Factors influencing outcomes of surgical therapy of peri-implantitis: A secondary analysis of 1-year results from a randomized clinical study

AIM

To identify predictors of treatment outcomes following surgical therapy of peri-implantitis.

MATERIALS AND METHODS

We performed a secondary analysis of data from a randomized controlled trial (RCT) comparing access flap with or without bone replacement graft. Outcomes at 12 months were probing pocket depth (PPD), bleeding on probing (BOP), soft-tissue recession (REC) and marginal bone level (MBL) change. Multilevel regression analyses were used to identify predictors. We also built an explanatory model for residual signs of inflammation.

RESULTS

Baseline PPD was the most relevant predictor, showing positive associations with final PPD, REC and MBL gain, and negative association with probability of pocket closure. Smokers presented higher residual PPD. Absence of keratinized mucosa at baseline increased the probability of BOP but was otherwise not indicative of outcomes. Plaque at 6 weeks was detrimental in terms of residual PPD and BOP. Treatment allocation had an effect on REC. Final BOP was explained by residual PPD ≥6 mm and plaque at more than two sites.

CONCLUSIONS

Baseline PPD was the most relevant predictor of the outcomes of surgical therapy of peri-implantitis. Pocket closure should be a primary goal of treatment. Bone replacement grafts may be indicated in aesthetically demanding cases to reduce soft-tissue recession. The importance of smoking cessation and patient-performed plaque control is also underlined.

Early bone healing to implants with different surface characteristics. A pre-clinical in vivo study

AIM

To examine early bone healing around implants with non-modified and modified surfaces.

MATERIAL & METHODS

Four implants with 4 different surface characteristics were installed in one side of the mandible following tooth extraction in 6 dogs. Implants in group A had a non-modified, turned surface, while implants in group B had a surface modification consisting of TiO-blasting and sequential acid-etching in oxalic and hydrofluoric acid. The surface modification of implants in group C was confined to sequential acid-etching in oxalic and hydrofluoric acid and Group D implants had a surface modification of TiO-blasting and acid-etching in hydrofluoric acid. The implant installation procedures were repeated in the opposite side of the mandible 4 weeks later. Biopsies were obtained and prepared for histological analysis 2 weeks later.

RESULTS

B and C implants had a higher degree of bone-to-implant contact (BIC%) than A and D implants at 2 weeks of healing. At 6 weeks of healing, the BIC% was higher at B than at A, C and D implants, and higher at C implants than at A implants. The amount of newly formed bone in contact with the implant within the defect area at 2 weeks was higher at implants with modified surfaces (groups B, C and D) than at implants with a non-modified surface (group A). Corresponding results at 6 weeks were superior at B implants.

CONCLUSION

It is suggested that an implant surface modification with acid-etching in oxalic and hydrofluoric acid promotes early formation of bone-to-implant contact.

Reconstructive surgical therapy of peri-implantitis: A multicenter randomized controlled clinical trial

OBJECTIVE

To evaluate the potential benefit of the use of a bone substitute material in the reconstructive surgical therapy of peri-implantitis.

METHODS

In this multicenter randomized clinical trial, 138 patients (147 implants) with peri-implantitis were treated surgically, randomized by coin toss to either a control (access flap surgery) or a test group (reconstructive surgery using bone substitute material). Clinical assessments, including probing pocket depth (PPD), bleeding and suppuration on probing (BOP & SOP) as well as soft tissue recession (REC), were recorded at baseline, 6 and 12 months. Marginal bone levels (MBL), measured on intra-oral radiographs, and patient-reported outcomes (PROs) were recorded at baseline and 12 months. No blinding to group allocation was performed. The primary outcome at 12 months was a composite measure including (i) implant not lost, (ii) absence of BOP/SOP at all aspects, (iii) PPD ≤5 mm at all aspects and (iv) ≤1 mm recession of mucosal margin on the buccal aspect of the implant. Secondary outcomes included (i) changes of MBL, (ii) changes of PPD, BOP%, and buccal KM, (iii) buccal REC and (iv) patient-reported outcomes.

RESULTS

During follow-up, four implants (one in the test group, three in the control group) in four patients were removed due to disease progression. At 12 months, a total of 69 implants in the test and 68 implants in the control group were examined. Thus, 16.4% and 13.5% of implants in the test and control group, respectively, met all predefined criteria of the composite outcome. PPD reduction and MBL gain were 3.7 mm and about 1.0 mm in both groups. Reduction in mean BOP% varied between 45% (test) and 50% (control), without significant differences between groups. Buccal REC was less pronounced in the test group (M = 0.7, SD = 0.9 mm) when compared to controls (M = 1.1, SD = 1.5 mm). PROs were favorable in both groups without significant differences. One case of allergic reaction to the antibiotic therapy was recorded. No other adverse events were noted.

CONCLUSIONS

Surgical therapy of peri-implantitis effectively improved the clinical and radiographic status at 12 months. While the use of a bone substitute material did not improve reductions of PPD and BOP, buccal REC was less pronounced in the test group. Patient satisfaction was high in both groups.

Surgical treatment of experimental peri-implantitis using mechanical and chemical decontamination procedures: A pre-clinical in vivo study

AIM

To evaluate the effect of surgical treatment of experimental peri-implantitis at implants with different surface characteristics using mechanical and chemical decontamination methods.

MATERIALS AND METHODS

Following extraction of mandibular premolars, four implants with two different surface characteristics (A, moderately rough and B, smooth) were placed in each side of the mandible of six dogs. Experimental peri-implantitis was induced. Surgical treatment of the peri-implantitis sites was carried out using four implant surface decontamination protocols: (i) deposition of a citric acid gel, (ii) mechanical cleaning using a rotating titanium brush, (iii) a combination of the mechanical and chemical procedures, and (iv) saline (control). Clinical and radiographic examinations were performed. Block biopsies were obtained 6 months after therapy and prepared for histological analysis.

RESULTS

Irrespective of the treatment group, treatment resulted in 0.63 ± 0.92 and 0.65 ± 0.67 mm radiographic bone gain around implants A and B, respectively. Histological analyses revealed that persisting soft tissue inflammation as assessed using an infiltrated connective tissue (ICT) score was significantly lower at implant type B than at implant type A for all treatment groups. The test decontamination procedures did not demonstrate better results regarding resolution of peri-implantitis lesions, as indicated by the ICT scores, than the control procedure. The control treatment resulted in significantly superior outcomes of resolution of peri-implantitis lesions than the citric acid regimen.

CONCLUSIONS

It is concluded that decontamination procedures including citric acid gel or rotating titanium brush did not improve outcomes following surgical treatment of experimental peri-implantitis. Results were, however, influenced by the implant surface characteristics.

A person-centred, theory-based, behavioural intervention programme for improved oral hygiene in adolescents: A randomized clinical field study

Aim

To test the effectiveness of a person‐centred and theory‐based educational intervention to increase adolescents′ adherence to adequate oral hygiene behaviour, that is, self‐performed periodontal infection control.

Materials and Methods

Data were derived from a prospective, multi‐centred, two‐arm, quasi‐randomized field study in which treatment was performed by dental hygienists (DHs) within the Public Dental Service, Västra Götaland, Sweden. Adolescents with poor oral hygiene conditions were invited to participate. The test intervention was based on cognitive behavioural theory and principles, and the DHs used a collaborative communicative approach, inspired by motivational interviewing. The control intervention consisted of conventional information/instruction. Clinical assessments and oral hygiene behaviours were evaluated at 6 months.

Results

Three‐hundred and twelve adolescents were enrolled, of whom 274 followed the treatment to 6‐month follow‐up. There were significant improvements in gingival bleeding and plaque scores for both treatment groups at 6 months, with significantly greater improvements in the test group. Adolescents in the test group brushed their teeth and used interdental cleaning aids more frequently compared to participants in the control group at 6 months.

Conclusion

A person‐centred and theory‐based oral health education programme is more effective than conventional oral health education in improving adolescents' oral hygiene behaviour and periodontal infection control. ClinicalTrials.gov (NCT02906098).

Accuracy of bone level assessments following reconstructive surgical treatment of experimental peri-implantitis

AIMS

The purpose was to evaluate the accuracy of bone level assessments using either cone beam computed tomography, intraoral periapical radiographs or histology following reconstructive treatment of experimental peri-implantitis.

MATERIALS AND METHODS

Six Labrador dogs were used. Experimental peri-implantitis was induced 3 months after implant placement. Surgical treatment of peri-implantitis was performed and peri-implant defects were allocated to one of four treatment categories; no augmentation, bone graft materials with or without a barrier membrane. Six months later, intraoral periapical radiographs and block biopsies from all implants sites were obtained. Marginal bone levels were measured using periapical radiographs, CBCT and histology.

RESULTS

Significant correlations of MBL assessments were observed between the three methods. The measurements in periapical radiographs consistently resulted in an overestimation of the bone level of about 0.3 - 0.4 mm. The agreement between methods was not influenced by the use of bone substitute materials in the management of the osseous defects.

CONCLUSIONS

Although MBL assessments obtained from PA radiographs showed an overestimation compared to MBL assessments on corresponding CBCT images and histological sections, PA radiographs can be considered a reliable technique for peri-implant bone level evaluations following reconstructive surgical therapy of experimental peri-implantitis.

Influence of implant geometry and osteotomy design on early bone healing: A pre-clinical in vivo study

OBJECTIVES

To analyze the early stages of osseointegration around implants with different geometry following installation in sites using different osteotomy protocols.

MATERIALS AND METHODS

Two types of implants were installed using regular or modified (reduced diameter) osteotomy protocols in mandibular premolar/molar regions following tooth extraction in six dogs. Three implant site categories were created: Reference (A implant and regular osteotomy), Test-1 (B implant and regular osteotomy), and Test-2 (B implant and modified osteotomy). Implant installation procedures were repeated after 4 and 6 weeks. The insertion torque (ITQ) was measured during implant installation and resonance frequency analysis providing implant stability quotient (ISQ) values was performed following implant installation and once every week during the course of the study. Biopsies were obtained immediately after the 3rd installation procedure and prepared for histological analysis.

RESULTS

The modified osteotomy protocol created a higher insertion torque (ITQ). The analysis also revealed a correlation between insertion torque at implant installation and radiographic bone loss after 6 weeks of healing. The decline in ISQ values during healing was more pronounced at Test-2 than other sites. While the degree of bone-to-implant contact (BIC%) in the marginal area was similar in test and reference sites at 6 weeks of healing, Test-2 implants presented with a significantly higher BIC% in the mid and apical areas than Test-1 implants.

CONCLUSIONS

It is suggested that placement of implants in undersized osteotomy sites will result in an increased remodeling of the cortical bone during the early healing process.

Effect of biofilm formation on implant abutments with an anti-bacterial coating: A pre-clinical in vivo study

OBJECTIVES

To analyse the long-term effect of plaque formation on implant abutments with an antibacterial coating and the ensuing host response in peri-implant tissues.

MATERIALS AND METHODS

Four implants were installed in each mandibular premolar region following tooth extraction in six dogs. Three months later, two test abutments with a titanium-bismuth-gallium (Ti-Bi-Ga) coating and two control titanium abutments were connected to the implants on each side of the mandible. After 2 months, ligatures were placed around the implants in one side of the mandible and plaque formation was allowed until the end of the experiment. The ligatures were removed after 4 weeks. Radiographs and microbiological samples were obtained from each implant site during the plaque formation period. Biopsies were obtained 8 months after abutment connection and prepared for histological analysis.

RESULTS

The analysis did not reveal any statistically significant differences in bone loss, bacterial growth and size of inflammatory lesions between implant units with and without the Ti-Bi-Ga coating. Implant sites exposed to the short period of ligature-induced breakdown demonstrated more pronounced bone loss and bacterial growth than non-ligature sites.

CONCLUSIONS

It is suggested that a Ti-Bi-Ga coating does not prevent biofilm formation on the implant device and does not influence the ensuing host response in the adjacent peri-implant mucosa.

Comparison of 6-mm and 11-mm dental implants in the posterior region supporting fixed dental prostheses: 5-year results of an open multicenter randomized controlled trial

Objective

The aim of this multicenter, randomized controlled trial was to compare the clinical and radiographic outcomes of 6‐mm or 11‐mm implants, placed in the posterior maxilla and mandible, during a 5‐year follow‐up period.

Materials and methods

Ninety‐five patients with adequate bone height for 11‐mm implants, were randomly allocated to a 6‐mm group (test group with short implants) or an 11‐mm group (control group with standard‐length implants). Two or three implants of the same length were placed in each patient and after 6 weeks loaded with a splinted provisional restoration. This was followed by definitive splinted restoration 6 months after implant placement. Clinical and radiographic parameters, including the occurrence of complications were recorded.

Results

A total of 49 patients were enrolled to receive 6‐mm implants (n = 108) and 46 patients to receive 11‐mm implants (n = 101). Three implants (two of 6 mm and one of 11 mm in length) were lost before loading and one 6‐mm implant after 15 months of function, and one 11‐mm implant was lost during the first year of function. The 5‐year survival rates were 96.0% and 98.9% in the 6‐mm and 11‐mm group, respectively. The mean marginal bone level changes 5 years post‐loading were 0.01 ± 0.45 mm (bone gain) in the 6‐mm group and −0.12 ± 0.93 mm (bone loss) in the 11‐mm group (p = .7670). Clinical parameters, including plaque, bleeding on probing and pocket probing depth were not significantly different between the groups, and also technical complications were low.

Conclusion

The clinical and radiographic outcomes of 6‐mm short and 11‐mm standard‐length implants were not different during a 5‐year evaluation period.

Spontaneous progression of experimental peri-implantitis in augmented and pristine bone: A pre-clinical in vivo study

OBJECTIVE

To examine the progression of experimental peri-implantitis around different implants placed in augmented and pristine sites.

MATERIALS AND METHODS

Six labrador dogs were used. Three months after tooth extraction, four implants with different surface modifications were installed on each side of the mandible. A standard osteotomy was applied on one side, while on the contralateral side the osteotomy was modified, resulting in a gap between the implant and the bone wall. The gap was filled with a bone substitute and covered by a resorbable membrane. Three months after implant installation, implants were exposed and healing abutments were connected. Two months later, oral hygiene procedures were abandoned and a cotton ligature was placed in a submarginal position around the neck of all implants and kept in place for 4 weeks. Following ligature removal, plaque formation continued for 6 months (spontaneous progression period). Radiographs were obtained throughout the experiment, and biopsies were collected and prepared for histological evaluation at the end of the spontaneous progression period.

RESULTS

Differences in bone loss during the spontaneous progression period between pristine and augmented sites were small. The size and vertical dimension of the peri-implantitis lesion were larger at augmented than at pristine sites. Implants with non-modified surfaces exhibited smaller amounts of bone loss and smaller dimensions of peri-implantitis lesions than implants with modified surfaces.

CONCLUSION

Small differences in spontaneous progression of peri-implantitis were detected between pristine and augmented sites. Implants with modified surfaces exhibited more bone loss and larger lesions than implants with non-modified surfaces, irrespective of the type of surrounding bone.

Periodontal disease among older people and its impact on oral health-related quality of life

OBJECTIVE

The aim of the study was to evaluate the associations between degree of periodontal disease and number of teeth on oral health-related quality of life among older individuals.

MATERIAL AND METHODS

Randomly selected 804 participants aged ≥70 derived from two cohorts were included in the analysis. Dental examinations and evaluation of OHRQL using the OHIP-14 (Oral Health Impact Profile-14) were performed. After categorisation of the participants according to the extent of periodontitis in three groups (none, localised with <30% of teeth affected, generalised with ≥30% of teeth affected) and the number of teeth, associations between periodontal status and the number of teeth and the OHIP-14 scores were analysed. Multivariable regression analyses were used taking into account level of periodontitis, number of teeth, age and sex.

RESULTS

Among 70-year-old men and women, generalised periodontitis showed an association with poor OHRQL. However, a multivariable analysis failed to demonstrate this association (OR = 1.02, 95% CI: 0.72-1.44). In participants with 1-10 remaining teeth, the OHIP-14 score was significantly increased indicating poor OHRQL, compared with participants with ≥21 remaining teeth (OR = 1.57, 95% CI: 1.13-2.19). Similar findings were observed among women aged 70-92 years.

CONCLUSIONS

Periodontitis did not show an association with poor OHRQL, however, a significant association between the number of teeth and poor OHRQL was found.

Peri-implant tissue healing at implants with different designs and placement protocols: An experimental study in dogs

OBJECTIVES

To compare the peri-implant tissue response to subcrestal or crestal placement of implants with or without "platform-switched" implant/abutment connections.

MATERIAL AND METHODS

On each side of the mandible in six Labrador dogs, two "platform-switched" (PS) implants and two implants with matching implant/abutment diameters (PM) were placed in a crestal or a 1.5 mm subcrestal position. Sulcus formers/abutments were connected, baseline radiographs obtained and the distance between the abutment-fixture junction (A/F) and the marginal bone level (B) was determined. Five months later, radiographic and clinical examinations were repeated and biopsies were obtained and processed for histological analysis.

RESULTS

The radiographic analysis showed that marginal bone level changes occurred during the first observation period (13 weeks). PS-implants showed minor marginal bone level alterations during the full observation period (20 weeks), regardless of placement depth. For PM-implants, placement had a significant impact on bone level changes; crestal placement resulted in a mean bone loss of 0.4 mm and subcrestal placement in a 1.5 mm bone loss. The histometric measurements resulted in a distance A/F-B of 0.6 and 0.0 mm for PS implants, placed in a crestal or subcrestal position, respectively. The corresponding distance at PM-implants was 1.5 mm irrespective of placement protocol. The peri-implant mucosa was thicker at subcrestally placed implants as compared to a crestal placement.

CONCLUSIONS

Bone remodeling occurred within the early healing phase. During the full 20 weeks of observation, PS-implants demonstrated significantly less crestal bone loss compared to PM-implants.

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.

Altered expectations on dental implant therapy; views of patients referred for treatment of peri-implantitis

AIM

The aim was to explore patients' reactions on being diagnosed with peri-implantitis, their opinions on dental implant therapy and expectations on treatment of the disease.

MATERIAL AND METHODS

The study subjects were patients referred to a specialist clinic for treatment of peri-implantitis. The method of grounded theory was used in collecting and analyzing data. Audiotaped, thematized open-ended interviews were conducted. The interviews were transcribed verbatim and consecutively analyzed in hierarchical coding processes that continued until saturation was met (n = 15).

RESULTS

In the analysis, a conceptual model was generated that illuminated a process among patients. From having very high initial expectations on dental implant therapy as a permanent solution of oral/dental problems, patients realized that dental implants, such as teeth, require continuous care and that there is no guarantee for that dental implants provides a treatment alternative free from future problems. The core concept of the model "altered expectations on dental implant therapy" was composed of three main categories: "initial expectations on dental implant therapy and living with dental implants", "being referred to periodontist and become diagnosed with peri-implantitis" and "investing again in an expensive therapy with no guarantee for the future".

CONCLUSION

Patients may have unrealistically high expectations on dental implant therapy. The results illuminate the importance of patient-centered communication in dentistry and that treatment decisions should be based not only on professional expertise but also on expectations, abilities, wishes and life circumstances of the individual patient.

Adjunctive Systemic and Local Antimicrobial Therapy in the Surgical Treatment of Peri-implantitis

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).

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.

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.

Spontaneous progression of ligatured induced peri-implantitis at implants with different surface characteristics. An experimental study in dogs II: histological observations

AIM

The aim of the present study was to analyze tissue reactions to plaque formation following ligature removal in experimental peri-implantitis at commercially available implants in dogs.

MATERIAL AND METHODS

Mandibular premolars and the three anterior premolars in both sides of the maxilla were extracted in six Labrador dogs. After 3 months, four implants representing four different implant systems--groups A (turned), B (TiOblast), C (SLA), D (TiUnite)--were placed in a randomized order in the right side of the mandible. Three months after implant installation, 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. After the subsequent 24-week period of continued plaque accumulation, block biopsies containing implants and their surrounding tissues were obtained and prepared for histological analysis.

RESULTS

All types of implants exhibited extensive inflammatory cell infiltrates and large associated crater-formed osseous defects. The lesions were consistently characterized by insufficient encapsulation of pus and biofilm layers and the inflammatory cell infiltrates extended apical of the pocket epithelium. The presence of numerous osteoclasts indicated active tissue destruction. The vertical dimension and the overall surface area of the infiltrated connective tissue (ICT) were larger at implants of group D than at other implant types.

CONCLUSION

It is suggested that spontaneous progression of peri-implantitis is associated with severe inflammation and tissue destruction.

Spontaneous progression of peri-implantitis at different types of implants. An experimental study in dogs. I: clinical and radiographic observations

AIM

The aim of the present study was to analyze tissue reactions to plaque formation following ligature removal at commercially available implants exposed to experimental peri-implantitis.

MATERIAL AND METHODS

Six Labrador dogs about 1 year old were used. All mandibular premolars and the three anterior premolars in both sides of the maxilla were extracted. After 3 months four implants representing four different implant systems with different surface characteristics--implant group A (turned), B (TiOblast), C (sandblasted acid-etched; SLA) and D (TiUnite)--were placed in a randomized order in the right side of the mandible. Three months after implant installation experimental peri-implantitis was initiated by placement of ligatures in a submarginal position and plaque accumulation. At week 12, when about 40-50% of the supporting bone was lost, the ligatures were removed. During the subsequent 24-week period plaque accumulation continued. Radiographic and clinical examinations were performed during the 'active breakdown' period (plaque accumulation and ligatures) and the plaque accumulation period after ligature removal. The experiment was terminated at week 36.

RESULTS

The bone loss that took place during the 'active breakdown' period varied between 3.5 and 4.6 mm. The additional bone loss that occurred during the plaque accumulation period after ligature removal was 1.84 (A), 1.72 (B), 1.55 (C) and 2.78 mm (D).

CONCLUSION

Spontaneous progression of experimentally induced peri-implantitis occurred at implants with different geometry and surface characteristics. Progression was most pronounced at implants of type D (TiUnite surface).

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.

Peri-implant hard and soft tissue integration to dental implants made of titanium and gold

OBJECTIVES

The aim of the study is to compare the peri-implant hard and soft tissue integration around dental implants made of commercially pure (c.p.) titanium or a gold alloy but with the same shape and surface roughness.

MATERIAL AND METHODS

In four beagle dogs, all mandibular premolars were extracted. Three months later, four experimental non-submerged implants were placed in each edentulous premolar region. Each implant comprised three different zones: zone A (coronal), zone B (central) and zone C (apical). Each zone was made of either c.p. titanium or a gold alloy. Four different combinations of metal and zone were used. A plaque control program was initiated and 6 months later, the animals were sacrificed and biopsies were obtained. The biopsies including the implant and the surrounding tissues were processed for ground sectioning.

RESULTS

The height of the peri-implant mucosa and the length of the barrier epithelium were similar at the four experimental sites. The marginal bone level in the different metal combinations was located between 4.5 and 4.8 mm apical of the implant rim. The percent of mineralized bone that was in direct contact with the implant surface (BIC%) was consistently greater in the marginal than in the apical portion of the implants. The BIC% for the marginal and apical zone were consistently greater for implant portions made of titanium than for portions made of gold alloy (zone B: 42.7% vs. 36.5%, zone C: 33.2% vs. 19%).

CONCLUSIONS

Osseointegration was achieved to surfaces made of both c.p. titanium and a gold alloy. BIC% was higher at titanium than at gold surfaces. Moreover, the peri-implant soft tissue dimensions were not influenced by the metal used in the 'marginal' zone of the implant.

Bone healing at implants with a fluoride-modified surface: an experimental study in dogs

OBJECTIVES

The aim of the present experiment was to study early stages of osseointegration to implants with a fluoride-modified surface.

MATERIAL AND METHODS

Six mongrel dogs, about 1-year old, were used. All mandibular premolars and the first mandibular molars were extracted. Three months later, mucoperiosteal flaps were elevated in one side of the mandible and six sites were identified for implant placement. The control implants (MicroThread) had a TiOblast surface, while the test implants (OsseoSpeed) had a fluoride-modified TiOblast surface. Both types of implants had a similar geometry, a diameter of 3.5 mm and were 8 mm long. Following installation, cover screws were placed and the flaps were adjusted and sutured to cover all implants. Four weeks after the first implant surgery, the installation procedure was repeated in the opposite side of the mandible. Two weeks later, biopsies were obtained and prepared for histological analysis. The void that occurred between the cut bone wall of the recipient site and the macro-threads of the implant immediately following implant installation was used to study early bone formation.

RESULTS

It was demonstrated that the amount of new bone that formed in the voids within the first 2 weeks of healing was larger at fluoride-modified implants (test) than at TiOblast (control) implants. It was further observed that the amount of bone-to-implant contact that had been established after 2 weeks in the macro-threaded portion of the implant was significantly larger at the test implants than at the controls.

CONCLUSION

It is suggested that the fluoride-modified implant surface promotes osseointegration in the early phase of healing following implant installation.

Soft tissue healing at titanium implants coated with type I collagen. An experimental study in dogs

OBJECTIVE

To analyse the soft tissue healing at titanium implants coated with type 1 collagen.

MATERIAL AND METHODS

Six dogs were used. The mandibular pre-molars and the three anterior maxillary pre-molars were extracted. Three months later mucoperiosteal flaps were raised and two test and two control implants were installed (3i TG Osseotite 3.75 x 10 and 2.8 mm transmucosal collar). The test implants were coated with a purified porcine type I collagen. Cover screws were placed and flaps were sutured. The sutures were removed 2 weeks later and a plaque-control programme was initiated. Another 2 weeks later, the procedure was repeated in the contra-lateral mandibular region. Four weeks after the second implant surgery, biopsies were obtained and prepared for histological examination.

RESULTS/CONCLUSION

The vertical dimensions of the epithelial and connective tissue components as well as the composition of the connective tissue portion facing the implant were similar at collagen-coated and uncoated implants after 4 and 8 weeks of healing. It is suggested that soft tissue healing to implants coated with type I collagen was similar to that at non-coated titanium implants and that no adverse reactions to the collagen-coated implants occurred.

Morphogenesis of the peri-implant mucosa: an experimental study in dogs

PURPOSE

The objective of the present experiment was to study the morphogenesis of the mucosal attachment to implants made of c.p. titanium.

MATERIAL AND METHODS

All mandibular premolars were extracted in 20 Labrador dogs. After a healing period of 3 months, four implants (ITI Dental Implant System) were placed in the right and left sides of the mandible. A non-submerged implant installation technique was used and the mucosal tissues were secured to the conical marginal portion of the implants with interrupted sutures. The sutures were removed after 2 weeks and a plaque control program including daily cleaning of the remaining teeth and the implants was initiated. The animals were sacrificed and biopsies were obtained at various intervals to provide healing periods extending from Day 0 (2 h) to 12 weeks. The mandibles were removed and placed in the fixative. The implant sites were dissected using a diamond saw and processed for histological analysis.

RESULTS

Large numbers of neutrophils infiltrated and degraded the coagulum that occupied the compartment between the mucosa and the implant during the initial phase of healing. At 2 weeks after surgery, fibroblasts were the dominating cell population in the connective tissue interface but at 4 weeks the density of fibroblasts had decreased. Furthermore, the first signs of epithelial proliferation were observed in specimens representing 1-2 weeks of healing and a mature barrier epithelium occurred after 6-8 weeks of healing. The collagen fibers of the mucosa were organized after 4-6 weeks of healing.

CONCLUSION

It is suggested that the soft-tissue attachment to implants placed using a non-submerged installation procedure is properly established after several weeks following surgery.

Probe penetration in periodontal and peri-implant tissues: An experimental study in the beagle dog

BACKGROUND

Today, periodontal probing is the best diagnostic tool to assess the health status and attachment level of periodontal tissues. There are, however, doubts as to whether the same method could be used for implants. Experiments comparing peri-implant and periodontal probing provide conflicting results. The impact and interpretation of peri-implant probing are still not sufficiently known.

PURPOSE

The purpose of the present study was to further analyze the histological level of probe penetration in healthy periodontal and peri-implant tissues.

MATERIAL AND METHODS

In four beagle dogs, all mandibular premolars were extracted. Three months later, four experimental non-submerged implants were placed in each edentulous premolar region. Six months later, probing depth was determined at the buccal aspect at two of the implants and at the bilateral first mandibular molars. A pressure-controlled probe with a diameter of 0.4 mm and 0.2 N probing force was used. Following the probing depth assessment, a metal periodontal probe tip was inserted into the previously measured depth and attached to the implants and teeth using a composite material. Block biopsies were obtained and prepared for histometric examinations.

RESULTS

The findings showed that probing resulted in similar probe extension at implants and teeth, that the probe extension corresponded to the extension of the barrier epithelium and that the distance between the probe tip and the bone was about 1 mm in both peri-implant and periodontal tissues.

CONCLUSIONS

This experiment showed that under healthy conditions, the probe tip penetration in the soft tissues at teeth and implants is similar when a probing force of 0.2 N is used. Probing around implants using a moderate force is a valuable diagnostic tool in the maintenance of implant patients.

Tissue Characteristics at Microthreaded Implants: An Experimental Study in Dogs

PURPOSE

The aim of the present study was to analyze bone tissue reactions at implants with and without a microthread configuration.

MATERIALS AND METHODS

In six beagle dogs, one test and two control implants were installed in one side of the mandible. While both implant types had a similar dimension and surface roughness, the test implants were designed with a microthread configuration in the marginal portion. Abutment connection was performed after 3 months. Another 3 months later, fixed partial dentures (FPDs) were cemented to the maxillary canine and premolars and FPDs were connected to the implants in the mandible. Ten months later, the animals were sacrificed and biopsies from each implant region were processed for histological analysis. Radiographs were obtained at implant placement after FPD connection and at the termination of the experiment.

RESULTS

The radiographic examination revealed that the marginal bone level was well preserved at both test and control implants during the entire 16-month period. The degree of bone-implant contact within the marginal portion of the implants was significantly higher at the test (microthread) implants (81.8%) than at the control implants (72.8%).

CONCLUSIONS

It was suggested that the microthread configuration offered improved conditions for osseointegration.

Bone reactions to longstanding functional load at implants: an experimental study in dogs

OBJECTIVES

The aims of the present investigation were (i) to study marginal bone level alterations following implant installation, abutment connection and functional loading and (ii) to analyse bone tissue reactions to functional load.

MATERIAL AND METHODS

Six beagle dogs, about 1-year old, were used. All mandibular pre-molars were extracted. Three months later four implants of the Astra Tech Implants Dental System were installed in one side of the mandible and four standard fixtures of the Brånemark System were placed in the contralateral side of the mandible. Abutment connection was performed 3 months later and a plaque control programme was initiated. Three months after abutment connection fixed partial dentures (FPDs) made in gold were cemented to the maxillary canines and pre-molars. FPDs were also connected to the three posterior implants in each side of the mandible, while the mesial implant in each side was used as an unloaded control. Radiographs were obtained from all implant sites following implant installation, abutment connection and FPD placement. Ten months after the FPD placement the radiographic examination was repeated. The animals were sacrificed and biopsies from all implant sites were obtained and prepared for histological analysis.

RESULTS

The radiographic analysis revealed that largest amount of bone loss occurred following implant installation and abutment connection and that this loss was more pronounced at Brånemark than at Astra implants. The bone level alterations that were observed at implants exposed to 10 months of functional load in both implant systems were small and did not differ from control sites. The histological analysis revealed that implants exposed to functional load exhibited a higher degree of bone-to-implant contact than control implants in both implant systems.

CONCLUSION

It is suggested that functional load at implants may enhance osseointegration and does not result in marginal bone loss.

Early bone formation adjacent to rough and turned endosseous implant surfaces. An experimental study in the dog

OBJECTIVE

To validate a proposed model (Berglundh et al. 2003) and to evaluate the rate and degree of osseointegration at turned (T) and sand blasted and acid etched (SLA) implant surfaces during early phases of healing.

MATERIAL AND METHODS

The devices used for the study of early healing had a geometry that corresponded to that of a solid screw implant with either a SLA or a T surface configuration. A circumferential trough had been prepared within the thread region (intra-osseous portion) that established a geometrically well-defined wound chamber. Twenty Labrador dogs received totally 160 experimental devices to allow the evaluation of healing between 2 h and 12 weeks. Both ground and decalcified sections were prepared from mesial/distal and buccal/lingual device sites. Histometric and morphometric analyses of the ground sections and morphometric analysis of the tissue components in decalcified sections were performed.

RESULTS

The ground sections provided an overview of the various phases of tissue formation, while the decalcified, thin sections enabled a more detailed study of events involved in bone tissue modeling and remodeling for both SLA and T surfaces. The initially empty wound chamber became occupied with a coagulum and a granulation tissue that was replaced by a provisional matrix. The process of bone formation started already during the first week. The newly formed bone present at the lateral border of the cut bony bed appeared to be continuous with the parent bone, but on the SLA surface woven bone was also found at a distance from the parent bone. Parallel-fibered and/or lamellar bone as well as bone marrow replaced this primary bone after 4 weeks. In the SLA chambers, more bone-to-device contact, more initial woven bone and earlier lamellar bone formation was found than in the T chambers.

CONCLUSION

Osseointegration represents a dynamic process both during its establishment and its maintenance. While healing showed similar characteristics with resorptive and appositional events for both SLA and T surfaces, the rate and degree of osseointegration were superior for the SLA compared with the T chambers.