Introduction
The introduction of osseointegrated implants in dentistry represents a turning point in dental clinical practice. (1) The delayed/conventional type protocol was developed about four decades ago and was based on the belief that implants can only be loaded after the osseointegration (bone growth around the implant) process is complete (20).
The next-generation immediate loading type has been around since 1990 and was researched and developed to address challenges posed by delayed loading, particularly the trauma and the lengthy period of up to 18 months that a patient has to wait. Ledermann showed as early as 1979 that immediate-loaded titanium plasma-sprayed screw implants could support overdentures in the mandible.
The first report on immediate-loaded Brånemark implants with fixed prostheses was presented in 1990 (27). The methods differ in the differential approaches they employ to allow bone healing and the osseointegration process to occur. These are however subject to many other factors accruing from the clinical situation and which have a major influence on the outcome of the implantation procedure.
In light of the lengthy periods associated with the highly successful conventional methods and the higher risk of biological implications that come with the immediate loading, it is imperative to note that both protocols have both recompense and shortcomings. This article reviews literature and critically compares the protocols, identifying the advantages and disadvantages of each, and gives recommendations concerning loading in different clinical situations.
Review of studies conducted for both immediate/early and delayed loading of dental implants
The delayed loading protocol represents an earlier developed teeth restoration procedure where the implants are positioned in the jaw bone and left untouched for four to six months for osseointegration and bone healing to occur (37). This is often a troubling predicament for patients who are seeking replacement of a front tooth or several teeth to wait for that long for a replacement to be done.
The reason for waiting for this period is to gain stability and anchorage through osseointegration (25). This treatment will cause the fixture to become firm and stable and thus allowing for placement of a restoration (25). After this period is complete, another surgery is performed to expose the implant and confirm that the osseointegration process has been completed, the implant is incorporated with the bone and is firm and stable to withstand the occlusal loads (14). After this has been confirmed a temporary restoration is loaded onto the implant, then in about 3 months a permanent restoration is built on the implant (14).
The evidence from clinical practice shows that the conventional delayed protocols may take anywhere from five months to two years for the patient to have fully functional new teeth (3). It took several years for an immediate implant loading protocol to be developed, finally, in 1990 a breakthrough was witnessed, the Sargon immediate load implant system was here. This newer protocol gives patients a chance to receive new teeth at once and has more other advantages than the conventional protocols (14). Benefits may include teeth and gums looking more natural than in the delayed placement of teeth which causes the immediate tissues to shrink. In addition, the teeth are fully functional after the placement.
Terminology
The terminology used in implant dentistry often varies and leads to confusion, for the present article, the following definitions will be used.
- Immediate/direct loading: the provisional/definitive prosthetic construction is attached to the implant within 24 hours of the implant is placed (30).
- Early loading/Early functional loading: the provisional/definitive prosthetic construction is attached to the implant within days/weeks of the implant is placed (5).
- Delayed loading: the provisional/definitive prosthetic construction is attached at a second procedure after a conventional healing period of three to six months (30).
- One-stage: the implant heals without the protection of the oral mucosa and is accessible through the mucosa during healing time (9).
- Two stages: the implant heals under the soft tissue and is, after a healing period, accessed through a second-stage surgery (30).
The need for loading of dental implants
Edentulous individuals looking for a cure to restore function and aesthetic appearance have traditionally received removable full or partial dentures (6). However, the use of detachable dentures is known to cause a considerable feeling of diffidence, reduced chewing capacity and taste, and low self-esteem (12). A controlled study was set up to investigate 26 denture patients before and at 3 months and 2 years after the insertion of an implant-supported bridge (32).
Many of them later acknowledged that there had been a significant improvement in their lives and that they had gained in self-confidence, and that, in contrast to their conventional denture, they had accepted the fixed bridge as part of their body (13). However, the placement of implants using the conventional delayed protocols involves a lengthy healing time, particularly when the treatment requires a tooth or teeth to be extracted before carrying out implantation. The use of immediate/early-loaded implants has obvious advantages because patients can be rehabilitated with functional crowns for immediate function and aesthetics (7).
Biological response studies
The original delayed loading implant protocol required a hassle-free prolong of three to six months for healing and complete osseointegration to occur. The prolonged undisturbed healing time was thought to be necessary to avoid fibrous tissue encapsulation around the implants instead of osseointegration (7). However, experiments and clinical trials carried out later established that implants osseointegrated even when left exposed to the oral cavity during healing (7).
Experimental histological studies of clinically retrieved implants have shown similar, and sometimes improved, bone-implant contact with immediate-loaded implants compared with conventional implants (10). In one conducted by Piattelli et al., the histological characteristics of non-submerged, unloaded and early-loaded titanium screw implants in monkeys were compared (27). The results of the examination revealed a tight attachment of the new bone to the surface of the implant (27).
In addition, “a more thick lamellar cortical bone was observed around the implant neck of early-loaded implants than the unloaded implants” (27). A pilot study was conducted in monkeys by Piatelli to examine bone responses to early-loaded titanium plasma-sprayed implants (27). Twenty implants were immediately loaded “and four implants served as controls” (27).
The average contact between implant and bone for the implants that were loaded “immediately was 67.2% in the maxilla (10 implants) and 80.71% for implants in the mandible (10 implants)” (27). Furthermore, the bone in which implants had been loaded showed a more compact form than those in the controls.
A different study conducted by Naert (7) revealed a bone-implant contact of 64.2% for a single immediate-loaded Osseotite implant compared to a bone–implant contact of 38.9% for a single submerged implant (7). In the exercise, 9 implants composed of oxidized titanium were extracted five to nine months after placement. Loading of two of the implants was carried out within24 hours after insertion and seven implants were loaded after 2 months of submerged healing (7).
The average value of contact between bone and implant for the two implants that were loaded immediately was found to be 92.9% and 81.4% for the later loaded implants. These studies reveal that immediately loaded implants often yield a higher percentage of contact between bone and implant. Frost postulated that not only excessive loading but also too modest loading of implants might result in a negative tissue response (7, 27).
An edentulous maxillae implant effect study was carried out by Widmark et al. in which a comparison was drawn between the immediate-loaded implants and the submerged implants. One hundred and twenty-six immediate-loaded implants were compared to 120 submerged implants with a healing period of 6 months (11). The subsequent resonance frequency testing indicated an inclination towards a faster increase in implant stability and less marginal bone restoration for the immediate-loaded implants compared with the submerged implants (11).
Clinical outcome studies for immediate, early, and delayed loading of dental implants
Studies for the completely edentulous mandible
Scientific reports in the past decade have described acceptable outcomes with early loading implants (1). A study was conducted in which 108 patients with edentulous mandibles were included. Each patient was treated with a full fixed prosthesis attached to four Brånemark System implants (39). The participants were then divided into 4 groups: group A (one-stage surgery), group B (two-stage surgery), group C (one-piece implants), and Group D (early loading) (39).
Twenty-six patients belonging to group D got 104 implants. The fixtures were allowed to heal for a period of between ten days to three weeks. Seven of the 104 (6.7%) implants in group D failed within 3 years of loading (39). In the control group (group B), three of 120 (2.5%) implants failed (39). The failure rates between the two groups produced a statistically insignificant dissimilarity. Patients belonging to group D showed a considerably less marginal bone loss than those in the control group (5). No significant difference was detected in the marginal bone change for study groups A and C
Initial works on immediate loading were done by Ledermann in 1979 who had shown that immediate-loaded titanium plasma-sprayed screw implants could support overdentures in the mandible (40). However, the earliest account on immediate-loaded Brånemark implants with fixed prostheses was presented in 1990 by Five Brånemark implants were placed between, and two additional fixtures were placed distally to, the mental foramina (14, 25, 40). Three of the fixed implants that were in favorable locations were linked to a temporary prosthesis, transformed using the patient’s denture.
The other fittings were left to heal in a conventional manner (3). It was concluded that the implant treatment was successful in seven patients, who were reconstructed with a mandibular fixed-detachable bridge devoid of wearing a removable prosthesis (40). In addition, the larger, continuing implant treatment was not negatively affected by the use of the immediate-loading protocol. A follow-up study was conducted whereby the Brånemark implants in 10 patients were straight away loaded with a screw-retained fixed provisional prosthesis.
Four of the immediate-loaded implants failed, while all implants with a conventional healing time survived (25, 40). Statistical examination indicated a considerably elevated failure rate for the immediate-loaded implants (3). The follow-up study confirmed the conclusion that even though the placement of immediately loaded implants into the mandible can bear a fixed short-term prosthesis, the long-term projection is secured for implants positioned for immediate function distally to the incisor region (3).
Studies conducted in several patients have established three to be the lowest number of implants needed for supporting a fixed partial denture in the edentulous mandible. Gatti studied 19 patients, who received five implants in the mandible, of which three were functionally loaded using the one-stage method (30). “The implants were then placed in a trivet arrangement, one positioned in the symphysis and two anterior to the mental foramen in the bicuspid area” (6, 30). Additional two implants were placed for protection purposes but not loaded. After the operation, “the implants were loaded with a relined denture” (30).
The participating “individuals received a 10- to 12-unit prosthetic reconstruction 4–5 weeks after the insertion procedures (15). 6 of the “sixty functionally loaded implants (10%) and three of 20 prostheses (15%) failed within the first year” (37). The researchers concluded that the result of therapy with a single-step surgery using three implants to support a fixed mandibular arch reconstruction was less favorable than the projected result of a standard criterion four- to six-implant construction (34, 18).
Presently, the use of between four and six implants in an edentulous mandible appears to be adequate for the retention of a fixed prosthesis with good long-term results (38). Survival/success rates of immediate-loaded implants need to be evaluated in comparison to those of the conventional two-step implant protocol. (16)In the fully edentulous mandible, an immediate-implant survival rate of 99% after 15 years was reported by Tarrow (39). The utilization of 3 immediate-loaded implants to carry a fixed prosthesis has resulted in survival rates ranging from 90 to 98% (39).
A repeat of the therapy at extra cost is needed if an implant gets lost, but the use of fewer implants at the start cuts down the initial costs of the treatment. Four or more immediate-loaded implants are sufficient to support a fixed prosthesis in the completely edentulous mandible, with a success rate of 95–100% (39). The selection of the patients must be correctly carried out to achieve high rates of success. The minor survival rate of immediate-loaded implants in comparison with the two-step implant protocol may be tolerable when the benefits of the former are considered, such as immediate handicap reduction, one-time surgery, and fewer total visits to the dental office (39,38).
Complete edentulous maxilla
A study was conducted to investigate early implant loading on 24 patients who had edentulous maxillae. The patients were divided into a study group of 16 and the remainder 8 were used as the control. All patients received five or six solid, screw-type titanium implants with sandblasted, large-grit, acid-etched surfaces. In total, 142 implants were placed and 139 implants were loaded with full-arch prostheses (32).
The collective success rate for the implants was 100% three years after loading. The 3-year radiographic evaluation showed minimal marginal bone resorption in the group that was loaded early as compared to controls (32). The conclusion arrived at was that the early loading procedure was a feasible alternative to the conventional procedure in the restoration of the completely edentulous maxilla with an implant-supported fixed prosthesis (6).
The survival rate of 168 immediately loaded sandblasted, large-grit, acid-etched implants in the edentulous maxilla of 28 patients after 8 months of loading was assessed by Randow et al. (33), each patient received a fixed provisional prosthesis within 24 hours of implant surgery. “After an average curative period of three and a half months, the patient received a definitive, screw-retained, implant-supported fixed prosthesis” (21, 33). Three of the 168 implants were not successful and failed in the course of the treatment period. The mean marginal bone resorption was 1.6 mm during an 8-month follow-up (31, 33). It was thus revealed that splinting of the implants immediately after insertion was important.
Successful therapy was conducted by Caudill (14) for twenty-six patients who had complete edentulous maxillae with implants loaded within 48 hours with either resin provisional prostheses, metal-reinforced provisional prostheses, or definitive prostheses (metal–acrylic or metal-ceramic) (14). Double acid-etched surface implants (Osseotite) were used, and patients were followed for 12–74 months. (140) After 12-74 months the success rate registered was 100%. The average radiographic bone level change was 0.56 mm at 12 months and 0.94 mm at 72 months (14). Thus it was concluded by Caudill that an “excellent success rate can be achieved if double acid-etched surface implants were immediately loaded with fixed full-arch restorations in the maxilla” (11, 14).
Not much information is available on immediately loaded implants in the edentulous maxilla (19). Many of the studies that have been reported on therapy make use of a larger number of implants, to support the prosthesis. Three studies conducted on early loading and one study on immediate loading with six to eight implants report implant survival rates from 93.4 to 100% after 1–3 years (3, 17, 34). This can be compared to survival rates of five years that are often seen in the conventional implant loading protocols.
A study conducted over five years showed no change in the survival rates as failures had been reported within the first six months. (39) The data show that if suitable initial implant stability is attained in areas with medium to dense bone quality, a successful outcome of immediate-loaded implants in the fully edentulous maxilla is likely to occur (16). Nevertheless, more data on long-term survival rates are required to qualify the immediate implant loading as standard protocol for a completely edentulous maxilla.
Partly edentulous maxilla or mandible
It is more difficult to carry out immediate or early loading for a partly edentulous mandible or maxilla than in completely edentulous cases. Partly edentulous individuals often require fewer that are normally positioned in a straight line and therefore prone to lateral forces. Implants in the completely edentulous individuals may be positioned in an arch shape for effective withstanding lateral forces.
Moreover, the posterior region of the oral cavity usually has less dense bone and experiences stronger bite forces compared to the anterior part of the mouth (6, 13, 27). However, reports from numerous histological studies indicate that immediate implants produce good results when applied in the partly edentulous posterior mandible. (38) A case in point is where obtained 9 oxidized implants were; 2 of the implants were loaded within 24 hours of surgery and the remaining 7 implants were loaded 2 months later when healing had taken place.
Testori reported on 475 Osseotite implants in a longitudinal, prospective multicenter study of early implant loading. All of them were inserted in the posterior regions of 175 partly edentulous individuals and all had restored 2 months after insertion (10). High several rates of 97.7% were established after three years of observation, six of the 475 implants were classified as early failures and three implants were classified as late failures presented a longitudinal, prospective, multicenter study on 383 sandblasted, large-grit, acid-etched implants placed in the posterior jaws of 307 patients (10).
Implants belonging to class 1 to 3 quality bones healed within 42 to 63 days while those in class 4 took 105 days. When the abutment was being placed, three implants were loose and were thus removed, additional three others were not completely stable and were reported to cause pain. The implants healed and stabilized in due course (10).
A study was conducted by bergendal et al. (26) on 36 implants inserted in the posterior maxilla of 29 non-smoking patients (26). Abutments were placed after 43 days and the implants were loaded with a temporary bridge in infraocclusion. Six weeks later, the placement of a fitting prosthesis was carried out. A 97.2% survival rate was realized one year later, this was due to the failure of a single implant.
In a split-mouth prospective study, Emmer compared 68 sandblasted, large-grit, acid-etched implants loaded 6 weeks after implant surgery and 68 titanium plasma-sprayed screw implants loaded 12 weeks after implant surgery (18). After 1 year of observation, a survival rate of 100 % was evident for the two groups and no major differences were observed on a clinical radiographic examination conducted on the groups.
Cooper et al reported a one-year multicenter follow-up study of an immediate/early loading implant protocol in the posterior maxilla and mandible (34). “In study 82 sandblasted, large-grit, acid-etched implants in 40 patients were loaded between 0 and 11 days after implant placement” (34). After observing for one year, the results obtained had no significant difference from those observed in the delayed protocol. In another study, 31 successive patients were included in a multicenter study.
Sums of 111 implants were subsequently positioned in 37 edentulous sites. The specific insertions included 69 implants into 22 partial edentulous ridges in the maxilla and 42 implants into 15 partial edentulous posterior ridges in the mandible. Placement of temporary prostheses was carried within nine days after implant insertion. A failure was reported in 1Out of the total 111 implants that were inserted, leading to the attainment of a 99.1% survival rate. The failed implant had been inserted in the posterior maxilla, thus the survival rate of the prosthesis was100%. The marginal bone restoration from decipherable (about 85%) radiographs was 0.8 mm (12, 34). It was concluded that a high implant survival rate can be achieved if a clinical procedure achieves exceptional implant stability and one that utilizes oxidized titanium implants in the initial loading in the maxilla or the posterior mandible (32, 34).
A prospective controlled clinical trial by Salvi et al. A prospective clinically controlled trial carried out by Salvi et al assessed the outcomes associated with early loading of sandblasted, large-grit, acid-etched implants (2,38). Twenty-seven patients were successively admitted and the bilateral edentulous posterior mandibular regions were included in the study (2). Implants were positioned bilaterally in the molar and premolar sites according to the conventional surgical procedures (2).
A test was conducted for 1 week and the control was prolonged for 5 weeks following implant insertion. A 35 N cm torque was used to connect the abutments and no temporary restoration was provided. 2 evaluation implants together with a single control implant installed during abutment connection were left without loading for an additional twelve weeks. Two weeks (test) and 6 weeks (control) after implant insertion the porcelain-fused-to-metal, single-tooth crowns were cemented (30). After 1 year, the implant survival rate was 100% (2).
An examination carried out a year later revealed that no significant dissimilarities between the test and control regions concerning the depth of pocket probing, clinical attachment level mean, mean percentage of sites bleeding on probing, mean width of keratinized mucosa, mean PerioTest values, or mean crestal bone loss measurement (2) It was concluded that loading the implants early, for instance, 2 weeks, does not seem to risk the osseointegration healing process in the posterior mandible (2).
A study involving the immediate loading of implants with partial fixed dentures in the posterior mandible was conducted by Tawse et al (31). Test and control treatment randomization was carried out for 44 patients. “The following was done test group; 22 patients were treated with 66 Brånemark System TiUnite surface implants supporting 24 fixed partial bridges,” all of which were linked on the day of implant placement (31).
For the control category, “22 patients received 55 Brånemark System turned-surface implants supporting 22 fixed partial bridges,” which were linked 12 hours within the implant insertion (31). All recuperative structures used had 2 – 4 bridges. Seven weeks after the loading was done there was a failure in 8 turned surface implants and three TiUnite implants (21). The cumulative success rate was 95.5% for TiUnite surface implants after 1 year of prosthetic loading in the posterior mandible (21). There was a significant statistical difference between the two forms of implant concerning marginal bone resorption a year after loading was carried out. The researchers concluded that rough surfaces, such as that of TiUnite implants, provided a 10% decrease in failure rate compared to turned implants.
In a report provided by Drago & Lazzara (22) ninety-three Osseotite implants were reinstated with fixed conditional crowns with no associated occlusion directly after implant insertion. 38 partly edentulous individuals were incorporated in the study. All fixtures were restored straight away with “pre-constructed abutments and cement-retained provisional crowns without centric or eccentric occlusal contacts” (22). After an estimated period of eight to twelve weeks of implant placement, the final restorations were inserted.
After the placement, a follow-up for all the patients who participated in the study was conducted for a minimum of eighteen months. “77 out of the ninety-three fixtures fulfilled the inclusion criteria, and 75 implants became osseointegrated. The overall implant survival rate was 97.4%.” (22) Radiographs taken to investigate bone loss at 18 months after implant insertion showed a 0.76mm mean of both interproximal surfaces (22).
20 patients suffering from chronic periodontitis were subjected to therapeutic implantation in the partially edentulous mandible. Machtei et al. conducted a study on the patients and the results showed that of the 49 implants used 10% of them failed. It was thus concluded that immediate loading procedures offer a predictable treatment in periodontal susceptible individuals, “but careful consideration should be given to implants placed in the molar region” (20).
In a separate study conducted by Collaert, ten patients presenting with bilateral partly edentulous posterior mandibles were treated (25). A split-mouth study design compared implants with either a turned surface or a titanium oxide surface (25). Forty-two implants comprising twenty test implants and twenty-two for control purposes were inserted and loading completed within a day.
On examination, it was established that two implants in the control group had failed while no failure was reported in the test group. Thus the aggregate success rate was 95%, representing a negligible statistical difference between the two groups. The conclusion arrived at was that immediate loading of implants in the posterior mandible may be an acceptable therapy option if implants are inserted with a torque exceeding 20 N cm and show an Implant Stability Quotient value above 60 N cm (36).
According to the available data, the longest follow-up conducted for implants loaded early is three years and one year for the immediately loaded ones. The generally established survival rate of implants ranges from 85 to 98.8%, which is less than the 5-year survival rates of 94–96% attained by conventional implant protocols (3,6,12). This implies that more studies are required before the immediate loading protocols are fully employed as a standard criterion for posterior maxilla/mandible therapy.
Single-tooth Replacement (2)
Most patients seeking implant replacement often require single tooth replacement as this is the most common tooth loss occurrence (12). The loss often presents a traumatic experience for most individuals and early/immediate implant loading is, therefore, an attractive treatment option (1, 12,). However, the replacement of a single tooth for aesthetic purposes always offers a more challenging clinical situation for a practitioner, even when the conventional implant protocols are employed. Careful evaluation is done as a routine for the determination of the bone volumes and the mucosal about the implant loading.
In instances whereby excessive bone resorption is observed, extension procedures for the bone and mucosa may be indicated. A retrospective study was conducted to determine patients’ feelings and professional evaluation of 43 implant-supported single-tooth replacements (7). Single implant crowns were evaluated according to “design, fit, occlusion/articulation, and aesthetics (7). According to Naert, the results showed that patients were very positive with “regard to aesthetics, phonetics, eating comfort, and overall satisfaction” (7).
Early/immediate loading protocols for single-tooth implant in the maxilla were evaluated by Randow, Provisional acrylic resin reinstallation which had constructed from impressions attained immediately after implant insertion, were linked 1 week later (33) Adjustments were performed to prevent instances of occlusive contacts. After six months, the temporary crowns were replaced with definitive ceramic crowns (21) Follow-up was conducted for 8 patients for five years.
Within the period no implant had been lost, and the average marginal bone level for all the 8 implants had increased by 0.53mm between placement and the final examination (21) Minimal complications were however observed and the satisfaction among the patients was generally good.
A prospective study on single-tooth restoration was done with fabricated crowns attached to implants loaded using the immediate loading procedures and compared to the conventional two-step implant protocol (33). Of the 22 patients with single tooth loss, 14 patients were included in the immediate loading protocol while 8 went for the two-step conventional protocol. The patients had to be non-smokers and have sufficient bone to receive a 13-mm implant with the regular platform diameter of 3.75 mm (37,38)
A Provisional crown was linked to the implant insertion within a day in the immediate loaded, and the stable crown was inserted after 6 months. Failure was reported in 2 the 14 immediately loaded implants approximately 5 months in service. Stability was maintained in the remaining implants and no loss was reported for the conventional two-step protocol. A radiographic evaluation 12 months later indicated an average loss of bone support of about 0.1 mm for both study groups.
Twenty-four patients who had received single-tooth implants according to an immediate-loaded implant placement protocol were evaluated by Zubery (17) 13 out of the 24 patients underwent implant insertion soon after tooth extraction. “All the implants were then placed in the aesthetic zone” (17).The surgical procedures intended to improve the initial implant firmness with the lowest inclusion torque of 40 N cm. A follow-up conducted between one and fifteen months indicated complete stability in all 24 patients.
Degidi evaluated 111 single implants that non-functionally had been immediately loaded. “All implants were placed with a minimum insertion torque of 25 N cm, during 5 years of follow up, the implant survival rate was 95.5%” (23). On analysis, a statistically significant difference in implant survival rate was found for healed and fresh-extraction implant regions (100% and 92.5%, respectively) and for type 1 and 4 quality bone (100% and 95.5%, respectively) (14).
A Clinical context for treatment with immediately loaded implants
A suitable therapeutic concept for assessing the immediate protocol loading of implants has been building developed since 1998. 1,420 immediate-loaded implants, with at least 3 years of follow-up, in 519 patients inserted on a variety of indications following a protocol aimed at reducing negative biomechanical factors (16).
Throughout the assessment prominence has been put on gaining firm initial implant stability, as measured by insertion torque and resonance frequency testing, to allow splinting within 12 hours in a fixed bridge structure with controlled occlusion (24). A section of the concept is to utilize the surface-modified implants which are thought to provide a better therapy in risky clinical situations.
The assessment was conducted for a period ranging between 3 and 7 years.670 implants were inserted by a two-stage method and 1,303 implants were immediately loaded. 2 cases where teeth were implanted within an hour and 48 other cases that utilized the Nobel direct implants have been omitted from this conclusion (40). There were significant differences in the clinical outcomes for both the two-step conventional protocol and the immediate type. However, a failure rate of 1.0% was observed in the two-step conventional protocol group 1.2% in the immediate-loaded group (17).
Therapy planning
Nowadays, most individuals who seek implant therapy are partially edentulous. Using the traditional delayed protocol a period of four to six months is often required for healing to occur after the teeth have been extracted. More ever, the traditional protocol usually needs a healing period of four to six months. Therefore a full implant therapy requires a period of between eight and twelve months. In the course of this time, fortunate patients will have removable dentures on. In a bid to provide the best service to their patients some clinicians evaluate to assess the state of the teeth to decide whether some teeth can be retained during the primary healing period of bone and mucosa illustrate different options for oral rehabilitations without using a complete denture during primary healing (13).
The main teeth, which may include canines can often be retained and later be used in the creating of a bridge during the healing period. By retaining some important teeth, the clinician not only helps the patient but also offers a different form of therapy. After the situation has been assessed and it has been found out that the therapy cannot be offered using the immediate loading protocols, the conventional delayed can be prescribed with a removable prosthesis if immediate loading is feasible. The remaining teeth can be extracted during surgery and replaced by implants (6,8).
During the conveyance of implant surgery, the posterior maxillary site should have healed sufficiently to implants in a tilted position to allow for adequate space between individual fixtures (32). After the surgery, the implants that remain should be inserted into fresh extraction regions or left to heal in a bone next to the extraction socket (23). In the latter situation, it can be difficult to achieve an optimal fixture position (25). However, this kind of therapy may lead to less predictable healing of bone and mucosa (25).
Selection of patients
Inclusion criteria
Individuals to be put on an immediate implant loading treatment should always receive occlusal and articulation adjustment before or during the temporary phase to avoid unnecessary trauma to the fixtures (25).
Exclusion criteria
Patients who appear to have reservations about the procedures involved in the immediate implant loading therapy should not be included. The most decisive contraindication of this protocol is a history of previous failures. In addition, irradiated cancer patients and smokers with uncontrolled diabetes are poor candidates for immediate-loaded implants (3,10). The following contraindications may be ignored; bruxism, large deviations in sagittal/vertical bite relations, and deep bite that may influence the loading of implants in an unfavorable way (29).
Clinical evaluation during and before surgery
The quality/quantity of the bone
These form some of the most important parameters to consider at the implant region for immediate implant loading procedures. Vital bone characteristics are hard to assess exclusively using radiography. The precise bone quality can only be determined pre-operatively; bony features differ within the edentulous jaw of the same patient, which often necessitates a site-specific analysis (25).
A bone belonging to class four quality is often regarded as not suitable for implantation procedures because of its softness. Where from a biomechanical perspective may challenge efforts to obtain firm initial stability for the implant (12). A study carried out by Esposito indicated an elevated implant failure rate of 35% in class 4 bone (24).
In a study of the early outcome of 4,641 Brånemark fixtures, Collaert concluded that most implant losses occurred in fully edentulous maxillae, in which the jawbone exhibited soft quality and severe resorption (25). Above 40 % of the class four bones usually result in failures when they are used to augment an implant. It should be stressed that the original studies linking the quality of a bone and chances of implant failure were done using turned implants and traditional protocols, involving pre-tapping even in the bone of class 4 quality (12).
Using the biological characteristics, it has been found out that the trabecular bone offers a better quality tissue in comparison to that of cortical bone. The bone offers a large surface area for extension, which is proximate to the “bone marrow and bone healing is much faster when compared to the healing pattern present in cortical bone” (12).
The stability of “an implant can be defined as its capacity to withstand loading forces in axial, lateral, and rotational directions” (12). Davarpanah postulated that the principal implant stability is often determined by bone quality and quantity, implant design, and surgical technique (12). From the quality and quantity of bone characteristics, dentists are required to formulate a drilling procedure and a proper choice of fixtures that are relevant to that particular clinical situation for the achievement of adequate primary stability of the implant.
Drill procedure and the nature of the fixture
The ability or skill of a dentist to make an informed decision about the implant region is vital for the success of the whole immediate implant loading exercise. Bone quality and quantity, as well as the thickness of the cortex, must be determined before proceeding to final drill and implant placement (12). Many studies have identified and documented different drill procedures that depend on the quality of the bone.
In a certain study 905, Brånemark-type implants were analyzed, whereby the varying bone quality determined the drill diameters and implant design (13). The stability of the implants was evaluated using resonance frequency during the insertion. (12) The influence of different patient, implant, and surgical factors on implant stability was estimated (15).
It was concluded that high primary stability could be achieved in all regions of the jaw when using an adapted surgical protocol (34). “The use of thin drills and/or tapered implants cannot fully compensate for the effect of soft bone, slightly tapered or tapered implant design and implant surface modification can dramatically improve implant survival rate in soft bone” (5, 11). Other than an enhanced drill procedure and proper implant design, increased initial stability may be realized by selecting a broader implant diameter. A wider implant will fit into the buccal and palatal compacta bone well and will increase the bone–metal surface contact (15).
Distribution of implants
The biomechanical rules in implant treatment have long been known and should be adhered to to ensure a successful outcome (12). If a patient is subjected to careful planning and treatment the implant outcome often presents a quality durable prognosis. The most important factor to be considered when inserting immediately loaded implants is to allow smooth osseointegration with no associated difficulties. Implants should preferably be positioned in a tripod or horseshoe pattern (1, 5).
Assessment of inserted implants
An ultimate torque of 30 N cm and an implant stability quotient above 60 is needed to adequately place immediate-loaded implants (37). Variation from this standard can be done if numerous implants are to be positioned into the mandible/maxilla using a cross-arch pattern (12, 20). The last implant to be inserted should always have the standard torque of 30N and an implant quotient of 60 or higher (12, 28). If this cannot be achieved then it is recommended that the implant placement be conducted using the two-stage protocols
Post-surgery patient care
In the first 10-days after the operation, it is suggested that the patient eats softer food substances, rinse his/her mouth twice daily with chlorhexidine, and, perhaps, take penicillin-V to minimize the risk of infection (14).
Prosthetic concerns
Splinting through provisional fabrication
Various techniques are available for provisional denture fabrication for different patient conditions and preferences. Dental technicians, for example, may convert an existing denture into an acrylic bridge (30). Laboratory protocols are optimally designed to provide a quality product and anesthetics, and more importantly, eliminate the chances of infection cropping into the inserted areas.
However, a laboratory-manufactured provisional fixture may be costly and may take longer to be completed. Temporary chair-side-made constructions have the advantage of immediate handicap reduction, immediate splinting, cost-effectiveness, and installation during the anesthesia phase of implant placement (23).
Several researchers argue that splinting of the implants lowers the occlusal load shift more efficiently as compared to freestanding units. It has been noted that optimum loading settings are realized through a firm implant elevated bridge. Possibly, splinting of implants to each other via a provisional bridge reduces micro-motions at the bone-implant interface, which in turn helps to reinforce osseointegration (30). Thus, a temporary bridge should be used to link the implant as quickly as possible following the insertion of the construct.
Splinting provides an option for reducing lateral forces on implants if three or more implants are placed in a tripod or a cross-arch configuration (13). This kind of arrangement allows the conversion of the lateral forces into the more suitable axial force and thus enhancing implant stability. The advantages of cross-arch stabilization are well-documented and depend on clinical situations by load measurements in vivo (32).
Micro-motion reduction
The level of micro-motion of fixtures can have a major impact on the integration of the implant. Various studies have cited that the lack of micro-motion of an implant is more essential for osseointegration to occur effectively as compared to the timing of implant loading (40). The proposed threshold level of micro-motion for a turned implant is 100 μm while the suggested acceptable micro-motion for roughened implants is 50–150 μm (13).
Check-up and maintenance
After the treatment has been completed checkups should be conducted in two weeks for the first check-up and once a month for the subsequent checkups. Oral hygiene, mucosal healing, the stability of the provisional bridge, and fixture status are evaluated (20). After sufficient healing of the mucosal has been attained, often in one to six months, depending on the patients healing factors and the region of the oral cavity, the stable prosthetic construction is made, preferably using a biocompatible material such as titanium or zirconia.
Occlusion and articulation contacts are carefully adjusted to minimize lateral forces (36). The cleaning of the oral cavity is normally enhanced when the final prosthesis is due to be delivered. After the final prosthesis, the checkups become less frequent and depend on the individual condition or preference, this may be done at an interval of six months to one year.
Clinical citations of the outlined method
Edentulous mandible
84 successive patients booked for prosthetic rehabilitation with implant-supported bridges in the completely edentulous mandible were evaluated (34). Insertions comprising 377 implants, 66 of which were turned and the bulky, 311 oxidized (23). The placement was carried out using a standard procedure for enhancing the initial stability, implying diminished final drilling in the soft bone to get the most out of bone to implant adherence. Patients received three (one patient, three implants), four (41 patients, 164 implants), or five (42 patients, 210 implants) implants.
All patients were also provided with a temporary, 10- to 12-unit fixed prosthesis within 12 hours of implant surgery (26). Delivery of permanent prosthetic was done from ten days to three months after implantation. The standard criteria for identification of bone quality were employed and the results were as follow; class 1 quality was seen in four (5%) patients, of class 2 in 32 (38%) patients, of class 3 in 38 (45%) patients, and of class 4 quality in 10 (12%) patients (13,35). Out of the 377 implants used 5 of them registered failures and thus giving an aggregate survival rate of 98.5% after 12 months of loading.
Completely edentulous maxilla (23)
20 patients scheduled “for prosthetic rehabilitation with implant-supported bridges in the edentulous maxilla were studied.” (12) In the study, “123 oxidized implants (TiUnite, Nobel Biocare) were placed using a surgical protocol for enhanced primary stability” (12). The delivery of the screw-retained provisional bridge was done within a day and the definite bridge in three months after the implant insertion. Twenty patients with one hundred and twenty fixtures placed using the conventional two-stage procedure were included for comparison (40).
1 failure in the immediate-loaded category was registered while there was no failure in the two-step conventional procedure. Evaluation conducted revealed that “marginal bone resorption was 0.78 mm in the immediate-loaded implant group and 0.91 mm in the two-stage implant group” (12, 14). Six months after the implant placement, the immediate-loaded category showed a higher stability measure than those inserted by the conventional two-step protocol (13). No significant statistical dissimilarity was observed in the two categories
Partly edentulous mandible
77 successive patients requiring implant therapy in the partly edentulous mandible participated in the study. A total of 111 bridges supported by 257 Brånemark System® implants (77 turned and 180 TiUnite™ implants) were studied (32). The initial stability of the implants was enhanced during the insertion. A provisional bridge was fixed within 24 hours and a final bridge was placed within 3 months of implantation (32).
Resonance frequency evaluation was used to test the stability of the constructs at the time of insertion and six months later. 4 of all the implants failed to integrate, giving an overall survival rate of 98.4% after 4 years (34). The average “marginal bone resorption was found to be 0.7 ± 0.7 mm within the first year of placement” (23). Direct loading of implants with firm primary stability in partially edentulous areas of the mandible constitutes a viable therapeutic procedure with a predictable outcome (15).
Temporary implants used in the partly edentulous mandible (7)
Temporary implants may be utilized to offer individuals with a provisional firm denture in the course of their healing for submerged constructs therapy. “20 female and 25 male patients were consecutively included in a prospective study of provisional implants.” (7).
Sixteen of the 45 patients were put on therapy for partial edentulism of the maxilla while twenty-nine were on therapy for total edentulism of the maxilla (7). Insertion of the permanent implants was done first, then as many temporary implants were fixed between the permanent ones (7). After insertion and suturing, impressions were obtained for use in the fabrication of temporary bridges to be attached to the temporary implants. “Five (2.2%) of the 230 permanent Brånemark System implants did not integrate” (7). It was not possible to connect any of the failures to the existence of the temporary fixtures between the permanent implants (7).
In the course of the study period, failures were witnessed in a total of 7 of the provisional implants. More ever, nine percent of all the temporary fixtures were found to be loose when the second surgery was performed despite having supported the temporary bridges without clinical symptoms (7, 13). 44 out of the forty-five patients presented with stable temporary implants bridges at the time of second-step surgery (14). In conclusion, it is established that temporary implants may be successfully utilized in providing patients with fixed temporary bridges during the healing period of permanent implants (12.16).
Studies on provisional implant prosthesis according to a chair-side concept (34)
In a study carried out by Pilliar et al (23) thirty-seven partly or complete edentulous older patients (mean age 66.7 years) were treated with chair-side Quick Bridge provisional restorations (23). “The prostheses ranged from two-unit bridges supported by two implants to a full arch construction supported by six implants” (23). The viable period of the provisional prostheses ranged between three and six months (24, 33). No losses in implants were reported in the course of observation. “One of the provisional prosthesis representing 3% fractured and a further 2 loosened in during the follow-up period” (23).
Use of Nobel Direct and Nobel Perfect One-Piece Implants (14)
The Nobel Direct™ and Nobel Perfect™ one-piece implant systems represent a new immediate-loading technique, including flapless surgery and placement of a one-piece titanium implant (13). The method provides an easy remedy for tooth loss because the surgery indicated is less intense and employs the use of traditional prosthetic techniques. The implant protocol is also indicated for use with immediate substitution of removed teeth.
This one-piece implant system is allegedly designed to minimize marginal bone resorption because there is no submucosal micro-gap, which is believed to cause the initial bone loss usually associated with two-piece implants (21). Furthermore, the whole implant comprises a fairly rough surface (TiUnite), which is thought to assist the adherence of the mucosa to the surface of the implant, thus creating conditions for better ‘soft tissue incorporation and durable aesthetic result (12, 13).
A study was conducted whereby 48 patients were facilitated with 115 one-piece implants for loading with a temporary crown or a bridge in one day and follow-up was conducted for a minimum of one year and included clinical and radiographic examinations (14). 97 patients who had been treated previously under similar conditions and with the same professional team were used as controls for the study. After 1 year, the average marginal bone loss was 2.1 ± 1.3 mm for one-piece implants and 0.8 ± 1.0 mm for two-piece implants (38). 20% of one-piece implants and 0.6% of two-piece implants showed bone loss exceeding 3 mm (38).
When “compensating for vertical insertion depth, one-piece implants still showed a lower marginal bone level and therefore more exposed threads than two-piece fixtures”(23). About the criteria applied, the survival rate for one-piece implants was found to be 46.1–72.2% compared to 85.0–91.6% for two-piece fixtures (23). The researchers concluded that the two types of implants (Nobel Direct and Nobel Perfect one-piece) showed lower survival rates and more bone resorption after one year (40). The clinical results observed may have been influenced by factors such as “insertion depth, rough implant surface towards the mucosa, and implant design “(13).
Conclusion
More short- and long-term data are required to completely assess and exhaust the benefits and hazards associated with the immediate and early-loaded implants (23). Only the results of immediate-loaded implants in the completely edentulous mandible can be considered well documented (7). With high primary implant stability, immediate-loaded implants in the completely edentulous maxilla show good short- and medium-term outcomes, although more data is required before the safety of the therapy can be fully established (14).
Outstanding short-term information has been generated for immediate/early loaded implants in partly edentulous jaws (17). However, it should be kept in mind that most of the studies reviewed in this paper were conducted by highly trained dental practitioners. Some long-term data on multicenter studies have been generated (16). More data is also required on the benefits of the implant protocols to the patients. Besides shorter treatment time for the doctor/patients with immediate/early-loaded implants, are there psychological factors for the patients that warrant more attention (34)?
The literature reviewed seems to suggest that the immediate loading technique works well when combined with implants with a high primary. However, surgical techniques need to be enhanced to provide better initial stability, especially for loading immediate implants into soft bones. The differences in bone quality need to be re-examined to generate more reliable data on quality and the applicable implant diameter.
Successful integration of immediate-loaded implants may require a final torque exceeding 30 N cm and an implant stability quotient value above 60 (25). Most of the studies conducted indicate that the popularity of the immediate protocols is growing faster and that conventional methods are only being utilized in risk situations. Such situations may include; poor bone quality, systemic risk, or Para-function (17).
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