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Removal of benign intraoral masses using the CO2 laser
J1ÍO A C LINICAL
T E C H N I Q U E S
Removal of benign intraoral masses using the C02laser E llio tt Abt, DDS, MS Harvey W igdor, DDS, MS Rocco Lobraico, M D
T
here is a wide spectrum of soft tissue masses that can occur intraorally. These lesions can be devel opmental, inflammatory, infectious, or neoplastic disorders. Treatm ent of benign masses of epithelial, connective, or ner vous tissue origin usually consists of sur gical removal using a scalpel. Occasion ally, electrosurgery (electrocauterization) is used to remove benign lesions. The CO 2 laser offers a surgical approach to treatment of the benign intraoral mass with distinct advantages to conventional surgery and electrosurgery. CO 2 laser surgery is a sterilizing, cutting, and cau terizing method that results in less post operative complications than convention al surgery.1,2 Laser surgery is virtually bloodless, and, because it is a noncontact technique, it is faster than electrosurgery, which requires constant cleaning of the surgical instrum ent. H ealing is not com plicated as the procedure sterilizes the area, cauterizes the blood vessels, and creates a decreased inflammatory response. CO 2 laser light is absorbed by water, and thus vaporizes living cells. When the beam is in focus it can be used as a precise cut ting tool, and biopsy specimens can be obtained. When the beam is retracted, the surgeon defocuses the laser light and removes the bulk of the mass.
Bruce Carlson, D PM David H arris, P hD R obert Pyrcz, R N
atenolol (Tenormin) 50 mg every m orn ing. Oral examination disclosed several folds of tissue in the m andibular left ves tibular mucosa (Fig 1). The inflammatory fibrous hyperplasia (epulis fissuratum) present in this patient is a common tissue reaction to over-extended or ill-fitting dentures. Standard therapy for this condi tion is removal of the redundant tissue and relining the denture, or construction of new dentures. It was decided that this lesion would be removed with the CO 2 laser using intravenous sedation (per patient request) and local anesthesia. T h e intravenous agents used were midazolam (Versed, a benzodiazapene) and fentanyl citrate (Sublimaze). After anesthesia had begun, the patient’s face and eyes were protected with dry, then wet, towels to absorb any scattered laser light. During the procedure clear protec tive glasses were worn by all personnel as the aqueous hum or of the eye can be damaged by the laser light. T he lesion was elevated with a tissue pick-up, and,
using the laser at 10 watts (in focus), a biopsy specimen was taken and immedi ately placed in 10% buffered formalin for histological examination. Microscopically, the specimen showed pseudoepitheliomatous hyperplasia and proliferation of the connective tissue (Fig 2). By increasing the distance between laser and tissue (defocusing), the remainder of the lesion may be removed. When exposed to laser light, a charred layer forms on tissue that must periodically be wiped with wet gauze (Fig 3). T he procedure was bloodless, and the patient was given only ibuprofen (Motrin) 400 mg for pain. T he patient was seen three days postoperatively and had no discomfort nor had she used any medica tion for pain (Fig 4). T he surgical site healed in 10 days. A soft reliner was placed on the patient’s m andibular denture while treatment was done. Case 2. An 89-year-old male had denture
irritation. He was taking no medication
Report of case Case 1. A 53-year-old female came to the
dental clinic with ill-fitting dentures. Her medical history was positive for hyperten sion and she was taking triamterene and hydrochlorothiazide (Dyazide) 50 mg and
F ig 1 ■ R em oval of the m an dibu lar denture
F ig 2 ■ H isto lo g ic a l exam in ation sh ow s that
reveals redundant tissue folds in the vestibular
epulis fissuration consists of pseudoepitheliom a-
mucosa.
tous hyperplasia and a fibrous connective tissue.
JADA, Vol. 115, N ovem ber 1987 ■ 729
CLINICAL
TECHNIQUES
and had a noncontributory medical his tory. T he patient wore a complete maxil lary denture and a partial m andibular denture. Removal of the partial denture showed ulceration of the mucosa of the lingual alveolar ridge leaving a small (1 cm diameter) portion of m andibular bone exposed in the mouth. Painful, erythem atous mucosa surrounded the border of the lesion. T he patient was instructed not to wear the partial denture for 1 week and to return to the clinic for observation. At the next appointm ent, granulation tissue was observed at the borders of the ulcer, and the patient informed that healing was occurring. The partial denture was to be left out again until the next visit. When the patient returned for observa tion, a nonindurated, pedunculated swell ing m easuring 1 cm x 1 cm x 0.5 cm had replaced the healing ulcer (Fig 5). On questioning, the patient admitted wear ing the denture periodically since his last visit. It was decided that the mass would be removed under local anesthesia. The lesion was removed with a scalpel and sent for biopsy (Fig 6). T he remainder of the lesion was removed using electro surgery. T he biopsy report confirmed the presence of granulation tissue covered by a norm al, although thinned epithelium. One week later, the lesion had recurred although the partial denture had not been worn. At this time, it was decided that the mass should be removed under local anes thesia using the CO 2 laser. T he patient was brought to the laser center, where he was gowned and dry and then wet towels were placed over the face an d eyes. After local anesthesia was administered, the laser was set at 10 watts super-pulsed and the lesion was elevated and severed at its stalk. T he laser was then defocused and the mass removed at the same power output. T he patient was seen 1, 3, and 7 days postoperatively with no recurrence of the lesion (Fig 7). This patient required no medication postoper atively.
Fig 3 ■ A charred layer forms on lased tissue; it is
Fig 4 ■ T he healing surgical site 3 days post-
then removed with wet gauze sponges.
operatively.
Fig 5 ■ Continued irritation from a mandibular
Fig 6 ■ H istological exam ination show s a thin
partial denture caused a pedunculated lesion
epithelium covering granulation tissue.
measuring 1 cm x 1 cm x 0.5 cm to form on the
Case 3. A 27 -year-old male was treated at
Cook County H ospital for phenytoininduced gingival hyperplasia. His past medical history included seizure disorders for which he was taking 100 mg phenytoin (Dilantin) three times a day. He had previously had a gingivectomy on the maxillary labial gingiva using electro surgery under local anesthesia. He was given ibuprofen (Motrin) 600 m g three times a day for pain after the procedure. T he patient stated he “lost sleep” for 3 days postoperatively because of the pain. 730 ■ JA DA, Vol. 115, Novem ber 1987
lingual aspect of the alveolar ridge.
T he patient requested that the rem ain der of his “swollen gum s” be removed. T he concept of laser therapy was intro duced and the patient agreed to the p ro ced u re an d requested a general anesthetic. T he gingival hyperplasia was of mod erate severity (Fig 8) and involved both facial and palatal (lingual) surfaces of both arches. Intraoperatively, the patient was given thiopental (Pentothal); atracu-
rium (Tracrium); and fentanyl citrate (Sublimaze) intravenously. Nasotracheal intubation was done using enflurane and N 2O /O 2 as inhalation agents. A red rubber tube, rather than the standard polyvinyl chloride tube, should be used during laser surgery as the latter may burn and ignite the flammable inhalation agents. Sterile dry, then wet towels were used to drape the patient’s face and eyes, and a wet throat pack was placed before the
CLINICAL
TECHNIQUES
caries removal, cavity preparation, fusing restorations to teeth, and endodontic therapy.3-'2 As laser costs decrease and usage increases, small portable lasers may become available in the private dental office, as they are now used by podiatrists and dermatologists. Summary
F ig 7 ■ H ealing is completed 7 days postoper-
Fig 8 ■ Hyperplastic gingiva covers the crowns
atively.
of the mandibular incisors.
Benign soft tissue lesions of the m outh can be removed using the CO 2 laser. T his type of laser surgery is faster and offers less postoperative com plication as com pared with conventional surgery and elec trosurgery. Presently, the CO 2 laser can be used for intraoral biopsy of benign masses, gingivectomies, and frenectomies.
------------------J$OA ------------------
Fig 9 ■ Elongated, thin epithelial ridges and a
Fig 10 ■ Seven days postoperatively, the gingival
fibrous connective tissue are characteristic of
tissue is restored to normal architecture.
phenytoin-induced gingival hyperplasia.
Fig 11 ■ H elium -neon aim ing light is seen in dental mirror during laser gingivectom y.
procedure. After insertion of a m outh p rop, the excess gingival tissue was reflected from the teeth using a periosteal elevator. The CO 2 laser was set at 10 watts superpulsed, and a small piece of gingi val tissue was removed and sent for biopsy (Fig 9). T h e hyperplastic tissue was removed using the defocused beam. Then, using the laser in focus, norm al architec ture was restored by contouring the gin gival tissue. T he procedure was bloodless and took approximately 45 minutes. T he patient was seen 1, 3, and 7 days postoperatively, and the tissue was heal ing well (Fig 10). Ibuprofen (Motrin) 600 mg was given three times a day for pain, and the patient stated there was less dis comfort postoperatively as compared with the first gingivectomy. Discussion
CO 2 laser light is characterized by high
energy and high energy density. This type of light is absorbed by water and destroys tissue by boiling or vaporizing cells. It leaves a sterile wound, and, as blood ves sels are cauterized, better visualization is afforded with a m inim al inflammatory response. Laser surgery is faster than elec trosurgery because it is not a contact technique. Patients who have had both procedures report less postoperative pain with laser surgery; however, this is diffi cult to measure scientifically. Laser surgery is simple in its operation. As it does not involve contact, the sur geon m ust develop a “feeling” for the procedure in that electrosurgery, conven tional surgery, and even the dental hand piece offer tactile sensation during opera tion. Lasers have helium-neon laser light that is emitted continuously and used for aim ing and defocusing (Fig 11). Future uses for lasers in dentistry may include hard tissue applications such as
Dr. A bt is atte n d in g staff, R avensw ood H o sp ital M edical C enter, an d is in private practice, G urnee, IL . Dr. W igdor is atte n d in g staff, a n d chief of d ental services; Dr. L ob raico is m edical director, Dr. C arlson is assistant director, Dr. H arris is educational director, an d Mr. Pyrez is safety coordinator, W enske Laser Center, Ravensw ood H osp ital M edical Center. Address requests for rep rin ts to Dr. Abt, R avensw ood D ental G ro u p , R avensw ood H o sp ital M edical Center, 1945 W ilson, C hicago, 60640. 1. Pick, R.M .; Pecaro, B.C.; an d Silberm an, C.J. T h e laser gingivectom y. T h e use of the C O 2 laser for the rem oval of p h en y to in hyperplasia. J Periodontol 56(8):492-496, 1985. 2. Melcer, J. L atest treatm ent in d entistry by m eans of the C O 2 laser beam. Lasers S urg Med 6:396-398, 1986. 3. Melcer, J., a n d others. T rea tm e n t o f dental decay by C O 2 laser beam : p re lim in a ry results. Lasers Surg Med 4:311-321, 1984. 4. L ib erm an , R., a n d others. A dhesion of com pos ite m aterials to enam el: com p ariso n betw een the use of acid an d lasin g as pretreatm ent. Lasers Surg Med 4:323-327, 1984. 5. W illenborg, G .C . T h e ev o lu tio n of lasers in d en tistry. Laser Focus/E lectro-O ptics. 82-89, O ct 1986. 6. B rune, D. In teractio n of p ulsed carbon dioxide laser beam s w ith teeth in vitro. Scand J D ent Res 88(4):301-305, 1980. 7. Borggreven, J.M .; V an D ijk, J.W .; an d Driessens, F.C. Effect of laser irrad iatio n o n the perm eability of bovine d ental enam el. A rch O ral Biol 25:831-832, 1980. 8. B jelkhagen, H ., an d others. E arly detection of enam el caries by th e lum inescence excited by visible laser light. Swed D ent J 6:1-7, 1982. 9. Y am am oto, H ., a n d Sato, K. Prevention of d en tal caries by acousto-optically Q -sw itched Nd:YAG laser irrad iatio n . J D ent Res 59(2): 137, 1980. 10. Colby, L.E., an d Bevis, R .R . Sim ulated in tra oral laser m icro w eld in g of o rth o d o n tic appliances. A ngle O rth o d 48(4):253-261, 1978. 11. Shoji, S.; N akam ura, M.; a n d H o riu ch i, H. H isto p ath o lo g ical changes in d ental p u lp s irradiated by C O 2 laser: a p relim in ary re p o rt o n laser p u lp o tom y. J E ndod ll(9):379-384, 1985. 12. D ederich, D .N .; Zakariasen, K .L.; an d T u lip , J. S can n in g electron m icroscopic analysis of canal w all d e n tin fo llo w in g n e o d y m iu m -y ttriu m -a lu m in u m g arn et laser irrad iatio n . J E ndod 10(9):428-431, 1984.
A bt-O thers : REM OV AL OF IN T R A O R A L MASSES U S IN G LASER ■ 731
T E C H N I Q U E S
Removal of benign intraoral masses using the C02laser E llio tt Abt, DDS, MS Harvey W igdor, DDS, MS Rocco Lobraico, M D
T
here is a wide spectrum of soft tissue masses that can occur intraorally. These lesions can be devel opmental, inflammatory, infectious, or neoplastic disorders. Treatm ent of benign masses of epithelial, connective, or ner vous tissue origin usually consists of sur gical removal using a scalpel. Occasion ally, electrosurgery (electrocauterization) is used to remove benign lesions. The CO 2 laser offers a surgical approach to treatment of the benign intraoral mass with distinct advantages to conventional surgery and electrosurgery. CO 2 laser surgery is a sterilizing, cutting, and cau terizing method that results in less post operative complications than convention al surgery.1,2 Laser surgery is virtually bloodless, and, because it is a noncontact technique, it is faster than electrosurgery, which requires constant cleaning of the surgical instrum ent. H ealing is not com plicated as the procedure sterilizes the area, cauterizes the blood vessels, and creates a decreased inflammatory response. CO 2 laser light is absorbed by water, and thus vaporizes living cells. When the beam is in focus it can be used as a precise cut ting tool, and biopsy specimens can be obtained. When the beam is retracted, the surgeon defocuses the laser light and removes the bulk of the mass.
Bruce Carlson, D PM David H arris, P hD R obert Pyrcz, R N
atenolol (Tenormin) 50 mg every m orn ing. Oral examination disclosed several folds of tissue in the m andibular left ves tibular mucosa (Fig 1). The inflammatory fibrous hyperplasia (epulis fissuratum) present in this patient is a common tissue reaction to over-extended or ill-fitting dentures. Standard therapy for this condi tion is removal of the redundant tissue and relining the denture, or construction of new dentures. It was decided that this lesion would be removed with the CO 2 laser using intravenous sedation (per patient request) and local anesthesia. T h e intravenous agents used were midazolam (Versed, a benzodiazapene) and fentanyl citrate (Sublimaze). After anesthesia had begun, the patient’s face and eyes were protected with dry, then wet, towels to absorb any scattered laser light. During the procedure clear protec tive glasses were worn by all personnel as the aqueous hum or of the eye can be damaged by the laser light. T he lesion was elevated with a tissue pick-up, and,
using the laser at 10 watts (in focus), a biopsy specimen was taken and immedi ately placed in 10% buffered formalin for histological examination. Microscopically, the specimen showed pseudoepitheliomatous hyperplasia and proliferation of the connective tissue (Fig 2). By increasing the distance between laser and tissue (defocusing), the remainder of the lesion may be removed. When exposed to laser light, a charred layer forms on tissue that must periodically be wiped with wet gauze (Fig 3). T he procedure was bloodless, and the patient was given only ibuprofen (Motrin) 400 mg for pain. T he patient was seen three days postoperatively and had no discomfort nor had she used any medica tion for pain (Fig 4). T he surgical site healed in 10 days. A soft reliner was placed on the patient’s m andibular denture while treatment was done. Case 2. An 89-year-old male had denture
irritation. He was taking no medication
Report of case Case 1. A 53-year-old female came to the
dental clinic with ill-fitting dentures. Her medical history was positive for hyperten sion and she was taking triamterene and hydrochlorothiazide (Dyazide) 50 mg and
F ig 1 ■ R em oval of the m an dibu lar denture
F ig 2 ■ H isto lo g ic a l exam in ation sh ow s that
reveals redundant tissue folds in the vestibular
epulis fissuration consists of pseudoepitheliom a-
mucosa.
tous hyperplasia and a fibrous connective tissue.
JADA, Vol. 115, N ovem ber 1987 ■ 729
CLINICAL
TECHNIQUES
and had a noncontributory medical his tory. T he patient wore a complete maxil lary denture and a partial m andibular denture. Removal of the partial denture showed ulceration of the mucosa of the lingual alveolar ridge leaving a small (1 cm diameter) portion of m andibular bone exposed in the mouth. Painful, erythem atous mucosa surrounded the border of the lesion. T he patient was instructed not to wear the partial denture for 1 week and to return to the clinic for observation. At the next appointm ent, granulation tissue was observed at the borders of the ulcer, and the patient informed that healing was occurring. The partial denture was to be left out again until the next visit. When the patient returned for observa tion, a nonindurated, pedunculated swell ing m easuring 1 cm x 1 cm x 0.5 cm had replaced the healing ulcer (Fig 5). On questioning, the patient admitted wear ing the denture periodically since his last visit. It was decided that the mass would be removed under local anesthesia. The lesion was removed with a scalpel and sent for biopsy (Fig 6). T he remainder of the lesion was removed using electro surgery. T he biopsy report confirmed the presence of granulation tissue covered by a norm al, although thinned epithelium. One week later, the lesion had recurred although the partial denture had not been worn. At this time, it was decided that the mass should be removed under local anes thesia using the CO 2 laser. T he patient was brought to the laser center, where he was gowned and dry and then wet towels were placed over the face an d eyes. After local anesthesia was administered, the laser was set at 10 watts super-pulsed and the lesion was elevated and severed at its stalk. T he laser was then defocused and the mass removed at the same power output. T he patient was seen 1, 3, and 7 days postoperatively with no recurrence of the lesion (Fig 7). This patient required no medication postoper atively.
Fig 3 ■ A charred layer forms on lased tissue; it is
Fig 4 ■ T he healing surgical site 3 days post-
then removed with wet gauze sponges.
operatively.
Fig 5 ■ Continued irritation from a mandibular
Fig 6 ■ H istological exam ination show s a thin
partial denture caused a pedunculated lesion
epithelium covering granulation tissue.
measuring 1 cm x 1 cm x 0.5 cm to form on the
Case 3. A 27 -year-old male was treated at
Cook County H ospital for phenytoininduced gingival hyperplasia. His past medical history included seizure disorders for which he was taking 100 mg phenytoin (Dilantin) three times a day. He had previously had a gingivectomy on the maxillary labial gingiva using electro surgery under local anesthesia. He was given ibuprofen (Motrin) 600 m g three times a day for pain after the procedure. T he patient stated he “lost sleep” for 3 days postoperatively because of the pain. 730 ■ JA DA, Vol. 115, Novem ber 1987
lingual aspect of the alveolar ridge.
T he patient requested that the rem ain der of his “swollen gum s” be removed. T he concept of laser therapy was intro duced and the patient agreed to the p ro ced u re an d requested a general anesthetic. T he gingival hyperplasia was of mod erate severity (Fig 8) and involved both facial and palatal (lingual) surfaces of both arches. Intraoperatively, the patient was given thiopental (Pentothal); atracu-
rium (Tracrium); and fentanyl citrate (Sublimaze) intravenously. Nasotracheal intubation was done using enflurane and N 2O /O 2 as inhalation agents. A red rubber tube, rather than the standard polyvinyl chloride tube, should be used during laser surgery as the latter may burn and ignite the flammable inhalation agents. Sterile dry, then wet towels were used to drape the patient’s face and eyes, and a wet throat pack was placed before the
CLINICAL
TECHNIQUES
caries removal, cavity preparation, fusing restorations to teeth, and endodontic therapy.3-'2 As laser costs decrease and usage increases, small portable lasers may become available in the private dental office, as they are now used by podiatrists and dermatologists. Summary
F ig 7 ■ H ealing is completed 7 days postoper-
Fig 8 ■ Hyperplastic gingiva covers the crowns
atively.
of the mandibular incisors.
Benign soft tissue lesions of the m outh can be removed using the CO 2 laser. T his type of laser surgery is faster and offers less postoperative com plication as com pared with conventional surgery and elec trosurgery. Presently, the CO 2 laser can be used for intraoral biopsy of benign masses, gingivectomies, and frenectomies.
------------------J$OA ------------------
Fig 9 ■ Elongated, thin epithelial ridges and a
Fig 10 ■ Seven days postoperatively, the gingival
fibrous connective tissue are characteristic of
tissue is restored to normal architecture.
phenytoin-induced gingival hyperplasia.
Fig 11 ■ H elium -neon aim ing light is seen in dental mirror during laser gingivectom y.
procedure. After insertion of a m outh p rop, the excess gingival tissue was reflected from the teeth using a periosteal elevator. The CO 2 laser was set at 10 watts superpulsed, and a small piece of gingi val tissue was removed and sent for biopsy (Fig 9). T h e hyperplastic tissue was removed using the defocused beam. Then, using the laser in focus, norm al architec ture was restored by contouring the gin gival tissue. T he procedure was bloodless and took approximately 45 minutes. T he patient was seen 1, 3, and 7 days postoperatively, and the tissue was heal ing well (Fig 10). Ibuprofen (Motrin) 600 mg was given three times a day for pain, and the patient stated there was less dis comfort postoperatively as compared with the first gingivectomy. Discussion
CO 2 laser light is characterized by high
energy and high energy density. This type of light is absorbed by water and destroys tissue by boiling or vaporizing cells. It leaves a sterile wound, and, as blood ves sels are cauterized, better visualization is afforded with a m inim al inflammatory response. Laser surgery is faster than elec trosurgery because it is not a contact technique. Patients who have had both procedures report less postoperative pain with laser surgery; however, this is diffi cult to measure scientifically. Laser surgery is simple in its operation. As it does not involve contact, the sur geon m ust develop a “feeling” for the procedure in that electrosurgery, conven tional surgery, and even the dental hand piece offer tactile sensation during opera tion. Lasers have helium-neon laser light that is emitted continuously and used for aim ing and defocusing (Fig 11). Future uses for lasers in dentistry may include hard tissue applications such as
Dr. A bt is atte n d in g staff, R avensw ood H o sp ital M edical C enter, an d is in private practice, G urnee, IL . Dr. W igdor is atte n d in g staff, a n d chief of d ental services; Dr. L ob raico is m edical director, Dr. C arlson is assistant director, Dr. H arris is educational director, an d Mr. Pyrez is safety coordinator, W enske Laser Center, Ravensw ood H osp ital M edical Center. Address requests for rep rin ts to Dr. Abt, R avensw ood D ental G ro u p , R avensw ood H o sp ital M edical Center, 1945 W ilson, C hicago, 60640. 1. Pick, R.M .; Pecaro, B.C.; an d Silberm an, C.J. T h e laser gingivectom y. T h e use of the C O 2 laser for the rem oval of p h en y to in hyperplasia. J Periodontol 56(8):492-496, 1985. 2. Melcer, J. L atest treatm ent in d entistry by m eans of the C O 2 laser beam. Lasers S urg Med 6:396-398, 1986. 3. Melcer, J., a n d others. T rea tm e n t o f dental decay by C O 2 laser beam : p re lim in a ry results. Lasers Surg Med 4:311-321, 1984. 4. L ib erm an , R., a n d others. A dhesion of com pos ite m aterials to enam el: com p ariso n betw een the use of acid an d lasin g as pretreatm ent. Lasers Surg Med 4:323-327, 1984. 5. W illenborg, G .C . T h e ev o lu tio n of lasers in d en tistry. Laser Focus/E lectro-O ptics. 82-89, O ct 1986. 6. B rune, D. In teractio n of p ulsed carbon dioxide laser beam s w ith teeth in vitro. Scand J D ent Res 88(4):301-305, 1980. 7. Borggreven, J.M .; V an D ijk, J.W .; an d Driessens, F.C. Effect of laser irrad iatio n o n the perm eability of bovine d ental enam el. A rch O ral Biol 25:831-832, 1980. 8. B jelkhagen, H ., an d others. E arly detection of enam el caries by th e lum inescence excited by visible laser light. Swed D ent J 6:1-7, 1982. 9. Y am am oto, H ., a n d Sato, K. Prevention of d en tal caries by acousto-optically Q -sw itched Nd:YAG laser irrad iatio n . J D ent Res 59(2): 137, 1980. 10. Colby, L.E., an d Bevis, R .R . Sim ulated in tra oral laser m icro w eld in g of o rth o d o n tic appliances. A ngle O rth o d 48(4):253-261, 1978. 11. Shoji, S.; N akam ura, M.; a n d H o riu ch i, H. H isto p ath o lo g ical changes in d ental p u lp s irradiated by C O 2 laser: a p relim in ary re p o rt o n laser p u lp o tom y. J E ndod ll(9):379-384, 1985. 12. D ederich, D .N .; Zakariasen, K .L.; an d T u lip , J. S can n in g electron m icroscopic analysis of canal w all d e n tin fo llo w in g n e o d y m iu m -y ttriu m -a lu m in u m g arn et laser irrad iatio n . J E ndod 10(9):428-431, 1984.
A bt-O thers : REM OV AL OF IN T R A O R A L MASSES U S IN G LASER ■ 731