

Fig. 12

Fig. 12

An analysis was performed by the same radiologist twice at two different sessions with a 1-week interval in between in an attempt to eliminate intraobserver error. The data of the two trials were pooled, and the mean was included in additional statistical analysis.

The collected data were revised, coded, tabulated, and introduced into a PC using statistical package for the social sciences (SPSS 15.0, 2001; SPSS Inc., Chicago, Illinois, USA) for windows. Data were presented and suitable analysis was carried out according to the type of data obtained for each parameter. The data are presented as mean±SD. A paired-sample T-test was used to assess the statistical significance of the difference between two means of one quantitative variable measured twice for the same study group.

The independent-sample T-test was used to assess the statistical significance of the difference between two study group means. The χ2-test was used to examine the relationship between two qualitative variables.

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Results

The study included eight patients (one was male and seven were female) seeking immediate implant placement in the maxillary anterior or premolar region. The age range of the patients included in the study was 25–45 years with a mean age of 37.75 years. The total number of implants was 12, six in each group.

The distribution of implants on the patients studied was as follows: four patients received one implant and four patients received two implants. The mean length of the utilized implants in the control group was 13 mm and the mean diameter was 3.8 mm. The mean length of the utilized implants in the study group was 12.3 mm and the mean diameter was 3.7 mm.

Successful implantation was achieved in all cases except for case number 6 in the control group (B6) whose ISQ value at 6 months postoperatively was 25 from the buccal aspect and 19 from the palatal aspect with a mean of 22. Thus, loading was not done for this implant and it missed the immediate postloading and 6-month postloading readings.

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Clinical findings

There were no statistically significant differences between control and study cases regarding changes in Osstell (ISQ) readings either for the immediate postoperative period until 3 months or until 6 months postoperatively during follow-up (Table 2).

Table 2

Table 2

There were no statistically significant differences between controls and patients regarding changes in probing depth from the immediate postloading period until 6 months postloading during the follow-up period (Table 3).

Table 3

Table 3

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Radiographic findings

The means changes in radiodensity readings immediately postoperatively until 1, 3, 6, and 12 months were higher in the study group than in the control group and those changes were statistically significant (Table 4).

Table 4

Table 4

The mean changes in vertical bone loss readings immediately postoperatively until 1, 3, 6, and 12 months postoperatively were lower in the study group than in the control group. Those changes were statistically significant at 1 month postoperatively and highly significant at 3, 6, and 12 months postoperatively (Table 5).

Table 5

Table 5

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Discussion

Dental implants have become a predictable treatment modality for prosthetic restoration in fully or partially edentulous patients. Immediate implant placement offers many advantages including reduction in treatment time, preservation of alveolar bone, maintenance of ideal soft-tissue contours, and better implant placement 28.

However, the time needed before implant loading is longer than that required in the delayed implant placement protocol 4.

In the present study bone enhancement using PEMFs was used to fasten bone healing and osseointegration in an attempt to shorten the healing time in immediate implantation. This could also shorten the overall treatment time of the implantation procedure.

The use of PEMFs was found to decrease the amount of vertical bone loss statistically significantly in the study group when compared with the control group before implant loading.

Increased radiodensity around orthopedic implants enhanced by PEMFs has been reported in previous studies 24–26. In the current study there was a statistically significant increase in radiodensity around enhanced bone in the study group.

However, all the previous studies included unloaded implants unlike the current research in which radiodensity was measured around dental implants before and after loading.

The assessment of dental implant osseointegration presents a problem because of the few credible methods.

The gold standard method used to evaluate the degree of osseointegration was microscopic or histologic analysis. However, because of the invasiveness of this method and related ethical issues, various other methods or analyses have been proposed, such as radiographs, cutting torque resistance, reverse torque, modal analysis, and recently RFA 29.

Osseointegration of immediate dental implants was investigated in this study using the RFA, which is an indirect indication of osseointegration that has been achieved at two levels: primary stability (mechanical fixation) and secondary stability (biological fixation) 30,31.

The Osstell device translates the RFA value into ISQ index. Classically, the ISQ value was found to vary between 40 and 80, where higher ISQ values correspond to higher implant stability 29.

The results regarding the ISQ values showed that in both the study and the control group the ISQ values increased at 3 and 6 months postoperatively, and this increase at 3 months postoperatively was higher in the study group than in the control group but this difference was not statistically significant. This could be explained by the small sample size.

The change in ISQ values of the study group from 3 months postoperatively until 6 months postoperatively was lower than that of the control group. Although statistically insignificant, which may be due to the small sample size, early loading of the implants at 3 months postoperatively can be recommended when using PEMFs, thus shortening the treatment time with relevant patient satisfaction.

It has been found that implant loading requires ISQ reading of 65 or more, whereas an ISQ lower than 50 may indicate potential failure 29. In the present study, case number 6 in the control group (B6) had a mean ISQ value of 22 at 6 months postoperatively. However, its bone density reading was not abnormally reduced.

The above-mentioned case could explain the present study finding that, although a statistically significant increase in bone density between two groups has been found, there was no statistically significant difference between the two groups in terms of Osstell readings. The relation between bone density and Osstell readings has been investigated with respect to primary implant stability, wherein higher bone density was associated with better primary stability, which is consistent with logical thinking in which primary stability is mechanical in origin 32.

However, there has been no previous research correlating bone density with secondary implant stability, which is biological in origin.

From the present limited series of patients, it can be concluded that PEMFs have an enhancing effect on bone healing around immediate dental implants. This enhancement tool might be an effective method in enhancement of osseointegration as Osstell readings at 3 months postoperatively are comparable to the value needed for implant loading and to 6-month readings.

This beneficial effect can be used in turn to shorten treatment time in immediate dental implant protocol or in cases when osseointegration is questionable.

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Acknowledgements

Conflicts of interest

There are no conflicts of interest.

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