A Technique for Vestibular Sulcus Extension

Prosthodontic considerations when using implants for orthodontic anchorage

Charles J. Goodacre, DDS, MSD, a David T. Brown, DDS, MS, b W. Eugene Roberts, DDS, PhD, ~ and M. Toufic Jeiroudi, DDS, MS a School of Dentistry, Loma Linda University, Loma Linda, Calif., and Indiana University School of Dentistry, Indianapolis, Ind.

Statement of problem. The use of implants for orthodontic anchorage can produce superior preprosthetic tooth positions. Their use often requires a crown or prosthesis to be fabricated for use as a connection between the orthodontic devices and the implant. Purpose. In this article, factors that affect the design of prostheses required for orthodontic movement and examples of prosthesis designs and materials, based on the authors' experience, are presented. (J Prosthet Dent 1997;77:162-70.)

N e w t o n ' s third law states that for every action there is an equal and opposite reaction. During orthodontic treatment, the planned movement of one tooth or group of teeth causes reciprocal movement of the teeth used for anchorage. 1 Therefore, anchorage control is fundamental to successful orthodontic treatment and dentofacial orthopedics. 2 Dental implants, because of their stability in bone, could serve as ideal anchorage units. The concept of using implants for orthodontic anchorage is not new; many articles have been published over the past 50 years. 3a

L I T E R A T U R E R E V I E W

Gainsforth and Higley 3 used Vitallium ramus screws in what is believed to be the first published use of implants for orthodontic anchorage. The screws effected tooth movement in all six dogs, but they loosened in 16 to 31 days, thereby limiting the magnitude of tooth movement. In several more recent animal studies, 4-7 various implant systems were used. Sherman 4 found that two of six vitreous carbon implants placed in dogs resisted 175 gm orthodontic forces, whereas the other four implants loosened or fractured. Using vitreous carbon implants in baboons, Oliver et al. s found that all the implants adequately resisted forces ranging from 30 to 200 gin. Other studies 6- 9 determined that bioglass-coated implants remained stable in rabbits and monkeys under orthodontic forces of 60 to 600 gm. Turley and Roth 10 and Turley et al. n reported that subperiosteal implants in dogs were stable against 300 gm orthodontic forces and 1300 gm orthopedic forces. Douglass and Killiany u placed 14-gauge base metal rods in 21 rats. Of the 11 rats that lived throughout the

Based on a presentation made before the American College of Prosthodontists, New Orleans, La., October, 1994.

~Professor and Dean, School of Dentistry, Loma Linda University. bAssociate Professor, Department of Restorative Dentistry, Indiana

University School of Dentistry, Indianapolis, Ind. cChairman, Department of Oral Facial Development, Indiana Unive>

sity School of Dentistry. eDirector, Advanced Education Program in Orthodontics, School of

Dentistry, Loma Linda University.

experiment, six had implants that loosened. In the remaining five rats, the rods were effectively used to produce tooth movement. ~2 In 1984, Roberts et al. 13 placed 20 titanium implants in the femurs of 14 rabbits. All but one remained rigid against the 100 gm loads that were applied for 4 to 8 weeks. Linder-Aronson et al. 14 placed titanium endosseous implants in two monkeys and determined that they successfully resisted 60 gm forces for 8 weeks. Wehrbein and Diedrich ~5 placed eight titanium endosseous implants in two dogs and used the implants for distalization of the second premolars over a 26-week period. In a study using four dogs, Roberts et al l 6 reported that titanium endosseous implants with as little as 10% direct bone contact resisted 3 N loads (approximately 300 gm) over the 20-week study. Kluemper et al.17 stud- ied the feasibility of using titanium extraosseous implants that clamped around the ramus. The clamp-type design permitted immediate loading and was tested in 12 sheep. They found adverse complications, such as bone resorp- tion and infection. Southard et al. TM used eight dogs to compare the effectiveness of implants and natural teeth as anchorage for orthodontic intrusion. They used 50 to 100 gm intrusive forces and found the implants to be superior to teeth for anchorage. Block and Hoffman ~9 described the use of a disk, coated on one side with hy- di'oxyapatite, that was placed against palatal bone and used for anchorage. They called the disk an "onplant" and tested its use in four dogs and four monkeys. The disks effectively moved premolars in the dogs without loosen- ing. In the monkeys, the disks were used to stabilize molars and retract the anterior teeth, using both cast gold transpalatal bars and 0.051 inch transpalatal wires.

Other animal studies have reported on the use of implants for orthopedic movement. Turley ct al.20 placed bioglass-coated aluminum oxide implants in the palate of three monkeys. Although the anterior implants failed, the posterior implants were effective in producing 6.0 mm of sutural expansion. Smalley et al. 2~ placed titanium endosseous implants in four different bones in monkeys (maxillary, zygomatic, frontal, and occipital). A force of 600 gm was applied until 8 mm of maxillary

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GOODACRE ET AL THE JOURNAL OF PROSTHETIC DENTISTRY

Fig. 1. A, Patient has extensive vertical overlap of anterior teeth. Mandibular incisors are contacting palatal soft tissue to create gingival trauma. B, Six remaining mandibular teeth are proclined facially and malaligned. Because of lack of posterior teeth for orthodontic anchorage, retraction and realignment of these teeth cannot be effectively accomplished. C, Mandibular cast shows location of four endosseous root form implants that have been placed to provide posterior anchorage for retraction and realignment of anterior teeth. Implant locations were determined with mounted casts that were sectioned to position existing malaligned maxillary and mandibular teeth in their postorthodontic positions. Implants are thereby located in positions where they can be used to support definitive posterior prostheses after completion of orthodontic therapy. D, Cast showing one of orthodontic-implant prostheses that provided orthodontic anchorage. Anteriorly cantilevered pontic was veneered with resin and orthodontic bracket bonded into resin veneer. Posterior bar-shaped portion of prosthesis was used to retain an overlay of acrylic resin. Resin overlay permits occlusal vertical dimension to be increased, separate anterior teeth, and provide space for their retraction and realignment. Acrylic resin thickness can be modified as anterior teeth are moved. E, Orthodontic treatment is nearing completion. Retraction of both maxillary and rnan- dibular anterior teeth has improved their relationship, eliminated palatal soft tissue trauma, and improved facial esthetics through changing lip contours. Without use of mandibular posterior implants, these improvements would not have been possible. Patient will soon be ready for definitive prosthodontic treatment that includes replacement of the incisor single crowns and fabrication of maxillary fixed partial dentures from canines to first molars. Mandibular posterior implants will be used to support and retain posterior prostheses.

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Fig. 2. A, Implant was placed in mandibular ramus and hook- shaped casting was fabricated and attached to implant abutment with gold prosthesis screw. B, Orthodontic elastics, wire, and coil spring attached to hooks and used to distally retract mandibular first molar, first and second premolars, and canine. This type of unilateral posterior movement would not be possible without implant or would result in undesirable position changes in other property aligned mandibular teeth. C, Orthodontic realignment completed.

displacement occurred. All of the implants remained stable over the 12- to 18-week treatment times. Turley et al. 22 found that titanium implants resisted 300 gm of orthodontic force and 1000 gm of orthopedic force when tested in six dogs.

Several patient treatment reports have been published. 23-3° One article 23 reported on the use ofa remov-

able orthodontic device to tip a blade implant in the bone, whereas the others 24-3° used implants as anchorage to move teeth. Linkow 24 published the first patient treatment report in 1969 of three patients who were treated with blade implants for anchorage. He published another report of six patients in 1970.2s A maxillary bone screw was used by Creekanore and Eklund 26 to move maxillary incisors in one patient over a 1-year period. O d m a n et al. 27 repor ted on the use o f t i tan ium endosseous implants to extrude teeth, to retract teeth, and to stabilize periodontically weakened teeth. Van Roekel z8 used three implants to correct a reverse occlusal relationship for a canine adjacent to the three implants. Haanaes et al? 9 reported on three patients where implants were used to align impacted third molars. Forces of 2.5 N were used over treatment times of 5 to 8 months. Higuchi and Slack 3° published 3-year results of the first prospective patient study, in which they placed 14 implants in seven patients and used forces between 150 and 400 gin. A mean treatment time of 26 months was reported with no significant complications.3° Prosterman et al? 1 used a fixed prosthesis to apply intrusive forces that corrected an anterior open occlusal relationship. The six-unit fixed prosthesis was supported by three 15 mm implants. Roberts et al? 2,33 demonstrated the use of a retromolar implant for anchorage to close edentulous first molar spaces.

Despite the relatively large number of articles that dis- cuss the use of implants for orthodontic anchorage, there is a lack of information specifically related to prosth- odontics. Therefore, the purposes of this article are to present: (1) prosthodontic advantages o f this concept, (2) factors that affect the design of prostheses that may be needed during orthodontic treatment, and (3) examples of clinical prosthesis designs and materials.

Prosthodontic advantages of implant-orthodontic anchorage

Orthodontic treatment has been a valuable adjunct to p r o s t h o d o n t i c s for decades. I n d e e d , cer ta in prosthodontic treatments are not possible or would be severely compromised without preprosthetic orthodontic therapy. This mutual ly beneficial or thodont ic- prosthodontic relationship has been significantly enhanced through advancements in adult orthodontic treatment. However, the ability to effect specific tooth movements before prosthodontic treatment can be limited by a lack of teeth available for anchorage.

The use of implants for orthodontic anchorage can produce superior preprosthetic tooth alignments. How- ever, the prosthodontic advantages of using implants for orthodontic anchorage are only fully realized when the location and angulation of the implants are carefully planned so that they are optimally located for prostheses that will be placed after orthodontic therapy. Plan- ning must include duplicate sets of mounted diagnostic

164 VOLUME 77 NUMBER2


casts. One set of casts serves as the record of existing tooth positions, and the other can be sectioned and the teeth moved to their proposed postorthodontic position. Prosthetic teeth or diagnostic wax patterns can then be formed on these casts so that definitive prosthodontic tooth positions are determined. Based on the final prosthodontic tooth positions, radiographic stents can be fabricated to assess bone adequacy and surgical stents can be fabricated to precisely guide the surgical placement. Smalley 34 described an organized, precise method of determining preorthodontic implant location and orientation.

Implants have been found to produce superior preprosthetic tooth positions in the following situations.

I. Retracting and realigning teeth. Proclined anterior tceth can present both esthetic and functional problems that may be compounded by palatal soft tissue trauma from the mandibular incisors because of extensive vertical overlap (Fig. 1, A and B). Retracting and realigning these t e e t h 2'I9,24'25'27 can be problematic when most or all of the posterior teeth are missing. Strategi- cally positioned posterior implants can be used as anchorage to effect movements of teeth anterior to the implant(s) that otherwise would not be possible (Fig. 1, C, D, and E). With proper diagnostic planning, the implants can s u b s e q u e n t l y be used for def in i t ive prosthodontic treatment. Implants can also be located posterior to malaligned teeth, in areas such as the retromolar area of the mandibular ramus or the maxillary tuberosity, and be used to retract and realign multiple teeth (Fig. 2).

2. Closing edentulous spaces so prostheses are not required. Retrornolar implants have been used 1,32,~3to close first molar edentulous spaces (Fig. 3). This treatment is particularly advantageous when potential abutments have large pulps or are intact, which makes their preparation difficult or undesirable. In addition, oral hygiene procedures are more complicated in the presence of fixed prostheses because of ponfics and connectors. Therefore, closing a space may facilitate oral hygiene and lessen the risk of caries and periodontal disease.

3. Correcting midline and anterior tooth spacing problems. Implants are particularly helpful when multiple posterior teeth are missing and the desired movement requires teeth be moved in only one direction around the arch circumference. 27

4. Reestablishing proper anteroposterior and mediolateral positions for malposed molar abutments. Implants facilitate achieving positional goals when there are multiple missing posterior teeth and particularly when the malaligned molar abutment is located at the end of a long edentulous span (Fig. 4). 2'29 Realignment of this type of molar can be problematic when only the remaining dentition is used because of the molar's distance from other teeth that will be used for anchorage. The required movement can also be difficult to accomplish without

m

Fig. 3. A, Sagittal view of retromolar implant used as anchorage to close an edentulous first molar extraction site. Second and third molars were translated mesially. Indirect anchorage mechanism stabilizes premolar via wire from implant (arrow) that was inserted in vertical tube of orthodontic bracket. (Adapted from Roberts et al. Angle Orthodontist iin press] with permission. See Roberts et al. J Clin Orthod 1995;28:693- 704 for treatment details.) B, Panoramic radiograpb of mandibular left edentulous first molar site. Endosseous root form implant was placed in left ramus that will be used to move second and third molars anteriorly so first molar space can be closed. C, Posttreatment panoramic radiograph of closure of mandibular first molar space, which eliminated need for prosthetic replacement of first molar. Ramus implant was removed with trephine drill after orthodontic treatment.

tooth eruption that may adversely affect the occlusal plane. 5. Intruding and/or extruding teeth. It is difficult to

intrude or extrude certain teeth. 18,27,29 It can be especialJy difficult to intrude one molar while extruding another, particularly if other posterior teeth are missing. Implant anchorage can greatly facilitate these movements.

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Fig. 4. A, Coping-shaped crown attached to retromolar implant. Facial recess was formed in coping wax pattern and bracket was attached to casting with resin, which interlocks into recess. Lone mandibular molar used as removable partial denture abutment because span between premolar and molar was quite long. B, Molar was moved mesially and span length decreased so that fixed prosthodontic treatment can be performed. Retromolar implant permitted uprighting and mesial transition of molar without displacing premolar mesially.

6. Correcting a reverse occlusal relationship. Cor- recting an anterior reverse occlusal relationship 1,28,3° (cross bite), as in a Class III patient, can be challenging and not always satisfactory. Retracting the entire mandibular arch with ramus implants is possible. 3° It is also possible to retract the mandibular arch with ramus implants while simultaneously protracting the maxillary arch with tuberosity implants. 3° Unilateral or localized reverse occlusal relationships may also be more effectively treated using implants. 28 When adjacent or op- posing teeth are missing, using conventional orthodontic treatment to correct reverse occlusal relationships may be difficult or produce undesirable movement of the teeth used for anchorage.

7. Correcting an anterior open occlusal relationship. Treatment of "open bite" occlusal relationships is significantly enhanced by using implants that permit intrusive forces to be applied posteriorly. ~1

8. Protracting/retracting one arch or the entire dentition. To improve facial esthetics and lip profile, anterior repositioning of teeth can be accomplished with implants located in each ramus and tuberosity, 3° or anterior implants may be used to retrude anteriorly dis- placed teeth (Fig. 5).

9. Providing stabilization for teeth with reduced bone support. Implants have been used for the attachment of wires or o ther devices to posi t ionally stabilize periodontally weakened teeth. 27

1 0. Providing anchorage for orthopedic movement.

Implants placed in the palate may be used to elicit palatal expansion. This form of treatment is particularly ap- plicable to partially edentulous patients and children with congenitally missing teeth (Fig 6).

Disadvantages of using implants for or thodontic anchorage

When implants are used for orthodontic anchorage, treatment time is as long or longer than conventional treatment methods. Although the active orthodontic treatment time may be less in certain situations because of superior anchorage, the implant surgical healing time often extends the overall treatment time.

The cost increase is also a disadvantage. If the implants are used in the definitive prosthodontic treatment, the increased cost is related only to fees associated with attaching the orthodontic wires to the implants and pro- visional crowns/prostheses that may be required to facilitate this attachment.

The location of bone available for implant placement can create access challenges for both surgical and prosthodontic procedures. Moreover, available bone quantity can limit location and alter the mechanical advantages afforded by implant anchorage.

Factors that affect the design of or thodontic implant prostheses

Although it is possible to attach orthodontic wires directly to implant cover screws or premachined implant


GOODACRE ET A/ THE JOURNAL OF PROSTHETIC DENTISTRY

Fig. 5. A, Panoramic radiograph of mandibular anterior defect that resulted from surgical removal of central giant cell granuloma. B, Anterior fixed prosthesis placed; metal casting, resin base, and prosthetic teeth were required to achieve appropriate esthetics and lip support. Prosthetic teeth were set in positions deemed to be appropriate after further facial growth and orthodontic repositioning of remaining teeth. Preorthodontic position of mandibular premolars. C, Panoramic radiograph of three anterior implants after completion of orthodontic treatment and placement of definitive fixed prosthesis. D, Final positions of teeth and definitive implant prosthesis.

components, the use of single crowns or fixed partial dentures attached to the implants may produce more effective and time efficient movement of the teeth, mini- mize gingival inflammation, and satisfy both the esthetic and the functional needs of some patients. Several factors affect the design of these "orthodontic implant prostheses." The following list of factors and accompanying questions helps identify the effect each factor has upon prosthesis design and aids in determining the most appropriate design and materials: 1. Functional requirements - Does the prosthesis need

to provide occlusal support during mandibular closure and chewing?

2. Occlusal forces - What is the magnitude ofocclusal forces present as evidenced by wear facets and parafunctional activity?

3. Esthetic parameters - Will the prosthesis be visible during talking or smiling?

4. Diagnostic requirements - Does the prosthesis need to provide diagnostic information about tooth form, tooth arrangement, or facial support?

5. Method of applying orthodontic forces - Will orth-

odontic wires or elastics be used? How will the orthodontic wires or elastics be attached to the prosthesis?

6. Durability requirements - What is the estimated orthodontic treatment time and how much stress is expected on the attachments?

7. Access - Where will the implants be located? Will the proposed implant location and angulation im- pede prosthesis placement, adjustment, and removal?

8. Oral hygiene - What is the patient's level of oral hygiene? Will the prosthesis form or location affect hygiene procedures?

9. Material selection - Will the prosthesis require re- shaping during treatment? Will it be necessary to add material to the prosthesis during treatment?

10. Treatment t ime/cost - Will multiple prostheses be required in response to changes in growth, occlusal function, or tooth position that occur during treat- mcnt?

When these questions are answered, the most appropriate materials and design can be determined, the prosthodontic fees identified, and the treatment plan fi- nalized.

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Fig. 7. Implants placed bilaterally in palate and cylindrical castings placed with occlusal rims. Wires will be adapted around casting base and attached to maxillary teeth. Occlusal rim prevents wire from slipping off casting.

Fig. 8. Resin-veneered single mandibular premolar was ce- mented on implant abutment and used to effect orthodontic movements of both molar and teeth anterior to crown.

Fig. 6. A, Pretreatment tooth relationships and arch form typical of Apert's syndrome. Constricted maxilla complicated by con- genital absence of multiple premolars and molars. B, Palatal expansion device has been anchored to implant in palate and implant in alveolar ridge, with midline separation of central incisors. C, Occlusal view of expanded maxillary arch with teeth appropriately aligned for definitive prosthodontic treatment.

C L I N I C A L P R O S T H E S I S D E S I G N S A N D M A T E R I A L S

Prosthesis form can be anatomic or nonanatomic, depending on esthetic and functional parameters. Although most prostheses will be fixed, occasionally removable prostheses can be used that overlay implants. All-resin, all-metal, resin veneered metal crowns, metal ceramic

crowns, fixed partial dentures, and metal substructures with prosthetic teeth have been used.

All-resin designs are more economic than metal designs but have limited durability. Although specific peri- ods of service are difficult to predict, it is generally advantageous to use either an all-metal or veneered metal design when orthodontic treatment will require many months to complete. All-resin crowns and fixed partial dentures are more likely to come loose or need remaining than metal castings. Replacing or remaking an all- resin prosthesis is inconvenient and the presence of arch wires and brackets adds to the complexity and cost.

All-metal designs can assume many forms such as hooks (Fig. 2, A), cylindrical castings with occlusal rims (Fig. 7), copings (Fig. 4, A) or anatomic castings. All- metal castings can be fabricated with recesses that re- semble a Class V cavity preparation. The recesses are used to retain composite resin and orthodontic brackets (Fig. 4, A). With appropriate anatomy, single unit all- metal castings are suitable for orthodontic bands.



Resin veneered castings and metal ceramic prostheses are used when esthetic and durability requirements dic- tate such designs. Castings veneered with laboratory pro- cessed composite resin have better durability and color stability than castings veneered with composite resins designed for use as direct restorative materials (Fig. 8). It is easier to reshape or apply additional material to resin- veneered castings than metal ceramic restorations. When metal ceramic crowns or fixed partial dentures are used to obtain maximal esthetics and durability, Class V cavity preparations can be formed in the glazed porcelain using new carbide burs. The Class V preparation is located where the orthodontic bracket will be positioned and terminated in dentin porcelain, leaving opaque porcelain to mask the metal. The porcelain is etched, unfilled bonding resin is applied, and then a composite resin restoration is placed to optimize bracket bonding.

Metal substructures with resin bases and prosthetic teeth may be required when multiple teeth are missing and larger amounts of soft and hard tissue are missing. This type of design permits the development of proper lip/cheek support and is revisable, making it advantageous for use in adolescents where growth is occurring (Figs. 5, B and D).

C O N C L U S I O N S

Our experience with the use of implants for orthodontic anchorage has produced superior preprosthetic tooth alignments for partially edentulous patients who required retracting or realigning teeth, closing spaces to eliminate the need for fixed or removable partial dentures, correcting midline tooth spacing problems, repositioning and stabilizing teeth (and jaws), improving occlusal relationships, and providing anchorage for orthopedic movement. However, their use frequently requires that a prosthesis be fabricated to optimally direct orthodontic forces between the implant(s) and the teeth to be moved.

The design of orthodontic implant prostheses should be determined by evaluating function, esthetics, durability, access, cleansability, material selection, time, and cost. Clinical prostheses can be fabricated with anatomic or nonanatomic forms, depending on esthetic and functional requirements. Materials used for the prostheses include resin, metal, ceramic, or combinations of these materials on the basis of esthetic and durability demands.

We acknowledge the participation of Dr. Charles Nelson in the surgical placement of the implants, Drs. William Hohlt and Gordon Arbuckle in the orthodontic treatments illustrated, and Drs. Rose Marie Jones, Charles Lin, and Edward Owens in the prosthodontic procedures illustrated.

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Am 1988;32:539-50. 2. Arbuck[e GR, Nelson CL, Roberts WE. Osseointegrated implants and orth-

odontics. Oral Maxil[ofac Surg Clin North Am 1991 ;3:903-19. 3. Gainsforth 8L, Higley LB. A study of orthodontic anchorage possibilities in

basal bone. Am J Orthod Oral Surg 1945;31:406-17.

4. Sherman AJ. Bone reaction to orthodontic forces on vitreous carbon dental implants. Am J Orthod 1978;74:79-87.

5. Oliver S, Mendez-Villamil C, Evans C, Schnitman P, Shulman L. Change in position of vitreous carbon implants subjected to orthodontic forces [Ab- stract]. J Dent Res 1980;59(Suppl):280.

6. Smith JR. Bone dynamics assodated with the controlled loading of bioglass- coated aluminum oxide endosteal implants. Am J Orthod 1979;76:618- 36.

7. Paige S, Clark AK, Costa P, King GL, Waldron JM. Orthodontic stress application to bioglass implants in rabbit femurs [Abstract]. I Dent Res 1980;59(Supp[):445.

8. Gray JB, Steen ME, King G J, Clark AK. Studies on the efficacy of implants as orthodontic anchorage. Am J Orthod 1983;83:311-7.

9. Lubberts R, Turley PK. Force application to bioglass coated ~lumina implants of various sizes [Abstract[. J Dent Res 1982;61 (Suppl):339.

10. Turley PK, Roth P. Orthodontic force application to vitallium subperiosteal implants [Abstract]. J Dent Res 1983;62A:681.

11. Turley PK, Gray JW, Kean CJ, Roberts WE. Titanium endosseous and vitallium subperiostea[ implants as orthodontic anchors ror tooth movement in dogs [Abstract]. J Dent Res 1984;63A:344.

12. Douglass JB, Killiany DM. Dental implants used as orthodontic anchorage. J Oral lmplantol 1987;13:28-38.

13. Roberts WE, Smith RK, Zilberman Y, Mozsary PG, Smith RS. Osseous ad- aptation to continuous loading of rigid endosseous implants. Am J Orthod 1984;86:95-111.

14. Linder-Aronson S, Nordenram A, Anneroth G. Titanium implant anchorage in orthodontic treatment: an experimental investigation in monkeys. Eur J Orthod 1990;12:414-9.

15. Wehrbein H, Diedrich P. Endosseous titanium implants during and after orthodontic load-an experimental study in the dog. Clin Oral Implants Res 1993;4:76-82.

16. Roberts WE, Helm FR, Marshall KJ, Gong[off RK. Rigid endosseous im plants for orthodontic and orthopedic anchorage. Angle Orthod 1989;59:247-56.

17. Kluemper GT, Marciano RD, Smith KJ. Biologic response to an intraoral extraosseous implant system: a pilot study. Implant Dent 1995;4:46- 49.

18. Southard TE, Buckley MJ, Spivey JD, Krizan KE, Casko JS. Intrusion anchorage potential of teeth versus rigid endosseous implants: a clinical and radiographic evaluation. Am J Orthod Dentofacial Orthop 1995;107:115- 20.

19. Block MS, Hoffman DR. A new device for absolute anchorage for orthodontics. Am J Orthod Dentofacia[ Orthop 1995;107:251-8.

20. Tudey PK, Shapiro PA, Moffett BC. The loading of bioglass-coated aluminum oxide implants to produce sutural expansion of the maxillary com- plex in the pigtail monkey (Macaca nemestrina). Arch Oral Biol 1980;25:459-69.

21. Smalley WM, Shapiro PA, Hohl TH, Kokich VG, Br~nemark P-I. Osseointegrated titanium implants for maxillofacial protraction in monkeys. Am J Orthod Dentofacial Orthop 1988;94:285-95.

22. Turley PK, Kean C, Schur J, Stefanac J, Gray J, Hennes J, Poon LC. Orth- odontic force application to titanium endosseous implants. Angle Orthod 1988;58:151-62.

23. Wigglesworth SW. The orthodontic movement of a metal implant. Br j Orthod 1977;4:2057.

24. Linkow LI. The endosseous blade implant and its use in orthodontics. Int j Orthod 1969;17:14%54.

25. Linkow LI. lmplanto-orthodontics. J Clin Orthod 1970;4:685-705. 26. Creekmore TD, Eklund MK. The possibility of skeletal anchorage. J Clin

Orthod 1983; 17:266-9. 27. Odman J, Lekholm U, Jemt T, Br~nemark P-l, Thilander 8. Osseointegrated

titanium implants-a new approach in orthodontic treatment. Eur J Orthod 1988;10:98-105.

28. Van Roekel NB. Use of Br~nemark system implants for orthodontic anchorage: report of a case. Int J Oral Maxillofac Implants 1989;4:341-4.

29. Haanaes HR, Stenvik A, Beyer-Oisen ES, Tryti T, Faehn O. The efficacy of two-stage titanium implants as orthodont ic anchorage in the preprosthodontic correction of third molars in adults-a report of three cases. Eur J Orthod 1991;13:287-92.

30. Higuchi KW, Slack JM. The use of titanium fixtures for intraoral anchorage to facilitate orthodontic tooth movement. Int J Oral Maxillofac Implants 1991 ;6:338-44.

31. Prosterman B, Prosterman L, Fisher R, Gornitsky M. The use of implants for orthodontic correction of an open bite. Am J Orthod Dentofacial Orthop 1995;107:245-50.

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32. Roberts WE, Marshall KJ, Mozsary PG. Rigid endosseous implant utilized as anchorage to protract molars and close an atrophic extraction site. Angle Orthod 1990;60:135-52.

33. Roberts WE, Nelson CL, Goodacre CJ. Rigid implant anchorage to close a mandibular first molar extraction site. J Clin Orthod 1994;28:693-704.

34. Smalley WM. Implants for tooth movement: determining implant location and orientation, l Esthetic Dent 1995;7:62-72.

Reprint requests to: DR. CHARLES J. GOODACRE SCHOOL OF DENTISTRY LOMA LINDA UNIVERSITY LOMA LINDA, CA 92350

Copyright © 1997 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/97/$5.00 + 0. 10/1/79109

A comparison of amalgam microleakage with a 4-META liner and copal varnish. Moore DS, Johnson WW, IGaplan I. IntJProsthodont 1995;8:461-6.

Purpose. The purpose of this in vitro study was to compare the effect of copal varnish and 4- META on the microleakage of Class V amalgam restorations 1 week, 6 months, and 1 year after placement. Material and Methods. Identical Class V amalgam preparations were completed in 180 ex- tracted human teeth. The control group specimens (n = 90) had amalgam condensed over two layers of copal varnish. The experimental group specimens (n = 90) had amalgam condensed over a 4-META liner. Each of the two groups was divided into three subgroups (n = 30 each). One subgroup from each group was stored for 1 week in normal saline at 37 ° C; the second subgroups were stored for 6 months; and the third subgroups were stored for 1 year. Specimens from all subgroups were periodically thermocycled 100 times between 4 ° and 58 ° C with a 1- minute dwell time. The specimens were stained with methylene blue, sectioned, and dye pen- etration (microleakage) was viewed with a microscope. The data were collected and analyzed with a Mann-Whitney test. Results. After 1-week and 6-month storage times, the 4-META lined restorations exhibited significantly less microleakage than the copal-lined restorations. After 1-year storage, the 4- META lined restorations demonstrated an increase in microleakage; however, the microleakage of the copal-lined restorations decreased. At 1 year no significant differences in microleakage existed between the groups. Conclusions. The results of this in vitro study suggest that cavity preparations lined with 4- META before amalgam condensation exhibit significantly less microleakage than amalgam-re- stored cavities lined with copal varnish. This was proved true for up to 6 months' storage time; however, the 4-META amalgam sealing ability was lessened as more time lapsed. 16 References. DL Dixon


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A Technique for Vestibular Sulcus Extension