Original study - ZZI 04/2010

Influence of different soft tissue management concepts on the rate of peri-implant inflammation and implant success

C. K. Müller1, M. Mtsariashvili1, S. Schultze-Mosgau1

Purpose: The aim of this study was to investigate the influence of different soft tissue management concepts on the rate of peri-implant inflammation and on implant success using a one- and two-stage procedure.

Material and methods: In an animal study using the Göttingen minipig model, flapless and flap surgery were compared with regard to the rate of peri-implant inflammation. One month after extraction of all upper premolars, twelve pigs had two Semados RI implants (4.1 mm x 10 mm, BEGO Implant Systems, Bremen, Germany) inserted per quadrant. The pigs were randomized to have minimally invasive exposure by trephine punch in one quadrant. The ridge was exposed conventionally on the contralateral side by raising a mucoperiosteal flap. Biopsies of the soft tissue were taken after a transmucosal healing period of one, two, four and twelve weeks and histological examination and pangenomic gene expression analysis were performed. In a retrospective clinical study involving 181 patients (521 implants), the influence of the main and releasing incisions as well as the exposure technique on implant success was evaluated by means of Kaplan-Meier survival analysis.

Results: The minipig study showed significantly greater inflammatory infiltration of the peri-implant soft tissue one week (p = 0.016), two (p = 0.010) and twelve (p = 0.039) weeks after insertion after flap surgery compared with flapless surgery. Immunofluorescence analysis confirmed macrophage predominance after one and two weeks and the absence of macrophages after twelve weeks. Pangenomic gene expression analysis showed reduced inflammation and improved wound detoxification in the early healing phases and faster re-epithelialization and reduced fibrosis in later phases following flapless surgery. The retrospective clinical study showed a significant (p = 0.022) influence of the releasing incisions on the implant survival rate.

Conclusions: The results of the minipig study suggest that the rate of peri-implant inflammation can be reduced by flapless surgery due to improved soft tissue architecture. An effect on the implant success rate was not found. When a two-stage implantation procedure is employed, only a very short distal releasing incision should be made during implant insertion.

Keywords: soft tissue management; peri-implant inflammation; implant survival rate

Introduction

Peri-implant and periodontal tissue differ in morphology from marginal epithelium and supracrestal connective tissue. The periodontal marginal epithelium is thicker, has more hemidesmosomes and is inserted further coronally than the peri-implant marginal epithelium. Compared with periodontal connective tissue, peri-implant connective tissue is characterized by relative hypocellularity and lower perfusion. Moreover, the collagen fibers follow a circular peri-implant course while they insert in the root cementum of healthy teeth. The morphological differences between peri-implant and periodontal tissue result in an increased tendency to inflammation of dental implants compared with healthy teeth [31]. The formation of a soft tissue cuff at the implant emergence site that is as stable as possible is consequently of crucial importance for both the functional and aesthetic long-term success of an implant-borne restoration [30].

Various systemic and local factors influence soft tissue consolidation at the implant emergence site [20, 25]. Underlying diseases such as diabetes mellitus and disorders of collagen metabolism and also certain long-term medications such as glucocorticoids are systemic factors that have a negative influence on the quality of the regenerated soft tissue. Local factors that jeopardize normal soft tissue regeneration are, in particular, smoking, a known history of radiotherapy [21], jaw reconstruction with microvascular anastomosis of the transplant [19] and poor oral hygiene. Furthermore, the technique of soft tissue management during implant insertion and exposure is extremely important for shaping the implant emergence site and can be influenced directly by the surgeon [1, 36].

In a systematic review, Esposito et al. showed that exposure of the alveolar ridge by punch (flapless surgery) in a one-stage procedure with transmucosal implant healing significantly reduces postoperative pain, swelling and analgesic use compared with the conventional method of flap surgery. However, it was found that there was a need for research into the influence of soft tissue management on the complication rate using one- and two-stage procedures [7].

The aim of this study was to investigate the influence of different soft tissue management concepts on the rate of peri-implant inflammation and implant success using a one- and two-stage procedure.

Material and methods

Influence of soft tissue management on the complication rate using a one-stage procedure

Animal model and operative protocol

The animal study was approved by the Thuringian Regional Food Safety and Consumer Protection Authority (TLLV) (Reg. no. 02-028/06). Twelve female Göttingen minipigs (age: twelve months, weight: ~ 35 kg; Ellegard, Dalmose, Denmark) underwent minimally invasive extraction of all upper premolars under intubation anesthesia with preservation of the vestibular socket wall. Four weeks later, two Semados RI implants (4.1 mm x 10 mm, BEGO Implant Systems, Bremen, Germany) were inserted in each quadrant as delayed immediate implantation.

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