Bone formation over partially exposed implants using guided tissue generation

Systematic review of pre-clinical models assessing implant integration in locally compromised sites and/or systemically compromised animals

OBJECTIVE

The aim was to systematically search the dental literature for pre-clinical models assessing implant integration in locally compromised sites (part 1) and systemically compromised animals (part 2), and to evaluate the quality of reporting of included publications.

METHODS

A Medline search (1966-2011) was performed, complimented by additional hand searching. The quality of reporting of the included publications was evaluated using the 20 items of the ARRIVE (Animals in Research In Vivo Experiments) guidelines.

RESULTS

One-hundred and seventy-six (part 1; mean ARRIVE score = 15.6 ± 2.4) and 104 (part 2; 16.2 ± 1.9) studies met the inclusion criteria. The overall mean score for all included studies amounted to 15.8 ± 2.2. Housing (38.3%), allocation of animals (37.9%), numbers analysed (50%) and adverse events (51.4%) of the ARRIVE guidelines were the least reported. Statistically significant differences in mean ARRIVE scores were found depending on the publication date (p < 0.05), with the highest score of 16.7 ± 1.6 for studies published within the last 2 years.

CONCLUSIONS

A large number of studies met the inclusion criteria. The ARRIVE scores revealed heterogeneity and missing information for selected items in more than 50% of the publications. The quality of reporting shifted towards better-reported pre-clinical trials within recent years.

Tissue-engineered injectable bone regeneration for osseointegrated dental implants

The present study investigated a correlation between osseointegration in dental implants and an injectable tissue-engineered bone, using mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP). Initially, the teeth in the mandible region were extracted and the healing period was 1 month. Bone defects on both sides of the mandible were prepared with a trephine bar. The defects were implanted with graft materials as follows: PRP, dog MSCs (dMSCs), and PRP, autogenous particulate cancellous bone and marrow (PCBM), and control (defect only). Two months later, the animals were evaluated by histology, and at the same time dental implants were installed. Two months later, the animals were sacrificed and nondecalcified sections were evaluated histologically and histometrically. According to the histological observations, the dMSCs/PRP group had well-formed mature bone and neovascularization, compared with the control (defect only) and PRP groups, as was the same for the PCBM group. A higher marginal bone level was observed around implants with PRP, PCBM, and dMSCs/PRP compared with the control. Furthermore, the values describing the amount of bone-implant contact (BIC) at the bone/implant interface were significantly different between the PRP, PCBM, dMSCs/PRP, and control groups. Significant differences were also found between the dMSCs/PRP and control groups in bone density. The findings of this experimental study indicate that the use of a mixture of dMSCs/PRP results in good results such as the amount of BIC and bone density comparable with that achieved by PCBM.

In vitro and in vivo evaluation of e-PTFE and alkali-cellulose membranes for guided bone regeneration

Guided bone regeneration (GBR) is employed to encourage the formation of new bone in osseous defects by restricting the infiltration of soft tissues. While a variety of membranes have been evaluated for this surgical procedure, the non-resorbable material of choice is currently expanded polytetrafluoroethylene (e-PTFE). A new alkali-cellulose membrane produced by a biotechnological process has been developed as an alternative to e-PTFE for GBR. In this study, the biocompatibility of this novel alkali-cellulose membrane and e-PTFE was compared using tissue culture and an in vivo GBR model. In vitro both materials supported the attachment, migration and differentiation of osteoblast-like cells in culture for up to 3 weeks. The in vivo model was based upon full-thickness transcortical bone defects in the mandibular rami of Sprague-Dawley rats. The right rami were used as controls, contralateral defects being covered bucally and lingually with either e-PTFE or alkali-cellulose membranes. Pathological and histomorphometric analysis was undertaken at 4 and 10 weeks post-implantation. Bone regeneration associated with alkali-cellulose membranes was predominantly endochondral in type in contrast to e-PTFE which induced direct bone formation (intramembranous ossification). The amount of new bone formed in defects was similar for both types of membrane, but alkali-cellulose membranes induced significantly greater inflammatory response; characterized by lymphocytes, macrophages and multinucleated giant cells. Degradation and possible exposure of individual cellulose fibres may account for the poor performance of alkali-cellulose membranes in vivo. This animal and in vitro study indicates that when choosing a non-resorbable membrane for GBR, e-PTFE membranes are likely to perform better than those produced from alkali-cellulose.

Efficacy of high-density versus semipermeable PTFE membranes in an elderly experimental model

OBJECTIVE

The clinical effectiveness of expanded polytetrafluoroethylene (PTFE) membranes for guided bone regeneration has been reported in the literature on several occasions. However, one major drawback of this material is the need for a second surgical operation for removal of the membrane. In addition, most studies involving guided bone regeneration in animal models have used young animals or animals of unspecified age, but in some clinical situations guided bone regeneration may be indicated in elderly jaw bones. The objectives of this investigation were (1) to evaluate the effectiveness of a newly introduced high-density PTFE membrane (TefGen-FD)-a material that does not require second-stage surgery for its removal-for enhancement of bone ingrowth in elderly rabbits' calvaria and (2) to compare the findings with those obtained with the commonly used semipermeable expanded PTFE membrane (Gore-Tex).

STUDY DESIGN

Eighteen elderly rabbits (each more than 30 months old) served as the experimental animals in this study. Two non-self-healing, full-thickness defects were created in each rabbit calvarium. One of the 2 defects was fully covered with macroprous expanded PTFE membrane (Gore-Tex); the other defect was covered with microporous PTFE membrane (TefGen-FD). Specimens were obtained at 4, 8, and 16 weeks and examined by means of light microscopy.

RESULTS

Clinically, the high-density TefGen membrane was much easier to detach from the underlying bone than was the semipermeable Gore-Tex membrane, which showed strict adherence to bone surface on removal. Microscopically, the Gore-Tex membrane lamellae were infiltrated by fibro-osseous tissue at the membrane's lower surface. A relatively greater speed and quantity of bone regeneration were observed in the defective cavities covered with Gore-Tex membrane than in those covered with TefGen membrane.

CONCLUSIONS

It appears that the semipermeable Gore-Tex membrane is more effective than the high-density TefGen-FD membrane with respect to guided bone regeneration in elderly bone. These findings have relevance for the clinical situation of using guided bone regeneration in conjunction with implant placement and ridge augmentation procedures in atrophic elderly jaws.

Managing complex orthodontic problems: the use of implants for anchorage

Today implants are commonly used to replace missing teeth in partially edentulous adult orthodontic patients. Because these patients are missing teeth, orthodontic mechanics may be complicated or often impossible because of insufficient anchorage. In these situations, it may be feasible to use the implant initially as an orthodontic anchor to facilitate complex tooth movement and secondarily as an abutment for a crown or fixed prosthesis. This article will discuss the ramifications and requirements for using implants as anchors and abutments in adult orthodontic patients.

Radiographic evaluation of implant-obscured bone. Comparison of digitally subtracted tomographic and periapical techniques

This study evaluated the diagnostic accuracy of digitized and substracted periapical and tomographic film images in the assessment of facial and lingual bone loss at implant-obscured sites. An edentulous dried human mandible was prepared with implants in the incisor, premolar, and molar regions. Successive bur sizes from quarter round to no. 6 were used to create circumferential infrabony periodontal defects in the alveolar crest adjacent to the implants. Periapical radiographs were made with the use of custom stents. Linear tomograms imaged sites in a cross-sectional orientation. An equal number of radiographs with and without lesions were digitized and subtracted from baseline images. Radiographic anatomy on the mesial and distal aspects of each implant was electronically masked before the evaluation by a series of eight observers. Receiver operating characteristics analysis and analysis of variance were used to evaluate accuracy of interpretation of the presence or absence of crestal defects. Observer accuracy in detecting facial or lingual bone defects was significantly greater with subtracted tomographic images than with substracted periapical images (p < 0.001).

Localized alveolar ridge augmentation before orthodontic treatment. A case report

Extraction spaces are usually characterized by narrow, atrophic alveolar ridges, which make it difficult to move teeth orthodontically within these areas. Guided tissue regeneration is often used for alveolar ridge augmentation in implantology. In the case presented, localized alveolar ridge augmentation was performed as a preliminary procedure before orthodontic closure of an edentulous space. Guided tissue regeneration enhances the possibilities of orthodontic treatment in adult patients.

Alveolar ridge changes in patients congenitally missing mandibular second premolars

This study investigated changes in ridge width over time in patients who were congenitally missing mandibular second premolars. Data were obtained from stone casts and radiographs of 35 edentulous sites on 22 patients representing three time periods: (1) before extraction of the primary mandibular second molar, (2) completion of orthodontic treatment, and (3) long-term evaluation. The findings indicate that ridge width decreases 25% within 3 years after primary molar extraction. The rate of decrease diminishes to 4% over the next 3 years. The change in ridge width had a weak association with the age of the patient at the time of the extraction but a small predictive value. No correlation was found between changes in ridge width and height and the time since the extraction or the age of the patient at the time of extraction.