IMPLANT DENTISTRY / VOLUME 24, NUMBER 3 2015
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Implant Stability Measurements in the Long-Term Follow-up of Dentis Implants: A Retrospective Study With Periotest Mi-Ae Jeong, RDH, PhD,* Mi-Kyung Jung, DDS, MSD,†Su-Gwan Kim, DDS, PhD,‥ and Ji-Su Oh, DDS, PhD§
he primary stability of an implant is determined by osseointegration.1,2 During the process of osseointegration, bones in the vicinity of implants become hard, and an interlock is formed between bones and implants that prevents the development of micromovement.3 Stability of an implant is deďŹ ned as a condition with no clinical movement, and it is affected by several factors, including the condition of adjacent bones, techniques used, and implant design. Destruction and resorption of bones adjacent to implants can be clinically diagnosed, and the depth and width can be assessed quantitatively using radiographs. By measuring stability, the level of destruction and resorption can be assessed.4 Such stability may appear different depending on the bone quality. According to Lekholm and Zarb,5 bone quality can be classiďŹ ed into 4 types, depending on the status of cortical and cancellous bone. Type I is a compact bone with
T
*Associate Professor, Department of Dental Hygiene, Kangwon National University, Samcheok, South Korea. †Graduate Student, Department of Oral and Maxillofacial Surgery, School of Dentistry, Chosun University, Gwangju, South Korea. ‥Professor and Chairman, Department of Oral and Maxillofacial Surgery, School of Dentistry, Chosun University, Gwangju, South Korea. §Associate Professor, Department of Oral and Maxillofacial Surgery, School of Dentistry, Chosun University, Gwangju, South Korea.
Reprint requests and correspondence to: Su-Gwan Kim, DDS, PhD, Department of Oral and Maxillofacial Surgery, School of Dentistry, Chosun University, 375, SeoSukDong, DongGu, Gwangju 501-759, South Korea, Phone: 82-62-220-3815, Fax: 82-62-228-7316, E-mail: sgckim@chosun.ac.kr ISSN 1056-6163/15/02403-263 Implant Dentistry Volume 24 Number 3 Copyright Š 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/ID.0000000000000239
Purpose: The purpose of this study was to evaluate retrospectively the stability of Dentis implant with the Periotest. Methods: In total, 36 patients and 88 implants were investigated. Periotest was used to measure implant stability, and a periapical view was taken immediately after surgery and again immediately after, 3 months after, 6 months and 5 years after prosthesis placement. Bone loss on the periapical view, bone quality according to tactile sensation, and area of implant installation were assessed. Results: The mean Periotest value (PTV) immediately after surgery was −1.02, and the mean bone
loss rate (bone loss/ďŹ xture length 3 100) at 6 months after prosthesis placement was 8.42%. PTV was higher with more bone loss (types III, IV vs types I, II bone). The lowest mean PTV was in the lower molar area (−1.48), followed by the lower anterior (−1.41), upper molar (0.11), and upper anterior area (5). One implant failed and survival rates were 98.9%. Conclusion: Implant stability was lower in cases with more bone loss and poor bone quality and in the maxilla versus the mandible. (Implant Dent 2015;24:263–266) Key Words: implant, PTV, stability, survival rate
high overall density; type 2 is a highdensity cancellous bone surrounded by thick cortical bone; type III is a highdensity cancellous bone surrounded by thin cortical bone; and type IV is a lowdensity cancellous bone surrounded by thin cortical bone. Several tools are available to measure the stability of implants. One is the percussion test, in which the upper plateau of the implant is tapped, for example, with a dental mirror, and stability can be estimated from the sounds generated. However, the quantity and quality of the information gained are limited. During placement, a method to measure torque can also be used; however, this is also not very accurate and may affect the implant. Noninvasive methods to measure stability without
injuring the implant include the Periotest and resonance frequency analysis; through numerical values, they can show relatively objective stability values.3 The Periotest used in this study measures the stiffness between the bone and implants, which is scored based on the level of the deection and deceleration of the implant. The range is −8 to 50 Periotest value (PTV), and Olive and Aparicio et al considered cases higher than 10 PTV to be failures.6,7 The purpose of this study was to measure the stability of Dentis implants (Dentis Co., Ltd., Daegu, Korea) placed in the Department of Oral and Maxillofacial Surgery, Chosun University over several years to examine factors that affect stability and to determine the implant survival rate.
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Location of Implants
1 21 14 52
Table 2. Distribution According to Diameters and Lengths of Implants Length/ Diameter (mm)
Ă˜3.7
Ă˜4.3
5 17 9 0 31
8 14 15 1 38
Ă˜4.8 Sum 5 6 8 0 19
18 37 32 1 88
Table 3. The Mean PTVs Over Time After Implant Placement Periods After Implant Placement
PTV −1.02 −1.83 −1.96 −2.03 −0.74
Immediately after surgery Immediately after prosthesis 3 mo after prosthesis 6 mo after prosthesis 5 y after prosthesis
ET AL
METHODS
AND
The subjects were 36 patients with 88 implants who visited the Department of Oral and Maxillofacial Surgery, Chosun University Hospital between January 2007 and June 2008 and who received a Dentis implant. The group consisted of 14 male and 22 female patients; their mean age was 50.7 years. Of the 88 implants placed, 22 implants were placed in the maxilla and 66 in the mandible. Regarding ďŹ xture diameter, 31 implants were Ă˜3.7, 38 were Ă˜4.3, and 19 were Ă˜4.8 (Tables 1 and 2). On December 2012, 19 of initial 36 patients and 35 of 88 initial implants were checked up for 5-year follow-up after prosthesis treatment. PTVs were obtained 3 times each on the buccal and lingual sides of implants using the Periotest (Siemens AG, Bensheim, Germany), and the average value was used for further analyses. Values were obtained immediately after surgery and again immediately after, 3 months after, 6 months and 5 years after prosthesis placement. Using periapical radiographs, the resorption rate of bone adjacent to implants was assessed immediately after surgery and again immediately after, 3 months after, 6 months and 5 years after prosthesis placement. Bone quality was assessed by the surgeons’ tactile examination during drilling; bone
Number of Implants
Anterior maxilla Posterior maxilla Anterior mandible Posterior mandible
JEONG
MATERIALS
Table 1. Distribution According to Locations of Implant Placement
8 10 12 14 Sum
RETROSPECTIVE STUDY WITH PERIOTEST
Table 4. PTVs According to Bone Quality Periods After Implant Placement
Type I
Type II
Type III
Type IV
Immediately after surgery Immediately after prosthesis 3 mo after prosthesis 6 mo after prosthesis
−3.52 −4.43 −4.52 −4.59
−2.03 −2.54 −2.66 −2.8
−1.88 −2.42 −2.49 −2.64
2.34 1.78 1.69 1.55
Type I: mainly very thick cortical bone, Type II: dense cortical and cancellous bone, Type III: thinner cortical bone and less dense cancellous bone, Type IV: very thin cortical bone and sparse cancellous bone.
Table 5. PTVs by Implant Placement Location Periods After Implant Placement Immediately after surgery Immediately after prosthesis 3 mo after prosthesis 6 mo after prosthesis 5 y after prosthesis
Anterior Maxilla
Posterior Maxilla
Anterior Mandible
Posterior Mandible
5 5
0 −1.57
−0.44 −1.14
−1.68 −2.25
3 3 d
−1.68 −1.72 0.2
−1.25 −1.32 −5.9
−2.31 −2.41 −0.24
quality was classiďŹ ed as type I, II, III, or IV, following Lekholm and Zarb.5
RESULTS Periotest Values
The average PTVs after implant placement were as follows: immediately after surgery, −1.02; immediately after prosthesis placement, −1.83; 3 months after prosthesis placement, −1.96; 6 months after prosthesis placement, −2.03; and 5 years after prosthesis placement, −0.74. Thus, PTV decreased slightly over time until 6 months after prosthesis placement, but according to result of 5-year follow-up PTV was increased (Table 3). PTV According to Bone Quality
Immediately after surgery, the PTV of type I bone was −3.52, that of type II was −2.03, of type III was −1.88, and of type IV was 2.34. At other time points, type I showed the lowest PTV and type IV the highest PTV, although little difference was seen between types II and III (Table 4). PTV and Location of Placement
Immediately after surgery, the PTV of the anterior maxilla was 5, that of the posterior maxilla was 0, of the anterior mandible was −0.44, and of the posterior mandible was −1.68. Thus, PTV was highest in the anterior maxilla and lowest in posterior mandible (Table 5). According to 5-year follow-up data, PTV decreased slightly over time until Table 6. Marginal Bone Loss Rate According to PTVs PTVs −6 −5 −4 −3 −2 −1 0 1 2 3 4 5
Bone Loss Rate (%) 0 1 2 6 8 10 13 14 14 17 26 28
Bone loss rate: bone resorption volume/length of implant ďŹ xture 3 100.
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IMPLANT DENTISTRY / VOLUME 24, NUMBER 3 2015 6 months after prosthesis placement but at 5-year follow-up PTV was increased at every site of implant placement (Table 5). Resorption Rate of Adjacent Bone According to PTV
The rate of resorption of adjacent bone was calculated as (bone resorption volume/length of implant fixture) 3 100. At PTVs of −6, −5, −4, −3, −2, and −1, the resorption rates were 0%, 1%, 2%, 6%, 8%, and 10%, respectively, and at a PTV 0, the rate was 13%. The resorption rates at PTVs of 1, 2, 3, 4, and 5 were 14%, 14%, 17%, 26%, and 28%, respectively. Thus, higher PTV levels were associated with higher rates of resorption of adjacent bone (Table 6). Implant Survival Rate
One implant was removed 6 months after placement because of severe mobility and the resorption of adjacent bone. Thus, one of 88 implants failed for a survival rate of 98.9%. At 5-year follow-up, no more implant showed failed result.
DISCUSSION Insertion torque, implant stability quotient (ISQ), which is measured by resonance frequency analysis, and PTVs are most common and noninvasive measurement technique to analyze implant stability,8 and Pommer et al9 reported that correlation among insertion torque, ISQ, and PTVs was highly significant. Although insertion torque showed the highest specificity and high sensitivity, the purpose of this study is to evaluate periodically the implant stability not at implant placement, but also after prosthesis, PTVs were selected as measurement. And the Periotest is a well-established parameter for the evaluation of reproducible implant stability and is considered to be a sufficient stability criterion.10 Choi et al11 reported that Periotest (PTV) and Osstell Mentor (ISQ) are both useful diagnostic devices for implant stability in detecting the circular bone loss through in vitro study. Factors examined for their possible association with implant stability were the time after placement, bone quality (types I–IV) by tactile examination, location of
implant placement, and the bone quantity of bone adjacent to the implant. The PTVs were shown to decrease with time after implant placement, and, at 6 months after prosthesis placement, they had decreased by an average of 1.01 compared with immediately after surgery. But on 5-year follow-up, increased PTV as an average 0.28 was shown compared with immediately after surgery. In terms of the relationship to bone quality, implant stability was highest in type I and lowest in type IV bone. However, little difference was seen between types II and III. With regard to placement location, implant stability was lowest in the anterior maxilla and highest in the posterior mandible. However, the number of implants placed in the anterior maxilla was small, and so more examples are needed before conclusions can be drawn. Higher rates of resorption of the bones adjacent to the implant were associated with lower PTVs. In studies reported by Meredith et al and Balleri et al, compared with the maxilla, higher implant stability was seen in the mandible, and Friberg reported that the stability of implants placed in compact bones was higher than in less compact bones. However, implant length was not found to be related to stability.12–15 Saadoun and Legall16 reported that bone quality mediates effects on implant stability, and in comparison with implants in the molar area, higher stability was seen in implants placed in the anterior area.17 Although they found poor stability in the molar areas of both the maxilla and mandible, no significant difference was detected between the maxilla and mandible. Manz et al18 reported that factors associated with PTV included changes in the site of the Periotest relative to the fixture, differences in the method of using the device between examiners, and the diameter and length of the implant. Furthermore, the implant length, appearance of bones in which the implant was placed, surface contacting implants, and the ratio of cortical bone to trabecular bone affected primary stability.19,20 Lee et al21 reported that primary stability is the result of osseointegration of the implant into the bone, and it is advantageous to place long implants to improve this. Several authors have claimed that implants with wider
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diameters improve the bone-implant contact within compact bones and thus are preferable.22–24 A study by Bischof et al25 investigated ITI implants and found that a higher ISQ was seen in the maxilla than in the mandible and in type I than in type III bone; however, stability was not significantly related to site of placement or implant length and diameter. Additionally, up to 4 to 6 weeks after placement, ISQ was maintained or slightly increased, and after 6 weeks, the range of increment became larger. In a study by Lim et al, Osstem implants were placed in pig ribs. Results showed that longer implants were associated with greater stability, and primary stability was increased in cases where the diameter of the implant recipient site was smaller than the implant diameter; however, these differences were not statistically significant.26 Additionally, a study reported by Sennerby showed that stability was lower in cases with a high resorption rate of bone adjacent to the implant.4
CONCLUSION Among the subjects in this study, 88 Dentis implants were placed between January 2007 and June 2008. One implant showed severe mobility and resorption of bone adjacent to the implant, and it was removed 6 months after placement; thus, the survival rate was 98.8%. The PTVs found in this study were comparable with those reported by others, and the factors affecting stability were similar. It is considered that ideal cases for obtaining excellent implant stability include those in the mandible rather than the maxilla, in type I bone, and where the resorption rate of bone adjacent to the implant is low.
DISCLOSURE The authors claim to have no financial interest, either directly or indirectly, in the products or information listed in the article.
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