Immediate Vs Early Loading of Bone Level Tapered Dental Implants With Hydrophilic Surface in Rehabilitation of Fully Edentulous Maxilla: Clinical and Patient Centered Outcomes Open Access

Rehabilitation of the edentulous maxilla is a challenging surgical and prosthetic procedure because of the anatomy (sinuses) and bone structure (thin cortex surrounding a loose medulla with low trabecular density). Different options have been proposed in the literature: (1) complete removable dentures, (2) implant supported full-arch removable dentures, and (3) implant-supported fixed full-arch dentures.¹ 

Implant-supported fixed full-arch dentures are considered a predictable edentulous maxilla treatment.^2–4  This approach provides the closest feeling to natural dentition and improves patient confidence resulting in a high degree of satisfaction.⁵  Mertens et al²  reported an implant survival rate of 99% at an 8-year follow-up when treating completely edentulous maxilla patients with implants supporting screw-retained full-arch prostheses. According to Schwarz,⁶  this treatment choice demonstrates significant better results than implant-supported removal prostheses and is associated with lower post-loading implant loss rates.

The type of loading protocol (immediate, early, and conventional loading) is reported not to influence the implant and prosthesis survival rates; thus, all loading protocols can be recommended for the treatment of edentulous patients.^7,8  Consequently, immediate loading protocols become the treatment of choice for patients as it reduces treatment time and increases patient comfort and satisfaction.

Loading is considered as immediate if it takes place less than 1 week after implant placement.⁹  Numerous studies have shown that immediately loaded fixed full-arch dentures supported by 6 implants are predictable options and offer long-term successful treatment for rehabilitation of the edentulous maxilla.^1,10–14  A systematic review that analyzed 15 prospective clinical studies with at least 1 year of follow-up, using 6 to 8 immediately loaded implants placed in the maxilla, reported a failure rate between 0 and 3.3%. Consequently, it was concluded that immediate loading of implants placed in the edentulous maxilla appears to be a predictable treatment option when a sufficient number of implants are placed.¹⁵  An implant survival rate of 96% was reported after a follow-up period of 10 years with implants immediately loaded through a full-arch denture.¹⁶  Another study at a 32-month end point demonstrated that implants loaded within 24 hours of placement had a survival rate similar to conventionally loaded ones. Again, immediately loaded splinted implants were shown to be a viable solution for the edentulous maxilla.¹⁰ 

The early loading protocol takes place between 1 week and 2 months after implant placement.⁹  Implant design is a prerequisite for primary and secondary stability. A micro-rough sandblasted, large grit and acid-etched chemically modified surface (SLActive; Straumann, Basel, Switzerland) is documented as an important factor to reduce the time of osseointegration. Several clinical trials have shown that implants with this type of surface can be loaded 3 weeks after the placement, even in poor-quality bone.^17–20 

For immediate and early loading the primary stability of implants is crucial for a successful osseointegration and it is suggested that in edentulous arch the primary stability of each implant must be controlled.⁸  The stability of dental implants is mostly assessed by insertion torque (IT) and resonance frequency analysis (RFA). IT measures the frictional pressure between the implant and bone as Ncm. RFA measures an absence of movement after surgical implant insertion represented as implant stability quotient (ISQ) on a scale of 1 to 100.²¹ 

IT is easily evaluated and can allow for data comparisons in everyday practice. An issue with this technique is that it can only be implemented at the time of placement and it is considered to be a poor predictor of implant success.²² 

The RFA method uses an electronic transducer placed on the implant. The metal peg (transducer) is stimulated by a range of electromagnetic waves to assess the RF. The two main devices used for measurement of RFA are Osstell and Penguin RFA instruments. The RFA evaluation has been well documented and can provide valuable information relating to future implant loss.²³ 

The recommended IT is a value ≥30 Ncm with an ISQ of >60.⁸  Implant stability, whether primary or secondary, is influenced by bone structure, quality, surgical instrumentation, and implant macro- and micro-design features. It was demonstrated that implants with a tapered design can achieve increased primary stability due to the high bone compression generated during the insertion.^24,25 

Edentulism is often associated with psychosocial issues and induces a profound negative effect on the patient's quality of life. Patient-centered outcomes may be the main factor determining treatment success and can constitute an important source of information for dentists desiring to improve the quality of their treatments.²⁶  Immediate and early loading of dental implants often has a significant positive effect on patient satisfaction, comfort, function, and esthetics. Ultimately, with placement of the final restoration, patient satisfaction increases even further.^27,28 

Immediate or early loading of dental implants is a contemporary treatment concept that contributes to success, provided important requirements are followed. Roccuzzo²⁹  and Marković²⁵  demonstrated encouraging results with immediate or early loading of splinted and unsplinted implants in anatomical regions where bone quality was considered deficient. Results indicate that immediate or early loading might be applied even in low-density bone if appropriate surgical protocol, adequate implant form (progressive thread design), and surface (SLActive) are applied.

The primary objective of the present randomized clinical trial was to compare changes among primary and secondary implant stability between immediate and early loaded BLT SLActive dental implants (Straumann) placed in edentulous maxillas using 2 different methods (Ostell).

The secondary aim was to compare the oral health related quality of life (OHRQoL) using the OHIP-19 questionnaire. A previous version of the OHIP-14 questionnaire has been confirmed as a suitable reference for the assessment of oral implant treatment on oral health-related quality of life.³⁰  Patients' and clinicians' satisfaction relating to maxillary prosthetic restorations in cases of immediate and early loading were also investigated with a visual analogue scale (VAS). Additionally, biological, mechanical, and procedural related complications (such as implant failure, infection, device loss/fracture, functional, and esthetic outcomes, etc.) were recorded.

The present prospective, single-institution, randomized, controlled clinical trial was conducted from March 2019 to March 2020. The study was approved December 12, 2018 (approval #: 36/16) by the Institutional Review Board of School of Dental Medicine in Belgrade prior to patient selections and conducted in accord with the Declaration of Helsinki.³¹  Research methodology was reviewed by an independent statistician.

Patients with edentulous maxilla who wanted oral rehabilitation using dental implants were invited through television and newspaper advertisements. Respondents' eligibility for participation in the Straumann Pro Arch concept approach study was based on the patient's medical history questionnaire and a clinical dental examination completed with a radiographic analysis.

Inclusion criteria for patient selection included:

1. Patients in good general health with no current history of systemic disease or medication use that could interfere with the treatment;

2. Patients with complete maxillary edentulism who had lost their teeth at least 6 to 8 weeks prior to the proposed “all-on-six” implant rehabilitation; and

3. Clinically compliant patients consenting to be enrolled into the study.

Exclusion criteria for patient selection included:

1. Active or chronic disease that affects bone metabolism or wound healing;

2. Diminished mental capacities that could mitigate the ability to comply with the protocol;

3. Residual roots or teeth;

4. History of maxillary augmentation;

5. Oral carcinoma or inflammatory changes; and

6. History of head and neck radiotherapy.

From all eligible responders, 24 were recruited using computer-generated random identifying numbers. Alternative treatments and possible complications were outlined for each patient. Each patient signed an individual informed consent form.

A computer-generated block randomization method, with block size 4, was used to allocate 24 patients (144 implant sites) into 2 groups:

1. Test group: 12 patients (6 implants per patient)—72 BLT SLActive Roxolid implants (Straumann) placed into edentulous maxilla and immediately loaded;

2. Control group: 12 patients (6 implants per patient)—72 BLT SLActive Roxolid implants (Straumann) placed into edentulous maxilla and loaded 6 weeks after placement.

Independent researchers generated the random allocation sequence, enrolled participants, and assigned participants to test groups. The independent researcher who allocated groups was unaware of the size of the blocks. To conceal the random allocation sequence until interventions were assigned, sequentially numbered opaque, sealed envelopes were used. Aluminum foil inside the envelope ensured that it became impermeable to light. Envelopes were opened sequentially only after the participant's name were written on the appropriate envelope. Corresponding envelopes were opened only after implant placement and immediately before the prosthodontic procedure.

Prior to surgery antibiotic prophylaxis (2 g amoxicillin with clavulonic acid or, in case of allergy, 0.6 g clindamycin, 1 hour before the procedure) and antiedema therapy (0.004 g dexamethasone 1 hour before the procedure) was administered. Patients rinsed their mouth using 15 mL of 0.12% chlorhexidine solution for 1 minute preoperatively. The surgical procedures were performed under local anesthesia using 4% articaine, 1:100.000 epinephrine. Centers of the intended implant sites were marked according to the reference marks present in the patient's existing complete removable denture that had been used as the radiographic stent (Figure 1a and b). A midcrestal incision was made, then full-thickness buccal and palatal flaps were elevated. Implant sites were prepared by strictly adhering to the manufacturer's protocol for low-density bone using drills of increasing diameter (Institut Straumann). To provide adequate primary implant stability, underpreparation was performed:

1. In low-density type D3 bone, the profile drill was skipped; and

2. In low-density type D4 bone, the final sequence and profile drills were skipped.

Intermittent drilling under copious irrigation was performed with low hand pressure and a physiodispenser running between 600 and 800 rpm. A total of 144 sites were prepared, followed by placement of 144 SLActive surface (Bone Level Tapered, Institut Straumann) implants. Bone quality was assessed according to the Lekholm and Zarb classification.³²  In sites with dehiscence or fenestration resulting in an exposed implant surface, localized bone augmentation was performed using bovine-derived xenograft (Geistlich Bio-Oss, Geistlich, Wolhusen, Switzerland) and covered with a type 1 collagen membrane (Geistlich Bio-Gide, Geistlich). Data relevant to bone augmentation procedures were recorded in the patient study charts. Healing screws (Institut Straumann; NC healing abutment Ø4.8 mm conical 5 mm and RC healing abutment Ø5 mm conical 6 mm) were placed and primary wound closure was achieved with 5-0 single resorbable sutures (AssuCryl Lactin, Assut Sutures of Switzerland, Pully-Lausanne, Switzerland) (Figure 2a and b). Patients were discharged with recommendations regarding dietetic and hygienic regimens. Antibiotic protocol consisted of 2 g amoxicillin with clavulonic acid (divided into 2 doses) or, in case of allergy, 1.8 g clindamycin daily (divided into 3 doses) for the following 5 days. Antiedema therapy (0.004 g dexamethasone) was administered 24 hours postoperatively.

After dental implant placement, patients were randomly assigned to immediate loading or early loading groups. Implants for patients from Group 1 were immediately loaded using S-R abutments (Institut Straumann) with temporary restorations (Figure 3). Patients from Group 2 did not receive any kind of prosthetic temporization and were left with healing abutments (Figure 4).

For Group 1 an open-tray impression technique was used for provisional restoration. Impressions were made using: A-Silicone material (Hydrorise implant, Zhermack, Badia Polesine, Italy), splinted impression posts (RC and NC impression post, Straumann) and a plastic impression tray (Miratray, Hager Werken, Duisburg, Germany). Provisional restorations were made digitally with polymethyl methacrylate (PMMA) (Telio CAD, Ivoclar Vivadent, Schaan, Lichtenstein)^33,34  (Figure 5). Plaster models with scan bodies were digitized with a laboratory scanner (3Shape E1, 3Shape, Copenhagen, Denmark). Final virtual design of provisional restoration was performed with 3D design software (exocad Matera 2.3, Exocad, Darmstadt, Germany). Drilling of PMMA blocks was performed in a 5-axis milling machine (Zenotec Select, Wieland, Pforzheim, Germany). The following final Straumann screw retained abutments for the prosthetic bridge (Institut Straumann) were chosen according to implant angulation and surrounding soft tissue height. For the interface between the screw-retained abutments and final prosthetic work, copings for screw-retained abutments (Institut Straumann) were used and bonded to the final prosthesis.

At the end of the 6-week healing period for both groups, definitive prosthetic restorations were delivered (Figure 6a and b). In preparation for the definitive prosthesis, a final open-tray impression was taken with an individual tray and polyether material (Impregum Soft, 3M Espe, Seefeld, Germany). An analog ceramic layering technique was performed in the process of producing a porcelain fused to metal restoration (Shofu Vintage Halo Porcelain, Shofu Dental Corporation, Ratingen, Germany). The metal framework was made using cobalt chromium metal powder material (Starbond Easy Powder 45, Scheftner, Mainz, Germany) with additive manufacturing technologies (EOS, Krailling, Germany).

The primary outcome measures of this trial were implant stability recorded by Osstell Mentor and Penguin using RFA methods. The secondary outcome measures were IT values, Oral Health Impact Profile questionnaire (OHIP-19) and patient/clinician satisfaction indexes.^{21,22,26,35,36} 

Insertion torque was measured with a torque wrench (Institut Straumann) and recorded in Ncm (Figure 7a). Resonance frequency was recorded using the Osstell Mentor (Osstell, Gothenburg, Sweden) (Figure 7b) and Penguin (PenguinRFA, Osstell) (Figure 7c) devices at the time of implant placement (baseline) and at post-op week 6 (prior to delivery of definitive prosthetic restoration). Results were recorded as an implant stability quotient (ISQ) from 1 to 100. The higher the ISQ, the more stable the implant was.²¹  Two consecutive measurements delivering the same ISQ values were considered authentic. Interrater and intrarater reliability were tested in the pilot study covering 4 patients for a total of 24 implants. To test interrater reliability, two different assessors measured implant stability on the same day, but at separate times. Each assessor repeated measurements 15 minutes later in random order to test the intrarater reliability. Unlike Osstell Mentor and Penguin, it was not possible to test the intrarater or interrater reliability for the insertion torque due to the nature of the procedure. OHIP-19 questionnaire was completed by patients prior to implant placements and 1 month after delivery of the definitive prosthetic restoration. This questionnaire consisted of 19 questions divided into 7 domains: functional limitation, physical disability, physical pain, psychological disability, psychological discomfort, social disability, and handicap. Responses were delivered on a 5-point Likert type scale ranging from 0-never to 4-constantly. The score for each domain was calculated and the sum of the 7-domain scores represented the total OHIP-19 score.³⁵ 

Patient and clinician satisfactions were assessed by the help of a VAS. Patients specified their level of satisfaction related to function, esthetics, and discomfort/pain by indicating a position along a 10-cm line between 2 endpoints where the beginning of the line was marked as complete unsatisfaction and the end as maximum satisfaction. Similarly, clinicians specified their satisfaction on a VAS.

Surgical and or prosthetic complications were recorded in the study charts (if occurred).

The primary hypothesis tested was that there was no difference in the changes in implant stability from implant placement to definitive restoration delivery at post-op week 6 between the groups. The secondary hypothesis was that there was no significant difference by group (time or interaction) regarding OHIP-19 domain scores, OHIP-19 total scores, or VAS. Descriptive statistics were calculated for: (1) patients' baseline and implant site characteristics, and (2) insertion torque and primary implant stability measured with Osstell and Penguin technologies. Non-normality of distribution of continuous variables was assessed with graphical representation of the data (histogram) and Shapiro-Wilk normality test. Differences in age and torque insertion of the two groups was tested with the exact Wilcoxon sum rank test³⁶  (after examining the equality of variances with the exact Ansari-Bradley test³⁷). Boschloo's exact test³⁸  was used for testing the difference in gender composition and presence of bone augmentation for both groups. Homogeneity of groups considering patient smoking status and bone density were examined with Pearson's chi square test of homogeneity (due to small expected counts, P values were computed by Monte Carlo simulation).

In the pilot study, authors calculated interrater and intrarater reliability coefficients³⁹  for two raters who repeatedly measured implant stability by Osstell and Penguin technologies. Due to nonnormality of the distribution of implant stability, we did not calculate the 95% confidence interval (CI) for the reliability coefficients.

Brunner-Langer mixed nonparametric analysis of variance (ANOVA)⁴⁰  was used for testing the effects of group, time, and interaction on OHIP-19 domain scores and on OHIP-19 total score. The results of the modified ANOVA-type statistic with Box approximation were presented for the significant effect of the group.

Effect of groups on VAS scores (function, esthetics, absence of pain, and clinician satisfaction) was examined with Brunner-Munzel test.⁴¹  We calculated Spearman's correlation coefficient between the patient's VAS aesthetic score and the clinician's VAS aesthetic score and then tested the presence of correlation with Spearman's correlation test.

Median of change in implant stability together with 95% CI for the median was calculated (based on exact Wilcoxon sign rank test⁴²). Effect of groups on changes in implant stability were measured by Ostell and Penguin technologies and tested with the exact Wilcoxon sum rank test.

The level of significance was set at 0.05. Statistical analysis was performed in statistical software R, version 4.0.2 (using R packages stats, coin, nparLD, exactRankTests, DescTools, lawstat, irr, plotrix^43-46).

This study was reported according to the CONSORT Statement.

Results were reviewed by an independent statistician. No protocol deviations occurred and the complete sets of data from 24 patients and 144 implants (12 patients and 72 dental implants per group) were analyzed.

Descriptive statistics of patients' baseline and implant site characteristics, insertion torque, and primary implant stability measured by Ostell and Penguin are presented in Table 1. There were no statistically significant differences between the test and control groups, except in bone density (X2 = 12.591, df = 5, P = .015) and primary implant stability measured by Osstell (Z = 2.049, P = .040), in favor of patients in the test group (Table 1).

In the pilot study, interrater and intrarater reliability coefficients for measurements of implant stability by two raters were high. For the implant stability by Osstell, interrater reliability coefficient was 0.963 and intrarater reliability coefficients 0.988 for the first rater and 0.984 for the second rater. For implant stability by Penguin, interrater reliability coefficient was 0.934 and intrarater reliability coefficients 0.992 for the first rater and 0.984 for the second rater.

Two implants were initially mobile: one implant was in the immediate loading group placed into a maxillary molar site with D4 bone density without bone augmentation; and the second implant was from the early loading group placed into the maxillary canine region with D3 bone density and simultaneous bone augmentation. At week 6, these 2 implants were stable resulting in survival rate of 100% for 144 implants. These 2 implants were not subjected to RFA analysis to avoid jeopardizing osseointegration. Therefore, the secondary stability measured at 6 week was recorded from 142 dental implants.

No biological complications were reported during the course of the study. However, two prosthetic complications occurred. In one patient, porcelain chipping occurred when the definitive bridge was secured by screws. In another patient, chipping of bridge was identified after 1-month function and was resolved by ceramic veneer application.

Median change of implant stability measured by Osstell was 2 with 95% CI = (0.5, 3.5) for the test group and 2 with 95% CI = (0.0, 3.5) for the control group (Figure 8). Median change in implant stability measured by Penguin was 1 with 95% CI = (−1.5, 2.0) for the test group and 1 with 95% CI = (−1.5, 2.5) for the control group (Figure 9). Further, the effect of group on changes of implant stability measured by Osstell (Z = 0.219, P = .828) or Penguin (Z = −0.152, P = .881) was not statistically significant.

Statistically significant effects on OHIP-19 domain scores, total OHIP-19 scores, and VAS scores, together with mean ranks of the groups, are presented in Table 2. There was a statistically significant effect of time on: (1) OHIP functional limitation score (F = 70.192, df1 = 1, df2 = ∞, P < .001), (2) OHIP physical pain score (F = 113.470, df1 = 1, df2 = ∞, P < .001), (3) OHIP psychological discomfort score (F = 26.028, df1 = 1, df2 = ∞, P < .001), (4) OHIP physical disability score (F = 67.562, df1 = 1, df2 = ∞, P < .001), (5) OHIP psychological disability score (F = 35.026, df1 = 1, df2 = ∞, P < .001), (6) OHIP social disability (F = 17.612, df1 = 1, df2 = ∞, P < .001), (7) OHIP handicap score (F = 63.141, df1 = 1, df2 = ∞, P < .001), and (8) OHIP total score (F = 79.502, df1 = 1, df2 = ∞, P < .001). Patients of both groups felt: (1) less pain in total and specifically, (2) less functional limitation, (3) lessdiscomfort, (4) less disability, and (5) less handicap 1 month after the definitive prosthetic restoration was placed compared with the beginning of the study.

Further, there was a statistically significant effect of group on: (1) OHIP physical pain score (F = 6.973, df1 = 1, df2 = 20.3, P = .016), (2) OHIP psychological disability score (F = 4.504, df1 = 1, df2 = 21.1, P = .046), (3) VAS function score (W = −2.803, df = 11, P = .009), and (4) VAS esthetics score (W = −2.803, df = 11, P = .009). Patients in the test group (immediate loading) felt less physical pain and psychological disability, and were more satisfied with the function and esthetics than patients in the control group.

The Spearman correlation coefficient between patients' VAS eesthetics score and clinicians' VAS score was −0.116 and no significant correlation was found (P = .590).

In the present study 144 bone level tapered implants with a modified SLActive surface (Institut Straumann) were placed in completely healed edentulous maxillas of 24 patients to retain a fixed bridge according to “Pro Arch” concept (Institut Straumann) to test clinical and patient-centered outcomes of two protocols: (1) immediate and (2) early loading. The main prerequisite for immediate loading was adequate primary implant stability that would prevent implant micromotions under occlusal loading and allow for osseointegration. Since the loading time is primarily determined by primary implant stability; the authors used two proven quantitative methods to measure stability, RFA and IT. Insertion torque, as a mechanical parameter, reflects rotational resistance during implant insertion. In the literature, various IT values are proposed as a threshold for immediate loading. Several studies suggested the minimum insertion torque of 30 Ncm for immediate loading of implants in edentulous patients whereas IT values lower than 20 Ncm were predictors of higher failure rates for immediately loaded implants.⁷  In contrast to this, some studies demonstrated relatively high survival rates of immediately loaded implants despite low insertion torques when they were splinted together to increase stability.⁴⁸  The implants used in our study achieved a mean insertion torque of 26.09 ± 10.35 Ncm and 142 of 144 implants stayed stable after 6 weeks except for 2 implants that were “spinners” placed in low-density bone sites with an IT of 15 Ncm.

The present authors agree that there is no linear correlation between IT and RFA methods of measuring primary stability and, therefore, these two parameters should be evaluated independently.^49,50  The present study determined RFA using Osstell and Penguin technologies. Both RFA devices allow for reliable and repeatable measurements of implant stability. Although 66.67% of implanted sites in the present study were bone type D4 or D3, the mean value of primary implant stability was: 71.87 ± 7.11 ISQ as measured by Osstell or 73.70 ± 7.88 ISQ as measured by Penguin.

Primary implant stability depends on various factors such as: (i) local bone quality and quantity, (ii) implant micro and macro design and (iii) surgical technique.^51–53  The possible reason for achieving such a high implant stability in edentulous maxilla might be the implant macro-design as well as the drilling protocol. The BLT implant has a hybrid design with an apically tapered implant body, 0.8 mm threads pitch and full depth thread to the apex with three cutting notches.⁵⁴  Such implant macro-design increases available surface of the implant and engages the surrounding bone to a great extent, thus achieving higher bone to implant contact resulting in optimal primary stability and adequate bony stress.^24,25,45,56  Eshkol-Yogev et al⁵⁷  also reported high values of primary implant stability with a mean ISQ value of 76.9 in their randomised prospective study.

The bone drilling protocol used in this study was proposed for BLT implants. It consists of skipping profile drill in soft bone type D3 and avoiding the last and profile drill in very soft bone type D4. This protocol exerts compressive forces along the implant-bone interface and improves primary implant stability. This means that for an implant with a diameter of 4.1 mm in a very soft bone (D4) the last drill would have a diameter of 2.8 mm, and in soft bone (D3) the last drill will have a 3.5 mm diameter without using a profile drill. Under preparation bone drilling protocols in the maxillary posterior region might be a sustainable option to improve primary implant stability⁵⁸  and to foster a favorable implant survival rate but might have limited benefit in dense bone.⁵⁹ 

In the present study, implant stability after six weeks remained high. Changes in implant stability from implant placement to week 6 was similar in immediate and early loading groups. Implants placed in this study presented with a SLActive® surface which may contribute to higher implant stability values in both immediate and early loaded groups of implants. The SLActive® surface is a micro-rough sandblasted, large grit, acid-etched chemically modified surface foreseen to enhance and reduce the time-period for osseointegration [60-63]. Our results are in correlation with those of Fischer et al,³  who concluded that immediate and early loading of tapered implants can be used in the posterior maxilla with good short-term outcomes.³  Chambrone et al⁶⁴  conducted a systematic review on 19 studies with the objective to compare the outcomes of SLA and SLActive® implants using immediate or early loading protocols. They did not find a significant difference in clinical parameters between immediately and early loaded implants. SLA surface implants demonstrated a 95% survival rate over a 60-month period and SLActive® demonstrated a 97% survival rate at the end of an 18 months follow up period. Although the results looked promissing Chambrone et al concluded that the number of randomized clinical trials was too small to conduct a proper analysis of SLActive® implants. A prospective multicenter study performed by Ganeles et al¹⁷  demonstrated that implants with SLActive® surface can be safely and predictably used for immediate and early loading even in soft bone (D3).¹⁷  Nicolau et al²⁰  came to the same conclusion regarding chemically modified implants used in the posterior maxilla for immediate and early loading protocols. An investigation performed by Zöllner et al⁶⁵  including 383 implants loaded on the day of the surgery (immediately) or after 24–38 days (early loading) showed that Straumann SLActive® implants can be predictably used in time-critical loading protocols.⁶⁵ 

Patient-centered outcomes are part of the Straumann® Pro Arch concept and important indicators of therapeutic protocol success or failure seen from the patients' perspective.

The Straumann® Pro Arch concept refers to the immediate insertion and restoration of 4 to 6 implants in the maxilla and/or mandible after extraction of all hopeless teeth.

The present study focused on patient satisfaction regarding the prosthetic restoration and oral health related quality of life. Edentulism has a negative impact on the patient's physical, psychological, and social sphere resulting in a decreased oral health related quality of life. A literature review finds there is limited data on the comparative analysis of health related quality of life effects of immediate and early loaded implant supported maxillary fixed full arch dental restorations. There are no publications on this matter, and the present study is the first to use the Oral Health Impact Profile (OHIP-19) questionnaire to assess the oral health related quality of life of patients before implant placement and one month after definitive restoration delivery. Following full arch rehabilitation, patients reported significant improvement in oral health related quality of life compared with the period before implant placement regardless of the loading protocol used. This improvement affected functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap in both immediate and early loading protocols. However, it appears that immediate loading could significantly reduce physical pain and psychological disability compared to early loading. Erkapers et al⁶⁶  placed six implants in completely edentulous maxillas and provided immediate restoration 24 hours after implant placement. They evaluated oral health related quality of life using a similar but different questionnaire (OHIP-49) and concluded that patients were reporting an increased quality of life after treatment.⁶⁶ 

In the present study, four weeks after delivering the definitive restoration, patients reported statistically significantly higher levels of satisfaction regarding aesthetics and function in the immediately loading protocol group compared with early loading group. Clinicians expressed a moderate level of aesthetics satisfaction. Evaluation was performed by two experienced clinicians that observed: (i) abutment visibility, (ii) appearance and presence of the papilla, (iii) aesthetic characteristics of dental restorations, (iv) the presence of pink ceramics, (v) external appearance of the patient and (vi) speech. It was observed that temporary crowns have significantly contributed to the preservation and stability of the papilla. Arunyanak SP et al⁶⁷  noted that clinicians are more critical for the esthetic outcomes than patients. Dierens et al²⁷  were also using a VAS scale and reported instant improvement of patient satisfaction when immediately loaded implants are placed in edentulous jaws. They investigated the following categories: (i) comfort of the patient, (ii) aesthetics, and (iii) function.²⁷  A prospective controlled study performed by Penarrocha et al²⁸  agrees with this present study regarding a higher level of patient satisfaction when implants were immediately loaded with fixed provisional. Patient satisfaction for immediate loading was significantly higher than for conventional loading during the 12-month period of osseointegration.²⁸  Huyhn-Ba et al⁶⁸  performed a literature review with the aim to evaluate how immediate loading compares to early or delayed loading protocols related to patient-reported outcome measures. They concluded that when one implant is placed and loaded immediately it is well accepted by patients, but the findings cannot be extended to restorations supported with multiple implants because of limited available literature.⁶⁸  These authors suggested: (i) that more evidence-based tools such as OHIP should be used, (ii) evaluation should be performed at least two times, prior and after treatment and (iii) multiple evaluations are desirable for long term satisfaction follow-up.⁶⁸ 

The present study has several limitations. Limited sample size that was not numerically driven might affect externally generalizing reported findings. However, bearing in mind the scarce information on this topic in the literature, the present findings might offer initial information for a larger scale study using a greater number of random samples in order to make a more general conclusion. The present study's statistical analysis revealed a significant difference regarding bone density and implant primary stability measured by Osstell, between the test and control groups. Although the higher frequency of dense bone in the test group may correlate with the statistically significantly higher primary stability in this group compared to the control group, this statistically significant difference is not clinically significant since the recorded ISQ values were not below the threshold required for implant loading.⁸  In support of this, the difference in primary implant stability measured by the same RFA method, but using Penguin technology, was not statistically significant between the groups. Further, during the study, the authors only performed localized bone augmentation in sites with dehiscence or fenestration resulting in exposed implant surface, which limits the extrapolation of our results to patients with sufficient bone volume. Future trials will determine the role of immediate loading protocols in clinical scenarios with various amounts of available jaw bone utilizing different numbers of implants to retain fixed prosthetic restoration in an edentulous maxilla.

Both, immediate and early loading protocols of 6 BLT implants with SLActive® surfaces for fixed rehabilitation of edentulous maxillas with sufficient jaw bone, demonstrate similar changes in implant stability 6 weeks after bone healing while maintaining adequate stability. Although both loading protocols could significantly improve oral health related quality of life in patients, immediate loading (according to the Straumann® Pro Arch concept) could significantly reduce physical pain and psychological disability while providing higher patient satisfaction in terms of function and aesthetics of the prosthodontic restoration.

OHRQoL: Oral health related quality of life

BLT SLActive®: Bone level tapered, micro-rough sandblasted, large grit and acid-etched chemically modified surface

OHIP-19: Oral Health Impact Profile questionnaire

RF: resonance frequency

IT: Insertion Torque

RFA: Resonance Frequency Analysis

ISQ: Implant Stability Quotient

VAS: Visual Analogue Scale

The authors acknowledge Institute Straumann AG, Basel, Switzerland for kindly providing free of charge the materials (dental implants, abutments, copings) used in this study.