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Written by Steven Cloyd, DDS Wednesday, 01 June 2005 00:00
Primary treatment options for replacement of a single missing tooth are a fixed partial denture (FPD) and an implant-supported crown.1 However, a 3-unit FPD can have lower success rates, and limited survival rates of abutment teeth, compared to a single-tooth implant. In an evaluation of 42 cases, FPDs had a survival rate of 74% for 15 years.2 Other studies report a mean life span of 10.3 years for an FPD3 and that abutment teeth of an FPD may be lost at rates as high as 30% in 8 to 14 years.4 Caries and/or endodontic failure of abutment teeth are the most common causes of FPD failure.5
Survival rates of dental implants and prostheses for single-tooth replacement range from a low of 94% to a high of 100% for as long as 10 years.6 Teeth adjacent to implants also have an excellent long-term prognosis. In one study, 78 single-tooth implants and 148 adjacent teeth were followed for a mean of 58 months. The coronal and periodontal status of teeth adjacent to implant-supported crowns was excellent, and no teeth were lost.7 Sullivan states that contributions by clinicians, researchers, and manufacturers have brought us to the point where it is possible to place and restore a single dental implant in the aesthetic zone with a success rate above 96%. Further, there is high probability that it will look very much like a natural tooth.8
Many general dentists are reluctant to treatment plan implants for their patients. One reason is lack of confidence in a procedure unfamiliar to them. Another reason is that most current dental insurance plans cover only a portion of implant therapy. Many patients are uncomfortable with the thought of a surgical procedure to place an implant, and some patients think that hospitalization is necessary. The surgical procedure for placing a straightforward, single-tooth implant is normally performed in a dental office by an implant surgeon using local anesthesia and is less traumatic than having a tooth extracted.
Until the 1990s, the protocol for replacement of a hopeless tooth by an implant was to extract the tooth and wait for the extraction site(s) to heal. In the past few years, an alternate approach for single-rooted teeth that are extracted is immediate placement of an implant. This technique has a number of advantages, including prevention of postextraction bone resorption. Carlsson, et al determined that approximately 23% of the anterior alveolar crest will resorb within 6 months following extraction.9 Another study demonstrated that average facial-lingual bone loss 6 months after tooth extraction was 4 mm.10
An important concern during immediate implant placement is whether bone forms between the implant and border of the socket. This intimate contact is achieved when an implant is placed into an edentulous area. Paolantonio and colleagues compared patients who had immediate implants with those who waited until an extraction site healed prior to implant placement. Their conclusion was that osseointegration around im-plants placed into extraction sites or edentulous areas was the same even when the gap between the immediate implant and bone was as much as 2 mm.11
It has been suggested that implants with an irregular surface be used for immediate placement and loading. This is because they achieve a higher percentage of bone-implant contact and higher removal torque values in mechanical testing as compared with a smooth titani-um surface.12 Coarse-surfaced implants tolerate greater micromovement than machined surface implants and can be placed under load sooner.13 A study of 236 implants placed in 34 patients and immediately loaded demonstrated a loss of 16 implants in 11 patients. The major cause of implant failure appeared to be micromovement during integration caused by a nonpassive temporary restoration or patient noncompliance.14
Stress analysis studies of implants indicate that magnitude and distribution of stress vary with implant shape. Most implant designs are threaded because threads serve to change the force distribution at the bone interface, and maturing bone aggregates on protruding surfaces of an implant such as ridges, crests, and thread edges under load.15
The immediate-loaded im-plant requires rigid fixation when the implant is placed. Hence, implant length is particularly important for immediate-loading protocols.16 Although an implant should engage as much of the wall of the extraction socket as possible, the implant should not place pressure on the thin facial plate of bone. The desired depth of implant placement is 3 to 4 mm below the free gingival margin of soft tissue to provide space for biologic width, proper emergence profile, aesthetics, and bone remodeling.17
A consensus conference on immediate function was held as part of the 2003 annual meeting of the American Academy of Implant Dentistry. Guidelines for immediate loading were suggested for single-tooth im-plants.18 These guidelines in-clude (1) implant placement in the aesthetic zone, (2) the presence of ideal soft-tissue conditions, (3) the presence of ideal osseous conditions, (4) the ability to achieve ideal implant position, (5) no occlusion on the transitional restoration, (6) D1 (dense cortical bone), D2 (dense cortical bone outside and coarse cancellous bone inside), and D3 (porous cortical bone outside and fine cancellous bone in region), (7) a screw-shaped implant form, (8) implant length greater than 12 mm, which engages cortical bone at the apex, (9) maintenance of a soft diet (the guidelines did not specify for how long a soft diet should be maintained; in the case report presented in this article, the patient maintained a soft diet for one month), and (10) transitional prosthesis retained with cement or a screw.
Contraindications for immediate loading include (1) parafunctional habits that load the transitional restoration (eg, gum chewing) and (2) ingestion of hard foods. The following case illustrates the application of these guidelines.
|Figure 1. Radiograph of tooth No. 10 (root tip).|
A 65-year-old white female presented to the College of Dentistry, University of Tennessee Health Science Center for treatment. Her chief complaint was that “my crown has broken off my front tooth and I want to get the crown replaced.” A periapical radiograph of tooth No. 10 revealed a short root with little remaining coronal portion of the tooth (Figure 1). In order to restore the tooth, crown lengthening, endodontic treatment, a post and core, and a porcelain-fused-to-metal (PFM) crown were necessary. Due to the expense of saving the tooth and poor long-term prognosis, the patient elected to have the tooth removed.
Among the patient’s options for replacement of the tooth was a fixed partial denture from tooth No. 9 to tooth No. 11 or an implant-supported crown. How-ever, tooth No. 11 served as the mesial abutment rest for a FPD, which the patient did not want replaced. As a temporary measure, the existing PFM crown for tooth No. 10 was adjusted out of function and seated with permanent cement. The patient was cautioned against chewing on the tooth.
The patient’s medical history included treatment for depression and arthritis, and she was taking medications for each condition. Her blood pressure was 140/74 with a pulse rate of 80. Her dental history was significant in that she had several restorations. These included serviceable PFM crowns on teeth Nos. 18 and 30 and a PFM crown on tooth No. 13 that served as the distal abutment for a FPD replacing tooth No. 12. Tooth No. 5 was missing, and an implant was planned for that site. Her occlusion was a class I cuspid/molar relationship, her teeth did not demonstrate excessive wear, and she had no parafunctional habits. The patient’s hygiene was excellent, and she came to the College of Dentistry for regular hygiene visits.
The patient could not return for treatment planning for more than one month. The PFM crown on tooth No. 10 remained cemented, and the tooth was asymptomatic with no signs of infection. A periapical radiograph revealed at least 8 mm of bone past the apex of the root of tooth No. 10. This situation met criteria for tooth extraction, immediate implant placement, and possible loading at the same visit. Advantages of immediate placement include preservation of soft tissue, less treatment time with fewer visits, and patient comfort and aesthetics. It is important to note that the patient had been compliant in regard to tooth No. 10 by not dislodging the temporarily cemented crown.
With this in mind, the decision was made to immediately load the implant if the abutment could be torqued to 35 Ncm without implant rotation. Minimum insertion torque re-sistance of 35 to 50 Ncm has been suggested for immediately loaded implants.18 It has also been demonstrated that functional loading does not impair bone maturation, but rather enhances it.19 A maxillary im-pression was made for construction of a provisional removable partial denture (RPD) in the event the implant could not be immediately loaded.
The patient was dispensed four 200-mg capsules of Celebrex (GD Searle) with instructions to take one capsule per day by mouth starting the day prior to surgery. This anti-inflammatory medication is usually all that is required for postoperative pain and swelling for routine implant surgery. She was also given a prescription for six 500-mg tablets of potassium penicillin and instructed to take 4 tablets one hour prior to surgery and 2 tablets 6 hours after the initial dose.
|Figure 2. Extraction of tooth No. 10 with crown in place using a periotome.||Figure 3. Preservation of bone and tissue after extraction of tooth No. 10.|
|Figure 4. Parallel pin/depth gauge in extraction site.||Figure 5. Radiograph of correct position of parallel pin/depth gauge in extraction site.|
|Figure 6. Implant bur on implant bur handle to form the osteotomy.||Figure 7. Osteotome used in osteotomy to compact cancellous bone.|
For surgery, tooth No. 10 was initially anesthetized with 37 mg of xylocaine with 0.019 mg epinephrine. After initial anesthesia, an additional 4 mg of bupivacaine with 0.004 mg of epinephrine was given for extended anesthesia. Using periotomes, tooth No. 10 was extracted with the PFM crown intact (Figure 2). The extraction procedure preserved the bone and tissue of the tooth socket (Figure 3). A 2.0-mm internally irrigated pilot drill on an implant handpiece turning at 1,200 rpm was placed into the lingual aspect at the apical portion of the tooth socket and taken to a depth of 13 mm from the crestal ridge. A parallel pin/depth gauge was placed into the osteotomy (Fig-ure 4), and a periapical radiograph was exposed to confirm depth and angulation (Figure 5). The osteotomy was carried 5 mm beyond the apex of the socket to ensure primary stability. It was completed using a combination of progressively larger implant burs in a hand instrument (Figure 6) in combination with progressively larger pointed osteotomes (Figure 7). The burs were used in a hand instrument for better control, and osteotomes were used to compact cancellous bone to produce a more dense osteotomy.
|Figure 8. Bone putty being placed after completion of osteotomy.||Figure 9. Camlog Rootline implant 3.8 mm. x 13 mm being placed into osteotomy.|
|Figure 10. Implant with fixture mount attached in correct position in osteotomy.||Figure 11. Photo micrograph of a Camlog internal abutment to attach to implant.|
|Figure 12. Photo micrograph of a Camlog implant to attach to abutment.|
After completion of the osteotomy, a small amount of bone putty was placed into the osteotomy to fill spaces where the implant would not be in contact with the tooth socket (Figure 8). A tapered screw implant (Camlog Biotechnolo-gies, Henry Schein) with a coarse surface, 3.8 mm in diameter by 13 mm in length, was self-threaded into the osteotomy and ratcheted into place (Figure 9). A force exceed-ing 35 Ncm was needed to complete implant placement. It was imperative that a flat side of the metal fixture attached to the implant be placed to the facial (Figure 10), thus ensuring that one of 3 cam slots in the implant would be turned to the facial after removal of the fixture. It was now possible for a prefabricated, angled abutment to be attached to the implant in a position that allowed for restoration. The design of the abutment connection-to-implant has 3 cams machined in the abutment (Figure 11) that slide into 3 slots of the implant (Figure 12). This properly seats the abutment and prevents rotation. The tube-in-tube internal connection of the abutment into the implant provides excellent stability and prevents microleakage. Unlike an externally hexed abutment, this unique internal connection distributes stress loads down the implant rather than at the crest of the residual ridge. Internally connected implants also provide superior strength to the implant-abutment connection.21
|Figure 13. Radiograph showing attachment of abutment to implant. No space should be detected between components.|
|Figure 14. Prepared, prefabricated abutment with cotton and IRM covering hex screw.|
|Figure 15. Provisional crown temporarily cemented on abutment.|
A 15º prefabricated abutment was placed into the im-plant, and a 0.5-mm hex screw was hand-tightened to complete connection to the implant. A periapical radiograph was ex-posed to confirm the junction of implant and abutment (Figure 13). The abutment was prepared in the mouth with a metal cutting bur on a high-speed handpiece using copious amounts of water. A cotton pellet was placed over the hex screw, and IRM (DENTSPLY/Caulk) was used to fill the abutment (Figure 14). A provisional acrylic crown was fabricated and adjusted without centric or protrusive contacts and cemented with temporary cement (Figure 15). The patient was cautioned against chewing on the provisional crown and was then dismissed.
|Figure 16. Abutment after osseointegration of implant and remodeling of tissue.||Figure 17. Final porcelain-fused-to-metal crown seated with temporary cement.|
|Figure 18. Lingual view of porcelain-fused-to-metal crown.||Figure 19. Three-year postoperative radiograph of implant-supported crown in No. 10 area.|
At 3 months, the provisional crown was removed. The im-plant was stable, and the gingival tissue had remodeled around the abutment. The tissue architecture and abutment had a natural tooth appearance (Figure 16). A conventional crown and bridge impression was made and sent to the laboratory. A die was made, and a PFM crown was fabricated. The crown was taken to the mouth, adjusted, and seated with a cement designed for cementation of implant-supported crowns (Figures 17 and 18). A periapical radiograph was made at completion of the restorative procedure (Figure 19). The implant and PFM crown have been stable for 3 years.
Placing an implant immediately after tooth extraction has become routine for anterior single teeth that require replacement. Advantages of this ap-proach include less treatment time and preservation of bone and tissue. However, the immediately restored single-tooth implant has a failure rate of about 5% in the first year. Further, this approach has been evaluated for the least amount of time in the literature.18 Ideal conditions should exist to increase the success of this procedure. Patients must be involved in their treatment. Implant loss usually occurs if patients are not compliant and do not protect the implant during the first crucial weeks after implant loading. Careful treatment planning and patient evaluation are essential in these cases.
1. American Dental Association. Changes in dental services rendered 1959-1990. In: 1990 Survey of Dental Services Rendered. Chicago, Ill: American Dental Association; 1994:24-38.
2. Creugers NH, Kayser HF, van’t Hof MA. A meta-analysis of durability data on conventional fixed bridges. Community Dent Oral Epidemiol. 1994;22:448-452.
3. Schwartz NL, Whitsett LD, Berry TG, et al. Unserviceable crowns and fixed partial dentures: life-span and causes for loss of serviceability. J Am Dent Assoc. 1970:81;1395-1401.
4. Shugars DA, Bader JD, White BA, et al. Survival rates of teeth adjacent to treated and untreated posterior bounded edentulous spaces. J Am Dent Assoc. 1998;129:1085-1095.
5. Misch CE. Tooth replacement and the standard of care. 1000 Gems Update. 2002;Spring:23-24.
6. Misch CE. Endosteal implants for posterior single tooth replacement: alternatives, indications, contraindications, and limitations. J Oral Implantol. 1999;25:80-94.
7. Krennmair G, Piehslinger E, Wagner H. Status of teeth adjacent to single-tooth implants. Int J Prosthodont. 2003;16;524-528.
8. Sullivan DY. Anterior single-tooth dental implant restorations: now is the perfect time to recall significant contributions. J Esthet Restor Dent. 2003;15:305-312.
9. Carlsson GE, Bergman B, Hedegard B. Changes in contour of the maxillary alveolar process under immediate dentures. A longitudinal clinical and x-ray cephalometric study covering 5 years. Acta Odontol Scand. 1967;25:45-75.
10. Lekovic V, Kenney EB, Weinlaender M, et al. A bone regenerative approach to alveolar ridge maintenance following tooth extraction. Report of 10 cases. J Periodontol. 1997;68:563-570.
11. Palantonio M, Dolci M, Scarano A, et al. Immediate implantation in fresh extraction sockets. A controlled clinical and histological study in man. J Periodontol. 2001;72:1560-1571.
12. Cochran DL. A comparison of endosseous dental implant surfaces. J Periodontol. 1999;70:1523-1539.
13. Taborelli M, Jobin M, Francois P, et al. Influence of surface treatments developed for oral implants on the physical and biological properties of titanium. (I) Surface characterization. Clin Oral Implants Res. 1997;8:208-216.
14. Jaffin RA, Kumar A, Berman CL. Immediate loading of dental implants in the completely edentulous maxilla: a clinical report. Int J Oral Maxillofac Implants. 2004;19:721-730.
15. Hakimi NM. Anterior single tooth dental implant: current concepts for enhanced aesthetics. Dentaltown. Mar 2004;54-60.
16. Misch CE, Wang HL. Immediate occlusal loading for fixed prostheses in implant dentistry. Dent Today. Aug 2003;22:50-56.
17. Schenk RK, Buser D. Osseointegration: a reality. Periodontol 2000. 1998;17:22-35.
18. Misch CE, Hahn J, Judy KW, et al; Immediate Function Consensus Conference. Workshop guidelines on immediate loading in implant dentistry. J Oral Implantol. 2004;30:283-288.
19. Brunski JB. Avoid pitfalls of overloading and micromotion of intraosseous implants. Dent Implantol Update. 1993;4:77-81.
20. Schenk RK. Bone regeneration: biologic basis. In: Buser D, Dahlin C, Schenk RK, eds. Guided Bone Regeneration in Implant Dentistry. Berlin: Quintessence; 1994:49-100.
21. Norton MR. In vitro evaluation of the strength of the conical implant-to-abutment joint in two commercially available implant systems. J Prosthet Dent. 2000;83:567-571.
Disclosure: Dr. Cloyd is a consul-tant for Camlog Biotechnologies.
Continuing Education Test No. 66.2
After reading this article, the individual will learn:
• advantages and disadvantages of a 3-unit fixed partial denture compared to a single-tooth implant when replacing a missing maxillary anterior tooth, and
• the basic principles of immediate placement and loading of a single maxillary anterior implant.
1. A meta-analysis of 42 reports on the durability of fixed partial dentures revealed what success rate at 15 years?
2. Survival rates of dental implants and prostheses for single-tooth replacement are in what range at 10 years?
a. 50% to 75%
b. 63% to 70%
c. 75% to 85%
d. 94% to 100%
3. Carlsson, et al determined that approximately ______ % of the anterior alveolar crest will resorb within 6 months following extraction.
4. According to Paolantonio and colleagues, what is the maximum gap between an implant and bone for osseointegration to occur?
a. 0.5 mm
b. 1.0 mm
c. 2.0 mm
d. 4.0 mm
5. The major cause of failure in an immediately loaded implant is ______:
a. micromovement during the osseointegration period.
b. poor nutrition during the healing phase.
c. placement in D-1 bone.
d. using a screw-shaped implant.
6. What bone density classification is NOT recommended for immediate loading according to the 2003 annual meeting of the American Academy of Implant Dentistry?
a. D-1 (dense cortical)
b. D-2 (dense cortical outside and coarse cancellous bone inside)
c. D-3 (porous cortical outside and fine cancellous inside)
d. D-4 (fine cancellous)
7. Advantages of immediate placement/loading of an implant to restore a single missing tooth include all of the following EXCEPT:
a. preservation of soft-tissue contours.
b. less treatment time and fewer treatment visits.
c. improved aesthetics.
d. higher survival rate than traditional treatment.
8. Minimum insertion torque resistance of ______ Ncm has been suggested for immediately loaded implants.
a. 5 to 10
b. 10 to 20
c. 35 to 50
d. 60 to 75
To submit Continuing Education answers, download the answer sheet in PDF format (click Download Now button below). Print the answer sheet, identify the article (this one is Test 66.2), place an X in the box corresponding to the answer you believe is correct, and mail to Dentistry Today Department of Continuing Education (complete address is on the answer sheet).
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