Conventional Drilling Versus Piezosurgery for Implant Site Preparation: A Meta-Analysis

Among the factors that affect osseointegration, the surgical technique is of critical importance.¹  An atraumatic surgical procedure can be achieved with constant cooling, adequate drill geometry,³  adequate drill speed,⁴  and careful tapping of the screws.¹  Due to their low-cost, easy handling, low-time consumption and efficiency, conventional drills are largely used in implant surgery.⁵  Nonetheless, this common system has disadvantages, such as the absence of a selective sectioning action,^5–7  which could damage the surrounding tissue.

In this context, piezoelectric surgery seems to be an alternative to the conventional preparation of the implant bed.^8,9  Recently, the performance of the use of sonic and ultrasonic devices for osteotomies was described in an in vitro study. The ultrasonic showed best results regarding speed and power. Other factors—such as thickness of osteotomy, presence of bone debris, and microroughness of the cortical bone—presented no relevant differences between study groups.¹⁰ 

These devices use ultrasound frequency to vibrate the cutting tips, generating electric potential in response to mechanical stress.^5,8,11  In addition to a selective sectioning action and a higher precision in bone surgery, the piezoelectric devices have been claimed to promote osteoblastic activity around the implant bed when compared with conventionally prepared sites in an animal model.¹² 

Few studies have compared piezosurgery with conventional drilling or with handheld devices for different bone surgeries, such as antrostomy for sinus floor elevation or implant bed preparation. The majority of those studies are animal and ex vivo trials. Histological studies suggest that implants placed with piezosurgery may result in the same amount of osseointegration.^11,13  Ultrasonic implant site preparation results in less traumatic osteotomy,^14,15  favorable wound healing,^14,16  and the decreased presence of microfractures and a smear layer,^15,17  appearing to be more efficient in the first stages of bone healing,¹⁴  inducing an increase in bone morphogenetic proteins (BMPs).¹²  However, piezosurgery appears to be more dependent on constant cooling, once it generates high temperatures during osteotomy.^7,18 

Primary stability, defined as the mechanical interlocking between the implant and the bone walls, is an important predictor of future osseointegration,^5,19  reducing the possibility of implant failure. Several noninvasive devices are available to clinically diagnose implant stability through vibration analysis, such as Periotest (Siemens AG, Bansheim, Germany) and Osstell (Osstell AB, Göteborg, Sweden).²⁰  Some studies have reported that implants placed with a piezoelectric device showed similar primary stability when compared with conventional drilling.^5,6,21  However, conflicting observations have been reported, suggesting that ultrasonic implant site preparation could improve fixture stability.^20,22,23 

This systematic review, according to the PICO framework, aimed to address the following focused question: “In patients undergoing dental implant placement, what is the stability of implants placed by piezosurgery compared with implants placed by conventional drilling?”

This systematic review was structured in accordance with guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)²⁴  and registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42016044066).

Only randomized controlled clinical trials that reported implant site preparation with piezosurgery and with conventional drilling were considered eligible for inclusion in this review. Letters to the editor, reviews, case series, case reports, in vivo, ex vivo, and in vitro studies were not included.

Studies that reported patients with immediate implants or who required any grafting procedure prior to implant placement, patients with a history of bisphosphonate therapy, or patients with osteoporosis were excluded from the review.

Implant site preparation with piezosurgery (test group) compared to conventional drilling (control group).

Implant stability quotient (ISQ).

A systematic literature search, without language restriction, was conducted in MEDLINE (PubMed), SCOPUS, and the Cochrane Library database until August 2, 2016. Publications were searched using the following keywords with Boolean operators to combine searches: ((dental implant) OR oral implant) AND ((((piezo) OR piezosurgery) OR piezoelectric) OR ultrasonic surgery). The electronic search was complemented by manual searches of the reference lists of the selected publications. Additionally, we searched for unpublished studies at OpenGray.

In the first phase of the review, 2 calibrated independent reviewers (D.I.S. and N.K.O.) screened titles and abstracts identified by the search strategy. Disagreements were resolved by discussion with another review author (C.M.P.). Studies appearing to meet the inclusion criteria, or those with unclear information in the title and abstract were selected for assessment of the full paper in the second phase of the review, which was conducted by the same reviewers. Reasons for the rejection of a study were recorded for each report.

Publications that met inclusion criteria had their data extracted by the same reviewers independently, using specially designed data-extraction forms.²³  The following variables were sought: (1) citation, (2) setting and location of trial, (3) characteristics of participants, (4) length of follow-up, (5) implant type and characteristics of the intervention, (6) sample size, (7) outcome measures, (8) author's conclusion, and (9) source of funding and conflict of interest. If data were missing, the authors of the original reports were contacted and asked to provide further details.

The risk of bias of the included studies was evaluated according to the Cochrane Collaboration's Tool for Assessing Risk of Bias.²⁴  The same reviewers performed the quality assessment of included studies independently. Briefly, the reviewers considered the following points and questions: selection bias (randomization and allocation concealment), performance bias (blinding of the study personnel), detection bias (blinding of the outcome assessors), attrition bias (incomplete outcome data), reporting bias, and other biases. Based on these domains, the overall risk of bias was categorized as follows: (1) a low risk of bias if all criteria were met (adequate randomization and allocation concealment, an affirmative answer to all questions about the completeness of outcome data and blinding, and a “no” answer to selective reporting and other sources of bias); (2) an unclear risk of bias if one or more criteria were partly met; or (3) a high risk of bias if one or more criteria were not met. Disagreements between reviewers were resolved by consensus after discussion with another review author (C.M.P.)

Analyses were performed using the software Review Manager (RevMan) Version 5.3. (Cochrane Community, Copenhagen, Denmark) by the authors of the present review. Data was reviewed by an experienced statistician. A random-effects meta-analysis was conducted for the implant stability quotient (dichotomous outcome). The estimates were presented as weighted mean differences (WMDs) and their respective 95% confidence intervals (CIs). Statistical heterogeneity among studies was assessed with the Cochrane Q test and I² .

Initially, 456 references were electronically retrieved. No additional references were identified manually. After reviewing abstracts and titles, 23 studies were qualified for data analysis after excluding publications having unrelated topics and information. Of those, 20 were excluded because they did not meet all selection criteria. The excluded studies and reasons for rejection are listed in supplementary Table 1 (https://doi.org/10.1563/aaid-joi-D-17-00091.S1). Three controlled clinical trials met the eligibility criteria and were included in this review (Figure 1).

Data regarding the characteristics of the included papers are depicted in the Table. All studies were randomized controlled trials with a crossover or split-mouth design. One study²⁷  was partially supported by Biomet 3i (Palm Beach Gardens, Fla), Mectron (Carasco, Italy), and Osstell AB (Göteborg, Sweden). Two publications^20,23  did not provide any funding information. The follow-up period ranged from 90 to 150 days. All studies reported similar exclusion criteria as follows: patients with insufficient bone volume to insert implants, uncontrolled or untreated periodontal disease, the presence of a relevant medical condition, or heavy smokers. In total, 138 implants in 65 patients were placed in all trials. Implants were from Sweden & Martina (Due Carrare, Italy), Neodent (Curitiba, Brazil), and Biomet 3i. The types of surfaces tested were sand-blasted, acid-etched, and nanosurfaces. The implant length varied from 10–13 mm, and the implant diameter varied from 3.5–4 mm. Publications reported 2 adjacent implants placed in the maxillary premolar region,²⁶  2 adjacent implants placed in the mandibular molar area,²⁰  or 2 implants placed in opposite maxillary premolar regions.²³  In one study, the test group consisted of a mixed traditional/piezoelectric preparation; only the final osteotomy was conducted with two ultrasonic tips.²⁰  The implant stability quotient (ISQ) was measured in all studies by the same device (Osstell, Osstell AB), with duplicate measurements from mesiodistal and buccolingual directions. Instrument calibration was verified in all studies. No implants submitted to immediate loading were reported. No dropouts occurred during the observational period in all trials.

Two studies reported blinding of the examiners with regard to the treatment procedures, an adequate method of randomization (computer-generated randomization tables), and allocation concealment (permuted block randomization approach). They were considered to have a low risk of bias. In one trial, considered to have a high risk of bias, there was no information about the method of randomization, allocation concealment, and masking of the outcome assessors (Figure 2).

Two meta-analyses were performed for ISQ at baseline and at 90 days follow-up, comparing the test group (piezosurgery) with conventional drilling. The pooled estimates suggested that there is no significant difference between piezosurgery and conventional drilling at baseline, as regards implant stability (WMD: 2.20; 95% CI: −5.09, 9,49; P = .55; Figure 3).

Considering ISQ at 90 days, the pooled estimates revealed a statistically significant difference (WMD: 3.63; 95% CI: 0.58, 6.67, P = .02) favoring piezosurgery (Figure 4). A subgroup analysis, where studies were stratified according to risk of bias, showed that the study considered to have a high risk of bias enhanced the positive effect of the piezoelectric devices. In addition, no heterogeneity was found in the studies considered to have low risk of bias (I² = 0%) at baseline and at 90 days. Considering publications regardless of their risk of bias, heterogeneity was I² = 92% at baseline and I² = 71% at 90 days (Figures 3 and 4).

Histological evidence in animal studies suggests that bone healing and formation is more favorable in ultrasonic osteotomy than conventional rotary instruments.^16,20  Piezosurgery is a well-established technique for maxillofacial surgery,²⁸  alveolar crest splitting,^29,30  and sinus floor elevation.³¹  Recent data suggesting their ability to enhance osteoblastic activity and increase BMPs have inspired researchers' interest in also applying the piezoelectric devices for implant site osteotomy,²⁰  expecting that fixtures placed in ultrasonic prepared beds would achieve a higher stability. The studies included in this systematic review indicate that piezosurgery may slightly favor implant stability after 90 days of follow-up. Notably, heterogeneity (>70%) was verified in both meta-analyses, considering studies regardless of their risk of bias, whereas no heterogeneity was found when only studies with low risk of bias were evaluated. It is important to note that this seems to be associated with some methodology limitations of the publication considered to have a high risk of bias, such as inadequate randomization or allocation concealment, which tends to overestimate the positive effect of the test group.

In the study by Canullo et al,²⁰  the test group showed that stability increased progressively through the observation period, while in the study by Stacchi et al.²⁷ 

ISQ values decreased in both groups in the initial observational periods. Nevertheless, implant stability started to increase after 14 days in the test group and after 21 days in the control group. This difference in the pattern of stability in the publications may be related to the location of the implants. In the study by Canullo et al,²⁰  fixations were placed in the posterior region of the mandible, a bone type I area according to the Lekholm and Zarb classification,³²  whereas in the study conducted by Stacchi et al,²⁷  implants were positioned in the upper premolar region, a more medullary bone area. In the study conducted by da Silva et al,²³  fixtures were also placed in the upper premolar region; however, they assessed stability immediately after surgery and at 90 and 150 days and, therefore, did not present available data from the first periods of bone healing. Nevertheless, values slightly decreased in the piezosurgery group at 90 days and increased at 150 days after implantation. Thus, the improvement of stability occurred in both cortical and medullary bones.

This positive result differs from other findings in the literature. Ex vivo studies utilizing bovine and pig rib samples suggest that ultrasonic preparation achieved similar implant stability in comparison to conventional drilling in cortical bone and a mixture of cortical and cancellous bone models.^5,6,21  However, the improvement of stability throughout the osseointegration process could not be analyzed in an ex vivo model, and the plausibility of the osteogenic activity and bone healing enhancement of the ultrasonic devices could not be observed.

Taking into account that there is a positive association between bone mineral density and implant stability³⁴  the results of this meta-analysis agree with a comparative clinical trial that evaluated bone densitometry to assess bone-healing.³³  The study showed that ultrasonic implant site preparation presented enhanced bone density and osteogenesis activity around dental implants, when compared with usual drilling.

In our quality assessment, 2 publications were considered to have low risk of bias, with important criteria fulfilled (ie, adequate method of randomization and allocation concealment, blinding of the examiners, and valid statistical analysis). One trial was considered to have high risk of bias, with lack of information in the publication, namely, the masking of examiners, methods of randomization, and allocation concealment. Furthermore, all the included papers present limitations of small sample size, short follow-up period, single operator performing all surgeries, and the use of resonance frequency analysis (RFA) to evaluate implant stability. Despite RFA being an ethical and noninvasive method to assess stability, controversies still exist over its accuracy to predict long-term stability and osseointegration.³⁵  The internal validity of the included studies may affect the inferences about the efficacy of piezosurgery; thus, the results of this review should be interpreted with caution.

Despite that, all the included papers reported an adequate control of confounding factors: all implants were evaluated before prosthetic rehabilitation; immediate implants were not reported in the publications; all the fixtures had comparable diameters and lengths; no grafting procedures were used; and the exclusion criteria were similar in all trials.

The search was carried out in 2 wide-ranging databases, with no language restriction and it was complemented by hand and gray literature searching. Still, there is a possibility of bias in the selection of the studies, which could be the result of as the use of a limited number of databases, hand search-confined to study references, publication bias, selective outcome reporting, ongoing research, and so on. These limitations, which are inherent to any reviewing process method, may limit the conclusions of this review.

Despite the slight increase of implant stability in the ultrasonic group, one should take into account that probably there is no clinical significance comparing both groups. In addition to that, piezosurgery is a more time-consuming technique⁷  (which could affect the clinical routine), piezoelectrics are considerably expensive devices, and the diameters of the ultrasonic cutting tips are still very limited and do not meet the wide commercially available implant systems.⁶ 

It important to take into consideration that meta-analysis is a form of casual-comparative investigation and does not have a proper experimental design. Limitations of the selection process, risk of bias of the included studies, and heterogeneity may lead to unsound inferences about the efficacy of piezosurgery. Thus, more randomized trials are needed to further investigate the efficacy and real indication of this technique.

Under the limits of this systematic review, it can be suggested that there is slight evidence that implant stability can be improved when osteotomy is performed by a piezoelectric device.

Abbreviations

BMPs

bone morphogenetic proteins

CI

confidence interval

ISQ

implant stability quotient

PICO

population, intervention, comparison, and outcome

PRISMA

preferred reporting items for systematic reviews and meta-analyses

PROSPERO

International Prospective Register of Systematic Reviews

RFA

resonance frequency analysis

WMD

weighted mean differences

The authors report no conflicts of interest related to this study. There was no source of funding for this systematic review.