Review Of Literature
Experimental and histological studies :
In a histological study of a human volunteer, four implants placed immediately after extraction and one control was placed in a healed site, at 6-months the histologic evaluation under light microscopic level revealed that all implants achieved osseointegration, but with a varying degree of bone-implant contact, the highest percentage of bone-implant contact was observed in the control one (72%) followed by the implants placed immediately in the canine sites (50%), while The lowest mean bone-implant contact (17%) was observed for the implants placed in the molar sites . This result gave a conclusion that the horizontal component of the peri-implant defect was evidently the most critical factor relating to the final amount of bone-implant contact (Wilson et al., 1997).
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Karabuda et al. (1999) have investigated the impact of different implant surfaces on oseointegration , the immediately implanted fixture in a mongrel dogs was studied by histologic and histomorphometric examination after 8 weeks, implants with hydroxyapatite layer showed better result but with evidence that the surface of hydroxyapatite layer can be resorbed that may affect the long-term stability .
Monkey experimental study revealed no statistically significant difference in the osseointegration of immediate implant in comparison with the delayed type placed in healed sites (Barzilay et al., 1996). In a controlled histological study in 48 patient 1 implant placed in the fresh socket and another in a healed socket without using membrane or filling material, 6 months later the implants were removed by a hollow drill and histologically examined, the histological picture dose not revealed connective tissue integration and there was no significant difference between the two categories regarding osseointegration (Paolantonio et al., 2001).
Regarding the importance of immediate implant in preserving alveolar ridge dimensions (Araujo et al. 2005) found in a study on dogs, after 3-months the immediate implant failed to prevent alveolar ridge resorbsion that occurred in the walls of the socket. And the vertical bone loss was more in the buccal aspect than at the lingual.
Mandibular premolars in a beagle dog model were removed, and implants were placed in the distal socket with the mesial site left to heal spontaneously, healing was assessed measuring the width of buccal and lingual walls at different levels. In the test group, the width of the crest was reduced between baseline and 8 weeks of healing, demonstrating a 62% reduction of the initial width, these differences were not observed in the control group The author concluded that implant placement in the socket after extraction may compromise the vertical bone remodelling of the socket. Furthermore, a tendency towards greater buccal horizontal resorption was observed in the most coronal aspect of the buccal bone crest. ( Discepoli et al., 2014).
In a 7-year retrospective study of 423 implants placed immediately after extraction, at the 1st year one implant was lost and an additional implant failed during the 7-year follow-up, with a final success rate of 99.53% (Cosci and Cosci, 1997). Huys (2001) implanted 556 implants with a submerged type, the implants were inserted together with a composite polymer without using a membrane. 96.6% success rate were observed by the follow-up of 7 to 10 years.
Fugazzotto (2008) found a cumulative 99.5% survival rate of 391 immediate implants at maxillary molar extraction site with a mean follow-up of 40.3 months. The same author observed 99.1% survival rate of 341 implants were placed at the time of mandibular molar extraction.
In comparison with implant placed in healed sites, Degidi et al. (2006) found that There were statistically significant differences between healed and post-extraction implant sites (100% and 92.5% respectively) during the 5-year follow-up period, All implants placed with a minimum of 25N insertion torque and immediately loaded, implant failure occurred only within the first 4 months of implant placement and loading. This result in opposite with a previous study in an equal follow up period but with conventional delay loading, where 117 implants placed immediately compared with 263 implants placed in a healed sites for full-arch fixed reconstruction, survival rate of 96% of the immediate implant and 89.4% for delayed type was observed, the cumulative survival rate more in the maxilla then in the mandible. (Schwartz-Arad et al., 2000).
Immediate implant placement in infected sites:
Animal experiments with fluorescence microscopy and histological studies have shown that implants placed in artificially induced periapical lesions and intentionally produced periodontitis can osseointegrate as well as implants placed in healthy sites (Novaes et al. 1998, 2003; Marcaccini et al. 2003; Papalexiou et al. 2004; Chang et al., 2009). Novaes et al. (1998) were the first to study the immediate placement of implants in surgically induced periapical lesions in four dogs, and concluded that chronic infection, such as periapical lesion, may not contraindicate immediate implants placement, if particular clinical management are taken.
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Villa and Rangart published a clinical study in 2005, the mandibular anterior teeth with presence of unrecoverable periodontitis and periapical lesion were included in the study. after extraction the lesions was curated and the implant sites were irrigated with an antibiotic solution, apical fistulae were present in two patients, and in four patients, pus drained from the surgical incision, The implant placed with torque of 50Ncm and restored with early loading protocol. 100% survival rate observed with no implant failure at total follow-up period of 44 months.
The first prospective, randomized study evaluating implants placed immediately into infected sites published by Lindeboom et al. 2006, Fifty implants were divided into two equal groups, an immediate placement group replacing teeth with an periapical lesion and the other group placed after 3-months of healing, After extraction, the sockets were thoroughly degranulated and the lesion were collected for microbial analysis. All implants submerged and primary flap closure was achieved, the implants were allowed to heal for 6 months. Immediate implants in an infected sites observed a 92% survival rate while 100% survival rate for the group who received delayed implant placement.
Crespi, et al. (2010) in a randomized, controlled study, 275 implants were inserted immediately after extraction, 197 of it in periodontally compromised sites, the other 78 implants were placed in sockets without signs of chronic infection, all implants immediately loaded, at 4 year follow-up the infected and non-infected groups recorded survival rate of 98.9% and 100% respectively, the authors concluded that there is no significant differences between the two groups.
Indications and contraindications:
Immediate implantation indicated for teeth extracted due to Traumatic fracture with a small amount of bone loss, badly carious non-restorable teeth without purulent exudates or cellulites, and teeth not amenable to perfect endodontic therapy, presence of severe periodontal bone loss without purulent exudates, adequate soft tissue health and the ability to obtain primary wound closure (Block and Kent, 1991).
Conditions and difficulties that make immediate implantation contraindicated include: presence of purulent exudates and acute inflammatory process at the site of extraction, adjacent soft tissue cellulites and granulation tissue, lack of an adequate bone apical to the socket and the ability to achieve primary stability, close proximity of vital structures such as of the mandibular neurovascular bundle, maxillary sinus and nasal cavity, poor anatomical configuration of remaining bone (Block and Kent, 1991).
Advantages and disadvantages:
The placement of implant at the time of extraction offers several advantages by reducing treatment time, preserving alveolar ridge dimensions, reducing number of surgeries, achieving ideal implant location both mesiodistally and buccoloigually and the crown become in harmony with the adjacent with maximum soft tissue support (Schwartz-Arad and chaushu, 1997). Decrease postoperative trauma by reducing heat generation during drilling, and finally give a positive psychological effect on the patient in relation to dental implants because immediate replacement of the extracted tooth obtained without delay while the patient waits for socket healing (Askary, 2007).
Immediate implant placement also can encounter disadvantages such as: lack of control of the final implant position as its guided by the location and direction of the extracted root/tooth, difficulty to obtain primary stability, inadequate soft tissue coverage, inability to inspect all aspects of the extraction site for defects or infection, difficulty in preparing the osteotomy site due to bur movement (chatter) on the walls of the extraction site, and possibility but not in all cases the need to use grafting material that give added cost to the patient (Bhola et al., 2008).
Hammerle and Chen, (2004) published a report classifying implant placement based on morphological, dimensional, and histologic changes that occur following tooth loss , each classification type from I to IV that not follow rigid time frame and to avoid time-based descriptions the classification used numeric data, the authors also mention the advantages and disadvantages to each type. (Table 1)
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