Buffered vs. Unbuffered Local Anesthesia in Mandibular Molars Diagnosed With Symptomatic Irreversible Pulpitis: A Controlled, Randomized Double-blind Study
Phase: PHASE4
Conditions: Symptomatic Irreversible Pulpitis
Sponsor: Indiana University

 
 
BUFFERED VS. UNBUFFERED LOCAL ANESTHESIA IN MANDIBULAR MOLARS 
DIAGNOSED WITH SYMPTOMATIC IRREVERSIBLE PULPITIS: A CONTROLLED, 
RANDOMIZED, DOUBLE-BLIND STUDY 
 
NCT05227300 
 
 
06/30/2022 
 
 
 
 
 
 
 
 
 
 
 
 
 

PRIMARY MATERIALS 
 
2% lidocaine with 1:100,000 epinephrine (Septodont Inc, New Castle, DE) was the only 
local anesthetic used in our study. A standard dental cartridge of 2% lidocaine w/ 1:100,000 
epinephrine contains 1.8mL of solution, and the adult maximum recommended dose equates to 
500mg (3.3mg/lb or 13.8 cartridges). For reasons of this study, we used a maximum of 3 total 
cartridges (5.4mL or 108mg) of 2% lidocaine w/ 1:100,000 epinephrine as the standard 
anesthetic dosage. The Onset 8.4% Sodium Bicarbonate buffering system is marketed by FDA-
approved Onpharma (Carson City, NV) that recommends its concurrent use with 2% lidocaine 
w/ 1:100k epi. Aside from the sodium bicarbonate buffer itself, Onpharma offers the Onset 
Mixing Pen along with an Onset Cartridge Connector to properly formulate the buffered local 
anesthetic solution. The Onpharma Onset mixing protocol was incorporated to properly prepare 
the buffered 2% lidocaine w/ 1:100,000 epinephrine cartridges. Vitality Scanner 2006 (Vitality 
Scanner 2006; SybronEndo, Orange, CA) is marketed and sold by Kerr Dental, and was used to 
confirm pulpal anesthesia via Electric Pulp Testing (EPT). Endo-Ice (1,1,1,2 tetrafluoroethane; 
Hygenic Corp, Akron, OH) was used to initially confirm vitality and a diagnosis of symptomatic 
irreversible pulpitis. 
 
 
VERIFICATION OF BUFFERING CAPACITY 
 
To verify the advertised buffering capacity of an Onset Sodium Bicarbonate Cartridge, a 
pilot study using 2% lidocaine w/ 1:100k epi with and without an added buffer was completed. 
Both pH strips (Lab Rat Supplies, https://www.labrat-supplies.com) and a calibrated digital pH 
meter (Dr. meter, https://drmeter.com) were used to measure the pH of 2% lidocaine with 1:100k 

epinephrine initially. Following Onpharma’s Onset directions for use, 0.18mL of sodium 
bicarbonate buffer was added to a 1.8mL cartridge of 2% lidocaine with 1:100k epinephrine. 
This quantity of added buffer is commonly suggested by the manufacturer, and a historically 
recommended 10% ratio of sodium bicarbonate buffer to local anesthetic. The respective pH of 
each anesthetic group was recorded using each company’s directions for use. Using the pH 
strips, we were able to observe that the 8.4% sodium bicarbonate buffer produced a pH between 
8 and 9, while the calibrated digital pH meter indicated a reading of 8.08. Using the pH strips, 
standard 2% lidocaine w/ 1:100k epi had a pH between 4 and 5, and 2% lidocaine w/ 1:100k epi 
plus 0.18mL of added buffer had a pH between 7 and 8. The digital pH meter produced a reading 
of 4.35 for standard 2% lidocaine w/ 1:100k epi [94], and a pH of 7.34 for 2% lidocaine w/ 
1:100k epi plus 0.18mL of added buffer (no precipitate ever formed). Ultimately, we were able 
to independently verify that the buffering capacity of Onpharma’s Onset sodium bicarbonate 
buffer system is as advertised using 2 different method. 
 
INCLUSION CRITERIA 
To participate, subjects must be between the ages of 18 and 80 years old, have the ability 
and willingness to independently consent to treatment and study participation. They must have 
an uncomplicated medical history (ASA I and II), not be pregnant, and have no allergies to local 
anesthetics/sulfites (confirmed or self-reported). Due to concerns about plasma half-life 
concentrations, they must not be taking any medications that may affect the proper assessment of 
the anesthetic (no acetaminophen or short-acting NSAIDs such as ibuprofen within the previous 
6 hours [96] [97]; no long-acting NSAIDs such as naproxen within the previous 16 hours). They 
must not require nitrous oxide during treatment, and the injection area should appear healthy 

with no other pre-existing conditions or infections that may compromise an accurate collection 
of data. Since a localized periodontal examination is a routine portion of the endodontic 
examination, the potential presence of periodontal disease will not interfere in making a proper 
endodontic diagnosis. Subjects also must be experiencing signs of irreversible pulpitis (an 
exaggerated response to cold that lingers longer than 10 seconds) in a mandibular molar at the 
time of conducting the study. 
 
EXCLUSION CRITERIA 
No subjects will have a negative response to cold in the proposed treatment tooth. Also, 
no subject may have a radiographic periradicular pathosis more advanced than a widened 
periodontal ligament or have an intraoral swelling. 
 
RECRUITMENT AND ENROLLMENT OF EXPERIMENTAL SUBJECTS 
Potential research subjects were pooled from patients scheduled to receive an endodontic 
evaluation and/or a non-surgical root canal therapy (NSRCT) in the Graduate Endodontic clinic 
at Indiana University School of Dentistry. All 7 endodontic residents were eligible to screen, 
diagnose, explain the study goals, and consent patients presenting to the graduate clinic with 
symptomatic irreversible pulpitis of a mandibular molar. It is important to note that a general 
script was provided to each endodontic resident outlining key points to discuss with prospective 
study participants to establish some uniformity in the consenting process and calibration of 
residents. Each prospective study participant was explicitly made aware that using 2% lidocaine 

w/ 1:100k epi is a standard anesthetic option in endodontic treatment regardless of their 
participation in the research study and the addition of a sodium bicarbonate buffer would not 
lead to a decrease in its efficacy. Participants were further informed that the addition of the 
buffer would either have no effect or actually improve the efficacy of a standard, customary local 
anesthetic.  
If an endodontic resident other than the student researcher made a relevant diagnosis, all 
inclusion/exclusion criteria were respected, and the patient consented to both an NSRCT and 
participating in the study, then the student researcher was notified. Once the student researcher 
confirmed all pre-requisites and answered any questions, a trained research assistant prepared a 
maximum of 3 cartridges of the respective local anesthetic formulation as determined by the 
randomization scheme immediately prior to the planned administration. A professional 
statistician helped provide a two-product randomization scheme that randomized each of the 
potential 60 subjects on the order of their entry into the study. Only the blinded student 
researcher was eligible to administer the local anesthetic. However, all endodontic residents were 
calibrated and eligible to acquire and record the data (soft tissue anesthesia as later described, 
EPT readings, and any pertinent patient discomfort experienced upon access/pulpotomy as 
reflected on the Wong-Baker FACES Visual Analog Scale) obtained after the student researcher 
finished giving all 3 cartridges of anesthetic.   
 
DIAGNOSIS 
The patient’s current chief complaint was recorded; “It hurts when I drink cold...”, etc. 
The tooth/teeth that the patient complained about and the control teeth were subject to standard 
pulp sensibility testing to ensure a proper diagnosis of symptomatic irreversible pulpitis. If 

applicable, this diagnosis was specifically confirmed on the same day that the warranted 
endodontic treatment was rendered. Prospective study participants were given brief instructions 
on cold and EPT usage/expectations. Regarding the cold testing, a cotton pellet was held with 
cotton forceps and thoroughly sprayed with Endo-Ice (Coltene) at -26.2 Celsius until the cotton 
pellet was soaked. The cotton pellet was then applied to the mid-buccal, natural surface of the 
tooth, and the patient’s response was monitored. The soaked cotton pellet was removed once the 
patient felt a painful sensation on the tested tooth or if no sensation was felt after 10 seconds of 
an application. If pain was felt, the amount of time until the sensation subsided was measured. A 
continued pain for 10 seconds or longer was considered “lingering” pain. Exaggerated or 
lingering pain, as compared to adjacent or control teeth, was considered acute pain and further 
quantified on the Wong-Baker FACES Visual Analog Scale (VAS), ranging from 0-10. Patients 
were immediately presented with this VAS, and their baseline response was recorded. After any 
previously induced pain had subsided, an electrical pulp testing exam was done using an Electric 
Pulp Tester (EPT) Sybron Analytic to establish a baseline reading. A 2-3 mm dab of toothpaste 
was placed on the dried buccal tooth structure. The tip of the EPT was placed on the toothpaste 
and the EPT was activated once the patient held the end of the wand, thereby completing the 
circuit. The test was stopped when the patient felt pain or a “tingling” sensation after letting go 
of the wand or if the measurements reached a maximum value of 80. The EPT number was 
recorded by the resident on a designated data sheet. Ultimately, a diagnosis of symptomatic 
irreversible pulpitis was made if the patient had acute, lingering pain cold as compared to the 
control tooth. 
 
BUFFERED ANESTHETIC PREPARATION 

Although other local anesthetics may still be employed, Onpharma markets its Onset sodium 
bicarbonate buffer to ideally be used in combination with a standard cartridge of 2% lidocaine w/ 
1:100k epi. Each of the Onset Sodium Bicarbonate Inj., 8.4%, USP Neutralizing Additive 
Solution cartridges contain 1.7 mL volume and are packaged in a four-cartridge package. A 
single cartridge can buffer 10 injections, 40 injections per 4-pack. Onset Sodium Bicarbonate 
Cartridges have a 3-year shelf life, but once a cartridge is placed in the Mixing Pen, the cartridge 
should ideally be used within 7 days. Before using, the Onset Mixing Pen was disassembled into 
its 2 parts, and a 3mL size cartridge was inserted into the Cartridge Chamber. The Mixing Pen 
should be re-assembled, and a 2nd fluid container (the 1.8mL anesthetic cartridge) was attached 
to the end of the Pen. To assist the attachment of the anesthetic cartridge to the end of the Pen, an 
Onset Cartridge Connector was used. Each number on the Mixing Pen corresponds with 
approximately .01 mL's of fluid, so the Pen's volume dispensing dial was adjusted to setting 
“18.” Ultimately 0.18mL of 8.4% sodium bicarbonate was transferred from the 3mL size 
cartridge into the lidocaine cartridge after the equivalent amount of anesthetic was displaced into 
the holding reservoir, resulting in a 10% buffered local anesthetic. This process was repeated by 
a trained research assistant to produce 3 equivalently buffered cartridges of 2% lidocaine with 
1:100,000 epinephrine immediately before it was given to the blinded student researcher.  
 
QUALITY ASSURANCE 
The same calibrated electronic pH meter (Dr.meter PH838) that was employed to test the 
pH in the pilot study was used to test a Sodium Bicarbonate Cartridge from the experimental 
pack and a cartridge of the standard 2% lidocaine w/ 1:100k epi from an experimental anesthetic 
package prior to the first administration of the study. Using the pH strips, standard 2% lidocaine 

w/ 1:100k epi had a pH between 4 and 5, and 2% lidocaine w/ 1:100k epi plus 0.18mL of added 
buffer had a pH between 7 and 8. The digital pH meter produced a reading of 4.99 for standard 
2% lidocaine w/ 1:100k epi, and a pH of 7.14 for 2% lidocaine w/ 1:100k epi plus 0.18mL of 
added buffer (no precipitate ever formed). These quality assurance measures are reflected in 
Figures 11-14. Ultimately, we were again able to independently verify that the buffering capacity 
of Onpharma’s Onset sodium bicarbonate buffer system is as advertised using 2 different 
methods [94, 95] prior to using those packages of local anesthetic and Onset buffer on our first 
research participant. 
 
ANESTHETIC ADMINISTRATION 
After applying topical benzocaine to the respective administration sites for 1 minute, the 
student researcher administered 2 cartridges (3.6mL) of the previously determined formulation of 
2% lidocaine w/ 1:100,000 epinephrine via IANB at the rate of 1.8mL per minute. Any patients 
who did not have signs of soft tissue anesthesia (successful IANB) within the following 10 
minutes would receive a supplementary 1/2 cartridge (0.9mL) of the same anesthetic formulation 
via buccal infiltration and a 1/2 cartridge (0.9mL) via lingual infiltration at the affected tooth’s 
apex with a rate of 1.8mL per minute. Along with being a commonplace clinical practice, 
previous studies have demonstrated an added effectiveness of supplementary buccal and lingual 
infiltrations in obtaining pulpal anesthesia. 
 
ANESTHETIC TESTING AND DOCUMENTATION 
Using an online stopwatch, the student researcher started the timer after administering 
both IANBs and then continually assessed soft tissue anesthesia of the respective side of the 

mandible. Soft tissue anesthesia was considered profound when the patient subjectively attested 
that their lip, chin, and tongue on the respective treatment side felt “full” or “numb,” and a light 
stimulation with the tip of an explorer did not elicit any sensation other than pressure as 
compared to a “sharp” feeling the contralateral side. In the event that the patient denied any signs 
of soft tissue anesthesia (absolutely no change in feeling) 10 minutes after the 2 cartridges of 
anesthetic were given via inferior alveolar nerve block (IANB), then the blocks were to be 
considered “missed,” and the patient would need to be re-blocked as clinically appropriate. This 
situation would be grounds for withdrawing the patient from the study (with documentation) 
since a lack of anesthesia following the protocol cannot be attributed to the anesthetic 
formulation itself but rather operator technique/variable patient anatomy.  
Once the patient attested to having soft tissue anesthesia, the amount of time surpassed 
since being blocked was documented on the designated datasheet, and the supplemental buccal 
and lingual infiltrations were then administered as previously described. The student researcher 
or other residents waited 2 minutes after all 3 cartridges of local anesthesia had been 
administered and then obtained an updated EPT reading on the tooth being treated. An EPT=80 
(maximum stimulation) indicated profound pulpal anesthesia, and the endodontic access was 
initiated. An EPT¹80 indicated a need to wait an additional time. We retested the tooth being 
treated using EPT at 2-minute intervals until EPT=80 or when a maximum of 20 minutes had 
passed since administering 2 IANBs. According to Whitcomb et al., waiting 10-15 minutes after 
administering the IANB should be adequate time to allow the onset of pulpal anesthesia in 
molars. Once EPT=80, the reading was reconfirmed in order to get a consecutive EPT=80 a 
minute after the initial reading. Participants who did not demonstrate total soft tissue and/or 
pulpal anesthesia within 20 minutes would be categorized as a failure and further managed 

according to the best clinical practice (additional block/supplementary injections) so that the 
endodontic treatment could continue appropriately. After confirming soft tissue anesthesia and 2 
consecutive EPT=80, the endodontic treatment could begin.  
Upon the completion of the pulpotomy, the patient was shown the same Visual Analog 
Scale to re-assess their level of comfort. However, any discomfort recognized during the pulpal 
access or pulpotomy paused the procedure, and the VAS was shown immediately. Patients who 
indicated moderate or severe pain (VAS scores of 4 or higher) elicited from the tooth undergoing 
treatment upon pulpal access or a complete pulpotomy were categorized as an anesthesia failure 
(lack of profoundness) and appropriately managed as previously described. Patients who 
indicated no pain or mild pain (VAS scores of 3 or lower) were categorized as an anesthesia 
success (obtained profoundness), and the endodontic treatment continued. When co-residents 
rendered the clinical endodontic treatment, they recorded and reported these failures to the 
student researcher after appropriately treating their patient. The student researcher charted the 
data for each uniquely identified study participant regarding the initial EPT readings (treated 
tooth and control), the amount of time taken to reach both soft tissue and pulpal anesthesia, VAS 
scores after both cold testing (baseline) and pulpotomy, and any other conditions that may have 
led to a “failed” profoundness of anesthesia.  
 
STUDY PROCEDURES 
1. Reviewed medical history as a standard of care for endodontic treatment (about 3-5 
minutes) 
2. Standard of care dental exam with sensibility testing that established baseline EPT 
reading and VAS score (about 5-10 minutes) 

3. Reviewed inclusion/exclusion criteria using data collected in steps 1 and 2 for a 
standard of care to ensure that the subject qualified to continue with the study (about 
3 minutes) 
4. Performed consenting procedures for both the Non-surgical Root Canal Therapy 
(NSRCT) and the research study (about 5-10 minutes) 
5. A trained research assistant prepared the cartridges of the type of anesthetic 
formulation (buffered vs. unbuffered) determined by the randomization scheme in a 
separate room immediately prior to it being administered. The assistant made a record 
using a unique identifying code for the type given to each patient. The Onpharma 
Onset protocol was used when indicated. The assistant “prepared” the unbuffered 
cartridges in the same amount of time as required for the buffered cartridges, as well 
as “puncturing” the unbuffered cartridges with the Onset pen so that each cartridge 
had a uniform appearance (about 3 minutes) 
6. Applied 20% topical benzocaine jelly (Ultradent Products Inc, South Jordan, UT) 
after thoroughly drying the tissues surrounding the inferior alveolar nerve block 
(IANB) injection site, buccal vestibule, and lingual vestibule of the treatment tooth 
(about 1 minute)   
7. The student researcher administered the 2 IANBs (about 2 minutes) and then started 
the timer immediately 
8. The patient was regularly re-assessed for soft tissue anesthesia (as previously 
described) 
a. If within 10 minutes the patient had confirmed soft tissue anesthesia, then the 
IANBs were considered successful, and 1 cartridge of the respective 

anesthetic formulation was supplementarily administered via apical buccal 
and lingual infiltrations (documented exact time elapsed) 
b. If at 10 minutes the patient did not have any indications of soft tissue 
anesthesia, then IANBs would be considered missed, and the patient would be 
withdrawn from the study. Administer additional local anesthetic as clinically 
appropriate 
9. Tested the treatment tooth using EPT in 2-minute intervals (starting at 2 minutes post-
supplementary infiltrations) 
a. If within 20 minutes post-IANBs pulpal anesthesia was confirmed with 2 
consecutive EPT=80, initiated NSRCT (document exact time elapsed) 
b. If at 20 minutes post-IANBs pulpal anesthesia was not confirmed with 2 
consecutive EPT=80, anesthesia was considered a failure, and additional local 
anesthetic was administered as clinically appropriate 
10. All pertinent data, including the patient’s VAS comfort assessment after pulp 
chamber access/pulpotomy, were recorded and analyzed with the help a professional 
statistician for statistical significance.  
 
STATISTICAL ANALYSIS 
 
The buffered anesthetic and unbuffered anesthetic groups were compared for differences 
in the percentage of subjects who achieved profound pulpal anesthesia using chi-square tests. 
The time needed to achieve profound pulpal anesthesia using buffered anesthetics and 
unbuffered anesthetics was compared using Kaplan-Meier survival curves and log-rank tests. A 
5% significance level was used for all tests. Comparisons of the VAS results were made using a 

Wilcoxon Rank Sum test. Up to 60 subjects were randomized to ensure that 40 evaluable 
subjects could complete the study. With a sample size of 20 subjects per group, the study had an 
80% power to detect a difference between 90% and 50% of subjects who achieved profound 
pulpal anesthesia. Calculations were based on a chi-square test with a two-sided 5% significance 
level. Sample size calculations were performed using PASS 2019 (NCSS, LLC. Kaysville, UT). 
All calculations were derived with professional assistance.