Evaluation of the integrity of dental sealants by optical coherence tomography

Objectives

The purpose of the present research was to demonstrate images of failures into the structure of pit and fissure sealants using optical coherence tomography (OCT).

Methods

Five human third molars were selected and the sealant ALPHA SEAL LIGHT/DFL was applied according to the manufacturer instructions. For evaluation of the structure of pit and fissure sealants, twenty OCT images of each tooth were performed before and after application of sealant. A total of 200 images were evaluated. A home built spectral OCT system used was operating in spectral domain (SD-OCT), at 840 nm and a measured spatial resolution of 10 μm. The system is based on the Michelson interferometer set-up and is controlled by the software OCT 800 - Complex Square/LabView, that collects data and generates the image. The occlusal surfaces were scanned in a bucco-lingual direction and tomographic images parallel to long axis of tooth were obtained. After the achievement of the images by OCT, the crown of each tooth was sectioned in a occlusogingival direction (buccolingually). Images from each section were obtained and evaluated by an optical microscope. OCT and microscopic images were compared.

Results

Representative images showed that OCT image provides the insight into sealant material. It was possible to clearly identify the internal structure of sealant and the subjacent enamel. Sealant and enamel are very well distinguished, and failures at the interior and at surface are well detected.

Significance

OCT could generate images of the features of fissures, bubbles and failures in the adaptation of sealants, opening up possibilities in the future to monitoring sealant application and retention in short and long term.     

Virulence factors of the oral spirochete Treponema denticola

There is compelling evidence that treponemes are involved in the etiology of several chronic diseases, including chronic periodontitis as well as other forms of periodontal disease. There are interesting parallels with other chronic diseases caused by treponemes that may indicate similar virulence characteristics. Chronic periodontitis is a polymicrobial disease, and recent animal studies indicate that co-infection of Treponema denticola with other periodontal pathogens can enhance alveolar bone resorption. The bacterium has a suite of molecular determinants that could enable it to cause tissue damage and subvert the host immune response. In addition to this, it has several non-classic virulence determinants that enable it to interact with other pathogenic bacteria and the host in ways that are likely to promote disease progression. Recent advances, especially in molecular-based methodologies, have greatly improved our knowledge of this bacterium and its role in disease.     

A calculation method for the range of occluding phase at the lower incisal point during chewing movements using the curved mesh diagram of mandibular excursion (CMDME)

The purpose of this study was to develop a method for calculating the range of the occluding phase in chewing movements. In this study, we defined 'range' as the distance of the movement at the lower incisal point while the mandible moves with tooth contact. First, mandibular excursions were measured using an opto-electronic movement analysis system, which can measure mandibular movement with six degrees-of-freedom at a sampling frequency of 100 Hz. With use of this measurement data, the curved mesh diagram of mandibular excursion (CMDME) previously reported was made. Then, chewing movements were measured using the same analysis system. The movements were separated into their component chewing cycles. Finally, we calculated the distance between each cycle and the CMDME. The occluding range of our subject was 0.4 mm at the closing phase and 3.4 mm at the opening phase. These results suggest that tooth contact occurs during chewing movement and demonstrate that the range of the occluding phase for the opening and closing phases of a subject can be calculated without morphological data from a dental cast.     

The limited value of three pathogen species in predicting healing of periodontal pockets

Baseline level of Actinobacillus actinomycetemcomitans has been suggested as being predictive of periodontal treatment outcome. We analyzed the presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia in 55 deep periodontal pockets of 29 patients (18 men, 11 women, 37-75 years) before and after periodontal treatment. At baseline and after treatment, 62% and 33%, respectively, of the subjects presented with 1, 2, or a combination of all 3 pathogens. The mean pocket depth of 6.6 mm (0.4 mm) before treatment decreased to 2.2 mm (0.4 mm) in response to treatment (P<0.001). The treatment plan of non-surgical or surgical treatment was based on pocket depths and tooth morphology only. No antimicrobial medications were used during the treatment. Eighty-two percent of the deep pockets healed satisfactorily to < or = 4 mm. The presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, or Prevotella intermedia at baseline was not associated with the outcome of the periodontal therapy. In conclusion, we found that the presence of the 3 periodontopathogen species had little or no value in predicting healing of periodontal pockets.     

Cytotoxicity of a trial resin composite liner containing TiK2F6 on rat dental pulp cells

The aim of this study was to assess the toxicological responses of a resin composite containing TiK2F6 and NaF in rat dental pulp cells. Trial resin composite liners were made, containing 3 wt% fluorides (TiK2F6 or NaF). These specimens were immersed in 5 ml of cell culture medium supplemented at 37 degrees C for 24 hours. The eluates were used for the experiments. We judged the cytotoxicity of the samples by the cell viability. The original elute solution was serially diluted and then the medium was exchanged for the dilute medium. The cell viability at 1, 2 or 5 days after commencement of re-culturing was calculated. The viability of cells in the eluate from the resin composite liners containing TiK2F6 and NaF decreased with time. The cytotoxicity of TiK2F6 was weaker than that of NaF at all times.     

An analysis of management of private dental clinics in Japan from the survey of the current economy of medicine and dentistry

We analyzed the current state of management of private dental offices in Japan using the 11th Survey of the Current Economy of Medicine and Dentistry conducted in September of 1997. The analysis was mainly performed by comparing the survey in 1997 with the survey conducted in 1989. The results show the medium-term tendencies in dental management. We also compared the data from dental offices with those from private medical offices without facilities for inpatients. The following are the results: the average income from dental practice for a dental office in 1997 was 4,050,000 yen, a decrease of 4.9% (about 210,000 yen) compared with the average income in 1989. The average income from treatment covered by insurance in 1997, which accounted for most of the total income, was 3,540,000 yen, a decrease of 2.8% compared with that in 1989. The average income from non-insured treatment was 490,000 yen, which was also a decrease of 17.4%. The average income from medical practice for a medical office in 1997 was 1,970,000 yen more than the average income from dental practice of the same year. The average medical practice expenses and the average balance in medicine were higher than those in dentistry by 1,360,000 yen and by 600,000 yen respectively. Although the average income from medical practice slightly increased, the average wage costs increased by as much as 42.8%, resulting in a decrease of 21.2% in the average balance. Dental offices attempted to weather the decreased income from dental practice by raising the average fee paid by an insured patient. The analysis in the present study suggested that a decreasing number of patients and increasing dental practice expenses diminished the balance.     

Eight-year trend of new patients at Clinic for Disabled Patients,University Hospital,Faculty of Dentistry,Tokyo Medical and Dental University

The trend of new patients was investigated at the Clinic for Disabled Patients, University Hospital, Faculty of Dentistry, Tokyo Medical and Dental University for eight years from 1989 to 1996. The purpose of this study was to explore the future role of this specialized clinic. The study revealed the following information: 1. A total of 1,388 new patients, corresponding to 173.5 new patients per year on average, visited the clinic. 2. The percentage of patients aged 30 or more increased. As a result, the mean patient age rose from 40.4 in 1989 to 47.6 in 1996. 3. Referrals accounted for more than 80% of new patients. Medical doctors referred more patients to our clinic than dentists did. 4. While the percentage of disabled patients tended to decrease, the percentage of medically compromised patients increased. 5. The predominant complaint was dental caries. Patients with cardiovascular diseases also complained of gingival bleeding and ill-fitting dentures. The growing percentage of medically compromised patients and the increasing mean age of patients over the eight-year period seems to reflect advances in medical science and the aging society. These tendencies could be more remarkable in the future. Therefore, much closer cooperation between dentists and medical doctors will be required.     

Generalized odontodysplasia--a case report

Odontodysplasia is a relatively uncommon condition that can affect both primary and permanent dentition. It is characterized by defective formation of both enamel and dentin, with enlarged pulp chambers and root canals with open apices. It is usually a localised condition where one or few teeth may be involved. Sometimes, an entire quadrant or more than one quadrant may be involved but generalized involvement is extremely rare. An interesting case of a generalized odontodysplasia affecting both primary and permanent dentition in an eight year old girl is presented here.     

The measurement of physiological tooth displacement in function

The purpose of this work was to investigate the physiological tooth displacement in function. We developed the tooth displacement transducer Type M-3 and measured the three dimensional displacement of the upper and lower left first molars in function. The summary is as follows: 1. Magnesensors were used in the tooth displacement transducer Type M-3. Its total weight was 48.7 g. and the measuring pressure was kept less than 0.4 g. It was fixed at the labial surface of the anterior teeth using a paraocclusal splint. 2. The linearity error of the transducer was less than 2% within a range of +/-200 microm. 3. The upper left first molar showed displacement in the palatal and apical direction during clenching at the intercuspal position with habitual occlusal force or during the biting of articulating papers. The displacement varied between 40 and 136 microm. 4. The lower left first molar showed displacement in the apical and lingual direction during clenching at the intercuspal position or during the biting of articulating papers. The displacement varied between 29 and 65 microm. 5. The upper left first molar showed displacement in the palatal and apical direction during mastication. The displacement varied between 68 microm and 79 microm. The upper teeth moved first in the apical direction, then moved toward the labial direction. 6. In the lingual direction, the lower left first molar showed displacement ranging from 11 to 71 microm and 17 to 39 microm in the buccal direction during mastication.     

Postoperative exposure of bioresorbable GTR membranes: effect on healing results

The goal of this investigation was to evaluate the effect of postoperative exposure of two different bioresorbable membranes on the guided tissue regeneration (GTR) healing results compared to nonexposed sites. In each of 25 patients one pair of contralateral intrabony lesions was treated either with polylactic acid (PLA) or polyglactin 910 (PG-910) membranes. Postoperative exposure occurred in 9 PLA and 13 PG-910 sites. Standardized clinical [papillary bleeding index (PBI), gingival recession (REC), probing pocket depth (PPD), probing attachment level (PAL)] and radiographic examinations (digital subtraction radiography) were performed immediately before (baseline) and 6 and 12 months postoperatively (p.o.). Subgingival bacterial samples from surgical sites were evaluated by culture at baseline, 6 weeks, and 6 and 12 months p.o. Six months after surgery the changes (Δ) of REC were significantly (P≤0.05) greater in exposed than in nonexposed sites, independently of the membrane material (median): exposed sites, ΔREC=–1 mm; nonexposed sites, ΔREC=0.0 mm. However, 12 months p.o. no significant differences were found due to a decrease in the initial recessions in exposed sites. Although a higher percentage of exposed than nonexposed sites harbored periodontal pathogens 6 weeks p.o. at the gingiva-faced membrane surface, membrane exposure did not have a significant negative effect on ΔPPD, ΔPAL, or radiographic bone density changes 6 and 12 months p.o. Both membranes showed significant gains in PAL and bone density in both exposed and nonexposed sites. In conclusion, this study demonstrates that with consistent infection control the postoperative exposure of PLA and PG-910 membranes has no significant negative effect on the regeneration outcome, although higher initial gingival recessions must be expected than in the nonexposed sites. However, in exposed sites plaque and infection control were clearly impeded by the rough, exposed membrane surfaces and by the initially negative gingival morphology. Received: 22 January 1997 / Accepted: 5 May 1997