International Journal of Periodontics & Restorative Dentistry, 01/2010

The purpose of the present prospective study was to evaluate implant survival and crestal bone levels around implants that used the platform-switching concept and were followed for a minimum of 11 years. Radiographs of 94 implants obtained 11 to 14 years after loading were evaluated by measuring the location of the crestal bone level relative to the implant platform. All implants had been placed at the crestal level at the time of surgery. Using the known distance of 0.8 mm between the peaks of adjacent threads, a determination was made on the radiographs of the amount of bone lost. Seventy-one of the 94 implants (75.5%) showed no bone loss on the mesial aspect, and 67 (71.3%) showed no bone loss on the distal aspect. Eighty-four percent of the mesial surfaces and 88% of the distal surfaces had 0.8 mm or less of bone loss. This is the longest follow-up to a prospective investigation of platform-switched implants and confirms the concept for preservation of crestal bone levels.

Part 1 of the present series presented a rationale for including prosthetic gingiva in the planning of a fixed restoration to ensure an esthetic result for patients with severe horizontal and vertical ridge deficiencies. The second part focused on the diagnostic and treatment planning aspects of the use of artificial gingiva. This third and final installment in the series focuses on the laboratory and clinical procedures involved in fabricating a prosthesis with artificial gingiva and provides information on proper maintenance of these restorations.

In this case series, a tissue-engineered bilayered live cell therapy (LCT) is examined as an alternative to free gingival grafts in subjects with oral mucosal defects. Four patients with five sites requiring mucogingival surgery because of limited vestibular depth and limited keratinized oral mucosa were selected for treatment. All included patients had limited graft availability or preferred to avoid autogenous soft tissue grafting. The oral mucosal defects were treated with a tissueengineered bilayered LCT, a circular disk of allogeneic live, human-derived, confluent, and bilayered keratinocyte and fibroblast cells. Sites were evaluated for wound healing, histologic appearance of the regenerated mucosa, and DNA persistence of the LCT. All sites healed uneventfully, with complete epithelialization by 14 days postoperative and no significant adverse events. The treated sites matched the surrounding tissues in both texture and color. Histologic samples revealed gingival tissue architecture characterized by a parakeratinized epithelium with a very sparse and diffuse chronic inflammatory response within the connective tissue. DNA persistence indicated that the pairs of samples (swab and biopsy) collected from each subject displayed the same identifier DNA, with no evidence of any other source. Further research is needed to evaluate the utility of LCT in clinical practice.

Forty patients received a total of 43 implants placed in fresh extraction sites in the anterior maxilla. Within 1 week, a provisional crown was placed without occlusal contact. After 1 year, the implant survival rate, marginal bone resorption, and papillae preservation were assessed. The overall survival rate was 95.3%. The 1-year marginal bone loss was not statiscally significant when compared to the marginal bone level at implant placement. In 78% of patients, the papilla was completely preserved. Single-tooth rehabilitation patients with buccal or circumferential defects can be predictably treated with a favorable esthetic outcome using the immediate provisionalization approach.

Eleven sinuses were grafted with a magnesium-enriched bioceramic bone substitute in granules (SINTlife) mixed with 10% autogenous bone retrieved from intraoral donor sites. Bone biopsies retrieved after 8 months were visually and quantitatively analyzed with microcomputed tomography (microCT). MicroCT evaluation of the grafted material was feasible, since the radiodensity of the bone substitute was different from the density of mineralized bone. MicroCT showed good integration of the graft in all treated cases. The tested bioceramic bone substitute, mixed with autogenous bone, seemed to have a positive effect in sinus grafting, with values of total mineralized tissue volume around 66%. Residual graft particles occupied 31% of the total volume of the specimen. Particles of the ceramic bone substitute seemed mainly unresorbed. MicroCT analysis evaluated several morphometric parameters, demonstrating that the newly formed bone could be used for placement and loading of implants.

The treatment of drug-induced gingival overgrowth is compounded by the high recurrence rate resulting from chronic use of the medication and the persistence of other risk factors. In this case series, the treatment outcome of a nonsurgical periodontal therapy, according to the concept of full-mouth disinfection in 11 patients with drug-induced gingival overgrowth, is described. All clinical parameters improved significantly after therapy. Only 6% of teeth received further surgical treatment. The clinical situation remained stable during the recall. The present case series suggests that full-mouth disinfection might be a beneficial treatment concept for drug-induced gingival overgrowth, reducing the need for further surgical intervention.

One of the therapeutic options proposed for reconstruction of the atrophic posterior mandible is inferior alveolar nerve (IAN) mobilization with simultaneous implant placement. However, studies on the functionality of this neurovascular bundle after its mobilization have shown mixed results. This variability can be attributed both to the test methodology, which typically requires subjective answers from patients, and to the surgical procedure itself, which is highly dependent on operator technique. This article reports on a series of 10 cases of IAN mobilization using a device specifically engineered to simplify bone surgery. This device enables the oral surgeon to avoid overstretching the nerve by creating a smaller bone window and using an apicocoronal inclination of instruments to capture the neurovascular bundle. Evaluation by means of neurosurgery function tests over a 36-month period found that all patients had a return to normal sensation after a brief period of neurosensory disturbance. Subjective responses to a patient questionnaire confirmed these findings. The implant success rate was 100%.

Bio-Oss (Geistlich) is composed of anorganic bovine bone and has been widely used in several bone regeneration procedures during oral surgery. However, how this biomaterial enhances osteoblast activity to promote bone formation is not completely understood. MicroRNAs (miRNAs) represent a class of small, functional, noncoding RNAs of 19 to 23 nucleotides that regulate the transcription of messenger RNAs (mRNAs) in proteins. In this study, the miRNA microarray technique was used to investigate translation regulation in an osteoblast-like cell line (MG63) exposed to Bio-Oss. Nine up-regulated miRNAs (mir-423, mir-492, mir-191, mir-23a, mir-377, mir-494, mir-214, mir-193b, mir-320) and 4 down-regulated miRNAs (mir-27a, mir-24, mir-188, let-7c) were identified. Because each miRNA regulates 100 mRNAs, only mRNAs related to bone formation were analyzed. The vast majority of detected mRNAs are down-regulated, including some homeobox genes (genes that regulate the morphogenesis of an entire segment of the body), such as noggin and EN1. An indirect positive effect was demonstrated on bone morphogenetic protein-4. To the authors' knowledge, the data reported here are the first on translation regulation in osteoblasts exposed to Bio-Oss. This study may be relevant in better understanding the molecular mechanism of bone regeneration and used as a potential tool for analyzing the combined use of cytokines.

The aim of this study was to evaluate the influence of the length, diameter, and geometry of Biotechnology Institute dental implants on stress distribution in bone. Three-dimensional finite element models of osseointegrated titanium dental implants were created for this study. A force of 150 N was applied at an angle of 30 degrees. The four implant systems used were: Tiny, Interna Universal, Interna Plus, and Interna Wide, and presented the following platforms: 3.5, 4.1, 4.1 (with a 4.8-mm neck), and 5.5 mm, respectively. Implant lengths of 8.5, 10.0, 11.5, 13.0, and 15.0 mm and diameters of 2.5, 3.3, 3.75, 4.0, 4.5, and 5.0 mm were evaluated. Results showed that the effect of implant diameter on stress distribution in bone was more significant than the effect of the implant's length or its geometry. The maximum stress was located around the neck of the implant and the majority of the stress, independent of the parameter being studied, was distributed in the bone adjacent to the first six threads of the implant. Based on these finite element studies, the use of wider implants may be better to dissipate the acting forces and thus reduce the stress in the bone surrounding the implant. Additionally, the use of shorter and wider implants might be a reasonable alternative in sites limited by the height of the residual ridge.

In addition to osseointegration and restoration of function, patient satisfaction is a key element in the success of implant therapy. Especially in the esthetic zone, an essential part of the procedure aims at creating a definitive implant restoration that cannot be distinguished from the adjacent natural teeth. The present patient shows that, after localized ridge defects are reconstructed during implant surgery, a favorable esthetic and functional result can be achieved employing the keyhole access expansion technique for stage-two surgery, which is easy to perform, safe, and minimally invasive.