The Influence of Bone Quality on Periotest Values of Endosseous Dental Implants at Stage II Surgery

J Oral Maxillofac Surg 55:55-61,1997, Suppl 5

The Influence of Bone Quality on Periotest Values of Endosseous Dental Implants at Stage II Surgery RICHARD S. TRUHLAR, DDS: FRANK LAUCIELLO, DDS,t HAROLD F. MORRIS, DDS, MS,; AND SHIGERU OCHI, PHD§ Periotest values (Periotest, Siemens AG, Bensheim, Germany) were recorded as a baseline variable at surgical uncovering in the ongoing multicenter, prospective clinical studies of the Dental Implant Clinical Research Group, which uses implants from the Spectra-System (Core-Vent Corporation, Las Vegas, NV). For 2,212 osseointegrated implants, the mean Periotest value (PTV) of mandibular implants was -4.14 (anterior, -4.22; posterior, -4.06) versus -3.24 for maxillary implants (anterior, -2.91; posterior, -3.91). Implants In the densest bone (quality 1) had the lowest mean PTV (-4.13), followed by quality 2 (-4.00), quality 3 (-3.58), and quality 4 (-2.64).

When a team of dentists is involved in treating a patient, as in implant dentistry, an objective, reproducible method of evaluation of the status of the boneimplant complex is desirable. Clinicians generally agree it is important to verify the status of osseointegration of dental implants before attachment of abutments, before insertion of the implant-supported prostheses, and at various times during the maintenance phase. 1.2 As originally defined, the term osseointegration described the direct bone-implant contact seen under light microscopy around rigidly fixed, immobile Implants.P

Because the status of the interface has been impossible to assess in any reproducible manner short of resection,"? Albrektsson et al 8 suggested redefining osseointegration on the basis of a clinical examination in which implants are evaluated for clinical stability and freedom from complications, with rigid fixation achieved and maintained in bone during functional loading. If one accepts this paradigm shift, what is the best technique for determining rigid fixation clinically? Traditional methods are not sufficiently sensitive to quantify the amount of bone in contact with an implant and may not always be safe. Routine evaluation by radiographs, probing, and mobility have not been universally accepted." Evaluation by serial radiographs poses certain safety questions associated with the use of ionizing radiation. Additionally, because radiographs are only capable of a maximum resolution of 0.1 mm, they are not sufficient for evaluation of the direct bone-implant contact that exists on the micron scale.'? Probing of an implant remains controversial because of the concern for disruption of the integrity of the soft tissue seal and possible penetration of the probe tip to alveolar bone. Clinically detectable mobility is a parameter of low sensitivity and high specificity. II With a clinical mobility index, only two evaluations are possible-mobility or no mobility. Evaluating osseointegration by the type of sound produced when the implant-abutment complex is tapped with the blunt end of a metallic instrument has not been validated scientifically.'? A "ringing" sound

* Clinical Investigator, Dental Implant Clinical Research Group; Staff Periodontist, Department of Veterans Affairs Medical Center. Northport. NY; Clinical Assistant Professor, Department of Periodontics, School of Dental Medicine, State University of New York, Stony Brook. t Co-chair study group B, Dental Implant Clinical Research Group; Staff Prosthodontist. Department of Veterans Affairs Medical Center, Buffalo, NY; Clinical Associate Professor. Department of Restorative Dentistry, School of Dental Medicine, State University of New York, Buffalo. :j: Codirector. Dental Clinical Research Center; Project Codirector. Dental Implant Clinical Research Group, Department of Veterans Affairs Medical Center. Dental Research, Ann Arbor, MI. § Codirector. Dental Clinical Research Center; Project Codirector and Biostatistician, Dental Implant Clinical Research Group. Department of Veterans Affairs Medical Center. Dental Research, Ann Arbor. MI. Address correspondence and reprint requests to Dr Morris: Department of Veterans Affairs Medical Center, Dental Research (154). 2215 Fuller Rd, Ann Arbor, MI 48105. This is a US government work. There are no restrictions on its use. 0278-2391/97/5512-5003$0.0010

55

56

STAGE II EFFECTS OF BONE QUALITY ON PERIOTEST

is considered to indicate proper osseointegration, whereas a "dull" sound would indicate a fibrous interface. Another technique uses a torque wrench with a measured amount of force. Demonstration of mobility by this technique is highly dependent on healing time, as reported Johansson and Albrektsson," as well as the animal model used.6.12.13 Application of torque forces of these magnitudes to test for osseointegration at the time of abutment connection is of questionable safety in humans, particularly for implants in bone of poor quantity or quality with short healing times." Possible results are bone microfractures and subsequent loss of the implant on loading. Sullivan et al 14 recommend counter-torque forces of 10 to 20 N-cm as a test for non integration at the time of uncovering, but conclude that this form of testing is not predictive of implant behavior under occlusal loading. A device called the Periotest (Siemens AG, Bensheim, Germany) holds the potential to be safe and effective for evaluating implant mobility. The literature indicates that the Periotest is capable of providing highly sensitive and reliable mobility data. IS• 17 Research by d'Hoedt et al" suggests that a range of -8 to +09 Periotest value (PTV) units corresponds to a clinical assessment of 0 on the Miller index." Because of its finer gradations of measurement, and the reproducibility of its readings, the Periotest may be capable of detecting slight changes in the bone-implant complex with a high degree of precision, even before pathologic changes are evident on dental radiographs. 19 For dental implants, a PTV of 10 or higher generally means osseointegration was not achieved or has been lost,20The average or median PTVs of osseointegrated implants tend to be close to zero or below zero." The purpose of this article is to report baseline Periotest values determined on a large number of implants in various sites at the time of surgical uncovering as they relate to bone quality.

Materials and Methods Periotest values were recorded as a baseline variable in the long-term clinical studies of the Dental Implant Clinical Research Group (DICRG) investigating the influence of implant design, application, and site of placement on clinical success and crestal bone height." The implants used were Spectra-System products (Core-Vent Corporation, Las Vegas, NV). They included basket, screw, cylinder, and grooved implant designs. Implant materials used were commercially pure titanium, titanium alloy, and hydroxyapatite (HA)-coated titanium alloy. In these ongoing studies, treatment cases were divided into one of five research strata of approximately

equal size (Table 1). Different implant designs and materials were used in each stratum. Implant assignment and location were determined by randomization for each case. Clinical centers include 30 Department of Veterans Affairs medical centers and two dental schools, which were assigned to one of two study groups (study group A, 17 clinical centers; study group B, 15 clinical centers). All clinical centers use the same study strata and randomization plan, but the study groups differed in their amount of prior surgical experience with implants." alloys assigned for restorations. and home care regimen assigned. Patients are for the most part white males from various socioeconomic groups and range in age between 20 and 90 years. All clinical investigators were trained in the surgical and restorative procedures associated with the specific implant system and in the data collection procedures of the DICRG. The Periotest has been described in detail by Schulte!9.2o.23 The PTV scale ranges from -8 (clinically firm) to +50 (very loose). Calibration of the device using the cap provided by the manufacturer and positioning the handpiece parallel to the floor and perpendicular to the surface of the implant abutment or healing collar are important for accuracy of readings (Fig I). Data were collected on standardized forms. At implant insertion, the type of implant, implant length and diameter, implant location (approximate tooth number), and bone quality" were recorded. Maxillary implants were allowed to heal longer than mandibular (6 months for implants in the upper jaw and 4 months for implants in the lower), which is consistent with DICRG guidelines for the length of time recommended between implant placement and surgical uncovering, By research stratum, the time elapsed between implant placement and surgical uncovering ranged from an average of 5.7 months (173 days) for implants in the completely edentulous mandible (lower completely edentulous stratum) to 7.6 months (232 days) for implants used for single tooth replacement in the anterior maxilla (upper single tooth stratum) (Fig 2). At the time of uncovering, the healing cap was removed, and a healing collar 3, 5, or, rarely, 7 mm long was screwed firmly into the implant. The handpiece of the Periotest was held slightly above the gingival tissues, aligned perpendicular to the healing collar. and then activated. Additional factors recorded at uncovering were the distance between top of implant and crest of bone (measured by manual plastic probe and electronic probe [Interprobe, Bausch & Lomb, Yorba Linda, CAl); type of incision (crestal, remote. tissuepunched); medications prescribed; and status of implant (osseointegrated, integrated/nonfunctional; not osseointegrated). Complications and implant failures were docu-

57

TRUHLAR ET AL

Table 1.

Implants and Prostheses In the DICRG Study Strata Number of Implants

Implant Design

Implant Name"

Implant Material

Upper completely edentulous (UCE)

5 or 6

Upper posterior partially edentulous (UP) Upper single tooth (UST) Lower completely edentulous (LCE)

2 or 3

Grooved Screw Screw Grooved' Cylinder Grooved Basket Screw Cylinder Basket Cylinder

Micro-Vent Screw-Vent Screw-Vent Micro-Vent Bio-Vent Micro-Vent Core-Vent Screw-Vent Bio-Vent Core-Vent Bio-Vent

HA-coated HA-coated Titanium-CP HA-coated HA-coated HA-coated Titanium alloy Titanium alloy HA-coated Titanium alloy HA-coated

Stratum

I

5 or 6

Lower posterior partially edentulous (LP)

2 or 3

Prosthetic Application Bar-retained overdenture (implant supported only) Fixed-detachable partial denture Single crown Fixed-detachable complete denture

Fixed-detachable partial denture

Abbreviations: CPo commercially pure; HA. hydroxyapatite. • Micro-Vent, Screw-Vent, Bio-Vent, and Core-Vent are Spectra-System products (Core-Vent Corporation. Las Vegas. NV).

mented on separate forms. "Implant failure" was defined as the removal of an implant for one or more of the following reasons: implant mobility when tested; evidence of complete peri-implant radiolucency; persistent pain or discomfort; or infection that is not resolved with the use of antibiotics or local treatment and occurs more than three times and requires treatment during the first year after loading. Data entry was done by the staff of the data management center, and data analysis was performed by the DICRG staff biostatistician. The distribution of Periotest values at the time of implant uncovering was skewed, and therefore the data were transformed to a log distribution before analysis because the results were similar to those without such transformation. They are reported here as the untransformed data set. Because it was assumed that implant materials, implant lengths, and healing collar lengths were randomly distributed, the influence of these variables was not taken into consideration in this study. As of May 1995, the DICRG database had 2,910 implants. Sixty-three replacement implants and 206 implants that were still covered were not included in this analysis. Of the 2,641 implants placed and uncovered, PTVs were recorded for 2,351. The Periotest

A - -:~:~:~ll+ --1- - -

8

-

........

FIGURE I. The correct angle of the Periotest device relative to the surface of the abutment is 90 degrees. A, Correct. B. Incorrect.

value (PTV) distribution curves for the two study groups were quite similar, except for Periotest + 3 for group A (Fig 3A). One of two hospitals that entered the study after the first group of 30 had Periotest measurements that differed significantly (Fig 3B). This station was found to be following incorrect procedures, and the readings (123 implants) were excluded from this analysis. Additionally, 16 implants that had failed at uncovering had PTVs recorded. Subtracting these 16 and the 123 implants from the one clinical center noted above brought the database for these analyses to 2,212 implants. Periotest values for 2,212 integrated implants at the time of uncovering in study groups A and B were similar and, when combined, gave a mean PTV of -3.75 (Table 2). For the 31 centers, 92.2% of the readings were PTV 0 or less, and 99.0% were +09 or less. PTVs by jaw arch for both study groups were also similar. The mean PTV of mandibular implants (-4.14) was lower than that of maxillary implants (-3.24) (Table 3). Implants placed in the anterior mandible had the lowest mean PTV (-4.22), followed by the posterior mandible (-4.06), posterior maxilla (-3.91), and the anterior maxilla (-2.91) (Table 4). By treatment category, single implants in the anterior maxilla had the lowest mean PTV (-4.74), and implants in the completely edentulous maxilla had the highest mean PTV (- 2.22) (Table 5). Based on bone quality, implants in the densest bone (quality 1) had the lowest mean PTV (-4.13), followed by quality 2 (-4.00), quality 3 (-3.58), and quality 4 (-2.64) (Table 6).

Discussion The 1994 report by the DICRG 25 reported PTV means ::t SD by quadrant and bone density. The relationships identified in that report remain consistent in

58

STAGE II EFFECTS OF BONE QUALITY ON PERIOTEST

300 r - - - - - - - - - - - - - - - - - - ,

A 500 . - - - - - - - - - - - - - - - -

250

400

f:1

--

200 ---

Group A ~

150

as

Group B

a. .5 200

100 50

o

300

-

Combined

100 LCE

LP

UCE

UP

UST

R....rch Str.ta

FIGURE 2. Average time elapsed between implant placement and implant uncovering. by DICRG study stratum and study group. LCE. lower completely edentulous; LP. lower posterior partially edentulous; UCE. upper completely edentulous; UP. upper posterior partially edentulous; UST, upper single tooth (n = 2625). An analysis of variance between the study groups A and B for the different study strata did not show a significant difference in the length of time to uncovering.

the current report, specifically that as bone density decreases, the PTVs become more positive in value. Similarly, the mandibular implants have the most negative PTV mean, whereas the maxillary implant mean PTV is more positive. Direct comparison with other studies using the Periotest for evaluation of implant mobility is difficult because of the use of different implant systems; measurements taken at different time intervals before or after prosthetic loading; and an inconsistency in reporting implant location in the mouth, local bone qualities, and type of prosthetic restoration. Comparisons that can be made are consistent with the current report. Olive and Aparicio" reported mean PTVs in the maxilla of -0.05 :t 0.31 for males and + \.59 :!: 0.41 for females after a mean healing time of 6.1 months, and mandibular mean PTVs of -1.51 :t 0.30 for males and -2.30 :t 0.21 for females after a mean healing time of 3.9 months for commercially pure titanium screws at the time of abutment connection. With the same implant design, Teerlinck et al 27 reported that 87.5% of their measurements were PTV 0 or less, with a mean PTV of - I ,83 after removal of Dolder bars from mandibular anterior implants that had functioned under overdentures from 2 to 8 months. Similar trends for the maxilla and mandible were reported by Haas et al,28 with a mean PTV of -0.5 for the maxilla and -4.0 for the mandible with IMZ implants (Interpore, Irvine, CA) after a mean of 36.8 months postimplantation. The form of prosthetic rehabilitation was not discussed. Finally, Buser et al!' reported a mean PTV of +0.60 in the maxilla and - 3. 78 in the mandible for 100 ITI (Straumann, Cambridge, MA) hollow cylinder and hol-

o -8 -7-6-5-4-3-2 -10

1 234 567 8910111213

Periotest Values

B 100 ,--

--,

80

-

~1 center

~ 60 tcJ as

a. S

....

31

40

c~nters

20

oLL.o......LL......L..l....i....:~~.....w. ...................................................J -8-7-6-5-4-3-2-101234 567891011121315

Perlotest Values FIGURE 3. A. Periotest value distribution curves for implants at surgical uncovering: Study group A-17 clinical centers, I.mn implants; study group B-15 clinical centers, 1.26H implants; cornbined data-32 clinical centers, 2,351 implants. 8. Periotest value distribution curves for implants at surgical uncovering: one clinical center in group A (123 implants) vs 31 clinical centers (2,22X implants).

low screw implants, 12 months after placement that were used to support either single crowns, or totally implant supported or combination implant-tooth supported fixed partial dentures. Of note in the current report is the finding of the lowest mean PTV for the UST stratum (upper single tooth), while the UCE stratum (upper completely edenTable 2. Perlotest Values of asseolntegrated Implants at Surgical Uncovering by Study Group DlCRG Group

Implants

Mean Periotest Value ± Sf)

Study group A Study group B Combined totals

957 1.255 2,212

-3.67 ,: 3.06 -3.75 ± 2.96

-3.H4 ±.

~.H~

59

TRUHLAR ET AL

Table 3. Perlotest Values of OsseoIntegrated Implants at Time of Uncovering by Jaw Arch and Study Group = 2212)

eN

Jaw Arch

Implants

Mean Periotest Value:!: SO

1.233 561 672 979 396 583

-4.14 :!: 2.92 -4.23 :!: '2.80 -4,07 :!: 3.02 -3,24 :!: 2.93 -3,29:!: 2.75 -3.21 :!: 3.05

Table 5. Perlotest Values of OsseoIntegrated Implants at Time of Uncovering by Treatment Category and Study Group (N = 2212) Mean Periotest Implants Value:!: SO

Treatment Category Mandible Study group Study group Maxilla Study group Study group

A B A B

Lower completely edentulous (LCE) Study group A Study group B Lower posterior partially edentulous (LP) Study group A Study group B Upper completely edentulous (UCE) Study group A Study group B Upper posterior partially edentulous (UP) Study group A Study group B Upper single tooth (UST) Study group A Study group B

668 303 365 565 258 307 472 186 286 331 127 204 176 83 93

-4.22 -4.25 -4.\9 -4.06 -4.21 - 3.93 -2.22 -2.30 -2.\7 -3.91 -3.79 -3.98 -4.74 -4.76 -4.73

:t :t :t :t :t :t :t :t :t :t

2.72 2.85 2.62 3.14 2.75 3.43 3.18 3.09 3.24 2.\4 :!: 1.97 :t 2.24 :t 2.51 :!: 2.02 :t 2.88

tulous) had the highest mean PTV. The most probable explanation for this is that the only type of implant placed in the UST stratum was an HA-coated grooved design. whereas the UCE stratum received HA-coated grooved implants, as well as HA-coated and commercially pure titanium screw designs. In a previous analysis of the DICRG database, Ochi et al 29 reported the mean PTV of -1.31 for commercially pure titanium screws to be significantly different (P < .05) from that for all other designs. The same effect also may account for why the mean PTV for the UP stratum (upper posterior partially edentulous) was more favorable than the UCE stratum, even though previous reports by the DICRG Jo •3 1 indicate a greater prevalence of type 4 bone in the posterior maxilla than in the anterior maxilla. Only HA-coated cylinders and HA-coated grooved fixtures were placed in the UP stratum. The HA-coated cylinder was reported by Ochi" to have a mean PTV of -4.80, which was significantly different (P < .05) from the other implant designs in the DICRG studies. Other biomechanical factors that may playa role in the low mean PTV for the UST stratum may be I) a difference in the bone adaptive capacity in the anterior maxilla, potentially initiated or controlled by mechani-

cal stimulation from the adjacent teeth with healthy, intact POLs. This effect would be missing in a fully edentulous maxilla. However, further study is needed on the exact mechanism by which bone responds to such stimuli"; 2) the UST stratum had the longest mean healing time at 7.6 months (232 days), allowing for further maturation of the bone-implant interface, which could manifest as more favorable PrV readings; and 3) protection of a maxillary anterior single implant by the adjacent teeth supporting and guiding the occlusion in centric occlusion and all excursions. Again, further study is indicated to establish the relative contributions of these variables. Causes for the variation seen in the range and standard deviations of the PTVs at uncovering may· be the number of cortical plates in contact with the implants

Table 4. Perlotest Values of Osseolntegrated Implants at Time of Uncovering by Jaw Quadrant and Study Group

Table 8. Perlotest Value. of Osseolntegrated Implants at Time of Uncovering by 80ne Quality at Implant Site and Study Group

Jaw Quadrant

Implants

Anterior mandible Study group A Study group B Posterior mandible Study group A Study group B Anterior maxilla Study group A Study group B Posterior maxilla Study group A Study group B

668 303 365 565 258 307 648 269 379 331 127 204

Mean Periotest Value:!: SO -4.22 :!: -4.25 :!: -4.19 :t -4.06 :t -4.21 :!: -3.93 :t -2.91 :!: -3.06:!: -2.80:!: -3.91 :!: -3.79 :!: -3.98 :!:

2.72 2.85 2.62 3.14 2.75 3.43 3.21 3.02 3.34 2.14 1.97 2.24

Bone Quality

Implants

Mean Periotest Value :t SO

Quality I Study group A Study group B Quality 2 Study group A Study group B Quality 3 Study group A Study group B Quality 4 Study group A Study group B

175 116 59 1,023 435 588 835 333 502 171 73 98

-4.13 :t 2.74 -4.45 :t 2.64 -3.51 :t 2.85 -4.00 :!: 2.84 -4.03 :t 2.84 -3.98 :t 2.85 -3.58 :!: 2.97 -3.66 :t 2.67 -3.53 :!: 3.15 -2.64 :!: 3.38 -2.60:!: 3.17 -2.66 :t 3.53

60 in qualities 2 through 4 bone as well as variations in cellular remodeling cycles that determine the rapidity of bone formation. As the bone-implant interface continues to mature. the change in PTVs may be more favorable in the latter group than in the former. Another potential source of variation for PTV readings includes abutment length. Olive and Aparicio" concluded that longer abutment lengths result in less favorable PTVs. However. in their design, when the coronal edge of the abutment was covered by gingival tissues. an additional 3·mm gold cylinder was attached to provide a surface for the Periotest to percuss. In their analysis. this deviation in protocol was not addressed. Teerlinck et al27 also concluded that abutment length significantly affected PTVs. but this was only when measurements were made without removing a Dolder bar that splinted the two implants. When the fixtureabutment complex was measured with the Dolder bar removed. abutment length had no significant effect on PTVs, Van Steenberghe and Quirynerr" have implied that the prognostic value of the Periotest remains unproven with regard to implants. because too few failures have been studied and reported in the literature. However. recent reports in the literature have suggested that the Periotest is sensitive enough to discriminate longitudinally among implant responses to loading forces.r':" Van Steenberghe et al reported that over 5 years the mean PTVs and standard deviations for 62 mandibular and 157 maxillary Branemark implants initially placed both decreased, It is anticipated that the current longterm clinical investigation by the DICRG will provide a sufficient quantity of prospective data to confirm the value of the Periotest in oral implantology. The clinical significance of the PTV numbers to clinicians and researchers is anticipated not only to be in determining whether an implant has properly integrated at uncovering. but also in monitoring the status of the bone-implant complex when individual implants are functioning under a prosthetic load. In the event a complication occurs that results in the failure of an implant. an accurate series of PTVs could help identify at what point in the treatment process the pathologic process started. Future data may show a correlation between an optimal PTV at uncovering and long-term clinical performance of the implant.

STAGE II EFFECTS OF BONE QUALITY ON PERIOTEST

4, 5. 6. 7. 8. 9. 10. II.

12. 13.

14. 15.

16. 17. 18. 19. 20. 21.

22. 23.

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61 32. Bidez MW, Misch CE: Issues in bone mechanics related to oral implants. Implant Dent 1:289, 1992 33. van Steenberghe D, Quirynen M: Reproducibility and detection threshold of peri-implant diagnostics. Adv Dent Res 7:191, 1993 34. van Steenberghe D, Tricio J, Naert I, et al: Damping characteristics of bone-to-implant interfaces: A clinical study with the Periotest@ device. Clin Oral Implants Res 6:31, 1995 35. Rotter BE, Blackwell R. Dalton G: Testing progressive loading of endosteal implants with the Periotest: A pilot study. Implant Dent 5:28, 1996 36. Walker L, Morris HF, Ochi S, et al: Periotest values of dental implants in the first 2 years after second-stage surgery: D1CRG interim report no. 8. Implant Dent 6:207, 1997