A principal components analysis: how pneumatization and edentulism contribute to maxillary atrophy.

OBJECTIVE: The aim of this retrospective cohort study was to investigate the role of sinus pneumatization and residual ridge resorption in maxillary bone loss in 400 computed tomography (CT) scans. MATERIALS AND METHODS: In 200 dentate and 200 edentulous patients, both sinuses were analysed using CT scans. The image analysis sequence consisted of manual placement of 24 reference points, followed by automated segmentation and final manual refinement. Finally, a principal components analysis was performed. RESULTS: A total of 788 sinuses were included into the analysis. The edentulous group (98 female: 67.77 ± 11.28 years, 99 male: 65.22 ± 9.87) was significantly older than the group with teeth (99 female: 46.89 ± 16.77 years, 96 male: 49.74 ± 16.2). Female and male patients did not differ regarding age. The alveolar height differed significantly between the groups (edentulous: 7.1 ± 4.3 mm, with teeth: 9.7 ± 4.1 mm), but not between gender (female: 8.3 ± 4.4 mm, male: 8.5 ± 4.4 mm). Principal components analysis was able to explain 90% of the variation in sinus morphology. CONCLUSIONS: Prolonged edentulism in the maxillary molar region leads to centripetal and to minor degrees centrifugal ridge resorption. Minor pneumatization occurs in the sinus walls, but the sinus depth underlies the anatomical variation independent of dentition.

The "puffed cheek method" to evaluate mucosal thickness: case series.

OBJECTIVES: Mucosal thickness should be considered in implant treatment planning. Needle probing to measure mucosal thickness is invasive and therefore not used in routine diagnosis. The "puffed cheek" method is an established technique to visualize the vestibule in computed tomography (CT). As CT assesses bone availability, a simultaneous mucosal thickness measurement would be useful. The aim of this study was to evaluate the reliability of mucosal thickness measurement in CT with distended cheeks. MATERIALS AND METHODS: Buccal maxillary mucosa thickness was evaluated at four measurement sites in the incisor and molar area of 11 patients. Each site was evaluated via CT with cheek distension and needle probing. Measurement area was identified with the aid of a thermoplastic splint to localize the exact position by a gutta-percha marker point. The comparison between the two methods was performed by Bland-Altman diagram. RESULTS: The mean clinical thickness was 1.17 mm (±0.31) compared to 1.11 mm (±0.31) in CT evaluation. The mean difference between the two methods was 0.07 mm (±0.40; CI-0.14;0.12, P = 0.88, Krippendorff α = 0.38). According to Bland-Altman diagram the mucosal thickness may diverge by up to 0.9 mm from the radiologic thickness. CONCLUSIONS: The two measurement methods may not be interchangeably used. As additional information to three-dimensional bone analyses, CT may be performed as a pre-operative soft tissue analysis at most implant sites with distended cheeks. Nevertheless, this method yields less valid and reliable results than the gold standard.

Trabecular bone structures in the edentulous diastema of osteoporotic sheep.

The edentulous ovine diastema represents a suitable region for implantological research. Due to distinctive embryonic origin and mechanical loading, the edentulous diastema may respond differently to osteoporosis than tooth-bearing areas. To test this assumption, we subjected geriatric sheep to ovariectomy, calcium-/vitamin-D-restricted diet, and methylprednisolone administration. Adult control sheep remained untreated. Structural parameters and bone mineral density were determined by microcomputed tomography and conventional computed tomography, respectively. We report that the trabecular microstructure in the diastema was preserved from catabolic changes. In contrast, the premolar maxillary region of osteoporotic sheep had diminished trabecular bone mineral density, with the corresponding structural deteriorations. These results suggest that maxillary trabecular bone of the edentulous diastema does not respond to catabolic changes which occur in the tooth-bearing area in osteoporosis. Our findings imply that regional anatomic domains must be considered in the planning of pre-clinical studies, taking osteoporotic changes into account.

Anatomical preconditions for the palatal sinus floor augmentation­A three-dimensional feasibility study.

OBJECTIVE: The aim of this study was to evaluate the anatomical feasibility of palatal sinus floor augmentation. MATERIAL AND METHODS: In 100 men and 100 women, both sinuses were analyzed using computed tomography. The patients were divided into four anatomical groups according to the remaining alveolar bone height: group 1 (0 ≤ × < 4), group 2 (4 ≤ × < 8), group 3 (8 ≤ × < 12), and group 4 (≥12). RESULTS: The 400 maxillary sinuses consisted of 23.5% (n = 94) group 1, 42.75% (n = 171) group 2, 23.5% (n = 98) group 3, and 9.25% (n = 37) group 4 sinuses. Optimal anatomical preconditions for palatal sinus floor augmentations (i.e., ≥5 mm height and <5 mm thickness of the window lid) were found in 93.6% of group 1 sinuses, 73.7% of group 2 sinuses, 23.5% of group 3 sinuses, and 5.4% of group 4 sinuses. CONCLUSION: The palatal approach is feasible in 93.6% of patients with remnant alveolar height of up to 4 mm. Limitations are alveolar heights of ≤5 mm as well as great palatal thickness and thus limited dimensions for a possible palatal window.

Periodontal histomorphometry and status of aged sheep subjected to ovariectomy, malnutrition and glucocorticoid application.

OBJECTIVE: Ageing, hypogonadism, malnutrition, and the application of glucocorticoids have adverse effects on skeletal homeostasis. Herein we determined to which extent the periodontium undergoes catabolic changes under these conditions in a sheep model. METHODS: Six old sheep with a mean age of 7.5+/-1.0 years were subjected to ovariectomy, calcium/vitamin D-restricted diet, and intramuscular administration of approximately 2g methylprednisolone. Six adult sheep with a mean age of 3.8+/-0.9 years remained untreated and served as controls. First and second premolars of both jaws were subjected to histological analysis. The distances from the gingival margin (GM) and from the alveolar bone crest (ABC) to the cemento-enamel junction (CEJ) were determined. Periodontal attachment was given as the ratio between the dimension of the periodontal ligament and the alveolar bone. Clinical data were collected by counting the number of teeth missing, teeth with gingival recession, and teeth with a probing depth > 4 mm. RESULTS: We report that distance between GM and CEJ (2.1+/-1.7 mm and 6.6+/-2.6mm maxilla; -0.4+/-1.4 mm and 3.2+/-1.5 mm mandible), and between ABC and CEJ (-3.4+/-1.3mm and 1.8+/-2.7 mm maxilla; -3.5+/-1.1mm and -0.1+/-1.4mm mandible) are significantly lower in test than in control animals. In line with these findings, periodontal attachment was 67% in the maxilla and 86% in the mandible of the test group and almost completely preserved in the control group. Clinical evaluation showed that the overall number of teeth with recessions was significantly higher in the test compared to the control group (4.9+/-2.4 and 2.3+/-3.6), but not the number of teeth missing and teeth with a probing depth>4mm. CONCLUSIONS: Together these findings suggest that in sheep, the cumulating effects of ageing, hypogonadism, malnutrition and glucocorticoid application can cause substantial catabolic changes of the periodontium.

Persistence of protective immunity following vaccination against tick-borne encephalitis--longer than expected?

A descriptive evaluation of protective immunity was performed on subjects with a complete primary tick-borne encephalitis (TBE) immunization (and additional regular boosters) more than 3 years after primary or booster TBE immunization, as measured by neutralization test and two different ELISA systems. The study population (n = 430) was stratified for age (i.e., 18-49 or 50 years of age) and for the number of years since last TBE vaccination. GMTs (NT) of all subgroups (at the time of the present evaluation) were above detection limit: 144 and 44 for the 18-49- and 50-year-old subjects, respectively. One percent of subjects aged 18-49 years, and 6% of subjects aged 50 years were ELISA-negative. A detailed sub analysis revealed that subjects with either low NT and/or negative to borderline ELISA test results are usually older and constitute a higher number of subjects without any TBE booster vaccination compared to the respective test-positive subject group. From the fourth year (exceeding 3 years after last vaccination) titers show a decline rate of 6-7%. This study indicates that after multiple TBE (booster) immunizations protection surpasses the currently advised TBE booster interval of 3 years, thus supporting reconsideration of the recommendations for booster intervals.

Immunogenicity and safety of a booster vaccination against tick-borne encephalitis more than 3 years following the last immunisation.

This study investigated the immune response and safety in 430 adults, when boosted more than 3 years after primary or booster TBE immunisation as measured by neutralization test (NT) and ELISA. Tested by NT, the post-booster day 21 geometric mean titer (GMT) was 331 and 142 for the 18-49 and > or =50 years old, respectively. The post-/pre-booster geometric mean titer ratio (GMR) was 2.29 for the 18-49 years old and 3.21 for the > or =50 years old. An at least four-fold increase of neutralizing TBE antibodies was observed in only 26 and 38% of subjects aged 18-49 and > or =50 years, respectively. The booster effect in subjects with only the primary vaccination course prior to study entry clearly depended on the time elapsed since last TBE vaccination with an estimated annual decline rate of 15%. In subjects with at least one additional booster vaccination virtually no antibody decline was observed. This study clearly indicates that (1) adults may be effectively and safely boosted with a different TBE vaccine and (2) following four immunisations protective antibodies can be detected far beyond a period of 3 years, thus, strongly supporting the reconsideration of currently recommended booster intervals.