INTRODUCTION

Dental implants have quickly become the standard of care in the treatment of the edentulous and partially edentulous jaw. The rise in implant placement in the dental clinic is largely due to its ability to restore both esthetics and function, supporting both fixed and removable prostheses. The surgical placement of a dental implant includes reflection of a gingival flap, drilling of an osteotomy hole, and finally the fusion of the titanium implant to the bone. This fusion of direct alveolar bone to implant contact is called osseointegration. The term osseointegration was first introduced by Branemark in 1969.1 After nearly a decade later, Andre Schroeder from the University of Bern (Switzerland) was next to not only study osseointegration, but also the soft tissue’s response to titanium implants.2 Branemark and Schroeder performed various preclinical and clinical studies to establish the fundamentals for modern implant dentistry, including forming the International Team for Implantology in Switzerland.3 Although both Branemark and Shroeder agreed on the basic surgical principles of implant surgery for osseointegration, they disagreed on the titanium implant surface textures and whether to preform submerged healing or non-submerged transmucosal healing. Partly, because the abutment was entirely part of all the implants.4 Together, both Branemark team and Schroeder developed the two of the most popular brands of dental implants on the market, Nobel Biocare and Straumann.4 Initially, Branemark only used implants in edentulous patients to support fixed prostheses. Shroeder and his team, placed implants in both the edentulous and partially edentulous jaws.3

As implants evolved from being placed in an edentulous jaw only, to partially edentulous, most implant protocols placed implants in an already healed extraction socket. To this day, most implants are placed this way, which is typically termed conventional implant placement. If a tooth is still present, the extraction healing in combination with implant healing can extend treatment upwards of one year.4 Generally, a longer treatment period is undesired for both the patient and clinician. Thus, many treatment modalities have been studied to decrease treatment time by placing an implant immediately into an extraction socket at the time of tooth removal. The concept of immediate implant placement (IIP) was first introduced in the late 1970’s, and has since garnered lots of attention.5–7

The protocol of early implant placement has become popular due to its shorter healing period compared with conventional placement.7 Obviously, the efforts to reduce treatment time include numerous modifications to the implant placement protocol in order to place it immediately after tooth extraction.5 Many studies have looked into the success and or failures of immediate implant placement in comparison to conventional implant placement.8–10 Overtime, several systematic reviews have been published, a systemic review by Lang NP et. al in 2012 has even demonstrate that the survival of immediate implants can reach up to of 98% after one year follow-up.11

IIP has many benefits including shorter treatment time, fewer surgical procedures, less cost, and more patient satisfaction compared to conventional delayed implant placement (DIP).8,10,11 A meta-analysis in 2014 found that the effect of IIP on crestal bone level showed favorable outcomes compared with implants placement in healed bone after at least twelve months of functional loading.8 It also concluded, that more marginal bone gain occurred in IIP than DIP. However, there are studies that have found that crestal bone loss and the incidence of peri-implantitis is higher in IIP than compared with DIP.12,13 A systematic review was published in 2016 has shown that after one year of placing single immediate implants in the aesthetic zone, soft tissue recession and alveolar process deficiency deteriorated around the implant.14 Moreover, papillary rescission was found to be higher in IIP in contrast with DIP.15

In posterior regions of the maxillary and mandible, IIP requires more considerations because of sensitive anatomical structures such as, inferior alveolar nerve, Submandibular fossa, lingual plate, floor of maxillary sinuses, and difficulty in achieving primary stability due to poor bone quality in posterior regions.10,11 It’s well known that an important factor for the success and survival of implants is the primary stability, without it implants failure occurs. Truthfully, the stabilization of immediate implant is not easily achieved. Practically, to achieve the primary stability surgeons must deepen the preparation site 3- 4 mm apically or underprepare the implant site. Moreover, specific measurements are needed using radiographs and Cone-Beam Computed Tomography (CBCT). Besides, atraumatic extractions should be performed to preserve interseptal bone and gently prepare implants sites. Otherwise, life-threatening complications may occur.5,6,9 A literature review was done in 2011, showed that inferior alveolar nerve injuries occurred as a result of dental implants procedures was up to 40%.16 For this reason, IIP must be done after comprehensive diagnosis and treatment planning and under an experienced practitioner in a well-selected case.

There are limited systemic reviews on immediate implant placed in posterior area of maxilla and mandible in comparison with immediate implant placed in anterior region. Accordingly, this systemic review aims to provide an update of IIP in fresh extracted socket in molar region compared with IIP in anterior region of maxillary and mandible.

Focus Question

Are posterior immediate implants as successful and or predictable as anterior immediate implants?

PICO Question

  • P: subjects who received at least one dental implant
  • I: immediate posterior implants with or without immediate loading.
  • C: Immediate anterior implants with or without immediate loading.
  • O: Success rate of immediate posterior implants.
    1. Failure rate of immediate posterior implants.
    2. Survival rate of immediate posterior implants.
    Success will be defined as no signs of inflammation, no probing pocket depths, and no radiographic bone loss

Materials and Methods

The present systematic review was conducted in accordance with the criteria outlined in the Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines was followed to conduct this systemic review.

Information sources

Electronic literature research was performed by 2 independent reviewers. A systemic electronic search was carried out for publication written in English language from 2010 to 2021 in human and clinical trials. PubMed was used by applying specific search strategies. Reference lists of relevant publications were also searched. Zotero software (version 5.0.96.3) was used to manage the references list.

Eligibility Criteria

Inclusion criteria of this review include: Human clinical trials, randomized controlled trials, non- randomized controlled trial including: systemic review, case report, case series, observational studies. Subjects included are healthy and not limited to an age group. Complications of surgery were also included, and at least 1 year follow up after dental implant insertion. Only studies with English language were included. We included studies that reported success rate or survival rate of immediate dental implant. The exclusion criteria include: Non-human studies, follow up period less than 1 year.

Data Extraction

The following data were extracted: citation (author/year), publication type, study design, participant, indicator/exposure, comparator, aim/study objectives, study duration, duration of participation, population description, matching criteria, total number of participants at the start of study, missing/dropouts, method of recruitment, age, gender, race/ethnicity, method of follow-up, subgroups measured, subgroups reported, oral/dental status reported, co-morbidities, type of implant, implant location, timing of implant placement, measurements, risk factors and risk indicators of immediate implant, outcome, unit of measurement, statistical analysis and conclusions of the study author(s).

Study Selection and Screening Process

Three authors reviewed all abstracts and excluded the one that didn’t match the inclusion criteria. Full text was reviewed for the eligible articles. Data was extracted from full text articles and organized in an Excel sheet. If relevant data were missing, the study authors were contacted with a request for additional information.

The success rate of immediate posterior implants and immediate anterior immediate implants were separately extracted from articles. Then a comparison was made between the success rate of immediate posterior implant and immediate anterior implants.

RESULTS

This systemic review included 10 studies. Two systemic reviews and meta-analysis were published in 2016 and 2020.17,18 One systematic review and pooled analysis was published in 2014.19 Two retrospective studies were published in 2018 and 2019.20,21 Two clinical studies22,23 published in 2015 and 2020, and three randomized controlled clinical trials (RCTs) were published in 2019 and 2021.24–26 Most studies had at least one-year follow-up. One study had 5-year follow-up.25 However, two studies had 11- year follow-ups.21

There were sixty-two sample sizes ranging between 12 to 40 participants from four studies.22–25 The other studies in this systematic review, there were a total number of nine-hundred and seventy nine participants in the sample size.17–19,21 One study didn’t mention the sample size.20 Unfortunately, in almost all studies gender was not equally distributed, female was more than male except for one study.26 Few studies didn’t mention the gender.18,20 Ages were range between 18 and 65 years.19,22–26 Four studies didn’t mention the ages.17,18,20,21

A total of 3406 implants were placed, 2301 implants in posterior region in maxilla and mandible, 1105 in maxillary esthetic zone (from 2nd premolar to 2nd premolar). Each participant received one implant in five studies.22–26 In several studies, a participant receive two or more implants.17,18,21 while two studies did not mention the number of implats.19,20 In some studies, participants didn’t finish the follow up period.

Systemic diseases and medical issues were excluded in five studies.19,21,22,24,26 While in one study, general health should not permit a surgical procedure.25 Four studies did not mention whether they have excluded systemic disease or not.17,18,20,24 A systemic review was published in 2019, revealed that there was no direct evidence in the effect of cardiovascular disease, neurologic disorders, hypothyroidism, rheumatoid arthritis, patients with Human Immunodeficiency Virus, osteoporosis or diabetes mullites on decrease rate of dental implants osteointegration. However, some evidence showed that Selective Serotonin Reuptake Inhibitors or Protein Pump Inhibitors decreased implants survival rates.27 Moreover, another systemic review showed no difference in dental implant survival rates between healthy patients and diabetic patients within the first 6 years. However, uncontrolled diabetic patients showed delayed in osseointegration.28 A recent systemic review in 2022, concluded that a prediabetes could possibly influence the developing of peri-implant diseases, yet in the same time has no influence on implants survival rate.29

Smokers were excluded in several studies.19,25,26 In two studies, only heavy smokers were excluded by more than 10 cigarettes a day.22,23 In other studies, smokers and nonsmokers were included.17,21 In two studies, smoking wasn’t mentioned.18,24 It was concluded that the failure rate of Implants was higher in smokers than non-smoker, and the higher rate of implant failure was associated with an increase in the number of cigarettes smoked per day. This comes in alignment with a recent systemic review published in 2021, and another prospective analysis for 10 years in 2020 where it was concluded that pre-implant diseases, implants failure and pre-implant bone loss were higher in smokers than non-smokers.30,31 In a systemic review and meta-analysis, dental implants in smokers increased the risk of implant failure by 123%, postoperative infection and marginal bone loss.32

DISCUSSION

The success of anterior immediate implants has been reviewed extensively and confirmed over the last twenty years. On the other hand, placing immediate implants in molar sites is still in debate. This is because of various factors including, the inferior alveolar nerve, maxillary sinus and ability to achieve primary stability. This systemic review aims to compare the survival and success rate of posterior immediate implants in the maxilla and mandible in comparison to anterior immediate implants.

The causes of teeth removal and future implant placement, includes decay, fracture, endodontic failure, and advanced bone loss. The technique of extraction was identical in almost all studies. To preserve the alveolar bone the mucoperiosteal flap is reflected, and the molar roots were sectioned and were removed individually. In the anterior, teeth were extracted using elevation. In one review, immediate implants were placed in molars site with both flap elevation and flapless procedures.18 This study showed no significant differences in implant survival rate between the flap and the minimal split-thickness envelope flap approaches.

The definition of implant success in this systemic review and meta- analysis, is an implant that is still in function and immobile. In one retrospective clinical study implants success rate measured if no mobility or bone loss less than 3mm detected.21 In another systemic review, implant success was defined as still present in the mouth.18 In the esthetic zone, implants success was defined by using the Smith and Zarb (1989) criteria for successful osseointegration, the percentage of functional implants five years after definitive crown placement.33 In the RCT by Chan et. al in 2019, implant survival is defined if the dental implants remain in situ (ITI consensus 2004), the criteria of successful implants set by Albretksson et al. (1986) was followed.24,34 Five studies didn’t mention the criteria for implant success.19,20,23,26

Infected sockets were excluded in five studies.22–26 However, in one retrospective clinical study periapical lesions were not excluded, only abscess, draining fistula, pus or exudate or any path involved adjacent teeth were excluded.21 Four studies didn’t mention wither infected sites were included or not.17–20 This comes in agreement with two systematic reviews and meta-analysis, placing immediate implants in infected site didn’t affect the survival rate, bone level and gingival level at all follow-up period.35,36

The survival and success rate of immediate implants in molar sites in one systemic review, was 98% in maxilla and 99% in mandible and there were no differences in survival of implants in maxillary and mandibular molars.17 In another systematic review, the mean implant survival rate was 96.6% with 95% CI (93.5–99.7). Implants survival rate in posterior maxilla was 100% and 97.4% in posterior mandible, the success rate was 97.5%. No significant difference in survival and success rates were found in relation to implants position (p = 0.233) and when comparing maxilla and mandible (p = 0.991).18 In the retrospective studies, the success rate was 99.06% and 97.3% respectively.20,21

The survival and success rate of immediate implants placed in esthetic zone was 100% in all three clinical studies included in this review.24–26 Nevertheless, a significant increase in intact facial bone and deficient facial bone was detected at 6 months follow up after implant placement. In one review, the survival rate of implants was 97%, 956 implants survived out of 985.19

The insertion torque of molar immediate implants was also reviewed in many of the articles. One retrospective study found that a minimum of 50 NCM was needed in order to achieve primary stability.21 On the other hand, three studies had an implant insertion torque of 30 NCM. In the systemic review the average of insertion torque of immediate implants in a flapless procedure was higher than flap procedures in maxillary anterior and premolar region. Some studies did not mention the insertion torque. two systemic reviews and meta-analysis revealed no differences when comparing high torque and regular or low torque implant placements in terms of survival rate and bone level. Also, in a systemic review, three studies found no statically significant difference between high insertion torque and low to moderate insertion torque in relation to bone loss at 3, 6 or 12- 15 months.17,18

Implants with diameter up to 6 mm is more predictable in immediate implants placement in molar sites based on the present meta- analysis. In another systematic review and meta-analysis < 5mm diameter placed in freshly extracted molar sockets had a survival rate of 96.1% with 95% CI (88.9–100), yet, the survival rate was 94.5% with 95% CI (88.2–100) for implants with diameter > 5 mm.18 While a RCT compared narrow implant diameter (3.3 mm) with regular diameter implants (4.1mm) placed in anteriors and premolars region in maxilla and mandible, survival rates were 100% for both groups, the success rate at 3-year follow-up was 100% for RDIs, while for NDIs was 95%.26 There was no statistical difference in mean bone loss, survival and success rates between the two diameters at 1–3-year follow-up. In the esthetic zone, five studies used implants diameter range from 3.5 mm to 4.5 mm.

The length of implants was reviewed in four studies, with a range of 10 mm to 13 mm length in both anterior and posterior regions. In one study, implants were placed in molar extracted sockets 10 mm was the commonly used length. However, all sizes were used in two studies. Four articles didn’t mention any certain size. One systematic review, showed the survival rates of implants placed in posterior alveolar ridges, ranged from 86.7 %–98.5 % for short implants (< 7 mm) and 95.1%–100% for long implants (≥7 mm), follow up period ranging from 5 – 10 years.17 It concluded that short implants in maxilla has a higher failure rates than long implants, whereas no difference in survival rates between long and short implants placed in mandible. However, in another RCT over the period of 5-years survival rate was higher in the 10 mm implants than the 6mm implants, 100% and 91% , respectively.25 Almost all studies used same implants type and surface texture which was tapered, single titanium endosseous or ceramic endosseous implants. Some studies didn’t mention implants type.

In posterior region, the survival rate of immediate implants with immediate loaded implants was 84.1% with 95% CI (74.6–98.6), while studies used delayed loading implants showed 97.7% with 95% CI.26 In two studies final restorations were delivered after 3-6 months. In the retrospective analysis, some immediate implants were immediately loaded.20 In the esthetic zone, the RCT and the clinical study, restorations were delivered after 3 -4 months.22–26 In the 5-year comparative study was done in the esthetic zone, one group received a screw-retained provisional restoration. While the other group received a provisional restoration after 3 months. Later, after three months a definitive restoration was placed in both groups. They found that Implants survival rate after 5 years was 100% for both groups, whereas restoration survival was 88.9% for the first group and 88.2% for the second group.25 Likewise, in the systemic review and pooled analysis the implants survival rate was not affected by timing of provisionalization. However, they found a significant association between delayed provisionalization and bone loss >0.50 mm (OR 58.03, 95% CI: 8.05 to 418.41, P <0.000).19 Although, in the RCT which aimed to compare immediately placed implant in the esthetic area with immediate provisionalization and with temporary abutment, the survival rate of implants without immediate temporalization was 100% and 90% in implants with immediate temporalization.24

The role of antibiotics in dental implants before implants surgery was shown to be effective in reducing implants failure. Though, A blinded RCT showed no statistically significant differences between four treatment groups, the prescription of antibiotics, or postsurgical procedure didn’t influence wound healing pattern.37 The prescription of antibiotics as prophylaxis and postoperative in the present study in most evidence was for an average of 5 days. Three articles didn’t mention the usage of antibiotic. Additionally, chlorohexidine 0.12% mouthwash mouth wash was prescribed in four studies for at least twice a day for 10 days. one study didn’t mention a specific mouth wash. Five articles didn’t mention the usage of mouthwash. Analgesic drugs were used in several studies after the implants surgery including paracetamol, non-steroidal anti-inflammatory drug (NSAID). The other studies did not mention analgesia prescription.

The overall mean bone loss after at least 1 year in the meta-analysis was 0.57 mm.17 In another systemic review and meta-analysis, there was more bone loss detected in immediate implant placement in molar sites.18 In the preliminary study, bone loss after immediate implant placement is considered within normal limits when there is no more than 1.5 mm MBL during the first year of function. On the other hand, only minor changes were observed in MBL in the esthetic area.22 The use of screw-retained provisional crown and delayed provisionalization were associated with marginal peri-implant bone loss in the systemic review and pooled analysis.19 In the RCT there were minimum changes in marginal level and papilla, but it was concluded that implants with a buccal shoulder position resulted in a more recession than implants with a lingual shoulder position.24–26 Four articles didn’t mention any complications.

The limitation of this study was the number of articles included were only ten, three out of 10 studies were RCTs. Gender was not equally distributed in almost all articles. In some studies, different approaches were followed to place dental implants. Furthermore, smokers were included in some evidence. Few studies reported success rates or survival rates and there was some variant in the criteria of success and survival rates. In the esthetic zone, bicuspid teeth (1st and 2nd premolars) were included in some studies. Timing of implants loading were different from one study to another. Some evidence compared immediate with delayed implants. Future RCTs investigation should compare anterior immediate implants with posterior immediate implants with larger sample sizes.

Conclusion

Molar immediate implants showed excellent success and survival rates. However, placing immediate implants in anterior region showed a higher success and survival rates. Careful precautions should be crucially followed to place implants immediately in freshly extracted sockets in posterior region in maxilla and mandible. Future RCTs are needed with a larger sample size to investigate the survival and success rate of immediate implants in maxillary and mandible molar region.