Healing differences in narrow diameter implants submitted to immediate and conventional loading in mandibular overdentures: A randomized clinical trial.

BACKGROUND: Biological responses to different loading protocols during the bone healing phase in subjects with long time since edentulism, rehabilitated with narrow diameter implants (NDIs) to retain mandibular overdentures (MOs), are still unavailable. OBJECTIVE: This randomized clinical trial compared the peri-implant health, implant stability, and concentrations of pro- and anti-inflammatory cytokines in the peri-implant crevicular fluid (PICF) in mandibular edentulous patients under conventional (CL) and immediate loading (IML) during healing. METHODOLOGY: Twenty totally edentulous patients received two NDIs (2.9 × 10 mm, Facility NeoPoros) placed in mandible anterior region and were randomly assigned to two loading protocols: CL (n = 10) and IML (n = 10). The following clinical outcomes were evaluated 1, 2, 4, 8, and 12 weeks after surgery: (a) peri-implant tissue health (gingival index-GI, plaque index-PI, calculus-presence CP, probing depth-PD, and bleeding on probing-BOP); (b) implant stability quotient (ISQ); and (c) IL-1ß, IL-6, IL-10, and TNF-α levels in the PICF analyzed by ELISA. RESULTS: The CL group showed significantly higher CP scores at weeks 8 and 12. The IML group showed significantly higher GI from the first week onwards. The IML group presented significantly lower PD at all follow-up times, and higher BOP rates than CL at week 12. The ISQ values of the CL group were higher than those of the IML group, except at week 4. The IML group released significantly more TNF-α between weeks 1 and 4 and more IL-1ß during week 4-12, while releasing less IL-6 until week 8, mainly at week 2 (-47.6%). The release of IL-10 was similar for both groups and increased progressively over time. At week 12, the IML group released 45.74% more IL-10 than the CL group. The survival rates were 95% and 90% for CL and IML, respectively. CONCLUSION: The IML group presented more favorable PD at all evaluation times; the differences between the other clinical parameters were less systematic. The implant stability and the inflammatory marker concentrations were more stable in the CL group.

Analysis of correlation between height of residual ridge and bone density of residual ridge crest at edentulous mandible using computed tomography.

PURPOSE: The aim of this study was to investigate the correlation between bone density of the edentulous mandibular ridge crest and residual bone height in edentulous subjects using multidetector computed tomography (MDCT) images. METHODS: A total of 194 bilateral MDCT images from 97 individuals with an edentulous mandible were selected for analysis. The residual ridge ratio (RRR), the CT values at the residual ridge crest, and the CT values at the lowest point of the mandible measured from MDCT images at molar region. RRR was classified into the three groups (Group 1: >2.0, Group 2: 1.5-2.0, Group 3: <1.5). Bone density at the residual ridge crest was evaluated by calculating the ratio of the CT value at the lowest point of the mandible and the CT value of the residual ridge crest ("ratio of CT values"). The relationship between the height of the residual ridge and the bone density of the residual ridge crest was evaluated by ratio of CT values. RESULTS: Median ratio of CT values was 0.62 in Group 1, 0.70 in Group 2, and 0.84 in Group 3, indicating significant differences between all 3 groups (p<0.05). The correlation coefficient for RRR and residual ridge crest bone density was -0.54 in males and -0.55 in females, implying a moderate correlation for both males and females. CONCLUSIONS: The present results suggest a negative correlation between residual bone height and the bone density of the edentulous mandibular ridge crest.

The mandibular ridge oral mucosa model of stromal influences on the endothelial tip cells: an immunohistochemical and TEM study.

This study aimed to evaluate by immunohistochemistry and transmission electron microscopy (TEM) the morphological features of the oral mucosa endothelial tip cells (ETCs) and to determine the immune and ultrastructural patterns of the stromal nonimmune cells which could influence healing processes. Immune labeling was performed on bioptic samples obtained from six edentulous patients undergoing surgery for dental implants placement; three normal samples were collected from patients prior to the extraction of the third mandibular molar. The antibodies were tested for CD34, CD117(c-kit), platelet derived growth factor receptor-alpha (PDGFR-α), Mast Cell Tryptase, CD44, vimentin, CD45, CD105, alpha-smooth muscle actin, FGF2, Ki67. In light microscopy, while stromal cells (StrCs) of the reparatory and normal oral mucosa, with a fibroblastic appearance, were found positive for a CD34/CD44/CD45/CD105/PDGFR-α/vimentin immune phenotype, the CD117/c-kit labeling led to a positive stromal reaction only in the reparatory mucosa. In TEM, non-immune StrCs presenting particular ultrastructural features were identified as circulating fibrocytes (CFCs). Within the lamina propria CFCs were in close contact with ETCs. Long processes of the ETCs were moniliform, and hook-like collaterals were arising from the dilated segments, suggestive for a different stage migration. Maintenance and healing of oral mucosa are so supported by extensive processes of angiogenesis, guided by ETCs that, in turn, are influenced by the CFCs that populate the stromal compartment both in normal and reparatory states. Therefore, CFCs could be targeted by specific therapies, with pro- or anti-angiogenic purposes.

Bone metabolism of residual ridge beneath the denture base of an RPD observed using NaF-PET/CT.

PATIENT: A 66-year-old woman, who had a bilateral free-end edentulous mandible and no experience with dentures, was examined for the chief complaint of masticatory dysfunction on left side of dental arch. A unilateral distal extension removable partial denture (RPD) replacing lower-left molars was selected. Tomographic images were obtained using Fluorine-18 NaF positron emission computerized tomography (NaF-PET)/computed tomography (CT) before the RPD use and at 1, 6, and 13 weeks after the RPD use to observe the metabolic changes in residual bone caused by the RPD use. PET standardized uptake values (SUVs) and CT values were calculated for lower-left edentulous site (test side) and lower-right edentulous site (control side). As a result, SUVs on the control side remained static after the RPD use, whereas those on the test side increased at 1 and 6 weeks after the RPD use and then decreased. However, CT images showed no obvious changes in the bone shape and structure beneath RPD, and CT values both on the control and test sides did not change either. DISCUSSION: This report shows that NaF-PET could detect bone metabolic changes soon after the RPD use, which cannot be detected by clinical X-rays. The SUV changes may be a mechanobiological reaction to the pressure due to the RPD use, and wearing of the RPD may increase the bone turnover beneath denture. CONCLUSION: This report demonstrates that wearing of an RPD increases bone turnover beneath denture immediately after the RPD use without clinically detectable changes in bone structure or volume.

Growth-associated protein-43 immunoreactivity in human oral mucosa in dentate subjects, in edentulous patients and after implant-anchored rehabilitation.

OBJECTIVES: This study investigates expression of the neural growth-associated protein 43 (GAP-43) in the oral mucosa of (A) normal dentate subjects, (B) edentulous patients rehabilitated with conventional denture and (C) those rehabilitated with mandibular implant-retained overdentures (MIR-OVD), in the long term. This study evaluates morphological changes in the distribution and representation of sensory terminations and corpuscles in the alveolar mucosa under the action of different masticatory or prosthetic loads, in the three clinical groups. MATERIAL AND METHODS: GAP-43 immunoreactivity (-ir) was compared with the distribution of nerves fibres in the mucosa, as visualised using anti-protein gene product 9.5 (PGP 9.5), a general marker for peripheral nerves and terminals. RESULTS: GAP-43-ir was found to be highly expressed in the corium and submucosa in specimens from edentulous subjects wearing conventional denture and presenting a reduced number of PGP 9.5-ir nerves in the mucosa, but not in specimens from control subjects or patients wearing MIR-OVD, which on the contrary show a higher number of PGP 9.5-ir mucosal sensory fibres. CONCLUSION: As the mucosa under traditional denture has been shown to possess reduced innervation and the histological aspect of chronic overloading, these results may be considered indicative of a tentative induction to nerve re-growth in the under-innervated epithelium, or as a response to chronic inflammation. The detection of GAP-43-ir suggests that human oral mucosa presents signs of potential nerve plasticity also in the elderly, and that the type of rehabilitation and the condition of masticatory load transfer to the mucosa have important effects on the nerves underneath.

[Effects of copper melting production on the composition and characteristics of oral fluid]. / Vliianie neblagopriiatnykh faktorov medeplavil'nogo proizvodstva na sostav i svoistva rotovoi zhidkosti.

Industrial air of copper-melting factory in Almalyk contains a considerable quantity of copper and antioxidant elements (selen and zinc) in combination with poor quantity of prooxidants (ferrum, cobolt, chrome). The workers saliva contains increased concentrations of selen and zinc resultant in lowering intensity of free radical oxidation of lipids in the saliva and subnormal activity of antioxidant system's enzymes. Increased hydroperoxides quantity was discovered in saliva of patients with partial secondary adentia accompanied by hyper activity of antioxidant system's enzymes.

Glycosaminoglycans in peri-implant sulcus fluid from implants placed in sinus-inlay bone grafts.

Glycosaminoglycans (GAG) present in peri-implant sulcus fluid (PISF) were used as an indicator of the metabolic activity in the supporting tissues of implants placed in maxillary bone or maxillary bone and bone grafts together. The study included 16 patients who received implants (Brånemark system(R)) and sinus-inlay bone grafts. In 12 of these patients, the implants were placed in either maxillary bone alone or maxillary bone and sinus-inlay bone grafts in combination. Altogether the patients received a total of 102 implants, of which 73 implants were placed in bone grafts and 29 implants in maxillary bone alone. Samples of PISF were tested at 2-8 days and at 6 months after abutment connection. Levels of the GAG's chondroitin-4-sulphate (C4S) and hyaluronan (HA) were assessed using cellulose acetate electrophoresis and densitometric scanning of Alcian blue-stained strips against known GAG standards. The C4S was used as a bone metabolic marker, and HA was used to reflect the progress of soft tissue healing. Comparing grafted and non-grafted regions, there was no significant difference in either C4S levels or HA levels during the first 8 days or at the 6 months period. The levels of HA from the first week collection did not differ significantly from the HA level after 6 months in either type of bone. However, the level of C4S was significantly lower after 6 months than during the first week, in both maxillary and grafted bone but consistent with a normal metabolic turnover. C4S can therefore be used as an indicator of the progressive healing of bone adjacent to implants.

A pilot study of mineralization distribution in the cortical bone of the human mandible.

Twenty-three specimens from immediately anteroinferior to the mental foramen were obtained from male and female, dentate and edentate, human mandibles. Planoparallel 80 microm thick sections were prepared from the mandibular specimens and computerized quantitative microradiography undertaken, which allowed the production of mineralization frequency distribution curves and mean mineralization. No differences in mean mineralization with age, sex, presence or absence of dentition were found, but mineralization distribution curves indicated differences between males and females. Within the age range and small sample size examined (40-90 years) there were no age-related differences. There was a lower level of mineralization distribution in the edentulous than the dentate mandible.

[Bone mineral density (BMD) distribution in edentulous mandible--a measuring system for bone mineral content with computed radiography (CR)].

The purpose of this study was to develop a measuring system for bone mineral density(BMD) using computed radiography and to measure BMD distribution in the edentulous mandible. Nine 2-3 mm thick sequential cross-sectional bone slices were obtained from five cadaveric mandibles. Each slice in cross-sectional view on X-ray image was divided into 64 elements and BMD distribution was investigated. The results were as followed: 1. BMD measuring system: The accuracy was 1.4%(relative error) and the reproducibility was 1.1%(CV). 2. BMD distribution in edentulous mandible: 1) BMD varied from slice to slice, decreasing from anterior to posterior in both cortical and cancellous bone on the inferior and lingual side. The BMD of buccal cancellous bone was relatively higher than that of the lingual side and remained fairly constant throughout. The BMD of buccal cortical bone showed a slight posterior increase. 2) Greater individual variation of BMD was observed near mental foramen and in incisor lingual and inferior cancellous bone. Our system demonstrated excellent precision and reproducibility BMD distribution varied near regions of muscle attachment and the mandibular canal. Further, it was suggested that strong implant stability in the molar region may be obtained by installation of the fixtures in the buccal cancellous area.

Mineral density in the mandibles of partially and totally edentate postmenopausal women.

Mineral density of the cortical bone in four regions and the spongiosa distal from the mental foramen of the mandible was determined by quantitative computed tomography (QCT) for 77 postmenopausal, 48-56-yr-old women. Of these women, 42 were totally edentulous and 35 had teeth in region d35-d45. The bone mineral densities of different regions of these two groups were compared. Mineral density of the cortical bone on lingual and buccal sides, distal from the mental foramen, was significantly higher among those who had been edentate 12-23 yr than among dentate subjects. No differences were found between those who had been edentate less than 12 or over 23 yr and the dentate group. This study indicates that muscular activity during different phases of edentulousness regulates the density of bone in regions where muscles are attached.

The mandibular bone mineral content in relation to vestibulolingual sulcoplasty. A 2-year follow-up.

The bone mineral content (BMC) in mandibles can now be measured in vivo with high precision by a specially constructed dual-photon scanner. This study analyzed, over a 2-year period, the BMC loss of endentulous mandibles in a group of young and older women after vestibulolingual sulcoplasty with free skin grafts, and its relationship to the initial mandibular BMC and the age-related mandibular BMC loss. BMC in the denture-wearing site and the standard site of the mandible was measured by this method. A significant negative relationship was found between the initial BMC values in the standard site and the BMC loss (in percent) in the denture-wearing site in both age groups, and a significant positive relationship between the BMC loss (in percent) in the two sites of the mandible in the elder group. The rate of residual ridge reduction may be predicted from the initial mandibular BMC value and seems to be dependent on the age-related mandibular BMC loss.

Intraoral hydrolysis of monofluorophosphate.

The intraoral hydrolysis of monofluorophosphate (MFP) was compared in nine subjects with natural teeth and in nine edentulous subjects after a 1-min mouthrinse with a 100 ppm MFP solution. Analyses of total F and F- in whole saliva samples collected up to 15 min after the rinse suggested that apatite catalyzed breakdown of MFP mediated by dental enamel contributes significantly to the intraoral hydrolysis of MFP.

Palatal mucosa under dentures: a qualitative histologic and histochemical analysis.

These histologic observations of the epithelium and connective tissue are in close agreement with a host of earlier workers. The striking feature is an increase in thickness of epithelium due to an increase in constituent cell layers, but a decrease in keratinization, with keratin mainly of the parakeratinized variety. There is a definite reduction of collagen fiber network in regions of stress where the fibers present an irregular arrangement in contrast to the normal wavy pattern. Marked chronic inflammatory exudate is also seen. Histochemical investigation of the connective tissue under dentures revealed the presence of a highly elastic and resistant oxytalan fiber network, especially in regions that showed a reduction in collagen fibers. Thus the connective tissue response under dentures is in sharp contrast to what is expected. This abnormal behavior of the connective tissue is probably a reaction to the changes in epithelium. As a result of reduction in keratinization, a highly resistant and protective layer, the connective tissue exhibits altered metabolism and function. We hypothesize that connective tissue takes up a more dominant role of protection and absorption of stress, a role hitherto fulfilled by the epithelium. Thus stresses exerted by dentures on connective tissues are prevented from reaching the bone where they could cause resorption. We therefore feel that denture wear not only results in change within the epithelium, but in an equally significant reaction of the connective tissue. This reaction results in the appearance of a highly resistant and elastic oxytalan fiber system, which assists the connective tissue to react successfully to the stresses exerted on it.