Assessment of peri-implant tissue dimensions following surgical therapy of advanced ligature-induced peri-implantitis defects.

BACKGROUND: To evaluate peri-implant tissue dimensions following implantoplasty and/or regenerative therapy of advanced ligature-induced peri-implantitis in dogs. MATERIAL AND METHODS: At all defect sites (n = 6 dogs, n = 48 implants), the intrabony component was filled with a particulate bovine-derived natural bone mineral (NBM). The supracrestal component was treated by either the application of an equine bone block (EB) or implantoplasty. In a split-mouth design, NBM and EB were soak-loaded with rhBMP-2 or sterile saline. All sites were covered using a native collagen membrane and left to heal in a submerged position for 12 weeks. The horizontal mucosal thickness (hMT) and bone thickness (hBT) were measured at four reference points: (v0) at the level of implant shoulder (IS), (v1) 50% of the distance IS-bone crest (BC), (v2) at the BC, and (v3) at the most coronal extension of the bone-to-implant contact. RESULTS: The general tendency indicated a gradual increase in hMT from the IS (v0) toward BC (v2), which was more pronounced at implant sites treated with the regenerative approach. The hBT values increased from v2 to v3, with the highest values at the v3 region measured for implant sites treated with adjunctive rhBMP-2. For sites treated with implantoplasty, the linear regression model demonstrated an inverse correlation between hMT and hBT, whereas a positive correlation was observed at those sites treated with the regenerative approach. CONCLUSION: Horizontal soft and hard tissue dimensions were similar among different treatment groups.

Assessment of soft and hard tissue dimensions following different treatment approaches of ligature-induced peri-implantitis defects.

OBJECTIVES: To evaluate peri-implant tissue dimensions following nonsurgical (NS) and surgical therapy (S) employing different decontamination protocols of advanced ligature-induced peri-implantitis in dogs. MATERIAL & METHODS: Peri-implantitis defects (n = 5 dogs, n = 30 implants) were randomly and equally allocated in a split-mouth design to NS or S treatment using either an Er:YAG laser (ERL), an ultrasonic device (VUS), or plastic curettes + local application of metronidazole gel (PCM), respectively. Horizontal bone thickness (hBT) and soft tissue thickness (hMT) were measured at different reference points: (v0) at the marginal portion of the peri-implant mucosa (PM); (v1) at 50% of the distance from PM to bone crest (BC); (v2) at the BC; (v3) at the most coronal extension of the bone-to-implant contact. Vertical peri-implant tissue height was calculated from PM to BC. RESULTS: All of the treatment groups showed a gradual hMT increase from v0 to the v2 reference point, followed by a reduction from v2 to the v3 region. The S-VUS subgroup tended to be associated with higher hMT values at the v0 region than the NS-VUS subgroup (0.44 mm versus 0.31 mm). PM-BC distance varied from 2.22 to 2.83 mm in the NS group, and from 2.07 to 2.38 in the S group. CONCLUSION: Vertical and horizontal peri-implant tissue dimensions were similar in different treatment groups.

Volumetric assessment of tissue changes following combined surgical therapy of peri-implantitis: A pilot study.

AIM: To assess volumetric tissue changes at peri-implantitis sites following combined surgical therapy of peri-implantitis over a 6-month follow-up period. MATERIALS AND METHODS: Twenty patients (n = 28 implants) diagnosed with peri-implantitis underwent access flap surgery, implantoplasty at supracrestally or bucally exposed implant surfaces and augmentation at intra-bony components using a natural bone mineral and application of a native collagen membrane during clinical routine treatments. The peri-implant region of interest (ROI) was intra-orally scanned pre-operatively (S0), and after 1 (S1) and 6 (S2) months following surgical therapy. Digital files were converted to standard tessellation language (STL) format for superimposition and assessment of peri-implant volumetric variations between time points. The change in thickness was assessed at a standardized ROI, subdivided into three equidistant sections (i.e. marginal, medial and apical). Peri-implant soft tissue contour area (STCA) (mm2 ) and its corresponding contraction rates (%) were also assessed. RESULTS: Peri-implant tissues revealed a mean thickness change (loss) of -0.11 and -0.28 mm at 1 and 6 months. S0 to S1 volumetric variations pointed to a thickness change of -0.46, 0.08 and 0.4 mm at marginal, medial and apical regions, respectively. S0 to S2 analysis exhibited corresponding thickness changes of -0.61, -0.25 and -0.09 mm, respectively. The thickness differences between the areas were statistically significant at both time periods. The mean peri-implant STCA totalled to 189.2, 175 and 158.9 mm2 at S0, S1 and S2, showing a significant STCA contraction rate of 7.9% from S0 to S1 and of 18.5% from S0 to S2. Linear regression analysis revealed a significant association between the pre-operative width of keratinized mucosa (KM) and STCA contraction rate. CONCLUSIONS: The peri-implant mucosa undergoes considerable volumetric changes after combined surgical therapy. However, tissue contraction appears to be influenced by the width of KM.

Histomorphometrical assessment of vertical alveolar ridge augmentation using extracted tooth roots in the canine.

OBJECTIVES: To histomorphometrically evaluate the influence of autoclavation on the efficacy of extracted tooth roots (TR) used for vertical alveolar ridge augmentation. MATERIALS AND METHODS: Upper premolars were randomly assigned to either autoclavation (TR-A) or an untreated control group (TR-C) and used as block grafts for vertical alveolar ridge augmentation in both lower quadrants (n = 4 beagle dogs). Tissue biopsies were obtained after 15 weeks of submerged healing. Histological analyses considered gain in ridge height (GRH), augmented area (AA), and the proportion of mineralized (MT) and non-mineralized tissue (NMT). RESULTS: TR-C and TR-A grafts were commonly associated with a complete replacement resorption and a marked gain in ridge height. Significant differences between groups were noted for mean GRH [TR-C: 2.35 ± 0.55 vs. TR-A: 2.46 ± 0.21 mm] and AA [TR-C: 11.88 ± 4.31 vs. TR-A: 8.65 ± 1.59 mm2] values. Within AA, both groups revealed a comparable distribution of mean MT and NMT values. The linear regression analysis pointed to a significant correlation between NMT and AA values. CONCLUSIONS: Both TR-C and TR-A grafts supported vertical alveolar ridge augmentation; however, GRH was improved in the TR-A group. CLINICAL RELEVANCE: TR grafts may serve as a potential alternative for vertical alveolar ridge augmentation.

Evaluation of precision and accuracy assessment of different 3-D surface imaging systems for biomedical purposes.

Three-dimensional (3-D) surface imaging has gained clinical acceptance, especially in the field of cranio-maxillo-facial and plastic, reconstructive, and aesthetic surgery. Six scanners based on different scanning principles (Minolta Vivid 910®, Polhemus FastSCAN™, GFM PRIMOS®, GFM TopoCAM®, Steinbichler Comet® Vario Zoom 250, 3dMD DSP 400®) were used to measure five sheep skulls of different sizes. In three areas with varying anatomical complexity (areas, 1 = high; 2 = moderate; 3 = low), 56 distances between 20 landmarks are defined on each skull. Manual measurement (MM), coordinate machine measurements (CMM) and computer tomography (CT) measurements were used to define a reference method for further precision and accuracy evaluation of different 3-D scanning systems. MM showed high correlation to CMM and CT measurements (both r = 0.987; p < 0.001) and served as the reference method. TopoCAM®, Comet® and Vivid 910® showed highest measurement precision over all areas of complexity; Vivid 910®, the Comet® and the DSP 400® demonstrated highest accuracy over all areas with Vivid 910® being most accurate in areas 1 and 3, and the DSP 400® most accurate in area 2. In accordance to the measured distance length, most 3-D devices present higher measurement precision and accuracy for large distances and lower degrees of precision and accuracy for short distances. In general, higher degrees of complexity are associated with lower 3-D assessment accuracy, suggesting that for optimal results, different types of scanners should be applied to specific clinical applications and medical problems according to their special construction designs and characteristics.

Assessment of surgically assisted rapid maxillary expansion regarding pterygomaxillary disjunction using thin volume-rendering technique: in variance analysis and in reliability, accuracy, and validity.

PURPOSE: To assess surgically assisted rapid maxillary expansion (SARME) with or without pterygomaxillary disjunction using a thin volume-rendering technique in variance analysis and in reliability, accuracy, and validity. MATERIALS AND METHODS: Thin volume-rendered images of 68 patients were evaluated preoperatively and 2.87 ± 1.59 months after expansion with respect to dentoskeletal effects. RESULTS: Variance analysis of SARME with pterygomaxillary disjunction showed an important decrease in transverse widening and segmental outward inclination and an increase in vestibular bone plate thickness (premolars) in patients younger than 20 years with bone-borne devices; the greatest increase in transverse widening was in patients with 3-segment osteotomy and tooth-borne devices. Analysis of SARME without pterygomaxillary disjunction showed an important decrease in transverse widening and segmental inward inclination in patients older than 20 years with bone-borne devices; the greatest pterygoid lateral bending was in patients with 2-segment osteotomy and bone-borne devices. CONCLUSION: The performance of pterygomaxillary disjunction should depend on patient age (ie, treatment with pterygomaxillary disjunction in those >20 years old; treatment without pterygomaxillary disjunction in those <20 years old). Patients with pterygomaxillary disjunction, 3-segment osteotomy, and tooth-borne devices tended to show an increase in transverse widening but at the price of greater attachment loss. Patients younger than 20 years with pterygomaxillary disjunction and bone-borne devices tended to show an increase in vestibular bone plate (premolars) but at the price of decrease in transverse widening.

Quantitative scanning acoustic microscopy compared to microradiography for assessment of new bone formation.

Recently, it has been shown that quantitative scanning acoustic microscopy (SAM) is a powerful tool to image the acoustic impedance of even inhomogeneous materials like bone. Therefore, the aim of our study was to compare SAM to conventional microradiography with respect to histomorphometrical assessment of undecalcified sections of newly formed bone. Forty specimens were harvested 12 weeks after implantation of either autogenous cancellous bone graft or 5.0 mg of Osteogenic Protein-1 (BMP-7) in a critical-sized defect model in sheep. Undecalcified transverse bone sections of 500 microm thickness were investigated with conventional microradiography and SAM. Linear regression analysis was carried out to compare the measurements of the area of new bone formation within the defect sites. Both methods allowed for good discrimination between newly formed bone and cortical bone at the edges of the former defect. Images obtained with SAM revealed a better resolution and sharpness compared to that of microradiographs since SAM imaging unlike microradiography does not depend on the thickness of bone sections. The results of quantitative histomorphometric analysis obtained by both methods showed no significant differences, and it was possible to predict 90% of the variability of each method (coefficient of determination r2 = 0.90; P < 0.0001). In conclusion, SAM offers comparable quantitative histomorphometric information with a better spatial resolution than conventional microradiography. Thus, SAM is a promising new micro-visualizing technique for basic bone research.