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Computer-controlled delivery versus syringedelivery of local anesthetic injections for therapeuticscaling and root planing

PETER M. LOOMER, D.D.S., Ph.D. and DOROTHY A. PERRY, Ph.D.

ABSTRACT

Background. The authors conducted a study to compare administrationof local

anesthetic using a computer-controlled delivery devicewith an aspirating syringe fortherapeutic scaling and root planing. The anterior middle superior alveolar, or AMSA,injectionwas compared with other maxillary injections.

Methods. Twenty healthy adults with moderate periodontal diseaseparticipated in

this single-blind crossover study. Subjects were evaluated by a trained examiner and

were treated by experienced dental hygienists. Subjects provided written and verbalpainratings via a visual analog scale, or VAS, and a verbal rating scale, or VRS.AMSA injections were compared with syringe-deliveredinjectionsgreater palatine,or GP, and nasopalatine, or NP, blocks, and anterior superior alveolar and middlesuperioralveolar injectionsin maxillary quadrants. Bleeding and changes inattachment were evaluated after one month.

Results. VAS and VRS scores for AMSA were significantly lowerfor computer-controlled delivery when compared with NP injections and combined maxillaryinjections (VAS scores) and with GP and combined maxillary injections (VRSscores). Mean injection times were similar for both groups. Mean gains in attachmentwere

equal, 0.19 millimeters for quadrants anesthetized using computer -

controlledinjections and 0.22 mm for syringe injections.

Conclusions. Subjects reported having less pain with GP and NP injectionsdelivered using the computer-controlled device,

and total injection time was similar to

that required for syringeinjections. Both techniques provided ade quate anesthesiafor

therapeutic scaling and root planing.

Clinical Implications. The two anesthetic delivery techniqueswere therapeutically

equivalent for mandibular injections, and the AMSA injection has clinically significantadvantages formaxillary injections.

Effective therapeutic periodontal scaling and root planing procedures

frequentlyrequire the use of local anesthetic to maintain patient comfort while permittingadequate instrumentation of root surfaces. This allows the clinician to adequatelyperform the procedures without fear of causing pain in the patient. However, manypatientsassociate injections of local anesthetic "shots in themouth"with paindespite the benefits to treatment. 1,2

The two anesthetic delivery techniques were therapeutically equivalent formandibular injections.

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each subject: a baseline examination, an appointmentto scale and root plane

randomly assigned maxillary and mandibularquadrants on one side of the mouth, asecond scaling and root

planing appointment to treat the opposite side of the

mouth,and an exit examination. e randomly assigned an anesthetic deliverydeviceeither the computer-controlled delivery

system or the conventional aspirating

syringeat the firstscaling and root planing appointment. uring the second

appointment, we used the other device, resulting in a sex-stratified crossoverdesignwith random assignments of delivery device and which side of the mouth was treatedfirst. Each subject served ashis or her own control.

At the first treatment appointment, we taught subjects the oral hygiene techniques oftoothbrushingusing the modified Bass methodand flossing, and we providedthemwith toothbrushes and floss for home use. All subjects were anesthetized using2 percent lidocaine with 1:100,000 epinephrine. One trained periodontist (P.M. .)performed all of the baseline and exit examinations and was not aware of which sideof themouth was anesthetized by the computer-controlled delivery device or whichside of the mouth was treated first. Three experienced dental hygienists provided theperiodontal treatment and collected data for the study. ue to the nature of the study

design, thesubjects and the dental hygienists knew which treatment was beingprovided at each visit. Subjects accepted into the study had probing depths of at least to 6 millimeters; sixteeth per quadrant, including at least one molar; and moderate-to-heavy subgingivalcalculus on morethan one-half of the teeth in the mouth. All subjects were in goodphysical health and did not have any systemic illnesses that would affect healingresponses. e obtained written consent from the subjects in accordance with the

ommittee on HumanResearch guidelines from the University of alifornia, Sanrancisco.

The periodontist conducted a complete periodontal examination at the baselineappointment. He recorded the following indexes: probing pocket depth, clinicalattachment loss, presence ofgingival bleeding and presence of visible plaque. Hecalculatedclinical attachment loss as the sum of the probing depth and the distancefrom gingival margin to the cementoenamel junction. The periodontist took adiagnostic series of full-mouth radiographsfor each subject so he could assess theamount of alveolar bone loss and other treatment needs.

The periodontist conducted the exit examination four to six weeks after the subjectscompleted treatment to allow sufficient healing time for accurate periodontal datacollection.5,6 Atthat time, he performed a second complete periodontalexamination

and repeated all index measurements except presence of visible

plaque.

Subjects requiring further dental or periodontal the rapy

were referred for treatment.

Anesthetic injection procedures. At the baseline examination, the periodontist trained

subjectsto use a visual analog scale, or VAS,7 to record the level ofpain they feltduring treatment procedures. VAS was scored on a 100-mm horizontal line with theleft endpoint marked "no pain" and the right endpoint marked "pain as bad as it canbe." Toeliminate people who were stoic about pain, we enrolled in the study onlysubjects who registered VAS pain scores of greaterthan 20 during periodontalprobing at the baseline examination.

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Figure 3. Clinical placement of the needle for the anterior middle superior alveolar

injection. Reproduced ith permission of Mark Friedman, D.D.S.

Subjects were encouraged to ask for more anesthetic if theyneeded it during thescaling and root planing procedure, and we trained the dental hygienists to ask thesubjects after thefirst 10 minutes of treatment if anesthesia was sufficient and tooffer more anesthetic when it was not. The hygienists recordedthe use and amountof additional anesthetic.

The hygienists administered the AMSA injection to the middle portion of the anteriorpalate through the fibrous palatal tissue, and the anesthetic was deposited next tothe palatal bone. Once the needle tip had reached the bone, the slow and steadydeliveryof anesthetic solution was continued until a sufficient amount of solution wasdeposited and diffused through the tissue. The injection required 0.6 to 0.9 millilitersof anesthetic solutionone-third

to one-half of a cartridge of anesthetic. It took 60 to

90 secondsto deliver.The palatal bone is porous enough to permit the anesthetic solution to diffusethrough the tissues and anesthetize both the anteriorand middle branches of the

superior alveolar nerve when theinjection is deliberately slow and steady. or thisreason,the successful deposition of the anesthetic solution through the fibrous tissueis said to be accomplished more easily with the use of a computer-controlled deliverydevice that regulatesthe pressure and volume ratio of solutiondelivered.

,

Attainingthis consistency in deposition of anesthetic solution isdifficult to achieve using a manual syringe.

The time needed for injections and treatm ent was recorded atevery visit. Theclinician noted the time required for administering

injections at each treatment

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appointment, the start and endtimes for the injections, and the half-mouth scaling

and rootplaning. This represented the time required to complete thescaling and rootplaning treatment appointment.

The dental hygienists telephoned the subjects the day aftertreatment and asked ascripted set of questions to identify possible adverse events.

Data analysis. e analyzed VAS and clinical att achment loss data usingthe ilcoxon signed rank test, a nonparametric test for paired samples. e analyzedVRS data using a binomial probability distribution. e used the Student paired ttestfor nondirectional data and correlated samples to assess data for time needed tocomplete

all injections required to anesthetize the half -mouth and for

total treatment

time.

RESULTS

Twenty subjects were enrolled in and completed the study. Therewere no adverse

events, and no reports of ulcerations, soreness or swelling related to the injectionswere reported by subjectsthe day after treatment. In addition, we noted no historyorclinical evidence of swelling or ulceration at any treatment visit or the exitexamination. Two subjects had incomplete data

scores for the PSA injection, and

one subject was missing the AMSA injection score. All other data points wererecorded and

available for analysis.

Each subject received seven injections per half-mouth usingthe conventionalsyringe, and four injections for the hal f-mouthusing the computer-controlled deliverysystem for anesthesia, resulting in 11 injections for each subject. Threesubjectsrequested additional anesthetic during the 0 treatment sessions, for a totalof four re-administered injections required of t he220 injections that were

administered.

Periodontal healing. e evaluated periodontal healing four to six weeks aftertreatment8,9to ensure that adequate treatment had been performed and that therewere no systematic differences in ability to perform treatment based on the type ofanesthetic delivery device. Because the dental hygienists were not blinded totreatment, we thought that the periodontal scaling and root planing could havebeenless vigorous when performed after anesthetic injections administered using thecomputer-controlled delivery system compared with the conventional syringetechniques that were more familiarand trusted.

The periodontist measured clinical attachment in all subjects (N = 20) for all teeth, six

surfaces per tooth. e measured

and compared attachment changes for allsurfaces, surfaces withsevere attachment loss (> 6 mm at baseline), surfaceswithmoderate attachment loss ( to 6 mm loss at baseline) and surfaces with mildattachment loss (< mm at baseline). Overall, the subjects demonstrated significantimprovement between the baseline and exit examinations. omparisons between thecomputer-controlled delivery device data and the conventional syringe deliverydatashowed that all subjects improved equally. Attachment loss data and statisticalcomparisons between the computer-controlled delivery data and the conventionalsyringe data are presented in Table 1.

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The percentage of sites with bleeding provides a commonly usedclinical

measurement of inflammation. 10 e compared the percentages of sites withbleeding per subject at the baseline and exit

examinations and between delivery

devices. Subjects improvedequally after receiving injections administered by bothdelivery

devices and demonstrated less bleeding after treatment than

at baseline.

Eighteen of 20 subjects had equal or fewer numbers of sites with bleeding on thesides of the mouth that received

the anesthetic injections using the computer -

controlled device,

and 17 of 20 subjects had equal or fewer sites with bleeding

on theside of the mouth that received the anesthetic using

the conventional syringe. There

were no statistical differences (P= .91) in percentages of sites with bleedingbetween the

two delivery devices at the exit examination.

Pain perception.VAS. e compared individually the pain scores for injectionsdeliveredwith the computer-controlled device with those of injections delivered usingconventional syringes. e also compared the area of the maxillary arch that wasanesthetized by the AMSA injection with the mean of the combination of pain scoresforthe corresponding conventional syringe injections (ASA, MSA, GP and NP).Perceived pain for the conventional syringe delivery NP injection was highlystatistically different from that ofthe computer-controlled delivery of the AMSA (P=

.008). Scoresfor the corresponding conventional syringe injections in the maxillaryarch compared with the scores for the AMSA computer-controlledinjection revealeda highly significant difference in favorof the computer-controlled device (P< .0001).

There wereno differences in the pain perceived by the subjects during the IA or Binjections in the mandibular arch. ata are shown in Table 2 and Table .

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VRS. e also measured subjects pain responses with a VRS that was recorded by

the clinician after each injection. The data indicated that the computer -controlled

injections were consideredless painful than the conventional syringe injections by

thepopulation studied. hen compared individually, the GP and the AMSA

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differences were statistically significant (P= .0117). e compared the mean of the

combined scores for the maxillary injections using the conventional syringe with the

computer-controlled delivery of the AMSA and found highly significantly differentpain

scores (P= .0002). ata are presented in Table .

Time. e compared the total time required by the computer-controlleddevice and

the conventional syringe to deliver all injections for one side of the mouth andperform scaling and root planing. e also compared the time needed to administerthe injectionsusing the computer-controlled delivery device and theconventional syringe; we included the time for readministered injections in the timetotal. Both indications of timetime required

for injections and treatment, and time

required for injections aloneincluded the additional time required for datacollection

after each injection.

Total treatment time data represent four injections per half-mouthusing the

computer-controlled device plus treatment time and readministered injections,compared with seven injections perhalf-mouth using the conventional syringetechnique plus treatment time and re-administered injections. Three subjectsrequireda total of four readministered injections. The readministered injections werethe B and GP using the conventional syringe for one subject, the IA using theconventional syringe for one subject, and the AMSA for one subject receivingcomputer-controlled anesthetic delivery. The mean minutes of treatment time required for injections plus

scaling and root

planing was 81.0 2 .5 standard deviation, or S , per subject using the computer-controlled delivery device,

and 80. 2 .0 S for the conventional syringe

injections.These means were not statistically different (P= .81). There was

considerable variation in total time required to treat thesubjects, ranging from 9 to

120 minutes. ifteen of the subjects had treatment times for the two scaling and rootplaning appointments

that were within 10 minutes or less of each other. The

otherfive subjects had treatment times that varied by 15 or 20 minutes (P= .287 ).

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Injections administered using the computer-controlled devicewere scored regularly

as less painful than were injections administered using the conventional syringe.

The mean number of minutes required for administering the injection and collectingdata for the half-mouths receiving anesthetic using the computer-controlled deliverydevice was 19. .5 S ; the mean number of minutes for the half -mouths

receivinganesthetic using the conventional syringe was 20.5 5.1 S . Thesedifferences were not statistically significant.

DISCUSSIO

It was important in this study for us to be assured that sub jectswho receivedinjections of anesthetic using the computer-controlleddelivery device demonstratedevidence of expected healing to ensure adequate therapy. our to six weeks aftertreatment, periodontal tissues usually have had time to heal and become lessinflamed and, therefore, demonstrate less bleeding on probing. 111

In addition,probing pocket depths generally are reduced aftertreatment by 1 to 2 mm,

representing both a reduction in gingival

swelling and a decrease in the ability of theprobe to penetrate the long junctional epithelial attachment. 1

,15 ithoutthatassurance in this study, subjects could have been attracted to a differentanesthetic technique because it was a noveltyand appealed to them on that basisalone, even if the clinician was unable to scale adequately. As a result, we monitoredthe

periodontal parameters during the study to ensure that anesthesia

was sufficient

enough to permit the clinicians to provide a high level of therapy. ata showed thatthe percentage of sites

with bleeding per subject was reduced from baseline to

exitexamination without any difference between modes of anesthetic delivery. Inaddition, we saw substantial healingmeasured

by 1 to 2 mm improvements in

attachment lossin deep pockets, and, as expected, smaller changes in shallowerpockets.

16These

findings were consistent with the healing seen after scaling

and root

planing procedures in a variety of studies17,18

and

indicated that the level ofanesthesia achieved using either

the computer-controlled delivery device or the

conventional syringe permitted adequate therapy to be performed.

Our data indicate that injections administered using the computer -controlleddevicewere scored regularly as less painful than were injections administered using theconventional syringe, though when compared individually the differences werestatistically significant only for the GP injection. ue to the nature of the computer -controlleddelivery device, it was possible for the dental hygienists to use the AMSAinjection recently described by riedman and Hochman

instead of the four maxillaryinjections delivered by conventional syringe: the ASA, MSA, GP and NP. The painscores the subjectsreported for the AMSA were significantly lower than the

meanscores for the conventional injections it replaced, suggesting that intraoralanesthesia of the anterior maxilla and palate can be achieved with fewer injectionsand less pain. It is conceivable that if the AMSA injection were administered with aconventional syringe, the pain response would be similar to that of theinjectionadministered using the computer-controlled device. However, we did notcompare the delivery of an AMSA injection using the computer-controlled device withdelivery using the conventionalsyringe because of the difficulty of delivering anadequatevolume of anesthetic solution over one minute or more with a conventionalsyringe. The performance of the computer-controlled device is based on the slow

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and consistent speed of depositionof the anesthetic, which allows for comfortable

penetrationinto the fibrous palatal tissue and adequate diffusion throughthe tissuesin the center of the hard palate to the bone and

nerve complex. The consistent

finding of lower pain scores with the computer-controlled device was confirmed at theexit examinationwhen subjects expressed clear preferences for computer -controlleddelivery of anesthetic. Nineteen of the 20 subjects endorsed the injections

as being less painful than any injections they had received previously.

The computer-controlled device uses a conventional dose of anesthetic delivereddrop by drop using a slow flow rate of one cartridge over 90 seconds or a faster flowrate of one cartridge over60 seconds. The slower flow rate is recom mended forinjectionsin dense tissue such as palatal mucosa, and we used it for all computer-controlled injections for this study. 19 This couldbe a concern for clinicians because itmight extend the timerequired for scaling and root planing treatmentappointments. uring this study, the time required to administer injections and treatthe subjects for the half-mouth periodontal scaling and root planing procedures wasnot statistically differentfor the two techniques. However, the total time foradministering injectionsclose to 20 minutes per half-mouthmayseem excessive.

These total times included the time it took subjects to complete VAS scoring sheetsand respond to VRS questions, so the times were greater than would be found inactual dentalpractice. Although the clinicians found that the computer-controlledinjections were slower to administer, fewer injections were required toachieve adequate anesthesia for the half -mouth treatments.

Total time required for administering anesthetic injections and for treatment wasconsistent among subjects, given that extra time was required to complete the datacollection. Total visit times varied from about one hour to about two hours among thesubjects. This variation commonly is the amount of time required to adequately scaleand root plane half -mouths forpatients with moderate periodontal diseasecharacterized by

substantial deposition of calculus. The variation in total

timerequired per subject more likely was related to the differe ncein time required toremove the calculus from the teeth because

total injection times were so similar for

the subjects.

CO CLUSIO S

The two anesthetic delivery techniques were therapeutically equivalent for

mandibular injections. The AMSA delivered by the computer-controlled device had

clinically significant advantages for maxillary injections. Anesthesia of sufficient depth

andduration was achieved to allow therapeutic periodontal scaling and root planing

procedures. The time required for providing the injections to achieve half-mouth

anesthesia was similarfor both techniques, but fewer injections were needed when

usingthe computer-controlled device.

This study was supported by a research grant from MilestoneScientific, ivingston, N. .

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