Clinical Research
12-month Healing Rates after Endodontic
Therapy Using the Novel GentleWave System:
A Prospective Multicenter Clinical Study
Asgeir Sigurdsson, DDS, MS,* Randy W. Garland, DDS,† Khang T. Le, DDS,‡
and Stacey M. Woo, DDS, PhD§
Abstract
Introduction: This multicenter, prospective, nonsignificant risk clinical study evaluated healing rates for molars 12 months after endodontic therapy using the
GentleWave System (Sonendo, Inc, Laguna Hills, CA).
Methods: Eighty-nine patients needing endodontic
therapy who met the inclusion criteria consented for
this clinical study. All enrolled patients were treated
with a standardized protocol consisting of conservative access, shaping of canals to #20/.07, GentleWave
treatment, and warm vertical obturation. Six endodontists performed the clinical procedures and
follow-up evaluations. Preoperative, intraoperative,
and postoperative data were collected from the consented patients. Each patient was evaluated for clinical signs and symptoms. Two trained, blinded, and
independent evaluators scored the subject’s radiographs for signs of apical periodontitis using a periapical index. The teeth classified as healing or healed
were considered as a success and accounted for the
cumulative success rate of healing. Statistical analysis
was performed by using the Fisher exact test, Pearson
correlation, and multivariate logistic regression analyses of the preoperative prognostic factors at P
= .05. Results: Seventy-five teeth in 75 patients
were evaluated at 12 months with a follow-up rate
of 84.3%. The cumulative success of endodontic
therapy was 97.3%. The success rates of necrotic
and irreversible pulpitis were 92.9% and 98.4%,
respectively; 3.8% of the patients experienced moderate postoperative pain within 2 days and no incidence of pain at 14 days, 6 months, and 12
months of initial therapy. Ten prognostic factors
were identified using bivariate analyses. Using logistic analyses, the prognostic significant variable that
was directly correlated to healing was the preoperative presence of lesions (P = .026). Conclusions: In
this 12-month prospective multicenter clinical study, the GentleWave System showed
a high level of success after a 12-month follow-up. (J Endod 2016;42:1040–1048)
Key Words
GentleWave, healing rate, molar, multisonic ultracleaning, root canal treatment,
Sonendo
E
ndodontic therapy aims
Significance
to remove vital or
Although in vitro studies have shown promising renecrotic tissue and irritants
sults using the GentleWave System, it is ultimately
from the root canal sysin vivo studies that are needed to test the perfortem and enhance healing
mance and benefits of any endodontic procedure.
(1, 2). Hence, optimal
This prospective clinical study reports on 12 month
root canal cleaning and
outcomes where the patients were treated with the
disinfection are essential
GentleWave System. The study also shows that
to achieve faster healing
when patients are treated with the GentleWave
of periradicular tissue and
System, the results provide consistently favorable
successful endodontic theand predictable outcomes.
rapy (3). Identifying the
prognostic factors will
help clinicians predict the outcome of endodontic therapy (2).
Many etiologic factors affect the outcome of endodontic therapy (4). It is well
accepted that current cleaning and shaping procedures cannot reach all the intricacies
of the root canal system (5). As such, chemomechanical preparation and instrumentation do not completely eradicate the tissue or microbiota present in the anatomic
complexities of the root canal system (6).
Different irrigation techniques and devices have been developed to improve
the cleaning of the root canal system, including ultrasonic irrigation, negative
pressure irrigation, sonic irrigation, photon-induced photoacoustic streaming,
and laser technologies. However, none of these systems have been shown to predictably provide root canals completely free of debris and biofilms. In addition,
certain concerns regarding the safety of some of the methods have been expressed (7–10). The positive pressure induced by conventional needle
syringe configurations and photon-induced photoacoustic streaming may result
in irrigant extrusion to the periapex, which may lead to severe patient trauma
and pain (7). Tissue debris and biofilm cleaning with even contemporary
From the *Department of Endodontics, New York University College of Dentistry, New York, New York; †Private Practice, Encinitas, California; ‡Private Practice,
Santa Ana, California; and §Private Practice, Whittier, California.
Address requests for reprints to Dr Asgeir Sigurdsson, Department of Endodontics, New York University College of Dentistry, 345 East 24 Street, New York,
NY 10010. E-mail address: [email protected]
0099-2399/$ - see front matter
Copyright ª 2016 American Association of Endodontists.
http://dx.doi.org/10.1016/j.joen.2016.04.017
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Sigurdsson et al.
JOE — Volume 42, Number 7, July 2016
Clinical Research
techniques is often insufficient to provide an environment conducive for long-term success (2, 7–10). Furthermore, most of these
techniques require increased dentin removal from the roots to
facilitate the penetration of irrigants into the root canal system,
which may weaken the remaining tooth and affect long-term healing rates (2, 11).
The GentleWave System (Sonendo, Inc, Laguna Hills, CA),
which consists of a console and a Treatment Instrument (TI),
has been developed as a novel approach to clean and disinfect
the root canal system (12–16). Haapasalo et al (12) showed
that the tissue dissolution efficacy of the GentleWave System is at
least 8 times greater than that of conventional irrigation systems,
ultrasonic irrigation, and a commercially available negative pressure system. Ma et al (13) performed micro–computed tomographic analysis and compared the cleaning efficiency of the
GentleWave System with passive ultrasonic system and conventional needle irrigation. The authors showed that in the apical
thirds of mesial canals, conventional needle irrigation configuration removed 47.82% 16.36%, passive ultrasonic irrigation
removed 61.66% 25.54%, and the GentleWave system removed
100% of calcium hydroxide (Ca[OH]2) (significantly more Ca
[OH]2, P < .05), respectively. However, these studies were performed in vitro using extracted teeth. Although in vitro studies
have shown promising results using the GentleWave System with
regard to canal cleanliness and system safety, it is ultimately the
in vivo studies that are needed to verify the higher-level evidence
of the performance and benefits of any endodontic therapy strategy
or device.
Recently, a 6-month healing study by Sigurdsson et al (17) showed
that the success of endodontic therapy after using the GentleWave System was 97.4%. The 2 prognostic significant variables that were directly
correlated to healing were the preoperative presence of periapical
lesions and the number of treatment visits.
Even though the healing rates were high at the 6-month
follow-up, we were interested in observing the healing rates at a
12-month follow-up. It was hypothesized that the healing rates
observed at 12 months would decrease when compared with those
at 6 months. The objective of this study was to account for the
healing rates for a 12-month follow-up period of in vivo cases
treated by the GentleWave System. In addition, the aim of the study
was to provide information on the preoperative, intraoperative, and
postoperative factors that could influence the healing rate when assessed at 12 months.
Materials and Methods
Study Cohort
The inception cohort was composed of 89 patients with 89
teeth, 1 tooth per patient, who were referred for endodontic treatment to 1 of 6 private endodontic clinics in Southern California.
The study protocol for the multicenter, prospective, nonsignificant
risk clinical study was approved by an institutional review board,
and the study was performed in accordance with the Declaration
of Helsinki. All patients signed an informed consent form before
being accepted into the study. The clinical study evaluated the
healing rates of endodontic treatments performed using the
GentleWave System. The purpose of the study was explained to
the patients, and written informed consent was obtained. All the
subjects adhered to previously defined inclusion and exclusion
criteria as stated in Table 1. After initiation of the study, the subjects were given the opportunity to withdraw.
Intervention
Six endodontists from Southern California participated as investigators in the multicenter, prospective, nonsignificant risk clinical study
to assess the long-term performance of the GentleWave System (PURE).
The investigators were trained to use the GentleWave System and performed a standardized treatment procedure at their independent private clinical sites. Using standard coded data sheets, the collected
redacted clinical and radiographic data pertaining to each treated tooth
before (preoperative), during (intraoperative), and at 3-month intervals up to 12 months after (postoperative) the initial treatment were
recorded. The data were directly transferred to a database.
The standard coded sheets used subject initials and a corresponding subject identification number. The investigators ensured that subject
names and data were kept confidential and that subject identity was
revealed only when patient confidentiality would compromise either
the safety of the patient or the study.
Preoperative Data Collection
Before treatment, the patients were clinically examined, and
radiographs were taken. The clinical examination involved an update
on the medical and dental history and an intraoral evaluation that
included periodontal pocket depths, mobility testing, the presence
and extent of swelling and soft tissue lesions, percussion, and palpation. Pulpal and periradicular diagnosis was completed and recorded.
TABLE 1. The PURE Clinical Study Inclusion and Exclusion Criteria
Inclusion criteria
Exclusion criteria
1. The patient is 18 to 75 years of age
2. The subject tooth is indicated for root
canal treatment
3. The subject tooth is a 1st or 2nd molar
4. Signed informed consent form
1. Subject tooth having previous or attempted pulpotomy, pulpectomy, or root canal
therapy
2. Immunocompromised patients (ie, corticosteroid usage)
3. Any known infectious diseases (eg, human immunodeficiency virus, hepatitis B,
hepatitis C, tuberculosis, or prion)
4. History of cancer within the oral-maxillofacial region
5. History of cancer within the last 2 years
6. History of head and/or neck radiation therapy
7. Subject tooth with a mobility score $2
8. Subject tooth with a periodontal pocket depth $6 mm
9. Subject tooth with open or incompletely formed root apices
10. Subject tooth that requires a post
11. Subject tooth with a vertical fracture or horizontal fracture extending below the
cementoenamel junction of the tooth
12. The 2 adjacent teeth in direct contact with the subject tooth requiring root canal
therapy
13. Nonodontogenic facial pain
JOE — Volume 42, Number 7, July 2016
Healing Rates and the GentleWave System
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Clinical Research
A parallel periapical radiograph was used for independent periapical
index score analyses.
Treatment Procedure
The patient was anesthetized per standard techniques; the type of
injection was left up to the discretion of the endodontist. The tooth was
isolated with a dental dam. Caries and existing restoration were removed.
Missing tooth structures were built up, and a conservative straight-line
access was performed. Patency was confirmed with #10 and
#15 K-type hand files (MANI K files, Utsunomiya, Japan), and the working
length (defined as the distance to the apical constriction or approximately
0.5–1 mm from the radiographic apex) was estimated using an electronic
apex locator and confirmed with radiographs. The coronal region was
not enlarged. Teeth were instrumented with a standardized minimal
instrumentation protocol that included the use of hand K-files up to
size ISO #20 and ProTaper file F1 (#20/.07; Dentsply, Tulsa Dental Specialties, Tulsa, OK) regardless of the initial canal size. In between each
instrument size, 1 mL saline was used to flush any dentinal debris using
a 30-G needle. The GentleWave TI was then placed on the endodontic access opening of the molars (17). GentleWave therapy was performed as
discussed previously (13–17). Briefly, the treatment consisted of up to
3% sodium hypochlorite (NaOCl; Clorox, Oakland, CA), water rinse,
8% ethylenediamineteacid (EDTA; Vista, Racine, WI), and a final rinse
with distilled water. Canals were subsequently dried with absorbent
paper points. The dried canals were obturated using warm vertical
technique with gutta-percha and AH Plus sealer (Dentsply Tulsa Dental
Specialties, Tulsa, OK). The pulp chamber floor was sealed with bonded
composite, and the patients were referred to a general dentist for final
post treatment restoration.
Intraoperative Data Collection
During the treatment, calcification, type of obturation and any
deviation, the root filling length, sealer extrusion if any, coronal seal,
and any complication during the treatment were documented.
Postoperative Data Collection
Post-treatment symptoms were assessed 2, 7, and 14 days after
treatment using the visual analog scale (0–10) to rank the level of experienced pain (18). Each investigator completed a follow-up assessment
every 3 months for patients enrolled at their respective clinical site.
Assessments were standardized and included both clinical and radiographic examinations. The clinical examination involved an update
on the medical and dental history and an intraoral evaluation that
included periodontal pocket depths, mobility testing, the presence
and extent of swelling and soft tissue lesions, percussion, and palpation.
Outcome Measures and Criteria
Teeth were assessed for healing using a composite end point that
included both clinical and radiographic components. Clinical signs and
symptoms, as discussed previously, were used for assessing the clinical
component. Periapical index (PAI) scoring was used to assess the tooth
using a periapical radiograph. The scores ranged from 1 (for normal
periradicular tissue) to 5 (severe periodontitis with exacerbating
features) (19).
Based on clinical signs/symptoms and PAI scores, teeth were
classified as healed, healing, or diseased (19, 20). In summary, the
diagnosed teeth were classified as follows:
1. Healed: Clinical normalcy other than tenderness to percussion
accompanied by radiographic PAI scores of 1 or 2
1042
Sigurdsson et al.
2. Healing: Clinical normalcy other than tenderness to percussion
accompanied by a reduction in the size of the periradicular lesion
or a reduction in the PAI score
3. Diseased: The presence of clinical signs and symptoms accompanied by a radiographic PAI score of 3 or higher or an increase in
the size of the periradicular lesion or an increase in the PAI score
The teeth classified as healed or healing were considered as successes. The combined success of these cases was termed as the success
of the endodontic therapy.
Calibration of Evaluators
The radiographs were blindly evaluated by 2 experienced endodontists. The images were coded and provided to the evaluators after
being randomized between different patients. Before evaluating the
images, the 2 examiners evaluated a series of radiographs independent
of the study sample that represented a wide range of periapical lesions
to account for interobserver reliability (19). The Cohen kappa score
was calculated. The exercise was independently performed 3 times to
increase the calibration.
Evaluating Radiographs
In general, each visible root on the radiographs was assigned a PAI
score. The highest PAI score for all the roots for a given tooth was
considered as the PAI score of the tooth. This PAI score was used for
further statistical evaluation. After the independent scoring sessions,
the examiners reached an agreement on the PAI scores if the scores
of their independent evaluations differed. The consensus scores for
all the radiograph images were considered as the final score and
were used for statistical analysis.
Statistical Analysis
All the tests were performed as 2 tailed with SPSS 15.0 (SPSS Inc,
Chicago, IL) at a significance level of 5%. When analyzing, the event of
interest was the success of endodontic therapy. A total of 34 variables
were investigated. Univariate and bivariate analyses with percentage of
frequencies and P values were generated to characterize the study
cohort. The bivariate analysis included outcome associations with
preoperative, intraoperative, and postoperative variables (the Fisher
exact test) to identify variables of interest. Pearson coefficients were
calculated to determine any correlation between these variables to
categorize potential outcome predictors. Finally, a multivariate analysis using logistic regression models was used to detect the significant
outcome predictors. The odds ratios (ORs) and confidence intervals
(CI) were calculated.
Results
Accounting for Statistical Power
A post hoc power analysis was performed using GPower (University of Dsseldorf, Dsseldorf, Germany) to ensure that results attained
adequate power. The power (1
b) was equal to 0.98 when
a = 0.05 and analysis parameters were set to a 2-tailed t test, hence
confirming adequate power with a sample size of N = 89.
Examination Reliability
The achieved Cohen kappa score for intraobserver agreement
between the independent reviewers was 0.73–0.75, indicating a modest
to good agreement (19).
JOE — Volume 42, Number 7, July 2016
Clinical Research
TABLE 2. Bivariate Analyses: Unadjusted Effects of Preoperative, Intraoperative, and Postoperative Tooth Factors Compared with the Event of Healing
Variables
Preoperative
Patients
Age
Sex
Oral hygiene
Diabetic history
Cardiovascular history
Tobacco use
Pain medication
Molars
Molars
Clinical symptoms
Probing depth
Mobility
Sinus tract
Periradicular diagnosis
Pulp diagnosis
PAI scores
Intraoperative
Number of visits
Number of roots
Final apical diameter
Calcification
Obturation type
Root filling length
Sealer extrusion
Coronal seal
Postoperative: 12-month follow-up
Patients
Post
Restoration
Crown and bite issues
Clinical symptoms
VAS
Percussion
Periodontal diagnosis
Palpation
Swelling
Soft tissue lesion
Probing depth
Mobility
Sinus tract
Periradicular diagnosis
PAI scores
Healing rate
Criteria
#35
Male
Good/fair
Maxillary
Right
#4
5–6
Present
Present
Normal periradicular tissue
Asymptomatic apical periodontitis
Chronic apical abscess
Acute apical abscess
Symptomatic apical periodontitis
Pulpal necrosis
Irreversible pulpitis
$3
Single
n (%)
89 (100)
29 (33)
39 (43.8)
77 (86.5)
5 (5.6)
7 (7.9)
2 (2.2)
36 (40.4)
29 (33.0)
39 (44.3)
58 (65.2)
83 (93)
6 (7)
3 (3.4)
4 (4.4)
27 (30.3)
6 (6.7)
3 (3.4)
3 (3.4)
50 (56.2)
17 (19.1)
72 (89.9)
20 (22.5)
0.2 mm
Coronal
Middle
Apical
Warm vertical compaction
Short: >2 mm above the
Flush: within 2 mm of the apex
Long: >2 mm below the apex
Present
Present
82 (92.1)
313 (100)
313 (100)
24 (7.7)
26 (8.3)
44 (14.1)
313 (100)
19 (6.1)
294 (93.9)
0 (0)
126 (40.3)
89 (100)
Absent
Temporary filing material
Temporary crown
Permanent crown
Absent
Present
Present
Present
Present
Present
Present
Present
#4
5–7
$8
Absent
Present
Normal periradicular tissue
Healing within normal limits
Asymptomatic apical periodontitis
Chronic apical abscess
Acute apical abscess
Symptomatic apical periodontitis
$3
Success
Healed
Healing
Diseased
75 (84.3)
74 (98.7)
5 (6.7)
31 (41.3)
39 (52.0)
72 (93.5)
8 (10.7)
1 (100)
6 (8)
3 (4)
2 (2.7)
0 (0)
0 (0)
73 (97.3)
2 (2.7)
0 (0)
75 (100)
0 (0)
70 (93.3)
2 (2.7)
2 (2.7)
0 (0)
0 (0)
1 (1.3)
2 (2.67)
73 (97.3)
69 (92)
4 (5.3)
2 (2.7)
P value
NA
.189
NA
.398
.651
.776
.451
.544
.047
.376
.121
.664
.224
.289
.062
.055
.026
.576
NA
NA
.986
NA
.88
.631
NA
NA
NA
.642
NA
0
.0000214
.0087
0
.005
0
0
.366
0
0
0
0
NA, not applicable; PAI, periapical index; VAS, visual analog scale.
Bold values are significant at the .05 level (2 tailed).
JOE — Volume 42, Number 7, July 2016
Healing Rates and the GentleWave System
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Clinical Research
Figure 1. Representative cone-beam computed tomographic images showing the (A) distobuccal and mesiobuccal roots and the (B) palatal root of subject tooth #2.
The figure shows the presence of a periapical lesion for all the roots before endodontic treatment using the GentleWave System. The roots were shaped to #20/.07 and
were obturated with gutta-percha and AH Plus using warm vertical technique. C and D show the healing of the periapical lesion 12 months after GentleWave treatment.
Medical History, Recall, and Healing
Eighty-nine patients met the inclusion criteria and consented to
participate in the clinical study. Of the 89 patients, 43.8% were male
and 56.2% were female; 5.6% and 7.9% had a history of diabetes
and cardiovascular disease, respectively, whereas 12.1% had a history
of tobacco use. Oral hygiene of the study cohort was good (67.4%) or
fair (32.6%). Seventy-five patients (84.3%) returned for the 12-month
follow-up. In total, 69 teeth were classified as healed, 4 teeth were classified as healing, and 2 were classified as diseased at the 12-month
follow-up. These results are summarized in Table 2.
Figure 1A–D shows representative cone-beam computed tomographic images of a case that was treated with the GentleWave System.
The mesiobuccal roots, distobuccal roots, and palatal root show the
presence of a periapical lesion before the endodontic treatment with
the GentleWave System. The healing of the periapical lesions is observed
12 months after GentleWave treatment. Figure 2A and B shows representative radiographs of a case that was treated with the GentleWave System. The mesial root shows the presence of a periapical lesion before
the endodontic treatment. Also in Figure 2, an isthmus is apparent
between the mesiobuccal and mesiolingual canals. The healing of the
Figure 2. Representative radiographs showing the mesial and distal root of subject tooth #19. A shows the presence of a periapical lesion for the mesial roots
before endodontic treatment using the GentleWave System. The roots were shaped to #20/.07 and were obturated with gutta-percha and AH Plus using warm vertical
technique. B shows the healing of the periapical lesion 3 months, 6 months, 9 months, and 12 months after GentleWave treatment.
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Sigurdsson et al.
JOE — Volume 42, Number 7, July 2016
Clinical Research
TABLE 3. Bivariate Analysis: Confidence Intervals and Pearson Correlation of Selected Unweighted Variables Associated with the Outcome (N = 75)
Variable
Sex
Female
Male
Age
#35
>35
Molar
Maxillary
Mandibular
Necrotic pulp
Preoperative sinus tract
Preoperative mobility
Preoperative PAI score ($3)
Intraoperative no. of visits (single)
Postoperative PAI score ($3)
Postoperative palpation
N
% Success
42
33
92.9
90.9
29
48
93.1
100
29
46
14
4
3
18
71
2
2
100
87.0
100
75
66.7
100
97
0
0
95% CI
Pearson correlation
NA
0.036
0.208–0.224
0.152
0.071–0.081
0.234*
NA
0.283–0.301
0.220 to 0.236
0.122–0.135
NA
0.004–0.008
0.004–0.008
0.070
0.149
0.191
0.193*
0.070
0.561†
0.561†
CI, confidence interval; NA, not applicable; PAI, periapical index.
Bold values are significant at the *0.05 level (2 tailed) and the †0.01 level (2 tailed).
periapical lesions for both the cases in Figure 1 and Figure 2 is observed
12 months after GentleWave treatment.
Identifying Predictor Factors
Table 2 also provides an overview of the preoperative, intraoperative, and postoperative factors.
Preoperative Factors. Two preoperative factors had a significant
difference when compared with healing. The type of molars (ie, maxillary vs mandibular molars) and the PAI scores were significantly
different with P values of .047 and .026, respectively. The P values
for age and oral hygiene were .669 and .34, respectively. The following
factors were also analyzed: periradicular diagnosis (P = .062), pulpal
diagnosis (P = .055), pocket depth (P = .664), preoperative clinical
symptoms (P = .121), and right versus left molars (P = .376).
Interoperative Factors. None of the intraoperative factors had a
significant difference when compared with the outcome of the therapy;
92.1% of the 89 enrolled patients were treated in a single-visit appointment. The P value for the intraoperative factor related to single- versus
2-appointment endodontic therapy was .576. Calcification (P = .986)
and root canal filling length (P = .88) showed no significant difference
in regard to healing.
Postoperative Factors. At the 12-month follow-up, data were
collected similar to those at the preoperative visit. Postoperative clinical
signs and symptoms including palpation (P = 0), PAI score (P = 0), and
visual analog scale (P = .000214) were significantly different. Pocket
depth (P = .366), percussion (P = .0087), and type of restoration
(P = .642) showed no significant difference.
Logistic Regression Model
Furthermore, as shown in Table 3, the Pearson correlations
showed that the preoperative PAI score (r = 0.193, significant), the
type of the molar maxillary/mandibular (r = 0.234, significant), the
postoperative PAI score (r = 0.561, very significant), and postoperative palpation (r = 0.561, very significant) correlated with healing.
These 4 pre- and postoperative predictors were used for predicting the
healing of periradicular lesions.
Logistic regression models of the pooled sample (Table 4) revealed
that the healing rates are associated with the 2 preoperative predictors:
preoperative PAI (OR = 4.545; 95% CI, 0.788–26.23) and the type of
molar (OR = 0.411; 95% CI, 0.066–2.567). The Hosmer and Lemeshow
test showed that the predictive models (Table 4) are good fits.
JOE — Volume 42, Number 7, July 2016
Temporal Response
Figure 3 shows the time-dependent healing rates for the 3-month,
6-month, and 12-month recall periods. Sixty-four patients (72%)
showed up for all 3 recalls. The success of endodontic therapy for these
64 patients was 92%, 97%, and 98%, respectively.
Discussion
This prospective study assessed the outcome of an endodontic
treatment at the 12-month follow-up. The patients were referred from
private practices and represent the general patient population. All the
treatments were performed by experienced clinicians. The treatment
procedures and the recording of the data followed a standardized
protocol established before the treatments were initiated.
Furthermore, all the root canals were instrumented to #20/.07.
In the present study, a standard warm vertical obturation technique
was used to fill the root canal system after GentleWave treatment.
Previously, in vitro studies were performed with the GentleWave
System after the root canal system was shaped to #15/.04 only.
These results provide an impetus to potentially reduce the instrumentation of the root canal system and hence preserve the root
structure when using the GentleWave System in vivo. The limiting
factor of further reducing the instrumentation is identifying an
optimal obturation technique.
In the present study, the 12-month recall rate was 84.3%. This high
recall rate might have been possible as a result of elaborate efforts of the
clinicians and their staff to encourage patients to attend the follow-up
examination including offering monetary incentives (20). Also, the
participation of private clinics might have added to the increased recall
rates.
TABLE 4. Logistic Regression Model Identifying Significant Predictors of
Success after Initial Root Canal Treatment (N = 75) with Preoperative
Periapical Index and the Type of Molar as Prognostic Variables
Prognostic variable
Preoperative PAI score
Type of molar
(maxillary versus
mandibular)
OR estimate
of healing
95% CI
P
value
4.545
0.411
0.788–26.23
0.066–2.567
.090
.341
CI, confidence interval; OR, odds ratio; PAI, periapical index.
P value is significant at the .05 level.
Healing Rates and the GentleWave System
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Clinical Research
Healing Rates
The goal of an endodontic therapy is to return the involved teeth to
the best feasible state of health and function as soon as possible without
surgical intervention (1, 2, 21). Some authors recommend that cases
with incomplete healing should be followed for a longer period of
time. However, Jesslen et al (22) showed that 95% of the cases at the
5-year follow-up could be predicted at the 12-month follow-up. In
the present study, the cases were followed up for 12 months.
Figure 3. The graph shows the success of the GentleWave therapy procedure
at 3 months, 6 months, and 12 months follow-up times.
Furthermore, the examiners who analyzed the radiographs were
experienced clinicians. They were blinded and calibrated. This ensured
that the direct comparison of related radiographs was avoided (eg, preoperative and postoperative and recall x-rays). One limitation of the radiographs acquired for each tooth was not using a custom made bite
stent because the process was cumbersome for the clinicians. However,
the radiographs were obtained in 3 standard views: parallel, distal, and
mesial views. To maintain consistency, only the parallel views were
analyzed to provide a PAI score for a root.
Understanding the GentleWave System
The GentleWave System aims to clean the root canal system
through generation and propagation of various physiochemical mechanisms including a broad spectrum of sound waves (ie, the multisonic
waves). Multisonic waves are initiated at the tip of the GentleWave TI,
which is positioned inside the pulp chamber of the root canal system.
A stream of treatment solution is delivered from the tip of the TI
into the pulp chamber while excess fluid is simultaneously removed
from the chamber by the built-in vented suction through the TI into a
waste canister inside the console. According to the manufacturer,
upon initiation of flow through the treatment tip of the TI, the stream
of the treatment fluid interacts with the stationary fluid inside the
pulp chamber creating a strong shear force, which causes hydrodynamic cavitation in the form of a cavitation cloud. The continuous formation and implosion of thousands of microbubbles inside the
cavitation cloud generate an acoustic field with broadband frequency
spectrum that travels through the fluid into the entire root canal system.
Throughout the treatment, the fluid starts with a maximum of 3% NaOCl
and changes to a maximum of 8% EDTA with a water rinse in between.
The treatment tip of the TI is designed to deflect the stream of treatment
fluid in such a way to generate a flow over the orifices of the root canals.
This flow induces gentle vortical flow as well as a slight negative pressure
within the root canal system. The energy and the vortical flow dissipate
as they travel apically into the root canal system. The treatment fluid is
degassed to minimize the energy loss and also to ensure energized treatment fluid is delivered throughout the root canal system. Each fluid at
equilibrium contains a certain amount of dissolved gas.
The interplay of the multisonic energy, vortical fluid dynamics, and
chemistry of the treatment fluid result in enhanced dissolution and the
removal of organic matter (ie, pulp tissue and biofilm from the root
canal system). The treatment tip is positioned inside the pulp chamber
and is not required to enter canals or orifices, therefore allowing for
minimal instrumentation of the root canals and saving the integrity
and strength of the tooth.
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Sigurdsson et al.
Comparison with Previous Work
Previous clinical studies were performed with different endodontic techniques and show various healing rates at 12-month
follow-ups (2, 23–25). Murphy et al (23) retrospectively quantified
the rate of healing of periapical radiolucencies after nonsurgical endodontic therapy as 70.6%. The technique used was not mentioned. Penesis et al (24), in the clinical trial, showed that 67% of the treated
teeth were healed. In the clinical trial, the canals were irrigated
with 5.25% NaOCl between instrumentation, 5 mL 17% EDTA for
1 minute, and a final irrigation with 5.25% NaOCl. In another study
by Pettiette et al (25), 80% of the treatments were successful when
nickel-titanium files were used, and 43% were successful when K-files
were used. In this study, 0.5% NaOCl was used in between biomechanical preparation. Also, the infected canals were treated in 2-visit
appointments after medicating them with calcium hydroxide. Furthermore, based on random effects meta-analyses, Ng et al (2) revealed
the pooled weighted success rates of healing to be 67.7%. A variable
concentration of NaOCl was used. In addition, other irrigants such as
10% povidone-iodine, 0.2% chlorhexidine gluconate, 17% EDTA, or
Smear-Clear (Kerr-Dental, Kerr, Orange, CA) were used. Needle syringe irrigation was performed, with or without supplementation by
ultrasonic agitation. For 2-visit appointments, calcium hydroxide
and barium sulfate were the standard interappointment medicaments.
The present study showed that the success of endodontic therapy
when the patients were treated with the GentleWave System at 12
months was 97.3% (75 patients). The null hypothesis that the healing
rates will reduce after 6 months was rejected.
It is well-known that in conventional endodontics, disinfection of
the apical root canal might be facilitated using ultrasonic tips, especially
in canal anastomoses (26). The exhibited healing rate of 97.3% in this
clinical study implies efficient eradication of tissue debris, biofilm, and
bacteria from the root canal system. Previously, it was shown in vitro
that 97.2% of tissue debris in the apical and middle region of mesial
roots of mandibular molars, including isthmi, was removed by the
GentleWave System using histologic analyses (14).
Furthermore, the healing rates of the present clinical study after 3
months, 6 months, and 12 months was monitored. As shown in Figure 3,
of particular interest is the consistency of the healing rate from the
3-month time period.
Accounting for Sex and Type of Molar
Epidemiologic studies of chronic orofacial pain show that women
were found to be approximately 4 times more likely than men to develop
chronic pain (27). In contrast, other studies did not find sex differences
in prevalence across various pressures of orofacial pain (28). In the
present study, the relationship of sex to the outcome of the endodontic
therapy remains equivocal. Even though mandibular teeth are indicated
to be a prognostic factor when compared with healing, it is important to
note that the number of maxillary teeth were only 33% of the total
molars treated endodontically. Hence, the correlation of success of
healing to mandibular molars is noncontributory.
JOE — Volume 42, Number 7, July 2016
Clinical Research
Single Visit Versus Multiple Visits
In recent years, single-visit appointment regimens have reported
numerous advantages including better patient acceptance, reduction
of the interappointment infection risks, time savings, and lower cost
(29, 30). Trope et al (30) showed that the healing rate of single-visit
endodontic therapy was 64%. In the present study, a total of 75 teeth
were treated in a single visit with 97.2% showing overall success. Of
the 75 teeth, 14 teeth were necrotic with 92.9% showing success,
and 61 teeth were diagnosed as pulpitis with 98.4% showing success.
Incidence of Pain
Unfortunately, postoperative pain is common after endodontic
therapy (27, 31, 32). The incidence of postoperative pain was
reported to range from 3%–58% (31). According to Ng et al (32),
12% of the patients experience severe pain within 2 days after therapy.
Polycarpou et al (27) showed that 12% of the patients presented with
persistent pain despite successful endodontic therapy. Additionally, significant postoperative pain has been reported after single-visit root canal therapies and for teeth having necrotic pulp (15, 31, 32). On the
contrary, in the present study using the GentleWave System,
postoperative pain was not correlated with a single-visit appointment
or necrotic teeth. Moreover, no patients (visual analog scale score
$9) experienced severe pain, whereas only 3.8% of the patients experienced moderate pain (visual analog scale score = 7–8) within 2 days
after the initial therapy. After 14 days, 6 months, and 12 months of initial
therapy, no patients experienced any pain. These results are in agreement with those reported in the study by Gondim et al (33) in which
the authors show that the negative pressure system resulted in significantly less postoperative pain. Interestingly, Charara et al (14)
compared the GentleWave System with another commercially available
negative pressure system and showed that both these negative pressure
systems led to zero extrusion to the periapical space in vitro. Conducive
to this finding, the present study shows a 3-fold decrease in the patients
who experienced pain 2 days after the initial therapy when compared
with preoperative scores.
Preserving Tooth Structure
A fundamental factor that determines prognosis is the preservation
of dentin structure in its native form (34, 35). It is noteworthy that the
present in vivo study was performed to exhibit minimal endodontics by
using methods that minimally remove dentin structure while accessing
the teeth and shaping the root canals. Previous studies showed that even
when molars were shaped to #15/.04 in vitro and cleaned using the
GentleWave System, a statistically significant clean root canal system
was observed (13–15). However, the present clinical study used
shaping to #20/.07 in order to facilitate standard obturation
techniques. The GentleWave System TI is placed in the pulp chamber
of the molars. Because the TI does not have to enter the roots, the
GentleWave System eliminates the need for shaping the roots using
large instrumentation, hence practicing a minimal endodontic
technique with dentinal conservation.
In the present study, longer follow-ups can improve the statistical investigation into prognostic factors for predicting tooth healing
after root canal therapy. Other in vivo studies are also needed to
compare the healing rates acquired by the GentleWave System with
those obtained with other conventional and contemporary endodontic
techniques.
In conclusion, the molars cleaned with the GentleWave System
showed a high level of success of endodontic therapy within 12 months
of the initial treatment. The molars treated with the GentleWave System
resulted in low reports of postoperative pain. The therapy outcomes
JOE — Volume 42, Number 7, July 2016
were predictable within a few months. This study shows that the system
allows for fast and predictable healing rates that may lead to improved
prognosis and patient care.
Acknowledgments
The authors acknowledge Dr Kimberly McLachlan, Dr Shahriar
A. Rassoulian, and Dr Farah Abbassi as participating clinicians in
the PURE clinical study. The authors would also like to thank Dr
Markus Haapasalo for his insightful comments on the manuscript.
The PURE clinical study is funded by Sonendo Inc.
Asgeir Sigurdsson and Randy Garland are consultants for Sonendo Inc.
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