A systematic review and meta-analysis was conducted to answer the clinical question “Does the piezoelectric surgical technique produce fewer postoperative sequelae after lower third molar surgery than conventional rotary instruments?” A systematic and electronic search of several databases with specific key words, a reference search, and a manual search were performed from respective dates of inception through November 2014. The inclusion criteria were clinical human studies, including randomized controlled trials (RCTs), controlled clinical trials (CCTs), and retrospective studies, with the aim of comparing the piezoelectric surgical osteotomy technique to the standard rotary instrument technique in lower third molar surgery. Postoperative sequelae (oedema, trismus, and pain), the total number of analgesics taken, and the duration of surgery were analyzed. A total of nine articles were included, six RCTs, two CCTs, and one retrospective study. Six studies had a low risk of bias and three had a moderate risk of bias. A statistically significant difference was found between piezoelectric surgery and conventional rotary instrument surgery for lower third molar extraction with regard to postoperative sequelae (oedema, trismus, and pain) and the total number of analgesics taken ( P = 0.0001, P = 0.0001, P < 0.00001, and P < 0.0001, respectively). However, a statistically significant increased surgery time was required in the piezoelectric osteotomy group ( P < 0.00001). The results of the meta-analysis showed that piezoelectric surgery significantly reduced the occurrence of postoperative sequelae (oedema, trismus, and pain) and the total number of analgesics taken compared to the conventional rotary instrument technique in lower third molar surgery, but required a longer surgery time.
Third molar surgery is one of the most common procedures performed by oral and maxillofacial surgeons. The extraction of a mandibular third molar can range from relatively easy to extremely difficult depending on its location, depth, and angulation, and on bone density. One of the most critical phases during extraction is the osteotomy, for which many techniques are used; if these techniques are performed improperly, they can be dangerous.
Piezoelectric surgery was introduced in 1988 and has since undergone improvements. The piezoelectric instrument produces a modulated ultrasonic frequency of 24–29 kHz and a microvibration amplitude between 60 and 200 mm/s. The amplitude of these microvibrations allows a clean, precise cut. Piezoelectric surgery is very efficient for osteotomy because it works selectively—the soft tissues, including nerves and blood vessels, are unaffected. This represents a significant advantage over the use of a bur. Microstreaming and the cavitation phenomenon are distinctive features of piezoelectric surgery. Microstreaming is generated by the continuous whirling movement of a fluid generated by a small vibrating insert that favours a mechanical action of debris removal. The cavitation phenomenon, caused by the implosion of gas bullae into blood vessels during osteotomy, produces an important haemostatic effect that optimizes intraoperative visibility. Piezoelectric surgery is a new osteotomy technique utilizing the microvibrations of scalpels at ultrasonic frequency to perform safe and effective osteotomies.
When used properly, piezoelectric surgery causes less damage at the structural and cellular levels when compared to other techniques; indeed the new bone formation is more rapid compared to that following surgery with a rotating drill. However, several previous studies have demonstrated that the micrometric cutting action of piezoelectric surgery requires a longer surgery time when compared to the use of a bur, and as a result may potentially cause greater discomfort in the postoperative period.
Furthermore, recent morphological analyses of bone samples have shown that a bur produces irregular surfaces and marginal osteonecrosis due to the high temperature generated during bone drilling. The preservation of the bone structure observed after the use of the ultrasonic technique seems to improve cellular reactivity thus favouring the healing process of the traumatized mineralized tissues.
The authors of the present study hypothesized that there is no difference between piezoelectric surgery and traditional rotary instruments used for the extraction of lower third molars with regard to postoperative sequelae. The aim of this study was to identify any significant differences in clinical outcomes between piezoelectric surgery and surgery performed with traditional rotary instruments for the extraction of lower third molars.
Materials and methods
Literature search strategy
An electronic search of the PubMed, Ovid MEDLINE, and Cochrane CENTRAL online databases was conducted from their respective dates of inception to November 2014. Free text words and medical subject heading (MeSH) terms were used. The heading sequence was (mandibular OR lower) AND (third molar OR wisdom) AND (Piezosurgery) AND (conventional OR standard OR traditional rotary osteotomy OR conventional hand-piece). The low yield led to the use of another search term omitting the reference to piezoelectric surgery versus rotary bur: (mandibular OR lower) AND (third molar OR wisdom) AND (pain OR swelling OR trismus OR infection OR bleeding OR lingual OR inferior alveolar OR trigeminal OR labial OR lingual OR nerve OR the postoperative symptoms severity scale). The abstracts of the results yielded were reviewed and the full text obtained for those with apparent relevance. The references of the papers identified were cross-checked for unidentified articles. The individual databases of key subject journals were also searched using the same terms as above: the Journal of Oral and Maxillofacial Surgery , International Journal of Oral and Maxillofacial Surgery , Journal of Oral Surgery , and British Journal of Oral and Maxillofacial Surgery . The searches were limited to articles published in the English language. An attempt was made to identify unpublished material or to contact authors of published studies for further information. To complete the search, the references of each selected publication on piezoelectric surgery versus conventional surgery in the extraction of third molars were searched by hand.
The inclusion criteria were developed using the PICOS guidelines. Population: patients had to be aged 18–25 years and require the removal of two impacted lower third molars with a mucoperiosteal flap and osteotomy, for orthodontic, prophylactic purposes. Intervention: surgical extraction of third molars using a piezoelectric device osteotomy technique. Comparator: surgical extraction of third molars using the conventional rotary bur osteotomy technique. Outcomes: the postoperative symptoms severity scales, facial swelling, pain assessed by visual analogue scale (VAS), trismus, number of analgesics taken, and duration of surgery. Study type: clinical human studies, including randomized controlled trials (RCTs), controlled clinical trials (CCTs), and retrospective studies with the aim of comparing clinical outcomes between piezoelectric surgery and the conventional rotary osteotomy technique in the surgical extraction of third molars, and reporting the incidence of postoperative complications.
The following exclusion criteria were applied: case reports, technical reports, animal or in vitro studies, review papers, and uncontrolled clinical studies; studies in which patients were taking antibiotics for a current infection, or had acute pericoronitis or severe periodontal disease at the time of the operation; studies involving forceps extractions not requiring osteotomy; studies that did not report the data (mean and standard deviation) required to perform a meta-analysis.
Data collection process
The authors carefully assessed the eligibility of all studies retrieved from the databases. Data were extracted independently by two review authors (E.A.A. and Y.A.A.). The following data were extracted from the studies included in the final analysis: authors, year of publication, study design, number of extracted third molars, sex (male to female ratio), mean age in years, follow-up period, duration of surgery, incision design, and preoperative and postoperative pharmacological therapy.
Risk of bias in individual studies
A methodological quality rating was performed by combining the proposed criteria of the Meta-analysis of Observational Studies in Epidemiology (MOOSE) statement, the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, to verify the strength of scientific evidence in clinical decision-making. The classification of the risk of bias potential for each study was based on the following five criteria: random selection in the population, definition of inclusion and exclusion criteria, report of losses to follow-up, validated measurements, and statistical analysis. A study that included all of these criteria was classified as having a low risk of bias, a study that did not include one of these criteria was classified as having a moderate risk of bias. When two or more criteria were missing, the study was considered to have a high risk of bias. The quality of the studies was determined independently by two reviewers (A.E.A. and A.S.A). Disagreements between the two review authors were resolved by consensus with a third reviewer (E.A.A.).
Synthesis of results
Meta-analyses were conducted only if there were studies of similar comparisons, reporting the same outcome measures. For binary outcomes, it was planned to calculate a standard estimation of the odds ratio (OR) by random-effects model if heterogeneity was detected. Otherwise a fixed-effects model with a 95% confidence interval (CI) was to be performed. The weighted mean difference (WMD) or standard mean difference (SMD) was used to construct forest plots of continuous data using the following equation :
SMD = Difference in mean outcome between groups Standard deviation of outcome among participants
The data were analyzed using the statistical software Review Manager version 5.2.6 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark, 2012).
Assessment of heterogeneity
The significance of any discrepancies in the estimates of the treatment effects of the different trials was assessed by means of Cochran’s test for heterogeneity and the I 2 statistic, which describes the percentage total variation across studies that is due to heterogeneity rather than chance. Heterogeneity was considered statistically significant if P < 0.1. A rough guide to the interpretation of I 2 given in the Cochrane Handbook is as follows: (1) at 0–40% the heterogeneity might not be important, (2) 30–60% may represent moderate heterogeneity, (3) 50–90% may represent substantial heterogeneity, and (4) 75–100% may represent considerable heterogeneity.
Investigation of publication bias
A funnel plot (plot of effect size versus standard error) was drawn. Asymmetry of the funnel plot may indicate publication bias and other biases related to sample size, although the asymmetry may also represent a true relationship between trial size and effect size.
If there were sufficient studies included, a sensitivity analysis was to be performed to assess the robustness of the review results by repeating the analysis with the following adjustment: exclusion of retrospective studies.
The study screening process is summarized in Fig. 1 . The electronic search resulted in 685 entries. Three additional articles were identified by hand-searching. Of these 688 articles, 400 were excluded because they had been retrieved in more than one search (duplications). After the initial screening of titles and abstracts, 200 articles were excluded because they were off-topic. The full-text reports of the remaining 88 articles were retrieved and 79 articles were excluded because they did not meet the inclusion criteria. Thus, a total of nine publications were included in the review.
Characteristics of the studies included
Detailed characteristics of the studies included in the review are shown in Table 1 . Six RCTs, two CCTs, and one retrospective study were included in the meta-analysis and critical appraisal. A total of 424 patients (682 third molars) were enrolled in the nine studies comparing the piezoelectric surgery osteotomy technique ( n = 341) to the conventional rotary instruments technique ( n = 341) for the surgical extraction of third molars.
|Author||Year published||Study design||Male to female ratio||Age, mean or range, years||No. of third molars||Follow-up period||Operative time (min)||Incision design||Pharmacological therapy (preop. or postop.)|
|Sortino et al.||2008||CCT||PSO: 23:27
|50||50||1 day||PSO: 22.92
|Triangular in shape (Archer flap)||No preop. drugs|
|Barone et al.||2010||RCT||PSO, CRO: 14:12||PSO, CRO: 24–45 (31.2)||13||13||1, 3, 5, 7 days||PSO: 34.3
|Full thickness buccal flap||Amoxicillin–clavulanic acid 2 g 1 h preop.; no cortisone|
|Sivolella et al.||2011||RCT||PSO: 10:16
|PSO, CRO: 15.4||26||26||7, 30 days||PSO: 11.77
|Three-sided flap||Chlorhexidine preop.; no cortisone|
|Troedhan et al.||2011||RS||56 male and female||PSO, CRO: 21–52||50||50||1, 3, 5, 7 days||PSO: 46.84
|Conventional Ward incision||Clindamycin 300 mg 1 day preop.; no cortisone|
|Goyal et al.||2012||CCT||PSO, CRO: 24:16||PSO, CRO: 22–36 (29)||20||20||1, 3, 5, 7, and 15||PSO: 45
|Conventional Ward incision||Amoxicillin–clavulanic acid 625 mg 1 h preop.; no cortisone|
|Rullo et al.||2013||RCT||PSO, CRO: 20:32||PSO, CRO: 18–54 (26.2)||52||52||6 days||Simple extraction:
|Triangular incision||Amoxicillin 500 mg 1 day preop.; no cortisone|
|Piersanti et al.||2014||RCT||PSO: 6:4
|PSO, CRO: 22.4||10||10||7 days||PSO: 36.8
|Conventional Ward incision||Amoxicillin–clavulanic acid 2 g 1 h preop.; no cortisone|
|Mantovani et al.||2014||RCT||PSO: 59:41
|PSO, CRO: 24.02||100||100||7 days||PSO: 18.16
|Triangular incision||Amoxicillin–clavulanic acid 2 g 1 h preop.; no cortisone|
|Chang et al.||2014||RCT||PSO, CRO: 18:2||PSO, CRO: 17–29||20||20||NM||CRO: 75% adequate, 25% slightly longer
PSO: 80% adequate, 20% slightly longer
Prophylactic therapy, consisting of amoxicillin with clavulanic acid 2 g (1 h before surgery) or clindamycin 300 mg (1 day before surgery), were administered to all patients in six studies. In all studies, the surgical procedures were performed by the same surgeon and assistant, under local anaesthesia using adrenaline 1:100,000. Eight studies reported the incision type: seven studies used a triangular full thickness flap and one used a buccal full thickness flap. In the rotary instruments group, the osteotomy was performed with round burs fitted on a straight hand-piece and using plentiful irrigation with sterile physiological solution. The piezoelectric osteotomy was completed with the piezoelectric surgical ablator under cooling with sterile physiological solution. For both osteotomies, tooth sectioning was performed as necessary. The wound was closed with 3–0 silk. An ice pack was applied for 15 min every hour for 6 h after surgery. The sutures were removed 1 week later. No corticosteroids were given either pre- or postoperatively in any study. All patients received an antibiotic (amoxicillin 500 mg every 8 h for 7 days, starting the day before surgery), an anti-inflammatory/analgesic (ibuprofen 600 mg every 8 h for 4 days, starting after surgery), and an antiseptic (chlorhexidine 0.12%, three mouth rinses per day for 7 days, starting the day after surgery).
Risk of bias within studies
Concerning the quality assessment of the studies included, six showed a low risk of bias and three showed a moderate risk of bias. The scores are summarized in Table 2 .