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At least 19 recordsLinked to original sources
PubMed1985

A biomechanical analysis of spinal instrumentation systems in thoracolumbar fractures. Comparison of traditional Harrington distraction instrumentation with segmental spinal instrumentation.

A total of 61 biomechanical tests were performed on 25 cadaveric spinal segments to investigate the comparative strengths of three instrumentation systems: 1) conventional Harrington distraction instrumentation (HRI), 2) segmentally wired Harrington distraction rods, and 3) Luque segmental spinal instrumentation (SSI). In type I testing in which axial preload was applied to normal specimens, and then progressive rotation until ultimate failure followed, five of six Harrington systems failed at the bone-metal interface. In contrast, all six Luque SSI vertebral segments disrupted in a location removed from the bone-metal interface. In Type-II testing (six specimens) in which axial loading of experimentally produced unstable burst fractures was applied, the most stable fixation in resisting compressive loads was segmentally wired Harrington distraction rods (P less than 0.001). In Type-III testing (six specimens), there was axial preloading, then progressive rotation applied to translational fracture-dislocations and this showed that the ability to resist torsion was lowest with plain HRI, slightly improved by segmentally wired HRI, and the stiffest system was Luque SSI (P less than 0.05). The three methods of testing cadaveric segments provided a relevant laboratory model for investigation of spinal instrumentation systems in thoracolumbar fracture stabilization. The results compare favorably with other biomechanical studies, information derived from in vitro and ex vivo animal models and clinical experience with failures of fixation. The biomechanical advantages of segmentally wired Harrington distraction instrumentation in resisting axial loads seem to justify this method of fixation in unstable burst fractures. Similarly, the use of Luque segmental spinal instrumentation with L-rods coupled together is the best method of achieving rotational stability in translational injuries (fracture-dislocations). However, the above biomechanical considerations should be balanced against the increased operative time, more exacting technical expertise required, and possible risk of iatrogenic neurologic sequelae in implementing segmental fixation in unstable thoracolumbar fracture management.

Adolescent↗
PubMed1987

A prospective randomized trial comparing periapical instrumentation to intracanal instrumentation in cases of asymptomatic pulpal-periapical lesions.

To clarify the divergent viewpoints with respect to method of instrumentation in asymptomatic teeth with pulpal necrosis and associated periapical radiolucent lesions (PN/PL), this prospective study was undertaken. The subjects were 106 patients with quiescent cases of PN/PL. Alternately, 53 had periapical instrumentation and 53 had intracanal instrumentation. Prophylactic antibiotics were not administered but the patients were told to take an antibiotic at the first sign of swelling. Flare-ups, non-flare-up-associated swelling and pain, and cases in which there were no postoperative problems were evaluated at 1-day, at 1 week, and at 2 months. A 6.6% incidence of flare-up was found with no statistically significant difference between periapical instrumentation (7.5%) and intracanal instrumentation (5.7%). A 27.4% incidence of swelling was found with no statistically significant difference between periapical instrumentation (24.5%) and intracanal instrumentation (30.2%). A 43.4% incidence of pain was found, with no statistically significant difference between periapical instrumentation (15.1%) and intracanal instrumentation (47.2%). When moderate pain and severe pain were combined, the incidence was 21.7%, with no statistically significant difference between periapical instrumentation (15.1%) and intracanal instrumentation (28.3%). An incidence of patients having no postoperative problems of 41.5% was found, with no statistically significant difference between periapical instrumentation (47.2%) and intracanal instrumentation (35.8%). When flare-ups were combined with swelling, the incidence was 34.0%, with no statistically significant difference between periapical instrumentation (32.1%) and intracanal instrumentation (35.8%). When flare-ups were combined with pain, the incidence was 50.0%, with no statistically significant difference between periapical instrumentation (47.2%) and intracanal instrumentation (52.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Root canal instruments for manual use: cutting efficiency and instrumentation of curved canals.

The cutting efficiency of different endodontic hand instruments and the effects of instrumentation on curved canal shape were investigated under standardized experimental conditions using an automatic testing device. Cutting efficiency in rotary motion was assessed by determination of the maximum penetration depth of the instruments into a cylindrical canal in a special resin block (size 25 and size 35 instruments). Changes in canal shape were determined by instrumentation of standardized canals (42 degrees curvature) incrementally from size 15 to size 35. Except in the case of one instrument, size 35, in both sizes tested flexible instruments reached significantly (P < 0.05) greater maximum penetration depths than conventional reamers or K-files. Changes in the canal shape differed significantly between the different instruments in 13 of the 14 measuring points. Drastic undesirable changes in the canal shape (e.g. straightening or zip and elbow) occurred after instrumentation with reamers and K-files, but these changes were less noticeable after instrumentation with flexible instruments with conventional tips. After instrumentation with flexible instruments with modified tips there were few undesirable changes in shape. The conclusion could be drawn that flexible instruments, especially those with modified tips, were clearly superior to conventional reamers and K-files with regard to cutting efficiency and instrumentation of curved canals.

Analysis of Variance↗
PubMed2002

Efficiency of rotary nickel-titanium FlexMaster instruments compared with stainless steel hand K-Flexofile--Part 2. Cleaning effectiveness and instrumentation results in severely curved root canals of extracted teeth.

AIM: To determine the cleaning effectiveness and the shaping ability of FlexMaster nickel-titanium rotary instruments and stainless steel hand K-Flexofiles during the preparation of curved root canals in extracted human teeth. METHODOLOGY: A total of 48 root canals with curvatures ranging between 25 degrees and 35 degrees were divided into two groups of 24 canals. Based on radiographs taken prior to the instrumentation with the initial instrument inserted into the canal, the groups were balanced with respect to the angle and the radius of canal curvature. Canals were prepared by FlexMaster instruments using a crown-down preparation technique or by K-Flexofiles using a reaming working motion up to size 35. After each instrument, the root canals were flushed with 5 mL of a 2.5% NaOCl solution and at the end of instrumentation with 5 mL of NaCl. Using the pre- and post-instrumentation radiographs, straightening of the canal curvatures was determined with a computer image analysis program. After splitting the roots longitudinally, the amount of debris and smear layer were quantified on the basis of a numerical evaluation scale, using a scanning electron microscope. RESULTS: Completely cleaned root canals were not found with any of the two instruments. In general, K-Flexofiles resulted in significantly less debris(P < 0.001) and less smear layer (P < 0.05) than Flex-Master instruments, but these differences were not significant in the apical third of the canals (P > 0.05). FlexMaster instruments maintained the original canal curvature significantly better (P < 0.0001) than K-Flexofiles. No significant differences were detected between the instruments (P > 0.05) for the time taken to prepare the canals. CONCLUSIONS: Under the conditions of this study, K-Flexofiles allowed significantly better canal cleaning than FlexMaster instruments. FlexMaster instruments maintained the original curvature significantly better.

Dental Instruments↗
PubMed2000

Canal shapes produced sequentially during instrumentation with Quantec LX rotary nickel-titanium instruments: a study in simulated canals.

AIM: The aim of this study was to determine the shaping ability of Quantec LX nickel-titanium rotary instruments in simulated root canals. METHODOLOGY: Forty simulated canals consisting of four different shapes in terms of angle and position of curvature were prepared with Quantec LX instruments. Sequential still images were taken of the canals using a video camera attached to a computer with image analysis software. Images were taken preoperatively; after, instrument 7 (Size 25, 0.05 taper), instrument 8 (size 25, 0.06 taper), and instrument 10 (size 45, 0.02 taper) were taken to length. Each sequential postoperative image was superimposed individually over the preoperative image in order to highlight the amount and position of material removed during preparation. Intra-canal impressions after preparation to size 10 were taken to evaluate three-dimensional canal form. RESULTS: Overall, the mean preparation time to size 10 was 4.7 min; canal shape did not have a significant effect on speed of preparation. No instruments fractured within the canal, but 7 instruments separated from the latch grip, and a further 3 instruments deformed. All canals remained patent. Following preparation to size 10, 29 canals (72%) retained their length, 7 (17%) lost length, and 4 gained length; the magnitude of the change in length was always below 1 mm. Zips were created in 3 canals (7%) after use of size 10 instruments, but no perforations or danger zones were produced. Excess removal of material along the outer aspect of the curve between the beginning of the curve and the end-point (outer widening) was found in 22 canals (55%) after instrument 7, in 30 (75%) canals after size 8 and in 35 canals (88%) after size 10. There was a significant difference (P < 0.0001) between canal shapes for the incidence of this aberration at all sizes. CONCLUSIONS: Under the conditions of the study, Quantec LX instruments tended to remove excess material from the outside of the curve between the beginning of the curve and the end-point. These aberrations increased in prevalence and severity following the use of larger instruments when they were taken to length. Size 8, 9 and 10 Quantec LX instruments should be used with care and short of length, especially in severely curved canals.

Analysis of Variance↗
PubMed2000

Instruments for transcervical chorionic villus sampling for prenatal diagnosis.

BACKGROUND: The type of instrument used in chorion villus sampling could have a significant impact on the success rate of the procedure. An ability to manoeuvre the instrument within the uterine cavity without puncturing the gestational sac, and to see the tip of the instrument on ultrasound scanning are particularly important. OBJECTIVES: The objective of this review was to assess the effects of different instruments for transcervical chorionic villus sampling on perinatal outcome, quality and quantity of obtained tissue, technical difficulties during the procedure and maternal adverse effects. SEARCH STRATEGY: The Cochrane Pregnancy and Childbirth Group trials register was searched. Date of last search: October 1998. SELECTION CRITERIA: Randomised trials comparing different instruments for transcervical chorionic villus sampling. DATA COLLECTION AND ANALYSIS: Eligibility and trial quality were assessed by one reviewer. MAIN RESULTS: Three trials involving 268 women were included. None of the trials mentioned method of randomisation. An adequate sample was more likely to be obtained using small forceps than aspiration cannula (odds ratio 7.29, 95% confidence interval 3. 39 to 15.67). However small forceps were more difficult to insert than an aspiration cannula (odds ratio 0.35, 95% confidence interval 0.13 to 0.96). Use of the Portex cannula was more likely to result in an inadequate sample and a difficult or painful procedure when compared with either the silver or aluminium cannula respectively. REVIEWER'S CONCLUSIONS: Although there is some evidence to support the use of small forceps for transcervical chorionic villus sampling, it is not strong enough to support change in practice for clinicians who have become familiar with aspiration cannulas.

Chorionic Villi Sampling↗
PubMed1994

Reusable instruments are more cost-effective than disposable instruments for laparoscopic cholecystectomy.

Health care costs are rising rapidly, and surgeons can play a role in limiting costs of operations. Of the 600,000 cholecystectomies performed each year in the United States, approximately 80% are performed with laparoscopic technique. The purpose of this study was to compare the costs of reusable vs disposable instruments used during laparoscopic cholecystectomy. The costs to the hospital of reusable and disposable instruments were obtained. Instruments studied were the Veress needle, trocars and sleeves (two 10 mm and two 5 mm), reducers, clip appliers, and clips. In addition, the costs of sterilization and sharpening for reusable instruments were calculated. The cost of reusable instruments was based on an assumed instrument life of 100 cases. Data from three private hospitals and a Canadian university hospital were collected and examined. Data from the four hospitals revealed that the costs of reusable instruments per case were $46.92-$50.67. The comparable costs for disposable instruments were $330.00-$460.00 per case. Theoretical advantages of disposable instruments such as safety, sterility, and better efficiency are not borne out in literature review. In addition, the environmental impact of increased refuse from disposable instruments could not be exactly defined. With the consideration of significant cost savings and the absence of data demonstrating disadvantages of their use, reusable instruments for laparoscopic cholecystectomy, are strongly recommended.

Cholecystectomy, Laparoscopic↗
PubMed2001

Canal shapes produced sequentially during instrumentation with Quantec SC rotary nickel-titanium instruments: a study in simulated canals.

AIM: The aim of this study was to determine the shaping ability of Quantec SC nickel-titanium rotary instruments in simulated root canals. METHODOLOGY: Forty simulated canals consisting of four different shapes in terms of angle and position of curvature were prepared with Quantec SC instruments. Sequential still images were taken of the canals using a video camera attached to a computer with image analysis software. Images were taken preoperatively, and then after instrument 7 (Size 25, 0.05 taper), instrument 8 (size 25, 0.06 taper), and instrument 10 (size 45, 0.02 taper) were taken to length. Each sequential postoperative image was superimposed individually over the preoperative image in order to highlight the amount and position of material removed during preparation. RESULTS: Overall, the mean preparation time to size 10 was 3.6 min with 12 mm canals taking on average less time than 8 mm canals. There was a highly significant difference between the canal types (P < 0.0001). No instruments fractured within the canal or deformed, although one instrument separated from the latch grip. All canals remained patent. Following preparation to size 10, 19 canals (48%) retained their length, eight (20%) lost length, and 13 (32%) gained length; the magnitude of the change in length was always 0.5 mm or below. Following preparation to size 7 instruments all canals showed aberrant shapes. Excess removal of material along the outer aspect of the curve between the beginning of the curve and the end-point (outer widening) was found in 26 canals (65%) after instrument 7. At the same stage of preparation six canals (15%) had zips, three (8%) had ledges and five (13%) had perforations. Following preparation to size 10, 27 (68%) canals were perforated. CONCLUSIONS: Under the conditions of the study, Quantec SC instruments consistently produced aberrations when canals were enlarged to size 7 (size 25, 0.05 taper) or above. Care should be exercised when using these instruments in real teeth.

Dental Alloys↗
PubMed2003

Preparation of curved root canals with rotary FlexMaster instruments compared to Lightspeed instruments and NiTi hand files.

AIM: To compare the recently introduced rotary FlexMaster instruments with Lightspeed instruments and NiTi hand files in preparing curved root canals. METHODOLOGY: Root canals of extracted molars were shaped with rotary FlexMaster instruments ('FM': n = 45), Lightspeed instruments ('LS': n = 46), and NiTi hand files (n = 45) using the balanced-force technique. The apical preparation size was 40. Root canal instrumentation was carried out in a phantom head under clinical conditions. A re-assembly technique allowed a comparison of the canal outline before and after preparation. Root sections 2.5 mm short of working length were used to calculate the percentage of prepared canal outline (= PPO) and the amount of root canal transportation. Loss of working length, fracture rate and time spent on complete preparation were also recorded. RESULTS: The highest PPO values were found in the LS group (mean = 63% [95% CI: 55%; 70%]). Although not statistically significant, lower PPO values were detected for FM instruments (mean = 55% [95% CI: 49%; 62%]) and for hand files (mean = 53% [95% CI: 47%; 59%]). The incidence of root canal transportation exceeding 0.1 mm was significantly lower in the LS group than in the FM group. Loss of working length of 0.5 mm occurred in five cases (LS group: 4x; FM group: 1x). Two LS instruments fractured. Half the time was needed for root canal preparation with FM instruments than with hand files. CONCLUSIONS: Rotary FM instruments are suitable for preparing curved root canals. They provided results similar to LS instruments with minimal risk of instrument fracture but increased risk of root canal transportation.

Dental Alloys↗
PubMed2002

Efficacy of bacterial removal from instrumented root canals in vitro related to instrumentation technique and size.

OBJECTIVE: This in vitro investigation assessed the efficacy of removing radioactively labeled bacteria from infected canals with 2 engine-driven rotary nickel titanium instrumentation techniques differing in sequence and apical enlargement size. STUDY DESIGN: A standard quantity of (3)H-thymidine-labeled Enterococcus faecalis (3.70 x 10(4) cpm, 2.0 x 10(7) colony-forming units) was used to inoculate the mesiobuccal canals of 50 extracted mandibular molars. The teeth were incubated for 5 days to allow infection of the surrounding dentin from the canals. Five of the teeth were used as controls to determine the number of cycles of irrigation and drying necessary to reduce the (3)H counts recovered from the canals to baseline levels. After this process, the unbound bacteria in the root canals of the remaining 45 teeth then were washed out with buffer until baseline levels of radioactivity were obtained. The mesiobuccal root of 1 of these 45 teeth was removed, decalcified, and digested, and the total radioactivity released from the root dentin was measured. Of the remaining 44 teeth, 22 then were instrumented with GT and Profile (Dentsply/Tulsa Dental Co, Tulsa, Okla) instruments to apical size #35 (group 1) and 22 teeth with Pow-R instruments (Moyco/Union Broach, York, Pa) to apical size #50 (group 2), in the presence of a standard quantity of phosphate-buffered saline solution placed in the canal. After instrumentation, the medium from each canal was collected with paper points and its radioactivity was counted with liquid scintillation spectrometry. RESULTS: The mean (3)H level recovered with instrumentation of canals in group 1 was 75 cpm (+/- 29, standard deviation) and in group 2 was 123 cpm (+/- 50, standard deviation). A 2-tailed Mann-Whitney test indicated that the radioactivity of samples from group 2 was significantly higher than that of samples from group 1. CONCLUSION: The results suggested that instrumentation to an apical size of #50, as performed with the Pow-R instruments, was more effective in debriding infected root canals than instrumentation to an apical size of #35, as performed with the GT and Profile instruments.

Colony Count, Microbial↗
PubMed1997

Effectiveness of subgingival instrumentation with power-driven instruments in the hands of experienced and inexperienced operators. A study on manikins.

Power instrumentation of periodontally-diseased root surfaces is gaining in significance as an alternative to conventional curette methods. In an experimental study employing manikins with simulated bone loss, we investigated whether inexperienced and experienced operators were able to achieve greater therapeutic success with power-driven devices than with hand instruments in subgingival scaling. 10 dentists experienced in periodontal treatment and 10 inexperienced dentists instrumented 7 teeth in the upper jaw, which had been covered with artificial deposits. Hand instruments, the Perioplaner system, a sonic and an ultrasonic scaler were used. The time required for treatment was measured and the % of residual deposits was calculated by means of image-processing techniques. Weight loss was also determined for the teeth that were scaled with the hand instruments and the Perioplaner system. Experienced operators left significantly less % of residual deposits on the teeth (18+/-7.6%) than the inexperienced (27+/-8.4%), regardless of the type of instrument selected. Both experienced and inexperienced operators left the smallest amounts of residual deposits with hand instruments (13+/-9.8%/24+/-9.5%). Both treatment groups removed more hard tooth structure with hand instruments than with the Perioplaner system (53+/-48mg versus 47+/-25.9 mg). Experienced operators needed somewhat more time for debridement than unexperienced. Use of the sonic/ultrasonic device required somewhat less time than hand instrumentation. Inexperienced operators are, however, unable to improve their treatment results by using the power-driven instruments included in the study.

Analysis of Variance↗
PubMed1996

[Comparative evaluation of different instruments for root canal preparation tested on extracted human teeth III. Study of sonic and ultrasonic instruments].

A total of 460 roots of extracted human teeth were divided into three groups i.e. straight, apically curved and entirely curved groups. Each of the three groups were divided into seven subgroups according to instrumentation by conventional hand, K-Flex file, 3-LD, 3-LDSY, Excalibur. MM 1400 and Endo Sonic. Radiographs were taken both clinical and proximal views before and after the enlargement of canals. An assessment of shaping characteristic of instrumentation was made on the basis of overimposed radiographs including perforation, ledge formation smoothness of wall contour incidence of elbow and zip measurements at the elbow level and asymmetry measurements. The majority of enlarged root canals were asymmetrical in shape. High differences were found between the incidence of elbow and zip formation. Under laboratory conditions the K-Flex file produced minor canal aberrations and significantly less asymmetry than the conventional instruments. But both the above mentioned instruments caused perforations on curved canals, such as the instrumentation by Excalibur. The loss of working distance was significant in all canal forms prepared with 3-LD and 3-LDSY instruments, which could have occurred through the packing of debris towards the apical constriction. The Excalibur appeared to be superior to the conventional hand instrument in straight canals, but its shaping characteristic was similar to conventional hand instrument in curved canals. The MM 1400 handpiece and ultrasonic instruments resulted in less aberration and significantly less asymmetry than the other tested instruments.

Dental Instruments↗
PubMedDate not supplied

Comparison of rotary and manual instrumentation techniques on cleaning capacity and instrumentation time in deciduous molars.

PURPOSE: The aim of this study was to evaluate, in vitro, the cleaning capacity and time needed for instrumentation of root canals of deciduous molars by manual and rotary instrumentation. METHODS: Thirty-three deciduous molar root canals were injected with India ink and divided into 3 groups: group I--the root canal instrumented manually with K files; group II--the root canal instrumented with rotary Profile .04 instruments; group III--control group, (ie, root canals not instrumented). Instrumentation time was recorded. The teeth were cleared and the removal of India ink was measured in the cervical, middle, and apical thirds. RESULTS: There was no significant difference for cleaning capacity between manual and rotary techniques in the 3 root thirds (P>.05), but both techniques were different from the control group (P<.001). Significantly less time was needed for instrumentation with the rotary technique (3.46 minutes) than with the manual technique (9.06 minutes). CONCLUSIONS: Although no differences were found for cleaning capacity, the reduction of instrumentation time by the rotary technique was a relevant clinical factor for endodontic treatment.

Dental Instruments↗
PubMed1999

Comparison of cutting efficiency and instrumentation of curved canals with nickel-titanium and stainless-steel instruments.

The cutting efficiency and the effects of instrumentation on curved canal shape of both stainless-steel and nickel-titanium nonstandardized ProFile Series 29 hand instruments and stainless-steel Flexoreamer were investigated under standardized conditions. Concerning cutting efficiency in rotary motion, the Flexoreamer had significantly (p < 0.01) greater cutting efficiency than stainless-steel ProFiles and nickel-titanium ProFiles. Changes in the canal shape differed significantly between the different instruments at all measuring points (p < 0.001). After instrumentation with Flexoreamers with inclusion of two half-sizes (#17 and #22), there were fewer undesirable changes in canal shape compared with both stainless-steel and nickel-titanium ProFile Series 29 instruments. In this study, it seemed that flexible stainless-steel instruments with noncutting tips were superior to the nonstandardized ProFile Series 29 instruments with regard to cutting efficiency and instrumentation of curved canals.

Analysis of Variance↗
PubMed1995

Properties of endodontic hand instruments used in rotary motion. Part 2. Instrumentation of curved canals.

The shaping abilities of nickel-titanium K-files, stainless steel reamers, K-files, and flexible stainless steel instruments with conventional cutting tips and with modified noncutting tips were investigated under standardized conditions using a computer-driven testing device simulating the clinical use of the instruments. Simulated root canals with a 42-degree curvature were sequentially enlarged from #15 to #35. Undesirable changes in the canal shape as a result of instrumentation occurred in all cases. None of the instruments were able to remove material on the whole length of the inner side of the curvature, whereas all instruments removed material on the whole length of the outer side of the curvature, resulting in slight to severe bulging. The extent of undesirable changes in the canal shape depended typically of the type of instrument used. Best instrumentation results were obtained with flexible instruments with noncutting tips.

Alloys↗
PubMed2000

A comparison of single-rod instrumentation with double-rod instrumentation in adolescent idiopathic scoliosis.

STUDY DESIGN: A consecutive series of patients with idiopathic scoliosis treated with single-rod instrumentation was followed prospectively. Outcomes were compared with results obtained from a retrospective review of a consecutive series of patients treated with double-rod instrumentation. OBJECTIVE: To compare single-rod instrumentation with segmental fixation with double-rod instrumentation for the treatment of adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Mechanical testing of single-rod instrumentation with segmental fixation at every level showed it to be as resistant to torsion as a double-rod construct. A clinical trial was initiated to document the clinical outcome in single-rod patients. METHODS: A total of 43 of 51 consecutive patients underwent spinal fusion with a single rod. Outcome was evaluated at a minimum of 2 years after surgery. The control group comprised 103 patients who had standard double-rod instrumentation at the same institution. RESULTS: The single- and double-rod groups were similar with respect to age, sex, curve type, length of follow-up, curve magnitude, and best bend. For King III-V curves undergoing posterior spinal fusion, there was significantly less blood loss in the single-rod group (703 mL vs 1011 mL), less cell saver collection (189 mL vs 367 mL), and less operating time (220 minutes vs 260 minutes). Blood loss and operating time were not different for patients with King I and King II curves. There were eight patients (19%) requiring reoperation because of hardware-related problems in the single-rod group compared with four (4%) in the double-rod group. There were nine patients (21%) with broken rods in the single-rod group, six of whom were symptomatic and five of whom required reoperation. Two patients required multiple operations because of pseudarthrosis in the single-rod group. There were no broken rods in the double-rod group. The single-rod group had 2 early postoperative infections and no late infections compared with 10 late infections in the double-rod group. There was a statistically significant relationship between hardware problems and fusion below L1 in the single-rod group. CONCLUSION: Because of rod failure, single-rod instrumentation should be considered only in curves that can be instrumented to L1 and higher.

Adolescent↗