Healing of buccal dehiscence defects at implants installed immediately into extraction sockets - an experimental study in dogs

Immediate implant placement with flap or flapless surgery: A systematic review and meta-analysis

AIM

To assess the impact of mucoperiosteal flap elevation for single immediate implant placement (IIP) on buccal hard and soft tissue changes, and on clinical, aesthetic and patient-reported outcomes.

MATERIALS AND METHODS

Two independent reviewers conducted an electronic literature search in Pubmed, Web of Science, Embase and Cochrane databases as well as a manual search to identify eligible clinical studies up to June 2022. Randomized controlled trials (RCTs) comparing IIP without flap elevation to IIP with flap elevation were included for a qualitative and quantitative analysis. The primary outcome was horizontal buccal bone change. Secondary outcomes were implant survival, vertical buccal bone change, pain, and clinical and aesthetic parameters.

RESULTS

Out of 1029 records, 5 RCTs were selected reporting on 140 patients who received 140 single immediate implants (flapless: 68; flap: 72). Patients had a mean age ranging from 30 to 67 years and were followed between 6 and 12 months. Four RCTs pertained to (nearly) intact alveoli. Risk of bias assessment yielded low risk for two RCTs and high risk for three RCTs. Meta-analysis demonstrated a mean difference of 0.48 mm (95% confidence interval [CI] [0.13, 0.84], p = .007) in horizontal buccal bone change between surgical approaches, favouring flapless surgery. Meta-analysis failed to demonstrate a significant difference in implant survival between the groups (RR 1.00, 95% CI [0.93, 1.07], p = .920). Given the scarcity of data, meta-analyses could not be performed on other secondary outcomes. Available studies were consistent in the direction of the effect favouring flapless surgery for vertical buccal bone change as well as for pain. Clinical and aesthetic parameters were underreported.

CONCLUSIONS

Based on CBCT data, flapless surgery resulted in more buccal bone preservation at immediate implants. However, the clinical relevance of this finding is unclear, since clinical and aesthetic outcomes were underreported.

Pre-Clinical Models in Implant Dentistry: Past, Present, Future

Biomedical research seeks to generate experimental results for translation to clinical settings. In order to improve the transition from bench to bedside, researchers must draw justifiable conclusions based on data from an appropriate model. Animal testing, as a prerequisite to human clinical exposure, is performed in a range of species, from laboratory mice to larger animals (such as dogs or non-human primates). Minipigs appear to be the animal of choice for studying bone surgery around intraoral dental implants. Dog models, well-known in the field of dental implant research, tend now to be used for studies conducted under compromised oral conditions (biofilm). Regarding small animal models, research studies mostly use rodents, with interest in rabbit models declining. Mouse models remain a reference for genetic studies. On the other hand, over the last decade, scientific advances and government guidelines have led to the replacement, reduction, and refinement of the use of all animal models in dental implant research. In new development strategies, some in vivo experiments are being progressively replaced by in vitro or biomaterial approaches. In this review, we summarize the key information on the animal models currently available for dental implant research and highlight (i) the pros and cons of each type, (ii) new levels of decisional procedures regarding study objectives, and (iii) the outlook for animal research, discussing possible non-animal options.

Healing of BoneCeramic™ at buccal dehiscence defects at implants installed immediately into extraction sockets. An experimental study in dogs

OBJECTIVE

To assess the healing outcomes at buccal dehiscence defects after 4 months following implant placement immediately into extraction sockets (IPIES) and filled with a mixture of synthetic hydroxyl apatite (HA) 60% and β-tri-calcium phosphate (β-TCP) 40% in comparison with leaving a blood clot.

MATERIAL AND METHODS

Eight Labrador dogs were used, and an implant was placed immediately following tooth extraction into the distal alveolus of the third premolars, bilaterally. Standardized buccal defects, 8 mm in depth and 4 mm in width at the coronal and 2 mm in width at the apical outlines were created. A mixture of synthetic HA 60% and β-TCP 40% was used to fill the defects at the test sites, while the control sites were left unfilled. Collagen membranes were used to cover the defects at both sides, and a non-submerged healing was allowed. After 4 months of healing, biopsies were obtained and processed for morphometric analysis.

RESULTS

A vertical gain in the extent of the bony crest and of osseointegration levels of 4.2 ± 2.4 and 3.3 ± 2.1 mm at the test sites and of 5.0 ± 0.8 and 4.6 ± 1.0 mm at the control sites, respectively, were observed. BIC% within the buccal defects reached similar levels (37-42%) both at test and control sites. None of the means of the variables differed significantly between the two groups. New bone formation within the defects was higher, and the percentage of the connective tissue was lower at the control (65.7 ± 11.7% and 2.5 ± 3.3%, respectively) compared to the test sites (16.8 ± 11.3% and 48.9 ± 29.5%, respectively). These differences were statistically significant.

CONCLUSIONS

The use of a mixture of synthetic HA 60% and β-TCP 40% to fill surgically created buccal dehiscence defects at IPIES sites covered with a collagen membrane did not improve osseointegration in the defect area.

Effect of Platform Shift on Crestal Bone Levels and Mucosal Profile Following Flap Surgery and Subcrestal Implant Placement in Presence/Absence of Gap Defects

BACKGROUND

Physiologic remodeling resulting in crestal bone loss appears a common corollary to dental implant surgery. Several hypotheses and clinical strategies have been advanced to explain and avert crestal remodeling; however, causative mechanisms remain unclear and the efficacy of clinical protocols uncertain.

PURPOSE

The objective of the present study was to provide a histologic account of crestal bone levels and mucosal profile at implant sites receiving platform shift/switch and standard abutments following conventional flap surgery and subcrestal implant placement in presence or absence of crestal gap defects using a dog model.

MATERIALS AND METHODS

Four dental implants were placed into the left/right edentulated posterior mandible in five adult male Hound Labrador mongrel dogs using flap surgery including subcrestal placement with/without a 1 × 5 mm (width × depth) gap defect, and using platform shift/switch and standard abutments. Block biopsies were collected for histological/histometric analysis following an 8-week healing interval.

RESULTS

No significant differences in crestal resorption were observed among experimental groups; crestal resorption being significantly more advanced at buccal than at lingual sites (p < .001). Similarly, crestal bone-implant contact was not significantly different among groups; crestal bone-implant contact being consistently below the implant platform at buccal sites (p < .01). Moreover, the peri-implant mucosal profile was not statistically different among groups, the mucosal height being significantly greater at buccal than at lingual sites (p < .001). Also, no significant differences among groups were observed for the apical extension of the epithelial attachment, the epithelial attachment being arrested more than 2 mm above the implant platform at both platform shift/switch and standard abutments.

CONCLUSIONS

Using a clinical strategy including flap surgery and subcrestal implant placement, implant technology comparing platform shift/switch with standard abutments, surgical approach, and abutment selection seems to have a limited impact on crestal remodeling, associated bone loss, and mucosal profile.

The platform switching concept revisited. An experimental study in dogs

OBJECTIVE

To evaluate the influence of the configuration of the marginal aspect of implants placed immediately into extraction sockets on peri-implant hard tissue adaptation.

MATERIAL AND METHODS

In 6 Labrador dogs, endodontic treatments of the mesial roots of 1 M1 were performed and the distal roots were removed. 2 P2 was extracted as well. Implants were immediately placed in the center of the distal alveoli. Cylindrical straight implants were installed in the right side of the mandible (Control), while, in the left side, implants with a reduced diameter in the coronal portion, yielding an indentation in the surface continuity (Test), were installed. Cover screws were affixed, and the flaps were sutured to allow non-submerged healing. After 4 months of healing, histological slides were obtained for assessments.

RESULTS

A buccal resorption of 1.58 ± 1.28 and 1.90 ± 1.93 mm at the control and of 0.26 ± 0.90 and 0.14 ± 0.66 mm at the test sites was observed at the premolar and molar regions, respectively. The buccal coronal level of osseointegration was located apically to the margin of the smooth/rough surface border by 2.40 ± 0.90 and 3.70 ± 0.87 mm at the control sites and 1.19 ± 0.45 and 2.16 ± 0.96 mm at the test sites at the premolar and molar sites, respectively. All differences yielded statistical significance.

CONCLUSIONS

The use of implants with a reduced diameter in their coronal aspect may contribute to preservation of the buccal bony crest in a more coronal level compared with conventional implants. Thus, the study confirmed the efficacy of the "platform switching" concept.

Relationships between different tooth shapes and patient's periodontal phenotype

BACKGROUND AND OBJECTIVE

The purpose of the present study was to establish whether any correlation exists between tooth shapes and patient-related factors such as gingival and periodontal characteristics.

MATERIAL AND METHODS

Clinical measurements, including the width and the height of maxillary central incisor crowns, the apico incisal height of the keratinized mucosa (KM), the buccal gingival thickness (GT), the depth of the sulcus (SD), the bone-sounding depth (BS) and the height of the interproximal maxillary central papilla (Ph), were investigated in 50 healthy individuals. These individuals were then divided into three groups based on the shape of their maxillary central incisor crowns: triangular; square; or square-tapered. The three groups were analyzed to determine any significant differences among the groups in the values obtained for clinical measurements.

RESULTS

There were no significant differences among the three groups in terms of the SD (p = 0.11) or the BS (p = 0.54), whilst statistically significant differences were observed for the KM (p < 0.001), the GT (p = 0.012) and the Ph (p < 0.001).

CONCLUSION

The results of this study indicate that different tooth shapes are associated with significantly different values for the extent of the KM, its bucco-lingual thickness and the height of the interproximal maxillary central papilla.