A randomized controlled clinical trial comparing small buccal dehiscence defects around dental implants treated with guided bone regeneration or left for spontaneous healing.

PURPOSE: The aim of the present randomized controlled clinical study was to test whether small bony dehiscence defects (≤5 mm) left to heal spontaneously result in the same clinical and radiological outcome as defects treated with guided bone regeneration (GBR). MATERIALS AND METHODS: Twenty-two patients who received at least one implant with a small bony dehiscence defect were enrolled in the study. If the defect height was ≤5 mm, the site was randomly assigned to either the spontaneous healing (SH) group or the GBR group. In the SH group, the defect was left without any treatment. In the GBR group, the defects around the implants were grafted with deproteinized bovine bone mineral (DBBM) and covered with a native collagen membrane. Clinical and radiographic measurements were performed 6 months after implant placement with a reentry surgery and at the time of crown insertion and the subsequent follow-up appointments at 3, 6, 12 and 18 months after loading. For statistical analyses, the mixed linear model was applied for the clinical and radiographic measurements observed around the implants. Simple comparisons of the location of the measurements in the two independent groups are performed with the Mann-Whitney U-test. In addition, the mixed model assumptions were checked. RESULTS: The implant and crown survival rate 18 months after loading was 100%, revealing no serious biologic or prosthetic complication. The mean changes of the buccal vertical bone height between implant placement and reentry surgery after 6 months revealed a small bone loss of -0.17 ± 1.79 mm (minimum -4 mm and maximum 2.5 mm) for the SH group and a bone gain of 1.79 ± 2.24 mm (minimum of -2.5 mm and maximum of 5 mm) for the GBR group, respectively (P = 0.017). Radiographic measurements demonstrated a slight bone loss of -0.39 ± 0.49 mm for the SH group and a stable bone level of 0.02 ± 0.48 mm for GBR group after 18 months. All peri-implant soft tissue parameters revealed healthy tissues with no difference between the two groups. CONCLUSION: Small bony dehiscence defects left for spontaneous healing demonstrated high implant survival rates with healthy and stable soft tissues. However, they revealed more vertical bone loss at the buccal aspect 6 months after implant insertion and also more marginal bone loss between crown insertion and 18 months after loading compared to sites treated with GBR.

Surface roughness of dental implants and treatment time using six different implantoplasty procedures.

OBJECTIVES: To test whether or not one of six implantoplasty procedures is superior to the others rendering a minimal final implant surface roughness and a short treatment time. MATERIAL AND METHODS: Forty-two one-piece implants were embedded in epoxy resin blocks with 6-mm rough implant surface exposed. The following implantoplasty polishing sequences were applied: Brownie(®) , Greenie(®) sequence (BG) (diamond rotary instruments 106-, 40-, 15-µm grit, Brownie(®) , Greenie(®) silicone polishers); Arkansas stone sequence (AS) (diamond 106-, 40-, 15-µm grit, Arkansas stone torpedo-shaped bur); Short diamond sequence (SD) (diamond 106-, 40-, 4-µm grit); Short diamond sequence with Greenie(®) (SDG) (diamond 106-, 40-, 4-µm grit, Greenie(®) ); Complete diamond sequence (CD) (diamond 106-, 40-, 15-, 8-, 4-µm grit); Complete diamond sequence with Greenie(®) (CDG) (106-, 40-, 15-, 8-, 4-µm grit, Greenie(®) ). The polished neck portion served as a positive control, the untreated sandblasted and acid-etched surface as negative control. Each implant was scanned with a contact profilometer rendering Ra values and Rz values as a measure of surface roughness. The time needed to polish the implant surface for each group was recorded. Simultaneous comparisons between more than two groups were done performing Kruskal-Wallis tests. Comparisons between two groups were analysed using Wilcoxon rank-sum tests. RESULTS: Mean Ra values amounted to 0.32 ± 0.14 µm (BG), 0.39 ± 0.13 µm (AS), 0.59 ± 0.19 µm (SDG), 0.71 ± 0.22 µm (SD), 0.75 ± 0.26 µm (CDG), 0.98 ± 0.30 µm (CD), 0.10 ± 0.01 µm (PC) and 1.94 ± 0.47 µm (NC). Pairwise one-sided comparisons between the test group revealed statistically significant differences (P < 0.05). The shortest treatment time was recorded for group AS (13 ± 2 min) and the longest for CDG (21 ± 2 min) and BG (21 ± 4 min). CONCLUSIONS: Considering final surface roughness and treatment duration, the use of rotary diamond burs in decreasing roughness, followed by an arkansas stone (group AS), appears to be an optimal treatment option.

Evaluation of a biodegradable synthetic hydrogel used as a guided bone regeneration membrane: an experimental study in dogs.

OBJECTIVES: To test whether or not an experimental polyethylene glycol (PEG) membrane maintains the bone graft volume and contributes to the preservation of the ridge contour in comparison with a commercially available synthetic membrane. MATERIALS AND METHODS: In 18 dogs, all mandibular premolars and the first molars were extracted. Ten weeks later, acute standardized defects were prepared. The defects of four dogs were randomly assigned to three modalities: (1) PEG plus deproteinized bovine bone mineral (DBBM) (PEG), (2) a resorbable glycolide trimethylene carbonate membrane plus DBBM (PGA-TMC), and (3) DBBM alone (DBBM). These dogs were then sacrificed for the baseline measurements. The remaining defects of 14 dogs were randomly assigned to (1) PEG plus DBBM, (2) PGA-TMC plus DBBM, (3) DBBM, and (4) empty defect. The dogs were sacrificed at baseline (n=4), 4 weeks (n=7), or at 16 weeks (n=7). Mixed model regressions and the non-parametric Brunner-Langer method were applied for statistical analysis. RESULTS: At baseline, equal tissue augmentation was observed in all groups. At 4 and 16 weeks, the greatest augmented area fractions were calculated for PEG (103%; 107%, respectively), followed by PGA-TMC (98%; 91%), DBBM (85%; 78%), and empty (46%; 54%), being statistically significant different (P<0.001) between PEG and empty at 4 and 16 weeks, and PEG and DBBM at 16 weeks. The overall decrease (P≤0.01) in the amount of bone graft between baseline and 16 weeks was -14% (PEG), -22% (PGA-TMC), and -23% (DBBM). CONCLUSIONS: The study demonstrates that the combination of the PEG membrane with DBBM maintains the bone graft volume over time better than controls. The PEG membrane with DBBM was also the most effective method to preserve the ridge contour.

Peri-implantitis prevalence and treatment in implant-oriented private practices: a cross-sectional postal and Internet survey.

This survey aimed to estimate the subjective prevalence of peri-implantitis and its management in the private with and without board certified specialization. For this purpose, a cross-sectional postal and internet survey of 521 dentists, representing all members of the Swiss Society of Oral Implantology (SGI) was conducted (year 2010). The questionnaire consisted of four sections assessing 1) general information regarding the practice setting and education, 2) general questions regarding implantation profile and 3) specific questions regarding the prevalence and experience with the management of peri-implantitis. In the fourth section, therapy options of three exemplary cases were assessed. The data were separately evaluated and compared for specialists (S) and n₋specialists (N-S). A total of 253 questionnaires could be included in the present study. The results revealed that specialists placed significantly more implants than non-specialists. The subjective prevalence of cases with peri₋implantitis was 5-6 and 7-9% after 5 and 10 years, respectively. The polled dentists perceived periodontitis (N-S: 72%; S: 80%), smoking (N-S: 71; S: 77%) and bad compliance (S: 53; N-S: 61%) as the most important risk factors for peri-implantitis. Chlorhexidine was the most frequently used antiseptic agent for disinfection. A surgical approach to treat peri-implantitis was reported by more than 80% of all dentists. Specialists used significantly more resective or regenerative approaches than non-specialists.

A feasibility study evaluating an in situ formed synthetic biodegradable membrane for guided bone regeneration in dogs.

PURPOSE: The aim was (1) to evaluate the soft-tissue reaction of a synthetic polyethylene glycol (PEG) hydrogel used as a barrier membrane for guided bone regeneration (GBR) compared with a collagen membrane and (2) to test whether or not the application of this in situ formed membrane will result in a similar amount of bone regeneration as the use of a collagen membrane. MATERIAL AND METHODS: Tooth extraction and preparation of osseous defects were performed in the mandibles of 11 beagle dogs. After 3 months, 44 cylindrical implants were placed within healed dehiscence-type bone defects resulting in approximately 6 mm exposed implant surface. The following four treatment modalities were randomly allocated: PEG+autogenous bone chips, PEG+hydroxyapatite (HA)/tricalcium phosphate (TCP) granules, bioresorbable collagen membrane+autogenous bone chips and autogenous bone chips without a membrane. After 2 and 6 months, six and five dogs were sacrificed, respectively. A semi-quantitative evaluation of the local tolerance and a histomorphometric analysis were performed. For statistical analysis, repeated measures analysis of variance (ANOVA) and subsequent pairwise Student's t-test were applied (P<0.05). RESULTS: No local adverse effects in association with the PEG compared with the collagen membrane was observed clinically and histologically at any time-point. Healing was uneventful and all implants were histologically integrated. Four out of 22 PEG membrane sites revealed a soft-tissue dehiscence after 1-2 weeks that subsequently healed uneventful. Histomorphometric measurement of the vertical bone gain showed after 2 months values between 31% and 45% and after 6 months between 31% and 38%. Bone-to-implant contact (BIC) within the former defect area was similarly high in all groups ranging from 71% to 82% after 2 months and 49% to 91% after 6 months. However, with regard to all evaluated parameters, the PEG and the collagen membranes did not show any statistically significant difference compared with sites treated with autogenous bone without a membrane. CONCLUSION: The in situ forming synthetic membrane made of PEG was safely used in the present study, revealing no biologically significant abnormal soft-tissue reaction and demonstrated similar amounts of newly formed bone for defects treated with the PEG membrane compared with defects treated with a standard collagen membrane.

A method to identify new molecular markers for assessing minimal residual disease in acute leukemia patients.

Acute leukemias (AL) comprise a heterogeneous group of hematologic malignancies, and individual patient responses to treatment can be difficult to predict. Monitoring of minimal residual disease (MRD) is thus very important and holds great potential for improving treatment strategies. Common MRD targets include recurrent cytogenetic abnormalities and mutations in important hematological genes; unfortunately well-characterized targets are lacking in many AL patients. Here we demonstrate a technical approach for the identification and mapping of novel clone-specific chromosomal abnormalities down to the nucleotide level. We used molecular cytogenetics, chromosome microdissection, amplification of the microdissected material, and next-generation sequencing to develop PCR-based MRD assays based on unique breakpoint sequences.

A randomized, controlled clinical evaluation of a synthetic gel membrane for guided bone regeneration around dental implants: clinical and radiologic 1- and 3-year results.

PURPOSE: The objective of this study was to determine whether a synthetic bioresorbable polyethylene glycol (PEG) hydrogel membrane could provide similar clinical and radiographic outcomes as a standard collagen membrane, both in combination with a membrane-supporting material, during follow-up periods of 1 and 3 years. MATERIALS AND METHODS: This study enrolled patients requiring implant treatment with an expected osseous defect in the posterior maxilla or mandible. Defects around the implants were grafted with deproteinized bovine bone mineral and covered with either a collagen membrane or a PEG hydrogel membrane, which is applied as a liquid and becomes a solid gel in situ. Surgical re-entry was performed after 6 months, and fixed partial dentures were inserted subsequently. Patients were examined clinically and radiographically 1 and 3 years after loading. RESULTS: Thirty-six of the 37 included patients were reexamined in the third year. The implant survival rate at 3 years was 100%. The peri-implant tissues were healthy, with no differences between the two groups. Compared to the time of surgery, the mean changes in the distance between the first bone-to-implant contact to the transition point (ie, rough implant surface to polished neck portion) were 0.43 ± 0.56 mm (PEG) and 0.21 ± 0.36 mm (collagen) at 1 year and 0.61 ± 0.89 mm (PEG) and 0.33 ± 0.64 mm (collagen) at 3 years. The respective differences between groups were 0.13 mm (1 year) and 0.31 mm (3 years), which were not significant at either time point (analysis of covariance). CONCLUSION: The tested PEG hydrogel was as successful as a standard collagen membrane for the treatment of bony dehiscence defects around dental implants after follow-up periods of 1 and 3 years.

Use of a new cross-linked collagen membrane for the treatment of peri-implant dehiscence defects: a randomised controlled double-blinded clinical trial.

PURPOSE: The aim of this randomised controlled double-blinded clinical trial was to determine the efficacy of a new cross-linked membrane (VN) in guided bone regeneration (GBR) around exposed dental implants compared to a native collagen membrane (BG). MATERIAL AND METHODS: A total of 16 patients in need of implant treatment at two different sites with osseous defects were planned for this split-mouth study. After inserting the dental implants, peri-implant defects were treated according to the GBR technique using a VN membrane with prolonged resorption time in the randomised test site and a BG membrane in the control site. After a healing time of 6 months, mucoperiosteal flaps were elevated for the evaluation of the primary (vertical bone fill [ΔDL] and quality of newly formed tissue [QT]) and secondary outcome variables (infrabony defect height [DH], defect width [DW], defect depth [DD] and augmentation depth [AD]) and the sampling of biopsies apical to the implant shoulder. RESULTS: A total of 16 patients fulfilled the initial non-surgical inclusion and exclusion criteria. However, the study was discontinued early after 9 surgically treated patients because unacceptable safety issues arose and severe infection related to the VN membranes. The VN membrane revealed statistically significantly more soft tissue dehiscence than the BG membrane (56% and 11%, respectively, P = 0.0455). In 3 of these 9 patients the VN membrane had to be removed due to infection early after the first follow-up visit. For the statistical analyses these sites were designated as the value of the baseline. The mean ΔDL values were 1.8 ± 1.6 mm at the VN site and 4.7 ± 3.3 mm at the BG site. The ΔDD values were 0.6 ± 1.0 mm and 1.1 ± 1.2 mm, respectively, and reached statistical significance (P = 0.0208, CI 95% = -2.9 [-5.2;-0.6]). The corresponding linear defect fill (DF) values were 44% and 78%, respectively. The clinical assessment of QT showed comparable median values at sites treated with VN (3, interquartile range: 0; 3.5) and BG (3, interquartile range: 3; 4) without statistical significance. The histomorphometric analysis showed an average area density of 24.4% (SD 10.3, range 8-35%) newly formed bone at the test sites and of 35.0% (SD 20.6, range 8-60%) at the control sites. The histological data showed only some trends and did not reach statistical significance. CONCLUSION: In the present study, the VN membranes with prolonged resorption time demonstrated significantly more adverse events and insufficient bone regeneration compared to the native BG membranes and no advantages in favour of the VN membranes were detectable.

New cytogenetically visible copy number variant in region 8q21.2.

BACKGROUND: Cytogenetically visible unbalanced chromosomal abnormalities (UBCA), reported for >50 euchromatic regions of almost all human autosomes, are comprised of a few megabases of DNA, and carriers are in many cases clinically healthy. It may be speculated, that some of the UBCA may be similar or identical to copy number variants (CNV) of the human genome. RESULTS: Here we report on a yet unreported cytogenetically visible copy number variant (CNV) in the long arm of chromosome 8, region 8q21.2, detected in three unrelated clinically healthy carriers. CONCLUSION: The first description of a cytogenetically visible CNV/UBCA in 8q21.2 shows that banding cytogenetics is far from being outdated. It is a cost efficient, up-to-date method for a single cell specific overview on the whole genome, still prepared to deliver unexpected findings.