Ingemar Abrahamsson

The mucosal barrier at implant abutments of different materials

OBJECTIVE The aim of the present study was to analyze the soft tissue barrier formed to implant abutments made of different materials. MATERIAL AND METHODS Six Labrador dogs, about 1 year old, were used. All mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later four implants (OsseoSpeed, 4.5 x 9 mm, Astra Tech Dental, Mölndal, Sweden) were placed in the edentulous premolar region on one side of the mandible and healing abutments were connected. One month later, the healing abutments were disconnected and four new abutments were placed in a randomized order. Two of the abutments were made of titanium (Ti), while the remaining abutments were made of ZrO(2) or AuPt-alloy. A 5-months plaque control program was initiated. Three months after implant surgery, the implant installation procedure and the subsequent abutment shift were repeated in the contra-lateral mandibular region. Two months later, the dogs were euthanized and biopsies containing the implant and the surrounding soft and hard peri-implant tissues were collected and prepared for histological analysis. RESULTS It was demonstrated that the soft tissue dimensions at Ti- and ZrO(2) abutments remained stable between 2 and 5 months of healing. At Au/Pt-alloy abutment sites, however, an apical shift of the barrier epithelium and the marginal bone occurred between 2 and 5 months of healing. In addition, the 80-mum-wide connective tissue zone lateral to the Au/Pt-alloy abutments contained lower amounts of collagen and fibroblasts and larger fractions of leukocytes than the corresponding connective tissue zone of abutments made of Ti and ZrO(2). CONCLUSION It is suggested that the soft tissue healing to abutments made of titanium and ZrO(2) is different to that at abutments made of AuPt-alloy.

Implant surface characteristics influence the outcome of treatment of peri-implantitis: an experimental study in dogs.

AIM To analyse the effect of surgical treatment of peri-implantitis without systemic antibiotics at different types of implants. MATERIAL AND METHODS Four implants representing four different implant systems - turned (Biomet 3i), TiOblast (Astra Tech AB), SLA (Straumann AG) and TiUnite (Nobel Biocare AB) were placed in the left side of the mandible in six dogs, 3 months after tooth extraction. Experimental peri-implantitis was initiated by placement of ligatures and plaque formation. The ligatures were removed when about 40-50% of the supporting bone was lost. Four weeks later, surgical therapy including mechanical cleaning of implant surfaces was performed. No systemic antibiotics or local chemical antimicrobial therapy were used. After 5 months, block biopsies were obtained and prepared for histological analysis. RESULTS Two of the TiUnite implants were lost after surgical therapy. Radiographic bone gain occurred at implants with turned, TiOblast and SLA surfaces, while at TiUnite implants additional bone loss was found after treatment. Resolution of peri-implantitis was achieved in tissues surrounding implants with turned and TiOblast surfaces. CONCLUSION Resolution of peri-implantitis following treatment without systemic or local antimicrobial therapy is possible but the outcome of treatment is influenced by implant surface characteristics.

Effects of different implant surfaces and designs on marginal bone‐level alterations: a review

OBJECTIVE The purpose of this review was to evaluate the effect of different implant surfaces and designs on marginal bone-level (MBL) alterations. MATERIAL AND METHODS A MEDLINE search (PubMed) was performed to identify clinical, prospective and controlled studies using a sufficient sample size (>10 subjects) and with a follow-up time of > or =3 years. RESULTS Ten publications fulfilled the inclusion criteria. Two studies evaluated the influence of implant surface characteristics and two studies reported on the effect of implant design on MBL changes. Six publications analyzed the combined effect of different implant surfaces and designs on MBL alterations. As revealed from available studies, there is no evidence that modified surfaces are superior to non-modified implant surfaces in marginal bone preservation. One study reported on significantly improved MBL preservation for implants with a conical and micro-threaded marginal collar than implants with a cylindrical and non-threaded marginal portion after 3 years in function. No implant system was found to be superior in marginal bone preservation.

Spontaneous progression of experimental peri-implantitis at implants with different surface characteristics: An experimental study in dogs

AIM To analyse spontaneous progression of ligature-induced peri-implantitis at implants with different surface characteristics. MATERIAL AND METHODS Four implants with similar geometry and with two different surface characteristics (turned/TiUnite; Nobel Biocare AB) were placed pairwise in one side of the mandible in five dogs, 3 months after tooth extraction. Experimental peri-implantitis was initiated by placement of ligatures and plaque formation. The ligatures were removed when about 40% of the supporting bone was lost. After 6 months, block biopsies were obtained and prepared for histological analysis. RESULTS The amount of bone loss that occurred during the plaque accumulation period after ligature removal was significantly larger at implants with a TiUnite surface than at implants with a turned surface. The histological analysis revealed that the vertical dimensions of the lesion and the pocket epithelium and the apical extension of the biofilm were significantly larger at TiUnite implants than at turned implants. CONCLUSION It is suggested that the implant surface characteristics influence progression of peri-implantitis.

Early healing of implants placed into fresh extraction sockets: an experimental study in the beagle dog. III: soft tissue findings

AIM To describe histologically the early phases of soft tissue healing to implants placed into fresh extraction sockets. MATERIALS AND METHODS In 16 beagle dogs, 64 3.25-mm-wide cylindrical screw implants were inserted into the distal sockets of the third and fourth lower premolars using a one-stage trans-mucosal healing protocol. Biopsies were then taken at 1, 2, 4 and 8 weeks and prepared for histological examination. RESULTS One-week specimens showed a junctional epithelium and an underlying loose connective tissue rich in inflammatory cells. At 2 weeks, signs of epithelial proliferation and a more organized connective tissue were observed. At 4 and 8 weeks, inflammation was absent; the epithelium appeared mature and in close contact with the surface of the healing abutment or the implant. The connective tissue was dense in an area close to the implant surface and the fibres were aligned parallel to the implant surface. The soft tissue dimensions at 8 weeks were approximately 5 mm, including about 3-3.5 mm of epithelium and 1-1.5 mm of connective tissue. CONCLUSION Soft tissue healing to implants placed in fresh extraction sockets may result in a longer epithelial interface than implants placed in a healed ridge.

Subcrestal placement of two‐part implants

OBJECTIVE The aim of the present experiment was to study the healing around two-part implants that were placed in a subcrestal position. MATERIAL AND METHODS Five mongrel dogs, about 2 years old, were included. The mandibular premolars and the first, second and third maxillary premolars were extracted. Three months later two test and two control implants (OsseoSpeed, 3.5 mm x 8 mm) were placed in one side of the mandible. The implants were placed in such a way that the implant margin was located 2 mm apical to the bone crest. In the test implants, the surface modification extended to the implant margin and, thus, included the shoulder part of the implant. Regular abutments with a turned surface (Zebra) were connected to the control implants, while experimental abutments with a modified surface (TiOblast) were connected to the test implants. A plaque control program that included cleaning of implants and teeth every second day was initiated. Four months later the dogs were euthanized and biopsies were obtained and prepared for histological analysis. RESULTS The marginal bone level at the test implants was identified in a more coronal position than that at the control implants. In 40% of the test implants, the bone-to-implant contact extended coronal of the abutment/fixture (A/F) border, i.e. in contact with the abutment part of the implant. The connective tissue portion of the peri-implant mucosa that was facing the test abutments contained a higher density of collagen and a smaller proportion of fibroblasts than that at the control sites. CONCLUSION It is suggested that osseointegration may occur coronal to the A/F interface of two-part implants. Such a result, however, appears to depend on the surface characteristics of the implant components.

Adjunctive Systemic and Local Antimicrobial Therapy in the Surgical Treatment of Peri-implantitis A Randomized Controlled Clinical Trial

The aim of the present randomized controlled clinical trial was to investigate the adjunctive effect of systemic antibiotics and the local use of chlorhexidine for implant surface decontamination in the surgical treatment of peri-implantitis. One hundred patients with severe peri-implantitis were recruited. Surgical therapy was performed with or without adjunctive systemic antibiotics or the local use of chlorhexidine for implant surface decontamination. Treatment outcomes were evaluated at 1 y. A binary logistic regression analysis was used to identify factors influencing the probability of treatment success, that is, probing pocket depth ≤5 mm, absence of bleeding/suppuration on probing, and no additional bone loss. Treatment success was obtained in 45% of all implants but was higher in implants with a nonmodified surface (79%) than those with a modified surface (34%). The local use of chlorhexidine had no overall effect on treatment outcomes. While adjunctive systemic antibiotics had no impact on treatment success at implants with a nonmodified surface, a positive effect on treatment success was observed at implants with a modified surface. The likelihood for treatment success using adjunctive systemic antibiotics in patients with implants with a modified surface, however, was low. As the effect of adjunctive systemic antibiotics depended on implant surface characteristics, recommendations for their use in the surgical treatment of peri-implantitis should be based on careful assessments of the targeted implant (ClinicalTrials.gov NCT01857804).

Temporal sequence of hard and soft tissue healing around titanium dental implants

The objective of the present review was to summarize the evidence available on the temporal sequence of hard and soft tissue healing around titanium dental implants in animal models and in humans. A search was undertaken to find animal and human studies reporting on the temporal dynamics of hard and soft tissue integration of titanium dental implants. Moreover, the influence of implant surface roughness and chemistry on the molecular mechanisms associated with osseointegration was also investigated. The findings indicated that the integration of titanium dental implants into hard and soft tissue represents the result of a complex cascade of biological events initiated by the surgical intervention. Implant placement into alveolar bone induces a cascade of healing events starting with clot formation and continuing with the maturation of bone in contact with the implant surface. From a genetic point of view, osseointegration is associated with a decrease in inflammation and an increase in osteogenesis-, angiogenesis- and neurogenesis-associated gene expression during the early stages of wound healing. The attachment and maturation of the soft tissue complex (i.e. epithelium and connective tissue) to implants becomes established 6-8 weeks following surgery. Based on the findings of the present review it can be concluded that improved understanding of the mechanisms associated with osseointegration will provide leads and targets for strategies aimed at enhancing the clinical performance of titanium dental implants.

Deposition of nanometer scaled calcium‐phosphate crystals to implants with a dual acid‐etched surface does not improve early tissue integration

OBJECTIVE To evaluate hard and soft tissue healing to implants with a dual acid-etched surface with and without deposition of calcium-phosphate crystals. MATERIALS AND METHODS Three months after extraction of mandibular premolars in six Labrador dogs, four osteotomy preparations, 8 mm deep and 3 mm wide, were performed. The prepared canals were widened in the marginal 4 mm zone to 3.74 mm. Implants with an 8 mm long and 3.75 mm wide intraosseous portion and a 5.0 mm high and 4.0 mm wide transmucosal part were placed in such a way that the base of the wider neck-portion of the implant coincided with the crestal bone. The implants were dual acid - etched (Osseotite(®); Biomet 3i). The surface of the test implants was, in addition, modified by a discrete deposition of calcium-phosphate crystals (Nanotite™; Biomet 3i). Every second implant placed was a test unit. After 2 weeks the implant installation procedure was repeated in the opposite side of the mandible. Two weeks later the animals were euthanized and biopsies were obtained and prepared for histological analysis. RESULTS The degree of bone-to implant contact (BIC%) was larger at implants without (Osseotite) than in those with (Nanotite) calcium-phosphate crystals. No differences were found regarding soft tissue dimensions and composition between the two types of implants. CONCLUSION It is suggested that deposition of nanometer-sized calcium-phosphate crystals to implants with a dual acid-etched surface does not improve early tissue integration.

Effect of cleansing of biofilm formed on titanium discs

OBJECTIVES To study the combined effect of mechanical and chemical cleansing on a 4-day biofilm grown intra-orally on titanium discs with different surface characteristics. MATERIAL AND METHODS Twenty subjects used a splint with two metal plates in the upper jaw. Each plate was placed in the premolar-molar region and carried four titanium discs with four different surface characteristics (OsseoSpeed(™), TiOblast(™), experimental and turned surface). After 4 days of biofilm growth, the discs were cleaned mechanically and chemically with saline or chlorhexidine. Following cleansing, microbial samples were obtained and analysed by culture. The titanium discs were processed for scanning electron microscope (SEM) analysis. The experiment was repeated 3 days later using delmopinol or a mixture of essential oils during cleansing. RESULTS The combination of mechanical and chemical cleansing was ineffective in complete biofilm removal from all four titanium discs. The microbiological analysis did not reveal any statistically significant differences between surface types or between cleaning agents regarding logarithmic mean counts of CFU for specific bacteria, aerobes, anaerobes or the TVC. Aerobes were more numerous than anaerobes on all surface types. The SEM analysis disclosed that the remaining biofilm on moderately rough surfaces (OsseoSpeed(™), TiOblast(™) and experimental) was complex and firmly attached, while the biofilm on turned surface had a pattern of spread bacteria forming less clusters. CONCLUSIONS Cleansing may call for prolonged time of chemomechanical debridement and/or more effective disinfectants to suppress biofilms on dental implant surfaces.