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Enamel surface abrasion from ceramic orthodontic brackets: A special case report
ce abrasion from ceramic ortho ecial ease report thony D. Viazis, DDS,” Ralph DeLong, DDS, MS, PhD,h Richard R. Bevis, DDS, llliam H. Douglas, BDS, MS, PhD,d and T. Michael Speidel, DDS,
MSD’
Minneapolis,
Minn.
The purpose of this report is to present a dramatic case of enamel abrasion from ceramic orthodontic appliances that was discovered only after appreciation of the initial findings of a study underway at the Department of Orthodontics, University of Minnesota. An artificial oral environment used in this study to simulate mastication also is described. The potential detrimental effects of ceramic appliances on tooth contact are discussed. All aspects of any new material should be investigated before its clinical application to prevent undesired side effects. (AM J QRTHOD DENTOFAC RTHOP
1989;96:514-8.)
he continuous need for effective esthetic as led to the development of the ceramic brackets. l-* Although a large number of private practitioners have already started using these new brackets, controversy exists concerning the clinical efficacy of these app!iances. Because thousands of patients are being treated with such appliances, we believe it is important to draw the practitioners’ attention to the various clinical implications involved when the physical properties of a material relative to natural tooth structure are not taken into consideration. To avoid misconception concerning newly marketed products, it is necessary to consider the physical properties of ceramic brackets.’ The purpose of this article is to present a case report demonstrating the effect of ceramic brackets in contact with teeth in the opposing arch. The “artificial mouth,” developed at the University of Minnesota Dental School in conjunction with MTS Systems Corporation, Minneapolis, is a system that enables investigators to evaluate dental materials at a statistically significant level under simulated conditions of an oral environmenP*’ (Fig. 1). Following the design of the protocol for a study conducted in the Department of Orthodontics, an upper premolar was brought in contact with a ceramic bracket bonded to a lower premolar tooth and subjected to a lateral excursion type of move-
From the University of Minnesota. This case report is based on the preliminary findings of a thesis in partial fulfillment of the requirements for a master’s of science degree. “Resident, Department of Orthodontics, School of Dentistry. bAssistant Professor, Biomaterials Program-Department of Fixed Prosthodontics, School of Dentistry. ‘Professor, Department of Orthodontics, School of Dentistry. “Professor and Director, Biomaterials Program, School of Dentistry. ‘Professor and Head, Department of Orthodontics, School of Dentistry. 8/4/l&%14
Fig. 1. The artificial cral environment
used for testing dental materials by simulating masticatory patterns.
Fig. 2. Computer profiles of a section of the tipper premolar (arrow pointing at buccal cusp) before and after contact wiih the ceramic bracket. Note the dramatic cusp tip loss. After a total of 100 cycles, 253 pm in vertical height and approximately 0.3 mm3 of volume of enamel material were lost after contact with the ceramic
appliance.
Volume 96 Number 6
Fig. 3. SEM photographs of the buccal tooth cusp of the upper premolar. A, Before testing. (Original magnification x 20.) 8, After testing. Note loss of cusp tip. (Original magnification x 21.) C, The grinding marks of aggressive abrasion. Half of the superior enamel surface has been delaminated, leaving the unmarked enamel underneath. (Original magnification x 51.)
ment by the artificial oral environment. This type of movement is most likely to occur clinically when an interference is present. A constant load of approximately 2 lbs was used for the masticatory force. The rate of chewing was 1 c/s. The teeth were subjected to 15, 60, and 100 masticatory cycles. The before and after occlusaI surfaces of the upper premolar were compared by means of a computerized profiling system that evaluates enamel wear characteristics by determining the volume of material removed (Fig. 2). The grinding marks of the abrasion after application of the masticatory movement were shown with scanning electron microscopy @EM) photographs. Fig. 3, C, shows that half the abraded area has been delaminated, leaving the unmarked enamel underneath. Having obtained these findings in the laboratory, a thorough examination of all the patients with ceramic appliances was undertaken at the orthodontic clinic of the University of Minnesota. Of ten patients being treated with ceramic appliances at the clinic, seven have ceramic brackets on the upper anterior teeth only. No abrasion of the opposing teeth was noted in these cases. The other three patients have full fixed upper and lower ceramic appliances (including the second premolars). Of these three, only one demonstrated severe abrasion of two teeth that came in contact with the opposing ceramic appliances.
A 42-year-old woman came to the orthodontic clinic of the University of Minnesota requesting the new ceramic brackets as recommended by her dentist. She had a Class I
molar occlusion but a Class I1 canine relationship and mild upper and lower crowding with excessoverjet, deep overbite, and a deep curve of Speeon the mandibular arch. The upper left lateral incisor along with the lower left second premolar had been extracted previously. Treatment objectivesincluded moving the upper left canineinto the position of the previously extracted left lateral incisor and, after termination of treatment, placing a porcelain crown on the canine with the morphology of a lateral incisor. The upper left first premolar would occlude in a Class I relationship with the lower left canine. All teeth were bonded with ceramic applianceswith the exception of the first molars, which were cemented with stainless steel bands. When the patient returned to the clinic: she reported that the lower Ieft canine bracket had slightIy interfered with the upper left canine, but only during the first day after appliance placement. Three months Iater, the initial results of the study were available. Immediate clinical examination of the upper left canine showed abrasive ind~~t~tio~s on the incisal surface of its metal crown (Fig. 4, D). In addition, severeenamel abrasion of the cusptip of the upper left first premolar was noted. Althougb this tooth was not in contact with the opposing ceramicbracket on appliance placement, leveling and spaceclosure proceduresbrought its cusp tip in contact with the superior surfaceof the bracket of the lower left first premolar. This lead to the aforementioned abrasion (Fig. 4). impressionsof these maxillary teeth were taken from the study models and from the patient’s mouth Acrylic replicas of these teeth were then fabricated and examined under the SEM (Fig. 5). The extent of enamel damage is quite apparent. DISCUSSION
The purpose of this report is to focus attention on the potential enamel surface abrasion resulting from its
Viazis el al.
Am. J. Orthod.
Dentofm. Orrhop. December 19x9
Fig. 4. A, Patient’s left buccal side immediately after appliance placement with the indirect technique, Note that the lower canine bracket interfers slightly with the upper three-quarter gold crown. The prominent cusp tip of the upper premolar is not in contact with the lower ceramic bracket. B, After alignment, leveling, and retraction initiation, the cusp tip of the premolar comes in contact with the bracket. C, Cusp tip of upper first premolar has been severely worn down. D, Occlusal surface. Note wear facet and cusp tip loss on the first premolar and the deep groove on the gold crown of the canine. Such damage might occur at a single sitting during a regular meal.
contact with ceramic brackets. It is not an exaggeration to correlate this type of attrition to a saw blade applied against a hard surface area. What makes this report even more dramatic is that the low occlusal force of approximately 2 lbs and the minimal number of masticatory cycles (100) used in the laboratory study showed marked similarity to the clinical reality. This implies that severe enamel wear from ceramic appliances might occur during a single meal, as it most probably did with the patient in the case reported herein. Clinicians should realize that the constraints faced by prosthodontists in not opposing natural enamel with porcelain apply equally to orthodontists. The patient should be informed of the various risks involved when
ceramic brackets are used for treatment especially on the posterior teeth and all of the lower anterior teeth. It would be rather simple to state that as long as the brackets are kept out of occlusion, this undesirable side effect is not to be expected. LJnfortunately, during the course of orthodontic treatment, one can not be sure of avoiding this problem, especially in extraction cases in which tooth retraction is initiated. The intention of this report is not to discourage clinicians from using ceramic appliances. It is merely to identify a potential problem that perhaps has not been taken into consideration. A compromised solution would be to use ceramic brackets on the upper anterior teeth since these teeth
Cafe report
Volume 96 Numbrr 6
517
. 5. SEM photographs of the clinical case presented. A, lncisal surface of the three-quarter gold crown of the canine before treatment. (Original magnification x 19.) B, Same surface after contact with the opposing ceramic appliance. (Original magnification x 19.) C, View of the buccal and lingual cusps of the upper first premolar. Note the prominent buccal cusp tip. (Original magnification x 22,) D, Loss of the buccal cusp tip of the premolar after contact with the opposing ceramic bracket. Note that the grinding abrasion marks cannot be seen because acrylic replicas of the original teeth were examined with the SEM. (Original magnification x 21.)
rarely interfere with the occlusion; but of course this should be done after the correction of any anterior crossbites. We have used this combination of ceramic/metal appliances on seven patients with complete patient satisfaction.
Taking into consideration the case report presented herein and the initial findings of the preliminary investigation using the artificial oral environment of the University of Minnesota, the following conclusions can be stated in regard to the clinical application of ceramic appliances.
1. Ceramic brackets used on the mandibular teeth should be kept out of occlusion at all times during treatment. Routine check of this matter is advised at every visit. 2. The patient should be informed of the potential disadvantages of such appliances and the risks that are to be undertaken. 3. Crossbites should first be corrected before the application of porcelain brackets. 4. Use of ceramic brackets on the anterior maxillary teeth possibly is the best way to benefit from the esthetics of porcelain while avoiding potentially deleterious enamel wear of occluding teeth.
Viazis
et al.
We would like to expressour appreciation to Dr. Dianne Rekow of ?heDepartment of Orthodontics, University of Minnesota, for her continuous support and guidance. We also wish to thank SusanM. Biller for typing the manuscript and Walter L. Gutzmer for preparation of the photographic material . RitFERENCES 1. Swartz ML. Ceramic brackets. .I Clin Orthod 1988;22:82-8. 2. Scott GE. Ceramic brackets. J Clin Orthod 1987;21:872. 3. Phillips NW. The advent of ceramics [The editor’s corner]. J Clin Orthod 1988;22:69-70. 4. Viazis AD. Direct bonding in orthodontics-Review. J Pedod 1986;1:1-23. 5. Watanabe LG, Karpac JR, Guess MB. Synthetic sapphire orthodontic bracket base strength. IADR 1988[Abstr 15971. 6. DeLong R, Douglas WH, Sakaguchi RL, Pintado MR. The wear of dental porcelain in an artificial mouth. Dent Mater 1986;2:
214-9. 7. DeLong
R, Douglas WH. Development of an artificial environment for the testing of dental restoratives: bio-axial force and movement control. .I Dent Res 1983:62:32-6.
BOUND
VOLUMES
AVAILABLE
8. DeLong in surface
R, Pintado M, Douglas WH. Measurement contour by computer graphics. Dent Mater
30. 9. Sakaguchi
RL, Douglas WH, DeLong R, Pintado MR. The wear of a posterior composite in an artificial mouth: a clinical correlation. Dent Mater 1986;2:235-40. 10. DeLong R, Sakaguchi RL, Douglas WH, Pintado MR. The wear of dental amalgam in an artificial mouth: a clinical correlation. Dent Mater 1985;1:238-42. 11. Lambrechts P, Braem M, Vanherle G. Quantitative in vivo wear of human enamel as acceptance standard for posterior composites. IADR 1987[Abstr 6051. Reprint requests to: Dr. Anthony D. Viazis Department of Orthodontics School of Dentistry University of Minnesota Moos Tower, Sixth Floor 515 Delaware St. SE Minneapolis, MN 55455
TO SUBSCRIBERS
Bound volumes of the AMERICAN JOURNAL OF ORTHODONTICS AND DENTOare available to subscribers (only) for the 1989 issues from the Publisher, at a cost of $42.00 ($52.00 international) for Vol. 95 (January-June) and Vol. 96 (July-December). Shipping charges are included. Each bound volume contains a subject and author index and all advertising is removed. Copies are shipped within 60 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact The C.V. Mosby Company, Circulation Department, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, USA; telephone (800)325-4177, ext. 351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular Journal subscription.
FACIAL ORTHOPEDICS
of change 1985;1:27-
MSD’
Minneapolis,
Minn.
The purpose of this report is to present a dramatic case of enamel abrasion from ceramic orthodontic appliances that was discovered only after appreciation of the initial findings of a study underway at the Department of Orthodontics, University of Minnesota. An artificial oral environment used in this study to simulate mastication also is described. The potential detrimental effects of ceramic appliances on tooth contact are discussed. All aspects of any new material should be investigated before its clinical application to prevent undesired side effects. (AM J QRTHOD DENTOFAC RTHOP
1989;96:514-8.)
he continuous need for effective esthetic as led to the development of the ceramic brackets. l-* Although a large number of private practitioners have already started using these new brackets, controversy exists concerning the clinical efficacy of these app!iances. Because thousands of patients are being treated with such appliances, we believe it is important to draw the practitioners’ attention to the various clinical implications involved when the physical properties of a material relative to natural tooth structure are not taken into consideration. To avoid misconception concerning newly marketed products, it is necessary to consider the physical properties of ceramic brackets.’ The purpose of this article is to present a case report demonstrating the effect of ceramic brackets in contact with teeth in the opposing arch. The “artificial mouth,” developed at the University of Minnesota Dental School in conjunction with MTS Systems Corporation, Minneapolis, is a system that enables investigators to evaluate dental materials at a statistically significant level under simulated conditions of an oral environmenP*’ (Fig. 1). Following the design of the protocol for a study conducted in the Department of Orthodontics, an upper premolar was brought in contact with a ceramic bracket bonded to a lower premolar tooth and subjected to a lateral excursion type of move-
From the University of Minnesota. This case report is based on the preliminary findings of a thesis in partial fulfillment of the requirements for a master’s of science degree. “Resident, Department of Orthodontics, School of Dentistry. bAssistant Professor, Biomaterials Program-Department of Fixed Prosthodontics, School of Dentistry. ‘Professor, Department of Orthodontics, School of Dentistry. “Professor and Director, Biomaterials Program, School of Dentistry. ‘Professor and Head, Department of Orthodontics, School of Dentistry. 8/4/l&%14
Fig. 1. The artificial cral environment
used for testing dental materials by simulating masticatory patterns.
Fig. 2. Computer profiles of a section of the tipper premolar (arrow pointing at buccal cusp) before and after contact wiih the ceramic bracket. Note the dramatic cusp tip loss. After a total of 100 cycles, 253 pm in vertical height and approximately 0.3 mm3 of volume of enamel material were lost after contact with the ceramic
appliance.
Volume 96 Number 6
Fig. 3. SEM photographs of the buccal tooth cusp of the upper premolar. A, Before testing. (Original magnification x 20.) 8, After testing. Note loss of cusp tip. (Original magnification x 21.) C, The grinding marks of aggressive abrasion. Half of the superior enamel surface has been delaminated, leaving the unmarked enamel underneath. (Original magnification x 51.)
ment by the artificial oral environment. This type of movement is most likely to occur clinically when an interference is present. A constant load of approximately 2 lbs was used for the masticatory force. The rate of chewing was 1 c/s. The teeth were subjected to 15, 60, and 100 masticatory cycles. The before and after occlusaI surfaces of the upper premolar were compared by means of a computerized profiling system that evaluates enamel wear characteristics by determining the volume of material removed (Fig. 2). The grinding marks of the abrasion after application of the masticatory movement were shown with scanning electron microscopy @EM) photographs. Fig. 3, C, shows that half the abraded area has been delaminated, leaving the unmarked enamel underneath. Having obtained these findings in the laboratory, a thorough examination of all the patients with ceramic appliances was undertaken at the orthodontic clinic of the University of Minnesota. Of ten patients being treated with ceramic appliances at the clinic, seven have ceramic brackets on the upper anterior teeth only. No abrasion of the opposing teeth was noted in these cases. The other three patients have full fixed upper and lower ceramic appliances (including the second premolars). Of these three, only one demonstrated severe abrasion of two teeth that came in contact with the opposing ceramic appliances.
A 42-year-old woman came to the orthodontic clinic of the University of Minnesota requesting the new ceramic brackets as recommended by her dentist. She had a Class I
molar occlusion but a Class I1 canine relationship and mild upper and lower crowding with excessoverjet, deep overbite, and a deep curve of Speeon the mandibular arch. The upper left lateral incisor along with the lower left second premolar had been extracted previously. Treatment objectivesincluded moving the upper left canineinto the position of the previously extracted left lateral incisor and, after termination of treatment, placing a porcelain crown on the canine with the morphology of a lateral incisor. The upper left first premolar would occlude in a Class I relationship with the lower left canine. All teeth were bonded with ceramic applianceswith the exception of the first molars, which were cemented with stainless steel bands. When the patient returned to the clinic: she reported that the lower Ieft canine bracket had slightIy interfered with the upper left canine, but only during the first day after appliance placement. Three months Iater, the initial results of the study were available. Immediate clinical examination of the upper left canine showed abrasive ind~~t~tio~s on the incisal surface of its metal crown (Fig. 4, D). In addition, severeenamel abrasion of the cusptip of the upper left first premolar was noted. Althougb this tooth was not in contact with the opposing ceramicbracket on appliance placement, leveling and spaceclosure proceduresbrought its cusp tip in contact with the superior surfaceof the bracket of the lower left first premolar. This lead to the aforementioned abrasion (Fig. 4). impressionsof these maxillary teeth were taken from the study models and from the patient’s mouth Acrylic replicas of these teeth were then fabricated and examined under the SEM (Fig. 5). The extent of enamel damage is quite apparent. DISCUSSION
The purpose of this report is to focus attention on the potential enamel surface abrasion resulting from its
Viazis el al.
Am. J. Orthod.
Dentofm. Orrhop. December 19x9
Fig. 4. A, Patient’s left buccal side immediately after appliance placement with the indirect technique, Note that the lower canine bracket interfers slightly with the upper three-quarter gold crown. The prominent cusp tip of the upper premolar is not in contact with the lower ceramic bracket. B, After alignment, leveling, and retraction initiation, the cusp tip of the premolar comes in contact with the bracket. C, Cusp tip of upper first premolar has been severely worn down. D, Occlusal surface. Note wear facet and cusp tip loss on the first premolar and the deep groove on the gold crown of the canine. Such damage might occur at a single sitting during a regular meal.
contact with ceramic brackets. It is not an exaggeration to correlate this type of attrition to a saw blade applied against a hard surface area. What makes this report even more dramatic is that the low occlusal force of approximately 2 lbs and the minimal number of masticatory cycles (100) used in the laboratory study showed marked similarity to the clinical reality. This implies that severe enamel wear from ceramic appliances might occur during a single meal, as it most probably did with the patient in the case reported herein. Clinicians should realize that the constraints faced by prosthodontists in not opposing natural enamel with porcelain apply equally to orthodontists. The patient should be informed of the various risks involved when
ceramic brackets are used for treatment especially on the posterior teeth and all of the lower anterior teeth. It would be rather simple to state that as long as the brackets are kept out of occlusion, this undesirable side effect is not to be expected. LJnfortunately, during the course of orthodontic treatment, one can not be sure of avoiding this problem, especially in extraction cases in which tooth retraction is initiated. The intention of this report is not to discourage clinicians from using ceramic appliances. It is merely to identify a potential problem that perhaps has not been taken into consideration. A compromised solution would be to use ceramic brackets on the upper anterior teeth since these teeth
Cafe report
Volume 96 Numbrr 6
517
. 5. SEM photographs of the clinical case presented. A, lncisal surface of the three-quarter gold crown of the canine before treatment. (Original magnification x 19.) B, Same surface after contact with the opposing ceramic appliance. (Original magnification x 19.) C, View of the buccal and lingual cusps of the upper first premolar. Note the prominent buccal cusp tip. (Original magnification x 22,) D, Loss of the buccal cusp tip of the premolar after contact with the opposing ceramic bracket. Note that the grinding abrasion marks cannot be seen because acrylic replicas of the original teeth were examined with the SEM. (Original magnification x 21.)
rarely interfere with the occlusion; but of course this should be done after the correction of any anterior crossbites. We have used this combination of ceramic/metal appliances on seven patients with complete patient satisfaction.
Taking into consideration the case report presented herein and the initial findings of the preliminary investigation using the artificial oral environment of the University of Minnesota, the following conclusions can be stated in regard to the clinical application of ceramic appliances.
1. Ceramic brackets used on the mandibular teeth should be kept out of occlusion at all times during treatment. Routine check of this matter is advised at every visit. 2. The patient should be informed of the potential disadvantages of such appliances and the risks that are to be undertaken. 3. Crossbites should first be corrected before the application of porcelain brackets. 4. Use of ceramic brackets on the anterior maxillary teeth possibly is the best way to benefit from the esthetics of porcelain while avoiding potentially deleterious enamel wear of occluding teeth.
Viazis
et al.
We would like to expressour appreciation to Dr. Dianne Rekow of ?heDepartment of Orthodontics, University of Minnesota, for her continuous support and guidance. We also wish to thank SusanM. Biller for typing the manuscript and Walter L. Gutzmer for preparation of the photographic material . RitFERENCES 1. Swartz ML. Ceramic brackets. .I Clin Orthod 1988;22:82-8. 2. Scott GE. Ceramic brackets. J Clin Orthod 1987;21:872. 3. Phillips NW. The advent of ceramics [The editor’s corner]. J Clin Orthod 1988;22:69-70. 4. Viazis AD. Direct bonding in orthodontics-Review. J Pedod 1986;1:1-23. 5. Watanabe LG, Karpac JR, Guess MB. Synthetic sapphire orthodontic bracket base strength. IADR 1988[Abstr 15971. 6. DeLong R, Douglas WH, Sakaguchi RL, Pintado MR. The wear of dental porcelain in an artificial mouth. Dent Mater 1986;2:
214-9. 7. DeLong
R, Douglas WH. Development of an artificial environment for the testing of dental restoratives: bio-axial force and movement control. .I Dent Res 1983:62:32-6.
BOUND
VOLUMES
AVAILABLE
8. DeLong in surface
R, Pintado M, Douglas WH. Measurement contour by computer graphics. Dent Mater
30. 9. Sakaguchi
RL, Douglas WH, DeLong R, Pintado MR. The wear of a posterior composite in an artificial mouth: a clinical correlation. Dent Mater 1986;2:235-40. 10. DeLong R, Sakaguchi RL, Douglas WH, Pintado MR. The wear of dental amalgam in an artificial mouth: a clinical correlation. Dent Mater 1985;1:238-42. 11. Lambrechts P, Braem M, Vanherle G. Quantitative in vivo wear of human enamel as acceptance standard for posterior composites. IADR 1987[Abstr 6051. Reprint requests to: Dr. Anthony D. Viazis Department of Orthodontics School of Dentistry University of Minnesota Moos Tower, Sixth Floor 515 Delaware St. SE Minneapolis, MN 55455
TO SUBSCRIBERS
Bound volumes of the AMERICAN JOURNAL OF ORTHODONTICS AND DENTOare available to subscribers (only) for the 1989 issues from the Publisher, at a cost of $42.00 ($52.00 international) for Vol. 95 (January-June) and Vol. 96 (July-December). Shipping charges are included. Each bound volume contains a subject and author index and all advertising is removed. Copies are shipped within 60 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact The C.V. Mosby Company, Circulation Department, 11830 Westline Industrial Drive, St. Louis, MO 63146-3318, USA; telephone (800)325-4177, ext. 351. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular Journal subscription.
FACIAL ORTHOPEDICS
of change 1985;1:27-