Original study - ZZI 03/2011

Immediate Function in a Dental Practice

D. Siebers1, P. Gehrke2, H. Schliephake3

Objectives: The aim of this study was to clarify whether immediate function or immediate loading in a private practice may be regarded as a safe treatment protocol for selected cases. This question is addressed using a longitudinal case control study of patients in a private practice.

Material and Methods: All 111 implants that had been treated according to an immediate function protocol between 2001 and 2004 were followed up. 111 implants with parameters as similar as possible served as controls. 96 parameters in 76 patients were recorded and analyzed. These included numerous risk factors mentioned in the literature, implant and denture parameters, and clinical and radiographic parameters. The implant success rate was evaluated and an aesthetic assessment of a reasonable proportion was performed.

Results: Five of the 222 implants were lost during the healing period (survival rate 97.7 % after 3.25 years on average). The Kaplan-Meier analysis showed statistically significantly better results for the control group (survival rate 100 %) compared with the test group (survival rate 95.5 %, p = 0.024) as well as for implantation in healed sites (99.4 %, p = 0.0055) compared with immediate implantation (93.1 %). Evaluation of implant success resulted
in a success rate of 97.75 % (Gettleman/Schnitman) and 95.5 % (Buser/Naert). The success rate was statistically significantly higher with delayed compared with immediate implantation (p = 0.017). The test group had significant advantages aesthetically compared with the control group (p = 0.0074).

There were also advantages for immediate compared with delayed implantation (p = 0.0076) and for the test group compared with the control group (p = 0.0092). The probing depth was less in the test group than in the control group (p = 0.011) and with immediate loading compared with the immediate restoration group (p = 0.025).

Conclusions: Immediate function of dental implants is a therapy with a high success rate of 95.5 % and high aesthetic potential. However, there is evidence that immediate function and immediate implantation are associated with a higher risk of failure. Therefore, an accurate risk analysis is required for each patient to avoid risk accumulation.

Keywords: dental implants; immediate function; immediate loading; immediate restoration; immediate implantation; clinical parameters; risk factors; risk accumulation; success; aesthetic evaluation

Introduction

Unloaded closed healing of implants for four to six months [12, 13] has now been a functioning concept in dental implantology for some decades and was for a long time regarded as
a „conditio sine qua non“. However, this concept was queried early from the aspect of improving patient comfort [51, 52]. Currently, there are two concepts for shortening the duration of treatment [22, 71]. They differ according to the time of implant insertion and the time of loading. Immediate function
is divided into two forms of loading [22, 71]. Immediate loading, in which a restoration in occlusion with the opposing teeth is fitted within 48 hours after implant insertion, contrasts with immediate restoration, which involves prosthetic restoration within the same period after implant insertion but without contact with the opposing teeth. Other authors use terms such as direct and indirect occlusal contacts [6] or immediate functional as opposed to immediate nonfunctional loading [27].

The available literature reviews, review articles, meta-analyses and consensus papers [3, 6, 21, 23, 33, 48, 60, 61] show a great degree of variation. Good to very good success rates of 90 % or more are recorded in all publications. In particular, immediate loading with interforaminal mandibular implantation is well documented scientifically [3, 21, 33, 70] and demonstrates a high success rate regardless of the implant type, surface structure and prosthesis design. There is less evidence for the maxilla and partially dentate situations [5, 21, 33]. In 2005, Attard et al. [6] confirmed the biological success of immediate loading. Glauser et al. [37] examined the available literature for the associations between marginal soft tissues and the loading protocol in a meta-analysis in 2006. They found that immediately restored and loaded implants after successful osseointegration demonstrate a soft tissue reaction with regard to periodontal and morphological aspects that is comparable with that seen with conventionally loaded implants. Many authors deplore the poor methodological quality of the studies [5, 21, 22, 37] and demand more long-term investigations with a stricter study design, greater implant numbers and longer follow-up periods. Data from private dental practices are extremely rare.

There is consensus that primary stability must be achieved with the insertion of implants that are to be restored immediately in order to limit relative movements at the implant-bone interface to physiologically acceptable levels. As practicing implantologists have few aids at their disposal for obtaining information about the structure and density of the local bone, apart from the relatively imprecise radiology, another measure for these parameters must be found. The only validated control mechanism for this is the insertion torque. The close correlation between bone density and the final insertion torque has been demonstrated [41, 54, 57]. Today, many authors therefore recommend final insertion torques between 25 and 40 Ncm [14, 26, 44], as these suggest adequate bone density. Other important requirements are careful case selection [29] and the use of adequate surgical techniques to spare the peri-implant tissue during tooth extraction [6, 7].

Complete evaluation of the success of immediate implantations is usually not possible by recording the fact that an implant is still in situ. Even when clinical and radiological findings are included in the evaluation of success [2, 16, 36, 65], the aesthetic outcome, which is an important aspect of immediate implantation, especially in the upper anterior region, is not recorded at the same time. Aesthetic aspects and the long-term stability of the peri-implant tissue must also be evaluated [10, 68]. Testori et al. [68] describe the implant aesthetic score, an extension of the papilla index [42], which allows evaluation of the aesthetic treatment result. The mesio-distal papilla, ridge, surface structure and color of the peri-implant soft tissue are assessed, along with the mucosal contour.

Unlike many clinical studies, the present investigation followed up not only clinical and radiological parameters but also the aesthetic results in patients treated with implant-based restorations, in the form of a longitudinal case-control study. Since there was no exclusion of risk factors in the patient selection, this results in a patient population treated routinely in dental practices.

 

Materials and methods

In a longitudinal study, all implants inserted in the dental practice of Dr. Derk Siebers in the years 2001 to 2004 and restored according to an immediate function protocol were followed up routinely in the period from June to December 2006. All implants in the test group had been restored within 48 hours after insertion with temporary or final prosthetic reconstructions. Seven patients with 17 immediately restored or loaded implants who did not attend for routine follow-up were excluded. Smoking, bruxism and treated chronic periodontal disease were recorded but not regarded as exclusion criteria. Within the immediate function test group, a distinction was made between immediate restoration (42.4 %) and immediate loading (57.6 %). The mean duration of observation of the test implants was 165 weeks (3.16 years) and that of the control implants was 185 weeks (3.55 years). The mean temporary loading duration in the test group was 45 weeks, or roughly ten months. The mean time in situ for all patients was 175 weeks, that is 3.36 years (three years, four months and nine days). The shortest observation period was 79 weeks (1.52 years), and the longest observation period (of a control implant) was
377 weeks (7.24 years).

The 111 immediately restored or loaded implants had been inserted in 44 patients, and these were compared with 111 control implants in 37 patients, which had been restored according to the conventional two-stage treatment protocol. For
25 implants in 17 patients in the test group, an equivalent implant in the same patient was used for follow-up. The control group was otherwise as similar as possible to the test group in all parameters (age, location, indication, time of insertion, risk factors [smoking, bruxism, periodontal disease, implant and dental prosthesis parameters etc.]). There were 76 patients in total, 42 women with 123 followed-up implants (55.4 %) and 34 men with 99 implants (44.6 %). In the case of one deceased patient with six immediately loaded implants, the results of his last routine follow-up examination in February 2006 were used.

All 222 implants were examined for the parameters listed in Table 1. Four different implant systems from three manufacturers were used. 193 Camlog Root-Line and six Camlog Screw-Line implants from Altatec were inserted, along with 21 Osseotite implants from implant manufacturer 3i and two Restore implants from Lifecore. 108 Camlog Root-Line and three Osseotite implants were inserted in the test group, and 85 Camlog Root-Line 18 Osseotite and two Restore implants were inserted in the control group (Fig. 1).

 

Surgical protocol

All patients followed a similar surgical protocol. Local anesthesia was provided with Ultracain with added epinephrine. Postoperative analgesia was achieved as needed with a combination of paracetamol and codeine. The implant preparation and insertion protocols of the various implant manufacturers were followed in the test and control groups. Immediate implantations were performed in both the test and control group. 58 implantations (26.1 %) were performed as immediate implantation. The number of immediate implantations was nearly four times higher in the test group at 46 than in the control group, where the number was twelve.

A precondition for immediate function was a final insertion torque of at least 25 Ncm and peri-implant defects of less than 3 mm in all directions. If peri-implant bone defects greater than 3 mm were present, a decision was made in favor of closed unloaded healing. Smaller augmentations of less than 3 mm in vertical and/or horizontal direction as part of the implantation were not a reason to abandon the protocol for planned immediate function. In the control group, too, this dimension of augmentation size was not exceeded when augmentation was performed simultaneously with implantation.

Temporary restoration on single implants was always performed with indirect loading, that is, without direct contact with the opposing tooth but, whenever possible, with approximal contact points to the neighboring teeth. If splinting of at least two implants was possible, a direct occlusal loading was always established, with contact to the opposing teeth. The superstructures on the immediately restored and loaded implants were either PEEK abutments from Camlog, or the final titanium abutments, and in one case, transmucosal implant extensions from this manufacturer were used. Restorations with immediate function were divided into four groups: single crowns with acrylic temporaries, bridge acrylic temporaries, definitive bridge constructions and „telescopic crowns“. Immediate loading was established with 64 implants (57.7 %), where splinting between at least two implants was possible. The remaining 47 implants (42.3 %) were restored according to an immediate restoration protocol. Immediate restoration was established if single implants had been inserted. The implants were loaded indirectly, that is, avoiding any occlusal or translatory contacts between the restoration and opposing dentition. As soon as at least two implants could be splinted together, immediate loading with direct loading was done. The implants were placed in direct occlusal contact with the opposing teeth. Figure 2 and Figure 3 show photos of a typical chairside temporary immediate restoration on a ground PEEK abutment.

 

Evaluation of success

The following periodontal parameters were evaluated during follow-up: implant survival, mobility, probing depth, bleeding on probing, presence of buccal and lingual keratinized mucosa, suppuration and the modified bleeding index [55]. Probing depth, suppuration and bleeding on probing were recorded at six points per implant and recorded with the Florida Probe (FP32, Florida Probe Version 6.6.1). Radiographs were also obtained at the time of follow up. A single digital radiograph at a right angle and an orthopantomograph of each implant were obtained (CCX Digital Trophy-Trex X-ray tube and RVG-5 sensor from Trophy, OP 100 D from Instrumentarium). The Rinn XCP-DS sensor holder was used to make the images as reproducible as possible. For each implant, the mesial and distal bone levels were evaluated in relation to the implant platform at the time of the radiograph. The height of the superstructure was measured and the ratio of the superstructure height to implant length was calculated. The various radiological parameters were measured with the ImageJ 1.36b freeware program of the National Institutes of Health (USA).

Photos of all test and control teeth were taken with a digital single-lens reflex camera (Nikon D200 with R1 macro flash kit). The aesthetic situation of 55 selected implants was evaluated using the Testori et al. [68] aesthetic implant index. The selection was limited to implants in the highly important aesthetic region (upper anterior and premolar region). Implants were excluded that exhibited major pre-implantation bone atrophy because of years of edentulousness or a history of periodontal disease and which would have had to be restored with a removable prosthesis to correct the vertical and horizontal tissue deficits but were restored with a fixed prosthesis at the patient’s wish. Figure 4 shows an example of a photo used for evaluation.

Implant success was evaluated according to the criteria proposed by Gettleman/Schnitman [36, 65]. These are: 1. implant in situ; 2. mobility 0–1; 3. vertical bone atrophy not more than 1/3 of the vertical implant length; 4. gingivitis accessible for treatment, no signs of infection; 5. no injury of nerves, teeth, maxillary sinus or floor of the nose. Because of the absence of standardized radiographs at the time of implant insertion, the criteria postulated by Albrektsson and Zarb [2] could not be used. The Gettleman/Schnitman criteria of success were compared with the very similar success criteria of Buser/Naert [15, 16, 56, 66]. The difference between the latter three indices and that of Gettleman/Schnitman consists only of minor qualitative differences in definition and mainly in the nonquantified radiological radiotranslucency. However, it must be noted that a periotest measurement was used to assess the success criteria of Naert [56]/Snauwaert [66], which was not carried out in the patients in this study.

All evaluations were performed with the STATISTICA program, StatSoft, Inc., Tulsa, USA (StatSoft, Inc.: STATISTICA for Windows [computer program manual, Version 7.1], Tulsa, OK, USA, 2005). Time in situ was analyzed and the rate of loss was calculated according to the method described by Kaplan and Meier (1958). Survival rates between several samples were compared using the log rank test (Peto and Peto , 1972). The significance level was 5 %.

Results

Figure 5 and Figure 6 give the distribution of the implants with regard to location and indication (classical classification).

Five of the inserted implants were lost in the study period. This corresponds to a loss of 2.25 % or survival of 97.75 % of the implants. All losses occurred within three months after insertion. Accordingly, the percentage of implants in situ fell in this period from 100 % to 97.75 % and remained at this level subsequently. The longest follow-up periods obtained were roughly 76 months (six years and four months). Losses occurred only in the test group with immediate function. The difference regarding the percentage of non-failed implants over time was statistically significant (log rank test, p = 0.024). 100 % survival was confirmed with the conventional protocol, whereas a 95.5% survival rate was recorded for immediate function.

The difference (log rank test, p = 0.0055) between immediate and delayed implantation was also significant. One implant in the delayed implantation group was lost, resulting in a survival rate of 99.4 %, whereas four implants were lost in the immediate implantation group (survival rate 93.1 %). No statistical significance was found for all other parameters, i. e., health and other risk factors (smoking, bruxism, periodontal disease, implant and prosthesis parameters).

Multivariate regression analysis (Cox regression) was performed for all parameters with a significance level less than p = 0.15 on univariate analysis (see Table 2). The global p value (highlighted gray) of 0.033 indicates a statistically significant result. Statistical significance was not confirmed for any of the included parameters (last column, all p > 0.05). However, the result for the parameters immediate implantation/delayed implantation (p = 0.11) and diameter (p = 0.12) just missed statistical significance.

Statistical analysis of the periodontal parameters yielded the following results. The mean probing depth for all patients was 2.101 mm with a standard deviation of 0.5946 mm. The minimum was 0 mm, and the maximum was 6 mm. Figure 7 shows the distribution of the probing depths at the six locations. Bleeding on probing was found in 28.3 % of the examined implant surfaces. Keratinized mucosa was present at 96.5 % of the locations. The mean modified bleeding index was 0.903 buccally and 0.899 lingually, giving an overall mean of 0.901 (Fig. 8). Suppuration and mobility were not present.

Analysis of the radiological parameters yielded a mean of 2.229 mm for the mesial and 2.29 mm for the distal bone level. This resulted in a mean bone level of 2.260 mm at the implant. The mean bone atrophy relative to implant length was 0.173 mm. On five of the implants, bony recession exceeded one third of the implant length.

Analysis of the aesthetic evaluation of 55 implants using the Testori index [68] gave an unsatisfactory result for 10.9 % of the examined teeth; 87.3 % showed acceptable results and only one case, or 1.8 %, was assessed as perfect according to the aesthetic index.

Evaluation of success in all the patients according to the indices described by Gettleman/Schnitman resulted in failure for 2.25 % and implant success accordingly was 97.75 %. However, the Buser/Naert indices, which are similar to but much stricter than those of Gettleman/Schnitman resulted in a failure rate of 4.5 % and thus a success rate of 95.5 %.

A statistically significant difference between the test group (immediate function) and the control group (conventional treatment protocol) was found with regard to the aesthetic index (Mann-Whitney U test; p = 0.0074). Immediate function achieved markedly better aesthetic results with 664 points than the control group with 876 points. In the test group, one implant was assessed as perfect and 26 as acceptable. In the control group, there was no aesthetically perfect result, 22 implants were assessed as acceptable and six implants as unsatisfactory (Fig. 9).

A statistically significant difference with regard to the peri-implant bone level was found between immediate and delayed implants (Mann-Whitney U test; p = 0.0076). While this was 2.3 ± 0.9 mm on average in the delayed implantation group, it was 2.0 ± 0.7 mm in the immediate implantation group (Fig. 10).

The mean probing depth in the immediate restoration group was 2.1 ± 0.6 mm and 1.9 ± 0.6 mm with immediate loading. This resulted in a statistically significant difference between immediate restoration and immediate loading (Mann-Whitney U test; p = 0.025).

When immediate function was compared with the conventional treatment protocol with regard to clinical parameters and radiological bone atrophy, statistically significant and highly statistically significant differences were found. The mean probing depth was 2.0 ± 0.6 mm in the test group and 2.2 ± 0.6 mm in the control group (Mann-Whitney U test; p = 0.011). A marked difference was also identified with the mean bleeding on probing. The mean was 0.21 with immediate restoration and loading, whereas the mean was 0.35 in the control group. These differences were highly significant (Mann-Whitney U test; p = 0.0050, Fig. 11). Statistically significant differences were also found in the peri-implant bone level. The mean crestal bone margin was 2.09 ± 0.8 mm in the test group and 2.42 ± 0.8 mm in the control group (Mann-Whitney U test; p = 0.0092, Fig. 12). When this bone atrophy is considered in relation to implant length, there was a statistically highly significant difference between the test group with a mean of 0.15 and the control group with 0.19 (Mann-Whitney U test; p = 0.00049).

Comparison of all assessments of success for the test and control group (immediate function vs. conventional procedure) did not show any statistically significant difference. The result of the comparison between assessment of success according to Gettleman/Schnitman and the time of implantation was statistically significant (Fisher test, p = 0.017). While an assessment of success was not available for only one of the 164 delayed implants (0.6 %), this percentage was 6.9 % (four out of 58) with the immediate implants. A statistically significant difference was not found for assessment of success according to Buser/Naert (p = 0.29).

 

Discussion

The decision on whether immediate function is possible and was established was dependent on various factors in this study. Naturally, the patient’s wishes for a maximally comfortable temporary prosthesis and short duration of treatment were a priority. However, clinical factors (e. g., adequate bone, adequate primary stability etc.) also played an essential part and some of these could only be decided at surgery. Thus, many of the factors held responsible in the literature for implant failure [58, 63] were markedly underrepresented in the immediate function group. This positive selection favors the test implant group, but is also present in other studies. The reverse applies for immediate implantation, which represents an increased risk for implant failure [5, 39, 58]. In this study, there are four times as many immediate implants in the test group as in the control group, resulting in an unintended risk accumulation.

The survival rates of 97.75 % of implants achieved in the entire patient population largely agree with the figures for implant survival given in the literature. If the immediate function implants are excluded, the survival rate of implants restored according to the conventional protocol is 100 %. In an analysis of numerous studies with a total of over 10.000 implants over a period of two to 16 years, the ADA Council of Scientific Affairs arrived at a mean survival rate of 94.4 %, ranging between 76 % and 98.7 % [1]. Other studies achieved a survival rate of 96.5 % [47] and 95.7 % [62] in their 5- and 10-year investigations and found that implants inserted conventionally (by specialists – surgeons, implantologists or periodontologists) also demonstrate a certain complication rate [62] after longer observation periods.

In this case control study, the achieved survival rate of immediately restored or loaded implants was 95.5 % compared with the control group, where the survival rate was 100 %. This resulted in a statistically significant difference between the two groups and largely agrees with the results obtained in the literature. Survival rates of 94 % [1] and 96.7 % [39] and a range of 96.15–100 % [70] or 70.8–100 % [8] are reported for immediate function protocols. Other authors have not found any difference with regard to implant survival and different loading protocols [26, 38, 60].

Very high success rates are generally found in the literature for immediate loading [5, 21, 70]. In contrast to the study by Degidi et al. [26] a statistically significant difference was not found in this study between the survival rate of immediately restored or immediately loaded implants. The survival rate with immediate restoration was 91.5 %, whereas immediate loading had a survival rate of 98.4 %. However, these obvious differences did not reach statistical significance because of the small size of the sample.

In the patients treated according to the conventional protocol, extremely incongruent results have been reported regarding the extent of the peri-implant bone atrophy and probing depths as well as bleeding on probing [38, 61, 62], so comparison with the results obtained in this study is difficult. There are hardly any prospective cohort studies [39] regarding these parameters. The probing depth at „healthy“ screw-fixed implants extends to about 1.4 mm above the bone level and, with successful implants, should not exceed 3 mm. A progressive increase in the clinical probing depth should be regarded as an “alarm signal” [64].

The success rates achieved in this study of 97.75 % according to Gettleman/Schnitman and 95.5 % according to Buser/Naert meet the demand of the NIH consensus conference of 1978, which requires a success rate of at least 75 %, and they are higher than the minimum success rate of 85 % demanded by Albrektsson et al. in 1986 [2]. It is interesting that no statistically significant difference was found for evaluation of success between the immediate function and control groups despite the very different success rates. Only partial comparison of the success rates of endosteal implants is possible due to the use of different implant systems and indications [72]. Clinician- or patient-related reasons and the choice of success parameters also play a crucial role in success statistics. When the success criteria were based purely on clinical parameters, without radiological analysis, the success rates increased markedly. The parameter of absence of mobility in particular is not suitable [2, 36, 56, 65]. Comparison of different studies with different criteria of success is virtually impossible, which is why there is hitherto no consensus on the success of endosteal implants [15, 63].

As regards analysis of retention time, evaluation of success and peri-implant bone level, there were statistically significant differences when immediate implantation was compared with delayed implantation. Other authors also found slightly poorer success rates in studies of immediate function in which implants had been placed in fresh extraction sockets [5, 8, 69]. The survival rates of immediately restored or loaded immediate implants fell by roughly 10 % compared with traditional loading concepts [39]. In general, a greater risk must be assumed with immediate implantation combined with immediate function [29, 39]. The literature is also controversial with regard to the peri-implant bone level with immediate implantation. The majority of authors confirm greater buccal recession after immediate implantation compared with a delayed or late procedure [4, 11, 30]. Other studies even diagnose less crestal bone atrophy for immediate implantation [5, 26]. It can be concluded from this that implant insertion as early as possible contributes to preservation of alveolar bone and the associated soft tissue due to functional loading. Immediate implantation in conjunction with immediate restoration is described rarely in the literature and the conclusions that can be drawn from the available studies are limited on account of the study design, short observation periods and other factors [6]. Determination of the tissue type has proved important for predicting a risk of recession with immediate implantations in the aesthetically important area [19, 30, 45, 50]. The type and quality of the soft tissue present and the periodontal status of the neighboring teeth influence the extent of resorption [46], as does the buccal positioning [30] of the implant shoulder. Thicker biotypes significantly induce thicker peri-implant mucosa [45], which in turn has an influence on the resorption and remodeling especially of the vestibulo-crestal lamella (buccal plate). However, other studies indicate that resorption processes cannot always be prevented with immediate implantation, despite additional hard and soft tissue augmentation [4, 11, 29]. The resulting impairment in the aesthetically important area due to potential recession is not predictable. The data are still completely inconclusive for both immediate and late implantation, especially as regards the long-term prognosis [29, 30, 38].

Statistically significant differences between the test and control groups were found in this study for peri-implant bone level, probing depth and bleeding on probing. In the literature, differences in the clinical parameters are controversial. In the great majority of publications, no differences were found between the different loading protocols [5, 38, 39, 48]. The data are controversial especially for the marginal bone level [5, 18, 38]. Comparison of these figures with those in the present study, where the bone level was 2.0 mm, is only partially possible because of the different implant and study designs. One explanation for the slightly better results obtained in this study for probing depth and bleeding on probing in the immediately restored or loaded test group compared with the conventionally loaded control group might be the wider ranging and more intense manner in which the patients in the test group were advised on the risk factor compared to those of the control group. The slightly better marginal bone level is attributable to the positive effects due to early functional loading to a certain controlled degree during the bone healing period, which has been described by various authors [14, 17, 25, 31]. Early induction of loading stimuli on the bone-implant interface leads to functional adaptation of the bone to the loading situation (remodeling) and to better differentiation of bone structures, which has the effect of a higher marginal bone level.

In this study, immediate function demonstrated markedly better aesthetic results than those in the control group treated according to the conventional protocol. Immediate implantation was markedly overrepresented in the immediate function group, where it was four times higher than in the control group. The aesthetic result of different treatment protocols is extremely controversial in the literature. Some authors have found that the loading protocol appears to have no or little influence on tissue development and the resulting aesthetic assessment [40, 70]. However, more recent results agree with the results of this study and show that the aesthetics of immediate restoration and implantation are at least no worse and sometimes even better than those achieved with late implantations. The reason might be that immediate implantations are performed to preserve existing mucogingival structures as well as possible. It therefore appears entirely logical that the aim of achieving „peri-implant architecture“ that is as natural as possible is easier to achieve in this way than with implantation in healed bone. Categorization of the investigated implants according to other factors therefore appears more useful. Numerous authors have proposed division into thick and thin morphological tissue types [46, 50]. A distinction is also made between a high and a low scalloped gingival margin [50, 67]. These factors might have a far greater influence on mucosal parameters and aesthetic assessment than certain treatment or loading protocols. Studies are therefore required that take these divisions into account and evaluate their influence on mucosal parameters and the aesthetic result [30]. Several factors might be the reason for the relatively incongruent results in the literature; there are relatively few studies on the association between different treatment protocols and their effects on the aesthetic results. The various indices presented in the literature (papilla index [42], implant aesthetic index [68], pink aesthetic score [32] and implant crown aesthetic index [53]) are very different and can therefore not be compared with one another. The majority of the indices [32, 42, 68] consider only the aesthetic situation of the soft tissue, but not the aesthetics of the dental reconstruction, as happens in the implant crown aesthetic index [53]. The validity and reproducibility of these indices for objective aesthetic analysis have not been adequately investigated hitherto and their reproducibility is more or less questionable [34, 35].

In this study, no statistically significant association was found between various individual risk factors such as smoking, diabetes, poor oral hygiene, periodontitis, bruxism, additional surgical procedures, small implant diameters, short implant lengths and impaired health status and effects on various clinical parameters and implant success. The only factors that can be regarded as statistically significant factors that influence implant retention time and implant success are immediate function and immediate implantation. Multivariate regression analysis did not identify any individual factor so that a summation effect of different influencing factors must be assumed. The relevance of the individual risk factors for implant success is also very controversial in the literature. One reason for the lack of evidence for individual risk factors is probably that failure is a relatively rare event in implant therapy. Even in large patient populations, there are only small numbers of failed implants, with the resulting negative consequences for statistical analysis. Further scientific studies involving much higher numbers of cases are therefore required to identify and isolate individual risk factors. Great importance must be attached to risk accumulation [9, 24].

For some years now, successful immediate function can be regarded as a successful and safe treatment protocol for selected cases in practices with clinicians familiar with this technique [5]. In their systematic Cochrane Database meta-analysis, Esposito et al. [28] stress that it is possible to load dental implants immediately or early in selected patients. However, they also point out that some practitioners have more failures with this technique. Careful and accurate case selection and observation of a strict surgical and prosthetic protocol are crucial for avoiding failures with immediate function [5, 21, 49, 70]:

  • 1. Adequate primary stability of at least 25 Ncm must be achieved. This can be obtained, on the one hand, by adequate
    bone quantity and quality, and on the other hand, closer bone contact and thus greater primary stability can be achieved with suitable surgical techniques (bone condensation and/or spreading, under-dimensioned preparation etc.).
  • 2. Precise operation and treatment planning in advance of surgical and prosthetic measures is essential.
  • 3. Macro movements or relative movements of the implant should be avoided. This can be achieved, for example, by prosthetic techniques such as splinting of immediately loaded implants (direct loading) or complete absence of occlusal load of immediately restored implants (indirect loading).
  • 4. It is essential that adequate patient compliance with regard to diet and avoidance of individual harmful factors be demanded.
  • 5. Risk accumulation must be avoided. If an identifiable summation of potentially harmful influencing factors occurs during the operative phase or even during treatment planning, a changeover should be made to the conventional two-stage treatment protocol.

Conclusion

This study confirms that immediate restoration or loading results in clinical parameters, marginal bone level and the assessment of success and aesthetics provide results that are at least no worse compared with the conventional loading protocol, so that it may be regarded as a successful treatment variant. Immediate function is a reliable treatment method with a predictably high success rate of 95.5 %. Thus, a success rate for immediate function similar to that in the literature was achieved in this study. Compared with the conventional treatment protocol, in which success rates of 96–100 % are achieved today, there is only a slightly increased risk [22, 43]. Naturally, at no time during the treatment may the fact be lost sight of that improvement of the patient’s treatment is the top priority. Variations in treatment that place the implant or implant-borne restoration at an unacceptably high level of risk are not acceptable. An accurate individual consideration of the risks and benefits or a risk analysis is required for each patient to minimize the risks and maximize the benefit for the patient. Because of the slightly increased risk, unreserved discussion with the patients is essential, not least because their collaboration is always required. They should have realistic expectations. They must understand that implant loss is a rare but realistic risk in immediate function. If the patient meets these criteria, immediate function can be regarded as an extremely beneficial and useful treatment variant with aesthetically ambitious results.

The preconditions for achieving and maintaining acceptable results are not yet fully known today. Clinically tested and proven surgical and prosthetic treatment concepts should therefore be followed. Because of the increased risk and as yet incompletely elucidated requirements for immediate function, immediate loading protocols as advanced and complex treatment variants are the domain of skilled and experienced practicing implantologists [22].

 

Conflict of interests: none stated

Correspondence address

Dr. med. dent. Derk Siebers MSc

Soorstr. 26 / Hölderlinstr. 19a

14050 Berlin

Tel.: 030 / 31802300

Fax: 030 / 30102966

E-Mail: info@zahnarzt-siebers.de

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Footnote

1 Private Practice, Berlin, Germany

2 Private Practice, Ludwigshafen, Germany

3 Director, Clinic for Oral and Maxillofacial Surgery, Georgia-Augusta-University, Göttingen, Germany

Übersetzung: LinguaDent

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