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Early and Immediate Loading of Implants

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Immediate Implants and Immediate Loading in Periodontally Compromised Patients—A 3-Year Prospective Clinical Study-Int J Periodontics Restorative Dent 2010;30:447–455

A total of 23 periodontally compromised patients (11 women, 12 men; 4 smokers, 4 controlled diabetics) were included in this study. Pretreatment casts weretaken and vertical dimension of occlusion was determined. In most patients, 6 Straumann implants were distributed along the arch according to the surgical guide or bone availability, with the most distal ones in the maxilla slightly tilted so they could emerge more distally. A total of 168 implants (146 Straumann, 10 Nobel Biocare, 8 Biomet 3i, and 4 Lifecore) were placed (83 in the maxilla, 85 in the mandible). Of those in the maxilla, 74 were loaded imme- diately (implant stability quotient mentor [ISQm] > 70) and 9 placed with delayed loading (ISQm = 70). Of the 85 implants placed in the mandible, all were loaded immediately (ISQm > 70). If an FPD had not been fabricated already, impressions were taken during surgery to do so. The prosthesis was then adapted (cemented or screwed) to the 6 implants within the first 48 hours postsurgery. After 2 months, definitive impressions were taken, and a definitive porcelain-fused-to-metal implant-supported 12-element FPD was fabricated and cemented or screwed to all 6 implants. Of the 168 implants, 108 were immediate implants and 159 immediately loaded. Only 2 implants (1 in the mandible, 1 in the maxilla) did not osseointegrate. This yields a 3-year cumulative survival rate of 98.74% (98.65% in the maxilla, 98.82% in the mandible). From a total of 26 immediately loaded prostheses (12 in the maxilla, 14 in the mandible), 6 were cemented and 20 screw-retained. The 3-year cumulative survival rate was 100%.
Immediate loading in mandibular and maxillary periodontally compromised patients presents itself as a predictable technique with a 100% cumulative survival rate for provisional and definitive prosthetic rehabilitations

Immediate Implant Loading: Current Status From Available Literature. Clinical Science and Techniques
Implant Dentistry. 16(3):235-245, September 2007. Avila, Gustavo DDS, PhD *; Galindo, Pablo DDS, PhD +; Rios, Hector DDS, PhD *; Wang, Hom-Lay DDS, MSD ++

Abstract:
The introduction of osseointegrated implants in dentistry represents a turning point in dental clinical practice. Thanks to their multiple therapeutic possibilities and the high predictability of success, implant therapy is now regarded as an extremely reliable approach to replace missing teeth. The concept of immediate implant loading has recently become popular due to less trauma, reduced overall treatment time, decreased patient's anxiety and discomfort, high patient acceptance and better function and esthetics. Nonetheless, research and understanding in this area are confuse and sometimes contradictory. Hence, it is the purpose of this review to provide rational for immediate implant loading, summarize current available literature, and analyze factors that influencing this newly introduced treatment method. Results from this review indicated that immediate implant loading achieved similar high success rate as that noted in the conventional approach (delayed protocols). However, a careful case selection, proper treatment plan, meticulous surgery and proper design of prosthesis are essential for optimal outcomes when this approach is adopted.

1. Listgarten, M.A., Clinical trials of endosseous implants: issues in analysis and interpretation. Ann Periodontol, 1997. 2(1): p. 299-313.
The majority of contemporary endosseous dental implant systems are based on designs and materials that, over the last three decades, have proved to be predictably reliable. With proper surgical and prosthetic protocols, rates of implant loss have been held to 15% or less over a 5-year period. This information was obtained largely through longitudinal descriptive studies, primarily aimed at obtaining implant survival rates under ideal clinical conditions, with strict inclusion and exclusion criteria for admitting patients into the studies.

It is important to emphasize that under conditions of routine clinical practice, where patient selection may be more relaxed than in clinical trials and clinicians attempt to stretch the limits of current technology, the survival rates may not necessarily match those reported in the literature. Since "surviving" implants may exhibit characteristics likely to lead to eventual loss of the implant, for example severe osseous defects, such implants may not necessarily be considered successful.

Successful implants should fulfill a list of other criteria considered essential for long-term survival. Differences in implant design preclude some of these criteria from being uniformly applied to all systems. There is a need to identify criteria for success that can be applied to the majority of implant systems. Implants that fail to meet these criteria should be considered failures. Since failure rates may include "failed" as well as "failing" ("ailing") implants, the two categories should be listed separately. From a practical standpoint, implant failures can be grouped into "early" failures, primarily the result of surgical and/or postoperative complications, and "late" failures that arise during and following the restorative phase.

The ability of individual systems to achieve excellent success rates, despite some major differences in their design from other systems, suggests that some requirements, initially considered essential for success, may not be as critical as originally believed. Examples include the need for submerging implants during initial wound healing or the need for stress breaking devices.

On the other hand, a basic requirement for implant success, such as primary stability at the time of insertion and following loading of the implant, may be the unifying principle behind the need for adequate bone volume and density, longer or wider implants, and the 3 to 6-month delay recommended before implants are placed in function. With relatively low failure rates, a large number of patients may have to be included in long-term clinical trials before a statistically significant association can be established between failure rates and potential contributing factors. For the same reasons, and to avoid type 2 errors, large populations may be needed to show that two systems have comparable success rates.

Proving the superiority of one system over another may require fewer subjects. Given the overall low failure rate and the tendency of failures to cluster in individual subjects, failure rates could be markedly affected by the attrition of a few critical subjects. Additional research is needed to validate methods in current use for the clinical determination of osseointegration, and the diagnosis and treatment of occlusal trauma and microbial infections around implants. Also, more reliable methods are needed for the identification of the primary cause(s) of implant morbidity; i.e., infection or occlusal factors.

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2. Holt, R., et al., Effect of early exposure on the integration of dental implants: Part 2--Clinical findings at 6 months postloading. Int J Periodontics Restorative Dent, 2001. 21(4): p. 407-14.
Implant exposure during initial healing after placement has been considered important in both implant integration and postloading effects. This study evaluated the effect of early implant exposure on the clinical findings prerestoration and 6 months postrestoration. Forty-eight implants (24 CPTi and 24 Ti-13-13) were placed in maxillary and mandibular posterior sites in six baboons. Implant exposure was evaluated for 24 of the submerged implants at placement and at each weekly visit for 3 weeks after implant placement. The crestal bone level at maxillary posterior sites was measured at 6-month uncovering, and mandibular sites were measured at 3-month uncovering.

All sites were again measured 6 months after restoration placement. Periotest readings were recorded at implant uncovering and again 6 months postloading. Arbitrary groupings of the Periotest values were assigned as good = -7 to -1; guarded = 0 to +2; and poor = +3 to +27. At 6 months postloading, there were no statistical differences between CPTi and Ti-13-13 for change in crestal bone height in either arch. The mean change in maxillary crestal bone height varied from a 0.59- to 1.35-mm loss. The differences between the mean exposed and nonexposed changes were not statistically significant

The mean change in mandibular crestal bone height varied from a 0.25- to 0.88-mm loss. Changes in crestal bone height for nonexposed sites from 3-month implant uncovering to 6 months postloading were statistically significant at the mesial, buccal, and lingual aspects. The mean change for the nonexposed distal aspect approached significance. The differences between the mean exposed and nonexposed changes were not statistically significant.

The overall percentage of maxillary implants in the good category for nonexposed sites decreased by 41% from uncovering to 6 months after loading, while no change occurred for exposed sites; the percentage of implants in the good category was comparable for early exposed and nonexposed sites (57% and 59%, respectively).

At 6 months after loading, the percentage of implants in the good category was more favorable for early exposed (88%) than nonexposed sites (50%). A one-stage implant approach should provide similar postloading clinical results as the two-stage surgical approach.

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3. Payne, A.G., et al., One-year prospective evaluation of the early loading of unsplinted conical Branemark fixtures with mandibular overdentures immediately following surgery. Clin Implant Dent Relat Res, 2001. 3(1): p. 9-19.

BACKGROUND: Prospective evaluation of the early loading of unsplinted Branemark implants with mandibular overdentures opposing conventional dentures is not evident in the implant-related literature.

PURPOSE: To clinically evaluate progressive and early loading of 20 unsplinted conical Branemark implants in edentulous mandibles with overdentures.

MATERIALS AND METHODS: Ten edentulous patients all had two conical Branemark implants placed in the anterior mandible with mandatory primary stability with bicortical anchorage. Ball abutment connection was performed simultaneously. Previously constructed conventional mandibular dentures were temporarily relined with tissue conditioner postoperatively and worn with moderation for the first 2 weeks to allow progressive loading. Early loading of the implants followed after 2 weeks, with inclusion of the respective matrices in the mandibular dentures, using a definitive reline procedure.

RESULTS: All patients successfully functioned with their mandibular implant overdentures from 2 to 52 weeks postoperatively. Mean marginal bone loss was within established criteria for success: 0.22 mm (SD = 0.48 mm) mesially and 0.30 mm (SD = 0.39 mm) distally on the conical implants. Mobility tests using the Periotest instrument became more negative, although not at statistically significant levels. Difficulties in the management of the peri-implant mucosa between surgery and loading at 2 weeks were observed in 40% of the patients.

CONCLUSIONS: These preliminary 1-year results show that successful early loading of unsplinted conical Branemark implants with mandibular overdentures is possible.

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4. Naert, I., et al., Biologic outcome of single-implant restorations as tooth replacements: a long-term follow-up study. Clin Implant Dent Relat Res, 2000. 2(4): p. 209-18.

BACKGROUND: The replacement of a single tooth or several teeth by means of single-implant restorations is an increasingly used method that needs long-term validation.

PURPOSE: The goal of this study was to evaluate the outcome of single-implant restorations by means of fixed restorations and to define the prognosis through marginal bone level estimations.

MATERIALS AND METHODS: From November 1986 to June 1998, 270 Branemark implants (215 in the upper jaw) were installed in 219 patients (106 males). Both anterior and posterior sites were involved. Of the 263 single restorations, 28 were placed in private dental offices. The patients were followed until June 1999.

RESULTS: Twelve implants failed before or at abutment connection or within 6 months afterward. Only four implants failed later. The cumulative success rates were 93% for the implants and 96.5% for the restorations over a period of 11 years. The marginal bone loss during the first 6 months after abutment connection reached 0.71 mm and then dropped to 0.036 mm annually over a period of 10 years.

CONCLUSIONS: Single-implant restorations (Branemark System) are a reliable treatment with a good long-term prognosis. Failures were concentrated during the healing period and early loading phase.

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5. Ericsson, I., et al., Early functional loading of Branemark dental implants: 5-year clinical follow-up study. Clin Implant Dent Relat Res, 2000. 2(2): p. 70-7.

BACKGROUND: Short-term clinical studies have indicated the possibility of one-stage surgery and early loading of machined titanium implants. However, long-term data comparing the outcome to the conventional two-stage technique are missing.

PURPOSE: A clinical and radiographic study was performed to compare the outcome of oral rehabilitation of the edentulous mandible by fixed suprastructures connected to implants installed according to either (1) a one-stage surgical procedure and early loading (experimental group--EG) or (2) the original two-stage concept (reference group--RG). The EG and RG comprised 16 and 11 subjects, respectively.

MATERIALS AND METHODS: The following specific inclusion criterion were adopted: (1) all patients had to consider themselves to be in good general health, (2) the amount of bone had to enable the installation of five to six, at least 10-mm long fixtures (Mk II fixtures; Nobel Biocare AB, Goteborg, Sweden) between the mental foramina, and (3) the patients had to be available for the follow-up and maintenance program. A total of 88 implants were placed in the EG compared to 30 in the RG. In the EG, fixed appliances were connected to the implants within 20 days following implant installation while the fixed appliances in the RG were connected about 4 months following fixture installation. At delivery of the suprastructures, all patients were radiographically examined, an examination that was repeated at the 18- and 60-month follow-ups.

RESULTS: The analysis of the radiographs from the EG disclosed that during the observation period, between 18 and 60 months, the mean loss of bone support amounted to 0.2 mm (SD = 0.4). The corresponding value observed in the RG was 0.0 mm (SD = 0.5). During the 60-month observation period, no fixture was lost in any of the two groups examined. The implants under study as well as those in the reference material were at all observation intervals found to be clinically stable.

CONCLUSIONS: This clinical study demonstrated that it is, at least based on a 5-year observation period, possible to successfully load via a permanent fixed rigid cross-arch suprastructure titanium dental implants soon after installation. However, such a treatment approach has to be strictly limited to the interforamina area of the edentulous mandible. Furthermore, the bone resorption was found to be within the same range around such implants as around implants installed and loaded according to the original two-stage protocol.

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6. Kronstrom, M., et al., Early implant failures in patients treated with Branemark System titanium dental implants: a retrospective study. Int J Oral Maxillofac Implants, 2001. 16(2): p. 201-7.
Implant failure has been associated with factors such as poor bone quality, insufficient bone volume, implant instability, unfavorable implant loading, and smoking habits. Infections and host responses may also be important factors in dental implant failure. The objectives of the present study were to identify various explanatory factors associated with titanium implant failure. Forty subjects with stage 1 non-osseointegrated titanium dental implants (NOTI) ad modum Branemark and 40 age- and gender-matched control subjects with successfully osseointegrated titanium implants (SOTI) were studied.

Clinical data and gamma G immunoglobulin (IgG) antibody titers were studied. An independent t test revealed that significantly longer implants were placed in subjects with SOTI (P < .05). Statistically significant differences in bone shape and resorption (BSR) scores were found between SOTI and NOTI (P < .05).

Logistic regression analysis identified 3 significant explanatory outcome variables: serum antibody avidity scores for Bacteroides forsythus (P < .0001), serum antibody titers to Staphylococcus aureus (P < .001), and the BSR scores (P < .05). Antibody avidity to B forsythus and antibody titer to S aureus were therefore the 2 most important factors associated with early implant failures and with a significant predictive ability. This indicates that immunologic factors are involved in osseointegration.

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7. Testori, T., et al., A prospective multicenter clinical study of the Osseotite implant: four-year interim report. Int J Oral Maxillofac Implants, 2001. 16(2): p. 193-200.
This article reports the 4-year interim results of a multicenter study evaluating the clinical performance of the Osseotite dental implant. At 4 study centers, 485 Osseotite implants were consecutively placed in 181 patients (219 were placed in the mandible and 266 in the maxilla). A total of 355 implants were placed in posterior regions. Short implants (10 mm or less) represented 31.5% (n = 153) of all implants placed in this study.

Patients were restored with 210 restorations, distributed as 123 short-span prostheses, 58 single-tooth replacements, 28 long-span prostheses, and 1 maxillary overdenture. At this 4-year interim evaluation, the mean time from implant placement to the most recent evaluation was 52.6 +/- 3.0 months, with a mean loading time of 43.3 +/- 3.8 months. Of the 485 implants placed, there have been 6 failures.

All implant failures occurred prior to loading and were categorized as early implant failures. Five of the 6 failures occurred in the maxilla. Only one of the 153 short implants failed to integrate. Baseline radiographs were obtained at prosthesis connection. Radiographic analysis 1 year post-restoration showed a mean bone loss of 0.09 +/- 0.7 mm. From baseline to the end of the second year of function, an overall mean bone loss of 0.13 +/- 0.8 mm was recorded, indicating no additional bone was lost after the first year of implant function.

At 4 years, the cumulative implant success rate for all implants placed in this study was 98.7%, with a 99.4% success rate in the posterior mandible and 98.4% success rate in the posterior maxilla. Results of this 4-year interim analysis indicate that this implant achieved a high success rate in posterior regions and that all failures with this implant in this patient population occurred prior to implant loading.

When the clinical success of implants 10 mm or shorter was compared to that of implants greater than 10 mm in length, the shorter implants in this study performed similarly to longer implants.

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8. Widmark, G., et al., Rehabilitation of patients with severely resorbed maxillae by means of implants with or without bone grafts: a 3- to 5-year follow-up clinical report. Int J Oral Maxillofac Implants, 2001. 16(1): p. 73-9.

Forty three patients with severely resorbed maxillae who had been referred for implant treatment were assigned to 1 of 3 treatment options: bone grafting and implant placement (graft group), modified implant placement with no bone grafting (trial group), or optimized complete dentures (no-implant group). Sixteen, 20, and 7 patients, respectively, were assigned to the 3 groups. The patients have been examined annually, and at the time of this report they had been followed for 3 to 5 years after treatment.

At the 1-year follow-up, 10% (22 of 221) of the implants had been lost, and at the 2-year follow-up, 18% of the implants had been lost (40 of 221; 25% in the graft and 13% in the trial group); after that time, no further losses occurred. Life table analysis showed cumulative success rates of 82% in the graft group and 96% in the trial group after 1 year, and 74% and 87%, respectively, at the final examination after 3 to 5 years. The failure rate was higher in smokers than in non-smokers.

A substantial reduction of the grafted bone, especially of onlay grafts, occurred early after grafting surgery in many patients. Mean marginal peri-implant bone loss was 0.6 mm during the period from prosthesis connection to the 1-year follow-up, and from the 1-year to the 3-year follow-up, average peri-implant bone loss was 0.3 mm in the graft group and 0.5 mm in the trial group.

The results corroborated previous findings that patients with severely resorbed maxillae have an increased risk of implant failure in comparison to patients with good bone quantity and quality. However, in this investigation, practically all implant losses occurred during the first 2 years, whereupon a steady state seemed to follow for up to 5 years after loading.

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9. Davarpanah, M., et al., The self-tapping and ICE 3i implants: a prospective 3-year multicenter evaluation. Int J Oral Maxillofac Implants, 2001. 16(1): p. 52-60.
This multicenter prospective clinical evaluation was undertaken to determine the therapeutic success and marginal bone level stability of 3i's self-tapping and ICE implants after 3 years of prosthetic loading. Between July 1995 and June 1996, 189 completely or partially edentulous patients were treated with 614 machined-surface screw-type commercially pure titanium implants (self-tapping or ICE).

Two hundred seventy-seven self-tapping implants were placed in 85 patients (average age of 56 years), and 337 ICE implants were placed in 104 patients (average age of 61 years). A total of 360 implants (58.6%) were placed in posterior segments.

Easier placement was reported with the ICE implant in normal or dense bone. For the self-tapping implants, survival rates of 92.9% and 91.6% were noted after 1 and 3 years of prosthetic loading, respectively. Survival rates of 95.4% and 93.8% were obtained with the ICE implant for the same periods.

Late failures (after loading) were more common than early failures (before loading) for both types of implants. The marginal bone level of 238 self-tapping implants (85.9%) and of 307 ICE implants (91%) was radiographically evaluated at 3 years. Marginal bone level was at the first thread for 95.1% of implants. A loss of marginal bone level of 2 to 4 threads was noted for 4.9% of the evaluated implants.

No implant showed bone loss greater than the fourth thread. Overall survival rates of 94.3% and 92.9% were obtained after 1 and 3 years of prosthetic loading, respectively, for 596 and 588 implants.

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10. Brunski, J.B., In vivo bone response to biomechanical loading at the bone/dental-implant interface. Adv Dent Res, 1999. 13: p. 99-119.
Since dental implants must withstand relatively large forces and moments in function, a better understanding of in vivo bone response to loading would aid implant design. The following topics are essential in this problem.

(1) Theoretical models and experimental data are available for understanding implant loading as an aid to case planning.
(2) At least for several months after surgery, bone healing in gaps between implant and bone as well as in pre-existing damaged bone will determine interface structure and properties. The ongoing healing creates a complicated environment.
(3) Recent studies reveal that an interfacial cement line exists between the implant surface and bone for titanium and hydroxyapatite (HA). Since cement lines in normal bone have been identified as weak interfaces, a cement line at a bone-biomaterial interface may also be a weak point. Indeed, data on interfacial shear and tensile "bond" strengths are consistent with this idea.
(4) Excessive interfacial micromotion early after implantation interferes with local bone healing and predisposes to a fibrous tissue interface instead of osseointegration.
(5) Large strains can damage bone. For implants that have healed in situ for several months before being loaded, data support the hypothesis that interfacial overload occurs if the strains are excessive in interfacial bone.

While bone "adaptation" to loading is a long-standing concept in bone physiology, researchers may sometimes be too willing to accept this paradigm as an exclusive explanation of in vivo tissue responses during experiments, while overlooking confounding variables, alternative (non-mechanical) explanations, and the possibility that different types of bone (e.g., woven bone, Haversian bone, plexiform bone) may have different sensitivities to loading under healing vs. quiescent conditions.

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11. Caudill, R., et al., Effect of unintentional exposure of 2-stage implants upon subsequent osseointegration: histologic findings 6 months postloading. Int J Periodontics Restorative Dent, 2000. 20(3): p. 307-14.
The purpose of this study was to evaluate the effect of early spontaneous exposure of 2-stage implants upon subsequent histologic bone contact following occlusal loading. As part of a study comparing 2 types of metallic threaded implants, 48 implants (24 CPTi and 24 Ti-13Nb-13Zr) were placed in maxillary and mandibular posterior sites in 6 baboons. Implant exposure was evaluated at time of placement and at each weekly visit for the first 3 weeks, then at 1, 2, and 3 months, and also at 6 months for the maxilla.

Block sections were removed 6 months after the implant restoration was placed into function. One third (33%) of the maxillary implants became exposed, while 66.5% of the mandibular implants became exposed, mostly at 1 to 3 weeks.

For all maxillary implants, fibrous tissue contact in the unintentionally exposed group (20.0%) was significantly greater than in the group that remained submerged (7.7%). Maxillary implants remaining submerged exhibited more sinus contact. For all mandibular implants, bone contact in the exposed group (38.9%) was significantly greater than in the submerged group (24.3%).

Similarly, exposed implants exhibited less fibrous tissue contact. All other parameters in both maxillary and mandibular arches were statistically similar when comparing unintentionally exposed implants to those that remained submerged. This study suggests that accidental exposure of 2-stage implants should result in overall similarities in postloading bone contact to 2-stage implants that remain submerged during the early postoperative healing period.

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12. van Winkelhoff, A.J., et al., Early colonization of dental implants by putative periodontal pathogens in partially edentulous patients. Clin Oral Implants Res, 2000. 11(6): p. 511-20.
There is limited scientific information available on the early colonization of the peri-implant pockets in partially edentulous individuals. Knowledge about this process is one step in better understanding the etiology and pathogenesis of peri-implantitis.

In this study, the early colonization of the peri-implant pockets by putative periodontal pathogens was studied in 20 partially edentulous individuals using anaerobic culture techniques. At baseline, the presence and levels of putative periodontal pathogens in the microflora of periodontal pockets and saliva were established. Immediately after loading of the titanium implants and after 6 and 12 months the presence and levels of selected putative periodontal pathogens were determined in periodontal and peri-implant pockets.

A second aim was to detect bacterial contamination of the implant site and the inside of the implant. At baseline, the most frequently isolated species from the periodontal pockets were Fusobacterium nucleatum, Prevotella intermedia and Peptostreptococcus micros. Bacteroides forsythus, Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis were isolated from 9, 2 and 3 patients respectively. Six months after placing of the bridges, the majority of the implant sites had detectable levels of most periodontal bacterial species with the exception of A. actinomycetemcomitans which could not be isolated from any of the peri-implant samples during the experimental period, although 2 patients had this organism at baseline.

In 2 patients with detectable subgingival P. gingivalis at baseline this species was found after 12 months in the peri-implant sites. One of these patients lost 2 implants which was associated with a high proportion of P. gingivalis in the peri-implant pockets. A second patient developed 2 fistulas around 2 implants at 8 months and this event was also associated with the presence of P. gingivalis.

It is concluded that proper periodontal infection control before installment of dental implants in partially edentulous patients may prevent early bacterial complications.

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13. Kovacs, A.F., Clinical analysis of implant losses in oral tumor and defect patients. Clin Oral Implants Res, 2000. 11(5): p. 494-504.
In the period between 1990 and 1996, 279 endosteal dental Bone-Lock implants were placed in 79 patients. Of them 63 have been treated with ablative tumor and reconstructive surgery in the oral cavity, the rest presented with maxillo-mandibular defects of different origin. The circumstances of implant loss were noted down for descriptive analysis concerning age, sex, topography, implant dimensions, loading, time in place and type of superstructure.

Failure analysis was done concerning the implants and the patients. Five causes for implant loss could be detected: lacking primary osseointegration, acute inflammation, bone loss, biomechanical overloading and tumor recurrence. No predictive factors for implant loss and no age influence on implant loss could be detected, no specific local implant site and no specific superstructure had an identifiable higher risk.

Survival rate of all placed implants in oral tumor and defect patients was 83.5% after 6 years observation. Male tumor patients were found to have a higher risk to lose implants than females. Free iliac bone grafts impaired osseointegration of implants. The mandible offered a better prognosis for the implants than the maxilla.

Shorter and thinner implants had a higher risk of being lost. A quarter of all patients (26.3%) had to face implant loss. Clustering of implant loss in several patients was caused by free iliac bone grafting and by prosthetic faults. Chemotherapy had no negative influence on implant survival. Most implants were lost early (76%) before fabrication of the prosthesis. After restoration there was a nearly 100% probability of function.

It is concluded that implant treatment can be equally effective for tumor and defect patients as it is known for healthy subjects.

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14. Zubery, Y., et al., Immediate loading of modular transitional implants: a histologic and histomorphometric study in dogs. Int J Periodontics Restorative Dent, 1999. 19(4): p. 343-53.
Modular Transitional Implants (MTI) are made from pure titanium and are used to support fixed provisional restorations during the osseointegration of definitive implants. This study histologically examined the jaw response to loaded MTIs in the dog mandible. Three implants were inserted transmucosally into each side of the mandible in 3 dogs.

Stability was examined using a Periotest. Anterior and posterior implants were splinted using a cemented acrylic resin fixed partial denture to allow immediate loading. The middle implant remained unloaded and was used as a control. Dogs were sacrificed 11 to 12 weeks after implantation, and tissue blocks containing the implants were removed. Histologic examination showed that 10 of the 18 implants had good bone-to-implant contact, with the percentage of bone contacting the threaded portion of the implant varying from 30% to 65%.

There was no statistical difference (p > 0.1) in percentage of bone-to-metal contact between loaded and unloaded implants. Six implants were entirely surrounded by connective tissue with or without inflammation; two implants were lost during the study. The success rate did not differ between loaded and unloaded implants. In the successful implants trabecular bone made good contact with the implant, forming supporting struts.

There was bone remodeling in some bone-to-metal contact areas. It is believed that success was mainly influenced by the initial bone density at the implant site and by the uncontrolled load that the animals applied to the implants during the early healing stage.

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15. Misch, C.E., Implant design considerations for the posterior regions of the mouth. Implant Dent, 1999. 8(4): p. 376-86.
The posterior regions of the mouth sustain greater forces, yet often present poorer bone density. A biomechanical approach, often presented to decrease risk factors in such regions, is to increase implant surface area. Most manufacturers provide implants in various lengths. The longest implants are typically inserted into the anterior regions of the mouth, where forces of less magnitude and superior bone quality are present.

A finite element analysis supports the hypothesis that implant length is a secondary parameter for stress distribution. A common approach is to enhance implant surface area in the posterior regions primarily by focusing on diameter.

However, this increases surface area by only 30% for conventional thread designs despite the fact that forces increase by > 300% in the posterior regions. A change in implant diameter and thread design may increase surface area by > 300%. Such increases in surface area may decrease stresses to the crestal bone regions and reduce both crestal bone loss and early loading implant failure.

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16. O'Mahony, A. and P. Spencer, Osseointegrated implant failures. J Ir Dent Assoc, 1999. 45(2): p. 44-51.
This article discusses the criteria used for implant success and failure, the classification of implant failures, the causative factors, and diagnosis of the failing and failed implant. In spite of the impressive success rates of osseointegrated dental implants, failures occur and in some studies the incidence of failure is high.

Many studies do not use objective criteria to define success and confuse survival with success. The criteria used affect reported success rates. Implant failures may occur early (primary) after implant placement or after the implant is loaded (secondary). There is no single aetiological factor and failures have been attributed to poor surgical technique, host factors that impair healing, poor bone quality, peri-implant infections, poor prosthesis design and traumatic loading conditions.

Early diagnosis of problems is critical and every effort should be made to treat the problem while the damage can still be managed or even reversed.

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17. Emmer, T.J., Jr., et al., Measurement of submucosal forces transmitted to dental implants. J Oral Implantol, 1999. 25(3): p. 155-60.
Early loading of dental implants after placement is believed to be a major cause for premature implant failure. If a transitional denture or partial denture is used during the healing period, occlusal forces may be transmitted to the submerged implant, leading to poorly differentiated growth of bone cells and/or potential inhibition of osseointegration at the bone-implant interface.

The objective of this study was to develop an experimental model to measure the force transmission and to characterize the effect of selected loading conditions and relief methods on the forces transmitted to the implant. The loading conditions studied included unilateral and bilateral loading of the prosthesis.

Forces were measured at two different relief conditions (relief with and without soft liner) and were compared against a control with no relief. The results show that fabrication of the prosthesis with a proper relief at the implant-denture junction can eliminate the submucosal force transmission to the implant on loading the denture both under unilateral and bilateral loading conditions.

When a soft liner is used at the relief site, the transmitted force is small, but a finite value is reproducibly recorded. With no relief, the submucosal force transmission is high and may adversely affect the healing process or osseointegration.

The experimental model is valuable in measuring and understanding the submucosal forces that are transmitted to the implant by loading the transitional prosthesis, and such measurement may assist in the proper design of the prosthesis for improved clinical durability and for other uses.

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18. Misch, C.E., et al., A bone quality-based implant system: first year of prosthetic loading. J Oral Implantol, 1999. 25(3): p. 185-97.
This interim report presents the data from a prospective study of BioHorizons, a bone quality-based implant system, with four implant designs. The surgical survival of 975 implants was 99.4%, with the survival 100% for D4 bone. Three critical phases of crestal bone loss have been identified: bone remodeling from stage I to stage II surgery; stage II uncovery to prosthesis delivery (transition period); and prosthesis delivery up to the first year of loading (early loading bone loss).

The stage I to stage II uncovery crestal bone remodeling resulted in a mean vertical bone loss of 0.21 mm to 0.36 mm (SD = 0.90 mm), dependent on whether the implant became exposed in the oral cavity during osseous healing. No statistically significant difference was found among the four implant designs, diameter, bone density, or location.

The stage II to prosthesis delivery mean vertical bone loss ranged from 0.12 mm to 0.20 mm. One hundred three consecutive patients (partially and totally edentulous) were restored, with 360 implants and 105 prostheses in function for a period of 12 to 26 months.

No early loading implant failure occurred, and all patients with implants are in satisfactory to optimum health according to the Misch Implant Quality Scale. The mean early loading bone loss was 0.29 mm (SD = 0.99 mm). Past clinical reports in the literature indicate most failures or crestal bone loss occur by the first year of loading.

This study suggests the bone quality based dental implant design minimizes overall implant failure and crestal bone loss, regardless of bone density.

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19. Majzoub, Z., et al., Bone response to orthodontic loading of endosseous implants in the rabbit calvaria: early continuous distalizing forces. Eur J Orthod, 1999. 21(3): p. 223-30.
The purpose of this experimental study was to evaluate the effect of early orthodontic loading on the stability and bone-implant interface of titanium implants in a rabbit model. Twenty-four short threaded titanium fixtures were inserted in the calvarial mid-sagittal suture of 10 rabbits. Two weeks following insertion, 20 implants (test group) were subjected to continuous distalization forces of 150 g for a period of 8 weeks. The remaining four implants (control group) were left unloaded for the same follow-up interval.

Clinically, all implants except for one test fixture were stable, and exhibited no mobility or displacement throughout the experimental loading period. Histologically, all stable implants were well-integrated into bone.

No differences could be found between the pressure and tension surfaces of the test implants relative to bone quality and density within a range of 1000 microns from the fixture surface.

Similarly, qualitative differences were not observed between the apical and coronal portions of test fixtures. Morphometrically, a mean percentage bone-to-implant contact of 76.00 +/- 18.73 per cent was found at the test pressure sides, 75.00 +/- 11.54 per cent at the test tension sides, and 68.00 +/- 15.55 per cent at the control unloaded surfaces.

No statistically significant differences in the percentage of bone-to-metal contact length fraction were found between test pressure surfaces, test tension surfaces, and unloaded control surfaces.

Marginal bone resorption around the implant collar or immediately beneath it was found in roughly the same percentage of analysed sites in the test and control fixtures. In contrast, slight bone apposition was demonstrated at the implant collar of the test pressure surfaces, while no apposition or resorption were observed in the test tension zones.

This study suggests that short endosseous implants can be used as anchoring units for orthodontic tooth movement early in the post-insertion healing period.

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20. Preiskel, H.W. and P. Tsolka, Treatment outcomes in implant therapy: the influence of surgical and prosthodontic experience. Int J Prosthodont, 1995. 8(3): p. 273-9.
In this retrospective study reviewing 30 months of treatment, 53 partially or completely edentulous patients were provided with implant-supported restorations. The restorative aspects of the therapy were undertaken by an experienced prosthodontist who had just begun involvement with implant rehabilitation techniques. Patients were treated in two centres, 21 in a major teaching institution (Group A) and 32 in a private practice (Group B).

In Group A, the implants were placed by experienced oral and maxillofacial surgeons just beginning involvement in implant techniques. The implants of the Group B patients were placed by surgeons with a minimum of 2 years implant experience. It appeared that the surgeon's experience had a major impact on the failure probability of unloaded implants.

Loading conditions and the design of the prosthesis may be the decisive determinants for the probability of success with loaded implants. The hazards of extensive cantilevered extensions were demonstrated.

The results suggest that those entering implant prosthodontics should not expect their early work to match the results obtained from established centres.

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21. Lazzara, R.J., et al., A prospective multicenter study evaluating loading of osseotite implants two months after placement: one-year results. J Esthet Dent, 1998. 10(6): p. 280-9.
Historically, the recommended time between placement and functional loading of machined-surface dental implants has been 3 months for the mandible and 6 months for the maxilla. However, such recommendations are a result of evaluating randomly chosen healing times during the initial phase of implant development and are based on the subsequent clinical outcome of either implant integration or mobility.

In recent years, histologic and experimental studies have shown that specifically designed micro-topographic implant surfaces can result in increased bone-to-implant contact at earlier healing times than obtained with machined-surface implants. Histologic and clinical studies investigating early and immediate implant loading support the premise that implants can be placed into function earlier than previously recommended. With the development of specifically designed implant surfaces and the utilization of time-saving surgical (one-stage surgical protocol) and prosthetic (implant position indexing) techniques, patients are now being restored and returning to function sooner than previously thought possible.

The purpose of this multicenter clinical investigation is to evaluate the efficacy of loading Osseotite dental implants (3i-Implant Innovations Inc., Palm Beach Gardens, Florida) at 2 months and to determine the effect of early loading on implant performance and survival. A total of 429 Osseotite implants were placed in 155 patients (87 females and 68 males; mean age 54.0 +/- 13.7 yr), at 10 study centers, and subsequently loaded 2.1 +/- 0.7 months following placement.

A single-stage surgical protocol was followed, with implants indexed immediately or impressed 4 to 6 weeks following placement. Patient restorative treatments included placement of 83 single-implant provisional restorations and 129 splinted, two-, three-, and four-implant supported maxillary and mandibular provisional restorations. The mean time from prosthetic loading to the most recent follow-up evaluation was 10 +/- 1.3 months. Seven of the 429 implants did not integrate; of these, six were identified prior to loading and one was identified 1 month after loading. The cumulative implant survival rate was 98.5% at 12.6 months. The cumulative post-loading implant survival rate was 99.8% at 10.5 months.

The preliminary results of this clinical investigation suggest that successful functional loading of the Osseotite dental implant is possible at 2 months following noncomplicated implant placement.

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22. Pilliar, R.M., Overview of surface variability of metallic endosseous dental implants: textured and porous surface-structured designs. Implant Dent, 1998. 7(4): p. 305-14.
A variety of successful endosseous dental implants with different surface forms are currently available for clinical use. These all achieve implant-to-bone fixation primarily (if not totally) through mechanical interlock of bone with implant surface features introduced by design or chance during implant fabrication.

Equally important to establishment of rigid fixation is the rate at which it is achieved, because faster rates allow earlier implant loading and less chance of inadvertent early loading that might prevent implant "osseointegration." Investigations of surface modification to favorably affect osteoconductivity and bone bonding represent an active area of research in the field of dental implant development.

This article presents a review of available surface designs and future research directions for improved devices.

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23. Esposito, M., et al., Biological factors contributing to failures of osseointegrated oral implants. (II). Etiopathogenesis. Eur J Oral Sci, 1998. 106(3): p. 721-64.
The aim of the present review is to evaluate the English language literature regarding factors associated with the loss of oral implants. An evidence-based format in conjunction, when possible, with a meta-analytic approach is used. The review identifies the following factors to be associated with biological failures of oral implants: medical status of the patient, smoking, bone quality, bone grafting, irradiation therapy, parafunctions, operator experience, degree of surgical trauma, bacterial contamination, lack of preoperative antibiotics, immediate loading, nonsubmerged procedure, number of implants supporting a prosthesis, implant surface characteristics and design.

Excessive surgical trauma together with an impaired healing ability, premature loading and infection are likely to be the most common causes of early implant losses. Whereas progressive chronic marginal infection (peri-implantitis) and overload in conjunction with the host characteristics are the major etiological agents causing late failures. Furthermore, it appears that implant surface properties (roughness and type of coating) may influence the failure pattern.

Various surface properties may therefore be indicated for different anatomical and host conditions. Finally, the histopathology of implant losses is described and discussed in relation to the clinical findings.

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24. Collaert, B. and H. De Bruyn, Comparison of Branemark fixture integration and short-term survival using one-stage or two-stage surgery in completely and partially edentulous mandibles. Clin Oral Implants Res, 1998. 9(2): p. 131-5.
The aim of this prospective study was to compare the clinical integration and survival of Branemark fixtures when using the conventional 2-stage surgical procedure to 1-stage surgical approach in completely and partially edentulous mandibles.

A total of 85 patients were consecutively treated for partial (n = 35) or complete (n = 50) mandibular edentulousness. Fixtures removed because of mobility, pain or infection were counted as failures.

The first 10 patients of each group were selected for radiographical analysis of crestal bone changes 1 year after prosthesis insertion.

In 33 patients with edentulous mandibles, 170 fixtures were placed in a 1-stage approach. In this group, 4 fixtures (2.4%) were lost prior to prosthetic restoration.

Seventeen edentulous patients received a total of 70 fixtures in a 2-stage procedure. Out of these, 5 fixtures (7.1%) were lost at abutment connection.

In 17 partially edentulous patients, 41 fixtures were inserted in a 1-stage approach. Two fixtures (5%) were lost in this group.

Finally, 18 partially edentulous patients received a total of 49 fixtures in a 2-stage procedure. Out of these, 6 fixtures (12%) were lost at abutment connection. In total 313 of the 330 installed mandibular implants were loaded between 6 and 12 months (94.8% success). No further losses occurred in the implants functioning at least 1 year (267 implants) or at least 2 years (59 implants).

Statistical analysis (Chi square test) revealed no difference in fixture survival between the treatment modalities. Radiographical analysis after 1 year of functional loading showed the typical bone resorption changes up to the most coronal implant thread in both modalities.

Although this study pertains to relatively early loading of 2 years, the results seem to indicate that in the mandible a 1-stage surgical approach with Branemark fixtures may be as predictable as the conventional 2-stage procedure.

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25. Bergendal, T. and B. Engquist, Implant-supported overdentures: a longitudinal prospective study. Int J Oral Maxillofac Implants, 1998. 13(2): p. 253-62.
The aim of this study was to evaluate the clinical function and long-term prognosis of overdentures retained by a small number of implants in the maxilla and mandible using one of two different attachment systems. Included in the study were all patients referred to specialty clinics in Jonkoping and Linkoping, Sweden, during the treatment period who needed an overdenture and could be provided with a minimum number of two bilaterally-placed implants. Excluded were patients with bone-grafted jaws, irradiated cancer patients, heavy bruxers, and patients who had lost a fixed prosthesis because of implant losses.

The patients were randomly assigned to receive one retentive system, either a round 2-mm-diameter bar with clips or ball attachments (Nobel Biocare). Eighteen overdentures were placed in maxillae and 32 in mandibles, supported by a total of 115 Branemark implants. Of the implants placed, 86.1% were continuously osseointegrated. The cumulative implant survival rates after 7 years of loading were 75.4% in the maxillae and 100% in the mandibles.

There was no difference in implant survival rate between the attachment systems. Patients with implant losses were characterized by severely resorbed maxillary ridges and inferior bone quality, together with unfavorable loading circumstances such as short implants combined with long leverages. Complications and prosthetic adjustments were mostly resolved early and easily.

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26. Piattelli, A., et al., Bone reactions to early occlusal loading of two-stage titanium plasma-sprayed implants: a pilot study in monkeys. Int J Periodontics Restorative Dent, 1997. 17(2): p. 162-9.
This pilot study analyzed the bone reactions to early loaded titanium plasma-sprayed implants. A total of 24 titanium plasma-sprayed implants (12 in the maxilla and 12 in the mandible) (Primary Healing Implant, Legnano) were inserted into four Macaca fascicularis monkeys with instruments specially designed to obtain a precise fit of the implant in the bone socket. A metal superstructure was cemented into 10 mandibular and 10 maxillary implants 15 days after implant insertion.

The four remaining implants were used as controls. Eight months after implant placement, a block section was carried out, the defect was filled with nonresorbable hydroxyapatite, and all 24 implants were retrieved. The implants were treated to obtain thin ground sections that were examined under normal and polarized light.

Histologic analysis showed that bone was observed around the implant surface in all implants. Morphometric analysis demonstrated that bone lined 67.2% (SD = 3.1%) of the maxillary implant surface, and 80.71% (SD = 4.6%) of the mandibular implant surface. No differences were found in the percentage of bone-implant contact in the control implants. In the loaded implants, however, the bone around the implants had a more compact appearance.

The study demonstrated that it is possible to obtain a high percentage of bone-implant contact in early loaded titanium plasma-sprayed implants.

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