A Systematic Review on Organ-on-a-Chip in PDMS or Hydrogel in Dentistry: An Update of the Literature

Organs-on-a-chip (OoCs) are microfluidic devices constituted by PDMS or hydrogel in which different layers of cells are separated by a semipermeable membrane. This technology can set many parameters, like fluid shear stress, chemical concentration gradient, tissue-organ interface, and cell interaction. The use of these devices in medical research permits the investigation of cell patterning, tissue-material interface, and organ-organ interaction, mimicking the complex structures and microenvironment of human and animal bodies. This technology allows us to reconstitute in vitro complex conditions that recapitulate in vivo environments. One of the main advantages of these systems is that they represent a very realistic model that, in many cases, can replace animal experimentation, eliminating costs and related ethical issues. Organ-on-a-chip can also contain bacteria or cancer cells. This technology could be beneficial in dentistry for testing novel antibacterial substances and biomaterials, performing studies on inflammatory disease, or planning preclinical studies. A significant number of publications and reviews have been published on this topic. Still, to our knowledge, they mainly focus on the materials used for fabrication and the different patterns of the chip applied to the experimentations. This review presents the most recent applications of organ-on-a-chip models in dentistry, starting from the reconstituted dental tissues to their clinical applications and future perspectives.

Stress-strain and fatigue life numerical evaluation of two different dental implants considering isotropic and anisotropic human jaw

Dental prostheses are currently a valid solution for replacing potential missing tooth or edentulism clinical condition. Nevertheless, the oral cavity is a dynamic and complex system: occlusal loads, external agents, or other unpleasant events can impact on implants functionality and stability causing a future revision surgery. One of the failure origins is certainly the dynamic loading originated from daily oral activities like eating, chewing, and so on. The aim of this paper was to evaluate, by a numerical analysis based on Finite Elements Method (FEM), and to discuss in a comparative way, firstly, the stress-strain of two different adopted dental implants and, subsequently, their fatigue life according to common standard of calculations. For this investigation, the jawbone was modeled accounting for either isotropic or anisotropic behavior. It was composed of cortical and cancellous regions, considering it completely osseointegrated with the implants. The impact of implants' fixture design, loading conditions, and their effect on the mandible bone was finally investigated, on the basis of the achieved numerical results. Lastly, the life cycle of the investigated implants was estimated according to the well-established theories of Goodman, Soderberg, and Gerber by exploiting the outcomes obtained by the numerical simulations, providing interesting conclusions useful in the dental practice.

Oral Healthcare and Idiopathic Thrombocytopenic Purpura: Early Recognition, Dental Management and Case Report

A 47-year-old Caucasian man, in good general, oral and periodontal health, presented with a non-bleeding bluish lesion on the back of his tongue, presumably due to an ecchymotic area of traumatic origin which was left untreated. The day after, other ecchymotic-type lesions on the mucous membranes of the cheeks and the upper lip, a bleeding lesion at the apex of the tongue and gingivorrhagia, along with petechiae on the back, scalp, lower limbs and feet, occurred, with rapid clinical deterioration, requiring immediate hospitalization. Oral, dermatological, and hematological evaluations lead to idiopathic thrombocytopenic purpura (ITP) diagnosis and hydrocortisone prescription, with a complete recovery in the next few days.The presented case of ITP, with early intra-oral manifestations, aimed both to emphasize the role of oral healthcare workers in theearly recognition of ITP, which may be especially relevant for those cases with extremely fast platelet depletion, high risk of internal bleeding and consequent potentially fatal complications, and in the differential diagnosis of the diseasethat may be aided by the diagnostic protocol described, and to provide dentists with recommendations on oral care management of cases of ITP, both in dental and multi-disciplinary settings.

Evidence-based Recommendations on Periodontal Practice and the Management of Periodontal Patients During and After the COVID-19 Era: Challenging Infectious Diseases Spread by Airborne Transmission

Background:

Periodontal care, which was completely suspended during the peak of the SARS-Cov-2 pandemic and was delayed and recurrently discontinued during the succeeding waves, must be safely provided in the COVID-19 era.

Objectives:

The study aimed to provide recommendations on periodontal practice, optimizing safety, ergonomics, and economic resources, and the management of periodontal patients, ensuring continuity, timing, and effectiveness of periodontal care in the COVID-19 era.

Methods:

Reported protocols for the dental practice in the context of the COVID-19 and current evidence on periodontitis treatment and prevention were reviewed.

Results:

Evidence-based recommendations on contamination control and ergonomic improvements for periodontal practice and the management of periodontal patients challenging COVID-19 and airborne infectious diseases have been provided.

Conclusion:

Due to the economic, ergonomic, and ethical concerns raised by limited periodontal care due to the SARS-Cov-2 pandemic, and awareness of other emerging airborne transmitted infections, the periodontal practice should integrate measures minimizing airborne cross-infections and optimizing time-space and economic resources. The management of periodontal patients in the COVID-19 era should comprise less complex treatments and more comprehensive and definitive approaches, reducing emergencies, session length and number, and, concurrently, extending the recall and maintenance intervals. Moreover, it should implement prevention strategies through teledentistry tools and apps, improving periodontal awareness and self-care, and also through the self-reporting of periodontitis and periodontal risk assessment tools, performing both “population-based” and “high-risk” surveillance of periodontitis. Finally, it should enhance inter-professional collaboration, through telehealth networks, especially targeting subjects at high-risk of both periodontitis and systemic disorders, each of the two variously linked to COVID-19 onset and worsening.

Vitamin C Acutely Affects Brain Perfusion and Mastication-Induced Perfusion Asymmetry in the Principal Trigeminal Nucleus

Prolonged mastication may induce an asymmetric modification of the local perfusion of the trigeminal principal nucleus. The aim of the present study was to evaluate the possible influence of vitamin C (vit. C) on such effect. Four groups of healthy volunteers underwent arterial spin labeling magnetic resonance imaging (ASL-MRI) to evaluate the local perfusion of the trigeminal nuclei after a vit. C-enriched lunch or a control lunch. Two ASL-MRI scans were acquired, respectively, before and after a 1 h-long masticating exercise or a 1 h long resting period. The results showed (i) an increased global perfusion of the brain in the vit. C-enriched lunch groups, (ii) an increased local perfusion of the right principal trigeminal nucleus (Vp) due to mastication, and (iii) a reduction of the rightward asymmetry of the Vp perfusion, due to mastication, after the vit C-enriched meal compared to the control meal. These results confirmed a long-lasting effect of prolonged mastication on Vp perfusion and also suggest a possible effect of vit. C on cerebral vascular tone regulation. Moreover, the data strongly draw attention on the side-to-side relation in Vp perfusion as a possible physiological parameter to be considered to understand the origin of pathological conditions like migraine.

Possible Association of Periodontal Disease and Macular Degeneration: A Case-Control Study

Oral pathogens have been identified in bioptic specimens from Age-Related Macular Degeneration (ARMD) patients, and alveolar bone loss has been related to ARMD. Therefore, the possible association between ARMD and periodontal disease was investigated in the present case-control study, evaluating clinical and radiographic periodontal parameters, primarily, in cases vs. controls and, secondarily, in relation to ARMD risk factors, in cases, to highlight a possible pathogenic link between the disorders. Forty ARMD cases and 40 non-ARMD controls, matched for age (±3 years) and gender and homogeneous for ARMD risk factors, therefore comparable, underwent full-mouth periodontal charting, panoramic radiograph, and medical data, including ARMD risk factors, collection. Statistical analysis was conducted using the language R. Comparisons between groups were made using both traditional t-tests and Yuen’s test with bootstrap calibration. Enrolled subjects were ≥55 years old, and 50 females and 30 males were equally distributed among the two groups. No statistically significant difference was found in clinical and radiographic periodontal parameters in cases vs. controls. In the case group, no differences were found when relating the periodontal parameters to ARMD risk factors, except for Clinical Attachment Level values that were statistically significantly higher in hypertensive ARMD subjects. A possible association between periodontal disease and ARMD may be hypothesized in hypertensive ARMD subjects, with hypertension as a possible pathogenic link between the disorders.

The Association between Periodontitis and Human Colorectal Cancer: Genetic and Pathogenic Linkage

Periodontitis has been associated with an increased risk of and mortality associated with human colorectal cancer (CRC). Current evidence attributes such an association to the direct and indirect effects of virulence factors belonging to periodontal pathogens, to inflammatory mediators and to genetic factors. The aims of the study were to assess the existence of a genetic linkage between periodontitis and human CRC, to identify genes considered predominant in such a linkage, thus named leader genes, and to determine pathogenic mechanisms related to the products of leader genes. Genes linking periodontitis and CRC were identified and classified in order of predominance, through an experimental investigation, performed via computer simulation, employing the leader gene approach. Pathogenic mechanisms relating to leader genes were determined through cross-search databases. Of the 83 genes linking periodontitis and CRC, 12 were classified as leader genes and were pathogenically implicated in cell cycle regulation and in the immune-inflammatory response. The current results, obtained via computer simulation and requiring further validation, support the existence of a genetic linkage between periodontitis and CRC. Cell cycle dysregulation and the alteration of the immuno-inflammatory response constitute the pathogenic mechanisms related to the products of leader genes.

Antibiotic's effectiveness after erupted tooth extractions: A retrospective study

OBJECTIVE

The purpose of this retrospective study was to assess the influence of antibiotics on the development of alveolitis after tooth extractions.

MATERIALS AND METHODS

The study population consisted of patients who had erupted tooth extractions in 3 centers. The patients' medical records were collected for several parameters. Moreover, use of antibiotics was evaluated. The primary outcome was the development of alveolitis during the postoperative period. The secondary outcome measure was the possible associations between alveolitis and other patients' characteristics.

RESULTS

A total of 1579 patient charts were screened. The patients enrolled in the study were 418 (159 males and 259 females). Alveolitis was reported for 12 extraction sites (2.87%). Six were in the group of patients that received antibiotics (2.14% out of 280 patients treated with antibiotics), and six were in the group of patients that did not receive antibiotics (4.35% out of 138 patients not receiving antibiotics). None of patient-level parameters showed any significant association with the development of alveolitis.

CONCLUSION

In conclusion, this study showed that the use of antibiotics after erupted tooth extractions is not useful in preventing alveolitis. Larger, prospective, and randomized studies are needed before incorporating these findings into the daily clinical practice.

Obesity and Periodontal Disease: A Narrative Review on Current Evidence and Putative Molecular Links

Background:

Obesity represents one of the main health problems worldwide and is considered a risk factor for several diseases, including periodontitis, which is a microbially-associated inflammatory disease affecting the tooth-supporting structures.

Objective:

The aim of this review was to report the current direct and indirect evidence concerning the possible association between obesity and periodontitis and their putative molecular links.

Methods:

A literature search was conducted between January 1999 and September 2019, in PubMed/MEDLINE and Science Direct databases, using pertinent keyword combined by Boolean operators. Through a multi-step screening process (literature search; articles title and abstract evaluation and full-text reading), studies fitting inclusion/exclusion criteria were considered for the review.

Results:

35 studies were included in the present review (17 observational studies; 7 systematic reviews; 11 systematic reviews with meta-analysis), focusing on the direct and indirect evidence of the possible association between obesity and periodontitis and their potential etiopathogenic molecular links

Conclusion:

Although the majority of the studies reported a positive association between obesity and periodontitis, the heterogeneity of the classification criteria and of the clinical parameters employed in the studies for both obesity and periodontitis evaluation, complicated the comparison of the results, thus considered inconclusive. Although several putative molecular pathogenic links between obesity and periodontitis have been highlighted, further studies, with longer follow-ups and with homogeneous clinical criteria, are needed to better understand the putative relation between obesity and periodontal disease.

A 5-year longitudinal cohort study on crown to implant ratio effect on marginal bone level in single implants

BACKGROUND

A 5-year longitudinal cohort study was carried out to evaluate the influence of anatomical crown to implant ratio (CIR) on peri-implant marginal bone level (MBL) in single implants.

MATERIALS AND METHODS

The longest possible implants, according to the availability of pristine bone, were inserted, one per patient, among periodontally healthy teeth in consecutively recruited subjects. CIR and MBL changes were measured on standardized radiographs. The relationship between MBL and multiple predictors was investigated. A statistical analysis suitable for mixed type distributions was conducted: for the discrete component a logistic regression model was used and for the continuous component the impact of the variables on MBL was examined by using robust nonparametric comparison tests.

RESULTS

Seventy-eight dental implants were inserted in 34 mandibles and 44 maxillae, with one stage procedure in 40 cases and two stage in 38 cases. Thirty-five implants were <10 mm, while 43 were ≥ 10 mm long; 28 implants had a CIR ≤1 and 50 had a CIR >1. No drop-outs or implant loss were observed. Bone loss occurred only in a few cases, measuring less than 0.5 mm and being significantly more pronounced for implant length ≥10 mm, for lower CIR values and for the two stage procedure.

CONCLUSION

Higher CIR values were not related to increased peri-implant bone loss; a <10 mm long implant insertion may be safely considered for reduced bone heights.

Computed tomography-aided descriptive analysis of maxillary and mandibular atrophies

INTRODUCTION

The aim of the present retrospective chart review was to analyze by Computed Tomography (CT) scan technique the degree of maxillomandibular atrophies, searching for differences between totally- and partially-edentulous subjects, and possibly identify and classify maxillomandibular atrophy staged patterns for implant planning in both totally- and partially- edentulous jaws.

MATERIAL AND METHODS

CT scans of 89 mandibles and 77 maxillae from 111 patients were classified according to six different patterns of residual ridge resorption and to two different groups of edentulism (totally- and partially-edentulous). Maxillomandibular absolute linear dimensions were calculated and results compared for statistically significant differences by Wilcoxon tests.

RESULTS

Maxillomandibular CT cross-section interpretation showed different patterns of linear bone remodelling (height values) between the two groups of edentulism joined with specific positions in the maxilla or mandible. The judgment of the investigator was uncertain in the analysis of the mandibular posterior areas with similar percentages for both totally- and partially-edentulous groups (12.5% and 11.5%, respectively).

DISCUSSION

The 3D analysis is self-explanatory and easy to apply, aided by CT scans. The measurements between the referring planes and inviolable anatomical structures (nasal floor NFD, lower border of mandible LBD, inferior alveolar nerve AND, and sinus floor SFD), showed that class III may not guarantee an optimal implant placement, especially in the totally-edentulous group, due to a major degree of pneumatisation.

Focus on periodontal disease and colorectal carcinoma

Diagnosis of focal disease, the theory that the human oral microbial (HOM) could affect the onset and development of systemic diseases, was very popular in the past, but the lack of scientific evidence has led to the abandonment of this idea. Interestingly, increasing evidence over the past 3 or so decades suggests that HOM can indeed serve as a reservoir for systemic dissemination of pathogenic bacteria and their toxins in distant body sites, favouring the developments of malignant tumours. Malignant tumours are complex communities of oncogenically transformed cells with aberrant genomes, associated non-neoplastic cells including immune and stromal cells, and sometimes HOM, including bacteria and viruses. Recent data suggest that HOM and periodontal disease play an active role in the pathogenesis of colorectal cancer, in fact HOM has been found within the colorectal cancer microenvironment, and the composition of the HOM was different from that of adjacent non-neoplastic tissue. An association of fusobacterium nucleatum with the colonic mucosa of colorectal cancer has been proven. Several questions thus arise. Is periodontal disease a risk factor for colorectal carcinoma? Given the connectivity of the digestive tract, could fusubacterium nucleatum or other HOM be involved in additional gastrointestinal disorders? Furthermore, based on the "mobility" of Fusubacterium nucleatum and the omnipresence of cadherins, could this organism be involved in cancers beyond the gastrointestinal tract? Answers to these questions will shed new lights on the role of the HOM in onset of diseases.

Evaluation of volumetric dimensional changes in posterior extraction sites with and without ARP using a novel imaging device

BACKGROUND

Alveolar ridge volume loss may be minimized when postextraction sockets are filled by bone substitutes.

PURPOSE

The aim of the study was to measure the effect of alveolar ridge preservation (ARP) in maintaining the external contour of the ridge after fresh socket grafting with or without particulate anorganic bovine bone mineral (BBM) and resorbable barrier covering.

MATERIALS AND METHODS

In the present controlled study, patients subjected to single-tooth extraction were allocated to 2 groups: postextraction sockets grafted with bovine bone mineral (bbm), and naturally healing sockets (nat). Before and at 5 months following tooth extraction, plaster cast contours of the sockets were acquired by means of an optical scanner; the 2 contours of each patient underwent voxelization and fusion using a matrix elaborator. Outcome variables at 5 months (volumetric, surface, and linear changes) were measured in digital fused plaster casts with a dental scan software analyzing a volume of interest ranging from residual papilla to 10 mm toward the apical point. Intra- and inter-group pair-wise variables' comparisons were conducted. Level of significance was set at 0.05.

RESULTS

Twenty-four sites were enrolled: 12 ARP and 12 naturally healed. Five-month percentage of volume loss of the bbm-group (21.7% ± 7.4%) was significantly lower (Ps < .0003) than that of the naturally healing group (38.8% ± 7.9%). When tooth position was investigated, volume loss in percentage registered a significantly better (P values ≤ .0485) behavior in molars (ΔV% = -19.1% ± 6.5% and ΔV% = -35.6% ± 7.6%, respectively, for bbm and nat) than that in premolars (ΔV% = -26.9% ± 7.2% and ΔV% = -45.1% ± 4.2%, respectively, for bbm and nat), in both the preserved and naturally healing groups.

CONCLUSION

The dimensional loss in postextraction sockets grafted with anorganic bovine bone substitute and covered by a resorbable collagen barrier was lower than that of the naturally healing sites. However, ridge preservation was able to maintain almost 80% of the pristine bone.

Mastication induces long-term increases in blood perfusion of the trigeminal principal nucleus

Understanding mechanisms for vessel tone regulation within the trigeminal nuclei is of great interest because some headache syndromes are due to dysregulation of such mechanisms. Previous experiments on animal models suggest that mastication may alter neuron metabolism and blood supply in these nuclei. To investigate this hypothesis in humans, arterial spin-labeling magnetic resonance imaging (MRI) was used to measure blood perfusion within the principal trigeminal nucleus (Vp) and in the dorsolateral-midbrain (DM, including the mesencephalic trigeminal nucleus) in healthy volunteers, before and immediately after a mastication exercise consisting of chewing a gum on one side of the mouth for 1 h at 1 bite/s. The side preference for masticating was evaluated with a chewing test and the volume of the masseter muscle was measured on T1-weighted MRI scans. The results demonstrated that the mastication exercise caused a perfusion increase within the Vp, but not in the DM. This change was correlated to the preference score for the side where the exercise took place. Moreover, the basal Vp perfusion was correlated to the masseter volume. These results indicate that the local vascular tone of the trigeminal nuclei can be constitutively altered by the chewing practice and by strong or sustained chewing.

Five-year outcome of bone remodelling around implants in the maxillary sinus: assessment of differences between implants placed in autogenous inlay bone blocks and in ungrafted maxilla

The placement of implants in the posterior maxillary area is considered a reliable procedure, offering recognized rehabilitative advantages. The aim of this study was to evaluate the performance of dental implants placed in the sinus floor augmented with a block autograft by comparing the outcomes over 5 years with those of dental implants positioned in non-augmented bone. This retrospective cohort study included 16 patients who had undergone prosthetic rehabilitation supported by dental implants between 2000 and 2006. One implant per patient was included and assigned to one of two predictor groups: grafted versus ungrafted maxillary sinus. Changes in marginal bone level (MBL) and apical bone level (ABL) over time, at 1, 3, and 5 years, were the primary outcome variables. Appropriate pair-wise comparison tests were performed. No significant differences were seen with regard to ABLs and among times between the grafted group (nine implants) and the ungrafted group (seven implants). Significant marginal bone resorption was found over time, primarily at the buccal aspect, in both study groups. The bone surrounding the apex of dental implants appeared stable after sinus augmentation in the grafted area. The behaviour of the two groups with regard to loss of MBLs over time was very similar.

A 5-Year Implant Follow-Up in Maxillary and Mandibular Horizontal Osseous Onlay Grafts and Native Bone

The purpose of this study is to analyze marginal bone levels (MBLs) around dental implants positioned in the upper and lower jaw with or without horizontal onlay grafting procedures, and to survey implant survival with a follow-up of 5 years. Seventeen patients were surveyed in the present retrospective chart review. A total of 27 dental implants positioned in pristine bone and 21 in horizontally grafted bone were enrolled. MBLs were recorded for 4 aspects during a radiologic survey of 5 years. Significant differences were searched for among times and surgical procedures with paired and unpaired comparison tests, respectively, and survival rates were calculated for the 2 groups. In the maxilla, no statistically-significant differences between pristine and augmented groups were obtained; the time comparisons for pristine implants showed an affection of palatal, mesial, and distal sides, whereas the resorption around implants placed into horizontally grafted bone of anterior maxilla seemed to be limited just to buccal and distal aspects. Comparisons with the pristine horizontal procedure revealed that just the buccal sides were involved. The analysis of time comparisons attested to a continuous alveolar bone remodeling during the entire time of the survey for the pristine group. Given the extremely unfavorable resorption at the buccal aspect of the augmented areas, clinicians should reserve dental implant positioning into horizontal bone graft to selected patients, in whom it may represent one of the last opportunities of rehabilitation with a fixed prosthesis.

A 5-year clinical and computerized tomographic implant follow-up in sinus-lifted maxillae and native bone

OBJECTIVES

The present study analysed apical and marginal bone remodelling around dental implants placed in both maxillary (sinus elevated with particulated autogenous osseous graft) and corresponding native bone areas, with a follow-up of 5 years. The clinical survival of implants was also observed.

MATERIALS AND METHODS

In this retrospective chart review, 27 patients were enrolled, with 55 dental implants inserted from 2000 to 2006, 26 of which were followed (one implant per patient); if required, patients were treated via sinus lift with autogenous bone and particulate technique. The internal controls were implants positioned in native areas beneath the sinus. Radiologic survey was assessed via computerized tomographic analysis measuring apical bone level (ABL) and marginal bone level (MBL), at 1- (T1 ), 3- (T2 ) and 5 years (T3 ), around implants (buccal, b; palatal, p; mesial, m; and distal sides, d). Clinical probing depth (CPD) and clinical attachment level (CAL) for all the four peri-implant aspects were measured. Cumulative survival rate (CSR) and survival rate (SR) of implants were calculated. Significances for paired and unpaired comparisons were searched for.

RESULTS

A significant degree of apical resorption was recorded between T1 and T3 for the mesial particulate group; again, a significant difference was discovered between the native and particulate procedures for mABL. A further feature was discovered for the particulate procedure, for which ABLs resulted negative at least for three of the aspects. Regarding MBL measurements, similar behaviours were revealed using time-comparison analysis for the two procedures at the buccal aspect. Comparisons among diameters, irrespective of the procedure, showed that resorption times for the bMBL were shorter as the diameter of the implant became wider. The implant CSR was 92% in native areas (two failures/25 implants) and 93.3% in sinuses lifted with particulate bone (two failures/30 implants).

CONCLUSIONS

The results suggest that a protrusion of the implant apices into augmented sinus lift occurred, whereas the bone remodelling of the coronal areas was not influenced by the events in the maxillary sinus. A diameter ranging from 4 to 5 mm might better guarantee a conservation of marginal peri-implant bone level compared with implants with smaller diameters.

Volumetric changes after sinus augmentation using blocks of autogenous iliac bone or freeze-dried allogeneic bone. A non-randomized study

OBJECTIVES

To compare volumetric bone changes after sinus augmentation for implant positioning using blocks of autogenous iliac bone or freeze-dried allogeneic bone (FDBA) from the hip. Variables were compared between the two sources and for each surgical procedure at set times (pre- and post-augmentation procedure).

PATIENTS AND METHODS

A non-randomized retrospective chart review of 7 patients who had autogenous and 7 allogeneic block grafts was carried out (1 procedure per patient). Analysis of Computer Tomographic (CT) data of maxillary sinuses, acquired with high-speed, double-detector CT scanner, was performed using dentascan software. The change between the preoperative (T0) and postoperative volume was measured at 4-6 months (T2) and 1.5 year after transplantation (T3). Annual- and overall-rates of bone change were calculated for the two sources.

RESULTS

All patients were partially edentulous with a residual maxillary floor thickness in the planned implant insertion sites of 2.7 (0.5) mm and 2.8 (0.5) mm for allogeneic and autogenous procedures respectively. From identical intraoperative volume of grafts (2.25 cc at T1), volumetric changes were recorded at T2 and T3. The final volume of the grafts was 1.44 cc for allogeneic group and 1.78 cc for the autogenous group. Significant volumetric changes over time of transplanted grafts for both sources (23% for autograft and 18% for allograft) were found at T2. At 1.5-years post-operatively comparisons of volumes and rates of bone loss between sources were not statistically significant. No failure was recorded for either bone grafts or dental implants.

CONCLUSIONS

Short-term sinus grafting procedure for dental implant placement performed with FDBA showed an outcome close to that reported for autogenous bone. Volumetric changes were comparable between the sources. These data suggest that performing maxillary sinus augmentation with dry-preserved bone allogeneic materials in block form could be considered even when the residual floor thickness is less than 3 mm.

Volume changes of iliac crest autogenous bone grafts after vertical and horizontal alveolar ridge augmentation of atrophic maxillas and mandibles: a 6-year computerized tomographic follow-up

PURPOSE

To evaluate by computerized tomography the long-term volume resorption of autogenous corticocancellous grafted bone harvested from the ilium and used in an alveolar augmentation procedure followed by endosseous dental implant placement.

PATIENTS AND METHODS

Eleven maxillary grafts (8 positioned horizontally) and 13 mandibular grafts (10 positioned vertically) were placed in 16 patients. Using software programs, pre- and postsurgical computerized tomographic scans were used to compare volumes of grafts over time (up to 6 yr) to determine the annual percentage of remaining bone and the overall percentage of bone resorption that could be expected. Yearly measurements of volumes and percentages of remaining bone were then compared statistically.

RESULTS

At the 6-year survey for blocks grafted in the mandible, an average resorption rate of 87% was obtained; for maxillary grafts at the same survey, complete resorption of the grafts (mean, 105.5%) was recorded. In general, bone resorption appeared slow, except for that recorded in the first 2 years of healing, the only period in which statistical comparisons among all time points showed significant differences for all variables.

CONCLUSIONS

Volumetric measurements of the grafts and their related percentages of remaining bone attested to a progressive and unavoidable bone resorption of almost all the grafted bone in the maxilla and mandible. Although the present data were from a heterogeneous group of defects treated with horizontal and vertical procedures, clinicians, when performing alveolar bone augmentation with an autogenous hip bone, should aim at titanium dental implant osseointegration, not only in the augmented bone but also in the native bone below the graft.

A comparative volumetric study of symphysis donor defects, unfilled or filled with bone substitute

OBJECTIVES

Background Intraoral autogenous bone grafts are a convenient source of bone in reconstruction of the residual ridge before dental implant placement.

PURPOSE

The aim of this study was to evaluate bone volume of symphysis donor defects filled with bone substitute compared with unfilled symphysis donor defects.

PATIENTS, MATERIALS AND METHODS

The study included 26 patients who underwent either alveolar ridge reconstruction or maxillary sinus elevation. Two groups were studied: symphyseal donor defects filled with bone substitute and unfilled symphyseal donor defects. Pre- and postoperative volumetric variables were determined using computed tomography scans and the software program SimPlant® (Materialise Dental Italia, Roma, Italy).

RESULTS

At 6 months postsurgery, the filled donor defects exhibited a significant increase in bone volume compared with unfilled donor defects (97.7% and 73.4%, respectively). At 18 months postsurgery, volume of unfilled donor defects was reevaluated with no significant increase in bone volume.

CONCLUSIONS

Six months following block harvesting procedure, filled donor defects maintained bone volume, while unfilled donor sites generated defects that cannot achieve full regeneration; even not 18 months postblock harvesting.

Apical and marginal bone alterations around implants in maxillary sinus augmentation grafted with autogenous bone or bovine bone material and simultaneous or delayed dental implant positioning

OBJECTIVE

A re-pneumatization phenomenon was recorded in sinuses grafted with different materials. The specific aims of this paper were to assess the dental implant survival rate and the behavior of marginal and apical bone remodeling around dental implants placed following sinus augmentation.

MATERIALS AND METHODS

A retrospective study was conducted on consecutive patients treated in two surgical centers. Different surgical techniques were adopted for sinus augmentation: simultaneous or delayed dental implant insertion with bovine bone-material augmentation or autologous bone grafting (chin and iliac crest). Survival rates were recorded for the overall number of implants (patients of group A). Apical and marginal bone levels (ABL and MBL, respectively) were radiographically measured, and statistical analysis was performed in implants of a subgroup of patients (group B).

RESULTS

A total of 282 dental implants were positioned. Recorded cumulative survival rates (CSRs) were 95.6% and 100% for autogenous and bovine bone material, respectively, while CSRs at 2-year follow-up for immediate and delayed procedures were 99.3% and 96.5%. For the subgroup B, 57 sinus augmentation procedures were performed in 39 patients, with the positioning of 154 implants. Generally, the apical- and marginal-bone resorption of the bovine bone-material group was less than that of the autogenous group. The differences between the ABL values of the bovine bone-material and iliac-crest groups were statistically significant at 1 year, whereas this significance disappeared at the 2-year follow-up; tests showed that a statistical difference was recorded in the bovine bone-material group between the 1- and 2-year follow-ups. With regard to MBL comparisons between simultaneous and delayed implantation, the differences maintained their significance at the 2-year follow-up also.

CONCLUSIONS

Differences regarding apical bone alteration between autogenous bone from the iliac crest and bovine bone material at the 1- and 2-year follow-ups, as well as in the bovine bone-material group between the 1- and 2-year follow-ups, attested to slower but more prolonged physiologic bone remodeling in the bovine-graft-material group than in the autogenous-bone group. The MBL analysis showed that remodeling in the delayed implant group demonstrated a greater resorption in the cervical portion than was seen in the simultaneous implant group.

Scanning Electron Microscopy Fractography Analysis of Fractured Hollow Implants

Fracture of the implant is one of the possible complications affecting dental implants; it is a rare event but of great clinical relevance. The aim of the present study was to perform a scanning electron microscopy (SEM) fractography evaluation of 7 International Team for oral Implantology (ITI) hollow implants removed because of fracture. The most common clinical risk factors, such as malocclusion, bruxism, and cantilevers on the prosthesis, were absent. Seven fractured ITI hollow implants were retrieved from 5 patients and were analyzed with the use of SEM. SEM analysis showed typical signs of a cleavage-type fracture. Fractures could be due to an association of multiple factors such as fatigue, inner defects, material electrochemical problems, and tensocorrosion.

Gene clustering analysis in human osseous remodeling

BACKGROUND

Tentative bioinformatic predictions were performed to comprehend the complexity of the gene interaction networks of the T lymphocyte cell cycle and of human periodontitis. This study aims to identify and rank genes involved in osseous augmentation or bone remodeling to obtain groups with more numerous predicted associations called the leader gene clusters.

METHODS

An iterative search (consisting of a consecutive expansion-filtering loop) was performed for which only genes involved in a specific process were identified. For each gene, predicted associations with all other involved genes were obtained from a Web-available database (Search Tool for the Retrieval of Interacting Genes/Proteins) and the weighted number of links (WNL), given by the sum of only high-confidence predicted associations (results with a score > or =0.9), allowing gene ranking. Genes belonging to higher clustering classes were identified.

RESULTS

A total of 161 genes potentially involved in bone-volume augmentation and 128 genes connected with the bone-remodeling phenomenon were identified. For the bone-volume augmentation process, only one gene belonged to the leader gene group, whereas six other genes were classified as cluster B genes; for the bone-remodeling phenomenon, three leader genes were identified, whereas six other genes formed the cluster B group. No one gene belonged to leader gene clusters of both processes, whereas one gene of each higher cluster group belonged to the immediately lower cluster of the opposite process. Only three genes of the higher clusters were experimentally involved in both analyses.

CONCLUSIONS

A de novo identification was performed based on the data mining of leader genes involved in bone-volume augmentation or bone remodeling to acquire primeval information about their molecular basis and to plan future ad hoc targeted experiments. For several genes of the upper clusters, an active role in the bone processes was already known, but the present analysis suggested that they play a major role in the analyzed phenomena. The role of the transcription factors as leader genes and the numerous orphan genes (genes with WNL = 0) recovered probably attest to a lack of information regarding these processes, which could be further clarified through specific DNA microarray experiments.

Volume changes of autogenous bone grafts after alveolar ridge augmentation of atrophic maxillae and mandibles

The aim of the present retrospective chart review was to determine the relationship between nonvascularized osseous graft remodeling and the three-dimensional (3D) features of grafts and recipient sites, the anatomical recipient regions and different graft sources. 32 iliac crest or chin grafts were onlay-positioned in the mandible or maxilla of 14 patients. CT scans, taken before implant positioning and after 1 year, revealed a mean volume resorption of 35-51%. For iliac crest grafts, the average resorption was 42% when the onlay was positioned in the anterior maxilla and 59% when it was positioned in the posterior mandible. Spearman correlation and 3D interpolation analysis revealed, for both iliac crest groups, a moderate or advanced remodeling pattern depending on 3D features, namely graft thickness and shape, basal bone volume of recipient site, and the basal bone/graft volume ratio of the recipient site. No statistically significant differences were found between the recipient and donor site groups. Retrospective analysis of the data indicates that iliac crest grafts, onlay-positioned on adequate basal bone volume, may register a reduced volume remodeling when shaped thick in the anterior maxilla or rounded and convex, on the external surface, in the posterior mandible.

Implant survival in maxillary and mandibular osseous onlay grafts and native bone: a 3-year clinical and computerized tomographic follow-up

PURPOSE

This article discusses a 3-year retrospective survey of implant clinical survival and computerized tomographic analysis of bone remodeling in atrophic alveolar crests reconstructed via various autogenous bone grafting procedures and in similar regions of native bone.

MATERIALS AND METHODS

The retrospective chart review included consecutive edentulous patients with severe alveolar crest atrophy treated between 2000 and 2002 with onlay autogenous bone grafts in the mandible and anterior maxilla (as needed) and implant insertion. Implant recipients were followed for 3 years. Defective areas were reconstructed by bone graft harvested from the chin or iliac crest. Implants in reconstructed areas were divided into two groups according to graft source. Implants in corresponding native areas served as controls. Cumulative survival rate (CSR), survival rate, and confidence interval (CI) were calculated, and linear measurements of bone remodeling around implants were assessed on computerized tomographic scans. Results were compared for statistically significant differences by Wilcoxon signed-rank test with a significance level a = .05.

RESULTS

Forty patients were treated with 109 screw-type, root-form, rough-surfaced implants inserted in 48 onlay grafts; 88 implants were placed in native bone. The implant 3-year CSRs were 98.9% (CI 96.7% to 100%) in native bone and 99.1% (CI 97.3% to 100%) in onlay grafts, irrespective of bone source. Mean resorption in the maxilla was 4.6 +/- 0.9 mm buccally and 3.8 +/- 0.8 mm palatally in areas reconstructed with chin grafts, 3.4 +/- 1.7 mm buccally and 2.6 +/- 1.4 mm palatally in areas reconstructed with iliac crest grafts, and 3.2 +/- 1.2 mm buccally and 2.1 +/- 0.9 mm palatally in native areas.

CONCLUSIONS

Similar implant CSRs were seen in native and grafted sites. Maximal implant CSR was observed in onlay grafts from the chin despite more marked linear bone remodeling in this group as compared to iliac crest grafts or native bone.

Implant success in sinus-lifted maxillae and native bone: a 3-year clinical and computerized tomographic follow-up

PURPOSE

The present study was a 3-year follow-up evaluation of implant clinical success and radiographic bone remodeling in sinus floors elevated with different autogenous bone-grafting procedures and in similar native bone regions.

MATERIALS AND METHODS

This retrospective chart review examined consecutive edentulous patients with severe jaw atrophy treated between 2000 and 2002 via sinus lift, when needed, and implant insertion. Implants in sinus lift areas were divided into four groups by graft source (iliac crest, chin area) and technique (bone block, particulate). Implants positioned in native areas beneath the sinus floor served as controls. The cumulative success rate (CSR) and success rate (SR) were calculated, and linear measurements of bone remodeling around implants were assessed on computerized tomographic scans. Results were statistically compared with the Wilcoxon signed rank test.

RESULTS

Twenty-eight patients were treated in the posterior maxilla via insertion of 70 screw-type, root-form, rough implants in 39 sinus-lifted areas. All surgical procedures were uneventful. Twenty-four implants were positioned in native areas beneath the sinus floor. The implant CSR was 95.8% in native areas (one failure/24 implants), 85% in sinuses lifted with particulate chin bone (three failures/20 implants), and 100% in the other three groups (eight in particulate iliac crest, 20 in chin block, and 22 in iliac crest block). Computerized tomographic scans revealed that bone remodeling around apices caused implants to bulge into the sinuses in both particulate bone graft groups. Crestal remodeling around implant necks was similar for all groups.

CONCLUSIONS

The use of particulate chin bone grafts in sinus lift procedures does not seem to yield optimal outcomes. Milled iliac crest and chin bone tends to remodel around the implant apices, leading to bulging within the sinuses. Grafting sinuses with either chin or.iliac crest bone blocks yields the highest implant success rates and stable sinus floors.

Histological and clinical survey of polylactic-polyglycolic acid and dextrane copolymer in maxillary sinus lift: a pilot in vivo study

Of various proposed alternatives to autogenous bone, a synthetic, degradable copolymer of PLA-GLA and dextrane seems to be a promising biomaterial for maxillary sinus lift. Consecutive partially edentulous patients showing severe monolateral posterior maxillary atrophy were treated via sinus lift using PLA-GLA-dextrane copolymer as the sole filler. Delayed implant positioning was performed and cores of regenerated tissues and native bone controls were retrieved and evaluated by light and electron microscopy, histomorphometry, microhardness and qualitative X-ray analysis. Seven sinuses in 7 patients were augmented with PLA-GLA-dextrane copolymer. Six to nine months after the copolymer 'graft', 17 bone cores were retrieved: all histological sections contained newly synthesized, mineralized material and new bone in various stages of development. Histomorphometry revealed average Trabecular Bone Volume (TBV) values ranging from 51% (6 months) to 77% (9 months). Backscattered scanning electron microscopy (BSE) in experimental and control samples confirmed histology findings. Microhardness values suggested newly formed bone at nine months was not as hard as native bone. Ca and P content was similar in 9-month regenerated and native bone. Seventeen implants were inserted in the second stage of surgery: resulting Implant Success (SR) and Cumulative Success (CSR) up to 3 years were 100% following Albrektssons criteria. Sinus lift augmentation using PLA-GLA-dextrane copolymer as the sole filler resulted in uneventful surgeries. New bone formation was evident histologically and its maturation was still in progress after 9 months. Successful, staged implant positioning was achieved in regenerated tissue.

Ribozymes: analytical solution of the one-substrate, two-intermediate reversible scheme for enzyme reactions

The paper presents a kinetic analysis of a reversible enzymatic reaction Sright arrow over left arrowP involving two intermediate compounds under the condition [E](0) >> [S](0) + [P](0). For the case of mono-exponential behavior, we derive an equation for k (obs) as a function of [E](0), which emphasizes the pitfalls of oversimplifying kinetic schemes (such as the Michaelis-Menten model) for ribozyme studies. This novel apparent rate constant, which has been arrived at through mechanistic considerations, is analyzed, and the characteristic parameters obtained. The equation, which seems to fit experimental data better than conventional approximations, is used to analyze a single turnover study on an ADC1 ribozyme drawn from hepatitis delta virus RNA. The microscopic kinetic constants for such enzyme are evaluated and its mono-exponential behavior verified.

Langerhans' cell histiocytosis: a case report of an eosinophilic granuloma of the mandible treated with bone graft surgery and endosseous titanium implants

Eosinophilic granuloma is the localized and most benign form of Langerhans' cell histiocytosis. The disease shows a particular predilection for the head and neck region and usually involves the skull bones, where it manifests as well-defined lytic lesions on standard radiographs. The case of an extensive lesion involving the body of the mandible in a 52-year-old man is reported. Operative procedures consisted of enucleation of the lytic lesion and follow-up with clinical examinations and computerized tomographic studies of the mandible at 2, 12, and 18 months postoperatively. Reconstructive surgery without radiotherapy was performed with an autologous bone graft from the iliac crest and implant placement to provide support for a dental restoration.

A clinical study of the outcomes and complications associated with maxillary sinus augmentation

PURPOSE

The aim of this study was to evaluate the rate of complications in maxillary sinus augmentation surgery and the impact of complications on subsequent implant treatment in a patient population with severe maxillary atrophy scheduled for treatment under general anesthesia.

MATERIALS AND METHODS

The study population consisted of 70 patients (124 sinuses) with severe maxillary atrophy who underwent maxillary sinus augmentation. Sixteen patients were scheduled to have a unilateral procedure and 54 patients a bilateral procedure. Sinus augmentation was performed with autogenous bone alone in 93 sinuses; in 31 sinuses, a 1:1 mixture of autogenous bone and corticocancellous pig bone particles was used. Twenty-six of 124 procedures involved both sinus augmentation and autogenous block grafting for the treatment of severely atrophic maxillae.

RESULTS

The most common intraoperative complication was the perforation of the sinus membrane, which was observed in 31 sinuses (25%). Seven (5.6%) sinuses in 7 patients exhibited suppuration of the maxillary sinus. Five of the 7 patients with sinus infection were smokers, showing a prevalence of complications significantly greater in smokers compared to nonsmokers. Moreover, the use of an onlay bone graft in conjunction with sinus augmentation appeared to significantly increase the rate of infective complications. Infections were treated by drainage and the administration of systemic antibiotics. Two clinical cases showing persistent signs of infection required an endoscopic inspection of the maxillary sinus.

DISCUSSION AND CONCLUSION

In the present study sinus membrane perforation was not shown to be a significant factor in the rate of implant complications. However, the combination of smoking and onlay bone grafting could significantly increase the rate of postoperative infection following sinus grafting.

Clinical and Histologic Analysis of Calcium Sulfate in Treatment of a Post-Extraction Defect: A Case Report

We report a case of a postextraction maxillary buccal dehiscence grafted with calcium sulfate to insert a dental implant. The clinical results were supported by histologic analysis of two specimens collected in the healed socket to better understand the biologic effects of calcium sulfate. A 42-year-old white female presented with an almost totally edentulous maxillary right arch with a wide postextraction defect in the canine region. Calcium sulfate mixed with sterile saline solution to a putty-like consistency was packed into the defect, and four dental implants were placed in the edentulous ridge. On re-entry, a dental implant and small amounts of calcium sulfate were placed in the grafted site. After 5 months, a specimen of the region implanted with calcium sulfate was retrieved for histologic evaluation. On surgical re-entry, a complete filling of the defect with mature, dense, newly formed bone occurred. Complete resorption of the grafted material and its substitution with newly formed bone tissue were confirmed by histologic analysis. All of the implants appeared to be osseointegrated successfully, and the patient was provided with a fixed implant-supported prosthesis. Calcium sulfate represents an aid in bone regeneration procedures.

Bucco-Lingual Crestal Bone Changes After Immediate and Delayed Implant Placement

BACKGROUND

Implants placed immediately after tooth extraction offer several advantages, but many authors have reported problems in filling the residual gap between the implant and the socket walls. Barrier and grafting techniques have been tested and yield varying results, so it has been suggested that the timing of implant placement may be important for success. The aim of this study was to analyze bone healing and coronal bone remodeling around 35 implants, 20 placed immediately after tooth removal and 15 placed 6 to 8 weeks after extraction.

METHODS

All the implants were submerged and placed within the alveoli confines, leaving circumferential defects because the implants did not contact the bone at their coronal aspects; stabilization was achieved in the bone apically. After implant placement the mean distance from buccal bone to lingual bone was 10 mm (SD 1.522) for immediate implants and 8.86 mm (SD 2.356) for delayed implants. No membrane or filling materials were used. Primary flap closure was accomplished in all cases.

RESULTS

At second-stage surgery all peri-implant defects were filled, and the mean distance from buccal bone to lingual bone was 8.1 mm (SD 1.334) for immediate implants and 5.8 mm (SD 1.265) for delayed implants. This pattern of coronal bone remodeling, showing a narrowing of the bucco-lingual width, was clinically similar for the two groups, although it should be noted that the delayed implants exhibited smaller bucco-lingual bone width already at the first measurement: it can be speculated that early remodeling may start immediately after tooth extraction and continue, non-uniformly, even after delayed implant placement.

CONCLUSIONS

This study suggests that circumferential defects could heal clinically without any guided bone regeneration (GBR) in both experimental groups, and that the procedure was virtually free from complications in the postoperative period, probably because of the absence of barrier membranes and/or grafting materials. Histologically, peri-implant defects of over 1.5 mm heal by connective tissue apposition, rather than by direct bone-to-implant contact, but clinically this healing may be very successful. No histological analysis was carried out in the present study, but even the largest residual gaps were filled with hard tissue that could not be probed. Thus, such outcomes can be considered clinically successful. The different rate of bone remodeling around immediate or delayed implants could have implications for the preferred timing of implant placement in sites of high esthetic concern.

Oral microbial biofilms and plaque-related diseases: microbial communities and their role in the shift from oral health to disease

Many oral pathologies, such as dental caries, periodontal disease and peri-implantitis are plaque-related. Dental plaque is a microbial biofilm formed by organisms tightly bound to a solid substrate and each other by means of an exopolymer matrix. Bacteria exhibit different properties when contained within a biofilm. Knowing the mechanisms controlling the formation and development of biofilms can help to understand the emergence and progression of such pathologies and to plan effective treatment. Most periodontal pathogens are common saprophytes of the oral cavity, expressing their virulence only in a susceptible host or when some changes come about in the oral environment. Physical, metabolic and physiological interactions may cause positive or negative effects among the various microbiota present. Such mechanisms of antagonism/synergy select the bacterial population and alterations of its composition affect the balance with the host and may lead to pathology. The effectiveness of antimicrobial agents, as measured through in vitro tests, is dramatically reduced in vivo due to the properties of the microbial community: mature, intact biofilms are less sensitive to such agents, as the exopolymer matrix, bacterial enzymes and slow growth rate hinder the action of chemotherapeutic agents. The present literature review aims to examine the most representative studies, focusing on the characteristics of bacterial communities and the crucial shift from oral health to plaque-related diseases.

Behavior of SaOS-2 cells cultured on different titanium surfaces

Surface properties may affect the clinical outcome of titanium dental implants. The aim of the present study was to investigate the effects of 3 different titanium surfaces-smooth (S), sandblasted (SB), and titanium plasma-sprayed (TPS)-on proliferation, differentiation, and apoptosis of human osteoblast-like cells, SaOS-2. Cell proliferation was significantly (p < 0.05) higher on the S surface, and synthesis of extracellular matrix proteins was more abundant on TPS and SB than on S surfaces. Analysis of integrin receptors showed a higher expression of alpha2, alpha5, alphaVbeta3, and ss1 on TPS as compared with SB and S surfaces. An increase in alkaline phosphatase activity was detected only on SB and TPS surfaces. Analysis of cell apoptosis did not demonstrate any significant difference among the 3 different surfaces. The results indicate that titanium surface topography affects proliferation and differentiation of osteoblast-like SaOS-2 cells, suggesting that surface properties might be important for bone response around dental implants in vivo.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) induces the osteoblastic differentiation of the human osteosarcoma cell line SaOS-2

The Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) is a hematopoietic growth factor that regulates the in vitro and in vivo proliferation and differentiation of hematopoietic cells through the interaction with a specific heterodimeric receptor complex (GM-CSFR), consisting of an alpha and a beta chain with molecular weights of 80 and 120 KDa, respectively. We have studied the expression of the GM-CSFR (alpha chain) on the surface of the human osteosarcoma cell line SaOS-2 and the in vitro effects of different concentrations (10, 100, and 200 ng/ml) of GM-CSF on GM-CSFR expression and the biological activity of SaOS-2 cells. Our data show that SaOS-2 cells express GM-CSFR and that GM-CSF can down-regulate the expression of its own receptor on these cells. Furthermore, to evaluate the biological effects of GM-CSF on SaOS-2 cells, we have investigated cell proliferation and differentiation of these cells treated with different doses of the growth factor through: (1) a morphological analysis of typical osteoblast differentiation markers such as osteopontin and BSP-II; (2) measurement of alkaline phosphatase (ALP) activity; (3) production of bone ECM components (collagen I, fibronectin, tenascin, and laminin); (4) production of interleukin-6 (IL-6) and osteocalcin in the culture medium. The results show that the in vitro treatment of SaOS-2 cells with recombinant human GM-CSF causes a decreased cell proliferation and an increased production of osteopontin, BSP-II, ALP, IL-6, and most but not all ECM components. These findings suggest that GM-CSF can regulate proliferation and differentiation of osteoblast-like SaOS-2 cells and could also play an unexpected role in the maturation of bone tissue.

[Biofilms of the oral cavity. Formation, development and involvement in the onset of diseases related to bacterial plaque increase]

Biofilm is defined as a community of bacteria intimately associated with each other and included within an exopolymer matrix: this biological unit exhibits its own properties, quite different in comparison with those showed by the single species in planktonic form. The oral cavity appears as an open ecosystem, with a dynamic balance between the entrance of microrganisms, colonisation modalities and host defences aimed to their removal: to avoid elimination, bacteria need to adhere to either hard dental surfaces or epithelial surfaces. The oral biofilm formation and development, and the inside selection of specific microrganisms have been correlated with the most common oral pathologies, such as dental caries, periodontal disease and peri-implantitis. Many of these bacteria are usual saprophytes of the oral environment, that, in particular situations, can overcome and express their virulence factors: to better understand the mechanisms of these pathologies it's necessary to know the complex interactions between all the bacterial species inside the biofilm and host tissues and responses. The present paper is a review of the most significant studies on the biofilm development modalities, their correlations with either health or illness of the oral cavity, the bacterial co-aggregation strategies and the biofilm response to antimicrobial agents.

[Periodontal disease and occlusal trauma: a still debated controversy? A review of the literature]

In the "Glossary of Periodontics Terms" written by the American Academy of Periodontology, the occlusal trauma is defined as "an injury to the attachment apparatus as a result of excessive occlusal forces". Nowadays, the effects of occlusal trauma on tooth support tissues, the onset and the progression of periodontal disease are still debated: many commonplaces have been disproved, but some doubts and not yet clear points remain, even owing to the difficult diagnosis of the presence and the real clinical impact of a traumatic occlusion. Then, ethical reasons prevent researchers from prospective clinical trials. At the beginning of the last century occlusal trauma has been supposed to be an etiologic factor of "alveolar pyorrhea", but several studies attending more strict scientific criteria failed to prove such correlation. On the basis of the bacterial genesis of periodontal disease, researchers started evaluating the possible effects of occlusal discrepancies on incidence, progression and treatment outcomes of periodontitis, but all the results underlined the more relevant role played by micro-organisms. The present review of the literature runs through this controversy again, analysing the most significant studies published.

[Bacterial virulence in the etiology of periodontal diseases]

Strong relationships have been very often described between various form of periodontal disease (PD) and certain bacterial species, so that nowadays periodontal disease is recognized as an infectious disease. Destruction of periodontal supporting tissues happens as a response to very intricate host-parasite interactions. When the clinician will be able to fully understand and identify such phenomena it would be possible to succeed in a properly diagnosis and control of the active phase of periodontal disease. The first step in such a direction would be to analyze the common characteristic of some bacterial species, the so called suspected periodontopathogens. Such species namely Gram-negative, associated with the outbreak of periodontal disease have in common the capacity to disrupt the integrity of the host defences by means of the so called virulence factors. These factors may enhance the bacterial colonization or may interfere with the host response that ultimately results in periodontal support breakdown. The present review focuses on the virulence factors of the main suspected periodontopathogens evaluating the effects on the host immune response and directly on the periodontal tissues.

[Implants in partially edentulous patients with history of periodontal disease]

BACKGROUND

Microbiota associated with periodontal diseases were also associated with periimplant diseases. The purpose of this study was to determine the clinical status and composition of subgingival microbiota of implants and natural teeth in a group of partially edentulous patients with history of periodontal disease.

METHODS

38 partially edentulous patients with history of periodontal disease, treated with dental implants, were selected for this study. Patients selected for the study were in good health condition and did not take any antibiotics in the last six months. One year after second stage surgery a total of 72 implants and 38 teeth underwent clinical and microbiological examination. Clinical parameters were PD, PAL, PI and GI. Subgingival plaque samples were analyzed by dark-field microscopy and cultural analysis.

RESULTS

Clinical parameters didn't show any significant differences between periodontal and periimplant tissues. Dark-field microscopic examination showed higher prevalence of rods and spirochetes around implants than around teeth. There were no differences detected by cultural examination in the subgingival microbiota at peri-implant and periodontal sites.

CONCLUSIONS

Findings from this study showed no differences between implants and teeth in partially edentulous patients with history of periodontal disease one year after second stage surgery. Implants were colonized by microbiota similar to that observed around teeth and were well-maintained in patients with a history of periodontitis.

Tetracycline fibres used to control bacterial infection during guided tissue regeneration (GTR)

AIMS

The colonization of suspected periodontal pathogens during the healing of periodontal defects treated by guided tissue regeneration (GTR) with e-PTFE membranes and tetracycline fibers was investigated.

METHODS

Fifteen patients, each with one pair of angular periodontal bone defects of comparable size and morphology were recruited for the study. In a matched-pair study design, the test defects were treated with e-PTFE membranes in combination with tetracycline fibers, while control defects were treated with e-PTFE membranes alone. Microbiological specimens were taken from control as well as from test sites preoperatively (T0), intraoperatively (T1), two weeks after surgery (T2) and from membranes at time of removal (T3). Cultural methods were used to identify the following species: Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), Fusobacterium nucleatum (Fn) and Actinobacillus actinomicetemcomitans (Aa).

RESULTS

At baseline and T1, none of the suspected periodontal pathogens were detected at test or control sites. Levels of P. intermedia and F. nucleatum, as mean percentages of total culturable microflora, were detected at levels significantly higher in control sites than test sites at times T2 and T3.

CONCLUSIONS

Findings from this study suggest that e-PTFE membranes are frequently colonized by periodontal pathogens, and that bacterial colonization of healing sites after GTR procedures can be kept under control with a controlled delivery system releasing tetracycline.