Petra Ratka-Krüger

Double Crown‐Retained Maxillary Overdentures: 5‐Year Follow‐Up

BACKGROUND There is a lack of data concerning implant-supported overdentures (IODs) retained by double crowns in the edentulous maxilla. PURPOSE To perform a retrospective evaluation of clinical outcomes (survival/success rates) of maxillary overdentures retained on four implants via double crowns. MATERIAL AND METHODS Between 1993 and 2011, 28 patients with edentulous maxillae were restored with overdentures supported by four implants with a Morse taper connection (Ankylos, Dentsply Friadent, Mannheim, Germany) and double crowns according to the Marburg Double Crown (MDC) technique in a private practice. For retrospective evaluation of implant and prosthetic survival (in situ criterion) and success (event-free observational period), only patients attending a professional maintenance program were included (n = 20). RESULTS Twenty patients (13 female/ seven male, mean age: 63.45 ± 7.18 years) with 80 implants met the inclusion criteria. The mean follow-up period was 5.64 ± 3.50 years. One implant was lost (cumulative survival rate: 98.75%). Eight implants (10.1%) in two patients (10%) showed peri-implantitis; both patients were active smokers (cumulative success rate: 88.75%). All dentures were still functional (prosthetic survival rate 100%) at the time of investigation. Technical maintenance procedures (e.g., abutment loosening, screw loosening, acrylic fracture or relining) were required at a rate of 0.222/patient-year. CONCLUSIONS Within the limitations of this study, we conclude that MDC-IODs are a promising treatment alternative for edentulous maxillae offering high implant and prosthesis survival rates > 98% and a limited incidence of biological and technical complications after a mean observational period of >5 years.

The effect of keratinized mucosa width on peri-implant outcome under supportive postimplant therapy.

BACKGROUND Long-ranging data on the influence of keratinized mucosa (KM) on peri-implant tissue status have been scarce. PURPOSE Retrospective evaluation of peri-implant diseases and KM width in patients with versus without mucogingival surgery. MATERIALS AND METHODS Under supportive postimplant therapy (SIT) in a private practice, 68 patients with peri-implant KM widths <1 mm were identified between 1992 and 2011 (eight dropouts). Thirty patients rejected surgery (control [C] group), and 30 patients agreed (intervention [I] group). After at least 1 year, KM width, mucositis, and peri-implant conditions were assessed. RESULTS Sixty nonsmoking patients (n = 105 implants) were available for assessment after 12.10 ± 4.93 years. No implants were lost (survival rate: 100%). An average of 10.69 years after surgery, the I group implants showed a mean KM gain of 3.10 ± 1.43 mm (C group: 0 mm). The mucositis rates were as follows: I group: 38.98%; C group: 31.91%. Peri-implantitis was detected in two implants (1.87%) and two individuals (6.67%) in the I group. No significant differences between groups were found, except that the KM width values were significantly greater in the I group (p < 0.001). CONCLUSIONS Low incidences of peri-implant diseases over long periods can be expected in patients attending SIT programs, independent of the absence or presence of KM.Background Long-ranging data on the influence of keratinized mucosa (KM) on peri-implant tissue status have been scarce. Purpose Retrospective evaluation of peri-implant diseases and KM width in patients with versus without mucogingival surgery. Materials and Methods Under supportive postimplant therapy (SIT) in a private practice, 68 patients with peri-implant KM widths <1 mm were identified between 1992 and 2011 (eight dropouts). Thirty patients rejected surgery (control [C] group), and 30 patients agreed (intervention [I] group). After at least 1 year, KM width, mucositis, and peri-implant conditions were assessed. Results Sixty nonsmoking patients (n = 105 implants) were available for assessment after 12.10 ± 4.93 years. No implants were lost (survival rate: 100%). An average of 10.69 years after surgery, the I group implants showed a mean KM gain of 3.10 ± 1.43 mm (C group: 0 mm). The mucositis rates were as follows: I group: 38.98%; C group: 31.91%. Peri-implantitis was detected in two implants (1.87%) and two individuals (6.67%) in the I group. No significant differences between groups were found, except that the KM width values were significantly greater in the I group (p < 0.001). Conclusions Low incidences of peri-implant diseases over long periods can be expected in patients attending SIT programs, independent of the absence or presence of KM.

Clinical Outcome of Double Crown-Retained Mandibular Removable Dentures Supported by a Combination of Residual Teeth and Strategic Implants.

PURPOSE There is a lack of data regarding the clinical outcome of removable partial dentures (RPDs) supported by a combination of residual natural teeth and implants placed in strategic positions. The aim of the present case series was to conduct a retrospective investigation of the clinical outcome of mandibular tooth-implant-retained partial dentures (TIRPD) rigidly retained via telescopic double crowns. MATERIAL AND METHODS Between 1999 and 2010, 18 patients with reduced residual dentition (1 to 3 natural abutment teeth) and in need of an RPD received 1 to 3 implants in strategic positions for support of the removable prostheses. All TIRPDs were rigidly retained by telescopic crowns according to the Marburg Double Crown (MDC) technique; all prostheses were placed in a private practice. Tooth/implant survival and success rates, prosthetic maintenance requirements, and peri-implant parameters were analyzed retrospectively using patient records and clinical examinations during the final recall appointments. Only patients attending at least annual supportive post-implant hygiene therapy visits (SIT) were included. RESULTS After a mean functional period of 5.84 ± 3 years (range: 3.01-12.21), 14 patients with 14 dentures supported by 24 implants and 27 teeth (mean number of abutments: 3.6) were available for assessment. Four teeth (survival rate: 85.19%) and no implants (survival rate: 100%) were lost. Peri-implantitis was observed around one implant (4.17%). All 14 dentures were functional (survival rate: 100%) and required only limited maintenance (i.e., screw loosening, acrylic resin fracture repairs, relining) amounting to 0.086 treatments per patient per year (T/P/Y). CONCLUSIONS Within the limitations of this case series, it can be concluded that TIRPDs retained via MDCs might represent a viable treatment option in mandibles with few remaining abutment teeth. Further long-term clinical evaluations with a greater sample size are needed for a more detailed evaluation of this treatment concept.

Melatonin as a Candidate Therapeutic Drug for Protecting Bone Cells From Chlorhexidine-Induced Damage

BACKGROUND Melatonin was proposed for use in periodontitis and peri-implantitis therapy due to its bone-supportive effects. This issue is of interest because standard adjuvant antiseptics, namely chlorhexidine (CHX), prove damaging for osteoblasts. Thus, the aim of this study is to investigate if melatonin is suitable as an auxiliary agent for protecting osteoblasts from CHX damage. METHODS MC3T3 osteoblast response was determined following administration of various CHX concentrations in the absence or presence of melatonin. Osteoblast morphology was evaluated, total reactive oxygen species (ROS) and superoxide levels were quantified, ratios of apoptotic and necrotic cells were identified by flow cytometry, metabolic activity of remaining cells was assessed, and effects were calculated with repeated measures analysis and post hoc P value adjustment. RESULTS CHX led to poor morphology, increased total ROS and superoxide levels, and rigorously diminished the number of vital and metabolic active osteoblasts in a concentration-dependent manner. However, simultaneous melatonin supply supported cell morphogenesis and growth, reduced ROS and superoxide generation, shifted the percentage of CHX-damaged cells from necrotic/late to early apoptotic events, and modulated metabolic activity in osteoblasts. CONCLUSION These data reveal that melatonin protects osteoblasts in the CHX context, thereby implicating melatonin as a promising drug in periodontitis and peri-implantitis treatment.

Shift of microbial composition of peri-implantitis-associated oral biofilm as revealed by 16S rRNA gene cloning

Purpose. Micro‐organisms are important triggers of peri‐implant inflammation and analysing their diversity is necessary for peri‐implantitis treatment. This study aimed to analyse and compare the microbiota associated with individuals with peri‐implantitis, as well as clinically healthy implant sites. Methodology. Subgingival biofilm samples were taken from 10 individuals with peri‐implantitis and from at least 1 clinically healthy implant. DNA was extracted and bacterial 16S rRNA genes were amplified using universal primers. After cloning the PCR‐products, amplified inserts of positive clones were digested using restriction endonucleases, and the chosen clones were sequenced. The 16S rDNA‐sequences were compared to those from the public sequence databases GenBank, EMBL and DDBJ to determine the corresponding taxa. Results. Differing distributions of taxa belonging to the phyla Firmicutes, Bacteroidetes, Fusobacteria, Actinobacteria, Proteobacteria, Synergistetes, Spirochaetae and TM 7 were detected in both the healthy implant (HI) and the peri‐implantitis (PI) groups. A significantly higher relative abundance of phylum Bacteroidetes, as well as of the species Fusobacterium nucleatum, were found in the PI group (P<0.05). The putative periodontal red complex (Porphyromonas gingivalis, Tannerella forsythia) was also detected at significantly higher levels in the PI group (P<0.05), whereas the yellow group, as well as the species Veillonella dispar, tended to be associated with the HI group. Conclusion. A shift in the healthy subgingival microbiota was shown in peri‐implantitis‐associated biofilm. Anaerobic Gram‐negative periopathogens, including P. gingivalis and T. forsythia, seem to play an important role in peri‐implantitis development and should be considered in treatment and prevention strategies.

A New Technique for Increasing Keratinized Tissue Around Dental Implants: The Partially Epithelialized Free Connective Tissue Graft. Retrospective Analysis of a Case Series.

F or decades, it has been known that the absence of keratinized gingiva around teeth and the resulting mobility of marginal tissues promote bacterial invasion of the gingival sulcus. In particular, the presence of keratinized gingiva improves the long-term prognosis of restored teeth. However, the relationship between a sufficiently wide zone of keratinized mucosa (KM) and the longterm success rate of oral implants remains controversial. A causal relationship has been postulated between the accumulation of bacterial plaque on implants and the progression of inflammatory processes in the peri-implant soft tissue. Mucositis around implants is very similar to gingivitis around natural teeth, a fact that has been demonstrated in humans. Some studies have shown that with adequate plaque control, peri-implant tissues can be maintained in a healthy state. In those studies, no correlation was found between implant survival or success and the presence of KM. Other studies, however, have noted that in clinical practice, consistently good oral hygiene around restorations is difficult to maintain if no keratinized gingiva is present. Several studies have demonstrated increased levels of plaque and inflammation around implants in the absence of KM. More recent studies have shown that in spite of good oral hygiene and maintenance therapy, implants with less than 2 mm of KM in the peri-implant region were significantly more prone to bleeding and exhibited greater radiologic bone loss, as well as buccal soft tissue recession. Moreover, elevated values of immunologicparameters (eg, PGE2) were observed in these implants. 17 In order to minimize these risks, various proposals have been made regarding a potential surgical extension of the zone of KM around implants. This article describes a novel technique developed by the authors to increase the width of KM around dental implants and presents results of a case series with up to 15 years of follow-up.

Minimizing Excess Cement in Implant-Supported Fixed Restorations Using an Extraoral Replica Technique: : A Prospective 1-Year Study

PURPOSE Cementation of implant-supported restorations poses two major challenges: (1) minimizing excess cement (reducing the risk of peri-implantitis), and (2) establishing sufficient retention (reducing the risk of decementation). This study presents the first data on a clinical cementation technique that might address both problems. MATERIALS AND METHODS Between 2011 and 2013, 39 patients were provided with 52 implants supporting 52 single crowns (SCs). All restorations were cemented extraorally using replicas made of pattern resin and zinc oxide cement. All decementation events and the peri-implant soft tissue status were assessed and compared with those from a group of 29 patients with 40 conventionally cemented SCs (control). RESULTS In the experimental group, after 12 months, decementation was recorded in three individuals (7.69%) with 3 SCs (5.77%). In the control group, after 12 months, no case of decementation was recorded. No cases of peri-implantitis were detected in either group. CONCLUSION Within the limitations of this study, the authors conclude that the use of zinc oxide cement initially establishes sufficient retention of implant-supported fixed restorations independent of conventional or replica cementation techniques.

A new technique for retaining double crowns on implants via custom-positioned vertical screws.

This report describes the use of custom-positioned vertical screws (CVS) to attach primary telescopic crowns to implant abutments. In a private practice setting, 37 patients with 40 double crown-retained implant overdentures (IODs) with a clearance fit (Marburg double crowns) were followed. All primary crowns on the 120 implant abutments were retained using CVS. After a mean followup period of 3.55 ± 1.37 years (range: 1.5 to 6.3 years), one abutment screwloosening incident was reported (incidence: 0.08%). No loosening of any of the screw-retained primary crowns occurred. CVS may represent a viable fixation concept for IODs.

Increasing the Width of Keratinized Mucosa in Maxillary Implant Areas Using a Split Palatal Bridge Flap: Surgical Technique and 1-Year Follow-Up

Sufficient soft-tissue coverage of maxillary implant sites may be difficult to achieve, especially after bone augmentation. The use of vestibular flaps moves keratinized mucosa (KM) toward the palate and may be disadvantageous for future peri-implant tissue stability. This study describes a new split palatal bridge flap (SPBF) that achieves tension-free wound closure and increases the KM width in maxillary implant areas. We began SPBF surgery with a horizontal incision in the palatal soft tissue to create a split-thickness flap. The second incision was performed perpendicular to the first, using a bridge design, at a distance of 10 to 15 mm. The superior layer can be moved crestally and sutured to cover the soft-tissue defect. The defect width was measured using a periodontal probe. The inferior layer was left exposed, and secondary wound healing created new KM in this region. This SPBF technique was performed on 37 patients. Of these, 16 patients were included in the assessment of clinical peri-implant outcomes. All of the SPBF procedures successfully resulted in a palatal regeneration of KM through secondary wound healing (mean regeneration width, 4.51 ± 1.17 mm; range, 3-6 mm). The 1-year follow-up of 16 patients revealed a mean pocket probing depth of 3.22 ± 0.6 mm with zero cases of peri-implantitis. The vestibular KM width at the involved implants was 2.82 ± 1.07 mm (range, 1.5-6 mm). Surgery for SPBF may be a promising technique for covering soft-tissue defects and increasing KM width in maxillary implant surgery.

Extraoral Cementation Technique to Minimize Cement-Associated Peri-implant Marginal Bone Loss: Can a Thin Layer of Zinc Oxide Cement Provide Sufficient Retention?

This report describes the use of laboratory-fabricated crown intaglio replicas for extraorally prepared cementation of fixed restorations to implants. This technique minimizes excess cement and may therefore reduce the risk of cement-related marginal peri-implant bone loss. It is unclear whether the remaining thin layer of luting agent provides sufficient retention if low-adhesive zinc oxide (ZnO) cement is used. In 85 consecutive patients, 113 single crowns were cemented to implants using extraoral cementation technique (ECT) and ZnO cement. All patients were followed for 6 months and investigated for decementation. Seven events of decementation (incidence: 6.19%) were found in 7 patients (8.24%). ECT may represent a viable cementation technique for implant-supported single crowns, even using low-adhesion cements.