Impact of salivary contamination during placement of implants with simultaneous bony augmentation in iliac bone in sheep.

Our aim was to investigate the possible impact of contamination with saliva on osseointegration during placement of implants with simultaneous bone augmentation. Six hemispheric shape bone defects (8mm in diameter×4mm deep) were prepared in each iliac bone of six sheep. A dental implant (2.9mm in diameter×10mm long) was placed in the centre of each defect, and then pairs of defects were filled with one of the following bone augmentation materials: autogenous bone, autogenous bone plus bovine bone, or resorbable biphasic ceramic bone substitute. One site in each augmentation group was impregnated with saliva (contaminated group), while the other was not (non-contaminated group). Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) within implant threads were measured after a healing period of five weeks, both in respect of the implant inserted in the augmented bone and in that inserted in the residual bone. Overall results showed that there was a significant difference between the contaminated and non-contaminated group for BIC in the augmented implant (p=0.028), while there were no significant differences in the implant in residual bone (p=0.722). For BAFO, there were no significant differences between the contaminated and non-contaminated groups among the different augmentation materials. The results showed that contamination with saliva during placement of an implant with simultaneous bone augmentation had a serious deleterious effect on osseointegration of the aspect of the implant within the augmented defect. Contamination with saliva during placement of an implant with simultaneous bone augmentation should therefore be avoided.

Impact of surface contamination of implants with saliva during placement in augmented bone defects in sheep calvaria.

Our aim was to try and find out whether contamination with saliva during insertion of dental implants affects osseointegration in bone that has been augmented with different grafts. Six bony defects were created in each of the calvaria of six sheep, and then augmented with three different materials (autogenous bone, bovine bone, and resorbable biphasic ceramic bone substitute) After five weeks of healing, three implants contaminated with saliva (contaminated group) and three not contaminated (uncontaminated group) were placed in the centre of the augmented areas. For histomorphometric analysis, bone implant contact, bone area fraction occupancy, bone and material area, and bony area were measured after a healing period of five weeks. There was a significant difference between the contaminated and uncontaminated groups (p=0.036) for bone implant contact only in the augmented areas, but there were no significant differences in bone area fraction occupancy, bone and material area, and bony area. We conclude that contamination with saliva during placement of dental implants can significantly compromise bone implant contact in augmented areas, but had no significant effect on the formation of bone in areas more distant from the surface of the implant. We suggest that salivary contamination should be avoided during placement of dental implants in augmented areas.

Gingival thickness assessment at the mandibular incisors with four methods: A cross-sectional study.

BACKGROUND: This study was conducted to determine accuracy, precision and repeatability of four different methods for assessing gingival thickness METHODS: This cross-sectional study evaluated gingival thickness on 200 consecutively included orthodontic patients. Gingival thickness was assessed at both central mandibular incisors with: 1) transgingival probing with a standard periodontal probe, 2) transgingival probing with a stainless-steel acupuncture needle, 3) ultrasound, and 4) a color-coded periodontal probe. Intra-examiner reproducibility and method error were also evaluated. RESULTS: Transgingival measurements with the standard periodontal probe were found to be more accurate than those with the acupuncture needle, after method error assessment. Acupuncture needle and ultrasound device yielded higher values than the probe. Expected differences between the two methods were 22% more for the mandibular left central incisor (95% confidence interval (CI) = 11% to 32%) and 26% more (95% CI = 13% to 39%) for the mandibular right central incisor when measured with the needle. Ultrasound measurements exceeded probe measurements on average by 0.16 mm at mandibular left central incisor (95% CI = 0.14 to 0.18) and by 0.11 mm for mandibular right central incisor (95% CI = 0.08 to 0.13). Intraclass correlation coefficient concluded good agreement for the color-coded periodontal probe (0.624). CONCLUSIONS: Within the inherent limit of the uncertainty about the true value of gingival thickness, the present results demonstrate the differences between the tested methods, as far as accuracy and reproducibility are concerned. Based on the reproducibility, the transgingival probing with the periodontal probe as well as the ultrasound determination, seem to present an adequate choice for every day practice.

In vivo expression of proteases and protease inhibitor, a serpin, by periodontal pathogens at teeth and implants.

Porphyromonas gingivalis and Tannerella forsythia secrete proteases, gingipains and KLIKK-proteases. In addition, T. forsythia produces a serpin (miropin) with broad inhibitory spectrum. The aim of this pilot study was to determine the level of expression of miropin and individual proteases in vivo in periodontal and peri-implant health and disease conditions. Biofilm and gingival crevicular fluid (GCF)/ peri-implant sulcular fluid (PISF) samples were taken from healthy tooth and implant sites (n = 10), gingivitis and mucositis sites (n = 12), and periodontitis and peri-implantitis sites (n = 10). Concentration of interleukin-8 (IL-8), IL-1ß and IL-10 in GCF was determined by enzyme-linked immunosorbent assay. Loads of P. gingivalis and T. forsythia and the presence of proteases and miropin genes were assessed in biofilm by quantitative PCR, whereas gene expression was estimated by quantitative RT-PCR. The presence of P. gingivalis and T. forsythia, as well as the level of IL-8 and IL-1ß, were associated with disease severity in the periodontal and peri-implant tissues. In biofilm samples harboring T. forsythia, genes encoding proteases were found to be present at 72.4% for karilysin and 100% for other KLIKK-protease genes and miropin. At the same time, detectable mRNA expression of individual genes ranged from 20.7% to 58.6% of samples (for forsylisin and miropsin-1, respectively). In comparison with the T. forsythia proteases, miropin and the gingipains were highly expressed. The level of expression of gingipains was associated with those of miropin and certain T. forsythia proteases around teeth but not implants. Cumulatively, KLIKK-proteases and especially miropin, might play a role in pathogenesis of both periodontal and peri-implant diseases.

A questionnaire-based study evaluating differences between dental students in Paris (F) and Malmö (SE) regarding diagnosis and treatment decisions of patients with different severity levels of periodontal diseases.

AIM: To evaluate differences between last-year dental students in Paris (F) and Malmö (SE) Dental Schools, in regard to their judgement and decision-making within periodontology. MATERIALS AND METHODS: Ninety-six last-year dental students from Paris and 45 from Malmö participated in a questionnaire study based on four patient cases: (i) Patient case with generalised alveolar bone loss but no signs of inflammation (Well-maintained), (ii) Patient case with generalised alveolar bone loss and signs of inflammation (Periodontitis), (iii) Patient case with no alveolar bone loss and no signs of inflammation (Healthy) and (iv) Patient case with no alveolar bone loss but with signs of inflammation (Gingivitis). Through multiple-choice questions, the students judged each case as healthy or diseased proposed a diagnosis and treatment measures and estimated the treatment time for each patient. Furthermore, they assessed the prognosis of each patient in case of no treatment. RESULTS: Based on a response rate of 83%, the majority in both groups judged all the patients as diseased. More Paris students diagnosed the healthy and the gingivitis case as having periodontitis (P < .05). Furthermore, a larger number of students from Paris recommended several treatment measures and estimated longer treatment times for all the cases (P < .05) and estimated a higher risk for disease progression for the healthy and the gingivitis case (P < .05). CONCLUSIONS: Significant variation between students from Paris and Malmö Dental Schools in regard to judgement and decision-making was observed; this may in turn imply that there is still need of improving consistency amongst undergraduate educations in periodontology in Europe.

Statins in nonsurgical and surgical periodontal therapy. A systematic review and meta-analysis of preclinical in vivo trials.

The cholesterol-lowering drugs, statins, possess anti-inflammatory, antimicrobial and pro-osteogenic properties, and thus have been tested as an adjunct to periodontal treatment. The present systematic review aimed to answer the following focused research question: What is the effect of local and/or systemic statin use on periodontal tissues in preclinical in vivo studies of experimentally induced periodontitis (EIP) and/or acute/chronified periodontal defect (ACP) models? A literature search (of Medline/PubMed, Embase/Ovid, CENTRAL/Ovid) using the following main eligibility criteria was performed: (i) English or German language; (ii) controlled preclinical in vivo trials; (iii) local and/or systemic statin use in EIP and/or ACP models; and (iv) quantitative evaluation of periodontal tissues (i.e., alveolar bone level/amount, attachment level, cementum formation, periodontal ligament formation). Sixteen studies in EIP models and 7 studies in ACP models evaluated simvastatin, atorvastatin or rosuvastatin. Thirteen of the EIP (81%) and 2 of the ACP (29%) studies presented significantly better results in terms of alveolar bone level/amount in favor of statins. Meta-analysis based on 14 EIP trials confirmed a significant benefit of local and systemic statin use (P < .001) in terms of alveolar bone level/amount; meta-regression revealed that statin type exhibited a significant effect (P = .014) in favor of atorvastatin. Three studies reported a significantly higher periodontal attachment level in favor of statin use (P < .001). Complete periodontal regeneration was never observed; furthermore, statins did not exert any apparent effect on cementum formation. Neither local nor systemic use of statins resulted in severe adverse effects. Statin use in periodontal indications has a positive effect on periodontal tissue parameters, supporting the positive results already observed in clinical trials. Nevertheless, not all statins available have been tested so far, and further research is needed to identify the maximum effective concentration/dose and optimal carrier.

Effect of common antivertiginous agents on the high velocity vestibulo-ocular reflex.

OBJECTIVE: It has long been suggested that antivertiginous medications exert their symptomatic effect through inhibition of the vestibulo-ocular reflex (VOR). We tested this hypothesis by directly measuring the VOR after administration of three agents from different substance classes: an antihistamine, a benzodiazepine and a calcium channel antagonist. METHODS: The gain and the variability of the high velocity VOR was assessed using video head impulses (vHIT) under the following conditions: baseline, after dimenhydrinate, after diazepam and after cinnarizine. RESULTS: We found that all three medications did not change any VOR gain or variability parameter: At 60ms, the gain was 0.95 at baseline, 0.99 under dimenhydrinate, 0.99 under diazepam and 0.96 under cinnarizine. The gain variability across repetitive head impulses remained also uninfluenced. CONCLUSIONS: The human high frequency VOR remains robust to pharmacological perturbations at common clinical doses and the assumption that symptomatic vertigo relief is achieved merely through impairment of the VOR requires re-examination. SIGNIFICANCE: Alternative mechanisms of pharmacological action might be operant, such as the modulation of vestibulo-cortical pathways, a differential effect on the low frequency VOR and an altered sensitivity to drugs in acute unilateral vestibulopathy.

Effect of Osteotomy Preparation on Osseointegration of Immediately Loaded, Tapered Dental Implants.

The aim of the present preclinical in vivo study was to evaluate whether a modified "drill-only" protocol, involving slight underpreparation of the implant site, may have an effect on aspects of osseointegration of a novel bone-level tapered implant, compared with the "standard drilling" protocol involving taping and profiling of the marginal aspect of the implant socket. In each side of the edentulated and completely healed mandible of 11 minipigs, 2 tapered implants (8 mm long × 4.1 mm Ø, BLT; Institut Straumann AG, Basel, Switzerland) were installed either with the drill-only or the standard drilling protocol. Significantly lower average insertion torque values were recorded for the standard drilling protocol group (52 ± 29 Ncm) compared with the drill-only group (70 ± 27 Ncm) (t test, P ≤ 0.05); no significant difference was observed between the 2 groups regarding implant stability, by means of resonance frequency analysis (75 ± 8 vs. 75 ± 6, respectively). Half of the implants were immediately loaded and the rest were submerged, providing observation times of 8 or 4 wk, respectively. Non-decalcified histological and histomorphometric analysis of the implants with surrounding tissues showed no significant differences between the 2 drilling protocols regarding the distance from the implant platform to the first coronal bone-to-implant contact (f-BIC), the total bone-to-implant contact (BIC) as a percentage of the total implant perimeter, and the bone density in an area extending 1 mm laterally from the implant (BATA) within 2 rectangular regions of interest (ROIs) 4 mm in height, representing the coronal (parallel-walled) and apical (tapered) aspect of the implant (ROI 1 and ROI 2, respectively) in non-submerged implants. In general, marginal peri-implant bone levels were at or slightly apical to the implant platform, and large amounts of bone-to-implant contact were observed. In contrast, immediately loaded implants placed with the drill-only protocol showed statistically significantly lower BIC values (66% ± 13.7%) compared with those installed with the standard drilling protocol (74.8% ± 11.2%) (P = 0.018). In addition, although marginal bone levels were in most of the immediately loaded implants at or slightly apical to the implant platform, some of the implants installed with the drill-only protocol showed marginal bone loss and crater formation. Thus, in this model system, even slight underpreparation of the implant socket appeared to compromise osseointegration of immediately loaded bone-level tapered implants.

Effect of avocado/soybean unsaponifiables on ligature-induced bone loss and bone repair after ligature removal in rats.

BACKGROUND AND OBJECTIVE: The aim of this study was to evaluate the effects of administration of avocado/soybean unsaponifiable (ASU), a drug that is commonly used in the treatment of rheumatoid arthritis, on ligature-induced bone loss and bone repair after ligature removal in rats. MATERIAL AND METHODS: Eighty-four rats were randomly assigned to four groups of equal size and received a daily gavage of either sterile saline [control (CTR)] or ASU (0.6 mg/kg), starting 7 d before (ASU/-7), on the day of (ASU/0) or 7 d after (ASU/+7) periodontitis induction. Periodontitis was induced by placing silk ligatures into the gingival sulcus of the second maxillary molars for 7 d; after 7 d, the ligatures were removed. Seven rats from each group were sacrificed, 7, 15 or 30 d after ligature removal. Bone resorption was evaluated by histomorphometry and micro-computed tomography (micro-CT). Immunohistochemistry was used to evaluate the expression of TRAP, RANKL and alkaline phosphatase (ALP), and quantitative PCR (qPCR) was used to evaluate the levels of interleukin-1beta (Il1ß), tumor necrosis factor alpha (Tnfα), interleukin-6 (Il-6), Rankl and Alp. Statistical analysis was performed using the Shapiro-Wilk test, ANOVA and Tukey's test for normal data, and using the Kruskall-Wallis and Dunnet's tests for non-normal data (p < 0.05). RESULTS: Histomorphometry and micro-CT analysis showed greater bone resorption in the CTR group than in the ASU/0 (15 d) and ASU/+7 (7 and 15 d) groups. The CTR group also presented with a higher expression of TRAP (15 and 30 d) and RANKL (7 and 15 d) compared with ASU/0 and ASU/+7 groups. Similarly, qPCR analysis showed higher levels of Rankl and Il1ß mRNAs, and lower levels of Alp mRNA, in the CTR group compared with all other groups (for all periods). CONCLUSION: ASU exhibited a positive effect on bone repair following ligature-induced periodontitis in rats.

Influence of a titanium mesh on the management of segmental long bone defects. An experimental study in a canine ulnar model.

OBJECTIVES: To evaluate the influence of titanium mesh on guided bone regeneration when used, either alone or in combination with autogenous bone block graft, in a canine ulnar model. METHODS: Thirty-two, purpose bred, adult, castrated male Beagles were used, divided into four equal-size groups. A unilateral mid-diaphyseal ulnar critical-size defect was created in each dog. The ulnar segments were stabilized with a stainless-steel plate and screws. Each defect was managed by: no further treatment (Group A) or by placement of a bone block graft taken from the ipsilateral iliac crest (Group B), or titanium mesh wrapped around the ulna (Group C), or a bone block graft and titanium mesh (Group D). After six months, bone block biopsies were performed and the samples were scanned using micro-computed tomography. Qualitative histological evaluation was performed on two non-decalcified longitudinal sections from each block. RESULTS: No significant differences in terms of mineralized bone volume were detected between the grafted sites (Groups B and D) or between the non-grafted ones (Groups A and C). The histological evaluation indicated good integration of the bone blocks irrespective of the use of titanium mesh. CLINICAL SIGNIFICANCE: The use of titanium mesh does not influence the amount of bone formation. The canine ulnar critical-size defect model seems to be a reliable model to use in experimental studies.

Continuing professional development in implant dentistry in Europe.

INTRODUCTION: Training for dental practitioners in implant dentistry ranges from 1- or 2-day short Continuing Professional Development (CPD) courses to certificate/diploma programmes run by universities. In general, the teaching of implant dentistry in Europe lacks structure and standardisation. This paper aims to: (i) identify the current trends in CPD in implant dentistry in Europe; (ii) identify potential and limitations with regards to the design and implementation of CPD activities in implant dentistry; (iii) provide recommendations on the future structure and development of CPD activities in implant dentistry. METHODS: A search of the literature was undertaken in PubMed for manuscripts published in English after 2000 reporting on CPD in dentistry and in implant dentistry in particular. In addition, an electronic survey was conducted, investigating the attitudes towards CPD among a wide group of stakeholders in implant dentistry education. CONCLUSIONS: There is a wide diversity of educational pathways towards achieving competences in implant dentistry through CPD. At present, there is a need for improving the CPD structures in implant dentistry, strengthening the quality assurance and encouraging standardisation and transparency of the learning outcomes. Development of a structured CPD system with clearly defined educational objectives mapped against specific levels of competence is recommended.

Current trends and status of continuing professional development in implant dentistry in Europe.

INTRODUCTION: Previous surveys have shown that newly graduated dentists, in most European countries, do not obtain adequate theoretical knowledge and, especially, clinical skills in implant dentistry (ID) through their undergraduate education and must therefore acquire knowledge and develop competencies through further postgraduate study. Moreover, clinicians, in general, need to continue to maintain the currency of their competence by undertaking ongoing continuing professional development (CPD). This seems particularly important in ID as techniques, and materials develop rapidly due to advances in biomedical technology. Despite recent developments, CPD in ID remains poorly organised with little standardisation or harmonisation across Europe. The objective of this survey was to explore the current status and trends within CPD education in ID in Europe. MATERIALS AND METHODS: Stakeholders and opinion leaders associated with ID education were invited by email to fill an online questionnaire (closing date: 30th April 2013). Two hundred and forty-seven questionnaires were distributed, and two separate reminders were sent to participants in 38 European countries. The survey contained 14 multiple-choice questions, and the data were collected using SurveyMonkey© software, exported in SPSS (Inc, Chicago, IL, USA) format and analysed using descriptive statistics. RESULTS: Two hundred respondents working in 24 countries replied to the survey (response rate of 81% of invitees and 63% of countries surveyed). The results demonstrated a wide divergence in the content and structure of CPD in ID in Europe. CONCLUSIONS: Dentists need CPD to develop their skills and to maintain their competence in ID. There is an urgent need for structured and accredited CPD, which should be readily available to all dentists practising ID. It should have pre-determined learning objectives, delivered by accredited CPD providers and educators, and have assessable outcome measures to ensure the best possible impact on clinical practice and patient safety.

Virtual tissue alignment and cutting plane definition--a new method to obtain optimal longitudinal histological sections.

Histomorphometric evaluation of the buccal aspects of periodontal tissues in rodents requires reproducible alignment of maxillae and highly precise sections containing central sections of buccal roots; this is a cumbersome and technically sensitive process due to the small specimen size. The aim of the present report is to describe and analyze a method to transfer virtual sections of micro-computer tomographic (CT)-generated image stacks to the microtome for undecalcified histological processing and to describe the anatomy of the periodontium in rat molars. A total of 84 undecalcified sections of all buccal roots of seven untreated rats was analyzed. The accuracy of section coordinate transfer from virtual micro-CT slice to the histological slice, right-left side differences and the measurement error for linear and angular measurements on micro-CT and on histological micrographs were calculated using the Bland-Altman method, interclass correlation coefficient and the method of moments estimator. Also, manual alignment of the micro-CT-scanned rat maxilla was compared with multiplanar computer-reconstructed alignment. The supra alveolar rat anatomy is rather similar to human anatomy, whereas the alveolar bone is of compact type and the keratinized gingival epithelium bends apical to join the junctional epithelium. The high methodological standardization presented herein ensures retrieval of histological slices with excellent display of anatomical microstructures, in a reproducible manner, minimizes random errors, and thereby may contribute to the reduction of number of animals needed.

A rat model for orthodontic translational expansive tooth movement.

OBJECTIVES: To present the development of an experimental model in rats for translational expansive tooth movement. SETTING AND SAMPLE: Section of Periodontology at Department of Dentistry Aarhus University. Twenty male Wistar rats in two pilot experimental settings plus seven animals without any intervention serving as controls. MATERIAL AND METHODS: The second molar (group P1) or the second and third molar (group P2) in the maxillae of the animals were moved buccally using transpalatal ß-titanium springs. In the group P2, two spring types (high force and low force) and two preangulations (0° passive or 30° torsion moment) were tested. The amount and type of tooth movement achieved and the resulting skeletal effect were assessed on microCT images, histological analysis was performed on few selected specimens. RESULTS: Expansive translational root movement amounting half a tooth width was achieved. Comparison of the amount of tooth movement at the right and left side of the maxilla showed that the expansion was rather symmetrical in the P2 group. Skeletal widening of the maxilla contributed in the P2 group to approximately one-third of the total root movement, whereas two-thirds were dental movement. CONCLUSION: With the model used in the P2 group, further research on translational expansive tooth movement and its effect on the periodontium can be pursued. In models for orthodontic expansion, it is strongly recommended to separately evaluate skeletal and dental effects.

Validity of wax and acrylic as soft-tissue simulation materials used in in vitro radiographic studies.

OBJECTIVE: To determine the thickness of wax and acrylic that provides a radiographic density similar to that of the human cheek. METHODS: An intraoral film radiograph of the human cheek including a 40×30×3 mm reference aluminium block was recorded under standardized conditions in 61 subjects. Radiographic density was measured by a densitometer in ten randomly selected sites of the film to serve as the gold standard for density values of the cheek soft tissues. Thereafter, the density of series of radiographs of two tissue-simulating materials-wax and acrylic-in systematically increasing thicknesses (wax, 1.5-30 mm; acrylic, 2-40 mm) plus the reference block were measured and compared with the gold-standard values. RESULTS: The radiographic density of wax with a thickness of 13-17 mm or acrylic with a thickness of 14.5 mm corresponded to the average density of the human cheek. CONCLUSION: The soft tissues of the average human cheek can be simulated with 13-17 mm wax or 14.5 mm acrylic in in vitro radiographic studies.

Growth and differentiation factors for periodontal regeneration: a review on factors with clinical testing.

BACKGROUND AND OBJECTIVE: A large body of evidence implies that growth and differentiation factors, based on their ability to regulate various functions of cells originating in the periodontal tissues, may support periodontal wound healing/regeneration, creating an environment conducive to and/or immediately inducing de novo tissue formation. This study presents a short systematic overview on growth and differentiation factor technologies evaluated in the clinic for their potential to enhance periodontal wound healing/regeneration. MATERIAL AND METHODS: Reports on growth and differentiation factor technologies evaluated in the clinic for their potential to enhance periodontal wound healing/regeneration were selected for review. RESULTS: Growth and differentiation factor technologies intended for periodontal wound healing/regeneration and evaluated clinically included platelet-derived growth factor, insulin-like growth factor-I and -II, basic fibroblast growth factor, bone morphogenetic protein-3 and growth differentiation factor-5; platelet-derived growth factor was the only Food and Drug Administration-approved commercially available growth and differentiation factor technology. In general, enhanced periodontal regeneration was observed in sites receiving growth and differentiation factors compared with control(s). However, improvements of relatively limited clinical magnitude have been shown thus far. CONCLUSION: Although growth and differentiation factors project considerable appeal as candidate technologies in support of periodontal wound healing/regeneration, current candidate and commercially available technologies enhance treatment outcomes only to a limited extent in clinical settings.

Maxillary sinus floor augmentation with Bio-Oss or Bio-Oss mixed with autogenous bone as graft in animals: a systematic review.

The objective of the present systematic review was to test the hypothesis of no differences between the use of Bio-Oss or Bio-Oss mixed with autogenous bone as graft for maxillary sinus floor augmentation (MSFA) applying the lateral window technique, as evaluated in animals. A MEDLINE (PubMed), Embase, and Cochrane Library search in combination with a hand-search of relevant journals was conducted by including animal studies published in English from 1 January 1990 to 1 June 2010. The search provided 879 titles and 14 studies fulfilled the inclusion criteria. The volumetric stability of the graft improved significantly with increased proportion of Bio-Oss. Bone regeneration, bone-to-implant contact (BIC), biomechanical implant test values, and biodegradation of Bio-Oss after MSFA with Bio-Oss or Bio-Oss mixed with autogenous bone have never been compared within the same study in animals. Thus, the hypothesis of no differences between the use of Bio-Oss and Bio-Oss mixed with autogenous bone as graft for MSFA could neither be confirmed nor rejected based on existing animal studies.

Evaluation of the RB-RB/LB-LB mnemonic rule for recording optimally projected intraoral images of dental implants: an in vitro study.

OBJECTIVE: The aim of this study was to evaluate a simple mnemonic rule (the RB-RB/LB-LB rule) for recording intra-oral radiographs with optimal projection for the control of dental implants. METHODS: 30 third-year dental students received a short lesson in the RB-RB/LB-LB mnemonic rule. The rule is as follows: if right blur then raise beam (RB-RB), i.e. if implant threads are blurred at the right side of the implant, the X-ray beam direction must be raised towards the ceiling to obtain sharp threads on both implant sides; if left blur then lower beam (LB-LB), i.e. if implant threads are blurred at the left side of the implant, the X-ray beam direction must be lowered towards the floor to obtain sharp threads on both implant sides. Intra-oral radiographs of four screw-type implants placed with different inclination in a Frasaco upper or lower jaw dental model (Frasaco GmbH, Tettnang, Germany) were recorded. The students were unaware of the inclination of the implants and were instructed to re-expose each implant, implementing the mnemonic rule, until an image of the implant with acceptable quality (subjectively judged by the instructor) was obtained. Subsequently, each radiograph was blindly assessed with respect to sharpness of the implant threads and assigned to one of four quality categories: (1) perfect, (2) not perfect, but clinically acceptable, (3) not acceptable and (4) hopeless. RESULTS: For all implants, from one non-perfect exposure to the following, a higher score was obtained in 64% of the cases, 28% received the same score and 8% obtained a lower score. Only a small variation was observed among exposures of implants with different inclination. On average, two exposures per implant (range: one to eight exposures) were needed to obtain a clinically acceptable image. CONCLUSION: The RB-RB/LB-LB mnemonic rule for recording intra-oral radiographs of dental implants with a correct projection was easy to implement by inexperienced examiners.

Formation of human cementum following different modalities of regenerative therapy.

The aim of the present study was to compare newly formed cementum following different types of regenerative therapy in humans. Eighteen patients, each displaying one advanced intrabony defect around teeth scheduled for extraction, were included in this study. The defects were treated with either guided tissue regeneration (GTR), enamel matrix protein derivative (EMD), EMD plus bioactive glass, bovine-derived xenograft (BDX), BDX plus GTR, or BDX plus EMD. After healing, the teeth were removed together with their surrounding soft and hard tissues. Cellular content, presence of artifactual splits between the new cementum and the old one or the dentin surface, and thickness of the new cementum were evaluated. Irrespective of treatment, the new cementum was of a reparative, cellular, extrinsic and intrinsic fiber type. There were no differences in cementum thickness among treatments. These findings indicate that in humans, (a) the new cementum formed after different types of regenerative therapy was, irrespective of the treatment, of a reparative, cellular, extrinsic and intrinsic fiber type, and (b) the regenerative modality does not seem to influence the type of newly formed cementum.

Healing of human intrabony defects following regenerative periodontal therapy with a bovine-derived xenograft and guided tissue regeneration.

The purpose of the present study was to histologically evaluate the healing of human intrabony defects following treatment with either a bovine-derived xenograft (BDX) and guided tissue regeneration (GTR) [BDX + GTR] or a bovine-derived xenograft mixed with collagen (BDX Coll) and GTR [BDX Coll + GTR]. Eight patients with chronic periodontitis and each with one very deep intrabony defect around a tooth scheduled for extraction were treated with either a combination of BDX + GTR (five patients) or with BDX Coll + GTR (three patients). The postoperative healing was uneventful in all eight cases. After a healing period of 6 months, the teeth or roots were extracted together with some of their surrounding soft and hard tissues and subsequently fixed in 10% buffered formalin. Following decalcification in EDTA, the specimens were embedded in paraffin and 8-microm histological sections were cut in the mesio-distal direction, parallel to the long axes of the teeth. The sections were alternatively stained with hematoxylin and eosin, van Giesson's connective tissue stain or with the Ladevig's connective tissue staining method and examined under the light microscope. Generally, formation of new cementum with inserting collagen fibers was found in seven out of the eight treated cases, whereas in the remaining case (treated with BDX + GTR) the healing was characterized by formation of a long junctional epithelium along the debrided root surface and no formation of cementum or bone. In the specimens demonstrating periodontal regeneration the new cementum was always of a cellular type. In most cases, the graft particles were surrounded by bone. In some areas, the bone tissue around the graft particles was connected by perpendicularly inserting collagen fibers to the newly formed cementum on the root surface. The epithelium downgrowth stopped always at the most coronal part of the newly formed cementum. No remnants of the membrane material were observed in any of the biopsies. Connective tissue encapsulation of the graft particles was rarely observed and was limited to the most coronal part of the defects. The findings of the present study provide evidence that treatment of intrabony defects with both BDX + GTR and BDX Coll + GTR may enhance periodontal regeneration in humans.