A Cell-based Screen in Actinomyces oris to Identify Sortase Inhibitors

Sortase enzymes are attractive antivirulence drug targets that attach virulence factors to the surface of Staphylococcus aureus and other medically significant bacterial pathogens. Prior efforts to discover a useful sortase inhibitor have relied upon an in vitro activity assay in which the enzyme is removed from its native site on the bacterial surface and truncated to improve solubility. To discover inhibitors that are effective in inactivating sortases in vivo, we developed and implemented a novel cell-based screen using Actinomyces oris, a key colonizer in the development of oral biofilms. A. oris is unique because it exhibits sortase-dependent growth in cell culture, providing a robust phenotype for high throughput screening (HTS). Three molecules representing two unique scaffolds were discovered by HTS and disrupt surface protein display in intact cells and inhibit enzyme activity in vitro. This represents the first HTS for sortase inhibitors that relies on the simple metric of cellular growth and suggests that A. oris may be a useful platform for discovery efforts targeting sortase.

P5728Association of systolic blood pressure and cardiovascular outcomes at different age groups in the healthy general population: a nationwide prospective cohort study

Background

Uncertainties remain regarding the effect of blood pressure on various cardiovascular outcomes in different age groups.

Purpose

We aimed to identify 1) whether a systolic blood pressure (SBP) of 130–139 mm Hg elevates cardiovascular disease (CVD) mortality and 2) whether SBP shows a linear association with cause-specific CVD mortality in all age groups among individuals without known hypertension and CVD.

Methods

We used the Korean National Health Insurance sample data (n=429,220). Participants were categorized into three groups by age (40–59, 60–69, and 70–80 years).

Results

A positive and graded association was generally observed between SBP and overall and cause-specific CVD mortality regardless of age, except for ischemic heart disease (IHD) mortality in those aged 70–80 years. Among those aged 70–80, the hazard ratios (HRs) (95% CIs) for overall CVD mortality were 1.08 (0.92–1.28), 1.14 (0.97–1.34), and 1.34 (1.14–1.58) for SBP values of 120–129, 130–139, and 140–149 mm Hg, respectively, compared to SBP <120 mm Hg. For total stroke mortality, the corresponding HRs were 1.29 (1.02–1.64), 1.37 (1.09–1.72), and 1.52 (1.20–1.93), while for IHD mortality, the corresponding HRs were 0.90 (0.64–1.26), 0.86 (0.62–1.19), and 1.29 (0.93–1.78). Nonlinear associations were significant for IHD (Fig 1).

Figure 1

Conclusion

In the elderly Korean population, SBPs of 130–139 mm Hg elevated total stroke mortality, but not IHD mortality, compared to normal BP, and a linear association was not observed for IHD mortality in the range <140 mm Hg. Regarding an appropriate diagnostic cutoff for hypertension, an individualized approach considering each person's organ susceptibility is needed for the elderly population.

Acknowledgement/Funding

None

NMR structure-based optimization of Staphylococcus aureus sortase A pyridazinone inhibitors

Staphylococcus aureus is a leading cause of hospital-acquired infections in the USA and is a major health concern as methicillin-resistant S. aureus and other antibiotic-resistant strains are common. Compounds that inhibit the S. aureus sortase (SrtA) cysteine transpeptidase may function as potent anti-infective agents as this enzyme attaches virulence factors to the bacterial cell wall. While a variety of SrtA inhibitors have been discovered, the vast majority of these small molecules have not been optimized using structure-based approaches. Here we have used NMR spectroscopy to determine the molecular basis through which pyridazinone-based small molecules inhibit SrtA. These inhibitors covalently modify the active cysteine thiol and partially mimic the natural substrate of SrtA by inducing the closure of an active site loop. Computational and synthetic chemistry methods led to second-generation analogues that are ~70-fold more potent than the lead molecule. These optimized molecules exhibit broad-spectrum activity against other types of class A sortases, have reduced cytotoxicity, and impair SrtA-mediated protein display on S. aureus cell surface. Our work shows that pyridazinone analogues are attractive candidates for further development into anti-infective agents, and highlights the utility of employing NMR spectroscopy and solubility-optimized small molecules in structure-based drug discovery.

The "Lid" in the Streptococcus pneumoniae SrtC1 Sortase Adopts a Rigid Structure that Regulates Substrate Access to the Active Site

Many species of Gram-positive bacteria use sortase enzymes to assemble long, proteinaceous pili structures that project from the cell surface to mediate microbial adhesion. Sortases construct highly stable structures by catalyzing a transpeptidation reaction that covalently links pilin subunits together via isopeptide bonds. Most Gram-positive pili are assembled by class C sortases that contain a "lid", a structurally unique N-terminal extension that occludes the active site. It has been hypothesized that the "lid" in many sortases is mobile and thus capable of readily being displaced from the enzyme to facilitate substrate binding. Here, we show using NMR dynamics measurements, in vitro assays, and molecular dynamics simulations that the lid in the class C sortase from Streptococcus pneumoniae (SrtC1) adopts a rigid conformation in solution that is devoid of large magnitude conformational excursions that occur on mechanistically relevant time scales. Additionally, we show that point mutations in the lid induce dynamic behavior that correlates with increased hydrolytic activity and sorting signal substrate access to the active site cysteine residue. These results suggest that the lid of the S. pneumoniae SrtC1 enzyme has a negative regulatory function and imply that a significant energetic barrier must be surmounted by currently unidentified factors to dislodge it from the active site to initiate pilus biogenesis.

Structure of the Bacillus anthracis Sortase A Enzyme Bound to Its Sorting Signal: A FLEXIBLE AMINO-TERMINAL APPENDAGE MODULATES SUBSTRATE ACCESS

The endospore forming bacterium Bacillus anthracis causes lethal anthrax disease in humans and animals. The ability of this pathogen to replicate within macrophages is dependent upon the display of bacterial surface proteins attached to the cell wall by the B. anthracis Sortase A ((Ba)SrtA) enzyme. Previously, we discovered that the class A (Ba)SrtA sortase contains a unique N-terminal appendage that wraps around the body of the protein to contact the active site of the enzyme. To gain insight into its function, we determined the NMR structure of (Ba)SrtA bound to a LPXTG sorting signal analog. The structure, combined with dynamics, kinetics, and whole cell protein display data suggest that the N terminus modulates substrate access to the enzyme. We propose that it may increase the efficiency of protein display by reducing the unproductive hydrolytic cleavage of enzyme-protein covalent intermediates that form during the cell wall anchoring reaction. Notably, a key active site loop (β7/β8 loop) undergoes a disordered to ordered transition upon binding the sorting signal, potentially facilitating recognition of lipid II.

Discovery of Staphylococcus aureus sortase A inhibitors using virtual screening and the relaxed complex scheme

Staphylococcus aureus is the leading cause of hospital-acquired infections in the United States. The emergence of multidrug-resistant strains of S. aureus has created an urgent need for new antibiotics. Staphylococcus aureus uses the sortase A enzyme to display surface virulence factors suggesting that compounds that inhibit its activity will function as potent anti-infective agents. Here, we report the identification of several inhibitors of sortase A using virtual screening methods that employ the relaxed complex scheme, an advanced computer-docking methodology that accounts for protein receptor flexibility. Experimental testing validates that several compounds identified in the screen inhibit the activity of sortase A. A lead compound based on the 2-phenyl-2,3-dihydro-1H-perimidine scaffold is particularly promising, and its binding mechanism was further investigated using molecular dynamics simulations and conducting preliminary structure-activity relationship studies.

Structural and computational studies of the Staphylococcus aureus sortase B-substrate complex reveal a substrate-stabilized oxyanion hole

Sortase cysteine transpeptidases covalently attach proteins to the bacterial cell wall or assemble fiber-like pili that promote bacterial adhesion. Members of this enzyme superfamily are widely distributed in Gram-positive bacteria that frequently utilize multiple sortases to elaborate their peptidoglycan. Sortases catalyze transpeptidation using a conserved active site His-Cys-Arg triad that joins a sorting signal located at the C terminus of their protein substrate to an amino nucleophile located on the cell surface. However, despite extensive study, the catalytic mechanism and molecular basis of substrate recognition remains poorly understood. Here we report the crystal structure of the Staphylococcus aureus sortase B enzyme in a covalent complex with an analog of its NPQTN sorting signal substrate, revealing the structural basis through which it displays the IsdC protein involved in heme-iron scavenging from human hemoglobin. The results of computational modeling, molecular dynamics simulations, and targeted amino acid mutagenesis indicate that the backbone amide of Glu(224) and the side chain of Arg(233) form an oxyanion hole in sortase B that stabilizes high energy tetrahedral catalytic intermediates. Surprisingly, a highly conserved threonine residue within the bound sorting signal substrate facilitates construction of the oxyanion hole by stabilizing the position of the active site arginine residue via hydrogen bonding. Molecular dynamics simulations and primary sequence conservation suggest that the sorting signal-stabilized oxyanion hole is a universal feature of enzymes within the sortase superfamily.

Discovery and structure-activity relationship analysis of Staphylococcus aureus sortase A inhibitors

Methicillin resistant Staphylococcus aureus (MRSA) is a major health problem that has created a pressing need for new antibiotics. Compounds that inhibit the S. aureus SrtA sortase may function as potent anti-infective agents as this enzyme attaches virulence factors to the cell wall. Using high-throughput screening, we have identified several compounds that inhibit the enzymatic activity of the SrtA. A structure-activity relationship (SAR) analysis led to the identification of several pyridazinone and pyrazolethione analogs that inhibit SrtA with IC(50) values in the sub-micromolar range. Many of these molecules also inhibit the sortase enzyme from Bacillus anthracis suggesting that they may be generalized sortase inhibitors.

Oxidative palladium(II) catalysis: A highly efficient and chemoselective cross-coupling method for carbon-carbon bond formation under base-free and nitrogenous-ligand conditions

We report herein the development of a general and mild protocol of oxygen-promoted Pd(II) catalysis resulting in the selective cross-couplings of alkenyl- and arylboron compounds with various olefins. Unlike most cross-coupling reactions, this new methodology works well even in the absence of bases, consequently averting undesired homo-couplings. Nitrogen-based ligands including dimethyl-phenanathroline enhance reactivities and offer a highly efficient and stereoselective methodology to overcome challenging substrate limitations. For instance, oxidative palladium(II) catalysis is effective with highly substituted alkenes and cyclic alkenes, which are known to be incompatible with other known catalytic conditions. Most examined reactions progressed smoothly to completion at low temperatures and in short times. These interesting results provide mechanistic insights and utilities for a new paradigm of palladium catalytic cycles without bases.

Oxygen-Promoted Palladium(II) Catalysis: Facile C(sp2)−C(sp2) Bond Formation via Cross-Coupling of Alkenylboronic Compounds and Olefins

[reaction: see text] Oxygen-promoted Pd(II) catalysis facilitated the synthesis of conjugated dienes by cross-coupling of alkenylboronic compounds and various olefins including highly substituted alkenes and cyclohexenone. Under mild conditions, these versatile reactions were efficient and highly stereoselective.

Implant-supported fixed prostheses for the rehabilitation of periodontally compromised dentitions: a 3-year prospective clinical study

BACKGROUND

The application of a strict hygiene maintenance care protocol following rehabilitation of periodontally compromised dentitions by means of tooth-supported fixed partial dentures has demonstrated excellent long-term treatment outcome.

PURPOSE

A clinical and radiographic study was performed to document and evaluate the short- and medium-term result of occlusal rehabilitation by means of implant-supported fixed prostheses (ISFPs) in patients treated for advanced periodontal disease.

MATERIALS AND METHODS

Forty-three consecutive patients were included. All patients were referred because of advanced periodontal disease. Before the implant therapy was initiated, periodontal treatment was performed and the outcome evaluated during at least a 6-month period. An individual maintenance care program was designed for each patient. All 125 implants were placed using a two-stage surgical approach. Following installation of the ISFPs, all patients underwent a baseline examination including evaluation of oral hygiene, periodontal or peri-implant conditions, and radiographs. These examinations were repeated annually during the 3-year observation period.

RESULTS

No single implant was lost during the 3-year follow-up period. The percentages of plaque-harboring surfaces and bleeding units on probing were found to be low (< 10%), and no soft-tissue complications were recorded. The mean marginal bone resorption during the observation period amounted to 0.21 mm. In a few patients, apposition of marginal bone was observed. Bone loss amounting to 0.5 mm or less was found around 81% of the implants (101/125 implants). The amount of bone loss around the remaining 24 implants (19%) varied between 0.5 and 2.0 mm.

CONCLUSIONS

The present clinical trial demonstrates that, at least during a 3-year period, the ISFP is an acceptable and predictable treatment option for rehabilitation in patients who have lost their teeth because of periodontal disease. This observation seems to be valid in edentulous and partially dentate jaws. A prerequisite to reach such a favorable treatment outcome is possibly the combination of the strict maintenance care program and the careful design of the ISFPs.

Prospective 3-year study of cross-arch fixed partial dentures in patients with advanced periodontal disease

STATEMENT OF PROBLEM

Several choices exist for the treatment of advanced periodontal disease. One is a combined periodontal and prosthetic treatment that includes cross-arch fixed partial dentures (FPDs). However, the outcomes of such therapy have been reported mainly from studies in Scandinavian countries.

PURPOSE

The aims of this study were: (1) to longitudinally evaluate, after periodontal and prosthodontic treatment that included cross-arch FPDs, treatment outcomes in Korean patients who suffered from severe periodontitis; and (2) to evaluate the patients' treatment assessments and the FPDs after 3 years.

MATERIAL AND METHODS

This survey included 39 Korean patients provided with 50 FPDs. Clinical and radiographic examinations were performed at the time of delivery of the FPDs and at the 3-year follow-up examinations. The prostheses were divided into 3 groups according to design (end abutments, unilateral cantilever, and bilateral cantilevers) and the amount of supporting tissues at the time of insertion. On average, only 26% of the total original periodontal tissue remained at the time of insertion. The FPDs consisted of 11 to 14 units, with a mean of 5 to 7 abutments in the 3 groups. The mean periodontal ligament area of the abutments was 79% of the total ligament area of the replaced teeth.

RESULTS

At the 3-year follow-up examination, the FPDs were stable in all patients, who in general displayed good oral hygiene and had healthy periodontal conditions. The change in periodontal ligament area over the 3-year observation period was negligible (1 mm(2) per dental unit) and showed no statistically significant difference in relation to FPD design. Most patients were satisfied with the function of their FPDs with respect to mastication, phonetics, hygiene, esthetics, and chewing comfort. A few patients stated that they were careful with the FPDs and avoided certain foods (for example, raw peanuts and grilled squid) because they felt insecure with the cantilever segments. Most patients reported that they would choose the same treatment again.

CONCLUSION

Patients with advanced periodontal disease demonstrated successful outcomes over a 3-year period and reported satisfaction with combined periodontal and restorative treatment that included cross-arch FPDs.

Patient evaluation of treatment with fixed implant-supported partial dentures

The aim of this study was to analyse the patient evaluation of functional treatment outcome in 40 periodontally compromised patients who received implant-supported prostheses (ISPs) as part of the total treatment. The treatment protocol comprised periodontal treatment, extraction of teeth with poor prognosis, placement of dental titanium implants, and after healing, insertion of fixed ISPs. Five of the patients became edentulous in one jaw after extraction of all teeth and received a complete ISP, whereas 35 patients became partially edentulous after extraction of some teeth, 12 receiving a partial ISP on > or = 3 implants, and 23 one on two implants. The follow-up period was on average 1.8 years after the connection of the prostheses, which provided the patients a dentition with a mean of 12 occluding dental units. The first author (S.-W. Yi) performed all implant treatment. Patients' opinions on oral functions--mastication, phonetics, oral hygiene, chewing comfort and aesthetics--were evaluated by means of a questionnaire both before implant installation and at the last follow-up. A control group of 30 subjects with a healthy dentition of 14 occluding natural pairs of teeth answered the same questionnaire on one occasion. A great majority of the patients were extremely satisfied with the oral function after treatment and experienced the ISPs as 'natural teeth'. There was no significant difference between the three treatment groups and the control group for mastication, phonetics, chewing comfort and aesthetics. Patients with ISPs reported a small but significantly greater difficulty with oral hygiene procedures than the controls with natural teeth. Most patients said that they would undergo the treatment again, if necessary, and recommend it to others. It was concluded that the rehabilitation of the periodontally compromised patients, including ISPs on osseointegrated dental titanium implants, resulted in subjectively improved and satisfactory oral function.

Effects of smoking on the mortality of lung cancer in Korean men

Few studies have examined the effects of smoking on the morbidity and mortality of lung cancer in Korean men. In Korea, where the prevalence of smoking is among the highest in the world, the morbidity and mortality of lung cancer are rapidly escalating. The objectives of this study were to prospectively examine the effects of smoking on lung cancer and to determine the combined effects of the amount, duration and age that smoking was started. The design was a prospective cohort study with a follow-up period of six years (1993-1998). The subjects included a total of 305,687 Korean men from 35 to 64 years of age who received health insurance from the Korea Medical Insurance Corporation and who had biennial medical evaluations in 1992. The main outcome measures were deaths from lung cancer. As a baseline, 58.2% were current cigarette smokers. Between 1993 and 1998, 891 lung cancer events (34.4/100,000 people per year) occurred. In multivariate Cox proportional hazards models controlling for age, exercise and alcohol use, current smoking increased the risk of lung cancer (risk ratio [RR], 5.6; 95% confidence interval [CI], 4.2 - 7.3). There were significant dose-response relationships to the amount, duration of smoking and age that smoking was started. Compared with nonsmokers, the RR from current smokers who smoked 20 cigarettes per day for over 30 years was 8.2 (5.9 - 11.3), the RR from current smokers who smoked for over 30 years and were less then 19 years of age when they started smoking was 7.8 (5.2 - 11.9), and the RR for those who smoke 20 cigarettes per day and were less than 19 years of age when they started smoking was 8.3 (5.9 -11.6). This study demonstrates that in Korea smoking is a major independent risk factor for lung cancer, and that the risk increases with an increased amount, longer duration, and younger starting age.

Incidence of presbycusis of Korean populations in Seoul, Kyunggi and Kangwon provinces

Presbycusis, a bilateral sensorineural hearing loss caused by changes in the inner ear, is related to multiple factors such as noise exposure and otologic disease. In institute-based studies, we tried to determine the incidence of presbycusis in Korean populations living in Seoul, Kyunggi and Kangwon provinces by gender and age groups. The subjects were people who had visited health promotion centers. Pure tone audiometry was done over 20 years on 6,028 subjects. In a community-based study, the subjects were elderly residents of Kanghwa-do area. There were no obvious factors that could cause hearing impairment in the subjects. For the pure tone audiometry, hearing threshold was obtained by using the six-dimension method. The incidence of presbycusis for subjects aged 65 years and older was 37.8% and 8.3% for > or = 27 dB HL criterion and > or = 41 dB HL criterion, respectively. The incidence increased with age. A statistically significant difference in the hearing threshold was found between men and women aged 65 years or older. No differences were found between the community-based study and the institute- based studies. There was a high incidence (about 40%) of presbycusis among Koreans aged 65 years or older (for > or = 27 dB HL criterion). With an aging population, we anticipate that this report could be used to provide a basic data for the study of presbycusis.

Bone probing measurement as a reliable evaluation of the bone level in periodontal defects

BACKGROUND

Evaluation of periodontal regeneration is usually made by clinical measurements despite their limitations in determining the precise nature of the healing response. In the present study, the possibility of using bone probing measurements under local anesthesia to determine bone level changes without a re-entry procedure was investigated.

METHODS

Thirty-eight (38) first molars in 28 patients with chronic periodontitis who were scheduled to have periodontal surgery were included in this study. A custom-made acrylic resin stent was used for proper orientation of the probe for the bone probing depth measurement as well as probing depth measurements and surgical and radiographic bone level evaluations. The mesial, distal, and middle sites in the buccal aspect of each tooth were used. The sites were divided into 2 groups according to probing depth: those with a probing depth < 4 mm and those with a probing depth > or = 4 mm.

RESULTS

The probing depth was not significant in the difference between actual bone level (SBL) and bone probing depth (BP) (P >0.05). The greatest correlation to SBL was found with BP (gamma = 0.92), followed by radiographic bone level (RBL) (gamma = 0.69). The morphology of the defects had no significant effect on the difference between SBL and other measurements, while tooth surface and probing depth had significant effects on the difference between RBL and SBL.

CONCLUSIONS

The results of this study suggest that, regardless of probing depth, probing surface, and the presence of intrabony defects, there is a minimal difference between the BP and SBL. Determining the bone probing depth measurement is a kind of reliable method to estimate the regenerated bone level following periodontal treatment.

A cationic lipid emulsion/DNA complex as a physically stable and serum-resistant gene delivery system

PURPOSE

To develop a non-viral gene delivery system in the form of an oil-in-water (o/w) lipid emulsion.

METHOD

Cationic lipid emulsions were formulated with soybean oil, 1,2-dioleoyl-sn-glycero-3-trimethylammonium-propane (DOTAP) as a cationic emulsifier and other co-emulsifiers. The physical characteristics of the lipid emulsion and the emulsion/DNA complex were determined. The in vitro transfection efficiency of the emulsion/DNA complex was determined in the presence of up to 90% serum.

RESULTS

The average droplet size and zeta potential of emulsions were ca. 180 nm and ca. +50 mV, respectively. Among the emulsions, a stable formulation was selected to form a complex with a plasmid DNA encoding chloramphenicol acetyltransferase. By increasing the ratio of emulsion to DNA. zeta-potential of the emulsion/DNA complex increased monotonously from negative to positive without any changes in the complex size. The complex was stable against DNase I digestion and an anionic poly-L-aspartic acid (PLAA). The complex delivered DNA into the cells successfully, and the transfection efficiency was not affected by complex formation time from 20 min to 2 h. More importantly, the cationic lipid emulsion facilitated the transfer of DNA in the presence of up to 90% serum.

CONCLUSIONS

The cationic lipid emulsion/DNA complex has physical stability and serum resistant properties for gene transfer.

Stable lipiodolized emulsions for hepatoma targeting and treatment by transcatheter arterial chemoembolization

We attempted to develop lipiodolized emulsions that remain in the tumour for a long period, release drug in a sustained release pattern, and thus improve the conventional treatment of hepatocellular carcinoma (HCC) [1]. Polyoxyethylene derivatives of hydrogenated castor oil (HCO) were the most suitable emulsifiers in stabilizing emulsions containing Lipiodol as an oil phase. The length of ethylene oxide coupled to HCO rather than the hydrophilic-lipophilic balance (HLB) values was an important factor in preparing stable emulsions and in achieving sustained-release characteristics. When distilled water was replaced with Iopamiro, a heavy water soluble contrast medium with a specific gravity of 1.335, more stable lipiodolized emulsions with longer sustained release behaviour could be prepared with smaller amount of HCO. To study the in vivo stability of the w/o Lipiodol emulsion and the sustained-release characteristics of doxorubicin from the emulsion, the pharmacokinetic study was performed with normal dogs using transcatheter arterial chemoembolization technique. The area under the plasma concentration-time curve for the first eight hours (AUC0-8) and AUCtotal values of the stabilized emulsion were three to four times higher than those of the coarse emulsion prepared lacking HCO 60. From the in vitro and in vivo studies, Lipiodol based water in oil emulsion with HCO 60 containing doxorubicin showed higher stability and released doxorubicin in a sustained fashion.

A path analysis on prisoners' health behavior and medical utilization

In this thesis, Korean prisoners' health behavior and the characteristics of their medical utilization were surveyed and analysed. Because prisoners are inclined to be mediators of communicable diseases or unhealthy behaviors between prison institution and the outside world, health care for prisoners is directly related to the national population. Data were collected through a self-administered survey of 5 Korean prisons out of a total of 38 correctional facilities and analysed in accordance with a causal model based on a path frame, by serial multiple regressions on health behavior, health status, and medical utilization, etc. According to the survey analysis, while prisoners were generally concerned with their health much more than they were before imprisonment, they perceived that their health status had deteriorated after imprisonment, and that their need for health services was increasing gradually during their time in prison. In the path analysis on the causal relations among variables related to the prisoners' health status and medical utilization, the prisoners' characteristics affected their health concern and health behavior, and subsequently affected their health status and medical utilization, respectively. To sum up these exploratory studies on prisoners' health behavior and health service utilization, some efforts to organize a health care system embracing the correctional institution and health care administration should be made on the level of establishing a health care delivery system for special social groups like prisoners.

Long-term follow-up of cross-arch fixed partial dentures in patients with advanced periodontal destruction: evaluation of occlusion and subjective function

The study aimed to investigate occlusal factors in fixed partial dentures (FPDs) still in service for more than 10 years, and to assess the patients' opinions regarding oral function with these constructions. Thirty-four patients with 43 FPDs were examined clinically concerning occlusion and by means of a questionnaire on functional aspects. The most common occlusal contact pattern was group function (51% on both sides, 7% on one side) while canine protected occlusion was recorded in 16% on both sides, 7% on one side. Balanced occlusion (19%) was mainly found when the FPD occluded against a complete denture and when there were few abutments and a small amount of abutment supporting tissue. The number and intensity of the occlusal contacts were assessed by means of thin occlusal sheets (50 microns). On average, one occlusal contact was observed on each dental unit with antagonist. The average number of sheets that could be introduced between the antagonists when the patient bit hard in the intercuspal position was two without significant differences between different areas (anterior/posterior) or type of dental unit (abutment, pontics, cantilever section). In the cantilever sections there were looser contacts (more interocclusal sheets) more distally. The great majority of patients were satisfied with the function of their FPDs (mastication, phonetics, aesthetics, comfort, and hygiene). Subjective function was not significantly influenced by FPD design, occlusal factors or number of FPD units. The only significant difference observed was that patients with a small amount of supporting tissues said they had more difficulties with hard foods than the others had. Although a stable occlusion was found in all FPDs, none of the other occlusal parameters examined were related to the long-term results.

Long-term follow-up of cross-arch fixed partial dentures in patients with advanced periodontal destruction. Evaluation of the supporting tissues

The aim of the study was to evaluate the periodontal conditions in patients treated more than 10 years ago for advanced periodontal disease and rehabilitated with cross-arch fixed partial dentures (FPDs). Of 50 randomly selected patients, 34 subjects carrying 43 FPDs agreed to participate in a clinical and radiographic follow-up examination. The FPDs were divided into three groups on the basis of prosthesis design (end abutments, unilateral cantilever, and bilateral cantilevers) and amount of supporting tissues at the time of bridge installation. Seventy per cent of the FPDs were found to be unchanged, whereas the rest had been modified due to various complications leading to extraction of one or more of the abutment teeth. Six FPDs (14%) had been partially replaced by FPDs anchored to osseointegrated dental implants. A total of 21 (8%) of the original 274 abutment teeth had been extracted. Longitudinal changes in the amount of periodontal support were minimal over the average of 15 years of follow-up. FPD design or initial amount of supporting tissues was found not to have significant influence on longitudinal changes in periodontal conditions. It was concluded that combined periodontal and prosthodontic treatment of patients with advanced loss of periodontal support may provide a high rate of long-term successful outcome, provided proper adequate periodontal and prosthetic treatment and maintenance care are given.