|Year : 2018 | Volume
| Issue : 4 | Page : 180-186
Clinical and radiographic outcomes of three different loading protocols for single-implant-supported prostheses: A randomized controlled trial
Rami M Galal1, Salah A Yousief2, Waleed M.S. Alqahtani3
1 Department of Fixed and Removable Prosthodontics, National Research Centre; Department of Fixed Prosthodontics, Al Nahda University (NUB), Beni Suef; Department of Fixed Prosthodontics, Ahram Canadian University, Cairo, Egypt
2 Department of Crown and Bridge, Faculty of Dental Medicine, Al Azhar University, Cairo, Egypt
3 Department of Restorative, Al Farabi Dental Colleges, Jeddah, Saudi Arabia
|Date of Web Publication||28-Aug-2018|
Dr. Rami M Galal
59 4th, Touristic District, 6th of October, City, Giza
Source of Support: None, Conflict of Interest: None
Aims: The aim of this study is to assess the effects of early, immediate, and progressive loading of dental implants clinically and radiographically. Materials and Methods: Twenty implants were inserted in 20 patients. Five implants were used for each group (early, immediate, progressive, and conventional loading). In early loading, implant was loaded after 1 week. In immediate loading, loaded with temporary crown within 48 hours then definitive prosthesis after 4 months. In progressive loading loaded with temporary crowns out of occlusion after 3 months for the mandibular sites and 4 months for the maxillary ones for 1 month, and then loading on centric occlusion for 1 month, then full occlusion for 2 months, then definitive prostheses were used. Radiographic assessment for crestal bone loss was done. Clinical assessment of periodontal pocket depth was performed at 3, 6, and 9 months. Results: At 9 months, probing depths were 1.80 ± 0.37, 2.10 ± 0.34, 2.25 ± 0.18, and 1.83 ± 0.38, for immediate, early, progressive, and control groups, respectively. Immediate group showed statistically nonsignificant bone loss after 3 months in the mesial side but showed statistically significant bone loss after 6 and 9 months whereas statistically significant bone loss through all periods in the distal side. Early group showed statistically significant bone lose. Progressive group showed statistically nonsignificant bone loss after 3 months but significant loss after 6 and 9 months. Control group showed statistically nonsignificant bone loss. Conclusions: Immediate loading showed excellent soft-tissue reaction, and early loading responses are identical to conventional two-staged procedure. Progressive loading demonstrated significantly less crestal bone loss than conventional one.
Keywords: Implant, loading, prostheses
|How to cite this article:|
Galal RM, Yousief SA, Alqahtani WM. Clinical and radiographic outcomes of three different loading protocols for single-implant-supported prostheses: A randomized controlled trial. J Int Oral Health 2018;10:180-6
|How to cite this URL:|
Galal RM, Yousief SA, Alqahtani WM. Clinical and radiographic outcomes of three different loading protocols for single-implant-supported prostheses: A randomized controlled trial. J Int Oral Health [serial online] 2018 [cited 2020 Feb 24];10:180-6. Available from: http://www.jioh.org/text.asp?2018/10/4/180/240017
| Introduction|| |
Researchers suggested two-staged technique to avoid any pressing forces with healing under soft tissues for better osseointegrated implants. It is assumed that increased forces on the implant during the healing phase result in implant motion, and fibrous tissue encapsulation, rather than the bone formation required for osseointegration.
Prediction of high rates of successful implants lead to rethinking about prolonged times for checking the surgery results and restorative suggested steps. Now less time waiting for healing is suggested, with subsequently more patient satisfaction, so immediately loaded implant appeared.
Immediate/early loading challenged the healing concept of 3–6 months without loads especially at the 1st week, giving shorter treatment times and immediate restoration of function. Clinical reports found immediate loading jeopardizing success at 3–5 weeks after implant insertion; being mobile with no bacterial invasion; due to occlusal overload.
Immediate/early loading per se was not necessarily causing excessive stresses preventing osseointegration. Heavy micromotion was the cause in forming a fibrous capsule around implants. Misch et al. introduced progressive loading reducing interproximal bone loss and increasing bone density in situ ations when withstanding full occlusion is not possible.
Successful loading techniques need properly selected patient with initially stable implant and predictable osseointegration.
Misch et al. classified loading into as follows: (1) Delayed loading: introduced by Brånemark et al., implant is not subjected to occlusal forces for 3–6 months, this can be used with submerged or nonsubmerged implants; (2) Early loading: implant is loaded with temporary prosthesis between 2 weeks and 3 months after implant insertion and can be divided into (a) functional early loading where the temporary prosthesis is in occlusal contact and (b) nonfunctional early loading if it is kept out of occlusion; (3) Immediate loading: loaded immediately with temporary prosthesis during surgery or within 2 weeks from insertion, it can be functional or nonfunctional. We aimed to evaluate the effects of the three different loading protocols clinically and radiographically on the success of implant-supported prostheses.
| Materials and Methods|| |
This study was conducted on 20 patients selected from a private clinic in Egypt and university clinic. Inclusion criteria were sufficient bone quantity and quality, vertical inter-arch space to accommodate restorative components, opposing natural teeth, single implant for lower premolars, and agreement to follow-up. Exclusion criteria were systemic diseases, smoking, recipient-site pathosis, over erupted opposing teeth, and parafunctional habits.
Written informed consent was obtained from all patients. Ethical committee approval was obtained. Patients were randomly divided into three groups and a control group according to type of loading.
- Group I – Early loading – consists of five patients, restored by definitive prosthesis after 1 week
- Group II – Immediate loading – consists of five patients, restored by temporary crowns in centric occlusion without eccentric contact within 48 h; after 4 months, permanent prostheses were fabricated
- Group III – Progressive loading – consists of five patients, restored by temporary crowns out of occlusion after 3 months for mandibular sites and 4 months for maxillary. Kept for 1 month out of occlusion, then in centric occlusion for 1 month in full occlusion for 2 months, then definitive prostheses were done.
- Group IV – Control group (conventional loading) – consists of five patients, restored by definitive prostheses after 3 months for the mandibular sites and 4 months for maxillary. The clinical trial outline is shown in [Figure 1].
Primary stability was tested according to insertion torque and resistance during insertion. Prosthetic procedures
In early group, prepared abutment was attached by torque wrench with a torque of 30 Ncm; metal ceramic crowns within 1 week were permanently cemented. In immediate group, provisional crown placed with narrow occlusal surface. Broad occlusal contact areas were done for distributing forces, then temporary cementation for 4 months. Flap was replaced.
In progressive group, healing screw was attached. Flap was repositioned for healing 3 months. Then attaching abutments for 2 weeks, and then provisional crown was placed into infraocclusion for 1 month. Then, occlusion was adjusted into light contact providing only axial forces. Two months later, provisional was adjusted into full occlusion. Occlusal contacts were axially directed. After 2 months, metal ceramic restoration with a metal occlusal surface was placed into full occlusion. Outcome variables were assessed 1 week postoperatively (base line) and at 3, 6, and 9 months using the same periodontal probe and the outcome variable was pocket probing depth (PD).
Control group with second surgery after 3 months for conventional loading; metal ceramic crowns in full occlusion.
Outcome variables were assessed 1 week postoperatively (base line) and at 3, 6, and 9 months using the same periodontal probe and the outcome variable was pocket probing depth (PD). Mobility tested using back and forth pressure by two instrument handles applied perpendicularly to the facial surface of crown, at distance 3 mm from implant shoulder, with patient being seated vertically. Percussion was done by tapping of mirror handle against abutment until listening of ringing sound as indication of osseointegration. In mobility, two points scale was used, namely nonmobile or mobile. Evaluation of discomfort, pain, and tenderness was calculated using a scale with score from 0 = worst to 100 = best situation.
Radiographs were performed immediately and at intervals 3, 6, 9 months. Radiographs were digitized and saved in tagged image file format (TIFF). Bone density and marginal levels were measured. With special software, areas were measured, called as regions of interest (ROIs) [Figure 2], and were selected (colour density selection); single pixel represented specific colour (white pixels on radiographs) could be elected, or threshold allowing automatic selection of other pixels in the ROI threshold areas could be traced and counted as number of pixels to calculate ratio of the whole ROI. Mean density was determined based on scale of 0–256, where 256 (8 bits) represented whitest pixel on screen and 0 represented areas of darkest pixels on screen. ROI of radiographs was circle of fixed size precisely containing critical size defect. The program calculated every pixel in the image and performed calculations obtaining number representing mean density of the pixels; number is between 0 and 256. Mesial and distal bone height was evaluated using linear measurement system by the Image J software (Image J 1.31 software: Downloadable through the Internet from National Institute of Health, USA). Line was drawn from reference point at implant shoulder to the first point of bone implant contact, the measurements in mm were noted both mesially and distally, and mean was calculated [Figure 3].
SPSS 16.0 (IBM Inc., Armonk, New York, USA) was used. The results were presented as mean and standard deviation. Analysis of variance (ANOVA) was used for comparing means of bone density and PD. Tukey's post hoc test was used for pair wise comparison between means when ANOVA test is significant. Due to the nonnormal distribution of bone height measurements, Kruskal–Wallis test was used. It is the nonparametric alternative to one-way ANOVA. Mann–Whitney U-test was used for pair-wise comparisons. Paired t-test was used to study changes by time in means of bone density and PD within each group. Wilcoxon signed-rank test was used to study the changes by time in crestal bone height. It is nonparametric alternative to paired t-test. The level of significance was set at P ≤ 0.05.
| Results|| |
Thirty-two patients were initially allocated with the age range from 20 to 45 years with an average 35 ± 1.23 years. Twelve patients were excluded: four for economic reasons, three presented extensive osseous defects that would require bone graft, one desired tooth supported bridge, and three decided to leave. The remaining 20 were included, five randomly allocated to each group. There were no dropouts and all patients attended the follow-ups.
Patients suffered from discomfort during 1st postoperative week. It was related to the surgical procedure and it disappeared within days. No patients expressed pain or tenderness all over the follow-up. All cases in immediate, early, and control group showed no mobility. One case in progressive group showed mobility.
Mean values for PD (in mm) are shown in [Table 1]. Results showed gradual reduction of PD during observation. Difference was not significant when comparing the baseline with 9 months for all groups; however, for early group, there was a significant decrease in the PD after 6 months [Table 2].
|Table 1: The means, standard deviation and P values of probing depth for all groups during different interval periods|
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|Table 2: The means, standard deviation and P values of probing depth during different interval periods within the early group|
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Regarding bone level, immediately, radiographic bone loss was recorded at fixed reference line at implant shoulder considered as baseline. Immediate group showed nonsignificant loss after 3 months mesially while significant loss after 6 and 9 months. Distally, there was significant loss through all periods in the immediate group. Early group showed significant loss through all periods mesially and distally. Progressive group showed nonsignificant loss after 3 months while significant loss after 6 and 9 months mesially and distally. Control group showed nonsignificant loss through all periods mesially and distally [Table 3].
|Table 3: The mean differences, standard deviation and P values of the bone height measurements through all periods for all groups|
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Results recorded no significant difference between bone density values in all groups through all periods mesially, apically, and distally. Moreover, paired t-test showed gradual increase of bone density during observation.
Kruskal–Wallis test used comparing between percentage changes in bone density of all interval periods [Figure 4]. Mesially, there was nonsignificant difference between mean percentage changes in bone density after 3 months. After 6 months, progressive group showed the significantly highest mean (23.5% ± 17.5%) versus control (9.1% ± 5.4%). No significant difference was found between immediate, early, and control groups showing significantly lowest values. After 9 months, progressive group showed significantly highest mean (28.8% ± 16.6%) versus control (15.9% ± 1.6%). No significant difference was found between immediate and control groups showing lower values. Early group showed significantly lowest percentage change [Figure 5].
|Figure 4: Line chart representing changes in the mean Probing depth of the four groups through all interval periods|
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|Figure 5: Histogram of the mean differences between % changes in bone density in the four groups|
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Apically, there was no significant difference between mean percentage changes in density after 3 and 6 months. No significant difference was found between immediate, progressive, and control groups, showing the significantly highest values. Early group showed the significantly lowest percentage change [Figure 5].
Distally, no significant difference was found between mean percentage changes in density after 3 and 6 months. No significant difference was found between immediate, progressive and control groups, showing the significantly highest values. Early group showed the significantly lowest percentage change [Figure 5].
| Discussion|| |
Shortening waiting period and increasing patient's satisfaction, with prematurely loaded implants, have been favored as stated by Gapaski et al. (2003). Nicolae in 2016 in a study found that immediate loading does not prevent successful implant prostheses success.
Progressive loading was used to reduce the bone loss and increase the density, in situ ations not withstanding full occlusion immediately, as advocated by Mish et al. (2005).
We studied different loading protocols for implants and compared them with conventional loading by different clinical, radiographic parameters; pain, tenderness, bleeding index, implant mobility, peri-implant PD, marginal bone loss, and density; as recommended by Salvi et al (2004), who reported that the use of these parameters are meaningful to discriminate between peri-implant health and disease.
The absence of mobility is the most important criterion for success in accordance with Buser et al. Lekholm et al., Patil and Bharadwaj in 2016 reviewed the various tests to examine primary implant stability and stated that it is of prime importance. It has been subjective here, so it is a point of weakness in our study.
The gradual reduction of the mean PD values during the observation periods of the present study might be due to the process of development of the sulcular lining epithelium around the implant surface and adaptation-healing period. This difference was not significant when comparing the baseline with 9 months for all groups. Findings are in agreement with the results obtained by Buser et al. (1990) and Zhang et al. Buser et al. (1990) correlated bone measures found on X-rays and the level of peri-implant probing penetration, found that probing stopped 1–3 mm in coronal position to the bone, and concluded that successful implants allow PD of approximately 3 mm. Göthberg in 2016 found that the loading protocol does not affect the bone level or PD.
Results found agreed with the findings of Lorenzoni et al., i.e. implant accompanied by immediate prosthesis showed 0.45 mm mesial bone loss and 0.75 mm distal loss at 6 and 12 months being less than results shown with the conventional group in this study. Furthermore, our findings agree with Cannizzaro and Leone noting that the radiographic loss of 0–1 mm on 95.7% of their immediate loading implants and 93.3% of the control at 24 months, proving that there were no significant differences between them. Moreover, Ericsson et al. reported that resorption ranged from 0.14 to 0.78 mm for immediate loading and the results with conventional loading were near that showing nonsignificant differences. Gjelvold et al. found that in both the immediate and delayed loading groups, there was significant difference in bone level between 0–6 months and 7–12 months with immediately loaded implants displaying the least loss. Chidagam et al. found the loss with immediately loaded implants within the permissible limits.
Amount of loss of the early group is comparable to the results obtained by Roccuzzo and Wilson comparing loss of implants with early loading with exposure to conventional. Resorption was about 0.65 mm for the implants loaded after 6 weeks and 0.77 mm for loading within 12 weeks. In addition, Salvi et al. found resorption of 0.57 mm in implants loaded after 1 week and 0.72 mm in loading after 6 weeks. Zhu et al. found that the resorption in the early loaded was from 0.17 to 2.55 mm at baseline and 0.97 to 2.87 mm after 1 year, whereas the resorption of conventionally loaded implants was 0.11–3.5 mm at baseline and 0.90–3.30 mm after 1 year. Therefore, there were no significant differences between the early and conventional loading in this meta-analysis. A clinical study by Dard et al. agreed with this.
More loss in the distal side may be explained due to occlusal forces and difficulty to clean with more plaque than the mesial side and this was with agreement with Ho et al. in 2016.
Progressive loading results are comparable to the results obtained by Appleton et al. (2005), stating significant difference in resorption level between implants with progressive and conventional loading. Furthermore, progressive loading of implants showed >50% diminished resorption than conventional. Verified with a 12-months study. Differences may be contributed to include mandibular premolar implants because the mandibular bone exhibits less and slowly detectable changes in density than the maxillary. Cumulative results did not record higher level of changes as maxillary bone especially with the short follow-up in contrary to Appleton et al. placing implants in posterior maxillary premolars, thus can show revealed increased differences in density and consequently less bone loss. Ghoveizi et al. showed that the mean values of resorption at 12 months were 0.11 mm with progressive and 0.36 mm for conventional loading, with significant difference indicating better bone reaction with progressive loading.
We found that immediate/early groups were comparable to control group. May be attributed to good primary stability (in agreement with Esposito et al. in 2016) using controlled occlusal force by the use of adjacent natural teeth protection from direct forces, also, premolars receive occlusal vertical forces. All these avoided overloading as primary factor for fibrous encapsulation, failure. Certain microstrain may lead to improved collagen mineralization at the titanium interface.
Regarding the bone density, the progressive group showed significant increase mesially, apically, and distally through all periods compared to the control. Results agreed with Rotter et al. stating that progressive loading increases bone rigidity. Results are comparable to the study by Appleton et al. (2005) concluding that the peri-implant density with progressive loading reveals more enhancement with time. The findings suggested that progressive loading controlled force directed to bone with force nearly resembles the bearing capability of the maturing bone, giving chance to maturation, and having less resorption as concluded by Misch.,
Bone density apically showed enhancement as stated by Barone et al. In contrast to our study, apically showed least significant bone density; may be due to progressive loading and control implants showing more load-bearing capability-decreasing load directed to bone. Decreasing stimulation leads to decreased density bone. Akoğlan et al. found that density after early loading is more than immediate or delayed. In addition, our results agreed with Stanley et al. regarding success of immediately loading. Morton and Pollini stated after literature reviewing that survival of implants is not affected by loading. Romanos et al. agreed with us that immediate loading has no negative influence on prognosis.
We did not evaluate the periodontium, microflora, their effect on the success; this could be a recommended study question for the future research.
This could be from the limitations of our study in addition to the subjective ways used for measuring initial stability and stability before taking the decision to load.
| Conclusions|| |
- Immediate loading of single-standing dental implants showed excellent soft tissues reaction with permissible level of PD, good stability, and marginal bone loss rate compared to conventional two-staged loading
- Early loading of single-implant responses observed in the present study are identical to the bone loss rate and density analysis of the same implant placed in a conventional two-staged loading
- Progressively loaded single implants demonstrated higher density and decreased peri-implant bone resorption than that of conventionally loaded implants.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3]