Noor F.doc J Bagh College Dentistry Vol. 27(3), September 2015 Assessment of dental Oral and Maxillofacial Surgery and Periodontics 109 Assessment of dental implant stability during healing period and determination of the factors that affect implant stability by means of resonance frequency analysis (Clinical study) Noor S. Ibraheem, B.D.S. (1) Sahar S. Al-Adili, B.D.S., M.Sc. (2) ABSTRACT Background: Implant stability is considered one of the most important factors affecting healing and successful osseointegration of dental implants. The aims of the study were to measure the implant stability quotient (ISQ) values during the healing period and to determine the factors that affect implant stability. Materials and methods: Thirty patients enrolled in the study (17 female, 13 male). They received 44 Implantium® Dental Implants located as the following: 22 implants in maxillary jaw, 22 implants in mandibular jaw from them 17 implants in anterior segment and 27 in posterior segment. The bone density determined using interactive CT scan and classified according to the Misch bone density classification (29 implants in (D3), 15 implants in (D4)). Resonance frequency analysis was used for direct measurement of implant stability on the day of implant placement and 8, 16 and 24 weeks after implant placement. Results: The lowest mean of average ISQ was at the 8th week (69.5) and then the mean increased to reach at the 24th week (76.8). Mandibular implants showed significantly higher ISQ values than maxillary implants. Implants placed in the posterior segment of the jaw had significantly higher ISQ values than implants in the anterior segment. A significant, positive linear correlation was observed between the implant diameter and the implant stability (r=0.343 p<0.001). Conclusion: Resonance frequency analysis was non-invasive diagnostic tool for detecting changes in implant stability during the healing period. The factors that affect implant stability were implant diameter and implant location (maxilla\ mandible, anterior\ posterior). Keywords: Dental implant, implant stability, implant stability quotient (ISQ), resonance frequency analysis. (J Bagh Coll Dentistry 2015; 27(3):109-115). INTRODUCTION Dental implants have recently become a reliable and predictable tool for oral rehabilitation. Even though the clinical outcome of an implant is influenced by many factors, including the implant body, skill of the surgeon, and the oral environment, the key factor for success is implant stability (1). Dental implant stability is a measure of the anchorage quality of an implant in the alveolar bone. Dental implant stability divided into primary stability at placement which is a mechanical phenomenon and secondary stability which is the increase in stability attributable to bone formation and remodeling at the implant- bone interface (2). Different diagnostic methods aimed to assess implant stability have been suggested: histology and histomorphometry, insertion torque, removal torque, push-through and pull-through, radiographic assessment, Periotest ultrasonic method, and resonance frequency analysis (RFA) (2). Among these test methods, RFA offers a clinical, noninvasive measure of stability and presumed osseointegration of implants (2-8). (1)Master student. Department of Oral and Maxillofacial Surgery, College of Dentistry, University of Baghdad. (2)Assistant Professor. Department of Oral and Maxillofacial Surgery, College of Dentistry, University of Baghdad. RFA technique is a bending test of the implant– bone complex where a transducer applies an extremely small bending force. The bending force applies a fixed lateral force to the implant and measures the displacement, thus mimicking the clinical loading (9). Osstell devices have been designed to measure implant stability using RFA since 1999 by the Integration Diagnostics Ltd. Company (Sävedalen, Sweden). Within the last decade, several generations of this device have been developed. The latest generation is the Osstell® ISQ. The RFA values are represented by a quantitative unit called the Implant Stability Quotient (ISQ) on a scale from 0 to 100 (100 being maximum implant stability) (10). Several studies demonstrated a good correlation between the obtained ISQ values and the degree of stiffness between the implant and the bone (2, 9-12). Achievement and maintenance of dental implant stability is the most important requirement for successful dental implant treatment (13). So it is important to determine the factors that influence implant stability. There are several factors affecting primary and secondary stability. Primary implant stability is affected by factors related to bone properties (i.e. bone density), implant design (i.e. diameter, length, shape and surface) and surgical technique. J Bagh College Dentistry Vol. 27(3), September 2015 Assessment of dental Oral and Maxillofacial Surgery and Periodontics 110 Secondary implant stability is affected by bone response to the surgery and implant material (14). From these factors bone density needs preoperative assessment as it considered a key factor to take into account when predicting implant stability (15). Several methods for bone density assessment have been reported: conventional radiography, drilling resistance, insertion torque force, digital image analysis, and computed tomography (CT) (16). Of these methods computed tomography (CT) provide more accurate determination of bone density before surgery (17). MATERIALS AND METHODS Thirty patients were drawn from patients attending the dental implant clinic in the Department of Oral and Maxillofacial Surgery/ College of Dentistry/ University of Baghdad participated in this clinical prospective study including 13 male and 17 female with age range (20-59) year’s old. The inclusion criteria were as follows: healthy patients with No signs and symptoms of any systemic diseases with age ranges from 20 to 60, non-smoker Patients, implant site does not need any bone augmentation or sinus lift and without any fenestrations or dehiscence and all the patients treated according to traditional protocol (delayed implant placement) six months or longer after tooth extraction. The patients received 44 dental implants (Implantium® (Dentium, seoul, korea)), 22 implants in the maxillary jaw and 22 implants in the mandibular jaw from them 17 implants in anterior segment and 27 in the posterior segment. According to interactive CT scan measurements, bone density at the implant sites ranged from 150 to 784 Hounsfield units. This means that the bone density of the implant sites of the sample is either D3 or D4 according to the Misch bone density classification (17). Preoperative standardized digital orthopantograph (OPG) and interactive CT scan were taken for each patient (OPG will give an overview of the anatomical structures of the jaw while the CT scan offers more specific data such as length, width and bone density in the proposed implant site). Prior to the surgical procedure, a case sheet was filled with all the required information about the patient and every patient signed an informed consent. Patient preparation Just right before the surgery, the patient rinsed his mouth with Chlorhexidine mouthwash for 1 minute to minimize the number of oral microorganisms. Then local anesthesia was given using infiltration technique for the maxillary and mandibular arches. Surgery After soft tissue incision, the flap was raised and the implant site was prepared by using high torque handpiece at low speed 800 rpm, with sharp drills and copious external irrigation to prevent excess thermal injury to the recipient bone. The implant osteotomy site was sequentially enlarged to the desired length and diameter. No countersink drills was used for all the patients. After reaching the desired length and diameter of the implant bony bed, the implant was placed with external irrigation to prevent heat generation due to friction of the implant and the bone. The cover screw was placed and then the wound edges were brought together and sutured. Verbal postoperative instructions were given to the patient. The patients provided with prescription of antibiotics and analgesics. Implant stability measurements Implant stability measurements were taken at surgery (primary stability) and at 8, 16, 24 weeks after surgery. The values were measured using Osstell® ISQ (Integration Diagnostics AB, Gothenburg, Sweden). Screw the SmartPeg® of Osstell® ISQ to the implant by using the SmartPeg Mount then hold the instrument probe close to the top of the SmartPeg® without touching it. An audible sound will be emitted when the instrument senses the SmartPeg® and an ISQ value is generated and shown on the display. The measurements were taken first from the mesio- distal direction (MD) (along the jaw line), then from the bucco-palatal direction (BP) (perpendicular to the jaw line). The measurements reflect the level of stability on the universal ISQ scale – from 1 to 100 (the higher the ISQ value, the more stable is the implant). Then unscrew the SmartPeg® using the SmartPeg Mount. All measurements were taken by another colleague. After the 24th week, the data were translated into a computerized database structure and statistical analyses were done using SPSS version 21 computer software (Statistical Package for Social Sciences) in association with Microsoft Excel 2010. J Bagh College Dentistry Vol. 27(3), September 2015 Assessment of dental Oral and Maxillofacial Surgery and Periodontics 111 RESULTS AND DISCUSSION The effect of healing time on Implant Stability Quotient (ISQ) By calculating the average ISQ of the two perpendicular measurements (Bucco-Palatal direction (BP) and Mesio-Distal direction (MD)) as shown in table (1), we found that the mean of average ISQ reduced by (3.7) units at the 8th week compared to the primary stability value. This mean reduction was statistically significant and rated as moderate effect. At the 16th week after surgery, the mean of average ISQ was increased by very small amount (0.3) compared to the primary stability value. This minor change was not significant statistically and rated as very week or almost no effect. At the 24th week (the end of the follow up period), the mean of average ISQ was increased by (3.6) units compared to the primary stability value. This increase was statistically significant and rated as moderate effect. Table 1: The changes in average ISQ of 2 perpendicular measurements (BP and MD) after 3 successive time intervals following surgery compared to primary stability achieved at surgery Time At surgery (primary stability) After 8 weeks Changes after 8 weeks compared to primary stability After 16 weeks Changes after 16 weeks compared to primary stability After 24 weeks Changes after 24 weeks compared to primary stability Range (56 to 85) (51 to 80) (-31 to 18) (62.5 to 82) (-14.5 to 20.5) (69.5 to 84) (-10 to 24) Mean 73.2 69.5 -3.7 73.5 0.3 76.8 3.6 SD 6.3 6.4 8.1 5 6.9 4.2 6.5 SE 0.96 0.96 1.22 0.75 1.04 0.63 0.97 N 44 44 44 44 44 44 44 Cohen's d (Effect size compared to primary stability) -0.46 0.04 0.55 Paired t-test 0.004 0.8[NS] <0.001 Rate of implants achieving high stability (ISQ≥70) at surgery and after 3 successive time intervals following surgery The threshold level in this study was set to 70 ISQ. At surgery, almost three quarters (72.7%) of the studied implants attained high mean ISQ (ISQ≥70). This rate decreased to (59.1%) after 8 weeks then increased to (72.7%) at the 16th week after surgery. At the end of the study period at the 24th week after surgery, almost all the studied implants attained high mean ISQ (97.7%) as shown in figure (1). Figure 1: Bar chart showing the rate of implants achieving high stability (ISQ≥70) at surgery and after 3 successive time intervals following surgery. J Bagh College Dentistry Vol. 27(3), September 2015 Assessment of dental Oral and Maxillofacial Surgery and Periodontics 112 The effect of each factor (gender, age, maxilla\mandible, anterior\posterior, bone density) on Implant Stability Quotient (ISQ) during the healing period The effect of the gender Implant Stability Quotient (ISQ) during the healing period As shown in table (2), we found that the mean of average of ISQ in male were higher than female with a difference in mean of (3.6) units at the time of surgery but this was not significant statistically and rated as moderate effect. At the 8th week after surgery, the difference in mean reduced to (1.9) units and male still higher than female but this was not significant statistically and rated as week effect. At the 16th week after surgery, the difference in mean reduced again to (1) unit and male still higher than female but this was not significant statistically and rated as weak effect. At the 24th week after surgery (the end of follow up period), the difference in mean were slightly raised by (1.3) units being higher in male than female but this was not significant statistically and rated as weak effect. Table 2: The mean of average ISQ of 2 perpendicular measurements (BP and MD) showing the female/ male difference in mean at surgery and after 3 successive time intervals following surgery Time Gender Range Mean SD SE N P Difference in mean Cohn’s d At surgery Female (56 - 82) 71.9 7 1.33 28 0.07[NS] 3.6 0.59 Male (66 - 85) 75.5 4.2 1.06 16 8th week Female (51 - 80) 68.8 6.7 1.26 28 0.34[NS] 1.9 0.3 Male (59 - 76) 70.7 5.8 1.45 16 16th week Female (65.5 - 82) 73.1 4.8 0.91 28 0.52[NS] 1 0.2 Male (62.5 - 79) 74.1 5.3 1.33 16 24th week Female (69.5 - 84) 76.4 4.3 0.81 28 0.31[NS] 1.3 0.31 Male (70.5 - 83.5) 77.7 3.9 0.97 16 The effect of the age Implant Stability Quotient (ISQ) during the healing period: As shown in table (3), there was no statistically significant difference between age groups during the healing period. Table 3: The mean of average ISQ of 2 perpendicular measurements (BP and MD) showing the age group difference in mean at surgery and after 3 successive time intervals following surgery Time Age group (years) Range Mean SD SE N P At surgery <= 29 (66 - 81) 74 4.7 1.22 15 0.51[NS] 30 - 39 (72 - 80) 76 2.9 1.29 5 40 - 49 (56 - 82) 71.1 9 2.73 11 50+ (65 - 85) 72.9 6.3 1.73 13 At 8th week <= 29 (59 - 80) 67.9 7.2 1.85 15 0.37[NS] 30 - 39 (66 - 76) 72.6 3.9 1.74 5 40 - 49 (63 - 80) 71.2 5.7 1.72 11 50+ (51 - 75) 68.5 6.6 1.82 13 At 16th week <= 29 (62.5 - 82) 72.2 6.1 1.57 15 0.56[NS] 30 - 39 (70.5 - 78) 75.5 2.9 1.31 5 40 - 49 (65.5 - 80) 74.3 5.5 1.65 11 50+ (67 - 79.5) 73.4 3.6 0.99 13 At 24th week <= 29 (70.5 - 83) 76 4.1 1.07 15 0.29[NS] 30 - 39 (76 - 83.5) 79.7 2.8 1.23 5 40 - 49 (69.5 - 84) 77.6 5.4 1.62 11 50+ (72 - 82) 76 3.1 0.87 13 The effect of the jaw on Implant Stability Quotient (ISQ) during the healing period As shown in table (4), mandibular jaw showed higher mean average ISQ compared to maxillary jaw, with a difference in mean of (3.2) units at the time of surgery but this was not significant statistically and rated as moderate effect. J Bagh College Dentistry Vol. 27(3), September 2015 Assessment of dental Oral and Maxillofacial Surgery and Periodontics 113 Mandibular jaw showed higher mean average ISQ compared to maxillary jaw, with a difference in mean of (2.5) units at the 8th week after surgery but this was not significant statistically and rated as moderate effect. Mandibular jaw compared to maxillary jaw showed statistically significant difference (p 0.012) being higher in mandibular jaw than in maxillary jaw, with a difference in mean of (3.7) at the 16th week after surgery and rated as strong effect. Mandibular jaw compared to maxillary jaw showed statistically significant difference (p 0.012) being higher in mandibular jaw than in maxillary jaw with a difference in mean of (3.1) at the 24th week after surgery and rated as strong effect. Table 4: The mean of average ISQ of 2 perpendicular measurements (BP and MD) showing the maxilla/mandible difference in mean at surgery and after 3 successive time intervals following surgery Time Jaw Range Mean SD SE N P Difference in mean Cohn’s d At surgery Maxilla (56 - 80) 71.6 6.4 1.36 22 0.09[NS] 3.2 0.52 Mandible (65 - 85) 74.8 6 1.29 22 8th week Maxilla (59 - 75) 68.2 5.6 1.2 22 0.2[NS] 2.5 0.39 Mandible (51 - 80) 70.7 7 1.48 22 16th week Maxilla (62.5 - 78) 71.6 4.8 1.02 22 0.012 3.7 0.8 Mandible (66.5 - 82) 75.3 4.5 0.97 22 24th week Maxilla (69.5 - 80.5) 75.3 3.7 0.78 22 0.012 3.1 0.79 Mandible (72 - 84) 78.4 4.1 0.87 22 The effect of the arch location on Implant Stability Quotient (ISQ) during the healing period As shown in table (5), implant arch location significantly affected implant stability (p<0.001), being lower in the anterior segment than the posterior segment, with a difference with a difference in mean of (-6.5) at the time of surgery and rated as strong effect. At the 8th week after surgery, we found that the mean of average of ISQ was lower in the anterior segment than the posterior, with a difference with a difference in mean of (-3.8) but this was not significant statistically and rated as moderate effect. At the 16th week after surgery, we found that the mean of average of ISQ was lower in the anterior segment than the posterior, with a difference in mean of (- 4.5) and this was significant statistically (p 0.003) and rated as strong effect. At the 24th week after surgery, we found that the mean of average of ISQ was lower in the anterior segment than the posterior, with a difference in mean of (-4.1) and this was significant statistically (p<0.001) and rated as strong effect. Table 5: The mean of average ISQ of 2 perpendicular measurements (BP and MD) showing the anterior/posterior difference in mean at surgery and after 3 successive time intervals following surgery Time Arch location Range Mean SD SE N P Difference in mean Cohn’s d At surgery Anterior (59 - 76.5) 69.2 5 1.2 17 <0.001 -6.5 -1.17 Posterior (56 - 85) 75.7 5.9 1.13 27 8th week Anterior (59 - 75) 67.1 5 1.22 17 0.05[NS] -3.8 -0.61 Posterior (51 - 80) 70.9 6.8 1.31 27 16th week Anterior (62.5 - 78) 70.7 4.5 1.09 17 0.003 -4.5 -1 Posterior (66.5 - 82) 75.2 4.5 0.87 27 24th week Anterior (69.5 - 80.5) 74.3 3.4 0.82 17 <0.001 -4.1 -1.12 Posterior (71.5 - 84) 78.4 3.8 0.74 27 The effect of the bone density on Implant Stability Quotient (ISQ) during the healing period As shown in table (6), we found that the mean of average of ISQ was slightly higher in very low bone density (D4) than low bone density (D3) at surgery, with a difference with a difference in mean of (0.6) but this was not significant statistically and rated as very week effect. At the 8th week, we found that the mean of average of ISQ was lower in very low bone density (D4) than low bone density (D3), with a difference with a J Bagh College Dentistry Vol. 27(3), September 2015 Assessment of dental Oral and Maxillofacial Surgery and Periodontics 114 difference in mean of (-5.2) this was significant statistically (p 0.008) and rated as strong effect. At the 16th week, we found that the mean of average of ISQ was lower in very low bone density (D4) than low bone density (D3), with a difference with a difference in mean of (-2.4) but this was not significant statistically and rated as moderate effect. At the 24th week, we found that the mean of average of ISQ was lower in very low bone density (D4) than low bone density (D3), with a difference with a difference in mean of (- 2.3) but this was not significant statistically and rated as moderate effect. Table 6: The mean of average ISQ of 2 perpendicular measurements (BP and MD) showing the low (D3)/very low (D4) bone density difference in mean at surgery and after 3 successive time intervals following surgery Time Bone density Range Mean SD SE N P Difference in mean Cohn’s d At surgery (D3) (59 - 85) 73 6.2 1.16 29 0.74[NS] 0.6 0.09 (D4) (56 - 82) 73.6 6.7 1.74 15 At 8th week (D3) (59 - 80) 71.2 5.3 0.98 29 0.008 -5.2 -0.88 (D4) (51 - 80) 66 7 1.82 15 At 16th week (D3) (62.5 - 80) 74.3 4.9 0.9 29 0.13[NS] -2.4 -0.49 (D4) (66.5 - 82) 71.9 4.9 1.27 15 At 24th week (D3) (70.5 - 84) 77.6 3.9 0.73 29 0.08[NS] -2.3 -0.57 (D4) (69.5 - 83) 75.3 4.3 1.1 15 The effect of implant dimensions (diameter and length) on Implant Stability Quotient (ISQ) during the healing period As shown in table (7), there was weak positive correlation but statistically significant between implant diameter and mean ISQ during the healing period. There was very weak negative correlation and not significant statistically between implant length and mean ISQ during the healing period. Table 7: Linear correlation coefficient Implant dimensions Mean ISQ Implant diameter (mm) r=0.343 P<0.001 Implant length (mm) r=-0.117 P=0.12[NS] The net effect of time on Implant Stability Quotient (ISQ) after adjusting the effect of (gender, age, maxilla\mandible, anterior\posterior, bone density, implant diameter and length) As shown in table (8), a multiple linear regression model was used to show the net and independent effect of healing time after surgery after adjusting for a set of explanatory variables on the average ISQ measured. The follow up period (weeks after surgery) was the strongest predictor for the magnitude of implant stability assessed by average ISQ, followed by Implant diameter (mm) and bone and implant arch location (Anterior compared to posterior). Implant length, age and jaw location ranked 5th 6th and 7th in order of importance as predictors of implant stability. Only gender had no important effect on magnitude of implant stability. REFERENCES 1. Fuh LJ, Huang HL, Chen CS, Fu KL, Shen YW, Tu MG, Shen WC, Hsu JT. Variations in bone density at dental implant sites in different regions of the jawbone. J Oral Rehabilit 2010; 37(5): 346-51. 2. Meredith N. Assessment of implant stability as a prognostic determinant. Int J Prosthodont 1998; 11: 491-01. 3. Balleri P, Cozzolino A, Ghelli L, Momicchioli G, Varriale A. Stability measurements of osseointegrated implants using Osstell in partially edentulous jaws after 1 year of loading: a pilot study. Clin Implant Dent Relat Res 2002; 4(3): 128-32. 4. Barewal RM, Oates TW, Meredith N, Cochran DL. Resonance frequency measurement of implant stability in vivo on implants with a sandblasted and acid-etched surface. Int J Oral Maxillofac Implants 2003; 18(5): 641-51. 5. 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Table 8: Multiple linear regression with average ISQ (of the two perpendicular measurements, namely BP and MD) as the dependent (response) variable and duration of follow up (after 8 weeks of surgery) in addition to age, gender, bone density, implant dimensions and location as explanatory (independent) variables Explanatory (independent) variables Partial regression coefficient P Standardized coefficient (Constant) 41.5 <0.001 Follow up period (weeks after surgery) 0.5 <0.001 0.502 Implant diameter (mm) 5.0 <0.001 0.349 Bone density (D4 compared to D3) -3.7 <0.001 0.295 Implant arch location (Anterior compared to posterior) -3.2 0.003 0.258 Implant length (mm) 0.9 0.002 0.237 Age (years) -0.1 0.032 0.142 Mandibular jaw compared to maxillary jaw 1.6 0.06[NS] 0.137 الخالصة كان الھدف من ھذه الدراسة ھو قیاس . یعتبر ثبات الزرعة واحد من أھم العوامل المؤثرة على الشفاء ونجاح عملیة االندماج العظمي للزرعات السنیة: الخلفیة .لتي تؤثر على ثبات الزرعةعلى فترات خالل فترة الشفاء بوصفھ عامال تنبؤیا لالندماج العظمي، وتحدید العوامل ا ISQقیم حاصل ثبات الزرعة وتقع على النحو Implantium زرعة سنیة من نوع 44تلقى المرضى .)ذكر 13انثى، 17(ثالثون مریضا تم ادخالھم في الدراسة : المواد وطرق العمل تم تحدید كثافة العظم باستخدام . لجزء الخلفيزرعة في ا 27زرعة في الجزء االمامي و 17زرعة في الفك السفلي منھا 22زرعة في الفك العلوي، 22: التالي تم استخدام تحلیل ). D4زرعة وضعت في 15، و D3 زرعة وضعت في 29(لكثافة العظم Mishاالشعة المقطعیة التفاعلیة وتم تصنفیفھا وفقا لتصنیف .بعد عملیة وضع الزرعة السنیة اسبوع 24و 16، 8الترددات الرنینیة للقیاس المباشر لثبات الزرعة في یوم الزراعة وفي ، ثم زاد المتوسط لیصل في االسبوع الرابع )69.5(عند االسبوع الثامن ISQكان أدنى متوسط لمعدل ). 73.2(عند الجراحة ISQكان متوسط معدل : النتائج بالنسبة للزرعات . الزرعات الموضوعة في الفك العلوي أعلى معنویا بالمقارنة مع ISQالزرعات الموضوعة في الفك السفلي أظھرت قیم ).76.8(والعشرون وقد لوحظت عالقة خطیة ایجابیة . أعلى معنویا بالمقارنة مع الزرعات الموضوعة في الجز االمامي ISQالموضوعة في الجزء الخلفي من الفك كانت قیم ).r=0.343 p<0.001(ومعنویة بین قطر الزرعة وثبات الزرعة وكانت . تحلیل الترددات الرنینیة أداة تشخیصیة بدون ادخال ادوات الى انسجة الجسم للكشف عن التغیرات في ثبات الزرعة خالل فترة الشفاءكان : االستنتاجات ).الخلفي \الفك السفلي، األمامي \الفك العلوي (العوامل التي أثرت على ثبات الزرعة ھي قطر الزرعة وموضع الزرعة