IMMEDIATE LOADING OF THREADED IMPLANTS AT STAGE I SURGERY IN ENDENTULOUS ARCHES: TEN CONSECUTIVE CASE REPORTS WITH 1- TO 5- YEAR DATA

Dennis P. Tarnow, DDS*/Shahram Emtiaz, DDS**?Anthony Classi, DMD***

Immediate loading of threaded with a fixed provisional restoration at stage I was evaluated in 10 consecutive patients. The patients selected had to be completely edentulous and have adequate bone for a minimum of 10-mm-long implants. A minimum of five implants were submerged initially for medicolegal reasons and allowed to heal without loading. The remaining implants were loaded the day of stage I surgery. Once the provisional restoration was relined, it was cemented or screw retained. A total of 107 implants were placed in these 10 patients; 6 had them placed in the mandible, and 4 in the maxilla. Six patients were treated with Nobel Biocare implants, one with ITI Bonefit implants, two with Astra Tech TiOblasta implants, and one with a 3I implant. Sixty-seven of 69 implants that were loaded integrated, and 37 of 38 submerged implants integrated. All 10 patients have been restored with a definitive prosthesis, and all and a fixed provisional prosthesis from stage I surgery. The result of this study indicate that immediate loading if multiple implants rigidly splinted around a completely edentulous arch can be a viable treatment modality. (INT J ORAL MAAXILLOFAC IMPLANTS 1997; 12:319-324)
Key word: immediate loading, implant, micromovement
According to Adell et al 1 and Brånemark et al, 2 one of the prerequisites for establishing osseointegration is a nonloaded condition.1,2 Strict surgical protocol requires a stress-free healing period of 3 to 6 months for osseointegration to occur between a titanium dental implant and the bone. 3 This stress-free healing period is achieved by submerging the implant below the soft tissue and allowing the surgical site to heal without placement of any direct load on the implant. If the patient is edentulous, a 2-week period is placed. When this protocol is followed, it is met with a high degree of success. 2,4

For many edentulous patients who have been wearing complete dentures and are to undergo implant therapy, the need to be without dentures for 2 weeks post-surgery or to spend several additional months with a removable prostheseis may be tolerated as a necessary inconvenience. Until recently, complete transitional dentures have beenthe only available method to restore dental function during the 3- to 6- month healing period of implant sites. Schnitman et al 5 described a technique that avoids the need for a removable denture during this interim they discussed allows the patient to wear an dinterim term success of the overall reconstruction, In their study, nine patients were selected, and 58 standard Nobel Biocare (Nobel Biocare, Göteborg, Sweeden) implants were placed in the mandibles of these patients. Schnitman 6 recently reported 9-year following results. All nine prostheses supported by 25 implants placed in immediate function at the time of implant placement were successful during a placed in immediate		 function, four failed, three prior to 6 months, and one at 18 months postimplantation. All failures of immediately loaded were distal to the incisor region. Of the 33 submerged implants, all were osseointegrated and remain in function to date. According to Schnitman, 6 the failures were probably the result of inadequate implant length (7mm for the posterior implants) and poor bone quality in the posterior mandible. Utilizing a small number of rhesus monkeys, Lum and coworkers 7 presented clinical and hisologic evidence of osseointegration of immediately loaded implants. They suggested that hydroxyapatitecoated blade implants may form a direct bony interface when they are loaded immediately after implant placement at stage I surgery, provided that they are splinted to a firm natural tooth. In 1992, Linkow et al 8 reported on an immediately loaded blade retrieved after 231 months of clinical function. Histologically, the bone-to-implant interface showed a mixture of interfacial tissue components and direct bone contact (46.4% to 82.3%) for classification as osseointegrated. Utilizing beagle dogs, Sagara et al 9 also showed evidence of osseointegration loaded with unilateral prosthesis. Their findings showed that osseointegration did occur, although the immediately loaded implants exhibited less direct bone contact than did the controls.

Salama et al 10 reported on two patients in whom titanium root form implants were immediately loaded and successfully utilized to support provisional fixed restorations in the maxilla and the mandible. Both implant patients were followed from 37 to 40 months after implant placement and immediate loading. All implants osseointegrated and were restored with a fixed prosthesis.
 
The purpose of the present study was to evaluate immediate loading of threaded cylinder implants at stage I surgery with a larger number of implants that were at least 10mm in length.

MATERIALS AND METHODS

Patient Criteria. Ten candidates for the study were selected from patients that presented for implant treatment at New York University, College of Dentistry, Department of Implant Dentistry. The patients selected for treatment had to meet the following criteria:

1. The patient was completely edentulous
2. The patient refused to wear a removable denture at any time during therapy.
3. For mandibular implants, there was adequate bone distal to the mental foramina bilaterally to allow placement of at least 10-mm long implants.
4. The patient consented to the experimental protocol.
5. A medical history revealed no contraindication to implant therapy.

Laboratory Procedure. A facebow transfer and centric relation were utilized mount diagnostic casts on a semiadjustable articulator. A diagnostic waxup for a provisional fixed prosthesis was fabricated. This waxup was duplicated twice, first to fabricate a custom surgical template from clear autopolymerizing resin (Figs 1a and 1b), and second to fabricate the fixed interim prosthesis. An irreversible hydrocolloid impression was made and poured in stone. The provisional heat-processed acrylic resin restoration had a lingual casting fabricated of semiprecious metal, to provide reinforcement (Figs 2a and 2b) (Emtiaz and Tarnow, submitted for publication). This also provided rigidity and cross bracing. 11		 Surgical Procedure. A minimum of 10 implants were placed in each patient's arch (Figs 3a and 3b). All implants were then tested for mobility (Periotest, Siemens Dental, Bensheim, Germany).12 The implants with the lower values (better resistance to load) and the most advantageous anterior-posterior distributions were selected for loading. 13-14 For medicolegal reasons, a minimum of five implants were submerged and allowed to heal without any loading. This protocol was followed in the first five patients to avoid the need for further implant surgery if the loaded implants were all to fail. More implants were immediately loaded in the last four patients (see Table 1) as a result of the high rate of success of the implants in the first five patients. The stable implants were loaded the day of stage I surgery. Dry foil was placed over the sutures to prevent any acrylic resin from contacting the surgical sites.

Once the provisional restoration was relined, it was either cemented or screw retained (Figs 4a and 4b). The first five restorations were cemented with temporary cement. The last five were secured with screws into temporary cylinder abutments. Ten patients were treated between October 1991 and March 1995. Six patients were treated with Nobel Biocare implants, one patient was treated with ITI Bonefit implants (Straumann, Waldenburg, Switerland), two patients with TiOblast implants (Astra Tech, Mölndal, Sweden), and one patient with 3I implants (Implant Innovations, West Palm Beach,Fl). A total of 107 implants were placed in these 10 patients. Sixty-nine implants were immediately loaded and 38 were submerged. Only completely edentulous arches were utilized in this study to ensure minimal rotation of the fixed provisional restorations.

Fig 1a Custom surgical template fabricated from clear polymerizing resin
Fig 1b Try-in of the surgical template

Fig 2a Lingual aspect of the cast waxed for fabrication of a lingual casting to provide reinforcement		 Fig 2b Casting placed on the lingual aspect of the
provisional prosthesis


Fig 3a Thirteen guide pins in place after osteotomies were made with
2-mm twist drills to ensure proper alignment at stage 1 surgery in the mandibular arch


Fig 3b Thirteen Nobel Biocare implants in place
Six mandibular arches and four maxillary arches were treated. Six of the mandibular restorations were opposed by complete maxillary dentures. Three of the maxillary prostheses were opposed by a fixed restoration supported by osseointegrated implants. One maxillary prothesis was opposed by natural dentition that included a four-unit metal-ceramic prothesis. Stage 2 surgeries were performed 4 to 6 months after placement of the submerged implants. Final restorations were then fabricated and placed (Fig 5). For patients 2 and 3, the provisional restoration was removed at each postsurgical visit to evaluate implant mobility during the healing period. This was not done for any of the other prostheses. Panoramic radiographs were taken yearly, and the definitive prostheses were removed at the 1-year postinsertion visit. The patients were recalled every year.

Results
Of the 107 implants placed, 104 osseointegrated (Table 1). One submerged implant failed because of an infection attributed to an adjacent extraction socket, and two loaded implants were lost 		When the cemented provisional restoration was tapped off to verify healing before 4 months of healing had elapsed. Both of these implants had been placed in immediate extraction sockets. All three implants that were lost were in patients 2 and 3. In patient 1 and in the last seven patients, no implants were lost. In these eight patients, the provisional restoration was no removed during the 4- to 6- month healing period. Of 69 implants that were loaded immediately, 67 integrated. Of the 38 submerged implants, 37 integrated successfully.

Discussion
The level of predictability and high success of current implant therapy have provided cause to reevaluated both the surgical and prosthetic protocol that have been proposed. A number of studies have reported that immediate loading of implants with a provisional prosthesis after stage I surgery can result in a high success rate. 5-10 The present study assessed the same concept, utilizing a larger number of implants within an arch as well as placement of some in the posterior region of the mandible. Except in two cases reported
 

two cases reported by Salama et al, 10 posterior mandibular placement has been avoided in most studies because poor bone quality in this region was expected to result in high failure rates. In this study, the same procedure was performed in the maxillary arch, which was attempted in only one of the aforementioned studies on immediate loading papers. The results of this study indicate no difference in success rate between maxillary and mandibular arches.

Brunski has stated, “Micromotion can be deleterious at the bone implant interface, especially if the micromotion occurs soon after implantation.”15,16 Most studies indicate a need for a 3- to 6- month period in which implants are not loaded for osseointegration to occur.3 According to Brunski, 16 micromotion of more than 100um should also be avoided, and motion greater than this level would cause the wound to undergo fibrous repair rather then the


Fig 4a provisional prosthesis seated with screws and access holes covered with cotton pellet and Cavit G.


Fig 4b Panoramic radiograph at stage 1 after implant placement and seating of the provisional prosthesis


Fig 5 Panoramic radiograph after seating of the definitive prostheses, a complete maxillary denture with a metal base and fixed implant-supported mandibular prosthesis.

desired osseous regeneration. In 1972, Cameron et al 17 reported that bonding, meaning integration, also occurs in the presence of micromovement. In 1973, he concluded that the ingrowth of the bone in pores of a porous substance will occur in the presence of micromovement, but not of macromovement. 18 According to Brunski and Cameron, as long as there is no macromovement and no micromovement of more than 100um, the concept of immediate loading of implants can still allow for osseointegration.

Implants stabilized at initial placement by splinting and utilizing the widest anterior-posterior distribution of the implants are able to resist the critical degree of micromovement at the boneimplant interface. Apparently, the type of castingreinforced provisional restoration used in this study both prevents any macromovemnt, or significant micromovement, and provides resistance to forces in all directions. 11

The only failures that occurred were in patients 2 and 3, in whom the provisional restoration was being tapped off to evaluate the implants with the Periotest instrument and to assess the mobility values obtained during the 4 to 6 months of healing. This removal created macromovement and lack of osseointegration. This probably caused two loaded implants to fail. For the last seven patients 7 and 8, fewer implants were integrating. In patients 9 and 10, all implants were loaded and none was submerged. The screw-retained provisional restoration also has the advantage of easy removal, which does not

These case reports, along with the others documented, may provide cause to reevaluate the essential principles of the Brånemark protocol for osseointegration. A submerged, nonload period of 3 to 6 months has certainly been proven to be a successful course of treatment. However, osseointegration can clearly be attained in selected immediately loaded situations as well. This in no way implies that submergence is no longer necessary. These results simply suggest that it is not essential in certain situstions.

These 10 consecutive guidelines to help ensure clinical success for immediate loading.

1. Immediate loading should be attempted in edentulous arches only, to create cross-arch stability.
2. Implants should be at least 10mm long.
3. A diagnostic wax up should be used for template and provisional restoration fabrication.
4. A rigid metal casting should be used on the lingual aspect of the provisional restoration.
5. A screw-retained provisional restoration should be used where possible.
6. If cemented, the provisional restoration should not
be removed during the 4- to 6- month healing
period.
7. All implants should be evaluated with Periotest at stage I, and the implants that show the least mobility should be selected for immediate loading.
8. The widest possible anterior-posterior distribution of implants should be utilized to provide resistance to rotational forces.
9. Cantilevers should be avoided in the provisional
restorations. Conclusions

These 1- to 5- year results in 10 consecutive patients suggest that threaded implants can be placed into immediate function to support a provisional fixed prosthesis in edentulous arches during a 4- to 6- month healing period, in both mandibular and maxillary arches. A delayed loading protocol still remains the treatment of choice; however for a particular population, immediate loading of multiple implants splinted across the arch may prove to be a valuable adjunct to therapy.

Acknowledgement
The technical support and help of Leonard Marotta MDT, is gratefully acknowledged.